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[FreeBSD/FreeBSD.git] / contrib / sendmail / cf / README

                SENDMAIL CONFIGURATION FILES

This document describes the sendmail configuration files.  It
explains how to create a sendmail.cf file for use with sendmail.
It also describes how to set options for sendmail which are explained
in the Sendmail Installation and Operation guide (doc/op/op.me).

To get started, you may want to look at tcpproto.mc (for TCP-only
sites) and clientproto.mc (for clusters of clients using a single
mail host), or the generic-*.mc files as operating system-specific
examples.

Table of Content:

INTRODUCTION AND EXAMPLE
A BRIEF INTRODUCTION TO M4
FILE LOCATIONS
OSTYPE
DOMAINS
MAILERS
FEATURES
HACKS
SITE CONFIGURATION
USING UUCP MAILERS
TWEAKING RULESETS
MASQUERADING AND RELAYING
USING LDAP FOR ALIASES, MAPS, AND CLASSES
LDAP ROUTING
ANTI-SPAM CONFIGURATION CONTROL
CONNECTION CONTROL
STARTTLS
SMTP AUTHENTICATION
ADDING NEW MAILERS OR RULESETS
ADDING NEW MAIL FILTERS
QUEUE GROUP DEFINITIONS
NON-SMTP BASED CONFIGURATIONS
WHO AM I?
ACCEPTING MAIL FOR MULTIPLE NAMES
USING MAILERTABLES
USING USERDB TO MAP FULL NAMES
MISCELLANEOUS SPECIAL FEATURES
SECURITY NOTES
TWEAKING CONFIGURATION OPTIONS
MESSAGE SUBMISSION PROGRAM
FORMAT OF FILES AND MAPS
DIRECTORY LAYOUT
ADMINISTRATIVE DETAILS


+--------------------------+
| INTRODUCTION AND EXAMPLE |
+--------------------------+

Configuration files are contained in the subdirectory "cf", with a
suffix ".mc".  They must be run through "m4" to produce a ".cf" file.
You must pre-load "cf.m4":

        m4 ${CFDIR}/m4/cf.m4 config.mc > config.cf

Alternatively, you can simply:

        cd ${CFDIR}/cf
        ./Build config.cf

where ${CFDIR} is the root of the cf directory and config.mc is the
name of your configuration file.  If you are running a version of M4
that understands the __file__ builtin (versions of GNU m4 >= 0.75 do
this, but the versions distributed with 4.4BSD and derivatives do not)
or the -I flag (ditto), then ${CFDIR} can be in an arbitrary directory.
For "traditional" versions, ${CFDIR} ***MUST*** be "..", or you MUST
use -D_CF_DIR_=/path/to/cf/dir/ -- note the trailing slash!  For example:

        m4 -D_CF_DIR_=${CFDIR}/ ${CFDIR}/m4/cf.m4 config.mc > config.cf

Let's examine a typical .mc file:

        divert(-1)
        #
        # Copyright (c) 1998-2005 Proofpoint, Inc. and its suppliers.
        #       All rights reserved.
        # Copyright (c) 1983 Eric P. Allman.  All rights reserved.
        # Copyright (c) 1988, 1993
        #       The Regents of the University of California.  All rights reserved.
        #
        # By using this file, you agree to the terms and conditions set
        # forth in the LICENSE file which can be found at the top level of
        # the sendmail distribution.
        #

        #
        #  This is a Berkeley-specific configuration file for HP-UX 9.x.
        #  It applies only to the Computer Science Division at Berkeley,
        #  and should not be used elsewhere.   It is provided on the sendmail
        #  distribution as a sample only.  To create your own configuration
        #  file, create an appropriate domain file in ../domain, change the
        #  `DOMAIN' macro below to reference that file, and copy the result
        #  to a name of your own choosing.
        #
        divert(0)

The divert(-1) will delete the crud in the resulting output file.
The copyright notice can be replaced by whatever your lawyers require;
our lawyers require the one that is included in these files.  A copyleft
is a copyright by another name.  The divert(0) restores regular output.

        VERSIONID(`<SCCS or RCS version id>')

VERSIONID is a macro that stuffs the version information into the
resulting file.  You could use SCCS, RCS, CVS, something else, or
omit it completely.  This is not the same as the version id included
in SMTP greeting messages -- this is defined in m4/version.m4.

        OSTYPE(`hpux9')dnl

You must specify an OSTYPE to properly configure things such as the
pathname of the help and status files, the flags needed for the local
mailer, and other important things.  If you omit it, you will get an
error when you try to build the configuration.  Look at the ostype
directory for the list of known operating system types.

        DOMAIN(`CS.Berkeley.EDU')dnl

This example is specific to the Computer Science Division at Berkeley.
You can use "DOMAIN(`generic')" to get a sufficiently bland definition
that may well work for you, or you can create a customized domain
definition appropriate for your environment.

        MAILER(`local')
        MAILER(`smtp')

These describe the mailers used at the default CS site.  The local
mailer is always included automatically.  Beware: MAILER declarations
should only be followed by LOCAL_* sections.  The general rules are
that the order should be:

        VERSIONID
        OSTYPE
        DOMAIN
        FEATURE
        local macro definitions
        MAILER
        LOCAL_CONFIG
        LOCAL_RULE_*
        LOCAL_RULESETS

There are a few exceptions to this rule.  Local macro definitions which
influence a FEATURE() should be done before that feature.  For example,
a define(`PROCMAIL_MAILER_PATH', ...) should be done before
FEATURE(`local_procmail').

*******************************************************************
***  BE SURE YOU CUSTOMIZE THESE FILES!  They have some         ***
***  Berkeley-specific assumptions built in, such as the name   ***
***  of their UUCP-relay.  You'll want to create your own       ***
***  domain description, and use that in place of               ***
***  domain/Berkeley.EDU.m4.                                    ***
*******************************************************************


Note:
Some rulesets, features, and options are only useful if the sendmail
binary has been compiled with the appropriate options, e.g., the
ruleset tls_server is only invoked if sendmail has been compiled
with STARTTLS. This is usually obvious from the context and hence
not further specified here.
There are also so called "For Future Releases" (FFR) compile time
options which might be included in a subsequent version or might
simply be removed as they turned out not to be really useful.
These are generally not documented but if they are, then the required
compile time options are listed in doc/op/op.* for rulesets and
macros, and for mc/cf specific options they are usually listed here.
In addition to compile time options for the sendmail binary, there
can also be FFRs for mc/cf which in general can be enabled when the
configuration file is generated by defining them at the top of your
.mc file:

define(`_FFR_NAME_HERE', 1)


+----------------------------+
| A BRIEF INTRODUCTION TO M4 |
+----------------------------+

Sendmail uses the M4 macro processor to ``compile'' the configuration
files.  The most important thing to know is that M4 is stream-based,
that is, it doesn't understand about lines.  For this reason, in some
places you may see the word ``dnl'', which stands for ``delete
through newline''; essentially, it deletes all characters starting
at the ``dnl'' up to and including the next newline character.  In
most cases sendmail uses this only to avoid lots of unnecessary
blank lines in the output.

Other important directives are define(A, B) which defines the macro
``A'' to have value ``B''.  Macros are expanded as they are read, so
one normally quotes both values to prevent expansion.  For example,

        define(`SMART_HOST', `smart.foo.com')

One word of warning:  M4 macros are expanded even in lines that appear
to be comments.  For example, if you have

        # See FEATURE(`foo') above

it will not do what you expect, because the FEATURE(`foo') will be
expanded.  This also applies to

        # And then define the $X macro to be the return address

because ``define'' is an M4 keyword.  If you want to use them, surround
them with directed quotes, `like this'.

Since m4 uses single quotes (opening "`" and closing "'") to quote
arguments, those quotes can't be used in arguments.  For example,
it is not possible to define a rejection message containing a single
quote. Usually there are simple workarounds by changing those
messages; in the worst case it might be ok to change the value
directly in the generated .cf file, which however is not advised.


Notice:
-------

This package requires a post-V7 version of m4; if you are running the
4.2bsd, SysV.2, or 7th Edition version.  SunOS's /usr/5bin/m4 or
BSD-Net/2's m4 both work.  GNU m4 version 1.1 or later also works.
Unfortunately, the M4 on BSDI 1.0 doesn't work -- you'll have to use a
Net/2 or GNU version.  GNU m4 is available from
ftp://ftp.gnu.org/pub/gnu/m4/m4-1.4.tar.gz (check for the latest version).
EXCEPTIONS: DEC's m4 on Digital UNIX 4.x is broken (3.x is fine).  Use GNU
m4 on this platform.


+----------------+
| FILE LOCATIONS |
+----------------+

sendmail 8.9 has introduced a new configuration directory for sendmail
related files, /etc/mail.  The new files available for sendmail 8.9 --
the class {R} /etc/mail/relay-domains and the access database
/etc/mail/access -- take advantage of this new directory.  Beginning with
8.10, all files will use this directory by default (some options may be
set by OSTYPE() files).  This new directory should help to restore
uniformity to sendmail's file locations.

Below is a table of some of the common changes:

Old filename                    New filename
------------                    ------------
/etc/bitdomain                  /etc/mail/bitdomain
/etc/domaintable                /etc/mail/domaintable
/etc/genericstable              /etc/mail/genericstable
/etc/uudomain                   /etc/mail/uudomain
/etc/virtusertable              /etc/mail/virtusertable
/etc/userdb                     /etc/mail/userdb

/etc/aliases                    /etc/mail/aliases
/etc/sendmail/aliases           /etc/mail/aliases
/etc/ucbmail/aliases            /etc/mail/aliases
/usr/adm/sendmail/aliases       /etc/mail/aliases
/usr/lib/aliases                /etc/mail/aliases
/usr/lib/mail/aliases           /etc/mail/aliases
/usr/ucblib/aliases             /etc/mail/aliases

/etc/sendmail.cw                /etc/mail/local-host-names
/etc/mail/sendmail.cw           /etc/mail/local-host-names
/etc/sendmail/sendmail.cw       /etc/mail/local-host-names

/etc/sendmail.ct                /etc/mail/trusted-users

/etc/sendmail.oE                /etc/mail/error-header

/etc/sendmail.hf                /etc/mail/helpfile
/etc/mail/sendmail.hf           /etc/mail/helpfile
/usr/ucblib/sendmail.hf         /etc/mail/helpfile
/etc/ucbmail/sendmail.hf        /etc/mail/helpfile
/usr/lib/sendmail.hf            /etc/mail/helpfile
/usr/share/lib/sendmail.hf      /etc/mail/helpfile
/usr/share/misc/sendmail.hf     /etc/mail/helpfile
/share/misc/sendmail.hf         /etc/mail/helpfile

/etc/service.switch             /etc/mail/service.switch

/etc/sendmail.st                /etc/mail/statistics
/etc/mail/sendmail.st           /etc/mail/statistics
/etc/mailer/sendmail.st         /etc/mail/statistics
/etc/sendmail/sendmail.st       /etc/mail/statistics
/usr/lib/sendmail.st            /etc/mail/statistics
/usr/ucblib/sendmail.st         /etc/mail/statistics

Note that all of these paths actually use a new m4 macro MAIL_SETTINGS_DIR
to create the pathnames.  The default value of this variable is
`/etc/mail/'.  If you set this macro to a different value, you MUST include
a trailing slash.

Notice: all filenames used in a .mc (or .cf) file should be absolute
(starting at the root, i.e., with '/').  Relative filenames most
likely cause surprises during operations (unless otherwise noted).


+--------+
| OSTYPE |
+--------+

You MUST define an operating system environment, or the configuration
file build will puke.  There are several environments available; look
at the "ostype" directory for the current list.  This macro changes
things like the location of the alias file and queue directory.  Some
of these files are identical to one another.

It is IMPERATIVE that the OSTYPE occur before any MAILER definitions.
In general, the OSTYPE macro should go immediately after any version
information, and MAILER definitions should always go last.

Operating system definitions are usually easy to write.  They may define
the following variables (everything defaults, so an ostype file may be
empty).  Unfortunately, the list of configuration-supported systems is
not as broad as the list of source-supported systems, since many of
the source contributors do not include corresponding ostype files.

ALIAS_FILE              [/etc/mail/aliases] The location of the text version
                        of the alias file(s).  It can be a comma-separated
                        list of names (but be sure you quote values with
                        commas in them -- for example, use
                                define(`ALIAS_FILE', `a,b')
                        to get "a" and "b" both listed as alias files;
                        otherwise the define() primitive only sees "a").
HELP_FILE               [/etc/mail/helpfile] The name of the file
                        containing information printed in response to
                        the SMTP HELP command.
QUEUE_DIR               [/var/spool/mqueue] The directory containing
                        queue files.  To use multiple queues, supply
                        a value ending with an asterisk.  For
                        example, /var/spool/mqueue/qd* will use all of the
                        directories or symbolic links to directories
                        beginning with 'qd' in /var/spool/mqueue as queue
                        directories.  The names 'qf', 'df', and 'xf' are
                        reserved as specific subdirectories for the
                        corresponding queue file types as explained in
                        doc/op/op.me.  See also QUEUE GROUP DEFINITIONS.
MSP_QUEUE_DIR           [/var/spool/clientmqueue] The directory containing
                        queue files for the MSP (Mail Submission Program,
                        see sendmail/SECURITY).
STATUS_FILE             [/etc/mail/statistics] The file containing status
                        information.
LOCAL_MAILER_PATH       [/bin/mail] The program used to deliver local mail.
LOCAL_MAILER_FLAGS      [Prmn9] The flags used by the local mailer.  The
                        flags lsDFMAw5:/|@q are always included.
LOCAL_MAILER_ARGS       [mail -d $u] The arguments passed to deliver local
                        mail.
LOCAL_MAILER_MAX        [undefined] If defined, the maximum size of local
                        mail that you are willing to accept.
LOCAL_MAILER_MAXMSGS    [undefined] If defined, the maximum number of
                        messages to deliver in a single connection.  Only
                        useful for LMTP local mailers.
LOCAL_MAILER_CHARSET    [undefined] If defined, messages containing 8-bit data
                        that ARRIVE from an address that resolves to the
                        local mailer and which are converted to MIME will be
                        labeled with this character set.
LOCAL_MAILER_EOL        [undefined] If defined, the string to use as the
                        end of line for the local mailer.
LOCAL_MAILER_DSN_DIAGNOSTIC_CODE
                        [X-Unix] The DSN Diagnostic-Code value for the
                        local mailer.  This should be changed with care.
LOCAL_SHELL_PATH        [/bin/sh] The shell used to deliver piped email.
LOCAL_SHELL_FLAGS       [eu9] The flags used by the shell mailer.  The
                        flags lsDFM are always included.
LOCAL_SHELL_ARGS        [sh -c $u] The arguments passed to deliver "prog"
                        mail.
LOCAL_SHELL_DIR         [$z:/] The directory search path in which the
                        shell should run.
LOCAL_MAILER_QGRP       [undefined] The queue group for the local mailer.
USENET_MAILER_PATH      [/usr/lib/news/inews] The name of the program
                        used to submit news.
USENET_MAILER_FLAGS     [rsDFMmn] The mailer flags for the usenet mailer.
USENET_MAILER_ARGS      [-m -h -n] The command line arguments for the
                        usenet mailer.  NOTE: Some versions of inews
                        (such as those shipped with newer versions of INN)
                        use different flags.  Double check the defaults
                        against the inews man page.
USENET_MAILER_MAX       [undefined] The maximum size of messages that will
                        be accepted by the usenet mailer.
USENET_MAILER_QGRP      [undefined] The queue group for the usenet mailer.
SMTP_MAILER_FLAGS       [undefined] Flags added to SMTP mailer.  Default
                        flags are `mDFMuX' for all SMTP-based mailers; the
                        "esmtp" mailer adds `a'; "smtp8" adds `8'; and
                        "dsmtp" adds `%'.
RELAY_MAILER_FLAGS      [undefined] Flags added to the relay mailer.  Default
                        flags are `mDFMuX' for all SMTP-based mailers; the
                        relay mailer adds `a8'.  If this is not defined,
                        then SMTP_MAILER_FLAGS is used.
SMTP_MAILER_MAX         [undefined] The maximum size of messages that will
                        be transported using the smtp, smtp8, esmtp, or dsmtp
                        mailers.
SMTP_MAILER_MAXMSGS     [undefined] If defined, the maximum number of
                        messages to deliver in a single connection for the
                        smtp, smtp8, esmtp, or dsmtp mailers.
SMTP_MAILER_MAXRCPTS    [undefined] If defined, the maximum number of
                        recipients to deliver in a single envelope for the
                        smtp, smtp8, esmtp, or dsmtp mailers.
SMTP_MAILER_ARGS        [TCP $h] The arguments passed to the smtp mailer.
                        About the only reason you would want to change this
                        would be to change the default port.
ESMTP_MAILER_ARGS       [TCP $h] The arguments passed to the esmtp mailer.
SMTP8_MAILER_ARGS       [TCP $h] The arguments passed to the smtp8 mailer.
DSMTP_MAILER_ARGS       [TCP $h] The arguments passed to the dsmtp mailer.
RELAY_MAILER_ARGS       [TCP $h] The arguments passed to the relay mailer.
SMTP_MAILER_QGRP        [undefined] The queue group for the smtp mailer.
ESMTP_MAILER_QGRP       [undefined] The queue group for the esmtp mailer.
SMTP8_MAILER_QGRP       [undefined] The queue group for the smtp8 mailer.
DSMTP_MAILER_QGRP       [undefined] The queue group for the dsmtp mailer.
RELAY_MAILER_QGRP       [undefined] The queue group for the relay mailer.
RELAY_MAILER_MAXMSGS    [undefined] If defined, the maximum number of
                        messages to deliver in a single connection for the
                        relay mailer.
SMTP_MAILER_CHARSET     [undefined] If defined, messages containing 8-bit data
                        that ARRIVE from an address that resolves to one of
                        the SMTP mailers and which are converted to MIME will
                        be labeled with this character set.
RELAY_MAILER_CHARSET    [undefined] If defined, messages containing 8-bit data
                        that ARRIVE from an address that resolves to the
                        relay mailers and which are converted to MIME will
                        be labeled with this character set.
SMTP_MAILER_LL          [990] The maximum line length for SMTP mailers
                        (except the relay mailer).
RELAY_MAILER_LL         [2040] The maximum line length for the relay mailer.
UUCP_MAILER_PATH        [/usr/bin/uux] The program used to send UUCP mail.
UUCP_MAILER_FLAGS       [undefined] Flags added to UUCP mailer.  Default
                        flags are `DFMhuU' (and `m' for uucp-new mailer,
                        minus `U' for uucp-dom mailer).
UUCP_MAILER_ARGS        [uux - -r -z -a$g -gC $h!rmail ($u)] The arguments
                        passed to the UUCP mailer.
UUCP_MAILER_MAX         [100000] The maximum size message accepted for
                        transmission by the UUCP mailers.
UUCP_MAILER_CHARSET     [undefined] If defined, messages containing 8-bit data
                        that ARRIVE from an address that resolves to one of
                        the UUCP mailers and which are converted to MIME will
                        be labeled with this character set.
UUCP_MAILER_QGRP        [undefined] The queue group for the UUCP mailers.
FAX_MAILER_PATH         [/usr/local/lib/fax/mailfax] The program used to
                        submit FAX messages.
FAX_MAILER_ARGS         [mailfax $u $h $f] The arguments passed to the FAX
                        mailer.
FAX_MAILER_MAX          [100000] The maximum size message accepted for
                        transmission by FAX.
POP_MAILER_PATH         [/usr/lib/mh/spop] The pathname of the POP mailer.
POP_MAILER_FLAGS        [Penu] Flags added to POP mailer.  Flags lsDFMq
                        are always added.
POP_MAILER_ARGS         [pop $u] The arguments passed to the POP mailer.
POP_MAILER_QGRP         [undefined] The queue group for the pop mailer.
PROCMAIL_MAILER_PATH    [/usr/local/bin/procmail] The path to the procmail
                        program.  This is also used by
                        FEATURE(`local_procmail').
PROCMAIL_MAILER_FLAGS   [SPhnu9] Flags added to Procmail mailer.  Flags
                        DFM are always set.  This is NOT used by
                        FEATURE(`local_procmail'); tweak LOCAL_MAILER_FLAGS
                        instead.
PROCMAIL_MAILER_ARGS    [procmail -Y -m $h $f $u] The arguments passed to
                        the Procmail mailer.  This is NOT used by
                        FEATURE(`local_procmail'); tweak LOCAL_MAILER_ARGS
                        instead.
PROCMAIL_MAILER_MAX     [undefined] If set, the maximum size message that
                        will be accepted by the procmail mailer.
PROCMAIL_MAILER_QGRP    [undefined] The queue group for the procmail mailer.
MAIL11_MAILER_PATH      [/usr/etc/mail11] The path to the mail11 mailer.
MAIL11_MAILER_FLAGS     [nsFx] Flags for the mail11 mailer.
MAIL11_MAILER_ARGS      [mail11 $g $x $h $u] Arguments passed to the mail11
                        mailer.
MAIL11_MAILER_QGRP      [undefined] The queue group for the mail11 mailer.
PH_MAILER_PATH          [/usr/local/etc/phquery] The path to the phquery
                        program.
PH_MAILER_FLAGS         [ehmu] Flags for the phquery mailer.  Flags nrDFM
                        are always set.
PH_MAILER_ARGS          [phquery -- $u] -- arguments to the phquery mailer.
PH_MAILER_QGRP          [undefined] The queue group for the ph mailer.
CYRUS_MAILER_FLAGS      [Ah5@/:|] The flags used by the cyrus mailer.  The
                        flags lsDFMnPq are always included.
CYRUS_MAILER_PATH       [/usr/cyrus/bin/deliver] The program used to deliver
                        cyrus mail.
CYRUS_MAILER_ARGS       [deliver -e -m $h -- $u] The arguments passed
                        to deliver cyrus mail.
CYRUS_MAILER_MAX        [undefined] If set, the maximum size message that
                        will be accepted by the cyrus mailer.
CYRUS_MAILER_USER       [cyrus:mail] The user and group to become when
                        running the cyrus mailer.
CYRUS_MAILER_QGRP       [undefined] The queue group for the cyrus mailer.
CYRUS_BB_MAILER_FLAGS   [u] The flags used by the cyrusbb mailer.
                        The flags lsDFMnP are always included.
CYRUS_BB_MAILER_ARGS    [deliver -e -m $u] The arguments passed
                        to deliver cyrusbb mail.
CYRUSV2_MAILER_FLAGS    [A@/:|m] The flags used by the cyrusv2 mailer.  The
                        flags lsDFMnqXz are always included.
CYRUSV2_MAILER_MAXMSGS  [undefined] If defined, the maximum number of
                        messages to deliver in a single connection for the
                        cyrusv2 mailer.
CYRUSV2_MAILER_MAXRCPTS [undefined] If defined, the maximum number of
                        recipients to deliver in a single connection for the
                        cyrusv2 mailer.
CYRUSV2_MAILER_ARGS     [FILE /var/imap/socket/lmtp] The arguments passed
                        to the cyrusv2 mailer.  This can be used to
                        change the name of the Unix domain socket, or
                        to switch to delivery via TCP (e.g., `TCP $h lmtp')
CYRUSV2_MAILER_QGRP     [undefined] The queue group for the cyrusv2 mailer.
CYRUSV2_MAILER_CHARSET  [undefined] If defined, messages containing 8-bit data
                        that ARRIVE from an address that resolves to one the
                        Cyrus mailer and which are converted to MIME will
                        be labeled with this character set.
confEBINDIR             [/usr/libexec] The directory for executables.
                        Currently used for FEATURE(`local_lmtp') and
                        FEATURE(`smrsh').
QPAGE_MAILER_FLAGS      [mDFMs] The flags used by the qpage mailer.
QPAGE_MAILER_PATH       [/usr/local/bin/qpage] The program used to deliver
                        qpage mail.
QPAGE_MAILER_ARGS       [qpage -l0 -m -P$u] The arguments passed
                        to deliver qpage mail.
QPAGE_MAILER_MAX        [4096] If set, the maximum size message that
                        will be accepted by the qpage mailer.
QPAGE_MAILER_QGRP       [undefined] The queue group for the qpage mailer.
LOCAL_PROG_QGRP         [undefined] The queue group for the prog mailer.

Note: to tweak Name_MAILER_FLAGS use the macro MODIFY_MAILER_FLAGS:
MODIFY_MAILER_FLAGS(`Name', `change') where Name is the first part
of the macro Name_MAILER_FLAGS (note: that means Name is entirely in
upper case) and change can be: flags that should be used directly
(thus overriding the default value), or if it starts with `+' (`-')
then those flags are added to (removed from) the default value.
Example:

        MODIFY_MAILER_FLAGS(`LOCAL', `+e')

will add the flag `e' to LOCAL_MAILER_FLAGS.  Notice: there are
several smtp mailers all of which are manipulated individually.
See the section MAILERS for the available mailer names.
WARNING: The FEATUREs local_lmtp and local_procmail set LOCAL_MAILER_FLAGS
unconditionally, i.e., without respecting any definitions in an
OSTYPE setting.


+---------+
| DOMAINS |
+---------+

You will probably want to collect domain-dependent defines into one
file, referenced by the DOMAIN macro.  For example, the Berkeley
domain file includes definitions for several internal distinguished
hosts:

UUCP_RELAY      The host that will accept UUCP-addressed email.
                If not defined, all UUCP sites must be directly
                connected.
BITNET_RELAY    The host that will accept BITNET-addressed email.
                If not defined, the .BITNET pseudo-domain won't work.
DECNET_RELAY    The host that will accept DECNET-addressed email.
                If not defined, the .DECNET pseudo-domain and addresses
                of the form node::user will not work.
FAX_RELAY       The host that will accept mail to the .FAX pseudo-domain.
                The "fax" mailer overrides this value.
LOCAL_RELAY     The site that will handle unqualified names -- that
                is, names without an @domain extension.
                Normally MAIL_HUB is preferred for this function.
                LOCAL_RELAY is mostly useful in conjunction with
                FEATURE(`stickyhost') -- see the discussion of
                stickyhost below.  If not set, they are assumed to
                belong on this machine.  This allows you to have a
                central site to store a company- or department-wide
                alias database.  This only works at small sites,
                and only with some user agents.
LUSER_RELAY     The site that will handle lusers -- that is, apparently
                local names that aren't local accounts or aliases.  To
                specify a local user instead of a site, set this to
                ``local:username''.

Any of these can be either ``mailer:hostname'' (in which case the
mailer is the internal mailer name, such as ``uucp-new'' and the hostname
is the name of the host as appropriate for that mailer) or just a
``hostname'', in which case a default mailer type (usually ``relay'',
a variant on SMTP) is used.  WARNING: if you have a wildcard MX
record matching your domain, you probably want to define these to
have a trailing dot so that you won't get the mail diverted back
to yourself.

The domain file can also be used to define a domain name, if needed
(using "DD<domain>") and set certain site-wide features.  If all hosts
at your site masquerade behind one email name, you could also use
MASQUERADE_AS here.

You do not have to define a domain -- in particular, if you are a
single machine sitting off somewhere, it is probably more work than
it's worth.  This is just a mechanism for combining "domain dependent
knowledge" into one place.


+---------+
| MAILERS |
+---------+

There are fewer mailers supported in this version than the previous
version, owing mostly to a simpler world.  As a general rule, put the
MAILER definitions last in your .mc file.

local           The local and prog mailers.  You will almost always
                need these; the only exception is if you relay ALL
                your mail to another site.  This mailer is included
                automatically.

smtp            The Simple Mail Transport Protocol mailer.  This does
                not hide hosts behind a gateway or another other
                such hack; it assumes a world where everyone is
                running the name server.  This file actually defines
                five mailers: "smtp" for regular (old-style) SMTP to
                other servers, "esmtp" for extended SMTP to other
                servers, "smtp8" to do SMTP to other servers without
                converting 8-bit data to MIME (essentially, this is
                your statement that you know the other end is 8-bit
                clean even if it doesn't say so), "dsmtp" to do on
                demand delivery, and "relay" for transmission to the
                RELAY_HOST, LUSER_RELAY, or MAIL_HUB.

uucp            The UNIX-to-UNIX Copy Program mailer.  Actually, this
                defines two mailers, "uucp-old" (a.k.a. "uucp") and
                "uucp-new" (a.k.a. "suucp").  The latter is for when you
                know that the UUCP mailer at the other end can handle
                multiple recipients in one transfer.  If the smtp mailer
                is included in your configuration, two other mailers
                ("uucp-dom" and "uucp-uudom") are also defined [warning: you
                MUST specify MAILER(`smtp') before MAILER(`uucp')].  When you
                include the uucp mailer, sendmail looks for all names in
                class {U} and sends them to the uucp-old mailer; all
                names in class {Y} are sent to uucp-new; and all
                names in class {Z} are sent to uucp-uudom.  Note that
                this is a function of what version of rmail runs on
                the receiving end, and hence may be out of your control.
                See the section below describing UUCP mailers in more
                detail.

usenet          Usenet (network news) delivery.  If this is specified,
                an extra rule is added to ruleset 0 that forwards all
                local email for users named ``group.usenet'' to the
                ``inews'' program.  Note that this works for all groups,
                and may be considered a security problem.

fax             Facsimile transmission.  This is experimental and based
                on Sam Leffler's HylaFAX software.  For more information,
                see http://www.hylafax.org/.

pop             Post Office Protocol.

procmail        An interface to procmail (does not come with sendmail).
                This is designed to be used in mailertables.  For example,
                a common question is "how do I forward all mail for a given
                domain to a single person?".  If you have this mailer
                defined, you could set up a mailertable reading:

                        host.com        procmail:/etc/procmailrcs/host.com

                with the file /etc/procmailrcs/host.com reading:

                        :0      # forward mail for host.com
                        ! -oi -f $1 person@other.host

                This would arrange for (anything)@host.com to be sent
                to person@other.host.  In a procmail script, $1 is the
                name of the sender and $2 is the name of the recipient.
                If you use this with FEATURE(`local_procmail'), the FEATURE
                should be listed first.

                Of course there are other ways to solve this particular
                problem, e.g., a catch-all entry in a virtusertable.

mail11          The DECnet mail11 mailer, useful only if you have the mail11
                program from gatekeeper.dec.com:/pub/DEC/gwtools (and
                DECnet, of course).  This is for Phase IV DECnet support;
                if you have Phase V at your site you may have additional
                problems.

phquery         The phquery program.  This is somewhat counterintuitively
                referenced as the "ph" mailer internally.  It can be used
                to do CCSO name server lookups.  The phquery program, which
                this mailer uses, is distributed with the ph client.

cyrus           The cyrus and cyrusbb mailers.  The cyrus mailer delivers to
                a local cyrus user.  this mailer can make use of the
                "user+detail@local.host" syntax (see
                FEATURE(`preserve_local_plus_detail')); it will deliver the
                mail to the user's "detail" mailbox if the mailbox's ACL
                permits.  The cyrusbb mailer delivers to a system-wide
                cyrus mailbox if the mailbox's ACL permits.  The cyrus
                mailer must be defined after the local mailer.

cyrusv2         The mailer for Cyrus v2.x.  The cyrusv2 mailer delivers to
                local cyrus users via LMTP.  This mailer can make use of the
                "user+detail@local.host" syntax (see
                FEATURE(`preserve_local_plus_detail')); it will deliver the
                mail to the user's "detail" mailbox if the mailbox's ACL
                permits.  The cyrusv2 mailer must be defined after the
                local mailer.

qpage           A mailer for QuickPage, a pager interface.  See
                http://www.qpage.org/ for further information.

The local mailer accepts addresses of the form "user+detail", where
the "+detail" is not used for mailbox matching but is available
to certain local mail programs (in particular, see
FEATURE(`local_procmail')).  For example, "eric", "eric+sendmail", and
"eric+sww" all indicate the same user, but additional arguments <null>,
"sendmail", and "sww" may be provided for use in sorting mail.


+----------+
| FEATURES |
+----------+

Special features can be requested using the "FEATURE" macro.  For
example, the .mc line:

        FEATURE(`use_cw_file')

tells sendmail that you want to have it read an /etc/mail/local-host-names
file to get values for class {w}.  A FEATURE may contain up to 9
optional parameters -- for example:

        FEATURE(`mailertable', `dbm /usr/lib/mailertable')

The default database map type for the table features can be set with

        define(`DATABASE_MAP_TYPE', `dbm')

which would set it to use ndbm databases.  The default is the Berkeley DB
hash database format.  Note that you must still declare a database map type
if you specify an argument to a FEATURE.  DATABASE_MAP_TYPE is only used
if no argument is given for the FEATURE.  It must be specified before any
feature that uses a map.

Also, features which can take a map definition as an argument can also take
the special keyword `LDAP'.  If that keyword is used, the map will use the
LDAP definition described in the ``USING LDAP FOR ALIASES, MAPS, AND
CLASSES'' section below.

Available features are:

use_cw_file     Read the file /etc/mail/local-host-names file to get
                alternate names for this host.  This might be used if you
                were on a host that MXed for a dynamic set of other hosts.
                If the set is static, just including the line "Cw<name1>
                <name2> ..." (where the names are fully qualified domain
                names) is probably superior.  The actual filename can be
                overridden by redefining confCW_FILE.

use_ct_file     Read the file /etc/mail/trusted-users file to get the
                names of users that will be ``trusted'', that is, able to
                set their envelope from address using -f without generating
                a warning message.  The actual filename can be overridden
                by redefining confCT_FILE.

redirect        Reject all mail addressed to "address.REDIRECT" with
                a ``551 User has moved; please try <address>'' message.
                If this is set, you can alias people who have left
                to their new address with ".REDIRECT" appended.

nouucp          Don't route UUCP addresses.  This feature takes one
                parameter:
                `reject': reject addresses which have "!" in the local
                        part unless it originates from a system
                        that is allowed to relay.
                `nospecial': don't do anything special with "!".
                Warnings: 1. See the notice in the anti-spam section.
                2. don't remove "!" from OperatorChars if `reject' is
                given as parameter.

nopercenthack   Don't treat % as routing character.  This feature takes one
                parameter:
                `reject': reject addresses which have % in the local
                        part unless it originates from a system
                        that is allowed to relay.
                `nospecial': don't do anything special with %.
                Warnings: 1. See the notice in the anti-spam section.
                2. Don't remove % from OperatorChars if `reject' is
                given as parameter.

nocanonify      Don't pass addresses to $[ ... $] for canonification
                by default, i.e., host/domain names are considered canonical,
                except for unqualified names, which must not be used in this
                mode (violation of the standard).  It can be changed by
                setting the DaemonPortOptions modifiers (M=).  That is,
                FEATURE(`nocanonify') will be overridden by setting the
                'c' flag.  Conversely, if FEATURE(`nocanonify') is not used,
                it can be emulated by setting the 'C' flag
                (DaemonPortOptions=Modifiers=C).  This would generally only
                be used by sites that only act as mail gateways or which have
                user agents that do full canonification themselves.  You may
                also want to use
                "define(`confBIND_OPTS', `-DNSRCH -DEFNAMES')" to turn off
                the usual resolver options that do a similar thing.

                An exception list for FEATURE(`nocanonify') can be
                specified with CANONIFY_DOMAIN or CANONIFY_DOMAIN_FILE,
                i.e., a list of domains which are nevertheless passed to
                $[ ... $] for canonification.  This is useful to turn on
                canonification for local domains, e.g., use
                CANONIFY_DOMAIN(`my.domain my') to canonify addresses
                which end in "my.domain" or "my".
                Another way to require canonification in the local
                domain is CANONIFY_DOMAIN(`$=m').

                A trailing dot is added to addresses with more than
                one component in it such that other features which
                expect a trailing dot (e.g., virtusertable) will
                still work.

                If `canonify_hosts' is specified as parameter, i.e.,
                FEATURE(`nocanonify', `canonify_hosts'), then
                addresses which have only a hostname, e.g.,
                <user@host>, will be canonified (and hopefully fully
                qualified), too.

stickyhost      This feature is sometimes used with LOCAL_RELAY,
                although it can be used for a different effect with
                MAIL_HUB.

                When used without MAIL_HUB, email sent to
                "user@local.host" are marked as "sticky" -- that
                is, the local addresses aren't matched against UDB,
                don't go through ruleset 5, and are not forwarded to
                the LOCAL_RELAY (if defined).

                With MAIL_HUB, mail addressed to "user@local.host"
                is forwarded to the mail hub, with the envelope
                address still remaining "user@local.host".
                Without stickyhost, the envelope would be changed
                to "user@mail_hub", in order to protect against
                mailing loops.

mailertable     Include a "mailer table" which can be used to override
                routing for particular domains (which are not in class {w},
                i.e.  local host names).  The argument of the FEATURE may be
                the key definition.  If none is specified, the definition
                used is:

                        hash /etc/mail/mailertable

                Keys in this database are fully qualified domain names
                or partial domains preceded by a dot -- for example,
                "vangogh.CS.Berkeley.EDU" or ".CS.Berkeley.EDU".  As a
                special case of the latter, "." matches any domain not
                covered by other keys.  Values must be of the form:
                        mailer:domain
                where "mailer" is the internal mailer name, and "domain"
                is where to send the message.  These maps are not
                reflected into the message header.  As a special case,
                the forms:
                        local:user
                will forward to the indicated user using the local mailer,
                        local:
                will forward to the original user in the e-mail address
                using the local mailer, and
                        error:code message
                        error:D.S.N:code message
                will give an error message with the indicated SMTP reply
                code and message, where D.S.N is an RFC 1893 compliant
                error code.

domaintable     Include a "domain table" which can be used to provide
                domain name mapping.  Use of this should really be
                limited to your own domains.  It may be useful if you
                change names (e.g., your company changes names from
                oldname.com to newname.com).  The argument of the
                FEATURE may be the key definition.  If none is specified,
                the definition used is:

                        hash /etc/mail/domaintable

                The key in this table is the domain name; the value is
                the new (fully qualified) domain.  Anything in the
                domaintable is reflected into headers; that is, this
                is done in ruleset 3.

bitdomain       Look up bitnet hosts in a table to try to turn them into
                internet addresses.  The table can be built using the
                bitdomain program contributed by John Gardiner Myers.
                The argument of the FEATURE may be the key definition; if
                none is specified, the definition used is:

                        hash /etc/mail/bitdomain

                Keys are the bitnet hostname; values are the corresponding
                internet hostname.

uucpdomain      Similar feature for UUCP hosts.  The default map definition
                is:

                        hash /etc/mail/uudomain

                At the moment there is no automagic tool to build this
                database.

always_add_domain
                Include the local host domain even on locally delivered
                mail.  Normally it is not added on unqualified names.
                However, if you use a shared message store but do not use
                the same user name space everywhere, you may need the host
                name on local names.  An optional argument specifies
                another domain to be added than the local.

allmasquerade   If masquerading is enabled (using MASQUERADE_AS), this
                feature will cause recipient addresses to also masquerade
                as being from the masquerade host.  Normally they get
                the local hostname.  Although this may be right for
                ordinary users, it can break local aliases.  For example,
                if you send to "localalias", the originating sendmail will
                find that alias and send to all members, but send the
                message with "To: localalias@masqueradehost".  Since that
                alias likely does not exist, replies will fail.  Use this
                feature ONLY if you can guarantee that the ENTIRE
                namespace on your masquerade host supersets all the
                local entries.

limited_masquerade
                Normally, any hosts listed in class {w} are masqueraded.  If
                this feature is given, only the hosts listed in class {M} (see
                below:  MASQUERADE_DOMAIN) are masqueraded.  This is useful
                if you have several domains with disjoint namespaces hosted
                on the same machine.

masquerade_entire_domain
                If masquerading is enabled (using MASQUERADE_AS) and
                MASQUERADE_DOMAIN (see below) is set, this feature will
                cause addresses to be rewritten such that the masquerading
                domains are actually entire domains to be hidden.  All
                hosts within the masquerading domains will be rewritten
                to the masquerade name (used in MASQUERADE_AS).  For example,
                if you have:

                        MASQUERADE_AS(`masq.com')
                        MASQUERADE_DOMAIN(`foo.org')
                        MASQUERADE_DOMAIN(`bar.com')

                then *foo.org and *bar.com are converted to masq.com.  Without
                this feature, only foo.org and bar.com are masqueraded.

                    NOTE: only domains within your jurisdiction and
                    current hierarchy should be masqueraded using this.

local_no_masquerade
                This feature prevents the local mailer from masquerading even
                if MASQUERADE_AS is used.  MASQUERADE_AS will only have effect
                on addresses of mail going outside the local domain.

masquerade_envelope
                If masquerading is enabled (using MASQUERADE_AS) or the
                genericstable is in use, this feature will cause envelope
                addresses to also masquerade as being from the masquerade
                host.  Normally only the header addresses are masqueraded.

genericstable   This feature will cause unqualified addresses (i.e., without
                a domain) and addresses with a domain listed in class {G}
                to be looked up in a map and turned into another ("generic")
                form, which can change both the domain name and the user name.
                Notice: if you use an MSP (as it is default starting with
                8.12), the MTA will only receive qualified addresses from the
                MSP (as required by the RFCs).  Hence you need to add your
                domain to class {G}.  This feature is similar to the userdb
                functionality.  The same types of addresses as for
                masquerading are looked up, i.e., only header sender
                addresses unless the allmasquerade and/or masquerade_envelope
                features are given.  Qualified addresses must have the domain
                part in class {G}; entries can be added to this class by the
                macros GENERICS_DOMAIN or GENERICS_DOMAIN_FILE (analogously
                to MASQUERADE_DOMAIN and MASQUERADE_DOMAIN_FILE, see below).

                The argument of FEATURE(`genericstable') may be the map
                definition; the default map definition is:

                        hash /etc/mail/genericstable

                The key for this table is either the full address, the domain
                (with a leading @; the localpart is passed as first argument)
                or the unqualified username (tried in the order mentioned);
                the value is the new user address.  If the new user address
                does not include a domain, it will be qualified in the standard
                manner, i.e., using $j or the masquerade name.  Note that the
                address being looked up must be fully qualified.  For local
                mail, it is necessary to use FEATURE(`always_add_domain')
                for the addresses to be qualified.
                The "+detail" of an address is passed as %1, so entries like

                        old+*@foo.org   new+%1@example.com
                        gen+*@foo.org   %1@example.com

                and other forms are possible.

generics_entire_domain
                If the genericstable is enabled and GENERICS_DOMAIN or
                GENERICS_DOMAIN_FILE is used, this feature will cause
                addresses to be searched in the map if their domain
                parts are subdomains of elements in class {G}.

virtusertable   A domain-specific form of aliasing, allowing multiple
                virtual domains to be hosted on one machine.  For example,
                if the virtuser table contains:

                        info@foo.com    foo-info
                        info@bar.com    bar-info
                        joe@bar.com     error:nouser 550 No such user here
                        jax@bar.com     error:5.7.0:550 Address invalid
                        @baz.org        jane@example.net

                then mail addressed to info@foo.com will be sent to the
                address foo-info, mail addressed to info@bar.com will be
                delivered to bar-info, and mail addressed to anyone at baz.org
                will be sent to jane@example.net, mail to joe@bar.com will
                be rejected with the specified error message, and mail to
                jax@bar.com will also have a RFC 1893 compliant error code
                5.7.0.

                The username from the original address is passed
                as %1 allowing:

                        @foo.org        %1@example.com

                meaning someone@foo.org will be sent to someone@example.com.
                Additionally, if the local part consists of "user+detail"
                then "detail" is passed as %2 and "+detail" is passed as %3
                when a match against user+* is attempted, so entries like

                        old+*@foo.org   new+%2@example.com
                        gen+*@foo.org   %2@example.com
                        +*@foo.org      %1%3@example.com
                        X++@foo.org     Z%3@example.com
                        @bar.org        %1%3

                and other forms are possible.  Note: to preserve "+detail"
                for a default case (@domain) %1%3 must be used as RHS.
                There are two wildcards after "+": "+" matches only a non-empty
                detail, "*" matches also empty details, e.g., user+@foo.org
                matches +*@foo.org but not ++@foo.org.  This can be used
                to ensure that the parameters %2 and %3 are not empty.

                All the host names on the left hand side (foo.com, bar.com,
                and baz.org) must be in class {w} or class {VirtHost}.  The
                latter can be defined by the macros VIRTUSER_DOMAIN or
                VIRTUSER_DOMAIN_FILE (analogously to MASQUERADE_DOMAIN and
                MASQUERADE_DOMAIN_FILE, see below).  If VIRTUSER_DOMAIN or
                VIRTUSER_DOMAIN_FILE is used, then the entries of class
                {VirtHost} are added to class {R}, i.e., relaying is allowed
                to (and from) those domains, which by default includes also
                all subdomains (see relay_hosts_only).  The default map
                definition is:

                        hash /etc/mail/virtusertable

                A new definition can be specified as the second argument of
                the FEATURE macro, such as

                        FEATURE(`virtusertable', `dbm /etc/mail/virtusers')

virtuser_entire_domain
                If the virtusertable is enabled and VIRTUSER_DOMAIN or
                VIRTUSER_DOMAIN_FILE is used, this feature will cause
                addresses to be searched in the map if their domain
                parts are subdomains of elements in class {VirtHost}.

ldap_routing    Implement LDAP-based e-mail recipient routing according to
                the Internet Draft draft-lachman-laser-ldap-mail-routing-01.
                This provides a method to re-route addresses with a
                domain portion in class {LDAPRoute} to either a
                different mail host or a different address.  Hosts can
                be added to this class using LDAPROUTE_DOMAIN and
                LDAPROUTE_DOMAIN_FILE (analogously to MASQUERADE_DOMAIN and
                MASQUERADE_DOMAIN_FILE, see below).

                See the LDAP ROUTING section below for more information.

nullclient      This is a special case -- it creates a configuration file
                containing nothing but support for forwarding all mail to a
                central hub via a local SMTP-based network.  The argument
                is the name of that hub.

                The only other feature that should be used in conjunction
                with this one is FEATURE(`nocanonify').  No mailers
                should be defined.  No aliasing or forwarding is done.

local_lmtp      Use an LMTP capable local mailer.  The argument to this
                feature is the pathname of an LMTP capable mailer.  By
                default, mail.local is used.  This is expected to be the
                mail.local which came with the 8.9 distribution which is
                LMTP capable.  The path to mail.local is set by the
                confEBINDIR m4 variable -- making the default
                LOCAL_MAILER_PATH /usr/libexec/mail.local.
                If a different LMTP capable mailer is used, its pathname
                can be specified as second parameter and the arguments
                passed to it (A=) as third parameter, e.g.,

                        FEATURE(`local_lmtp', `/usr/local/bin/lmtp', `lmtp')

                WARNING: This feature sets LOCAL_MAILER_FLAGS unconditionally,
                i.e., without respecting any definitions in an OSTYPE setting.

local_procmail  Use procmail or another delivery agent as the local mailer.
                The argument to this feature is the pathname of the
                delivery agent, which defaults to PROCMAIL_MAILER_PATH.
                Note that this does NOT use PROCMAIL_MAILER_FLAGS or
                PROCMAIL_MAILER_ARGS for the local mailer; tweak
                LOCAL_MAILER_FLAGS and LOCAL_MAILER_ARGS instead, or
                specify the appropriate parameters.  When procmail is used,
                the local mailer can make use of the
                "user+indicator@local.host" syntax; normally the +indicator
                is just tossed, but by default it is passed as the -a
                argument to procmail.

                This feature can take up to three arguments:

                1. Path to the mailer program
                   [default: /usr/local/bin/procmail]
                2. Argument vector including name of the program
                   [default: procmail -Y -a $h -d $u]
                3. Flags for the mailer [default: SPfhn9]

                Empty arguments cause the defaults to be taken.
                Note that if you are on a system with a broken
                setreuid() call, you may need to add -f $f to the procmail
                argument vector to pass the proper sender to procmail.

                For example, this allows it to use the maildrop mailer
                instead by specifying:

                FEATURE(`local_procmail', `/usr/local/bin/maildrop',
                 `maildrop -d $u')

                or scanmails using:

                FEATURE(`local_procmail', `/usr/local/bin/scanmails')

                WARNING: This feature sets LOCAL_MAILER_FLAGS unconditionally,
                i.e., without respecting any definitions in an OSTYPE setting.

bestmx_is_local Accept mail as though locally addressed for any host that
                lists us as the best possible MX record.  This generates
                additional DNS traffic, but should be OK for low to
                medium traffic hosts.  The argument may be a set of
                domains, which will limit the feature to only apply to
                these domains -- this will reduce unnecessary DNS
                traffic.  THIS FEATURE IS FUNDAMENTALLY INCOMPATIBLE WITH
                WILDCARD MX RECORDS!!!  If you have a wildcard MX record
                that matches your domain, you cannot use this feature.

smrsh           Use the SendMail Restricted SHell (smrsh) provided
                with the distribution instead of /bin/sh for mailing
                to programs.  This improves the ability of the local
                system administrator to control what gets run via
                e-mail.  If an argument is provided it is used as the
                pathname to smrsh; otherwise, the path defined by
                confEBINDIR is used for the smrsh binary -- by default,
                /usr/libexec/smrsh is assumed.

promiscuous_relay
                By default, the sendmail configuration files do not permit
                mail relaying (that is, accepting mail from outside your
                local host (class {w}) and sending it to another host than
                your local host).  This option sets your site to allow
                mail relaying from any site to any site.  In almost all
                cases, it is better to control relaying more carefully
                with the access map, class {R}, or authentication.  Domains
                can be added to class {R} by the macros RELAY_DOMAIN or
                RELAY_DOMAIN_FILE (analogously to MASQUERADE_DOMAIN and
                MASQUERADE_DOMAIN_FILE, see below).

relay_entire_domain
                This option allows any host in your domain as defined by
                class {m} to use your server for relaying.  Notice: make
                sure that your domain is not just a top level domain,
                e.g., com.  This can happen if you give your host a name
                like example.com instead of host.example.com.

relay_hosts_only
                By default, names that are listed as RELAY in the access
                db and class {R} are treated as domain names, not host names.
                For example, if you specify ``foo.com'', then mail to or
                from foo.com, abc.foo.com, or a.very.deep.domain.foo.com
                will all be accepted for relaying.  This feature changes
                the behaviour to look up individual host names only.

relay_based_on_MX
                Turns on the ability to allow relaying based on the MX
                records of the host portion of an incoming recipient; that
                is, if an MX record for host foo.com points to your site,
                you will accept and relay mail addressed to foo.com.  See
                description below for more information before using this
                feature.  Also, see the KNOWNBUGS entry regarding bestmx
                map lookups.

                FEATURE(`relay_based_on_MX') does not necessarily allow
                routing of these messages which you expect to be allowed,
                if route address syntax (or %-hack syntax) is used.  If
                this is a problem, add entries to the access-table or use
                FEATURE(`loose_relay_check').

relay_mail_from
                Allows relaying if the mail sender is listed as RELAY in
                the access map.  If an optional argument `domain' (this
                is the literal word `domain', not a placeholder) is given,
                relaying can be allowed just based on the domain portion
                of the sender address.  This feature should only be used if
                absolutely necessary as the sender address can be easily
                forged.  Use of this feature requires the "From:" tag to
                be used for the key in the access map; see the discussion
                of tags and FEATURE(`relay_mail_from') in the section on
                anti-spam configuration control.

relay_local_from
                Allows relaying if the domain portion of the mail sender
                is a local host.  This should only be used if absolutely
                necessary as it opens a window for spammers.  Specifically,
                they can send mail to your mail server that claims to be
                from your domain (either directly or via a routed address),
                and you will go ahead and relay it out to arbitrary hosts
                on the Internet.

accept_unqualified_senders
                Normally, MAIL FROM: commands in the SMTP session will be
                refused if the connection is a network connection and the
                sender address does not include a domain name.  If your
                setup sends local mail unqualified (i.e., MAIL FROM:<joe>),
                you will need to use this feature to accept unqualified
                sender addresses.  Setting the DaemonPortOptions modifier
                'u' overrides the default behavior, i.e., unqualified
                addresses are accepted even without this FEATURE.
                If this FEATURE is not used, the DaemonPortOptions modifier
                'f' can be used to enforce fully qualified addresses.

accept_unresolvable_domains
                Normally, MAIL FROM: commands in the SMTP session will be
                refused if the host part of the argument to MAIL FROM:
                cannot be located in the host name service (e.g., an A or
                MX record in DNS).  If you are inside a firewall that has
                only a limited view of the Internet host name space, this
                could cause problems.  In this case you probably want to
                use this feature to accept all domains on input, even if
                they are unresolvable.

access_db       Turns on the access database feature.  The access db gives
                you the ability to allow or refuse to accept mail from
                specified domains for administrative reasons.  Moreover,
                it can control the behavior of sendmail in various situations.
                By default, the access database specification is:

                        hash -T<TMPF> /etc/mail/access

                See the anti-spam configuration control section for further
                important information about this feature.  Notice:
                "-T<TMPF>" is meant literal, do not replace it by anything.

blocklist_recipients
                Turns on the ability to block incoming mail for certain
                recipient usernames, hostnames, or addresses.  For
                example, you can block incoming mail to user nobody,
                host foo.mydomain.com, or guest@bar.mydomain.com.
                These specifications are put in the access db as
                described in the anti-spam configuration control section
                later in this document.

delay_checks    The rulesets check_mail and check_relay will not be called
                when a client connects or issues a MAIL command, respectively.
                Instead, those rulesets will be called by the check_rcpt
                ruleset; they will be skipped under certain circumstances.
                See "Delay all checks" in the anti-spam configuration control
                section.  Note: this feature is incompatible to the versions
                in 8.10 and 8.11.

check_other     Enable a default check_other ruleset which terminates
                an SMTP session when it encounters a command which matches
                a regular expression given as argument. If no argument
                is given, then the default (to match potential headers) is:
                        ^[[:print:]]+ *:

use_client_ptr  If this feature is enabled then check_relay will override
                its first argument with $&{client_ptr}.  This is useful for
                rejections based on the unverified hostname of client,
                which turns on the same behavior as in earlier sendmail
                versions when delay_checks was not in use.  See doc/op/op.*
                about check_relay, {client_name}, and {client_ptr}.

dnsbl           Turns on rejection, discarding, or quarantining of hosts
                found in a DNS based list.  The first argument is used as
                the domain in which blocked hosts are listed.  A second
                argument can be used to change the default error message,
                or select one of the operations `discard' and `quarantine'.
                Without that second argument, the error message will be

                        Rejected: IP-ADDRESS listed at SERVER

                where IP-ADDRESS and SERVER are replaced by the appropriate
                information.  By default, temporary lookup failures are
                ignored.  This behavior can be changed by specifying a
                third argument, which must be either `t' or a full error
                message.  See the anti-spam configuration control section for
                an example.  The dnsbl feature can be included several times
                to query different DNS based rejection lists.  See also
                enhdnsbl for an enhanced version.

                Set the DNSBL_MAP mc option to change the default map
                definition from `host'.  Set the DNSBL_MAP_OPT mc option
                to add additional options to the map specification used.

                Note: currently only IPv4 addresses are checked.

                Some DNS based rejection lists cause failures if asked
                for AAAA records. If your sendmail version is compiled
                with IPv6 support (NETINET6) and you experience this
                problem, add

                        define(`DNSBL_MAP', `dns -R A')

                before the first use of this feature.  Alternatively you
                can use enhdnsbl instead (see below).  Moreover, this
                statement can be used to reduce the number of DNS retries,
                e.g.,

                        define(`DNSBL_MAP', `dns -R A -r2')

                See below (EDNSBL_TO) for an explanation.

enhdnsbl        Enhanced version of dnsbl (see above).  Further arguments
                (up to 5) can be used to specify specific return values
                from lookups.  Temporary lookup failures are ignored unless
                a third argument is given, which must be either `t' or a full
                error message.  By default, any successful lookup will
                generate an error.  Otherwise the result of the lookup is
                compared with the supplied argument(s), and only if a match
                occurs an error is generated.  For example,

                FEATURE(`enhdnsbl', `dnsbl.example.com', `', `t', `127.0.0.2')

                will reject the e-mail if the lookup returns the value
                ``127.0.0.2'', or generate a 451 response if the lookup
                temporarily failed.  The arguments can contain metasymbols
                as they are allowed in the LHS of rules.  As the example
                shows, the default values are also used if an empty argument,
                i.e., `', is specified.  This feature requires that sendmail
                has been compiled with the flag DNSMAP (see sendmail/README).

                Set the EDNSBL_TO mc option to change the DNS retry count
                from the default value of 5, this can be very useful when
                a DNS server is not responding, which in turn may cause
                clients to time out (an entry stating

                        did not issue MAIL/EXPN/VRFY/ETRN

                will be logged).

ratecontrol     Enable simple ruleset to do connection rate control
                checking.  This requires entries in access_db of the form

                        ClientRate:IP.ADD.RE.SS         LIMIT

                The RHS specifies the maximum number of connections
                (an integer number) over the time interval defined
                by ConnectionRateWindowSize, where 0 means unlimited.

                Take the following example:

                        ClientRate:10.1.2.3             4
                        ClientRate:127.0.0.1            0
                        ClientRate:                     10

                10.1.2.3 can only make up to 4 connections, the
                general limit it 10, and 127.0.0.1 can make an unlimited
                number of connections per ConnectionRateWindowSize.

                See also CONNECTION CONTROL.

conncontrol     Enable a simple check of the number of incoming SMTP
                connections.  This requires entries in access_db of the
                form

                        ClientConn:IP.ADD.RE.SS         LIMIT

                The RHS specifies the maximum number of open connections
                (an integer number).

                Take the following example:

                        ClientConn:10.1.2.3             4
                        ClientConn:127.0.0.1            0
                        ClientConn:                     10

                10.1.2.3 can only have up to 4 open connections, the
                general limit it 10, and 127.0.0.1 does not have any
                explicit limit.

                See also CONNECTION CONTROL.

mtamark         Experimental support for "Marking Mail Transfer Agents in
                Reverse DNS with TXT RRs" (MTAMark), see
                draft-stumpf-dns-mtamark-01.  Optional arguments are:

                1. Error message, default:

                        550 Rejected: $&{client_addr} not listed as MTA

                2. Temporary lookup failures are ignored unless a second
                argument is given, which must be either `t' or a full
                error message.

                3. Lookup prefix, default: _perm._smtp._srv.  This should
                not be changed unless the draft changes it.

                Example:

                        FEATURE(`mtamark', `', `t')

lookupdotdomain Look up also .domain in the access map.  This allows to
                match only subdomains.  It does not work well with
                FEATURE(`relay_hosts_only'), because most lookups for
                subdomains are suppressed by the latter feature.

loose_relay_check
                Normally, if % addressing is used for a recipient, e.g.
                user%site@othersite, and othersite is in class {R}, the
                check_rcpt ruleset will strip @othersite and recheck
                user@site for relaying.  This feature changes that
                behavior.  It should not be needed for most installations.

authinfo        Provide a separate map for client side authentication
                information.  See SMTP AUTHENTICATION for details.
                By default, the authinfo database specification is:

                        hash /etc/mail/authinfo

preserve_luser_host
                Preserve the name of the recipient host if LUSER_RELAY is
                used.  Without this option, the domain part of the
                recipient address will be replaced by the host specified as
                LUSER_RELAY.  This feature only works if the hostname is
                passed to the mailer (see mailer triple in op.me).  Note
                that in the default configuration the local mailer does not
                receive the hostname, i.e., the mailer triple has an empty
                hostname.

preserve_local_plus_detail
                Preserve the +detail portion of the address when passing
                address to local delivery agent.  Disables alias and
                .forward +detail stripping (e.g., given user+detail, only
                that address will be looked up in the alias file; user+* and
                user will not be looked up).  Only use if the local
                delivery agent in use supports +detail addressing.
                Moreover, this will most likely not work if the 'w' flag
                for the local mailer is set as the entire local address
                including +detail is passed to the user lookup function.

compat_check    Enable ruleset check_compat to look up pairs of addresses
                with the Compat: tag -- Compat:sender<@>recipient -- in the
                access map.  Valid values for the RHS include
                        DISCARD silently discard recipient
                        TEMP:   return a temporary error
                        ERROR:  return a permanent error
                In the last two cases, a 4xy/5xy SMTP reply code should
                follow the colon.

no_default_msa  Don't generate the default MSA daemon, i.e.,
                DAEMON_OPTIONS(`Port=587,Name=MSA,M=E')
                To define a MSA daemon with other parameters, use this
                FEATURE and introduce new settings via DAEMON_OPTIONS().

msp             Defines config file for Message Submission Program.
                See sendmail/SECURITY for details and cf/cf/submit.mc how
                to use it.  An optional argument can be used to override
                the default of `[localhost]' to use as host to send all
                e-mails to.  Note that MX records will be used if the
                specified hostname is not in square brackets (e.g.,
                [hostname]).  If `MSA' is specified as second argument then
                port 587 is used to contact the server.  Example:

                        FEATURE(`msp', `', `MSA')

                Some more hints about possible changes can be found below
                in the section MESSAGE SUBMISSION PROGRAM.

                Note: Due to many problems, submit.mc uses

                        FEATURE(`msp', `[127.0.0.1]')

                by default.  If you have a machine with IPv6 only,
                change it to

                        FEATURE(`msp', `[IPv6:0:0:0:0:0:0:0:1]')

                If you want to continue using '[localhost]', (the behavior
                up to 8.12.6), use

                        FEATURE(`msp')

queuegroup      A simple example how to select a queue group based
                on the full e-mail address or the domain of the
                recipient.  Selection is done via entries in the
                access map using the tag QGRP:, for example:

                        QGRP:example.com        main
                        QGRP:friend@some.org    others
                        QGRP:my.domain          local

                where "main", "others", and "local" are names of
                queue groups.  If an argument is specified, it is used
                as default queue group.

                Note: please read the warning in doc/op/op.me about
                queue groups and possible queue manipulations.

greet_pause     Adds the greet_pause ruleset which enables open proxy
                and SMTP slamming protection.  The feature can take an
                argument specifying the milliseconds to wait:

                        FEATURE(`greet_pause', `5000')  dnl 5 seconds

                If FEATURE(`access_db') is enabled, an access database
                lookup with the GreetPause tag is done using client
                hostname, domain, IP address, or subnet to determine the
                pause time:

                        GreetPause:my.domain    0
                        GreetPause:example.com  5000
                        GreetPause:10.1.2       2000
                        GreetPause:127.0.0.1    0

                When using FEATURE(`access_db'), the optional
                FEATURE(`greet_pause') argument becomes the default if
                nothing is found in the access database.  A ruleset called
                Local_greet_pause can be used for local modifications, e.g.,

                        LOCAL_RULESETS
                        SLocal_greet_pause
                        R$*             $: $&{daemon_flags}
                        R$* a $*        $# 0

block_bad_helo  Reject messages from SMTP clients which provide a HELO/EHLO
                argument which is either unqualified, or is one of our own
                names (i.e., the server name instead of the client name).
                This check is performed at RCPT stage and disabled for the
                following cases:
                - authenticated sessions,
                - connections from IP addresses in class $={R}.
                Currently access_db lookups can not be used to
                (selectively) disable this test, moreover,

                FEATURE(`delay_checks')

                is required.  Note, the block_bad_helo feature automatically
                adds the IPv6 and IPv4 localhost IP addresses to $={w} (local
                host names) and $={R} (relay permitted).

require_rdns    Reject mail from connecting SMTP clients without proper
                rDNS (reverse DNS), functional gethostbyaddr() resolution.
                Note: this feature will cause false positives, i.e., there
                are legitimate MTAs that do not have proper DNS entries.
                Rejecting mails from those MTAs is a local policy decision.

                The basic policy is to reject message with a 5xx error if
                the IP address fails to resolve.  However, if this is a
                temporary failure, a 4xx temporary failure is returned.
                If the look-up succeeds, but returns an apparently forged
                value, this is treated as a temporary failure with a 4xx
                error code.

                EXCEPTIONS:

                Exceptions based on access entries are discussed below.
                Any IP address matched using $=R (the "relay-domains" file)
                is excepted from the rules.  Since we have explicitly
                allowed relaying for this host, based on IP address, we
                ignore the rDNS failure.

                The philosophical assumption here is that most users do
                not control their rDNS.  They should be able to send mail
                through their ISP, whether or not they have valid rDNS.
                The class $=R, roughly speaking, contains those IP addresses
                and address ranges for which we are the ISP, or are acting
                as if the ISP.

                If `delay_checks' is in effect (recommended), then any
                sender who has authenticated is also excepted from the
                restrictions.  This happens because the rules produced by
                this FEATURE() will not be applied to authenticated senders
                (assuming `delay_checks').

                ACCESS MAP ENTRIES:

                Entries such as
                        Connect:1.2.3.4         OK
                        Connect:1.3             RELAY
                will allowlist IP address 1.2.3.4 and IP net 1.3.*
                so that the rDNS blocking does apply not to those IPs.

                Entries such as
                        Connect:1.2.3.4         REJECT
                will have the effect of forcing a temporary failure for
                that address to be treated as a permanent failure.

badmx           Reject envelope sender addresses (MAIL) whose domain part
                resolves to a "bad" MX record.  By default these are
                MX records which resolve to A records that match the
                regular expression:

                ^(127\.|10\.|0\.0\.0\.0)

                This default regular expression can be overridden by
                specifying an argument, e.g.,

                FEATURE(`badmx', `^127\.0\.0\.1')

                Note: this feature requires that the sendmail binary
                has been compiled with the options MAP_REGEX and
                DNSMAP.

sts             Experimental support for Strict Transport Security
                (MTA-STS, see RFC 8461).  It sets the option
                StrictTransportSecurity and takes one optional
                argument: the socket map specification to access
                postfix-mta-sts-resolver (see feature/sts.m4
                for the default value).
                For more information see doc/op/op.me.

fips3           Basic support for FIPS in OpenSSL 3 by setting
                the environment variables OPENSSL_CONF and
                OPENSSL_MODULES to the first and second argument,
                respectively.  For details, see the file and
                the OpenSSL documentation.

+-------+
| HACKS |
+-------+

Some things just can't be called features.  To make this clear,
they go in the hack subdirectory and are referenced using the HACK
macro.  These will tend to be site-dependent.  The release
includes the Berkeley-dependent "cssubdomain" hack (that makes
sendmail accept local names in either Berkeley.EDU or CS.Berkeley.EDU;
this is intended as a short-term aid while moving hosts into
subdomains.


+--------------------+
| SITE CONFIGURATION |
+--------------------+

    *****************************************************
    * This section is really obsolete, and is preserved *
    * only for back compatibility.  You should plan on  *
    * using mailertables for new installations.  In     *
    * particular, it doesn't work for the newer forms   *
    * of UUCP mailers, such as uucp-uudom.              *
    *****************************************************

Complex sites will need more local configuration information, such as
lists of UUCP hosts they speak with directly.  This can get a bit more
tricky.  For an example of a "complex" site, see cf/ucbvax.mc.

The SITECONFIG macro allows you to indirectly reference site-dependent
configuration information stored in the siteconfig subdirectory.  For
example, the line

        SITECONFIG(`uucp.ucbvax', `ucbvax', `U')

reads the file uucp.ucbvax for local connection information.  The
second parameter is the local name (in this case just "ucbvax" since
it is locally connected, and hence a UUCP hostname).  The third
parameter is the name of both a macro to store the local name (in
this case, {U}) and the name of the class (e.g., {U}) in which to store
the host information read from the file.  Another SITECONFIG line reads

        SITECONFIG(`uucp.ucbarpa', `ucbarpa.Berkeley.EDU', `W')

This says that the file uucp.ucbarpa contains the list of UUCP sites
connected to ucbarpa.Berkeley.EDU.  Class {W} will be used to
store this list, and $W is defined to be ucbarpa.Berkeley.EDU, that
is, the name of the relay to which the hosts listed in uucp.ucbarpa
are connected.  [The machine ucbarpa is gone now, but this
out-of-date configuration file has been left around to demonstrate
how you might do this.]

Note that the case of SITECONFIG with a third parameter of ``U'' is
special; the second parameter is assumed to be the UUCP name of the
local site, rather than the name of a remote site, and the UUCP name
is entered into class {w} (the list of local hostnames) as $U.UUCP.

The siteconfig file (e.g., siteconfig/uucp.ucbvax.m4) contains nothing
more than a sequence of SITE macros describing connectivity.  For
example:

        SITE(`cnmat')
        SITE(`sgi olympus')

The second example demonstrates that you can use two names on the
same line; these are usually aliases for the same host (or are at
least in the same company).

The macro LOCAL_UUCP can be used to add rules into the generated
cf file at the place where MAILER(`uucp') inserts its rules.  This
should only be used if really necessary.


+--------------------+
| USING UUCP MAILERS |
+--------------------+

It's hard to get UUCP mailers right because of the extremely ad hoc
nature of UUCP addressing.  These config files are really designed
for domain-based addressing, even for UUCP sites.

There are four UUCP mailers available.  The choice of which one to
use is partly a matter of local preferences and what is running at
the other end of your UUCP connection.  Unlike good protocols that
define what will go over the wire, UUCP uses the policy that you
should do what is right for the other end; if they change, you have
to change.  This makes it hard to do the right thing, and discourages
people from updating their software.  In general, if you can avoid
UUCP, please do.

The major choice is whether to go for a domainized scheme or a
non-domainized scheme.  This depends entirely on what the other
end will recognize.  If at all possible, you should encourage the
other end to go to a domain-based system -- non-domainized addresses
don't work entirely properly.

The four mailers are:

    uucp-old (obsolete name: "uucp")
        This is the oldest, the worst (but the closest to UUCP) way of
        sending messages across UUCP connections.  It does bangify
        everything and prepends $U (your UUCP name) to the sender's
        address (which can already be a bang path itself).  It can
        only send to one address at a time, so it spends a lot of
        time copying duplicates of messages.  Avoid this if at all
        possible.

    uucp-new (obsolete name: "suucp")
        The same as above, except that it assumes that in one rmail
        command you can specify several recipients.  It still has a
        lot of other problems.

    uucp-dom
        This UUCP mailer keeps everything as domain addresses.
        Basically, it uses the SMTP mailer rewriting rules.  This mailer
        is only included if MAILER(`smtp') is specified before
        MAILER(`uucp').

        Unfortunately, a lot of UUCP mailer transport agents require
        bangified addresses in the envelope, although you can use
        domain-based addresses in the message header.  (The envelope
        shows up as the From_ line on UNIX mail.)  So....

    uucp-uudom
        This is a cross between uucp-new (for the envelope addresses)
        and uucp-dom (for the header addresses).  It bangifies the
        envelope sender (From_ line in messages) without adding the
        local hostname, unless there is no host name on the address
        at all (e.g., "wolf") or the host component is a UUCP host name
        instead of a domain name ("somehost!wolf" instead of
        "some.dom.ain!wolf").  This is also included only if MAILER(`smtp')
        is also specified earlier.

Examples:

On host grasp.insa-lyon.fr (UUCP host name "grasp"), the following
summarizes the sender rewriting for various mailers.

Mailer          sender          rewriting in the envelope
------          ------          -------------------------
uucp-{old,new}  wolf            grasp!wolf
uucp-dom        wolf            wolf@grasp.insa-lyon.fr
uucp-uudom      wolf            grasp.insa-lyon.fr!wolf

uucp-{old,new}  wolf@fr.net     grasp!fr.net!wolf
uucp-dom        wolf@fr.net     wolf@fr.net
uucp-uudom      wolf@fr.net     fr.net!wolf

uucp-{old,new}  somehost!wolf   grasp!somehost!wolf
uucp-dom        somehost!wolf   somehost!wolf@grasp.insa-lyon.fr
uucp-uudom      somehost!wolf   grasp.insa-lyon.fr!somehost!wolf

If you are using one of the domainized UUCP mailers, you really want
to convert all UUCP addresses to domain format -- otherwise, it will
do it for you (and probably not the way you expected).  For example,
if you have the address foo!bar!baz (and you are not sending to foo),
the heuristics will add the @uucp.relay.name or @local.host.name to
this address.  However, if you map foo to foo.host.name first, it
will not add the local hostname.  You can do this using the uucpdomain
feature.


+-------------------+
| TWEAKING RULESETS |
+-------------------+

For more complex configurations, you can define special rules.
The macro LOCAL_RULE_3 introduces rules that are used in canonicalizing
the names.  Any modifications made here are reflected in the header.

A common use is to convert old UUCP addresses to SMTP addresses using
the UUCPSMTP macro.  For example:

        LOCAL_RULE_3
        UUCPSMTP(`decvax',      `decvax.dec.com')
        UUCPSMTP(`research',    `research.att.com')

will cause addresses of the form "decvax!user" and "research!user"
to be converted to "user@decvax.dec.com" and "user@research.att.com"
respectively.

This could also be used to look up hosts in a database map:

        LOCAL_RULE_3
        R$* < @ $+ > $*         $: $1 < @ $(hostmap $2 $) > $3

This map would be defined in the LOCAL_CONFIG portion, as shown below.

Similarly, LOCAL_RULE_0 can be used to introduce new parsing rules.
For example, new rules are needed to parse hostnames that you accept
via MX records.  For example, you might have:

        LOCAL_RULE_0
        R$+ <@ host.dom.ain.>   $#uucp $@ cnmat $: $1 < @ host.dom.ain.>

You would use this if you had installed an MX record for cnmat.Berkeley.EDU
pointing at this host; this rule catches the message and forwards it on
using UUCP.

You can also tweak rulesets 1 and 2 using LOCAL_RULE_1 and LOCAL_RULE_2.
These rulesets are normally empty.

A similar macro is LOCAL_CONFIG.  This introduces lines added after the
boilerplate option setting but before rulesets.  Do not declare rulesets in
the LOCAL_CONFIG section.  It can be used to declare local database maps or
whatever.  For example:

        LOCAL_CONFIG
        Khostmap hash /etc/mail/hostmap
        Kyplocal nis -m hosts.byname


+---------------------------+
| MASQUERADING AND RELAYING |
+---------------------------+

You can have your host masquerade as another using

        MASQUERADE_AS(`host.domain')

This causes mail being sent to be labeled as coming from the
indicated host.domain, rather than $j.  One normally masquerades as
one of one's own subdomains (for example, it's unlikely that
Berkeley would choose to masquerade as an MIT site).  This
behaviour is modified by a plethora of FEATUREs; in particular, see
masquerade_envelope, allmasquerade, limited_masquerade, and
masquerade_entire_domain.

The masquerade name is not normally canonified, so it is important
that it be your One True Name, that is, fully qualified and not a
CNAME.  However, if you use a CNAME, the receiving side may canonify
it for you, so don't think you can cheat CNAME mapping this way.

Normally the only addresses that are masqueraded are those that come
from this host (that is, are either unqualified or in class {w}, the list
of local domain names).  You can augment this list, which is realized
by class {M} using

        MASQUERADE_DOMAIN(`otherhost.domain')

The effect of this is that although mail to user@otherhost.domain
will not be delivered locally, any mail including any user@otherhost.domain
will, when relayed, be rewritten to have the MASQUERADE_AS address.
This can be a space-separated list of names.

If these names are in a file, you can use

        MASQUERADE_DOMAIN_FILE(`filename')

to read the list of names from the indicated file (i.e., to add
elements to class {M}).

To exempt hosts or subdomains from being masqueraded, you can use

        MASQUERADE_EXCEPTION(`host.domain')

This can come handy if you want to masquerade a whole domain
except for one (or a few) host(s).  If these names are in a file,
you can use

        MASQUERADE_EXCEPTION_FILE(`filename')

Normally only header addresses are masqueraded.  If you want to
masquerade the envelope as well, use

        FEATURE(`masquerade_envelope')

There are always users that need to be "exposed" -- that is, their
internal site name should be displayed instead of the masquerade name.
Root is an example (which has been "exposed" by default prior to 8.10).
You can add users to this list using

        EXPOSED_USER(`usernames')

This adds users to class {E}; you could also use

        EXPOSED_USER_FILE(`filename')

You can also arrange to relay all unqualified names (that is, names
without @host) to a relay host.  For example, if you have a central
email server, you might relay to that host so that users don't have
to have .forward files or aliases.  You can do this using

        define(`LOCAL_RELAY', `mailer:hostname')

The ``mailer:'' can be omitted, in which case the mailer defaults to
"relay".  There are some user names that you don't want relayed, perhaps
because of local aliases.  A common example is root, which may be
locally aliased.  You can add entries to this list using

        LOCAL_USER(`usernames')

This adds users to class {L}; you could also use

        LOCAL_USER_FILE(`filename')

If you want all incoming mail sent to a centralized hub, as for a
shared /var/spool/mail scheme, use

        define(`MAIL_HUB', `mailer:hostname')

Again, ``mailer:'' defaults to "relay".  If you define both LOCAL_RELAY
and MAIL_HUB _AND_ you have FEATURE(`stickyhost'), unqualified names will
be sent to the LOCAL_RELAY and other local names will be sent to MAIL_HUB.
Note: there is a (long standing) bug which keeps this combination from
working for addresses of the form user+detail.
Names in class {L} will be delivered locally, so you MUST have aliases or
.forward files for them.

For example, if you are on machine mastodon.CS.Berkeley.EDU and you have
FEATURE(`stickyhost'), the following combinations of settings will have the
indicated effects:

email sent to....       eric                      eric@mastodon.CS.Berkeley.EDU

LOCAL_RELAY set to      mail.CS.Berkeley.EDU      (delivered locally)
mail.CS.Berkeley.EDU      (no local aliasing)       (aliasing done)

MAIL_HUB set to         mammoth.CS.Berkeley.EDU   mammoth.CS.Berkeley.EDU
mammoth.CS.Berkeley.EDU   (aliasing done)           (aliasing done)

Both LOCAL_RELAY and    mail.CS.Berkeley.EDU      mammoth.CS.Berkeley.EDU
MAIL_HUB set as above     (no local aliasing)       (aliasing done)

If you do not have FEATURE(`stickyhost') set, then LOCAL_RELAY and
MAIL_HUB act identically, with MAIL_HUB taking precedence.

If you want all outgoing mail to go to a central relay site, define
SMART_HOST as well.  Briefly:

        LOCAL_RELAY applies to unqualified names (e.g., "eric").
        MAIL_HUB applies to names qualified with the name of the
                local host (e.g., "eric@mastodon.CS.Berkeley.EDU").
        SMART_HOST applies to names qualified with other hosts or
                bracketed addresses (e.g., "eric@mastodon.CS.Berkeley.EDU"
                or "eric@[127.0.0.1]").

However, beware that other relays (e.g., UUCP_RELAY, BITNET_RELAY,
DECNET_RELAY, and FAX_RELAY) take precedence over SMART_HOST, so if you
really want absolutely everything to go to a single central site you will
need to unset all the other relays -- or better yet, find or build a
minimal config file that does this.

For duplicate suppression to work properly, the host name is best
specified with a terminal dot:

        define(`MAIL_HUB', `host.domain.')
              note the trailing dot ---^


+-------------------------------------------+
| USING LDAP FOR ALIASES, MAPS, AND CLASSES |
+-------------------------------------------+

LDAP can be used for aliases, maps, and classes by either specifying your
own LDAP map specification or using the built-in default LDAP map
specification.  The built-in default specifications all provide lookups
which match against either the machine's fully qualified hostname (${j}) or
a "cluster".  The cluster allows you to share LDAP entries among a large
number of machines without having to enter each of the machine names into
each LDAP entry.  To set the LDAP cluster name to use for a particular
machine or set of machines, set the confLDAP_CLUSTER m4 variable to a
unique name.  For example:

        define(`confLDAP_CLUSTER', `Servers')

Here, the word `Servers' will be the cluster name.  As an example, assume
that smtp.sendmail.org, etrn.sendmail.org, and mx.sendmail.org all belong
to the Servers cluster.

Some of the LDAP LDIF examples below show use of the Servers cluster.
Every entry must have either a sendmailMTAHost or sendmailMTACluster
attribute or it will be ignored.  Be careful as mixing clusters and
individual host records can have surprising results (see the CAUTION
sections below).

See the file cf/sendmail.schema for the actual LDAP schemas.  Note that
this schema (and therefore the lookups and examples below) is experimental
at this point as it has had little public review.  Therefore, it may change
in future versions.  Feedback via sendmail-YYYY@support.sendmail.org is
encouraged (replace YYYY with the current year, e.g., 2005).

-------
Aliases
-------

The ALIAS_FILE (O AliasFile) option can be set to use LDAP for alias
lookups.  To use the default schema, simply use:

        define(`ALIAS_FILE', `ldap:')

By doing so, you will use the default schema which expands to a map
declared as follows:

        ldap -k (&(objectClass=sendmailMTAAliasObject)
                  (sendmailMTAAliasGrouping=aliases)
                  (|(sendmailMTACluster=${sendmailMTACluster})
                    (sendmailMTAHost=$j))
                  (sendmailMTAKey=%0))
             -v sendmailMTAAliasValue,sendmailMTAAliasSearch:FILTER:sendmailMTAAliasObject,sendmailMTAAliasURL:URL:sendmailMTAAliasObject


NOTE: The macros shown above ${sendmailMTACluster} and $j are not actually
used when the binary expands the `ldap:' token as the AliasFile option is
not actually macro-expanded when read from the sendmail.cf file.

Example LDAP LDIF entries might be:

        dn: sendmailMTAKey=sendmail-list, dc=sendmail, dc=org
        objectClass: sendmailMTA
        objectClass: sendmailMTAAlias
        objectClass: sendmailMTAAliasObject
        sendmailMTAAliasGrouping: aliases
        sendmailMTAHost: etrn.sendmail.org
        sendmailMTAKey: sendmail-list
        sendmailMTAAliasValue: ca@example.org
        sendmailMTAAliasValue: eric
        sendmailMTAAliasValue: gshapiro@example.com

        dn: sendmailMTAKey=owner-sendmail-list, dc=sendmail, dc=org
        objectClass: sendmailMTA
        objectClass: sendmailMTAAlias
        objectClass: sendmailMTAAliasObject
        sendmailMTAAliasGrouping: aliases
        sendmailMTAHost: etrn.sendmail.org
        sendmailMTAKey: owner-sendmail-list
        sendmailMTAAliasValue: eric

        dn: sendmailMTAKey=postmaster, dc=sendmail, dc=org
        objectClass: sendmailMTA
        objectClass: sendmailMTAAlias
        objectClass: sendmailMTAAliasObject
        sendmailMTAAliasGrouping: aliases
        sendmailMTACluster: Servers
        sendmailMTAKey: postmaster
        sendmailMTAAliasValue: eric

Here, the aliases sendmail-list and owner-sendmail-list will be available
only on etrn.sendmail.org but the postmaster alias will be available on
every machine in the Servers cluster (including etrn.sendmail.org).

CAUTION: aliases are additive so that entries like these:

        dn: sendmailMTAKey=bob, dc=sendmail, dc=org
        objectClass: sendmailMTA
        objectClass: sendmailMTAAlias
        objectClass: sendmailMTAAliasObject
        sendmailMTAAliasGrouping: aliases
        sendmailMTACluster: Servers
        sendmailMTAKey: bob
        sendmailMTAAliasValue: eric

        dn: sendmailMTAKey=bobetrn, dc=sendmail, dc=org
        objectClass: sendmailMTA
        objectClass: sendmailMTAAlias
        objectClass: sendmailMTAAliasObject
        sendmailMTAAliasGrouping: aliases
        sendmailMTAHost: etrn.sendmail.org
        sendmailMTAKey: bob
        sendmailMTAAliasValue: gshapiro

would mean that on all of the hosts in the cluster, mail to bob would go to
eric EXCEPT on etrn.sendmail.org in which case it would go to BOTH eric and
gshapiro.

If you prefer not to use the default LDAP schema for your aliases, you can
specify the map parameters when setting ALIAS_FILE.  For example:

        define(`ALIAS_FILE', `ldap:-k (&(objectClass=mailGroup)(mail=%0)) -v mgrpRFC822MailMember')

----
Maps
----

FEATURE()'s which take an optional map definition argument (e.g., access,
mailertable, virtusertable, etc.) can instead take the special keyword
`LDAP', e.g.:

        FEATURE(`access_db', `LDAP')
        FEATURE(`virtusertable', `LDAP')

When this keyword is given, that map will use LDAP lookups consisting of
the objectClass sendmailMTAClassObject, the attribute sendmailMTAMapName
with the map name, a search attribute of sendmailMTAKey, and the value
attribute sendmailMTAMapValue.

The values for sendmailMTAMapName are:

        FEATURE()               sendmailMTAMapName
        ---------               ------------------
        access_db               access
        authinfo                authinfo
        bitdomain               bitdomain
        domaintable             domain
        genericstable           generics
        mailertable             mailer
        uucpdomain              uucpdomain
        virtusertable           virtuser

For example, FEATURE(`mailertable', `LDAP') would use the map definition:

        Kmailertable ldap -k (&(objectClass=sendmailMTAMapObject)
                               (sendmailMTAMapName=mailer)
                               (|(sendmailMTACluster=${sendmailMTACluster})
                                 (sendmailMTAHost=$j))
                               (sendmailMTAKey=%0))
                          -1 -v sendmailMTAMapValue,sendmailMTAMapSearch:FILTER:sendmailMTAMapObject,sendmailMTAMapURL:URL:sendmailMTAMapObject

An example LDAP LDIF entry using this map might be:

        dn: sendmailMTAMapName=mailer, dc=sendmail, dc=org
        objectClass: sendmailMTA
        objectClass: sendmailMTAMap
        sendmailMTACluster: Servers
        sendmailMTAMapName: mailer

        dn: sendmailMTAKey=example.com, sendmailMTAMapName=mailer, dc=sendmail, dc=org
        objectClass: sendmailMTA
        objectClass: sendmailMTAMap
        objectClass: sendmailMTAMapObject
        sendmailMTAMapName: mailer
        sendmailMTACluster: Servers
        sendmailMTAKey: example.com
        sendmailMTAMapValue: relay:[smtp.example.com]

CAUTION: If your LDAP database contains the record above and *ALSO* a host
specific record such as:

        dn: sendmailMTAKey=example.com@etrn, sendmailMTAMapName=mailer, dc=sendmail, dc=org
        objectClass: sendmailMTA
        objectClass: sendmailMTAMap
        objectClass: sendmailMTAMapObject
        sendmailMTAMapName: mailer
        sendmailMTAHost: etrn.sendmail.org
        sendmailMTAKey: example.com
        sendmailMTAMapValue: relay:[mx.example.com]

then these entries will give unexpected results.  When the lookup is done
on etrn.sendmail.org, the effect is that there is *NO* match at all as maps
require a single match.  Since the host etrn.sendmail.org is also in the
Servers cluster, LDAP would return two answers for the example.com map key
in which case sendmail would treat this as no match at all.

If you prefer not to use the default LDAP schema for your maps, you can
specify the map parameters when using the FEATURE().  For example:

        FEATURE(`access_db', `ldap:-1 -k (&(objectClass=mapDatabase)(key=%0)) -v value')

-------
Classes
-------

Normally, classes can be filled via files or programs.  As of 8.12, they
can also be filled via map lookups using a new syntax:

        F{ClassName}mapkey@mapclass:mapspec

mapkey is optional and if not provided the map key will be empty.  This can
be used with LDAP to read classes from LDAP.  Note that the lookup is only
done when sendmail is initially started.  Use the special value `@LDAP' to
use the default LDAP schema.  For example:

        RELAY_DOMAIN_FILE(`@LDAP')

would put all of the attribute sendmailMTAClassValue values of LDAP records
with objectClass sendmailMTAClass and an attribute sendmailMTAClassName of
'R' into class $={R}.  In other words, it is equivalent to the LDAP map
specification:

        F{R}@ldap:-k (&(objectClass=sendmailMTAClass)
                       (sendmailMTAClassName=R)
                       (|(sendmailMTACluster=${sendmailMTACluster})
                         (sendmailMTAHost=$j)))
                  -v sendmailMTAClassValue,sendmailMTAClassSearch:FILTER:sendmailMTAClass,sendmailMTAClassURL:URL:sendmailMTAClass

NOTE: The macros shown above ${sendmailMTACluster} and $j are not actually
used when the binary expands the `@LDAP' token as class declarations are
not actually macro-expanded when read from the sendmail.cf file.

This can be used with class related commands such as RELAY_DOMAIN_FILE(),
MASQUERADE_DOMAIN_FILE(), etc:

        Command                         sendmailMTAClassName
        -------                         --------------------
        CANONIFY_DOMAIN_FILE()          Canonify
        EXPOSED_USER_FILE()             E
        GENERICS_DOMAIN_FILE()          G
        LDAPROUTE_DOMAIN_FILE()         LDAPRoute
        LDAPROUTE_EQUIVALENT_FILE()     LDAPRouteEquiv
        LOCAL_USER_FILE()               L
        MASQUERADE_DOMAIN_FILE()        M
        MASQUERADE_EXCEPTION_FILE()     N
        RELAY_DOMAIN_FILE()             R
        VIRTUSER_DOMAIN_FILE()          VirtHost

You can also add your own as any 'F'ile class of the form:

        F{ClassName}@LDAP
          ^^^^^^^^^
will use "ClassName" for the sendmailMTAClassName.

An example LDAP LDIF entry would look like:

        dn: sendmailMTAClassName=R, dc=sendmail, dc=org
        objectClass: sendmailMTA
        objectClass: sendmailMTAClass
        sendmailMTACluster: Servers
        sendmailMTAClassName: R
        sendmailMTAClassValue: sendmail.org
        sendmailMTAClassValue: example.com
        sendmailMTAClassValue: 10.56.23

CAUTION: If your LDAP database contains the record above and *ALSO* a host
specific record such as:

        dn: sendmailMTAClassName=R@etrn.sendmail.org, dc=sendmail, dc=org
        objectClass: sendmailMTA
        objectClass: sendmailMTAClass
        sendmailMTAHost: etrn.sendmail.org
        sendmailMTAClassName: R
        sendmailMTAClassValue: example.com

the result will be similar to the aliases caution above.  When the lookup
is done on etrn.sendmail.org, $={R} would contain all of the entries (from
both the cluster match and the host match).  In other words, the effective
is additive.

If you prefer not to use the default LDAP schema for your classes, you can
specify the map parameters when using the class command.  For example:

        VIRTUSER_DOMAIN_FILE(`@ldap:-k (&(objectClass=virtHosts)(host=*)) -v host')

Remember, macros can not be used in a class declaration as the binary does
not expand them.


+--------------+
| LDAP ROUTING |
+--------------+

FEATURE(`ldap_routing') can be used to implement the IETF Internet Draft
LDAP Schema for Intranet Mail Routing
(draft-lachman-laser-ldap-mail-routing-01).  This feature enables
LDAP-based rerouting of a particular address to either a different host
or a different address.  The LDAP lookup is first attempted on the full
address (e.g., user@example.com) and then on the domain portion
(e.g., @example.com).  Be sure to setup your domain for LDAP routing using
LDAPROUTE_DOMAIN(), e.g.:

        LDAPROUTE_DOMAIN(`example.com')

Additionally, you can specify equivalent domains for LDAP routing using
LDAPROUTE_EQUIVALENT() and LDAPROUTE_EQUIVALENT_FILE().  'Equivalent'
hostnames are mapped to $M (the masqueraded hostname for the server) before
the LDAP query.  For example, if the mail is addressed to
user@host1.example.com, normally the LDAP lookup would only be done for
'user@host1.example.com' and '@host1.example.com'.   However, if
LDAPROUTE_EQUIVALENT(`host1.example.com') is used, the lookups would also be
done on 'user@example.com' and '@example.com' after attempting the
host1.example.com lookups.

By default, the feature will use the schemas as specified in the draft
and will not reject addresses not found by the LDAP lookup.  However,
this behavior can be changed by giving additional arguments to the FEATURE()
command:

 FEATURE(`ldap_routing', <mailHost>, <mailRoutingAddress>, <bounce>,
                 <detail>, <nodomain>, <tempfail>)

where <mailHost> is a map definition describing how to look up an alternative
mail host for a particular address; <mailRoutingAddress> is a map definition
describing how to look up an alternative address for a particular address;
the <bounce> argument, if present and not the word "passthru", dictates
that mail should be bounced if neither a mailHost nor mailRoutingAddress
is found, if set to "sendertoo", the sender will be rejected if not
found in LDAP; and <detail> indicates what actions to take if the address
contains +detail information -- `strip' tries the lookup with the +detail
and if no matches are found, strips the +detail and tries the lookup again;
`preserve', does the same as `strip' but if a mailRoutingAddress match is
found, the +detail information is copied to the new address; the <nodomain>
argument, if present, will prevent the @domain lookup if the full
address is not found in LDAP; the <tempfail> argument, if set to
"tempfail", instructs the rules to give an SMTP 4XX temporary
error if the LDAP server gives the MTA a temporary failure, or if set to
"queue" (the default), the MTA will locally queue the mail.

The default <mailHost> map definition is:

        ldap -1 -T<TMPF> -v mailHost -k (&(objectClass=inetLocalMailRecipient)
                                 (mailLocalAddress=%0))

The default <mailRoutingAddress> map definition is:

        ldap -1 -T<TMPF> -v mailRoutingAddress
                         -k (&(objectClass=inetLocalMailRecipient)
                              (mailLocalAddress=%0))

Note that neither includes the LDAP server hostname (-h server) or base DN
(-b o=org,c=COUNTRY), both necessary for LDAP queries.  It is presumed that
your .mc file contains a setting for the confLDAP_DEFAULT_SPEC option with
these settings.  If this is not the case, the map definitions should be
changed as described above.  The "-T<TMPF>" is required in any user
specified map definition to catch temporary errors.

The following possibilities exist as a result of an LDAP lookup on an
address:

        mailHost is     mailRoutingAddress is   Results in
        -----------     ---------------------   ----------
        set to a        set                     mail delivered to
        "local" host                            mailRoutingAddress

        set to a        not set                 delivered to
        "local" host                            original address

        set to a        set                     mailRoutingAddress
        remote host                             relayed to mailHost

        set to a        not set                 original address
        remote host                             relayed to mailHost

        not set         set                     mail delivered to
                                                mailRoutingAddress

        not set         not set                 delivered to
                                                original address *OR*
                                                bounced as unknown user

The term "local" host above means the host specified is in class {w}.  If
the result would mean sending the mail to a different host, that host is
looked up in the mailertable before delivery.

Note that the last case depends on whether the third argument is given
to the FEATURE() command.  The default is to deliver the message to the
original address.

The LDAP entries should be set up with an objectClass of
inetLocalMailRecipient and the address be listed in a mailLocalAddress
attribute.  If present, there must be only one mailHost attribute and it
must contain a fully qualified host name as its value.  Similarly, if
present, there must be only one mailRoutingAddress attribute and it must
contain an RFC 822 compliant address.  Some example LDAP records (in LDIF
format):

        dn: uid=tom, o=example.com, c=US
        objectClass: inetLocalMailRecipient
        mailLocalAddress: tom@example.com
        mailRoutingAddress: thomas@mailhost.example.com

This would deliver mail for tom@example.com to thomas@mailhost.example.com.

        dn: uid=dick, o=example.com, c=US
        objectClass: inetLocalMailRecipient
        mailLocalAddress: dick@example.com
        mailHost: eng.example.com

This would relay mail for dick@example.com to the same address but redirect
the mail to MX records listed for the host eng.example.com (unless the
mailertable overrides).

        dn: uid=harry, o=example.com, c=US
        objectClass: inetLocalMailRecipient
        mailLocalAddress: harry@example.com
        mailHost: mktmail.example.com
        mailRoutingAddress: harry@mkt.example.com

This would relay mail for harry@example.com to the MX records listed for
the host mktmail.example.com using the new address harry@mkt.example.com
when talking to that host.

        dn: uid=virtual.example.com, o=example.com, c=US
        objectClass: inetLocalMailRecipient
        mailLocalAddress: @virtual.example.com
        mailHost: server.example.com
        mailRoutingAddress: virtual@example.com

This would send all mail destined for any username @virtual.example.com to
the machine server.example.com's MX servers and deliver to the address
virtual@example.com on that relay machine.


+---------------------------------+
| ANTI-SPAM CONFIGURATION CONTROL |
+---------------------------------+

The primary anti-spam features available in sendmail are:

* Relaying is denied by default.
* Better checking on sender information.
* Access database.
* Header checks.

Relaying (transmission of messages from a site outside your host (class
{w}) to another site except yours) is denied by default.  Note that this
changed in sendmail 8.9; previous versions allowed relaying by default.
If you really want to revert to the old behaviour, you will need to use
FEATURE(`promiscuous_relay').  You can allow certain domains to relay
through your server by adding their domain name or IP address to class
{R} using RELAY_DOMAIN() and RELAY_DOMAIN_FILE() or via the access database
(described below).  Note that IPv6 addresses must be prefaced with "IPv6:".
The file consists (like any other file based class) of entries listed on
separate lines, e.g.,

        sendmail.org
        128.32
        IPv6:2002:c0a8:02c7
        IPv6:2002:c0a8:51d2::23f4
        host.mydomain.com
        [UNIX:localhost]

Notice: the last entry allows relaying for connections via a UNIX
socket to the MTA/MSP.  This might be necessary if your configuration
doesn't allow relaying by other means in that case, e.g., by having
localhost.$m in class {R} (make sure $m is not just a top level
domain).

If you use

        FEATURE(`relay_entire_domain')

then any host in any of your local domains (that is, class {m})
will be relayed (that is, you will accept mail either to or from any
host in your domain).

You can also allow relaying based on the MX records of the host
portion of an incoming recipient address by using

        FEATURE(`relay_based_on_MX')

For example, if your server receives a recipient of user@domain.com
and domain.com lists your server in its MX records, the mail will be
accepted for relay to domain.com.  This feature may cause problems
if MX lookups for the recipient domain are slow or time out.  In that
case, mail will be temporarily rejected.  It is usually better to
maintain a list of hosts/domains for which the server acts as relay.
Note also that this feature will stop spammers from using your host
to relay spam but it will not stop outsiders from using your server
as a relay for their site (that is, they set up an MX record pointing
to your mail server, and you will relay mail addressed to them
without any prior arrangement).  Along the same lines,

        FEATURE(`relay_local_from')

will allow relaying if the sender specifies a return path (i.e.
MAIL FROM:<user@domain>) domain which is a local domain.  This is a
dangerous feature as it will allow spammers to spam using your mail
server by simply specifying a return address of user@your.domain.com.
It should not be used unless absolutely necessary.
A slightly better solution is

        FEATURE(`relay_mail_from')

which allows relaying if the mail sender is listed as RELAY in the
access map.  If an optional argument `domain' (this is the literal
word `domain', not a placeholder) is given, the domain portion of
the mail sender is also checked to allowing relaying.  This option
only works together with the tag From: for the LHS of the access
map entries.  This feature allows spammers to abuse your mail server
by specifying a return address that you enabled in your access file.
This may be harder to figure out for spammers, but it should not
be used unless necessary.  Instead use SMTP AUTH or STARTTLS to
allow relaying for roaming users.


If source routing is used in the recipient address (e.g.,
RCPT TO:<user%site.com@othersite.com>), sendmail will check
user@site.com for relaying if othersite.com is an allowed relay host
in either class {R}, class {m} if FEATURE(`relay_entire_domain') is used,
or the access database if FEATURE(`access_db') is used.  To prevent
the address from being stripped down, use:

        FEATURE(`loose_relay_check')

If you think you need to use this feature, you probably do not.  This
should only be used for sites which have no control over the addresses
that they provide a gateway for.  Use this FEATURE with caution as it
can allow spammers to relay through your server if not setup properly.

NOTICE: It is possible to relay mail through a system which the
anti-relay rules do not prevent: the case of a system that does use
FEATURE(`nouucp', `nospecial') / FEATURE(`nopercenthack', `nospecial')
(system A) and relays local messages to a mail hub (e.g., via
LOCAL_RELAY or LUSER_RELAY) (system B).  If system B doesn't use the
same feature (nouucp / nopercenthack) at all, addresses of the form
<example.net!user@local.host> / <user%example.net@local.host>
would be relayed to <user@example.net>.
System A doesn't recognize `!' / `%' as an address separator and
therefore forwards it to the mail hub which in turns relays it
because it came from a trusted local host.  So if a mailserver
allows UUCP (bang-format) / %-hack addresses, all systems from which
it allows relaying should do the same or reject those addresses.

As of 8.9, sendmail will refuse mail if the MAIL FROM: parameter has
an unresolvable domain (i.e., one that DNS, your local name service,
or special case rules in ruleset 3 cannot locate).  This also applies
to addresses that use domain literals, e.g., <user@[1.2.3.4]>, if the
IP address can't be mapped to a host name.  If you want to continue
to accept such domains, e.g., because you are inside a firewall that
has only a limited view of the Internet host name space (note that you
will not be able to return mail to them unless you have some "smart
host" forwarder), use

        FEATURE(`accept_unresolvable_domains')

Alternatively, you can allow specific addresses by adding them to
the access map, e.g.,

        From:unresolvable.domain        OK
        From:[1.2.3.4]                  OK
        From:[1.2.4]                    OK

Notice: domains which are temporarily unresolvable are (temporarily)
rejected with a 451 reply code.  If those domains should be accepted
(which is discouraged) then you can use

        LOCAL_CONFIG
        C{ResOk}TEMP

sendmail will also refuse mail if the MAIL FROM: parameter is not
fully qualified (i.e., contains a domain as well as a user).  If you
want to continue to accept such senders, use

        FEATURE(`accept_unqualified_senders')

Setting the DaemonPortOptions modifier 'u' overrides the default behavior,
i.e., unqualified addresses are accepted even without this FEATURE.  If
this FEATURE is not used, the DaemonPortOptions modifier 'f' can be used
to enforce fully qualified domain names.

An ``access'' database can be created to accept or reject mail from
selected domains.  For example, you may choose to reject all mail
originating from known spammers.  To enable such a database, use

        FEATURE(`access_db')

Notice: the access database is applied to the envelope addresses
and the connection information, not to the header.

The FEATURE macro can accept as second parameter the key file
definition for the database; for example

        FEATURE(`access_db', `hash -T<TMPF> /etc/mail/access_map')

Notice: If a second argument is specified it must contain the option
`-T<TMPF>' as shown above.  The optional parameters may be

        `skip'                  enables SKIP as value part (see below).
        `lookupdotdomain'       another way to enable the feature of the
                                same name (see above).
        `relaytofulladdress'    enable entries of the form
                                To:user@example.com     RELAY
                                to allow relaying to just a specific
                                e-mail address instead of an entire domain.

Remember, since /etc/mail/access is a database, after creating the text
file as described below, you must use makemap to create the database
map.  For example:

        makemap hash /etc/mail/access < /etc/mail/access

The table itself uses e-mail addresses, domain names, and network
numbers as keys.  Note that IPv6 addresses must be prefaced with "IPv6:".
For example,

        From:spammer@aol.com                    REJECT
        From:cyberspammer.com                   REJECT
        Connect:cyberspammer.com                REJECT
        Connect:TLD                             REJECT
        Connect:192.168.212                     REJECT
        Connect:IPv6:2002:c0a8:02c7             RELAY
        Connect:IPv6:2002:c0a8:51d2::23f4       REJECT

would refuse mail from spammer@aol.com, any user from cyberspammer.com
(or any host within the cyberspammer.com domain), any host in the entire
top level domain TLD, 192.168.212.* network, and the IPv6 address
2002:c0a8:51d2::23f4.  It would allow relay for the IPv6 network
2002:c0a8:02c7::/48.

Entries in the access map should be tagged according to their type.
These tags are applicable:

        Connect:        connection information (${client_addr}, ${client_name})
        From:           envelope sender
        To:             envelope recipient

Notice: untagged entries are deprecated.

If the required item is looked up in a map, it will be tried first
with the corresponding tag in front, then (as fallback to enable
backward compatibility) without any tag, unless the specific feature
requires a tag.  For example,

        From:spammer@some.dom   REJECT
        To:friend.domain        RELAY
        Connect:friend.domain   OK
        Connect:from.domain     RELAY
        From:good@another.dom   OK
        From:another.dom        REJECT

This would deny mails from spammer@some.dom but you could still
send mail to that address even if FEATURE(`blocklist_recipients')
is enabled.  Your system will allow relaying to friend.domain, but
not from it (unless enabled by other means).  Connections from that
domain will be allowed even if it ends up in one of the DNS based
rejection lists.  Relaying is enabled from from.domain but not to
it (since relaying is based on the connection information for
outgoing relaying, the tag Connect: must be used; for incoming
relaying, which is based on the recipient address, To: must be
used).  The last two entries allow mails from good@another.dom but
reject mail from all other addresses with another.dom as domain
part.


The value part of the map can contain:

        OK              Accept mail even if other rules in the running
                        ruleset would reject it, for example, if the domain
                        name is unresolvable.  "Accept" does not mean
                        "relay", but at most acceptance for local
                        recipients.  That is, OK allows less than RELAY.
        RELAY           Accept mail addressed to the indicated domain
                        (or address if `relaytofulladdress' is set) or
                        received from the indicated domain for relaying
                        through your SMTP server.  RELAY also serves as
                        an implicit OK for the other checks.
        REJECT          Reject the sender or recipient with a general
                        purpose message.
        DISCARD         Discard the message completely using the
                        $#discard mailer.  If it is used in check_compat,
                        it affects only the designated recipient, not
                        the whole message as it does in all other cases.
                        This should only be used if really necessary.
        SKIP            This can only be used for host/domain names
                        and IP addresses/nets.  It will abort the current
                        search for this entry without accepting or rejecting
                        it but causing the default action.
        ### any text    where ### is an RFC 821 compliant error code and
                        "any text" is a message to return for the command.
                        The entire string should be quoted to avoid
                        surprises:

                                "### any text"

                        Otherwise sendmail formats the text as email
                        addresses, e.g., it may remove spaces.
                        This type is deprecated, use one of the two
                        ERROR:  entries below instead.
        ERROR:### any text
                        as above, but useful to mark error messages as such.
                        If quotes need to be used to avoid modifications
                        (see above), they should be placed like this:

                                ERROR:"### any text"

        ERROR:D.S.N:### any text
                        where D.S.N is an RFC 1893 compliant error code
                        and the rest as above.  If quotes need to be used
                        to avoid modifications, they should be placed
                        like this:

                                ERROR:D.S.N:"### any text"

        QUARANTINE:any text
                        Quarantine the message using the given text as the
                        quarantining reason.

For example:

        From:cyberspammer.com   ERROR:"550 We don't accept mail from spammers"
        From:okay.cyberspammer.com      OK
        Connect:sendmail.org            RELAY
        To:sendmail.org                 RELAY
        Connect:128.32                  RELAY
        Connect:128.32.2                SKIP
        Connect:IPv6:1:2:3:4:5:6:7      RELAY
        Connect:suspicious.example.com  QUARANTINE:Mail from suspicious host
        Connect:[127.0.0.3]             OK
        Connect:[IPv6:1:2:3:4:5:6:7:8]  OK

would accept mail from okay.cyberspammer.com, but would reject mail
from all other hosts at cyberspammer.com with the indicated message.
It would allow relaying mail from and to any hosts in the sendmail.org
domain, and allow relaying from the IPv6 1:2:3:4:5:6:7:* network
and from the 128.32.*.* network except for the 128.32.2.* network,
which shows how SKIP is useful to exempt subnets/subdomains.  The
last two entries are for checks against ${client_name} if the IP
address doesn't resolve to a hostname (or is considered as "may be
forged").  That is, using square brackets means these are host
names, not network numbers.

Warning: if you change the RFC 821 compliant error code from the default
value of 550, then you should probably also change the RFC 1893 compliant
error code to match it.  For example, if you use

        To:user@example.com     ERROR:450 mailbox full

the error returned would be "450 5.0.0 mailbox full" which is wrong.
Use "ERROR:4.2.2:450 mailbox full" instead.

Note, UUCP users may need to add hostname.UUCP to the access database
or class {R}.

If you also use:

        FEATURE(`relay_hosts_only')

then the above example will allow relaying for sendmail.org, but not
hosts within the sendmail.org domain.  Note that this will also require
hosts listed in class {R} to be fully qualified host names.

You can also use the access database to block sender addresses based on
the username portion of the address.  For example:

        From:FREE.STEALTH.MAILER@       ERROR:550 Spam not accepted

Note that you must include the @ after the username to signify that
this database entry is for checking only the username portion of the
sender address.

If you use:

        FEATURE(`blocklist_recipients')

then you can add entries to the map for local users, hosts in your
domains, or addresses in your domain which should not receive mail:

        To:badlocaluser@        ERROR:550 Mailbox disabled for badlocaluser
        To:host.my.TLD          ERROR:550 That host does not accept mail
        To:user@other.my.TLD    ERROR:550 Mailbox disabled for this recipient

This would prevent a recipient of badlocaluser in any of the local
domains (class {w}), any user at host.my.TLD, and the single address
user@other.my.TLD from receiving mail.  Please note: a local username
must be now tagged with an @ (this is consistent with the check of
the sender address, and hence it is possible to distinguish between
hostnames and usernames).  Enabling this feature will keep you from
sending mails to all addresses that have an error message or REJECT
as value part in the access map.  Taking the example from above:

        spammer@aol.com         REJECT
        cyberspammer.com        REJECT

Mail can't be sent to spammer@aol.com or anyone at cyberspammer.com.
That's why tagged entries should be used.

There are several DNS based blocklists which can be found by
querying a search engine.  These are databases of spammers
maintained in DNS.  To use such a database, specify

        FEATURE(`dnsbl', `dnsbl.example.com')

This will cause sendmail to reject mail from any site listed in the
DNS based blocklist.  You must select a DNS based blocklist domain
to check by specifying an argument to the FEATURE.  The default
error message is

        Rejected: IP-ADDRESS listed at SERVER

where IP-ADDRESS and SERVER are replaced by the appropriate
information.  A second argument can be used to specify a different
text or action.  For example,

        FEATURE(`dnsbl', `dnsbl.example.com', `quarantine')

would quarantine the message if the client IP address is listed
at `dnsbl.example.com'.

By default, temporary lookup failures are ignored
and hence cause the connection not to be rejected by the DNS based
rejection list.  This behavior can be changed by specifying a third
argument, which must be either `t' or a full error message.  For
example:

        FEATURE(`dnsbl', `dnsbl.example.com', `',
        `"451 Temporary lookup failure for " $&{client_addr} " in dnsbl.example.com"')

If `t' is used, the error message is:

        451 Temporary lookup failure of IP-ADDRESS at SERVER

where IP-ADDRESS and SERVER are replaced by the appropriate
information.

This FEATURE can be included several times to query different
DNS based rejection lists.

Notice: to avoid checking your own local domains against those
blocklists, use the access_db feature and add:

        Connect:10.1            OK
        Connect:127.0.0.1       RELAY

to the access map, where 10.1 is your local network.  You may
want to use "RELAY" instead of "OK" to allow also relaying
instead of just disabling the DNS lookups in the blocklists.


The features described above make use of the check_relay, check_mail,
and check_rcpt rulesets.  Note that check_relay checks the SMTP
client hostname and IP address when the connection is made to your
server.  It does not check if a mail message is being relayed to
another server.  That check is done in check_rcpt.  If you wish to
include your own checks, you can put your checks in the rulesets
Local_check_relay, Local_check_mail, and Local_check_rcpt.  For
example if you wanted to block senders with all numeric usernames
(i.e. 2312343@bigisp.com), you would use Local_check_mail and the
regex map:

        LOCAL_CONFIG
        Kallnumbers regex -a@MATCH ^[0-9]+$

        LOCAL_RULESETS
        SLocal_check_mail
        # check address against various regex checks
        R$*                             $: $>Parse0 $>3 $1
        R$+ < @ bigisp.com. > $*        $: $(allnumbers $1 $)
        R@MATCH                         $#error $: 553 Address Error

These rules are called with the original arguments of the corresponding
check_* ruleset.  If the local ruleset returns $#OK, no further checking
is done by the features described above and the mail is accepted.  If
the local ruleset resolves to a mailer (such as $#error or $#discard),
the appropriate action is taken.  Other results starting with $# are
interpreted by sendmail and may lead to unspecified behavior.  Note: do
NOT create a mailer with the name OK.  Return values that do not start
with $# are ignored, i.e., normal processing continues.

Delay all checks
----------------

By using FEATURE(`delay_checks') the rulesets check_mail and check_relay
will not be called when a client connects or issues a MAIL command,
respectively.  Instead, those rulesets will be called by the check_rcpt
ruleset; they will be skipped if a sender has been authenticated using
a "trusted" mechanism, i.e., one that is defined via TRUST_AUTH_MECH().
If check_mail returns an error then the RCPT TO command will be rejected
with that error.  If it returns some other result starting with $# then
check_relay will be skipped.  If the sender address (or a part of it) is
listed in the access map and it has a RHS of OK or RELAY, then check_relay
will be skipped.  This has an interesting side effect: if your domain is
my.domain and you have

        my.domain       RELAY

in the access map, then any e-mail with a sender address of
<user@my.domain> will not be rejected by check_relay even though
it would match the hostname or IP address.  This allows spammers
to get around DNS based blocklist by faking the sender address.  To
avoid this problem you have to use tagged entries:

        To:my.domain            RELAY
        Connect:my.domain       RELAY

if you need those entries at all (class {R} may take care of them).

FEATURE(`delay_checks') can take an optional argument:

        FEATURE(`delay_checks', `friend')
                 enables spamfriend test
        FEATURE(`delay_checks', `hater')
                 enables spamhater test

If such an argument is given, the recipient will be looked up in the
access map (using the tag Spam:).  If the argument is `friend', then
the default behavior is to apply the other rulesets and make a SPAM
friend the exception.  The rulesets check_mail and check_relay will be
skipped only if the recipient address is found and has RHS FRIEND.  If
the argument is `hater', then the default behavior is to skip the rulesets
check_mail and check_relay and make a SPAM hater the exception.  The
other two rulesets will be applied only if the recipient address is
found and has RHS HATER.

This allows for simple exceptions from the tests, e.g., by activating
the friend option and having

        Spam:abuse@     FRIEND

in the access map, mail to abuse@localdomain will get through (where
"localdomain" is any domain in class {w}).  It is also possible to
specify a full address or an address with +detail:

        Spam:abuse@my.domain    FRIEND
        Spam:me+abuse@          FRIEND
        Spam:spam.domain        FRIEND

Note: The required tag has been changed in 8.12 from To: to Spam:.
This change is incompatible to previous versions.  However, you can
(for now) simply add the new entries to the access map, the old
ones will be ignored.  As soon as you removed the old entries from
the access map, specify a third parameter (`n') to this feature and
the backward compatibility rules will not be in the generated .cf
file.

Header Checks
-------------

You can also reject mail on the basis of the contents of headers.
This is done by adding a ruleset call to the 'H' header definition command
in sendmail.cf.  For example, this can be used to check the validity of
a Message-ID: header:

        LOCAL_CONFIG
        HMessage-Id: $>CheckMessageId

        LOCAL_RULESETS
        SCheckMessageId
        R< $+ @ $+ >            $@ OK
        R$*                     $#error $: 553 Header Error

The alternative format:

        HSubject: $>+CheckSubject

that is, $>+ instead of $>, gives the full Subject: header including
comments to the ruleset (comments in parentheses () are stripped
by default).

A default ruleset for headers which don't have a specific ruleset
defined for them can be given by:

        H*: $>CheckHdr

Notice:
1. All rules act on tokens as explained in doc/op/op.{me,ps,txt}.
That may cause problems with simple header checks due to the
tokenization.  It might be simpler to use a regex map and apply it
to $&{currHeader}.
2. There are no default rulesets coming with this distribution of
sendmail.  You can write your own, can search the WWW for examples,
or take a look at cf/cf/knecht.mc.
3. When using a default ruleset for headers, the name of the header
currently being checked can be found in the $&{hdr_name} macro.

After all of the headers are read, the check_eoh ruleset will be called for
any final header-related checks.  The ruleset is called with the number of
headers and the size of all of the headers in bytes separated by $|.  One
example usage is to reject messages which do not have a Message-Id:
header.  However, the Message-Id: header is *NOT* a required header and is
not a guaranteed spam indicator.  This ruleset is an example and should
probably not be used in production.

        LOCAL_CONFIG
        Kstorage macro
        HMessage-Id: $>CheckMessageId

        LOCAL_RULESETS
        SCheckMessageId
        # Record the presence of the header
        R$*                     $: $(storage {MessageIdCheck} $@ OK $) $1
        R< $+ @ $+ >            $@ OK
        R$*                     $#error $: 553 Header Error

        Scheck_eoh
        # Check the macro
        R$*                     $: < $&{MessageIdCheck} >
        # Clear the macro for the next message
        R$*                     $: $(storage {MessageIdCheck} $) $1
        # Has a Message-Id: header
        R< $+ >                 $@ OK
        # Allow missing Message-Id: from local mail
        R$*                     $: < $&{client_name} >
        R< >                    $@ OK
        R< $=w >                $@ OK
        # Otherwise, reject the mail
        R$*                     $#error $: 553 Header Error


+--------------------+
| CONNECTION CONTROL |
+--------------------+

The features ratecontrol and conncontrol allow to establish connection
limits per client IP address or net.  These features can limit the
rate of connections (connections per time unit) or the number of
incoming SMTP connections, respectively.  If enabled, appropriate
rulesets are called at the end of check_relay, i.e., after DNS
blocklists and generic access_db operations.  The features require
FEATURE(`access_db') to be listed earlier in the mc file.

Note: FEATURE(`delay_checks') delays those connection control checks
after a recipient address has been received, hence making these
connection control features less useful.  To run the checks as early
as possible, specify the parameter `nodelay', e.g.,

        FEATURE(`ratecontrol', `nodelay')

In that case, FEATURE(`delay_checks') has no effect on connection
control (and it must be specified earlier in the mc file).

An optional second argument `terminate' specifies whether the
rulesets should return the error code 421 which will cause
sendmail to terminate the session with that error if it is
returned from check_relay, i.e., not delayed as explained in
the previous paragraph.  Example:

        FEATURE(`ratecontrol', `nodelay', `terminate')


+----------+
| STARTTLS |
+----------+

In this text, cert will be used as an abbreviation for X.509 certificate,
DN (CN) is the distinguished (common) name of a cert, and CA is a
certification authority, which signs (issues) certs.

For STARTTLS to be offered by sendmail you need to set at least
these variables (the file names and paths are just examples):

        define(`confCACERT_PATH', `/etc/mail/certs/')
        define(`confCACERT', `/etc/mail/certs/CA.cert.pem')
        define(`confSERVER_CERT', `/etc/mail/certs/my.cert.pem')
        define(`confSERVER_KEY', `/etc/mail/certs/my.key.pem')

On systems which do not have the compile flag HASURANDOM set (see
sendmail/README) you also must set confRAND_FILE.

See doc/op/op.{me,ps,txt} for more information about these options,
especially the sections ``Certificates for STARTTLS'' and ``PRNG for
STARTTLS''.

Macros related to STARTTLS are:

${cert_issuer} holds the DN of the CA (the cert issuer).
${cert_subject} holds the DN of the cert (called the cert subject).
${cn_issuer} holds the CN of the CA (the cert issuer).
${cn_subject} holds the CN of the cert (called the cert subject).
${tls_version} the TLS/SSL version used for the connection, e.g., TLSv1,
        TLSv1/SSLv3, SSLv3, SSLv2.
${cipher} the cipher used for the connection, e.g., EDH-DSS-DES-CBC3-SHA,
        EDH-RSA-DES-CBC-SHA, DES-CBC-MD5, DES-CBC3-SHA.
${cipher_bits} the keylength (in bits) of the symmetric encryption algorithm
        used for the connection.
${verify} holds the result of the verification of the presented cert.
        Possible values are:
        OK       verification succeeded.
        NO       no cert presented.
        NOT      no cert requested.
        FAIL     cert presented but could not be verified,
                 e.g., the cert of the signing CA is missing.
        NONE     STARTTLS has not been performed.
        TEMP     temporary error occurred.
        PROTOCOL protocol error occurred (SMTP level).
        SOFTWARE STARTTLS handshake failed.
${server_name} the name of the server of the current outgoing SMTP
        connection.
${server_addr} the address of the server of the current outgoing SMTP
        connection.

Relaying
--------

SMTP STARTTLS can allow relaying for remote SMTP clients which have
successfully authenticated themselves.  If the verification of the cert
failed (${verify} != OK), relaying is subject to the usual rules.
Otherwise the DN of the issuer is looked up in the access map using the
tag CERTISSUER.  If the resulting value is RELAY, relaying is allowed.
If it is SUBJECT, the DN of the cert subject is looked up next in the
access map using the tag CERTSUBJECT.  If the value is RELAY, relaying
is allowed.

To make things a bit more flexible (or complicated), the values for
${cert_issuer} and ${cert_subject} can be optionally modified by regular
expressions defined in the m4 variables _CERT_REGEX_ISSUER_ and
_CERT_REGEX_SUBJECT_, respectively.  To avoid problems with those macros in
rulesets and map lookups, they are modified as follows: each non-printable
character and the characters '<', '>', '(', ')', '"', '+', ' ' are replaced
by their HEX value with a leading '+'.  For example:

/C=US/ST=California/O=endmail.org/OU=private/CN=Darth Mail (Cert)/emailAddress=
darth+cert@endmail.org

is encoded as:

/C=US/ST=California/O=endmail.org/OU=private/CN=
Darth+20Mail+20+28Cert+29/emailAddress=darth+2Bcert@endmail.org

(line breaks have been inserted for readability).

The macros which are subject to this encoding are ${cert_subject},
${cert_issuer}, ${cn_subject}, and ${cn_issuer}.

Examples:

To allow relaying for everyone who can present a cert signed by

/C=US/ST=California/O=endmail.org/OU=private/CN=
Darth+20Mail+20+28Cert+29/emailAddress=darth+2Bcert@endmail.org

simply use:

CertIssuer:/C=US/ST=California/O=endmail.org/OU=private/CN=
Darth+20Mail+20+28Cert+29/emailAddress=darth+2Bcert@endmail.org RELAY

To allow relaying only for a subset of machines that have a cert signed by

/C=US/ST=California/O=endmail.org/OU=private/CN=
Darth+20Mail+20+28Cert+29/emailAddress=darth+2Bcert@endmail.org

use:

CertIssuer:/C=US/ST=California/O=endmail.org/OU=private/CN=
Darth+20Mail+20+28Cert+29/emailAddress=darth+2Bcert@endmail.org SUBJECT
CertSubject:/C=US/ST=California/O=endmail.org/OU=private/CN=
DeathStar/emailAddress=deathstar@endmail.org            RELAY

Note: line breaks have been inserted after "CN=" for readability,
each tagged entry must be one (long) line in the access map.

Of course it is also possible to write a simple ruleset that allows
relaying for everyone who can present a cert that can be verified, e.g.,

LOCAL_RULESETS
SLocal_check_rcpt
R$*     $: $&{verify}
ROK     $# OK

Allowing Connections
--------------------

The rulesets tls_server, tls_client, and tls_rcpt are used to decide whether
an SMTP connection is accepted (or should continue).

tls_server is called when sendmail acts as client after a STARTTLS command
(should) have been issued.  The parameter is the value of ${verify}.

tls_client is called when sendmail acts as server, after a STARTTLS command
has been issued, and from check_mail.  The parameter is the value of
${verify} and STARTTLS or MAIL, respectively.

Both rulesets behave the same.  If no access map is in use, the connection
will be accepted unless ${verify} is SOFTWARE, in which case the connection
is always aborted.  For tls_server/tls_client, ${client_name}/${server_name}
is looked up in the access map using the tag TLS_Srv/TLS_Clt, which is done
with the ruleset LookUpDomain.  If no entry is found, ${client_addr}
(${server_addr}) is looked up in the access map (same tag, ruleset
LookUpAddr).  If this doesn't result in an entry either, just the tag is
looked up in the access map (included the trailing colon).  Notice:
requiring that e-mail is sent to a server only encrypted, e.g., via

TLS_Srv:secure.domain   ENCR:112

doesn't necessarily mean that e-mail sent to that domain is encrypted.
If the domain has multiple MX servers, e.g.,

secure.domain.  IN MX 10        mail.secure.domain.
secure.domain.  IN MX 50        mail.other.domain.

then mail to user@secure.domain may go unencrypted to mail.other.domain.
tls_rcpt can be used to address this problem.

tls_rcpt is called before a RCPT TO: command is sent.  The parameter is the
current recipient.  This ruleset is only defined if FEATURE(`access_db')
is selected.  A recipient address user@domain is looked up in the access
map in four formats: TLS_Rcpt:user@domain, TLS_Rcpt:user@, TLS_Rcpt:domain,
and TLS_Rcpt:; the first match is taken.

The result of the lookups is then used to call the ruleset TLS_connection,
which checks the requirement specified by the RHS in the access map against
the actual parameters of the current TLS connection, esp. ${verify} and
${cipher_bits}.  Legal RHSs in the access map are:

VERIFY          verification must have succeeded
VERIFY:bits     verification must have succeeded and ${cipher_bits} must
                be greater than or equal bits.
ENCR:bits       ${cipher_bits} must be greater than or equal bits.

The RHS can optionally be prefixed by TEMP+ or PERM+ to select a temporary
or permanent error.  The default is a temporary error code unless
the macro TLS_PERM_ERR is set during generation of the .cf file.

If a certain level of encryption is required, then it might also be
possible that this level is provided by the security layer from a SASL
algorithm, e.g., DIGEST-MD5.

Furthermore, there can be a list of extensions added.  Such a list
starts with '+' and the items are separated by '++'.  Allowed
extensions are:

CN:name         name must match ${cn_subject}
CN              ${client_name}/${server_name} must match ${cn_subject}
CS:name         name must match ${cert_subject}
CI:name         name must match ${cert_issuer}
CITag:MYTag     look up MYTag:${cert_issuer} in access map; the check
                only succeeds if it is found with a RHS of OK.

Example: e-mail sent to secure.example.com should only use an encrypted
connection.  E-mail received from hosts within the laptop.example.com domain
should only be accepted if they have been authenticated.  The host which
receives e-mail for darth@endmail.org must present a cert that uses the
CN smtp.endmail.org.  E-mail sent to safe.example.com must be verified,
have a matching CN, and must present a cert signed by a CA with one of
the listed DNs.

TLS_Srv:secure.example.com      ENCR:112
TLS_Clt:laptop.example.com      PERM+VERIFY:112
TLS_Rcpt:darth@endmail.org      ENCR:112+CN:smtp.endmail.org
TLS_Srv:safe.example.net        VERIFY+CN++CITag:MyCA
MyCA:/C=US/ST=CA/O=safe/CN=example.net/         OK
MyCA:/C=US/ST=CA/O=secure/CN=example.net/       OK


TLS Options per Session
-----------------------

By default STARTTLS is used whenever possible.  However, there are
MTAs with STARTTLS interoperability issues.  To be able to send to
(or receive from) those MTAs several features are available:

1) Various TLS options be be set per IP/domain.
2) STARTTLS can be turned off for specific IP addresses/domains.

About 1): the rulesets tls_srv_features and tls_clt_features can
be used to return a (semicolon separated) list of TLS related
options:

- Options: compare {Server,Client}SSLOptions.
- CipherList: same as the global option.
- CertFile, KeyFile: {Server,Client}{Cert,Key}File
- Flags: see doc/op/op.me for details.

If FEATURE(`tls_session_features') and FEATURE(`access_db') are
used, then default rulesets are activated which look up entries in
the access map with the tags TLS_Srv_features and TLS_Clt_features,
respectively.  For example, these entries:

TLS_Srv_features:10.0.2.4       CipherList=MEDIUM+aRSA;
TLS_Clt_features:10.1.0.1       Options=SSL_OP_NO_TLSv1_2; CipherList=ALL:-EXPORT

specify a cipherlist with MEDIUM strength ciphers that use RSA
certificates only for the client with the IP address 10.0.2.4,
and turn off TLSv1.2 when connecting to the server with the IP
address 10.1.0.1 as well as setting a specific cipherlist.
If FEATURE(`tls_session_features') is not used the user can provide
their own rulesets which must return the appropriate data.
If the rulesets are not defined or do not return a value, the
default TLS options are not modified.

About 2): the rulesets try_tls, srv_features, and clt_features can
be used together with the access map.  Entries for the access map
must be tagged with Try_TLS, Srv_Features, Clt_Features and refer
to the hostname or IP address of the connecting system (the latter
is not available for clt_features).  A default case can be specified
by using just the tag.  For example, the following entries in the
access map:

        Try_TLS:broken.server   NO
        Srv_Features:my.domain  v
        Srv_Features:           V
        Clt_Features:broken.sts M

will turn off STARTTLS when sending to broken.server (or any host
in that domain), request a client certificate during the TLS handshake
only for hosts in my.domain, and disable MTA-STS for broken.sts.
The valid entries on the RHS for Srv_Features and Clt_Features are
listed in the Sendmail Installation and Operations Guide.


Received: Header
----------------

The Received: header reveals whether STARTTLS has been used.  It contains an
extra line:

(version=${tls_version} cipher=${cipher} bits=${cipher_bits} verify=${verify})


+---------------------+
| SMTP AUTHENTICATION |
+---------------------+

The macros ${auth_authen}, ${auth_author}, and ${auth_type} can be
used in anti-relay rulesets to allow relaying for those users that
authenticated themselves.  A very simple example is:

SLocal_check_rcpt
R$*             $: $&{auth_type}
R$+             $# OK

which checks whether a user has successfully authenticated using
any available mechanism.  Depending on the setup of the Cyrus SASL
library, more sophisticated rulesets might be required, e.g.,

SLocal_check_rcpt
R$*             $: $&{auth_type} $| $&{auth_authen}
RDIGEST-MD5 $| $+@$=w   $# OK

to allow relaying for users that authenticated using DIGEST-MD5
and have an identity in the local domains.

The ruleset trust_auth is used to determine whether a given AUTH=
parameter (that is passed to this ruleset) should be trusted.  This
ruleset may make use of the other ${auth_*} macros.  Only if the
ruleset resolves to the error mailer, the AUTH= parameter is not
trusted.  A user supplied ruleset Local_trust_auth can be written
to modify the default behavior, which only trust the AUTH=
parameter if it is identical to the authenticated user.

Per default, relaying is allowed for any user who authenticated
via a "trusted" mechanism, i.e., one that is defined via
TRUST_AUTH_MECH(`list of mechanisms')
For example:
TRUST_AUTH_MECH(`KERBEROS_V4 DIGEST-MD5')

If the selected mechanism provides a security layer the number of
bits used for the key of the symmetric cipher is stored in the
macro ${auth_ssf}.

Providing SMTP AUTH Data when sendmail acts as Client
-----------------------------------------------------

If sendmail acts as client, it needs some information how to
authenticate against another MTA.  This information can be provided
by the ruleset authinfo or by the option DefaultAuthInfo.  The
authinfo ruleset looks up {server_name} using the tag AuthInfo: in
the access map.  If no entry is found, {server_addr} is looked up
in the same way and finally just the tag AuthInfo: to provide
default values.  Note: searches for domain parts or IP nets are
only performed if the access map is used; if the authinfo feature
is used then only up to three lookups are performed (two exact
matches, one default).

Note: If your daemon does client authentication when sending, and
if it uses either PLAIN or LOGIN authentication, then you *must*
prevent ordinary users from seeing verbose output.  Do NOT install
sendmail set-user-ID.  Use PrivacyOptions to turn off verbose output
("goaway" works for this).

Notice: the default configuration file causes the option DefaultAuthInfo
to fail since the ruleset authinfo is in the .cf file. If you really
want to use DefaultAuthInfo (it is deprecated) then you have to
remove the ruleset.

The RHS for an AuthInfo: entry in the access map should consists of a
list of tokens, each of which has the form: "TDstring" (including
the quotes).  T is a tag which describes the item, D is a delimiter,
either ':' for simple text or '=' for a base64 encoded string.
Valid values for the tag are:

        U       user (authorization) id
        I       authentication id
        P       password
        R       realm
        M       list of mechanisms delimited by spaces

Example entries are:

AuthInfo:other.dom "U:user" "I:user" "P:secret" "R:other.dom" "M:DIGEST-MD5"
AuthInfo:host.more.dom "U:user" "P=c2VjcmV0"

User id or authentication id must exist as well as the password.  All
other entries have default values.  If one of user or authentication
id is missing, the existing value is used for the missing item.
If "R:" is not specified, realm defaults to $j.  The list of mechanisms
defaults to those specified by AuthMechanisms.

Since this map contains sensitive information, either the access
map must be unreadable by everyone but root (or the trusted user)
or FEATURE(`authinfo') must be used which provides a separate map.
Notice: It is not checked whether the map is actually
group/world-unreadable, this is left to the user.


+--------------------------------+
| ADDING NEW MAILERS OR RULESETS |
+--------------------------------+

Sometimes you may need to add entirely new mailers or rulesets.  They
should be introduced with the constructs MAILER_DEFINITIONS and
LOCAL_RULESETS respectively.  For example:

        MAILER_DEFINITIONS
        Mmymailer, ...
        ...

        LOCAL_RULESETS
        Smyruleset
        ...

Local additions for the rulesets srv_features, clt_features, try_tls,
tls_rcpt, tls_client, and tls_server can be made using LOCAL_SRV_FEATURES,
LOCAL_CLT_FEATURES, LOCAL_TRY_TLS, LOCAL_TLS_RCPT, LOCAL_TLS_CLIENT,
and LOCAL_TLS_SERVER, respectively.  For example, to add a local
ruleset that decides whether to try STARTTLS in a sendmail client, use:

        LOCAL_TRY_TLS
        R...

Note: you don't need to add a name for the ruleset, it is implicitly
defined by using the appropriate macro.


+-------------------------+
| ADDING NEW MAIL FILTERS |
+-------------------------+

Sendmail supports mail filters to filter incoming SMTP messages according
to the "Sendmail Mail Filter API" documentation.  These filters can be
configured in your mc file using the two commands:

        MAIL_FILTER(`name', `equates')
        INPUT_MAIL_FILTER(`name', `equates')

The first command, MAIL_FILTER(), simply defines a filter with the given
name and equates.  For example:

        MAIL_FILTER(`archive', `S=local:/var/run/archivesock, F=R')

This creates the equivalent sendmail.cf entry:

        Xarchive, S=local:/var/run/archivesock, F=R

The INPUT_MAIL_FILTER() command performs the same actions as MAIL_FILTER
but also populates the m4 variable `confINPUT_MAIL_FILTERS' with the name
of the filter such that the filter will actually be called by sendmail.

For example, the two commands:

        INPUT_MAIL_FILTER(`archive', `S=local:/var/run/archivesock, F=R')
        INPUT_MAIL_FILTER(`spamcheck', `S=inet:2525@localhost, F=T')

are equivalent to the three commands:

        MAIL_FILTER(`archive', `S=local:/var/run/archivesock, F=R')
        MAIL_FILTER(`spamcheck', `S=inet:2525@localhost, F=T')
        define(`confINPUT_MAIL_FILTERS', `archive, spamcheck')

In general, INPUT_MAIL_FILTER() should be used unless you need to define
more filters than you want to use for `confINPUT_MAIL_FILTERS'.

Note that setting `confINPUT_MAIL_FILTERS' after any INPUT_MAIL_FILTER()
commands will clear the list created by the prior INPUT_MAIL_FILTER()
commands.


+-------------------------+
| QUEUE GROUP DEFINITIONS |
+-------------------------+

In addition to the queue directory (which is the default queue group
called "mqueue"), sendmail can deal with multiple queue groups, which
are collections of queue directories with the same behaviour.  Queue
groups can be defined using the command:

        QUEUE_GROUP(`name', `equates')

For details about queue groups, please see doc/op/op.{me,ps,txt}.


+-------------------------------+
| NON-SMTP BASED CONFIGURATIONS |
+-------------------------------+

These configuration files are designed primarily for use by
SMTP-based sites.  They may not be well tuned for UUCP-only or
UUCP-primarily nodes (the latter is defined as a small local net
connected to the rest of the world via UUCP).  However, there is
one hook to handle some special cases.

You can define a ``smart host'' that understands a richer address syntax
using:

        define(`SMART_HOST', `mailer:hostname')

In this case, the ``mailer:'' defaults to "relay".  Any messages that
can't be handled using the usual UUCP rules are passed to this host.

If you are on a local SMTP-based net that connects to the outside
world via UUCP, you can use LOCAL_NET_CONFIG to add appropriate rules.
For example:

        define(`SMART_HOST', `uucp-new:uunet')
        LOCAL_NET_CONFIG
        R$* < @ $* .$m. > $*    $#smtp $@ $2.$m. $: $1 < @ $2.$m. > $3

This will cause all names that end in your domain name ($m) to be sent
via SMTP; anything else will be sent via uucp-new (smart UUCP) to uunet.
If you have FEATURE(`nocanonify'), you may need to omit the dots after
the $m.  If you are running a local DNS inside your domain which is
not otherwise connected to the outside world, you probably want to
use:

        define(`SMART_HOST', `smtp:fire.wall.com')
        LOCAL_NET_CONFIG
        R$* < @ $* . > $*       $#smtp $@ $2. $: $1 < @ $2. > $3

That is, send directly only to things you found in your DNS lookup;
anything else goes through SMART_HOST.

You may need to turn off the anti-spam rules in order to accept
UUCP mail with FEATURE(`promiscuous_relay') and
FEATURE(`accept_unresolvable_domains').


+-----------+
| WHO AM I? |
+-----------+

Normally, the $j macro is automatically defined to be your fully
qualified domain name (FQDN).  Sendmail does this by getting your
host name using gethostname and then calling gethostbyname on the
result.  For example, in some environments gethostname returns
only the root of the host name (such as "foo"); gethostbyname is
supposed to return the FQDN ("foo.bar.com").  In some (fairly rare)
cases, gethostbyname may fail to return the FQDN.  In this case
you MUST define confDOMAIN_NAME to be your fully qualified domain
name.  This is usually done using:

        Dmbar.com
        define(`confDOMAIN_NAME', `$w.$m')dnl


+-----------------------------------+
| ACCEPTING MAIL FOR MULTIPLE NAMES |
+-----------------------------------+

If your host is known by several different names, you need to augment
class {w}.  This is a list of names by which your host is known, and
anything sent to an address using a host name in this list will be
treated as local mail.  You can do this in two ways:  either create the
file /etc/mail/local-host-names containing a list of your aliases (one per
line), and use ``FEATURE(`use_cw_file')'' in the .mc file, or add
``LOCAL_DOMAIN(`alias.host.name')''.  Be sure you use the fully-qualified
name of the host, rather than a short name.

If you want to have different address in different domains, take
a look at the virtusertable feature, which is also explained at
http://www.sendmail.org/virtual-hosting.html


+--------------------+
| USING MAILERTABLES |
+--------------------+

To use FEATURE(`mailertable'), you will have to create an external
database containing the routing information for various domains.
For example, a mailertable file in text format might be:

        .my.domain              xnet:%1.my.domain
        uuhost1.my.domain       uucp-new:uuhost1
        .bitnet                 smtp:relay.bit.net

This should normally be stored in /etc/mail/mailertable.  The actual
database version of the mailertable is built using:

        makemap hash /etc/mail/mailertable < /etc/mail/mailertable

The semantics are simple.  Any LHS entry that does not begin with
a dot matches the full host name indicated.  LHS entries beginning
with a dot match anything ending with that domain name (including
the leading dot) -- that is, they can be thought of as having a
leading ".+" regular expression pattern for a non-empty sequence of
characters.  Matching is done in order of most-to-least qualified
-- for example, even though ".my.domain" is listed first in the
above example, an entry of "uuhost1.my.domain" will match the second
entry since it is more explicit.  Note: e-mail to "user@my.domain"
does not match any entry in the above table.  You need to have
something like:

        my.domain               esmtp:host.my.domain

The RHS should always be a "mailer:host" pair.  The mailer is the
configuration name of a mailer (that is, an M line in the
sendmail.cf file).  The "host" will be the hostname passed to
that mailer.  In domain-based matches (that is, those with leading
dots) the "%1" may be used to interpolate the wildcarded part of
the host name.  For example, the first line above sends everything
addressed to "anything.my.domain" to that same host name, but using
the (presumably experimental) xnet mailer.

In some cases you may want to temporarily turn off MX records,
particularly on gateways.  For example, you may want to MX
everything in a domain to one machine that then forwards it
directly.  To do this, you might use the DNS configuration:

        *.domain.       IN      MX      0       relay.machine

and on relay.machine use the mailertable:

        .domain         smtp:[gateway.domain]

The [square brackets] turn off MX records for this host only.
If you didn't do this, the mailertable would use the MX record
again, which would give you an MX loop.  Note that the use of
wildcard MX records is almost always a bad idea.  Please avoid
using them if possible.


+--------------------------------+
| USING USERDB TO MAP FULL NAMES |
+--------------------------------+

The user database was not originally intended for mapping full names
to login names (e.g., Eric.Allman => eric), but some people are using
it that way.  (it is recommended that you set up aliases for this
purpose instead -- since you can specify multiple alias files, this
is fairly easy.)  The intent was to locate the default maildrop at
a site, but allow you to override this by sending to a specific host.

If you decide to set up the user database in this fashion, it is
imperative that you not use FEATURE(`stickyhost') -- otherwise,
e-mail sent to Full.Name@local.host.name will be rejected.

To build the internal form of the user database, use:

        makemap btree /etc/mail/userdb < /etc/mail/userdb.txt

As a general rule, it is an extremely bad idea to using full names
as e-mail addresses, since they are not in any sense unique.  For
example, the UNIX software-development community has at least two
well-known Peter Deutsches, and at one time Bell Labs had two
Stephen R. Bournes with offices along the same hallway.  Which one
will be forced to suffer the indignity of being Stephen_R_Bourne_2?
The less famous of the two, or the one that was hired later?

Finger should handle full names (and be fuzzy).  Mail should use
handles, and not be fuzzy.


+--------------------------------+
| MISCELLANEOUS SPECIAL FEATURES |
+--------------------------------+

Plussed users
        Sometimes it is convenient to merge configuration on a
        centralized mail machine, for example, to forward all
        root mail to a mail server.  In this case it might be
        useful to be able to treat the root addresses as a class
        of addresses with subtle differences.  You can do this
        using plussed users.  For example, a client might include
        the alias:

                root:  root+client1@server

        On the server, this will match an alias for "root+client1".
        If that is not found, the alias "root+*" will be tried,
        then "root".


+----------------+
| SECURITY NOTES |
+----------------+

A lot of sendmail security comes down to you.  Sendmail 8 is much
more careful about checking for security problems than previous
versions, but there are some things that you still need to watch
for.  In particular:

* Make sure the aliases file is not writable except by trusted
  system personnel.  This includes both the text and database
  version.

* Make sure that other files that sendmail reads, such as the
  mailertable, are only writable by trusted system personnel.

* The queue directory should not be world writable PARTICULARLY
  if your system allows "file giveaways" (that is, if a non-root
  user can chown any file they own to any other user).

* If your system allows file giveaways, DO NOT create a publicly
  writable directory for forward files.  This will allow anyone
  to steal anyone else's e-mail.  Instead, create a script that
  copies the .forward file from users' home directories once a
  night (if you want the non-NFS-mounted forward directory).

* If your system allows file giveaways, you'll find that
  sendmail is much less trusting of :include: files -- in
  particular, you'll have to have /SENDMAIL/ANY/SHELL/ in
  /etc/shells before they will be trusted (that is, before
  files and programs listed in them will be honored).

In general, file giveaways are a mistake -- if you can turn them
off, do so.


+--------------------------------+
| TWEAKING CONFIGURATION OPTIONS |
+--------------------------------+

There are a large number of configuration options that don't normally
need to be changed.  However, if you feel you need to tweak them,
you can define the following M4 variables. Note that some of these
variables require formats that are defined in RFC 2821 or RFC 2822.
Before changing them you need to make sure you do not violate those
(and other relevant) RFCs.

This list is shown in four columns:  the name you define, the default
value for that definition, the option or macro that is affected
(either Ox for an option or Dx for a macro), and a brief description.
Greater detail of the semantics can be found in the Installation
and Operations Guide.

Some options are likely to be deprecated in future versions -- that is,
the option is only included to provide back-compatibility.  These are
marked with "*".

Remember that these options are M4 variables, and hence may need to
be quoted.  In particular, arguments with commas will usually have to
be ``double quoted, like this phrase'' to avoid having the comma
confuse things.  This is common for alias file definitions and for
the read timeout.

M4 Variable Name        Configuration   [Default] & Description
================        =============   =======================
confMAILER_NAME         $n macro        [MAILER-DAEMON] The sender name used
                                        for internally generated outgoing
                                        messages.
confDOMAIN_NAME         $j macro        If defined, sets $j.  This should
                                        only be done if your system cannot
                                        determine your local domain name,
                                        and then it should be set to
                                        $w.Foo.COM, where Foo.COM is your
                                        domain name.
confCF_VERSION          $Z macro        If defined, this is appended to the
                                        configuration version name.
confLDAP_CLUSTER        ${sendmailMTACluster} macro
                                        If defined, this is the LDAP
                                        cluster to use for LDAP searches
                                        as described above in ``USING LDAP
                                        FOR ALIASES, MAPS, AND CLASSES''.
confFROM_HEADER         From:           [$?x$x <$g>$|$g$.] The format of an
                                        internally generated From: address.
confRECEIVED_HEADER     Received:
                [$?sfrom $s $.$?_($?s$|from $.$_)
                        $.$?{auth_type}(authenticated)
                        $.by $j ($v/$Z)$?r with $r$. id $i$?u
                        for $u; $|;
                        $.$b]
                                        The format of the Received: header
                                        in messages passed through this host.
                                        It is unwise to try to change this.
confMESSAGEID_HEADER    Message-Id:     [<$t.$i@$j>] The format of an
                                        internally generated Message-Id:
                                        header.
confCW_FILE             Fw class        [/etc/mail/local-host-names] Name
                                        of file used to get the local
                                        additions to class {w} (local host
                                        names).
confCT_FILE             Ft class        [/etc/mail/trusted-users] Name of
                                        file used to get the local additions
                                        to class {t} (trusted users).
confCR_FILE             FR class        [/etc/mail/relay-domains] Name of
                                        file used to get the local additions
                                        to class {R} (hosts allowed to relay).
confTRUSTED_USERS       Ct class        [no default] Names of users to add to
                                        the list of trusted users.  This list
                                        always includes root, uucp, and daemon.
                                        See also FEATURE(`use_ct_file').
confTRUSTED_USER        TrustedUser     [no default] Trusted user for file
                                        ownership and starting the daemon.
                                        Not to be confused with
                                        confTRUSTED_USERS (see above).
confSMTP_MAILER         -               [esmtp] The mailer name used when
                                        SMTP connectivity is required.
                                        One of "smtp", "smtp8",
                                        "esmtp", or "dsmtp".
confUUCP_MAILER         -               [uucp-old] The mailer to be used by
                                        default for bang-format recipient
                                        addresses.  See also discussion of
                                        class {U}, class {Y}, and class {Z}
                                        in the MAILER(`uucp') section.
confLOCAL_MAILER        -               [local] The mailer name used when
                                        local connectivity is required.
                                        Almost always "local".
confRELAY_MAILER        -               [relay] The default mailer name used
                                        for relaying any mail (e.g., to a
                                        BITNET_RELAY, a SMART_HOST, or
                                        whatever).  This can reasonably be
                                        "uucp-new" if you are on a
                                        UUCP-connected site.
confSEVEN_BIT_INPUT     SevenBitInput   [False] Force input to seven bits?
confEIGHT_BIT_HANDLING  EightBitMode    [pass8] 8-bit data handling
confALIAS_WAIT          AliasWait       [10m] Time to wait for alias file
                                        rebuild until you get bored and
                                        decide that the apparently pending
                                        rebuild failed.
confMIN_FREE_BLOCKS     MinFreeBlocks   [100] Minimum number of free blocks on
                                        queue filesystem to accept SMTP mail.
                                        (Prior to 8.7 this was minfree/maxsize,
                                        where minfree was the number of free
                                        blocks and maxsize was the maximum
                                        message size.  Use confMAX_MESSAGE_SIZE
                                        for the second value now.)
confMAX_MESSAGE_SIZE    MaxMessageSize  [infinite] The maximum size of messages
                                        that will be accepted (in bytes).
confBLANK_SUB           BlankSub        [.] Blank (space) substitution
                                        character.
confCON_EXPENSIVE       HoldExpensive   [False] Avoid connecting immediately
                                        to mailers marked expensive.
confCHECKPOINT_INTERVAL CheckpointInterval
                                        [10] Checkpoint queue files every N
                                        recipients.
confDELIVERY_MODE       DeliveryMode    [background] Default delivery mode.
confERROR_MODE          ErrorMode       [print] Error message mode.
confERROR_MESSAGE       ErrorHeader     [undefined] Error message header/file.
confSAVE_FROM_LINES     SaveFromLine    Save extra leading From_ lines.
confTEMP_FILE_MODE      TempFileMode    [0600] Temporary file mode.
confMATCH_GECOS         MatchGECOS      [False] Match GECOS field.
confMAX_HOP             MaxHopCount     [25] Maximum hop count.
confIGNORE_DOTS*        IgnoreDots      [False; always False in -bs or -bd
                                        mode] Ignore dot as terminator for
                                        incoming messages?
confBIND_OPTS           ResolverOptions [undefined] Default options for DNS
                                        resolver.
confMIME_FORMAT_ERRORS* SendMimeErrors  [True] Send error messages as MIME-
                                        encapsulated messages per RFC 1344.
confFORWARD_PATH        ForwardPath     [$z/.forward.$w:$z/.forward]
                                        The colon-separated list of places to
                                        search for .forward files.  N.B.: see
                                        the Security Notes section.
confMCI_CACHE_SIZE      ConnectionCacheSize
                                        [2] Size of open connection cache.
confMCI_CACHE_TIMEOUT   ConnectionCacheTimeout
                                        [5m] Open connection cache timeout.
confHOST_STATUS_DIRECTORY HostStatusDirectory
                                        [undefined] If set, host status is kept
                                        on disk between sendmail runs in the
                                        named directory tree.  This need not be
                                        a full pathname, in which case it is
                                        interpreted relative to the queue
                                        directory.
confSINGLE_THREAD_DELIVERY  SingleThreadDelivery
                                        [False] If this option and the
                                        HostStatusDirectory option are both
                                        set, single thread deliveries to other
                                        hosts.  That is, don't allow any two
                                        sendmails on this host to connect
                                        simultaneously to any other single
                                        host.  This can slow down delivery in
                                        some cases, in particular since a
                                        cached but otherwise idle connection
                                        to a host will prevent other sendmails
                                        from connecting to the other host.
confUSE_COMPRESSED_IPV6_ADDRESSES
                        UseCompressedIPv6Addresses
                                        [undefined] If set, use the compressed
                                        form of IPv6 addresses, such as
                                        IPV6:::1, instead of the uncompressed
                                        form, such as IPv6:0:0:0:0:0:0:0:1.
confUSE_ERRORS_TO*      UseErrorsTo     [False] Use the Errors-To: header to
                                        deliver error messages.  This should
                                        not be necessary because of general
                                        acceptance of the envelope/header
                                        distinction.
confLOG_LEVEL           LogLevel        [9] Log level.
confME_TOO              MeToo           [True] Include sender in group
                                        expansions.  This option is
                                        deprecated and will be removed from
                                        a future version.
confCHECK_ALIASES       CheckAliases    [False] Check RHS of aliases when
                                        running newaliases.  Since this does
                                        DNS lookups on every address, it can
                                        slow down the alias rebuild process
                                        considerably on large alias files.
confOLD_STYLE_HEADERS*  OldStyleHeaders [True] Assume that headers without
                                        special chars are old style.
confPRIVACY_FLAGS       PrivacyOptions  [authwarnings] Privacy flags.
confCOPY_ERRORS_TO      PostmasterCopy  [undefined] Address for additional
                                        copies of all error messages.
confQUEUE_FACTOR        QueueFactor     [600000] Slope of queue-only function.
confQUEUE_FILE_MODE     QueueFileMode   [undefined] Default permissions for
                                        queue files (octal).  If not set,
                                        sendmail uses 0600 unless its real
                                        and effective uid are different in
                                        which case it uses 0644.
confDONT_PRUNE_ROUTES   DontPruneRoutes [False] Don't prune down route-addr
                                        syntax addresses to the minimum
                                        possible.
confSAFE_QUEUE*         SuperSafe       [True] Commit all messages to disk
                                        before forking.
confTO_INITIAL          Timeout.initial [5m] The timeout waiting for a response
                                        on the initial connect.
confTO_CONNECT          Timeout.connect [0] The timeout waiting for an initial
                                        connect() to complete.  This can only
                                        shorten connection timeouts; the kernel
                                        silently enforces an absolute maximum
                                        (which varies depending on the system).
confTO_ICONNECT         Timeout.iconnect
                                        [undefined] Like Timeout.connect, but
                                        applies only to the very first attempt
                                        to connect to a host in a message.
                                        This allows a single very fast pass
                                        followed by more careful delivery
                                        attempts in the future.
confTO_ACONNECT         Timeout.aconnect
                                        [0] The overall timeout waiting for
                                        all connection for a single delivery
                                        attempt to succeed.  If 0, no overall
                                        limit is applied.
confTO_HELO             Timeout.helo    [5m] The timeout waiting for a response
                                        to a HELO or EHLO command.
confTO_MAIL             Timeout.mail    [10m] The timeout waiting for a
                                        response to the MAIL command.
confTO_RCPT             Timeout.rcpt    [1h] The timeout waiting for a response
                                        to the RCPT command.
confTO_DATAINIT         Timeout.datainit
                                        [5m] The timeout waiting for a 354
                                        response from the DATA command.
confTO_DATABLOCK        Timeout.datablock
                                        [1h] The timeout waiting for a block
                                        during DATA phase.
confTO_DATAFINAL        Timeout.datafinal
                                        [1h] The timeout waiting for a response
                                        to the final "." that terminates a
                                        message.
confTO_RSET             Timeout.rset    [5m] The timeout waiting for a response
                                        to the RSET command.
confTO_QUIT             Timeout.quit    [2m] The timeout waiting for a response
                                        to the QUIT command.
confTO_MISC             Timeout.misc    [2m] The timeout waiting for a response
                                        to other SMTP commands.
confTO_COMMAND          Timeout.command [1h] In server SMTP, the timeout
                                        waiting for a command to be issued.
confTO_IDENT            Timeout.ident   [5s] The timeout waiting for a
                                        response to an IDENT query.
confTO_FILEOPEN         Timeout.fileopen
                                        [60s] The timeout waiting for a file
                                        (e.g., :include: file) to be opened.
confTO_LHLO             Timeout.lhlo    [2m] The timeout waiting for a response
                                        to an LMTP LHLO command.
confTO_AUTH             Timeout.auth    [10m] The timeout waiting for a
                                        response in an AUTH dialogue.
confTO_STARTTLS         Timeout.starttls
                                        [1h] The timeout waiting for a
                                        response to an SMTP STARTTLS command.
confTO_CONTROL          Timeout.control
                                        [2m] The timeout for a complete
                                        control socket transaction to complete.
confTO_QUEUERETURN      Timeout.queuereturn
                                        [5d] The timeout before a message is
                                        returned as undeliverable.
confTO_QUEUERETURN_NORMAL
                        Timeout.queuereturn.normal
                                        [undefined] As above, for normal
                                        priority messages.
confTO_QUEUERETURN_URGENT
                        Timeout.queuereturn.urgent
                                        [undefined] As above, for urgent
                                        priority messages.
confTO_QUEUERETURN_NONURGENT
                        Timeout.queuereturn.non-urgent
                                        [undefined] As above, for non-urgent
                                        (low) priority messages.
confTO_QUEUERETURN_DSN
                        Timeout.queuereturn.dsn
                                        [undefined] As above, for delivery
                                        status notification messages.
confTO_QUEUEWARN        Timeout.queuewarn
                                        [4h] The timeout before a warning
                                        message is sent to the sender telling
                                        them that the message has been
                                        deferred.
confTO_QUEUEWARN_NORMAL Timeout.queuewarn.normal
                                        [undefined] As above, for normal
                                        priority messages.
confTO_QUEUEWARN_URGENT Timeout.queuewarn.urgent
                                        [undefined] As above, for urgent
                                        priority messages.
confTO_QUEUEWARN_NONURGENT
                        Timeout.queuewarn.non-urgent
                                        [undefined] As above, for non-urgent
                                        (low) priority messages.
confTO_QUEUEWARN_DSN
                        Timeout.queuewarn.dsn
                                        [undefined] As above, for delivery
                                        status notification messages.
confTO_HOSTSTATUS       Timeout.hoststatus
                                        [30m] How long information about host
                                        statuses will be maintained before it
                                        is considered stale and the host should
                                        be retried.  This applies both within
                                        a single queue run and to persistent
                                        information (see below).
confTO_RESOLVER_RETRANS Timeout.resolver.retrans
                                        [varies] Sets the resolver's
                                        retransmission time interval (in
                                        seconds).  Sets both
                                        Timeout.resolver.retrans.first and
                                        Timeout.resolver.retrans.normal.
confTO_RESOLVER_RETRANS_FIRST  Timeout.resolver.retrans.first
                                        [varies] Sets the resolver's
                                        retransmission time interval (in
                                        seconds) for the first attempt to
                                        deliver a message.
confTO_RESOLVER_RETRANS_NORMAL  Timeout.resolver.retrans.normal
                                        [varies] Sets the resolver's
                                        retransmission time interval (in
                                        seconds) for all resolver lookups
                                        except the first delivery attempt.
confTO_RESOLVER_RETRY   Timeout.resolver.retry
                                        [varies] Sets the number of times
                                        to retransmit a resolver query.
                                        Sets both
                                        Timeout.resolver.retry.first and
                                        Timeout.resolver.retry.normal.
confTO_RESOLVER_RETRY_FIRST  Timeout.resolver.retry.first
                                        [varies] Sets the number of times
                                        to retransmit a resolver query for
                                        the first attempt to deliver a
                                        message.
confTO_RESOLVER_RETRY_NORMAL  Timeout.resolver.retry.normal
                                        [varies] Sets the number of times
                                        to retransmit a resolver query for
                                        all resolver lookups except the
                                        first delivery attempt.
confTIME_ZONE           TimeZoneSpec    [USE_SYSTEM] Time zone info -- can be
                                        USE_SYSTEM to use the system's idea,
                                        USE_TZ to use the user's TZ envariable,
                                        or something else to force that value.
confDEF_USER_ID         DefaultUser     [1:1] Default user id.
confUSERDB_SPEC         UserDatabaseSpec
                                        [undefined] User database
                                        specification.
confFALLBACK_MX         FallbackMXhost  [undefined] Fallback MX host.
confFALLBACK_SMARTHOST  FallbackSmartHost
                                        [undefined] Fallback smart host.
confTLS_FALLBACK_TO_CLEAR       TLSFallbacktoClear
                                        [undefined] If set, immediately try
                                        a connection again without STARTTLS
                                        after a TLS handshake failure.
confTRY_NULL_MX_LIST    TryNullMXList   [False] If this host is the best MX
                                        for a host and other arrangements
                                        haven't been made, try connecting
                                        to the host directly; normally this
                                        would be a config error.
confQUEUE_LA            QueueLA         [varies] Load average at which
                                        queue-only function kicks in.
                                        Default values is (8 * numproc)
                                        where numproc is the number of
                                        processors online (if that can be
                                        determined).
confREFUSE_LA           RefuseLA        [varies] Load average at which
                                        incoming SMTP connections are
                                        refused.  Default values is (12 *
                                        numproc) where numproc is the
                                        number of processors online (if
                                        that can be determined).
confREJECT_LOG_INTERVAL RejectLogInterval       [3h] Log interval when
                                        refusing connections for this long.
confDELAY_LA            DelayLA         [0] Load average at which sendmail
                                        will sleep for one second on most
                                        SMTP commands and before accepting
                                        connections.  0 means no limit.
confMAX_ALIAS_RECURSION MaxAliasRecursion
                                        [10] Maximum depth of alias recursion.
confMAX_DAEMON_CHILDREN MaxDaemonChildren
                                        [undefined] The maximum number of
                                        children the daemon will permit.  After
                                        this number, connections will be
                                        rejected.  If not set or <= 0, there is
                                        no limit.
confMAX_HEADERS_LENGTH  MaxHeadersLength
                                        [32768] Maximum length of the sum
                                        of all headers.
confMAX_MIME_HEADER_LENGTH  MaxMimeHeaderLength
                                        [undefined] Maximum length of
                                        certain MIME header field values.
confCONNECTION_RATE_THROTTLE ConnectionRateThrottle
                                        [undefined] The maximum number of
                                        connections permitted per second per
                                        daemon.  After this many connections
                                        are accepted, further connections
                                        will be delayed.  If not set or <= 0,
                                        there is no limit.
confCONNECTION_RATE_WINDOW_SIZE ConnectionRateWindowSize
                                        [60s] Define the length of the
                                        interval for which the number of
                                        incoming connections is maintained.
confWORK_RECIPIENT_FACTOR
                        RecipientFactor [30000] Cost of each recipient.
confSEPARATE_PROC       ForkEachJob     [False] Run all deliveries in a
                                        separate process.
confWORK_CLASS_FACTOR   ClassFactor     [1800] Priority multiplier for class.
confWORK_TIME_FACTOR    RetryFactor     [90000] Cost of each delivery attempt.
confQUEUE_SORT_ORDER    QueueSortOrder  [Priority] Queue sort algorithm:
                                        Priority, Host, Filename, Random,
                                        Modification, or Time.
confMAX_QUEUE_AGE       MaxQueueAge     [undefined] If set to a value greater
                                        than zero, entries in the queue
                                        will be retried during a queue run
                                        only if the individual retry time
                                        has been reached which is doubled
                                        for each attempt.  The maximum retry
                                        time is limited by the specified value.
confMIN_QUEUE_AGE       MinQueueAge     [0] The minimum amount of time a job
                                        must sit in the queue between queue
                                        runs.  This allows you to set the
                                        queue run interval low for better
                                        responsiveness without trying all
                                        jobs in each run.
confDEF_CHAR_SET        DefaultCharSet  [unknown-8bit] When converting
                                        unlabeled 8 bit input to MIME, the
                                        character set to use by default.
confSERVICE_SWITCH_FILE ServiceSwitchFile
                                        [/etc/mail/service.switch] The file
                                        to use for the service switch on
                                        systems that do not have a
                                        system-defined switch.
confHOSTS_FILE          HostsFile       [/etc/hosts] The file to use when doing
                                        "file" type access of hosts names.
confDIAL_DELAY          DialDelay       [0s] If a connection fails, wait this
                                        long and try again.  Zero means "don't
                                        retry".  This is to allow "dial on
                                        demand" connections to have enough time
                                        to complete a connection.
confNO_RCPT_ACTION      NoRecipientAction
                                        [none] What to do if there are no legal
                                        recipient fields (To:, Cc: or Bcc:)
                                        in the message.  Legal values can
                                        be "none" to just leave the
                                        nonconforming message as is, "add-to"
                                        to add a To: header with all the
                                        known recipients (which may expose
                                        blind recipients), "add-apparently-to"
                                        to do the same but use Apparently-To:
                                        instead of To: (strongly discouraged
                                        in accordance with IETF standards),
                                        "add-bcc" to add an empty Bcc:
                                        header, or "add-to-undisclosed" to
                                        add the header
                                        ``To: undisclosed-recipients:;''.
confSAFE_FILE_ENV       SafeFileEnvironment
                                        [undefined] If set, sendmail will do a
                                        chroot() into this directory before
                                        writing files.
confCOLON_OK_IN_ADDR    ColonOkInAddr   [True unless Configuration Level > 6]
                                        If set, colons are treated as a regular
                                        character in addresses.  If not set,
                                        they are treated as the introducer to
                                        the RFC 822 "group" syntax.  Colons are
                                        handled properly in route-addrs.  This
                                        option defaults on for V5 and lower
                                        configuration files.
confMAX_QUEUE_RUN_SIZE  MaxQueueRunSize [0] If set, limit the maximum size of
                                        any given queue run to this number of
                                        entries.  Essentially, this will stop
                                        reading each queue directory after this
                                        number of entries are reached; it does
                                        _not_ pick the highest priority jobs,
                                        so this should be as large as your
                                        system can tolerate.  If not set, there
                                        is no limit.
confMAX_QUEUE_CHILDREN  MaxQueueChildren
                                        [undefined] Limits the maximum number
                                        of concurrent queue runners active.
                                        This is to keep system resources used
                                        within a reasonable limit.  Relates to
                                        Queue Groups and ForkEachJob.
confMAX_RUNNERS_PER_QUEUE       MaxRunnersPerQueue
                                        [1] Only active when MaxQueueChildren
                                        defined.  Controls the maximum number
                                        of queue runners (aka queue children)
                                        active at the same time in a work
                                        group.  See also MaxQueueChildren.
confDONT_EXPAND_CNAMES  DontExpandCnames
                                        [False] If set, $[ ... $] lookups that
                                        do DNS based lookups do not expand
                                        CNAME records.  This currently violates
                                        the published standards, but the IETF
                                        seems to be moving toward legalizing
                                        this.  For example, if "FTP.Foo.ORG"
                                        is a CNAME for "Cruft.Foo.ORG", then
                                        with this option set a lookup of
                                        "FTP" will return "FTP.Foo.ORG"; if
                                        clear it returns "Cruft.FOO.ORG".  N.B.
                                        you may not see any effect until your
                                        downstream neighbors stop doing CNAME
                                        lookups as well.
confFROM_LINE           UnixFromLine    [From $g $d] The From_ line used
                                        when sending to files or programs.
confSINGLE_LINE_FROM_HEADER  SingleLineFromHeader
                                        [False] From: lines that have
                                        embedded newlines are unwrapped
                                        onto one line.
confALLOW_BOGUS_HELO    AllowBogusHELO  [False] Allow HELO SMTP command that
                                        does not include a host name.
confMUST_QUOTE_CHARS    MustQuoteChars  [.'] Characters to be quoted in a full
                                        name phrase (@,;:\()[] are automatic).
confOPERATORS           OperatorChars   [.:%@!^/[]+] Address operator
                                        characters.
confSMTP_LOGIN_MSG      SmtpGreetingMessage
                                        [$j Sendmail $v/$Z; $b]
                                        The initial (spontaneous) SMTP
                                        greeting message.  The word "ESMTP"
                                        will be inserted between the first and
                                        second words to convince other
                                        sendmails to try to speak ESMTP.
confDONT_INIT_GROUPS    DontInitGroups  [False] If set, the initgroups(3)
                                        routine will never be invoked.  You
                                        might want to do this if you are
                                        running NIS and you have a large group
                                        map, since this call does a sequential
                                        scan of the map; in a large site this
                                        can cause your ypserv to run
                                        essentially full time.  If you set
                                        this, agents run on behalf of users
                                        will only have their primary
                                        (/etc/passwd) group permissions.
confUNSAFE_GROUP_WRITES UnsafeGroupWrites
                                        [True] If set, group-writable
                                        :include: and .forward files are
                                        considered "unsafe", that is, programs
                                        and files cannot be directly referenced
                                        from such files.  World-writable files
                                        are always considered unsafe.
                                        Notice: this option is deprecated and
                                        will be removed in future versions;
                                        Set GroupWritableForwardFileSafe
                                        and GroupWritableIncludeFileSafe in
                                        DontBlameSendmail if required.
confCONNECT_ONLY_TO     ConnectOnlyTo   [undefined] override connection
                                        address (for testing).
confCONTROL_SOCKET_NAME ControlSocketName
                                        [undefined] Control socket for daemon
                                        management.
confDOUBLE_BOUNCE_ADDRESS  DoubleBounceAddress
                                        [postmaster] If an error occurs when
                                        sending an error message, send that
                                        "double bounce" error message to this
                                        address.  If it expands to an empty
                                        string, double bounces are dropped.
confSOFT_BOUNCE         SoftBounce      [False] If set, issue temporary errors
                                        (4xy) instead of permanent errors
                                        (5xy).  This can be useful during
                                        testing of a new configuration to
                                        avoid erroneous bouncing of mails.
confDEAD_LETTER_DROP    DeadLetterDrop  [undefined] Filename to save bounce
                                        messages which could not be returned
                                        to the user or sent to postmaster.
                                        If not set, the queue file will
                                        be renamed.
confRRT_IMPLIES_DSN     RrtImpliesDsn   [False] Return-Receipt-To: header
                                        implies DSN request.
confRUN_AS_USER         RunAsUser       [undefined] If set, become this user
                                        when reading and delivering mail.
                                        Causes all file reads (e.g., .forward
                                        and :include: files) to be done as
                                        this user.  Also, all programs will
                                        be run as this user, and all output
                                        files will be written as this user.
confMAX_RCPTS_PER_MESSAGE  MaxRecipientsPerMessage
                                        [infinite] If set, allow no more than
                                        the specified number of recipients in
                                        an SMTP envelope.  Further recipients
                                        receive a 452 error code (i.e., they
                                        are deferred for the next delivery
                                        attempt).
confBAD_RCPT_THROTTLE   BadRcptThrottle [infinite] If set and the specified
                                        number of recipients in a single SMTP
                                        transaction have been rejected, sleep
                                        for one second after each subsequent
                                        RCPT command in that transaction.
confDONT_PROBE_INTERFACES  DontProbeInterfaces
                                        [False] If set, sendmail will _not_
                                        insert the names and addresses of any
                                        local interfaces into class {w}
                                        (list of known "equivalent" addresses).
                                        If you set this, you must also include
                                        some support for these addresses (e.g.,
                                        in a mailertable entry) -- otherwise,
                                        mail to addresses in this list will
                                        bounce with a configuration error.
                                        If set to "loopback" (without
                                        quotes), sendmail will skip
                                        loopback interfaces (e.g., "lo0").
confPID_FILE            PidFile         [system dependent] Location of pid
                                        file.
confPROCESS_TITLE_PREFIX  ProcessTitlePrefix
                                        [undefined] Prefix string for the
                                        process title shown on 'ps' listings.
confDONT_BLAME_SENDMAIL DontBlameSendmail
                                        [safe] Override sendmail's file
                                        safety checks.  This will definitely
                                        compromise system security and should
                                        not be used unless absolutely
                                        necessary.
confREJECT_MSG          -               [550 Access denied] The message
                                        given if the access database contains
                                        REJECT in the value portion.
confRELAY_MSG           -               [550 Relaying denied] The message
                                        given if an unauthorized relaying
                                        attempt is rejected.
confDF_BUFFER_SIZE      DataFileBufferSize
                                        [4096] The maximum size of a
                                        memory-buffered data (df) file
                                        before a disk-based file is used.
confXF_BUFFER_SIZE      XScriptFileBufferSize
                                        [4096] The maximum size of a
                                        memory-buffered transcript (xf)
                                        file before a disk-based file is
                                        used.
confAUTH_MECHANISMS     AuthMechanisms  [EXTERNAL GSSAPI KERBEROS_V4 DIGEST-MD5
                                        CRAM-MD5] List of authentication
                                        mechanisms for AUTH (separated by
                                        spaces).  The advertised list of
                                        authentication mechanisms will be the
                                        intersection of this list and the list
                                        of available mechanisms as determined
                                        by the Cyrus SASL library.
confAUTH_REALM          AuthRealm       [undefined] The authentication realm
                                        that is passed to the Cyrus SASL
                                        library.  If no realm is specified,
                                        $j is used.  See KNOWNBUGS.
confDEF_AUTH_INFO       DefaultAuthInfo [undefined] Name of file that contains
                                        authentication information for
                                        outgoing connections.  This file must
                                        contain the user id, the authorization
                                        id, the password (plain text), the
                                        realm to use, and the list of
                                        mechanisms to try, each on a separate
                                        line and must be readable by root (or
                                        the trusted user) only.  If no realm
                                        is specified, $j is used.  If no
                                        mechanisms are given in the file,
                                        AuthMechanisms is used.  Notice: this
                                        option is deprecated and will be
                                        removed in future versions; it doesn't
                                        work for the MSP since it can't read
                                        the file.  Use the authinfo ruleset
                                        instead.  See also the section SMTP
                                        AUTHENTICATION.
confAUTH_OPTIONS        AuthOptions     [undefined] If this option is 'A'
                                        then the AUTH= parameter for the
                                        MAIL FROM command is only issued
                                        when authentication succeeded.
                                        See doc/op/op.me for more options
                                        and details.
confAUTH_MAX_BITS       AuthMaxBits     [INT_MAX] Limit the maximum encryption
                                        strength for the security layer in
                                        SMTP AUTH (SASL).  Default is
                                        essentially unlimited.
confTLS_SRV_OPTIONS     TLSSrvOptions   If this option is 'V' no client
                                        verification is performed, i.e.,
                                        the server doesn't ask for a
                                        certificate.
confSERVER_SSL_OPTIONS  ServerSSLOptions        [undefined] SSL related
                                        options for server side.  See
                                        SSL_CTX_set_options(3) for a list.
confCLIENT_SSL_OPTIONS  ClientSSLOptions        [undefined] SSL related
                                        options for client side. See
                                        SSL_CTX_set_options(3) for a list.
confCIPHER_LIST         CipherList      [undefined] Cipher list for TLS.
                                        See ciphers(1) for possible values.
confLDAP_DEFAULT_SPEC   LDAPDefaultSpec [undefined] Default map
                                        specification for LDAP maps.  The
                                        value should only contain LDAP
                                        specific settings such as "-h host
                                        -p port -d bindDN", etc.  The
                                        settings will be used for all LDAP
                                        maps unless they are specified in
                                        the individual map specification
                                        ('K' command).
confCACERT_PATH         CACertPath      [undefined] Path to directory with
                                        certificates of CAs which must contain
                                        their hashes as filenames or links.
confCACERT              CACertFile      [undefined] File containing at least
                                        one CA certificate.
confSERVER_CERT         ServerCertFile  [undefined] File containing the
                                        cert of the server, i.e., this cert
                                        is used when sendmail acts as
                                        server.
confSERVER_KEY          ServerKeyFile   [undefined] File containing the
                                        private key belonging to the server
                                        cert.
confCLIENT_CERT         ClientCertFile  [undefined] File containing the
                                        cert of the client, i.e., this cert
                                        is used when sendmail acts as
                                        client.
confCLIENT_KEY          ClientKeyFile   [undefined] File containing the
                                        private key belonging to the client
                                        cert.
confCRL                 CRLFile         [undefined] File containing certificate
                                        revocation status, useful for X.509v3
                                        authentication.
confCRL_PATH            CRLPath         [undefined] Directory containing
                                        hashes pointing to certificate
                                        revocation status files.
confDH_PARAMETERS       DHParameters    [undefined] File containing the
                                        DH parameters.
confDANE                DANE            [false] Enable DANE support.
confRAND_FILE           RandFile        [undefined] File containing random
                                        data (use prefix file:) or the
                                        name of the UNIX socket if EGD is
                                        used (use prefix egd:).  STARTTLS
                                        requires this option if the compile
                                        flag HASURANDOM is not set (see
                                        sendmail/README).
confCERT_FINGERPRINT_ALGORITHM  CertFingerprintAlgorithm
                                        [undefined] The fingerprint algorithm
                                        (digest) to use for the presented
                                        cert.
confSSL_ENGINE          SSLEngine       [undefined] Name of SSLEngine.
confSSL_ENGINE_PATH     SSLEnginePath   [undefined] Path to dynamic library
                                        for SSLEngine.
confOPENSSL_CNF                         [/etc/mail/sendmail.ossl] Set the
                                        environment variable OPENSSL_CONF.
                                        An empty value disables setting it.
confNICE_QUEUE_RUN      NiceQueueRun    [undefined]  If set, the priority of
                                        queue runners is set the given value
                                        (nice(3)).
confDIRECT_SUBMISSION_MODIFIERS DirectSubmissionModifiers
                                        [undefined] Defines {daemon_flags}
                                        for direct submissions.
confUSE_MSP             UseMSP          [undefined] Use as mail submission
                                        program, see sendmail/SECURITY.
confDELIVER_BY_MIN      DeliverByMin    [0] Minimum time for Deliver By
                                        SMTP Service Extension (RFC 2852).
confREQUIRES_DIR_FSYNC  RequiresDirfsync        [true] RequiresDirfsync can
                                        be used to turn off the compile time
                                        flag REQUIRES_DIR_FSYNC at runtime.
                                        See sendmail/README for details.
confSHARED_MEMORY_KEY   SharedMemoryKey [0] Key for shared memory.
confSHARED_MEMORY_KEY_FILE
                        SharedMemoryKeyFile
                                        [undefined] File where the
                                        automatically selected key for
                                        shared memory is stored.
confFAST_SPLIT          FastSplit       [1] If set to a value greater than
                                        zero, the initial MX lookups on
                                        addresses is suppressed when they
                                        are sorted which may result in
                                        faster envelope splitting.  If the
                                        mail is submitted directly from the
                                        command line, then the value also
                                        limits the number of processes to
                                        deliver the envelopes.
confMAILBOX_DATABASE    MailboxDatabase [pw] Type of lookup to find
                                        information about local mailboxes.
confDEQUOTE_OPTS        -               [empty] Additional options for the
                                        dequote map.
confMAX_NOOP_COMMANDS   MaxNOOPCommands [20] Maximum number of "useless"
                                        commands before the SMTP server
                                        will slow down responding.
confHELO_NAME           HeloName        If defined, use as name for EHLO/HELO
                                        command (instead of $j).
confINPUT_MAIL_FILTERS  InputMailFilters
                                        A comma separated list of filters
                                        which determines which filters and
                                        the invocation sequence are
                                        contacted for incoming SMTP
                                        messages.  If none are set, no
                                        filters will be contacted.
confMILTER_LOG_LEVEL    Milter.LogLevel [9] Log level for input mail filter
                                        actions, defaults to LogLevel.
confMILTER_MACROS_CONNECT       Milter.macros.connect
                                        [j, _, {daemon_name}, {if_name},
                                        {if_addr}] Macros to transmit to
                                        milters when a session connection
                                        starts.
confMILTER_MACROS_HELO  Milter.macros.helo
                                        [{tls_version}, {cipher},
                                        {cipher_bits}, {cert_subject},
                                        {cert_issuer}] Macros to transmit to
                                        milters after HELO/EHLO command.
confMILTER_MACROS_ENVFROM       Milter.macros.envfrom
                                        [i, {auth_type}, {auth_authen},
                                        {auth_ssf}, {auth_author},
                                        {mail_mailer}, {mail_host},
                                        {mail_addr}] Macros to transmit to
                                        milters after MAIL FROM command.
confMILTER_MACROS_ENVRCPT       Milter.macros.envrcpt
                                        [{rcpt_mailer}, {rcpt_host},
                                        {rcpt_addr}] Macros to transmit to
                                        milters after RCPT TO command.
confMILTER_MACROS_EOM           Milter.macros.eom
                                        [{msg_id}] Macros to transmit to
                                        milters after the terminating
                                        DATA '.' is received.
confMILTER_MACROS_EOH           Milter.macros.eoh
                                        Macros to transmit to milters
                                        after the end of headers.
confMILTER_MACROS_DATA          Milter.macros.data
                                        Macros to transmit to milters
                                        after DATA command is received.


See also the description of OSTYPE for some parameters that can be
tweaked (generally pathnames to mailers).

ClientPortOptions and DaemonPortOptions are special cases since multiple
clients/daemons can be defined.  This can be done via

        CLIENT_OPTIONS(`field1=value1,field2=value2,...')
        DAEMON_OPTIONS(`field1=value1,field2=value2,...')

Note that multiple CLIENT_OPTIONS() commands (and therefore multiple
ClientPortOptions settings) are allowed in order to give settings for each
protocol family (e.g., one for Family=inet and one for Family=inet6).  A
restriction placed on one family only affects outgoing connections on that
particular family.

If DAEMON_OPTIONS is not used, then the default is

        DAEMON_OPTIONS(`Port=smtp, Name=MTA')
        DAEMON_OPTIONS(`Port=587, Name=MSA, M=E')

If you use one DAEMON_OPTIONS macro, it will alter the parameters
of the first of these.  The second will still be defaulted; it
represents a "Message Submission Agent" (MSA) as defined by RFC
2476 (see below).  To turn off the default definition for the MSA,
use FEATURE(`no_default_msa') (see also FEATURES).  If you use
additional DAEMON_OPTIONS macros, they will add additional daemons.

Example 1:  To change the port for the SMTP listener, while
still using the MSA default, use
        DAEMON_OPTIONS(`Port=925, Name=MTA')

Example 2:  To change the port for the MSA daemon, while still
using the default SMTP port, use
        FEATURE(`no_default_msa')
        DAEMON_OPTIONS(`Name=MTA')
        DAEMON_OPTIONS(`Port=987, Name=MSA, M=E')

Note that if the first of those DAEMON_OPTIONS lines were omitted, then
there would be no listener on the standard SMTP port.

Example 3: To listen on both IPv4 and IPv6 interfaces, use

        DAEMON_OPTIONS(`Name=MTA-v4, Family=inet')
        DAEMON_OPTIONS(`Name=MTA-v6, Family=inet6')

A "Message Submission Agent" still uses all of the same rulesets for
processing the message (and therefore still allows message rejection via
the check_* rulesets).  In accordance with the RFC, the MSA will ensure
that all domains in envelope addresses are fully qualified if the message
is relayed to another MTA.  It will also enforce the normal address syntax
rules and log error messages.  Additionally, by using the M=a modifier you
can require authentication before messages are accepted by the MSA.
Notice: Do NOT use the 'a' modifier on a public accessible MTA!  Finally,
the M=E modifier shown above disables ETRN as required by RFC 2476.

Mail filters can be defined using the INPUT_MAIL_FILTER() and MAIL_FILTER()
commands:

        INPUT_MAIL_FILTER(`sample', `S=local:/var/run/f1.sock')
        MAIL_FILTER(`myfilter', `S=inet:3333@localhost')

The INPUT_MAIL_FILTER() command causes the filter(s) to be called in the
same order they were specified by also setting confINPUT_MAIL_FILTERS.  A
filter can be defined without adding it to the input filter list by using
MAIL_FILTER() instead of INPUT_MAIL_FILTER() in your .mc file.
Alternatively, you can reset the list of filters and their order by setting
confINPUT_MAIL_FILTERS option after all INPUT_MAIL_FILTER() commands in
your .mc file.


+----------------------------+
| MESSAGE SUBMISSION PROGRAM |
+----------------------------+

The purpose of the message submission program (MSP) is explained
in sendmail/SECURITY.  This section contains a list of caveats and
a few hints how for those who want to tweak the default configuration
for it (which is installed as submit.cf).

Notice: do not add options/features to submit.mc unless you are
absolutely sure you need them.  Options you may want to change
include:

- confTRUSTED_USERS, FEATURE(`use_ct_file'), and confCT_FILE for
  avoiding X-Authentication warnings.
- confTIME_ZONE to change it from the default `USE_TZ'.
- confDELIVERY_MODE is set to interactive in msp.m4 instead
  of the default background mode.
- FEATURE(stickyhost) and LOCAL_RELAY to send unqualified addresses
  to the LOCAL_RELAY instead of the default relay.
- confRAND_FILE if you use STARTTLS and sendmail is not compiled with
  the flag HASURANDOM.

The MSP performs hostname canonicalization by default.  As also
explained in sendmail/SECURITY, mail may end up for various DNS
related reasons in the MSP queue. This problem can be minimized by
using

        FEATURE(`nocanonify', `canonify_hosts')
        define(`confDIRECT_SUBMISSION_MODIFIERS', `C')

See the discussion about nocanonify for possible side effects.

Some things are not intended to work with the MSP.  These include
features that influence the delivery process (e.g., mailertable,
aliases), or those that are only important for a SMTP server (e.g.,
virtusertable, DaemonPortOptions, multiple queues).  Moreover,
relaxing certain restrictions (RestrictQueueRun, permissions on
queue directory) or adding features (e.g., enabling prog/file mailer)
can cause security problems.

Other things don't work well with the MSP and require tweaking or
workarounds.  For example, to allow for client authentication it
is not just sufficient to provide a client certificate and the
corresponding key, but it is also necessary to make the key group
(smmsp) readable and tell sendmail not to complain about that, i.e.,

        define(`confDONT_BLAME_SENDMAIL', `GroupReadableKeyFile')

If the MSP should actually use AUTH then the necessary data
should be placed in a map as explained in SMTP AUTHENTICATION:

FEATURE(`authinfo', `DATABASE_MAP_TYPE /etc/mail/msp-authinfo')

/etc/mail/msp-authinfo should contain an entry like:

        AuthInfo:127.0.0.1      "U:smmsp" "P:secret" "M:DIGEST-MD5"

The file and the map created by makemap should be owned by smmsp,
its group should be smmsp, and it should have mode 640.  The database
used by the MTA for AUTH must have a corresponding entry.
Additionally the MTA must trust this authentication data so the AUTH=
part will be relayed on to the next hop.  This can be achieved by
adding the following to your sendmail.mc file:

        LOCAL_RULESETS
        SLocal_trust_auth
        R$*     $: $&{auth_authen}
        Rsmmsp  $# OK

Note: the authentication data can leak to local users who invoke
the MSP with debug options or even with -v.  For that reason either
an authentication mechanism that does not show the password in the
AUTH dialogue (e.g., DIGEST-MD5) or a different authentication
method like STARTTLS should be used.

feature/msp.m4 defines almost all settings for the MSP.  Most of
those should not be changed at all.  Some of the features and options
can be overridden if really necessary.  It is a bit tricky to do
this, because it depends on the actual way the option is defined
in feature/msp.m4.  If it is directly defined (i.e., define()) then
the modified value must be defined after

        FEATURE(`msp')

If it is conditionally defined (i.e., ifdef()) then the desired
value must be defined before the FEATURE line in the .mc file.
To see how the options are defined read feature/msp.m4.


+--------------------------+
| FORMAT OF FILES AND MAPS |
+--------------------------+

Files that define classes, i.e., F{classname}, consist of lines
each of which contains a single element of the class.  For example,
/etc/mail/local-host-names may have the following content:

my.domain
another.domain

Maps must be created using makemap(8) , e.g.,

        makemap hash MAP < MAP

In general, a text file from which a map is created contains lines
of the form

key     value

where 'key' and 'value' are also called LHS and RHS, respectively.
By default, the delimiter between LHS and RHS is a non-empty sequence
of white space characters.


+------------------+
| DIRECTORY LAYOUT |
+------------------+

Within this directory are several subdirectories, to wit:

m4              General support routines.  These are typically
                very important and should not be changed without
                very careful consideration.

cf              The configuration files themselves.  They have
                ".mc" suffixes, and must be run through m4 to
                become complete.  The resulting output should
                have a ".cf" suffix.

ostype          Definitions describing a particular operating
                system type.  These should always be referenced
                using the OSTYPE macro in the .mc file.  Examples
                include "bsd4.3", "bsd4.4", "sunos3.5", and
                "sunos4.1".

domain          Definitions describing a particular domain, referenced
                using the DOMAIN macro in the .mc file.  These are
                site dependent; for example, "CS.Berkeley.EDU.m4"
                describes hosts in the CS.Berkeley.EDU subdomain.

mailer          Descriptions of mailers.  These are referenced using
                the MAILER macro in the .mc file.

sh              Shell files used when building the .cf file from the
                .mc file in the cf subdirectory.

feature         These hold special orthogonal features that you might
                want to include.  They should be referenced using
                the FEATURE macro.

hack            Local hacks.  These can be referenced using the HACK
                macro.  They shouldn't be of more than voyeuristic
                interest outside the .Berkeley.EDU domain, but who knows?

siteconfig      Site configuration -- e.g., tables of locally connected
                UUCP sites.


+------------------------+
| ADMINISTRATIVE DETAILS |
+------------------------+

The following sections detail usage of certain internal parts of the
sendmail.cf file.  Read them carefully if you are trying to modify
the current model.  If you find the above descriptions adequate, these
should be {boring, confusing, tedious, ridiculous} (pick one or more).

RULESETS (* means built in to sendmail)

   0 *  Parsing
   1 *  Sender rewriting
   2 *  Recipient rewriting
   3 *  Canonicalization
   4 *  Post cleanup
   5 *  Local address rewrite (after aliasing)
  1x    mailer rules (sender qualification)
  2x    mailer rules (recipient qualification)
  3x    mailer rules (sender header qualification)
  4x    mailer rules (recipient header qualification)
  5x    mailer subroutines (general)
  6x    mailer subroutines (general)
  7x    mailer subroutines (general)
  8x    reserved
  90    Mailertable host stripping
  96    Bottom half of Ruleset 3 (ruleset 6 in old sendmail)
  97    Hook for recursive ruleset 0 call (ruleset 7 in old sendmail)
  98    Local part of ruleset 0 (ruleset 8 in old sendmail)


MAILERS

   0    local, prog     local and program mailers
   1    [e]smtp, relay  SMTP channel
   2    uucp-*          UNIX-to-UNIX Copy Program
   3    netnews         Network News delivery
   4    fax             Sam Leffler's HylaFAX software
   5    mail11          DECnet mailer


MACROS

   A
   B    Bitnet Relay
   C    DECnet Relay
   D    The local domain -- usually not needed
   E    reserved for X.400 Relay
   F    FAX Relay
   G
   H    mail Hub (for mail clusters)
   I
   J
   K
   L    Luser Relay
   M    Masquerade (who you claim to be)
   N
   O
   P
   Q
   R    Relay (for unqualified names)
   S    Smart Host
   T
   U    my UUCP name (if you have a UUCP connection)
   V    UUCP Relay (class {V} hosts)
   W    UUCP Relay (class {W} hosts)
   X    UUCP Relay (class {X} hosts)
   Y    UUCP Relay (all other hosts)
   Z    Version number


CLASSES

   A
   B    domains that are candidates for bestmx lookup
   C
   D
   E    addresses that should not seem to come from $M
   F    hosts this system forward for
   G    domains that should be looked up in genericstable
   H
   I
   J
   K
   L    addresses that should not be forwarded to $R
   M    domains that should be mapped to $M
   N    host/domains that should not be mapped to $M
   O    operators that indicate network operations (cannot be in local names)
   P    top level pseudo-domains: BITNET, DECNET, FAX, UUCP, etc.
   Q
   R    domains this system is willing to relay (pass anti-spam filters)
   S
   T
   U    locally connected UUCP hosts
   V    UUCP hosts connected to relay $V
   W    UUCP hosts connected to relay $W
   X    UUCP hosts connected to relay $X
   Y    locally connected smart UUCP hosts
   Z    locally connected domain-ized UUCP hosts
   .    the class containing only a dot
   [    the class containing only a left bracket


M4 DIVERSIONS

   1    Local host detection and resolution
   2    Local Ruleset 3 additions
   3    Local Ruleset 0 additions
   4    UUCP Ruleset 0 additions
   5    locally interpreted names (overrides $R)
   6    local configuration (at top of file)
   7    mailer definitions
   8    DNS based blocklists
   9    special local rulesets (1 and 2)