NEW SENDMAIL CONFIGURATION FILES Eric Allman @(#)README 6.2 (Berkeley) %G% This document describes the sendmail configuration files being used at Berkeley. These use features in the new (R6) sendmail, and although there is an ``OLDSENDMAIL'' mode, they haven't really been tested on old versions of sendmail and cannot be expected to work well. These configuration files are probably not as general as previous versions, and don't handle as many of the wierd cases automagically. I was able to simplify by 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 wierd world, things are going to get wierder 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 (which is a language unto itself) also works, but I don't intend to work so hard to keep this up in the future. [Note to GNU folks: the construct "define(`FOO')" should work without my having to add a null value.] 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. +--------------------------+ | 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. Let's examine a typical .mc file (cf/cs-exposed.mc): divert(-1) # # Copyright (c) 1983 Eric P. Allman # Copyright (c) 1988 The Regents of the University of California. # All rights reserved. # # Redistribution and use in source and binary forms are permitted # provided that the above copyright notice and this paragraph are # duplicated in all such forms and that any documentation, # advertising materials, and other materials related to such # distribution and use acknowledge that the software was developed # by the University of California, Berkeley. The name of the # University may not be used to endorse or promote products derived # from this software without specific prior written permission. # THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR # IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED # WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE. # The divert(-1) will delete the crud in the resulting output file. The copyright notice is what your lawyers require. Our lawyers require the one that I've included in my files. A copyleft is a copyright by another name. The next line MUST be include(`../m4/cf.m4') This will pull in the M4 macros you will need to make sense of everything else. As the saying goes, don't think about it, just do it. If you don't do it, don't bother reading the rest of this file. 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. DOMAIN(cs.exposed) This example exposes the host inside of the CS subdomain -- that is, it doesn't try to hide the name of the workstation to the outside world. Changing this to DOMAIN(cs.hidden) would have made outgoing messages refer to "@CS.Berkeley.EDU" instead of using the local hostname. Internaly this is effected by using "MASQUERADE_AS(CS.Berkeley.EDU)". MAILER(smtp) These describe the mailers used at the default CS site site. The local mailer is always included automatically. +--------+ | OSTYPE | +--------+ Note that cf/cs-exposed.mc omits an OSTYPE macro -- this assumes default Computer Science Division environment. There are several explicit environments available: bsd4.3, bsd4.4, hpux, irix, osf1, riscos4.5, sunos3.5, sunos4.1, and ultrix4.1. These change things like the location of the alias file and queue directory. Some of these files are identical to one another. Operating system definitions are easy to write. They may define the following variables (everything defaults, so an ostype file may be empty). ALIAS_FILE [/etc/aliases] The location of the text version of the alias file. HELP_FILE [/usr/lib/sendmail.hf] The name of the file containing information printed in response to the SMTP HELP command. LOCAL_MAILER [/bin/mail] The program used to deliver local mail. LOCAL_SHELL [/bin/sh] The shell used to deliver piped email. QUEUE_DIR [/var/spool/mqueue] The directory containing queue files. STATUS_FILE [/etc/sendmail.st] The file containing status information. LOCAL_MAILER_FLAGS [rn] The flags used by the local mailer. The flags lsDFMm are always included. HOSTMAP_SPEC [dbm -o /etc/hostmap] The value for the builtin hostmap key definition. You can redefine this to change the class, flags, and filename of the hostmap. The default flag (-o) makes this map optional. In addition, the following boolean flags may be defined -- the value is ignored. NEED_DOMAIN If set, the $j macro is defined as $w.$D. If not set, $j is defined as $w. If this is set, the domain must be defined using the line DD (probably in the domain file, but possibly in the .mc file). You will only need this if you define your system hostname without a domain (type "hostname" -- if it has no dots in the output, you qualify) or if you are running Ultrix or OSF/1 sendmail. Either of these is probably a mistake. +---------+ | 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 forward UUCP-addressed email. If not defined, all UUCP sites must be directly connected. BITNET_RELAY The host that will forward BITNET-addressed email. If not defined, the .BITNET pseudo-domain won't work. CSNET_RELAY The host that will forward CSNET-addressed email. If not defined, the .CSNET pseudo-domain won't work. LOCAL_RELAY 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 there are better methods. The domain file can also be used to define a domain name, if needed (using "DD") and set certain site-wide features, such as no_wildcard_MX. If all hosts at your site masquerade behind one email name, you could also use MASQUERADE_AS here. +---------+ | MAILERS | +---------+ There are fewer mailers supported in this version than the previous version, owing mostly to a simpler world. 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. uucp The Unix-to-Unix Copy Program mailer. Actually, this defines two mailers, "uucp" and "suucp". The latter is for when you know that the UUCP mailer at the other end can handle multiple recipients in one transfer. When you invoke this, sendmail looks for all names in the $=U class and sends them to the uucp mailer; all names in the $=Y class are sent to suucp. Note that this is a function of what version of rmail runs on the receiving end, and hence may be out of your control. +----------+ | 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. 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 ..." is probably superior. no_wildcard_MX This domain does not have a wildcard MX record that matches it. For example, I am in domain CS.Berkeley.EDU, and there is no MX record that matches *.CS.Berkeley.EDU or *.Berkeley.EDU, so I can safely use this feature. If you set this, you get better name server performance. Other FEATUREs should be defined, but I was trying to keep these config files fairly lean and mean. +-------+ | 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 | +--------------------+ 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) and the name of the class in which to store the host information. 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 $=W class will be used to store this list. [The machine ucbarpa is gone now, but I've left this out-of-date configuration file around to demonstrate how you might do this.] The siteconfig file (e.g., siteconfig/uucp.ucbvax.m4) contains nothing more than a sequence of SITE macros describing connectivity. For example: SITE(cnmat) SITE(sgi olympus) The second example demonstrates that you can use two names on the same line; these are usually aliases for the same host (or are at least in the same company). +-------------------+ | TWEAKING RULESETS | +-------------------+ For more complex configurations, you can define special rules. The macro LOCAL_RULE_3 introduces rules that are used in canonicalizing the names. Any modifications made here are reflected in the header. A common use is to convert old UUCP addreses to SMTP addresses using the UUCPSMTP macro. For example: LOCAL_RULE_3 UUCPSMTP(decvax, decvax.dec.com) UUCPSMTP(research, research.att.com) will cause addresses of the form "decvax!user" and "research!user" to be converted to "user@decvax.dec.com" and "user@research.att.com" respectively. This could also be used to look hosts in a database map: LOCAL_RULE_3 R$* < @ $+ > $* $: $1 < @ $(hostmap $2 $) > $3 This map would be defined in the LOCAL_CONFIG portion, as shown below. Similarly, LOCAL_RULE_0 can be used to introduce new parsing rules. For example, new rules are needed to parse hostnames that you accept via MX records. For example, you might have: LOCAL_RULE_0 R$+ < @ cnmat.Berkeley.EDU > $#uucp $@ cnmat $: $1 You would use this if you had installed an MX record for cnmat.Berkeley.EDU pointing at this host; this rule catches the message and forwards it on using UUCP. A similar macro is LOCAL_CONFIG. This introduces lines added after the boilerplate option setting but before rulesets, and can be used to override default options, declare local database maps, or whatever. For example: LOCAL_CONFIG Khostmap hash /etc/hostmap.db Kyplocal nis -m hosts.byname OJ/var/forward/$u:$z/.forward OL3 +---------------------------+ | MASQUERADING AND RELAYING | +---------------------------+ You can have your host masquerade as another using MASQUERADE_AS(host.domain) This causes outgoing SMTP mail to be labelled as coming from the indicated domain, rather than $j. One normally masquerades as one of your own subdomains (for example, it's unlikely that I would choose to masquerade as an MIT site). 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', hostname) 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 mail sent to a centralized hub, as for a shared /var/spool/mail scheme, use define(`MAIL_HUB', hostname) If you define both LOCAL_RELAY and MAIL_HUB, unqualified names and names in class L will be sent to the LOCAL_RELAY and other local names will be sent to MAIL_HUB. For example, if are on machine mastodon.CS.Berkeley.EDU, 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 MAIL_HUB set to mammoth.CS.Berkeley.EDU mammoth.CS.Berkeley.EDU mammoth.CS.Berkeley.EDU Both LOCAL_RELAY and mail.CS.Berkeley.EDU mammoth.CS.Berkeley.EDU MAIL_HUB set as above +-----------+ | 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, we contribute "cs.exposed.m4" and "cs.hidden.m4" which both describe hosts in the CS.Berkeley.EDU subdomain; the former displays the local hostname (e.g., mammoth.CS.Berkeley.EDU), whereas the latter does its best to hide the identity of the local workstation inside the CS 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 peccadilloes. 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) 6 Bottom half of Ruleset 3 7 Hook for recursive ruleset 0 call 8 9 MAILERS 0 local, prog local and program mailers 1 smtp SMTP channel 2 uucp MACROS A B Bitnet Relay C CSNET Relay D The local domain -- usually not needed E F G H mail Hub (for mail clusters) I J K L M Masquerade (who I claim to be) N O P Q R Relay (for unqualified names) S 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 C D E addresses that should not seem to come from $M F hosts we forward for G H I J K L addresses that should not be forwarded to $R M N O operators that indicate network operations (cannot be in local names) P Q R 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 . the class containing only a dot M4 DIVERSIONS 1 2 Local Ruleset 0 additions 3 Local Ruleset 3 additions 4 UUCP Ruleset 0 additions 5 locally interpreted names (overrides $R) 6 local configuration (at top of file) 7 mailer definitions 8 special local name recognition (late in ruleset 3) 9