NEW SENDMAIL CONFIGURATION FILES Eric Allman @(#)README 8.174 (Berkeley) 6/30/98 This document describes the sendmail configuration files being used at Berkeley. These use features in the new (R8) sendmail; they will not work on other versions. These configuration files are probably not as general as previous versions, and don't handle as many of the weird cases automagically. I was able to simplify them for two reasons. First, the network has become more consistent -- for example, at this point, everyone on the internet is supposed to be running a name server, so hacks to handle NIC-registered hosts can go away. Second, I assumed that a subdomain would be running SMTP internally -- UUCP is presumed to be a long-haul protocol. I realize that this is not universal, but it does describe the vast majority of sites with which I am familiar, including those outside the US. Of course, the downside of this is that if you do live in a weird world, things are going to get weirder for you. I'm sorry about that, but at the time we at Berkeley had a problem, and it seemed like the right thing to do. This package requires a post-V7 version of m4; if you are running the 4.2bsd, SysV.2, or 7th Edition version, I suggest finding a friend with a newer version. You can m4-expand on their system, then run locally. SunOS's /usr/5bin/m4 or BSD-Net/2's m4 both work. GNU m4 version 1.1 or later also works. Unfortunately, I'm told that 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/m4-1.4.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. IF YOU DON'T HAVE A BERKELEY MAKE, don't despair! Just run "m4 ../m4/cf.m4 foo.mc > foo.cf" -- that should be all you need. There is also a fairly crude (but functional) Makefile.dist that works on the old version of make. To get started, you may want to look at tcpproto.mc (for TCP-only sites), uucpproto.mc (for UUCP-only sites), and clientproto.mc (for clusters of clients using a single mail host). Others are versions that we use at Berkeley, although not all are in current use. For example, ucbvax has gone away, but I've left ucbvax.mc in because it demonstrates some interesting techniques. I'm not pretending that this README describes everything that these configuration files can do; clever people can probably tweak them to great effect. But it should get you started. ******************************************************************* *** BE SURE YOU CUSTOMIZE THESE FILES! They have some *** *** Berkeley-specific assumptions built in, such as the name *** *** of our UUCP-relay. You'll want to create your own domain *** *** description, and use that in place of *** *** domain/Berkeley.EDU.m4. *** ******************************************************************* +--------------------------+ | 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 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 Sendmail, Inc. 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 I've included in my files. A copyleft is a copyright by another name. The divert(0) restores regular output. VERSIONID(`') VERSIONID is a macro that stuffs the version information into the resulting file. We use SCCS; you could use RCS, 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 site. The local mailer is always included automatically. Beware: MAILER declarations should always be at the end of the configuration file, and MAILER(smtp) should always precede MAILER(uucp). The general rules are that the order should be: VERSIONID OSTYPE DOMAIN FEATURE local macro definitions MAILER LOCAL_RULESET_* +----------------------------+ | 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'. +----------------+ | 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. 8.9 will serve as a transition release. Beginning with 8.10, all of the files will use this directory by default. +--------+ | 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/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 [/usr/lib/sendmail.hf] 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. STATUS_FILE [/etc/sendmail.st] The file containing status information. LOCAL_MAILER_PATH [/bin/mail] The program used to deliver local mail. LOCAL_MAILER_FLAGS [rmn9] The flags used by the local mailer. The flags lsDFM 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_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_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. USENET_MAILER_PATH [/usr/lib/news/inews] The name of the program used to submit news. USENET_MAILER_FLAGS [rlsDFMmn] The mailer flags for the usenet mailer. USENET_MAILER_ARGS [-m -h -n] The command line arguments for the usenet mailer. USENET_MAILER_MAX [100000] The maximum size of messages that will be accepted by 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' and "smtp8" adds `8'. SMTP_MAILER_MAX [undefined] The maximum size of messages that will be transported using the smtp, smtp8, or esmtp mailers. SMTP_MAILER_ARGS [IPC $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 [IPC $h] The arguments passed to the esmtp mailer. SMTP8_MAILER_ARGS [IPC $h] The arguments passed to the smtp8 mailer. RELAY_MAILER_ARGS [IPC $h] The arguments passed to the relay mailer. SMTP_MAILER_CHARSET [undefined] If defined, messages containing 8-bit data that ARRIVE from an address that resolves to one of the SMTP mailers and which are converted to MIME will be labeled with this character set. UUCP_MAILER_PATH [/usr/bin/uux] The program used to send UUCP mail. UUCP_MAILER_FLAGS [undefined] Flags added to UUCP mailer. Default flags are `DFMhuU' (and `m' for uucp-new mailer, minus `U' for uucp-dom mailer). UUCP_MAILER_ARGS [uux - -r -z -a$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. 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 "lsDFM" are always added. POP_MAILER_ARGS [pop $u] The arguments passed to 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. 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. PH_MAILER_PATH [/usr/local/etc/phquery] The path to the phquery program. PH_MAILER_FLAGS [ehmu] Flags for the phquery mailer. PH_MAILER_ARGS [phquery -- $u] -- arguments to the phquery mailer. CYRUS_MAILER_FLAGS [A5@/:|] 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_BB_MAILER_FLAGS [undefined] 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. confEBINDIR [/usr/libexec] The directory for executables. Currently used for FEATURE(local_lmtp) and FEATURE(smrsh). +---------+ | DOMAINS | +---------+ You will probably want to collect domain-dependent defines into one file, referenced by the DOMAIN macro. For example, our 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 DEPRECATED. The site that will handle unqualified names -- that is, names with out an @domain extension. 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. 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") 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, and always put MAILER(smtp) before MAILER(uucp) -- several features and definitions will modify the definition of mailers, and the smtp mailer modifies the UUCP mailer. 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 four 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), and "relay" for transmission to our RELAY_HOST, LUSER_RELAY, or MAILER_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 also 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 the $=U class and sends them to the uucp-old mailer; all names in the $=Y class are sent to uucp-new; and all names in the $=Z class 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.vix.com/hylafax/. 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. Within the 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. 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; 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 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 , "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/sendmail.cw file to get values for class $=w. The FEATURE may contain a single optional parameter -- 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. Available features are: use_cw_file Read the file /etc/sendmail.cw 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 ..." (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/sendmail.ct 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 not local; please try
'' message. If this is set, you can alias people who have left to their new address with ".REDIRECT" appended. nouucp Don't do anything special with UUCP addresses at all. nocanonify Don't pass addresses to $[ ... $] for canonification. 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. stickyhost If set, email sent to "user@local.host" are marked as "sticky" -- that is, the local addresses aren't matched against UDB and don't go through ruleset 5. This is used if you want a set up where "user" is not necessarily the same as "user@local.host", e.g., to make a distinct domain-wide namespace. Prior to 8.7 this was the default, and notsticky was used to turn this off. mailertable Include a "mailer table" which can be used to override routing for particular domains. The argument of the FEATURE may be the key definition. If none is specified, the definition used is: hash -o /etc/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". 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 will give an error message with the indicated code and message. 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 -o /etc/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 -o /etc/bitdomain.db Keys are the bitnet hostname; values are the corresponding internet hostname. uucpdomain Similar feature for UUCP hosts. The default map definition is: hash -o /etc/uudomain.db 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. 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 $=w are masqueraded. If this feature is given, only the hosts listed in $=M 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. genericstable This feature will cause certain addresses originating locally (i.e. that are unqualified) or a domain listed in $=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. This 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 the list of names given by the 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 -o /etc/genericstable The key for this table is either the full address or the unqualified username (the former is tried first); 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. virtusertable A domain-specific form of aliasing, allowing multiple virtual domains to be hosted on one machine. For example, if the virtuser table contained: info@foo.com foo-info info@bar.com bar-info @baz.org jane@elsewhere.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@elsewhere.net. The username from the original address is passed as %1 allowing: @foo.org %1@elsewhere.com meaning someone@foo.org will be sent to someone@elsewhere.com. All the host names on the left hand side (foo.com, bar.com, and baz.org) must be in $=w. The default map definition is: hash -o /etc/virtusertable A new definition can be specified as the second argument of the FEATURE macro, such as FEATURE(virtusertable, dbm -o /etc/mail/virtusers) nodns We aren't running DNS at our site (for example, we are UUCP-only connected). It's hard to consider this a "feature", but hey, it had to go somewhere. Actually, as of 8.7 this is a no-op -- remove "dns" from the hosts service switch entry instead. nullclient This is a special case -- it creates a stripped down 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 "nocanonify" (this causes addresses to be sent unqualified via the SMTP connection; normally they are qualified with the masquerade name, which defaults to the name of the hub machine). 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. local_procmail Use procmail as the local mailer. This 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. The argument to this feature is the pathname of procmail, 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. 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 domain and sending it to another host outside your domain). This option sets your site to allow mail relaying from any site to any site. In general, it is better to control the relaying more carefully with the access db and the 'R' class ($=R). 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 By default, only hosts listed as RELAY in the access db will be allowed to relay. This option also allows any host in your domain as defined by the 'm' class ($=m). relay_hosts_only By default, names that are listed as RELAY in the access db and class 'R' ($=R) are 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 lookup 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. See description below for more information before using this feature. 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. 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: ), you will need to use this feature to accept unqualified sender 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., 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. By default, the access database specification is ``hash -o /etc/mail/access''. The format of the database is described below. 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 below. rbl Turns on rejection of hosts found in the Realtime Blackhole List. If an argument is provided it is used as the name sever to contact; otherwise, the main RBL server at rbl.maps.vix.com is used. For details, see http://maps.vix.com/rbl/. loose_relay_check Normally, if a recipient using % addressing is used, 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. +-------+ | 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 we move 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. If your host is known by several different names, you need to augment the $=w class. This is a list of names by which you are 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/sendmail.cw containing a list of your aliases (one per line), and use ``FEATURE(use_cw_file)'' in the .mc file, or add the line: Cw alias.host.name at the end of that file. See the ``vangogh.mc'' file for an example. Be sure you use the fully-qualified name of the host, rather than a short name. 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. The $=W class 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 I've left this out-of-date configuration file 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 $=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). +--------------------+ | 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 accros 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 also specified. 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. Examples: We are 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, and can be used to declare local database maps or whatever. For example: LOCAL_CONFIG Khostmap hash /etc/hostmap.db 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 I 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 $=w, the list of local domain names). You can augment this list 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. 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. You can add users to this list using EXPOSED_USER(usernames) This adds users to class E; you could also use something like FE/etc/sendmail.cE 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 something like FL/etc/sendmail.cL 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. Names in $=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. 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 ---^ +---------------------------------+ | 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 domain to another site outside your domain) is denied by default. Note that this changed in sendmail 8.9; previous versions allowed relaying by default. If you 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' ($=R) using RELAY_DOMAIN() and RELAY_DOMAIN_FILE() or via the access database (described below). If you use FEATURE(relay_entire_domain) then any host in any of your local domains (that is, the $=m class) will be relayed. 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. Note that this 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. Along the same lines, FEATURE(relay_local_from) will allow relaying if the sender specifies a return path (i.e. MAIL FROM: ) domain which is a local domain. This 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. If source routing is used in the recipient address (i.e. RCPT TO: ), 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. 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). 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) 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) 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) The FEATURE macro can accept a second parameter giving the key file definition for the database; for example FEATURE(access_db, hash -o /etc/mail/access) The table itself uses e-mail addresses, domain names, and network numbers as keys. For example, spammer@aol.com REJECT cyberspammer.com REJECT 206.117.147 REJECT would refuse mail from spammer@aol.com, any user from cyberspammer.com (or any host within the cyberspammer.com domain), and any host on the 206.117.147.* network. The value part of the map can contain: OK accept mail even if other rules in the running ruleset would reject it. RELAY Allow domain to relay through your SMTP server. RELAY also serves an implicit OK for the other checks. REJECT reject the sender/recipient with a general purpose message. DISCARD discard the message completely using the $#discard mailer ### any text where ### is an RFC 821 compliant error code and "any text" is a message to return for the command. For example: cyberspammer.com 550 We don't accept mail from spammers okay.cyberspammer.com OK sendmail.org OK 128.32 RELAY would accept mail from okay.cyberspammer.com, but would reject mail from all other hosts at cyberspammer.com with the indicated message. It would allow accept mail from any hosts in the sendmail.org domain, and allow relaying for the 128.32.*.* network. Note, UUCP users may need to add hostname.UUCP to the access database or class 'R' ($=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' ($=R) to be fully qualified host names. You can also use the access database to block sender addresses based on the username portion of the address. For example: FREE.STEALTH.MAILER@ 550 Spam not accepted Note that you must include the @ after the username to signify that this database entry is for checking only the username portion of the sender address. If you use: FEATURE(blacklist_recipients) then you can add entries to the map for local users, hosts in your domains, or addresses in your domain which should not receive mail: badlocaluser 550 Mailbox disabled for this username host.mydomain.com 550 That host does not accept mail user@otherhost.mydomain.com 550 Mailbox disabled for this recipient This would prevent a recipient of badlocaluser@mydomain.com, any user at host.mydomain.com, and the single address user@otherhost.mydomain.com from receiving mail. There is also a ``Realtime Blackhole List'' run by the MAPS project at http://maps.vix.com/. This is a database maintained in DNS of spammers. To use this database, use FEATURE(rbl) This will cause sendmail to reject mail from any site in the Realtime Blackhole List database. You can specify an alternative RBL name server to contact by specifying an argument to the FEATURE. The features described above make use of the check_relay, check_mail, and check_rcpt rulesets. If you wish to include your own checks, you can put your checks in the rulesets Local_check_relay, Local_check_mail, and Local_check_rcpt. For example if you wanted to block senders with all numeric usernames (i.e. 2312343@bigisp.com), you would use Local_check_mail and the new regex map: LOCAL_CONFIG Kallnumbers regex -a@MATCH ^[0-9]+$ 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. Otherwise, the results of the local rewriting are ignored. 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_RULESETS HMessage-Id: $>CheckMessageId SCheckMessageId R< $+ @ $+ > $@ OK R$* $#error $: 553 Header Error +--------------------------------+ | ADDING NEW MAILERS OR RULESETS | +--------------------------------+ Sometimes you may need to add entirely new mailers or rulesets. They should be introduced with the constructs MAILER_DEFINITIONS and LOCAL_RULESETS respectively. For example: MAILER_DEFINITIONS Mmymailer, ... ... LOCAL_RULESETS Smyruleset ... +-------------------------------+ | NON-SMTP BASED CONFIGURATIONS | +-------------------------------+ These configuration files are designed primarily for use by SMTP-based sites. I don't pretend that they are well tuned for UUCP-only or UUCP-primarily nodes (the latter is defined as a small local net connected to the rest of the world via UUCP). However, there is one hook to handle some special cases. You can define a ``smart host'' that understands a richer address syntax using: define(`SMART_HOST', mailer:hostname) In this case, the ``mailer:'' defaults to "relay". Any messages that can't be handled using the usual UUCP rules are passed to this host. If you are on a local SMTP-based net that connects to the outside world via UUCP, you can use LOCAL_NET_CONFIG to add appropriate rules. For example: define(`SMART_HOST', suucp:uunet) LOCAL_NET_CONFIG R$* < @ $* .$m. > $* $#smtp $@ $2.$m. $: $1 < @ $2.$m. > $3 This will cause all names that end in your domain name ($m) via SMTP; anything else will be sent via suucp (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 +--------------------+ | 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 suucp:uuhost1 .bitnet smtp:relay.bit.net This should normally be stored in /etc/mailertable. The actual database version of the mailertable is built using: makemap hash /etc/mailertable.db < /etc/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 -- that is, they can be thought of as having a leading "*" wildcard. 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. 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. +--------------------------------+ | 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. (I would recommend 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 /usr/data/base.db < /usr/data/base.txt As a general rule, I am adamantly opposed to using full names as e-mail addresses, since they are not in any sense unique. For example, the Unix software-development community has two Andy Tannenbaums, 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. [Not that I expect anyone to pay any attention to my opinions.] +--------------------------------+ | 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". LDAP For notes on use LDAP in sendmail, see http://www.stanford.edu/~bbense/Inst.html +----------------+ | 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 isn't 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 I recommend you 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. 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 Description & [Default] ================ ============= ======================= 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 $Z macro If defined, this is appended to the configuration version name. confFROM_HEADER From: [$?x$x <$g>$|$g$.] The format of an internally generated From: address. confRECEIVED_HEADER Received: [$?sfrom $s $.$?_($?s$|from $.$_) $.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. confCW_FILE Fw class [/etc/sendmail.cw] Name of file used to get the local additions to the $=w (local host names) class. confCT_FILE Ft class [/etc/sendmail.ct] Name of file used to get the local additions to the $=t (trusted users) class. confCR_FILE FR class [/etc/mail/relay-domains] Name of file used to get the local additions to the $=R (hosts allowed to relay) class. 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). confSMTP_MAILER - [esmtp] The mailer name used when SMTP connectivity is required. One of "smtp", "smtp8", or "esmtp". confUUCP_MAILER - [uucp-old] The mailer to be used by default for bang-format recipient addresses. See also discussion of $=U, $=Y, and $=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. confAUTO_REBUILD AutoRebuildAliases [False] Automatically rebuild alias file if needed. confERROR_MODE ErrorMode [print] Error message mode. confERROR_MESSAGE ErrorHeader [undefined] Error message header/file. confSAVE_FROM_LINES SafeFromLine 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* UserErrorsTo [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 [False] Include sender in group expansions. 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. confDAEMON_OPTIONS DaemonPortOptions [none] SMTP daemon options. 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. 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_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 [30s] 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_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_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_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). 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. confTRY_NULL_MX_LIST TryNullMXList [False] If we are the best MX for a host and haven't made other arrangements, try connecting to the host directly; normally this would be a config error. confQUEUE_LA QueueLA [8] Load average at which queue-only function kicks in. confREFUSE_LA RefuseLA [12] Load average at which incoming SMTP connections are refused. 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. confCONNECTION_RATE_THROTTLE ConnectionRateThrottle [undefined] The maximum number of connections permitted per second. After this many connections are accepted, further connections will be delayed. If not set or <= 0, there is no limit. 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, 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/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:, "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 the 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. 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 [False] 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. confDOUBLE_BOUNCE_ADDRESS DoubleBounceAddress [postmaster] If an error occurs when sending an error message, send that "double bounce" error message to this address. 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. Intended for use only on firewalls where users do not have accounts. 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). confDONT_PROBE_INTERFACES DontProbeInterfaces [False] If set, sendmail will _not_ insert the names and addresses of any local interfaces into the $=w class (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. 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. See also the description of OSTYPE for some parameters that can be tweaked (generally pathnames to mailers). +-----------+ | HIERARCHY | +-----------+ 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? We've all got our own peccadillos. 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) 99 Guaranteed null (for debugging) 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 I claim to be) N O P Q R Relay (for unqualified names) S Smart Host T U my UUCP name (if I 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 we 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 O operators that indicate network operations (cannot be in local names) P top level pseudo-domains: BITNET, DECNET, FAX, UUCP, etc. Q R domains we are 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 9 special local rulesets (1 and 2)