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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. ***
*******************************************************************
+----------------------------+
| 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 connection 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 $h] The arguments passed to the relay mailer.
SMTP_MAILER_QGRP [undefined] The queue group for the smtp mailer.
ESMTP_MAILER_QGRP [undefined] The queue group for the esmtp mailer.
SMTP8_MAILER_QGRP [undefined] The queue group for the smtp8 mailer.
DSMTP_MAILER_QGRP [undefined] The queue group for the dsmtp mailer.
RELAY_MAILER_QGRP [undefined] The queue group for the relay mailer.
RELAY_MAILER_MAXMSGS [undefined] If defined, the maximum number of
messages to deliver in a single connection for the
relay mailer.
SMTP_MAILER_CHARSET [undefined] If defined, messages containing 8-bit data
that ARRIVE from an address that resolves to one of
the SMTP mailers and which are converted to MIME will
be labeled with this character set.
SMTP_MAILER_LL [990] The maximum line length for SMTP mailers
(except the relay mailer).
RELAY_MAILER_LL [2040] The maximum line length for the relay mailer.
UUCP_MAILER_PATH [/usr/bin/uux] The program used to send UUCP mail.
UUCP_MAILER_FLAGS [undefined] Flags added to UUCP mailer. Default
flags are `DFMhuU' (and `m' for uucp-new mailer,
minus `U' for uucp-dom mailer).
UUCP_MAILER_ARGS [uux - -r -z -a$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.
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
(http://www.flounder.net/~mrsam/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.
blacklist_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.
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.
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:::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.
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:1.2 RELAY
will whitelist IP address 1.2.3.4, so that the rDNS
blocking does apply to that IP address
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.
+-------+
| 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') (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
FEATURE(`nouucp') at all, addresses of the form
<example.net!user@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)
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.
Three tags are available:
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(`blacklist_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(`blacklist_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 blacklists 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 blacklist. You must select a DNS based blacklist 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 " $&{client_addr} " in dnsbl.example.com"')
If `t' is used, the error message is:
451 Temporary lookup failure of IP-ADDRESS at SERVER
where IP-ADDRESS and SERVER are replaced by the appropriate
information.
This FEATURE can be included several times to query different
DNS based rejection lists.
Notice: to avoid checking your own local domains against those
blacklists, use the access_db feature and add:
Connect:10.1 OK
Connect:127.0.0.1 RELAY
to the access map, where 10.1 is your local network. You may
want to use "RELAY" instead of "OK" to allow also relaying
instead of just disabling the DNS lookups in the blacklists.
The features described above make use of the check_relay, check_mail,
and check_rcpt rulesets. Note that check_relay checks the SMTP
client hostname and IP address when the connection is made to your
server. It does not check if a mail message is being relayed to
another server. That check is done in check_rcpt. If you wish to
include your own checks, you can put your checks in the rulesets
Local_check_relay, Local_check_mail, and Local_check_rcpt. For
example if you wanted to block senders with all numeric usernames
(i.e. 2312343@bigisp.com), you would use Local_check_mail and the
regex map:
LOCAL_CONFIG
Kallnumbers regex -a@MATCH ^[0-9]+$
LOCAL_RULESETS
SLocal_check_mail
# check address against various regex checks
R$* $: $>Parse0 $>3 $1
R$+ < @ bigisp.com. > $* $: $(allnumbers $1 $)
R@MATCH $#error $: 553 Header 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 blacklist 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
blacklists 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)/Email=
darth+cert@endmail.org
is encoded as:
/C=US/ST=California/O=endmail.org/OU=private/CN=
Darth+20Mail+20+28Cert+29/Email=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 ${cn_issuer}.
Examples:
To allow relaying for everyone who can present a cert signed by
/C=US/ST=California/O=endmail.org/OU=private/CN=
Darth+20Mail+20+28Cert+29/Email=darth+2Bcert@endmail.org
simply use:
CertIssuer:/C=US/ST=California/O=endmail.org/OU=private/CN=
Darth+20Mail+20+28Cert+29/Email=darth+2Bcert@endmail.org RELAY
To allow relaying only for a subset of machines that have a cert signed by
/C=US/ST=California/O=endmail.org/OU=private/CN=
Darth+20Mail+20+28Cert+29/Email=darth+2Bcert@endmail.org
use:
CertIssuer:/C=US/ST=California/O=endmail.org/OU=private/CN=
Darth+20Mail+20+28Cert+29/Email=darth+2Bcert@endmail.org SUBJECT
CertSubject:/C=US/ST=California/O=endmail.org/OU=private/CN=
DeathStar/Email=deathstar@endmail.org RELAY
Notes:
- line breaks have been inserted after "CN=" for readability,
each tagged entry must be one (long) line in the access map.
- if OpenSSL 0.9.7 or newer is used then the "Email=" part of a DN
is replaced by "emailAddress=".
Of course it is also possible to write a simple ruleset that allows
relaying for everyone who can present a cert that can be verified, e.g.,
LOCAL_RULESETS
SLocal_check_rcpt
R$* $: $&{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 (403 4.7.0)
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 ${cert_issuer}
Example: e-mail sent to secure.example.com should only use an encrypted
connection. E-mail received from hosts within the laptop.example.com domain
should only be accepted if they have been authenticated. The host which
receives e-mail for darth@endmail.org must present a cert that uses the
CN smtp.endmail.org.
TLS_Srv:secure.example.com ENCR:112
TLS_Clt:laptop.example.com PERM+VERIFY:112
TLS_Rcpt:darth@endmail.org ENCR:112+CN:smtp.endmail.org
Disabling STARTTLS And Setting SMTP Server Features
---------------------------------------------------
By default STARTTLS is used whenever possible. However, there are
some broken MTAs that don't properly implement STARTTLS. To be able
to send to (or receive from) those MTAs, the ruleset try_tls
(srv_features) can be used that work together with the access map.
Entries for the access map must be tagged with Try_TLS (Srv_Features)
and refer to the hostname or IP address of the connecting system.
A default case can be specified by using just the tag. For example,
the following entries in the access map:
Try_TLS:broken.server NO
Srv_Features:my.domain v
Srv_Features: V
will turn off STARTTLS when sending to broken.server (or any host
in that domain), and request a client certificate during the TLS
handshake only for hosts in my.domain. The valid entries on the RHS
for Srv_Features are listed in the Sendmail Installation and
Operations Guide.
Received: Header
----------------
The Received: header reveals whether STARTTLS has been used. It contains an
extra line:
(version=${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, try_tls, tls_rcpt,
tls_client, and tls_server can be made using LOCAL_SRV_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 publically
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_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.
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.
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 [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.
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.
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 certs of CAs.
confCACERT CACertFile [undefined] File containing one CA
cert.
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. Note that CRL requires
at least OpenSSL version 0.9.7.
confDH_PARAMETERS DHParameters [undefined] File containing the
DH parameters.
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).
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 blacklists
9 special local rulesets (1 and 2)
$Revision: 8.730 $, Last updated $Date: 2014-01-16 15:55:51 $