1 . /////////////////////////////////////////////////////////////////////////////
2 . This is the primary source of the Exim Manual. It is an xfpt document that is
3 . converted into DocBook XML for subsequent conversion into printing and online
4 . formats. The markup used herein is "standard" xfpt markup, with some extras.
5 . The markup is summarized in a file called Markup.txt.
7 . WARNING: When you use the .new macro, make sure it appears *before* any
8 . adjacent index items; otherwise you get an empty "paragraph" which causes
9 . unwanted vertical space.
10 . /////////////////////////////////////////////////////////////////////////////
15 . /////////////////////////////////////////////////////////////////////////////
16 . This outputs the standard DocBook boilerplate.
17 . /////////////////////////////////////////////////////////////////////////////
21 . /////////////////////////////////////////////////////////////////////////////
22 . These lines are processing instructions for the Simple DocBook Processor that
23 . Philip Hazel has developed as a less cumbersome way of making PostScript and
24 . PDFs than using xmlto and fop. They will be ignored by all other XML
26 . /////////////////////////////////////////////////////////////////////////////
30 foot_right_recto="&chaptertitle; (&chapternumber;)"
31 foot_right_verso="&chaptertitle; (&chapternumber;)"
32 toc_chapter_blanks="yes,yes"
33 table_warn_overflow="overprint"
37 . /////////////////////////////////////////////////////////////////////////////
38 . This generate the outermost <book> element that wraps then entire document.
39 . /////////////////////////////////////////////////////////////////////////////
43 . /////////////////////////////////////////////////////////////////////////////
44 . These definitions set some parameters and save some typing. Remember that
45 . the <bookinfo> element must also be updated for each new edition.
46 . /////////////////////////////////////////////////////////////////////////////
48 .set previousversion "4.80"
51 .set ACL "access control lists (ACLs)"
52 .set I " "
55 . /////////////////////////////////////////////////////////////////////////////
56 . Additional xfpt markup used by this document, over and above the default
57 . provided in the xfpt library.
58 . /////////////////////////////////////////////////////////////////////////////
60 . --- Override the &$ flag to automatically insert a $ with the variable name
62 .flag &$ $& "<varname>$" "</varname>"
64 . --- Short flags for daggers in option headings. They will always be inside
65 . --- an italic string, but we want the daggers to be roman.
67 .flag &!! "</emphasis>†<emphasis>"
68 .flag &!? "</emphasis>‡<emphasis>"
70 . --- A macro for an Exim option definition heading, generating a one-line
71 . --- table with four columns. For cases when the option name is given with
72 . --- a space, so that it can be split, a fifth argument is used for the
82 .itable all 0 0 4 8* left 6* center 6* center 6* right
83 .row "&%$1%&" "Use: &'$2'&" "Type: &'$3'&" "Default: &'$4'&"
87 . --- A macro for the common 2-column tables. The width of the first column
88 . --- is suitable for the many tables at the start of the main options chapter;
89 . --- the small number of other 2-column tables override it.
91 .macro table2 196pt 254pt
92 .itable none 0 0 2 $1 left $2 left
95 . --- A macro that generates .row, but puts &I; at the start of the first
96 . --- argument, thus indenting it. Assume a minimum of two arguments, and
97 . --- allow up to four arguments, which is as many as we'll ever need.
101 .row "&I;$1" "$2" "$3" "$4"
105 .row "&I;$1" "$2" "$3"
113 . --- Macros for option, variable, and concept index entries. For a "range"
114 . --- style of entry, use .scindex for the start and .ecindex for the end. The
115 . --- first argument of .scindex and the only argument of .ecindex must be the
116 . --- ID that ties them together.
119 &<indexterm role="concept">&
120 &<primary>&$1&</primary>&
122 &<secondary>&$2&</secondary>&
128 &<indexterm role="concept" id="$1" class="startofrange">&
129 &<primary>&$2&</primary>&
131 &<secondary>&$3&</secondary>&
137 &<indexterm role="concept" startref="$1" class="endofrange"/>&
141 &<indexterm role="option">&
142 &<primary>&$1&</primary>&
144 &<secondary>&$2&</secondary>&
150 &<indexterm role="variable">&
151 &<primary>&$1&</primary>&
153 &<secondary>&$2&</secondary>&
159 .echo "** Don't use .index; use .cindex or .oindex or .vindex"
161 . ////////////////////////////////////////////////////////////////////////////
164 . ////////////////////////////////////////////////////////////////////////////
165 . The <bookinfo> element is removed from the XML before processing for Ascii
167 . ////////////////////////////////////////////////////////////////////////////
171 <title>Specification of the Exim Mail Transfer Agent</title>
172 <titleabbrev>The Exim MTA</titleabbrev>
173 <date>17 May 2012</date>
174 <author><firstname>Exim</firstname><surname>Maintainers</surname></author>
175 <authorinitials>EM</authorinitials>
176 <revhistory><revision>
177 <revnumber>4.80</revnumber>
178 <date>17 May 2012</date>
179 <authorinitials>EM</authorinitials>
180 </revision></revhistory>
181 <copyright><year>2012</year><holder>University of Cambridge</holder></copyright>
186 . /////////////////////////////////////////////////////////////////////////////
187 . This chunk of literal XML implements index entries of the form "x, see y" and
188 . "x, see also y". However, the DocBook DTD doesn't allow <indexterm> entries
189 . at the top level, so we have to put the .chapter directive first.
190 . /////////////////////////////////////////////////////////////////////////////
192 .chapter "Introduction" "CHID1"
195 <indexterm role="variable">
196 <primary>$1, $2, etc.</primary>
197 <see><emphasis>numerical variables</emphasis></see>
199 <indexterm role="concept">
200 <primary>address</primary>
201 <secondary>rewriting</secondary>
202 <see><emphasis>rewriting</emphasis></see>
204 <indexterm role="concept">
205 <primary>Bounce Address Tag Validation</primary>
206 <see><emphasis>BATV</emphasis></see>
208 <indexterm role="concept">
209 <primary>Client SMTP Authorization</primary>
210 <see><emphasis>CSA</emphasis></see>
212 <indexterm role="concept">
213 <primary>CR character</primary>
214 <see><emphasis>carriage return</emphasis></see>
216 <indexterm role="concept">
217 <primary>CRL</primary>
218 <see><emphasis>certificate revocation list</emphasis></see>
220 <indexterm role="concept">
221 <primary>delivery</primary>
222 <secondary>failure report</secondary>
223 <see><emphasis>bounce message</emphasis></see>
225 <indexterm role="concept">
226 <primary>dialup</primary>
227 <see><emphasis>intermittently connected hosts</emphasis></see>
229 <indexterm role="concept">
230 <primary>exiscan</primary>
231 <see><emphasis>content scanning</emphasis></see>
233 <indexterm role="concept">
234 <primary>failover</primary>
235 <see><emphasis>fallback</emphasis></see>
237 <indexterm role="concept">
238 <primary>fallover</primary>
239 <see><emphasis>fallback</emphasis></see>
241 <indexterm role="concept">
242 <primary>filter</primary>
243 <secondary>Sieve</secondary>
244 <see><emphasis>Sieve filter</emphasis></see>
246 <indexterm role="concept">
247 <primary>ident</primary>
248 <see><emphasis>RFC 1413</emphasis></see>
250 <indexterm role="concept">
251 <primary>LF character</primary>
252 <see><emphasis>linefeed</emphasis></see>
254 <indexterm role="concept">
255 <primary>maximum</primary>
256 <seealso><emphasis>limit</emphasis></seealso>
258 <indexterm role="concept">
259 <primary>monitor</primary>
260 <see><emphasis>Exim monitor</emphasis></see>
262 <indexterm role="concept">
263 <primary>no_<emphasis>xxx</emphasis></primary>
264 <see>entry for xxx</see>
266 <indexterm role="concept">
267 <primary>NUL</primary>
268 <see><emphasis>binary zero</emphasis></see>
270 <indexterm role="concept">
271 <primary>passwd file</primary>
272 <see><emphasis>/etc/passwd</emphasis></see>
274 <indexterm role="concept">
275 <primary>process id</primary>
276 <see><emphasis>pid</emphasis></see>
278 <indexterm role="concept">
279 <primary>RBL</primary>
280 <see><emphasis>DNS list</emphasis></see>
282 <indexterm role="concept">
283 <primary>redirection</primary>
284 <see><emphasis>address redirection</emphasis></see>
286 <indexterm role="concept">
287 <primary>return path</primary>
288 <seealso><emphasis>envelope sender</emphasis></seealso>
290 <indexterm role="concept">
291 <primary>scanning</primary>
292 <see><emphasis>content scanning</emphasis></see>
294 <indexterm role="concept">
295 <primary>SSL</primary>
296 <see><emphasis>TLS</emphasis></see>
298 <indexterm role="concept">
299 <primary>string</primary>
300 <secondary>expansion</secondary>
301 <see><emphasis>expansion</emphasis></see>
303 <indexterm role="concept">
304 <primary>top bit</primary>
305 <see><emphasis>8-bit characters</emphasis></see>
307 <indexterm role="concept">
308 <primary>variables</primary>
309 <see><emphasis>expansion, variables</emphasis></see>
311 <indexterm role="concept">
312 <primary>zero, binary</primary>
313 <see><emphasis>binary zero</emphasis></see>
319 . /////////////////////////////////////////////////////////////////////////////
320 . This is the real start of the first chapter. See the comment above as to why
321 . we can't have the .chapter line here.
322 . chapter "Introduction"
323 . /////////////////////////////////////////////////////////////////////////////
325 Exim is a mail transfer agent (MTA) for hosts that are running Unix or
326 Unix-like operating systems. It was designed on the assumption that it would be
327 run on hosts that are permanently connected to the Internet. However, it can be
328 used on intermittently connected hosts with suitable configuration adjustments.
330 Configuration files currently exist for the following operating systems: AIX,
331 BSD/OS (aka BSDI), Darwin (Mac OS X), DGUX, Dragonfly, FreeBSD, GNU/Hurd,
332 GNU/Linux, HI-OSF (Hitachi), HI-UX, HP-UX, IRIX, MIPS RISCOS, NetBSD, OpenBSD,
333 OpenUNIX, QNX, SCO, SCO SVR4.2 (aka UNIX-SV), Solaris (aka SunOS5), SunOS4,
334 Tru64-Unix (formerly Digital UNIX, formerly DEC-OSF1), Ultrix, and Unixware.
335 Some of these operating systems are no longer current and cannot easily be
336 tested, so the configuration files may no longer work in practice.
338 There are also configuration files for compiling Exim in the Cygwin environment
339 that can be installed on systems running Windows. However, this document does
340 not contain any information about running Exim in the Cygwin environment.
342 The terms and conditions for the use and distribution of Exim are contained in
343 the file &_NOTICE_&. Exim is distributed under the terms of the GNU General
344 Public Licence, a copy of which may be found in the file &_LICENCE_&.
346 The use, supply or promotion of Exim for the purpose of sending bulk,
347 unsolicited electronic mail is incompatible with the basic aims of the program,
348 which revolve around the free provision of a service that enhances the quality
349 of personal communications. The author of Exim regards indiscriminate
350 mass-mailing as an antisocial, irresponsible abuse of the Internet.
352 Exim owes a great deal to Smail 3 and its author, Ron Karr. Without the
353 experience of running and working on the Smail 3 code, I could never have
354 contemplated starting to write a new MTA. Many of the ideas and user interfaces
355 were originally taken from Smail 3, though the actual code of Exim is entirely
356 new, and has developed far beyond the initial concept.
358 Many people, both in Cambridge and around the world, have contributed to the
359 development and the testing of Exim, and to porting it to various operating
360 systems. I am grateful to them all. The distribution now contains a file called
361 &_ACKNOWLEDGMENTS_&, in which I have started recording the names of
365 .section "Exim documentation" "SECID1"
366 . Keep this example change bar when updating the documentation!
369 .cindex "documentation"
370 This edition of the Exim specification applies to version &version; of Exim.
371 Substantive changes from the &previousversion; edition are marked in some
372 renditions of the document; this paragraph is so marked if the rendition is
373 capable of showing a change indicator.
376 This document is very much a reference manual; it is not a tutorial. The reader
377 is expected to have some familiarity with the SMTP mail transfer protocol and
378 with general Unix system administration. Although there are some discussions
379 and examples in places, the information is mostly organized in a way that makes
380 it easy to look up, rather than in a natural order for sequential reading.
381 Furthermore, the manual aims to cover every aspect of Exim in detail, including
382 a number of rarely-used, special-purpose features that are unlikely to be of
385 .cindex "books about Exim"
386 An &"easier"& discussion of Exim which provides more in-depth explanatory,
387 introductory, and tutorial material can be found in a book entitled &'The Exim
388 SMTP Mail Server'& (second edition, 2007), published by UIT Cambridge
389 (&url(http://www.uit.co.uk/exim-book/)).
391 This book also contains a chapter that gives a general introduction to SMTP and
392 Internet mail. Inevitably, however, the book is unlikely to be fully up-to-date
393 with the latest release of Exim. (Note that the earlier book about Exim,
394 published by O'Reilly, covers Exim 3, and many things have changed in Exim 4.)
396 .cindex "Debian" "information sources"
397 If you are using a Debian distribution of Exim, you will find information about
398 Debian-specific features in the file
399 &_/usr/share/doc/exim4-base/README.Debian_&.
400 The command &(man update-exim.conf)& is another source of Debian-specific
403 .cindex "&_doc/NewStuff_&"
404 .cindex "&_doc/ChangeLog_&"
406 As the program develops, there may be features in newer versions that have not
407 yet made it into this document, which is updated only when the most significant
408 digit of the fractional part of the version number changes. Specifications of
409 new features that are not yet in this manual are placed in the file
410 &_doc/NewStuff_& in the Exim distribution.
412 Some features may be classified as &"experimental"&. These may change
413 incompatibly while they are developing, or even be withdrawn. For this reason,
414 they are not documented in this manual. Information about experimental features
415 can be found in the file &_doc/experimental.txt_&.
417 All changes to the program (whether new features, bug fixes, or other kinds of
418 change) are noted briefly in the file called &_doc/ChangeLog_&.
420 .cindex "&_doc/spec.txt_&"
421 This specification itself is available as an ASCII file in &_doc/spec.txt_& so
422 that it can easily be searched with a text editor. Other files in the &_doc_&
426 .row &_OptionLists.txt_& "list of all options in alphabetical order"
427 .row &_dbm.discuss.txt_& "discussion about DBM libraries"
428 .row &_exim.8_& "a man page of Exim's command line options"
429 .row &_experimental.txt_& "documentation of experimental features"
430 .row &_filter.txt_& "specification of the filter language"
431 .row &_Exim3.upgrade_& "upgrade notes from release 2 to release 3"
432 .row &_Exim4.upgrade_& "upgrade notes from release 3 to release 4"
435 The main specification and the specification of the filtering language are also
436 available in other formats (HTML, PostScript, PDF, and Texinfo). Section
437 &<<SECTavail>>& below tells you how to get hold of these.
441 .section "FTP and web sites" "SECID2"
444 The primary site for Exim source distributions is currently the University of
445 Cambridge's FTP site, whose contents are described in &'Where to find the Exim
446 distribution'& below. In addition, there is a web site and an FTP site at
447 &%exim.org%&. These are now also hosted at the University of Cambridge. The
448 &%exim.org%& site was previously hosted for a number of years by Energis
449 Squared, formerly Planet Online Ltd, whose support I gratefully acknowledge.
453 As well as Exim distribution tar files, the Exim web site contains a number of
454 differently formatted versions of the documentation. A recent addition to the
455 online information is the Exim wiki (&url(http://wiki.exim.org)),
456 which contains what used to be a separate FAQ, as well as various other
457 examples, tips, and know-how that have been contributed by Exim users.
460 An Exim Bugzilla exists at &url(http://bugs.exim.org). You can use
461 this to report bugs, and also to add items to the wish list. Please search
462 first to check that you are not duplicating a previous entry.
466 .section "Mailing lists" "SECID3"
467 .cindex "mailing lists" "for Exim users"
468 The following Exim mailing lists exist:
471 .row &'exim-announce@exim.org'& "Moderated, low volume announcements list"
472 .row &'exim-users@exim.org'& "General discussion list"
473 .row &'exim-dev@exim.org'& "Discussion of bugs, enhancements, etc."
474 .row &'exim-cvs@exim.org'& "Automated commit messages from the VCS"
477 You can subscribe to these lists, change your existing subscriptions, and view
478 or search the archives via the mailing lists link on the Exim home page.
479 .cindex "Debian" "mailing list for"
480 If you are using a Debian distribution of Exim, you may wish to subscribe to
481 the Debian-specific mailing list &'pkg-exim4-users@lists.alioth.debian.org'&
484 &url(http://lists.alioth.debian.org/mailman/listinfo/pkg-exim4-users)
486 Please ask Debian-specific questions on this list and not on the general Exim
489 .section "Exim training" "SECID4"
490 .cindex "training courses"
491 Training courses in Cambridge (UK) used to be run annually by the author of
492 Exim, before he retired. At the time of writing, there are no plans to run
493 further Exim courses in Cambridge. However, if that changes, relevant
494 information will be posted at &url(http://www-tus.csx.cam.ac.uk/courses/exim/).
496 .section "Bug reports" "SECID5"
497 .cindex "bug reports"
498 .cindex "reporting bugs"
499 Reports of obvious bugs can be emailed to &'bugs@exim.org'& or reported
500 via the Bugzilla (&url(http://bugs.exim.org)). However, if you are unsure
501 whether some behaviour is a bug or not, the best thing to do is to post a
502 message to the &'exim-dev'& mailing list and have it discussed.
506 .section "Where to find the Exim distribution" "SECTavail"
508 .cindex "distribution" "ftp site"
509 The master ftp site for the Exim distribution is
511 &*ftp://ftp.csx.cam.ac.uk/pub/software/email/exim*&
515 &*ftp://ftp.exim.org/pub/exim*&
517 The file references that follow are relative to the &_exim_& directories at
518 these sites. There are now quite a number of independent mirror sites around
519 the world. Those that I know about are listed in the file called &_Mirrors_&.
521 Within the &_exim_& directory there are subdirectories called &_exim3_& (for
522 previous Exim 3 distributions), &_exim4_& (for the latest Exim 4
523 distributions), and &_Testing_& for testing versions. In the &_exim4_&
524 subdirectory, the current release can always be found in files called
527 &_exim-n.nn.tar.bz2_&
529 where &'n.nn'& is the highest such version number in the directory. The two
530 files contain identical data; the only difference is the type of compression.
531 The &_.bz2_& file is usually a lot smaller than the &_.gz_& file.
533 .cindex "distribution" "signing details"
534 .cindex "distribution" "public key"
535 .cindex "public key for signed distribution"
536 The distributions are currently signed with Nigel Metheringham's GPG key. The
537 corresponding public key is available from a number of keyservers, and there is
538 also a copy in the file &_nigel-pubkey.asc_&. The signatures for the tar bundles are
541 &_exim-n.nn.tar.gz.asc_&
542 &_exim-n.nn.tar.bz2.asc_&
544 For each released version, the log of changes is made separately available in a
545 separate file in the directory &_ChangeLogs_& so that it is possible to
546 find out what has changed without having to download the entire distribution.
548 .cindex "documentation" "available formats"
549 The main distribution contains ASCII versions of this specification and other
550 documentation; other formats of the documents are available in separate files
551 inside the &_exim4_& directory of the FTP site:
553 &_exim-html-n.nn.tar.gz_&
554 &_exim-pdf-n.nn.tar.gz_&
555 &_exim-postscript-n.nn.tar.gz_&
556 &_exim-texinfo-n.nn.tar.gz_&
558 These tar files contain only the &_doc_& directory, not the complete
559 distribution, and are also available in &_.bz2_& as well as &_.gz_& forms.
562 .section "Limitations" "SECID6"
564 .cindex "limitations of Exim"
565 .cindex "bang paths" "not handled by Exim"
566 Exim is designed for use as an Internet MTA, and therefore handles addresses in
567 RFC 2822 domain format only. It cannot handle UUCP &"bang paths"&, though
568 simple two-component bang paths can be converted by a straightforward rewriting
569 configuration. This restriction does not prevent Exim from being interfaced to
570 UUCP as a transport mechanism, provided that domain addresses are used.
572 .cindex "domainless addresses"
573 .cindex "address" "without domain"
574 Exim insists that every address it handles has a domain attached. For incoming
575 local messages, domainless addresses are automatically qualified with a
576 configured domain value. Configuration options specify from which remote
577 systems unqualified addresses are acceptable. These are then qualified on
580 .cindex "transport" "external"
581 .cindex "external transports"
582 The only external transport mechanisms that are currently implemented are SMTP
583 and LMTP over a TCP/IP network (including support for IPv6). However, a pipe
584 transport is available, and there are facilities for writing messages to files
585 and pipes, optionally in &'batched SMTP'& format; these facilities can be used
586 to send messages to other transport mechanisms such as UUCP, provided they can
587 handle domain-style addresses. Batched SMTP input is also catered for.
589 Exim is not designed for storing mail for dial-in hosts. When the volumes of
590 such mail are large, it is better to get the messages &"delivered"& into files
591 (that is, off Exim's queue) and subsequently passed on to the dial-in hosts by
594 Although Exim does have basic facilities for scanning incoming messages, these
595 are not comprehensive enough to do full virus or spam scanning. Such operations
596 are best carried out using additional specialized software packages. If you
597 compile Exim with the content-scanning extension, straightforward interfaces to
598 a number of common scanners are provided.
602 .section "Run time configuration" "SECID7"
603 Exim's run time configuration is held in a single text file that is divided
604 into a number of sections. The entries in this file consist of keywords and
605 values, in the style of Smail 3 configuration files. A default configuration
606 file which is suitable for simple online installations is provided in the
607 distribution, and is described in chapter &<<CHAPdefconfil>>& below.
610 .section "Calling interface" "SECID8"
611 .cindex "Sendmail compatibility" "command line interface"
612 Like many MTAs, Exim has adopted the Sendmail command line interface so that it
613 can be a straight replacement for &_/usr/lib/sendmail_& or
614 &_/usr/sbin/sendmail_& when sending mail, but you do not need to know anything
615 about Sendmail in order to run Exim. For actions other than sending messages,
616 Sendmail-compatible options also exist, but those that produce output (for
617 example, &%-bp%&, which lists the messages on the queue) do so in Exim's own
618 format. There are also some additional options that are compatible with Smail
619 3, and some further options that are new to Exim. Chapter &<<CHAPcommandline>>&
620 documents all Exim's command line options. This information is automatically
621 made into the man page that forms part of the Exim distribution.
623 Control of messages on the queue can be done via certain privileged command
624 line options. There is also an optional monitor program called &'eximon'&,
625 which displays current information in an X window, and which contains a menu
626 interface to Exim's command line administration options.
630 .section "Terminology" "SECID9"
631 .cindex "terminology definitions"
632 .cindex "body of message" "definition of"
633 The &'body'& of a message is the actual data that the sender wants to transmit.
634 It is the last part of a message, and is separated from the &'header'& (see
635 below) by a blank line.
637 .cindex "bounce message" "definition of"
638 When a message cannot be delivered, it is normally returned to the sender in a
639 delivery failure message or a &"non-delivery report"& (NDR). The term
640 &'bounce'& is commonly used for this action, and the error reports are often
641 called &'bounce messages'&. This is a convenient shorthand for &"delivery
642 failure error report"&. Such messages have an empty sender address in the
643 message's &'envelope'& (see below) to ensure that they cannot themselves give
644 rise to further bounce messages.
646 The term &'default'& appears frequently in this manual. It is used to qualify a
647 value which is used in the absence of any setting in the configuration. It may
648 also qualify an action which is taken unless a configuration setting specifies
651 The term &'defer'& is used when the delivery of a message to a specific
652 destination cannot immediately take place for some reason (a remote host may be
653 down, or a user's local mailbox may be full). Such deliveries are &'deferred'&
656 The word &'domain'& is sometimes used to mean all but the first component of a
657 host's name. It is &'not'& used in that sense here, where it normally refers to
658 the part of an email address following the @ sign.
660 .cindex "envelope, definition of"
661 .cindex "sender" "definition of"
662 A message in transit has an associated &'envelope'&, as well as a header and a
663 body. The envelope contains a sender address (to which bounce messages should
664 be delivered), and any number of recipient addresses. References to the
665 sender or the recipients of a message usually mean the addresses in the
666 envelope. An MTA uses these addresses for delivery, and for returning bounce
667 messages, not the addresses that appear in the header lines.
669 .cindex "message" "header, definition of"
670 .cindex "header section" "definition of"
671 The &'header'& of a message is the first part of a message's text, consisting
672 of a number of lines, each of which has a name such as &'From:'&, &'To:'&,
673 &'Subject:'&, etc. Long header lines can be split over several text lines by
674 indenting the continuations. The header is separated from the body by a blank
677 .cindex "local part" "definition of"
678 .cindex "domain" "definition of"
679 The term &'local part'&, which is taken from RFC 2822, is used to refer to that
680 part of an email address that precedes the @ sign. The part that follows the
681 @ sign is called the &'domain'& or &'mail domain'&.
683 .cindex "local delivery" "definition of"
684 .cindex "remote delivery, definition of"
685 The terms &'local delivery'& and &'remote delivery'& are used to distinguish
686 delivery to a file or a pipe on the local host from delivery by SMTP over
687 TCP/IP to another host. As far as Exim is concerned, all hosts other than the
688 host it is running on are &'remote'&.
690 .cindex "return path" "definition of"
691 &'Return path'& is another name that is used for the sender address in a
694 .cindex "queue" "definition of"
695 The term &'queue'& is used to refer to the set of messages awaiting delivery,
696 because this term is in widespread use in the context of MTAs. However, in
697 Exim's case the reality is more like a pool than a queue, because there is
698 normally no ordering of waiting messages.
700 .cindex "queue runner" "definition of"
701 The term &'queue runner'& is used to describe a process that scans the queue
702 and attempts to deliver those messages whose retry times have come. This term
703 is used by other MTAs, and also relates to the command &%runq%&, but in Exim
704 the waiting messages are normally processed in an unpredictable order.
706 .cindex "spool directory" "definition of"
707 The term &'spool directory'& is used for a directory in which Exim keeps the
708 messages on its queue &-- that is, those that it is in the process of
709 delivering. This should not be confused with the directory in which local
710 mailboxes are stored, which is called a &"spool directory"& by some people. In
711 the Exim documentation, &"spool"& is always used in the first sense.
718 . ////////////////////////////////////////////////////////////////////////////
719 . ////////////////////////////////////////////////////////////////////////////
721 .chapter "Incorporated code" "CHID2"
722 .cindex "incorporated code"
723 .cindex "regular expressions" "library"
725 A number of pieces of external code are included in the Exim distribution.
728 Regular expressions are supported in the main Exim program and in the
729 Exim monitor using the freely-distributable PCRE library, copyright
730 © University of Cambridge. The source to PCRE is no longer shipped with
731 Exim, so you will need to use the version of PCRE shipped with your system,
732 or obtain and install the full version of the library from
733 &url(ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre).
735 .cindex "cdb" "acknowledgment"
736 Support for the cdb (Constant DataBase) lookup method is provided by code
737 contributed by Nigel Metheringham of (at the time he contributed it) Planet
738 Online Ltd. The implementation is completely contained within the code of Exim.
739 It does not link against an external cdb library. The code contains the
740 following statements:
743 Copyright © 1998 Nigel Metheringham, Planet Online Ltd
745 This program is free software; you can redistribute it and/or modify it under
746 the terms of the GNU General Public License as published by the Free Software
747 Foundation; either version 2 of the License, or (at your option) any later
749 This code implements Dan Bernstein's Constant DataBase (cdb) spec. Information,
750 the spec and sample code for cdb can be obtained from
751 &url(http://www.pobox.com/~djb/cdb.html). This implementation borrows
752 some code from Dan Bernstein's implementation (which has no license
753 restrictions applied to it).
756 .cindex "SPA authentication"
757 .cindex "Samba project"
758 .cindex "Microsoft Secure Password Authentication"
759 Client support for Microsoft's &'Secure Password Authentication'& is provided
760 by code contributed by Marc Prud'hommeaux. Server support was contributed by
761 Tom Kistner. This includes code taken from the Samba project, which is released
765 .cindex "&'pwcheck'& daemon"
766 .cindex "&'pwauthd'& daemon"
767 Support for calling the Cyrus &'pwcheck'& and &'saslauthd'& daemons is provided
768 by code taken from the Cyrus-SASL library and adapted by Alexander S.
769 Sabourenkov. The permission notice appears below, in accordance with the
770 conditions expressed therein.
773 Copyright © 2001 Carnegie Mellon University. All rights reserved.
775 Redistribution and use in source and binary forms, with or without
776 modification, are permitted provided that the following conditions
780 Redistributions of source code must retain the above copyright
781 notice, this list of conditions and the following disclaimer.
783 Redistributions in binary form must reproduce the above copyright
784 notice, this list of conditions and the following disclaimer in
785 the documentation and/or other materials provided with the
788 The name &"Carnegie Mellon University"& must not be used to
789 endorse or promote products derived from this software without
790 prior written permission. For permission or any other legal
791 details, please contact
793 Office of Technology Transfer
794 Carnegie Mellon University
796 Pittsburgh, PA 15213-3890
797 (412) 268-4387, fax: (412) 268-7395
798 tech-transfer@andrew.cmu.edu
801 Redistributions of any form whatsoever must retain the following
804 &"This product includes software developed by Computing Services
805 at Carnegie Mellon University (&url(http://www.cmu.edu/computing/)."&
807 CARNEGIE MELLON UNIVERSITY DISCLAIMS ALL WARRANTIES WITH REGARD TO
808 THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
809 AND FITNESS, IN NO EVENT SHALL CARNEGIE MELLON UNIVERSITY BE LIABLE
810 FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
811 WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN
812 AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
813 OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
818 .cindex "Exim monitor" "acknowledgment"
821 The Exim Monitor program, which is an X-Window application, includes
822 modified versions of the Athena StripChart and TextPop widgets.
823 This code is copyright by DEC and MIT, and their permission notice appears
824 below, in accordance with the conditions expressed therein.
827 Copyright 1987, 1988 by Digital Equipment Corporation, Maynard, Massachusetts,
828 and the Massachusetts Institute of Technology, Cambridge, Massachusetts.
832 Permission to use, copy, modify, and distribute this software and its
833 documentation for any purpose and without fee is hereby granted,
834 provided that the above copyright notice appear in all copies and that
835 both that copyright notice and this permission notice appear in
836 supporting documentation, and that the names of Digital or MIT not be
837 used in advertising or publicity pertaining to distribution of the
838 software without specific, written prior permission.
840 DIGITAL DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING
841 ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL
842 DIGITAL BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR
843 ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
844 WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
845 ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
850 Many people have contributed code fragments, some large, some small, that were
851 not covered by any specific licence requirements. It is assumed that the
852 contributors are happy to see their code incorporated into Exim under the GPL.
859 . ////////////////////////////////////////////////////////////////////////////
860 . ////////////////////////////////////////////////////////////////////////////
862 .chapter "How Exim receives and delivers mail" "CHID11" &&&
863 "Receiving and delivering mail"
866 .section "Overall philosophy" "SECID10"
867 .cindex "design philosophy"
868 Exim is designed to work efficiently on systems that are permanently connected
869 to the Internet and are handling a general mix of mail. In such circumstances,
870 most messages can be delivered immediately. Consequently, Exim does not
871 maintain independent queues of messages for specific domains or hosts, though
872 it does try to send several messages in a single SMTP connection after a host
873 has been down, and it also maintains per-host retry information.
876 .section "Policy control" "SECID11"
877 .cindex "policy control" "overview"
878 Policy controls are now an important feature of MTAs that are connected to the
879 Internet. Perhaps their most important job is to stop MTAs being abused as
880 &"open relays"& by misguided individuals who send out vast amounts of
881 unsolicited junk, and want to disguise its source. Exim provides flexible
882 facilities for specifying policy controls on incoming mail:
885 .cindex "&ACL;" "introduction"
886 Exim 4 (unlike previous versions of Exim) implements policy controls on
887 incoming mail by means of &'Access Control Lists'& (ACLs). Each list is a
888 series of statements that may either grant or deny access. ACLs can be used at
889 several places in the SMTP dialogue while receiving a message from a remote
890 host. However, the most common places are after each RCPT command, and at the
891 very end of the message. The sysadmin can specify conditions for accepting or
892 rejecting individual recipients or the entire message, respectively, at these
893 two points (see chapter &<<CHAPACL>>&). Denial of access results in an SMTP
896 An ACL is also available for locally generated, non-SMTP messages. In this
897 case, the only available actions are to accept or deny the entire message.
899 When Exim is compiled with the content-scanning extension, facilities are
900 provided in the ACL mechanism for passing the message to external virus and/or
901 spam scanning software. The result of such a scan is passed back to the ACL,
902 which can then use it to decide what to do with the message.
904 When a message has been received, either from a remote host or from the local
905 host, but before the final acknowledgment has been sent, a locally supplied C
906 function called &[local_scan()]& can be run to inspect the message and decide
907 whether to accept it or not (see chapter &<<CHAPlocalscan>>&). If the message
908 is accepted, the list of recipients can be modified by the function.
910 Using the &[local_scan()]& mechanism is another way of calling external scanner
911 software. The &%SA-Exim%& add-on package works this way. It does not require
912 Exim to be compiled with the content-scanning extension.
914 After a message has been accepted, a further checking mechanism is available in
915 the form of the &'system filter'& (see chapter &<<CHAPsystemfilter>>&). This
916 runs at the start of every delivery process.
921 .section "User filters" "SECID12"
922 .cindex "filter" "introduction"
923 .cindex "Sieve filter"
924 In a conventional Exim configuration, users are able to run private filters by
925 setting up appropriate &_.forward_& files in their home directories. See
926 chapter &<<CHAPredirect>>& (about the &(redirect)& router) for the
927 configuration needed to support this, and the separate document entitled
928 &'Exim's interfaces to mail filtering'& for user details. Two different kinds
929 of filtering are available:
932 Sieve filters are written in the standard filtering language that is defined
935 Exim filters are written in a syntax that is unique to Exim, but which is more
936 powerful than Sieve, which it pre-dates.
939 User filters are run as part of the routing process, described below.
943 .section "Message identification" "SECTmessiden"
944 .cindex "message ids" "details of format"
945 .cindex "format" "of message id"
946 .cindex "id of message"
951 Every message handled by Exim is given a &'message id'& which is sixteen
952 characters long. It is divided into three parts, separated by hyphens, for
953 example &`16VDhn-0001bo-D3`&. Each part is a sequence of letters and digits,
954 normally encoding numbers in base 62. However, in the Darwin operating
955 system (Mac OS X) and when Exim is compiled to run under Cygwin, base 36
956 (avoiding the use of lower case letters) is used instead, because the message
957 id is used to construct file names, and the names of files in those systems are
958 not always case-sensitive.
960 .cindex "pid (process id)" "re-use of"
961 The detail of the contents of the message id have changed as Exim has evolved.
962 Earlier versions relied on the operating system not re-using a process id (pid)
963 within one second. On modern operating systems, this assumption can no longer
964 be made, so the algorithm had to be changed. To retain backward compatibility,
965 the format of the message id was retained, which is why the following rules are
969 The first six characters of the message id are the time at which the message
970 started to be received, to a granularity of one second. That is, this field
971 contains the number of seconds since the start of the epoch (the normal Unix
972 way of representing the date and time of day).
974 After the first hyphen, the next six characters are the id of the process that
975 received the message.
977 There are two different possibilities for the final two characters:
979 .oindex "&%localhost_number%&"
980 If &%localhost_number%& is not set, this value is the fractional part of the
981 time of reception, normally in units of 1/2000 of a second, but for systems
982 that must use base 36 instead of base 62 (because of case-insensitive file
983 systems), the units are 1/1000 of a second.
985 If &%localhost_number%& is set, it is multiplied by 200 (100) and added to
986 the fractional part of the time, which in this case is in units of 1/200
991 After a message has been received, Exim waits for the clock to tick at the
992 appropriate resolution before proceeding, so that if another message is
993 received by the same process, or by another process with the same (re-used)
994 pid, it is guaranteed that the time will be different. In most cases, the clock
995 will already have ticked while the message was being received.
998 .section "Receiving mail" "SECID13"
999 .cindex "receiving mail"
1000 .cindex "message" "reception"
1001 The only way Exim can receive mail from another host is using SMTP over
1002 TCP/IP, in which case the sender and recipient addresses are transferred using
1003 SMTP commands. However, from a locally running process (such as a user's MUA),
1004 there are several possibilities:
1007 If the process runs Exim with the &%-bm%& option, the message is read
1008 non-interactively (usually via a pipe), with the recipients taken from the
1009 command line, or from the body of the message if &%-t%& is also used.
1011 If the process runs Exim with the &%-bS%& option, the message is also read
1012 non-interactively, but in this case the recipients are listed at the start of
1013 the message in a series of SMTP RCPT commands, terminated by a DATA
1014 command. This is so-called &"batch SMTP"& format,
1015 but it isn't really SMTP. The SMTP commands are just another way of passing
1016 envelope addresses in a non-interactive submission.
1018 If the process runs Exim with the &%-bs%& option, the message is read
1019 interactively, using the SMTP protocol. A two-way pipe is normally used for
1020 passing data between the local process and the Exim process.
1021 This is &"real"& SMTP and is handled in the same way as SMTP over TCP/IP. For
1022 example, the ACLs for SMTP commands are used for this form of submission.
1024 A local process may also make a TCP/IP call to the host's loopback address
1025 (127.0.0.1) or any other of its IP addresses. When receiving messages, Exim
1026 does not treat the loopback address specially. It treats all such connections
1027 in the same way as connections from other hosts.
1031 .cindex "message sender, constructed by Exim"
1032 .cindex "sender" "constructed by Exim"
1033 In the three cases that do not involve TCP/IP, the sender address is
1034 constructed from the login name of the user that called Exim and a default
1035 qualification domain (which can be set by the &%qualify_domain%& configuration
1036 option). For local or batch SMTP, a sender address that is passed using the
1037 SMTP MAIL command is ignored. However, the system administrator may allow
1038 certain users (&"trusted users"&) to specify a different sender address
1039 unconditionally, or all users to specify certain forms of different sender
1040 address. The &%-f%& option or the SMTP MAIL command is used to specify these
1041 different addresses. See section &<<SECTtrustedadmin>>& for details of trusted
1042 users, and the &%untrusted_set_sender%& option for a way of allowing untrusted
1043 users to change sender addresses.
1045 Messages received by either of the non-interactive mechanisms are subject to
1046 checking by the non-SMTP ACL, if one is defined. Messages received using SMTP
1047 (either over TCP/IP, or interacting with a local process) can be checked by a
1048 number of ACLs that operate at different times during the SMTP session. Either
1049 individual recipients, or the entire message, can be rejected if local policy
1050 requirements are not met. The &[local_scan()]& function (see chapter
1051 &<<CHAPlocalscan>>&) is run for all incoming messages.
1053 Exim can be configured not to start a delivery process when a message is
1054 received; this can be unconditional, or depend on the number of incoming SMTP
1055 connections or the system load. In these situations, new messages wait on the
1056 queue until a queue runner process picks them up. However, in standard
1057 configurations under normal conditions, delivery is started as soon as a
1058 message is received.
1064 .section "Handling an incoming message" "SECID14"
1065 .cindex "spool directory" "files that hold a message"
1066 .cindex "file" "how a message is held"
1067 When Exim accepts a message, it writes two files in its spool directory. The
1068 first contains the envelope information, the current status of the message, and
1069 the header lines, and the second contains the body of the message. The names of
1070 the two spool files consist of the message id, followed by &`-H`& for the
1071 file containing the envelope and header, and &`-D`& for the data file.
1073 .cindex "spool directory" "&_input_& sub-directory"
1074 By default all these message files are held in a single directory called
1075 &_input_& inside the general Exim spool directory. Some operating systems do
1076 not perform very well if the number of files in a directory gets large; to
1077 improve performance in such cases, the &%split_spool_directory%& option can be
1078 used. This causes Exim to split up the input files into 62 sub-directories
1079 whose names are single letters or digits. When this is done, the queue is
1080 processed one sub-directory at a time instead of all at once, which can improve
1081 overall performance even when there are not enough files in each directory to
1082 affect file system performance.
1084 The envelope information consists of the address of the message's sender and
1085 the addresses of the recipients. This information is entirely separate from
1086 any addresses contained in the header lines. The status of the message includes
1087 a list of recipients who have already received the message. The format of the
1088 first spool file is described in chapter &<<CHAPspool>>&.
1090 .cindex "rewriting" "addresses"
1091 Address rewriting that is specified in the rewrite section of the configuration
1092 (see chapter &<<CHAPrewrite>>&) is done once and for all on incoming addresses,
1093 both in the header lines and the envelope, at the time the message is accepted.
1094 If during the course of delivery additional addresses are generated (for
1095 example, via aliasing), these new addresses are rewritten as soon as they are
1096 generated. At the time a message is actually delivered (transported) further
1097 rewriting can take place; because this is a transport option, it can be
1098 different for different forms of delivery. It is also possible to specify the
1099 addition or removal of certain header lines at the time the message is
1100 delivered (see chapters &<<CHAProutergeneric>>& and
1101 &<<CHAPtransportgeneric>>&).
1105 .section "Life of a message" "SECID15"
1106 .cindex "message" "life of"
1107 .cindex "message" "frozen"
1108 A message remains in the spool directory until it is completely delivered to
1109 its recipients or to an error address, or until it is deleted by an
1110 administrator or by the user who originally created it. In cases when delivery
1111 cannot proceed &-- for example, when a message can neither be delivered to its
1112 recipients nor returned to its sender, the message is marked &"frozen"& on the
1113 spool, and no more deliveries are attempted.
1115 .cindex "frozen messages" "thawing"
1116 .cindex "message" "thawing frozen"
1117 An administrator can &"thaw"& such messages when the problem has been
1118 corrected, and can also freeze individual messages by hand if necessary. In
1119 addition, an administrator can force a delivery error, causing a bounce message
1122 .oindex "&%timeout_frozen_after%&"
1123 .oindex "&%ignore_bounce_errors_after%&"
1124 There are options called &%ignore_bounce_errors_after%& and
1125 &%timeout_frozen_after%&, which discard frozen messages after a certain time.
1126 The first applies only to frozen bounces, the second to any frozen messages.
1128 .cindex "message" "log file for"
1129 .cindex "log" "file for each message"
1130 While Exim is working on a message, it writes information about each delivery
1131 attempt to its main log file. This includes successful, unsuccessful, and
1132 delayed deliveries for each recipient (see chapter &<<CHAPlog>>&). The log
1133 lines are also written to a separate &'message log'& file for each message.
1134 These logs are solely for the benefit of the administrator, and are normally
1135 deleted along with the spool files when processing of a message is complete.
1136 The use of individual message logs can be disabled by setting
1137 &%no_message_logs%&; this might give an improvement in performance on very busy
1140 .cindex "journal file"
1141 .cindex "file" "journal"
1142 All the information Exim itself needs to set up a delivery is kept in the first
1143 spool file, along with the header lines. When a successful delivery occurs, the
1144 address is immediately written at the end of a journal file, whose name is the
1145 message id followed by &`-J`&. At the end of a delivery run, if there are some
1146 addresses left to be tried again later, the first spool file (the &`-H`& file)
1147 is updated to indicate which these are, and the journal file is then deleted.
1148 Updating the spool file is done by writing a new file and renaming it, to
1149 minimize the possibility of data loss.
1151 Should the system or the program crash after a successful delivery but before
1152 the spool file has been updated, the journal is left lying around. The next
1153 time Exim attempts to deliver the message, it reads the journal file and
1154 updates the spool file before proceeding. This minimizes the chances of double
1155 deliveries caused by crashes.
1159 .section "Processing an address for delivery" "SECTprocaddress"
1160 .cindex "drivers" "definition of"
1161 .cindex "router" "definition of"
1162 .cindex "transport" "definition of"
1163 The main delivery processing elements of Exim are called &'routers'& and
1164 &'transports'&, and collectively these are known as &'drivers'&. Code for a
1165 number of them is provided in the source distribution, and compile-time options
1166 specify which ones are included in the binary. Run time options specify which
1167 ones are actually used for delivering messages.
1169 .cindex "drivers" "instance definition"
1170 Each driver that is specified in the run time configuration is an &'instance'&
1171 of that particular driver type. Multiple instances are allowed; for example,
1172 you can set up several different &(smtp)& transports, each with different
1173 option values that might specify different ports or different timeouts. Each
1174 instance has its own identifying name. In what follows we will normally use the
1175 instance name when discussing one particular instance (that is, one specific
1176 configuration of the driver), and the generic driver name when discussing
1177 the driver's features in general.
1179 A &'router'& is a driver that operates on an address, either determining how
1180 its delivery should happen, by assigning it to a specific transport, or
1181 converting the address into one or more new addresses (for example, via an
1182 alias file). A router may also explicitly choose to fail an address, causing it
1185 A &'transport'& is a driver that transmits a copy of the message from Exim's
1186 spool to some destination. There are two kinds of transport: for a &'local'&
1187 transport, the destination is a file or a pipe on the local host, whereas for a
1188 &'remote'& transport the destination is some other host. A message is passed
1189 to a specific transport as a result of successful routing. If a message has
1190 several recipients, it may be passed to a number of different transports.
1192 .cindex "preconditions" "definition of"
1193 An address is processed by passing it to each configured router instance in
1194 turn, subject to certain preconditions, until a router accepts the address or
1195 specifies that it should be bounced. We will describe this process in more
1196 detail shortly. First, as a simple example, we consider how each recipient
1197 address in a message is processed in a small configuration of three routers.
1199 To make this a more concrete example, it is described in terms of some actual
1200 routers, but remember, this is only an example. You can configure Exim's
1201 routers in many different ways, and there may be any number of routers in a
1204 The first router that is specified in a configuration is often one that handles
1205 addresses in domains that are not recognized specially by the local host. These
1206 are typically addresses for arbitrary domains on the Internet. A precondition
1207 is set up which looks for the special domains known to the host (for example,
1208 its own domain name), and the router is run for addresses that do &'not'&
1209 match. Typically, this is a router that looks up domains in the DNS in order to
1210 find the hosts to which this address routes. If it succeeds, the address is
1211 assigned to a suitable SMTP transport; if it does not succeed, the router is
1212 configured to fail the address.
1214 The second router is reached only when the domain is recognized as one that
1215 &"belongs"& to the local host. This router does redirection &-- also known as
1216 aliasing and forwarding. When it generates one or more new addresses from the
1217 original, each of them is routed independently from the start. Otherwise, the
1218 router may cause an address to fail, or it may simply decline to handle the
1219 address, in which case the address is passed to the next router.
1221 The final router in many configurations is one that checks to see if the
1222 address belongs to a local mailbox. The precondition may involve a check to
1223 see if the local part is the name of a login account, or it may look up the
1224 local part in a file or a database. If its preconditions are not met, or if
1225 the router declines, we have reached the end of the routers. When this happens,
1226 the address is bounced.
1230 .section "Processing an address for verification" "SECID16"
1231 .cindex "router" "for verification"
1232 .cindex "verifying address" "overview"
1233 As well as being used to decide how to deliver to an address, Exim's routers
1234 are also used for &'address verification'&. Verification can be requested as
1235 one of the checks to be performed in an ACL for incoming messages, on both
1236 sender and recipient addresses, and it can be tested using the &%-bv%& and
1237 &%-bvs%& command line options.
1239 When an address is being verified, the routers are run in &"verify mode"&. This
1240 does not affect the way the routers work, but it is a state that can be
1241 detected. By this means, a router can be skipped or made to behave differently
1242 when verifying. A common example is a configuration in which the first router
1243 sends all messages to a message-scanning program, unless they have been
1244 previously scanned. Thus, the first router accepts all addresses without any
1245 checking, making it useless for verifying. Normally, the &%no_verify%& option
1246 would be set for such a router, causing it to be skipped in verify mode.
1251 .section "Running an individual router" "SECTrunindrou"
1252 .cindex "router" "running details"
1253 .cindex "preconditions" "checking"
1254 .cindex "router" "result of running"
1255 As explained in the example above, a number of preconditions are checked before
1256 running a router. If any are not met, the router is skipped, and the address is
1257 passed to the next router. When all the preconditions on a router &'are'& met,
1258 the router is run. What happens next depends on the outcome, which is one of
1262 &'accept'&: The router accepts the address, and either assigns it to a
1263 transport, or generates one or more &"child"& addresses. Processing the
1264 original address ceases,
1265 .oindex "&%unseen%&"
1266 unless the &%unseen%& option is set on the router. This option
1267 can be used to set up multiple deliveries with different routing (for example,
1268 for keeping archive copies of messages). When &%unseen%& is set, the address is
1269 passed to the next router. Normally, however, an &'accept'& return marks the
1272 Any child addresses generated by the router are processed independently,
1273 starting with the first router by default. It is possible to change this by
1274 setting the &%redirect_router%& option to specify which router to start at for
1275 child addresses. Unlike &%pass_router%& (see below) the router specified by
1276 &%redirect_router%& may be anywhere in the router configuration.
1278 &'pass'&: The router recognizes the address, but cannot handle it itself. It
1279 requests that the address be passed to another router. By default the address
1280 is passed to the next router, but this can be changed by setting the
1281 &%pass_router%& option. However, (unlike &%redirect_router%&) the named router
1282 must be below the current router (to avoid loops).
1284 &'decline'&: The router declines to accept the address because it does not
1285 recognize it at all. By default, the address is passed to the next router, but
1286 this can be prevented by setting the &%no_more%& option. When &%no_more%& is
1287 set, all the remaining routers are skipped. In effect, &%no_more%& converts
1288 &'decline'& into &'fail'&.
1290 &'fail'&: The router determines that the address should fail, and queues it for
1291 the generation of a bounce message. There is no further processing of the
1292 original address unless &%unseen%& is set on the router.
1294 &'defer'&: The router cannot handle the address at the present time. (A
1295 database may be offline, or a DNS lookup may have timed out.) No further
1296 processing of the address happens in this delivery attempt. It is tried again
1297 next time the message is considered for delivery.
1299 &'error'&: There is some error in the router (for example, a syntax error in
1300 its configuration). The action is as for defer.
1303 If an address reaches the end of the routers without having been accepted by
1304 any of them, it is bounced as unrouteable. The default error message in this
1305 situation is &"unrouteable address"&, but you can set your own message by
1306 making use of the &%cannot_route_message%& option. This can be set for any
1307 router; the value from the last router that &"saw"& the address is used.
1309 Sometimes while routing you want to fail a delivery when some conditions are
1310 met but others are not, instead of passing the address on for further routing.
1311 You can do this by having a second router that explicitly fails the delivery
1312 when the relevant conditions are met. The &(redirect)& router has a &"fail"&
1313 facility for this purpose.
1316 .section "Duplicate addresses" "SECID17"
1317 .cindex "case of local parts"
1318 .cindex "address duplicate, discarding"
1319 .cindex "duplicate addresses"
1320 Once routing is complete, Exim scans the addresses that are assigned to local
1321 and remote transports, and discards any duplicates that it finds. During this
1322 check, local parts are treated as case-sensitive. This happens only when
1323 actually delivering a message; when testing routers with &%-bt%&, all the
1324 routed addresses are shown.
1328 .section "Router preconditions" "SECTrouprecon"
1329 .cindex "router" "preconditions, order of processing"
1330 .cindex "preconditions" "order of processing"
1331 The preconditions that are tested for each router are listed below, in the
1332 order in which they are tested. The individual configuration options are
1333 described in more detail in chapter &<<CHAProutergeneric>>&.
1336 The &%local_part_prefix%& and &%local_part_suffix%& options can specify that
1337 the local parts handled by the router may or must have certain prefixes and/or
1338 suffixes. If a mandatory affix (prefix or suffix) is not present, the router is
1339 skipped. These conditions are tested first. When an affix is present, it is
1340 removed from the local part before further processing, including the evaluation
1341 of any other conditions.
1343 Routers can be designated for use only when not verifying an address, that is,
1344 only when routing it for delivery (or testing its delivery routing). If the
1345 &%verify%& option is set false, the router is skipped when Exim is verifying an
1347 Setting the &%verify%& option actually sets two options, &%verify_sender%& and
1348 &%verify_recipient%&, which independently control the use of the router for
1349 sender and recipient verification. You can set these options directly if
1350 you want a router to be used for only one type of verification.
1352 If the &%address_test%& option is set false, the router is skipped when Exim is
1353 run with the &%-bt%& option to test an address routing. This can be helpful
1354 when the first router sends all new messages to a scanner of some sort; it
1355 makes it possible to use &%-bt%& to test subsequent delivery routing without
1356 having to simulate the effect of the scanner.
1358 Routers can be designated for use only when verifying an address, as
1359 opposed to routing it for delivery. The &%verify_only%& option controls this.
1361 Individual routers can be explicitly skipped when running the routers to
1362 check an address given in the SMTP EXPN command (see the &%expn%& option).
1364 If the &%domains%& option is set, the domain of the address must be in the set
1365 of domains that it defines.
1367 .vindex "&$local_part_prefix$&"
1368 .vindex "&$local_part$&"
1369 .vindex "&$local_part_suffix$&"
1370 If the &%local_parts%& option is set, the local part of the address must be in
1371 the set of local parts that it defines. If &%local_part_prefix%& or
1372 &%local_part_suffix%& is in use, the prefix or suffix is removed from the local
1373 part before this check. If you want to do precondition tests on local parts
1374 that include affixes, you can do so by using a &%condition%& option (see below)
1375 that uses the variables &$local_part$&, &$local_part_prefix$&, and
1376 &$local_part_suffix$& as necessary.
1378 .vindex "&$local_user_uid$&"
1379 .vindex "&$local_user_gid$&"
1381 If the &%check_local_user%& option is set, the local part must be the name of
1382 an account on the local host. If this check succeeds, the uid and gid of the
1383 local user are placed in &$local_user_uid$& and &$local_user_gid$& and the
1384 user's home directory is placed in &$home$&; these values can be used in the
1385 remaining preconditions.
1387 If the &%router_home_directory%& option is set, it is expanded at this point,
1388 because it overrides the value of &$home$&. If this expansion were left till
1389 later, the value of &$home$& as set by &%check_local_user%& would be used in
1390 subsequent tests. Having two different values of &$home$& in the same router
1391 could lead to confusion.
1393 If the &%senders%& option is set, the envelope sender address must be in the
1394 set of addresses that it defines.
1396 If the &%require_files%& option is set, the existence or non-existence of
1397 specified files is tested.
1399 .cindex "customizing" "precondition"
1400 If the &%condition%& option is set, it is evaluated and tested. This option
1401 uses an expanded string to allow you to set up your own custom preconditions.
1402 Expanded strings are described in chapter &<<CHAPexpand>>&.
1406 Note that &%require_files%& comes near the end of the list, so you cannot use
1407 it to check for the existence of a file in which to lookup up a domain, local
1408 part, or sender. However, as these options are all expanded, you can use the
1409 &%exists%& expansion condition to make such tests within each condition. The
1410 &%require_files%& option is intended for checking files that the router may be
1411 going to use internally, or which are needed by a specific transport (for
1412 example, &_.procmailrc_&).
1416 .section "Delivery in detail" "SECID18"
1417 .cindex "delivery" "in detail"
1418 When a message is to be delivered, the sequence of events is as follows:
1421 If a system-wide filter file is specified, the message is passed to it. The
1422 filter may add recipients to the message, replace the recipients, discard the
1423 message, cause a new message to be generated, or cause the message delivery to
1424 fail. The format of the system filter file is the same as for Exim user filter
1425 files, described in the separate document entitled &'Exim's interfaces to mail
1427 .cindex "Sieve filter" "not available for system filter"
1428 (&*Note*&: Sieve cannot be used for system filter files.)
1430 Some additional features are available in system filters &-- see chapter
1431 &<<CHAPsystemfilter>>& for details. Note that a message is passed to the system
1432 filter only once per delivery attempt, however many recipients it has. However,
1433 if there are several delivery attempts because one or more addresses could not
1434 be immediately delivered, the system filter is run each time. The filter
1435 condition &%first_delivery%& can be used to detect the first run of the system
1438 Each recipient address is offered to each configured router in turn, subject to
1439 its preconditions, until one is able to handle it. If no router can handle the
1440 address, that is, if they all decline, the address is failed. Because routers
1441 can be targeted at particular domains, several locally handled domains can be
1442 processed entirely independently of each other.
1444 .cindex "routing" "loops in"
1445 .cindex "loop" "while routing"
1446 A router that accepts an address may assign it to a local or a remote
1447 transport. However, the transport is not run at this time. Instead, the address
1448 is placed on a list for the particular transport, which will be run later.
1449 Alternatively, the router may generate one or more new addresses (typically
1450 from alias, forward, or filter files). New addresses are fed back into this
1451 process from the top, but in order to avoid loops, a router ignores any address
1452 which has an identically-named ancestor that was processed by itself.
1454 When all the routing has been done, addresses that have been successfully
1455 handled are passed to their assigned transports. When local transports are
1456 doing real local deliveries, they handle only one address at a time, but if a
1457 local transport is being used as a pseudo-remote transport (for example, to
1458 collect batched SMTP messages for transmission by some other means) multiple
1459 addresses can be handled. Remote transports can always handle more than one
1460 address at a time, but can be configured not to do so, or to restrict multiple
1461 addresses to the same domain.
1463 Each local delivery to a file or a pipe runs in a separate process under a
1464 non-privileged uid, and these deliveries are run one at a time. Remote
1465 deliveries also run in separate processes, normally under a uid that is private
1466 to Exim (&"the Exim user"&), but in this case, several remote deliveries can be
1467 run in parallel. The maximum number of simultaneous remote deliveries for any
1468 one message is set by the &%remote_max_parallel%& option.
1469 The order in which deliveries are done is not defined, except that all local
1470 deliveries happen before any remote deliveries.
1472 .cindex "queue runner"
1473 When it encounters a local delivery during a queue run, Exim checks its retry
1474 database to see if there has been a previous temporary delivery failure for the
1475 address before running the local transport. If there was a previous failure,
1476 Exim does not attempt a new delivery until the retry time for the address is
1477 reached. However, this happens only for delivery attempts that are part of a
1478 queue run. Local deliveries are always attempted when delivery immediately
1479 follows message reception, even if retry times are set for them. This makes for
1480 better behaviour if one particular message is causing problems (for example,
1481 causing quota overflow, or provoking an error in a filter file).
1483 .cindex "delivery" "retry in remote transports"
1484 Remote transports do their own retry handling, since an address may be
1485 deliverable to one of a number of hosts, each of which may have a different
1486 retry time. If there have been previous temporary failures and no host has
1487 reached its retry time, no delivery is attempted, whether in a queue run or
1488 not. See chapter &<<CHAPretry>>& for details of retry strategies.
1490 If there were any permanent errors, a bounce message is returned to an
1491 appropriate address (the sender in the common case), with details of the error
1492 for each failing address. Exim can be configured to send copies of bounce
1493 messages to other addresses.
1495 .cindex "delivery" "deferral"
1496 If one or more addresses suffered a temporary failure, the message is left on
1497 the queue, to be tried again later. Delivery of these addresses is said to be
1500 When all the recipient addresses have either been delivered or bounced,
1501 handling of the message is complete. The spool files and message log are
1502 deleted, though the message log can optionally be preserved if required.
1508 .section "Retry mechanism" "SECID19"
1509 .cindex "delivery" "retry mechanism"
1510 .cindex "retry" "description of mechanism"
1511 .cindex "queue runner"
1512 Exim's mechanism for retrying messages that fail to get delivered at the first
1513 attempt is the queue runner process. You must either run an Exim daemon that
1514 uses the &%-q%& option with a time interval to start queue runners at regular
1515 intervals, or use some other means (such as &'cron'&) to start them. If you do
1516 not arrange for queue runners to be run, messages that fail temporarily at the
1517 first attempt will remain on your queue for ever. A queue runner process works
1518 its way through the queue, one message at a time, trying each delivery that has
1519 passed its retry time.
1520 You can run several queue runners at once.
1522 Exim uses a set of configured rules to determine when next to retry the failing
1523 address (see chapter &<<CHAPretry>>&). These rules also specify when Exim
1524 should give up trying to deliver to the address, at which point it generates a
1525 bounce message. If no retry rules are set for a particular host, address, and
1526 error combination, no retries are attempted, and temporary errors are treated
1531 .section "Temporary delivery failure" "SECID20"
1532 .cindex "delivery" "temporary failure"
1533 There are many reasons why a message may not be immediately deliverable to a
1534 particular address. Failure to connect to a remote machine (because it, or the
1535 connection to it, is down) is one of the most common. Temporary failures may be
1536 detected during routing as well as during the transport stage of delivery.
1537 Local deliveries may be delayed if NFS files are unavailable, or if a mailbox
1538 is on a file system where the user is over quota. Exim can be configured to
1539 impose its own quotas on local mailboxes; where system quotas are set they will
1542 If a host is unreachable for a period of time, a number of messages may be
1543 waiting for it by the time it recovers, and sending them in a single SMTP
1544 connection is clearly beneficial. Whenever a delivery to a remote host is
1546 .cindex "hints database"
1547 Exim makes a note in its hints database, and whenever a successful
1548 SMTP delivery has happened, it looks to see if any other messages are waiting
1549 for the same host. If any are found, they are sent over the same SMTP
1550 connection, subject to a configuration limit as to the maximum number in any
1555 .section "Permanent delivery failure" "SECID21"
1556 .cindex "delivery" "permanent failure"
1557 .cindex "bounce message" "when generated"
1558 When a message cannot be delivered to some or all of its intended recipients, a
1559 bounce message is generated. Temporary delivery failures turn into permanent
1560 errors when their timeout expires. All the addresses that fail in a given
1561 delivery attempt are listed in a single message. If the original message has
1562 many recipients, it is possible for some addresses to fail in one delivery
1563 attempt and others to fail subsequently, giving rise to more than one bounce
1564 message. The wording of bounce messages can be customized by the administrator.
1565 See chapter &<<CHAPemsgcust>>& for details.
1567 .cindex "&'X-Failed-Recipients:'& header line"
1568 Bounce messages contain an &'X-Failed-Recipients:'& header line that lists the
1569 failed addresses, for the benefit of programs that try to analyse such messages
1572 .cindex "bounce message" "recipient of"
1573 A bounce message is normally sent to the sender of the original message, as
1574 obtained from the message's envelope. For incoming SMTP messages, this is the
1575 address given in the MAIL command. However, when an address is expanded via a
1576 forward or alias file, an alternative address can be specified for delivery
1577 failures of the generated addresses. For a mailing list expansion (see section
1578 &<<SECTmailinglists>>&) it is common to direct bounce messages to the manager
1583 .section "Failures to deliver bounce messages" "SECID22"
1584 .cindex "bounce message" "failure to deliver"
1585 If a bounce message (either locally generated or received from a remote host)
1586 itself suffers a permanent delivery failure, the message is left on the queue,
1587 but it is frozen, awaiting the attention of an administrator. There are options
1588 that can be used to make Exim discard such failed messages, or to keep them
1589 for only a short time (see &%timeout_frozen_after%& and
1590 &%ignore_bounce_errors_after%&).
1596 . ////////////////////////////////////////////////////////////////////////////
1597 . ////////////////////////////////////////////////////////////////////////////
1599 .chapter "Building and installing Exim" "CHID3"
1600 .scindex IIDbuex "building Exim"
1602 .section "Unpacking" "SECID23"
1603 Exim is distributed as a gzipped or bzipped tar file which, when unpacked,
1604 creates a directory with the name of the current release (for example,
1605 &_exim-&version;_&) into which the following files are placed:
1608 .irow &_ACKNOWLEDGMENTS_& "contains some acknowledgments"
1609 .irow &_CHANGES_& "contains a reference to where changes are &&&
1611 .irow &_LICENCE_& "the GNU General Public Licence"
1612 .irow &_Makefile_& "top-level make file"
1613 .irow &_NOTICE_& "conditions for the use of Exim"
1614 .irow &_README_& "list of files, directories and simple build &&&
1618 Other files whose names begin with &_README_& may also be present. The
1619 following subdirectories are created:
1622 .irow &_Local_& "an empty directory for local configuration files"
1623 .irow &_OS_& "OS-specific files"
1624 .irow &_doc_& "documentation files"
1625 .irow &_exim_monitor_& "source files for the Exim monitor"
1626 .irow &_scripts_& "scripts used in the build process"
1627 .irow &_src_& "remaining source files"
1628 .irow &_util_& "independent utilities"
1631 The main utility programs are contained in the &_src_& directory, and are built
1632 with the Exim binary. The &_util_& directory contains a few optional scripts
1633 that may be useful to some sites.
1636 .section "Multiple machine architectures and operating systems" "SECID24"
1637 .cindex "building Exim" "multiple OS/architectures"
1638 The building process for Exim is arranged to make it easy to build binaries for
1639 a number of different architectures and operating systems from the same set of
1640 source files. Compilation does not take place in the &_src_& directory.
1641 Instead, a &'build directory'& is created for each architecture and operating
1643 .cindex "symbolic link" "to build directory"
1644 Symbolic links to the sources are installed in this directory, which is where
1645 the actual building takes place. In most cases, Exim can discover the machine
1646 architecture and operating system for itself, but the defaults can be
1647 overridden if necessary.
1650 .section "PCRE library" "SECTpcre"
1651 .cindex "PCRE library"
1652 Exim no longer has an embedded PCRE library as the vast majority of
1653 modern systems include PCRE as a system library, although you may need
1654 to install the PCRE or PCRE development package for your operating
1655 system. If your system has a normal PCRE installation the Exim build
1656 process will need no further configuration. If the library or the
1657 headers are in an unusual location you will need to either set the PCRE_LIBS
1658 and INCLUDE directives appropriately,
1659 or set PCRE_CONFIG=yes to use the installed &(pcre-config)& command.
1660 If your operating system has no
1661 PCRE support then you will need to obtain and build the current PCRE
1662 from &url(ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre/).
1663 More information on PCRE is available at &url(http://www.pcre.org/).
1665 .section "DBM libraries" "SECTdb"
1666 .cindex "DBM libraries" "discussion of"
1667 .cindex "hints database" "DBM files used for"
1668 Even if you do not use any DBM files in your configuration, Exim still needs a
1669 DBM library in order to operate, because it uses indexed files for its hints
1670 databases. Unfortunately, there are a number of DBM libraries in existence, and
1671 different operating systems often have different ones installed.
1673 .cindex "Solaris" "DBM library for"
1674 .cindex "IRIX, DBM library for"
1675 .cindex "BSD, DBM library for"
1676 .cindex "Linux, DBM library for"
1677 If you are using Solaris, IRIX, one of the modern BSD systems, or a modern
1678 Linux distribution, the DBM configuration should happen automatically, and you
1679 may be able to ignore this section. Otherwise, you may have to learn more than
1680 you would like about DBM libraries from what follows.
1682 .cindex "&'ndbm'& DBM library"
1683 Licensed versions of Unix normally contain a library of DBM functions operating
1684 via the &'ndbm'& interface, and this is what Exim expects by default. Free
1685 versions of Unix seem to vary in what they contain as standard. In particular,
1686 some early versions of Linux have no default DBM library, and different
1687 distributors have chosen to bundle different libraries with their packaged
1688 versions. However, the more recent releases seem to have standardized on the
1689 Berkeley DB library.
1691 Different DBM libraries have different conventions for naming the files they
1692 use. When a program opens a file called &_dbmfile_&, there are several
1696 A traditional &'ndbm'& implementation, such as that supplied as part of
1697 Solaris, operates on two files called &_dbmfile.dir_& and &_dbmfile.pag_&.
1699 .cindex "&'gdbm'& DBM library"
1700 The GNU library, &'gdbm'&, operates on a single file. If used via its &'ndbm'&
1701 compatibility interface it makes two different hard links to it with names
1702 &_dbmfile.dir_& and &_dbmfile.pag_&, but if used via its native interface, the
1703 file name is used unmodified.
1705 .cindex "Berkeley DB library"
1706 The Berkeley DB package, if called via its &'ndbm'& compatibility interface,
1707 operates on a single file called &_dbmfile.db_&, but otherwise looks to the
1708 programmer exactly the same as the traditional &'ndbm'& implementation.
1710 If the Berkeley package is used in its native mode, it operates on a single
1711 file called &_dbmfile_&; the programmer's interface is somewhat different to
1712 the traditional &'ndbm'& interface.
1714 To complicate things further, there are several very different versions of the
1715 Berkeley DB package. Version 1.85 was stable for a very long time, releases
1716 2.&'x'& and 3.&'x'& were current for a while, but the latest versions are now
1717 numbered 4.&'x'&. Maintenance of some of the earlier releases has ceased. All
1718 versions of Berkeley DB can be obtained from
1719 &url(http://www.sleepycat.com/).
1721 .cindex "&'tdb'& DBM library"
1722 Yet another DBM library, called &'tdb'&, is available from
1723 &url(http://download.sourceforge.net/tdb). It has its own interface, and also
1724 operates on a single file.
1728 .cindex "DBM libraries" "configuration for building"
1729 Exim and its utilities can be compiled to use any of these interfaces. In order
1730 to use any version of the Berkeley DB package in native mode, you must set
1731 USE_DB in an appropriate configuration file (typically
1732 &_Local/Makefile_&). For example:
1736 Similarly, for gdbm you set USE_GDBM, and for tdb you set USE_TDB. An
1737 error is diagnosed if you set more than one of these.
1739 At the lowest level, the build-time configuration sets none of these options,
1740 thereby assuming an interface of type (1). However, some operating system
1741 configuration files (for example, those for the BSD operating systems and
1742 Linux) assume type (4) by setting USE_DB as their default, and the
1743 configuration files for Cygwin set USE_GDBM. Anything you set in
1744 &_Local/Makefile_&, however, overrides these system defaults.
1746 As well as setting USE_DB, USE_GDBM, or USE_TDB, it may also be
1747 necessary to set DBMLIB, to cause inclusion of the appropriate library, as
1748 in one of these lines:
1753 Settings like that will work if the DBM library is installed in the standard
1754 place. Sometimes it is not, and the library's header file may also not be in
1755 the default path. You may need to set INCLUDE to specify where the header
1756 file is, and to specify the path to the library more fully in DBMLIB, as in
1759 INCLUDE=-I/usr/local/include/db-4.1
1760 DBMLIB=/usr/local/lib/db-4.1/libdb.a
1762 There is further detailed discussion about the various DBM libraries in the
1763 file &_doc/dbm.discuss.txt_& in the Exim distribution.
1767 .section "Pre-building configuration" "SECID25"
1768 .cindex "building Exim" "pre-building configuration"
1769 .cindex "configuration for building Exim"
1770 .cindex "&_Local/Makefile_&"
1771 .cindex "&_src/EDITME_&"
1772 Before building Exim, a local configuration file that specifies options
1773 independent of any operating system has to be created with the name
1774 &_Local/Makefile_&. A template for this file is supplied as the file
1775 &_src/EDITME_&, and it contains full descriptions of all the option settings
1776 therein. These descriptions are therefore not repeated here. If you are
1777 building Exim for the first time, the simplest thing to do is to copy
1778 &_src/EDITME_& to &_Local/Makefile_&, then read it and edit it appropriately.
1780 There are three settings that you must supply, because Exim will not build
1781 without them. They are the location of the run time configuration file
1782 (CONFIGURE_FILE), the directory in which Exim binaries will be installed
1783 (BIN_DIRECTORY), and the identity of the Exim user (EXIM_USER and
1784 maybe EXIM_GROUP as well). The value of CONFIGURE_FILE can in fact be
1785 a colon-separated list of file names; Exim uses the first of them that exists.
1787 There are a few other parameters that can be specified either at build time or
1788 at run time, to enable the same binary to be used on a number of different
1789 machines. However, if the locations of Exim's spool directory and log file
1790 directory (if not within the spool directory) are fixed, it is recommended that
1791 you specify them in &_Local/Makefile_& instead of at run time, so that errors
1792 detected early in Exim's execution (such as a malformed configuration file) can
1795 .cindex "content scanning" "specifying at build time"
1796 Exim's interfaces for calling virus and spam scanning software directly from
1797 access control lists are not compiled by default. If you want to include these
1798 facilities, you need to set
1800 WITH_CONTENT_SCAN=yes
1802 in your &_Local/Makefile_&. For details of the facilities themselves, see
1803 chapter &<<CHAPexiscan>>&.
1806 .cindex "&_Local/eximon.conf_&"
1807 .cindex "&_exim_monitor/EDITME_&"
1808 If you are going to build the Exim monitor, a similar configuration process is
1809 required. The file &_exim_monitor/EDITME_& must be edited appropriately for
1810 your installation and saved under the name &_Local/eximon.conf_&. If you are
1811 happy with the default settings described in &_exim_monitor/EDITME_&,
1812 &_Local/eximon.conf_& can be empty, but it must exist.
1814 This is all the configuration that is needed in straightforward cases for known
1815 operating systems. However, the building process is set up so that it is easy
1816 to override options that are set by default or by operating-system-specific
1817 configuration files, for example to change the name of the C compiler, which
1818 defaults to &%gcc%&. See section &<<SECToverride>>& below for details of how to
1823 .section "Support for iconv()" "SECID26"
1824 .cindex "&[iconv()]& support"
1826 The contents of header lines in messages may be encoded according to the rules
1827 described RFC 2047. This makes it possible to transmit characters that are not
1828 in the ASCII character set, and to label them as being in a particular
1829 character set. When Exim is inspecting header lines by means of the &%$h_%&
1830 mechanism, it decodes them, and translates them into a specified character set
1831 (default ISO-8859-1). The translation is possible only if the operating system
1832 supports the &[iconv()]& function.
1834 However, some of the operating systems that supply &[iconv()]& do not support
1835 very many conversions. The GNU &%libiconv%& library (available from
1836 &url(http://www.gnu.org/software/libiconv/)) can be installed on such
1837 systems to remedy this deficiency, as well as on systems that do not supply
1838 &[iconv()]& at all. After installing &%libiconv%&, you should add
1842 to your &_Local/Makefile_& and rebuild Exim.
1846 .section "Including TLS/SSL encryption support" "SECTinctlsssl"
1847 .cindex "TLS" "including support for TLS"
1848 .cindex "encryption" "including support for"
1849 .cindex "SUPPORT_TLS"
1850 .cindex "OpenSSL" "building Exim with"
1851 .cindex "GnuTLS" "building Exim with"
1852 Exim can be built to support encrypted SMTP connections, using the STARTTLS
1853 command as per RFC 2487. It can also support legacy clients that expect to
1854 start a TLS session immediately on connection to a non-standard port (see the
1855 &%tls_on_connect_ports%& runtime option and the &%-tls-on-connect%& command
1858 If you want to build Exim with TLS support, you must first install either the
1859 OpenSSL or GnuTLS library. There is no cryptographic code in Exim itself for
1862 If OpenSSL is installed, you should set
1865 TLS_LIBS=-lssl -lcrypto
1867 in &_Local/Makefile_&. You may also need to specify the locations of the
1868 OpenSSL library and include files. For example:
1871 TLS_LIBS=-L/usr/local/openssl/lib -lssl -lcrypto
1872 TLS_INCLUDE=-I/usr/local/openssl/include/
1874 .cindex "pkg-config" "OpenSSL"
1875 If you have &'pkg-config'& available, then instead you can just use:
1878 USE_OPENSSL_PC=openssl
1880 .cindex "USE_GNUTLS"
1881 If GnuTLS is installed, you should set
1885 TLS_LIBS=-lgnutls -ltasn1 -lgcrypt
1887 in &_Local/Makefile_&, and again you may need to specify the locations of the
1888 library and include files. For example:
1892 TLS_LIBS=-L/usr/gnu/lib -lgnutls -ltasn1 -lgcrypt
1893 TLS_INCLUDE=-I/usr/gnu/include
1895 .cindex "pkg-config" "GnuTLS"
1896 If you have &'pkg-config'& available, then instead you can just use:
1900 USE_GNUTLS_PC=gnutls
1903 You do not need to set TLS_INCLUDE if the relevant directory is already
1904 specified in INCLUDE. Details of how to configure Exim to make use of TLS are
1905 given in chapter &<<CHAPTLS>>&.
1910 .section "Use of tcpwrappers" "SECID27"
1912 .cindex "tcpwrappers, building Exim to support"
1913 .cindex "USE_TCP_WRAPPERS"
1914 .cindex "TCP_WRAPPERS_DAEMON_NAME"
1915 .cindex "tcp_wrappers_daemon_name"
1916 Exim can be linked with the &'tcpwrappers'& library in order to check incoming
1917 SMTP calls using the &'tcpwrappers'& control files. This may be a convenient
1918 alternative to Exim's own checking facilities for installations that are
1919 already making use of &'tcpwrappers'& for other purposes. To do this, you
1920 should set USE_TCP_WRAPPERS in &_Local/Makefile_&, arrange for the file
1921 &_tcpd.h_& to be available at compile time, and also ensure that the library
1922 &_libwrap.a_& is available at link time, typically by including &%-lwrap%& in
1923 EXTRALIBS_EXIM. For example, if &'tcpwrappers'& is installed in &_/usr/local_&,
1926 USE_TCP_WRAPPERS=yes
1927 CFLAGS=-O -I/usr/local/include
1928 EXTRALIBS_EXIM=-L/usr/local/lib -lwrap
1930 in &_Local/Makefile_&. The daemon name to use in the &'tcpwrappers'& control
1931 files is &"exim"&. For example, the line
1933 exim : LOCAL 192.168.1. .friendly.domain.example
1935 in your &_/etc/hosts.allow_& file allows connections from the local host, from
1936 the subnet 192.168.1.0/24, and from all hosts in &'friendly.domain.example'&.
1937 All other connections are denied. The daemon name used by &'tcpwrappers'&
1938 can be changed at build time by setting TCP_WRAPPERS_DAEMON_NAME in
1939 in &_Local/Makefile_&, or by setting tcp_wrappers_daemon_name in the
1940 configure file. Consult the &'tcpwrappers'& documentation for
1944 .section "Including support for IPv6" "SECID28"
1945 .cindex "IPv6" "including support for"
1946 Exim contains code for use on systems that have IPv6 support. Setting
1947 &`HAVE_IPV6=YES`& in &_Local/Makefile_& causes the IPv6 code to be included;
1948 it may also be necessary to set IPV6_INCLUDE and IPV6_LIBS on systems
1949 where the IPv6 support is not fully integrated into the normal include and
1952 Two different types of DNS record for handling IPv6 addresses have been
1953 defined. AAAA records (analogous to A records for IPv4) are in use, and are
1954 currently seen as the mainstream. Another record type called A6 was proposed
1955 as better than AAAA because it had more flexibility. However, it was felt to be
1956 over-complex, and its status was reduced to &"experimental"&. It is not known
1957 if anyone is actually using A6 records. Exim has support for A6 records, but
1958 this is included only if you set &`SUPPORT_A6=YES`& in &_Local/Makefile_&. The
1959 support has not been tested for some time.
1963 .section "Dynamically loaded lookup module support" "SECTdynamicmodules"
1964 .cindex "lookup modules"
1965 .cindex "dynamic modules"
1966 .cindex ".so building"
1967 On some platforms, Exim supports not compiling all lookup types directly into
1968 the main binary, instead putting some into external modules which can be loaded
1970 This permits packagers to build Exim with support for lookups with extensive
1971 library dependencies without requiring all users to install all of those
1973 Most, but not all, lookup types can be built this way.
1975 Set &`LOOKUP_MODULE_DIR`& to the directory into which the modules will be
1976 installed; Exim will only load modules from that directory, as a security
1977 measure. You will need to set &`CFLAGS_DYNAMIC`& if not already defined
1978 for your OS; see &_OS/Makefile-Linux_& for an example.
1979 Some other requirements for adjusting &`EXTRALIBS`& may also be necessary,
1980 see &_src/EDITME_& for details.
1982 Then, for each module to be loaded dynamically, define the relevant
1983 &`LOOKUP_`&<&'lookup_type'&> flags to have the value "2" instead of "yes".
1984 For example, this will build in lsearch but load sqlite and mysql support
1993 .section "The building process" "SECID29"
1994 .cindex "build directory"
1995 Once &_Local/Makefile_& (and &_Local/eximon.conf_&, if required) have been
1996 created, run &'make'& at the top level. It determines the architecture and
1997 operating system types, and creates a build directory if one does not exist.
1998 For example, on a Sun system running Solaris 8, the directory
1999 &_build-SunOS5-5.8-sparc_& is created.
2000 .cindex "symbolic link" "to source files"
2001 Symbolic links to relevant source files are installed in the build directory.
2003 &*Warning*&: The &%-j%& (parallel) flag must not be used with &'make'&; the
2004 building process fails if it is set.
2006 If this is the first time &'make'& has been run, it calls a script that builds
2007 a make file inside the build directory, using the configuration files from the
2008 &_Local_& directory. The new make file is then passed to another instance of
2009 &'make'&. This does the real work, building a number of utility scripts, and
2010 then compiling and linking the binaries for the Exim monitor (if configured), a
2011 number of utility programs, and finally Exim itself. The command &`make
2012 makefile`& can be used to force a rebuild of the make file in the build
2013 directory, should this ever be necessary.
2015 If you have problems building Exim, check for any comments there may be in the
2016 &_README_& file concerning your operating system, and also take a look at the
2017 FAQ, where some common problems are covered.
2021 .section 'Output from &"make"&' "SECID283"
2022 The output produced by the &'make'& process for compile lines is often very
2023 unreadable, because these lines can be very long. For this reason, the normal
2024 output is suppressed by default, and instead output similar to that which
2025 appears when compiling the 2.6 Linux kernel is generated: just a short line for
2026 each module that is being compiled or linked. However, it is still possible to
2027 get the full output, by calling &'make'& like this:
2031 The value of FULLECHO defaults to &"@"&, the flag character that suppresses
2032 command reflection in &'make'&. When you ask for the full output, it is
2033 given in addition to the short output.
2037 .section "Overriding build-time options for Exim" "SECToverride"
2038 .cindex "build-time options, overriding"
2039 The main make file that is created at the beginning of the building process
2040 consists of the concatenation of a number of files which set configuration
2041 values, followed by a fixed set of &'make'& instructions. If a value is set
2042 more than once, the last setting overrides any previous ones. This provides a
2043 convenient way of overriding defaults. The files that are concatenated are, in
2046 &_OS/Makefile-Default_&
2047 &_OS/Makefile-_&<&'ostype'&>
2049 &_Local/Makefile-_&<&'ostype'&>
2050 &_Local/Makefile-_&<&'archtype'&>
2051 &_Local/Makefile-_&<&'ostype'&>-<&'archtype'&>
2052 &_OS/Makefile-Base_&
2054 .cindex "&_Local/Makefile_&"
2055 .cindex "building Exim" "operating system type"
2056 .cindex "building Exim" "architecture type"
2057 where <&'ostype'&> is the operating system type and <&'archtype'&> is the
2058 architecture type. &_Local/Makefile_& is required to exist, and the building
2059 process fails if it is absent. The other three &_Local_& files are optional,
2060 and are often not needed.
2062 The values used for <&'ostype'&> and <&'archtype'&> are obtained from scripts
2063 called &_scripts/os-type_& and &_scripts/arch-type_& respectively. If either of
2064 the environment variables EXIM_OSTYPE or EXIM_ARCHTYPE is set, their
2065 values are used, thereby providing a means of forcing particular settings.
2066 Otherwise, the scripts try to get values from the &%uname%& command. If this
2067 fails, the shell variables OSTYPE and ARCHTYPE are inspected. A number
2068 of &'ad hoc'& transformations are then applied, to produce the standard names
2069 that Exim expects. You can run these scripts directly from the shell in order
2070 to find out what values are being used on your system.
2073 &_OS/Makefile-Default_& contains comments about the variables that are set
2074 therein. Some (but not all) are mentioned below. If there is something that
2075 needs changing, review the contents of this file and the contents of the make
2076 file for your operating system (&_OS/Makefile-<ostype>_&) to see what the
2080 .cindex "building Exim" "overriding default settings"
2081 If you need to change any of the values that are set in &_OS/Makefile-Default_&
2082 or in &_OS/Makefile-<ostype>_&, or to add any new definitions, you do not
2083 need to change the original files. Instead, you should make the changes by
2084 putting the new values in an appropriate &_Local_& file. For example,
2085 .cindex "Tru64-Unix build-time settings"
2086 when building Exim in many releases of the Tru64-Unix (formerly Digital UNIX,
2087 formerly DEC-OSF1) operating system, it is necessary to specify that the C
2088 compiler is called &'cc'& rather than &'gcc'&. Also, the compiler must be
2089 called with the option &%-std1%&, to make it recognize some of the features of
2090 Standard C that Exim uses. (Most other compilers recognize Standard C by
2091 default.) To do this, you should create a file called &_Local/Makefile-OSF1_&
2092 containing the lines
2097 If you are compiling for just one operating system, it may be easier to put
2098 these lines directly into &_Local/Makefile_&.
2100 Keeping all your local configuration settings separate from the distributed
2101 files makes it easy to transfer them to new versions of Exim simply by copying
2102 the contents of the &_Local_& directory.
2105 .cindex "NIS lookup type" "including support for"
2106 .cindex "NIS+ lookup type" "including support for"
2107 .cindex "LDAP" "including support for"
2108 .cindex "lookup" "inclusion in binary"
2109 Exim contains support for doing LDAP, NIS, NIS+, and other kinds of file
2110 lookup, but not all systems have these components installed, so the default is
2111 not to include the relevant code in the binary. All the different kinds of file
2112 and database lookup that Exim supports are implemented as separate code modules
2113 which are included only if the relevant compile-time options are set. In the
2114 case of LDAP, NIS, and NIS+, the settings for &_Local/Makefile_& are:
2120 and similar settings apply to the other lookup types. They are all listed in
2121 &_src/EDITME_&. In many cases the relevant include files and interface
2122 libraries need to be installed before compiling Exim.
2123 .cindex "cdb" "including support for"
2124 However, there are some optional lookup types (such as cdb) for which
2125 the code is entirely contained within Exim, and no external include
2126 files or libraries are required. When a lookup type is not included in the
2127 binary, attempts to configure Exim to use it cause run time configuration
2130 .cindex "pkg-config" "lookups"
2131 .cindex "pkg-config" "authenticators"
2132 Many systems now use a tool called &'pkg-config'& to encapsulate information
2133 about how to compile against a library; Exim has some initial support for
2134 being able to use pkg-config for lookups and authenticators. For any given
2135 makefile variable which starts &`LOOKUP_`& or &`AUTH_`&, you can add a new
2136 variable with the &`_PC`& suffix in the name and assign as the value the
2137 name of the package to be queried. The results of querying via the
2138 &'pkg-config'& command will be added to the appropriate Makefile variables
2139 with &`+=`& directives, so your version of &'make'& will need to support that
2140 syntax. For instance:
2143 LOOKUP_SQLITE_PC=sqlite3
2145 AUTH_GSASL_PC=libgsasl
2146 AUTH_HEIMDAL_GSSAPI=yes
2147 AUTH_HEIMDAL_GSSAPI_PC=heimdal-gssapi
2150 .cindex "Perl" "including support for"
2151 Exim can be linked with an embedded Perl interpreter, allowing Perl
2152 subroutines to be called during string expansion. To enable this facility,
2156 must be defined in &_Local/Makefile_&. Details of this facility are given in
2157 chapter &<<CHAPperl>>&.
2159 .cindex "X11 libraries, location of"
2160 The location of the X11 libraries is something that varies a lot between
2161 operating systems, and there may be different versions of X11 to cope
2162 with. Exim itself makes no use of X11, but if you are compiling the Exim
2163 monitor, the X11 libraries must be available.
2164 The following three variables are set in &_OS/Makefile-Default_&:
2167 XINCLUDE=-I$(X11)/include
2168 XLFLAGS=-L$(X11)/lib
2170 These are overridden in some of the operating-system configuration files. For
2171 example, in &_OS/Makefile-SunOS5_& there is
2174 XINCLUDE=-I$(X11)/include
2175 XLFLAGS=-L$(X11)/lib -R$(X11)/lib
2177 If you need to override the default setting for your operating system, place a
2178 definition of all three of these variables into your
2179 &_Local/Makefile-<ostype>_& file.
2182 If you need to add any extra libraries to the link steps, these can be put in a
2183 variable called EXTRALIBS, which appears in all the link commands, but by
2184 default is not defined. In contrast, EXTRALIBS_EXIM is used only on the
2185 command for linking the main Exim binary, and not for any associated utilities.
2187 .cindex "DBM libraries" "configuration for building"
2188 There is also DBMLIB, which appears in the link commands for binaries that
2189 use DBM functions (see also section &<<SECTdb>>&). Finally, there is
2190 EXTRALIBS_EXIMON, which appears only in the link step for the Exim monitor
2191 binary, and which can be used, for example, to include additional X11
2194 .cindex "configuration file" "editing"
2195 The make file copes with rebuilding Exim correctly if any of the configuration
2196 files are edited. However, if an optional configuration file is deleted, it is
2197 necessary to touch the associated non-optional file (that is,
2198 &_Local/Makefile_& or &_Local/eximon.conf_&) before rebuilding.
2201 .section "OS-specific header files" "SECID30"
2203 .cindex "building Exim" "OS-specific C header files"
2204 The &_OS_& directory contains a number of files with names of the form
2205 &_os.h-<ostype>_&. These are system-specific C header files that should not
2206 normally need to be changed. There is a list of macro settings that are
2207 recognized in the file &_OS/os.configuring_&, which should be consulted if you
2208 are porting Exim to a new operating system.
2212 .section "Overriding build-time options for the monitor" "SECID31"
2213 .cindex "building Eximon"
2214 A similar process is used for overriding things when building the Exim monitor,
2215 where the files that are involved are
2217 &_OS/eximon.conf-Default_&
2218 &_OS/eximon.conf-_&<&'ostype'&>
2219 &_Local/eximon.conf_&
2220 &_Local/eximon.conf-_&<&'ostype'&>
2221 &_Local/eximon.conf-_&<&'archtype'&>
2222 &_Local/eximon.conf-_&<&'ostype'&>-<&'archtype'&>
2224 .cindex "&_Local/eximon.conf_&"
2225 As with Exim itself, the final three files need not exist, and in this case the
2226 &_OS/eximon.conf-<ostype>_& file is also optional. The default values in
2227 &_OS/eximon.conf-Default_& can be overridden dynamically by setting environment
2228 variables of the same name, preceded by EXIMON_. For example, setting
2229 EXIMON_LOG_DEPTH in the environment overrides the value of
2230 LOG_DEPTH at run time.
2234 .section "Installing Exim binaries and scripts" "SECID32"
2235 .cindex "installing Exim"
2236 .cindex "BIN_DIRECTORY"
2237 The command &`make install`& runs the &(exim_install)& script with no
2238 arguments. The script copies binaries and utility scripts into the directory
2239 whose name is specified by the BIN_DIRECTORY setting in &_Local/Makefile_&.
2240 .cindex "setuid" "installing Exim with"
2241 The install script copies files only if they are newer than the files they are
2242 going to replace. The Exim binary is required to be owned by root and have the
2243 &'setuid'& bit set, for normal configurations. Therefore, you must run &`make
2244 install`& as root so that it can set up the Exim binary in this way. However, in
2245 some special situations (for example, if a host is doing no local deliveries)
2246 it may be possible to run Exim without making the binary setuid root (see
2247 chapter &<<CHAPsecurity>>& for details).
2249 .cindex "CONFIGURE_FILE"
2250 Exim's run time configuration file is named by the CONFIGURE_FILE setting
2251 in &_Local/Makefile_&. If this names a single file, and the file does not
2252 exist, the default configuration file &_src/configure.default_& is copied there
2253 by the installation script. If a run time configuration file already exists, it
2254 is left alone. If CONFIGURE_FILE is a colon-separated list, naming several
2255 alternative files, no default is installed.
2257 .cindex "system aliases file"
2258 .cindex "&_/etc/aliases_&"
2259 One change is made to the default configuration file when it is installed: the
2260 default configuration contains a router that references a system aliases file.
2261 The path to this file is set to the value specified by
2262 SYSTEM_ALIASES_FILE in &_Local/Makefile_& (&_/etc/aliases_& by default).
2263 If the system aliases file does not exist, the installation script creates it,
2264 and outputs a comment to the user.
2266 The created file contains no aliases, but it does contain comments about the
2267 aliases a site should normally have. Mail aliases have traditionally been
2268 kept in &_/etc/aliases_&. However, some operating systems are now using
2269 &_/etc/mail/aliases_&. You should check if yours is one of these, and change
2270 Exim's configuration if necessary.
2272 The default configuration uses the local host's name as the only local domain,
2273 and is set up to do local deliveries into the shared directory &_/var/mail_&,
2274 running as the local user. System aliases and &_.forward_& files in users' home
2275 directories are supported, but no NIS or NIS+ support is configured. Domains
2276 other than the name of the local host are routed using the DNS, with delivery
2279 It is possible to install Exim for special purposes (such as building a binary
2280 distribution) in a private part of the file system. You can do this by a
2283 make DESTDIR=/some/directory/ install
2285 This has the effect of pre-pending the specified directory to all the file
2286 paths, except the name of the system aliases file that appears in the default
2287 configuration. (If a default alias file is created, its name &'is'& modified.)
2288 For backwards compatibility, ROOT is used if DESTDIR is not set,
2289 but this usage is deprecated.
2291 .cindex "installing Exim" "what is not installed"
2292 Running &'make install'& does not copy the Exim 4 conversion script
2293 &'convert4r4'&. You will probably run this only once if you are
2294 upgrading from Exim 3. None of the documentation files in the &_doc_&
2295 directory are copied, except for the info files when you have set
2296 INFO_DIRECTORY, as described in section &<<SECTinsinfdoc>>& below.
2298 For the utility programs, old versions are renamed by adding the suffix &_.O_&
2299 to their names. The Exim binary itself, however, is handled differently. It is
2300 installed under a name that includes the version number and the compile number,
2301 for example &_exim-&version;-1_&. The script then arranges for a symbolic link
2302 called &_exim_& to point to the binary. If you are updating a previous version
2303 of Exim, the script takes care to ensure that the name &_exim_& is never absent
2304 from the directory (as seen by other processes).
2306 .cindex "installing Exim" "testing the script"
2307 If you want to see what the &'make install'& will do before running it for
2308 real, you can pass the &%-n%& option to the installation script by this
2311 make INSTALL_ARG=-n install
2313 The contents of the variable INSTALL_ARG are passed to the installation
2314 script. You do not need to be root to run this test. Alternatively, you can run
2315 the installation script directly, but this must be from within the build
2316 directory. For example, from the top-level Exim directory you could use this
2319 (cd build-SunOS5-5.5.1-sparc; ../scripts/exim_install -n)
2321 .cindex "installing Exim" "install script options"
2322 There are two other options that can be supplied to the installation script.
2325 &%-no_chown%& bypasses the call to change the owner of the installed binary
2326 to root, and the call to make it a setuid binary.
2328 &%-no_symlink%& bypasses the setting up of the symbolic link &_exim_& to the
2332 INSTALL_ARG can be used to pass these options to the script. For example:
2334 make INSTALL_ARG=-no_symlink install
2336 The installation script can also be given arguments specifying which files are
2337 to be copied. For example, to install just the Exim binary, and nothing else,
2338 without creating the symbolic link, you could use:
2340 make INSTALL_ARG='-no_symlink exim' install
2345 .section "Installing info documentation" "SECTinsinfdoc"
2346 .cindex "installing Exim" "&'info'& documentation"
2347 Not all systems use the GNU &'info'& system for documentation, and for this
2348 reason, the Texinfo source of Exim's documentation is not included in the main
2349 distribution. Instead it is available separately from the ftp site (see section
2352 If you have defined INFO_DIRECTORY in &_Local/Makefile_& and the Texinfo
2353 source of the documentation is found in the source tree, running &`make
2354 install`& automatically builds the info files and installs them.
2358 .section "Setting up the spool directory" "SECID33"
2359 .cindex "spool directory" "creating"
2360 When it starts up, Exim tries to create its spool directory if it does not
2361 exist. The Exim uid and gid are used for the owner and group of the spool
2362 directory. Sub-directories are automatically created in the spool directory as
2368 .section "Testing" "SECID34"
2369 .cindex "testing" "installation"
2370 Having installed Exim, you can check that the run time configuration file is
2371 syntactically valid by running the following command, which assumes that the
2372 Exim binary directory is within your PATH environment variable:
2376 If there are any errors in the configuration file, Exim outputs error messages.
2377 Otherwise it outputs the version number and build date,
2378 the DBM library that is being used, and information about which drivers and
2379 other optional code modules are included in the binary.
2380 Some simple routing tests can be done by using the address testing option. For
2383 &`exim -bt`& <&'local username'&>
2385 should verify that it recognizes a local mailbox, and
2387 &`exim -bt`& <&'remote address'&>
2389 a remote one. Then try getting it to deliver mail, both locally and remotely.
2390 This can be done by passing messages directly to Exim, without going through a
2391 user agent. For example:
2393 exim -v postmaster@your.domain.example
2394 From: user@your.domain.example
2395 To: postmaster@your.domain.example
2396 Subject: Testing Exim
2398 This is a test message.
2401 The &%-v%& option causes Exim to output some verification of what it is doing.
2402 In this case you should see copies of three log lines, one for the message's
2403 arrival, one for its delivery, and one containing &"Completed"&.
2405 .cindex "delivery" "problems with"
2406 If you encounter problems, look at Exim's log files (&'mainlog'& and
2407 &'paniclog'&) to see if there is any relevant information there. Another source
2408 of information is running Exim with debugging turned on, by specifying the
2409 &%-d%& option. If a message is stuck on Exim's spool, you can force a delivery
2410 with debugging turned on by a command of the form
2412 &`exim -d -M`& <&'exim-message-id'&>
2414 You must be root or an &"admin user"& in order to do this. The &%-d%& option
2415 produces rather a lot of output, but you can cut this down to specific areas.
2416 For example, if you use &%-d-all+route%& only the debugging information
2417 relevant to routing is included. (See the &%-d%& option in chapter
2418 &<<CHAPcommandline>>& for more details.)
2420 .cindex '&"sticky"& bit'
2421 .cindex "lock files"
2422 One specific problem that has shown up on some sites is the inability to do
2423 local deliveries into a shared mailbox directory, because it does not have the
2424 &"sticky bit"& set on it. By default, Exim tries to create a lock file before
2425 writing to a mailbox file, and if it cannot create the lock file, the delivery
2426 is deferred. You can get round this either by setting the &"sticky bit"& on the
2427 directory, or by setting a specific group for local deliveries and allowing
2428 that group to create files in the directory (see the comments above the
2429 &(local_delivery)& transport in the default configuration file). Another
2430 approach is to configure Exim not to use lock files, but just to rely on
2431 &[fcntl()]& locking instead. However, you should do this only if all user
2432 agents also use &[fcntl()]& locking. For further discussion of locking issues,
2433 see chapter &<<CHAPappendfile>>&.
2435 One thing that cannot be tested on a system that is already running an MTA is
2436 the receipt of incoming SMTP mail on the standard SMTP port. However, the
2437 &%-oX%& option can be used to run an Exim daemon that listens on some other
2438 port, or &'inetd'& can be used to do this. The &%-bh%& option and the
2439 &'exim_checkaccess'& utility can be used to check out policy controls on
2442 Testing a new version on a system that is already running Exim can most easily
2443 be done by building a binary with a different CONFIGURE_FILE setting. From
2444 within the run time configuration, all other file and directory names
2445 that Exim uses can be altered, in order to keep it entirely clear of the
2449 .section "Replacing another MTA with Exim" "SECID35"
2450 .cindex "replacing another MTA"
2451 Building and installing Exim for the first time does not of itself put it in
2452 general use. The name by which the system's MTA is called by mail user agents
2453 is either &_/usr/sbin/sendmail_&, or &_/usr/lib/sendmail_& (depending on the
2454 operating system), and it is necessary to make this name point to the &'exim'&
2455 binary in order to get the user agents to pass messages to Exim. This is
2456 normally done by renaming any existing file and making &_/usr/sbin/sendmail_&
2457 or &_/usr/lib/sendmail_&
2458 .cindex "symbolic link" "to &'exim'& binary"
2459 a symbolic link to the &'exim'& binary. It is a good idea to remove any setuid
2460 privilege and executable status from the old MTA. It is then necessary to stop
2461 and restart the mailer daemon, if one is running.
2463 .cindex "FreeBSD, MTA indirection"
2464 .cindex "&_/etc/mail/mailer.conf_&"
2465 Some operating systems have introduced alternative ways of switching MTAs. For
2466 example, if you are running FreeBSD, you need to edit the file
2467 &_/etc/mail/mailer.conf_& instead of setting up a symbolic link as just
2468 described. A typical example of the contents of this file for running Exim is
2471 sendmail /usr/exim/bin/exim
2472 send-mail /usr/exim/bin/exim
2473 mailq /usr/exim/bin/exim -bp
2474 newaliases /usr/bin/true
2476 Once you have set up the symbolic link, or edited &_/etc/mail/mailer.conf_&,
2477 your Exim installation is &"live"&. Check it by sending a message from your
2478 favourite user agent.
2480 You should consider what to tell your users about the change of MTA. Exim may
2481 have different capabilities to what was previously running, and there are
2482 various operational differences such as the text of messages produced by
2483 command line options and in bounce messages. If you allow your users to make
2484 use of Exim's filtering capabilities, you should make the document entitled
2485 &'Exim's interface to mail filtering'& available to them.
2489 .section "Upgrading Exim" "SECID36"
2490 .cindex "upgrading Exim"
2491 If you are already running Exim on your host, building and installing a new
2492 version automatically makes it available to MUAs, or any other programs that
2493 call the MTA directly. However, if you are running an Exim daemon, you do need
2494 to send it a HUP signal, to make it re-execute itself, and thereby pick up the
2495 new binary. You do not need to stop processing mail in order to install a new
2496 version of Exim. The install script does not modify an existing runtime
2502 .section "Stopping the Exim daemon on Solaris" "SECID37"
2503 .cindex "Solaris" "stopping Exim on"
2504 The standard command for stopping the mailer daemon on Solaris is
2506 /etc/init.d/sendmail stop
2508 If &_/usr/lib/sendmail_& has been turned into a symbolic link, this script
2509 fails to stop Exim because it uses the command &'ps -e'& and greps the output
2510 for the text &"sendmail"&; this is not present because the actual program name
2511 (that is, &"exim"&) is given by the &'ps'& command with these options. A
2512 solution is to replace the line that finds the process id with something like
2514 pid=`cat /var/spool/exim/exim-daemon.pid`
2516 to obtain the daemon's pid directly from the file that Exim saves it in.
2518 Note, however, that stopping the daemon does not &"stop Exim"&. Messages can
2519 still be received from local processes, and if automatic delivery is configured
2520 (the normal case), deliveries will still occur.
2525 . ////////////////////////////////////////////////////////////////////////////
2526 . ////////////////////////////////////////////////////////////////////////////
2528 .chapter "The Exim command line" "CHAPcommandline"
2529 .scindex IIDclo1 "command line" "options"
2530 .scindex IIDclo2 "options" "command line"
2531 Exim's command line takes the standard Unix form of a sequence of options,
2532 each starting with a hyphen character, followed by a number of arguments. The
2533 options are compatible with the main options of Sendmail, and there are also
2534 some additional options, some of which are compatible with Smail 3. Certain
2535 combinations of options do not make sense, and provoke an error if used.
2536 The form of the arguments depends on which options are set.
2539 .section "Setting options by program name" "SECID38"
2541 If Exim is called under the name &'mailq'&, it behaves as if the option &%-bp%&
2542 were present before any other options.
2543 The &%-bp%& option requests a listing of the contents of the mail queue on the
2545 This feature is for compatibility with some systems that contain a command of
2546 that name in one of the standard libraries, symbolically linked to
2547 &_/usr/sbin/sendmail_& or &_/usr/lib/sendmail_&.
2550 If Exim is called under the name &'rsmtp'& it behaves as if the option &%-bS%&
2551 were present before any other options, for compatibility with Smail. The
2552 &%-bS%& option is used for reading in a number of messages in batched SMTP
2556 If Exim is called under the name &'rmail'& it behaves as if the &%-i%& and
2557 &%-oee%& options were present before any other options, for compatibility with
2558 Smail. The name &'rmail'& is used as an interface by some UUCP systems.
2561 .cindex "queue runner"
2562 If Exim is called under the name &'runq'& it behaves as if the option &%-q%&
2563 were present before any other options, for compatibility with Smail. The &%-q%&
2564 option causes a single queue runner process to be started.
2566 .cindex "&'newaliases'&"
2567 .cindex "alias file" "building"
2568 .cindex "Sendmail compatibility" "calling Exim as &'newaliases'&"
2569 If Exim is called under the name &'newaliases'& it behaves as if the option
2570 &%-bi%& were present before any other options, for compatibility with Sendmail.
2571 This option is used for rebuilding Sendmail's alias file. Exim does not have
2572 the concept of a single alias file, but can be configured to run a given
2573 command if called with the &%-bi%& option.
2576 .section "Trusted and admin users" "SECTtrustedadmin"
2577 Some Exim options are available only to &'trusted users'& and others are
2578 available only to &'admin users'&. In the description below, the phrases &"Exim
2579 user"& and &"Exim group"& mean the user and group defined by EXIM_USER and
2580 EXIM_GROUP in &_Local/Makefile_& or set by the &%exim_user%& and
2581 &%exim_group%& options. These do not necessarily have to use the name &"exim"&.
2584 .cindex "trusted users" "definition of"
2585 .cindex "user" "trusted definition of"
2586 The trusted users are root, the Exim user, any user listed in the
2587 &%trusted_users%& configuration option, and any user whose current group or any
2588 supplementary group is one of those listed in the &%trusted_groups%&
2589 configuration option. Note that the Exim group is not automatically trusted.
2591 .cindex '&"From"& line'
2592 .cindex "envelope sender"
2593 Trusted users are always permitted to use the &%-f%& option or a leading
2594 &"From&~"& line to specify the envelope sender of a message that is passed to
2595 Exim through the local interface (see the &%-bm%& and &%-f%& options below).
2596 See the &%untrusted_set_sender%& option for a way of permitting non-trusted
2597 users to set envelope senders.
2599 .cindex "&'From:'& header line"
2600 .cindex "&'Sender:'& header line"
2601 For a trusted user, there is never any check on the contents of the &'From:'&
2602 header line, and a &'Sender:'& line is never added. Furthermore, any existing
2603 &'Sender:'& line in incoming local (non-TCP/IP) messages is not removed.
2605 Trusted users may also specify a host name, host address, interface address,
2606 protocol name, ident value, and authentication data when submitting a message
2607 locally. Thus, they are able to insert messages into Exim's queue locally that
2608 have the characteristics of messages received from a remote host. Untrusted
2609 users may in some circumstances use &%-f%&, but can never set the other values
2610 that are available to trusted users.
2612 .cindex "user" "admin definition of"
2613 .cindex "admin user" "definition of"
2614 The admin users are root, the Exim user, and any user that is a member of the
2615 Exim group or of any group listed in the &%admin_groups%& configuration option.
2616 The current group does not have to be one of these groups.
2618 Admin users are permitted to list the queue, and to carry out certain
2619 operations on messages, for example, to force delivery failures. It is also
2620 necessary to be an admin user in order to see the full information provided by
2621 the Exim monitor, and full debugging output.
2623 By default, the use of the &%-M%&, &%-q%&, &%-R%&, and &%-S%& options to cause
2624 Exim to attempt delivery of messages on its queue is restricted to admin users.
2625 However, this restriction can be relaxed by setting the &%prod_requires_admin%&
2626 option false (that is, specifying &%no_prod_requires_admin%&).
2628 Similarly, the use of the &%-bp%& option to list all the messages in the queue
2629 is restricted to admin users unless &%queue_list_requires_admin%& is set
2634 &*Warning*&: If you configure your system so that admin users are able to
2635 edit Exim's configuration file, you are giving those users an easy way of
2636 getting root. There is further discussion of this issue at the start of chapter
2642 .section "Command line options" "SECID39"
2643 Exim's command line options are described in alphabetical order below. If none
2644 of the options that specifies a specific action (such as starting the daemon or
2645 a queue runner, or testing an address, or receiving a message in a specific
2646 format, or listing the queue) are present, and there is at least one argument
2647 on the command line, &%-bm%& (accept a local message on the standard input,
2648 with the arguments specifying the recipients) is assumed. Otherwise, Exim
2649 outputs a brief message about itself and exits.
2651 . ////////////////////////////////////////////////////////////////////////////
2652 . Insert a stylized XML comment here, to identify the start of the command line
2653 . options. This is for the benefit of the Perl script that automatically
2654 . creates a man page for the options.
2655 . ////////////////////////////////////////////////////////////////////////////
2658 <!-- === Start of command line options === -->
2665 .cindex "options" "command line; terminating"
2666 This is a pseudo-option whose only purpose is to terminate the options and
2667 therefore to cause subsequent command line items to be treated as arguments
2668 rather than options, even if they begin with hyphens.
2671 .oindex "&%--help%&"
2672 This option causes Exim to output a few sentences stating what it is.
2673 The same output is generated if the Exim binary is called with no options and
2676 .vitem &%--version%&
2677 .oindex "&%--version%&"
2678 This option is an alias for &%-bV%& and causes version information to be
2686 These options are used by Sendmail for selecting configuration files and are
2690 .vitem &%-B%&<&'type'&>
2692 .cindex "8-bit characters"
2693 .cindex "Sendmail compatibility" "8-bit characters"
2694 This is a Sendmail option for selecting 7 or 8 bit processing. Exim is 8-bit
2695 clean; it ignores this option.
2700 .cindex "SMTP" "listener"
2701 .cindex "queue runner"
2702 This option runs Exim as a daemon, awaiting incoming SMTP connections. Usually
2703 the &%-bd%& option is combined with the &%-q%&<&'time'&> option, to specify
2704 that the daemon should also initiate periodic queue runs.
2706 The &%-bd%& option can be used only by an admin user. If either of the &%-d%&
2707 (debugging) or &%-v%& (verifying) options are set, the daemon does not
2708 disconnect from the controlling terminal. When running this way, it can be
2709 stopped by pressing ctrl-C.
2711 By default, Exim listens for incoming connections to the standard SMTP port on
2712 all the host's running interfaces. However, it is possible to listen on other
2713 ports, on multiple ports, and only on specific interfaces. Chapter
2714 &<<CHAPinterfaces>>& contains a description of the options that control this.
2716 When a listening daemon
2717 .cindex "daemon" "process id (pid)"
2718 .cindex "pid (process id)" "of daemon"
2719 is started without the use of &%-oX%& (that is, without overriding the normal
2720 configuration), it writes its process id to a file called &_exim-daemon.pid_&
2721 in Exim's spool directory. This location can be overridden by setting
2722 PID_FILE_PATH in &_Local/Makefile_&. The file is written while Exim is still
2725 When &%-oX%& is used on the command line to start a listening daemon, the
2726 process id is not written to the normal pid file path. However, &%-oP%& can be
2727 used to specify a path on the command line if a pid file is required.
2731 .cindex "daemon" "restarting"
2732 can be used to cause the daemon to re-execute itself. This should be done
2733 whenever Exim's configuration file, or any file that is incorporated into it by
2734 means of the &%.include%& facility, is changed, and also whenever a new version
2735 of Exim is installed. It is not necessary to do this when other files that are
2736 referenced from the configuration (for example, alias files) are changed,
2737 because these are reread each time they are used.
2741 This option has the same effect as &%-bd%& except that it never disconnects
2742 from the controlling terminal, even when no debugging is specified.
2746 .cindex "testing" "string expansion"
2747 .cindex "expansion" "testing"
2748 Run Exim in expansion testing mode. Exim discards its root privilege, to
2749 prevent ordinary users from using this mode to read otherwise inaccessible
2750 files. If no arguments are given, Exim runs interactively, prompting for lines
2751 of data. Otherwise, it processes each argument in turn.
2753 If Exim was built with USE_READLINE=yes in &_Local/Makefile_&, it tries
2754 to load the &%libreadline%& library dynamically whenever the &%-be%& option is
2755 used without command line arguments. If successful, it uses the &[readline()]&
2756 function, which provides extensive line-editing facilities, for reading the
2757 test data. A line history is supported.
2759 Long expansion expressions can be split over several lines by using backslash
2760 continuations. As in Exim's run time configuration, white space at the start of
2761 continuation lines is ignored. Each argument or data line is passed through the
2762 string expansion mechanism, and the result is output. Variable values from the
2763 configuration file (for example, &$qualify_domain$&) are available, but no
2764 message-specific values (such as &$sender_domain$&) are set, because no message
2765 is being processed (but see &%-bem%& and &%-Mset%&).
2767 &*Note*&: If you use this mechanism to test lookups, and you change the data
2768 files or databases you are using, you must exit and restart Exim before trying
2769 the same lookup again. Otherwise, because each Exim process caches the results
2770 of lookups, you will just get the same result as before.
2772 .vitem &%-bem%&&~<&'filename'&>
2774 .cindex "testing" "string expansion"
2775 .cindex "expansion" "testing"
2776 This option operates like &%-be%& except that it must be followed by the name
2777 of a file. For example:
2779 exim -bem /tmp/testmessage
2781 The file is read as a message (as if receiving a locally-submitted non-SMTP
2782 message) before any of the test expansions are done. Thus, message-specific
2783 variables such as &$message_size$& and &$header_from:$& are available. However,
2784 no &'Received:'& header is added to the message. If the &%-t%& option is set,
2785 recipients are read from the headers in the normal way, and are shown in the
2786 &$recipients$& variable. Note that recipients cannot be given on the command
2787 line, because further arguments are taken as strings to expand (just like
2790 .vitem &%-bF%&&~<&'filename'&>
2792 .cindex "system filter" "testing"
2793 .cindex "testing" "system filter"
2794 This option is the same as &%-bf%& except that it assumes that the filter being
2795 tested is a system filter. The additional commands that are available only in
2796 system filters are recognized.
2798 .vitem &%-bf%&&~<&'filename'&>
2800 .cindex "filter" "testing"
2801 .cindex "testing" "filter file"
2802 .cindex "forward file" "testing"
2803 .cindex "testing" "forward file"
2804 .cindex "Sieve filter" "testing"
2805 This option runs Exim in user filter testing mode; the file is the filter file
2806 to be tested, and a test message must be supplied on the standard input. If
2807 there are no message-dependent tests in the filter, an empty file can be
2810 If you want to test a system filter file, use &%-bF%& instead of &%-bf%&. You
2811 can use both &%-bF%& and &%-bf%& on the same command, in order to test a system
2812 filter and a user filter in the same run. For example:
2814 exim -bF /system/filter -bf /user/filter </test/message
2816 This is helpful when the system filter adds header lines or sets filter
2817 variables that are used by the user filter.
2819 If the test filter file does not begin with one of the special lines
2824 it is taken to be a normal &_.forward_& file, and is tested for validity under
2825 that interpretation. See sections &<<SECTitenonfilred>>& to
2826 &<<SECTspecitredli>>& for a description of the possible contents of non-filter
2829 The result of an Exim command that uses &%-bf%&, provided no errors are
2830 detected, is a list of the actions that Exim would try to take if presented
2831 with the message for real. More details of filter testing are given in the
2832 separate document entitled &'Exim's interfaces to mail filtering'&.
2834 When testing a filter file,
2835 .cindex "&""From""& line"
2836 .cindex "envelope sender"
2837 .oindex "&%-f%&" "for filter testing"
2838 the envelope sender can be set by the &%-f%& option,
2839 or by a &"From&~"& line at the start of the test message. Various parameters
2840 that would normally be taken from the envelope recipient address of the message
2841 can be set by means of additional command line options (see the next four
2844 .vitem &%-bfd%&&~<&'domain'&>
2846 .vindex "&$qualify_domain$&"
2847 This sets the domain of the recipient address when a filter file is being
2848 tested by means of the &%-bf%& option. The default is the value of
2851 .vitem &%-bfl%&&~<&'local&~part'&>
2853 This sets the local part of the recipient address when a filter file is being
2854 tested by means of the &%-bf%& option. The default is the username of the
2855 process that calls Exim. A local part should be specified with any prefix or
2856 suffix stripped, because that is how it appears to the filter when a message is
2857 actually being delivered.
2859 .vitem &%-bfp%&&~<&'prefix'&>
2861 This sets the prefix of the local part of the recipient address when a filter
2862 file is being tested by means of the &%-bf%& option. The default is an empty
2865 .vitem &%-bfs%&&~<&'suffix'&>
2867 This sets the suffix of the local part of the recipient address when a filter
2868 file is being tested by means of the &%-bf%& option. The default is an empty
2871 .vitem &%-bh%&&~<&'IP&~address'&>
2873 .cindex "testing" "incoming SMTP"
2874 .cindex "SMTP" "testing incoming"
2875 .cindex "testing" "relay control"
2876 .cindex "relaying" "testing configuration"
2877 .cindex "policy control" "testing"
2878 .cindex "debugging" "&%-bh%& option"
2879 This option runs a fake SMTP session as if from the given IP address, using the
2880 standard input and output. The IP address may include a port number at the end,
2881 after a full stop. For example:
2883 exim -bh 10.9.8.7.1234
2884 exim -bh fe80::a00:20ff:fe86:a061.5678
2886 When an IPv6 address is given, it is converted into canonical form. In the case
2887 of the second example above, the value of &$sender_host_address$& after
2888 conversion to the canonical form is
2889 &`fe80:0000:0000:0a00:20ff:fe86:a061.5678`&.
2891 Comments as to what is going on are written to the standard error file. These
2892 include lines beginning with &"LOG"& for anything that would have been logged.
2893 This facility is provided for testing configuration options for incoming
2894 messages, to make sure they implement the required policy. For example, you can
2895 test your relay controls using &%-bh%&.
2899 You can test features of the configuration that rely on ident (RFC 1413)
2900 information by using the &%-oMt%& option. However, Exim cannot actually perform
2901 an ident callout when testing using &%-bh%& because there is no incoming SMTP
2904 &*Warning 2*&: Address verification callouts (see section &<<SECTcallver>>&)
2905 are also skipped when testing using &%-bh%&. If you want these callouts to
2906 occur, use &%-bhc%& instead.
2908 Messages supplied during the testing session are discarded, and nothing is
2909 written to any of the real log files. There may be pauses when DNS (and other)
2910 lookups are taking place, and of course these may time out. The &%-oMi%& option
2911 can be used to specify a specific IP interface and port if this is important,
2912 and &%-oMaa%& and &%-oMai%& can be used to set parameters as if the SMTP
2913 session were authenticated.
2915 The &'exim_checkaccess'& utility is a &"packaged"& version of &%-bh%& whose
2916 output just states whether a given recipient address from a given host is
2917 acceptable or not. See section &<<SECTcheckaccess>>&.
2919 Features such as authentication and encryption, where the client input is not
2920 plain text, cannot easily be tested with &%-bh%&. Instead, you should use a
2921 specialized SMTP test program such as
2922 &url(http://jetmore.org/john/code/#swaks,swaks).
2924 .vitem &%-bhc%&&~<&'IP&~address'&>
2926 This option operates in the same way as &%-bh%&, except that address
2927 verification callouts are performed if required. This includes consulting and
2928 updating the callout cache database.
2932 .cindex "alias file" "building"
2933 .cindex "building alias file"
2934 .cindex "Sendmail compatibility" "&%-bi%& option"
2935 Sendmail interprets the &%-bi%& option as a request to rebuild its alias file.
2936 Exim does not have the concept of a single alias file, and so it cannot mimic
2937 this behaviour. However, calls to &_/usr/lib/sendmail_& with the &%-bi%& option
2938 tend to appear in various scripts such as NIS make files, so the option must be
2941 If &%-bi%& is encountered, the command specified by the &%bi_command%&
2942 configuration option is run, under the uid and gid of the caller of Exim. If
2943 the &%-oA%& option is used, its value is passed to the command as an argument.
2944 The command set by &%bi_command%& may not contain arguments. The command can
2945 use the &'exim_dbmbuild'& utility, or some other means, to rebuild alias files
2946 if this is required. If the &%bi_command%& option is not set, calling Exim with
2950 . // Keep :help first, then the rest in alphabetical order
2952 .oindex "&%-bI:help%&"
2953 .cindex "querying exim information"
2954 We shall provide various options starting &`-bI:`& for querying Exim for
2955 information. The output of many of these will be intended for machine
2956 consumption. This one is not. The &%-bI:help%& option asks Exim for a
2957 synopsis of supported options beginning &`-bI:`&. Use of any of these
2958 options shall cause Exim to exit after producing the requested output.
2961 .oindex "&%-bI:dscp%&"
2962 .cindex "DSCP" "values"
2963 This option causes Exim to emit an alphabetically sorted list of all
2964 recognised DSCP names.
2966 .vitem &%-bI:sieve%&
2967 .oindex "&%-bI:sieve%&"
2968 .cindex "Sieve filter" "capabilities"
2969 This option causes Exim to emit an alphabetically sorted list of all supported
2970 Sieve protocol extensions on stdout, one per line. This is anticipated to be
2971 useful for ManageSieve (RFC 5804) implementations, in providing that protocol's
2972 &`SIEVE`& capability response line. As the precise list may depend upon
2973 compile-time build options, which this option will adapt to, this is the only
2974 way to guarantee a correct response.
2979 .cindex "local message reception"
2980 This option runs an Exim receiving process that accepts an incoming,
2981 locally-generated message on the current input. The recipients are given as the
2982 command arguments (except when &%-t%& is also present &-- see below). Each
2983 argument can be a comma-separated list of RFC 2822 addresses. This is the
2984 default option for selecting the overall action of an Exim call; it is assumed
2985 if no other conflicting option is present.
2987 If any addresses in the message are unqualified (have no domain), they are
2988 qualified by the values of the &%qualify_domain%& or &%qualify_recipient%&
2989 options, as appropriate. The &%-bnq%& option (see below) provides a way of
2990 suppressing this for special cases.
2992 Policy checks on the contents of local messages can be enforced by means of
2993 the non-SMTP ACL. See chapter &<<CHAPACL>>& for details.
2995 .cindex "return code" "for &%-bm%&"
2996 The return code is zero if the message is successfully accepted. Otherwise, the
2997 action is controlled by the &%-oe%&&'x'& option setting &-- see below.
3000 .cindex "message" "format"
3001 .cindex "format" "message"
3002 .cindex "&""From""& line"
3003 .cindex "UUCP" "&""From""& line"
3004 .cindex "Sendmail compatibility" "&""From""& line"
3005 of the message must be as defined in RFC 2822, except that, for
3006 compatibility with Sendmail and Smail, a line in one of the forms
3008 From sender Fri Jan 5 12:55 GMT 1997
3009 From sender Fri, 5 Jan 97 12:55:01
3011 (with the weekday optional, and possibly with additional text after the date)
3012 is permitted to appear at the start of the message. There appears to be no
3013 authoritative specification of the format of this line. Exim recognizes it by
3014 matching against the regular expression defined by the &%uucp_from_pattern%&
3015 option, which can be changed if necessary.
3017 .oindex "&%-f%&" "overriding &""From""& line"
3018 The specified sender is treated as if it were given as the argument to the
3019 &%-f%& option, but if a &%-f%& option is also present, its argument is used in
3020 preference to the address taken from the message. The caller of Exim must be a
3021 trusted user for the sender of a message to be set in this way.
3023 .vitem &%-bmalware%&&~<&'filename'&>
3024 .oindex "&%-bmalware%&"
3025 .cindex "testing", "malware"
3026 .cindex "malware scan test"
3027 This debugging option causes Exim to scan the given file,
3028 using the malware scanning framework. The option of &%av_scanner%& influences
3029 this option, so if &%av_scanner%&'s value is dependent upon an expansion then
3030 the expansion should have defaults which apply to this invocation. ACLs are
3031 not invoked, so if &%av_scanner%& references an ACL variable then that variable
3032 will never be populated and &%-bmalware%& will fail.
3034 Exim will have changed working directory before resolving the filename, so
3035 using fully qualified pathnames is advisable. Exim will be running as the Exim
3036 user when it tries to open the file, rather than as the invoking user.
3037 This option requires admin privileges.
3039 The &%-bmalware%& option will not be extended to be more generally useful,
3040 there are better tools for file-scanning. This option exists to help
3041 administrators verify their Exim and AV scanner configuration.
3045 .cindex "address qualification, suppressing"
3046 By default, Exim automatically qualifies unqualified addresses (those
3047 without domains) that appear in messages that are submitted locally (that
3048 is, not over TCP/IP). This qualification applies both to addresses in
3049 envelopes, and addresses in header lines. Sender addresses are qualified using
3050 &%qualify_domain%&, and recipient addresses using &%qualify_recipient%& (which
3051 defaults to the value of &%qualify_domain%&).
3053 Sometimes, qualification is not wanted. For example, if &%-bS%& (batch SMTP) is
3054 being used to re-submit messages that originally came from remote hosts after
3055 content scanning, you probably do not want to qualify unqualified addresses in
3056 header lines. (Such lines will be present only if you have not enabled a header
3057 syntax check in the appropriate ACL.)
3059 The &%-bnq%& option suppresses all qualification of unqualified addresses in
3060 messages that originate on the local host. When this is used, unqualified
3061 addresses in the envelope provoke errors (causing message rejection) and
3062 unqualified addresses in header lines are left alone.
3067 .cindex "configuration options" "extracting"
3068 .cindex "options" "configuration &-- extracting"
3069 If this option is given with no arguments, it causes the values of all Exim's
3070 main configuration options to be written to the standard output. The values
3071 of one or more specific options can be requested by giving their names as
3072 arguments, for example:
3074 exim -bP qualify_domain hold_domains
3076 .cindex "hiding configuration option values"
3077 .cindex "configuration options" "hiding value of"
3078 .cindex "options" "hiding value of"
3079 However, any option setting that is preceded by the word &"hide"& in the
3080 configuration file is not shown in full, except to an admin user. For other
3081 users, the output is as in this example:
3083 mysql_servers = <value not displayable>
3085 If &%configure_file%& is given as an argument, the name of the run time
3086 configuration file is output.
3087 If a list of configuration files was supplied, the value that is output here
3088 is the name of the file that was actually used.
3091 .cindex "options" "hiding name of"
3092 If the &%-n%& flag is given, then for most modes of &%-bP%& operation the
3093 name will not be output.
3096 .cindex "daemon" "process id (pid)"
3097 .cindex "pid (process id)" "of daemon"
3098 If &%log_file_path%& or &%pid_file_path%& are given, the names of the
3099 directories where log files and daemon pid files are written are output,
3100 respectively. If these values are unset, log files are written in a
3101 sub-directory of the spool directory called &%log%&, and the pid file is
3102 written directly into the spool directory.
3104 If &%-bP%& is followed by a name preceded by &`+`&, for example,
3106 exim -bP +local_domains
3108 it searches for a matching named list of any type (domain, host, address, or
3109 local part) and outputs what it finds.
3111 .cindex "options" "router &-- extracting"
3112 .cindex "options" "transport &-- extracting"
3113 .cindex "options" "authenticator &-- extracting"
3114 If one of the words &%router%&, &%transport%&, or &%authenticator%& is given,
3115 followed by the name of an appropriate driver instance, the option settings for
3116 that driver are output. For example:
3118 exim -bP transport local_delivery
3120 The generic driver options are output first, followed by the driver's private
3121 options. A list of the names of drivers of a particular type can be obtained by
3122 using one of the words &%router_list%&, &%transport_list%&, or
3123 &%authenticator_list%&, and a complete list of all drivers with their option
3124 settings can be obtained by using &%routers%&, &%transports%&, or
3127 .cindex "options" "macro &-- extracting"
3128 If invoked by an admin user, then &%macro%&, &%macro_list%& and &%macros%&
3129 are available, similarly to the drivers. Because macros are sometimes used
3130 for storing passwords, this option is restricted.
3131 The output format is one item per line.
3135 .cindex "queue" "listing messages on"
3136 .cindex "listing" "messages on the queue"
3137 This option requests a listing of the contents of the mail queue on the
3138 standard output. If the &%-bp%& option is followed by a list of message ids,
3139 just those messages are listed. By default, this option can be used only by an
3140 admin user. However, the &%queue_list_requires_admin%& option can be set false
3141 to allow any user to see the queue.
3143 Each message on the queue is displayed as in the following example:
3145 25m 2.9K 0t5C6f-0000c8-00 <alice@wonderland.fict.example>
3146 red.king@looking-glass.fict.example
3149 .cindex "message" "size in queue listing"
3150 .cindex "size" "of message"
3151 The first line contains the length of time the message has been on the queue
3152 (in this case 25 minutes), the size of the message (2.9K), the unique local
3153 identifier for the message, and the message sender, as contained in the
3154 envelope. For bounce messages, the sender address is empty, and appears as
3155 &"<>"&. If the message was submitted locally by an untrusted user who overrode
3156 the default sender address, the user's login name is shown in parentheses
3157 before the sender address.
3159 .cindex "frozen messages" "in queue listing"
3160 If the message is frozen (attempts to deliver it are suspended) then the text
3161 &"*** frozen ***"& is displayed at the end of this line.
3163 The recipients of the message (taken from the envelope, not the headers) are
3164 displayed on subsequent lines. Those addresses to which the message has already
3165 been delivered are marked with the letter D. If an original address gets
3166 expanded into several addresses via an alias or forward file, the original is
3167 displayed with a D only when deliveries for all of its child addresses are
3173 This option operates like &%-bp%&, but in addition it shows delivered addresses
3174 that were generated from the original top level address(es) in each message by
3175 alias or forwarding operations. These addresses are flagged with &"+D"& instead
3181 .cindex "queue" "count of messages on"
3182 This option counts the number of messages on the queue, and writes the total
3183 to the standard output. It is restricted to admin users, unless
3184 &%queue_list_requires_admin%& is set false.
3189 This option operates like &%-bp%&, but the output is not sorted into
3190 chronological order of message arrival. This can speed it up when there are
3191 lots of messages on the queue, and is particularly useful if the output is
3192 going to be post-processed in a way that doesn't need the sorting.
3196 This option is a combination of &%-bpr%& and &%-bpa%&.
3200 This option is a combination of &%-bpr%& and &%-bpu%&.
3205 This option operates like &%-bp%& but shows only undelivered top-level
3206 addresses for each message displayed. Addresses generated by aliasing or
3207 forwarding are not shown, unless the message was deferred after processing by a
3208 router with the &%one_time%& option set.
3213 .cindex "testing" "retry configuration"
3214 .cindex "retry" "configuration testing"
3215 This option is for testing retry rules, and it must be followed by up to three
3216 arguments. It causes Exim to look for a retry rule that matches the values
3217 and to write it to the standard output. For example:
3219 exim -brt bach.comp.mus.example
3220 Retry rule: *.comp.mus.example F,2h,15m; F,4d,30m;
3222 See chapter &<<CHAPretry>>& for a description of Exim's retry rules. The first
3223 argument, which is required, can be a complete address in the form
3224 &'local_part@domain'&, or it can be just a domain name. If the second argument
3225 contains a dot, it is interpreted as an optional second domain name; if no
3226 retry rule is found for the first argument, the second is tried. This ties in
3227 with Exim's behaviour when looking for retry rules for remote hosts &-- if no
3228 rule is found that matches the host, one that matches the mail domain is
3229 sought. Finally, an argument that is the name of a specific delivery error, as
3230 used in setting up retry rules, can be given. For example:
3232 exim -brt haydn.comp.mus.example quota_3d
3233 Retry rule: *@haydn.comp.mus.example quota_3d F,1h,15m
3238 .cindex "testing" "rewriting"
3239 .cindex "rewriting" "testing"
3240 This option is for testing address rewriting rules, and it must be followed by
3241 a single argument, consisting of either a local part without a domain, or a
3242 complete address with a fully qualified domain. Exim outputs how this address
3243 would be rewritten for each possible place it might appear. See chapter
3244 &<<CHAPrewrite>>& for further details.
3248 .cindex "SMTP" "batched incoming"
3249 .cindex "batched SMTP input"
3250 This option is used for batched SMTP input, which is an alternative interface
3251 for non-interactive local message submission. A number of messages can be
3252 submitted in a single run. However, despite its name, this is not really SMTP
3253 input. Exim reads each message's envelope from SMTP commands on the standard
3254 input, but generates no responses. If the caller is trusted, or
3255 &%untrusted_set_sender%& is set, the senders in the SMTP MAIL commands are
3256 believed; otherwise the sender is always the caller of Exim.
3258 The message itself is read from the standard input, in SMTP format (leading
3259 dots doubled), terminated by a line containing just a single dot. An error is
3260 provoked if the terminating dot is missing. A further message may then follow.
3262 As for other local message submissions, the contents of incoming batch SMTP
3263 messages can be checked using the non-SMTP ACL (see chapter &<<CHAPACL>>&).
3264 Unqualified addresses are automatically qualified using &%qualify_domain%& and
3265 &%qualify_recipient%&, as appropriate, unless the &%-bnq%& option is used.
3267 Some other SMTP commands are recognized in the input. HELO and EHLO act
3268 as RSET; VRFY, EXPN, ETRN, and HELP act as NOOP;
3269 QUIT quits, ignoring the rest of the standard input.
3271 .cindex "return code" "for &%-bS%&"
3272 If any error is encountered, reports are written to the standard output and
3273 error streams, and Exim gives up immediately. The return code is 0 if no error
3274 was detected; it is 1 if one or more messages were accepted before the error
3275 was detected; otherwise it is 2.
3277 More details of input using batched SMTP are given in section
3278 &<<SECTincomingbatchedSMTP>>&.
3282 .cindex "SMTP" "local input"
3283 .cindex "local SMTP input"
3284 This option causes Exim to accept one or more messages by reading SMTP commands
3285 on the standard input, and producing SMTP replies on the standard output. SMTP
3286 policy controls, as defined in ACLs (see chapter &<<CHAPACL>>&) are applied.
3287 Some user agents use this interface as a way of passing locally-generated
3288 messages to the MTA.
3291 .cindex "sender" "source of"
3292 this usage, if the caller of Exim is trusted, or &%untrusted_set_sender%& is
3293 set, the senders of messages are taken from the SMTP MAIL commands.
3294 Otherwise the content of these commands is ignored and the sender is set up as
3295 the calling user. Unqualified addresses are automatically qualified using
3296 &%qualify_domain%& and &%qualify_recipient%&, as appropriate, unless the
3297 &%-bnq%& option is used.
3301 &%-bs%& option is also used to run Exim from &'inetd'&, as an alternative to
3302 using a listening daemon. Exim can distinguish the two cases by checking
3303 whether the standard input is a TCP/IP socket. When Exim is called from
3304 &'inetd'&, the source of the mail is assumed to be remote, and the comments
3305 above concerning senders and qualification do not apply. In this situation,
3306 Exim behaves in exactly the same way as it does when receiving a message via
3307 the listening daemon.
3311 .cindex "testing" "addresses"
3312 .cindex "address" "testing"
3313 This option runs Exim in address testing mode, in which each argument is taken
3314 as a recipient address to be tested for deliverability. The results are
3315 written to the standard output. If a test fails, and the caller is not an admin
3316 user, no details of the failure are output, because these might contain
3317 sensitive information such as usernames and passwords for database lookups.
3319 If no arguments are given, Exim runs in an interactive manner, prompting with a
3320 right angle bracket for addresses to be tested.
3322 Unlike the &%-be%& test option, you cannot arrange for Exim to use the
3323 &[readline()]& function, because it is running as &'root'& and there are
3326 Each address is handled as if it were the recipient address of a message
3327 (compare the &%-bv%& option). It is passed to the routers and the result is
3328 written to the standard output. However, any router that has
3329 &%no_address_test%& set is bypassed. This can make &%-bt%& easier to use for
3330 genuine routing tests if your first router passes everything to a scanner
3333 .cindex "return code" "for &%-bt%&"
3334 The return code is 2 if any address failed outright; it is 1 if no address
3335 failed outright but at least one could not be resolved for some reason. Return
3336 code 0 is given only when all addresses succeed.
3338 .cindex "duplicate addresses"
3339 &*Note*&: When actually delivering a message, Exim removes duplicate recipient
3340 addresses after routing is complete, so that only one delivery takes place.
3341 This does not happen when testing with &%-bt%&; the full results of routing are
3344 &*Warning*&: &%-bt%& can only do relatively simple testing. If any of the
3345 routers in the configuration makes any tests on the sender address of a
3347 .oindex "&%-f%&" "for address testing"
3348 you can use the &%-f%& option to set an appropriate sender when running
3349 &%-bt%& tests. Without it, the sender is assumed to be the calling user at the
3350 default qualifying domain. However, if you have set up (for example) routers
3351 whose behaviour depends on the contents of an incoming message, you cannot test
3352 those conditions using &%-bt%&. The &%-N%& option provides a possible way of
3357 .cindex "version number of Exim"
3358 This option causes Exim to write the current version number, compilation
3359 number, and compilation date of the &'exim'& binary to the standard output.
3360 It also lists the DBM library that is being used, the optional modules (such as
3361 specific lookup types), the drivers that are included in the binary, and the
3362 name of the run time configuration file that is in use.
3364 As part of its operation, &%-bV%& causes Exim to read and syntax check its
3365 configuration file. However, this is a static check only. It cannot check
3366 values that are to be expanded. For example, although a misspelt ACL verb is
3367 detected, an error in the verb's arguments is not. You cannot rely on &%-bV%&
3368 alone to discover (for example) all the typos in the configuration; some
3369 realistic testing is needed. The &%-bh%& and &%-N%& options provide more
3370 dynamic testing facilities.
3374 .cindex "verifying address" "using &%-bv%&"
3375 .cindex "address" "verification"
3376 This option runs Exim in address verification mode, in which each argument is
3377 taken as a recipient address to be verified by the routers. (This does
3378 not involve any verification callouts). During normal operation, verification
3379 happens mostly as a consequence processing a &%verify%& condition in an ACL
3380 (see chapter &<<CHAPACL>>&). If you want to test an entire ACL, possibly
3381 including callouts, see the &%-bh%& and &%-bhc%& options.
3383 If verification fails, and the caller is not an admin user, no details of the
3384 failure are output, because these might contain sensitive information such as
3385 usernames and passwords for database lookups.
3387 If no arguments are given, Exim runs in an interactive manner, prompting with a
3388 right angle bracket for addresses to be verified.
3390 Unlike the &%-be%& test option, you cannot arrange for Exim to use the
3391 &[readline()]& function, because it is running as &'exim'& and there are
3394 Verification differs from address testing (the &%-bt%& option) in that routers
3395 that have &%no_verify%& set are skipped, and if the address is accepted by a
3396 router that has &%fail_verify%& set, verification fails. The address is
3397 verified as a recipient if &%-bv%& is used; to test verification for a sender
3398 address, &%-bvs%& should be used.
3400 If the &%-v%& option is not set, the output consists of a single line for each
3401 address, stating whether it was verified or not, and giving a reason in the
3402 latter case. Without &%-v%&, generating more than one address by redirection
3403 causes verification to end successfully, without considering the generated
3404 addresses. However, if just one address is generated, processing continues,
3405 and the generated address must verify successfully for the overall verification
3408 When &%-v%& is set, more details are given of how the address has been handled,
3409 and in the case of address redirection, all the generated addresses are also
3410 considered. Verification may succeed for some and fail for others.
3413 .cindex "return code" "for &%-bv%&"
3414 return code is 2 if any address failed outright; it is 1 if no address
3415 failed outright but at least one could not be resolved for some reason. Return
3416 code 0 is given only when all addresses succeed.
3418 If any of the routers in the configuration makes any tests on the sender
3419 address of a message, you should use the &%-f%& option to set an appropriate
3420 sender when running &%-bv%& tests. Without it, the sender is assumed to be the
3421 calling user at the default qualifying domain.
3425 This option acts like &%-bv%&, but verifies the address as a sender rather
3426 than a recipient address. This affects any rewriting and qualification that
3433 .cindex "inetd" "wait mode"
3434 This option runs Exim as a daemon, awaiting incoming SMTP connections,
3435 similarly to the &%-bd%& option. All port specifications on the command-line
3436 and in the configuration file are ignored. Queue-running may not be specified.
3438 In this mode, Exim expects to be passed a socket as fd 0 (stdin) which is
3439 listening for connections. This permits the system to start up and have
3440 inetd (or equivalent) listen on the SMTP ports, starting an Exim daemon for
3441 each port only when the first connection is received.
3443 If the option is given as &%-bw%&<&'time'&> then the time is a timeout, after
3444 which the daemon will exit, which should cause inetd to listen once more.
3446 .vitem &%-C%&&~<&'filelist'&>
3448 .cindex "configuration file" "alternate"
3449 .cindex "CONFIGURE_FILE"
3450 .cindex "alternate configuration file"
3451 This option causes Exim to find the run time configuration file from the given
3452 list instead of from the list specified by the CONFIGURE_FILE
3453 compile-time setting. Usually, the list will consist of just a single file
3454 name, but it can be a colon-separated list of names. In this case, the first
3455 file that exists is used. Failure to open an existing file stops Exim from
3456 proceeding any further along the list, and an error is generated.
3458 When this option is used by a caller other than root, and the list is different
3459 from the compiled-in list, Exim gives up its root privilege immediately, and
3460 runs with the real and effective uid and gid set to those of the caller.
3461 However, if a TRUSTED_CONFIG_LIST file is defined in &_Local/Makefile_&, that
3462 file contains a list of full pathnames, one per line, for configuration files
3463 which are trusted. Root privilege is retained for any configuration file so
3464 listed, as long as the caller is the Exim user (or the user specified in the
3465 CONFIGURE_OWNER option, if any), and as long as the configuration file is
3466 not writeable by inappropriate users or groups.
3468 Leaving TRUSTED_CONFIG_LIST unset precludes the possibility of testing a
3469 configuration using &%-C%& right through message reception and delivery,
3470 even if the caller is root. The reception works, but by that time, Exim is
3471 running as the Exim user, so when it re-executes to regain privilege for the
3472 delivery, the use of &%-C%& causes privilege to be lost. However, root can
3473 test reception and delivery using two separate commands (one to put a message
3474 on the queue, using &%-odq%&, and another to do the delivery, using &%-M%&).
3476 If ALT_CONFIG_PREFIX is defined &_in Local/Makefile_&, it specifies a
3477 prefix string with which any file named in a &%-C%& command line option
3478 must start. In addition, the file name must not contain the sequence &`/../`&.
3479 However, if the value of the &%-C%& option is identical to the value of
3480 CONFIGURE_FILE in &_Local/Makefile_&, Exim ignores &%-C%& and proceeds as
3481 usual. There is no default setting for ALT_CONFIG_PREFIX; when it is
3482 unset, any file name can be used with &%-C%&.
3484 ALT_CONFIG_PREFIX can be used to confine alternative configuration files
3485 to a directory to which only root has access. This prevents someone who has
3486 broken into the Exim account from running a privileged Exim with an arbitrary
3489 The &%-C%& facility is useful for ensuring that configuration files are
3490 syntactically correct, but cannot be used for test deliveries, unless the
3491 caller is privileged, or unless it is an exotic configuration that does not
3492 require privilege. No check is made on the owner or group of the files
3493 specified by this option.
3496 .vitem &%-D%&<&'macro'&>=<&'value'&>
3498 .cindex "macro" "setting on command line"
3499 This option can be used to override macro definitions in the configuration file
3500 (see section &<<SECTmacrodefs>>&). However, like &%-C%&, if it is used by an
3501 unprivileged caller, it causes Exim to give up its root privilege.
3502 If DISABLE_D_OPTION is defined in &_Local/Makefile_&, the use of &%-D%& is
3503 completely disabled, and its use causes an immediate error exit.
3505 If WHITELIST_D_MACROS is defined in &_Local/Makefile_& then it should be a
3506 colon-separated list of macros which are considered safe and, if &%-D%& only
3507 supplies macros from this list, and the values are acceptable, then Exim will
3508 not give up root privilege if the caller is root, the Exim run-time user, or
3509 the CONFIGURE_OWNER, if set. This is a transition mechanism and is expected
3510 to be removed in the future. Acceptable values for the macros satisfy the
3511 regexp: &`^[A-Za-z0-9_/.-]*$`&
3513 The entire option (including equals sign if present) must all be within one
3514 command line item. &%-D%& can be used to set the value of a macro to the empty
3515 string, in which case the equals sign is optional. These two commands are
3521 To include spaces in a macro definition item, quotes must be used. If you use
3522 quotes, spaces are permitted around the macro name and the equals sign. For
3525 exim '-D ABC = something' ...
3527 &%-D%& may be repeated up to 10 times on a command line.
3530 .vitem &%-d%&<&'debug&~options'&>
3532 .cindex "debugging" "list of selectors"
3533 .cindex "debugging" "&%-d%& option"
3534 This option causes debugging information to be written to the standard
3535 error stream. It is restricted to admin users because debugging output may show
3536 database queries that contain password information. Also, the details of users'
3537 filter files should be protected. If a non-admin user uses &%-d%&, Exim
3538 writes an error message to the standard error stream and exits with a non-zero
3541 When &%-d%& is used, &%-v%& is assumed. If &%-d%& is given on its own, a lot of
3542 standard debugging data is output. This can be reduced, or increased to include
3543 some more rarely needed information, by directly following &%-d%& with a string
3544 made up of names preceded by plus or minus characters. These add or remove sets
3545 of debugging data, respectively. For example, &%-d+filter%& adds filter
3546 debugging, whereas &%-d-all+filter%& selects only filter debugging. Note that
3547 no spaces are allowed in the debug setting. The available debugging categories
3550 &`acl `& ACL interpretation
3551 &`auth `& authenticators
3552 &`deliver `& general delivery logic
3553 &`dns `& DNS lookups (see also resolver)
3554 &`dnsbl `& DNS black list (aka RBL) code
3555 &`exec `& arguments for &[execv()]& calls
3556 &`expand `& detailed debugging for string expansions
3557 &`filter `& filter handling
3558 &`hints_lookup `& hints data lookups
3559 &`host_lookup `& all types of name-to-IP address handling
3560 &`ident `& ident lookup
3561 &`interface `& lists of local interfaces
3562 &`lists `& matching things in lists
3563 &`load `& system load checks
3564 &`local_scan `& can be used by &[local_scan()]& (see chapter &&&
3565 &<<CHAPlocalscan>>&)
3566 &`lookup `& general lookup code and all lookups
3567 &`memory `& memory handling
3568 &`pid `& add pid to debug output lines
3569 &`process_info `& setting info for the process log
3570 &`queue_run `& queue runs
3571 &`receive `& general message reception logic
3572 &`resolver `& turn on the DNS resolver's debugging output
3573 &`retry `& retry handling
3574 &`rewrite `& address rewriting
3575 &`route `& address routing
3576 &`timestamp `& add timestamp to debug output lines
3578 &`transport `& transports
3579 &`uid `& changes of uid/gid and looking up uid/gid
3580 &`verify `& address verification logic
3581 &`all `& almost all of the above (see below), and also &%-v%&
3583 The &`all`& option excludes &`memory`& when used as &`+all`&, but includes it
3584 for &`-all`&. The reason for this is that &`+all`& is something that people
3585 tend to use when generating debug output for Exim maintainers. If &`+memory`&
3586 is included, an awful lot of output that is very rarely of interest is
3587 generated, so it now has to be explicitly requested. However, &`-all`& does
3588 turn everything off.
3590 .cindex "resolver, debugging output"
3591 .cindex "DNS resolver, debugging output"
3592 The &`resolver`& option produces output only if the DNS resolver was compiled
3593 with DEBUG enabled. This is not the case in some operating systems. Also,
3594 unfortunately, debugging output from the DNS resolver is written to stdout
3597 The default (&%-d%& with no argument) omits &`expand`&, &`filter`&,
3598 &`interface`&, &`load`&, &`memory`&, &`pid`&, &`resolver`&, and &`timestamp`&.
3599 However, the &`pid`& selector is forced when debugging is turned on for a
3600 daemon, which then passes it on to any re-executed Exims. Exim also
3601 automatically adds the pid to debug lines when several remote deliveries are
3604 The &`timestamp`& selector causes the current time to be inserted at the start
3605 of all debug output lines. This can be useful when trying to track down delays
3608 If the &%debug_print%& option is set in any driver, it produces output whenever
3609 any debugging is selected, or if &%-v%& is used.
3611 .vitem &%-dd%&<&'debug&~options'&>
3613 This option behaves exactly like &%-d%& except when used on a command that
3614 starts a daemon process. In that case, debugging is turned off for the
3615 subprocesses that the daemon creates. Thus, it is useful for monitoring the
3616 behaviour of the daemon without creating as much output as full debugging does.
3619 .oindex "&%-dropcr%&"
3620 This is an obsolete option that is now a no-op. It used to affect the way Exim
3621 handled CR and LF characters in incoming messages. What happens now is
3622 described in section &<<SECTlineendings>>&.
3626 .cindex "bounce message" "generating"
3627 This option specifies that an incoming message is a locally-generated delivery
3628 failure report. It is used internally by Exim when handling delivery failures
3629 and is not intended for external use. Its only effect is to stop Exim
3630 generating certain messages to the postmaster, as otherwise message cascades
3631 could occur in some situations. As part of the same option, a message id may
3632 follow the characters &%-E%&. If it does, the log entry for the receipt of the
3633 new message contains the id, following &"R="&, as a cross-reference.
3636 .oindex "&%-e%&&'x'&"
3637 There are a number of Sendmail options starting with &%-oe%& which seem to be
3638 called by various programs without the leading &%o%& in the option. For
3639 example, the &%vacation%& program uses &%-eq%&. Exim treats all options of the
3640 form &%-e%&&'x'& as synonymous with the corresponding &%-oe%&&'x'& options.
3642 .vitem &%-F%&&~<&'string'&>
3644 .cindex "sender" "name"
3645 .cindex "name" "of sender"
3646 This option sets the sender's full name for use when a locally-generated
3647 message is being accepted. In the absence of this option, the user's &'gecos'&
3648 entry from the password data is used. As users are generally permitted to alter
3649 their &'gecos'& entries, no security considerations are involved. White space
3650 between &%-F%& and the <&'string'&> is optional.
3652 .vitem &%-f%&&~<&'address'&>
3654 .cindex "sender" "address"
3655 .cindex "address" "sender"
3656 .cindex "trusted users"
3657 .cindex "envelope sender"
3658 .cindex "user" "trusted"
3659 This option sets the address of the envelope sender of a locally-generated
3660 message (also known as the return path). The option can normally be used only
3661 by a trusted user, but &%untrusted_set_sender%& can be set to allow untrusted
3664 Processes running as root or the Exim user are always trusted. Other
3665 trusted users are defined by the &%trusted_users%& or &%trusted_groups%&
3666 options. In the absence of &%-f%&, or if the caller is not trusted, the sender
3667 of a local message is set to the caller's login name at the default qualify
3670 There is one exception to the restriction on the use of &%-f%&: an empty sender
3671 can be specified by any user, trusted or not, to create a message that can
3672 never provoke a bounce. An empty sender can be specified either as an empty
3673 string, or as a pair of angle brackets with nothing between them, as in these
3674 examples of shell commands:
3676 exim -f '<>' user@domain
3677 exim -f "" user@domain
3679 In addition, the use of &%-f%& is not restricted when testing a filter file
3680 with &%-bf%& or when testing or verifying addresses using the &%-bt%& or
3683 Allowing untrusted users to change the sender address does not of itself make
3684 it possible to send anonymous mail. Exim still checks that the &'From:'& header
3685 refers to the local user, and if it does not, it adds a &'Sender:'& header,
3686 though this can be overridden by setting &%no_local_from_check%&.
3689 .cindex "&""From""& line"
3690 space between &%-f%& and the <&'address'&> is optional (that is, they can be
3691 given as two arguments or one combined argument). The sender of a
3692 locally-generated message can also be set (when permitted) by an initial
3693 &"From&~"& line in the message &-- see the description of &%-bm%& above &-- but
3694 if &%-f%& is also present, it overrides &"From&~"&.
3698 .cindex "Sendmail compatibility" "&%-G%& option ignored"
3699 This is a Sendmail option which is ignored by Exim.
3701 .vitem &%-h%&&~<&'number'&>
3703 .cindex "Sendmail compatibility" "&%-h%& option ignored"
3704 This option is accepted for compatibility with Sendmail, but has no effect. (In
3705 Sendmail it overrides the &"hop count"& obtained by counting &'Received:'&
3710 .cindex "Solaris" "&'mail'& command"
3711 .cindex "dot" "in incoming non-SMTP message"
3712 This option, which has the same effect as &%-oi%&, specifies that a dot on a
3713 line by itself should not terminate an incoming, non-SMTP message. I can find
3714 no documentation for this option in Solaris 2.4 Sendmail, but the &'mailx'&
3715 command in Solaris 2.4 uses it. See also &%-ti%&.
3718 .vitem &%-L%&&~<&'tag'&>
3720 .cindex "syslog" "process name; set with flag"
3721 This option is equivalent to setting &%syslog_processname%& in the config
3722 file and setting &%log_file_path%& to &`syslog`&.
3723 Its use is restricted to administrators. The configuration file has to be
3724 read and parsed, to determine access rights, before this is set and takes
3725 effect, so early configuration file errors will not honour this flag.
3727 The tag should not be longer than 32 characters.
3730 .vitem &%-M%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3732 .cindex "forcing delivery"
3733 .cindex "delivery" "forcing attempt"
3734 .cindex "frozen messages" "forcing delivery"
3735 This option requests Exim to run a delivery attempt on each message in turn. If
3736 any of the messages are frozen, they are automatically thawed before the
3737 delivery attempt. The settings of &%queue_domains%&, &%queue_smtp_domains%&,
3738 and &%hold_domains%& are ignored.
3741 .cindex "hints database" "overriding retry hints"
3742 hints for any of the addresses are overridden &-- Exim tries to deliver even if
3743 the normal retry time has not yet been reached. This option requires the caller
3744 to be an admin user. However, there is an option called &%prod_requires_admin%&
3745 which can be set false to relax this restriction (and also the same requirement
3746 for the &%-q%&, &%-R%&, and &%-S%& options).
3748 The deliveries happen synchronously, that is, the original Exim process does
3749 not terminate until all the delivery attempts have finished. No output is
3750 produced unless there is a serious error. If you want to see what is happening,
3751 use the &%-v%& option as well, or inspect Exim's main log.
3753 .vitem &%-Mar%&&~<&'message&~id'&>&~<&'address'&>&~<&'address'&>&~...
3755 .cindex "message" "adding recipients"
3756 .cindex "recipient" "adding"
3757 This option requests Exim to add the addresses to the list of recipients of the
3758 message (&"ar"& for &"add recipients"&). The first argument must be a message
3759 id, and the remaining ones must be email addresses. However, if the message is
3760 active (in the middle of a delivery attempt), it is not altered. This option
3761 can be used only by an admin user.
3763 .vitem "&%-MC%&&~<&'transport'&>&~<&'hostname'&>&~<&'sequence&~number'&>&&&
3764 &~<&'message&~id'&>"
3766 .cindex "SMTP" "passed connection"
3767 .cindex "SMTP" "multiple deliveries"
3768 .cindex "multiple SMTP deliveries"
3769 This option is not intended for use by external callers. It is used internally
3770 by Exim to invoke another instance of itself to deliver a waiting message using
3771 an existing SMTP connection, which is passed as the standard input. Details are
3772 given in chapter &<<CHAPSMTP>>&. This must be the final option, and the caller
3773 must be root or the Exim user in order to use it.
3777 This option is not intended for use by external callers. It is used internally
3778 by Exim in conjunction with the &%-MC%& option. It signifies that the
3779 connection to the remote host has been authenticated.
3783 This option is not intended for use by external callers. It is used internally
3784 by Exim in conjunction with the &%-MC%& option. It signifies that the server to
3785 which Exim is connected supports pipelining.
3787 .vitem &%-MCQ%&&~<&'process&~id'&>&~<&'pipe&~fd'&>
3789 This option is not intended for use by external callers. It is used internally
3790 by Exim in conjunction with the &%-MC%& option when the original delivery was
3791 started by a queue runner. It passes on the process id of the queue runner,
3792 together with the file descriptor number of an open pipe. Closure of the pipe
3793 signals the final completion of the sequence of processes that are passing
3794 messages through the same SMTP connection.
3798 This option is not intended for use by external callers. It is used internally
3799 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
3800 SMTP SIZE option should be used on messages delivered down the existing
3805 This option is not intended for use by external callers. It is used internally
3806 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
3807 host to which Exim is connected supports TLS encryption.
3809 .vitem &%-Mc%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3811 .cindex "hints database" "not overridden by &%-Mc%&"
3812 .cindex "delivery" "manually started &-- not forced"
3813 This option requests Exim to run a delivery attempt on each message in turn,
3814 but unlike the &%-M%& option, it does check for retry hints, and respects any
3815 that are found. This option is not very useful to external callers. It is
3816 provided mainly for internal use by Exim when it needs to re-invoke itself in
3817 order to regain root privilege for a delivery (see chapter &<<CHAPsecurity>>&).
3818 However, &%-Mc%& can be useful when testing, in order to run a delivery that
3819 respects retry times and other options such as &%hold_domains%& that are
3820 overridden when &%-M%& is used. Such a delivery does not count as a queue run.
3821 If you want to run a specific delivery as if in a queue run, you should use
3822 &%-q%& with a message id argument. A distinction between queue run deliveries
3823 and other deliveries is made in one or two places.
3825 .vitem &%-Mes%&&~<&'message&~id'&>&~<&'address'&>
3827 .cindex "message" "changing sender"
3828 .cindex "sender" "changing"
3829 This option requests Exim to change the sender address in the message to the
3830 given address, which must be a fully qualified address or &"<>"& (&"es"& for
3831 &"edit sender"&). There must be exactly two arguments. The first argument must
3832 be a message id, and the second one an email address. However, if the message
3833 is active (in the middle of a delivery attempt), its status is not altered.
3834 This option can be used only by an admin user.
3836 .vitem &%-Mf%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3838 .cindex "freezing messages"
3839 .cindex "message" "manually freezing"
3840 This option requests Exim to mark each listed message as &"frozen"&. This
3841 prevents any delivery attempts taking place until the message is &"thawed"&,
3842 either manually or as a result of the &%auto_thaw%& configuration option.
3843 However, if any of the messages are active (in the middle of a delivery
3844 attempt), their status is not altered. This option can be used only by an admin
3847 .vitem &%-Mg%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3849 .cindex "giving up on messages"
3850 .cindex "message" "abandoning delivery attempts"
3851 .cindex "delivery" "abandoning further attempts"
3852 This option requests Exim to give up trying to deliver the listed messages,
3853 including any that are frozen. However, if any of the messages are active,
3854 their status is not altered. For non-bounce messages, a delivery error message
3855 is sent to the sender, containing the text &"cancelled by administrator"&.
3856 Bounce messages are just discarded. This option can be used only by an admin
3859 .vitem &%-Mmad%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3861 .cindex "delivery" "cancelling all"
3862 This option requests Exim to mark all the recipient addresses in the messages
3863 as already delivered (&"mad"& for &"mark all delivered"&). However, if any
3864 message is active (in the middle of a delivery attempt), its status is not
3865 altered. This option can be used only by an admin user.
3867 .vitem &%-Mmd%&&~<&'message&~id'&>&~<&'address'&>&~<&'address'&>&~...
3869 .cindex "delivery" "cancelling by address"
3870 .cindex "recipient" "removing"
3871 .cindex "removing recipients"
3872 This option requests Exim to mark the given addresses as already delivered
3873 (&"md"& for &"mark delivered"&). The first argument must be a message id, and
3874 the remaining ones must be email addresses. These are matched to recipient
3875 addresses in the message in a case-sensitive manner. If the message is active
3876 (in the middle of a delivery attempt), its status is not altered. This option
3877 can be used only by an admin user.
3879 .vitem &%-Mrm%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3881 .cindex "removing messages"
3882 .cindex "abandoning mail"
3883 .cindex "message" "manually discarding"
3884 This option requests Exim to remove the given messages from the queue. No
3885 bounce messages are sent; each message is simply forgotten. However, if any of
3886 the messages are active, their status is not altered. This option can be used
3887 only by an admin user or by the user who originally caused the message to be
3888 placed on the queue.
3890 .vitem &%-Mset%&&~<&'message&~id'&>
3892 .cindex "testing" "string expansion"
3893 .cindex "expansion" "testing"
3894 This option is useful only in conjunction with &%-be%& (that is, when testing
3895 string expansions). Exim loads the given message from its spool before doing
3896 the test expansions, thus setting message-specific variables such as
3897 &$message_size$& and the header variables. The &$recipients$& variable is made
3898 available. This feature is provided to make it easier to test expansions that
3899 make use of these variables. However, this option can be used only by an admin
3900 user. See also &%-bem%&.
3902 .vitem &%-Mt%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3904 .cindex "thawing messages"
3905 .cindex "unfreezing messages"
3906 .cindex "frozen messages" "thawing"
3907 .cindex "message" "thawing frozen"
3908 This option requests Exim to &"thaw"& any of the listed messages that are
3909 &"frozen"&, so that delivery attempts can resume. However, if any of the
3910 messages are active, their status is not altered. This option can be used only
3913 .vitem &%-Mvb%&&~<&'message&~id'&>
3915 .cindex "listing" "message body"
3916 .cindex "message" "listing body of"
3917 This option causes the contents of the message body (-D) spool file to be
3918 written to the standard output. This option can be used only by an admin user.
3920 .vitem &%-Mvc%&&~<&'message&~id'&>
3922 .cindex "message" "listing in RFC 2822 format"
3923 .cindex "listing" "message in RFC 2822 format"
3924 This option causes a copy of the complete message (header lines plus body) to
3925 be written to the standard output in RFC 2822 format. This option can be used
3926 only by an admin user.
3928 .vitem &%-Mvh%&&~<&'message&~id'&>
3930 .cindex "listing" "message headers"
3931 .cindex "header lines" "listing"
3932 .cindex "message" "listing header lines"
3933 This option causes the contents of the message headers (-H) spool file to be
3934 written to the standard output. This option can be used only by an admin user.
3936 .vitem &%-Mvl%&&~<&'message&~id'&>
3938 .cindex "listing" "message log"
3939 .cindex "message" "listing message log"
3940 This option causes the contents of the message log spool file to be written to
3941 the standard output. This option can be used only by an admin user.
3945 This is apparently a synonym for &%-om%& that is accepted by Sendmail, so Exim
3946 treats it that way too.
3950 .cindex "debugging" "&%-N%& option"
3951 .cindex "debugging" "suppressing delivery"
3952 This is a debugging option that inhibits delivery of a message at the transport
3953 level. It implies &%-v%&. Exim goes through many of the motions of delivery &--
3954 it just doesn't actually transport the message, but instead behaves as if it
3955 had successfully done so. However, it does not make any updates to the retry
3956 database, and the log entries for deliveries are flagged with &"*>"& rather
3959 Because &%-N%& discards any message to which it applies, only root or the Exim
3960 user are allowed to use it with &%-bd%&, &%-q%&, &%-R%& or &%-M%&. In other
3961 words, an ordinary user can use it only when supplying an incoming message to
3962 which it will apply. Although transportation never fails when &%-N%& is set, an
3963 address may be deferred because of a configuration problem on a transport, or a
3964 routing problem. Once &%-N%& has been used for a delivery attempt, it sticks to
3965 the message, and applies to any subsequent delivery attempts that may happen
3970 This option is interpreted by Sendmail to mean &"no aliasing"&.
3971 For normal modes of operation, it is ignored by Exim.
3972 When combined with &%-bP%& it suppresses the name of an option from being output.
3974 .vitem &%-O%&&~<&'data'&>
3976 This option is interpreted by Sendmail to mean &`set option`&. It is ignored by
3979 .vitem &%-oA%&&~<&'file&~name'&>
3981 .cindex "Sendmail compatibility" "&%-oA%& option"
3982 This option is used by Sendmail in conjunction with &%-bi%& to specify an
3983 alternative alias file name. Exim handles &%-bi%& differently; see the
3986 .vitem &%-oB%&&~<&'n'&>
3988 .cindex "SMTP" "passed connection"
3989 .cindex "SMTP" "multiple deliveries"
3990 .cindex "multiple SMTP deliveries"
3991 This is a debugging option which limits the maximum number of messages that can
3992 be delivered down one SMTP connection, overriding the value set in any &(smtp)&
3993 transport. If <&'n'&> is omitted, the limit is set to 1.
3997 .cindex "background delivery"
3998 .cindex "delivery" "in the background"
3999 This option applies to all modes in which Exim accepts incoming messages,
4000 including the listening daemon. It requests &"background"& delivery of such
4001 messages, which means that the accepting process automatically starts a
4002 delivery process for each message received, but does not wait for the delivery
4003 processes to finish.
4005 When all the messages have been received, the reception process exits,
4006 leaving the delivery processes to finish in their own time. The standard output
4007 and error streams are closed at the start of each delivery process.
4008 This is the default action if none of the &%-od%& options are present.
4010 If one of the queueing options in the configuration file
4011 (&%queue_only%& or &%queue_only_file%&, for example) is in effect, &%-odb%&
4012 overrides it if &%queue_only_override%& is set true, which is the default
4013 setting. If &%queue_only_override%& is set false, &%-odb%& has no effect.
4017 .cindex "foreground delivery"
4018 .cindex "delivery" "in the foreground"
4019 This option requests &"foreground"& (synchronous) delivery when Exim has
4020 accepted a locally-generated message. (For the daemon it is exactly the same as
4021 &%-odb%&.) A delivery process is automatically started to deliver the message,
4022 and Exim waits for it to complete before proceeding.
4024 The original Exim reception process does not finish until the delivery
4025 process for the final message has ended. The standard error stream is left open
4028 However, like &%-odb%&, this option has no effect if &%queue_only_override%& is
4029 false and one of the queueing options in the configuration file is in effect.
4031 If there is a temporary delivery error during foreground delivery, the
4032 message is left on the queue for later delivery, and the original reception
4033 process exits. See chapter &<<CHAPnonqueueing>>& for a way of setting up a
4034 restricted configuration that never queues messages.
4039 This option is synonymous with &%-odf%&. It is provided for compatibility with
4044 .cindex "non-immediate delivery"
4045 .cindex "delivery" "suppressing immediate"
4046 .cindex "queueing incoming messages"
4047 This option applies to all modes in which Exim accepts incoming messages,
4048 including the listening daemon. It specifies that the accepting process should
4049 not automatically start a delivery process for each message received. Messages
4050 are placed on the queue, and remain there until a subsequent queue runner
4051 process encounters them. There are several configuration options (such as
4052 &%queue_only%&) that can be used to queue incoming messages under certain
4053 conditions. This option overrides all of them and also &%-odqs%&. It always
4058 .cindex "SMTP" "delaying delivery"
4059 This option is a hybrid between &%-odb%&/&%-odi%& and &%-odq%&.
4060 However, like &%-odb%& and &%-odi%&, this option has no effect if
4061 &%queue_only_override%& is false and one of the queueing options in the
4062 configuration file is in effect.
4064 When &%-odqs%& does operate, a delivery process is started for each incoming
4065 message, in the background by default, but in the foreground if &%-odi%& is
4066 also present. The recipient addresses are routed, and local deliveries are done
4067 in the normal way. However, if any SMTP deliveries are required, they are not
4068 done at this time, so the message remains on the queue until a subsequent queue
4069 runner process encounters it. Because routing was done, Exim knows which
4070 messages are waiting for which hosts, and so a number of messages for the same
4071 host can be sent in a single SMTP connection. The &%queue_smtp_domains%&
4072 configuration option has the same effect for specific domains. See also the
4077 .cindex "error" "reporting"
4078 If an error is detected while a non-SMTP message is being received (for
4079 example, a malformed address), the error is reported to the sender in a mail
4082 .cindex "return code" "for &%-oee%&"
4084 this error message is successfully sent, the Exim receiving process
4085 exits with a return code of zero. If not, the return code is 2 if the problem
4086 is that the original message has no recipients, or 1 any other error. This is
4087 the default &%-oe%&&'x'& option if Exim is called as &'rmail'&.
4091 .cindex "error" "reporting"
4092 .cindex "return code" "for &%-oem%&"
4093 This is the same as &%-oee%&, except that Exim always exits with a non-zero
4094 return code, whether or not the error message was successfully sent.
4095 This is the default &%-oe%&&'x'& option, unless Exim is called as &'rmail'&.
4099 .cindex "error" "reporting"
4100 If an error is detected while a non-SMTP message is being received, the
4101 error is reported by writing a message to the standard error file (stderr).
4102 .cindex "return code" "for &%-oep%&"
4103 The return code is 1 for all errors.
4107 .cindex "error" "reporting"
4108 This option is supported for compatibility with Sendmail, but has the same
4113 .cindex "error" "reporting"
4114 This option is supported for compatibility with Sendmail, but has the same
4119 .cindex "dot" "in incoming non-SMTP message"
4120 This option, which has the same effect as &%-i%&, specifies that a dot on a
4121 line by itself should not terminate an incoming, non-SMTP message. Otherwise, a
4122 single dot does terminate, though Exim does no special processing for other
4123 lines that start with a dot. This option is set by default if Exim is called as
4124 &'rmail'&. See also &%-ti%&.
4127 .oindex "&%-oitrue%&"
4128 This option is treated as synonymous with &%-oi%&.
4130 .vitem &%-oMa%&&~<&'host&~address'&>
4132 .cindex "sender" "host address, specifying for local message"
4133 A number of options starting with &%-oM%& can be used to set values associated
4134 with remote hosts on locally-submitted messages (that is, messages not received
4135 over TCP/IP). These options can be used by any caller in conjunction with the
4136 &%-bh%&, &%-be%&, &%-bf%&, &%-bF%&, &%-bt%&, or &%-bv%& testing options. In
4137 other circumstances, they are ignored unless the caller is trusted.
4139 The &%-oMa%& option sets the sender host address. This may include a port
4140 number at the end, after a full stop (period). For example:
4142 exim -bs -oMa 10.9.8.7.1234
4144 An alternative syntax is to enclose the IP address in square brackets,
4145 followed by a colon and the port number:
4147 exim -bs -oMa [10.9.8.7]:1234
4149 The IP address is placed in the &$sender_host_address$& variable, and the
4150 port, if present, in &$sender_host_port$&. If both &%-oMa%& and &%-bh%&
4151 are present on the command line, the sender host IP address is taken from
4152 whichever one is last.
4154 .vitem &%-oMaa%&&~<&'name'&>
4156 .cindex "authentication" "name, specifying for local message"
4157 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMaa%&
4158 option sets the value of &$sender_host_authenticated$& (the authenticator
4159 name). See chapter &<<CHAPSMTPAUTH>>& for a discussion of SMTP authentication.
4160 This option can be used with &%-bh%& and &%-bs%& to set up an
4161 authenticated SMTP session without actually using the SMTP AUTH command.
4163 .vitem &%-oMai%&&~<&'string'&>
4165 .cindex "authentication" "id, specifying for local message"
4166 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMai%&
4167 option sets the value of &$authenticated_id$& (the id that was authenticated).
4168 This overrides the default value (the caller's login id, except with &%-bh%&,
4169 where there is no default) for messages from local sources. See chapter
4170 &<<CHAPSMTPAUTH>>& for a discussion of authenticated ids.
4172 .vitem &%-oMas%&&~<&'address'&>
4174 .cindex "authentication" "sender, specifying for local message"
4175 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMas%&
4176 option sets the authenticated sender value in &$authenticated_sender$&. It
4177 overrides the sender address that is created from the caller's login id for
4178 messages from local sources, except when &%-bh%& is used, when there is no
4179 default. For both &%-bh%& and &%-bs%&, an authenticated sender that is
4180 specified on a MAIL command overrides this value. See chapter
4181 &<<CHAPSMTPAUTH>>& for a discussion of authenticated senders.
4183 .vitem &%-oMi%&&~<&'interface&~address'&>
4185 .cindex "interface" "address, specifying for local message"
4186 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMi%&
4187 option sets the IP interface address value. A port number may be included,
4188 using the same syntax as for &%-oMa%&. The interface address is placed in
4189 &$received_ip_address$& and the port number, if present, in &$received_port$&.
4191 .vitem &%-oMr%&&~<&'protocol&~name'&>
4193 .cindex "protocol, specifying for local message"
4194 .vindex "&$received_protocol$&"
4195 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMr%&
4196 option sets the received protocol value that is stored in
4197 &$received_protocol$&. However, it does not apply (and is ignored) when &%-bh%&
4198 or &%-bs%& is used. For &%-bh%&, the protocol is forced to one of the standard
4199 SMTP protocol names (see the description of &$received_protocol$& in section
4200 &<<SECTexpvar>>&). For &%-bs%&, the protocol is always &"local-"& followed by
4201 one of those same names. For &%-bS%& (batched SMTP) however, the protocol can
4204 .vitem &%-oMs%&&~<&'host&~name'&>
4206 .cindex "sender" "host name, specifying for local message"
4207 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMs%&
4208 option sets the sender host name in &$sender_host_name$&. When this option is
4209 present, Exim does not attempt to look up a host name from an IP address; it
4210 uses the name it is given.
4212 .vitem &%-oMt%&&~<&'ident&~string'&>
4214 .cindex "sender" "ident string, specifying for local message"
4215 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMt%&
4216 option sets the sender ident value in &$sender_ident$&. The default setting for
4217 local callers is the login id of the calling process, except when &%-bh%& is
4218 used, when there is no default.
4222 .cindex "Sendmail compatibility" "&%-om%& option ignored"
4223 In Sendmail, this option means &"me too"&, indicating that the sender of a
4224 message should receive a copy of the message if the sender appears in an alias
4225 expansion. Exim always does this, so the option does nothing.
4229 .cindex "Sendmail compatibility" "&%-oo%& option ignored"
4230 This option is ignored. In Sendmail it specifies &"old style headers"&,
4231 whatever that means.
4233 .vitem &%-oP%&&~<&'path'&>
4235 .cindex "pid (process id)" "of daemon"
4236 .cindex "daemon" "process id (pid)"
4237 This option is useful only in conjunction with &%-bd%& or &%-q%& with a time
4238 value. The option specifies the file to which the process id of the daemon is
4239 written. When &%-oX%& is used with &%-bd%&, or when &%-q%& with a time is used
4240 without &%-bd%&, this is the only way of causing Exim to write a pid file,
4241 because in those cases, the normal pid file is not used.
4243 .vitem &%-or%&&~<&'time'&>
4245 .cindex "timeout" "for non-SMTP input"
4246 This option sets a timeout value for incoming non-SMTP messages. If it is not
4247 set, Exim will wait forever for the standard input. The value can also be set
4248 by the &%receive_timeout%& option. The format used for specifying times is
4249 described in section &<<SECTtimeformat>>&.
4251 .vitem &%-os%&&~<&'time'&>
4253 .cindex "timeout" "for SMTP input"
4254 .cindex "SMTP" "input timeout"
4255 This option sets a timeout value for incoming SMTP messages. The timeout
4256 applies to each SMTP command and block of data. The value can also be set by
4257 the &%smtp_receive_timeout%& option; it defaults to 5 minutes. The format used
4258 for specifying times is described in section &<<SECTtimeformat>>&.
4262 This option has exactly the same effect as &%-v%&.
4264 .vitem &%-oX%&&~<&'number&~or&~string'&>
4266 .cindex "TCP/IP" "setting listening ports"
4267 .cindex "TCP/IP" "setting listening interfaces"
4268 .cindex "port" "receiving TCP/IP"
4269 This option is relevant only when the &%-bd%& (start listening daemon) option
4270 is also given. It controls which ports and interfaces the daemon uses. Details
4271 of the syntax, and how it interacts with configuration file options, are given
4272 in chapter &<<CHAPinterfaces>>&. When &%-oX%& is used to start a daemon, no pid
4273 file is written unless &%-oP%& is also present to specify a pid file name.
4277 .cindex "Perl" "starting the interpreter"
4278 This option applies when an embedded Perl interpreter is linked with Exim (see
4279 chapter &<<CHAPperl>>&). It overrides the setting of the &%perl_at_start%&
4280 option, forcing the starting of the interpreter to be delayed until it is
4285 .cindex "Perl" "starting the interpreter"
4286 This option applies when an embedded Perl interpreter is linked with Exim (see
4287 chapter &<<CHAPperl>>&). It overrides the setting of the &%perl_at_start%&
4288 option, forcing the starting of the interpreter to occur as soon as Exim is
4291 .vitem &%-p%&<&'rval'&>:<&'sval'&>
4293 For compatibility with Sendmail, this option is equivalent to
4295 &`-oMr`& <&'rval'&> &`-oMs`& <&'sval'&>
4297 It sets the incoming protocol and host name (for trusted callers). The
4298 host name and its colon can be omitted when only the protocol is to be set.
4299 Note the Exim already has two private options, &%-pd%& and &%-ps%&, that refer
4300 to embedded Perl. It is therefore impossible to set a protocol value of &`p`&
4301 or &`s`& using this option (but that does not seem a real limitation).
4305 .cindex "queue runner" "starting manually"
4306 This option is normally restricted to admin users. However, there is a
4307 configuration option called &%prod_requires_admin%& which can be set false to
4308 relax this restriction (and also the same requirement for the &%-M%&, &%-R%&,
4309 and &%-S%& options).
4311 .cindex "queue runner" "description of operation"
4312 The &%-q%& option starts one queue runner process. This scans the queue of
4313 waiting messages, and runs a delivery process for each one in turn. It waits
4314 for each delivery process to finish before starting the next one. A delivery
4315 process may not actually do any deliveries if the retry times for the addresses
4316 have not been reached. Use &%-qf%& (see below) if you want to override this.
4319 .cindex "SMTP" "passed connection"
4320 .cindex "SMTP" "multiple deliveries"
4321 .cindex "multiple SMTP deliveries"
4322 the delivery process spawns other processes to deliver other messages down
4323 passed SMTP connections, the queue runner waits for these to finish before
4326 When all the queued messages have been considered, the original queue runner
4327 process terminates. In other words, a single pass is made over the waiting
4328 mail, one message at a time. Use &%-q%& with a time (see below) if you want
4329 this to be repeated periodically.
4331 Exim processes the waiting messages in an unpredictable order. It isn't very
4332 random, but it is likely to be different each time, which is all that matters.
4333 If one particular message screws up a remote MTA, other messages to the same
4334 MTA have a chance of getting through if they get tried first.
4336 It is possible to cause the messages to be processed in lexical message id
4337 order, which is essentially the order in which they arrived, by setting the
4338 &%queue_run_in_order%& option, but this is not recommended for normal use.
4340 .vitem &%-q%&<&'qflags'&>
4341 The &%-q%& option may be followed by one or more flag letters that change its
4342 behaviour. They are all optional, but if more than one is present, they must
4343 appear in the correct order. Each flag is described in a separate item below.
4347 .cindex "queue" "double scanning"
4348 .cindex "queue" "routing"
4349 .cindex "routing" "whole queue before delivery"
4350 An option starting with &%-qq%& requests a two-stage queue run. In the first
4351 stage, the queue is scanned as if the &%queue_smtp_domains%& option matched
4352 every domain. Addresses are routed, local deliveries happen, but no remote
4355 .cindex "hints database" "remembering routing"
4356 The hints database that remembers which messages are waiting for specific hosts
4357 is updated, as if delivery to those hosts had been deferred. After this is
4358 complete, a second, normal queue scan happens, with routing and delivery taking
4359 place as normal. Messages that are routed to the same host should mostly be
4360 delivered down a single SMTP
4361 .cindex "SMTP" "passed connection"
4362 .cindex "SMTP" "multiple deliveries"
4363 .cindex "multiple SMTP deliveries"
4364 connection because of the hints that were set up during the first queue scan.
4365 This option may be useful for hosts that are connected to the Internet
4368 .vitem &%-q[q]i...%&
4370 .cindex "queue" "initial delivery"
4371 If the &'i'& flag is present, the queue runner runs delivery processes only for
4372 those messages that haven't previously been tried. (&'i'& stands for &"initial
4373 delivery"&.) This can be helpful if you are putting messages on the queue using
4374 &%-odq%& and want a queue runner just to process the new messages.
4376 .vitem &%-q[q][i]f...%&
4378 .cindex "queue" "forcing delivery"
4379 .cindex "delivery" "forcing in queue run"
4380 If one &'f'& flag is present, a delivery attempt is forced for each non-frozen
4381 message, whereas without &'f'& only those non-frozen addresses that have passed
4382 their retry times are tried.
4384 .vitem &%-q[q][i]ff...%&
4386 .cindex "frozen messages" "forcing delivery"
4387 If &'ff'& is present, a delivery attempt is forced for every message, whether
4390 .vitem &%-q[q][i][f[f]]l%&
4392 .cindex "queue" "local deliveries only"
4393 The &'l'& (the letter &"ell"&) flag specifies that only local deliveries are to
4394 be done. If a message requires any remote deliveries, it remains on the queue
4397 .vitem &%-q%&<&'qflags'&>&~<&'start&~id'&>&~<&'end&~id'&>
4398 .cindex "queue" "delivering specific messages"
4399 When scanning the queue, Exim can be made to skip over messages whose ids are
4400 lexically less than a given value by following the &%-q%& option with a
4401 starting message id. For example:
4403 exim -q 0t5C6f-0000c8-00
4405 Messages that arrived earlier than &`0t5C6f-0000c8-00`& are not inspected. If a
4406 second message id is given, messages whose ids are lexically greater than it
4407 are also skipped. If the same id is given twice, for example,
4409 exim -q 0t5C6f-0000c8-00 0t5C6f-0000c8-00
4411 just one delivery process is started, for that message. This differs from
4412 &%-M%& in that retry data is respected, and it also differs from &%-Mc%& in
4413 that it counts as a delivery from a queue run. Note that the selection
4414 mechanism does not affect the order in which the messages are scanned. There
4415 are also other ways of selecting specific sets of messages for delivery in a
4416 queue run &-- see &%-R%& and &%-S%&.
4418 .vitem &%-q%&<&'qflags'&><&'time'&>
4419 .cindex "queue runner" "starting periodically"
4420 .cindex "periodic queue running"
4421 When a time value is present, the &%-q%& option causes Exim to run as a daemon,
4422 starting a queue runner process at intervals specified by the given time value
4423 (whose format is described in section &<<SECTtimeformat>>&). This form of the
4424 &%-q%& option is commonly combined with the &%-bd%& option, in which case a
4425 single daemon process handles both functions. A common way of starting up a
4426 combined daemon at system boot time is to use a command such as
4428 /usr/exim/bin/exim -bd -q30m
4430 Such a daemon listens for incoming SMTP calls, and also starts a queue runner
4431 process every 30 minutes.
4433 When a daemon is started by &%-q%& with a time value, but without &%-bd%&, no
4434 pid file is written unless one is explicitly requested by the &%-oP%& option.
4436 .vitem &%-qR%&<&'rsflags'&>&~<&'string'&>
4438 This option is synonymous with &%-R%&. It is provided for Sendmail
4441 .vitem &%-qS%&<&'rsflags'&>&~<&'string'&>
4443 This option is synonymous with &%-S%&.
4445 .vitem &%-R%&<&'rsflags'&>&~<&'string'&>
4447 .cindex "queue runner" "for specific recipients"
4448 .cindex "delivery" "to given domain"
4449 .cindex "domain" "delivery to"
4450 The <&'rsflags'&> may be empty, in which case the white space before the string
4451 is optional, unless the string is &'f'&, &'ff'&, &'r'&, &'rf'&, or &'rff'&,
4452 which are the possible values for <&'rsflags'&>. White space is required if
4453 <&'rsflags'&> is not empty.
4455 This option is similar to &%-q%& with no time value, that is, it causes Exim to
4456 perform a single queue run, except that, when scanning the messages on the
4457 queue, Exim processes only those that have at least one undelivered recipient
4458 address containing the given string, which is checked in a case-independent
4459 way. If the <&'rsflags'&> start with &'r'&, <&'string'&> is interpreted as a
4460 regular expression; otherwise it is a literal string.
4462 If you want to do periodic queue runs for messages with specific recipients,
4463 you can combine &%-R%& with &%-q%& and a time value. For example:
4465 exim -q25m -R @special.domain.example
4467 This example does a queue run for messages with recipients in the given domain
4468 every 25 minutes. Any additional flags that are specified with &%-q%& are
4469 applied to each queue run.
4471 Once a message is selected for delivery by this mechanism, all its addresses
4472 are processed. For the first selected message, Exim overrides any retry
4473 information and forces a delivery attempt for each undelivered address. This
4474 means that if delivery of any address in the first message is successful, any
4475 existing retry information is deleted, and so delivery attempts for that
4476 address in subsequently selected messages (which are processed without forcing)
4477 will run. However, if delivery of any address does not succeed, the retry
4478 information is updated, and in subsequently selected messages, the failing
4479 address will be skipped.
4481 .cindex "frozen messages" "forcing delivery"
4482 If the <&'rsflags'&> contain &'f'& or &'ff'&, the delivery forcing applies to
4483 all selected messages, not just the first; frozen messages are included when
4486 The &%-R%& option makes it straightforward to initiate delivery of all messages
4487 to a given domain after a host has been down for some time. When the SMTP
4488 command ETRN is accepted by its ACL (see chapter &<<CHAPACL>>&), its default
4489 effect is to run Exim with the &%-R%& option, but it can be configured to run
4490 an arbitrary command instead.
4494 This is a documented (for Sendmail) obsolete alternative name for &%-f%&.
4496 .vitem &%-S%&<&'rsflags'&>&~<&'string'&>
4498 .cindex "delivery" "from given sender"
4499 .cindex "queue runner" "for specific senders"
4500 This option acts like &%-R%& except that it checks the string against each
4501 message's sender instead of against the recipients. If &%-R%& is also set, both
4502 conditions must be met for a message to be selected. If either of the options
4503 has &'f'& or &'ff'& in its flags, the associated action is taken.
4505 .vitem &%-Tqt%&&~<&'times'&>
4507 This an option that is exclusively for use by the Exim testing suite. It is not
4508 recognized when Exim is run normally. It allows for the setting up of explicit
4509 &"queue times"& so that various warning/retry features can be tested.
4513 .cindex "recipient" "extracting from header lines"
4514 .cindex "&'Bcc:'& header line"
4515 .cindex "&'Cc:'& header line"
4516 .cindex "&'To:'& header line"
4517 When Exim is receiving a locally-generated, non-SMTP message on its standard
4518 input, the &%-t%& option causes the recipients of the message to be obtained
4519 from the &'To:'&, &'Cc:'&, and &'Bcc:'& header lines in the message instead of
4520 from the command arguments. The addresses are extracted before any rewriting
4521 takes place and the &'Bcc:'& header line, if present, is then removed.
4523 .cindex "Sendmail compatibility" "&%-t%& option"
4524 If the command has any arguments, they specify addresses to which the message
4525 is &'not'& to be delivered. That is, the argument addresses are removed from
4526 the recipients list obtained from the headers. This is compatible with Smail 3
4527 and in accordance with the documented behaviour of several versions of
4528 Sendmail, as described in man pages on a number of operating systems (e.g.
4529 Solaris 8, IRIX 6.5, HP-UX 11). However, some versions of Sendmail &'add'&
4530 argument addresses to those obtained from the headers, and the O'Reilly
4531 Sendmail book documents it that way. Exim can be made to add argument addresses
4532 instead of subtracting them by setting the option
4533 &%extract_addresses_remove_arguments%& false.
4535 .cindex "&%Resent-%& header lines" "with &%-t%&"
4536 If there are any &%Resent-%& header lines in the message, Exim extracts
4537 recipients from all &'Resent-To:'&, &'Resent-Cc:'&, and &'Resent-Bcc:'& header
4538 lines instead of from &'To:'&, &'Cc:'&, and &'Bcc:'&. This is for compatibility
4539 with Sendmail and other MTAs. (Prior to release 4.20, Exim gave an error if
4540 &%-t%& was used in conjunction with &%Resent-%& header lines.)
4542 RFC 2822 talks about different sets of &%Resent-%& header lines (for when a
4543 message is resent several times). The RFC also specifies that they should be
4544 added at the front of the message, and separated by &'Received:'& lines. It is
4545 not at all clear how &%-t%& should operate in the present of multiple sets,
4546 nor indeed exactly what constitutes a &"set"&.
4547 In practice, it seems that MUAs do not follow the RFC. The &%Resent-%& lines
4548 are often added at the end of the header, and if a message is resent more than
4549 once, it is common for the original set of &%Resent-%& headers to be renamed as
4550 &%X-Resent-%& when a new set is added. This removes any possible ambiguity.
4554 This option is exactly equivalent to &%-t%& &%-i%&. It is provided for
4555 compatibility with Sendmail.
4557 .vitem &%-tls-on-connect%&
4558 .oindex "&%-tls-on-connect%&"
4559 .cindex "TLS" "use without STARTTLS"
4560 .cindex "TLS" "automatic start"
4561 This option is available when Exim is compiled with TLS support. It forces all
4562 incoming SMTP connections to behave as if the incoming port is listed in the
4563 &%tls_on_connect_ports%& option. See section &<<SECTsupobssmt>>& and chapter
4564 &<<CHAPTLS>>& for further details.
4569 .cindex "Sendmail compatibility" "&%-U%& option ignored"
4570 Sendmail uses this option for &"initial message submission"&, and its
4571 documentation states that in future releases, it may complain about
4572 syntactically invalid messages rather than fixing them when this flag is not
4573 set. Exim ignores this option.
4577 This option causes Exim to write information to the standard error stream,
4578 describing what it is doing. In particular, it shows the log lines for
4579 receiving and delivering a message, and if an SMTP connection is made, the SMTP
4580 dialogue is shown. Some of the log lines shown may not actually be written to
4581 the log if the setting of &%log_selector%& discards them. Any relevant
4582 selectors are shown with each log line. If none are shown, the logging is
4587 AIX uses &%-x%& for a private purpose (&"mail from a local mail program has
4588 National Language Support extended characters in the body of the mail item"&).
4589 It sets &%-x%& when calling the MTA from its &%mail%& command. Exim ignores
4593 .vitem &%-X%&&~<&'logfile'&>
4595 This option is interpreted by Sendmail to cause debug information to be sent
4596 to the named file. It is ignored by Exim.
4604 . ////////////////////////////////////////////////////////////////////////////
4605 . Insert a stylized DocBook comment here, to identify the end of the command
4606 . line options. This is for the benefit of the Perl script that automatically
4607 . creates a man page for the options.
4608 . ////////////////////////////////////////////////////////////////////////////
4611 <!-- === End of command line options === -->
4618 . ////////////////////////////////////////////////////////////////////////////
4619 . ////////////////////////////////////////////////////////////////////////////
4622 .chapter "The Exim run time configuration file" "CHAPconf" &&&
4623 "The runtime configuration file"
4625 .cindex "run time configuration"
4626 .cindex "configuration file" "general description"
4627 .cindex "CONFIGURE_FILE"
4628 .cindex "configuration file" "errors in"
4629 .cindex "error" "in configuration file"
4630 .cindex "return code" "for bad configuration"
4631 Exim uses a single run time configuration file that is read whenever an Exim
4632 binary is executed. Note that in normal operation, this happens frequently,
4633 because Exim is designed to operate in a distributed manner, without central
4636 If a syntax error is detected while reading the configuration file, Exim
4637 writes a message on the standard error, and exits with a non-zero return code.
4638 The message is also written to the panic log. &*Note*&: Only simple syntax
4639 errors can be detected at this time. The values of any expanded options are
4640 not checked until the expansion happens, even when the expansion does not
4641 actually alter the string.
4643 The name of the configuration file is compiled into the binary for security
4644 reasons, and is specified by the CONFIGURE_FILE compilation option. In
4645 most configurations, this specifies a single file. However, it is permitted to
4646 give a colon-separated list of file names, in which case Exim uses the first
4647 existing file in the list.
4650 .cindex "EXIM_GROUP"
4651 .cindex "CONFIGURE_OWNER"
4652 .cindex "CONFIGURE_GROUP"
4653 .cindex "configuration file" "ownership"
4654 .cindex "ownership" "configuration file"
4655 The run time configuration file must be owned by root or by the user that is
4656 specified at compile time by the CONFIGURE_OWNER option (if set). The
4657 configuration file must not be world-writeable, or group-writeable unless its
4658 group is the root group or the one specified at compile time by the
4659 CONFIGURE_GROUP option.
4661 &*Warning*&: In a conventional configuration, where the Exim binary is setuid
4662 to root, anybody who is able to edit the run time configuration file has an
4663 easy way to run commands as root. If you specify a user or group in the
4664 CONFIGURE_OWNER or CONFIGURE_GROUP options, then that user and/or any users
4665 who are members of that group will trivially be able to obtain root privileges.
4667 Up to Exim version 4.72, the run time configuration file was also permitted to
4668 be writeable by the Exim user and/or group. That has been changed in Exim 4.73
4669 since it offered a simple privilege escalation for any attacker who managed to
4670 compromise the Exim user account.
4672 A default configuration file, which will work correctly in simple situations,
4673 is provided in the file &_src/configure.default_&. If CONFIGURE_FILE
4674 defines just one file name, the installation process copies the default
4675 configuration to a new file of that name if it did not previously exist. If
4676 CONFIGURE_FILE is a list, no default is automatically installed. Chapter
4677 &<<CHAPdefconfil>>& is a &"walk-through"& discussion of the default
4682 .section "Using a different configuration file" "SECID40"
4683 .cindex "configuration file" "alternate"
4684 A one-off alternate configuration can be specified by the &%-C%& command line
4685 option, which may specify a single file or a list of files. However, when
4686 &%-C%& is used, Exim gives up its root privilege, unless called by root (or
4687 unless the argument for &%-C%& is identical to the built-in value from
4688 CONFIGURE_FILE), or is listed in the TRUSTED_CONFIG_LIST file and the caller
4689 is the Exim user or the user specified in the CONFIGURE_OWNER setting. &%-C%&
4690 is useful mainly for checking the syntax of configuration files before
4691 installing them. No owner or group checks are done on a configuration file
4692 specified by &%-C%&, if root privilege has been dropped.
4694 Even the Exim user is not trusted to specify an arbitrary configuration file
4695 with the &%-C%& option to be used with root privileges, unless that file is
4696 listed in the TRUSTED_CONFIG_LIST file. This locks out the possibility of
4697 testing a configuration using &%-C%& right through message reception and
4698 delivery, even if the caller is root. The reception works, but by that time,
4699 Exim is running as the Exim user, so when it re-execs to regain privilege for
4700 the delivery, the use of &%-C%& causes privilege to be lost. However, root
4701 can test reception and delivery using two separate commands (one to put a
4702 message on the queue, using &%-odq%&, and another to do the delivery, using
4705 If ALT_CONFIG_PREFIX is defined &_in Local/Makefile_&, it specifies a
4706 prefix string with which any file named in a &%-C%& command line option must
4707 start. In addition, the file name must not contain the sequence &"&`/../`&"&.
4708 There is no default setting for ALT_CONFIG_PREFIX; when it is unset, any file
4709 name can be used with &%-C%&.
4711 One-off changes to a configuration can be specified by the &%-D%& command line
4712 option, which defines and overrides values for macros used inside the
4713 configuration file. However, like &%-C%&, the use of this option by a
4714 non-privileged user causes Exim to discard its root privilege.
4715 If DISABLE_D_OPTION is defined in &_Local/Makefile_&, the use of &%-D%& is
4716 completely disabled, and its use causes an immediate error exit.
4718 The WHITELIST_D_MACROS option in &_Local/Makefile_& permits the binary builder
4719 to declare certain macro names trusted, such that root privilege will not
4720 necessarily be discarded.
4721 WHITELIST_D_MACROS defines a colon-separated list of macros which are
4722 considered safe and, if &%-D%& only supplies macros from this list, and the
4723 values are acceptable, then Exim will not give up root privilege if the caller
4724 is root, the Exim run-time user, or the CONFIGURE_OWNER, if set. This is a
4725 transition mechanism and is expected to be removed in the future. Acceptable
4726 values for the macros satisfy the regexp: &`^[A-Za-z0-9_/.-]*$`&
4728 Some sites may wish to use the same Exim binary on different machines that
4729 share a file system, but to use different configuration files on each machine.
4730 If CONFIGURE_FILE_USE_NODE is defined in &_Local/Makefile_&, Exim first
4731 looks for a file whose name is the configuration file name followed by a dot
4732 and the machine's node name, as obtained from the &[uname()]& function. If this
4733 file does not exist, the standard name is tried. This processing occurs for
4734 each file name in the list given by CONFIGURE_FILE or &%-C%&.
4736 In some esoteric situations different versions of Exim may be run under
4737 different effective uids and the CONFIGURE_FILE_USE_EUID is defined to
4738 help with this. See the comments in &_src/EDITME_& for details.
4742 .section "Configuration file format" "SECTconffilfor"
4743 .cindex "configuration file" "format of"
4744 .cindex "format" "configuration file"
4745 Exim's configuration file is divided into a number of different parts. General
4746 option settings must always appear at the start of the file. The other parts
4747 are all optional, and may appear in any order. Each part other than the first
4748 is introduced by the word &"begin"& followed by the name of the part. The
4752 &'ACL'&: Access control lists for controlling incoming SMTP mail (see chapter
4755 .cindex "AUTH" "configuration"
4756 &'authenticators'&: Configuration settings for the authenticator drivers. These
4757 are concerned with the SMTP AUTH command (see chapter &<<CHAPSMTPAUTH>>&).
4759 &'routers'&: Configuration settings for the router drivers. Routers process
4760 addresses and determine how the message is to be delivered (see chapters
4761 &<<CHAProutergeneric>>&&--&<<CHAPredirect>>&).
4763 &'transports'&: Configuration settings for the transport drivers. Transports
4764 define mechanisms for copying messages to destinations (see chapters
4765 &<<CHAPtransportgeneric>>&&--&<<CHAPsmtptrans>>&).
4767 &'retry'&: Retry rules, for use when a message cannot be delivered immediately.
4768 If there is no retry section, or if it is empty (that is, no retry rules are
4769 defined), Exim will not retry deliveries. In this situation, temporary errors
4770 are treated the same as permanent errors. Retry rules are discussed in chapter
4773 &'rewrite'&: Global address rewriting rules, for use when a message arrives and
4774 when new addresses are generated during delivery. Rewriting is discussed in
4775 chapter &<<CHAPrewrite>>&.
4777 &'local_scan'&: Private options for the &[local_scan()]& function. If you
4778 want to use this feature, you must set
4780 LOCAL_SCAN_HAS_OPTIONS=yes
4782 in &_Local/Makefile_& before building Exim. Details of the &[local_scan()]&
4783 facility are given in chapter &<<CHAPlocalscan>>&.
4786 .cindex "configuration file" "leading white space in"
4787 .cindex "configuration file" "trailing white space in"
4788 .cindex "white space" "in configuration file"
4789 Leading and trailing white space in configuration lines is always ignored.
4791 Blank lines in the file, and lines starting with a # character (ignoring
4792 leading white space) are treated as comments and are ignored. &*Note*&: A
4793 # character other than at the beginning of a line is not treated specially,
4794 and does not introduce a comment.
4796 Any non-comment line can be continued by ending it with a backslash. Note that
4797 the general rule for white space means that trailing white space after the
4798 backslash and leading white space at the start of continuation
4799 lines is ignored. Comment lines beginning with # (but not empty lines) may
4800 appear in the middle of a sequence of continuation lines.
4802 A convenient way to create a configuration file is to start from the
4803 default, which is supplied in &_src/configure.default_&, and add, delete, or
4804 change settings as required.
4806 The ACLs, retry rules, and rewriting rules have their own syntax which is
4807 described in chapters &<<CHAPACL>>&, &<<CHAPretry>>&, and &<<CHAPrewrite>>&,
4808 respectively. The other parts of the configuration file have some syntactic
4809 items in common, and these are described below, from section &<<SECTcos>>&
4810 onwards. Before that, the inclusion, macro, and conditional facilities are
4815 .section "File inclusions in the configuration file" "SECID41"
4816 .cindex "inclusions in configuration file"
4817 .cindex "configuration file" "including other files"
4818 .cindex "&`.include`& in configuration file"
4819 .cindex "&`.include_if_exists`& in configuration file"
4820 You can include other files inside Exim's run time configuration file by
4823 &`.include`& <&'file name'&>
4824 &`.include_if_exists`& <&'file name'&>
4826 on a line by itself. Double quotes round the file name are optional. If you use
4827 the first form, a configuration error occurs if the file does not exist; the
4828 second form does nothing for non-existent files. In all cases, an absolute file
4831 Includes may be nested to any depth, but remember that Exim reads its
4832 configuration file often, so it is a good idea to keep them to a minimum.
4833 If you change the contents of an included file, you must HUP the daemon,
4834 because an included file is read only when the configuration itself is read.
4836 The processing of inclusions happens early, at a physical line level, so, like
4837 comment lines, an inclusion can be used in the middle of an option setting,
4840 hosts_lookup = a.b.c \
4843 Include processing happens after macro processing (see below). Its effect is to
4844 process the lines of the included file as if they occurred inline where the
4849 .section "Macros in the configuration file" "SECTmacrodefs"
4850 .cindex "macro" "description of"
4851 .cindex "configuration file" "macros"
4852 If a line in the main part of the configuration (that is, before the first
4853 &"begin"& line) begins with an upper case letter, it is taken as a macro
4854 definition, and must be of the form
4856 <&'name'&> = <&'rest of line'&>
4858 The name must consist of letters, digits, and underscores, and need not all be
4859 in upper case, though that is recommended. The rest of the line, including any
4860 continuations, is the replacement text, and has leading and trailing white
4861 space removed. Quotes are not removed. The replacement text can never end with
4862 a backslash character, but this doesn't seem to be a serious limitation.
4864 Macros may also be defined between router, transport, authenticator, or ACL
4865 definitions. They may not, however, be defined within an individual driver or
4866 ACL, or in the &%local_scan%&, retry, or rewrite sections of the configuration.
4868 .section "Macro substitution" "SECID42"
4869 Once a macro is defined, all subsequent lines in the file (and any included
4870 files) are scanned for the macro name; if there are several macros, the line is
4871 scanned for each in turn, in the order in which the macros are defined. The
4872 replacement text is not re-scanned for the current macro, though it is scanned
4873 for subsequently defined macros. For this reason, a macro name may not contain
4874 the name of a previously defined macro as a substring. You could, for example,
4877 &`ABCD_XYZ = `&<&'something'&>
4878 &`ABCD = `&<&'something else'&>
4880 but putting the definitions in the opposite order would provoke a configuration
4881 error. Macro expansion is applied to individual physical lines from the file,
4882 before checking for line continuation or file inclusion (see above). If a line
4883 consists solely of a macro name, and the expansion of the macro is empty, the
4884 line is ignored. A macro at the start of a line may turn the line into a
4885 comment line or a &`.include`& line.
4888 .section "Redefining macros" "SECID43"
4889 Once defined, the value of a macro can be redefined later in the configuration
4890 (or in an included file). Redefinition is specified by using &'=='& instead of
4895 MAC == updated value
4897 Redefinition does not alter the order in which the macros are applied to the
4898 subsequent lines of the configuration file. It is still the same order in which
4899 the macros were originally defined. All that changes is the macro's value.
4900 Redefinition makes it possible to accumulate values. For example:
4904 MAC == MAC and something added
4906 This can be helpful in situations where the configuration file is built
4907 from a number of other files.
4909 .section "Overriding macro values" "SECID44"
4910 The values set for macros in the configuration file can be overridden by the
4911 &%-D%& command line option, but Exim gives up its root privilege when &%-D%& is
4912 used, unless called by root or the Exim user. A definition on the command line
4913 using the &%-D%& option causes all definitions and redefinitions within the
4918 .section "Example of macro usage" "SECID45"
4919 As an example of macro usage, consider a configuration where aliases are looked
4920 up in a MySQL database. It helps to keep the file less cluttered if long
4921 strings such as SQL statements are defined separately as macros, for example:
4923 ALIAS_QUERY = select mailbox from user where \
4924 login='${quote_mysql:$local_part}';
4926 This can then be used in a &(redirect)& router setting like this:
4928 data = ${lookup mysql{ALIAS_QUERY}}
4930 In earlier versions of Exim macros were sometimes used for domain, host, or
4931 address lists. In Exim 4 these are handled better by named lists &-- see
4932 section &<<SECTnamedlists>>&.
4935 .section "Conditional skips in the configuration file" "SECID46"
4936 .cindex "configuration file" "conditional skips"
4937 .cindex "&`.ifdef`&"
4938 You can use the directives &`.ifdef`&, &`.ifndef`&, &`.elifdef`&,
4939 &`.elifndef`&, &`.else`&, and &`.endif`& to dynamically include or exclude
4940 portions of the configuration file. The processing happens whenever the file is
4941 read (that is, when an Exim binary starts to run).
4943 The implementation is very simple. Instances of the first four directives must
4944 be followed by text that includes the names of one or macros. The condition
4945 that is tested is whether or not any macro substitution has taken place in the
4949 message_size_limit = 50M
4951 message_size_limit = 100M
4954 sets a message size limit of 50M if the macro &`AAA`& is defined, and 100M
4955 otherwise. If there is more than one macro named on the line, the condition
4956 is true if any of them are defined. That is, it is an &"or"& condition. To
4957 obtain an &"and"& condition, you need to use nested &`.ifdef`&s.
4959 Although you can use a macro expansion to generate one of these directives,
4960 it is not very useful, because the condition &"there was a macro substitution
4961 in this line"& will always be true.
4963 Text following &`.else`& and &`.endif`& is ignored, and can be used as comment
4964 to clarify complicated nestings.
4968 .section "Common option syntax" "SECTcos"
4969 .cindex "common option syntax"
4970 .cindex "syntax of common options"
4971 .cindex "configuration file" "common option syntax"
4972 For the main set of options, driver options, and &[local_scan()]& options,
4973 each setting is on a line by itself, and starts with a name consisting of
4974 lower-case letters and underscores. Many options require a data value, and in
4975 these cases the name must be followed by an equals sign (with optional white
4976 space) and then the value. For example:
4978 qualify_domain = mydomain.example.com
4980 .cindex "hiding configuration option values"
4981 .cindex "configuration options" "hiding value of"
4982 .cindex "options" "hiding value of"
4983 Some option settings may contain sensitive data, for example, passwords for
4984 accessing databases. To stop non-admin users from using the &%-bP%& command
4985 line option to read these values, you can precede the option settings with the
4986 word &"hide"&. For example:
4988 hide mysql_servers = localhost/users/admin/secret-password
4990 For non-admin users, such options are displayed like this:
4992 mysql_servers = <value not displayable>
4994 If &"hide"& is used on a driver option, it hides the value of that option on
4995 all instances of the same driver.
4997 The following sections describe the syntax used for the different data types
4998 that are found in option settings.
5001 .section "Boolean options" "SECID47"
5002 .cindex "format" "boolean"
5003 .cindex "boolean configuration values"
5004 .oindex "&%no_%&&'xxx'&"
5005 .oindex "&%not_%&&'xxx'&"
5006 Options whose type is given as boolean are on/off switches. There are two
5007 different ways of specifying such options: with and without a data value. If
5008 the option name is specified on its own without data, the switch is turned on;
5009 if it is preceded by &"no_"& or &"not_"& the switch is turned off. However,
5010 boolean options may be followed by an equals sign and one of the words
5011 &"true"&, &"false"&, &"yes"&, or &"no"&, as an alternative syntax. For example,
5012 the following two settings have exactly the same effect:
5017 The following two lines also have the same (opposite) effect:
5022 You can use whichever syntax you prefer.
5027 .section "Integer values" "SECID48"
5028 .cindex "integer configuration values"
5029 .cindex "format" "integer"
5030 If an option's type is given as &"integer"&, the value can be given in decimal,
5031 hexadecimal, or octal. If it starts with a digit greater than zero, a decimal
5032 number is assumed. Otherwise, it is treated as an octal number unless it starts
5033 with the characters &"0x"&, in which case the remainder is interpreted as a
5036 If an integer value is followed by the letter K, it is multiplied by 1024; if
5037 it is followed by the letter M, it is multiplied by 1024x1024. When the values
5038 of integer option settings are output, values which are an exact multiple of
5039 1024 or 1024x1024 are sometimes, but not always, printed using the letters K
5040 and M. The printing style is independent of the actual input format that was
5044 .section "Octal integer values" "SECID49"
5045 .cindex "integer format"
5046 .cindex "format" "octal integer"
5047 If an option's type is given as &"octal integer"&, its value is always
5048 interpreted as an octal number, whether or not it starts with the digit zero.
5049 Such options are always output in octal.
5052 .section "Fixed point numbers" "SECID50"
5053 .cindex "fixed point configuration values"
5054 .cindex "format" "fixed point"
5055 If an option's type is given as &"fixed-point"&, its value must be a decimal
5056 integer, optionally followed by a decimal point and up to three further digits.
5060 .section "Time intervals" "SECTtimeformat"
5061 .cindex "time interval" "specifying in configuration"
5062 .cindex "format" "time interval"
5063 A time interval is specified as a sequence of numbers, each followed by one of
5064 the following letters, with no intervening white space:
5074 For example, &"3h50m"& specifies 3 hours and 50 minutes. The values of time
5075 intervals are output in the same format. Exim does not restrict the values; it
5076 is perfectly acceptable, for example, to specify &"90m"& instead of &"1h30m"&.
5080 .section "String values" "SECTstrings"
5081 .cindex "string" "format of configuration values"
5082 .cindex "format" "string"
5083 If an option's type is specified as &"string"&, the value can be specified with
5084 or without double-quotes. If it does not start with a double-quote, the value
5085 consists of the remainder of the line plus any continuation lines, starting at
5086 the first character after any leading white space, with trailing white space
5087 removed, and with no interpretation of the characters in the string. Because
5088 Exim removes comment lines (those beginning with #) at an early stage, they can
5089 appear in the middle of a multi-line string. The following two settings are
5090 therefore equivalent:
5092 trusted_users = uucp:mail
5093 trusted_users = uucp:\
5094 # This comment line is ignored
5097 .cindex "string" "quoted"
5098 .cindex "escape characters in quoted strings"
5099 If a string does start with a double-quote, it must end with a closing
5100 double-quote, and any backslash characters other than those used for line
5101 continuation are interpreted as escape characters, as follows:
5104 .irow &`\\`& "single backslash"
5105 .irow &`\n`& "newline"
5106 .irow &`\r`& "carriage return"
5108 .irow "&`\`&<&'octal digits'&>" "up to 3 octal digits specify one character"
5109 .irow "&`\x`&<&'hex digits'&>" "up to 2 hexadecimal digits specify one &&&
5113 If a backslash is followed by some other character, including a double-quote
5114 character, that character replaces the pair.
5116 Quoting is necessary only if you want to make use of the backslash escapes to
5117 insert special characters, or if you need to specify a value with leading or
5118 trailing spaces. These cases are rare, so quoting is almost never needed in
5119 current versions of Exim. In versions of Exim before 3.14, quoting was required
5120 in order to continue lines, so you may come across older configuration files
5121 and examples that apparently quote unnecessarily.
5124 .section "Expanded strings" "SECID51"
5125 .cindex "expansion" "definition of"
5126 Some strings in the configuration file are subjected to &'string expansion'&,
5127 by which means various parts of the string may be changed according to the
5128 circumstances (see chapter &<<CHAPexpand>>&). The input syntax for such strings
5129 is as just described; in particular, the handling of backslashes in quoted
5130 strings is done as part of the input process, before expansion takes place.
5131 However, backslash is also an escape character for the expander, so any
5132 backslashes that are required for that reason must be doubled if they are
5133 within a quoted configuration string.
5136 .section "User and group names" "SECID52"
5137 .cindex "user name" "format of"
5138 .cindex "format" "user name"
5139 .cindex "groups" "name format"
5140 .cindex "format" "group name"
5141 User and group names are specified as strings, using the syntax described
5142 above, but the strings are interpreted specially. A user or group name must
5143 either consist entirely of digits, or be a name that can be looked up using the
5144 &[getpwnam()]& or &[getgrnam()]& function, as appropriate.
5147 .section "List construction" "SECTlistconstruct"
5148 .cindex "list" "syntax of in configuration"
5149 .cindex "format" "list item in configuration"
5150 .cindex "string" "list, definition of"
5151 The data for some configuration options is a list of items, with colon as the
5152 default separator. Many of these options are shown with type &"string list"& in
5153 the descriptions later in this document. Others are listed as &"domain list"&,
5154 &"host list"&, &"address list"&, or &"local part list"&. Syntactically, they
5155 are all the same; however, those other than &"string list"& are subject to
5156 particular kinds of interpretation, as described in chapter
5157 &<<CHAPdomhosaddlists>>&.
5159 In all these cases, the entire list is treated as a single string as far as the
5160 input syntax is concerned. The &%trusted_users%& setting in section
5161 &<<SECTstrings>>& above is an example. If a colon is actually needed in an item
5162 in a list, it must be entered as two colons. Leading and trailing white space
5163 on each item in a list is ignored. This makes it possible to include items that
5164 start with a colon, and in particular, certain forms of IPv6 address. For
5167 local_interfaces = 127.0.0.1 : ::::1
5169 contains two IP addresses, the IPv4 address 127.0.0.1 and the IPv6 address ::1.
5171 &*Note*&: Although leading and trailing white space is ignored in individual
5172 list items, it is not ignored when parsing the list. The space after the first
5173 colon in the example above is necessary. If it were not there, the list would
5174 be interpreted as the two items 127.0.0.1:: and 1.
5176 .section "Changing list separators" "SECID53"
5177 .cindex "list separator" "changing"
5178 .cindex "IPv6" "addresses in lists"
5179 Doubling colons in IPv6 addresses is an unwelcome chore, so a mechanism was
5180 introduced to allow the separator character to be changed. If a list begins
5181 with a left angle bracket, followed by any punctuation character, that
5182 character is used instead of colon as the list separator. For example, the list
5183 above can be rewritten to use a semicolon separator like this:
5185 local_interfaces = <; 127.0.0.1 ; ::1
5187 This facility applies to all lists, with the exception of the list in
5188 &%log_file_path%&. It is recommended that the use of non-colon separators be
5189 confined to circumstances where they really are needed.
5191 .cindex "list separator" "newline as"
5192 .cindex "newline" "as list separator"
5193 It is also possible to use newline and other control characters (those with
5194 code values less than 32, plus DEL) as separators in lists. Such separators
5195 must be provided literally at the time the list is processed. For options that
5196 are string-expanded, you can write the separator using a normal escape
5197 sequence. This will be processed by the expander before the string is
5198 interpreted as a list. For example, if a newline-separated list of domains is
5199 generated by a lookup, you can process it directly by a line such as this:
5201 domains = <\n ${lookup mysql{.....}}
5203 This avoids having to change the list separator in such data. You are unlikely
5204 to want to use a control character as a separator in an option that is not
5205 expanded, because the value is literal text. However, it can be done by giving
5206 the value in quotes. For example:
5208 local_interfaces = "<\n 127.0.0.1 \n ::1"
5210 Unlike printing character separators, which can be included in list items by
5211 doubling, it is not possible to include a control character as data when it is
5212 set as the separator. Two such characters in succession are interpreted as
5213 enclosing an empty list item.
5217 .section "Empty items in lists" "SECTempitelis"
5218 .cindex "list" "empty item in"
5219 An empty item at the end of a list is always ignored. In other words, trailing
5220 separator characters are ignored. Thus, the list in
5222 senders = user@domain :
5224 contains only a single item. If you want to include an empty string as one item
5225 in a list, it must not be the last item. For example, this list contains three
5226 items, the second of which is empty:
5228 senders = user1@domain : : user2@domain
5230 &*Note*&: There must be white space between the two colons, as otherwise they
5231 are interpreted as representing a single colon data character (and the list
5232 would then contain just one item). If you want to specify a list that contains
5233 just one, empty item, you can do it as in this example:
5237 In this case, the first item is empty, and the second is discarded because it
5238 is at the end of the list.
5243 .section "Format of driver configurations" "SECTfordricon"
5244 .cindex "drivers" "configuration format"
5245 There are separate parts in the configuration for defining routers, transports,
5246 and authenticators. In each part, you are defining a number of driver
5247 instances, each with its own set of options. Each driver instance is defined by
5248 a sequence of lines like this:
5250 <&'instance name'&>:
5255 In the following example, the instance name is &(localuser)&, and it is
5256 followed by three options settings:
5261 transport = local_delivery
5263 For each driver instance, you specify which Exim code module it uses &-- by the
5264 setting of the &%driver%& option &-- and (optionally) some configuration
5265 settings. For example, in the case of transports, if you want a transport to
5266 deliver with SMTP you would use the &(smtp)& driver; if you want to deliver to
5267 a local file you would use the &(appendfile)& driver. Each of the drivers is
5268 described in detail in its own separate chapter later in this manual.
5270 You can have several routers, transports, or authenticators that are based on
5271 the same underlying driver (each must have a different instance name).
5273 The order in which routers are defined is important, because addresses are
5274 passed to individual routers one by one, in order. The order in which
5275 transports are defined does not matter at all. The order in which
5276 authenticators are defined is used only when Exim, as a client, is searching
5277 them to find one that matches an authentication mechanism offered by the
5280 .cindex "generic options"
5281 .cindex "options" "generic &-- definition of"
5282 Within a driver instance definition, there are two kinds of option: &'generic'&
5283 and &'private'&. The generic options are those that apply to all drivers of the
5284 same type (that is, all routers, all transports or all authenticators). The
5285 &%driver%& option is a generic option that must appear in every definition.
5286 .cindex "private options"
5287 The private options are special for each driver, and none need appear, because
5288 they all have default values.
5290 The options may appear in any order, except that the &%driver%& option must
5291 precede any private options, since these depend on the particular driver. For
5292 this reason, it is recommended that &%driver%& always be the first option.
5294 Driver instance names, which are used for reference in log entries and
5295 elsewhere, can be any sequence of letters, digits, and underscores (starting
5296 with a letter) and must be unique among drivers of the same type. A router and
5297 a transport (for example) can each have the same name, but no two router
5298 instances can have the same name. The name of a driver instance should not be
5299 confused with the name of the underlying driver module. For example, the
5300 configuration lines:
5305 create an instance of the &(smtp)& transport driver whose name is
5306 &(remote_smtp)&. The same driver code can be used more than once, with
5307 different instance names and different option settings each time. A second
5308 instance of the &(smtp)& transport, with different options, might be defined
5314 command_timeout = 10s
5316 The names &(remote_smtp)& and &(special_smtp)& would be used to reference
5317 these transport instances from routers, and these names would appear in log
5320 Comment lines may be present in the middle of driver specifications. The full
5321 list of option settings for any particular driver instance, including all the
5322 defaulted values, can be extracted by making use of the &%-bP%& command line
5330 . ////////////////////////////////////////////////////////////////////////////
5331 . ////////////////////////////////////////////////////////////////////////////
5333 .chapter "The default configuration file" "CHAPdefconfil"
5334 .scindex IIDconfiwal "configuration file" "default &""walk through""&"
5335 .cindex "default" "configuration file &""walk through""&"
5336 The default configuration file supplied with Exim as &_src/configure.default_&
5337 is sufficient for a host with simple mail requirements. As an introduction to
5338 the way Exim is configured, this chapter &"walks through"& the default
5339 configuration, giving brief explanations of the settings. Detailed descriptions
5340 of the options are given in subsequent chapters. The default configuration file
5341 itself contains extensive comments about ways you might want to modify the
5342 initial settings. However, note that there are many options that are not
5343 mentioned at all in the default configuration.
5347 .section "Main configuration settings" "SECTdefconfmain"
5348 The main (global) configuration option settings must always come first in the
5349 file. The first thing you'll see in the file, after some initial comments, is
5352 # primary_hostname =
5354 This is a commented-out setting of the &%primary_hostname%& option. Exim needs
5355 to know the official, fully qualified name of your host, and this is where you
5356 can specify it. However, in most cases you do not need to set this option. When
5357 it is unset, Exim uses the &[uname()]& system function to obtain the host name.
5359 The first three non-comment configuration lines are as follows:
5361 domainlist local_domains = @
5362 domainlist relay_to_domains =
5363 hostlist relay_from_hosts = 127.0.0.1
5365 These are not, in fact, option settings. They are definitions of two named
5366 domain lists and one named host list. Exim allows you to give names to lists of
5367 domains, hosts, and email addresses, in order to make it easier to manage the
5368 configuration file (see section &<<SECTnamedlists>>&).
5370 The first line defines a domain list called &'local_domains'&; this is used
5371 later in the configuration to identify domains that are to be delivered
5374 .cindex "@ in a domain list"
5375 There is just one item in this list, the string &"@"&. This is a special form
5376 of entry which means &"the name of the local host"&. Thus, if the local host is
5377 called &'a.host.example'&, mail to &'any.user@a.host.example'& is expected to
5378 be delivered locally. Because the local host's name is referenced indirectly,
5379 the same configuration file can be used on different hosts.
5381 The second line defines a domain list called &'relay_to_domains'&, but the
5382 list itself is empty. Later in the configuration we will come to the part that
5383 controls mail relaying through the local host; it allows relaying to any
5384 domains in this list. By default, therefore, no relaying on the basis of a mail
5385 domain is permitted.
5387 The third line defines a host list called &'relay_from_hosts'&. This list is
5388 used later in the configuration to permit relaying from any host or IP address
5389 that matches the list. The default contains just the IP address of the IPv4
5390 loopback interface, which means that processes on the local host are able to
5391 submit mail for relaying by sending it over TCP/IP to that interface. No other
5392 hosts are permitted to submit messages for relaying.
5394 Just to be sure there's no misunderstanding: at this point in the configuration
5395 we aren't actually setting up any controls. We are just defining some domains
5396 and hosts that will be used in the controls that are specified later.
5398 The next two configuration lines are genuine option settings:
5400 acl_smtp_rcpt = acl_check_rcpt
5401 acl_smtp_data = acl_check_data
5403 These options specify &'Access Control Lists'& (ACLs) that are to be used
5404 during an incoming SMTP session for every recipient of a message (every RCPT
5405 command), and after the contents of the message have been received,
5406 respectively. The names of the lists are &'acl_check_rcpt'& and
5407 &'acl_check_data'&, and we will come to their definitions below, in the ACL
5408 section of the configuration. The RCPT ACL controls which recipients are
5409 accepted for an incoming message &-- if a configuration does not provide an ACL
5410 to check recipients, no SMTP mail can be accepted. The DATA ACL allows the
5411 contents of a message to be checked.
5413 Two commented-out option settings are next:
5415 # av_scanner = clamd:/tmp/clamd
5416 # spamd_address = 127.0.0.1 783
5418 These are example settings that can be used when Exim is compiled with the
5419 content-scanning extension. The first specifies the interface to the virus
5420 scanner, and the second specifies the interface to SpamAssassin. Further
5421 details are given in chapter &<<CHAPexiscan>>&.
5423 Three more commented-out option settings follow:
5425 # tls_advertise_hosts = *
5426 # tls_certificate = /etc/ssl/exim.crt
5427 # tls_privatekey = /etc/ssl/exim.pem
5429 These are example settings that can be used when Exim is compiled with
5430 support for TLS (aka SSL) as described in section &<<SECTinctlsssl>>&. The
5431 first one specifies the list of clients that are allowed to use TLS when
5432 connecting to this server; in this case the wildcard means all clients. The
5433 other options specify where Exim should find its TLS certificate and private
5434 key, which together prove the server's identity to any clients that connect.
5435 More details are given in chapter &<<CHAPTLS>>&.
5437 Another two commented-out option settings follow:
5439 # daemon_smtp_ports = 25 : 465 : 587
5440 # tls_on_connect_ports = 465
5442 .cindex "port" "465 and 587"
5443 .cindex "port" "for message submission"
5444 .cindex "message" "submission, ports for"
5445 .cindex "ssmtp protocol"
5446 .cindex "smtps protocol"
5447 .cindex "SMTP" "ssmtp protocol"
5448 .cindex "SMTP" "smtps protocol"
5449 These options provide better support for roaming users who wish to use this
5450 server for message submission. They are not much use unless you have turned on
5451 TLS (as described in the previous paragraph) and authentication (about which
5452 more in section &<<SECTdefconfauth>>&). The usual SMTP port 25 is often blocked
5453 on end-user networks, so RFC 4409 specifies that message submission should use
5454 port 587 instead. However some software (notably Microsoft Outlook) cannot be
5455 configured to use port 587 correctly, so these settings also enable the
5456 non-standard &"smtps"& (aka &"ssmtp"&) port 465 (see section
5457 &<<SECTsupobssmt>>&).
5459 Two more commented-out options settings follow:
5462 # qualify_recipient =
5464 The first of these specifies a domain that Exim uses when it constructs a
5465 complete email address from a local login name. This is often needed when Exim
5466 receives a message from a local process. If you do not set &%qualify_domain%&,
5467 the value of &%primary_hostname%& is used. If you set both of these options,
5468 you can have different qualification domains for sender and recipient
5469 addresses. If you set only the first one, its value is used in both cases.
5471 .cindex "domain literal" "recognizing format"
5472 The following line must be uncommented if you want Exim to recognize
5473 addresses of the form &'user@[10.11.12.13]'& that is, with a &"domain literal"&
5474 (an IP address within square brackets) instead of a named domain.
5476 # allow_domain_literals
5478 The RFCs still require this form, but many people think that in the modern
5479 Internet it makes little sense to permit mail to be sent to specific hosts by
5480 quoting their IP addresses. This ancient format has been used by people who
5481 try to abuse hosts by using them for unwanted relaying. However, some
5482 people believe there are circumstances (for example, messages addressed to
5483 &'postmaster'&) where domain literals are still useful.
5485 The next configuration line is a kind of trigger guard:
5489 It specifies that no delivery must ever be run as the root user. The normal
5490 convention is to set up &'root'& as an alias for the system administrator. This
5491 setting is a guard against slips in the configuration.
5492 The list of users specified by &%never_users%& is not, however, the complete
5493 list; the build-time configuration in &_Local/Makefile_& has an option called
5494 FIXED_NEVER_USERS specifying a list that cannot be overridden. The
5495 contents of &%never_users%& are added to this list. By default
5496 FIXED_NEVER_USERS also specifies root.
5498 When a remote host connects to Exim in order to send mail, the only information
5499 Exim has about the host's identity is its IP address. The next configuration
5504 specifies that Exim should do a reverse DNS lookup on all incoming connections,
5505 in order to get a host name. This improves the quality of the logging
5506 information, but if you feel it is too expensive, you can remove it entirely,
5507 or restrict the lookup to hosts on &"nearby"& networks.
5508 Note that it is not always possible to find a host name from an IP address,
5509 because not all DNS reverse zones are maintained, and sometimes DNS servers are
5512 The next two lines are concerned with &'ident'& callbacks, as defined by RFC
5513 1413 (hence their names):
5516 rfc1413_query_timeout = 5s
5518 These settings cause Exim to make ident callbacks for all incoming SMTP calls.
5519 You can limit the hosts to which these calls are made, or change the timeout
5520 that is used. If you set the timeout to zero, all ident calls are disabled.
5521 Although they are cheap and can provide useful information for tracing problem
5522 messages, some hosts and firewalls have problems with ident calls. This can
5523 result in a timeout instead of an immediate refused connection, leading to
5524 delays on starting up an incoming SMTP session.
5526 When Exim receives messages over SMTP connections, it expects all addresses to
5527 be fully qualified with a domain, as required by the SMTP definition. However,
5528 if you are running a server to which simple clients submit messages, you may
5529 find that they send unqualified addresses. The two commented-out options:
5531 # sender_unqualified_hosts =
5532 # recipient_unqualified_hosts =
5534 show how you can specify hosts that are permitted to send unqualified sender
5535 and recipient addresses, respectively.
5537 The &%percent_hack_domains%& option is also commented out:
5539 # percent_hack_domains =
5541 It provides a list of domains for which the &"percent hack"& is to operate.
5542 This is an almost obsolete form of explicit email routing. If you do not know
5543 anything about it, you can safely ignore this topic.
5545 The last two settings in the main part of the default configuration are
5546 concerned with messages that have been &"frozen"& on Exim's queue. When a
5547 message is frozen, Exim no longer continues to try to deliver it. Freezing
5548 occurs when a bounce message encounters a permanent failure because the sender
5549 address of the original message that caused the bounce is invalid, so the
5550 bounce cannot be delivered. This is probably the most common case, but there
5551 are also other conditions that cause freezing, and frozen messages are not
5552 always bounce messages.
5554 ignore_bounce_errors_after = 2d
5555 timeout_frozen_after = 7d
5557 The first of these options specifies that failing bounce messages are to be
5558 discarded after 2 days on the queue. The second specifies that any frozen
5559 message (whether a bounce message or not) is to be timed out (and discarded)
5560 after a week. In this configuration, the first setting ensures that no failing
5561 bounce message ever lasts a week.
5565 .section "ACL configuration" "SECID54"
5566 .cindex "default" "ACLs"
5567 .cindex "&ACL;" "default configuration"
5568 In the default configuration, the ACL section follows the main configuration.
5569 It starts with the line
5573 and it contains the definitions of two ACLs, called &'acl_check_rcpt'& and
5574 &'acl_check_data'&, that were referenced in the settings of &%acl_smtp_rcpt%&
5575 and &%acl_smtp_data%& above.
5577 .cindex "RCPT" "ACL for"
5578 The first ACL is used for every RCPT command in an incoming SMTP message. Each
5579 RCPT command specifies one of the message's recipients. The ACL statements
5580 are considered in order, until the recipient address is either accepted or
5581 rejected. The RCPT command is then accepted or rejected, according to the
5582 result of the ACL processing.
5586 This line, consisting of a name terminated by a colon, marks the start of the
5591 This ACL statement accepts the recipient if the sending host matches the list.
5592 But what does that strange list mean? It doesn't actually contain any host
5593 names or IP addresses. The presence of the colon puts an empty item in the
5594 list; Exim matches this only if the incoming message did not come from a remote
5595 host, because in that case, the remote hostname is empty. The colon is
5596 important. Without it, the list itself is empty, and can never match anything.
5598 What this statement is doing is to accept unconditionally all recipients in
5599 messages that are submitted by SMTP from local processes using the standard
5600 input and output (that is, not using TCP/IP). A number of MUAs operate in this
5603 deny message = Restricted characters in address
5604 domains = +local_domains
5605 local_parts = ^[.] : ^.*[@%!/|]
5607 deny message = Restricted characters in address
5608 domains = !+local_domains
5609 local_parts = ^[./|] : ^.*[@%!] : ^.*/\\.\\./
5611 These statements are concerned with local parts that contain any of the
5612 characters &"@"&, &"%"&, &"!"&, &"/"&, &"|"&, or dots in unusual places.
5613 Although these characters are entirely legal in local parts (in the case of
5614 &"@"& and leading dots, only if correctly quoted), they do not commonly occur
5615 in Internet mail addresses.
5617 The first three have in the past been associated with explicitly routed
5618 addresses (percent is still sometimes used &-- see the &%percent_hack_domains%&
5619 option). Addresses containing these characters are regularly tried by spammers
5620 in an attempt to bypass relaying restrictions, and also by open relay testing
5621 programs. Unless you really need them it is safest to reject these characters
5622 at this early stage. This configuration is heavy-handed in rejecting these
5623 characters for all messages it accepts from remote hosts. This is a deliberate
5624 policy of being as safe as possible.
5626 The first rule above is stricter, and is applied to messages that are addressed
5627 to one of the local domains handled by this host. This is implemented by the
5628 first condition, which restricts it to domains that are listed in the
5629 &'local_domains'& domain list. The &"+"& character is used to indicate a
5630 reference to a named list. In this configuration, there is just one domain in
5631 &'local_domains'&, but in general there may be many.
5633 The second condition on the first statement uses two regular expressions to
5634 block local parts that begin with a dot or contain &"@"&, &"%"&, &"!"&, &"/"&,
5635 or &"|"&. If you have local accounts that include these characters, you will
5636 have to modify this rule.
5638 Empty components (two dots in a row) are not valid in RFC 2822, but Exim
5639 allows them because they have been encountered in practice. (Consider the
5640 common convention of local parts constructed as
5641 &"&'first-initial.second-initial.family-name'&"& when applied to someone like
5642 the author of Exim, who has no second initial.) However, a local part starting
5643 with a dot or containing &"/../"& can cause trouble if it is used as part of a
5644 file name (for example, for a mailing list). This is also true for local parts
5645 that contain slashes. A pipe symbol can also be troublesome if the local part
5646 is incorporated unthinkingly into a shell command line.
5648 The second rule above applies to all other domains, and is less strict. This
5649 allows your own users to send outgoing messages to sites that use slashes
5650 and vertical bars in their local parts. It blocks local parts that begin
5651 with a dot, slash, or vertical bar, but allows these characters within the
5652 local part. However, the sequence &"/../"& is barred. The use of &"@"&, &"%"&,
5653 and &"!"& is blocked, as before. The motivation here is to prevent your users
5654 (or your users' viruses) from mounting certain kinds of attack on remote sites.
5656 accept local_parts = postmaster
5657 domains = +local_domains
5659 This statement, which has two conditions, accepts an incoming address if the
5660 local part is &'postmaster'& and the domain is one of those listed in the
5661 &'local_domains'& domain list. The &"+"& character is used to indicate a
5662 reference to a named list. In this configuration, there is just one domain in
5663 &'local_domains'&, but in general there may be many.
5665 The presence of this statement means that mail to postmaster is never blocked
5666 by any of the subsequent tests. This can be helpful while sorting out problems
5667 in cases where the subsequent tests are incorrectly denying access.
5669 require verify = sender
5671 This statement requires the sender address to be verified before any subsequent
5672 ACL statement can be used. If verification fails, the incoming recipient
5673 address is refused. Verification consists of trying to route the address, to
5674 see if a bounce message could be delivered to it. In the case of remote
5675 addresses, basic verification checks only the domain, but &'callouts'& can be
5676 used for more verification if required. Section &<<SECTaddressverification>>&
5677 discusses the details of address verification.
5679 accept hosts = +relay_from_hosts
5680 control = submission
5682 This statement accepts the address if the message is coming from one of the
5683 hosts that are defined as being allowed to relay through this host. Recipient
5684 verification is omitted here, because in many cases the clients are dumb MUAs
5685 that do not cope well with SMTP error responses. For the same reason, the
5686 second line specifies &"submission mode"& for messages that are accepted. This
5687 is described in detail in section &<<SECTsubmodnon>>&; it causes Exim to fix
5688 messages that are deficient in some way, for example, because they lack a
5689 &'Date:'& header line. If you are actually relaying out from MTAs, you should
5690 probably add recipient verification here, and disable submission mode.
5692 accept authenticated = *
5693 control = submission
5695 This statement accepts the address if the client host has authenticated itself.
5696 Submission mode is again specified, on the grounds that such messages are most
5697 likely to come from MUAs. The default configuration does not define any
5698 authenticators, though it does include some nearly complete commented-out
5699 examples described in &<<SECTdefconfauth>>&. This means that no client can in
5700 fact authenticate until you complete the authenticator definitions.
5702 require message = relay not permitted
5703 domains = +local_domains : +relay_domains
5705 This statement rejects the address if its domain is neither a local domain nor
5706 one of the domains for which this host is a relay.
5708 require verify = recipient
5710 This statement requires the recipient address to be verified; if verification
5711 fails, the address is rejected.
5713 # deny message = rejected because $sender_host_address \
5714 # is in a black list at $dnslist_domain\n\
5716 # dnslists = black.list.example
5718 # warn dnslists = black.list.example
5719 # add_header = X-Warning: $sender_host_address is in \
5720 # a black list at $dnslist_domain
5721 # log_message = found in $dnslist_domain
5723 These commented-out lines are examples of how you could configure Exim to check
5724 sending hosts against a DNS black list. The first statement rejects messages
5725 from blacklisted hosts, whereas the second just inserts a warning header
5728 # require verify = csa
5730 This commented-out line is an example of how you could turn on client SMTP
5731 authorization (CSA) checking. Such checks do DNS lookups for special SRV
5736 The final statement in the first ACL unconditionally accepts any recipient
5737 address that has successfully passed all the previous tests.
5741 This line marks the start of the second ACL, and names it. Most of the contents
5742 of this ACL are commented out:
5745 # message = This message contains a virus \
5748 These lines are examples of how to arrange for messages to be scanned for
5749 viruses when Exim has been compiled with the content-scanning extension, and a
5750 suitable virus scanner is installed. If the message is found to contain a
5751 virus, it is rejected with the given custom error message.
5753 # warn spam = nobody
5754 # message = X-Spam_score: $spam_score\n\
5755 # X-Spam_score_int: $spam_score_int\n\
5756 # X-Spam_bar: $spam_bar\n\
5757 # X-Spam_report: $spam_report
5759 These lines are an example of how to arrange for messages to be scanned by
5760 SpamAssassin when Exim has been compiled with the content-scanning extension,
5761 and SpamAssassin has been installed. The SpamAssassin check is run with
5762 &`nobody`& as its user parameter, and the results are added to the message as a
5763 series of extra header line. In this case, the message is not rejected,
5764 whatever the spam score.
5768 This final line in the DATA ACL accepts the message unconditionally.
5771 .section "Router configuration" "SECID55"
5772 .cindex "default" "routers"
5773 .cindex "routers" "default"
5774 The router configuration comes next in the default configuration, introduced
5779 Routers are the modules in Exim that make decisions about where to send
5780 messages. An address is passed to each router in turn, until it is either
5781 accepted, or failed. This means that the order in which you define the routers
5782 matters. Each router is fully described in its own chapter later in this
5783 manual. Here we give only brief overviews.
5786 # driver = ipliteral
5787 # domains = !+local_domains
5788 # transport = remote_smtp
5790 .cindex "domain literal" "default router"
5791 This router is commented out because the majority of sites do not want to
5792 support domain literal addresses (those of the form &'user@[10.9.8.7]'&). If
5793 you uncomment this router, you also need to uncomment the setting of
5794 &%allow_domain_literals%& in the main part of the configuration.
5798 domains = ! +local_domains
5799 transport = remote_smtp
5800 ignore_target_hosts = 0.0.0.0 : 127.0.0.0/8
5803 The first uncommented router handles addresses that do not involve any local
5804 domains. This is specified by the line
5806 domains = ! +local_domains
5808 The &%domains%& option lists the domains to which this router applies, but the
5809 exclamation mark is a negation sign, so the router is used only for domains
5810 that are not in the domain list called &'local_domains'& (which was defined at
5811 the start of the configuration). The plus sign before &'local_domains'&
5812 indicates that it is referring to a named list. Addresses in other domains are
5813 passed on to the following routers.
5815 The name of the router driver is &(dnslookup)&,
5816 and is specified by the &%driver%& option. Do not be confused by the fact that
5817 the name of this router instance is the same as the name of the driver. The
5818 instance name is arbitrary, but the name set in the &%driver%& option must be
5819 one of the driver modules that is in the Exim binary.
5821 The &(dnslookup)& router routes addresses by looking up their domains in the
5822 DNS in order to obtain a list of hosts to which the address is routed. If the
5823 router succeeds, the address is queued for the &(remote_smtp)& transport, as
5824 specified by the &%transport%& option. If the router does not find the domain
5825 in the DNS, no further routers are tried because of the &%no_more%& setting, so
5826 the address fails and is bounced.
5828 The &%ignore_target_hosts%& option specifies a list of IP addresses that are to
5829 be entirely ignored. This option is present because a number of cases have been
5830 encountered where MX records in the DNS point to host names
5831 whose IP addresses are 0.0.0.0 or are in the 127 subnet (typically 127.0.0.1).
5832 Completely ignoring these IP addresses causes Exim to fail to route the
5833 email address, so it bounces. Otherwise, Exim would log a routing problem, and
5834 continue to try to deliver the message periodically until the address timed
5841 data = ${lookup{$local_part}lsearch{/etc/aliases}}
5843 file_transport = address_file
5844 pipe_transport = address_pipe
5846 Control reaches this and subsequent routers only for addresses in the local
5847 domains. This router checks to see whether the local part is defined as an
5848 alias in the &_/etc/aliases_& file, and if so, redirects it according to the
5849 data that it looks up from that file. If no data is found for the local part,
5850 the value of the &%data%& option is empty, causing the address to be passed to
5853 &_/etc/aliases_& is a conventional name for the system aliases file that is
5854 often used. That is why it is referenced by from the default configuration
5855 file. However, you can change this by setting SYSTEM_ALIASES_FILE in
5856 &_Local/Makefile_& before building Exim.
5861 # local_part_suffix = +* : -*
5862 # local_part_suffix_optional
5863 file = $home/.forward
5868 file_transport = address_file
5869 pipe_transport = address_pipe
5870 reply_transport = address_reply
5872 This is the most complicated router in the default configuration. It is another
5873 redirection router, but this time it is looking for forwarding data set up by
5874 individual users. The &%check_local_user%& setting specifies a check that the
5875 local part of the address is the login name of a local user. If it is not, the
5876 router is skipped. The two commented options that follow &%check_local_user%&,
5879 # local_part_suffix = +* : -*
5880 # local_part_suffix_optional
5882 .vindex "&$local_part_suffix$&"
5883 show how you can specify the recognition of local part suffixes. If the first
5884 is uncommented, a suffix beginning with either a plus or a minus sign, followed
5885 by any sequence of characters, is removed from the local part and placed in the
5886 variable &$local_part_suffix$&. The second suffix option specifies that the
5887 presence of a suffix in the local part is optional. When a suffix is present,
5888 the check for a local login uses the local part with the suffix removed.
5890 When a local user account is found, the file called &_.forward_& in the user's
5891 home directory is consulted. If it does not exist, or is empty, the router
5892 declines. Otherwise, the contents of &_.forward_& are interpreted as
5893 redirection data (see chapter &<<CHAPredirect>>& for more details).
5895 .cindex "Sieve filter" "enabling in default router"
5896 Traditional &_.forward_& files contain just a list of addresses, pipes, or
5897 files. Exim supports this by default. However, if &%allow_filter%& is set (it
5898 is commented out by default), the contents of the file are interpreted as a set
5899 of Exim or Sieve filtering instructions, provided the file begins with &"#Exim
5900 filter"& or &"#Sieve filter"&, respectively. User filtering is discussed in the
5901 separate document entitled &'Exim's interfaces to mail filtering'&.
5903 The &%no_verify%& and &%no_expn%& options mean that this router is skipped when
5904 verifying addresses, or when running as a consequence of an SMTP EXPN command.
5905 There are two reasons for doing this:
5908 Whether or not a local user has a &_.forward_& file is not really relevant when
5909 checking an address for validity; it makes sense not to waste resources doing
5912 More importantly, when Exim is verifying addresses or handling an EXPN
5913 command during an SMTP session, it is running as the Exim user, not as root.
5914 The group is the Exim group, and no additional groups are set up.
5915 It may therefore not be possible for Exim to read users' &_.forward_& files at
5919 The setting of &%check_ancestor%& prevents the router from generating a new
5920 address that is the same as any previous address that was redirected. (This
5921 works round a problem concerning a bad interaction between aliasing and
5922 forwarding &-- see section &<<SECTredlocmai>>&).
5924 The final three option settings specify the transports that are to be used when
5925 forwarding generates a direct delivery to a file, or to a pipe, or sets up an
5926 auto-reply, respectively. For example, if a &_.forward_& file contains
5928 a.nother@elsewhere.example, /home/spqr/archive
5930 the delivery to &_/home/spqr/archive_& is done by running the &%address_file%&
5936 # local_part_suffix = +* : -*
5937 # local_part_suffix_optional
5938 transport = local_delivery
5940 The final router sets up delivery into local mailboxes, provided that the local
5941 part is the name of a local login, by accepting the address and assigning it to
5942 the &(local_delivery)& transport. Otherwise, we have reached the end of the
5943 routers, so the address is bounced. The commented suffix settings fulfil the
5944 same purpose as they do for the &(userforward)& router.
5947 .section "Transport configuration" "SECID56"
5948 .cindex "default" "transports"
5949 .cindex "transports" "default"
5950 Transports define mechanisms for actually delivering messages. They operate
5951 only when referenced from routers, so the order in which they are defined does
5952 not matter. The transports section of the configuration starts with
5956 One remote transport and four local transports are defined.
5961 This transport is used for delivering messages over SMTP connections. All its
5962 options are defaulted. The list of remote hosts comes from the router.
5966 file = /var/mail/$local_part
5973 This &(appendfile)& transport is used for local delivery to user mailboxes in
5974 traditional BSD mailbox format. By default it runs under the uid and gid of the
5975 local user, which requires the sticky bit to be set on the &_/var/mail_&
5976 directory. Some systems use the alternative approach of running mail deliveries
5977 under a particular group instead of using the sticky bit. The commented options
5978 show how this can be done.
5980 Exim adds three headers to the message as it delivers it: &'Delivery-date:'&,
5981 &'Envelope-to:'& and &'Return-path:'&. This action is requested by the three
5982 similarly-named options above.
5988 This transport is used for handling deliveries to pipes that are generated by
5989 redirection (aliasing or users' &_.forward_& files). The &%return_output%&
5990 option specifies that any output generated by the pipe is to be returned to the
5999 This transport is used for handling deliveries to files that are generated by
6000 redirection. The name of the file is not specified in this instance of
6001 &(appendfile)&, because it comes from the &(redirect)& router.
6006 This transport is used for handling automatic replies generated by users'
6011 .section "Default retry rule" "SECID57"
6012 .cindex "retry" "default rule"
6013 .cindex "default" "retry rule"
6014 The retry section of the configuration file contains rules which affect the way
6015 Exim retries deliveries that cannot be completed at the first attempt. It is
6016 introduced by the line
6020 In the default configuration, there is just one rule, which applies to all
6023 * * F,2h,15m; G,16h,1h,1.5; F,4d,6h
6025 This causes any temporarily failing address to be retried every 15 minutes for
6026 2 hours, then at intervals starting at one hour and increasing by a factor of
6027 1.5 until 16 hours have passed, then every 6 hours up to 4 days. If an address
6028 is not delivered after 4 days of temporary failure, it is bounced.
6030 If the retry section is removed from the configuration, or is empty (that is,
6031 if no retry rules are defined), Exim will not retry deliveries. This turns
6032 temporary errors into permanent errors.
6035 .section "Rewriting configuration" "SECID58"
6036 The rewriting section of the configuration, introduced by
6040 contains rules for rewriting addresses in messages as they arrive. There are no
6041 rewriting rules in the default configuration file.
6045 .section "Authenticators configuration" "SECTdefconfauth"
6046 .cindex "AUTH" "configuration"
6047 The authenticators section of the configuration, introduced by
6049 begin authenticators
6051 defines mechanisms for the use of the SMTP AUTH command. The default
6052 configuration file contains two commented-out example authenticators
6053 which support plaintext username/password authentication using the
6054 standard PLAIN mechanism and the traditional but non-standard LOGIN
6055 mechanism, with Exim acting as the server. PLAIN and LOGIN are enough
6056 to support most MUA software.
6058 The example PLAIN authenticator looks like this:
6061 # driver = plaintext
6062 # server_set_id = $auth2
6063 # server_prompts = :
6064 # server_condition = Authentication is not yet configured
6065 # server_advertise_condition = ${if def:tls_cipher }
6067 And the example LOGIN authenticator looks like this:
6070 # driver = plaintext
6071 # server_set_id = $auth1
6072 # server_prompts = <| Username: | Password:
6073 # server_condition = Authentication is not yet configured
6074 # server_advertise_condition = ${if def:tls_cipher }
6077 The &%server_set_id%& option makes Exim remember the authenticated username
6078 in &$authenticated_id$&, which can be used later in ACLs or routers. The
6079 &%server_prompts%& option configures the &(plaintext)& authenticator so
6080 that it implements the details of the specific authentication mechanism,
6081 i.e. PLAIN or LOGIN. The &%server_advertise_condition%& setting controls
6082 when Exim offers authentication to clients; in the examples, this is only
6083 when TLS or SSL has been started, so to enable the authenticators you also
6084 need to add support for TLS as described in section &<<SECTdefconfmain>>&.
6086 The &%server_condition%& setting defines how to verify that the username and
6087 password are correct. In the examples it just produces an error message.
6088 To make the authenticators work, you can use a string expansion
6089 expression like one of the examples in chapter &<<CHAPplaintext>>&.
6091 Beware that the sequence of the parameters to PLAIN and LOGIN differ; the
6092 usercode and password are in different positions.
6093 Chapter &<<CHAPplaintext>>& covers both.
6095 .ecindex IIDconfiwal
6099 . ////////////////////////////////////////////////////////////////////////////
6100 . ////////////////////////////////////////////////////////////////////////////
6102 .chapter "Regular expressions" "CHAPregexp"
6104 .cindex "regular expressions" "library"
6106 Exim supports the use of regular expressions in many of its options. It
6107 uses the PCRE regular expression library; this provides regular expression
6108 matching that is compatible with Perl 5. The syntax and semantics of
6109 regular expressions is discussed in many Perl reference books, and also in
6110 Jeffrey Friedl's &'Mastering Regular Expressions'&, which is published by
6111 O'Reilly (see &url(http://www.oreilly.com/catalog/regex2/)).
6113 The documentation for the syntax and semantics of the regular expressions that
6114 are supported by PCRE is included in the PCRE distribution, and no further
6115 description is included here. The PCRE functions are called from Exim using
6116 the default option settings (that is, with no PCRE options set), except that
6117 the PCRE_CASELESS option is set when the matching is required to be
6120 In most cases, when a regular expression is required in an Exim configuration,
6121 it has to start with a circumflex, in order to distinguish it from plain text
6122 or an &"ends with"& wildcard. In this example of a configuration setting, the
6123 second item in the colon-separated list is a regular expression.
6125 domains = a.b.c : ^\\d{3} : *.y.z : ...
6127 The doubling of the backslash is required because of string expansion that
6128 precedes interpretation &-- see section &<<SECTlittext>>& for more discussion
6129 of this issue, and a way of avoiding the need for doubling backslashes. The
6130 regular expression that is eventually used in this example contains just one
6131 backslash. The circumflex is included in the regular expression, and has the
6132 normal effect of &"anchoring"& it to the start of the string that is being
6135 There are, however, two cases where a circumflex is not required for the
6136 recognition of a regular expression: these are the &%match%& condition in a
6137 string expansion, and the &%matches%& condition in an Exim filter file. In
6138 these cases, the relevant string is always treated as a regular expression; if
6139 it does not start with a circumflex, the expression is not anchored, and can
6140 match anywhere in the subject string.
6142 In all cases, if you want a regular expression to match at the end of a string,
6143 you must code the $ metacharacter to indicate this. For example:
6145 domains = ^\\d{3}\\.example
6147 matches the domain &'123.example'&, but it also matches &'123.example.com'&.
6150 domains = ^\\d{3}\\.example\$
6152 if you want &'example'& to be the top-level domain. The backslash before the
6153 $ is needed because string expansion also interprets dollar characters.
6157 . ////////////////////////////////////////////////////////////////////////////
6158 . ////////////////////////////////////////////////////////////////////////////
6160 .chapter "File and database lookups" "CHAPfdlookup"
6161 .scindex IIDfidalo1 "file" "lookups"
6162 .scindex IIDfidalo2 "database" "lookups"
6163 .cindex "lookup" "description of"
6164 Exim can be configured to look up data in files or databases as it processes
6165 messages. Two different kinds of syntax are used:
6168 A string that is to be expanded may contain explicit lookup requests. These
6169 cause parts of the string to be replaced by data that is obtained from the
6170 lookup. Lookups of this type are conditional expansion items. Different results
6171 can be defined for the cases of lookup success and failure. See chapter
6172 &<<CHAPexpand>>&, where string expansions are described in detail.
6174 Lists of domains, hosts, and email addresses can contain lookup requests as a
6175 way of avoiding excessively long linear lists. In this case, the data that is
6176 returned by the lookup is often (but not always) discarded; whether the lookup
6177 succeeds or fails is what really counts. These kinds of list are described in
6178 chapter &<<CHAPdomhosaddlists>>&.
6181 String expansions, lists, and lookups interact with each other in such a way
6182 that there is no order in which to describe any one of them that does not
6183 involve references to the others. Each of these three chapters makes more sense
6184 if you have read the other two first. If you are reading this for the first
6185 time, be aware that some of it will make a lot more sense after you have read
6186 chapters &<<CHAPdomhosaddlists>>& and &<<CHAPexpand>>&.
6188 .section "Examples of different lookup syntax" "SECID60"
6189 It is easy to confuse the two different kinds of lookup, especially as the
6190 lists that may contain the second kind are always expanded before being
6191 processed as lists. Therefore, they may also contain lookups of the first kind.
6192 Be careful to distinguish between the following two examples:
6194 domains = ${lookup{$sender_host_address}lsearch{/some/file}}
6195 domains = lsearch;/some/file
6197 The first uses a string expansion, the result of which must be a domain list.
6198 No strings have been specified for a successful or a failing lookup; the
6199 defaults in this case are the looked-up data and an empty string, respectively.
6200 The expansion takes place before the string is processed as a list, and the
6201 file that is searched could contain lines like this:
6203 192.168.3.4: domain1:domain2:...
6204 192.168.1.9: domain3:domain4:...
6206 When the lookup succeeds, the result of the expansion is a list of domains (and
6207 possibly other types of item that are allowed in domain lists).
6209 In the second example, the lookup is a single item in a domain list. It causes
6210 Exim to use a lookup to see if the domain that is being processed can be found
6211 in the file. The file could contains lines like this:
6216 Any data that follows the keys is not relevant when checking that the domain
6217 matches the list item.
6219 It is possible, though no doubt confusing, to use both kinds of lookup at once.
6220 Consider a file containing lines like this:
6222 192.168.5.6: lsearch;/another/file
6224 If the value of &$sender_host_address$& is 192.168.5.6, expansion of the
6225 first &%domains%& setting above generates the second setting, which therefore
6226 causes a second lookup to occur.
6228 The rest of this chapter describes the different lookup types that are
6229 available. Any of them can be used in any part of the configuration where a
6230 lookup is permitted.
6233 .section "Lookup types" "SECID61"
6234 .cindex "lookup" "types of"
6235 .cindex "single-key lookup" "definition of"
6236 Two different types of data lookup are implemented:
6239 The &'single-key'& type requires the specification of a file in which to look,
6240 and a single key to search for. The key must be a non-empty string for the
6241 lookup to succeed. The lookup type determines how the file is searched.
6243 .cindex "query-style lookup" "definition of"
6244 The &'query-style'& type accepts a generalized database query. No particular
6245 key value is assumed by Exim for query-style lookups. You can use whichever
6246 Exim variables you need to construct the database query.
6249 The code for each lookup type is in a separate source file that is included in
6250 the binary of Exim only if the corresponding compile-time option is set. The
6251 default settings in &_src/EDITME_& are:
6256 which means that only linear searching and DBM lookups are included by default.
6257 For some types of lookup (e.g. SQL databases), you need to install appropriate
6258 libraries and header files before building Exim.
6263 .section "Single-key lookup types" "SECTsinglekeylookups"
6264 .cindex "lookup" "single-key types"
6265 .cindex "single-key lookup" "list of types"
6266 The following single-key lookup types are implemented:
6269 .cindex "cdb" "description of"
6270 .cindex "lookup" "cdb"
6271 .cindex "binary zero" "in lookup key"
6272 &(cdb)&: The given file is searched as a Constant DataBase file, using the key
6273 string without a terminating binary zero. The cdb format is designed for
6274 indexed files that are read frequently and never updated, except by total
6275 re-creation. As such, it is particularly suitable for large files containing
6276 aliases or other indexed data referenced by an MTA. Information about cdb can
6277 be found in several places:
6279 &url(http://www.pobox.com/~djb/cdb.html)
6280 &url(ftp://ftp.corpit.ru/pub/tinycdb/)
6281 &url(http://packages.debian.org/stable/utils/freecdb.html)
6283 A cdb distribution is not needed in order to build Exim with cdb support,
6284 because the code for reading cdb files is included directly in Exim itself.
6285 However, no means of building or testing cdb files is provided with Exim, so
6286 you need to obtain a cdb distribution in order to do this.
6288 .cindex "DBM" "lookup type"
6289 .cindex "lookup" "dbm"
6290 .cindex "binary zero" "in lookup key"
6291 &(dbm)&: Calls to DBM library functions are used to extract data from the given
6292 DBM file by looking up the record with the given key. A terminating binary
6293 zero is included in the key that is passed to the DBM library. See section
6294 &<<SECTdb>>& for a discussion of DBM libraries.
6296 .cindex "Berkeley DB library" "file format"
6297 For all versions of Berkeley DB, Exim uses the DB_HASH style of database
6298 when building DBM files using the &%exim_dbmbuild%& utility. However, when
6299 using Berkeley DB versions 3 or 4, it opens existing databases for reading with
6300 the DB_UNKNOWN option. This enables it to handle any of the types of database
6301 that the library supports, and can be useful for accessing DBM files created by
6302 other applications. (For earlier DB versions, DB_HASH is always used.)
6304 .cindex "lookup" "dbmjz"
6305 .cindex "lookup" "dbm &-- embedded NULs"
6307 .cindex "dbmjz lookup type"
6308 &(dbmjz)&: This is the same as &(dbm)&, except that the lookup key is
6309 interpreted as an Exim list; the elements of the list are joined together with
6310 ASCII NUL characters to form the lookup key. An example usage would be to
6311 authenticate incoming SMTP calls using the passwords from Cyrus SASL's
6312 &_/etc/sasldb2_& file with the &(gsasl)& authenticator or Exim's own
6313 &(cram_md5)& authenticator.
6315 .cindex "lookup" "dbmnz"
6316 .cindex "lookup" "dbm &-- terminating zero"
6317 .cindex "binary zero" "in lookup key"
6319 .cindex "&_/etc/userdbshadow.dat_&"
6320 .cindex "dbmnz lookup type"
6321 &(dbmnz)&: This is the same as &(dbm)&, except that a terminating binary zero
6322 is not included in the key that is passed to the DBM library. You may need this
6323 if you want to look up data in files that are created by or shared with some
6324 other application that does not use terminating zeros. For example, you need to
6325 use &(dbmnz)& rather than &(dbm)& if you want to authenticate incoming SMTP
6326 calls using the passwords from Courier's &_/etc/userdbshadow.dat_& file. Exim's
6327 utility program for creating DBM files (&'exim_dbmbuild'&) includes the zeros
6328 by default, but has an option to omit them (see section &<<SECTdbmbuild>>&).
6330 .cindex "lookup" "dsearch"
6331 .cindex "dsearch lookup type"
6332 &(dsearch)&: The given file must be a directory; this is searched for an entry
6333 whose name is the key by calling the &[lstat()]& function. The key may not
6334 contain any forward slash characters. If &[lstat()]& succeeds, the result of
6335 the lookup is the name of the entry, which may be a file, directory,
6336 symbolic link, or any other kind of directory entry. An example of how this
6337 lookup can be used to support virtual domains is given in section
6338 &<<SECTvirtualdomains>>&.
6340 .cindex "lookup" "iplsearch"
6341 .cindex "iplsearch lookup type"
6342 &(iplsearch)&: The given file is a text file containing keys and data. A key is
6343 terminated by a colon or white space or the end of the line. The keys in the
6344 file must be IP addresses, or IP addresses with CIDR masks. Keys that involve
6345 IPv6 addresses must be enclosed in quotes to prevent the first internal colon
6346 being interpreted as a key terminator. For example:
6348 1.2.3.4: data for 1.2.3.4
6349 192.168.0.0/16: data for 192.168.0.0/16
6350 "abcd::cdab": data for abcd::cdab
6351 "abcd:abcd::/32" data for abcd:abcd::/32
6353 The key for an &(iplsearch)& lookup must be an IP address (without a mask). The
6354 file is searched linearly, using the CIDR masks where present, until a matching
6355 key is found. The first key that matches is used; there is no attempt to find a
6356 &"best"& match. Apart from the way the keys are matched, the processing for
6357 &(iplsearch)& is the same as for &(lsearch)&.
6359 &*Warning 1*&: Unlike most other single-key lookup types, a file of data for
6360 &(iplsearch)& can &'not'& be turned into a DBM or cdb file, because those
6361 lookup types support only literal keys.
6363 &*Warning 2*&: In a host list, you must always use &(net-iplsearch)& so that
6364 the implicit key is the host's IP address rather than its name (see section
6365 &<<SECThoslispatsikey>>&).
6367 .cindex "linear search"
6368 .cindex "lookup" "lsearch"
6369 .cindex "lsearch lookup type"
6370 .cindex "case sensitivity" "in lsearch lookup"
6371 &(lsearch)&: The given file is a text file that is searched linearly for a
6372 line beginning with the search key, terminated by a colon or white space or the
6373 end of the line. The search is case-insensitive; that is, upper and lower case
6374 letters are treated as the same. The first occurrence of the key that is found
6375 in the file is used.
6377 White space between the key and the colon is permitted. The remainder of the
6378 line, with leading and trailing white space removed, is the data. This can be
6379 continued onto subsequent lines by starting them with any amount of white
6380 space, but only a single space character is included in the data at such a
6381 junction. If the data begins with a colon, the key must be terminated by a
6386 Empty lines and lines beginning with # are ignored, even if they occur in the
6387 middle of an item. This is the traditional textual format of alias files. Note
6388 that the keys in an &(lsearch)& file are literal strings. There is no
6389 wildcarding of any kind.
6391 .cindex "lookup" "lsearch &-- colons in keys"
6392 .cindex "white space" "in lsearch key"
6393 In most &(lsearch)& files, keys are not required to contain colons or #
6394 characters, or white space. However, if you need this feature, it is available.
6395 If a key begins with a doublequote character, it is terminated only by a
6396 matching quote (or end of line), and the normal escaping rules apply to its
6397 contents (see section &<<SECTstrings>>&). An optional colon is permitted after
6398 quoted keys (exactly as for unquoted keys). There is no special handling of
6399 quotes for the data part of an &(lsearch)& line.
6402 .cindex "NIS lookup type"
6403 .cindex "lookup" "NIS"
6404 .cindex "binary zero" "in lookup key"
6405 &(nis)&: The given file is the name of a NIS map, and a NIS lookup is done with
6406 the given key, without a terminating binary zero. There is a variant called
6407 &(nis0)& which does include the terminating binary zero in the key. This is
6408 reportedly needed for Sun-style alias files. Exim does not recognize NIS
6409 aliases; the full map names must be used.
6412 .cindex "wildlsearch lookup type"
6413 .cindex "lookup" "wildlsearch"
6414 .cindex "nwildlsearch lookup type"
6415 .cindex "lookup" "nwildlsearch"
6416 &(wildlsearch)& or &(nwildlsearch)&: These search a file linearly, like
6417 &(lsearch)&, but instead of being interpreted as a literal string, each key in
6418 the file may be wildcarded. The difference between these two lookup types is
6419 that for &(wildlsearch)&, each key in the file is string-expanded before being
6420 used, whereas for &(nwildlsearch)&, no expansion takes place.
6422 .cindex "case sensitivity" "in (n)wildlsearch lookup"
6423 Like &(lsearch)&, the testing is done case-insensitively. However, keys in the
6424 file that are regular expressions can be made case-sensitive by the use of
6425 &`(-i)`& within the pattern. The following forms of wildcard are recognized:
6427 . ==== As this is a nested list, any displays it contains must be indented
6428 . ==== as otherwise they are too far to the left.
6431 The string may begin with an asterisk to mean &"ends with"&. For example:
6433 *.a.b.c data for anything.a.b.c
6434 *fish data for anythingfish
6437 The string may begin with a circumflex to indicate a regular expression. For
6438 example, for &(wildlsearch)&:
6440 ^\N\d+\.a\.b\N data for <digits>.a.b
6442 Note the use of &`\N`& to disable expansion of the contents of the regular
6443 expression. If you are using &(nwildlsearch)&, where the keys are not
6444 string-expanded, the equivalent entry is:
6446 ^\d+\.a\.b data for <digits>.a.b
6448 The case-insensitive flag is set at the start of compiling the regular
6449 expression, but it can be turned off by using &`(-i)`& at an appropriate point.
6450 For example, to make the entire pattern case-sensitive:
6452 ^(?-i)\d+\.a\.b data for <digits>.a.b
6455 If the regular expression contains white space or colon characters, you must
6456 either quote it (see &(lsearch)& above), or represent these characters in other
6457 ways. For example, &`\s`& can be used for white space and &`\x3A`& for a
6458 colon. This may be easier than quoting, because if you quote, you have to
6459 escape all the backslashes inside the quotes.
6461 &*Note*&: It is not possible to capture substrings in a regular expression
6462 match for later use, because the results of all lookups are cached. If a lookup
6463 is repeated, the result is taken from the cache, and no actual pattern matching
6464 takes place. The values of all the numeric variables are unset after a
6465 &((n)wildlsearch)& match.
6468 Although I cannot see it being of much use, the general matching function that
6469 is used to implement &((n)wildlsearch)& means that the string may begin with a
6470 lookup name terminated by a semicolon, and followed by lookup data. For
6473 cdb;/some/file data for keys that match the file
6475 The data that is obtained from the nested lookup is discarded.
6478 Keys that do not match any of these patterns are interpreted literally. The
6479 continuation rules for the data are the same as for &(lsearch)&, and keys may
6480 be followed by optional colons.
6482 &*Warning*&: Unlike most other single-key lookup types, a file of data for
6483 &((n)wildlsearch)& can &'not'& be turned into a DBM or cdb file, because those
6484 lookup types support only literal keys.
6488 .section "Query-style lookup types" "SECID62"
6489 .cindex "lookup" "query-style types"
6490 .cindex "query-style lookup" "list of types"
6491 The supported query-style lookup types are listed below. Further details about
6492 many of them are given in later sections.
6495 .cindex "DNS" "as a lookup type"
6496 .cindex "lookup" "DNS"
6497 &(dnsdb)&: This does a DNS search for one or more records whose domain names
6498 are given in the supplied query. The resulting data is the contents of the
6499 records. See section &<<SECTdnsdb>>&.
6501 .cindex "InterBase lookup type"
6502 .cindex "lookup" "InterBase"
6503 &(ibase)&: This does a lookup in an InterBase database.
6505 .cindex "LDAP" "lookup type"
6506 .cindex "lookup" "LDAP"
6507 &(ldap)&: This does an LDAP lookup using a query in the form of a URL, and
6508 returns attributes from a single entry. There is a variant called &(ldapm)&
6509 that permits values from multiple entries to be returned. A third variant
6510 called &(ldapdn)& returns the Distinguished Name of a single entry instead of
6511 any attribute values. See section &<<SECTldap>>&.
6513 .cindex "MySQL" "lookup type"
6514 .cindex "lookup" "MySQL"
6515 &(mysql)&: The format of the query is an SQL statement that is passed to a
6516 MySQL database. See section &<<SECTsql>>&.
6518 .cindex "NIS+ lookup type"
6519 .cindex "lookup" "NIS+"
6520 &(nisplus)&: This does a NIS+ lookup using a query that can specify the name of
6521 the field to be returned. See section &<<SECTnisplus>>&.
6523 .cindex "Oracle" "lookup type"
6524 .cindex "lookup" "Oracle"
6525 &(oracle)&: The format of the query is an SQL statement that is passed to an
6526 Oracle database. See section &<<SECTsql>>&.
6528 .cindex "lookup" "passwd"
6529 .cindex "passwd lookup type"
6530 .cindex "&_/etc/passwd_&"
6531 &(passwd)& is a query-style lookup with queries that are just user names. The
6532 lookup calls &[getpwnam()]& to interrogate the system password data, and on
6533 success, the result string is the same as you would get from an &(lsearch)&
6534 lookup on a traditional &_/etc/passwd file_&, though with &`*`& for the
6535 password value. For example:
6537 *:42:42:King Rat:/home/kr:/bin/bash
6540 .cindex "PostgreSQL lookup type"
6541 .cindex "lookup" "PostgreSQL"
6542 &(pgsql)&: The format of the query is an SQL statement that is passed to a
6543 PostgreSQL database. See section &<<SECTsql>>&.
6546 .cindex "sqlite lookup type"
6547 .cindex "lookup" "sqlite"
6548 &(sqlite)&: The format of the query is a file name followed by an SQL statement
6549 that is passed to an SQLite database. See section &<<SECTsqlite>>&.
6552 &(testdb)&: This is a lookup type that is used for testing Exim. It is
6553 not likely to be useful in normal operation.
6555 .cindex "whoson lookup type"
6556 .cindex "lookup" "whoson"
6557 &(whoson)&: &'Whoson'& (&url(http://whoson.sourceforge.net)) is a protocol that
6558 allows a server to check whether a particular (dynamically allocated) IP
6559 address is currently allocated to a known (trusted) user and, optionally, to
6560 obtain the identity of the said user. For SMTP servers, &'Whoson'& was popular
6561 at one time for &"POP before SMTP"& authentication, but that approach has been
6562 superseded by SMTP authentication. In Exim, &'Whoson'& can be used to implement
6563 &"POP before SMTP"& checking using ACL statements such as
6565 require condition = \
6566 ${lookup whoson {$sender_host_address}{yes}{no}}
6568 The query consists of a single IP address. The value returned is the name of
6569 the authenticated user, which is stored in the variable &$value$&. However, in
6570 this example, the data in &$value$& is not used; the result of the lookup is
6571 one of the fixed strings &"yes"& or &"no"&.
6576 .section "Temporary errors in lookups" "SECID63"
6577 .cindex "lookup" "temporary error in"
6578 Lookup functions can return temporary error codes if the lookup cannot be
6579 completed. For example, an SQL or LDAP database might be unavailable. For this
6580 reason, it is not advisable to use a lookup that might do this for critical
6581 options such as a list of local domains.
6583 When a lookup cannot be completed in a router or transport, delivery
6584 of the message (to the relevant address) is deferred, as for any other
6585 temporary error. In other circumstances Exim may assume the lookup has failed,
6586 or may give up altogether.
6590 .section "Default values in single-key lookups" "SECTdefaultvaluelookups"
6591 .cindex "wildcard lookups"
6592 .cindex "lookup" "default values"
6593 .cindex "lookup" "wildcard"
6594 .cindex "lookup" "* added to type"
6595 .cindex "default" "in single-key lookups"
6596 In this context, a &"default value"& is a value specified by the administrator
6597 that is to be used if a lookup fails.
6599 &*Note:*& This section applies only to single-key lookups. For query-style
6600 lookups, the facilities of the query language must be used. An attempt to
6601 specify a default for a query-style lookup provokes an error.
6603 If &"*"& is added to a single-key lookup type (for example, &%lsearch*%&)
6604 and the initial lookup fails, the key &"*"& is looked up in the file to
6605 provide a default value. See also the section on partial matching below.
6607 .cindex "*@ with single-key lookup"
6608 .cindex "lookup" "*@ added to type"
6609 .cindex "alias file" "per-domain default"
6610 Alternatively, if &"*@"& is added to a single-key lookup type (for example
6611 &%dbm*@%&) then, if the initial lookup fails and the key contains an @
6612 character, a second lookup is done with everything before the last @ replaced
6613 by *. This makes it possible to provide per-domain defaults in alias files
6614 that include the domains in the keys. If the second lookup fails (or doesn't
6615 take place because there is no @ in the key), &"*"& is looked up.
6616 For example, a &(redirect)& router might contain:
6618 data = ${lookup{$local_part@$domain}lsearch*@{/etc/mix-aliases}}
6620 Suppose the address that is being processed is &'jane@eyre.example'&. Exim
6621 looks up these keys, in this order:
6627 The data is taken from whichever key it finds first. &*Note*&: In an
6628 &(lsearch)& file, this does not mean the first of these keys in the file. A
6629 complete scan is done for each key, and only if it is not found at all does
6630 Exim move on to try the next key.
6634 .section "Partial matching in single-key lookups" "SECTpartiallookup"
6635 .cindex "partial matching"
6636 .cindex "wildcard lookups"
6637 .cindex "lookup" "partial matching"
6638 .cindex "lookup" "wildcard"
6639 .cindex "asterisk" "in search type"
6640 The normal operation of a single-key lookup is to search the file for an exact
6641 match with the given key. However, in a number of situations where domains are
6642 being looked up, it is useful to be able to do partial matching. In this case,
6643 information in the file that has a key starting with &"*."& is matched by any
6644 domain that ends with the components that follow the full stop. For example, if
6645 a key in a DBM file is
6647 *.dates.fict.example
6649 then when partial matching is enabled this is matched by (amongst others)
6650 &'2001.dates.fict.example'& and &'1984.dates.fict.example'&. It is also matched
6651 by &'dates.fict.example'&, if that does not appear as a separate key in the
6654 &*Note*&: Partial matching is not available for query-style lookups. It is
6655 also not available for any lookup items in address lists (see section
6656 &<<SECTaddresslist>>&).
6658 Partial matching is implemented by doing a series of separate lookups using
6659 keys constructed by modifying the original subject key. This means that it can
6660 be used with any of the single-key lookup types, provided that
6661 partial matching keys
6662 beginning with a special prefix (default &"*."&) are included in the data file.
6663 Keys in the file that do not begin with the prefix are matched only by
6664 unmodified subject keys when partial matching is in use.
6666 Partial matching is requested by adding the string &"partial-"& to the front of
6667 the name of a single-key lookup type, for example, &%partial-dbm%&. When this
6668 is done, the subject key is first looked up unmodified; if that fails, &"*."&
6669 is added at the start of the subject key, and it is looked up again. If that
6670 fails, further lookups are tried with dot-separated components removed from the
6671 start of the subject key, one-by-one, and &"*."& added on the front of what
6674 A minimum number of two non-* components are required. This can be adjusted
6675 by including a number before the hyphen in the search type. For example,
6676 &%partial3-lsearch%& specifies a minimum of three non-* components in the
6677 modified keys. Omitting the number is equivalent to &"partial2-"&. If the
6678 subject key is &'2250.dates.fict.example'& then the following keys are looked
6679 up when the minimum number of non-* components is two:
6681 2250.dates.fict.example
6682 *.2250.dates.fict.example
6683 *.dates.fict.example
6686 As soon as one key in the sequence is successfully looked up, the lookup
6689 .cindex "lookup" "partial matching &-- changing prefix"
6690 .cindex "prefix" "for partial matching"
6691 The use of &"*."& as the partial matching prefix is a default that can be
6692 changed. The motivation for this feature is to allow Exim to operate with file
6693 formats that are used by other MTAs. A different prefix can be supplied in
6694 parentheses instead of the hyphen after &"partial"&. For example:
6696 domains = partial(.)lsearch;/some/file
6698 In this example, if the domain is &'a.b.c'&, the sequence of lookups is
6699 &`a.b.c`&, &`.a.b.c`&, and &`.b.c`& (the default minimum of 2 non-wild
6700 components is unchanged). The prefix may consist of any punctuation characters
6701 other than a closing parenthesis. It may be empty, for example:
6703 domains = partial1()cdb;/some/file
6705 For this example, if the domain is &'a.b.c'&, the sequence of lookups is
6706 &`a.b.c`&, &`b.c`&, and &`c`&.
6708 If &"partial0"& is specified, what happens at the end (when the lookup with
6709 just one non-wild component has failed, and the original key is shortened right
6710 down to the null string) depends on the prefix:
6713 If the prefix has zero length, the whole lookup fails.
6715 If the prefix has length 1, a lookup for just the prefix is done. For
6716 example, the final lookup for &"partial0(.)"& is for &`.`& alone.
6718 Otherwise, if the prefix ends in a dot, the dot is removed, and the
6719 remainder is looked up. With the default prefix, therefore, the final lookup is
6720 for &"*"& on its own.
6722 Otherwise, the whole prefix is looked up.
6726 If the search type ends in &"*"& or &"*@"& (see section
6727 &<<SECTdefaultvaluelookups>>& above), the search for an ultimate default that
6728 this implies happens after all partial lookups have failed. If &"partial0"& is
6729 specified, adding &"*"& to the search type has no effect with the default
6730 prefix, because the &"*"& key is already included in the sequence of partial
6731 lookups. However, there might be a use for lookup types such as
6732 &"partial0(.)lsearch*"&.
6734 The use of &"*"& in lookup partial matching differs from its use as a wildcard
6735 in domain lists and the like. Partial matching works only in terms of
6736 dot-separated components; a key such as &`*fict.example`&
6737 in a database file is useless, because the asterisk in a partial matching
6738 subject key is always followed by a dot.
6743 .section "Lookup caching" "SECID64"
6744 .cindex "lookup" "caching"
6745 .cindex "caching" "lookup data"
6746 Exim caches all lookup results in order to avoid needless repetition of
6747 lookups. However, because (apart from the daemon) Exim operates as a collection
6748 of independent, short-lived processes, this caching applies only within a
6749 single Exim process. There is no inter-process lookup caching facility.
6751 For single-key lookups, Exim keeps the relevant files open in case there is
6752 another lookup that needs them. In some types of configuration this can lead to
6753 many files being kept open for messages with many recipients. To avoid hitting
6754 the operating system limit on the number of simultaneously open files, Exim
6755 closes the least recently used file when it needs to open more files than its
6756 own internal limit, which can be changed via the &%lookup_open_max%& option.
6758 The single-key lookup files are closed and the lookup caches are flushed at
6759 strategic points during delivery &-- for example, after all routing is
6765 .section "Quoting lookup data" "SECID65"
6766 .cindex "lookup" "quoting"
6767 .cindex "quoting" "in lookups"
6768 When data from an incoming message is included in a query-style lookup, there
6769 is the possibility of special characters in the data messing up the syntax of
6770 the query. For example, a NIS+ query that contains
6774 will be broken if the local part happens to contain a closing square bracket.
6775 For NIS+, data can be enclosed in double quotes like this:
6777 [name="$local_part"]
6779 but this still leaves the problem of a double quote in the data. The rule for
6780 NIS+ is that double quotes must be doubled. Other lookup types have different
6781 rules, and to cope with the differing requirements, an expansion operator
6782 of the following form is provided:
6784 ${quote_<lookup-type>:<string>}
6786 For example, the safest way to write the NIS+ query is
6788 [name="${quote_nisplus:$local_part}"]
6790 See chapter &<<CHAPexpand>>& for full coverage of string expansions. The quote
6791 operator can be used for all lookup types, but has no effect for single-key
6792 lookups, since no quoting is ever needed in their key strings.
6797 .section "More about dnsdb" "SECTdnsdb"
6798 .cindex "dnsdb lookup"
6799 .cindex "lookup" "dnsdb"
6800 .cindex "DNS" "as a lookup type"
6801 The &(dnsdb)& lookup type uses the DNS as its database. A simple query consists
6802 of a record type and a domain name, separated by an equals sign. For example,
6803 an expansion string could contain:
6805 ${lookup dnsdb{mx=a.b.example}{$value}fail}
6807 If the lookup succeeds, the result is placed in &$value$&, which in this case
6808 is used on its own as the result. If the lookup does not succeed, the
6809 &`fail`& keyword causes a &'forced expansion failure'& &-- see section
6810 &<<SECTforexpfai>>& for an explanation of what this means.
6812 The supported DNS record types are A, CNAME, MX, NS, PTR, SPF, SRV, and TXT,
6813 and, when Exim is compiled with IPv6 support, AAAA (and A6 if that is also
6814 configured). If no type is given, TXT is assumed. When the type is PTR,
6815 the data can be an IP address, written as normal; inversion and the addition of
6816 &%in-addr.arpa%& or &%ip6.arpa%& happens automatically. For example:
6818 ${lookup dnsdb{ptr=192.168.4.5}{$value}fail}
6820 If the data for a PTR record is not a syntactically valid IP address, it is not
6821 altered and nothing is added.
6823 .cindex "MX record" "in &(dnsdb)& lookup"
6824 .cindex "SRV record" "in &(dnsdb)& lookup"
6825 For an MX lookup, both the preference value and the host name are returned for
6826 each record, separated by a space. For an SRV lookup, the priority, weight,
6827 port, and host name are returned for each record, separated by spaces.
6829 For any record type, if multiple records are found (or, for A6 lookups, if a
6830 single record leads to multiple addresses), the data is returned as a
6831 concatenation, with newline as the default separator. The order, of course,
6832 depends on the DNS resolver. You can specify a different separator character
6833 between multiple records by putting a right angle-bracket followed immediately
6834 by the new separator at the start of the query. For example:
6836 ${lookup dnsdb{>: a=host1.example}}
6838 It is permitted to specify a space as the separator character. Further
6839 white space is ignored.
6841 .cindex "TXT record" "in &(dnsdb)& lookup"
6842 .cindex "SPF record" "in &(dnsdb)& lookup"
6843 For TXT records with multiple items of data, only the first item is returned,
6844 unless a separator for them is specified using a comma after the separator
6845 character followed immediately by the TXT record item separator. To concatenate
6846 items without a separator, use a semicolon instead. For SPF records the
6847 default behaviour is to concatenate multiple items without using a separator.
6849 ${lookup dnsdb{>\n,: txt=a.b.example}}
6850 ${lookup dnsdb{>\n; txt=a.b.example}}
6851 ${lookup dnsdb{spf=example.org}}
6853 It is permitted to specify a space as the separator character. Further
6854 white space is ignored.
6856 .section "Pseudo dnsdb record types" "SECID66"
6857 .cindex "MX record" "in &(dnsdb)& lookup"
6858 By default, both the preference value and the host name are returned for
6859 each MX record, separated by a space. If you want only host names, you can use
6860 the pseudo-type MXH:
6862 ${lookup dnsdb{mxh=a.b.example}}
6864 In this case, the preference values are omitted, and just the host names are
6867 .cindex "name server for enclosing domain"
6868 Another pseudo-type is ZNS (for &"zone NS"&). It performs a lookup for NS
6869 records on the given domain, but if none are found, it removes the first
6870 component of the domain name, and tries again. This process continues until NS
6871 records are found or there are no more components left (or there is a DNS
6872 error). In other words, it may return the name servers for a top-level domain,
6873 but it never returns the root name servers. If there are no NS records for the
6874 top-level domain, the lookup fails. Consider these examples:
6876 ${lookup dnsdb{zns=xxx.quercite.com}}
6877 ${lookup dnsdb{zns=xxx.edu}}
6879 Assuming that in each case there are no NS records for the full domain name,
6880 the first returns the name servers for &%quercite.com%&, and the second returns
6881 the name servers for &%edu%&.
6883 You should be careful about how you use this lookup because, unless the
6884 top-level domain does not exist, the lookup always returns some host names. The
6885 sort of use to which this might be put is for seeing if the name servers for a
6886 given domain are on a blacklist. You can probably assume that the name servers
6887 for the high-level domains such as &%com%& or &%co.uk%& are not going to be on
6890 .cindex "CSA" "in &(dnsdb)& lookup"
6891 A third pseudo-type is CSA (Client SMTP Authorization). This looks up SRV
6892 records according to the CSA rules, which are described in section
6893 &<<SECTverifyCSA>>&. Although &(dnsdb)& supports SRV lookups directly, this is
6894 not sufficient because of the extra parent domain search behaviour of CSA. The
6895 result of a successful lookup such as:
6897 ${lookup dnsdb {csa=$sender_helo_name}}
6899 has two space-separated fields: an authorization code and a target host name.
6900 The authorization code can be &"Y"& for yes, &"N"& for no, &"X"& for explicit
6901 authorization required but absent, or &"?"& for unknown.
6904 .section "Multiple dnsdb lookups" "SECID67"
6905 In the previous sections, &(dnsdb)& lookups for a single domain are described.
6906 However, you can specify a list of domains or IP addresses in a single
6907 &(dnsdb)& lookup. The list is specified in the normal Exim way, with colon as
6908 the default separator, but with the ability to change this. For example:
6910 ${lookup dnsdb{one.domain.com:two.domain.com}}
6911 ${lookup dnsdb{a=one.host.com:two.host.com}}
6912 ${lookup dnsdb{ptr = <; 1.2.3.4 ; 4.5.6.8}}
6914 In order to retain backwards compatibility, there is one special case: if
6915 the lookup type is PTR and no change of separator is specified, Exim looks
6916 to see if the rest of the string is precisely one IPv6 address. In this
6917 case, it does not treat it as a list.
6919 The data from each lookup is concatenated, with newline separators by default,
6920 in the same way that multiple DNS records for a single item are handled. A
6921 different separator can be specified, as described above.
6923 The &(dnsdb)& lookup fails only if all the DNS lookups fail. If there is a
6924 temporary DNS error for any of them, the behaviour is controlled by
6925 an optional keyword followed by a comma that may appear before the record
6926 type. The possible keywords are &"defer_strict"&, &"defer_never"&, and
6927 &"defer_lax"&. With &"strict"& behaviour, any temporary DNS error causes the
6928 whole lookup to defer. With &"never"& behaviour, a temporary DNS error is
6929 ignored, and the behaviour is as if the DNS lookup failed to find anything.
6930 With &"lax"& behaviour, all the queries are attempted, but a temporary DNS
6931 error causes the whole lookup to defer only if none of the other lookups
6932 succeed. The default is &"lax"&, so the following lookups are equivalent:
6934 ${lookup dnsdb{defer_lax,a=one.host.com:two.host.com}}
6935 ${lookup dnsdb{a=one.host.com:two.host.com}}
6937 Thus, in the default case, as long as at least one of the DNS lookups
6938 yields some data, the lookup succeeds.
6943 .section "More about LDAP" "SECTldap"
6944 .cindex "LDAP" "lookup, more about"
6945 .cindex "lookup" "LDAP"
6946 .cindex "Solaris" "LDAP"
6947 The original LDAP implementation came from the University of Michigan; this has
6948 become &"Open LDAP"&, and there are now two different releases. Another
6949 implementation comes from Netscape, and Solaris 7 and subsequent releases
6950 contain inbuilt LDAP support. Unfortunately, though these are all compatible at
6951 the lookup function level, their error handling is different. For this reason
6952 it is necessary to set a compile-time variable when building Exim with LDAP, to
6953 indicate which LDAP library is in use. One of the following should appear in
6954 your &_Local/Makefile_&:
6956 LDAP_LIB_TYPE=UMICHIGAN
6957 LDAP_LIB_TYPE=OPENLDAP1
6958 LDAP_LIB_TYPE=OPENLDAP2
6959 LDAP_LIB_TYPE=NETSCAPE
6960 LDAP_LIB_TYPE=SOLARIS
6962 If LDAP_LIB_TYPE is not set, Exim assumes &`OPENLDAP1`&, which has the
6963 same interface as the University of Michigan version.
6965 There are three LDAP lookup types in Exim. These behave slightly differently in
6966 the way they handle the results of a query:
6969 &(ldap)& requires the result to contain just one entry; if there are more, it
6972 &(ldapdn)& also requires the result to contain just one entry, but it is the
6973 Distinguished Name that is returned rather than any attribute values.
6975 &(ldapm)& permits the result to contain more than one entry; the attributes
6976 from all of them are returned.
6980 For &(ldap)& and &(ldapm)&, if a query finds only entries with no attributes,
6981 Exim behaves as if the entry did not exist, and the lookup fails. The format of
6982 the data returned by a successful lookup is described in the next section.
6983 First we explain how LDAP queries are coded.
6986 .section "Format of LDAP queries" "SECTforldaque"
6987 .cindex "LDAP" "query format"
6988 An LDAP query takes the form of a URL as defined in RFC 2255. For example, in
6989 the configuration of a &(redirect)& router one might have this setting:
6991 data = ${lookup ldap \
6992 {ldap:///cn=$local_part,o=University%20of%20Cambridge,\
6993 c=UK?mailbox?base?}}
6995 .cindex "LDAP" "with TLS"
6996 The URL may begin with &`ldap`& or &`ldaps`& if your LDAP library supports
6997 secure (encrypted) LDAP connections. The second of these ensures that an
6998 encrypted TLS connection is used.
7000 With sufficiently modern LDAP libraries, Exim supports forcing TLS over regular
7001 LDAP connections, rather than the SSL-on-connect &`ldaps`&.
7002 See the &%ldap_start_tls%& option.
7005 .section "LDAP quoting" "SECID68"
7006 .cindex "LDAP" "quoting"
7007 Two levels of quoting are required in LDAP queries, the first for LDAP itself
7008 and the second because the LDAP query is represented as a URL. Furthermore,
7009 within an LDAP query, two different kinds of quoting are required. For this
7010 reason, there are two different LDAP-specific quoting operators.
7012 The &%quote_ldap%& operator is designed for use on strings that are part of
7013 filter specifications. Conceptually, it first does the following conversions on
7021 in accordance with RFC 2254. The resulting string is then quoted according
7022 to the rules for URLs, that is, all non-alphanumeric characters except
7026 are converted to their hex values, preceded by a percent sign. For example:
7028 ${quote_ldap: a(bc)*, a<yz>; }
7032 %20a%5C28bc%5C29%5C2A%2C%20a%3Cyz%3E%3B%20
7034 Removing the URL quoting, this is (with a leading and a trailing space):
7036 a\28bc\29\2A, a<yz>;
7038 The &%quote_ldap_dn%& operator is designed for use on strings that are part of
7039 base DN specifications in queries. Conceptually, it first converts the string
7040 by inserting a backslash in front of any of the following characters:
7044 It also inserts a backslash before any leading spaces or # characters, and
7045 before any trailing spaces. (These rules are in RFC 2253.) The resulting string
7046 is then quoted according to the rules for URLs. For example:
7048 ${quote_ldap_dn: a(bc)*, a<yz>; }
7052 %5C%20a(bc)*%5C%2C%20a%5C%3Cyz%5C%3E%5C%3B%5C%20
7054 Removing the URL quoting, this is (with a trailing space):
7056 \ a(bc)*\, a\<yz\>\;\
7058 There are some further comments about quoting in the section on LDAP
7059 authentication below.
7062 .section "LDAP connections" "SECID69"
7063 .cindex "LDAP" "connections"
7064 The connection to an LDAP server may either be over TCP/IP, or, when OpenLDAP
7065 is in use, via a Unix domain socket. The example given above does not specify
7066 an LDAP server. A server that is reached by TCP/IP can be specified in a query
7069 ldap://<hostname>:<port>/...
7071 If the port (and preceding colon) are omitted, the standard LDAP port (389) is
7072 used. When no server is specified in a query, a list of default servers is
7073 taken from the &%ldap_default_servers%& configuration option. This supplies a
7074 colon-separated list of servers which are tried in turn until one successfully
7075 handles a query, or there is a serious error. Successful handling either
7076 returns the requested data, or indicates that it does not exist. Serious errors
7077 are syntactical, or multiple values when only a single value is expected.
7078 Errors which cause the next server to be tried are connection failures, bind
7079 failures, and timeouts.
7081 For each server name in the list, a port number can be given. The standard way
7082 of specifying a host and port is to use a colon separator (RFC 1738). Because
7083 &%ldap_default_servers%& is a colon-separated list, such colons have to be
7084 doubled. For example
7086 ldap_default_servers = ldap1.example.com::145:ldap2.example.com
7088 If &%ldap_default_servers%& is unset, a URL with no server name is passed
7089 to the LDAP library with no server name, and the library's default (normally
7090 the local host) is used.
7092 If you are using the OpenLDAP library, you can connect to an LDAP server using
7093 a Unix domain socket instead of a TCP/IP connection. This is specified by using
7094 &`ldapi`& instead of &`ldap`& in LDAP queries. What follows here applies only
7095 to OpenLDAP. If Exim is compiled with a different LDAP library, this feature is
7098 For this type of connection, instead of a host name for the server, a pathname
7099 for the socket is required, and the port number is not relevant. The pathname
7100 can be specified either as an item in &%ldap_default_servers%&, or inline in
7101 the query. In the former case, you can have settings such as
7103 ldap_default_servers = /tmp/ldap.sock : backup.ldap.your.domain
7105 When the pathname is given in the query, you have to escape the slashes as
7106 &`%2F`& to fit in with the LDAP URL syntax. For example:
7108 ${lookup ldap {ldapi://%2Ftmp%2Fldap.sock/o=...
7110 When Exim processes an LDAP lookup and finds that the &"hostname"& is really
7111 a pathname, it uses the Unix domain socket code, even if the query actually
7112 specifies &`ldap`& or &`ldaps`&. In particular, no encryption is used for a
7113 socket connection. This behaviour means that you can use a setting of
7114 &%ldap_default_servers%& such as in the example above with traditional &`ldap`&
7115 or &`ldaps`& queries, and it will work. First, Exim tries a connection via
7116 the Unix domain socket; if that fails, it tries a TCP/IP connection to the
7119 If an explicit &`ldapi`& type is given in a query when a host name is
7120 specified, an error is diagnosed. However, if there are more items in
7121 &%ldap_default_servers%&, they are tried. In other words:
7124 Using a pathname with &`ldap`& or &`ldaps`& forces the use of the Unix domain
7127 Using &`ldapi`& with a host name causes an error.
7131 Using &`ldapi`& with no host or path in the query, and no setting of
7132 &%ldap_default_servers%&, does whatever the library does by default.
7136 .section "LDAP authentication and control information" "SECID70"
7137 .cindex "LDAP" "authentication"
7138 The LDAP URL syntax provides no way of passing authentication and other control
7139 information to the server. To make this possible, the URL in an LDAP query may
7140 be preceded by any number of <&'name'&>=<&'value'&> settings, separated by
7141 spaces. If a value contains spaces it must be enclosed in double quotes, and
7142 when double quotes are used, backslash is interpreted in the usual way inside
7143 them. The following names are recognized:
7145 &`DEREFERENCE`& set the dereferencing parameter
7146 &`NETTIME `& set a timeout for a network operation
7147 &`USER `& set the DN, for authenticating the LDAP bind
7148 &`PASS `& set the password, likewise
7149 &`REFERRALS `& set the referrals parameter
7150 &`SIZE `& set the limit for the number of entries returned
7151 &`TIME `& set the maximum waiting time for a query
7153 The value of the DEREFERENCE parameter must be one of the words &"never"&,
7154 &"searching"&, &"finding"&, or &"always"&. The value of the REFERRALS parameter
7155 must be &"follow"& (the default) or &"nofollow"&. The latter stops the LDAP
7156 library from trying to follow referrals issued by the LDAP server.
7158 The name CONNECT is an obsolete name for NETTIME, retained for
7159 backwards compatibility. This timeout (specified as a number of seconds) is
7160 enforced from the client end for operations that can be carried out over a
7161 network. Specifically, it applies to network connections and calls to the
7162 &'ldap_result()'& function. If the value is greater than zero, it is used if
7163 LDAP_OPT_NETWORK_TIMEOUT is defined in the LDAP headers (OpenLDAP), or
7164 if LDAP_X_OPT_CONNECT_TIMEOUT is defined in the LDAP headers (Netscape
7165 SDK 4.1). A value of zero forces an explicit setting of &"no timeout"& for
7166 Netscape SDK; for OpenLDAP no action is taken.
7168 The TIME parameter (also a number of seconds) is passed to the server to
7169 set a server-side limit on the time taken to complete a search.
7172 Here is an example of an LDAP query in an Exim lookup that uses some of these
7173 values. This is a single line, folded to fit on the page:
7176 {user="cn=manager,o=University of Cambridge,c=UK" pass=secret
7177 ldap:///o=University%20of%20Cambridge,c=UK?sn?sub?(cn=foo)}
7180 The encoding of spaces as &`%20`& is a URL thing which should not be done for
7181 any of the auxiliary data. Exim configuration settings that include lookups
7182 which contain password information should be preceded by &"hide"& to prevent
7183 non-admin users from using the &%-bP%& option to see their values.
7185 The auxiliary data items may be given in any order. The default is no
7186 connection timeout (the system timeout is used), no user or password, no limit
7187 on the number of entries returned, and no time limit on queries.
7189 When a DN is quoted in the USER= setting for LDAP authentication, Exim
7190 removes any URL quoting that it may contain before passing it LDAP. Apparently
7191 some libraries do this for themselves, but some do not. Removing the URL
7192 quoting has two advantages:
7195 It makes it possible to use the same &%quote_ldap_dn%& expansion for USER=
7196 DNs as with DNs inside actual queries.
7198 It permits spaces inside USER= DNs.
7201 For example, a setting such as
7203 USER=cn=${quote_ldap_dn:$1}
7205 should work even if &$1$& contains spaces.
7207 Expanded data for the PASS= value should be quoted using the &%quote%&
7208 expansion operator, rather than the LDAP quote operators. The only reason this
7209 field needs quoting is to ensure that it conforms to the Exim syntax, which
7210 does not allow unquoted spaces. For example:
7214 The LDAP authentication mechanism can be used to check passwords as part of
7215 SMTP authentication. See the &%ldapauth%& expansion string condition in chapter
7220 .section "Format of data returned by LDAP" "SECID71"
7221 .cindex "LDAP" "returned data formats"
7222 The &(ldapdn)& lookup type returns the Distinguished Name from a single entry
7223 as a sequence of values, for example
7225 cn=manager, o=University of Cambridge, c=UK
7227 The &(ldap)& lookup type generates an error if more than one entry matches the
7228 search filter, whereas &(ldapm)& permits this case, and inserts a newline in
7229 the result between the data from different entries. It is possible for multiple
7230 values to be returned for both &(ldap)& and &(ldapm)&, but in the former case
7231 you know that whatever values are returned all came from a single entry in the
7234 In the common case where you specify a single attribute in your LDAP query, the
7235 result is not quoted, and does not contain the attribute name. If the attribute
7236 has multiple values, they are separated by commas.
7238 If you specify multiple attributes, the result contains space-separated, quoted
7239 strings, each preceded by the attribute name and an equals sign. Within the
7240 quotes, the quote character, backslash, and newline are escaped with
7241 backslashes, and commas are used to separate multiple values for the attribute.
7242 Apart from the escaping, the string within quotes takes the same form as the
7243 output when a single attribute is requested. Specifying no attributes is the
7244 same as specifying all of an entry's attributes.
7246 Here are some examples of the output format. The first line of each pair is an
7247 LDAP query, and the second is the data that is returned. The attribute called
7248 &%attr1%& has two values, whereas &%attr2%& has only one value:
7250 ldap:///o=base?attr1?sub?(uid=fred)
7253 ldap:///o=base?attr2?sub?(uid=fred)
7256 ldap:///o=base?attr1,attr2?sub?(uid=fred)
7257 attr1="value1.1, value1.2" attr2="value two"
7259 ldap:///o=base??sub?(uid=fred)
7260 objectClass="top" attr1="value1.1, value1.2" attr2="value two"
7262 The &%extract%& operator in string expansions can be used to pick out
7263 individual fields from data that consists of &'key'&=&'value'& pairs. You can
7264 make use of Exim's &%-be%& option to run expansion tests and thereby check the
7265 results of LDAP lookups.
7270 .section "More about NIS+" "SECTnisplus"
7271 .cindex "NIS+ lookup type"
7272 .cindex "lookup" "NIS+"
7273 NIS+ queries consist of a NIS+ &'indexed name'& followed by an optional colon
7274 and field name. If this is given, the result of a successful query is the
7275 contents of the named field; otherwise the result consists of a concatenation
7276 of &'field-name=field-value'& pairs, separated by spaces. Empty values and
7277 values containing spaces are quoted. For example, the query
7279 [name=mg1456],passwd.org_dir
7281 might return the string
7283 name=mg1456 passwd="" uid=999 gid=999 gcos="Martin Guerre"
7284 home=/home/mg1456 shell=/bin/bash shadow=""
7286 (split over two lines here to fit on the page), whereas
7288 [name=mg1456],passwd.org_dir:gcos
7294 with no quotes. A NIS+ lookup fails if NIS+ returns more than one table entry
7295 for the given indexed key. The effect of the &%quote_nisplus%& expansion
7296 operator is to double any quote characters within the text.
7300 .section "SQL lookups" "SECTsql"
7301 .cindex "SQL lookup types"
7302 .cindex "MySQL" "lookup type"
7303 .cindex "PostgreSQL lookup type"
7304 .cindex "lookup" "MySQL"
7305 .cindex "lookup" "PostgreSQL"
7306 .cindex "Oracle" "lookup type"
7307 .cindex "lookup" "Oracle"
7308 .cindex "InterBase lookup type"
7309 .cindex "lookup" "InterBase"
7310 Exim can support lookups in InterBase, MySQL, Oracle, PostgreSQL, and SQLite
7311 databases. Queries for these databases contain SQL statements, so an example
7314 ${lookup mysql{select mailbox from users where id='userx'}\
7317 If the result of the query contains more than one field, the data for each
7318 field in the row is returned, preceded by its name, so the result of
7320 ${lookup pgsql{select home,name from users where id='userx'}\
7325 home=/home/userx name="Mister X"
7327 Empty values and values containing spaces are double quoted, with embedded
7328 quotes escaped by a backslash. If the result of the query contains just one
7329 field, the value is passed back verbatim, without a field name, for example:
7333 If the result of the query yields more than one row, it is all concatenated,
7334 with a newline between the data for each row.
7337 .section "More about MySQL, PostgreSQL, Oracle, and InterBase" "SECID72"
7338 .cindex "MySQL" "lookup type"
7339 .cindex "PostgreSQL lookup type"
7340 .cindex "lookup" "MySQL"
7341 .cindex "lookup" "PostgreSQL"
7342 .cindex "Oracle" "lookup type"
7343 .cindex "lookup" "Oracle"
7344 .cindex "InterBase lookup type"
7345 .cindex "lookup" "InterBase"
7346 If any MySQL, PostgreSQL, Oracle, or InterBase lookups are used, the
7347 &%mysql_servers%&, &%pgsql_servers%&, &%oracle_servers%&, or &%ibase_servers%&
7348 option (as appropriate) must be set to a colon-separated list of server
7350 (For MySQL and PostgreSQL only, the global option need not be set if all
7351 queries contain their own server information &-- see section
7352 &<<SECTspeserque>>&.) Each item in the list is a slash-separated list of four
7353 items: host name, database name, user name, and password. In the case of
7354 Oracle, the host name field is used for the &"service name"&, and the database
7355 name field is not used and should be empty. For example:
7357 hide oracle_servers = oracle.plc.example//userx/abcdwxyz
7359 Because password data is sensitive, you should always precede the setting with
7360 &"hide"&, to prevent non-admin users from obtaining the setting via the &%-bP%&
7361 option. Here is an example where two MySQL servers are listed:
7363 hide mysql_servers = localhost/users/root/secret:\
7364 otherhost/users/root/othersecret
7366 For MySQL and PostgreSQL, a host may be specified as <&'name'&>:<&'port'&> but
7367 because this is a colon-separated list, the colon has to be doubled. For each
7368 query, these parameter groups are tried in order until a connection is made and
7369 a query is successfully processed. The result of a query may be that no data is
7370 found, but that is still a successful query. In other words, the list of
7371 servers provides a backup facility, not a list of different places to look.
7373 The &%quote_mysql%&, &%quote_pgsql%&, and &%quote_oracle%& expansion operators
7374 convert newline, tab, carriage return, and backspace to \n, \t, \r, and \b
7375 respectively, and the characters single-quote, double-quote, and backslash
7376 itself are escaped with backslashes. The &%quote_pgsql%& expansion operator, in
7377 addition, escapes the percent and underscore characters. This cannot be done
7378 for MySQL because these escapes are not recognized in contexts where these
7379 characters are not special.
7381 .section "Specifying the server in the query" "SECTspeserque"
7382 For MySQL and PostgreSQL lookups (but not currently for Oracle and InterBase),
7383 it is possible to specify a list of servers with an individual query. This is
7384 done by starting the query with
7386 &`servers=`&&'server1:server2:server3:...'&&`;`&
7388 Each item in the list may take one of two forms:
7390 If it contains no slashes it is assumed to be just a host name. The appropriate
7391 global option (&%mysql_servers%& or &%pgsql_servers%&) is searched for a host
7392 of the same name, and the remaining parameters (database, user, password) are
7395 If it contains any slashes, it is taken as a complete parameter set.
7397 The list of servers is used in exactly the same way as the global list.
7398 Once a connection to a server has happened and a query has been
7399 successfully executed, processing of the lookup ceases.
7401 This feature is intended for use in master/slave situations where updates
7402 are occurring and you want to update the master rather than a slave. If the
7403 master is in the list as a backup for reading, you might have a global setting
7406 mysql_servers = slave1/db/name/pw:\
7410 In an updating lookup, you could then write:
7412 ${lookup mysql{servers=master; UPDATE ...} }
7414 That query would then be sent only to the master server. If, on the other hand,
7415 the master is not to be used for reading, and so is not present in the global
7416 option, you can still update it by a query of this form:
7418 ${lookup pgsql{servers=master/db/name/pw; UPDATE ...} }
7422 .section "Special MySQL features" "SECID73"
7423 For MySQL, an empty host name or the use of &"localhost"& in &%mysql_servers%&
7424 causes a connection to the server on the local host by means of a Unix domain
7425 socket. An alternate socket can be specified in parentheses. The full syntax of
7426 each item in &%mysql_servers%& is:
7428 <&'hostname'&>::<&'port'&>(<&'socket name'&>)/<&'database'&>/&&&
7429 <&'user'&>/<&'password'&>
7431 Any of the three sub-parts of the first field can be omitted. For normal use on
7432 the local host it can be left blank or set to just &"localhost"&.
7434 No database need be supplied &-- but if it is absent here, it must be given in
7437 If a MySQL query is issued that does not request any data (an insert, update,
7438 or delete command), the result of the lookup is the number of rows affected.
7440 &*Warning*&: This can be misleading. If an update does not actually change
7441 anything (for example, setting a field to the value it already has), the result
7442 is zero because no rows are affected.
7445 .section "Special PostgreSQL features" "SECID74"
7446 PostgreSQL lookups can also use Unix domain socket connections to the database.
7447 This is usually faster and costs less CPU time than a TCP/IP connection.
7448 However it can be used only if the mail server runs on the same machine as the
7449 database server. A configuration line for PostgreSQL via Unix domain sockets
7452 hide pgsql_servers = (/tmp/.s.PGSQL.5432)/db/user/password : ...
7454 In other words, instead of supplying a host name, a path to the socket is
7455 given. The path name is enclosed in parentheses so that its slashes aren't
7456 visually confused with the delimiters for the other server parameters.
7458 If a PostgreSQL query is issued that does not request any data (an insert,
7459 update, or delete command), the result of the lookup is the number of rows
7462 .section "More about SQLite" "SECTsqlite"
7463 .cindex "lookup" "SQLite"
7464 .cindex "sqlite lookup type"
7465 SQLite is different to the other SQL lookups because a file name is required in
7466 addition to the SQL query. An SQLite database is a single file, and there is no
7467 daemon as in the other SQL databases. The interface to Exim requires the name
7468 of the file, as an absolute path, to be given at the start of the query. It is
7469 separated from the query by white space. This means that the path name cannot
7470 contain white space. Here is a lookup expansion example:
7472 ${lookup sqlite {/some/thing/sqlitedb \
7473 select name from aliases where id='userx';}}
7475 In a list, the syntax is similar. For example:
7477 domainlist relay_domains = sqlite;/some/thing/sqlitedb \
7478 select * from relays where ip='$sender_host_address';
7480 The only character affected by the &%quote_sqlite%& operator is a single
7481 quote, which it doubles.
7483 The SQLite library handles multiple simultaneous accesses to the database
7484 internally. Multiple readers are permitted, but only one process can
7485 update at once. Attempts to access the database while it is being updated
7486 are rejected after a timeout period, during which the SQLite library
7487 waits for the lock to be released. In Exim, the default timeout is set
7488 to 5 seconds, but it can be changed by means of the &%sqlite_lock_timeout%&
7494 . ////////////////////////////////////////////////////////////////////////////
7495 . ////////////////////////////////////////////////////////////////////////////
7497 .chapter "Domain, host, address, and local part lists" &&&
7498 "CHAPdomhosaddlists" &&&
7499 "Domain, host, and address lists"
7500 .scindex IIDdohoadli "lists of domains; hosts; etc."
7501 A number of Exim configuration options contain lists of domains, hosts,
7502 email addresses, or local parts. For example, the &%hold_domains%& option
7503 contains a list of domains whose delivery is currently suspended. These lists
7504 are also used as data in ACL statements (see chapter &<<CHAPACL>>&), and as
7505 arguments to expansion conditions such as &%match_domain%&.
7507 Each item in one of these lists is a pattern to be matched against a domain,
7508 host, email address, or local part, respectively. In the sections below, the
7509 different types of pattern for each case are described, but first we cover some
7510 general facilities that apply to all four kinds of list.
7514 .section "Expansion of lists" "SECID75"
7515 .cindex "expansion" "of lists"
7516 Each list is expanded as a single string before it is used. The result of
7517 expansion must be a list, possibly containing empty items, which is split up
7518 into separate items for matching. By default, colon is the separator character,
7519 but this can be varied if necessary. See sections &<<SECTlistconstruct>>& and
7520 &<<SECTempitelis>>& for details of the list syntax; the second of these
7521 discusses the way to specify empty list items.
7524 If the string expansion is forced to fail, Exim behaves as if the item it is
7525 testing (domain, host, address, or local part) is not in the list. Other
7526 expansion failures cause temporary errors.
7528 If an item in a list is a regular expression, backslashes, dollars and possibly
7529 other special characters in the expression must be protected against
7530 misinterpretation by the string expander. The easiest way to do this is to use
7531 the &`\N`& expansion feature to indicate that the contents of the regular
7532 expression should not be expanded. For example, in an ACL you might have:
7534 deny senders = \N^\d{8}\w@.*\.baddomain\.example$\N : \
7535 ${lookup{$domain}lsearch{/badsenders/bydomain}}
7537 The first item is a regular expression that is protected from expansion by
7538 &`\N`&, whereas the second uses the expansion to obtain a list of unwanted
7539 senders based on the receiving domain.
7544 .section "Negated items in lists" "SECID76"
7545 .cindex "list" "negation"
7546 .cindex "negation" "in lists"
7547 Items in a list may be positive or negative. Negative items are indicated by a
7548 leading exclamation mark, which may be followed by optional white space. A list
7549 defines a set of items (domains, etc). When Exim processes one of these lists,
7550 it is trying to find out whether a domain, host, address, or local part
7551 (respectively) is in the set that is defined by the list. It works like this:
7553 The list is scanned from left to right. If a positive item is matched, the
7554 subject that is being checked is in the set; if a negative item is matched, the
7555 subject is not in the set. If the end of the list is reached without the
7556 subject having matched any of the patterns, it is in the set if the last item
7557 was a negative one, but not if it was a positive one. For example, the list in
7559 domainlist relay_domains = !a.b.c : *.b.c
7561 matches any domain ending in &'.b.c'& except for &'a.b.c'&. Domains that match
7562 neither &'a.b.c'& nor &'*.b.c'& do not match, because the last item in the
7563 list is positive. However, if the setting were
7565 domainlist relay_domains = !a.b.c
7567 then all domains other than &'a.b.c'& would match because the last item in the
7568 list is negative. In other words, a list that ends with a negative item behaves
7569 as if it had an extra item &`:*`& on the end.
7571 Another way of thinking about positive and negative items in lists is to read
7572 the connector as &"or"& after a positive item and as &"and"& after a negative
7577 .section "File names in lists" "SECTfilnamlis"
7578 .cindex "list" "file name in"
7579 If an item in a domain, host, address, or local part list is an absolute file
7580 name (beginning with a slash character), each line of the file is read and
7581 processed as if it were an independent item in the list, except that further
7582 file names are not allowed,
7583 and no expansion of the data from the file takes place.
7584 Empty lines in the file are ignored, and the file may also contain comment
7588 For domain and host lists, if a # character appears anywhere in a line of the
7589 file, it and all following characters are ignored.
7591 Because local parts may legitimately contain # characters, a comment in an
7592 address list or local part list file is recognized only if # is preceded by
7593 white space or the start of the line. For example:
7595 not#comment@x.y.z # but this is a comment
7599 Putting a file name in a list has the same effect as inserting each line of the
7600 file as an item in the list (blank lines and comments excepted). However, there
7601 is one important difference: the file is read each time the list is processed,
7602 so if its contents vary over time, Exim's behaviour changes.
7604 If a file name is preceded by an exclamation mark, the sense of any match
7605 within the file is inverted. For example, if
7607 hold_domains = !/etc/nohold-domains
7609 and the file contains the lines
7614 then &'a.b.c'& is in the set of domains defined by &%hold_domains%&, whereas
7615 any domain matching &`*.b.c`& is not.
7619 .section "An lsearch file is not an out-of-line list" "SECID77"
7620 As will be described in the sections that follow, lookups can be used in lists
7621 to provide indexed methods of checking list membership. There has been some
7622 confusion about the way &(lsearch)& lookups work in lists. Because
7623 an &(lsearch)& file contains plain text and is scanned sequentially, it is
7624 sometimes thought that it is allowed to contain wild cards and other kinds of
7625 non-constant pattern. This is not the case. The keys in an &(lsearch)& file are
7626 always fixed strings, just as for any other single-key lookup type.
7628 If you want to use a file to contain wild-card patterns that form part of a
7629 list, just give the file name on its own, without a search type, as described
7630 in the previous section. You could also use the &(wildlsearch)& or
7631 &(nwildlsearch)&, but there is no advantage in doing this.
7636 .section "Named lists" "SECTnamedlists"
7637 .cindex "named lists"
7638 .cindex "list" "named"
7639 A list of domains, hosts, email addresses, or local parts can be given a name
7640 which is then used to refer to the list elsewhere in the configuration. This is
7641 particularly convenient if the same list is required in several different
7642 places. It also allows lists to be given meaningful names, which can improve
7643 the readability of the configuration. For example, it is conventional to define
7644 a domain list called &'local_domains'& for all the domains that are handled
7645 locally on a host, using a configuration line such as
7647 domainlist local_domains = localhost:my.dom.example
7649 Named lists are referenced by giving their name preceded by a plus sign, so,
7650 for example, a router that is intended to handle local domains would be
7651 configured with the line
7653 domains = +local_domains
7655 The first router in a configuration is often one that handles all domains
7656 except the local ones, using a configuration with a negated item like this:
7660 domains = ! +local_domains
7661 transport = remote_smtp
7664 The four kinds of named list are created by configuration lines starting with
7665 the words &%domainlist%&, &%hostlist%&, &%addresslist%&, or &%localpartlist%&,
7666 respectively. Then there follows the name that you are defining, followed by an
7667 equals sign and the list itself. For example:
7669 hostlist relay_hosts = 192.168.23.0/24 : my.friend.example
7670 addresslist bad_senders = cdb;/etc/badsenders
7672 A named list may refer to other named lists:
7674 domainlist dom1 = first.example : second.example
7675 domainlist dom2 = +dom1 : third.example
7676 domainlist dom3 = fourth.example : +dom2 : fifth.example
7678 &*Warning*&: If the last item in a referenced list is a negative one, the
7679 effect may not be what you intended, because the negation does not propagate
7680 out to the higher level. For example, consider:
7682 domainlist dom1 = !a.b
7683 domainlist dom2 = +dom1 : *.b
7685 The second list specifies &"either in the &%dom1%& list or &'*.b'&"&. The first
7686 list specifies just &"not &'a.b'&"&, so the domain &'x.y'& matches it. That
7687 means it matches the second list as well. The effect is not the same as
7689 domainlist dom2 = !a.b : *.b
7691 where &'x.y'& does not match. It's best to avoid negation altogether in
7692 referenced lists if you can.
7694 Named lists may have a performance advantage. When Exim is routing an
7695 address or checking an incoming message, it caches the result of tests on named
7696 lists. So, if you have a setting such as
7698 domains = +local_domains
7700 on several of your routers
7701 or in several ACL statements,
7702 the actual test is done only for the first one. However, the caching works only
7703 if there are no expansions within the list itself or any sublists that it
7704 references. In other words, caching happens only for lists that are known to be
7705 the same each time they are referenced.
7707 By default, there may be up to 16 named lists of each type. This limit can be
7708 extended by changing a compile-time variable. The use of domain and host lists
7709 is recommended for concepts such as local domains, relay domains, and relay
7710 hosts. The default configuration is set up like this.
7714 .section "Named lists compared with macros" "SECID78"
7715 .cindex "list" "named compared with macro"
7716 .cindex "macro" "compared with named list"
7717 At first sight, named lists might seem to be no different from macros in the
7718 configuration file. However, macros are just textual substitutions. If you
7721 ALIST = host1 : host2
7722 auth_advertise_hosts = !ALIST
7724 it probably won't do what you want, because that is exactly the same as
7726 auth_advertise_hosts = !host1 : host2
7728 Notice that the second host name is not negated. However, if you use a host
7731 hostlist alist = host1 : host2
7732 auth_advertise_hosts = ! +alist
7734 the negation applies to the whole list, and so that is equivalent to
7736 auth_advertise_hosts = !host1 : !host2
7740 .section "Named list caching" "SECID79"
7741 .cindex "list" "caching of named"
7742 .cindex "caching" "named lists"
7743 While processing a message, Exim caches the result of checking a named list if
7744 it is sure that the list is the same each time. In practice, this means that
7745 the cache operates only if the list contains no $ characters, which guarantees
7746 that it will not change when it is expanded. Sometimes, however, you may have
7747 an expanded list that you know will be the same each time within a given
7748 message. For example:
7750 domainlist special_domains = \
7751 ${lookup{$sender_host_address}cdb{/some/file}}
7753 This provides a list of domains that depends only on the sending host's IP
7754 address. If this domain list is referenced a number of times (for example,
7755 in several ACL lines, or in several routers) the result of the check is not
7756 cached by default, because Exim does not know that it is going to be the
7757 same list each time.
7759 By appending &`_cache`& to &`domainlist`& you can tell Exim to go ahead and
7760 cache the result anyway. For example:
7762 domainlist_cache special_domains = ${lookup{...
7764 If you do this, you should be absolutely sure that caching is going to do
7765 the right thing in all cases. When in doubt, leave it out.
7769 .section "Domain lists" "SECTdomainlist"
7770 .cindex "domain list" "patterns for"
7771 .cindex "list" "domain list"
7772 Domain lists contain patterns that are to be matched against a mail domain.
7773 The following types of item may appear in domain lists:
7776 .cindex "primary host name"
7777 .cindex "host name" "matched in domain list"
7778 .oindex "&%primary_hostname%&"
7779 .cindex "domain list" "matching primary host name"
7780 .cindex "@ in a domain list"
7781 If a pattern consists of a single @ character, it matches the local host name,
7782 as set by the &%primary_hostname%& option (or defaulted). This makes it
7783 possible to use the same configuration file on several different hosts that
7784 differ only in their names.
7786 .cindex "@[] in a domain list"
7787 .cindex "domain list" "matching local IP interfaces"
7788 .cindex "domain literal"
7789 If a pattern consists of the string &`@[]`& it matches an IP address enclosed
7790 in square brackets (as in an email address that contains a domain literal), but
7791 only if that IP address is recognized as local for email routing purposes. The
7792 &%local_interfaces%& and &%extra_local_interfaces%& options can be used to
7793 control which of a host's several IP addresses are treated as local.
7794 In today's Internet, the use of domain literals is controversial.
7797 .cindex "@mx_primary"
7798 .cindex "@mx_secondary"
7799 .cindex "domain list" "matching MX pointers to local host"
7800 If a pattern consists of the string &`@mx_any`& it matches any domain that
7801 has an MX record pointing to the local host or to any host that is listed in
7802 .oindex "&%hosts_treat_as_local%&"
7803 &%hosts_treat_as_local%&. The items &`@mx_primary`& and &`@mx_secondary`&
7804 are similar, except that the first matches only when a primary MX target is the
7805 local host, and the second only when no primary MX target is the local host,
7806 but a secondary MX target is. &"Primary"& means an MX record with the lowest
7807 preference value &-- there may of course be more than one of them.
7809 The MX lookup that takes place when matching a pattern of this type is
7810 performed with the resolver options for widening names turned off. Thus, for
7811 example, a single-component domain will &'not'& be expanded by adding the
7812 resolver's default domain. See the &%qualify_single%& and &%search_parents%&
7813 options of the &(dnslookup)& router for a discussion of domain widening.
7815 Sometimes you may want to ignore certain IP addresses when using one of these
7816 patterns. You can specify this by following the pattern with &`/ignore=`&<&'ip
7817 list'&>, where <&'ip list'&> is a list of IP addresses. These addresses are
7818 ignored when processing the pattern (compare the &%ignore_target_hosts%& option
7819 on a router). For example:
7821 domains = @mx_any/ignore=127.0.0.1
7823 This example matches any domain that has an MX record pointing to one of
7824 the local host's IP addresses other than 127.0.0.1.
7826 The list of IP addresses is in fact processed by the same code that processes
7827 host lists, so it may contain CIDR-coded network specifications and it may also
7828 contain negative items.
7830 Because the list of IP addresses is a sublist within a domain list, you have to
7831 be careful about delimiters if there is more than one address. Like any other
7832 list, the default delimiter can be changed. Thus, you might have:
7834 domains = @mx_any/ignore=<;127.0.0.1;0.0.0.0 : \
7835 an.other.domain : ...
7837 so that the sublist uses semicolons for delimiters. When IPv6 addresses are
7838 involved, it is easiest to change the delimiter for the main list as well:
7840 domains = <? @mx_any/ignore=<;127.0.0.1;::1 ? \
7841 an.other.domain ? ...
7844 .cindex "asterisk" "in domain list"
7845 .cindex "domain list" "asterisk in"
7846 .cindex "domain list" "matching &""ends with""&"
7847 If a pattern starts with an asterisk, the remaining characters of the pattern
7848 are compared with the terminating characters of the domain. The use of &"*"& in
7849 domain lists differs from its use in partial matching lookups. In a domain
7850 list, the character following the asterisk need not be a dot, whereas partial
7851 matching works only in terms of dot-separated components. For example, a domain
7852 list item such as &`*key.ex`& matches &'donkey.ex'& as well as
7856 .cindex "regular expressions" "in domain list"
7857 .cindex "domain list" "matching regular expression"
7858 If a pattern starts with a circumflex character, it is treated as a regular
7859 expression, and matched against the domain using a regular expression matching
7860 function. The circumflex is treated as part of the regular expression.
7861 Email domains are case-independent, so this regular expression match is by
7862 default case-independent, but you can make it case-dependent by starting it
7863 with &`(?-i)`&. References to descriptions of the syntax of regular expressions
7864 are given in chapter &<<CHAPregexp>>&.
7866 &*Warning*&: Because domain lists are expanded before being processed, you
7867 must escape any backslash and dollar characters in the regular expression, or
7868 use the special &`\N`& sequence (see chapter &<<CHAPexpand>>&) to specify that
7869 it is not to be expanded (unless you really do want to build a regular
7870 expression by expansion, of course).
7872 .cindex "lookup" "in domain list"
7873 .cindex "domain list" "matching by lookup"
7874 If a pattern starts with the name of a single-key lookup type followed by a
7875 semicolon (for example, &"dbm;"& or &"lsearch;"&), the remainder of the pattern
7876 must be a file name in a suitable format for the lookup type. For example, for
7877 &"cdb;"& it must be an absolute path:
7879 domains = cdb;/etc/mail/local_domains.cdb
7881 The appropriate type of lookup is done on the file using the domain name as the
7882 key. In most cases, the data that is looked up is not used; Exim is interested
7883 only in whether or not the key is present in the file. However, when a lookup
7884 is used for the &%domains%& option on a router
7885 or a &%domains%& condition in an ACL statement, the data is preserved in the
7886 &$domain_data$& variable and can be referred to in other router options or
7887 other statements in the same ACL.
7890 Any of the single-key lookup type names may be preceded by
7891 &`partial`&<&'n'&>&`-`&, where the <&'n'&> is optional, for example,
7893 domains = partial-dbm;/partial/domains
7895 This causes partial matching logic to be invoked; a description of how this
7896 works is given in section &<<SECTpartiallookup>>&.
7899 .cindex "asterisk" "in lookup type"
7900 Any of the single-key lookup types may be followed by an asterisk. This causes
7901 a default lookup for a key consisting of a single asterisk to be done if the
7902 original lookup fails. This is not a useful feature when using a domain list to
7903 select particular domains (because any domain would match), but it might have
7904 value if the result of the lookup is being used via the &$domain_data$&
7907 If the pattern starts with the name of a query-style lookup type followed by a
7908 semicolon (for example, &"nisplus;"& or &"ldap;"&), the remainder of the
7909 pattern must be an appropriate query for the lookup type, as described in
7910 chapter &<<CHAPfdlookup>>&. For example:
7912 hold_domains = mysql;select domain from holdlist \
7913 where domain = '${quote_mysql:$domain}';
7915 In most cases, the data that is looked up is not used (so for an SQL query, for
7916 example, it doesn't matter what field you select). Exim is interested only in
7917 whether or not the query succeeds. However, when a lookup is used for the
7918 &%domains%& option on a router, the data is preserved in the &$domain_data$&
7919 variable and can be referred to in other options.
7921 .cindex "domain list" "matching literal domain name"
7922 If none of the above cases apply, a caseless textual comparison is made
7923 between the pattern and the domain.
7926 Here is an example that uses several different kinds of pattern:
7928 domainlist funny_domains = \
7931 *.foundation.fict.example : \
7932 \N^[1-2]\d{3}\.fict\.example$\N : \
7933 partial-dbm;/opt/data/penguin/book : \
7934 nis;domains.byname : \
7935 nisplus;[name=$domain,status=local],domains.org_dir
7937 There are obvious processing trade-offs among the various matching modes. Using
7938 an asterisk is faster than a regular expression, and listing a few names
7939 explicitly probably is too. The use of a file or database lookup is expensive,
7940 but may be the only option if hundreds of names are required. Because the
7941 patterns are tested in order, it makes sense to put the most commonly matched
7946 .section "Host lists" "SECThostlist"
7947 .cindex "host list" "patterns in"
7948 .cindex "list" "host list"
7949 Host lists are used to control what remote hosts are allowed to do. For
7950 example, some hosts may be allowed to use the local host as a relay, and some
7951 may be permitted to use the SMTP ETRN command. Hosts can be identified in
7952 two different ways, by name or by IP address. In a host list, some types of
7953 pattern are matched to a host name, and some are matched to an IP address.
7954 You need to be particularly careful with this when single-key lookups are
7955 involved, to ensure that the right value is being used as the key.
7958 .section "Special host list patterns" "SECID80"
7959 .cindex "empty item in hosts list"
7960 .cindex "host list" "empty string in"
7961 If a host list item is the empty string, it matches only when no remote host is
7962 involved. This is the case when a message is being received from a local
7963 process using SMTP on the standard input, that is, when a TCP/IP connection is
7966 .cindex "asterisk" "in host list"
7967 The special pattern &"*"& in a host list matches any host or no host. Neither
7968 the IP address nor the name is actually inspected.
7972 .section "Host list patterns that match by IP address" "SECThoslispatip"
7973 .cindex "host list" "matching IP addresses"
7974 If an IPv4 host calls an IPv6 host and the call is accepted on an IPv6 socket,
7975 the incoming address actually appears in the IPv6 host as
7976 &`::ffff:`&<&'v4address'&>. When such an address is tested against a host
7977 list, it is converted into a traditional IPv4 address first. (Not all operating
7978 systems accept IPv4 calls on IPv6 sockets, as there have been some security
7981 The following types of pattern in a host list check the remote host by
7982 inspecting its IP address:
7985 If the pattern is a plain domain name (not a regular expression, not starting
7986 with *, not a lookup of any kind), Exim calls the operating system function
7987 to find the associated IP address(es). Exim uses the newer
7988 &[getipnodebyname()]& function when available, otherwise &[gethostbyname()]&.
7989 This typically causes a forward DNS lookup of the name. The result is compared
7990 with the IP address of the subject host.
7992 If there is a temporary problem (such as a DNS timeout) with the host name
7993 lookup, a temporary error occurs. For example, if the list is being used in an
7994 ACL condition, the ACL gives a &"defer"& response, usually leading to a
7995 temporary SMTP error code. If no IP address can be found for the host name,
7996 what happens is described in section &<<SECTbehipnot>>& below.
7999 .cindex "@ in a host list"
8000 If the pattern is &"@"&, the primary host name is substituted and used as a
8001 domain name, as just described.
8004 If the pattern is an IP address, it is matched against the IP address of the
8005 subject host. IPv4 addresses are given in the normal &"dotted-quad"& notation.
8006 IPv6 addresses can be given in colon-separated format, but the colons have to
8007 be doubled so as not to be taken as item separators when the default list
8008 separator is used. IPv6 addresses are recognized even when Exim is compiled
8009 without IPv6 support. This means that if they appear in a host list on an
8010 IPv4-only host, Exim will not treat them as host names. They are just addresses
8011 that can never match a client host.
8014 .cindex "@[] in a host list"
8015 If the pattern is &"@[]"&, it matches the IP address of any IP interface on
8016 the local host. For example, if the local host is an IPv4 host with one
8017 interface address 10.45.23.56, these two ACL statements have the same effect:
8019 accept hosts = 127.0.0.1 : 10.45.23.56
8023 .cindex "CIDR notation"
8024 If the pattern is an IP address followed by a slash and a mask length (for
8025 example 10.11.42.0/24), it is matched against the IP address of the subject
8026 host under the given mask. This allows, an entire network of hosts to be
8027 included (or excluded) by a single item. The mask uses CIDR notation; it
8028 specifies the number of address bits that must match, starting from the most
8029 significant end of the address.
8031 &*Note*&: The mask is &'not'& a count of addresses, nor is it the high number
8032 of a range of addresses. It is the number of bits in the network portion of the
8033 address. The above example specifies a 24-bit netmask, so it matches all 256
8034 addresses in the 10.11.42.0 network. An item such as
8038 matches just two addresses, 192.168.23.236 and 192.168.23.237. A mask value of
8039 32 for an IPv4 address is the same as no mask at all; just a single address
8042 Here is another example which shows an IPv4 and an IPv6 network:
8044 recipient_unqualified_hosts = 192.168.0.0/16: \
8045 3ffe::ffff::836f::::/48
8047 The doubling of list separator characters applies only when these items
8048 appear inline in a host list. It is not required when indirecting via a file.
8051 recipient_unqualified_hosts = /opt/exim/unqualnets
8053 could make use of a file containing
8058 to have exactly the same effect as the previous example. When listing IPv6
8059 addresses inline, it is usually more convenient to use the facility for
8060 changing separator characters. This list contains the same two networks:
8062 recipient_unqualified_hosts = <; 172.16.0.0/12; \
8065 The separator is changed to semicolon by the leading &"<;"& at the start of the
8071 .section "Host list patterns for single-key lookups by host address" &&&
8072 "SECThoslispatsikey"
8073 .cindex "host list" "lookup of IP address"
8074 When a host is to be identified by a single-key lookup of its complete IP
8075 address, the pattern takes this form:
8077 &`net-<`&&'single-key-search-type'&&`>;<`&&'search-data'&&`>`&
8081 hosts_lookup = net-cdb;/hosts-by-ip.db
8083 The text form of the IP address of the subject host is used as the lookup key.
8084 IPv6 addresses are converted to an unabbreviated form, using lower case
8085 letters, with dots as separators because colon is the key terminator in
8086 &(lsearch)& files. [Colons can in fact be used in keys in &(lsearch)& files by
8087 quoting the keys, but this is a facility that was added later.] The data
8088 returned by the lookup is not used.
8090 .cindex "IP address" "masking"
8091 .cindex "host list" "masked IP address"
8092 Single-key lookups can also be performed using masked IP addresses, using
8093 patterns of this form:
8095 &`net<`&&'number'&&`>-<`&&'single-key-search-type'&&`>;<`&&'search-data'&&`>`&
8099 net24-dbm;/networks.db
8101 The IP address of the subject host is masked using <&'number'&> as the mask
8102 length. A textual string is constructed from the masked value, followed by the
8103 mask, and this is used as the lookup key. For example, if the host's IP address
8104 is 192.168.34.6, the key that is looked up for the above example is
8105 &"192.168.34.0/24"&.
8107 When an IPv6 address is converted to a string, dots are normally used instead
8108 of colons, so that keys in &(lsearch)& files need not contain colons (which
8109 terminate &(lsearch)& keys). This was implemented some time before the ability
8110 to quote keys was made available in &(lsearch)& files. However, the more
8111 recently implemented &(iplsearch)& files do require colons in IPv6 keys
8112 (notated using the quoting facility) so as to distinguish them from IPv4 keys.
8113 For this reason, when the lookup type is &(iplsearch)&, IPv6 addresses are
8114 converted using colons and not dots. In all cases, full, unabbreviated IPv6
8115 addresses are always used.
8117 Ideally, it would be nice to tidy up this anomalous situation by changing to
8118 colons in all cases, given that quoting is now available for &(lsearch)&.
8119 However, this would be an incompatible change that might break some existing
8122 &*Warning*&: Specifying &%net32-%& (for an IPv4 address) or &%net128-%& (for an
8123 IPv6 address) is not the same as specifying just &%net-%& without a number. In
8124 the former case the key strings include the mask value, whereas in the latter
8125 case the IP address is used on its own.
8129 .section "Host list patterns that match by host name" "SECThoslispatnam"
8130 .cindex "host" "lookup failures"
8131 .cindex "unknown host name"
8132 .cindex "host list" "matching host name"
8133 There are several types of pattern that require Exim to know the name of the
8134 remote host. These are either wildcard patterns or lookups by name. (If a
8135 complete hostname is given without any wildcarding, it is used to find an IP
8136 address to match against, as described in the section &<<SECThoslispatip>>&
8139 If the remote host name is not already known when Exim encounters one of these
8140 patterns, it has to be found from the IP address.
8141 Although many sites on the Internet are conscientious about maintaining reverse
8142 DNS data for their hosts, there are also many that do not do this.
8143 Consequently, a name cannot always be found, and this may lead to unwanted
8144 effects. Take care when configuring host lists with wildcarded name patterns.
8145 Consider what will happen if a name cannot be found.
8147 Because of the problems of determining host names from IP addresses, matching
8148 against host names is not as common as matching against IP addresses.
8150 By default, in order to find a host name, Exim first does a reverse DNS lookup;
8151 if no name is found in the DNS, the system function (&[gethostbyaddr()]& or
8152 &[getipnodebyaddr()]& if available) is tried. The order in which these lookups
8153 are done can be changed by setting the &%host_lookup_order%& option. For
8154 security, once Exim has found one or more names, it looks up the IP addresses
8155 for these names and compares them with the IP address that it started with.
8156 Only those names whose IP addresses match are accepted. Any other names are
8157 discarded. If no names are left, Exim behaves as if the host name cannot be
8158 found. In the most common case there is only one name and one IP address.
8160 There are some options that control what happens if a host name cannot be
8161 found. These are described in section &<<SECTbehipnot>>& below.
8163 .cindex "host" "alias for"
8164 .cindex "alias for host"
8165 As a result of aliasing, hosts may have more than one name. When processing any
8166 of the following types of pattern, all the host's names are checked:
8169 .cindex "asterisk" "in host list"
8170 If a pattern starts with &"*"& the remainder of the item must match the end of
8171 the host name. For example, &`*.b.c`& matches all hosts whose names end in
8172 &'.b.c'&. This special simple form is provided because this is a very common
8173 requirement. Other kinds of wildcarding require the use of a regular
8176 .cindex "regular expressions" "in host list"
8177 .cindex "host list" "regular expression in"
8178 If the item starts with &"^"& it is taken to be a regular expression which is
8179 matched against the host name. Host names are case-independent, so this regular
8180 expression match is by default case-independent, but you can make it
8181 case-dependent by starting it with &`(?-i)`&. References to descriptions of the
8182 syntax of regular expressions are given in chapter &<<CHAPregexp>>&. For
8187 is a regular expression that matches either of the two hosts &'a.c.d'& or
8188 &'b.c.d'&. When a regular expression is used in a host list, you must take care
8189 that backslash and dollar characters are not misinterpreted as part of the
8190 string expansion. The simplest way to do this is to use &`\N`& to mark that
8191 part of the string as non-expandable. For example:
8193 sender_unqualified_hosts = \N^(a|b)\.c\.d$\N : ....
8195 &*Warning*&: If you want to match a complete host name, you must include the
8196 &`$`& terminating metacharacter in the regular expression, as in the above
8197 example. Without it, a match at the start of the host name is all that is
8204 .section "Behaviour when an IP address or name cannot be found" "SECTbehipnot"
8205 .cindex "host" "lookup failures, permanent"
8206 While processing a host list, Exim may need to look up an IP address from a
8207 name (see section &<<SECThoslispatip>>&), or it may need to look up a host name
8208 from an IP address (see section &<<SECThoslispatnam>>&). In either case, the
8209 behaviour when it fails to find the information it is seeking is the same.
8211 &*Note*&: This section applies to permanent lookup failures. It does &'not'&
8212 apply to temporary DNS errors, whose handling is described in the next section.
8214 .cindex "&`+include_unknown`&"
8215 .cindex "&`+ignore_unknown`&"
8216 By default, Exim behaves as if the host does not match the list. This may not
8217 always be what you want to happen. To change Exim's behaviour, the special
8218 items &`+include_unknown`& or &`+ignore_unknown`& may appear in the list (at
8219 top level &-- they are not recognized in an indirected file).
8222 If any item that follows &`+include_unknown`& requires information that
8223 cannot found, Exim behaves as if the host does match the list. For example,
8225 host_reject_connection = +include_unknown:*.enemy.ex
8227 rejects connections from any host whose name matches &`*.enemy.ex`&, and also
8228 any hosts whose name it cannot find.
8231 If any item that follows &`+ignore_unknown`& requires information that cannot
8232 be found, Exim ignores that item and proceeds to the rest of the list. For
8235 accept hosts = +ignore_unknown : friend.example : \
8238 accepts from any host whose name is &'friend.example'& and from 192.168.4.5,
8239 whether or not its host name can be found. Without &`+ignore_unknown`&, if no
8240 name can be found for 192.168.4.5, it is rejected.
8243 Both &`+include_unknown`& and &`+ignore_unknown`& may appear in the same
8244 list. The effect of each one lasts until the next, or until the end of the
8248 .section "Temporary DNS errors when looking up host information" &&&
8250 .cindex "host" "lookup failures, temporary"
8251 .cindex "&`+include_defer`&"
8252 .cindex "&`+ignore_defer`&"
8253 A temporary DNS lookup failure normally causes a defer action (except when
8254 &%dns_again_means_nonexist%& converts it into a permanent error). However,
8255 host lists can include &`+ignore_defer`& and &`+include_defer`&, analagous to
8256 &`+ignore_unknown`& and &`+include_unknown`&, as described in the previous
8257 section. These options should be used with care, probably only in non-critical
8258 host lists such as whitelists.
8262 .section "Host list patterns for single-key lookups by host name" &&&
8263 "SECThoslispatnamsk"
8264 .cindex "unknown host name"
8265 .cindex "host list" "matching host name"
8266 If a pattern is of the form
8268 <&'single-key-search-type'&>;<&'search-data'&>
8272 dbm;/host/accept/list
8274 a single-key lookup is performed, using the host name as its key. If the
8275 lookup succeeds, the host matches the item. The actual data that is looked up
8278 &*Reminder*&: With this kind of pattern, you must have host &'names'& as
8279 keys in the file, not IP addresses. If you want to do lookups based on IP
8280 addresses, you must precede the search type with &"net-"& (see section
8281 &<<SECThoslispatsikey>>&). There is, however, no reason why you could not use
8282 two items in the same list, one doing an address lookup and one doing a name
8283 lookup, both using the same file.
8287 .section "Host list patterns for query-style lookups" "SECID81"
8288 If a pattern is of the form
8290 <&'query-style-search-type'&>;<&'query'&>
8292 the query is obeyed, and if it succeeds, the host matches the item. The actual
8293 data that is looked up is not used. The variables &$sender_host_address$& and
8294 &$sender_host_name$& can be used in the query. For example:
8296 hosts_lookup = pgsql;\
8297 select ip from hostlist where ip='$sender_host_address'
8299 The value of &$sender_host_address$& for an IPv6 address contains colons. You
8300 can use the &%sg%& expansion item to change this if you need to. If you want to
8301 use masked IP addresses in database queries, you can use the &%mask%& expansion
8304 If the query contains a reference to &$sender_host_name$&, Exim automatically
8305 looks up the host name if has not already done so. (See section
8306 &<<SECThoslispatnam>>& for comments on finding host names.)
8308 Historical note: prior to release 4.30, Exim would always attempt to find a
8309 host name before running the query, unless the search type was preceded by
8310 &`net-`&. This is no longer the case. For backwards compatibility, &`net-`& is
8311 still recognized for query-style lookups, but its presence or absence has no
8312 effect. (Of course, for single-key lookups, &`net-`& &'is'& important.
8313 See section &<<SECThoslispatsikey>>&.)
8317 .section "Mixing wildcarded host names and addresses in host lists" &&&
8319 .cindex "host list" "mixing names and addresses in"
8320 If you have name lookups or wildcarded host names and IP addresses in the same
8321 host list, you should normally put the IP addresses first. For example, in an
8324 accept hosts = 10.9.8.7 : *.friend.example
8326 The reason for this lies in the left-to-right way that Exim processes lists.
8327 It can test IP addresses without doing any DNS lookups, but when it reaches an
8328 item that requires a host name, it fails if it cannot find a host name to
8329 compare with the pattern. If the above list is given in the opposite order, the
8330 &%accept%& statement fails for a host whose name cannot be found, even if its
8331 IP address is 10.9.8.7.
8333 If you really do want to do the name check first, and still recognize the IP
8334 address, you can rewrite the ACL like this:
8336 accept hosts = *.friend.example
8337 accept hosts = 10.9.8.7
8339 If the first &%accept%& fails, Exim goes on to try the second one. See chapter
8340 &<<CHAPACL>>& for details of ACLs.
8346 .section "Address lists" "SECTaddresslist"
8347 .cindex "list" "address list"
8348 .cindex "address list" "empty item"
8349 .cindex "address list" "patterns"
8350 Address lists contain patterns that are matched against mail addresses. There
8351 is one special case to be considered: the sender address of a bounce message is
8352 always empty. You can test for this by providing an empty item in an address
8353 list. For example, you can set up a router to process bounce messages by
8354 using this option setting:
8358 The presence of the colon creates an empty item. If you do not provide any
8359 data, the list is empty and matches nothing. The empty sender can also be
8360 detected by a regular expression that matches an empty string,
8361 and by a query-style lookup that succeeds when &$sender_address$& is empty.
8363 Non-empty items in an address list can be straightforward email addresses. For
8366 senders = jbc@askone.example : hs@anacreon.example
8368 A certain amount of wildcarding is permitted. If a pattern contains an @
8369 character, but is not a regular expression and does not begin with a
8370 semicolon-terminated lookup type (described below), the local part of the
8371 subject address is compared with the local part of the pattern, which may start
8372 with an asterisk. If the local parts match, the domain is checked in exactly
8373 the same way as for a pattern in a domain list. For example, the domain can be
8374 wildcarded, refer to a named list, or be a lookup:
8376 deny senders = *@*.spamming.site:\
8377 *@+hostile_domains:\
8378 bozo@partial-lsearch;/list/of/dodgy/sites:\
8379 *@dbm;/bad/domains.db
8381 .cindex "local part" "starting with !"
8382 .cindex "address list" "local part starting with !"
8383 If a local part that begins with an exclamation mark is required, it has to be
8384 specified using a regular expression, because otherwise the exclamation mark is
8385 treated as a sign of negation, as is standard in lists.
8387 If a non-empty pattern that is not a regular expression or a lookup does not
8388 contain an @ character, it is matched against the domain part of the subject
8389 address. The only two formats that are recognized this way are a literal
8390 domain, or a domain pattern that starts with *. In both these cases, the effect
8391 is the same as if &`*@`& preceded the pattern. For example:
8393 deny senders = enemy.domain : *.enemy.domain
8396 The following kinds of more complicated address list pattern can match any
8397 address, including the empty address that is characteristic of bounce message
8401 .cindex "regular expressions" "in address list"
8402 .cindex "address list" "regular expression in"
8403 If (after expansion) a pattern starts with &"^"&, a regular expression match is
8404 done against the complete address, with the pattern as the regular expression.
8405 You must take care that backslash and dollar characters are not misinterpreted
8406 as part of the string expansion. The simplest way to do this is to use &`\N`&
8407 to mark that part of the string as non-expandable. For example:
8409 deny senders = \N^.*this.*@example\.com$\N : \
8410 \N^\d{8}.+@spamhaus.example$\N : ...
8412 The &`\N`& sequences are removed by the expansion, so these items do indeed
8413 start with &"^"& by the time they are being interpreted as address patterns.
8416 .cindex "address list" "lookup for complete address"
8417 Complete addresses can be looked up by using a pattern that starts with a
8418 lookup type terminated by a semicolon, followed by the data for the lookup. For
8421 deny senders = cdb;/etc/blocked.senders : \
8422 mysql;select address from blocked where \
8423 address='${quote_mysql:$sender_address}'
8425 Both query-style and single-key lookup types can be used. For a single-key
8426 lookup type, Exim uses the complete address as the key. However, empty keys are
8427 not supported for single-key lookups, so a match against the empty address
8428 always fails. This restriction does not apply to query-style lookups.
8430 Partial matching for single-key lookups (section &<<SECTpartiallookup>>&)
8431 cannot be used, and is ignored if specified, with an entry being written to the
8433 .cindex "*@ with single-key lookup"
8434 However, you can configure lookup defaults, as described in section
8435 &<<SECTdefaultvaluelookups>>&, but this is useful only for the &"*@"& type of
8436 default. For example, with this lookup:
8438 accept senders = lsearch*@;/some/file
8440 the file could contains lines like this:
8442 user1@domain1.example
8445 and for the sender address &'nimrod@jaeger.example'&, the sequence of keys
8448 nimrod@jaeger.example
8452 &*Warning 1*&: Do not include a line keyed by &"*"& in the file, because that
8453 would mean that every address matches, thus rendering the test useless.
8455 &*Warning 2*&: Do not confuse these two kinds of item:
8457 deny recipients = dbm*@;/some/file
8458 deny recipients = *@dbm;/some/file
8460 The first does a whole address lookup, with defaulting, as just described,
8461 because it starts with a lookup type. The second matches the local part and
8462 domain independently, as described in a bullet point below.
8466 The following kinds of address list pattern can match only non-empty addresses.
8467 If the subject address is empty, a match against any of these pattern types
8472 .cindex "@@ with single-key lookup"
8473 .cindex "address list" "@@ lookup type"
8474 .cindex "address list" "split local part and domain"
8475 If a pattern starts with &"@@"& followed by a single-key lookup item
8476 (for example, &`@@lsearch;/some/file`&), the address that is being checked is
8477 split into a local part and a domain. The domain is looked up in the file. If
8478 it is not found, there is no match. If it is found, the data that is looked up
8479 from the file is treated as a colon-separated list of local part patterns, each
8480 of which is matched against the subject local part in turn.
8482 .cindex "asterisk" "in address list"
8483 The lookup may be a partial one, and/or one involving a search for a default
8484 keyed by &"*"& (see section &<<SECTdefaultvaluelookups>>&). The local part
8485 patterns that are looked up can be regular expressions or begin with &"*"&, or
8486 even be further lookups. They may also be independently negated. For example,
8489 deny senders = @@dbm;/etc/reject-by-domain
8491 the data from which the DBM file is built could contain lines like
8493 baddomain.com: !postmaster : *
8495 to reject all senders except &%postmaster%& from that domain.
8497 .cindex "local part" "starting with !"
8498 If a local part that actually begins with an exclamation mark is required, it
8499 has to be specified using a regular expression. In &(lsearch)& files, an entry
8500 may be split over several lines by indenting the second and subsequent lines,
8501 but the separating colon must still be included at line breaks. White space
8502 surrounding the colons is ignored. For example:
8504 aol.com: spammer1 : spammer2 : ^[0-9]+$ :
8507 As in all colon-separated lists in Exim, a colon can be included in an item by
8510 If the last item in the list starts with a right angle-bracket, the remainder
8511 of the item is taken as a new key to look up in order to obtain a continuation
8512 list of local parts. The new key can be any sequence of characters. Thus one
8513 might have entries like
8515 aol.com: spammer1 : spammer 2 : >*
8516 xyz.com: spammer3 : >*
8519 in a file that was searched with &%@@dbm*%&, to specify a match for 8-digit
8520 local parts for all domains, in addition to the specific local parts listed for
8521 each domain. Of course, using this feature costs another lookup each time a
8522 chain is followed, but the effort needed to maintain the data is reduced.
8524 .cindex "loop" "in lookups"
8525 It is possible to construct loops using this facility, and in order to catch
8526 them, the chains may be no more than fifty items long.
8529 The @@<&'lookup'&> style of item can also be used with a query-style
8530 lookup, but in this case, the chaining facility is not available. The lookup
8531 can only return a single list of local parts.
8534 &*Warning*&: There is an important difference between the address list items
8535 in these two examples:
8538 senders = *@+my_list
8540 In the first one, &`my_list`& is a named address list, whereas in the second
8541 example it is a named domain list.
8546 .section "Case of letters in address lists" "SECTcasletadd"
8547 .cindex "case of local parts"
8548 .cindex "address list" "case forcing"
8549 .cindex "case forcing in address lists"
8550 Domains in email addresses are always handled caselessly, but for local parts
8551 case may be significant on some systems (see &%caseful_local_part%& for how
8552 Exim deals with this when routing addresses). However, RFC 2505 (&'Anti-Spam
8553 Recommendations for SMTP MTAs'&) suggests that matching of addresses to
8554 blocking lists should be done in a case-independent manner. Since most address
8555 lists in Exim are used for this kind of control, Exim attempts to do this by
8558 The domain portion of an address is always lowercased before matching it to an
8559 address list. The local part is lowercased by default, and any string
8560 comparisons that take place are done caselessly. This means that the data in
8561 the address list itself, in files included as plain file names, and in any file
8562 that is looked up using the &"@@"& mechanism, can be in any case. However, the
8563 keys in files that are looked up by a search type other than &(lsearch)& (which
8564 works caselessly) must be in lower case, because these lookups are not
8567 .cindex "&`+caseful`&"
8568 To allow for the possibility of caseful address list matching, if an item in
8569 an address list is the string &"+caseful"&, the original case of the local
8570 part is restored for any comparisons that follow, and string comparisons are no
8571 longer case-independent. This does not affect the domain, which remains in
8572 lower case. However, although independent matches on the domain alone are still
8573 performed caselessly, regular expressions that match against an entire address
8574 become case-sensitive after &"+caseful"& has been seen.
8578 .section "Local part lists" "SECTlocparlis"
8579 .cindex "list" "local part list"
8580 .cindex "local part" "list"
8581 Case-sensitivity in local part lists is handled in the same way as for address
8582 lists, as just described. The &"+caseful"& item can be used if required. In a
8583 setting of the &%local_parts%& option in a router with &%caseful_local_part%&
8584 set false, the subject is lowercased and the matching is initially
8585 case-insensitive. In this case, &"+caseful"& will restore case-sensitive
8586 matching in the local part list, but not elsewhere in the router. If
8587 &%caseful_local_part%& is set true in a router, matching in the &%local_parts%&
8588 option is case-sensitive from the start.
8590 If a local part list is indirected to a file (see section &<<SECTfilnamlis>>&),
8591 comments are handled in the same way as address lists &-- they are recognized
8592 only if the # is preceded by white space or the start of the line.
8593 Otherwise, local part lists are matched in the same way as domain lists, except
8594 that the special items that refer to the local host (&`@`&, &`@[]`&,
8595 &`@mx_any`&, &`@mx_primary`&, and &`@mx_secondary`&) are not recognized.
8596 Refer to section &<<SECTdomainlist>>& for details of the other available item
8598 .ecindex IIDdohoadli
8603 . ////////////////////////////////////////////////////////////////////////////
8604 . ////////////////////////////////////////////////////////////////////////////
8606 .chapter "String expansions" "CHAPexpand"
8607 .scindex IIDstrexp "expansion" "of strings"
8608 Many strings in Exim's run time configuration are expanded before use. Some of
8609 them are expanded every time they are used; others are expanded only once.
8611 When a string is being expanded it is copied verbatim from left to right except
8612 when a dollar or backslash character is encountered. A dollar specifies the
8613 start of a portion of the string that is interpreted and replaced as described
8614 below in section &<<SECTexpansionitems>>& onwards. Backslash is used as an
8615 escape character, as described in the following section.
8617 Whether a string is expanded depends upon the context. Usually this is solely
8618 dependent upon the option for which a value is sought; in this documentation,
8619 options for which string expansion is performed are marked with † after
8620 the data type. ACL rules always expand strings. A couple of expansion
8621 conditions do not expand some of the brace-delimited branches, for security
8626 .section "Literal text in expanded strings" "SECTlittext"
8627 .cindex "expansion" "including literal text"
8628 An uninterpreted dollar can be included in an expanded string by putting a
8629 backslash in front of it. A backslash can be used to prevent any special
8630 character being treated specially in an expansion, including backslash itself.
8631 If the string appears in quotes in the configuration file, two backslashes are
8632 required because the quotes themselves cause interpretation of backslashes when
8633 the string is read in (see section &<<SECTstrings>>&).
8635 .cindex "expansion" "non-expandable substrings"
8636 A portion of the string can specified as non-expandable by placing it between
8637 two occurrences of &`\N`&. This is particularly useful for protecting regular
8638 expressions, which often contain backslashes and dollar signs. For example:
8640 deny senders = \N^\d{8}[a-z]@some\.site\.example$\N
8642 On encountering the first &`\N`&, the expander copies subsequent characters
8643 without interpretation until it reaches the next &`\N`& or the end of the
8648 .section "Character escape sequences in expanded strings" "SECID82"
8649 .cindex "expansion" "escape sequences"
8650 A backslash followed by one of the letters &"n"&, &"r"&, or &"t"& in an
8651 expanded string is recognized as an escape sequence for the character newline,
8652 carriage return, or tab, respectively. A backslash followed by up to three
8653 octal digits is recognized as an octal encoding for a single character, and a
8654 backslash followed by &"x"& and up to two hexadecimal digits is a hexadecimal
8657 These escape sequences are also recognized in quoted strings when they are read
8658 in. Their interpretation in expansions as well is useful for unquoted strings,
8659 and for other cases such as looked-up strings that are then expanded.
8662 .section "Testing string expansions" "SECID83"
8663 .cindex "expansion" "testing"
8664 .cindex "testing" "string expansion"
8666 Many expansions can be tested by calling Exim with the &%-be%& option. This
8667 takes the command arguments, or lines from the standard input if there are no
8668 arguments, runs them through the string expansion code, and writes the results
8669 to the standard output. Variables based on configuration values are set up, but
8670 since no message is being processed, variables such as &$local_part$& have no
8671 value. Nevertheless the &%-be%& option can be useful for checking out file and
8672 database lookups, and the use of expansion operators such as &%sg%&, &%substr%&
8675 Exim gives up its root privilege when it is called with the &%-be%& option, and
8676 instead runs under the uid and gid it was called with, to prevent users from
8677 using &%-be%& for reading files to which they do not have access.
8680 If you want to test expansions that include variables whose values are taken
8681 from a message, there are two other options that can be used. The &%-bem%&
8682 option is like &%-be%& except that it is followed by a file name. The file is
8683 read as a message before doing the test expansions. For example:
8685 exim -bem /tmp/test.message '$h_subject:'
8687 The &%-Mset%& option is used in conjunction with &%-be%& and is followed by an
8688 Exim message identifier. For example:
8690 exim -be -Mset 1GrA8W-0004WS-LQ '$recipients'
8692 This loads the message from Exim's spool before doing the test expansions, and
8693 is therefore restricted to admin users.
8696 .section "Forced expansion failure" "SECTforexpfai"
8697 .cindex "expansion" "forced failure"
8698 A number of expansions that are described in the following section have
8699 alternative &"true"& and &"false"& substrings, enclosed in brace characters
8700 (which are sometimes called &"curly brackets"&). Which of the two strings is
8701 used depends on some condition that is evaluated as part of the expansion. If,
8702 instead of a &"false"& substring, the word &"fail"& is used (not in braces),
8703 the entire string expansion fails in a way that can be detected by the code
8704 that requested the expansion. This is called &"forced expansion failure"&, and
8705 its consequences depend on the circumstances. In some cases it is no different
8706 from any other expansion failure, but in others a different action may be
8707 taken. Such variations are mentioned in the documentation of the option that is
8713 .section "Expansion items" "SECTexpansionitems"
8714 The following items are recognized in expanded strings. White space may be used
8715 between sub-items that are keywords or substrings enclosed in braces inside an
8716 outer set of braces, to improve readability. &*Warning*&: Within braces,
8717 white space is significant.
8720 .vitem &*$*&<&'variable&~name'&>&~or&~&*${*&<&'variable&~name'&>&*}*&
8721 .cindex "expansion" "variables"
8722 Substitute the contents of the named variable, for example:
8727 The second form can be used to separate the name from subsequent alphanumeric
8728 characters. This form (using braces) is available only for variables; it does
8729 &'not'& apply to message headers. The names of the variables are given in
8730 section &<<SECTexpvar>>& below. If the name of a non-existent variable is
8731 given, the expansion fails.
8733 .vitem &*${*&<&'op'&>&*:*&<&'string'&>&*}*&
8734 .cindex "expansion" "operators"
8735 The string is first itself expanded, and then the operation specified by
8736 <&'op'&> is applied to it. For example:
8740 The string starts with the first character after the colon, which may be
8741 leading white space. A list of operators is given in section &<<SECTexpop>>&
8742 below. The operator notation is used for simple expansion items that have just
8743 one argument, because it reduces the number of braces and therefore makes the
8744 string easier to understand.
8746 .vitem &*$bheader_*&<&'header&~name'&>&*:*&&~or&~&*$bh_*&<&'header&~name'&>&*:*&
8747 This item inserts &"basic"& header lines. It is described with the &%header%&
8748 expansion item below.
8750 .vitem "&*${dlfunc{*&<&'file'&>&*}{*&<&'function'&>&*}{*&<&'arg'&>&*}&&&
8751 {*&<&'arg'&>&*}...}*&"
8753 This expansion dynamically loads and then calls a locally-written C function.
8754 This functionality is available only if Exim is compiled with
8758 set in &_Local/Makefile_&. Once loaded, Exim remembers the dynamically loaded
8759 object so that it doesn't reload the same object file in the same Exim process
8760 (but of course Exim does start new processes frequently).
8762 There may be from zero to eight arguments to the function. When compiling
8763 a local function that is to be called in this way, &_local_scan.h_& should be
8764 included. The Exim variables and functions that are defined by that API
8765 are also available for dynamically loaded functions. The function itself
8766 must have the following type:
8768 int dlfunction(uschar **yield, int argc, uschar *argv[])
8770 Where &`uschar`& is a typedef for &`unsigned char`& in &_local_scan.h_&. The
8771 function should return one of the following values:
8773 &`OK`&: Success. The string that is placed in the variable &'yield'& is put
8774 into the expanded string that is being built.
8776 &`FAIL`&: A non-forced expansion failure occurs, with the error message taken
8777 from &'yield'&, if it is set.
8779 &`FAIL_FORCED`&: A forced expansion failure occurs, with the error message
8780 taken from &'yield'& if it is set.
8782 &`ERROR`&: Same as &`FAIL`&, except that a panic log entry is written.
8784 When compiling a function that is to be used in this way with gcc,
8785 you need to add &%-shared%& to the gcc command. Also, in the Exim build-time
8786 configuration, you must add &%-export-dynamic%& to EXTRALIBS.
8788 .vitem "&*${extract{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}&&&
8789 {*&<&'string3'&>&*}}*&"
8790 .cindex "expansion" "extracting substrings by key"
8791 .cindex "&%extract%&" "substrings by key"
8792 The key and <&'string1'&> are first expanded separately. Leading and trailing
8793 white space is removed from the key (but not from any of the strings). The key
8794 must not consist entirely of digits. The expanded <&'string1'&> must be of the
8797 <&'key1'&> = <&'value1'&> <&'key2'&> = <&'value2'&> ...
8800 where the equals signs and spaces (but not both) are optional. If any of the
8801 values contain white space, they must be enclosed in double quotes, and any
8802 values that are enclosed in double quotes are subject to escape processing as
8803 described in section &<<SECTstrings>>&. The expanded <&'string1'&> is searched
8804 for the value that corresponds to the key. The search is case-insensitive. If
8805 the key is found, <&'string2'&> is expanded, and replaces the whole item;
8806 otherwise <&'string3'&> is used. During the expansion of <&'string2'&> the
8807 variable &$value$& contains the value that has been extracted. Afterwards, it
8808 is restored to any previous value it might have had.
8810 If {<&'string3'&>} is omitted, the item is replaced by an empty string if the
8811 key is not found. If {<&'string2'&>} is also omitted, the value that was
8812 extracted is used. Thus, for example, these two expansions are identical, and
8815 ${extract{gid}{uid=1984 gid=2001}}
8816 ${extract{gid}{uid=1984 gid=2001}{$value}}
8818 Instead of {<&'string3'&>} the word &"fail"& (not in curly brackets) can
8819 appear, for example:
8821 ${extract{Z}{A=... B=...}{$value} fail }
8823 This forces an expansion failure (see section &<<SECTforexpfai>>&);
8824 {<&'string2'&>} must be present for &"fail"& to be recognized.
8827 .vitem "&*${extract{*&<&'number'&>&*}{*&<&'separators'&>&*}&&&
8828 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
8829 .cindex "expansion" "extracting substrings by number"
8830 .cindex "&%extract%&" "substrings by number"
8831 The <&'number'&> argument must consist entirely of decimal digits,
8832 apart from leading and trailing white space, which is ignored.
8833 This is what distinguishes this form of &%extract%& from the previous kind. It
8834 behaves in the same way, except that, instead of extracting a named field, it
8835 extracts from <&'string1'&> the field whose number is given as the first
8836 argument. You can use &$value$& in <&'string2'&> or &`fail`& instead of
8837 <&'string3'&> as before.
8839 The fields in the string are separated by any one of the characters in the
8840 separator string. These may include space or tab characters.
8841 The first field is numbered one. If the number is negative, the fields are
8842 counted from the end of the string, with the rightmost one numbered -1. If the
8843 number given is zero, the entire string is returned. If the modulus of the
8844 number is greater than the number of fields in the string, the result is the
8845 expansion of <&'string3'&>, or the empty string if <&'string3'&> is not
8846 provided. For example:
8848 ${extract{2}{:}{x:42:99:& Mailer::/bin/bash}}
8852 ${extract{-4}{:}{x:42:99:& Mailer::/bin/bash}}
8854 yields &"99"&. Two successive separators mean that the field between them is
8855 empty (for example, the fifth field above).
8858 .vitem &*${filter{*&<&'string'&>&*}{*&<&'condition'&>&*}}*&
8859 .cindex "list" "selecting by condition"
8860 .cindex "expansion" "selecting from list by condition"
8862 After expansion, <&'string'&> is interpreted as a list, colon-separated by
8863 default, but the separator can be changed in the usual way. For each item
8864 in this list, its value is place in &$item$&, and then the condition is
8865 evaluated. If the condition is true, &$item$& is added to the output as an
8866 item in a new list; if the condition is false, the item is discarded. The
8867 separator used for the output list is the same as the one used for the
8868 input, but a separator setting is not included in the output. For example:
8870 ${filter{a:b:c}{!eq{$item}{b}}
8872 yields &`a:c`&. At the end of the expansion, the value of &$item$& is restored
8873 to what it was before. See also the &*map*& and &*reduce*& expansion items.
8876 .vitem &*${hash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
8877 .cindex "hash function" "textual"
8878 .cindex "expansion" "textual hash"
8879 This is a textual hashing function, and was the first to be implemented in
8880 early versions of Exim. In current releases, there are other hashing functions
8881 (numeric, MD5, and SHA-1), which are described below.
8883 The first two strings, after expansion, must be numbers. Call them <&'m'&> and
8884 <&'n'&>. If you are using fixed values for these numbers, that is, if
8885 <&'string1'&> and <&'string2'&> do not change when they are expanded, you can
8886 use the simpler operator notation that avoids some of the braces:
8888 ${hash_<n>_<m>:<string>}
8890 The second number is optional (in both notations). If <&'n'&> is greater than
8891 or equal to the length of the string, the expansion item returns the string.
8892 Otherwise it computes a new string of length <&'n'&> by applying a hashing
8893 function to the string. The new string consists of characters taken from the
8894 first <&'m'&> characters of the string
8896 abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQWRSTUVWXYZ0123456789
8898 If <&'m'&> is not present the value 26 is used, so that only lower case
8899 letters appear. For example:
8901 &`$hash{3}{monty}} `& yields &`jmg`&
8902 &`$hash{5}{monty}} `& yields &`monty`&
8903 &`$hash{4}{62}{monty python}}`& yields &`fbWx`&
8906 .vitem "&*$header_*&<&'header&~name'&>&*:*&&~or&~&&&
8907 &*$h_*&<&'header&~name'&>&*:*&" &&&
8908 "&*$bheader_*&<&'header&~name'&>&*:*&&~or&~&&&
8909 &*$bh_*&<&'header&~name'&>&*:*&" &&&
8910 "&*$rheader_*&<&'header&~name'&>&*:*&&~or&~&&&
8911 &*$rh_*&<&'header&~name'&>&*:*&"
8912 .cindex "expansion" "header insertion"
8913 .vindex "&$header_$&"
8914 .vindex "&$bheader_$&"
8915 .vindex "&$rheader_$&"
8916 .cindex "header lines" "in expansion strings"
8917 .cindex "header lines" "character sets"
8918 .cindex "header lines" "decoding"
8919 Substitute the contents of the named message header line, for example
8923 The newline that terminates a header line is not included in the expansion, but
8924 internal newlines (caused by splitting the header line over several physical
8925 lines) may be present.
8927 The difference between &%rheader%&, &%bheader%&, and &%header%& is in the way
8928 the data in the header line is interpreted.
8931 .cindex "white space" "in header lines"
8932 &%rheader%& gives the original &"raw"& content of the header line, with no
8933 processing at all, and without the removal of leading and trailing white space.
8936 .cindex "base64 encoding" "in header lines"
8937 &%bheader%& removes leading and trailing white space, and then decodes base64
8938 or quoted-printable MIME &"words"& within the header text, but does no
8939 character set translation. If decoding of what looks superficially like a MIME
8940 &"word"& fails, the raw string is returned. If decoding
8941 .cindex "binary zero" "in header line"
8942 produces a binary zero character, it is replaced by a question mark &-- this is
8943 what Exim does for binary zeros that are actually received in header lines.
8946 &%header%& tries to translate the string as decoded by &%bheader%& to a
8947 standard character set. This is an attempt to produce the same string as would
8948 be displayed on a user's MUA. If translation fails, the &%bheader%& string is
8949 returned. Translation is attempted only on operating systems that support the
8950 &[iconv()]& function. This is indicated by the compile-time macro HAVE_ICONV in
8951 a system Makefile or in &_Local/Makefile_&.
8954 In a filter file, the target character set for &%header%& can be specified by a
8955 command of the following form:
8957 headers charset "UTF-8"
8959 This command affects all references to &$h_$& (or &$header_$&) expansions in
8960 subsequently obeyed filter commands. In the absence of this command, the target
8961 character set in a filter is taken from the setting of the &%headers_charset%&
8962 option in the runtime configuration. The value of this option defaults to the
8963 value of HEADERS_CHARSET in &_Local/Makefile_&. The ultimate default is
8966 Header names follow the syntax of RFC 2822, which states that they may contain
8967 any printing characters except space and colon. Consequently, curly brackets
8968 &'do not'& terminate header names, and should not be used to enclose them as
8969 if they were variables. Attempting to do so causes a syntax error.
8971 Only header lines that are common to all copies of a message are visible to
8972 this mechanism. These are the original header lines that are received with the
8973 message, and any that are added by an ACL statement or by a system
8974 filter. Header lines that are added to a particular copy of a message by a
8975 router or transport are not accessible.
8977 For incoming SMTP messages, no header lines are visible in ACLs that are obeyed
8978 before the DATA ACL, because the header structure is not set up until the
8979 message is received. Header lines that are added in a RCPT ACL (for example)
8980 are saved until the message's incoming header lines are available, at which
8981 point they are added. When a DATA ACL is running, however, header lines added
8982 by earlier ACLs are visible.
8984 Upper case and lower case letters are synonymous in header names. If the
8985 following character is white space, the terminating colon may be omitted, but
8986 this is not recommended, because you may then forget it when it is needed. When
8987 white space terminates the header name, it is included in the expanded string.
8988 If the message does not contain the given header, the expansion item is
8989 replaced by an empty string. (See the &%def%& condition in section
8990 &<<SECTexpcond>>& for a means of testing for the existence of a header.)
8992 If there is more than one header with the same name, they are all concatenated
8993 to form the substitution string, up to a maximum length of 64K. Unless
8994 &%rheader%& is being used, leading and trailing white space is removed from
8995 each header before concatenation, and a completely empty header is ignored. A
8996 newline character is then inserted between non-empty headers, but there is no
8997 newline at the very end. For the &%header%& and &%bheader%& expansion, for
8998 those headers that contain lists of addresses, a comma is also inserted at the
8999 junctions between headers. This does not happen for the &%rheader%& expansion.
9002 .vitem &*${hmac{*&<&'hashname'&>&*}{*&<&'secret'&>&*}{*&<&'string'&>&*}}*&
9003 .cindex "expansion" "hmac hashing"
9005 This function uses cryptographic hashing (either MD5 or SHA-1) to convert a
9006 shared secret and some text into a message authentication code, as specified in
9007 RFC 2104. This differs from &`${md5:secret_text...}`& or
9008 &`${sha1:secret_text...}`& in that the hmac step adds a signature to the
9009 cryptographic hash, allowing for authentication that is not possible with MD5
9010 or SHA-1 alone. The hash name must expand to either &`md5`& or &`sha1`& at
9011 present. For example:
9013 ${hmac{md5}{somesecret}{$primary_hostname $tod_log}}
9015 For the hostname &'mail.example.com'& and time 2002-10-17 11:30:59, this
9018 dd97e3ba5d1a61b5006108f8c8252953
9020 As an example of how this might be used, you might put in the main part of
9021 an Exim configuration:
9023 SPAMSCAN_SECRET=cohgheeLei2thahw
9025 In a router or a transport you could then have:
9028 X-Spam-Scanned: ${primary_hostname} ${message_exim_id} \
9029 ${hmac{md5}{SPAMSCAN_SECRET}\
9030 {${primary_hostname},${message_exim_id},$h_message-id:}}
9032 Then given a message, you can check where it was scanned by looking at the
9033 &'X-Spam-Scanned:'& header line. If you know the secret, you can check that
9034 this header line is authentic by recomputing the authentication code from the
9035 host name, message ID and the &'Message-id:'& header line. This can be done
9036 using Exim's &%-be%& option, or by other means, for example by using the
9037 &'hmac_md5_hex()'& function in Perl.
9040 .vitem &*${if&~*&<&'condition'&>&*&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
9041 .cindex "expansion" "conditional"
9042 .cindex "&%if%&, expansion item"
9043 If <&'condition'&> is true, <&'string1'&> is expanded and replaces the whole
9044 item; otherwise <&'string2'&> is used. The available conditions are described
9045 in section &<<SECTexpcond>>& below. For example:
9047 ${if eq {$local_part}{postmaster} {yes}{no} }
9049 The second string need not be present; if it is not and the condition is not
9050 true, the item is replaced with nothing. Alternatively, the word &"fail"& may
9051 be present instead of the second string (without any curly brackets). In this
9052 case, the expansion is forced to fail if the condition is not true (see section
9053 &<<SECTforexpfai>>&).
9055 If both strings are omitted, the result is the string &`true`& if the condition
9056 is true, and the empty string if the condition is false. This makes it less
9057 cumbersome to write custom ACL and router conditions. For example, instead of
9059 condition = ${if >{$acl_m4}{3}{true}{false}}
9063 condition = ${if >{$acl_m4}{3}}
9066 .vitem &*${length{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
9067 .cindex "expansion" "string truncation"
9068 .cindex "&%length%& expansion item"
9069 The &%length%& item is used to extract the initial portion of a string. Both
9070 strings are expanded, and the first one must yield a number, <&'n'&>, say. If
9071 you are using a fixed value for the number, that is, if <&'string1'&> does not
9072 change when expanded, you can use the simpler operator notation that avoids
9075 ${length_<n>:<string>}
9077 The result of this item is either the first <&'n'&> characters or the whole
9078 of <&'string2'&>, whichever is the shorter. Do not confuse &%length%& with
9079 &%strlen%&, which gives the length of a string.
9082 .vitem "&*${lookup{*&<&'key'&>&*}&~*&<&'search&~type'&>&*&~&&&
9083 {*&<&'file'&>&*}&~{*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&"
9084 This is the first of one of two different types of lookup item, which are both
9085 described in the next item.
9087 .vitem "&*${lookup&~*&<&'search&~type'&>&*&~{*&<&'query'&>&*}&~&&&
9088 {*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&"
9089 .cindex "expansion" "lookup in"
9090 .cindex "file" "lookups"
9091 .cindex "lookup" "in expanded string"
9092 The two forms of lookup item specify data lookups in files and databases, as
9093 discussed in chapter &<<CHAPfdlookup>>&. The first form is used for single-key
9094 lookups, and the second is used for query-style lookups. The <&'key'&>,
9095 <&'file'&>, and <&'query'&> strings are expanded before use.
9097 If there is any white space in a lookup item which is part of a filter command,
9098 a retry or rewrite rule, a routing rule for the &(manualroute)& router, or any
9099 other place where white space is significant, the lookup item must be enclosed
9100 in double quotes. The use of data lookups in users' filter files may be locked
9101 out by the system administrator.
9104 If the lookup succeeds, <&'string1'&> is expanded and replaces the entire item.
9105 During its expansion, the variable &$value$& contains the data returned by the
9106 lookup. Afterwards it reverts to the value it had previously (at the outer
9107 level it is empty). If the lookup fails, <&'string2'&> is expanded and replaces
9108 the entire item. If {<&'string2'&>} is omitted, the replacement is the empty
9109 string on failure. If <&'string2'&> is provided, it can itself be a nested
9110 lookup, thus providing a mechanism for looking up a default value when the
9111 original lookup fails.
9113 If a nested lookup is used as part of <&'string1'&>, &$value$& contains the
9114 data for the outer lookup while the parameters of the second lookup are
9115 expanded, and also while <&'string2'&> of the second lookup is expanded, should
9116 the second lookup fail. Instead of {<&'string2'&>} the word &"fail"& can
9117 appear, and in this case, if the lookup fails, the entire expansion is forced
9118 to fail (see section &<<SECTforexpfai>>&). If both {<&'string1'&>} and
9119 {<&'string2'&>} are omitted, the result is the looked up value in the case of a
9120 successful lookup, and nothing in the case of failure.
9122 For single-key lookups, the string &"partial"& is permitted to precede the
9123 search type in order to do partial matching, and * or *@ may follow a search
9124 type to request default lookups if the key does not match (see sections
9125 &<<SECTdefaultvaluelookups>>& and &<<SECTpartiallookup>>& for details).
9127 .cindex "numerical variables (&$1$& &$2$& etc)" "in lookup expansion"
9128 If a partial search is used, the variables &$1$& and &$2$& contain the wild
9129 and non-wild parts of the key during the expansion of the replacement text.
9130 They return to their previous values at the end of the lookup item.
9132 This example looks up the postmaster alias in the conventional alias file:
9134 ${lookup {postmaster} lsearch {/etc/aliases} {$value}}
9136 This example uses NIS+ to look up the full name of the user corresponding to
9137 the local part of an address, forcing the expansion to fail if it is not found:
9139 ${lookup nisplus {[name=$local_part],passwd.org_dir:gcos} \
9144 .vitem &*${map{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
9145 .cindex "expansion" "list creation"
9147 After expansion, <&'string1'&> is interpreted as a list, colon-separated by
9148 default, but the separator can be changed in the usual way. For each item
9149 in this list, its value is place in &$item$&, and then <&'string2'&> is
9150 expanded and added to the output as an item in a new list. The separator used
9151 for the output list is the same as the one used for the input, but a separator
9152 setting is not included in the output. For example:
9154 ${map{a:b:c}{[$item]}} ${map{<- x-y-z}{($item)}}
9156 expands to &`[a]:[b]:[c] (x)-(y)-(z)`&. At the end of the expansion, the
9157 value of &$item$& is restored to what it was before. See also the &*filter*&
9158 and &*reduce*& expansion items.
9160 .vitem &*${nhash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
9161 .cindex "expansion" "numeric hash"
9162 .cindex "hash function" "numeric"
9163 The three strings are expanded; the first two must yield numbers. Call them
9164 <&'n'&> and <&'m'&>. If you are using fixed values for these numbers, that is,
9165 if <&'string1'&> and <&'string2'&> do not change when they are expanded, you
9166 can use the simpler operator notation that avoids some of the braces:
9168 ${nhash_<n>_<m>:<string>}
9170 The second number is optional (in both notations). If there is only one number,
9171 the result is a number in the range 0&--<&'n'&>-1. Otherwise, the string is
9172 processed by a div/mod hash function that returns two numbers, separated by a
9173 slash, in the ranges 0 to <&'n'&>-1 and 0 to <&'m'&>-1, respectively. For
9176 ${nhash{8}{64}{supercalifragilisticexpialidocious}}
9178 returns the string &"6/33"&.
9182 .vitem &*${perl{*&<&'subroutine'&>&*}{*&<&'arg'&>&*}{*&<&'arg'&>&*}...}*&
9183 .cindex "Perl" "use in expanded string"
9184 .cindex "expansion" "calling Perl from"
9185 This item is available only if Exim has been built to include an embedded Perl
9186 interpreter. The subroutine name and the arguments are first separately
9187 expanded, and then the Perl subroutine is called with those arguments. No
9188 additional arguments need be given; the maximum number permitted, including the
9189 name of the subroutine, is nine.
9191 The return value of the subroutine is inserted into the expanded string, unless
9192 the return value is &%undef%&. In that case, the expansion fails in the same
9193 way as an explicit &"fail"& on a lookup item. The return value is a scalar.
9194 Whatever you return is evaluated in a scalar context. For example, if you
9195 return the name of a Perl vector, the return value is the size of the vector,
9198 If the subroutine exits by calling Perl's &%die%& function, the expansion fails
9199 with the error message that was passed to &%die%&. More details of the embedded
9200 Perl facility are given in chapter &<<CHAPperl>>&.
9202 The &(redirect)& router has an option called &%forbid_filter_perl%& which locks
9203 out the use of this expansion item in filter files.
9206 .vitem &*${prvs{*&<&'address'&>&*}{*&<&'secret'&>&*}{*&<&'keynumber'&>&*}}*&
9207 .cindex "&%prvs%& expansion item"
9208 The first argument is a complete email address and the second is secret
9209 keystring. The third argument, specifying a key number, is optional. If absent,
9210 it defaults to 0. The result of the expansion is a prvs-signed email address,
9211 to be typically used with the &%return_path%& option on an &(smtp)& transport
9212 as part of a bounce address tag validation (BATV) scheme. For more discussion
9213 and an example, see section &<<SECTverifyPRVS>>&.
9215 .vitem "&*${prvscheck{*&<&'address'&>&*}{*&<&'secret'&>&*}&&&
9216 {*&<&'string'&>&*}}*&"
9217 .cindex "&%prvscheck%& expansion item"
9218 This expansion item is the complement of the &%prvs%& item. It is used for
9219 checking prvs-signed addresses. If the expansion of the first argument does not
9220 yield a syntactically valid prvs-signed address, the whole item expands to the
9221 empty string. When the first argument does expand to a syntactically valid
9222 prvs-signed address, the second argument is expanded, with the prvs-decoded
9223 version of the address and the key number extracted from the address in the
9224 variables &$prvscheck_address$& and &$prvscheck_keynum$&, respectively.
9226 These two variables can be used in the expansion of the second argument to
9227 retrieve the secret. The validity of the prvs-signed address is then checked
9228 against the secret. The result is stored in the variable &$prvscheck_result$&,
9229 which is empty for failure or &"1"& for success.
9231 The third argument is optional; if it is missing, it defaults to an empty
9232 string. This argument is now expanded. If the result is an empty string, the
9233 result of the expansion is the decoded version of the address. This is the case
9234 whether or not the signature was valid. Otherwise, the result of the expansion
9235 is the expansion of the third argument.
9237 All three variables can be used in the expansion of the third argument.
9238 However, once the expansion is complete, only &$prvscheck_result$& remains set.
9239 For more discussion and an example, see section &<<SECTverifyPRVS>>&.
9241 .vitem &*${readfile{*&<&'file&~name'&>&*}{*&<&'eol&~string'&>&*}}*&
9242 .cindex "expansion" "inserting an entire file"
9243 .cindex "file" "inserting into expansion"
9244 .cindex "&%readfile%& expansion item"
9245 The file name and end-of-line string are first expanded separately. The file is
9246 then read, and its contents replace the entire item. All newline characters in
9247 the file are replaced by the end-of-line string if it is present. Otherwise,
9248 newlines are left in the string.
9249 String expansion is not applied to the contents of the file. If you want this,
9250 you must wrap the item in an &%expand%& operator. If the file cannot be read,
9251 the string expansion fails.
9253 The &(redirect)& router has an option called &%forbid_filter_readfile%& which
9254 locks out the use of this expansion item in filter files.
9258 .vitem "&*${readsocket{*&<&'name'&>&*}{*&<&'request'&>&*}&&&
9259 {*&<&'timeout'&>&*}{*&<&'eol&~string'&>&*}{*&<&'fail&~string'&>&*}}*&"
9260 .cindex "expansion" "inserting from a socket"
9261 .cindex "socket, use of in expansion"
9262 .cindex "&%readsocket%& expansion item"
9263 This item inserts data from a Unix domain or Internet socket into the expanded
9264 string. The minimal way of using it uses just two arguments, as in these
9267 ${readsocket{/socket/name}{request string}}
9268 ${readsocket{inet:some.host:1234}{request string}}
9270 For a Unix domain socket, the first substring must be the path to the socket.
9271 For an Internet socket, the first substring must contain &`inet:`& followed by
9272 a host name or IP address, followed by a colon and a port, which can be a
9273 number or the name of a TCP port in &_/etc/services_&. An IP address may
9274 optionally be enclosed in square brackets. This is best for IPv6 addresses. For
9277 ${readsocket{inet:[::1]:1234}{request string}}
9279 Only a single host name may be given, but if looking it up yields more than
9280 one IP address, they are each tried in turn until a connection is made. For
9281 both kinds of socket, Exim makes a connection, writes the request string
9282 (unless it is an empty string) and reads from the socket until an end-of-file
9283 is read. A timeout of 5 seconds is applied. Additional, optional arguments
9284 extend what can be done. Firstly, you can vary the timeout. For example:
9286 ${readsocket{/socket/name}{request string}{3s}}
9288 A fourth argument allows you to change any newlines that are in the data
9289 that is read, in the same way as for &%readfile%& (see above). This example
9290 turns them into spaces:
9292 ${readsocket{inet:127.0.0.1:3294}{request string}{3s}{ }}
9294 As with all expansions, the substrings are expanded before the processing
9295 happens. Errors in these sub-expansions cause the expansion to fail. In
9296 addition, the following errors can occur:
9299 Failure to create a socket file descriptor;
9301 Failure to connect the socket;
9303 Failure to write the request string;
9305 Timeout on reading from the socket.
9308 By default, any of these errors causes the expansion to fail. However, if
9309 you supply a fifth substring, it is expanded and used when any of the above
9310 errors occurs. For example:
9312 ${readsocket{/socket/name}{request string}{3s}{\n}\
9315 You can test for the existence of a Unix domain socket by wrapping this
9316 expansion in &`${if exists`&, but there is a race condition between that test
9317 and the actual opening of the socket, so it is safer to use the fifth argument
9318 if you want to be absolutely sure of avoiding an expansion error for a
9319 non-existent Unix domain socket, or a failure to connect to an Internet socket.
9321 The &(redirect)& router has an option called &%forbid_filter_readsocket%& which
9322 locks out the use of this expansion item in filter files.
9325 .vitem &*${reduce{*&<&'string1'&>}{<&'string2'&>&*}{*&<&'string3'&>&*}}*&
9326 .cindex "expansion" "reducing a list to a scalar"
9327 .cindex "list" "reducing to a scalar"
9330 This operation reduces a list to a single, scalar string. After expansion,
9331 <&'string1'&> is interpreted as a list, colon-separated by default, but the
9332 separator can be changed in the usual way. Then <&'string2'&> is expanded and
9333 assigned to the &$value$& variable. After this, each item in the <&'string1'&>
9334 list is assigned to &$item$& in turn, and <&'string3'&> is expanded for each of
9335 them. The result of that expansion is assigned to &$value$& before the next
9336 iteration. When the end of the list is reached, the final value of &$value$& is
9337 added to the expansion output. The &*reduce*& expansion item can be used in a
9338 number of ways. For example, to add up a list of numbers:
9340 ${reduce {<, 1,2,3}{0}{${eval:$value+$item}}}
9342 The result of that expansion would be &`6`&. The maximum of a list of numbers
9345 ${reduce {3:0:9:4:6}{0}{${if >{$item}{$value}{$item}{$value}}}}
9347 At the end of a &*reduce*& expansion, the values of &$item$& and &$value$& are
9348 restored to what they were before. See also the &*filter*& and &*map*&
9351 .vitem &*$rheader_*&<&'header&~name'&>&*:*&&~or&~&*$rh_*&<&'header&~name'&>&*:*&
9352 This item inserts &"raw"& header lines. It is described with the &%header%&
9353 expansion item above.
9355 .vitem "&*${run{*&<&'command'&>&*&~*&<&'args'&>&*}{*&<&'string1'&>&*}&&&
9356 {*&<&'string2'&>&*}}*&"
9357 .cindex "expansion" "running a command"
9358 .cindex "&%run%& expansion item"
9359 The command and its arguments are first expanded separately, and then the
9360 command is run in a separate process, but under the same uid and gid. As in
9361 other command executions from Exim, a shell is not used by default. If you want
9362 a shell, you must explicitly code it.
9364 The standard input for the command exists, but is empty. The standard output
9365 and standard error are set to the same file descriptor.
9366 .cindex "return code" "from &%run%& expansion"
9368 If the command succeeds (gives a zero return code) <&'string1'&> is expanded
9369 and replaces the entire item; during this expansion, the standard output/error
9370 from the command is in the variable &$value$&. If the command fails,
9371 <&'string2'&>, if present, is expanded and used. Once again, during the
9372 expansion, the standard output/error from the command is in the variable
9375 If <&'string2'&> is absent, the result is empty. Alternatively, <&'string2'&>
9376 can be the word &"fail"& (not in braces) to force expansion failure if the
9377 command does not succeed. If both strings are omitted, the result is contents
9378 of the standard output/error on success, and nothing on failure.
9381 The return code from the command is put in the variable &$runrc$&, and this
9382 remains set afterwards, so in a filter file you can do things like this:
9384 if "${run{x y z}{}}$runrc" is 1 then ...
9385 elif $runrc is 2 then ...
9389 If execution of the command fails (for example, the command does not exist),
9390 the return code is 127 &-- the same code that shells use for non-existent
9393 &*Warning*&: In a router or transport, you cannot assume the order in which
9394 option values are expanded, except for those preconditions whose order of
9395 testing is documented. Therefore, you cannot reliably expect to set &$runrc$&
9396 by the expansion of one option, and use it in another.
9398 The &(redirect)& router has an option called &%forbid_filter_run%& which locks
9399 out the use of this expansion item in filter files.
9402 .vitem &*${sg{*&<&'subject'&>&*}{*&<&'regex'&>&*}{*&<&'replacement'&>&*}}*&
9403 .cindex "expansion" "string substitution"
9404 .cindex "&%sg%& expansion item"
9405 This item works like Perl's substitution operator (s) with the global (/g)
9406 option; hence its name. However, unlike the Perl equivalent, Exim does not
9407 modify the subject string; instead it returns the modified string for insertion
9408 into the overall expansion. The item takes three arguments: the subject string,
9409 a regular expression, and a substitution string. For example:
9411 ${sg{abcdefabcdef}{abc}{xyz}}
9413 yields &"xyzdefxyzdef"&. Because all three arguments are expanded before use,
9414 if any $ or \ characters are required in the regular expression or in the
9415 substitution string, they have to be escaped. For example:
9417 ${sg{abcdef}{^(...)(...)\$}{\$2\$1}}
9419 yields &"defabc"&, and
9421 ${sg{1=A 4=D 3=C}{\N(\d+)=\N}{K\$1=}}
9423 yields &"K1=A K4=D K3=C"&. Note the use of &`\N`& to protect the contents of
9424 the regular expression from string expansion.
9428 .vitem &*${substr{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
9429 .cindex "&%substr%& expansion item"
9430 .cindex "substring extraction"
9431 .cindex "expansion" "substring extraction"
9432 The three strings are expanded; the first two must yield numbers. Call them
9433 <&'n'&> and <&'m'&>. If you are using fixed values for these numbers, that is,
9434 if <&'string1'&> and <&'string2'&> do not change when they are expanded, you
9435 can use the simpler operator notation that avoids some of the braces:
9437 ${substr_<n>_<m>:<string>}
9439 The second number is optional (in both notations).
9440 If it is absent in the simpler format, the preceding underscore must also be
9443 The &%substr%& item can be used to extract more general substrings than
9444 &%length%&. The first number, <&'n'&>, is a starting offset, and <&'m'&> is the
9445 length required. For example
9447 ${substr{3}{2}{$local_part}}
9449 If the starting offset is greater than the string length the result is the
9450 null string; if the length plus starting offset is greater than the string
9451 length, the result is the right-hand part of the string, starting from the
9452 given offset. The first character in the string has offset zero.
9454 The &%substr%& expansion item can take negative offset values to count
9455 from the right-hand end of its operand. The last character is offset -1, the
9456 second-last is offset -2, and so on. Thus, for example,
9458 ${substr{-5}{2}{1234567}}
9460 yields &"34"&. If the absolute value of a negative offset is greater than the
9461 length of the string, the substring starts at the beginning of the string, and
9462 the length is reduced by the amount of overshoot. Thus, for example,
9464 ${substr{-5}{2}{12}}
9466 yields an empty string, but
9468 ${substr{-3}{2}{12}}
9472 When the second number is omitted from &%substr%&, the remainder of the string
9473 is taken if the offset is positive. If it is negative, all characters in the
9474 string preceding the offset point are taken. For example, an offset of -1 and
9475 no length, as in these semantically identical examples:
9478 ${substr{-1}{abcde}}
9480 yields all but the last character of the string, that is, &"abcd"&.
9484 .vitem "&*${tr{*&<&'subject'&>&*}{*&<&'characters'&>&*}&&&
9485 {*&<&'replacements'&>&*}}*&"
9486 .cindex "expansion" "character translation"
9487 .cindex "&%tr%& expansion item"
9488 This item does single-character translation on its subject string. The second
9489 argument is a list of characters to be translated in the subject string. Each
9490 matching character is replaced by the corresponding character from the
9491 replacement list. For example
9493 ${tr{abcdea}{ac}{13}}
9495 yields &`1b3de1`&. If there are duplicates in the second character string, the
9496 last occurrence is used. If the third string is shorter than the second, its
9497 last character is replicated. However, if it is empty, no translation takes
9503 .section "Expansion operators" "SECTexpop"
9504 .cindex "expansion" "operators"
9505 For expansion items that perform transformations on a single argument string,
9506 the &"operator"& notation is used because it is simpler and uses fewer braces.
9507 The substring is first expanded before the operation is applied to it. The
9508 following operations can be performed:
9511 .vitem &*${address:*&<&'string'&>&*}*&
9512 .cindex "expansion" "RFC 2822 address handling"
9513 .cindex "&%address%& expansion item"
9514 The string is interpreted as an RFC 2822 address, as it might appear in a
9515 header line, and the effective address is extracted from it. If the string does
9516 not parse successfully, the result is empty.
9519 .vitem &*${addresses:*&<&'string'&>&*}*&
9520 .cindex "expansion" "RFC 2822 address handling"
9521 .cindex "&%addresses%& expansion item"
9522 The string (after expansion) is interpreted as a list of addresses in RFC
9523 2822 format, such as can be found in a &'To:'& or &'Cc:'& header line. The
9524 operative address (&'local-part@domain'&) is extracted from each item, and the
9525 result of the expansion is a colon-separated list, with appropriate
9526 doubling of colons should any happen to be present in the email addresses.
9527 Syntactically invalid RFC2822 address items are omitted from the output.
9529 It is possible to specify a character other than colon for the output
9530 separator by starting the string with > followed by the new separator
9531 character. For example:
9533 ${addresses:>& Chief <ceo@up.stairs>, sec@base.ment (dogsbody)}
9535 expands to &`ceo@up.stairs&&sec@base.ment`&. Compare the &*address*& (singular)
9536 expansion item, which extracts the working address from a single RFC2822
9537 address. See the &*filter*&, &*map*&, and &*reduce*& items for ways of
9541 .vitem &*${base62:*&<&'digits'&>&*}*&
9542 .cindex "&%base62%& expansion item"
9543 .cindex "expansion" "conversion to base 62"
9544 The string must consist entirely of decimal digits. The number is converted to
9545 base 62 and output as a string of six characters, including leading zeros. In
9546 the few operating environments where Exim uses base 36 instead of base 62 for
9547 its message identifiers (because those systems do not have case-sensitive file
9548 names), base 36 is used by this operator, despite its name. &*Note*&: Just to
9549 be absolutely clear: this is &'not'& base64 encoding.
9551 .vitem &*${base62d:*&<&'base-62&~digits'&>&*}*&
9552 .cindex "&%base62d%& expansion item"
9553 .cindex "expansion" "conversion to base 62"
9554 The string must consist entirely of base-62 digits, or, in operating
9555 environments where Exim uses base 36 instead of base 62 for its message
9556 identifiers, base-36 digits. The number is converted to decimal and output as a
9559 .vitem &*${domain:*&<&'string'&>&*}*&
9560 .cindex "domain" "extraction"
9561 .cindex "expansion" "domain extraction"
9562 The string is interpreted as an RFC 2822 address and the domain is extracted
9563 from it. If the string does not parse successfully, the result is empty.
9566 .vitem &*${escape:*&<&'string'&>&*}*&
9567 .cindex "expansion" "escaping non-printing characters"
9568 .cindex "&%escape%& expansion item"
9569 If the string contains any non-printing characters, they are converted to
9570 escape sequences starting with a backslash. Whether characters with the most
9571 significant bit set (so-called &"8-bit characters"&) count as printing or not
9572 is controlled by the &%print_topbitchars%& option.
9575 .vitem &*${eval:*&<&'string'&>&*}*&&~and&~&*${eval10:*&<&'string'&>&*}*&
9576 .cindex "expansion" "expression evaluation"
9577 .cindex "expansion" "arithmetic expression"
9578 .cindex "&%eval%& expansion item"
9579 These items supports simple arithmetic and bitwise logical operations in
9580 expansion strings. The string (after expansion) must be a conventional
9581 arithmetic expression, but it is limited to basic arithmetic operators, bitwise
9582 logical operators, and parentheses. All operations are carried out using
9583 integer arithmetic. The operator priorities are as follows (the same as in the
9584 C programming language):
9586 .irow &'highest:'& "not (~), negate (-)"
9587 .irow "" "multiply (*), divide (/), remainder (%)"
9588 .irow "" "plus (+), minus (-)"
9589 .irow "" "shift-left (<<), shift-right (>>)"
9592 .irow &'lowest:'& "or (|)"
9594 Binary operators with the same priority are evaluated from left to right. White
9595 space is permitted before or after operators.
9597 For &%eval%&, numbers may be decimal, octal (starting with &"0"&) or
9598 hexadecimal (starting with &"0x"&). For &%eval10%&, all numbers are taken as
9599 decimal, even if they start with a leading zero; hexadecimal numbers are not
9600 permitted. This can be useful when processing numbers extracted from dates or
9601 times, which often do have leading zeros.
9603 A number may be followed by &"K"&, &"M"& or &"G"& to multiply it by 1024, 1024*1024
9605 respectively. Negative numbers are supported. The result of the computation is
9606 a decimal representation of the answer (without &"K"&, &"M"& or &"G"&). For example:
9609 &`${eval:1+1} `& yields 2
9610 &`${eval:1+2*3} `& yields 7
9611 &`${eval:(1+2)*3} `& yields 9
9612 &`${eval:2+42%5} `& yields 4
9613 &`${eval:0xc&5} `& yields 4
9614 &`${eval:0xc|5} `& yields 13
9615 &`${eval:0xc^5} `& yields 9
9616 &`${eval:0xc>>1} `& yields 6
9617 &`${eval:0xc<<1} `& yields 24
9618 &`${eval:~255&0x1234} `& yields 4608
9619 &`${eval:-(~255&0x1234)} `& yields -4608
9622 As a more realistic example, in an ACL you might have
9624 deny message = Too many bad recipients
9627 {>{$rcpt_count}{10}} \
9630 {$recipients_count} \
9631 {${eval:$rcpt_count/2}} \
9635 The condition is true if there have been more than 10 RCPT commands and
9636 fewer than half of them have resulted in a valid recipient.
9639 .vitem &*${expand:*&<&'string'&>&*}*&
9640 .cindex "expansion" "re-expansion of substring"
9641 The &%expand%& operator causes a string to be expanded for a second time. For
9644 ${expand:${lookup{$domain}dbm{/some/file}{$value}}}
9646 first looks up a string in a file while expanding the operand for &%expand%&,
9647 and then re-expands what it has found.
9650 .vitem &*${from_utf8:*&<&'string'&>&*}*&
9652 .cindex "UTF-8" "conversion from"
9653 .cindex "expansion" "UTF-8 conversion"
9654 .cindex "&%from_utf8%& expansion item"
9655 The world is slowly moving towards Unicode, although there are no standards for
9656 email yet. However, other applications (including some databases) are starting
9657 to store data in Unicode, using UTF-8 encoding. This operator converts from a
9658 UTF-8 string to an ISO-8859-1 string. UTF-8 code values greater than 255 are
9659 converted to underscores. The input must be a valid UTF-8 string. If it is not,
9660 the result is an undefined sequence of bytes.
9662 Unicode code points with values less than 256 are compatible with ASCII and
9663 ISO-8859-1 (also known as Latin-1).
9664 For example, character 169 is the copyright symbol in both cases, though the
9665 way it is encoded is different. In UTF-8, more than one byte is needed for
9666 characters with code values greater than 127, whereas ISO-8859-1 is a
9667 single-byte encoding (but thereby limited to 256 characters). This makes
9668 translation from UTF-8 to ISO-8859-1 straightforward.
9671 .vitem &*${hash_*&<&'n'&>&*_*&<&'m'&>&*:*&<&'string'&>&*}*&
9672 .cindex "hash function" "textual"
9673 .cindex "expansion" "textual hash"
9674 The &%hash%& operator is a simpler interface to the hashing function that can
9675 be used when the two parameters are fixed numbers (as opposed to strings that
9676 change when expanded). The effect is the same as
9678 ${hash{<n>}{<m>}{<string>}}
9680 See the description of the general &%hash%& item above for details. The
9681 abbreviation &%h%& can be used when &%hash%& is used as an operator.
9685 .vitem &*${hex2b64:*&<&'hexstring'&>&*}*&
9686 .cindex "base64 encoding" "conversion from hex"
9687 .cindex "expansion" "hex to base64"
9688 .cindex "&%hex2b64%& expansion item"
9689 This operator converts a hex string into one that is base64 encoded. This can
9690 be useful for processing the output of the MD5 and SHA-1 hashing functions.
9693 .vitem &*${lc:*&<&'string'&>&*}*&
9694 .cindex "case forcing in strings"
9695 .cindex "string" "case forcing"
9696 .cindex "lower casing"
9697 .cindex "expansion" "case forcing"
9698 .cindex "&%lc%& expansion item"
9699 This forces the letters in the string into lower-case, for example:
9704 .vitem &*${length_*&<&'number'&>&*:*&<&'string'&>&*}*&
9705 .cindex "expansion" "string truncation"
9706 .cindex "&%length%& expansion item"
9707 The &%length%& operator is a simpler interface to the &%length%& function that
9708 can be used when the parameter is a fixed number (as opposed to a string that
9709 changes when expanded). The effect is the same as
9711 ${length{<number>}{<string>}}
9713 See the description of the general &%length%& item above for details. Note that
9714 &%length%& is not the same as &%strlen%&. The abbreviation &%l%& can be used
9715 when &%length%& is used as an operator.
9718 .vitem &*${local_part:*&<&'string'&>&*}*&
9719 .cindex "expansion" "local part extraction"
9720 .cindex "&%local_part%& expansion item"
9721 The string is interpreted as an RFC 2822 address and the local part is
9722 extracted from it. If the string does not parse successfully, the result is
9726 .vitem &*${mask:*&<&'IP&~address'&>&*/*&<&'bit&~count'&>&*}*&
9727 .cindex "masked IP address"
9728 .cindex "IP address" "masking"
9729 .cindex "CIDR notation"
9730 .cindex "expansion" "IP address masking"
9731 .cindex "&%mask%& expansion item"
9732 If the form of the string to be operated on is not an IP address followed by a
9733 slash and an integer (that is, a network address in CIDR notation), the
9734 expansion fails. Otherwise, this operator converts the IP address to binary,
9735 masks off the least significant bits according to the bit count, and converts
9736 the result back to text, with mask appended. For example,
9738 ${mask:10.111.131.206/28}
9740 returns the string &"10.111.131.192/28"&. Since this operation is expected to
9741 be mostly used for looking up masked addresses in files, the result for an IPv6
9742 address uses dots to separate components instead of colons, because colon
9743 terminates a key string in lsearch files. So, for example,
9745 ${mask:3ffe:ffff:836f:0a00:000a:0800:200a:c031/99}
9749 3ffe.ffff.836f.0a00.000a.0800.2000.0000/99
9751 Letters in IPv6 addresses are always output in lower case.
9754 .vitem &*${md5:*&<&'string'&>&*}*&
9756 .cindex "expansion" "MD5 hash"
9757 .cindex "&%md5%& expansion item"
9758 The &%md5%& operator computes the MD5 hash value of the string, and returns it
9759 as a 32-digit hexadecimal number, in which any letters are in lower case.
9762 .vitem &*${nhash_*&<&'n'&>&*_*&<&'m'&>&*:*&<&'string'&>&*}*&
9763 .cindex "expansion" "numeric hash"
9764 .cindex "hash function" "numeric"
9765 The &%nhash%& operator is a simpler interface to the numeric hashing function
9766 that can be used when the two parameters are fixed numbers (as opposed to
9767 strings that change when expanded). The effect is the same as
9769 ${nhash{<n>}{<m>}{<string>}}
9771 See the description of the general &%nhash%& item above for details.
9774 .vitem &*${quote:*&<&'string'&>&*}*&
9775 .cindex "quoting" "in string expansions"
9776 .cindex "expansion" "quoting"
9777 .cindex "&%quote%& expansion item"
9778 The &%quote%& operator puts its argument into double quotes if it
9779 is an empty string or
9780 contains anything other than letters, digits, underscores, dots, and hyphens.
9781 Any occurrences of double quotes and backslashes are escaped with a backslash.
9782 Newlines and carriage returns are converted to &`\n`& and &`\r`&,
9783 respectively For example,
9791 The place where this is useful is when the argument is a substitution from a
9792 variable or a message header.
9794 .vitem &*${quote_local_part:*&<&'string'&>&*}*&
9795 .cindex "&%quote_local_part%& expansion item"
9796 This operator is like &%quote%&, except that it quotes the string only if
9797 required to do so by the rules of RFC 2822 for quoting local parts. For
9798 example, a plus sign would not cause quoting (but it would for &%quote%&).
9799 If you are creating a new email address from the contents of &$local_part$&
9800 (or any other unknown data), you should always use this operator.
9803 .vitem &*${quote_*&<&'lookup-type'&>&*:*&<&'string'&>&*}*&
9804 .cindex "quoting" "lookup-specific"
9805 This operator applies lookup-specific quoting rules to the string. Each
9806 query-style lookup type has its own quoting rules which are described with
9807 the lookups in chapter &<<CHAPfdlookup>>&. For example,
9809 ${quote_ldap:two * two}
9815 For single-key lookup types, no quoting is ever necessary and this operator
9816 yields an unchanged string.
9819 .vitem &*${randint:*&<&'n'&>&*}*&
9820 .cindex "random number"
9821 This operator returns a somewhat random number which is less than the
9822 supplied number and is at least 0. The quality of this randomness depends
9823 on how Exim was built; the values are not suitable for keying material.
9824 If Exim is linked against OpenSSL then RAND_pseudo_bytes() is used.
9825 If Exim is linked against GnuTLS then gnutls_rnd(GNUTLS_RND_NONCE) is used,
9826 for versions of GnuTLS with that function.
9827 Otherwise, the implementation may be arc4random(), random() seeded by
9828 srandomdev() or srandom(), or a custom implementation even weaker than
9832 .vitem &*${reverse_ip:*&<&'ipaddr'&>&*}*&
9833 .cindex "expansion" "IP address"
9834 This operator reverses an IP address; for IPv4 addresses, the result is in
9835 dotted-quad decimal form, while for IPv6 addreses the result is in
9836 dotted-nibble hexadecimal form. In both cases, this is the "natural" form
9837 for DNS. For example,
9839 ${reverse_ip:192.0.2.4}
9840 ${reverse_ip:2001:0db8:c42:9:1:abcd:192.0.2.3}
9845 3.0.2.0.0.0.0.c.d.c.b.a.1.0.0.0.9.0.0.0.2.4.c.0.8.b.d.0.1.0.0.2
9849 .vitem &*${rfc2047:*&<&'string'&>&*}*&
9850 .cindex "expansion" "RFC 2047"
9851 .cindex "RFC 2047" "expansion operator"
9852 .cindex "&%rfc2047%& expansion item"
9853 This operator encodes text according to the rules of RFC 2047. This is an
9854 encoding that is used in header lines to encode non-ASCII characters. It is
9855 assumed that the input string is in the encoding specified by the
9856 &%headers_charset%& option, which defaults to ISO-8859-1. If the string
9857 contains only characters in the range 33&--126, and no instances of the
9860 ? = ( ) < > @ , ; : \ " . [ ] _
9862 it is not modified. Otherwise, the result is the RFC 2047 encoding of the
9863 string, using as many &"encoded words"& as necessary to encode all the
9867 .vitem &*${rfc2047d:*&<&'string'&>&*}*&
9868 .cindex "expansion" "RFC 2047"
9869 .cindex "RFC 2047" "decoding"
9870 .cindex "&%rfc2047d%& expansion item"
9871 This operator decodes strings that are encoded as per RFC 2047. Binary zero
9872 bytes are replaced by question marks. Characters are converted into the
9873 character set defined by &%headers_charset%&. Overlong RFC 2047 &"words"& are
9874 not recognized unless &%check_rfc2047_length%& is set false.
9876 &*Note*&: If you use &%$header%&_&'xxx'&&*:*& (or &%$h%&_&'xxx'&&*:*&) to
9877 access a header line, RFC 2047 decoding is done automatically. You do not need
9878 to use this operator as well.
9882 .vitem &*${rxquote:*&<&'string'&>&*}*&
9883 .cindex "quoting" "in regular expressions"
9884 .cindex "regular expressions" "quoting"
9885 .cindex "&%rxquote%& expansion item"
9886 The &%rxquote%& operator inserts a backslash before any non-alphanumeric
9887 characters in its argument. This is useful when substituting the values of
9888 variables or headers inside regular expressions.
9891 .vitem &*${sha1:*&<&'string'&>&*}*&
9892 .cindex "SHA-1 hash"
9893 .cindex "expansion" "SHA-1 hashing"
9894 .cindex "&%sha2%& expansion item"
9895 The &%sha1%& operator computes the SHA-1 hash value of the string, and returns
9896 it as a 40-digit hexadecimal number, in which any letters are in upper case.
9899 .vitem &*${stat:*&<&'string'&>&*}*&
9900 .cindex "expansion" "statting a file"
9901 .cindex "file" "extracting characteristics"
9902 .cindex "&%stat%& expansion item"
9903 The string, after expansion, must be a file path. A call to the &[stat()]&
9904 function is made for this path. If &[stat()]& fails, an error occurs and the
9905 expansion fails. If it succeeds, the data from the stat replaces the item, as a
9906 series of <&'name'&>=<&'value'&> pairs, where the values are all numerical,
9907 except for the value of &"smode"&. The names are: &"mode"& (giving the mode as
9908 a 4-digit octal number), &"smode"& (giving the mode in symbolic format as a
9909 10-character string, as for the &'ls'& command), &"inode"&, &"device"&,
9910 &"links"&, &"uid"&, &"gid"&, &"size"&, &"atime"&, &"mtime"&, and &"ctime"&. You
9911 can extract individual fields using the &%extract%& expansion item.
9913 The use of the &%stat%& expansion in users' filter files can be locked out by
9914 the system administrator. &*Warning*&: The file size may be incorrect on 32-bit
9915 systems for files larger than 2GB.
9917 .vitem &*${str2b64:*&<&'string'&>&*}*&
9918 .cindex "expansion" "base64 encoding"
9919 .cindex "base64 encoding" "in string expansion"
9920 .cindex "&%str2b64%& expansion item"
9921 This operator converts a string into one that is base64 encoded.
9925 .vitem &*${strlen:*&<&'string'&>&*}*&
9926 .cindex "expansion" "string length"
9927 .cindex "string" "length in expansion"
9928 .cindex "&%strlen%& expansion item"
9929 The item is replace by the length of the expanded string, expressed as a
9930 decimal number. &*Note*&: Do not confuse &%strlen%& with &%length%&.
9933 .vitem &*${substr_*&<&'start'&>&*_*&<&'length'&>&*:*&<&'string'&>&*}*&
9934 .cindex "&%substr%& expansion item"
9935 .cindex "substring extraction"
9936 .cindex "expansion" "substring expansion"
9937 The &%substr%& operator is a simpler interface to the &%substr%& function that
9938 can be used when the two parameters are fixed numbers (as opposed to strings
9939 that change when expanded). The effect is the same as
9941 ${substr{<start>}{<length>}{<string>}}
9943 See the description of the general &%substr%& item above for details. The
9944 abbreviation &%s%& can be used when &%substr%& is used as an operator.
9946 .vitem &*${time_eval:*&<&'string'&>&*}*&
9947 .cindex "&%time_eval%& expansion item"
9948 .cindex "time interval" "decoding"
9949 This item converts an Exim time interval such as &`2d4h5m`& into a number of
9952 .vitem &*${time_interval:*&<&'string'&>&*}*&
9953 .cindex "&%time_interval%& expansion item"
9954 .cindex "time interval" "formatting"
9955 The argument (after sub-expansion) must be a sequence of decimal digits that
9956 represents an interval of time as a number of seconds. It is converted into a
9957 number of larger units and output in Exim's normal time format, for example,
9960 .vitem &*${uc:*&<&'string'&>&*}*&
9961 .cindex "case forcing in strings"
9962 .cindex "string" "case forcing"
9963 .cindex "upper casing"
9964 .cindex "expansion" "case forcing"
9965 .cindex "&%uc%& expansion item"
9966 This forces the letters in the string into upper-case.
9974 .section "Expansion conditions" "SECTexpcond"
9975 .scindex IIDexpcond "expansion" "conditions"
9976 The following conditions are available for testing by the &%${if%& construct
9977 while expanding strings:
9980 .vitem &*!*&<&'condition'&>
9981 .cindex "expansion" "negating a condition"
9982 .cindex "negation" "in expansion condition"
9983 Preceding any condition with an exclamation mark negates the result of the
9986 .vitem <&'symbolic&~operator'&>&~&*{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
9987 .cindex "numeric comparison"
9988 .cindex "expansion" "numeric comparison"
9989 There are a number of symbolic operators for doing numeric comparisons. They
9995 &`>= `& greater or equal
9997 &`<= `& less or equal
10001 ${if >{$message_size}{10M} ...
10003 Note that the general negation operator provides for inequality testing. The
10004 two strings must take the form of optionally signed decimal integers,
10005 optionally followed by one of the letters &"K"& or &"M"& (in either upper or
10006 lower case), signifying multiplication by 1024 or 1024*1024, respectively.
10007 As a special case, the numerical value of an empty string is taken as
10010 In all cases, a relative comparator OP is testing if <&'string1'&> OP
10011 <&'string2'&>; the above example is checking if &$message_size$& is larger than
10012 10M, not if 10M is larger than &$message_size$&.
10015 .vitem &*bool&~{*&<&'string'&>&*}*&
10016 .cindex "expansion" "boolean parsing"
10017 .cindex "&%bool%& expansion condition"
10018 This condition turns a string holding a true or false representation into
10019 a boolean state. It parses &"true"&, &"false"&, &"yes"& and &"no"&
10020 (case-insensitively); also positive integer numbers map to true if non-zero,
10022 An empty string is treated as false.
10023 Leading and trailing whitespace is ignored;
10024 thus a string consisting only of whitespace is false.
10025 All other string values will result in expansion failure.
10027 When combined with ACL variables, this expansion condition will let you
10028 make decisions in one place and act on those decisions in another place.
10031 ${if bool{$acl_m_privileged_sender} ...
10035 .vitem &*bool_lax&~{*&<&'string'&>&*}*&
10036 .cindex "expansion" "boolean parsing"
10037 .cindex "&%bool_lax%& expansion condition"
10038 Like &%bool%&, this condition turns a string into a boolean state. But
10039 where &%bool%& accepts a strict set of strings, &%bool_lax%& uses the same
10040 loose definition that the Router &%condition%& option uses. The empty string
10041 and the values &"false"&, &"no"& and &"0"& map to false, all others map to
10042 true. Leading and trailing whitespace is ignored.
10044 Note that where &"bool{00}"& is false, &"bool_lax{00}"& is true.
10046 .vitem &*crypteq&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10047 .cindex "expansion" "encrypted comparison"
10048 .cindex "encrypted strings, comparing"
10049 .cindex "&%crypteq%& expansion condition"
10050 This condition is included in the Exim binary if it is built to support any
10051 authentication mechanisms (see chapter &<<CHAPSMTPAUTH>>&). Otherwise, it is
10052 necessary to define SUPPORT_CRYPTEQ in &_Local/Makefile_& to get &%crypteq%&
10053 included in the binary.
10055 The &%crypteq%& condition has two arguments. The first is encrypted and
10056 compared against the second, which is already encrypted. The second string may
10057 be in the LDAP form for storing encrypted strings, which starts with the
10058 encryption type in curly brackets, followed by the data. If the second string
10059 does not begin with &"{"& it is assumed to be encrypted with &[crypt()]& or
10060 &[crypt16()]& (see below), since such strings cannot begin with &"{"&.
10061 Typically this will be a field from a password file. An example of an encrypted
10062 string in LDAP form is:
10064 {md5}CY9rzUYh03PK3k6DJie09g==
10066 If such a string appears directly in an expansion, the curly brackets have to
10067 be quoted, because they are part of the expansion syntax. For example:
10069 ${if crypteq {test}{\{md5\}CY9rzUYh03PK3k6DJie09g==}{yes}{no}}
10071 The following encryption types (whose names are matched case-independently) are
10076 .cindex "base64 encoding" "in encrypted password"
10077 &%{md5}%& computes the MD5 digest of the first string, and expresses this as
10078 printable characters to compare with the remainder of the second string. If the
10079 length of the comparison string is 24, Exim assumes that it is base64 encoded
10080 (as in the above example). If the length is 32, Exim assumes that it is a
10081 hexadecimal encoding of the MD5 digest. If the length not 24 or 32, the
10085 .cindex "SHA-1 hash"
10086 &%{sha1}%& computes the SHA-1 digest of the first string, and expresses this as
10087 printable characters to compare with the remainder of the second string. If the
10088 length of the comparison string is 28, Exim assumes that it is base64 encoded.
10089 If the length is 40, Exim assumes that it is a hexadecimal encoding of the
10090 SHA-1 digest. If the length is not 28 or 40, the comparison fails.
10093 .cindex "&[crypt()]&"
10094 &%{crypt}%& calls the &[crypt()]& function, which traditionally used to use
10095 only the first eight characters of the password. However, in modern operating
10096 systems this is no longer true, and in many cases the entire password is used,
10097 whatever its length.
10100 .cindex "&[crypt16()]&"
10101 &%{crypt16}%& calls the &[crypt16()]& function, which was originally created to
10102 use up to 16 characters of the password in some operating systems. Again, in
10103 modern operating systems, more characters may be used.
10105 Exim has its own version of &[crypt16()]&, which is just a double call to
10106 &[crypt()]&. For operating systems that have their own version, setting
10107 HAVE_CRYPT16 in &_Local/Makefile_& when building Exim causes it to use the
10108 operating system version instead of its own. This option is set by default in
10109 the OS-dependent &_Makefile_& for those operating systems that are known to
10110 support &[crypt16()]&.
10112 Some years after Exim's &[crypt16()]& was implemented, a user discovered that
10113 it was not using the same algorithm as some operating systems' versions. It
10114 turns out that as well as &[crypt16()]& there is a function called
10115 &[bigcrypt()]& in some operating systems. This may or may not use the same
10116 algorithm, and both of them may be different to Exim's built-in &[crypt16()]&.
10118 However, since there is now a move away from the traditional &[crypt()]&
10119 functions towards using SHA1 and other algorithms, tidying up this area of
10120 Exim is seen as very low priority.
10122 If you do not put a encryption type (in curly brackets) in a &%crypteq%&
10123 comparison, the default is usually either &`{crypt}`& or &`{crypt16}`&, as
10124 determined by the setting of DEFAULT_CRYPT in &_Local/Makefile_&. The default
10125 default is &`{crypt}`&. Whatever the default, you can always use either
10126 function by specifying it explicitly in curly brackets.
10128 .vitem &*def:*&<&'variable&~name'&>
10129 .cindex "expansion" "checking for empty variable"
10130 .cindex "&%def%& expansion condition"
10131 The &%def%& condition must be followed by the name of one of the expansion
10132 variables defined in section &<<SECTexpvar>>&. The condition is true if the
10133 variable does not contain the empty string. For example:
10135 ${if def:sender_ident {from $sender_ident}}
10137 Note that the variable name is given without a leading &%$%& character. If the
10138 variable does not exist, the expansion fails.
10140 .vitem "&*def:header_*&<&'header&~name'&>&*:*&&~&~or&~&&&
10141 &~&*def:h_*&<&'header&~name'&>&*:*&"
10142 .cindex "expansion" "checking header line existence"
10143 This condition is true if a message is being processed and the named header
10144 exists in the message. For example,
10146 ${if def:header_reply-to:{$h_reply-to:}{$h_from:}}
10148 &*Note*&: No &%$%& appears before &%header_%& or &%h_%& in the condition, and
10149 the header name must be terminated by a colon if white space does not follow.
10151 .vitem &*eq&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
10152 &*eqi&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10153 .cindex "string" "comparison"
10154 .cindex "expansion" "string comparison"
10155 .cindex "&%eq%& expansion condition"
10156 .cindex "&%eqi%& expansion condition"
10157 The two substrings are first expanded. The condition is true if the two
10158 resulting strings are identical. For &%eq%& the comparison includes the case of
10159 letters, whereas for &%eqi%& the comparison is case-independent.
10161 .vitem &*exists&~{*&<&'file&~name'&>&*}*&
10162 .cindex "expansion" "file existence test"
10163 .cindex "file" "existence test"
10164 .cindex "&%exists%&, expansion condition"
10165 The substring is first expanded and then interpreted as an absolute path. The
10166 condition is true if the named file (or directory) exists. The existence test
10167 is done by calling the &[stat()]& function. The use of the &%exists%& test in
10168 users' filter files may be locked out by the system administrator.
10170 .vitem &*first_delivery*&
10171 .cindex "delivery" "first"
10172 .cindex "first delivery"
10173 .cindex "expansion" "first delivery test"
10174 .cindex "&%first_delivery%& expansion condition"
10175 This condition, which has no data, is true during a message's first delivery
10176 attempt. It is false during any subsequent delivery attempts.
10179 .vitem "&*forall{*&<&'a list'&>&*}{*&<&'a condition'&>&*}*&" &&&
10180 "&*forany{*&<&'a list'&>&*}{*&<&'a condition'&>&*}*&"
10181 .cindex "list" "iterative conditions"
10182 .cindex "expansion" "&*forall*& condition"
10183 .cindex "expansion" "&*forany*& condition"
10185 These conditions iterate over a list. The first argument is expanded to form
10186 the list. By default, the list separator is a colon, but it can be changed by
10187 the normal method. The second argument is interpreted as a condition that is to
10188 be applied to each item in the list in turn. During the interpretation of the
10189 condition, the current list item is placed in a variable called &$item$&.
10191 For &*forany*&, interpretation stops if the condition is true for any item, and
10192 the result of the whole condition is true. If the condition is false for all
10193 items in the list, the overall condition is false.
10195 For &*forall*&, interpretation stops if the condition is false for any item,
10196 and the result of the whole condition is false. If the condition is true for
10197 all items in the list, the overall condition is true.
10199 Note that negation of &*forany*& means that the condition must be false for all
10200 items for the overall condition to succeed, and negation of &*forall*& means
10201 that the condition must be false for at least one item. In this example, the
10202 list separator is changed to a comma:
10204 ${if forany{<, $recipients}{match{$item}{^user3@}}{yes}{no}}
10206 The value of &$item$& is saved and restored while &*forany*& or &*forall*& is
10207 being processed, to enable these expansion items to be nested.
10210 .vitem &*ge&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
10211 &*gei&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10212 .cindex "string" "comparison"
10213 .cindex "expansion" "string comparison"
10214 .cindex "&%ge%& expansion condition"
10215 .cindex "&%gei%& expansion condition"
10216 The two substrings are first expanded. The condition is true if the first
10217 string is lexically greater than or equal to the second string. For &%ge%& the
10218 comparison includes the case of letters, whereas for &%gei%& the comparison is
10221 .vitem &*gt&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
10222 &*gti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10223 .cindex "string" "comparison"
10224 .cindex "expansion" "string comparison"
10225 .cindex "&%gt%& expansion condition"
10226 .cindex "&%gti%& expansion condition"
10227 The two substrings are first expanded. The condition is true if the first
10228 string is lexically greater than the second string. For &%gt%& the comparison
10229 includes the case of letters, whereas for &%gti%& the comparison is
10232 .vitem &*inlist&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
10233 &*inlisti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10234 .cindex "string" "comparison"
10235 .cindex "list" "iterative conditions"
10236 Both strings are expanded; the second string is treated as a list of simple
10237 strings; if the first string is a member of the second, then the condition
10240 These are simpler to use versions of the more powerful &*forany*& condition.
10241 Examples, and the &*forany*& equivalents:
10243 ${if inlist{needle}{foo:needle:bar}}
10244 ${if forany{foo:needle:bar}{eq{$item}{needle}}}
10245 ${if inlisti{Needle}{fOo:NeeDLE:bAr}}
10246 ${if forany{fOo:NeeDLE:bAr}{eqi{$item}{Needle}}}
10249 .vitem &*isip&~{*&<&'string'&>&*}*& &&&
10250 &*isip4&~{*&<&'string'&>&*}*& &&&
10251 &*isip6&~{*&<&'string'&>&*}*&
10252 .cindex "IP address" "testing string format"
10253 .cindex "string" "testing for IP address"
10254 .cindex "&%isip%& expansion condition"
10255 .cindex "&%isip4%& expansion condition"
10256 .cindex "&%isip6%& expansion condition"
10257 The substring is first expanded, and then tested to see if it has the form of
10258 an IP address. Both IPv4 and IPv6 addresses are valid for &%isip%&, whereas
10259 &%isip4%& and &%isip6%& test specifically for IPv4 or IPv6 addresses.
10261 For an IPv4 address, the test is for four dot-separated components, each of
10262 which consists of from one to three digits. For an IPv6 address, up to eight
10263 colon-separated components are permitted, each containing from one to four
10264 hexadecimal digits. There may be fewer than eight components if an empty
10265 component (adjacent colons) is present. Only one empty component is permitted.
10267 &*Note*&: The checks are just on the form of the address; actual numerical
10268 values are not considered. Thus, for example, 999.999.999.999 passes the IPv4
10269 check. The main use of these tests is to distinguish between IP addresses and
10270 host names, or between IPv4 and IPv6 addresses. For example, you could use
10272 ${if isip4{$sender_host_address}...
10274 to test which IP version an incoming SMTP connection is using.
10276 .vitem &*ldapauth&~{*&<&'ldap&~query'&>&*}*&
10277 .cindex "LDAP" "use for authentication"
10278 .cindex "expansion" "LDAP authentication test"
10279 .cindex "&%ldapauth%& expansion condition"
10280 This condition supports user authentication using LDAP. See section
10281 &<<SECTldap>>& for details of how to use LDAP in lookups and the syntax of
10282 queries. For this use, the query must contain a user name and password. The
10283 query itself is not used, and can be empty. The condition is true if the
10284 password is not empty, and the user name and password are accepted by the LDAP
10285 server. An empty password is rejected without calling LDAP because LDAP binds
10286 with an empty password are considered anonymous regardless of the username, and
10287 will succeed in most configurations. See chapter &<<CHAPSMTPAUTH>>& for details
10288 of SMTP authentication, and chapter &<<CHAPplaintext>>& for an example of how
10292 .vitem &*le&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
10293 &*lei&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10294 .cindex "string" "comparison"
10295 .cindex "expansion" "string comparison"
10296 .cindex "&%le%& expansion condition"
10297 .cindex "&%lei%& expansion condition"
10298 The two substrings are first expanded. The condition is true if the first
10299 string is lexically less than or equal to the second string. For &%le%& the
10300 comparison includes the case of letters, whereas for &%lei%& the comparison is
10303 .vitem &*lt&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
10304 &*lti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10305 .cindex "string" "comparison"
10306 .cindex "expansion" "string comparison"
10307 .cindex "&%lt%& expansion condition"
10308 .cindex "&%lti%& expansion condition"
10309 The two substrings are first expanded. The condition is true if the first
10310 string is lexically less than the second string. For &%lt%& the comparison
10311 includes the case of letters, whereas for &%lti%& the comparison is
10315 .vitem &*match&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10316 .cindex "expansion" "regular expression comparison"
10317 .cindex "regular expressions" "match in expanded string"
10318 .cindex "&%match%& expansion condition"
10319 The two substrings are first expanded. The second is then treated as a regular
10320 expression and applied to the first. Because of the pre-expansion, if the
10321 regular expression contains dollar, or backslash characters, they must be
10322 escaped. Care must also be taken if the regular expression contains braces
10323 (curly brackets). A closing brace must be escaped so that it is not taken as a
10324 premature termination of <&'string2'&>. The easiest approach is to use the
10325 &`\N`& feature to disable expansion of the regular expression.
10328 ${if match {$local_part}{\N^\d{3}\N} ...
10330 If the whole expansion string is in double quotes, further escaping of
10331 backslashes is also required.
10333 The condition is true if the regular expression match succeeds.
10334 The regular expression is not required to begin with a circumflex
10335 metacharacter, but if there is no circumflex, the expression is not anchored,
10336 and it may match anywhere in the subject, not just at the start. If you want
10337 the pattern to match at the end of the subject, you must include the &`$`&
10338 metacharacter at an appropriate point.
10340 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%if%& expansion"
10341 At the start of an &%if%& expansion the values of the numeric variable
10342 substitutions &$1$& etc. are remembered. Obeying a &%match%& condition that
10343 succeeds causes them to be reset to the substrings of that condition and they
10344 will have these values during the expansion of the success string. At the end
10345 of the &%if%& expansion, the previous values are restored. After testing a
10346 combination of conditions using &%or%&, the subsequent values of the numeric
10347 variables are those of the condition that succeeded.
10349 .vitem &*match_address&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10350 .cindex "&%match_address%& expansion condition"
10351 See &*match_local_part*&.
10353 .vitem &*match_domain&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10354 .cindex "&%match_domain%& expansion condition"
10355 See &*match_local_part*&.
10357 .vitem &*match_ip&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10358 .cindex "&%match_ip%& expansion condition"
10359 This condition matches an IP address to a list of IP address patterns. It must
10360 be followed by two argument strings. The first (after expansion) must be an IP
10361 address or an empty string. The second (not expanded) is a restricted host
10362 list that can match only an IP address, not a host name. For example:
10364 ${if match_ip{$sender_host_address}{1.2.3.4:5.6.7.8}{...}{...}}
10366 The specific types of host list item that are permitted in the list are:
10369 An IP address, optionally with a CIDR mask.
10371 A single asterisk, which matches any IP address.
10373 An empty item, which matches only if the IP address is empty. This could be
10374 useful for testing for a locally submitted message or one from specific hosts
10375 in a single test such as
10376 . ==== As this is a nested list, any displays it contains must be indented
10377 . ==== as otherwise they are too far to the left. This comment applies to
10378 . ==== the use of xmlto plus fop. There's no problem when formatting with
10379 . ==== sdop, with or without the extra indent.
10381 ${if match_ip{$sender_host_address}{:4.3.2.1:...}{...}{...}}
10383 where the first item in the list is the empty string.
10385 The item @[] matches any of the local host's interface addresses.
10387 Single-key lookups are assumed to be like &"net-"& style lookups in host lists,
10388 even if &`net-`& is not specified. There is never any attempt to turn the IP
10389 address into a host name. The most common type of linear search for
10390 &*match_ip*& is likely to be &*iplsearch*&, in which the file can contain CIDR
10391 masks. For example:
10393 ${if match_ip{$sender_host_address}{iplsearch;/some/file}...
10395 It is of course possible to use other kinds of lookup, and in such a case, you
10396 do need to specify the &`net-`& prefix if you want to specify a specific
10397 address mask, for example:
10399 ${if match_ip{$sender_host_address}{net24-dbm;/some/file}...
10401 However, unless you are combining a &%match_ip%& condition with others, it is
10402 just as easy to use the fact that a lookup is itself a condition, and write:
10404 ${lookup{${mask:$sender_host_address/24}}dbm{/a/file}...
10408 Note that <&'string2'&> is not itself subject to string expansion, unless
10409 Exim was built with the EXPAND_LISTMATCH_RHS option.
10411 Consult section &<<SECThoslispatip>>& for further details of these patterns.
10413 .vitem &*match_local_part&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10414 .cindex "domain list" "in expansion condition"
10415 .cindex "address list" "in expansion condition"
10416 .cindex "local part" "list, in expansion condition"
10417 .cindex "&%match_local_part%& expansion condition"
10418 This condition, together with &%match_address%& and &%match_domain%&, make it
10419 possible to test domain, address, and local part lists within expansions. Each
10420 condition requires two arguments: an item and a list to match. A trivial
10423 ${if match_domain{a.b.c}{x.y.z:a.b.c:p.q.r}{yes}{no}}
10425 In each case, the second argument may contain any of the allowable items for a
10426 list of the appropriate type. Also, because the second argument (after
10427 expansion) is a standard form of list, it is possible to refer to a named list.
10428 Thus, you can use conditions like this:
10430 ${if match_domain{$domain}{+local_domains}{...
10432 .cindex "&`+caseful`&"
10433 For address lists, the matching starts off caselessly, but the &`+caseful`&
10434 item can be used, as in all address lists, to cause subsequent items to
10435 have their local parts matched casefully. Domains are always matched
10438 Note that <&'string2'&> is not itself subject to string expansion, unless
10439 Exim was built with the EXPAND_LISTMATCH_RHS option.
10441 &*Note*&: Host lists are &'not'& supported in this way. This is because
10442 hosts have two identities: a name and an IP address, and it is not clear
10443 how to specify cleanly how such a test would work. However, IP addresses can be
10444 matched using &%match_ip%&.
10446 .vitem &*pam&~{*&<&'string1'&>&*:*&<&'string2'&>&*:...}*&
10447 .cindex "PAM authentication"
10448 .cindex "AUTH" "with PAM"
10449 .cindex "Solaris" "PAM support"
10450 .cindex "expansion" "PAM authentication test"
10451 .cindex "&%pam%& expansion condition"
10452 &'Pluggable Authentication Modules'&
10453 (&url(http://www.kernel.org/pub/linux/libs/pam/)) are a facility that is
10454 available in the latest releases of Solaris and in some GNU/Linux
10455 distributions. The Exim support, which is intended for use in conjunction with
10456 the SMTP AUTH command, is available only if Exim is compiled with
10460 in &_Local/Makefile_&. You probably need to add &%-lpam%& to EXTRALIBS, and
10461 in some releases of GNU/Linux &%-ldl%& is also needed.
10463 The argument string is first expanded, and the result must be a
10464 colon-separated list of strings. Leading and trailing white space is ignored.
10465 The PAM module is initialized with the service name &"exim"& and the user name
10466 taken from the first item in the colon-separated data string (<&'string1'&>).
10467 The remaining items in the data string are passed over in response to requests
10468 from the authentication function. In the simple case there will only be one
10469 request, for a password, so the data consists of just two strings.
10471 There can be problems if any of the strings are permitted to contain colon
10472 characters. In the usual way, these have to be doubled to avoid being taken as
10473 separators. If the data is being inserted from a variable, the &%sg%& expansion
10474 item can be used to double any existing colons. For example, the configuration
10475 of a LOGIN authenticator might contain this setting:
10477 server_condition = ${if pam{$auth1:${sg{$auth2}{:}{::}}}}
10479 For a PLAIN authenticator you could use:
10481 server_condition = ${if pam{$auth2:${sg{$auth3}{:}{::}}}}
10483 In some operating systems, PAM authentication can be done only from a process
10484 running as root. Since Exim is running as the Exim user when receiving
10485 messages, this means that PAM cannot be used directly in those systems.
10486 A patched version of the &'pam_unix'& module that comes with the
10487 Linux PAM package is available from &url(http://www.e-admin.de/pam_exim/).
10488 The patched module allows one special uid/gid combination, in addition to root,
10489 to authenticate. If you build the patched module to allow the Exim user and
10490 group, PAM can then be used from an Exim authenticator.
10493 .vitem &*pwcheck&~{*&<&'string1'&>&*:*&<&'string2'&>&*}*&
10494 .cindex "&'pwcheck'& daemon"
10496 .cindex "expansion" "&'pwcheck'& authentication test"
10497 .cindex "&%pwcheck%& expansion condition"
10498 This condition supports user authentication using the Cyrus &'pwcheck'& daemon.
10499 This is one way of making it possible for passwords to be checked by a process
10500 that is not running as root. &*Note*&: The use of &'pwcheck'& is now
10501 deprecated. Its replacement is &'saslauthd'& (see below).
10503 The pwcheck support is not included in Exim by default. You need to specify
10504 the location of the pwcheck daemon's socket in &_Local/Makefile_& before
10505 building Exim. For example:
10507 CYRUS_PWCHECK_SOCKET=/var/pwcheck/pwcheck
10509 You do not need to install the full Cyrus software suite in order to use
10510 the pwcheck daemon. You can compile and install just the daemon alone
10511 from the Cyrus SASL library. Ensure that &'exim'& is the only user that has
10512 access to the &_/var/pwcheck_& directory.
10514 The &%pwcheck%& condition takes one argument, which must be the user name and
10515 password, separated by a colon. For example, in a LOGIN authenticator
10516 configuration, you might have this:
10518 server_condition = ${if pwcheck{$auth1:$auth2}}
10520 Again, for a PLAIN authenticator configuration, this would be:
10522 server_condition = ${if pwcheck{$auth2:$auth3}}
10524 .vitem &*queue_running*&
10525 .cindex "queue runner" "detecting when delivering from"
10526 .cindex "expansion" "queue runner test"
10527 .cindex "&%queue_running%& expansion condition"
10528 This condition, which has no data, is true during delivery attempts that are
10529 initiated by queue runner processes, and false otherwise.
10532 .vitem &*radius&~{*&<&'authentication&~string'&>&*}*&
10534 .cindex "expansion" "Radius authentication"
10535 .cindex "&%radius%& expansion condition"
10536 Radius authentication (RFC 2865) is supported in a similar way to PAM. You must
10537 set RADIUS_CONFIG_FILE in &_Local/Makefile_& to specify the location of
10538 the Radius client configuration file in order to build Exim with Radius
10541 With just that one setting, Exim expects to be linked with the &%radiusclient%&
10542 library, using the original API. If you are using release 0.4.0 or later of
10543 this library, you need to set
10545 RADIUS_LIB_TYPE=RADIUSCLIENTNEW
10547 in &_Local/Makefile_& when building Exim. You can also link Exim with the
10548 &%libradius%& library that comes with FreeBSD. To do this, set
10550 RADIUS_LIB_TYPE=RADLIB
10552 in &_Local/Makefile_&, in addition to setting RADIUS_CONFIGURE_FILE.
10553 You may also have to supply a suitable setting in EXTRALIBS so that the
10554 Radius library can be found when Exim is linked.
10556 The string specified by RADIUS_CONFIG_FILE is expanded and passed to the
10557 Radius client library, which calls the Radius server. The condition is true if
10558 the authentication is successful. For example:
10560 server_condition = ${if radius{<arguments>}}
10564 .vitem "&*saslauthd&~{{*&<&'user'&>&*}{*&<&'password'&>&*}&&&
10565 {*&<&'service'&>&*}{*&<&'realm'&>&*}}*&"
10566 .cindex "&'saslauthd'& daemon"
10568 .cindex "expansion" "&'saslauthd'& authentication test"
10569 .cindex "&%saslauthd%& expansion condition"
10570 This condition supports user authentication using the Cyrus &'saslauthd'&
10571 daemon. This replaces the older &'pwcheck'& daemon, which is now deprecated.
10572 Using this daemon is one way of making it possible for passwords to be checked
10573 by a process that is not running as root.
10575 The saslauthd support is not included in Exim by default. You need to specify
10576 the location of the saslauthd daemon's socket in &_Local/Makefile_& before
10577 building Exim. For example:
10579 CYRUS_SASLAUTHD_SOCKET=/var/state/saslauthd/mux
10581 You do not need to install the full Cyrus software suite in order to use
10582 the saslauthd daemon. You can compile and install just the daemon alone
10583 from the Cyrus SASL library.
10585 Up to four arguments can be supplied to the &%saslauthd%& condition, but only
10586 two are mandatory. For example:
10588 server_condition = ${if saslauthd{{$auth1}{$auth2}}}
10590 The service and the realm are optional (which is why the arguments are enclosed
10591 in their own set of braces). For details of the meaning of the service and
10592 realm, and how to run the daemon, consult the Cyrus documentation.
10597 .section "Combining expansion conditions" "SECID84"
10598 .cindex "expansion" "combining conditions"
10599 Several conditions can be tested at once by combining them using the &%and%&
10600 and &%or%& combination conditions. Note that &%and%& and &%or%& are complete
10601 conditions on their own, and precede their lists of sub-conditions. Each
10602 sub-condition must be enclosed in braces within the overall braces that contain
10603 the list. No repetition of &%if%& is used.
10607 .vitem &*or&~{{*&<&'cond1'&>&*}{*&<&'cond2'&>&*}...}*&
10608 .cindex "&""or""& expansion condition"
10609 .cindex "expansion" "&""or""& of conditions"
10610 The sub-conditions are evaluated from left to right. The condition is true if
10611 any one of the sub-conditions is true.
10614 ${if or {{eq{$local_part}{spqr}}{eq{$domain}{testing.com}}}...
10616 When a true sub-condition is found, the following ones are parsed but not
10617 evaluated. If there are several &"match"& sub-conditions the values of the
10618 numeric variables afterwards are taken from the first one that succeeds.
10620 .vitem &*and&~{{*&<&'cond1'&>&*}{*&<&'cond2'&>&*}...}*&
10621 .cindex "&""and""& expansion condition"
10622 .cindex "expansion" "&""and""& of conditions"
10623 The sub-conditions are evaluated from left to right. The condition is true if
10624 all of the sub-conditions are true. If there are several &"match"&
10625 sub-conditions, the values of the numeric variables afterwards are taken from
10626 the last one. When a false sub-condition is found, the following ones are
10627 parsed but not evaluated.
10629 .ecindex IIDexpcond
10634 .section "Expansion variables" "SECTexpvar"
10635 .cindex "expansion" "variables, list of"
10636 This section contains an alphabetical list of all the expansion variables. Some
10637 of them are available only when Exim is compiled with specific options such as
10638 support for TLS or the content scanning extension.
10641 .vitem "&$0$&, &$1$&, etc"
10642 .cindex "numerical variables (&$1$& &$2$& etc)"
10643 When a &%match%& expansion condition succeeds, these variables contain the
10644 captured substrings identified by the regular expression during subsequent
10645 processing of the success string of the containing &%if%& expansion item.
10646 However, they do not retain their values afterwards; in fact, their previous
10647 values are restored at the end of processing an &%if%& item. The numerical
10648 variables may also be set externally by some other matching process which
10649 precedes the expansion of the string. For example, the commands available in
10650 Exim filter files include an &%if%& command with its own regular expression
10651 matching condition.
10653 .vitem "&$acl_c...$&"
10654 Values can be placed in these variables by the &%set%& modifier in an ACL. They
10655 can be given any name that starts with &$acl_c$& and is at least six characters
10656 long, but the sixth character must be either a digit or an underscore. For
10657 example: &$acl_c5$&, &$acl_c_mycount$&. The values of the &$acl_c...$&
10658 variables persist throughout the lifetime of an SMTP connection. They can be
10659 used to pass information between ACLs and between different invocations of the
10660 same ACL. When a message is received, the values of these variables are saved
10661 with the message, and can be accessed by filters, routers, and transports
10662 during subsequent delivery.
10664 .vitem "&$acl_m...$&"
10665 These variables are like the &$acl_c...$& variables, except that their values
10666 are reset after a message has been received. Thus, if several messages are
10667 received in one SMTP connection, &$acl_m...$& values are not passed on from one
10668 message to the next, as &$acl_c...$& values are. The &$acl_m...$& variables are
10669 also reset by MAIL, RSET, EHLO, HELO, and after starting a TLS session. When a
10670 message is received, the values of these variables are saved with the message,
10671 and can be accessed by filters, routers, and transports during subsequent
10674 .vitem &$acl_verify_message$&
10675 .vindex "&$acl_verify_message$&"
10676 After an address verification has failed, this variable contains the failure
10677 message. It retains its value for use in subsequent modifiers. The message can
10678 be preserved by coding like this:
10680 warn !verify = sender
10681 set acl_m0 = $acl_verify_message
10683 You can use &$acl_verify_message$& during the expansion of the &%message%& or
10684 &%log_message%& modifiers, to include information about the verification
10687 .vitem &$address_data$&
10688 .vindex "&$address_data$&"
10689 This variable is set by means of the &%address_data%& option in routers. The
10690 value then remains with the address while it is processed by subsequent routers
10691 and eventually a transport. If the transport is handling multiple addresses,
10692 the value from the first address is used. See chapter &<<CHAProutergeneric>>&
10693 for more details. &*Note*&: The contents of &$address_data$& are visible in
10696 If &$address_data$& is set when the routers are called from an ACL to verify
10697 a recipient address, the final value is still in the variable for subsequent
10698 conditions and modifiers of the ACL statement. If routing the address caused it
10699 to be redirected to just one address, the child address is also routed as part
10700 of the verification, and in this case the final value of &$address_data$& is
10701 from the child's routing.
10703 If &$address_data$& is set when the routers are called from an ACL to verify a
10704 sender address, the final value is also preserved, but this time in
10705 &$sender_address_data$&, to distinguish it from data from a recipient
10708 In both cases (recipient and sender verification), the value does not persist
10709 after the end of the current ACL statement. If you want to preserve
10710 these values for longer, you can save them in ACL variables.
10712 .vitem &$address_file$&
10713 .vindex "&$address_file$&"
10714 When, as a result of aliasing, forwarding, or filtering, a message is directed
10715 to a specific file, this variable holds the name of the file when the transport
10716 is running. At other times, the variable is empty. For example, using the
10717 default configuration, if user &%r2d2%& has a &_.forward_& file containing
10719 /home/r2d2/savemail
10721 then when the &(address_file)& transport is running, &$address_file$&
10722 contains the text string &`/home/r2d2/savemail`&.
10723 .cindex "Sieve filter" "value of &$address_file$&"
10724 For Sieve filters, the value may be &"inbox"& or a relative folder name. It is
10725 then up to the transport configuration to generate an appropriate absolute path
10726 to the relevant file.
10728 .vitem &$address_pipe$&
10729 .vindex "&$address_pipe$&"
10730 When, as a result of aliasing or forwarding, a message is directed to a pipe,
10731 this variable holds the pipe command when the transport is running.
10733 .vitem "&$auth1$& &-- &$auth3$&"
10734 .vindex "&$auth1$&, &$auth2$&, etc"
10735 These variables are used in SMTP authenticators (see chapters
10736 &<<CHAPplaintext>>&&--&<<CHAPspa>>&). Elsewhere, they are empty.
10738 .vitem &$authenticated_id$&
10739 .cindex "authentication" "id"
10740 .vindex "&$authenticated_id$&"
10741 When a server successfully authenticates a client it may be configured to
10742 preserve some of the authentication information in the variable
10743 &$authenticated_id$& (see chapter &<<CHAPSMTPAUTH>>&). For example, a
10744 user/password authenticator configuration might preserve the user name for use
10745 in the routers. Note that this is not the same information that is saved in
10746 &$sender_host_authenticated$&.
10747 When a message is submitted locally (that is, not over a TCP connection)
10748 the value of &$authenticated_id$& is normally the login name of the calling
10749 process. However, a trusted user can override this by means of the &%-oMai%&
10750 command line option.
10755 .vitem &$authenticated_sender$&
10756 .cindex "sender" "authenticated"
10757 .cindex "authentication" "sender"
10758 .cindex "AUTH" "on MAIL command"
10759 .vindex "&$authenticated_sender$&"
10760 When acting as a server, Exim takes note of the AUTH= parameter on an incoming
10761 SMTP MAIL command if it believes the sender is sufficiently trusted, as
10762 described in section &<<SECTauthparamail>>&. Unless the data is the string
10763 &"<>"&, it is set as the authenticated sender of the message, and the value is
10764 available during delivery in the &$authenticated_sender$& variable. If the
10765 sender is not trusted, Exim accepts the syntax of AUTH=, but ignores the data.
10767 .vindex "&$qualify_domain$&"
10768 When a message is submitted locally (that is, not over a TCP connection), the
10769 value of &$authenticated_sender$& is an address constructed from the login
10770 name of the calling process and &$qualify_domain$&, except that a trusted user
10771 can override this by means of the &%-oMas%& command line option.
10774 .vitem &$authentication_failed$&
10775 .cindex "authentication" "failure"
10776 .vindex "&$authentication_failed$&"
10777 This variable is set to &"1"& in an Exim server if a client issues an AUTH
10778 command that does not succeed. Otherwise it is set to &"0"&. This makes it
10779 possible to distinguish between &"did not try to authenticate"&
10780 (&$sender_host_authenticated$& is empty and &$authentication_failed$& is set to
10781 &"0"&) and &"tried to authenticate but failed"& (&$sender_host_authenticated$&
10782 is empty and &$authentication_failed$& is set to &"1"&). Failure includes any
10783 negative response to an AUTH command, including (for example) an attempt to use
10784 an undefined mechanism.
10786 .vitem &$av_failed$&
10787 .cindex "content scanning" "AV scanner failure"
10788 This variable is available when Exim is compiled with the content-scanning
10789 extension. It is set to &"0"& by default, but will be set to &"1"& if any
10790 problem occurs with the virus scanner (specified by &%av_scanner%&) during
10791 the ACL malware condition.
10793 .vitem &$body_linecount$&
10794 .cindex "message body" "line count"
10795 .cindex "body of message" "line count"
10796 .vindex "&$body_linecount$&"
10797 When a message is being received or delivered, this variable contains the
10798 number of lines in the message's body. See also &$message_linecount$&.
10800 .vitem &$body_zerocount$&
10801 .cindex "message body" "binary zero count"
10802 .cindex "body of message" "binary zero count"
10803 .cindex "binary zero" "in message body"
10804 .vindex "&$body_zerocount$&"
10805 When a message is being received or delivered, this variable contains the
10806 number of binary zero bytes (ASCII NULs) in the message's body.
10808 .vitem &$bounce_recipient$&
10809 .vindex "&$bounce_recipient$&"
10810 This is set to the recipient address of a bounce message while Exim is creating
10811 it. It is useful if a customized bounce message text file is in use (see
10812 chapter &<<CHAPemsgcust>>&).
10814 .vitem &$bounce_return_size_limit$&
10815 .vindex "&$bounce_return_size_limit$&"
10816 This contains the value set in the &%bounce_return_size_limit%& option, rounded
10817 up to a multiple of 1000. It is useful when a customized error message text
10818 file is in use (see chapter &<<CHAPemsgcust>>&).
10820 .vitem &$caller_gid$&
10821 .cindex "gid (group id)" "caller"
10822 .vindex "&$caller_gid$&"
10823 The real group id under which the process that called Exim was running. This is
10824 not the same as the group id of the originator of a message (see
10825 &$originator_gid$&). If Exim re-execs itself, this variable in the new
10826 incarnation normally contains the Exim gid.
10828 .vitem &$caller_uid$&
10829 .cindex "uid (user id)" "caller"
10830 .vindex "&$caller_uid$&"
10831 The real user id under which the process that called Exim was running. This is
10832 not the same as the user id of the originator of a message (see
10833 &$originator_uid$&). If Exim re-execs itself, this variable in the new
10834 incarnation normally contains the Exim uid.
10836 .vitem &$compile_date$&
10837 .vindex "&$compile_date$&"
10838 The date on which the Exim binary was compiled.
10840 .vitem &$compile_number$&
10841 .vindex "&$compile_number$&"
10842 The building process for Exim keeps a count of the number
10843 of times it has been compiled. This serves to distinguish different
10844 compilations of the same version of the program.
10846 .vitem &$demime_errorlevel$&
10847 .vindex "&$demime_errorlevel$&"
10848 This variable is available when Exim is compiled with
10849 the content-scanning extension and the obsolete &%demime%& condition. For
10850 details, see section &<<SECTdemimecond>>&.
10852 .vitem &$demime_reason$&
10853 .vindex "&$demime_reason$&"
10854 This variable is available when Exim is compiled with the
10855 content-scanning extension and the obsolete &%demime%& condition. For details,
10856 see section &<<SECTdemimecond>>&.
10858 .vitem &$dnslist_domain$& &&&
10859 &$dnslist_matched$& &&&
10860 &$dnslist_text$& &&&
10862 .vindex "&$dnslist_domain$&"
10863 .vindex "&$dnslist_matched$&"
10864 .vindex "&$dnslist_text$&"
10865 .vindex "&$dnslist_value$&"
10866 .cindex "black list (DNS)"
10867 When a DNS (black) list lookup succeeds, these variables are set to contain
10868 the following data from the lookup: the list's domain name, the key that was
10869 looked up, the contents of any associated TXT record, and the value from the
10870 main A record. See section &<<SECID204>>& for more details.
10873 .vindex "&$domain$&"
10874 When an address is being routed, or delivered on its own, this variable
10875 contains the domain. Uppercase letters in the domain are converted into lower
10876 case for &$domain$&.
10878 Global address rewriting happens when a message is received, so the value of
10879 &$domain$& during routing and delivery is the value after rewriting. &$domain$&
10880 is set during user filtering, but not during system filtering, because a
10881 message may have many recipients and the system filter is called just once.
10883 When more than one address is being delivered at once (for example, several
10884 RCPT commands in one SMTP delivery), &$domain$& is set only if they all
10885 have the same domain. Transports can be restricted to handling only one domain
10886 at a time if the value of &$domain$& is required at transport time &-- this is
10887 the default for local transports. For further details of the environment in
10888 which local transports are run, see chapter &<<CHAPenvironment>>&.
10890 .oindex "&%delay_warning_condition%&"
10891 At the end of a delivery, if all deferred addresses have the same domain, it is
10892 set in &$domain$& during the expansion of &%delay_warning_condition%&.
10894 The &$domain$& variable is also used in some other circumstances:
10897 When an ACL is running for a RCPT command, &$domain$& contains the domain of
10898 the recipient address. The domain of the &'sender'& address is in
10899 &$sender_address_domain$& at both MAIL time and at RCPT time. &$domain$& is not
10900 normally set during the running of the MAIL ACL. However, if the sender address
10901 is verified with a callout during the MAIL ACL, the sender domain is placed in
10902 &$domain$& during the expansions of &%hosts%&, &%interface%&, and &%port%& in
10903 the &(smtp)& transport.
10906 When a rewrite item is being processed (see chapter &<<CHAPrewrite>>&),
10907 &$domain$& contains the domain portion of the address that is being rewritten;
10908 it can be used in the expansion of the replacement address, for example, to
10909 rewrite domains by file lookup.
10912 With one important exception, whenever a domain list is being scanned,
10913 &$domain$& contains the subject domain. &*Exception*&: When a domain list in
10914 a &%sender_domains%& condition in an ACL is being processed, the subject domain
10915 is in &$sender_address_domain$& and not in &$domain$&. It works this way so
10916 that, in a RCPT ACL, the sender domain list can be dependent on the
10917 recipient domain (which is what is in &$domain$& at this time).
10920 .cindex "ETRN" "value of &$domain$&"
10921 .oindex "&%smtp_etrn_command%&"
10922 When the &%smtp_etrn_command%& option is being expanded, &$domain$& contains
10923 the complete argument of the ETRN command (see section &<<SECTETRN>>&).
10927 .vitem &$domain_data$&
10928 .vindex "&$domain_data$&"
10929 When the &%domains%& option on a router matches a domain by
10930 means of a lookup, the data read by the lookup is available during the running
10931 of the router as &$domain_data$&. In addition, if the driver routes the
10932 address to a transport, the value is available in that transport. If the
10933 transport is handling multiple addresses, the value from the first address is
10936 &$domain_data$& is also set when the &%domains%& condition in an ACL matches a
10937 domain by means of a lookup. The data read by the lookup is available during
10938 the rest of the ACL statement. In all other situations, this variable expands
10941 .vitem &$exim_gid$&
10942 .vindex "&$exim_gid$&"
10943 This variable contains the numerical value of the Exim group id.
10945 .vitem &$exim_path$&
10946 .vindex "&$exim_path$&"
10947 This variable contains the path to the Exim binary.
10949 .vitem &$exim_uid$&
10950 .vindex "&$exim_uid$&"
10951 This variable contains the numerical value of the Exim user id.
10953 .vitem &$found_extension$&
10954 .vindex "&$found_extension$&"
10955 This variable is available when Exim is compiled with the
10956 content-scanning extension and the obsolete &%demime%& condition. For details,
10957 see section &<<SECTdemimecond>>&.
10959 .vitem &$header_$&<&'name'&>
10960 This is not strictly an expansion variable. It is expansion syntax for
10961 inserting the message header line with the given name. Note that the name must
10962 be terminated by colon or white space, because it may contain a wide variety of
10963 characters. Note also that braces must &'not'& be used.
10967 When the &%check_local_user%& option is set for a router, the user's home
10968 directory is placed in &$home$& when the check succeeds. In particular, this
10969 means it is set during the running of users' filter files. A router may also
10970 explicitly set a home directory for use by a transport; this can be overridden
10971 by a setting on the transport itself.
10973 When running a filter test via the &%-bf%& option, &$home$& is set to the value
10974 of the environment variable HOME.
10978 If a router assigns an address to a transport (any transport), and passes a
10979 list of hosts with the address, the value of &$host$& when the transport starts
10980 to run is the name of the first host on the list. Note that this applies both
10981 to local and remote transports.
10983 .cindex "transport" "filter"
10984 .cindex "filter" "transport filter"
10985 For the &(smtp)& transport, if there is more than one host, the value of
10986 &$host$& changes as the transport works its way through the list. In
10987 particular, when the &(smtp)& transport is expanding its options for encryption
10988 using TLS, or for specifying a transport filter (see chapter
10989 &<<CHAPtransportgeneric>>&), &$host$& contains the name of the host to which it
10992 When used in the client part of an authenticator configuration (see chapter
10993 &<<CHAPSMTPAUTH>>&), &$host$& contains the name of the server to which the
10994 client is connected.
10997 .vitem &$host_address$&
10998 .vindex "&$host_address$&"
10999 This variable is set to the remote host's IP address whenever &$host$& is set
11000 for a remote connection. It is also set to the IP address that is being checked
11001 when the &%ignore_target_hosts%& option is being processed.
11003 .vitem &$host_data$&
11004 .vindex "&$host_data$&"
11005 If a &%hosts%& condition in an ACL is satisfied by means of a lookup, the
11006 result of the lookup is made available in the &$host_data$& variable. This
11007 allows you, for example, to do things like this:
11009 deny hosts = net-lsearch;/some/file
11010 message = $host_data
11012 .vitem &$host_lookup_deferred$&
11013 .cindex "host name" "lookup, failure of"
11014 .vindex "&$host_lookup_deferred$&"
11015 This variable normally contains &"0"&, as does &$host_lookup_failed$&. When a
11016 message comes from a remote host and there is an attempt to look up the host's
11017 name from its IP address, and the attempt is not successful, one of these
11018 variables is set to &"1"&.
11021 If the lookup receives a definite negative response (for example, a DNS lookup
11022 succeeded, but no records were found), &$host_lookup_failed$& is set to &"1"&.
11025 If there is any kind of problem during the lookup, such that Exim cannot
11026 tell whether or not the host name is defined (for example, a timeout for a DNS
11027 lookup), &$host_lookup_deferred$& is set to &"1"&.
11030 Looking up a host's name from its IP address consists of more than just a
11031 single reverse lookup. Exim checks that a forward lookup of at least one of the
11032 names it receives from a reverse lookup yields the original IP address. If this
11033 is not the case, Exim does not accept the looked up name(s), and
11034 &$host_lookup_failed$& is set to &"1"&. Thus, being able to find a name from an
11035 IP address (for example, the existence of a PTR record in the DNS) is not
11036 sufficient on its own for the success of a host name lookup. If the reverse
11037 lookup succeeds, but there is a lookup problem such as a timeout when checking
11038 the result, the name is not accepted, and &$host_lookup_deferred$& is set to
11039 &"1"&. See also &$sender_host_name$&.
11041 .vitem &$host_lookup_failed$&
11042 .vindex "&$host_lookup_failed$&"
11043 See &$host_lookup_deferred$&.
11047 .vindex "&$inode$&"
11048 The only time this variable is set is while expanding the &%directory_file%&
11049 option in the &(appendfile)& transport. The variable contains the inode number
11050 of the temporary file which is about to be renamed. It can be used to construct
11051 a unique name for the file.
11053 .vitem &$interface_address$&
11054 .vindex "&$interface_address$&"
11055 This is an obsolete name for &$received_ip_address$&.
11057 .vitem &$interface_port$&
11058 .vindex "&$interface_port$&"
11059 This is an obsolete name for &$received_port$&.
11063 This variable is used during the expansion of &*forall*& and &*forany*&
11064 conditions (see section &<<SECTexpcond>>&), and &*filter*&, &*map*&, and
11065 &*reduce*& items (see section &<<SECTexpcond>>&). In other circumstances, it is
11069 .vindex "&$ldap_dn$&"
11070 This variable, which is available only when Exim is compiled with LDAP support,
11071 contains the DN from the last entry in the most recently successful LDAP
11074 .vitem &$load_average$&
11075 .vindex "&$load_average$&"
11076 This variable contains the system load average, multiplied by 1000 so that it
11077 is an integer. For example, if the load average is 0.21, the value of the
11078 variable is 210. The value is recomputed every time the variable is referenced.
11080 .vitem &$local_part$&
11081 .vindex "&$local_part$&"
11082 When an address is being routed, or delivered on its own, this
11083 variable contains the local part. When a number of addresses are being
11084 delivered together (for example, multiple RCPT commands in an SMTP
11085 session), &$local_part$& is not set.
11087 Global address rewriting happens when a message is received, so the value of
11088 &$local_part$& during routing and delivery is the value after rewriting.
11089 &$local_part$& is set during user filtering, but not during system filtering,
11090 because a message may have many recipients and the system filter is called just
11093 .vindex "&$local_part_prefix$&"
11094 .vindex "&$local_part_suffix$&"
11095 If a local part prefix or suffix has been recognized, it is not included in the
11096 value of &$local_part$& during routing and subsequent delivery. The values of
11097 any prefix or suffix are in &$local_part_prefix$& and
11098 &$local_part_suffix$&, respectively.
11100 When a message is being delivered to a file, pipe, or autoreply transport as a
11101 result of aliasing or forwarding, &$local_part$& is set to the local part of
11102 the parent address, not to the file name or command (see &$address_file$& and
11105 When an ACL is running for a RCPT command, &$local_part$& contains the
11106 local part of the recipient address.
11108 When a rewrite item is being processed (see chapter &<<CHAPrewrite>>&),
11109 &$local_part$& contains the local part of the address that is being rewritten;
11110 it can be used in the expansion of the replacement address, for example.
11112 In all cases, all quoting is removed from the local part. For example, for both
11115 "abc:xyz"@test.example
11116 abc\:xyz@test.example
11118 the value of &$local_part$& is
11122 If you use &$local_part$& to create another address, you should always wrap it
11123 inside a quoting operator. For example, in a &(redirect)& router you could
11126 data = ${quote_local_part:$local_part}@new.domain.example
11128 &*Note*&: The value of &$local_part$& is normally lower cased. If you want
11129 to process local parts in a case-dependent manner in a router, you can set the
11130 &%caseful_local_part%& option (see chapter &<<CHAProutergeneric>>&).
11132 .vitem &$local_part_data$&
11133 .vindex "&$local_part_data$&"
11134 When the &%local_parts%& option on a router matches a local part by means of a
11135 lookup, the data read by the lookup is available during the running of the
11136 router as &$local_part_data$&. In addition, if the driver routes the address
11137 to a transport, the value is available in that transport. If the transport is
11138 handling multiple addresses, the value from the first address is used.
11140 &$local_part_data$& is also set when the &%local_parts%& condition in an ACL
11141 matches a local part by means of a lookup. The data read by the lookup is
11142 available during the rest of the ACL statement. In all other situations, this
11143 variable expands to nothing.
11145 .vitem &$local_part_prefix$&
11146 .vindex "&$local_part_prefix$&"
11147 When an address is being routed or delivered, and a
11148 specific prefix for the local part was recognized, it is available in this
11149 variable, having been removed from &$local_part$&.
11151 .vitem &$local_part_suffix$&
11152 .vindex "&$local_part_suffix$&"
11153 When an address is being routed or delivered, and a
11154 specific suffix for the local part was recognized, it is available in this
11155 variable, having been removed from &$local_part$&.
11157 .vitem &$local_scan_data$&
11158 .vindex "&$local_scan_data$&"
11159 This variable contains the text returned by the &[local_scan()]& function when
11160 a message is received. See chapter &<<CHAPlocalscan>>& for more details.
11162 .vitem &$local_user_gid$&
11163 .vindex "&$local_user_gid$&"
11164 See &$local_user_uid$&.
11166 .vitem &$local_user_uid$&
11167 .vindex "&$local_user_uid$&"
11168 This variable and &$local_user_gid$& are set to the uid and gid after the
11169 &%check_local_user%& router precondition succeeds. This means that their values
11170 are available for the remaining preconditions (&%senders%&, &%require_files%&,
11171 and &%condition%&), for the &%address_data%& expansion, and for any
11172 router-specific expansions. At all other times, the values in these variables
11173 are &`(uid_t)(-1)`& and &`(gid_t)(-1)`&, respectively.
11175 .vitem &$localhost_number$&
11176 .vindex "&$localhost_number$&"
11177 This contains the expanded value of the
11178 &%localhost_number%& option. The expansion happens after the main options have
11181 .vitem &$log_inodes$&
11182 .vindex "&$log_inodes$&"
11183 The number of free inodes in the disk partition where Exim's
11184 log files are being written. The value is recalculated whenever the variable is
11185 referenced. If the relevant file system does not have the concept of inodes,
11186 the value of is -1. See also the &%check_log_inodes%& option.
11188 .vitem &$log_space$&
11189 .vindex "&$log_space$&"
11190 The amount of free space (as a number of kilobytes) in the disk
11191 partition where Exim's log files are being written. The value is recalculated
11192 whenever the variable is referenced. If the operating system does not have the
11193 ability to find the amount of free space (only true for experimental systems),
11194 the space value is -1. See also the &%check_log_space%& option.
11197 .vitem &$mailstore_basename$&
11198 .vindex "&$mailstore_basename$&"
11199 This variable is set only when doing deliveries in &"mailstore"& format in the
11200 &(appendfile)& transport. During the expansion of the &%mailstore_prefix%&,
11201 &%mailstore_suffix%&, &%message_prefix%&, and &%message_suffix%& options, it
11202 contains the basename of the files that are being written, that is, the name
11203 without the &".tmp"&, &".env"&, or &".msg"& suffix. At all other times, this
11206 .vitem &$malware_name$&
11207 .vindex "&$malware_name$&"
11208 This variable is available when Exim is compiled with the
11209 content-scanning extension. It is set to the name of the virus that was found
11210 when the ACL &%malware%& condition is true (see section &<<SECTscanvirus>>&).
11212 .vitem &$max_received_linelength$&
11213 .vindex "&$max_received_linelength$&"
11214 .cindex "maximum" "line length"
11215 .cindex "line length" "maximum"
11216 This variable contains the number of bytes in the longest line that was
11217 received as part of the message, not counting the line termination
11220 .vitem &$message_age$&
11221 .cindex "message" "age of"
11222 .vindex "&$message_age$&"
11223 This variable is set at the start of a delivery attempt to contain the number
11224 of seconds since the message was received. It does not change during a single
11227 .vitem &$message_body$&
11228 .cindex "body of message" "expansion variable"
11229 .cindex "message body" "in expansion"
11230 .cindex "binary zero" "in message body"
11231 .vindex "&$message_body$&"
11232 .oindex "&%message_body_visible%&"
11233 This variable contains the initial portion of a message's body while it is
11234 being delivered, and is intended mainly for use in filter files. The maximum
11235 number of characters of the body that are put into the variable is set by the
11236 &%message_body_visible%& configuration option; the default is 500.
11238 .oindex "&%message_body_newlines%&"
11239 By default, newlines are converted into spaces in &$message_body$&, to make it
11240 easier to search for phrases that might be split over a line break. However,
11241 this can be disabled by setting &%message_body_newlines%& to be true. Binary
11242 zeros are always converted into spaces.
11244 .vitem &$message_body_end$&
11245 .cindex "body of message" "expansion variable"
11246 .cindex "message body" "in expansion"
11247 .vindex "&$message_body_end$&"
11248 This variable contains the final portion of a message's
11249 body while it is being delivered. The format and maximum size are as for
11252 .vitem &$message_body_size$&
11253 .cindex "body of message" "size"
11254 .cindex "message body" "size"
11255 .vindex "&$message_body_size$&"
11256 When a message is being delivered, this variable contains the size of the body
11257 in bytes. The count starts from the character after the blank line that
11258 separates the body from the header. Newlines are included in the count. See
11259 also &$message_size$&, &$body_linecount$&, and &$body_zerocount$&.
11261 .vitem &$message_exim_id$&
11262 .vindex "&$message_exim_id$&"
11263 When a message is being received or delivered, this variable contains the
11264 unique message id that is generated and used by Exim to identify the message.
11265 An id is not created for a message until after its header has been successfully
11266 received. &*Note*&: This is &'not'& the contents of the &'Message-ID:'& header
11267 line; it is the local id that Exim assigns to the message, for example:
11268 &`1BXTIK-0001yO-VA`&.
11270 .vitem &$message_headers$&
11271 .vindex &$message_headers$&
11272 This variable contains a concatenation of all the header lines when a message
11273 is being processed, except for lines added by routers or transports. The header
11274 lines are separated by newline characters. Their contents are decoded in the
11275 same way as a header line that is inserted by &%bheader%&.
11277 .vitem &$message_headers_raw$&
11278 .vindex &$message_headers_raw$&
11279 This variable is like &$message_headers$& except that no processing of the
11280 contents of header lines is done.
11282 .vitem &$message_id$&
11283 This is an old name for &$message_exim_id$&, which is now deprecated.
11285 .vitem &$message_linecount$&
11286 .vindex "&$message_linecount$&"
11287 This variable contains the total number of lines in the header and body of the
11288 message. Compare &$body_linecount$&, which is the count for the body only.
11289 During the DATA and content-scanning ACLs, &$message_linecount$& contains the
11290 number of lines received. Before delivery happens (that is, before filters,
11291 routers, and transports run) the count is increased to include the
11292 &'Received:'& header line that Exim standardly adds, and also any other header
11293 lines that are added by ACLs. The blank line that separates the message header
11294 from the body is not counted.
11296 As with the special case of &$message_size$&, during the expansion of the
11297 appendfile transport's maildir_tag option in maildir format, the value of
11298 &$message_linecount$& is the precise size of the number of newlines in the
11299 file that has been written (minus one for the blank line between the
11300 header and the body).
11302 Here is an example of the use of this variable in a DATA ACL:
11304 deny message = Too many lines in message header
11306 ${if <{250}{${eval:$message_linecount - $body_linecount}}}
11308 In the MAIL and RCPT ACLs, the value is zero because at that stage the
11309 message has not yet been received.
11311 .vitem &$message_size$&
11312 .cindex "size" "of message"
11313 .cindex "message" "size"
11314 .vindex "&$message_size$&"
11315 When a message is being processed, this variable contains its size in bytes. In
11316 most cases, the size includes those headers that were received with the
11317 message, but not those (such as &'Envelope-to:'&) that are added to individual
11318 deliveries as they are written. However, there is one special case: during the
11319 expansion of the &%maildir_tag%& option in the &(appendfile)& transport while
11320 doing a delivery in maildir format, the value of &$message_size$& is the
11321 precise size of the file that has been written. See also
11322 &$message_body_size$&, &$body_linecount$&, and &$body_zerocount$&.
11324 .cindex "RCPT" "value of &$message_size$&"
11325 While running a per message ACL (mail/rcpt/predata), &$message_size$&
11326 contains the size supplied on the MAIL command, or -1 if no size was given. The
11327 value may not, of course, be truthful.
11329 .vitem &$mime_$&&'xxx'&
11330 A number of variables whose names start with &$mime$& are
11331 available when Exim is compiled with the content-scanning extension. For
11332 details, see section &<<SECTscanmimepart>>&.
11334 .vitem "&$n0$& &-- &$n9$&"
11335 These variables are counters that can be incremented by means
11336 of the &%add%& command in filter files.
11338 .vitem &$original_domain$&
11339 .vindex "&$domain$&"
11340 .vindex "&$original_domain$&"
11341 When a top-level address is being processed for delivery, this contains the
11342 same value as &$domain$&. However, if a &"child"& address (for example,
11343 generated by an alias, forward, or filter file) is being processed, this
11344 variable contains the domain of the original address (lower cased). This
11345 differs from &$parent_domain$& only when there is more than one level of
11346 aliasing or forwarding. When more than one address is being delivered in a
11347 single transport run, &$original_domain$& is not set.
11349 If a new address is created by means of a &%deliver%& command in a system
11350 filter, it is set up with an artificial &"parent"& address. This has the local
11351 part &'system-filter'& and the default qualify domain.
11353 .vitem &$original_local_part$&
11354 .vindex "&$local_part$&"
11355 .vindex "&$original_local_part$&"
11356 When a top-level address is being processed for delivery, this contains the
11357 same value as &$local_part$&, unless a prefix or suffix was removed from the
11358 local part, because &$original_local_part$& always contains the full local
11359 part. When a &"child"& address (for example, generated by an alias, forward, or
11360 filter file) is being processed, this variable contains the full local part of
11361 the original address.
11363 If the router that did the redirection processed the local part
11364 case-insensitively, the value in &$original_local_part$& is in lower case.
11365 This variable differs from &$parent_local_part$& only when there is more than
11366 one level of aliasing or forwarding. When more than one address is being
11367 delivered in a single transport run, &$original_local_part$& is not set.
11369 If a new address is created by means of a &%deliver%& command in a system
11370 filter, it is set up with an artificial &"parent"& address. This has the local
11371 part &'system-filter'& and the default qualify domain.
11373 .vitem &$originator_gid$&
11374 .cindex "gid (group id)" "of originating user"
11375 .cindex "sender" "gid"
11376 .vindex "&$caller_gid$&"
11377 .vindex "&$originator_gid$&"
11378 This variable contains the value of &$caller_gid$& that was set when the
11379 message was received. For messages received via the command line, this is the
11380 gid of the sending user. For messages received by SMTP over TCP/IP, this is
11381 normally the gid of the Exim user.
11383 .vitem &$originator_uid$&
11384 .cindex "uid (user id)" "of originating user"
11385 .cindex "sender" "uid"
11386 .vindex "&$caller_uid$&"
11387 .vindex "&$originaltor_uid$&"
11388 The value of &$caller_uid$& that was set when the message was received. For
11389 messages received via the command line, this is the uid of the sending user.
11390 For messages received by SMTP over TCP/IP, this is normally the uid of the Exim
11393 .vitem &$parent_domain$&
11394 .vindex "&$parent_domain$&"
11395 This variable is similar to &$original_domain$& (see
11396 above), except that it refers to the immediately preceding parent address.
11398 .vitem &$parent_local_part$&
11399 .vindex "&$parent_local_part$&"
11400 This variable is similar to &$original_local_part$&
11401 (see above), except that it refers to the immediately preceding parent address.
11404 .cindex "pid (process id)" "of current process"
11406 This variable contains the current process id.
11408 .vitem &$pipe_addresses$&
11409 .cindex "filter" "transport filter"
11410 .cindex "transport" "filter"
11411 .vindex "&$pipe_addresses$&"
11412 This is not an expansion variable, but is mentioned here because the string
11413 &`$pipe_addresses`& is handled specially in the command specification for the
11414 &(pipe)& transport (chapter &<<CHAPpipetransport>>&) and in transport filters
11415 (described under &%transport_filter%& in chapter &<<CHAPtransportgeneric>>&).
11416 It cannot be used in general expansion strings, and provokes an &"unknown
11417 variable"& error if encountered.
11419 .vitem &$primary_hostname$&
11420 .vindex "&$primary_hostname$&"
11421 This variable contains the value set by &%primary_hostname%& in the
11422 configuration file, or read by the &[uname()]& function. If &[uname()]& returns
11423 a single-component name, Exim calls &[gethostbyname()]& (or
11424 &[getipnodebyname()]& where available) in an attempt to acquire a fully
11425 qualified host name. See also &$smtp_active_hostname$&.
11428 .vitem &$prvscheck_address$&
11429 This variable is used in conjunction with the &%prvscheck%& expansion item,
11430 which is described in sections &<<SECTexpansionitems>>& and
11431 &<<SECTverifyPRVS>>&.
11433 .vitem &$prvscheck_keynum$&
11434 This variable is used in conjunction with the &%prvscheck%& expansion item,
11435 which is described in sections &<<SECTexpansionitems>>& and
11436 &<<SECTverifyPRVS>>&.
11438 .vitem &$prvscheck_result$&
11439 This variable is used in conjunction with the &%prvscheck%& expansion item,
11440 which is described in sections &<<SECTexpansionitems>>& and
11441 &<<SECTverifyPRVS>>&.
11443 .vitem &$qualify_domain$&
11444 .vindex "&$qualify_domain$&"
11445 The value set for the &%qualify_domain%& option in the configuration file.
11447 .vitem &$qualify_recipient$&
11448 .vindex "&$qualify_recipient$&"
11449 The value set for the &%qualify_recipient%& option in the configuration file,
11450 or if not set, the value of &$qualify_domain$&.
11452 .vitem &$rcpt_count$&
11453 .vindex "&$rcpt_count$&"
11454 When a message is being received by SMTP, this variable contains the number of
11455 RCPT commands received for the current message. If this variable is used in a
11456 RCPT ACL, its value includes the current command.
11458 .vitem &$rcpt_defer_count$&
11459 .vindex "&$rcpt_defer_count$&"
11460 .cindex "4&'xx'& responses" "count of"
11461 When a message is being received by SMTP, this variable contains the number of
11462 RCPT commands in the current message that have previously been rejected with a
11463 temporary (4&'xx'&) response.
11465 .vitem &$rcpt_fail_count$&
11466 .vindex "&$rcpt_fail_count$&"
11467 When a message is being received by SMTP, this variable contains the number of
11468 RCPT commands in the current message that have previously been rejected with a
11469 permanent (5&'xx'&) response.
11471 .vitem &$received_count$&
11472 .vindex "&$received_count$&"
11473 This variable contains the number of &'Received:'& header lines in the message,
11474 including the one added by Exim (so its value is always greater than zero). It
11475 is available in the DATA ACL, the non-SMTP ACL, and while routing and
11478 .vitem &$received_for$&
11479 .vindex "&$received_for$&"
11480 If there is only a single recipient address in an incoming message, this
11481 variable contains that address when the &'Received:'& header line is being
11482 built. The value is copied after recipient rewriting has happened, but before
11483 the &[local_scan()]& function is run.
11485 .vitem &$received_ip_address$&
11486 .vindex "&$received_ip_address$&"
11487 As soon as an Exim server starts processing an incoming TCP/IP connection, this
11488 variable is set to the address of the local IP interface, and &$received_port$&
11489 is set to the local port number. (The remote IP address and port are in
11490 &$sender_host_address$& and &$sender_host_port$&.) When testing with &%-bh%&,
11491 the port value is -1 unless it has been set using the &%-oMi%& command line
11494 As well as being useful in ACLs (including the &"connect"& ACL), these variable
11495 could be used, for example, to make the file name for a TLS certificate depend
11496 on which interface and/or port is being used for the incoming connection. The
11497 values of &$received_ip_address$& and &$received_port$& are saved with any
11498 messages that are received, thus making these variables available at delivery
11501 &*Note:*& There are no equivalent variables for outgoing connections, because
11502 the values are unknown (unless they are explicitly set by options of the
11503 &(smtp)& transport).
11505 .vitem &$received_port$&
11506 .vindex "&$received_port$&"
11507 See &$received_ip_address$&.
11509 .vitem &$received_protocol$&
11510 .vindex "&$received_protocol$&"
11511 When a message is being processed, this variable contains the name of the
11512 protocol by which it was received. Most of the names used by Exim are defined
11513 by RFCs 821, 2821, and 3848. They start with &"smtp"& (the client used HELO) or
11514 &"esmtp"& (the client used EHLO). This can be followed by &"s"& for secure
11515 (encrypted) and/or &"a"& for authenticated. Thus, for example, if the protocol
11516 is set to &"esmtpsa"&, the message was received over an encrypted SMTP
11517 connection and the client was successfully authenticated.
11519 Exim uses the protocol name &"smtps"& for the case when encryption is
11520 automatically set up on connection without the use of STARTTLS (see
11521 &%tls_on_connect_ports%&), and the client uses HELO to initiate the
11522 encrypted SMTP session. The name &"smtps"& is also used for the rare situation
11523 where the client initially uses EHLO, sets up an encrypted connection using
11524 STARTTLS, and then uses HELO afterwards.
11526 The &%-oMr%& option provides a way of specifying a custom protocol name for
11527 messages that are injected locally by trusted callers. This is commonly used to
11528 identify messages that are being re-injected after some kind of scanning.
11530 .vitem &$received_time$&
11531 .vindex "&$received_time$&"
11532 This variable contains the date and time when the current message was received,
11533 as a number of seconds since the start of the Unix epoch.
11535 .vitem &$recipient_data$&
11536 .vindex "&$recipient_data$&"
11537 This variable is set after an indexing lookup success in an ACL &%recipients%&
11538 condition. It contains the data from the lookup, and the value remains set
11539 until the next &%recipients%& test. Thus, you can do things like this:
11541 &`require recipients = cdb*@;/some/file`&
11542 &`deny `&&'some further test involving'& &`$recipient_data`&
11544 &*Warning*&: This variable is set only when a lookup is used as an indexing
11545 method in the address list, using the semicolon syntax as in the example above.
11546 The variable is not set for a lookup that is used as part of the string
11547 expansion that all such lists undergo before being interpreted.
11549 .vitem &$recipient_verify_failure$&
11550 .vindex "&$recipient_verify_failure$&"
11551 In an ACL, when a recipient verification fails, this variable contains
11552 information about the failure. It is set to one of the following words:
11555 &"qualify"&: The address was unqualified (no domain), and the message
11556 was neither local nor came from an exempted host.
11559 &"route"&: Routing failed.
11562 &"mail"&: Routing succeeded, and a callout was attempted; rejection occurred at
11563 or before the MAIL command (that is, on initial connection, HELO, or
11567 &"recipient"&: The RCPT command in a callout was rejected.
11570 &"postmaster"&: The postmaster check in a callout was rejected.
11573 The main use of this variable is expected to be to distinguish between
11574 rejections of MAIL and rejections of RCPT.
11576 .vitem &$recipients$&
11577 .vindex "&$recipients$&"
11578 This variable contains a list of envelope recipients for a message. A comma and
11579 a space separate the addresses in the replacement text. However, the variable
11580 is not generally available, to prevent exposure of Bcc recipients in
11581 unprivileged users' filter files. You can use &$recipients$& only in these
11585 In a system filter file.
11587 In the ACLs associated with the DATA command and with non-SMTP messages, that
11588 is, the ACLs defined by &%acl_smtp_predata%&, &%acl_smtp_data%&,
11589 &%acl_smtp_mime%&, &%acl_not_smtp_start%&, &%acl_not_smtp%&, and
11590 &%acl_not_smtp_mime%&.
11592 From within a &[local_scan()]& function.
11596 .vitem &$recipients_count$&
11597 .vindex "&$recipients_count$&"
11598 When a message is being processed, this variable contains the number of
11599 envelope recipients that came with the message. Duplicates are not excluded
11600 from the count. While a message is being received over SMTP, the number
11601 increases for each accepted recipient. It can be referenced in an ACL.
11604 .vitem &$regex_match_string$&
11605 .vindex "&$regex_match_string$&"
11606 This variable is set to contain the matching regular expression after a
11607 &%regex%& ACL condition has matched (see section &<<SECTscanregex>>&).
11610 .vitem &$reply_address$&
11611 .vindex "&$reply_address$&"
11612 When a message is being processed, this variable contains the contents of the
11613 &'Reply-To:'& header line if one exists and it is not empty, or otherwise the
11614 contents of the &'From:'& header line. Apart from the removal of leading
11615 white space, the value is not processed in any way. In particular, no RFC 2047
11616 decoding or character code translation takes place.
11618 .vitem &$return_path$&
11619 .vindex "&$return_path$&"
11620 When a message is being delivered, this variable contains the return path &--
11621 the sender field that will be sent as part of the envelope. It is not enclosed
11622 in <> characters. At the start of routing an address, &$return_path$& has the
11623 same value as &$sender_address$&, but if, for example, an incoming message to a
11624 mailing list has been expanded by a router which specifies a different address
11625 for bounce messages, &$return_path$& subsequently contains the new bounce
11626 address, whereas &$sender_address$& always contains the original sender address
11627 that was received with the message. In other words, &$sender_address$& contains
11628 the incoming envelope sender, and &$return_path$& contains the outgoing
11631 .vitem &$return_size_limit$&
11632 .vindex "&$return_size_limit$&"
11633 This is an obsolete name for &$bounce_return_size_limit$&.
11636 .cindex "return code" "from &%run%& expansion"
11637 .vindex "&$runrc$&"
11638 This variable contains the return code from a command that is run by the
11639 &%${run...}%& expansion item. &*Warning*&: In a router or transport, you cannot
11640 assume the order in which option values are expanded, except for those
11641 preconditions whose order of testing is documented. Therefore, you cannot
11642 reliably expect to set &$runrc$& by the expansion of one option, and use it in
11645 .vitem &$self_hostname$&
11646 .oindex "&%self%&" "value of host name"
11647 .vindex "&$self_hostname$&"
11648 When an address is routed to a supposedly remote host that turns out to be the
11649 local host, what happens is controlled by the &%self%& generic router option.
11650 One of its values causes the address to be passed to another router. When this
11651 happens, &$self_hostname$& is set to the name of the local host that the
11652 original router encountered. In other circumstances its contents are null.
11654 .vitem &$sender_address$&
11655 .vindex "&$sender_address$&"
11656 When a message is being processed, this variable contains the sender's address
11657 that was received in the message's envelope. The case of letters in the address
11658 is retained, in both the local part and the domain. For bounce messages, the
11659 value of this variable is the empty string. See also &$return_path$&.
11661 .vitem &$sender_address_data$&
11662 .vindex "&$address_data$&"
11663 .vindex "&$sender_address_data$&"
11664 If &$address_data$& is set when the routers are called from an ACL to verify a
11665 sender address, the final value is preserved in &$sender_address_data$&, to
11666 distinguish it from data from a recipient address. The value does not persist
11667 after the end of the current ACL statement. If you want to preserve it for
11668 longer, you can save it in an ACL variable.
11670 .vitem &$sender_address_domain$&
11671 .vindex "&$sender_address_domain$&"
11672 The domain portion of &$sender_address$&.
11674 .vitem &$sender_address_local_part$&
11675 .vindex "&$sender_address_local_part$&"
11676 The local part portion of &$sender_address$&.
11678 .vitem &$sender_data$&
11679 .vindex "&$sender_data$&"
11680 This variable is set after a lookup success in an ACL &%senders%& condition or
11681 in a router &%senders%& option. It contains the data from the lookup, and the
11682 value remains set until the next &%senders%& test. Thus, you can do things like
11685 &`require senders = cdb*@;/some/file`&
11686 &`deny `&&'some further test involving'& &`$sender_data`&
11688 &*Warning*&: This variable is set only when a lookup is used as an indexing
11689 method in the address list, using the semicolon syntax as in the example above.
11690 The variable is not set for a lookup that is used as part of the string
11691 expansion that all such lists undergo before being interpreted.
11693 .vitem &$sender_fullhost$&
11694 .vindex "&$sender_fullhost$&"
11695 When a message is received from a remote host, this variable contains the host
11696 name and IP address in a single string. It ends with the IP address in square
11697 brackets, followed by a colon and a port number if the logging of ports is
11698 enabled. The format of the rest of the string depends on whether the host
11699 issued a HELO or EHLO SMTP command, and whether the host name was verified by
11700 looking up its IP address. (Looking up the IP address can be forced by the
11701 &%host_lookup%& option, independent of verification.) A plain host name at the
11702 start of the string is a verified host name; if this is not present,
11703 verification either failed or was not requested. A host name in parentheses is
11704 the argument of a HELO or EHLO command. This is omitted if it is identical to
11705 the verified host name or to the host's IP address in square brackets.
11707 .vitem &$sender_helo_name$&
11708 .vindex "&$sender_helo_name$&"
11709 When a message is received from a remote host that has issued a HELO or EHLO
11710 command, the argument of that command is placed in this variable. It is also
11711 set if HELO or EHLO is used when a message is received using SMTP locally via
11712 the &%-bs%& or &%-bS%& options.
11714 .vitem &$sender_host_address$&
11715 .vindex "&$sender_host_address$&"
11716 When a message is received from a remote host, this variable contains that
11717 host's IP address. For locally submitted messages, it is empty.
11719 .vitem &$sender_host_authenticated$&
11720 .vindex "&$sender_host_authenticated$&"
11721 This variable contains the name (not the public name) of the authenticator
11722 driver that successfully authenticated the client from which the message was
11723 received. It is empty if there was no successful authentication. See also
11724 &$authenticated_id$&.
11727 .vitem &$sender_host_dnssec$&
11728 .vindex "&$sender_host_dnssec$&"
11729 If &$sender_host_name$& has been populated (by reference, &%hosts_lookup%& or
11730 otherwise) then this boolean will have been set true if, and only if, the
11731 resolver library states that the reverse DNS was authenticated data. At all
11732 other times, this variable is false.
11734 It is likely that you will need to coerce DNSSEC support on in the resolver
11735 library, by setting:
11740 Exim does not perform DNSSEC validation itself, instead leaving that to a
11741 validating resolver (eg, unbound, or bind with suitable configuration).
11743 Exim does not (currently) check to see if the forward DNS was also secured
11744 with DNSSEC, only the reverse DNS.
11746 If you have changed &%host_lookup_order%& so that &`bydns`& is not the first
11747 mechanism in the list, then this variable will be false.
11751 .vitem &$sender_host_name$&
11752 .vindex "&$sender_host_name$&"
11753 When a message is received from a remote host, this variable contains the
11754 host's name as obtained by looking up its IP address. For messages received by
11755 other means, this variable is empty.
11757 .vindex "&$host_lookup_failed$&"
11758 If the host name has not previously been looked up, a reference to
11759 &$sender_host_name$& triggers a lookup (for messages from remote hosts).
11760 A looked up name is accepted only if it leads back to the original IP address
11761 via a forward lookup. If either the reverse or the forward lookup fails to find
11762 any data, or if the forward lookup does not yield the original IP address,
11763 &$sender_host_name$& remains empty, and &$host_lookup_failed$& is set to &"1"&.
11765 .vindex "&$host_lookup_deferred$&"
11766 However, if either of the lookups cannot be completed (for example, there is a
11767 DNS timeout), &$host_lookup_deferred$& is set to &"1"&, and
11768 &$host_lookup_failed$& remains set to &"0"&.
11770 Once &$host_lookup_failed$& is set to &"1"&, Exim does not try to look up the
11771 host name again if there is a subsequent reference to &$sender_host_name$&
11772 in the same Exim process, but it does try again if &$host_lookup_deferred$&
11775 Exim does not automatically look up every calling host's name. If you want
11776 maximum efficiency, you should arrange your configuration so that it avoids
11777 these lookups altogether. The lookup happens only if one or more of the
11778 following are true:
11781 A string containing &$sender_host_name$& is expanded.
11783 The calling host matches the list in &%host_lookup%&. In the default
11784 configuration, this option is set to *, so it must be changed if lookups are
11785 to be avoided. (In the code, the default for &%host_lookup%& is unset.)
11787 Exim needs the host name in order to test an item in a host list. The items
11788 that require this are described in sections &<<SECThoslispatnam>>& and
11789 &<<SECThoslispatnamsk>>&.
11791 The calling host matches &%helo_try_verify_hosts%& or &%helo_verify_hosts%&.
11792 In this case, the host name is required to compare with the name quoted in any
11793 EHLO or HELO commands that the client issues.
11795 The remote host issues a EHLO or HELO command that quotes one of the
11796 domains in &%helo_lookup_domains%&. The default value of this option is
11797 . ==== As this is a nested list, any displays it contains must be indented
11798 . ==== as otherwise they are too far to the left.
11800 helo_lookup_domains = @ : @[]
11802 which causes a lookup if a remote host (incorrectly) gives the server's name or
11803 IP address in an EHLO or HELO command.
11807 .vitem &$sender_host_port$&
11808 .vindex "&$sender_host_port$&"
11809 When a message is received from a remote host, this variable contains the port
11810 number that was used on the remote host.
11812 .vitem &$sender_ident$&
11813 .vindex "&$sender_ident$&"
11814 When a message is received from a remote host, this variable contains the
11815 identification received in response to an RFC 1413 request. When a message has
11816 been received locally, this variable contains the login name of the user that
11819 .vitem &$sender_rate_$&&'xxx'&
11820 A number of variables whose names begin &$sender_rate_$& are set as part of the
11821 &%ratelimit%& ACL condition. Details are given in section
11822 &<<SECTratelimiting>>&.
11824 .vitem &$sender_rcvhost$&
11825 .cindex "DNS" "reverse lookup"
11826 .cindex "reverse DNS lookup"
11827 .vindex "&$sender_rcvhost$&"
11828 This is provided specifically for use in &'Received:'& headers. It starts with
11829 either the verified host name (as obtained from a reverse DNS lookup) or, if
11830 there is no verified host name, the IP address in square brackets. After that
11831 there may be text in parentheses. When the first item is a verified host name,
11832 the first thing in the parentheses is the IP address in square brackets,
11833 followed by a colon and a port number if port logging is enabled. When the
11834 first item is an IP address, the port is recorded as &"port=&'xxxx'&"& inside
11837 There may also be items of the form &"helo=&'xxxx'&"& if HELO or EHLO
11838 was used and its argument was not identical to the real host name or IP
11839 address, and &"ident=&'xxxx'&"& if an RFC 1413 ident string is available. If
11840 all three items are present in the parentheses, a newline and tab are inserted
11841 into the string, to improve the formatting of the &'Received:'& header.
11843 .vitem &$sender_verify_failure$&
11844 .vindex "&$sender_verify_failure$&"
11845 In an ACL, when a sender verification fails, this variable contains information
11846 about the failure. The details are the same as for
11847 &$recipient_verify_failure$&.
11849 .vitem &$sending_ip_address$&
11850 .vindex "&$sending_ip_address$&"
11851 This variable is set whenever an outgoing SMTP connection to another host has
11852 been set up. It contains the IP address of the local interface that is being
11853 used. This is useful if a host that has more than one IP address wants to take
11854 on different personalities depending on which one is being used. For incoming
11855 connections, see &$received_ip_address$&.
11857 .vitem &$sending_port$&
11858 .vindex "&$sending_port$&"
11859 This variable is set whenever an outgoing SMTP connection to another host has
11860 been set up. It contains the local port that is being used. For incoming
11861 connections, see &$received_port$&.
11863 .vitem &$smtp_active_hostname$&
11864 .vindex "&$smtp_active_hostname$&"
11865 During an incoming SMTP session, this variable contains the value of the active
11866 host name, as specified by the &%smtp_active_hostname%& option. The value of
11867 &$smtp_active_hostname$& is saved with any message that is received, so its
11868 value can be consulted during routing and delivery.
11870 .vitem &$smtp_command$&
11871 .vindex "&$smtp_command$&"
11872 During the processing of an incoming SMTP command, this variable contains the
11873 entire command. This makes it possible to distinguish between HELO and EHLO in
11874 the HELO ACL, and also to distinguish between commands such as these:
11879 For a MAIL command, extra parameters such as SIZE can be inspected. For a RCPT
11880 command, the address in &$smtp_command$& is the original address before any
11881 rewriting, whereas the values in &$local_part$& and &$domain$& are taken from
11882 the address after SMTP-time rewriting.
11884 .vitem &$smtp_command_argument$&
11885 .cindex "SMTP" "command, argument for"
11886 .vindex "&$smtp_command_argument$&"
11887 While an ACL is running to check an SMTP command, this variable contains the
11888 argument, that is, the text that follows the command name, with leading white
11889 space removed. Following the introduction of &$smtp_command$&, this variable is
11890 somewhat redundant, but is retained for backwards compatibility.
11892 .vitem &$smtp_count_at_connection_start$&
11893 .vindex "&$smtp_count_at_connection_start$&"
11894 This variable is set greater than zero only in processes spawned by the Exim
11895 daemon for handling incoming SMTP connections. The name is deliberately long,
11896 in order to emphasize what the contents are. When the daemon accepts a new
11897 connection, it increments this variable. A copy of the variable is passed to
11898 the child process that handles the connection, but its value is fixed, and
11899 never changes. It is only an approximation of how many incoming connections
11900 there actually are, because many other connections may come and go while a
11901 single connection is being processed. When a child process terminates, the
11902 daemon decrements its copy of the variable.
11904 .vitem "&$sn0$& &-- &$sn9$&"
11905 These variables are copies of the values of the &$n0$& &-- &$n9$& accumulators
11906 that were current at the end of the system filter file. This allows a system
11907 filter file to set values that can be tested in users' filter files. For
11908 example, a system filter could set a value indicating how likely it is that a
11909 message is junk mail.
11911 .vitem &$spam_$&&'xxx'&
11912 A number of variables whose names start with &$spam$& are available when Exim
11913 is compiled with the content-scanning extension. For details, see section
11914 &<<SECTscanspamass>>&.
11917 .vitem &$spool_directory$&
11918 .vindex "&$spool_directory$&"
11919 The name of Exim's spool directory.
11921 .vitem &$spool_inodes$&
11922 .vindex "&$spool_inodes$&"
11923 The number of free inodes in the disk partition where Exim's spool files are
11924 being written. The value is recalculated whenever the variable is referenced.
11925 If the relevant file system does not have the concept of inodes, the value of
11926 is -1. See also the &%check_spool_inodes%& option.
11928 .vitem &$spool_space$&
11929 .vindex "&$spool_space$&"
11930 The amount of free space (as a number of kilobytes) in the disk partition where
11931 Exim's spool files are being written. The value is recalculated whenever the
11932 variable is referenced. If the operating system does not have the ability to
11933 find the amount of free space (only true for experimental systems), the space
11934 value is -1. For example, to check in an ACL that there is at least 50
11935 megabytes free on the spool, you could write:
11937 condition = ${if > {$spool_space}{50000}}
11939 See also the &%check_spool_space%& option.
11942 .vitem &$thisaddress$&
11943 .vindex "&$thisaddress$&"
11944 This variable is set only during the processing of the &%foranyaddress%&
11945 command in a filter file. Its use is explained in the description of that
11946 command, which can be found in the separate document entitled &'Exim's
11947 interfaces to mail filtering'&.
11949 .vitem &$tls_bits$&
11950 .vindex "&$tls_bits$&"
11951 Contains an approximation of the TLS cipher's bit-strength; the meaning of
11952 this depends upon the TLS implementation used.
11953 If TLS has not been negotiated, the value will be 0.
11954 The value of this is automatically fed into the Cyrus SASL authenticator
11955 when acting as a server, to specify the "external SSF" (a SASL term).
11957 .vitem &$tls_certificate_verified$&
11958 .vindex "&$tls_certificate_verified$&"
11959 This variable is set to &"1"& if a TLS certificate was verified when the
11960 message was received, and &"0"& otherwise.
11962 .vitem &$tls_cipher$&
11963 .vindex "&$tls_cipher$&"
11964 When a message is received from a remote host over an encrypted SMTP
11965 connection, this variable is set to the cipher suite that was negotiated, for
11966 example DES-CBC3-SHA. In other circumstances, in particular, for message
11967 received over unencrypted connections, the variable is empty. Testing
11968 &$tls_cipher$& for emptiness is one way of distinguishing between encrypted and
11969 non-encrypted connections during ACL processing.
11971 The &$tls_cipher$& variable retains its value during message delivery, except
11972 when an outward SMTP delivery takes place via the &(smtp)& transport. In this
11973 case, &$tls_cipher$& is cleared before any outgoing SMTP connection is made,
11974 and then set to the outgoing cipher suite if one is negotiated. See chapter
11975 &<<CHAPTLS>>& for details of TLS support and chapter &<<CHAPsmtptrans>>& for
11976 details of the &(smtp)& transport.
11978 .vitem &$tls_peerdn$&
11979 .vindex "&$tls_peerdn$&"
11980 When a message is received from a remote host over an encrypted SMTP
11981 connection, and Exim is configured to request a certificate from the client,
11982 the value of the Distinguished Name of the certificate is made available in the
11983 &$tls_peerdn$& during subsequent processing. Like &$tls_cipher$&, the
11984 value is retained during message delivery, except during outbound SMTP
11988 .vindex "&$tls_sni$&"
11989 .cindex "TLS" "Server Name Indication"
11990 When a TLS session is being established, if the client sends the Server
11991 Name Indication extension, the value will be placed in this variable.
11992 If the variable appears in &%tls_certificate%& then this option and
11993 some others, described in &<<SECTtlssni>>&,
11994 will be re-expanded early in the TLS session, to permit
11995 a different certificate to be presented (and optionally a different key to be
11996 used) to the client, based upon the value of the SNI extension.
11998 The value will be retained for the lifetime of the message. During outbound
11999 SMTP deliveries, it reflects the value of the &%tls_sni%& option on
12002 .vitem &$tod_bsdinbox$&
12003 .vindex "&$tod_bsdinbox$&"
12004 The time of day and the date, in the format required for BSD-style mailbox
12005 files, for example: Thu Oct 17 17:14:09 1995.
12007 .vitem &$tod_epoch$&
12008 .vindex "&$tod_epoch$&"
12009 The time and date as a number of seconds since the start of the Unix epoch.
12011 .vitem &$tod_epoch_l$&
12012 .vindex "&$tod_epoch_l$&"
12013 The time and date as a number of microseconds since the start of the Unix epoch.
12015 .vitem &$tod_full$&
12016 .vindex "&$tod_full$&"
12017 A full version of the time and date, for example: Wed, 16 Oct 1995 09:51:40
12018 +0100. The timezone is always given as a numerical offset from UTC, with
12019 positive values used for timezones that are ahead (east) of UTC, and negative
12020 values for those that are behind (west).
12023 .vindex "&$tod_log$&"
12024 The time and date in the format used for writing Exim's log files, for example:
12025 1995-10-12 15:32:29, but without a timezone.
12027 .vitem &$tod_logfile$&
12028 .vindex "&$tod_logfile$&"
12029 This variable contains the date in the format yyyymmdd. This is the format that
12030 is used for datestamping log files when &%log_file_path%& contains the &`%D`&
12033 .vitem &$tod_zone$&
12034 .vindex "&$tod_zone$&"
12035 This variable contains the numerical value of the local timezone, for example:
12038 .vitem &$tod_zulu$&
12039 .vindex "&$tod_zulu$&"
12040 This variable contains the UTC date and time in &"Zulu"& format, as specified
12041 by ISO 8601, for example: 20030221154023Z.
12044 .vindex "&$value$&"
12045 This variable contains the result of an expansion lookup, extraction operation,
12046 or external command, as described above. It is also used during a
12047 &*reduce*& expansion.
12049 .vitem &$version_number$&
12050 .vindex "&$version_number$&"
12051 The version number of Exim.
12053 .vitem &$warn_message_delay$&
12054 .vindex "&$warn_message_delay$&"
12055 This variable is set only during the creation of a message warning about a
12056 delivery delay. Details of its use are explained in section &<<SECTcustwarn>>&.
12058 .vitem &$warn_message_recipients$&
12059 .vindex "&$warn_message_recipients$&"
12060 This variable is set only during the creation of a message warning about a
12061 delivery delay. Details of its use are explained in section &<<SECTcustwarn>>&.
12067 . ////////////////////////////////////////////////////////////////////////////
12068 . ////////////////////////////////////////////////////////////////////////////
12070 .chapter "Embedded Perl" "CHAPperl"
12071 .scindex IIDperl "Perl" "calling from Exim"
12072 Exim can be built to include an embedded Perl interpreter. When this is done,
12073 Perl subroutines can be called as part of the string expansion process. To make
12074 use of the Perl support, you need version 5.004 or later of Perl installed on
12075 your system. To include the embedded interpreter in the Exim binary, include
12080 in your &_Local/Makefile_& and then build Exim in the normal way.
12083 .section "Setting up so Perl can be used" "SECID85"
12084 .oindex "&%perl_startup%&"
12085 Access to Perl subroutines is via a global configuration option called
12086 &%perl_startup%& and an expansion string operator &%${perl ...}%&. If there is
12087 no &%perl_startup%& option in the Exim configuration file then no Perl
12088 interpreter is started and there is almost no overhead for Exim (since none of
12089 the Perl library will be paged in unless used). If there is a &%perl_startup%&
12090 option then the associated value is taken to be Perl code which is executed in
12091 a newly created Perl interpreter.
12093 The value of &%perl_startup%& is not expanded in the Exim sense, so you do not
12094 need backslashes before any characters to escape special meanings. The option
12095 should usually be something like
12097 perl_startup = do '/etc/exim.pl'
12099 where &_/etc/exim.pl_& is Perl code which defines any subroutines you want to
12100 use from Exim. Exim can be configured either to start up a Perl interpreter as
12101 soon as it is entered, or to wait until the first time it is needed. Starting
12102 the interpreter at the beginning ensures that it is done while Exim still has
12103 its setuid privilege, but can impose an unnecessary overhead if Perl is not in
12104 fact used in a particular run. Also, note that this does not mean that Exim is
12105 necessarily running as root when Perl is called at a later time. By default,
12106 the interpreter is started only when it is needed, but this can be changed in
12110 .oindex "&%perl_at_start%&"
12111 Setting &%perl_at_start%& (a boolean option) in the configuration requests
12112 a startup when Exim is entered.
12114 The command line option &%-ps%& also requests a startup when Exim is entered,
12115 overriding the setting of &%perl_at_start%&.
12118 There is also a command line option &%-pd%& (for delay) which suppresses the
12119 initial startup, even if &%perl_at_start%& is set.
12122 .section "Calling Perl subroutines" "SECID86"
12123 When the configuration file includes a &%perl_startup%& option you can make use
12124 of the string expansion item to call the Perl subroutines that are defined
12125 by the &%perl_startup%& code. The operator is used in any of the following
12129 ${perl{foo}{argument}}
12130 ${perl{foo}{argument1}{argument2} ... }
12132 which calls the subroutine &%foo%& with the given arguments. A maximum of eight
12133 arguments may be passed. Passing more than this results in an expansion failure
12134 with an error message of the form
12136 Too many arguments passed to Perl subroutine "foo" (max is 8)
12138 The return value of the Perl subroutine is evaluated in a scalar context before
12139 it is passed back to Exim to be inserted into the expanded string. If the
12140 return value is &'undef'&, the expansion is forced to fail in the same way as
12141 an explicit &"fail"& on an &%if%& or &%lookup%& item. If the subroutine aborts
12142 by obeying Perl's &%die%& function, the expansion fails with the error message
12143 that was passed to &%die%&.
12146 .section "Calling Exim functions from Perl" "SECID87"
12147 Within any Perl code called from Exim, the function &'Exim::expand_string()'&
12148 is available to call back into Exim's string expansion function. For example,
12151 my $lp = Exim::expand_string('$local_part');
12153 makes the current Exim &$local_part$& available in the Perl variable &$lp$&.
12154 Note those are single quotes and not double quotes to protect against
12155 &$local_part$& being interpolated as a Perl variable.
12157 If the string expansion is forced to fail by a &"fail"& item, the result of
12158 &'Exim::expand_string()'& is &%undef%&. If there is a syntax error in the
12159 expansion string, the Perl call from the original expansion string fails with
12160 an appropriate error message, in the same way as if &%die%& were used.
12162 .cindex "debugging" "from embedded Perl"
12163 .cindex "log" "writing from embedded Perl"
12164 Two other Exim functions are available for use from within Perl code.
12165 &'Exim::debug_write()'& writes a string to the standard error stream if Exim's
12166 debugging is enabled. If you want a newline at the end, you must supply it.
12167 &'Exim::log_write()'& writes a string to Exim's main log, adding a leading
12168 timestamp. In this case, you should not supply a terminating newline.
12171 .section "Use of standard output and error by Perl" "SECID88"
12172 .cindex "Perl" "standard output and error"
12173 You should not write to the standard error or output streams from within your
12174 Perl code, as it is not defined how these are set up. In versions of Exim
12175 before 4.50, it is possible for the standard output or error to refer to the
12176 SMTP connection during message reception via the daemon. Writing to this stream
12177 is certain to cause chaos. From Exim 4.50 onwards, the standard output and
12178 error streams are connected to &_/dev/null_& in the daemon. The chaos is
12179 avoided, but the output is lost.
12181 .cindex "Perl" "use of &%warn%&"
12182 The Perl &%warn%& statement writes to the standard error stream by default.
12183 Calls to &%warn%& may be embedded in Perl modules that you use, but over which
12184 you have no control. When Exim starts up the Perl interpreter, it arranges for
12185 output from the &%warn%& statement to be written to the Exim main log. You can
12186 change this by including appropriate Perl magic somewhere in your Perl code.
12187 For example, to discard &%warn%& output completely, you need this:
12189 $SIG{__WARN__} = sub { };
12191 Whenever a &%warn%& is obeyed, the anonymous subroutine is called. In this
12192 example, the code for the subroutine is empty, so it does nothing, but you can
12193 include any Perl code that you like. The text of the &%warn%& message is passed
12194 as the first subroutine argument.
12198 . ////////////////////////////////////////////////////////////////////////////
12199 . ////////////////////////////////////////////////////////////////////////////
12201 .chapter "Starting the daemon and the use of network interfaces" &&&
12202 "CHAPinterfaces" &&&
12203 "Starting the daemon"
12204 .cindex "daemon" "starting"
12205 .cindex "interface" "listening"
12206 .cindex "network interface"
12207 .cindex "interface" "network"
12208 .cindex "IP address" "for listening"
12209 .cindex "daemon" "listening IP addresses"
12210 .cindex "TCP/IP" "setting listening interfaces"
12211 .cindex "TCP/IP" "setting listening ports"
12212 A host that is connected to a TCP/IP network may have one or more physical
12213 hardware network interfaces. Each of these interfaces may be configured as one
12214 or more &"logical"& interfaces, which are the entities that a program actually
12215 works with. Each of these logical interfaces is associated with an IP address.
12216 In addition, TCP/IP software supports &"loopback"& interfaces (127.0.0.1 in
12217 IPv4 and ::1 in IPv6), which do not use any physical hardware. Exim requires
12218 knowledge about the host's interfaces for use in three different circumstances:
12221 When a listening daemon is started, Exim needs to know which interfaces
12222 and ports to listen on.
12224 When Exim is routing an address, it needs to know which IP addresses
12225 are associated with local interfaces. This is required for the correct
12226 processing of MX lists by removing the local host and others with the
12227 same or higher priority values. Also, Exim needs to detect cases
12228 when an address is routed to an IP address that in fact belongs to the
12229 local host. Unless the &%self%& router option or the &%allow_localhost%&
12230 option of the smtp transport is set (as appropriate), this is treated
12231 as an error situation.
12233 When Exim connects to a remote host, it may need to know which interface to use
12234 for the outgoing connection.
12238 Exim's default behaviour is likely to be appropriate in the vast majority
12239 of cases. If your host has only one interface, and you want all its IP
12240 addresses to be treated in the same way, and you are using only the
12241 standard SMTP port, you should not need to take any special action. The
12242 rest of this chapter does not apply to you.
12244 In a more complicated situation you may want to listen only on certain
12245 interfaces, or on different ports, and for this reason there are a number of
12246 options that can be used to influence Exim's behaviour. The rest of this
12247 chapter describes how they operate.
12249 When a message is received over TCP/IP, the interface and port that were
12250 actually used are set in &$received_ip_address$& and &$received_port$&.
12254 .section "Starting a listening daemon" "SECID89"
12255 When a listening daemon is started (by means of the &%-bd%& command line
12256 option), the interfaces and ports on which it listens are controlled by the
12260 &%daemon_smtp_ports%& contains a list of default ports. (For backward
12261 compatibility, this option can also be specified in the singular.)
12263 &%local_interfaces%& contains list of interface IP addresses on which to
12264 listen. Each item may optionally also specify a port.
12267 The default list separator in both cases is a colon, but this can be changed as
12268 described in section &<<SECTlistconstruct>>&. When IPv6 addresses are involved,
12269 it is usually best to change the separator to avoid having to double all the
12270 colons. For example:
12272 local_interfaces = <; 127.0.0.1 ; \
12275 3ffe:ffff:836f::fe86:a061
12277 There are two different formats for specifying a port along with an IP address
12278 in &%local_interfaces%&:
12281 The port is added onto the address with a dot separator. For example, to listen
12282 on port 1234 on two different IP addresses:
12284 local_interfaces = <; 192.168.23.65.1234 ; \
12285 3ffe:ffff:836f::fe86:a061.1234
12288 The IP address is enclosed in square brackets, and the port is added
12289 with a colon separator, for example:
12291 local_interfaces = <; [192.168.23.65]:1234 ; \
12292 [3ffe:ffff:836f::fe86:a061]:1234
12296 When a port is not specified, the value of &%daemon_smtp_ports%& is used. The
12297 default setting contains just one port:
12299 daemon_smtp_ports = smtp
12301 If more than one port is listed, each interface that does not have its own port
12302 specified listens on all of them. Ports that are listed in
12303 &%daemon_smtp_ports%& can be identified either by name (defined in
12304 &_/etc/services_&) or by number. However, when ports are given with individual
12305 IP addresses in &%local_interfaces%&, only numbers (not names) can be used.
12309 .section "Special IP listening addresses" "SECID90"
12310 The addresses 0.0.0.0 and ::0 are treated specially. They are interpreted
12311 as &"all IPv4 interfaces"& and &"all IPv6 interfaces"&, respectively. In each
12312 case, Exim tells the TCP/IP stack to &"listen on all IPv&'x'& interfaces"&
12313 instead of setting up separate listening sockets for each interface. The
12314 default value of &%local_interfaces%& is
12316 local_interfaces = 0.0.0.0
12318 when Exim is built without IPv6 support; otherwise it is:
12320 local_interfaces = <; ::0 ; 0.0.0.0
12322 Thus, by default, Exim listens on all available interfaces, on the SMTP port.
12326 .section "Overriding local_interfaces and daemon_smtp_ports" "SECID91"
12327 The &%-oX%& command line option can be used to override the values of
12328 &%daemon_smtp_ports%& and/or &%local_interfaces%& for a particular daemon
12329 instance. Another way of doing this would be to use macros and the &%-D%&
12330 option. However, &%-oX%& can be used by any admin user, whereas modification of
12331 the runtime configuration by &%-D%& is allowed only when the caller is root or
12334 The value of &%-oX%& is a list of items. The default colon separator can be
12335 changed in the usual way if required. If there are any items that do not
12336 contain dots or colons (that is, are not IP addresses), the value of
12337 &%daemon_smtp_ports%& is replaced by the list of those items. If there are any
12338 items that do contain dots or colons, the value of &%local_interfaces%& is
12339 replaced by those items. Thus, for example,
12343 overrides &%daemon_smtp_ports%&, but leaves &%local_interfaces%& unchanged,
12346 -oX 192.168.34.5.1125
12348 overrides &%local_interfaces%&, leaving &%daemon_smtp_ports%& unchanged.
12349 (However, since &%local_interfaces%& now contains no items without ports, the
12350 value of &%daemon_smtp_ports%& is no longer relevant in this example.)
12354 .section "Support for the obsolete SSMTP (or SMTPS) protocol" "SECTsupobssmt"
12355 .cindex "ssmtp protocol"
12356 .cindex "smtps protocol"
12357 .cindex "SMTP" "ssmtp protocol"
12358 .cindex "SMTP" "smtps protocol"
12359 Exim supports the obsolete SSMTP protocol (also known as SMTPS) that was used
12360 before the STARTTLS command was standardized for SMTP. Some legacy clients
12361 still use this protocol. If the &%tls_on_connect_ports%& option is set to a
12362 list of port numbers, connections to those ports must use SSMTP. The most
12363 common use of this option is expected to be
12365 tls_on_connect_ports = 465
12367 because 465 is the usual port number used by the legacy clients. There is also
12368 a command line option &%-tls-on-connect%&, which forces all ports to behave in
12369 this way when a daemon is started.
12371 &*Warning*&: Setting &%tls_on_connect_ports%& does not of itself cause the
12372 daemon to listen on those ports. You must still specify them in
12373 &%daemon_smtp_ports%&, &%local_interfaces%&, or the &%-oX%& option. (This is
12374 because &%tls_on_connect_ports%& applies to &%inetd%& connections as well as to
12375 connections via the daemon.)
12380 .section "IPv6 address scopes" "SECID92"
12381 .cindex "IPv6" "address scopes"
12382 IPv6 addresses have &"scopes"&, and a host with multiple hardware interfaces
12383 can, in principle, have the same link-local IPv6 address on different
12384 interfaces. Thus, additional information is needed, over and above the IP
12385 address, to distinguish individual interfaces. A convention of using a
12386 percent sign followed by something (often the interface name) has been
12387 adopted in some cases, leading to addresses like this:
12389 fe80::202:b3ff:fe03:45c1%eth0
12391 To accommodate this usage, a percent sign followed by an arbitrary string is
12392 allowed at the end of an IPv6 address. By default, Exim calls &[getaddrinfo()]&
12393 to convert a textual IPv6 address for actual use. This function recognizes the
12394 percent convention in operating systems that support it, and it processes the
12395 address appropriately. Unfortunately, some older libraries have problems with
12396 &[getaddrinfo()]&. If
12398 IPV6_USE_INET_PTON=yes
12400 is set in &_Local/Makefile_& (or an OS-dependent Makefile) when Exim is built,
12401 Exim uses &'inet_pton()'& to convert a textual IPv6 address for actual use,
12402 instead of &[getaddrinfo()]&. (Before version 4.14, it always used this
12403 function.) Of course, this means that the additional functionality of
12404 &[getaddrinfo()]& &-- recognizing scoped addresses &-- is lost.
12406 .section "Disabling IPv6" "SECID93"
12407 .cindex "IPv6" "disabling"
12408 Sometimes it happens that an Exim binary that was compiled with IPv6 support is
12409 run on a host whose kernel does not support IPv6. The binary will fall back to
12410 using IPv4, but it may waste resources looking up AAAA records, and trying to
12411 connect to IPv6 addresses, causing delays to mail delivery. If you set the
12412 .oindex "&%disable_ipv6%&"
12413 &%disable_ipv6%& option true, even if the Exim binary has IPv6 support, no IPv6
12414 activities take place. AAAA records are never looked up, and any IPv6 addresses
12415 that are listed in &%local_interfaces%&, data for the &(manualroute)& router,
12416 etc. are ignored. If IP literals are enabled, the &(ipliteral)& router declines
12417 to handle IPv6 literal addresses.
12419 On the other hand, when IPv6 is in use, there may be times when you want to
12420 disable it for certain hosts or domains. You can use the &%dns_ipv4_lookup%&
12421 option to globally suppress the lookup of AAAA records for specified domains,
12422 and you can use the &%ignore_target_hosts%& generic router option to ignore
12423 IPv6 addresses in an individual router.
12427 .section "Examples of starting a listening daemon" "SECID94"
12428 The default case in an IPv6 environment is
12430 daemon_smtp_ports = smtp
12431 local_interfaces = <; ::0 ; 0.0.0.0
12433 This specifies listening on the smtp port on all IPv6 and IPv4 interfaces.
12434 Either one or two sockets may be used, depending on the characteristics of
12435 the TCP/IP stack. (This is complicated and messy; for more information,
12436 read the comments in the &_daemon.c_& source file.)
12438 To specify listening on ports 25 and 26 on all interfaces:
12440 daemon_smtp_ports = 25 : 26
12442 (leaving &%local_interfaces%& at the default setting) or, more explicitly:
12444 local_interfaces = <; ::0.25 ; ::0.26 \
12445 0.0.0.0.25 ; 0.0.0.0.26
12447 To listen on the default port on all IPv4 interfaces, and on port 26 on the
12448 IPv4 loopback address only:
12450 local_interfaces = 0.0.0.0 : 127.0.0.1.26
12452 To specify listening on the default port on specific interfaces only:
12454 local_interfaces = 192.168.34.67 : 192.168.34.67
12456 &*Warning*&: Such a setting excludes listening on the loopback interfaces.
12460 .section "Recognizing the local host" "SECTreclocipadd"
12461 The &%local_interfaces%& option is also used when Exim needs to determine
12462 whether or not an IP address refers to the local host. That is, the IP
12463 addresses of all the interfaces on which a daemon is listening are always
12466 For this usage, port numbers in &%local_interfaces%& are ignored. If either of
12467 the items 0.0.0.0 or ::0 are encountered, Exim gets a complete list of
12468 available interfaces from the operating system, and extracts the relevant
12469 (that is, IPv4 or IPv6) addresses to use for checking.
12471 Some systems set up large numbers of virtual interfaces in order to provide
12472 many virtual web servers. In this situation, you may want to listen for
12473 email on only a few of the available interfaces, but nevertheless treat all
12474 interfaces as local when routing. You can do this by setting
12475 &%extra_local_interfaces%& to a list of IP addresses, possibly including the
12476 &"all"& wildcard values. These addresses are recognized as local, but are not
12477 used for listening. Consider this example:
12479 local_interfaces = <; 127.0.0.1 ; ::1 ; \
12481 3ffe:2101:12:1:a00:20ff:fe86:a061
12483 extra_local_interfaces = <; ::0 ; 0.0.0.0
12485 The daemon listens on the loopback interfaces and just one IPv4 and one IPv6
12486 address, but all available interface addresses are treated as local when
12489 In some environments the local host name may be in an MX list, but with an IP
12490 address that is not assigned to any local interface. In other cases it may be
12491 desirable to treat other host names as if they referred to the local host. Both
12492 these cases can be handled by setting the &%hosts_treat_as_local%& option.
12493 This contains host names rather than IP addresses. When a host is referenced
12494 during routing, either via an MX record or directly, it is treated as the local
12495 host if its name matches &%hosts_treat_as_local%&, or if any of its IP
12496 addresses match &%local_interfaces%& or &%extra_local_interfaces%&.
12500 .section "Delivering to a remote host" "SECID95"
12501 Delivery to a remote host is handled by the smtp transport. By default, it
12502 allows the system's TCP/IP functions to choose which interface to use (if
12503 there is more than one) when connecting to a remote host. However, the
12504 &%interface%& option can be set to specify which interface is used. See the
12505 description of the smtp transport in chapter &<<CHAPsmtptrans>>& for more
12511 . ////////////////////////////////////////////////////////////////////////////
12512 . ////////////////////////////////////////////////////////////////////////////
12514 .chapter "Main configuration" "CHAPmainconfig"
12515 .scindex IIDconfima "configuration file" "main section"
12516 .scindex IIDmaiconf "main configuration"
12517 The first part of the run time configuration file contains three types of item:
12520 Macro definitions: These lines start with an upper case letter. See section
12521 &<<SECTmacrodefs>>& for details of macro processing.
12523 Named list definitions: These lines start with one of the words &"domainlist"&,
12524 &"hostlist"&, &"addresslist"&, or &"localpartlist"&. Their use is described in
12525 section &<<SECTnamedlists>>&.
12527 Main configuration settings: Each setting occupies one line of the file
12528 (with possible continuations). If any setting is preceded by the word
12529 &"hide"&, the &%-bP%& command line option displays its value to admin users
12530 only. See section &<<SECTcos>>& for a description of the syntax of these option
12534 This chapter specifies all the main configuration options, along with their
12535 types and default values. For ease of finding a particular option, they appear
12536 in alphabetical order in section &<<SECTalomo>>& below. However, because there
12537 are now so many options, they are first listed briefly in functional groups, as
12538 an aid to finding the name of the option you are looking for. Some options are
12539 listed in more than one group.
12541 .section "Miscellaneous" "SECID96"
12543 .row &%bi_command%& "to run for &%-bi%& command line option"
12544 .row &%disable_ipv6%& "do no IPv6 processing"
12545 .row &%keep_malformed%& "for broken files &-- should not happen"
12546 .row &%localhost_number%& "for unique message ids in clusters"
12547 .row &%message_body_newlines%& "retain newlines in &$message_body$&"
12548 .row &%message_body_visible%& "how much to show in &$message_body$&"
12549 .row &%mua_wrapper%& "run in &""MUA wrapper""& mode"
12550 .row &%print_topbitchars%& "top-bit characters are printing"
12551 .row &%timezone%& "force time zone"
12555 .section "Exim parameters" "SECID97"
12557 .row &%exim_group%& "override compiled-in value"
12558 .row &%exim_path%& "override compiled-in value"
12559 .row &%exim_user%& "override compiled-in value"
12560 .row &%primary_hostname%& "default from &[uname()]&"
12561 .row &%split_spool_directory%& "use multiple directories"
12562 .row &%spool_directory%& "override compiled-in value"
12567 .section "Privilege controls" "SECID98"
12569 .row &%admin_groups%& "groups that are Exim admin users"
12570 .row &%deliver_drop_privilege%& "drop root for delivery processes"
12571 .row &%local_from_check%& "insert &'Sender:'& if necessary"
12572 .row &%local_from_prefix%& "for testing &'From:'& for local sender"
12573 .row &%local_from_suffix%& "for testing &'From:'& for local sender"
12574 .row &%local_sender_retain%& "keep &'Sender:'& from untrusted user"
12575 .row &%never_users%& "do not run deliveries as these"
12576 .row &%prod_requires_admin%& "forced delivery requires admin user"
12577 .row &%queue_list_requires_admin%& "queue listing requires admin user"
12578 .row &%trusted_groups%& "groups that are trusted"
12579 .row &%trusted_users%& "users that are trusted"
12584 .section "Logging" "SECID99"
12586 .row &%hosts_connection_nolog%& "exemption from connect logging"
12587 .row &%log_file_path%& "override compiled-in value"
12588 .row &%log_selector%& "set/unset optional logging"
12589 .row &%log_timezone%& "add timezone to log lines"
12590 .row &%message_logs%& "create per-message logs"
12591 .row &%preserve_message_logs%& "after message completion"
12592 .row &%process_log_path%& "for SIGUSR1 and &'exiwhat'&"
12593 .row &%syslog_duplication%& "controls duplicate log lines on syslog"
12594 .row &%syslog_facility%& "set syslog &""facility""& field"
12595 .row &%syslog_processname%& "set syslog &""ident""& field"
12596 .row &%syslog_timestamp%& "timestamp syslog lines"
12597 .row &%write_rejectlog%& "control use of message log"
12602 .section "Frozen messages" "SECID100"
12604 .row &%auto_thaw%& "sets time for retrying frozen messages"
12605 .row &%freeze_tell%& "send message when freezing"
12606 .row &%move_frozen_messages%& "to another directory"
12607 .row &%timeout_frozen_after%& "keep frozen messages only so long"
12612 .section "Data lookups" "SECID101"
12614 .row &%ibase_servers%& "InterBase servers"
12615 .row &%ldap_ca_cert_dir%& "dir of CA certs to verify LDAP server's"
12616 .row &%ldap_ca_cert_file%& "file of CA certs to verify LDAP server's"
12617 .row &%ldap_cert_file%& "client cert file for LDAP"
12618 .row &%ldap_cert_key%& "client key file for LDAP"
12619 .row &%ldap_cipher_suite%& "TLS negotiation preference control"
12620 .row &%ldap_default_servers%& "used if no server in query"
12621 .row &%ldap_require_cert%& "action to take without LDAP server cert"
12622 .row &%ldap_start_tls%& "require TLS within LDAP"
12623 .row &%ldap_version%& "set protocol version"
12624 .row &%lookup_open_max%& "lookup files held open"
12625 .row &%mysql_servers%& "default MySQL servers"
12626 .row &%oracle_servers%& "Oracle servers"
12627 .row &%pgsql_servers%& "default PostgreSQL servers"
12628 .row &%sqlite_lock_timeout%& "as it says"
12633 .section "Message ids" "SECID102"
12635 .row &%message_id_header_domain%& "used to build &'Message-ID:'& header"
12636 .row &%message_id_header_text%& "ditto"
12641 .section "Embedded Perl Startup" "SECID103"
12643 .row &%perl_at_start%& "always start the interpreter"
12644 .row &%perl_startup%& "code to obey when starting Perl"
12649 .section "Daemon" "SECID104"
12651 .row &%daemon_smtp_ports%& "default ports"
12652 .row &%daemon_startup_retries%& "number of times to retry"
12653 .row &%daemon_startup_sleep%& "time to sleep between tries"
12654 .row &%extra_local_interfaces%& "not necessarily listened on"
12655 .row &%local_interfaces%& "on which to listen, with optional ports"
12656 .row &%pid_file_path%& "override compiled-in value"
12657 .row &%queue_run_max%& "maximum simultaneous queue runners"
12662 .section "Resource control" "SECID105"
12664 .row &%check_log_inodes%& "before accepting a message"
12665 .row &%check_log_space%& "before accepting a message"
12666 .row &%check_spool_inodes%& "before accepting a message"
12667 .row &%check_spool_space%& "before accepting a message"
12668 .row &%deliver_queue_load_max%& "no queue deliveries if load high"
12669 .row &%queue_only_load%& "queue incoming if load high"
12670 .row &%queue_only_load_latch%& "don't re-evaluate load for each message"
12671 .row &%queue_run_max%& "maximum simultaneous queue runners"
12672 .row &%remote_max_parallel%& "parallel SMTP delivery per message"
12673 .row &%smtp_accept_max%& "simultaneous incoming connections"
12674 .row &%smtp_accept_max_nonmail%& "non-mail commands"
12675 .row &%smtp_accept_max_nonmail_hosts%& "hosts to which the limit applies"
12676 .row &%smtp_accept_max_per_connection%& "messages per connection"
12677 .row &%smtp_accept_max_per_host%& "connections from one host"
12678 .row &%smtp_accept_queue%& "queue mail if more connections"
12679 .row &%smtp_accept_queue_per_connection%& "queue if more messages per &&&
12681 .row &%smtp_accept_reserve%& "only reserve hosts if more connections"
12682 .row &%smtp_check_spool_space%& "from SIZE on MAIL command"
12683 .row &%smtp_connect_backlog%& "passed to TCP/IP stack"
12684 .row &%smtp_load_reserve%& "SMTP from reserved hosts if load high"
12685 .row &%smtp_reserve_hosts%& "these are the reserve hosts"
12690 .section "Policy controls" "SECID106"
12692 .row &%acl_not_smtp%& "ACL for non-SMTP messages"
12693 .row &%acl_not_smtp_mime%& "ACL for non-SMTP MIME parts"
12694 .row &%acl_not_smtp_start%& "ACL for start of non-SMTP message"
12695 .row &%acl_smtp_auth%& "ACL for AUTH"
12696 .row &%acl_smtp_connect%& "ACL for connection"
12697 .row &%acl_smtp_data%& "ACL for DATA"
12698 .row &%acl_smtp_dkim%& "ACL for DKIM verification"
12699 .row &%acl_smtp_etrn%& "ACL for ETRN"
12700 .row &%acl_smtp_expn%& "ACL for EXPN"
12701 .row &%acl_smtp_helo%& "ACL for EHLO or HELO"
12702 .row &%acl_smtp_mail%& "ACL for MAIL"
12703 .row &%acl_smtp_mailauth%& "ACL for AUTH on MAIL command"
12704 .row &%acl_smtp_mime%& "ACL for MIME parts"
12705 .row &%acl_smtp_predata%& "ACL for start of data"
12706 .row &%acl_smtp_quit%& "ACL for QUIT"
12707 .row &%acl_smtp_rcpt%& "ACL for RCPT"
12708 .row &%acl_smtp_starttls%& "ACL for STARTTLS"
12709 .row &%acl_smtp_vrfy%& "ACL for VRFY"
12710 .row &%av_scanner%& "specify virus scanner"
12711 .row &%check_rfc2047_length%& "check length of RFC 2047 &""encoded &&&
12713 .row &%dns_csa_search_limit%& "control CSA parent search depth"
12714 .row &%dns_csa_use_reverse%& "en/disable CSA IP reverse search"
12715 .row &%header_maxsize%& "total size of message header"
12716 .row &%header_line_maxsize%& "individual header line limit"
12717 .row &%helo_accept_junk_hosts%& "allow syntactic junk from these hosts"
12718 .row &%helo_allow_chars%& "allow illegal chars in HELO names"
12719 .row &%helo_lookup_domains%& "lookup hostname for these HELO names"
12720 .row &%helo_try_verify_hosts%& "HELO soft-checked for these hosts"
12721 .row &%helo_verify_hosts%& "HELO hard-checked for these hosts"
12722 .row &%host_lookup%& "host name looked up for these hosts"
12723 .row &%host_lookup_order%& "order of DNS and local name lookups"
12724 .row &%host_reject_connection%& "reject connection from these hosts"
12725 .row &%hosts_treat_as_local%& "useful in some cluster configurations"
12726 .row &%local_scan_timeout%& "timeout for &[local_scan()]&"
12727 .row &%message_size_limit%& "for all messages"
12728 .row &%percent_hack_domains%& "recognize %-hack for these domains"
12729 .row &%spamd_address%& "set interface to SpamAssassin"
12730 .row &%strict_acl_vars%& "object to unset ACL variables"
12735 .section "Callout cache" "SECID107"
12737 .row &%callout_domain_negative_expire%& "timeout for negative domain cache &&&
12739 .row &%callout_domain_positive_expire%& "timeout for positive domain cache &&&
12741 .row &%callout_negative_expire%& "timeout for negative address cache item"
12742 .row &%callout_positive_expire%& "timeout for positive address cache item"
12743 .row &%callout_random_local_part%& "string to use for &""random""& testing"
12748 .section "TLS" "SECID108"
12750 .row &%gnutls_compat_mode%& "use GnuTLS compatibility mode"
12751 .row &%openssl_options%& "adjust OpenSSL compatibility options"
12752 .row &%tls_advertise_hosts%& "advertise TLS to these hosts"
12753 .row &%tls_certificate%& "location of server certificate"
12754 .row &%tls_crl%& "certificate revocation list"
12755 .row &%tls_dh_max_bits%& "clamp D-H bit count suggestion"
12756 .row &%tls_dhparam%& "DH parameters for server"
12757 .row &%tls_on_connect_ports%& "specify SSMTP (SMTPS) ports"
12758 .row &%tls_privatekey%& "location of server private key"
12759 .row &%tls_remember_esmtp%& "don't reset after starting TLS"
12760 .row &%tls_require_ciphers%& "specify acceptable ciphers"
12761 .row &%tls_try_verify_hosts%& "try to verify client certificate"
12762 .row &%tls_verify_certificates%& "expected client certificates"
12763 .row &%tls_verify_hosts%& "insist on client certificate verify"
12768 .section "Local user handling" "SECID109"
12770 .row &%finduser_retries%& "useful in NIS environments"
12771 .row &%gecos_name%& "used when creating &'Sender:'&"
12772 .row &%gecos_pattern%& "ditto"
12773 .row &%max_username_length%& "for systems that truncate"
12774 .row &%unknown_login%& "used when no login name found"
12775 .row &%unknown_username%& "ditto"
12776 .row &%uucp_from_pattern%& "for recognizing &""From ""& lines"
12777 .row &%uucp_from_sender%& "ditto"
12782 .section "All incoming messages (SMTP and non-SMTP)" "SECID110"
12784 .row &%header_maxsize%& "total size of message header"
12785 .row &%header_line_maxsize%& "individual header line limit"
12786 .row &%message_size_limit%& "applies to all messages"
12787 .row &%percent_hack_domains%& "recognize %-hack for these domains"
12788 .row &%received_header_text%& "expanded to make &'Received:'&"
12789 .row &%received_headers_max%& "for mail loop detection"
12790 .row &%recipients_max%& "limit per message"
12791 .row &%recipients_max_reject%& "permanently reject excess recipients"
12797 .section "Non-SMTP incoming messages" "SECID111"
12799 .row &%receive_timeout%& "for non-SMTP messages"
12806 .section "Incoming SMTP messages" "SECID112"
12807 See also the &'Policy controls'& section above.
12810 .row &%host_lookup%& "host name looked up for these hosts"
12811 .row &%host_lookup_order%& "order of DNS and local name lookups"
12812 .row &%recipient_unqualified_hosts%& "may send unqualified recipients"
12813 .row &%rfc1413_hosts%& "make ident calls to these hosts"
12814 .row &%rfc1413_query_timeout%& "zero disables ident calls"
12815 .row &%sender_unqualified_hosts%& "may send unqualified senders"
12816 .row &%smtp_accept_keepalive%& "some TCP/IP magic"
12817 .row &%smtp_accept_max%& "simultaneous incoming connections"
12818 .row &%smtp_accept_max_nonmail%& "non-mail commands"
12819 .row &%smtp_accept_max_nonmail_hosts%& "hosts to which the limit applies"
12820 .row &%smtp_accept_max_per_connection%& "messages per connection"
12821 .row &%smtp_accept_max_per_host%& "connections from one host"
12822 .row &%smtp_accept_queue%& "queue mail if more connections"
12823 .row &%smtp_accept_queue_per_connection%& "queue if more messages per &&&
12825 .row &%smtp_accept_reserve%& "only reserve hosts if more connections"
12826 .row &%smtp_active_hostname%& "host name to use in messages"
12827 .row &%smtp_banner%& "text for welcome banner"
12828 .row &%smtp_check_spool_space%& "from SIZE on MAIL command"
12829 .row &%smtp_connect_backlog%& "passed to TCP/IP stack"
12830 .row &%smtp_enforce_sync%& "of SMTP command/responses"
12831 .row &%smtp_etrn_command%& "what to run for ETRN"
12832 .row &%smtp_etrn_serialize%& "only one at once"
12833 .row &%smtp_load_reserve%& "only reserve hosts if this load"
12834 .row &%smtp_max_unknown_commands%& "before dropping connection"
12835 .row &%smtp_ratelimit_hosts%& "apply ratelimiting to these hosts"
12836 .row &%smtp_ratelimit_mail%& "ratelimit for MAIL commands"
12837 .row &%smtp_ratelimit_rcpt%& "ratelimit for RCPT commands"
12838 .row &%smtp_receive_timeout%& "per command or data line"
12839 .row &%smtp_reserve_hosts%& "these are the reserve hosts"
12840 .row &%smtp_return_error_details%& "give detail on rejections"
12845 .section "SMTP extensions" "SECID113"
12847 .row &%accept_8bitmime%& "advertise 8BITMIME"
12848 .row &%auth_advertise_hosts%& "advertise AUTH to these hosts"
12849 .row &%ignore_fromline_hosts%& "allow &""From ""& from these hosts"
12850 .row &%ignore_fromline_local%& "allow &""From ""& from local SMTP"
12851 .row &%pipelining_advertise_hosts%& "advertise pipelining to these hosts"
12852 .row &%tls_advertise_hosts%& "advertise TLS to these hosts"
12857 .section "Processing messages" "SECID114"
12859 .row &%allow_domain_literals%& "recognize domain literal syntax"
12860 .row &%allow_mx_to_ip%& "allow MX to point to IP address"
12861 .row &%allow_utf8_domains%& "in addresses"
12862 .row &%check_rfc2047_length%& "check length of RFC 2047 &""encoded &&&
12864 .row &%delivery_date_remove%& "from incoming messages"
12865 .row &%envelope_to_remove%& "from incoming messages"
12866 .row &%extract_addresses_remove_arguments%& "affects &%-t%& processing"
12867 .row &%headers_charset%& "default for translations"
12868 .row &%qualify_domain%& "default for senders"
12869 .row &%qualify_recipient%& "default for recipients"
12870 .row &%return_path_remove%& "from incoming messages"
12871 .row &%strip_excess_angle_brackets%& "in addresses"
12872 .row &%strip_trailing_dot%& "at end of addresses"
12873 .row &%untrusted_set_sender%& "untrusted can set envelope sender"
12878 .section "System filter" "SECID115"
12880 .row &%system_filter%& "locate system filter"
12881 .row &%system_filter_directory_transport%& "transport for delivery to a &&&
12883 .row &%system_filter_file_transport%& "transport for delivery to a file"
12884 .row &%system_filter_group%& "group for filter running"
12885 .row &%system_filter_pipe_transport%& "transport for delivery to a pipe"
12886 .row &%system_filter_reply_transport%& "transport for autoreply delivery"
12887 .row &%system_filter_user%& "user for filter running"
12892 .section "Routing and delivery" "SECID116"
12894 .row &%disable_ipv6%& "do no IPv6 processing"
12895 .row &%dns_again_means_nonexist%& "for broken domains"
12896 .row &%dns_check_names_pattern%& "pre-DNS syntax check"
12897 .row &%dns_ipv4_lookup%& "only v4 lookup for these domains"
12898 .row &%dns_retrans%& "parameter for resolver"
12899 .row &%dns_retry%& "parameter for resolver"
12901 .row &%dns_use_dnssec%& "parameter for resolver"
12903 .row &%dns_use_edns0%& "parameter for resolver"
12904 .row &%hold_domains%& "hold delivery for these domains"
12905 .row &%local_interfaces%& "for routing checks"
12906 .row &%queue_domains%& "no immediate delivery for these"
12907 .row &%queue_only%& "no immediate delivery at all"
12908 .row &%queue_only_file%& "no immediate delivery if file exists"
12909 .row &%queue_only_load%& "no immediate delivery if load is high"
12910 .row &%queue_only_load_latch%& "don't re-evaluate load for each message"
12911 .row &%queue_only_override%& "allow command line to override"
12912 .row &%queue_run_in_order%& "order of arrival"
12913 .row &%queue_run_max%& "of simultaneous queue runners"
12914 .row &%queue_smtp_domains%& "no immediate SMTP delivery for these"
12915 .row &%remote_max_parallel%& "parallel SMTP delivery per message"
12916 .row &%remote_sort_domains%& "order of remote deliveries"
12917 .row &%retry_data_expire%& "timeout for retry data"
12918 .row &%retry_interval_max%& "safety net for retry rules"
12923 .section "Bounce and warning messages" "SECID117"
12925 .row &%bounce_message_file%& "content of bounce"
12926 .row &%bounce_message_text%& "content of bounce"
12927 .row &%bounce_return_body%& "include body if returning message"
12928 .row &%bounce_return_message%& "include original message in bounce"
12929 .row &%bounce_return_size_limit%& "limit on returned message"
12930 .row &%bounce_sender_authentication%& "send authenticated sender with bounce"
12931 .row &%dsn_from%& "set &'From:'& contents in bounces"
12932 .row &%errors_copy%& "copy bounce messages"
12933 .row &%errors_reply_to%& "&'Reply-to:'& in bounces"
12934 .row &%delay_warning%& "time schedule"
12935 .row &%delay_warning_condition%& "condition for warning messages"
12936 .row &%ignore_bounce_errors_after%& "discard undeliverable bounces"
12937 .row &%smtp_return_error_details%& "give detail on rejections"
12938 .row &%warn_message_file%& "content of warning message"
12943 .section "Alphabetical list of main options" "SECTalomo"
12944 Those options that undergo string expansion before use are marked with
12947 .option accept_8bitmime main boolean true
12949 .cindex "8-bit characters"
12950 This option causes Exim to send 8BITMIME in its response to an SMTP
12951 EHLO command, and to accept the BODY= parameter on MAIL commands.
12952 However, though Exim is 8-bit clean, it is not a protocol converter, and it
12953 takes no steps to do anything special with messages received by this route.
12955 Historically Exim kept this option off by default, but the maintainers
12956 feel that in today's Internet, this causes more problems than it solves.
12957 It now defaults to true.
12958 A more detailed analysis of the issues is provided by Dan Bernstein:
12960 &url(http://cr.yp.to/smtp/8bitmime.html)
12963 .option acl_not_smtp main string&!! unset
12964 .cindex "&ACL;" "for non-SMTP messages"
12965 .cindex "non-SMTP messages" "ACLs for"
12966 This option defines the ACL that is run when a non-SMTP message has been
12967 read and is on the point of being accepted. See chapter &<<CHAPACL>>& for
12970 .option acl_not_smtp_mime main string&!! unset
12971 This option defines the ACL that is run for individual MIME parts of non-SMTP
12972 messages. It operates in exactly the same way as &%acl_smtp_mime%& operates for
12975 .option acl_not_smtp_start main string&!! unset
12976 .cindex "&ACL;" "at start of non-SMTP message"
12977 .cindex "non-SMTP messages" "ACLs for"
12978 This option defines the ACL that is run before Exim starts reading a
12979 non-SMTP message. See chapter &<<CHAPACL>>& for further details.
12981 .option acl_smtp_auth main string&!! unset
12982 .cindex "&ACL;" "setting up for SMTP commands"
12983 .cindex "AUTH" "ACL for"
12984 This option defines the ACL that is run when an SMTP AUTH command is
12985 received. See chapter &<<CHAPACL>>& for further details.
12987 .option acl_smtp_connect main string&!! unset
12988 .cindex "&ACL;" "on SMTP connection"
12989 This option defines the ACL that is run when an SMTP connection is received.
12990 See chapter &<<CHAPACL>>& for further details.
12992 .option acl_smtp_data main string&!! unset
12993 .cindex "DATA" "ACL for"
12994 This option defines the ACL that is run after an SMTP DATA command has been
12995 processed and the message itself has been received, but before the final
12996 acknowledgment is sent. See chapter &<<CHAPACL>>& for further details.
12998 .option acl_smtp_etrn main string&!! unset
12999 .cindex "ETRN" "ACL for"
13000 This option defines the ACL that is run when an SMTP ETRN command is
13001 received. See chapter &<<CHAPACL>>& for further details.
13003 .option acl_smtp_expn main string&!! unset
13004 .cindex "EXPN" "ACL for"
13005 This option defines the ACL that is run when an SMTP EXPN command is
13006 received. See chapter &<<CHAPACL>>& for further details.
13008 .option acl_smtp_helo main string&!! unset
13009 .cindex "EHLO" "ACL for"
13010 .cindex "HELO" "ACL for"
13011 This option defines the ACL that is run when an SMTP EHLO or HELO
13012 command is received. See chapter &<<CHAPACL>>& for further details.
13015 .option acl_smtp_mail main string&!! unset
13016 .cindex "MAIL" "ACL for"
13017 This option defines the ACL that is run when an SMTP MAIL command is
13018 received. See chapter &<<CHAPACL>>& for further details.
13020 .option acl_smtp_mailauth main string&!! unset
13021 .cindex "AUTH" "on MAIL command"
13022 This option defines the ACL that is run when there is an AUTH parameter on
13023 a MAIL command. See chapter &<<CHAPACL>>& for details of ACLs, and chapter
13024 &<<CHAPSMTPAUTH>>& for details of authentication.
13026 .option acl_smtp_mime main string&!! unset
13027 .cindex "MIME content scanning" "ACL for"
13028 This option is available when Exim is built with the content-scanning
13029 extension. It defines the ACL that is run for each MIME part in a message. See
13030 section &<<SECTscanmimepart>>& for details.
13032 .option acl_smtp_predata main string&!! unset
13033 This option defines the ACL that is run when an SMTP DATA command is
13034 received, before the message itself is received. See chapter &<<CHAPACL>>& for
13037 .option acl_smtp_quit main string&!! unset
13038 .cindex "QUIT, ACL for"
13039 This option defines the ACL that is run when an SMTP QUIT command is
13040 received. See chapter &<<CHAPACL>>& for further details.
13042 .option acl_smtp_rcpt main string&!! unset
13043 .cindex "RCPT" "ACL for"
13044 This option defines the ACL that is run when an SMTP RCPT command is
13045 received. See chapter &<<CHAPACL>>& for further details.
13047 .option acl_smtp_starttls main string&!! unset
13048 .cindex "STARTTLS, ACL for"
13049 This option defines the ACL that is run when an SMTP STARTTLS command is
13050 received. See chapter &<<CHAPACL>>& for further details.
13052 .option acl_smtp_vrfy main string&!! unset
13053 .cindex "VRFY" "ACL for"
13054 This option defines the ACL that is run when an SMTP VRFY command is
13055 received. See chapter &<<CHAPACL>>& for further details.
13057 .option admin_groups main "string list&!!" unset
13058 .cindex "admin user"
13059 This option is expanded just once, at the start of Exim's processing. If the
13060 current group or any of the supplementary groups of an Exim caller is in this
13061 colon-separated list, the caller has admin privileges. If all your system
13062 programmers are in a specific group, for example, you can give them all Exim
13063 admin privileges by putting that group in &%admin_groups%&. However, this does
13064 not permit them to read Exim's spool files (whose group owner is the Exim gid).
13065 To permit this, you have to add individuals to the Exim group.
13067 .option allow_domain_literals main boolean false
13068 .cindex "domain literal"
13069 If this option is set, the RFC 2822 domain literal format is permitted in
13070 email addresses. The option is not set by default, because the domain literal
13071 format is not normally required these days, and few people know about it. It
13072 has, however, been exploited by mail abusers.
13074 Unfortunately, it seems that some DNS black list maintainers are using this
13075 format to report black listing to postmasters. If you want to accept messages
13076 addressed to your hosts by IP address, you need to set
13077 &%allow_domain_literals%& true, and also to add &`@[]`& to the list of local
13078 domains (defined in the named domain list &%local_domains%& in the default
13079 configuration). This &"magic string"& matches the domain literal form of all
13080 the local host's IP addresses.
13083 .option allow_mx_to_ip main boolean false
13084 .cindex "MX record" "pointing to IP address"
13085 It appears that more and more DNS zone administrators are breaking the rules
13086 and putting domain names that look like IP addresses on the right hand side of
13087 MX records. Exim follows the rules and rejects this, giving an error message
13088 that explains the mis-configuration. However, some other MTAs support this
13089 practice, so to avoid &"Why can't Exim do this?"& complaints,
13090 &%allow_mx_to_ip%& exists, in order to enable this heinous activity. It is not
13091 recommended, except when you have no other choice.
13093 .option allow_utf8_domains main boolean false
13094 .cindex "domain" "UTF-8 characters in"
13095 .cindex "UTF-8" "in domain name"
13096 Lots of discussion is going on about internationalized domain names. One
13097 camp is strongly in favour of just using UTF-8 characters, and it seems
13098 that at least two other MTAs permit this. This option allows Exim users to
13099 experiment if they wish.
13101 If it is set true, Exim's domain parsing function allows valid
13102 UTF-8 multicharacters to appear in domain name components, in addition to
13103 letters, digits, and hyphens. However, just setting this option is not
13104 enough; if you want to look up these domain names in the DNS, you must also
13105 adjust the value of &%dns_check_names_pattern%& to match the extended form. A
13106 suitable setting is:
13108 dns_check_names_pattern = (?i)^(?>(?(1)\.|())[a-z0-9\xc0-\xff]\
13109 (?>[-a-z0-9\x80-\xff]*[a-z0-9\x80-\xbf])?)+$
13111 Alternatively, you can just disable this feature by setting
13113 dns_check_names_pattern =
13115 That is, set the option to an empty string so that no check is done.
13118 .option auth_advertise_hosts main "host list&!!" *
13119 .cindex "authentication" "advertising"
13120 .cindex "AUTH" "advertising"
13121 If any server authentication mechanisms are configured, Exim advertises them in
13122 response to an EHLO command only if the calling host matches this list.
13123 Otherwise, Exim does not advertise AUTH.
13124 Exim does not accept AUTH commands from clients to which it has not
13125 advertised the availability of AUTH. The advertising of individual
13126 authentication mechanisms can be controlled by the use of the
13127 &%server_advertise_condition%& generic authenticator option on the individual
13128 authenticators. See chapter &<<CHAPSMTPAUTH>>& for further details.
13130 Certain mail clients (for example, Netscape) require the user to provide a name
13131 and password for authentication if AUTH is advertised, even though it may
13132 not be needed (the host may accept messages from hosts on its local LAN without
13133 authentication, for example). The &%auth_advertise_hosts%& option can be used
13134 to make these clients more friendly by excluding them from the set of hosts to
13135 which Exim advertises AUTH.
13137 .cindex "AUTH" "advertising when encrypted"
13138 If you want to advertise the availability of AUTH only when the connection
13139 is encrypted using TLS, you can make use of the fact that the value of this
13140 option is expanded, with a setting like this:
13142 auth_advertise_hosts = ${if eq{$tls_cipher}{}{}{*}}
13144 .vindex "&$tls_cipher$&"
13145 If &$tls_cipher$& is empty, the session is not encrypted, and the result of
13146 the expansion is empty, thus matching no hosts. Otherwise, the result of the
13147 expansion is *, which matches all hosts.
13150 .option auto_thaw main time 0s
13151 .cindex "thawing messages"
13152 .cindex "unfreezing messages"
13153 If this option is set to a time greater than zero, a queue runner will try a
13154 new delivery attempt on any frozen message, other than a bounce message, if
13155 this much time has passed since it was frozen. This may result in the message
13156 being re-frozen if nothing has changed since the last attempt. It is a way of
13157 saying &"keep on trying, even though there are big problems"&.
13159 &*Note*&: This is an old option, which predates &%timeout_frozen_after%& and
13160 &%ignore_bounce_errors_after%&. It is retained for compatibility, but it is not
13161 thought to be very useful any more, and its use should probably be avoided.
13164 .option av_scanner main string "see below"
13165 This option is available if Exim is built with the content-scanning extension.
13166 It specifies which anti-virus scanner to use. The default value is:
13168 sophie:/var/run/sophie
13170 If the value of &%av_scanner%& starts with a dollar character, it is expanded
13171 before use. See section &<<SECTscanvirus>>& for further details.
13174 .option bi_command main string unset
13176 This option supplies the name of a command that is run when Exim is called with
13177 the &%-bi%& option (see chapter &<<CHAPcommandline>>&). The string value is
13178 just the command name, it is not a complete command line. If an argument is
13179 required, it must come from the &%-oA%& command line option.
13182 .option bounce_message_file main string unset
13183 .cindex "bounce message" "customizing"
13184 .cindex "customizing" "bounce message"
13185 This option defines a template file containing paragraphs of text to be used
13186 for constructing bounce messages. Details of the file's contents are given in
13187 chapter &<<CHAPemsgcust>>&. See also &%warn_message_file%&.
13190 .option bounce_message_text main string unset
13191 When this option is set, its contents are included in the default bounce
13192 message immediately after &"This message was created automatically by mail
13193 delivery software."& It is not used if &%bounce_message_file%& is set.
13195 .option bounce_return_body main boolean true
13196 .cindex "bounce message" "including body"
13197 This option controls whether the body of an incoming message is included in a
13198 bounce message when &%bounce_return_message%& is true. The default setting
13199 causes the entire message, both header and body, to be returned (subject to the
13200 value of &%bounce_return_size_limit%&). If this option is false, only the
13201 message header is included. In the case of a non-SMTP message containing an
13202 error that is detected during reception, only those header lines preceding the
13203 point at which the error was detected are returned.
13204 .cindex "bounce message" "including original"
13206 .option bounce_return_message main boolean true
13207 If this option is set false, none of the original message is included in
13208 bounce messages generated by Exim. See also &%bounce_return_size_limit%& and
13209 &%bounce_return_body%&.
13212 .option bounce_return_size_limit main integer 100K
13213 .cindex "size" "of bounce, limit"
13214 .cindex "bounce message" "size limit"
13215 .cindex "limit" "bounce message size"
13216 This option sets a limit in bytes on the size of messages that are returned to
13217 senders as part of bounce messages when &%bounce_return_message%& is true. The
13218 limit should be less than the value of the global &%message_size_limit%& and of
13219 any &%message_size_limit%& settings on transports, to allow for the bounce text
13220 that Exim generates. If this option is set to zero there is no limit.
13222 When the body of any message that is to be included in a bounce message is
13223 greater than the limit, it is truncated, and a comment pointing this out is
13224 added at the top. The actual cutoff may be greater than the value given, owing
13225 to the use of buffering for transferring the message in chunks (typically 8K in
13226 size). The idea is to save bandwidth on those undeliverable 15-megabyte
13229 .option bounce_sender_authentication main string unset
13230 .cindex "bounce message" "sender authentication"
13231 .cindex "authentication" "bounce message"
13232 .cindex "AUTH" "on bounce message"
13233 This option provides an authenticated sender address that is sent with any
13234 bounce messages generated by Exim that are sent over an authenticated SMTP
13235 connection. A typical setting might be:
13237 bounce_sender_authentication = mailer-daemon@my.domain.example
13239 which would cause bounce messages to be sent using the SMTP command:
13241 MAIL FROM:<> AUTH=mailer-daemon@my.domain.example
13243 The value of &%bounce_sender_authentication%& must always be a complete email
13246 .option callout_domain_negative_expire main time 3h
13247 .cindex "caching" "callout timeouts"
13248 .cindex "callout" "caching timeouts"
13249 This option specifies the expiry time for negative callout cache data for a
13250 domain. See section &<<SECTcallver>>& for details of callout verification, and
13251 section &<<SECTcallvercache>>& for details of the caching.
13254 .option callout_domain_positive_expire main time 7d
13255 This option specifies the expiry time for positive callout cache data for a
13256 domain. See section &<<SECTcallver>>& for details of callout verification, and
13257 section &<<SECTcallvercache>>& for details of the caching.
13260 .option callout_negative_expire main time 2h
13261 This option specifies the expiry time for negative callout cache data for an
13262 address. See section &<<SECTcallver>>& for details of callout verification, and
13263 section &<<SECTcallvercache>>& for details of the caching.
13266 .option callout_positive_expire main time 24h
13267 This option specifies the expiry time for positive callout cache data for an
13268 address. See section &<<SECTcallver>>& for details of callout verification, and
13269 section &<<SECTcallvercache>>& for details of the caching.
13272 .option callout_random_local_part main string&!! "see below"
13273 This option defines the &"random"& local part that can be used as part of
13274 callout verification. The default value is
13276 $primary_hostname-$tod_epoch-testing
13278 See section &<<CALLaddparcall>>& for details of how this value is used.
13281 .option check_log_inodes main integer 0
13282 See &%check_spool_space%& below.
13285 .option check_log_space main integer 0
13286 See &%check_spool_space%& below.
13288 .oindex "&%check_rfc2047_length%&"
13289 .cindex "RFC 2047" "disabling length check"
13290 .option check_rfc2047_length main boolean true
13291 RFC 2047 defines a way of encoding non-ASCII characters in headers using a
13292 system of &"encoded words"&. The RFC specifies a maximum length for an encoded
13293 word; strings to be encoded that exceed this length are supposed to use
13294 multiple encoded words. By default, Exim does not recognize encoded words that
13295 exceed the maximum length. However, it seems that some software, in violation
13296 of the RFC, generates overlong encoded words. If &%check_rfc2047_length%& is
13297 set false, Exim recognizes encoded words of any length.
13300 .option check_spool_inodes main integer 0
13301 See &%check_spool_space%& below.
13304 .option check_spool_space main integer 0
13305 .cindex "checking disk space"
13306 .cindex "disk space, checking"
13307 .cindex "spool directory" "checking space"
13308 The four &%check_...%& options allow for checking of disk resources before a
13309 message is accepted.
13311 .vindex "&$log_inodes$&"
13312 .vindex "&$log_space$&"
13313 .vindex "&$spool_inodes$&"
13314 .vindex "&$spool_space$&"
13315 When any of these options are set, they apply to all incoming messages. If you
13316 want to apply different checks to different kinds of message, you can do so by
13317 testing the variables &$log_inodes$&, &$log_space$&, &$spool_inodes$&, and
13318 &$spool_space$& in an ACL with appropriate additional conditions.
13321 &%check_spool_space%& and &%check_spool_inodes%& check the spool partition if
13322 either value is greater than zero, for example:
13324 check_spool_space = 10M
13325 check_spool_inodes = 100
13327 The spool partition is the one that contains the directory defined by
13328 SPOOL_DIRECTORY in &_Local/Makefile_&. It is used for holding messages in
13331 &%check_log_space%& and &%check_log_inodes%& check the partition in which log
13332 files are written if either is greater than zero. These should be set only if
13333 &%log_file_path%& and &%spool_directory%& refer to different partitions.
13335 If there is less space or fewer inodes than requested, Exim refuses to accept
13336 incoming mail. In the case of SMTP input this is done by giving a 452 temporary
13337 error response to the MAIL command. If ESMTP is in use and there was a
13338 SIZE parameter on the MAIL command, its value is added to the
13339 &%check_spool_space%& value, and the check is performed even if
13340 &%check_spool_space%& is zero, unless &%no_smtp_check_spool_space%& is set.
13342 The values for &%check_spool_space%& and &%check_log_space%& are held as a
13343 number of kilobytes. If a non-multiple of 1024 is specified, it is rounded up.
13345 For non-SMTP input and for batched SMTP input, the test is done at start-up; on
13346 failure a message is written to stderr and Exim exits with a non-zero code, as
13347 it obviously cannot send an error message of any kind.
13349 .option daemon_smtp_ports main string &`smtp`&
13350 .cindex "port" "for daemon"
13351 .cindex "TCP/IP" "setting listening ports"
13352 This option specifies one or more default SMTP ports on which the Exim daemon
13353 listens. See chapter &<<CHAPinterfaces>>& for details of how it is used. For
13354 backward compatibility, &%daemon_smtp_port%& (singular) is a synonym.
13356 .option daemon_startup_retries main integer 9
13357 .cindex "daemon startup, retrying"
13358 This option, along with &%daemon_startup_sleep%&, controls the retrying done by
13359 the daemon at startup when it cannot immediately bind a listening socket
13360 (typically because the socket is already in use): &%daemon_startup_retries%&
13361 defines the number of retries after the first failure, and
13362 &%daemon_startup_sleep%& defines the length of time to wait between retries.
13364 .option daemon_startup_sleep main time 30s
13365 See &%daemon_startup_retries%&.
13367 .option delay_warning main "time list" 24h
13368 .cindex "warning of delay"
13369 .cindex "delay warning, specifying"
13370 When a message is delayed, Exim sends a warning message to the sender at
13371 intervals specified by this option. The data is a colon-separated list of times
13372 after which to send warning messages. If the value of the option is an empty
13373 string or a zero time, no warnings are sent. Up to 10 times may be given. If a
13374 message has been on the queue for longer than the last time, the last interval
13375 between the times is used to compute subsequent warning times. For example,
13378 delay_warning = 4h:8h:24h
13380 the first message is sent after 4 hours, the second after 8 hours, and
13381 the third one after 24 hours. After that, messages are sent every 16 hours,
13382 because that is the interval between the last two times on the list. If you set
13383 just one time, it specifies the repeat interval. For example, with:
13387 messages are repeated every six hours. To stop warnings after a given time, set
13388 a very large time at the end of the list. For example:
13390 delay_warning = 2h:12h:99d
13393 .option delay_warning_condition main string&!! "see below"
13394 .vindex "&$domain$&"
13395 The string is expanded at the time a warning message might be sent. If all the
13396 deferred addresses have the same domain, it is set in &$domain$& during the
13397 expansion. Otherwise &$domain$& is empty. If the result of the expansion is a
13398 forced failure, an empty string, or a string matching any of &"0"&, &"no"& or
13399 &"false"& (the comparison being done caselessly) then the warning message is
13400 not sent. The default is:
13402 delay_warning_condition = ${if or {\
13403 { !eq{$h_list-id:$h_list-post:$h_list-subscribe:}{} }\
13404 { match{$h_precedence:}{(?i)bulk|list|junk} }\
13405 { match{$h_auto-submitted:}{(?i)auto-generated|auto-replied} }\
13408 This suppresses the sending of warnings for messages that contain &'List-ID:'&,
13409 &'List-Post:'&, or &'List-Subscribe:'& headers, or have &"bulk"&, &"list"& or
13410 &"junk"& in a &'Precedence:'& header, or have &"auto-generated"& or
13411 &"auto-replied"& in an &'Auto-Submitted:'& header.
13413 .option deliver_drop_privilege main boolean false
13414 .cindex "unprivileged delivery"
13415 .cindex "delivery" "unprivileged"
13416 If this option is set true, Exim drops its root privilege at the start of a
13417 delivery process, and runs as the Exim user throughout. This severely restricts
13418 the kinds of local delivery that are possible, but is viable in certain types
13419 of configuration. There is a discussion about the use of root privilege in
13420 chapter &<<CHAPsecurity>>&.
13422 .option deliver_queue_load_max main fixed-point unset
13423 .cindex "load average"
13424 .cindex "queue runner" "abandoning"
13425 When this option is set, a queue run is abandoned if the system load average
13426 becomes greater than the value of the option. The option has no effect on
13427 ancient operating systems on which Exim cannot determine the load average.
13428 See also &%queue_only_load%& and &%smtp_load_reserve%&.
13431 .option delivery_date_remove main boolean true
13432 .cindex "&'Delivery-date:'& header line"
13433 Exim's transports have an option for adding a &'Delivery-date:'& header to a
13434 message when it is delivered, in exactly the same way as &'Return-path:'& is
13435 handled. &'Delivery-date:'& records the actual time of delivery. Such headers
13436 should not be present in incoming messages, and this option causes them to be
13437 removed at the time the message is received, to avoid any problems that might
13438 occur when a delivered message is subsequently sent on to some other recipient.
13440 .option disable_fsync main boolean false
13441 .cindex "&[fsync()]&, disabling"
13442 This option is available only if Exim was built with the compile-time option
13443 ENABLE_DISABLE_FSYNC. When this is not set, a reference to &%disable_fsync%& in
13444 a runtime configuration generates an &"unknown option"& error. You should not
13445 build Exim with ENABLE_DISABLE_FSYNC or set &%disable_fsync%& unless you
13446 really, really, really understand what you are doing. &'No pre-compiled
13447 distributions of Exim should ever make this option available.'&
13449 When &%disable_fsync%& is set true, Exim no longer calls &[fsync()]& to force
13450 updated files' data to be written to disc before continuing. Unexpected events
13451 such as crashes and power outages may cause data to be lost or scrambled.
13452 Here be Dragons. &*Beware.*&
13455 .option disable_ipv6 main boolean false
13456 .cindex "IPv6" "disabling"
13457 If this option is set true, even if the Exim binary has IPv6 support, no IPv6
13458 activities take place. AAAA records are never looked up, and any IPv6 addresses
13459 that are listed in &%local_interfaces%&, data for the &%manualroute%& router,
13460 etc. are ignored. If IP literals are enabled, the &(ipliteral)& router declines
13461 to handle IPv6 literal addresses.
13464 .option dns_again_means_nonexist main "domain list&!!" unset
13465 .cindex "DNS" "&""try again""& response; overriding"
13466 DNS lookups give a &"try again"& response for the DNS errors
13467 &"non-authoritative host not found"& and &"SERVERFAIL"&. This can cause Exim to
13468 keep trying to deliver a message, or to give repeated temporary errors to
13469 incoming mail. Sometimes the effect is caused by a badly set up name server and
13470 may persist for a long time. If a domain which exhibits this problem matches
13471 anything in &%dns_again_means_nonexist%&, it is treated as if it did not exist.
13472 This option should be used with care. You can make it apply to reverse lookups
13473 by a setting such as this:
13475 dns_again_means_nonexist = *.in-addr.arpa
13477 This option applies to all DNS lookups that Exim does. It also applies when the
13478 &[gethostbyname()]& or &[getipnodebyname()]& functions give temporary errors,
13479 since these are most likely to be caused by DNS lookup problems. The
13480 &(dnslookup)& router has some options of its own for controlling what happens
13481 when lookups for MX or SRV records give temporary errors. These more specific
13482 options are applied after this global option.
13484 .option dns_check_names_pattern main string "see below"
13485 .cindex "DNS" "pre-check of name syntax"
13486 When this option is set to a non-empty string, it causes Exim to check domain
13487 names for characters that are not allowed in host names before handing them to
13488 the DNS resolver, because some resolvers give temporary errors for names that
13489 contain unusual characters. If a domain name contains any unwanted characters,
13490 a &"not found"& result is forced, and the resolver is not called. The check is
13491 done by matching the domain name against a regular expression, which is the
13492 value of this option. The default pattern is
13494 dns_check_names_pattern = \
13495 (?i)^(?>(?(1)\.|())[^\W_](?>[a-z0-9/-]*[^\W_])?)+$
13497 which permits only letters, digits, slashes, and hyphens in components, but
13498 they must start and end with a letter or digit. Slashes are not, in fact,
13499 permitted in host names, but they are found in certain NS records (which can be
13500 accessed in Exim by using a &%dnsdb%& lookup). If you set
13501 &%allow_utf8_domains%&, you must modify this pattern, or set the option to an
13504 .option dns_csa_search_limit main integer 5
13505 This option controls the depth of parental searching for CSA SRV records in the
13506 DNS, as described in more detail in section &<<SECTverifyCSA>>&.
13508 .option dns_csa_use_reverse main boolean true
13509 This option controls whether or not an IP address, given as a CSA domain, is
13510 reversed and looked up in the reverse DNS, as described in more detail in
13511 section &<<SECTverifyCSA>>&.
13513 .option dns_ipv4_lookup main "domain list&!!" unset
13514 .cindex "IPv6" "DNS lookup for AAAA records"
13515 .cindex "DNS" "IPv6 lookup for AAAA records"
13516 When Exim is compiled with IPv6 support and &%disable_ipv6%& is not set, it
13517 looks for IPv6 address records (AAAA records) as well as IPv4 address records
13518 (A records) when trying to find IP addresses for hosts, unless the host's
13519 domain matches this list.
13521 This is a fudge to help with name servers that give big delays or otherwise do
13522 not work for the AAAA record type. In due course, when the world's name
13523 servers have all been upgraded, there should be no need for this option.
13526 .option dns_retrans main time 0s
13527 .cindex "DNS" "resolver options"
13528 The options &%dns_retrans%& and &%dns_retry%& can be used to set the
13529 retransmission and retry parameters for DNS lookups. Values of zero (the
13530 defaults) leave the system default settings unchanged. The first value is the
13531 time between retries, and the second is the number of retries. It isn't
13532 totally clear exactly how these settings affect the total time a DNS lookup may
13533 take. I haven't found any documentation about timeouts on DNS lookups; these
13534 parameter values are available in the external resolver interface structure,
13535 but nowhere does it seem to describe how they are used or what you might want
13539 .option dns_retry main integer 0
13540 See &%dns_retrans%& above.
13544 .option dns_use_dnssec main integer -1
13545 .cindex "DNS" "resolver options"
13546 .cindex "DNS" "DNSSEC"
13547 If this option is set to a non-negative number then Exim will initialise the
13548 DNS resolver library to either use or not use DNSSEC, overriding the system
13549 default. A value of 0 coerces DNSSEC off, a value of 1 coerces DNSSEC on.
13551 If the resolver library does not support DNSSEC then this option has no effect.
13555 .option dns_use_edns0 main integer -1
13556 .cindex "DNS" "resolver options"
13557 .cindex "DNS" "EDNS0"
13558 If this option is set to a non-negative number then Exim will initialise the
13559 DNS resolver library to either use or not use EDNS0 extensions, overriding
13560 the system default. A value of 0 coerces EDNS0 off, a value of 1 coerces EDNS0
13563 If the resolver library does not support EDNS0 then this option has no effect.
13566 .option drop_cr main boolean false
13567 This is an obsolete option that is now a no-op. It used to affect the way Exim
13568 handled CR and LF characters in incoming messages. What happens now is
13569 described in section &<<SECTlineendings>>&.
13571 .option dsn_from main "string&!!" "see below"
13572 .cindex "&'From:'& header line" "in bounces"
13573 .cindex "bounce messages" "&'From:'& line, specifying"
13574 This option can be used to vary the contents of &'From:'& header lines in
13575 bounces and other automatically generated messages (&"Delivery Status
13576 Notifications"& &-- hence the name of the option). The default setting is:
13578 dsn_from = Mail Delivery System <Mailer-Daemon@$qualify_domain>
13580 The value is expanded every time it is needed. If the expansion fails, a
13581 panic is logged, and the default value is used.
13583 .option envelope_to_remove main boolean true
13584 .cindex "&'Envelope-to:'& header line"
13585 Exim's transports have an option for adding an &'Envelope-to:'& header to a
13586 message when it is delivered, in exactly the same way as &'Return-path:'& is
13587 handled. &'Envelope-to:'& records the original recipient address from the
13588 messages's envelope that caused the delivery to happen. Such headers should not
13589 be present in incoming messages, and this option causes them to be removed at
13590 the time the message is received, to avoid any problems that might occur when a
13591 delivered message is subsequently sent on to some other recipient.
13594 .option errors_copy main "string list&!!" unset
13595 .cindex "bounce message" "copy to other address"
13596 .cindex "copy of bounce message"
13597 Setting this option causes Exim to send bcc copies of bounce messages that it
13598 generates to other addresses. &*Note*&: This does not apply to bounce messages
13599 coming from elsewhere. The value of the option is a colon-separated list of
13600 items. Each item consists of a pattern, terminated by white space, followed by
13601 a comma-separated list of email addresses. If a pattern contains spaces, it
13602 must be enclosed in double quotes.
13604 Each pattern is processed in the same way as a single item in an address list
13605 (see section &<<SECTaddresslist>>&). When a pattern matches the recipient of
13606 the bounce message, the message is copied to the addresses on the list. The
13607 items are scanned in order, and once a matching one is found, no further items
13608 are examined. For example:
13610 errors_copy = spqr@mydomain postmaster@mydomain.example :\
13611 rqps@mydomain hostmaster@mydomain.example,\
13612 postmaster@mydomain.example
13614 .vindex "&$domain$&"
13615 .vindex "&$local_part$&"
13616 The address list is expanded before use. The expansion variables &$local_part$&
13617 and &$domain$& are set from the original recipient of the error message, and if
13618 there was any wildcard matching in the pattern, the expansion
13619 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%errors_copy%&"
13620 variables &$0$&, &$1$&, etc. are set in the normal way.
13623 .option errors_reply_to main string unset
13624 .cindex "bounce message" "&'Reply-to:'& in"
13625 By default, Exim's bounce and delivery warning messages contain the header line
13627 &`From: Mail Delivery System <Mailer-Daemon@`&&'qualify-domain'&&`>`&
13629 .oindex &%quota_warn_message%&
13630 where &'qualify-domain'& is the value of the &%qualify_domain%& option.
13631 A warning message that is generated by the &%quota_warn_message%& option in an
13632 &(appendfile)& transport may contain its own &'From:'& header line that
13633 overrides the default.
13635 Experience shows that people reply to bounce messages. If the
13636 &%errors_reply_to%& option is set, a &'Reply-To:'& header is added to bounce
13637 and warning messages. For example:
13639 errors_reply_to = postmaster@my.domain.example
13641 The value of the option is not expanded. It must specify a valid RFC 2822
13642 address. However, if a warning message that is generated by the
13643 &%quota_warn_message%& option in an &(appendfile)& transport contain its
13644 own &'Reply-To:'& header line, the value of the &%errors_reply_to%& option is
13648 .option exim_group main string "compile-time configured"
13649 .cindex "gid (group id)" "Exim's own"
13650 .cindex "Exim group"
13651 This option changes the gid under which Exim runs when it gives up root
13652 privilege. The default value is compiled into the binary. The value of this
13653 option is used only when &%exim_user%& is also set. Unless it consists entirely
13654 of digits, the string is looked up using &[getgrnam()]&, and failure causes a
13655 configuration error. See chapter &<<CHAPsecurity>>& for a discussion of
13659 .option exim_path main string "see below"
13660 .cindex "Exim binary, path name"
13661 This option specifies the path name of the Exim binary, which is used when Exim
13662 needs to re-exec itself. The default is set up to point to the file &'exim'& in
13663 the directory configured at compile time by the BIN_DIRECTORY setting. It
13664 is necessary to change &%exim_path%& if, exceptionally, Exim is run from some
13666 &*Warning*&: Do not use a macro to define the value of this option, because
13667 you will break those Exim utilities that scan the configuration file to find
13668 where the binary is. (They then use the &%-bP%& option to extract option
13669 settings such as the value of &%spool_directory%&.)
13672 .option exim_user main string "compile-time configured"
13673 .cindex "uid (user id)" "Exim's own"
13674 .cindex "Exim user"
13675 This option changes the uid under which Exim runs when it gives up root
13676 privilege. The default value is compiled into the binary. Ownership of the run
13677 time configuration file and the use of the &%-C%& and &%-D%& command line
13678 options is checked against the values in the binary, not what is set here.
13680 Unless it consists entirely of digits, the string is looked up using
13681 &[getpwnam()]&, and failure causes a configuration error. If &%exim_group%& is
13682 not also supplied, the gid is taken from the result of &[getpwnam()]& if it is
13683 used. See chapter &<<CHAPsecurity>>& for a discussion of security issues.
13686 .option extra_local_interfaces main "string list" unset
13687 This option defines network interfaces that are to be considered local when
13688 routing, but which are not used for listening by the daemon. See section
13689 &<<SECTreclocipadd>>& for details.
13692 . Allow this long option name to split; give it unsplit as a fifth argument
13693 . for the automatic .oindex that is generated by .option.
13695 .option "extract_addresses_remove_ &~&~arguments" main boolean true &&&
13696 extract_addresses_remove_arguments
13698 .cindex "command line" "addresses with &%-t%&"
13699 .cindex "Sendmail compatibility" "&%-t%& option"
13700 According to some Sendmail documentation (Sun, IRIX, HP-UX), if any addresses
13701 are present on the command line when the &%-t%& option is used to build an
13702 envelope from a message's &'To:'&, &'Cc:'& and &'Bcc:'& headers, the command
13703 line addresses are removed from the recipients list. This is also how Smail
13704 behaves. However, other Sendmail documentation (the O'Reilly book) states that
13705 command line addresses are added to those obtained from the header lines. When
13706 &%extract_addresses_remove_arguments%& is true (the default), Exim subtracts
13707 argument headers. If it is set false, Exim adds rather than removes argument
13711 .option finduser_retries main integer 0
13712 .cindex "NIS, retrying user lookups"
13713 On systems running NIS or other schemes in which user and group information is
13714 distributed from a remote system, there can be times when &[getpwnam()]& and
13715 related functions fail, even when given valid data, because things time out.
13716 Unfortunately these failures cannot be distinguished from genuine &"not found"&
13717 errors. If &%finduser_retries%& is set greater than zero, Exim will try that
13718 many extra times to find a user or a group, waiting for one second between
13721 .cindex "&_/etc/passwd_&" "multiple reading of"
13722 You should not set this option greater than zero if your user information is in
13723 a traditional &_/etc/passwd_& file, because it will cause Exim needlessly to
13724 search the file multiple times for non-existent users, and also cause delay.
13728 .option freeze_tell main "string list, comma separated" unset
13729 .cindex "freezing messages" "sending a message when freezing"
13730 On encountering certain errors, or when configured to do so in a system filter,
13731 ACL, or special router, Exim freezes a message. This means that no further
13732 delivery attempts take place until an administrator thaws the message, or the
13733 &%auto_thaw%&, &%ignore_bounce_errors_after%&, or &%timeout_frozen_after%&
13734 feature cause it to be processed. If &%freeze_tell%& is set, Exim generates a
13735 warning message whenever it freezes something, unless the message it is
13736 freezing is a locally-generated bounce message. (Without this exception there
13737 is the possibility of looping.) The warning message is sent to the addresses
13738 supplied as the comma-separated value of this option. If several of the
13739 message's addresses cause freezing, only a single message is sent. If the
13740 freezing was automatic, the reason(s) for freezing can be found in the message
13741 log. If you configure freezing in a filter or ACL, you must arrange for any
13742 logging that you require.
13745 .option gecos_name main string&!! unset
13747 .cindex "&""gecos""& field, parsing"
13748 Some operating systems, notably HP-UX, use the &"gecos"& field in the system
13749 password file to hold other information in addition to users' real names. Exim
13750 looks up this field for use when it is creating &'Sender:'& or &'From:'&
13751 headers. If either &%gecos_pattern%& or &%gecos_name%& are unset, the contents
13752 of the field are used unchanged, except that, if an ampersand is encountered,
13753 it is replaced by the user's login name with the first character forced to
13754 upper case, since this is a convention that is observed on many systems.
13756 When these options are set, &%gecos_pattern%& is treated as a regular
13757 expression that is to be applied to the field (again with && replaced by the
13758 login name), and if it matches, &%gecos_name%& is expanded and used as the
13761 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%gecos_name%&"
13762 Numeric variables such as &$1$&, &$2$&, etc. can be used in the expansion to
13763 pick up sub-fields that were matched by the pattern. In HP-UX, where the user's
13764 name terminates at the first comma, the following can be used:
13766 gecos_pattern = ([^,]*)
13770 .option gecos_pattern main string unset
13771 See &%gecos_name%& above.
13774 .option gnutls_compat_mode main boolean unset
13775 This option controls whether GnuTLS is used in compatibility mode in an Exim
13776 server. This reduces security slightly, but improves interworking with older
13777 implementations of TLS.
13779 .option headers_charset main string "see below"
13780 This option sets a default character set for translating from encoded MIME
13781 &"words"& in header lines, when referenced by an &$h_xxx$& expansion item. The
13782 default is the value of HEADERS_CHARSET in &_Local/Makefile_&. The
13783 ultimate default is ISO-8859-1. For more details see the description of header
13784 insertions in section &<<SECTexpansionitems>>&.
13788 .option header_maxsize main integer "see below"
13789 .cindex "header section" "maximum size of"
13790 .cindex "limit" "size of message header section"
13791 This option controls the overall maximum size of a message's header
13792 section. The default is the value of HEADER_MAXSIZE in
13793 &_Local/Makefile_&; the default for that is 1M. Messages with larger header
13794 sections are rejected.
13797 .option header_line_maxsize main integer 0
13798 .cindex "header lines" "maximum size of"
13799 .cindex "limit" "size of one header line"
13800 This option limits the length of any individual header line in a message, after
13801 all the continuations have been joined together. Messages with individual
13802 header lines that are longer than the limit are rejected. The default value of
13803 zero means &"no limit"&.
13808 .option helo_accept_junk_hosts main "host list&!!" unset
13809 .cindex "HELO" "accepting junk data"
13810 .cindex "EHLO" "accepting junk data"
13811 Exim checks the syntax of HELO and EHLO commands for incoming SMTP
13812 mail, and gives an error response for invalid data. Unfortunately, there are
13813 some SMTP clients that send syntactic junk. They can be accommodated by setting
13814 this option. Note that this is a syntax check only. See &%helo_verify_hosts%&
13815 if you want to do semantic checking.
13816 See also &%helo_allow_chars%& for a way of extending the permitted character
13820 .option helo_allow_chars main string unset
13821 .cindex "HELO" "underscores in"
13822 .cindex "EHLO" "underscores in"
13823 .cindex "underscore in EHLO/HELO"
13824 This option can be set to a string of rogue characters that are permitted in
13825 all EHLO and HELO names in addition to the standard letters, digits,
13826 hyphens, and dots. If you really must allow underscores, you can set
13828 helo_allow_chars = _
13830 Note that the value is one string, not a list.
13833 .option helo_lookup_domains main "domain list&!!" &`@:@[]`&
13834 .cindex "HELO" "forcing reverse lookup"
13835 .cindex "EHLO" "forcing reverse lookup"
13836 If the domain given by a client in a HELO or EHLO command matches this
13837 list, a reverse lookup is done in order to establish the host's true name. The
13838 default forces a lookup if the client host gives the server's name or any of
13839 its IP addresses (in brackets), something that broken clients have been seen to
13843 .option helo_try_verify_hosts main "host list&!!" unset
13844 .cindex "HELO verifying" "optional"
13845 .cindex "EHLO" "verifying, optional"
13846 By default, Exim just checks the syntax of HELO and EHLO commands (see
13847 &%helo_accept_junk_hosts%& and &%helo_allow_chars%&). However, some sites like
13848 to do more extensive checking of the data supplied by these commands. The ACL
13849 condition &`verify = helo`& is provided to make this possible.
13850 Formerly, it was necessary also to set this option (&%helo_try_verify_hosts%&)
13851 to force the check to occur. From release 4.53 onwards, this is no longer
13852 necessary. If the check has not been done before &`verify = helo`& is
13853 encountered, it is done at that time. Consequently, this option is obsolete.
13854 Its specification is retained here for backwards compatibility.
13856 When an EHLO or HELO command is received, if the calling host matches
13857 &%helo_try_verify_hosts%&, Exim checks that the host name given in the HELO or
13858 EHLO command either:
13861 is an IP literal matching the calling address of the host, or
13863 .cindex "DNS" "reverse lookup"
13864 .cindex "reverse DNS lookup"
13865 matches the host name that Exim obtains by doing a reverse lookup of the
13866 calling host address, or
13868 when looked up using &[gethostbyname()]& (or &[getipnodebyname()]& when
13869 available) yields the calling host address.
13872 However, the EHLO or HELO command is not rejected if any of the checks
13873 fail. Processing continues, but the result of the check is remembered, and can
13874 be detected later in an ACL by the &`verify = helo`& condition.
13876 .option helo_verify_hosts main "host list&!!" unset
13877 .cindex "HELO verifying" "mandatory"
13878 .cindex "EHLO" "verifying, mandatory"
13879 Like &%helo_try_verify_hosts%&, this option is obsolete, and retained only for
13880 backwards compatibility. For hosts that match this option, Exim checks the host
13881 name given in the HELO or EHLO in the same way as for
13882 &%helo_try_verify_hosts%&. If the check fails, the HELO or EHLO command is
13883 rejected with a 550 error, and entries are written to the main and reject logs.
13884 If a MAIL command is received before EHLO or HELO, it is rejected with a 503
13887 .option hold_domains main "domain list&!!" unset
13888 .cindex "domain" "delaying delivery"
13889 .cindex "delivery" "delaying certain domains"
13890 This option allows mail for particular domains to be held on the queue
13891 manually. The option is overridden if a message delivery is forced with the
13892 &%-M%&, &%-qf%&, &%-Rf%& or &%-Sf%& options, and also while testing or
13893 verifying addresses using &%-bt%& or &%-bv%&. Otherwise, if a domain matches an
13894 item in &%hold_domains%&, no routing or delivery for that address is done, and
13895 it is deferred every time the message is looked at.
13897 This option is intended as a temporary operational measure for delaying the
13898 delivery of mail while some problem is being sorted out, or some new
13899 configuration tested. If you just want to delay the processing of some
13900 domains until a queue run occurs, you should use &%queue_domains%& or
13901 &%queue_smtp_domains%&, not &%hold_domains%&.
13903 A setting of &%hold_domains%& does not override Exim's code for removing
13904 messages from the queue if they have been there longer than the longest retry
13905 time in any retry rule. If you want to hold messages for longer than the normal
13906 retry times, insert a dummy retry rule with a long retry time.
13909 .option host_lookup main "host list&!!" unset
13910 .cindex "host name" "lookup, forcing"
13911 Exim does not look up the name of a calling host from its IP address unless it
13912 is required to compare against some host list, or the host matches
13913 &%helo_try_verify_hosts%& or &%helo_verify_hosts%&, or the host matches this
13914 option (which normally contains IP addresses rather than host names). The
13915 default configuration file contains
13919 which causes a lookup to happen for all hosts. If the expense of these lookups
13920 is felt to be too great, the setting can be changed or removed.
13922 After a successful reverse lookup, Exim does a forward lookup on the name it
13923 has obtained, to verify that it yields the IP address that it started with. If
13924 this check fails, Exim behaves as if the name lookup failed.
13926 .vindex "&$host_lookup_failed$&"
13927 .vindex "&$sender_host_name$&"
13928 After any kind of failure, the host name (in &$sender_host_name$&) remains
13929 unset, and &$host_lookup_failed$& is set to the string &"1"&. See also
13930 &%dns_again_means_nonexist%&, &%helo_lookup_domains%&, and
13931 &`verify = reverse_host_lookup`& in ACLs.
13934 .option host_lookup_order main "string list" &`bydns:byaddr`&
13935 This option specifies the order of different lookup methods when Exim is trying
13936 to find a host name from an IP address. The default is to do a DNS lookup
13937 first, and then to try a local lookup (using &[gethostbyaddr()]& or equivalent)
13938 if that fails. You can change the order of these lookups, or omit one entirely,
13941 &*Warning*&: The &"byaddr"& method does not always yield aliases when there are
13942 multiple PTR records in the DNS and the IP address is not listed in
13943 &_/etc/hosts_&. Different operating systems give different results in this
13944 case. That is why the default tries a DNS lookup first.
13948 .option host_reject_connection main "host list&!!" unset
13949 .cindex "host" "rejecting connections from"
13950 If this option is set, incoming SMTP calls from the hosts listed are rejected
13951 as soon as the connection is made.
13952 This option is obsolete, and retained only for backward compatibility, because
13953 nowadays the ACL specified by &%acl_smtp_connect%& can also reject incoming
13954 connections immediately.
13956 The ability to give an immediate rejection (either by this option or using an
13957 ACL) is provided for use in unusual cases. Many hosts will just try again,
13958 sometimes without much delay. Normally, it is better to use an ACL to reject
13959 incoming messages at a later stage, such as after RCPT commands. See
13960 chapter &<<CHAPACL>>&.
13963 .option hosts_connection_nolog main "host list&!!" unset
13964 .cindex "host" "not logging connections from"
13965 This option defines a list of hosts for which connection logging does not
13966 happen, even though the &%smtp_connection%& log selector is set. For example,
13967 you might want not to log SMTP connections from local processes, or from
13968 127.0.0.1, or from your local LAN. This option is consulted in the main loop of
13969 the daemon; you should therefore strive to restrict its value to a short inline
13970 list of IP addresses and networks. To disable logging SMTP connections from
13971 local processes, you must create a host list with an empty item. For example:
13973 hosts_connection_nolog = :
13975 If the &%smtp_connection%& log selector is not set, this option has no effect.
13979 .option hosts_treat_as_local main "domain list&!!" unset
13980 .cindex "local host" "domains treated as"
13981 .cindex "host" "treated as local"
13982 If this option is set, any host names that match the domain list are treated as
13983 if they were the local host when Exim is scanning host lists obtained from MX
13985 or other sources. Note that the value of this option is a domain list, not a
13986 host list, because it is always used to check host names, not IP addresses.
13988 This option also applies when Exim is matching the special items
13989 &`@mx_any`&, &`@mx_primary`&, and &`@mx_secondary`& in a domain list (see
13990 section &<<SECTdomainlist>>&), and when checking the &%hosts%& option in the
13991 &(smtp)& transport for the local host (see the &%allow_localhost%& option in
13992 that transport). See also &%local_interfaces%&, &%extra_local_interfaces%&, and
13993 chapter &<<CHAPinterfaces>>&, which contains a discussion about local network
13994 interfaces and recognizing the local host.
13997 .option ibase_servers main "string list" unset
13998 .cindex "InterBase" "server list"
13999 This option provides a list of InterBase servers and associated connection data,
14000 to be used in conjunction with &(ibase)& lookups (see section &<<SECID72>>&).
14001 The option is available only if Exim has been built with InterBase support.
14005 .option ignore_bounce_errors_after main time 10w
14006 .cindex "bounce message" "discarding"
14007 .cindex "discarding bounce message"
14008 This option affects the processing of bounce messages that cannot be delivered,
14009 that is, those that suffer a permanent delivery failure. (Bounce messages that
14010 suffer temporary delivery failures are of course retried in the usual way.)
14012 After a permanent delivery failure, bounce messages are frozen,
14013 because there is no sender to whom they can be returned. When a frozen bounce
14014 message has been on the queue for more than the given time, it is unfrozen at
14015 the next queue run, and a further delivery is attempted. If delivery fails
14016 again, the bounce message is discarded. This makes it possible to keep failed
14017 bounce messages around for a shorter time than the normal maximum retry time
14018 for frozen messages. For example,
14020 ignore_bounce_errors_after = 12h
14022 retries failed bounce message deliveries after 12 hours, discarding any further
14023 failures. If the value of this option is set to a zero time period, bounce
14024 failures are discarded immediately. Setting a very long time (as in the default
14025 value) has the effect of disabling this option. For ways of automatically
14026 dealing with other kinds of frozen message, see &%auto_thaw%& and
14027 &%timeout_frozen_after%&.
14030 .option ignore_fromline_hosts main "host list&!!" unset
14031 .cindex "&""From""& line"
14032 .cindex "UUCP" "&""From""& line"
14033 Some broken SMTP clients insist on sending a UUCP-like &"From&~"& line before
14034 the headers of a message. By default this is treated as the start of the
14035 message's body, which means that any following headers are not recognized as
14036 such. Exim can be made to ignore it by setting &%ignore_fromline_hosts%& to
14037 match those hosts that insist on sending it. If the sender is actually a local
14038 process rather than a remote host, and is using &%-bs%& to inject the messages,
14039 &%ignore_fromline_local%& must be set to achieve this effect.
14042 .option ignore_fromline_local main boolean false
14043 See &%ignore_fromline_hosts%& above.
14046 .option keep_malformed main time 4d
14047 This option specifies the length of time to keep messages whose spool files
14048 have been corrupted in some way. This should, of course, never happen. At the
14049 next attempt to deliver such a message, it gets removed. The incident is
14053 .option ldap_ca_cert_dir main string unset
14054 .cindex "LDAP", "TLS CA certificate directory"
14055 This option indicates which directory contains CA certificates for verifying
14056 a TLS certificate presented by an LDAP server.
14057 While Exim does not provide a default value, your SSL library may.
14058 Analogous to &%tls_verify_certificates%& but as a client-side option for LDAP
14059 and constrained to be a directory.
14062 .option ldap_ca_cert_file main string unset
14063 .cindex "LDAP", "TLS CA certificate file"
14064 This option indicates which file contains CA certificates for verifying
14065 a TLS certificate presented by an LDAP server.
14066 While Exim does not provide a default value, your SSL library may.
14067 Analogous to &%tls_verify_certificates%& but as a client-side option for LDAP
14068 and constrained to be a file.
14071 .option ldap_cert_file main string unset
14072 .cindex "LDAP" "TLS client certificate file"
14073 This option indicates which file contains an TLS client certificate which
14074 Exim should present to the LDAP server during TLS negotiation.
14075 Should be used together with &%ldap_cert_key%&.
14078 .option ldap_cert_key main string unset
14079 .cindex "LDAP" "TLS client key file"
14080 This option indicates which file contains the secret/private key to use
14081 to prove identity to the LDAP server during TLS negotiation.
14082 Should be used together with &%ldap_cert_file%&, which contains the
14083 identity to be proven.
14086 .option ldap_cipher_suite main string unset
14087 .cindex "LDAP" "TLS cipher suite"
14088 This controls the TLS cipher-suite negotiation during TLS negotiation with
14089 the LDAP server. See &<<SECTreqciphssl>>& for more details of the format of
14090 cipher-suite options with OpenSSL (as used by LDAP client libraries).
14093 .option ldap_default_servers main "string list" unset
14094 .cindex "LDAP" "default servers"
14095 This option provides a list of LDAP servers which are tried in turn when an
14096 LDAP query does not contain a server. See section &<<SECTforldaque>>& for
14097 details of LDAP queries. This option is available only when Exim has been built
14101 .option ldap_require_cert main string unset.
14102 .cindex "LDAP" "policy for LDAP server TLS cert presentation"
14103 This should be one of the values "hard", "demand", "allow", "try" or "never".
14104 A value other than one of these is interpreted as "never".
14105 See the entry "TLS_REQCERT" in your system man page for ldap.conf(5).
14106 Although Exim does not set a default, the LDAP library probably defaults
14110 .option ldap_start_tls main boolean false
14111 .cindex "LDAP" "whether or not to negotiate TLS"
14112 If set, Exim will attempt to negotiate TLS with the LDAP server when
14113 connecting on a regular LDAP port. This is the LDAP equivalent of SMTP's
14114 "STARTTLS". This is distinct from using "ldaps", which is the LDAP form
14116 In the event of failure to negotiate TLS, the action taken is controlled
14117 by &%ldap_require_cert%&.
14120 .option ldap_version main integer unset
14121 .cindex "LDAP" "protocol version, forcing"
14122 This option can be used to force Exim to set a specific protocol version for
14123 LDAP. If it option is unset, it is shown by the &%-bP%& command line option as
14124 -1. When this is the case, the default is 3 if LDAP_VERSION3 is defined in
14125 the LDAP headers; otherwise it is 2. This option is available only when Exim
14126 has been built with LDAP support.
14130 .option local_from_check main boolean true
14131 .cindex "&'Sender:'& header line" "disabling addition of"
14132 .cindex "&'From:'& header line" "disabling checking of"
14133 When a message is submitted locally (that is, not over a TCP/IP connection) by
14134 an untrusted user, Exim removes any existing &'Sender:'& header line, and
14135 checks that the &'From:'& header line matches the login of the calling user and
14136 the domain specified by &%qualify_domain%&.
14138 &*Note*&: An unqualified address (no domain) in the &'From:'& header in a
14139 locally submitted message is automatically qualified by Exim, unless the
14140 &%-bnq%& command line option is used.
14142 You can use &%local_from_prefix%& and &%local_from_suffix%& to permit affixes
14143 on the local part. If the &'From:'& header line does not match, Exim adds a
14144 &'Sender:'& header with an address constructed from the calling user's login
14145 and the default qualify domain.
14147 If &%local_from_check%& is set false, the &'From:'& header check is disabled,
14148 and no &'Sender:'& header is ever added. If, in addition, you want to retain
14149 &'Sender:'& header lines supplied by untrusted users, you must also set
14150 &%local_sender_retain%& to be true.
14152 .cindex "envelope sender"
14153 These options affect only the header lines in the message. The envelope sender
14154 is still forced to be the login id at the qualify domain unless
14155 &%untrusted_set_sender%& permits the user to supply an envelope sender.
14157 For messages received over TCP/IP, an ACL can specify &"submission mode"& to
14158 request similar header line checking. See section &<<SECTthesenhea>>&, which
14159 has more details about &'Sender:'& processing.
14164 .option local_from_prefix main string unset
14165 When Exim checks the &'From:'& header line of locally submitted messages for
14166 matching the login id (see &%local_from_check%& above), it can be configured to
14167 ignore certain prefixes and suffixes in the local part of the address. This is
14168 done by setting &%local_from_prefix%& and/or &%local_from_suffix%& to
14169 appropriate lists, in the same form as the &%local_part_prefix%& and
14170 &%local_part_suffix%& router options (see chapter &<<CHAProutergeneric>>&). For
14173 local_from_prefix = *-
14175 is set, a &'From:'& line containing
14177 From: anything-user@your.domain.example
14179 will not cause a &'Sender:'& header to be added if &'user@your.domain.example'&
14180 matches the actual sender address that is constructed from the login name and
14184 .option local_from_suffix main string unset
14185 See &%local_from_prefix%& above.
14188 .option local_interfaces main "string list" "see below"
14189 This option controls which network interfaces are used by the daemon for
14190 listening; they are also used to identify the local host when routing. Chapter
14191 &<<CHAPinterfaces>>& contains a full description of this option and the related
14192 options &%daemon_smtp_ports%&, &%extra_local_interfaces%&,
14193 &%hosts_treat_as_local%&, and &%tls_on_connect_ports%&. The default value for
14194 &%local_interfaces%& is
14196 local_interfaces = 0.0.0.0
14198 when Exim is built without IPv6 support; otherwise it is
14200 local_interfaces = <; ::0 ; 0.0.0.0
14203 .option local_scan_timeout main time 5m
14204 .cindex "timeout" "for &[local_scan()]& function"
14205 .cindex "&[local_scan()]& function" "timeout"
14206 This timeout applies to the &[local_scan()]& function (see chapter
14207 &<<CHAPlocalscan>>&). Zero means &"no timeout"&. If the timeout is exceeded,
14208 the incoming message is rejected with a temporary error if it is an SMTP
14209 message. For a non-SMTP message, the message is dropped and Exim ends with a
14210 non-zero code. The incident is logged on the main and reject logs.
14214 .option local_sender_retain main boolean false
14215 .cindex "&'Sender:'& header line" "retaining from local submission"
14216 When a message is submitted locally (that is, not over a TCP/IP connection) by
14217 an untrusted user, Exim removes any existing &'Sender:'& header line. If you
14218 do not want this to happen, you must set &%local_sender_retain%&, and you must
14219 also set &%local_from_check%& to be false (Exim will complain if you do not).
14220 See also the ACL modifier &`control = suppress_local_fixups`&. Section
14221 &<<SECTthesenhea>>& has more details about &'Sender:'& processing.
14226 .option localhost_number main string&!! unset
14227 .cindex "host" "locally unique number for"
14228 .cindex "message ids" "with multiple hosts"
14229 .vindex "&$localhost_number$&"
14230 Exim's message ids are normally unique only within the local host. If
14231 uniqueness among a set of hosts is required, each host must set a different
14232 value for the &%localhost_number%& option. The string is expanded immediately
14233 after reading the configuration file (so that a number can be computed from the
14234 host name, for example) and the result of the expansion must be a number in the
14235 range 0&--16 (or 0&--10 on operating systems with case-insensitive file
14236 systems). This is available in subsequent string expansions via the variable
14237 &$localhost_number$&. When &%localhost_number is set%&, the final two
14238 characters of the message id, instead of just being a fractional part of the
14239 time, are computed from the time and the local host number as described in
14240 section &<<SECTmessiden>>&.
14244 .option log_file_path main "string list&!!" "set at compile time"
14245 .cindex "log" "file path for"
14246 This option sets the path which is used to determine the names of Exim's log
14247 files, or indicates that logging is to be to syslog, or both. It is expanded
14248 when Exim is entered, so it can, for example, contain a reference to the host
14249 name. If no specific path is set for the log files at compile or run time, they
14250 are written in a sub-directory called &_log_& in Exim's spool directory.
14251 Chapter &<<CHAPlog>>& contains further details about Exim's logging, and
14252 section &<<SECTwhelogwri>>& describes how the contents of &%log_file_path%& are
14253 used. If this string is fixed at your installation (contains no expansion
14254 variables) it is recommended that you do not set this option in the
14255 configuration file, but instead supply the path using LOG_FILE_PATH in
14256 &_Local/Makefile_& so that it is available to Exim for logging errors detected
14257 early on &-- in particular, failure to read the configuration file.
14260 .option log_selector main string unset
14261 .cindex "log" "selectors"
14262 This option can be used to reduce or increase the number of things that Exim
14263 writes to its log files. Its argument is made up of names preceded by plus or
14264 minus characters. For example:
14266 log_selector = +arguments -retry_defer
14268 A list of possible names and what they control is given in the chapter on
14269 logging, in section &<<SECTlogselector>>&.
14272 .option log_timezone main boolean false
14273 .cindex "log" "timezone for entries"
14274 .vindex "&$tod_log$&"
14275 .vindex "&$tod_zone$&"
14276 By default, the timestamps on log lines are in local time without the
14277 timezone. This means that if your timezone changes twice a year, the timestamps
14278 in log lines are ambiguous for an hour when the clocks go back. One way of
14279 avoiding this problem is to set the timezone to UTC. An alternative is to set
14280 &%log_timezone%& true. This turns on the addition of the timezone offset to
14281 timestamps in log lines. Turning on this option can add quite a lot to the size
14282 of log files because each line is extended by 6 characters. Note that the
14283 &$tod_log$& variable contains the log timestamp without the zone, but there is
14284 another variable called &$tod_zone$& that contains just the timezone offset.
14287 .option lookup_open_max main integer 25
14288 .cindex "too many open files"
14289 .cindex "open files, too many"
14290 .cindex "file" "too many open"
14291 .cindex "lookup" "maximum open files"
14292 .cindex "limit" "open files for lookups"
14293 This option limits the number of simultaneously open files for single-key
14294 lookups that use regular files (that is, &(lsearch)&, &(dbm)&, and &(cdb)&).
14295 Exim normally keeps these files open during routing, because often the same
14296 file is required several times. If the limit is reached, Exim closes the least
14297 recently used file. Note that if you are using the &'ndbm'& library, it
14298 actually opens two files for each logical DBM database, though it still counts
14299 as one for the purposes of &%lookup_open_max%&. If you are getting &"too many
14300 open files"& errors with NDBM, you need to reduce the value of
14301 &%lookup_open_max%&.
14304 .option max_username_length main integer 0
14305 .cindex "length of login name"
14306 .cindex "user name" "maximum length"
14307 .cindex "limit" "user name length"
14308 Some operating systems are broken in that they truncate long arguments to
14309 &[getpwnam()]& to eight characters, instead of returning &"no such user"&. If
14310 this option is set greater than zero, any attempt to call &[getpwnam()]& with
14311 an argument that is longer behaves as if &[getpwnam()]& failed.
14314 .option message_body_newlines main bool false
14315 .cindex "message body" "newlines in variables"
14316 .cindex "newline" "in message body variables"
14317 .vindex "&$message_body$&"
14318 .vindex "&$message_body_end$&"
14319 By default, newlines in the message body are replaced by spaces when setting
14320 the &$message_body$& and &$message_body_end$& expansion variables. If this
14321 option is set true, this no longer happens.
14324 .option message_body_visible main integer 500
14325 .cindex "body of message" "visible size"
14326 .cindex "message body" "visible size"
14327 .vindex "&$message_body$&"
14328 .vindex "&$message_body_end$&"
14329 This option specifies how much of a message's body is to be included in the
14330 &$message_body$& and &$message_body_end$& expansion variables.
14333 .option message_id_header_domain main string&!! unset
14334 .cindex "&'Message-ID:'& header line"
14335 If this option is set, the string is expanded and used as the right hand side
14336 (domain) of the &'Message-ID:'& header that Exim creates if a
14337 locally-originated incoming message does not have one. &"Locally-originated"&
14338 means &"not received over TCP/IP."&
14339 Otherwise, the primary host name is used.
14340 Only letters, digits, dot and hyphen are accepted; any other characters are
14341 replaced by hyphens. If the expansion is forced to fail, or if the result is an
14342 empty string, the option is ignored.
14345 .option message_id_header_text main string&!! unset
14346 If this variable is set, the string is expanded and used to augment the text of
14347 the &'Message-id:'& header that Exim creates if a locally-originated incoming
14348 message does not have one. The text of this header is required by RFC 2822 to
14349 take the form of an address. By default, Exim uses its internal message id as
14350 the local part, and the primary host name as the domain. If this option is set,
14351 it is expanded, and provided the expansion is not forced to fail, and does not
14352 yield an empty string, the result is inserted into the header immediately
14353 before the @, separated from the internal message id by a dot. Any characters
14354 that are illegal in an address are automatically converted into hyphens. This
14355 means that variables such as &$tod_log$& can be used, because the spaces and
14356 colons will become hyphens.
14359 .option message_logs main boolean true
14360 .cindex "message logs" "disabling"
14361 .cindex "log" "message log; disabling"
14362 If this option is turned off, per-message log files are not created in the
14363 &_msglog_& spool sub-directory. This reduces the amount of disk I/O required by
14364 Exim, by reducing the number of files involved in handling a message from a
14365 minimum of four (header spool file, body spool file, delivery journal, and
14366 per-message log) to three. The other major I/O activity is Exim's main log,
14367 which is not affected by this option.
14370 .option message_size_limit main string&!! 50M
14371 .cindex "message" "size limit"
14372 .cindex "limit" "message size"
14373 .cindex "size" "of message, limit"
14374 This option limits the maximum size of message that Exim will process. The
14375 value is expanded for each incoming connection so, for example, it can be made
14376 to depend on the IP address of the remote host for messages arriving via
14377 TCP/IP. After expansion, the value must be a sequence of decimal digits,
14378 optionally followed by K or M.
14380 &*Note*&: This limit cannot be made to depend on a message's sender or any
14381 other properties of an individual message, because it has to be advertised in
14382 the server's response to EHLO. String expansion failure causes a temporary
14383 error. A value of zero means no limit, but its use is not recommended. See also
14384 &%bounce_return_size_limit%&.
14386 Incoming SMTP messages are failed with a 552 error if the limit is
14387 exceeded; locally-generated messages either get a stderr message or a delivery
14388 failure message to the sender, depending on the &%-oe%& setting. Rejection of
14389 an oversized message is logged in both the main and the reject logs. See also
14390 the generic transport option &%message_size_limit%&, which limits the size of
14391 message that an individual transport can process.
14393 If you use a virus-scanner and set this option to to a value larger than the
14394 maximum size that your virus-scanner is configured to support, you may get
14395 failures triggered by large mails. The right size to configure for the
14396 virus-scanner depends upon what data is passed and the options in use but it's
14397 probably safest to just set it to a little larger than this value. Eg, with a
14398 default Exim message size of 50M and a default ClamAV StreamMaxLength of 10M,
14399 some problems may result.
14401 A value of 0 will disable size limit checking; Exim will still advertise the
14402 SIZE extension in an EHLO response, but without a limit, so as to permit
14403 SMTP clients to still indicate the message size along with the MAIL verb.
14406 .option move_frozen_messages main boolean false
14407 .cindex "frozen messages" "moving"
14408 This option, which is available only if Exim has been built with the setting
14410 SUPPORT_MOVE_FROZEN_MESSAGES=yes
14412 in &_Local/Makefile_&, causes frozen messages and their message logs to be
14413 moved from the &_input_& and &_msglog_& directories on the spool to &_Finput_&
14414 and &_Fmsglog_&, respectively. There is currently no support in Exim or the
14415 standard utilities for handling such moved messages, and they do not show up in
14416 lists generated by &%-bp%& or by the Exim monitor.
14419 .option mua_wrapper main boolean false
14420 Setting this option true causes Exim to run in a very restrictive mode in which
14421 it passes messages synchronously to a smart host. Chapter &<<CHAPnonqueueing>>&
14422 contains a full description of this facility.
14426 .option mysql_servers main "string list" unset
14427 .cindex "MySQL" "server list"
14428 This option provides a list of MySQL servers and associated connection data, to
14429 be used in conjunction with &(mysql)& lookups (see section &<<SECID72>>&). The
14430 option is available only if Exim has been built with MySQL support.
14433 .option never_users main "string list&!!" unset
14434 This option is expanded just once, at the start of Exim's processing. Local
14435 message deliveries are normally run in processes that are setuid to the
14436 recipient, and remote deliveries are normally run under Exim's own uid and gid.
14437 It is usually desirable to prevent any deliveries from running as root, as a
14440 When Exim is built, an option called FIXED_NEVER_USERS can be set to a
14441 list of users that must not be used for local deliveries. This list is fixed in
14442 the binary and cannot be overridden by the configuration file. By default, it
14443 contains just the single user name &"root"&. The &%never_users%& runtime option
14444 can be used to add more users to the fixed list.
14446 If a message is to be delivered as one of the users on the fixed list or the
14447 &%never_users%& list, an error occurs, and delivery is deferred. A common
14450 never_users = root:daemon:bin
14452 Including root is redundant if it is also on the fixed list, but it does no
14453 harm. This option overrides the &%pipe_as_creator%& option of the &(pipe)&
14457 .option openssl_options main "string list" "+no_sslv2"
14458 .cindex "OpenSSL "compatibility options"
14459 This option allows an administrator to adjust the SSL options applied
14460 by OpenSSL to connections. It is given as a space-separated list of items,
14461 each one to be +added or -subtracted from the current value.
14463 This option is only available if Exim is built against OpenSSL. The values
14464 available for this option vary according to the age of your OpenSSL install.
14465 The &"all"& value controls a subset of flags which are available, typically
14466 the bug workaround options. The &'SSL_CTX_set_options'& man page will
14467 list the values known on your system and Exim should support all the
14468 &"bug workaround"& options and many of the &"modifying"& options. The Exim
14469 names lose the leading &"SSL_OP_"& and are lower-cased.
14471 Note that adjusting the options can have severe impact upon the security of
14472 SSL as used by Exim. It is possible to disable safety checks and shoot
14473 yourself in the foot in various unpleasant ways. This option should not be
14474 adjusted lightly. An unrecognised item will be detected at startup, by
14475 invoking Exim with the &%-bV%& flag.
14477 Historical note: prior to release 4.80, Exim defaulted this value to
14478 "+dont_insert_empty_fragments", which may still be needed for compatibility
14479 with some clients, but which lowers security by increasing exposure to
14480 some now infamous attacks.
14484 # Make both old MS and old Eudora happy:
14485 openssl_options = -all +microsoft_big_sslv3_buffer \
14486 +dont_insert_empty_fragments
14489 Possible options may include:
14493 &`allow_unsafe_legacy_renegotiation`&
14495 &`cipher_server_preference`&
14497 &`dont_insert_empty_fragments`&
14501 &`legacy_server_connect`&
14503 &`microsoft_big_sslv3_buffer`&
14505 &`microsoft_sess_id_bug`&
14507 &`msie_sslv2_rsa_padding`&
14509 &`netscape_challenge_bug`&
14511 &`netscape_reuse_cipher_change_bug`&
14515 &`no_session_resumption_on_renegotiation`&
14531 &`single_ecdh_use`&
14533 &`ssleay_080_client_dh_bug`&
14535 &`sslref2_reuse_cert_type_bug`&
14537 &`tls_block_padding_bug`&
14541 &`tls_rollback_bug`&
14545 .option oracle_servers main "string list" unset
14546 .cindex "Oracle" "server list"
14547 This option provides a list of Oracle servers and associated connection data,
14548 to be used in conjunction with &(oracle)& lookups (see section &<<SECID72>>&).
14549 The option is available only if Exim has been built with Oracle support.
14552 .option percent_hack_domains main "domain list&!!" unset
14553 .cindex "&""percent hack""&"
14554 .cindex "source routing" "in email address"
14555 .cindex "address" "source-routed"
14556 The &"percent hack"& is the convention whereby a local part containing a
14557 percent sign is re-interpreted as a new email address, with the percent
14558 replaced by @. This is sometimes called &"source routing"&, though that term is
14559 also applied to RFC 2822 addresses that begin with an @ character. If this
14560 option is set, Exim implements the percent facility for those domains listed,
14561 but no others. This happens before an incoming SMTP address is tested against
14564 &*Warning*&: The &"percent hack"& has often been abused by people who are
14565 trying to get round relaying restrictions. For this reason, it is best avoided
14566 if at all possible. Unfortunately, a number of less security-conscious MTAs
14567 implement it unconditionally. If you are running Exim on a gateway host, and
14568 routing mail through to internal MTAs without processing the local parts, it is
14569 a good idea to reject recipient addresses with percent characters in their
14570 local parts. Exim's default configuration does this.
14573 .option perl_at_start main boolean false
14574 This option is available only when Exim is built with an embedded Perl
14575 interpreter. See chapter &<<CHAPperl>>& for details of its use.
14578 .option perl_startup main string unset
14579 This option is available only when Exim is built with an embedded Perl
14580 interpreter. See chapter &<<CHAPperl>>& for details of its use.
14583 .option pgsql_servers main "string list" unset
14584 .cindex "PostgreSQL lookup type" "server list"
14585 This option provides a list of PostgreSQL servers and associated connection
14586 data, to be used in conjunction with &(pgsql)& lookups (see section
14587 &<<SECID72>>&). The option is available only if Exim has been built with
14588 PostgreSQL support.
14591 .option pid_file_path main string&!! "set at compile time"
14592 .cindex "daemon" "pid file path"
14593 .cindex "pid file, path for"
14594 This option sets the name of the file to which the Exim daemon writes its
14595 process id. The string is expanded, so it can contain, for example, references
14598 pid_file_path = /var/log/$primary_hostname/exim.pid
14600 If no path is set, the pid is written to the file &_exim-daemon.pid_& in Exim's
14602 The value set by the option can be overridden by the &%-oP%& command line
14603 option. A pid file is not written if a &"non-standard"& daemon is run by means
14604 of the &%-oX%& option, unless a path is explicitly supplied by &%-oP%&.
14607 .option pipelining_advertise_hosts main "host list&!!" *
14608 .cindex "PIPELINING" "suppressing advertising"
14609 This option can be used to suppress the advertisement of the SMTP
14610 PIPELINING extension to specific hosts. See also the &*no_pipelining*&
14611 control in section &<<SECTcontrols>>&. When PIPELINING is not advertised and
14612 &%smtp_enforce_sync%& is true, an Exim server enforces strict synchronization
14613 for each SMTP command and response. When PIPELINING is advertised, Exim assumes
14614 that clients will use it; &"out of order"& commands that are &"expected"& do
14615 not count as protocol errors (see &%smtp_max_synprot_errors%&).
14618 .option preserve_message_logs main boolean false
14619 .cindex "message logs" "preserving"
14620 If this option is set, message log files are not deleted when messages are
14621 completed. Instead, they are moved to a sub-directory of the spool directory
14622 called &_msglog.OLD_&, where they remain available for statistical or debugging
14623 purposes. This is a dangerous option to set on systems with any appreciable
14624 volume of mail. Use with care!
14627 .option primary_hostname main string "see below"
14628 .cindex "name" "of local host"
14629 .cindex "host" "name of local"
14630 .cindex "local host" "name of"
14631 .vindex "&$primary_hostname$&"
14632 This specifies the name of the current host. It is used in the default EHLO or
14633 HELO command for outgoing SMTP messages (changeable via the &%helo_data%&
14634 option in the &(smtp)& transport), and as the default for &%qualify_domain%&.
14635 The value is also used by default in some SMTP response messages from an Exim
14636 server. This can be changed dynamically by setting &%smtp_active_hostname%&.
14638 If &%primary_hostname%& is not set, Exim calls &[uname()]& to find the host
14639 name. If this fails, Exim panics and dies. If the name returned by &[uname()]&
14640 contains only one component, Exim passes it to &[gethostbyname()]& (or
14641 &[getipnodebyname()]& when available) in order to obtain the fully qualified
14642 version. The variable &$primary_hostname$& contains the host name, whether set
14643 explicitly by this option, or defaulted.
14646 .option print_topbitchars main boolean false
14647 .cindex "printing characters"
14648 .cindex "8-bit characters"
14649 By default, Exim considers only those characters whose codes lie in the range
14650 32&--126 to be printing characters. In a number of circumstances (for example,
14651 when writing log entries) non-printing characters are converted into escape
14652 sequences, primarily to avoid messing up the layout. If &%print_topbitchars%&
14653 is set, code values of 128 and above are also considered to be printing
14656 This option also affects the header syntax checks performed by the
14657 &(autoreply)& transport, and whether Exim uses RFC 2047 encoding of
14658 the user's full name when constructing From: and Sender: addresses (as
14659 described in section &<<SECTconstr>>&). Setting this option can cause
14660 Exim to generate eight bit message headers that do not conform to the
14664 .option process_log_path main string unset
14665 .cindex "process log path"
14666 .cindex "log" "process log"
14667 .cindex "&'exiwhat'&"
14668 This option sets the name of the file to which an Exim process writes its
14669 &"process log"& when sent a USR1 signal. This is used by the &'exiwhat'&
14670 utility script. If this option is unset, the file called &_exim-process.info_&
14671 in Exim's spool directory is used. The ability to specify the name explicitly
14672 can be useful in environments where two different Exims are running, using
14673 different spool directories.
14676 .option prod_requires_admin main boolean true
14680 The &%-M%&, &%-R%&, and &%-q%& command-line options require the caller to be an
14681 admin user unless &%prod_requires_admin%& is set false. See also
14682 &%queue_list_requires_admin%&.
14685 .option qualify_domain main string "see below"
14686 .cindex "domain" "for qualifying addresses"
14687 .cindex "address" "qualification"
14688 This option specifies the domain name that is added to any envelope sender
14689 addresses that do not have a domain qualification. It also applies to
14690 recipient addresses if &%qualify_recipient%& is not set. Unqualified addresses
14691 are accepted by default only for locally-generated messages. Qualification is
14692 also applied to addresses in header lines such as &'From:'& and &'To:'& for
14693 locally-generated messages, unless the &%-bnq%& command line option is used.
14695 Messages from external sources must always contain fully qualified addresses,
14696 unless the sending host matches &%sender_unqualified_hosts%& or
14697 &%recipient_unqualified_hosts%& (as appropriate), in which case incoming
14698 addresses are qualified with &%qualify_domain%& or &%qualify_recipient%& as
14699 necessary. Internally, Exim always works with fully qualified envelope
14700 addresses. If &%qualify_domain%& is not set, it defaults to the
14701 &%primary_hostname%& value.
14704 .option qualify_recipient main string "see below"
14705 This option allows you to specify a different domain for qualifying recipient
14706 addresses to the one that is used for senders. See &%qualify_domain%& above.
14710 .option queue_domains main "domain list&!!" unset
14711 .cindex "domain" "specifying non-immediate delivery"
14712 .cindex "queueing incoming messages"
14713 .cindex "message" "queueing certain domains"
14714 This option lists domains for which immediate delivery is not required.
14715 A delivery process is started whenever a message is received, but only those
14716 domains that do not match are processed. All other deliveries wait until the
14717 next queue run. See also &%hold_domains%& and &%queue_smtp_domains%&.
14720 .option queue_list_requires_admin main boolean true
14722 The &%-bp%& command-line option, which lists the messages that are on the
14723 queue, requires the caller to be an admin user unless
14724 &%queue_list_requires_admin%& is set false. See also &%prod_requires_admin%&.
14727 .option queue_only main boolean false
14728 .cindex "queueing incoming messages"
14729 .cindex "message" "queueing unconditionally"
14730 If &%queue_only%& is set, a delivery process is not automatically started
14731 whenever a message is received. Instead, the message waits on the queue for the
14732 next queue run. Even if &%queue_only%& is false, incoming messages may not get
14733 delivered immediately when certain conditions (such as heavy load) occur.
14735 The &%-odq%& command line has the same effect as &%queue_only%&. The &%-odb%&
14736 and &%-odi%& command line options override &%queue_only%& unless
14737 &%queue_only_override%& is set false. See also &%queue_only_file%&,
14738 &%queue_only_load%&, and &%smtp_accept_queue%&.
14741 .option queue_only_file main string unset
14742 .cindex "queueing incoming messages"
14743 .cindex "message" "queueing by file existence"
14744 This option can be set to a colon-separated list of absolute path names, each
14745 one optionally preceded by &"smtp"&. When Exim is receiving a message,
14746 it tests for the existence of each listed path using a call to &[stat()]&. For
14747 each path that exists, the corresponding queueing option is set.
14748 For paths with no prefix, &%queue_only%& is set; for paths prefixed by
14749 &"smtp"&, &%queue_smtp_domains%& is set to match all domains. So, for example,
14751 queue_only_file = smtp/some/file
14753 causes Exim to behave as if &%queue_smtp_domains%& were set to &"*"& whenever
14754 &_/some/file_& exists.
14757 .option queue_only_load main fixed-point unset
14758 .cindex "load average"
14759 .cindex "queueing incoming messages"
14760 .cindex "message" "queueing by load"
14761 If the system load average is higher than this value, incoming messages from
14762 all sources are queued, and no automatic deliveries are started. If this
14763 happens during local or remote SMTP input, all subsequent messages received on
14764 the same SMTP connection are queued by default, whatever happens to the load in
14765 the meantime, but this can be changed by setting &%queue_only_load_latch%&
14768 Deliveries will subsequently be performed by queue runner processes. This
14769 option has no effect on ancient operating systems on which Exim cannot
14770 determine the load average. See also &%deliver_queue_load_max%& and
14771 &%smtp_load_reserve%&.
14774 .option queue_only_load_latch main boolean true
14775 .cindex "load average" "re-evaluating per message"
14776 When this option is true (the default), once one message has been queued
14777 because the load average is higher than the value set by &%queue_only_load%&,
14778 all subsequent messages received on the same SMTP connection are also queued.
14779 This is a deliberate choice; even though the load average may fall below the
14780 threshold, it doesn't seem right to deliver later messages on the same
14781 connection when not delivering earlier ones. However, there are special
14782 circumstances such as very long-lived connections from scanning appliances
14783 where this is not the best strategy. In such cases, &%queue_only_load_latch%&
14784 should be set false. This causes the value of the load average to be
14785 re-evaluated for each message.
14788 .option queue_only_override main boolean true
14789 .cindex "queueing incoming messages"
14790 When this option is true, the &%-od%&&'x'& command line options override the
14791 setting of &%queue_only%& or &%queue_only_file%& in the configuration file. If
14792 &%queue_only_override%& is set false, the &%-od%&&'x'& options cannot be used
14793 to override; they are accepted, but ignored.
14796 .option queue_run_in_order main boolean false
14797 .cindex "queue runner" "processing messages in order"
14798 If this option is set, queue runs happen in order of message arrival instead of
14799 in an arbitrary order. For this to happen, a complete list of the entire queue
14800 must be set up before the deliveries start. When the queue is all held in a
14801 single directory (the default), a single list is created for both the ordered
14802 and the non-ordered cases. However, if &%split_spool_directory%& is set, a
14803 single list is not created when &%queue_run_in_order%& is false. In this case,
14804 the sub-directories are processed one at a time (in a random order), and this
14805 avoids setting up one huge list for the whole queue. Thus, setting
14806 &%queue_run_in_order%& with &%split_spool_directory%& may degrade performance
14807 when the queue is large, because of the extra work in setting up the single,
14808 large list. In most situations, &%queue_run_in_order%& should not be set.
14812 .option queue_run_max main integer 5
14813 .cindex "queue runner" "maximum number of"
14814 This controls the maximum number of queue runner processes that an Exim daemon
14815 can run simultaneously. This does not mean that it starts them all at once,
14816 but rather that if the maximum number are still running when the time comes to
14817 start another one, it refrains from starting another one. This can happen with
14818 very large queues and/or very sluggish deliveries. This option does not,
14819 however, interlock with other processes, so additional queue runners can be
14820 started by other means, or by killing and restarting the daemon.
14822 Setting this option to zero does not suppress queue runs; rather, it disables
14823 the limit, allowing any number of simultaneous queue runner processes to be
14824 run. If you do not want queue runs to occur, omit the &%-q%&&'xx'& setting on
14825 the daemon's command line.
14827 .option queue_smtp_domains main "domain list&!!" unset
14828 .cindex "queueing incoming messages"
14829 .cindex "message" "queueing remote deliveries"
14830 When this option is set, a delivery process is started whenever a message is
14831 received, routing is performed, and local deliveries take place.
14832 However, if any SMTP deliveries are required for domains that match
14833 &%queue_smtp_domains%&, they are not immediately delivered, but instead the
14834 message waits on the queue for the next queue run. Since routing of the message
14835 has taken place, Exim knows to which remote hosts it must be delivered, and so
14836 when the queue run happens, multiple messages for the same host are delivered
14837 over a single SMTP connection. The &%-odqs%& command line option causes all
14838 SMTP deliveries to be queued in this way, and is equivalent to setting
14839 &%queue_smtp_domains%& to &"*"&. See also &%hold_domains%& and
14843 .option receive_timeout main time 0s
14844 .cindex "timeout" "for non-SMTP input"
14845 This option sets the timeout for accepting a non-SMTP message, that is, the
14846 maximum time that Exim waits when reading a message on the standard input. If
14847 the value is zero, it will wait for ever. This setting is overridden by the
14848 &%-or%& command line option. The timeout for incoming SMTP messages is
14849 controlled by &%smtp_receive_timeout%&.
14851 .option received_header_text main string&!! "see below"
14852 .cindex "customizing" "&'Received:'& header"
14853 .cindex "&'Received:'& header line" "customizing"
14854 This string defines the contents of the &'Received:'& message header that is
14855 added to each message, except for the timestamp, which is automatically added
14856 on at the end (preceded by a semicolon). The string is expanded each time it is
14857 used. If the expansion yields an empty string, no &'Received:'& header line is
14858 added to the message. Otherwise, the string should start with the text
14859 &"Received:"& and conform to the RFC 2822 specification for &'Received:'&
14860 header lines. The default setting is:
14863 received_header_text = Received: \
14864 ${if def:sender_rcvhost {from $sender_rcvhost\n\t}\
14865 {${if def:sender_ident \
14866 {from ${quote_local_part:$sender_ident} }}\
14867 ${if def:sender_helo_name {(helo=$sender_helo_name)\n\t}}}}\
14868 by $primary_hostname \
14869 ${if def:received_protocol {with $received_protocol}} \
14870 ${if def:tls_cipher {($tls_cipher)\n\t}}\
14871 (Exim $version_number)\n\t\
14872 ${if def:sender_address \
14873 {(envelope-from <$sender_address>)\n\t}}\
14874 id $message_exim_id\
14875 ${if def:received_for {\n\tfor $received_for}}
14878 The reference to the TLS cipher is omitted when Exim is built without TLS
14879 support. The use of conditional expansions ensures that this works for both
14880 locally generated messages and messages received from remote hosts, giving
14881 header lines such as the following:
14883 Received: from scrooge.carol.example ([192.168.12.25] ident=root)
14884 by marley.carol.example with esmtp (Exim 4.00)
14885 (envelope-from <bob@carol.example>)
14886 id 16IOWa-00019l-00
14887 for chas@dickens.example; Tue, 25 Dec 2001 14:43:44 +0000
14888 Received: by scrooge.carol.example with local (Exim 4.00)
14889 id 16IOWW-000083-00; Tue, 25 Dec 2001 14:43:41 +0000
14891 Until the body of the message has been received, the timestamp is the time when
14892 the message started to be received. Once the body has arrived, and all policy
14893 checks have taken place, the timestamp is updated to the time at which the
14894 message was accepted.
14897 .option received_headers_max main integer 30
14898 .cindex "loop" "prevention"
14899 .cindex "mail loop prevention"
14900 .cindex "&'Received:'& header line" "counting"
14901 When a message is to be delivered, the number of &'Received:'& headers is
14902 counted, and if it is greater than this parameter, a mail loop is assumed to
14903 have occurred, the delivery is abandoned, and an error message is generated.
14904 This applies to both local and remote deliveries.
14907 .option recipient_unqualified_hosts main "host list&!!" unset
14908 .cindex "unqualified addresses"
14909 .cindex "host" "unqualified addresses from"
14910 This option lists those hosts from which Exim is prepared to accept unqualified
14911 recipient addresses in message envelopes. The addresses are made fully
14912 qualified by the addition of the &%qualify_recipient%& value. This option also
14913 affects message header lines. Exim does not reject unqualified recipient
14914 addresses in headers, but it qualifies them only if the message came from a
14915 host that matches &%recipient_unqualified_hosts%&,
14916 or if the message was submitted locally (not using TCP/IP), and the &%-bnq%&
14917 option was not set.
14920 .option recipients_max main integer 0
14921 .cindex "limit" "number of recipients"
14922 .cindex "recipient" "maximum number"
14923 If this option is set greater than zero, it specifies the maximum number of
14924 original recipients for any message. Additional recipients that are generated
14925 by aliasing or forwarding do not count. SMTP messages get a 452 response for
14926 all recipients over the limit; earlier recipients are delivered as normal.
14927 Non-SMTP messages with too many recipients are failed, and no deliveries are
14930 .cindex "RCPT" "maximum number of incoming"
14931 &*Note*&: The RFCs specify that an SMTP server should accept at least 100
14932 RCPT commands in a single message.
14935 .option recipients_max_reject main boolean false
14936 If this option is set true, Exim rejects SMTP messages containing too many
14937 recipients by giving 552 errors to the surplus RCPT commands, and a 554
14938 error to the eventual DATA command. Otherwise (the default) it gives a 452
14939 error to the surplus RCPT commands and accepts the message on behalf of the
14940 initial set of recipients. The remote server should then re-send the message
14941 for the remaining recipients at a later time.
14944 .option remote_max_parallel main integer 2
14945 .cindex "delivery" "parallelism for remote"
14946 This option controls parallel delivery of one message to a number of remote
14947 hosts. If the value is less than 2, parallel delivery is disabled, and Exim
14948 does all the remote deliveries for a message one by one. Otherwise, if a single
14949 message has to be delivered to more than one remote host, or if several copies
14950 have to be sent to the same remote host, up to &%remote_max_parallel%&
14951 deliveries are done simultaneously. If more than &%remote_max_parallel%&
14952 deliveries are required, the maximum number of processes are started, and as
14953 each one finishes, another is begun. The order of starting processes is the
14954 same as if sequential delivery were being done, and can be controlled by the
14955 &%remote_sort_domains%& option. If parallel delivery takes place while running
14956 with debugging turned on, the debugging output from each delivery process is
14957 tagged with its process id.
14959 This option controls only the maximum number of parallel deliveries for one
14960 message in one Exim delivery process. Because Exim has no central queue
14961 manager, there is no way of controlling the total number of simultaneous
14962 deliveries if the configuration allows a delivery attempt as soon as a message
14965 .cindex "number of deliveries"
14966 .cindex "delivery" "maximum number of"
14967 If you want to control the total number of deliveries on the system, you
14968 need to set the &%queue_only%& option. This ensures that all incoming messages
14969 are added to the queue without starting a delivery process. Then set up an Exim
14970 daemon to start queue runner processes at appropriate intervals (probably
14971 fairly often, for example, every minute), and limit the total number of queue
14972 runners by setting the &%queue_run_max%& parameter. Because each queue runner
14973 delivers only one message at a time, the maximum number of deliveries that can
14974 then take place at once is &%queue_run_max%& multiplied by
14975 &%remote_max_parallel%&.
14977 If it is purely remote deliveries you want to control, use
14978 &%queue_smtp_domains%& instead of &%queue_only%&. This has the added benefit of
14979 doing the SMTP routing before queueing, so that several messages for the same
14980 host will eventually get delivered down the same connection.
14983 .option remote_sort_domains main "domain list&!!" unset
14984 .cindex "sorting remote deliveries"
14985 .cindex "delivery" "sorting remote"
14986 When there are a number of remote deliveries for a message, they are sorted by
14987 domain into the order given by this list. For example,
14989 remote_sort_domains = *.cam.ac.uk:*.uk
14991 would attempt to deliver to all addresses in the &'cam.ac.uk'& domain first,
14992 then to those in the &%uk%& domain, then to any others.
14995 .option retry_data_expire main time 7d
14996 .cindex "hints database" "data expiry"
14997 This option sets a &"use before"& time on retry information in Exim's hints
14998 database. Any older retry data is ignored. This means that, for example, once a
14999 host has not been tried for 7 days, Exim behaves as if it has no knowledge of
15003 .option retry_interval_max main time 24h
15004 .cindex "retry" "limit on interval"
15005 .cindex "limit" "on retry interval"
15006 Chapter &<<CHAPretry>>& describes Exim's mechanisms for controlling the
15007 intervals between delivery attempts for messages that cannot be delivered
15008 straight away. This option sets an overall limit to the length of time between
15009 retries. It cannot be set greater than 24 hours; any attempt to do so forces
15013 .option return_path_remove main boolean true
15014 .cindex "&'Return-path:'& header line" "removing"
15015 RFC 2821, section 4.4, states that an SMTP server must insert a
15016 &'Return-path:'& header line into a message when it makes a &"final delivery"&.
15017 The &'Return-path:'& header preserves the sender address as received in the
15018 MAIL command. This description implies that this header should not be present
15019 in an incoming message. If &%return_path_remove%& is true, any existing
15020 &'Return-path:'& headers are removed from messages at the time they are
15021 received. Exim's transports have options for adding &'Return-path:'& headers at
15022 the time of delivery. They are normally used only for final local deliveries.
15025 .option return_size_limit main integer 100K
15026 This option is an obsolete synonym for &%bounce_return_size_limit%&.
15029 .option rfc1413_hosts main "host list&!!" *
15031 .cindex "host" "for RFC 1413 calls"
15032 RFC 1413 identification calls are made to any client host which matches an item
15035 .option rfc1413_query_timeout main time 5s
15036 .cindex "RFC 1413" "query timeout"
15037 .cindex "timeout" "for RFC 1413 call"
15038 This sets the timeout on RFC 1413 identification calls. If it is set to zero,
15039 no RFC 1413 calls are ever made.
15042 .option sender_unqualified_hosts main "host list&!!" unset
15043 .cindex "unqualified addresses"
15044 .cindex "host" "unqualified addresses from"
15045 This option lists those hosts from which Exim is prepared to accept unqualified
15046 sender addresses. The addresses are made fully qualified by the addition of
15047 &%qualify_domain%&. This option also affects message header lines. Exim does
15048 not reject unqualified addresses in headers that contain sender addresses, but
15049 it qualifies them only if the message came from a host that matches
15050 &%sender_unqualified_hosts%&, or if the message was submitted locally (not
15051 using TCP/IP), and the &%-bnq%& option was not set.
15054 .option smtp_accept_keepalive main boolean true
15055 .cindex "keepalive" "on incoming connection"
15056 This option controls the setting of the SO_KEEPALIVE option on incoming
15057 TCP/IP socket connections. When set, it causes the kernel to probe idle
15058 connections periodically, by sending packets with &"old"& sequence numbers. The
15059 other end of the connection should send an acknowledgment if the connection is
15060 still okay or a reset if the connection has been aborted. The reason for doing
15061 this is that it has the beneficial effect of freeing up certain types of
15062 connection that can get stuck when the remote host is disconnected without
15063 tidying up the TCP/IP call properly. The keepalive mechanism takes several
15064 hours to detect unreachable hosts.
15068 .option smtp_accept_max main integer 20
15069 .cindex "limit" "incoming SMTP connections"
15070 .cindex "SMTP" "incoming connection count"
15072 This option specifies the maximum number of simultaneous incoming SMTP calls
15073 that Exim will accept. It applies only to the listening daemon; there is no
15074 control (in Exim) when incoming SMTP is being handled by &'inetd'&. If the
15075 value is set to zero, no limit is applied. However, it is required to be
15076 non-zero if either &%smtp_accept_max_per_host%& or &%smtp_accept_queue%& is
15077 set. See also &%smtp_accept_reserve%& and &%smtp_load_reserve%&.
15079 A new SMTP connection is immediately rejected if the &%smtp_accept_max%& limit
15080 has been reached. If not, Exim first checks &%smtp_accept_max_per_host%&. If
15081 that limit has not been reached for the client host, &%smtp_accept_reserve%&
15082 and &%smtp_load_reserve%& are then checked before accepting the connection.
15085 .option smtp_accept_max_nonmail main integer 10
15086 .cindex "limit" "non-mail SMTP commands"
15087 .cindex "SMTP" "limiting non-mail commands"
15088 Exim counts the number of &"non-mail"& commands in an SMTP session, and drops
15089 the connection if there are too many. This option defines &"too many"&. The
15090 check catches some denial-of-service attacks, repeated failing AUTHs, or a mad
15091 client looping sending EHLO, for example. The check is applied only if the
15092 client host matches &%smtp_accept_max_nonmail_hosts%&.
15094 When a new message is expected, one occurrence of RSET is not counted. This
15095 allows a client to send one RSET between messages (this is not necessary,
15096 but some clients do it). Exim also allows one uncounted occurrence of HELO
15097 or EHLO, and one occurrence of STARTTLS between messages. After
15098 starting up a TLS session, another EHLO is expected, and so it too is not
15099 counted. The first occurrence of AUTH in a connection, or immediately
15100 following STARTTLS is not counted. Otherwise, all commands other than
15101 MAIL, RCPT, DATA, and QUIT are counted.
15104 .option smtp_accept_max_nonmail_hosts main "host list&!!" *
15105 You can control which hosts are subject to the &%smtp_accept_max_nonmail%&
15106 check by setting this option. The default value makes it apply to all hosts. By
15107 changing the value, you can exclude any badly-behaved hosts that you have to
15111 . Allow this long option name to split; give it unsplit as a fifth argument
15112 . for the automatic .oindex that is generated by .option.
15114 .option "smtp_accept_max_per_ &~&~connection" main integer 1000 &&&
15115 smtp_accept_max_per_connection
15116 .cindex "SMTP" "limiting incoming message count"
15117 .cindex "limit" "messages per SMTP connection"
15118 The value of this option limits the number of MAIL commands that Exim is
15119 prepared to accept over a single SMTP connection, whether or not each command
15120 results in the transfer of a message. After the limit is reached, a 421
15121 response is given to subsequent MAIL commands. This limit is a safety
15122 precaution against a client that goes mad (incidents of this type have been
15126 .option smtp_accept_max_per_host main string&!! unset
15127 .cindex "limit" "SMTP connections from one host"
15128 .cindex "host" "limiting SMTP connections from"
15129 This option restricts the number of simultaneous IP connections from a single
15130 host (strictly, from a single IP address) to the Exim daemon. The option is
15131 expanded, to enable different limits to be applied to different hosts by
15132 reference to &$sender_host_address$&. Once the limit is reached, additional
15133 connection attempts from the same host are rejected with error code 421. This
15134 is entirely independent of &%smtp_accept_reserve%&. The option's default value
15135 of zero imposes no limit. If this option is set greater than zero, it is
15136 required that &%smtp_accept_max%& be non-zero.
15138 &*Warning*&: When setting this option you should not use any expansion
15139 constructions that take an appreciable amount of time. The expansion and test
15140 happen in the main daemon loop, in order to reject additional connections
15141 without forking additional processes (otherwise a denial-of-service attack
15142 could cause a vast number or processes to be created). While the daemon is
15143 doing this processing, it cannot accept any other incoming connections.
15147 .option smtp_accept_queue main integer 0
15148 .cindex "SMTP" "incoming connection count"
15149 .cindex "queueing incoming messages"
15150 .cindex "message" "queueing by SMTP connection count"
15151 If the number of simultaneous incoming SMTP connections being handled via the
15152 listening daemon exceeds this value, messages received by SMTP are just placed
15153 on the queue; no delivery processes are started automatically. The count is
15154 fixed at the start of an SMTP connection. It cannot be updated in the
15155 subprocess that receives messages, and so the queueing or not queueing applies
15156 to all messages received in the same connection.
15158 A value of zero implies no limit, and clearly any non-zero value is useful only
15159 if it is less than the &%smtp_accept_max%& value (unless that is zero). See
15160 also &%queue_only%&, &%queue_only_load%&, &%queue_smtp_domains%&, and the
15161 various &%-od%&&'x'& command line options.
15164 . Allow this long option name to split; give it unsplit as a fifth argument
15165 . for the automatic .oindex that is generated by .option.
15167 .option "smtp_accept_queue_per_ &~&~connection" main integer 10 &&&
15168 smtp_accept_queue_per_connection
15169 .cindex "queueing incoming messages"
15170 .cindex "message" "queueing by message count"
15171 This option limits the number of delivery processes that Exim starts
15172 automatically when receiving messages via SMTP, whether via the daemon or by
15173 the use of &%-bs%& or &%-bS%&. If the value of the option is greater than zero,
15174 and the number of messages received in a single SMTP session exceeds this
15175 number, subsequent messages are placed on the queue, but no delivery processes
15176 are started. This helps to limit the number of Exim processes when a server
15177 restarts after downtime and there is a lot of mail waiting for it on other
15178 systems. On large systems, the default should probably be increased, and on
15179 dial-in client systems it should probably be set to zero (that is, disabled).
15182 .option smtp_accept_reserve main integer 0
15183 .cindex "SMTP" "incoming call count"
15184 .cindex "host" "reserved"
15185 When &%smtp_accept_max%& is set greater than zero, this option specifies a
15186 number of SMTP connections that are reserved for connections from the hosts
15187 that are specified in &%smtp_reserve_hosts%&. The value set in
15188 &%smtp_accept_max%& includes this reserve pool. The specified hosts are not
15189 restricted to this number of connections; the option specifies a minimum number
15190 of connection slots for them, not a maximum. It is a guarantee that this group
15191 of hosts can always get at least &%smtp_accept_reserve%& connections. However,
15192 the limit specified by &%smtp_accept_max_per_host%& is still applied to each
15195 For example, if &%smtp_accept_max%& is set to 50 and &%smtp_accept_reserve%& is
15196 set to 5, once there are 45 active connections (from any hosts), new
15197 connections are accepted only from hosts listed in &%smtp_reserve_hosts%&,
15198 provided the other criteria for acceptance are met.
15201 .option smtp_active_hostname main string&!! unset
15202 .cindex "host" "name in SMTP responses"
15203 .cindex "SMTP" "host name in responses"
15204 .vindex "&$primary_hostname$&"
15205 This option is provided for multi-homed servers that want to masquerade as
15206 several different hosts. At the start of an incoming SMTP connection, its value
15207 is expanded and used instead of the value of &$primary_hostname$& in SMTP
15208 responses. For example, it is used as domain name in the response to an
15209 incoming HELO or EHLO command.
15211 .vindex "&$smtp_active_hostname$&"
15212 The active hostname is placed in the &$smtp_active_hostname$& variable, which
15213 is saved with any messages that are received. It is therefore available for use
15214 in routers and transports when the message is later delivered.
15216 If this option is unset, or if its expansion is forced to fail, or if the
15217 expansion results in an empty string, the value of &$primary_hostname$& is
15218 used. Other expansion failures cause a message to be written to the main and
15219 panic logs, and the SMTP command receives a temporary error. Typically, the
15220 value of &%smtp_active_hostname%& depends on the incoming interface address.
15223 smtp_active_hostname = ${if eq{$received_ip_address}{10.0.0.1}\
15224 {cox.mydomain}{box.mydomain}}
15227 Although &$smtp_active_hostname$& is primarily concerned with incoming
15228 messages, it is also used as the default for HELO commands in callout
15229 verification if there is no remote transport from which to obtain a
15230 &%helo_data%& value.
15232 .option smtp_banner main string&!! "see below"
15233 .cindex "SMTP" "welcome banner"
15234 .cindex "banner for SMTP"
15235 .cindex "welcome banner for SMTP"
15236 .cindex "customizing" "SMTP banner"
15237 This string, which is expanded every time it is used, is output as the initial
15238 positive response to an SMTP connection. The default setting is:
15240 smtp_banner = $smtp_active_hostname ESMTP Exim \
15241 $version_number $tod_full
15243 Failure to expand the string causes a panic error. If you want to create a
15244 multiline response to the initial SMTP connection, use &"\n"& in the string at
15245 appropriate points, but not at the end. Note that the 220 code is not included
15246 in this string. Exim adds it automatically (several times in the case of a
15247 multiline response).
15250 .option smtp_check_spool_space main boolean true
15251 .cindex "checking disk space"
15252 .cindex "disk space, checking"
15253 .cindex "spool directory" "checking space"
15254 When this option is set, if an incoming SMTP session encounters the SIZE
15255 option on a MAIL command, it checks that there is enough space in the
15256 spool directory's partition to accept a message of that size, while still
15257 leaving free the amount specified by &%check_spool_space%& (even if that value
15258 is zero). If there isn't enough space, a temporary error code is returned.
15261 .option smtp_connect_backlog main integer 20
15262 .cindex "connection backlog"
15263 .cindex "SMTP" "connection backlog"
15264 .cindex "backlog of connections"
15265 This option specifies a maximum number of waiting SMTP connections. Exim passes
15266 this value to the TCP/IP system when it sets up its listener. Once this number
15267 of connections are waiting for the daemon's attention, subsequent connection
15268 attempts are refused at the TCP/IP level. At least, that is what the manuals
15269 say; in some circumstances such connection attempts have been observed to time
15270 out instead. For large systems it is probably a good idea to increase the
15271 value (to 50, say). It also gives some protection against denial-of-service
15272 attacks by SYN flooding.
15275 .option smtp_enforce_sync main boolean true
15276 .cindex "SMTP" "synchronization checking"
15277 .cindex "synchronization checking in SMTP"
15278 The SMTP protocol specification requires the client to wait for a response from
15279 the server at certain points in the dialogue. Without PIPELINING these
15280 synchronization points are after every command; with PIPELINING they are
15281 fewer, but they still exist.
15283 Some spamming sites send out a complete set of SMTP commands without waiting
15284 for any response. Exim protects against this by rejecting a message if the
15285 client has sent further input when it should not have. The error response &"554
15286 SMTP synchronization error"& is sent, and the connection is dropped. Testing
15287 for this error cannot be perfect because of transmission delays (unexpected
15288 input may be on its way but not yet received when Exim checks). However, it
15289 does detect many instances.
15291 The check can be globally disabled by setting &%smtp_enforce_sync%& false.
15292 If you want to disable the check selectively (for example, only for certain
15293 hosts), you can do so by an appropriate use of a &%control%& modifier in an ACL
15294 (see section &<<SECTcontrols>>&). See also &%pipelining_advertise_hosts%&.
15298 .option smtp_etrn_command main string&!! unset
15299 .cindex "ETRN" "command to be run"
15300 .vindex "&$domain$&"
15301 If this option is set, the given command is run whenever an SMTP ETRN
15302 command is received from a host that is permitted to issue such commands (see
15303 chapter &<<CHAPACL>>&). The string is split up into separate arguments which
15304 are independently expanded. The expansion variable &$domain$& is set to the
15305 argument of the ETRN command, and no syntax checking is done on it. For
15308 smtp_etrn_command = /etc/etrn_command $domain \
15309 $sender_host_address
15311 A new process is created to run the command, but Exim does not wait for it to
15312 complete. Consequently, its status cannot be checked. If the command cannot be
15313 run, a line is written to the panic log, but the ETRN caller still receives
15314 a 250 success response. Exim is normally running under its own uid when
15315 receiving SMTP, so it is not possible for it to change the uid before running
15319 .option smtp_etrn_serialize main boolean true
15320 .cindex "ETRN" "serializing"
15321 When this option is set, it prevents the simultaneous execution of more than
15322 one identical command as a result of ETRN in an SMTP connection. See
15323 section &<<SECTETRN>>& for details.
15326 .option smtp_load_reserve main fixed-point unset
15327 .cindex "load average"
15328 If the system load average ever gets higher than this, incoming SMTP calls are
15329 accepted only from those hosts that match an entry in &%smtp_reserve_hosts%&.
15330 If &%smtp_reserve_hosts%& is not set, no incoming SMTP calls are accepted when
15331 the load is over the limit. The option has no effect on ancient operating
15332 systems on which Exim cannot determine the load average. See also
15333 &%deliver_queue_load_max%& and &%queue_only_load%&.
15337 .option smtp_max_synprot_errors main integer 3
15338 .cindex "SMTP" "limiting syntax and protocol errors"
15339 .cindex "limit" "SMTP syntax and protocol errors"
15340 Exim rejects SMTP commands that contain syntax or protocol errors. In
15341 particular, a syntactically invalid email address, as in this command:
15343 RCPT TO:<abc xyz@a.b.c>
15345 causes immediate rejection of the command, before any other tests are done.
15346 (The ACL cannot be run if there is no valid address to set up for it.) An
15347 example of a protocol error is receiving RCPT before MAIL. If there are
15348 too many syntax or protocol errors in one SMTP session, the connection is
15349 dropped. The limit is set by this option.
15351 .cindex "PIPELINING" "expected errors"
15352 When the PIPELINING extension to SMTP is in use, some protocol errors are
15353 &"expected"&, for instance, a RCPT command after a rejected MAIL command.
15354 Exim assumes that PIPELINING will be used if it advertises it (see
15355 &%pipelining_advertise_hosts%&), and in this situation, &"expected"& errors do
15356 not count towards the limit.
15360 .option smtp_max_unknown_commands main integer 3
15361 .cindex "SMTP" "limiting unknown commands"
15362 .cindex "limit" "unknown SMTP commands"
15363 If there are too many unrecognized commands in an incoming SMTP session, an
15364 Exim server drops the connection. This is a defence against some kinds of abuse
15367 into making connections to SMTP ports; in these circumstances, a number of
15368 non-SMTP command lines are sent first.
15372 .option smtp_ratelimit_hosts main "host list&!!" unset
15373 .cindex "SMTP" "rate limiting"
15374 .cindex "limit" "rate of message arrival"
15375 .cindex "RCPT" "rate limiting"
15376 Some sites find it helpful to be able to limit the rate at which certain hosts
15377 can send them messages, and the rate at which an individual message can specify
15380 Exim has two rate-limiting facilities. This section describes the older
15381 facility, which can limit rates within a single connection. The newer
15382 &%ratelimit%& ACL condition can limit rates across all connections. See section
15383 &<<SECTratelimiting>>& for details of the newer facility.
15385 When a host matches &%smtp_ratelimit_hosts%&, the values of
15386 &%smtp_ratelimit_mail%& and &%smtp_ratelimit_rcpt%& are used to control the
15387 rate of acceptance of MAIL and RCPT commands in a single SMTP session,
15388 respectively. Each option, if set, must contain a set of four comma-separated
15392 A threshold, before which there is no rate limiting.
15394 An initial time delay. Unlike other times in Exim, numbers with decimal
15395 fractional parts are allowed here.
15397 A factor by which to increase the delay each time.
15399 A maximum value for the delay. This should normally be less than 5 minutes,
15400 because after that time, the client is liable to timeout the SMTP command.
15403 For example, these settings have been used successfully at the site which
15404 first suggested this feature, for controlling mail from their customers:
15406 smtp_ratelimit_mail = 2,0.5s,1.05,4m
15407 smtp_ratelimit_rcpt = 4,0.25s,1.015,4m
15409 The first setting specifies delays that are applied to MAIL commands after
15410 two have been received over a single connection. The initial delay is 0.5
15411 seconds, increasing by a factor of 1.05 each time. The second setting applies
15412 delays to RCPT commands when more than four occur in a single message.
15415 .option smtp_ratelimit_mail main string unset
15416 See &%smtp_ratelimit_hosts%& above.
15419 .option smtp_ratelimit_rcpt main string unset
15420 See &%smtp_ratelimit_hosts%& above.
15423 .option smtp_receive_timeout main time 5m
15424 .cindex "timeout" "for SMTP input"
15425 .cindex "SMTP" "input timeout"
15426 This sets a timeout value for SMTP reception. It applies to all forms of SMTP
15427 input, including batch SMTP. If a line of input (either an SMTP command or a
15428 data line) is not received within this time, the SMTP connection is dropped and
15429 the message is abandoned.
15430 A line is written to the log containing one of the following messages:
15432 SMTP command timeout on connection from...
15433 SMTP data timeout on connection from...
15435 The former means that Exim was expecting to read an SMTP command; the latter
15436 means that it was in the DATA phase, reading the contents of a message.
15440 The value set by this option can be overridden by the
15441 &%-os%& command-line option. A setting of zero time disables the timeout, but
15442 this should never be used for SMTP over TCP/IP. (It can be useful in some cases
15443 of local input using &%-bs%& or &%-bS%&.) For non-SMTP input, the reception
15444 timeout is controlled by &%receive_timeout%& and &%-or%&.
15447 .option smtp_reserve_hosts main "host list&!!" unset
15448 This option defines hosts for which SMTP connections are reserved; see
15449 &%smtp_accept_reserve%& and &%smtp_load_reserve%& above.
15452 .option smtp_return_error_details main boolean false
15453 .cindex "SMTP" "details policy failures"
15454 .cindex "policy control" "rejection, returning details"
15455 In the default state, Exim uses bland messages such as
15456 &"Administrative prohibition"& when it rejects SMTP commands for policy
15457 reasons. Many sysadmins like this because it gives away little information
15458 to spammers. However, some other sysadmins who are applying strict checking
15459 policies want to give out much fuller information about failures. Setting
15460 &%smtp_return_error_details%& true causes Exim to be more forthcoming. For
15461 example, instead of &"Administrative prohibition"&, it might give:
15463 550-Rejected after DATA: '>' missing at end of address:
15464 550 failing address in "From" header is: <user@dom.ain
15467 .option spamd_address main string "see below"
15468 This option is available when Exim is compiled with the content-scanning
15469 extension. It specifies how Exim connects to SpamAssassin's &%spamd%& daemon.
15470 The default value is
15474 See section &<<SECTscanspamass>>& for more details.
15478 .option split_spool_directory main boolean false
15479 .cindex "multiple spool directories"
15480 .cindex "spool directory" "split"
15481 .cindex "directories, multiple"
15482 If this option is set, it causes Exim to split its input directory into 62
15483 subdirectories, each with a single alphanumeric character as its name. The
15484 sixth character of the message id is used to allocate messages to
15485 subdirectories; this is the least significant base-62 digit of the time of
15486 arrival of the message.
15488 Splitting up the spool in this way may provide better performance on systems
15489 where there are long mail queues, by reducing the number of files in any one
15490 directory. The msglog directory is also split up in a similar way to the input
15491 directory; however, if &%preserve_message_logs%& is set, all old msglog files
15492 are still placed in the single directory &_msglog.OLD_&.
15494 It is not necessary to take any special action for existing messages when
15495 changing &%split_spool_directory%&. Exim notices messages that are in the
15496 &"wrong"& place, and continues to process them. If the option is turned off
15497 after a period of being on, the subdirectories will eventually empty and be
15498 automatically deleted.
15500 When &%split_spool_directory%& is set, the behaviour of queue runner processes
15501 changes. Instead of creating a list of all messages in the queue, and then
15502 trying to deliver each one in turn, it constructs a list of those in one
15503 sub-directory and tries to deliver them, before moving on to the next
15504 sub-directory. The sub-directories are processed in a random order. This
15505 spreads out the scanning of the input directories, and uses less memory. It is
15506 particularly beneficial when there are lots of messages on the queue. However,
15507 if &%queue_run_in_order%& is set, none of this new processing happens. The
15508 entire queue has to be scanned and sorted before any deliveries can start.
15511 .option spool_directory main string&!! "set at compile time"
15512 .cindex "spool directory" "path to"
15513 This defines the directory in which Exim keeps its spool, that is, the messages
15514 it is waiting to deliver. The default value is taken from the compile-time
15515 configuration setting, if there is one. If not, this option must be set. The
15516 string is expanded, so it can contain, for example, a reference to
15517 &$primary_hostname$&.
15519 If the spool directory name is fixed on your installation, it is recommended
15520 that you set it at build time rather than from this option, particularly if the
15521 log files are being written to the spool directory (see &%log_file_path%&).
15522 Otherwise log files cannot be used for errors that are detected early on, such
15523 as failures in the configuration file.
15525 By using this option to override the compiled-in path, it is possible to run
15526 tests of Exim without using the standard spool.
15528 .option sqlite_lock_timeout main time 5s
15529 .cindex "sqlite lookup type" "lock timeout"
15530 This option controls the timeout that the &(sqlite)& lookup uses when trying to
15531 access an SQLite database. See section &<<SECTsqlite>>& for more details.
15533 .option strict_acl_vars main boolean false
15534 .cindex "&ACL;" "variables, handling unset"
15535 This option controls what happens if a syntactically valid but undefined ACL
15536 variable is referenced. If it is false (the default), an empty string
15537 is substituted; if it is true, an error is generated. See section
15538 &<<SECTaclvariables>>& for details of ACL variables.
15540 .option strip_excess_angle_brackets main boolean false
15541 .cindex "angle brackets, excess"
15542 If this option is set, redundant pairs of angle brackets round &"route-addr"&
15543 items in addresses are stripped. For example, &'<<xxx@a.b.c.d>>'& is
15544 treated as &'<xxx@a.b.c.d>'&. If this is in the envelope and the message is
15545 passed on to another MTA, the excess angle brackets are not passed on. If this
15546 option is not set, multiple pairs of angle brackets cause a syntax error.
15549 .option strip_trailing_dot main boolean false
15550 .cindex "trailing dot on domain"
15551 .cindex "dot" "trailing on domain"
15552 If this option is set, a trailing dot at the end of a domain in an address is
15553 ignored. If this is in the envelope and the message is passed on to another
15554 MTA, the dot is not passed on. If this option is not set, a dot at the end of a
15555 domain causes a syntax error.
15556 However, addresses in header lines are checked only when an ACL requests header
15560 .option syslog_duplication main boolean true
15561 .cindex "syslog" "duplicate log lines; suppressing"
15562 When Exim is logging to syslog, it writes the log lines for its three
15563 separate logs at different syslog priorities so that they can in principle
15564 be separated on the logging hosts. Some installations do not require this
15565 separation, and in those cases, the duplication of certain log lines is a
15566 nuisance. If &%syslog_duplication%& is set false, only one copy of any
15567 particular log line is written to syslog. For lines that normally go to
15568 both the main log and the reject log, the reject log version (possibly
15569 containing message header lines) is written, at LOG_NOTICE priority.
15570 Lines that normally go to both the main and the panic log are written at
15571 the LOG_ALERT priority.
15574 .option syslog_facility main string unset
15575 .cindex "syslog" "facility; setting"
15576 This option sets the syslog &"facility"& name, used when Exim is logging to
15577 syslog. The value must be one of the strings &"mail"&, &"user"&, &"news"&,
15578 &"uucp"&, &"daemon"&, or &"local&'x'&"& where &'x'& is a digit between 0 and 7.
15579 If this option is unset, &"mail"& is used. See chapter &<<CHAPlog>>& for
15580 details of Exim's logging.
15584 .option syslog_processname main string &`exim`&
15585 .cindex "syslog" "process name; setting"
15586 This option sets the syslog &"ident"& name, used when Exim is logging to
15587 syslog. The value must be no longer than 32 characters. See chapter
15588 &<<CHAPlog>>& for details of Exim's logging.
15592 .option syslog_timestamp main boolean true
15593 .cindex "syslog" "timestamps"
15594 If &%syslog_timestamp%& is set false, the timestamps on Exim's log lines are
15595 omitted when these lines are sent to syslog. See chapter &<<CHAPlog>>& for
15596 details of Exim's logging.
15599 .option system_filter main string&!! unset
15600 .cindex "filter" "system filter"
15601 .cindex "system filter" "specifying"
15602 .cindex "Sieve filter" "not available for system filter"
15603 This option specifies an Exim filter file that is applied to all messages at
15604 the start of each delivery attempt, before any routing is done. System filters
15605 must be Exim filters; they cannot be Sieve filters. If the system filter
15606 generates any deliveries to files or pipes, or any new mail messages, the
15607 appropriate &%system_filter_..._transport%& option(s) must be set, to define
15608 which transports are to be used. Details of this facility are given in chapter
15609 &<<CHAPsystemfilter>>&.
15612 .option system_filter_directory_transport main string&!! unset
15613 .vindex "&$address_file$&"
15614 This sets the name of the transport driver that is to be used when the
15615 &%save%& command in a system message filter specifies a path ending in &"/"&,
15616 implying delivery of each message into a separate file in some directory.
15617 During the delivery, the variable &$address_file$& contains the path name.
15620 .option system_filter_file_transport main string&!! unset
15621 .cindex "file" "transport for system filter"
15622 This sets the name of the transport driver that is to be used when the &%save%&
15623 command in a system message filter specifies a path not ending in &"/"&. During
15624 the delivery, the variable &$address_file$& contains the path name.
15626 .option system_filter_group main string unset
15627 .cindex "gid (group id)" "system filter"
15628 This option is used only when &%system_filter_user%& is also set. It sets the
15629 gid under which the system filter is run, overriding any gid that is associated
15630 with the user. The value may be numerical or symbolic.
15632 .option system_filter_pipe_transport main string&!! unset
15633 .cindex "&(pipe)& transport" "for system filter"
15634 .vindex "&$address_pipe$&"
15635 This specifies the transport driver that is to be used when a &%pipe%& command
15636 is used in a system filter. During the delivery, the variable &$address_pipe$&
15637 contains the pipe command.
15640 .option system_filter_reply_transport main string&!! unset
15641 .cindex "&(autoreply)& transport" "for system filter"
15642 This specifies the transport driver that is to be used when a &%mail%& command
15643 is used in a system filter.
15646 .option system_filter_user main string unset
15647 .cindex "uid (user id)" "system filter"
15648 If this option is set to root, the system filter is run in the main Exim
15649 delivery process, as root. Otherwise, the system filter runs in a separate
15650 process, as the given user, defaulting to the Exim run-time user.
15651 Unless the string consists entirely of digits, it
15652 is looked up in the password data. Failure to find the named user causes a
15653 configuration error. The gid is either taken from the password data, or
15654 specified by &%system_filter_group%&. When the uid is specified numerically,
15655 &%system_filter_group%& is required to be set.
15657 If the system filter generates any pipe, file, or reply deliveries, the uid
15658 under which the filter is run is used when transporting them, unless a
15659 transport option overrides.
15662 .option tcp_nodelay main boolean true
15663 .cindex "daemon" "TCP_NODELAY on sockets"
15664 .cindex "Nagle algorithm"
15665 .cindex "TCP_NODELAY on listening sockets"
15666 If this option is set false, it stops the Exim daemon setting the
15667 TCP_NODELAY option on its listening sockets. Setting TCP_NODELAY
15668 turns off the &"Nagle algorithm"&, which is a way of improving network
15669 performance in interactive (character-by-character) situations. Turning it off
15670 should improve Exim's performance a bit, so that is what happens by default.
15671 However, it appears that some broken clients cannot cope, and time out. Hence
15672 this option. It affects only those sockets that are set up for listening by the
15673 daemon. Sockets created by the smtp transport for delivering mail always set
15677 .option timeout_frozen_after main time 0s
15678 .cindex "frozen messages" "timing out"
15679 .cindex "timeout" "frozen messages"
15680 If &%timeout_frozen_after%& is set to a time greater than zero, a frozen
15681 message of any kind that has been on the queue for longer than the given time
15682 is automatically cancelled at the next queue run. If the frozen message is a
15683 bounce message, it is just discarded; otherwise, a bounce is sent to the
15684 sender, in a similar manner to cancellation by the &%-Mg%& command line option.
15685 If you want to timeout frozen bounce messages earlier than other kinds of
15686 frozen message, see &%ignore_bounce_errors_after%&.
15688 &*Note:*& the default value of zero means no timeouts; with this setting,
15689 frozen messages remain on the queue forever (except for any frozen bounce
15690 messages that are released by &%ignore_bounce_errors_after%&).
15693 .option timezone main string unset
15694 .cindex "timezone, setting"
15695 The value of &%timezone%& is used to set the environment variable TZ while
15696 running Exim (if it is different on entry). This ensures that all timestamps
15697 created by Exim are in the required timezone. If you want all your timestamps
15698 to be in UTC (aka GMT) you should set
15702 The default value is taken from TIMEZONE_DEFAULT in &_Local/Makefile_&,
15703 or, if that is not set, from the value of the TZ environment variable when Exim
15704 is built. If &%timezone%& is set to the empty string, either at build or run
15705 time, any existing TZ variable is removed from the environment when Exim
15706 runs. This is appropriate behaviour for obtaining wall-clock time on some, but
15707 unfortunately not all, operating systems.
15710 .option tls_advertise_hosts main "host list&!!" unset
15711 .cindex "TLS" "advertising"
15712 .cindex "encryption" "on SMTP connection"
15713 .cindex "SMTP" "encrypted connection"
15714 When Exim is built with support for TLS encrypted connections, the availability
15715 of the STARTTLS command to set up an encrypted session is advertised in
15716 response to EHLO only to those client hosts that match this option. See
15717 chapter &<<CHAPTLS>>& for details of Exim's support for TLS.
15720 .option tls_certificate main string&!! unset
15721 .cindex "TLS" "server certificate; location of"
15722 .cindex "certificate" "server, location of"
15723 The value of this option is expanded, and must then be the absolute path to a
15724 file which contains the server's certificates. The server's private key is also
15725 assumed to be in this file if &%tls_privatekey%& is unset. See chapter
15726 &<<CHAPTLS>>& for further details.
15728 &*Note*&: The certificates defined by this option are used only when Exim is
15729 receiving incoming messages as a server. If you want to supply certificates for
15730 use when sending messages as a client, you must set the &%tls_certificate%&
15731 option in the relevant &(smtp)& transport.
15733 If the option contains &$tls_sni$& and Exim is built against OpenSSL, then
15734 if the OpenSSL build supports TLS extensions and the TLS client sends the
15735 Server Name Indication extension, then this option and others documented in
15736 &<<SECTtlssni>>& will be re-expanded.
15738 .option tls_crl main string&!! unset
15739 .cindex "TLS" "server certificate revocation list"
15740 .cindex "certificate" "revocation list for server"
15741 This option specifies a certificate revocation list. The expanded value must
15742 be the name of a file that contains a CRL in PEM format.
15744 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
15747 .option tls_dh_max_bits main integer 2236
15748 .cindex "TLS" "D-H bit count"
15749 The number of bits used for Diffie-Hellman key-exchange may be suggested by
15750 the chosen TLS library. That value might prove to be too high for
15751 interoperability. This option provides a maximum clamp on the value
15752 suggested, trading off security for interoperability.
15754 The value must be at least 1024.
15756 The value 2236 was chosen because, at time of adding the option, it was the
15757 hard-coded maximum value supported by the NSS cryptographic library, as used
15758 by Thunderbird, while GnuTLS was suggesting 2432 bits as normal.
15760 If you prefer more security and are willing to break some clients, raise this
15763 Note that the value passed to GnuTLS for *generating* a new prime may be a
15764 little less than this figure, because GnuTLS is inexact and may produce a
15765 larger prime than requested.
15768 .option tls_dhparam main string&!! unset
15769 .cindex "TLS" "D-H parameters for server"
15770 The value of this option is expanded and indicates the source of DH parameters
15771 to be used by Exim.
15773 If it is a filename starting with a &`/`&, then it names a file from which DH
15774 parameters should be loaded. If the file exists, it should hold a PEM-encoded
15775 PKCS#3 representation of the DH prime. If the file does not exist, for
15776 OpenSSL it is an error. For GnuTLS, Exim will attempt to create the file and
15777 fill it with a generated DH prime. For OpenSSL, if the DH bit-count from
15778 loading the file is greater than &%tls_dh_max_bits%& then it will be ignored,
15779 and treated as though the &%tls_dhparam%& were set to "none".
15781 If this option expands to the string "none", then no DH parameters will be
15784 If this option expands to the string "historic" and Exim is using GnuTLS, then
15785 Exim will attempt to load a file from inside the spool directory. If the file
15786 does not exist, Exim will attempt to create it.
15787 See section &<<SECTgnutlsparam>>& for further details.
15789 If Exim is using OpenSSL and this option is empty or unset, then Exim will load
15790 a default DH prime; the default is the 2048 bit prime described in section
15791 2.2 of RFC 5114, "2048-bit MODP Group with 224-bit Prime Order Subgroup", which
15792 in IKE is assigned number 23.
15794 Otherwise, the option must expand to the name used by Exim for any of a number
15795 of DH primes specified in RFC 2409, RFC 3526 and RFC 5114. As names, Exim uses
15796 "ike" followed by the number used by IKE, of "default" which corresponds to
15799 The available primes are:
15800 &`ike1`&, &`ike2`&, &`ike5`&,
15801 &`ike14`&, &`ike15`&, &`ike16`&, &`ike17`&, &`ike18`&,
15802 &`ike22`&, &`ike23`& (aka &`default`&) and &`ike24`&.
15804 Some of these will be too small to be accepted by clients.
15805 Some may be too large to be accepted by clients.
15808 .option tls_on_connect_ports main "string list" unset
15809 This option specifies a list of incoming SSMTP (aka SMTPS) ports that should
15810 operate the obsolete SSMTP (SMTPS) protocol, where a TLS session is immediately
15811 set up without waiting for the client to issue a STARTTLS command. For
15812 further details, see section &<<SECTsupobssmt>>&.
15816 .option tls_privatekey main string&!! unset
15817 .cindex "TLS" "server private key; location of"
15818 The value of this option is expanded, and must then be the absolute path to a
15819 file which contains the server's private key. If this option is unset, or if
15820 the expansion is forced to fail, or the result is an empty string, the private
15821 key is assumed to be in the same file as the server's certificates. See chapter
15822 &<<CHAPTLS>>& for further details.
15824 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
15827 .option tls_remember_esmtp main boolean false
15828 .cindex "TLS" "esmtp state; remembering"
15829 .cindex "TLS" "broken clients"
15830 If this option is set true, Exim violates the RFCs by remembering that it is in
15831 &"esmtp"& state after successfully negotiating a TLS session. This provides
15832 support for broken clients that fail to send a new EHLO after starting a
15836 .option tls_require_ciphers main string&!! unset
15837 .cindex "TLS" "requiring specific ciphers"
15838 .cindex "cipher" "requiring specific"
15839 This option controls which ciphers can be used for incoming TLS connections.
15840 The &(smtp)& transport has an option of the same name for controlling outgoing
15841 connections. This option is expanded for each connection, so can be varied for
15842 different clients if required. The value of this option must be a list of
15843 permitted cipher suites. The OpenSSL and GnuTLS libraries handle cipher control
15844 in somewhat different ways. If GnuTLS is being used, the client controls the
15845 preference order of the available ciphers. Details are given in sections
15846 &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&.
15849 .option tls_try_verify_hosts main "host list&!!" unset
15850 .cindex "TLS" "client certificate verification"
15851 .cindex "certificate" "verification of client"
15852 See &%tls_verify_hosts%& below.
15855 .option tls_verify_certificates main string&!! unset
15856 .cindex "TLS" "client certificate verification"
15857 .cindex "certificate" "verification of client"
15858 The value of this option is expanded, and must then be the absolute path to
15859 a file containing permitted certificates for clients that
15860 match &%tls_verify_hosts%& or &%tls_try_verify_hosts%&. Alternatively, if you
15861 are using OpenSSL, you can set &%tls_verify_certificates%& to the name of a
15862 directory containing certificate files. This does not work with GnuTLS; the
15863 option must be set to the name of a single file if you are using GnuTLS.
15865 These certificates should be for the certificate authorities trusted, rather
15866 than the public cert of individual clients. With both OpenSSL and GnuTLS, if
15867 the value is a file then the certificates are sent by Exim as a server to
15868 connecting clients, defining the list of accepted certificate authorities.
15869 Thus the values defined should be considered public data. To avoid this,
15870 use OpenSSL with a directory.
15872 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
15875 .option tls_verify_hosts main "host list&!!" unset
15876 .cindex "TLS" "client certificate verification"
15877 .cindex "certificate" "verification of client"
15878 This option, along with &%tls_try_verify_hosts%&, controls the checking of
15879 certificates from clients. The expected certificates are defined by
15880 &%tls_verify_certificates%&, which must be set. A configuration error occurs if
15881 either &%tls_verify_hosts%& or &%tls_try_verify_hosts%& is set and
15882 &%tls_verify_certificates%& is not set.
15884 Any client that matches &%tls_verify_hosts%& is constrained by
15885 &%tls_verify_certificates%&. When the client initiates a TLS session, it must
15886 present one of the listed certificates. If it does not, the connection is
15887 aborted. &*Warning*&: Including a host in &%tls_verify_hosts%& does not require
15888 the host to use TLS. It can still send SMTP commands through unencrypted
15889 connections. Forcing a client to use TLS has to be done separately using an
15890 ACL to reject inappropriate commands when the connection is not encrypted.
15892 A weaker form of checking is provided by &%tls_try_verify_hosts%&. If a client
15893 matches this option (but not &%tls_verify_hosts%&), Exim requests a
15894 certificate and checks it against &%tls_verify_certificates%&, but does not
15895 abort the connection if there is no certificate or if it does not match. This
15896 state can be detected in an ACL, which makes it possible to implement policies
15897 such as &"accept for relay only if a verified certificate has been received,
15898 but accept for local delivery if encrypted, even without a verified
15901 Client hosts that match neither of these lists are not asked to present
15905 .option trusted_groups main "string list&!!" unset
15906 .cindex "trusted groups"
15907 .cindex "groups" "trusted"
15908 This option is expanded just once, at the start of Exim's processing. If this
15909 option is set, any process that is running in one of the listed groups, or
15910 which has one of them as a supplementary group, is trusted. The groups can be
15911 specified numerically or by name. See section &<<SECTtrustedadmin>>& for
15912 details of what trusted callers are permitted to do. If neither
15913 &%trusted_groups%& nor &%trusted_users%& is set, only root and the Exim user
15916 .option trusted_users main "string list&!!" unset
15917 .cindex "trusted users"
15918 .cindex "user" "trusted"
15919 This option is expanded just once, at the start of Exim's processing. If this
15920 option is set, any process that is running as one of the listed users is
15921 trusted. The users can be specified numerically or by name. See section
15922 &<<SECTtrustedadmin>>& for details of what trusted callers are permitted to do.
15923 If neither &%trusted_groups%& nor &%trusted_users%& is set, only root and the
15924 Exim user are trusted.
15926 .option unknown_login main string&!! unset
15927 .cindex "uid (user id)" "unknown caller"
15928 .vindex "&$caller_uid$&"
15929 This is a specialized feature for use in unusual configurations. By default, if
15930 the uid of the caller of Exim cannot be looked up using &[getpwuid()]&, Exim
15931 gives up. The &%unknown_login%& option can be used to set a login name to be
15932 used in this circumstance. It is expanded, so values like &%user$caller_uid%&
15933 can be set. When &%unknown_login%& is used, the value of &%unknown_username%&
15934 is used for the user's real name (gecos field), unless this has been set by the
15937 .option unknown_username main string unset
15938 See &%unknown_login%&.
15940 .option untrusted_set_sender main "address list&!!" unset
15941 .cindex "trusted users"
15942 .cindex "sender" "setting by untrusted user"
15943 .cindex "untrusted user setting sender"
15944 .cindex "user" "untrusted setting sender"
15945 .cindex "envelope sender"
15946 When an untrusted user submits a message to Exim using the standard input, Exim
15947 normally creates an envelope sender address from the user's login and the
15948 default qualification domain. Data from the &%-f%& option (for setting envelope
15949 senders on non-SMTP messages) or the SMTP MAIL command (if &%-bs%& or &%-bS%&
15950 is used) is ignored.
15952 However, untrusted users are permitted to set an empty envelope sender address,
15953 to declare that a message should never generate any bounces. For example:
15955 exim -f '<>' user@domain.example
15957 .vindex "&$sender_ident$&"
15958 The &%untrusted_set_sender%& option allows you to permit untrusted users to set
15959 other envelope sender addresses in a controlled way. When it is set, untrusted
15960 users are allowed to set envelope sender addresses that match any of the
15961 patterns in the list. Like all address lists, the string is expanded. The
15962 identity of the user is in &$sender_ident$&, so you can, for example, restrict
15963 users to setting senders that start with their login ids
15964 followed by a hyphen
15965 by a setting like this:
15967 untrusted_set_sender = ^$sender_ident-
15969 If you want to allow untrusted users to set envelope sender addresses without
15970 restriction, you can use
15972 untrusted_set_sender = *
15974 The &%untrusted_set_sender%& option applies to all forms of local input, but
15975 only to the setting of the envelope sender. It does not permit untrusted users
15976 to use the other options which trusted user can use to override message
15977 parameters. Furthermore, it does not stop Exim from removing an existing
15978 &'Sender:'& header in the message, or from adding a &'Sender:'& header if
15979 necessary. See &%local_sender_retain%& and &%local_from_check%& for ways of
15980 overriding these actions. The handling of the &'Sender:'& header is also
15981 described in section &<<SECTthesenhea>>&.
15983 The log line for a message's arrival shows the envelope sender following
15984 &"<="&. For local messages, the user's login always follows, after &"U="&. In
15985 &%-bp%& displays, and in the Exim monitor, if an untrusted user sets an
15986 envelope sender address, the user's login is shown in parentheses after the
15990 .option uucp_from_pattern main string "see below"
15991 .cindex "&""From""& line"
15992 .cindex "UUCP" "&""From""& line"
15993 Some applications that pass messages to an MTA via a command line interface use
15994 an initial line starting with &"From&~"& to pass the envelope sender. In
15995 particular, this is used by UUCP software. Exim recognizes such a line by means
15996 of a regular expression that is set in &%uucp_from_pattern%&. When the pattern
15997 matches, the sender address is constructed by expanding the contents of
15998 &%uucp_from_sender%&, provided that the caller of Exim is a trusted user. The
15999 default pattern recognizes lines in the following two forms:
16001 From ph10 Fri Jan 5 12:35 GMT 1996
16002 From ph10 Fri, 7 Jan 97 14:00:00 GMT
16004 The pattern can be seen by running
16006 exim -bP uucp_from_pattern
16008 It checks only up to the hours and minutes, and allows for a 2-digit or 4-digit
16009 year in the second case. The first word after &"From&~"& is matched in the
16010 regular expression by a parenthesized subpattern. The default value for
16011 &%uucp_from_sender%& is &"$1"&, which therefore just uses this first word
16012 (&"ph10"& in the example above) as the message's sender. See also
16013 &%ignore_fromline_hosts%&.
16016 .option uucp_from_sender main string&!! &`$1`&
16017 See &%uucp_from_pattern%& above.
16020 .option warn_message_file main string unset
16021 .cindex "warning of delay" "customizing the message"
16022 .cindex "customizing" "warning message"
16023 This option defines a template file containing paragraphs of text to be used
16024 for constructing the warning message which is sent by Exim when a message has
16025 been on the queue for a specified amount of time, as specified by
16026 &%delay_warning%&. Details of the file's contents are given in chapter
16027 &<<CHAPemsgcust>>&. See also &%bounce_message_file%&.
16030 .option write_rejectlog main boolean true
16031 .cindex "reject log" "disabling"
16032 If this option is set false, Exim no longer writes anything to the reject log.
16033 See chapter &<<CHAPlog>>& for details of what Exim writes to its logs.
16034 .ecindex IIDconfima
16035 .ecindex IIDmaiconf
16040 . ////////////////////////////////////////////////////////////////////////////
16041 . ////////////////////////////////////////////////////////////////////////////
16043 .chapter "Generic options for routers" "CHAProutergeneric"
16044 .scindex IIDgenoprou1 "options" "generic; for routers"
16045 .scindex IIDgenoprou2 "generic options" "router"
16046 This chapter describes the generic options that apply to all routers.
16047 Those that are preconditions are marked with ‡ in the &"use"& field.
16049 For a general description of how a router operates, see sections
16050 &<<SECTrunindrou>>& and &<<SECTrouprecon>>&. The latter specifies the order in
16051 which the preconditions are tested. The order of expansion of the options that
16052 provide data for a transport is: &%errors_to%&, &%headers_add%&,
16053 &%headers_remove%&, &%transport%&.
16057 .option address_data routers string&!! unset
16058 .cindex "router" "data attached to address"
16059 The string is expanded just before the router is run, that is, after all the
16060 precondition tests have succeeded. If the expansion is forced to fail, the
16061 router declines, the value of &%address_data%& remains unchanged, and the
16062 &%more%& option controls what happens next. Other expansion failures cause
16063 delivery of the address to be deferred.
16065 .vindex "&$address_data$&"
16066 When the expansion succeeds, the value is retained with the address, and can be
16067 accessed using the variable &$address_data$& in the current router, subsequent
16068 routers, and the eventual transport.
16070 &*Warning*&: If the current or any subsequent router is a &(redirect)& router
16071 that runs a user's filter file, the contents of &$address_data$& are accessible
16072 in the filter. This is not normally a problem, because such data is usually
16073 either not confidential or it &"belongs"& to the current user, but if you do
16074 put confidential data into &$address_data$& you need to remember this point.
16076 Even if the router declines or passes, the value of &$address_data$& remains
16077 with the address, though it can be changed by another &%address_data%& setting
16078 on a subsequent router. If a router generates child addresses, the value of
16079 &$address_data$& propagates to them. This also applies to the special kind of
16080 &"child"& that is generated by a router with the &%unseen%& option.
16082 The idea of &%address_data%& is that you can use it to look up a lot of data
16083 for the address once, and then pick out parts of the data later. For example,
16084 you could use a single LDAP lookup to return a string of the form
16086 uid=1234 gid=5678 mailbox=/mail/xyz forward=/home/xyz/.forward
16088 In the transport you could pick out the mailbox by a setting such as
16090 file = ${extract{mailbox}{$address_data}}
16092 This makes the configuration file less messy, and also reduces the number of
16093 lookups (though Exim does cache lookups).
16095 .vindex "&$sender_address_data$&"
16096 .vindex "&$address_data$&"
16097 The &%address_data%& facility is also useful as a means of passing information
16098 from one router to another, and from a router to a transport. In addition, if
16099 &$address_data$& is set by a router when verifying a recipient address from an
16100 ACL, it remains available for use in the rest of the ACL statement. After
16101 verifying a sender, the value is transferred to &$sender_address_data$&.
16105 .option address_test routers&!? boolean true
16107 .cindex "router" "skipping when address testing"
16108 If this option is set false, the router is skipped when routing is being tested
16109 by means of the &%-bt%& command line option. This can be a convenience when
16110 your first router sends messages to an external scanner, because it saves you
16111 having to set the &"already scanned"& indicator when testing real address
16116 .option cannot_route_message routers string&!! unset
16117 .cindex "router" "customizing &""cannot route""& message"
16118 .cindex "customizing" "&""cannot route""& message"
16119 This option specifies a text message that is used when an address cannot be
16120 routed because Exim has run out of routers. The default message is
16121 &"Unrouteable address"&. This option is useful only on routers that have
16122 &%more%& set false, or on the very last router in a configuration, because the
16123 value that is used is taken from the last router that is considered. This
16124 includes a router that is skipped because its preconditions are not met, as
16125 well as a router that declines. For example, using the default configuration,
16128 cannot_route_message = Remote domain not found in DNS
16130 on the first router, which is a &(dnslookup)& router with &%more%& set false,
16133 cannot_route_message = Unknown local user
16135 on the final router that checks for local users. If string expansion fails for
16136 this option, the default message is used. Unless the expansion failure was
16137 explicitly forced, a message about the failure is written to the main and panic
16138 logs, in addition to the normal message about the routing failure.
16141 .option caseful_local_part routers boolean false
16142 .cindex "case of local parts"
16143 .cindex "router" "case of local parts"
16144 By default, routers handle the local parts of addresses in a case-insensitive
16145 manner, though the actual case is preserved for transmission with the message.
16146 If you want the case of letters to be significant in a router, you must set
16147 this option true. For individual router options that contain address or local
16148 part lists (for example, &%local_parts%&), case-sensitive matching can be
16149 turned on by &"+caseful"& as a list item. See section &<<SECTcasletadd>>& for
16152 .vindex "&$local_part$&"
16153 .vindex "&$original_local_part$&"
16154 .vindex "&$parent_local_part$&"
16155 The value of the &$local_part$& variable is forced to lower case while a
16156 router is running unless &%caseful_local_part%& is set. When a router assigns
16157 an address to a transport, the value of &$local_part$& when the transport runs
16158 is the same as it was in the router. Similarly, when a router generates child
16159 addresses by aliasing or forwarding, the values of &$original_local_part$&
16160 and &$parent_local_part$& are those that were used by the redirecting router.
16162 This option applies to the processing of an address by a router. When a
16163 recipient address is being processed in an ACL, there is a separate &%control%&
16164 modifier that can be used to specify case-sensitive processing within the ACL
16165 (see section &<<SECTcontrols>>&).
16169 .option check_local_user routers&!? boolean false
16170 .cindex "local user, checking in router"
16171 .cindex "router" "checking for local user"
16172 .cindex "&_/etc/passwd_&"
16174 When this option is true, Exim checks that the local part of the recipient
16175 address (with affixes removed if relevant) is the name of an account on the
16176 local system. The check is done by calling the &[getpwnam()]& function rather
16177 than trying to read &_/etc/passwd_& directly. This means that other methods of
16178 holding password data (such as NIS) are supported. If the local part is a local
16179 user, &$home$& is set from the password data, and can be tested in other
16180 preconditions that are evaluated after this one (the order of evaluation is
16181 given in section &<<SECTrouprecon>>&). However, the value of &$home$& can be
16182 overridden by &%router_home_directory%&. If the local part is not a local user,
16183 the router is skipped.
16185 If you want to check that the local part is either the name of a local user
16186 or matches something else, you cannot combine &%check_local_user%& with a
16187 setting of &%local_parts%&, because that specifies the logical &'and'& of the
16188 two conditions. However, you can use a &(passwd)& lookup in a &%local_parts%&
16189 setting to achieve this. For example:
16191 local_parts = passwd;$local_part : lsearch;/etc/other/users
16193 Note, however, that the side effects of &%check_local_user%& (such as setting
16194 up a home directory) do not occur when a &(passwd)& lookup is used in a
16195 &%local_parts%& (or any other) precondition.
16199 .option condition routers&!? string&!! unset
16200 .cindex "router" "customized precondition"
16201 This option specifies a general precondition test that has to succeed for the
16202 router to be called. The &%condition%& option is the last precondition to be
16203 evaluated (see section &<<SECTrouprecon>>&). The string is expanded, and if the
16204 result is a forced failure, or an empty string, or one of the strings &"0"& or
16205 &"no"& or &"false"& (checked without regard to the case of the letters), the
16206 router is skipped, and the address is offered to the next one.
16208 If the result is any other value, the router is run (as this is the last
16209 precondition to be evaluated, all the other preconditions must be true).
16211 This option is unique in that multiple &%condition%& options may be present.
16212 All &%condition%& options must succeed.
16214 The &%condition%& option provides a means of applying custom conditions to the
16215 running of routers. Note that in the case of a simple conditional expansion,
16216 the default expansion values are exactly what is wanted. For example:
16218 condition = ${if >{$message_age}{600}}
16220 Because of the default behaviour of the string expansion, this is equivalent to
16222 condition = ${if >{$message_age}{600}{true}{}}
16225 A multiple condition example, which succeeds:
16227 condition = ${if >{$message_age}{600}}
16228 condition = ${if !eq{${lc:$local_part}}{postmaster}}
16232 If the expansion fails (other than forced failure) delivery is deferred. Some
16233 of the other precondition options are common special cases that could in fact
16234 be specified using &%condition%&.
16237 .option debug_print routers string&!! unset
16238 .cindex "testing" "variables in drivers"
16239 If this option is set and debugging is enabled (see the &%-d%& command line
16240 option), the string is expanded and included in the debugging output.
16241 If expansion of the string fails, the error message is written to the debugging
16242 output, and Exim carries on processing.
16243 This option is provided to help with checking out the values of variables and
16244 so on when debugging router configurations. For example, if a &%condition%&
16245 option appears not to be working, &%debug_print%& can be used to output the
16246 variables it references. The output happens after checks for &%domains%&,
16247 &%local_parts%&, and &%check_local_user%& but before any other preconditions
16248 are tested. A newline is added to the text if it does not end with one.
16252 .option disable_logging routers boolean false
16253 If this option is set true, nothing is logged for any routing errors
16254 or for any deliveries caused by this router. You should not set this option
16255 unless you really, really know what you are doing. See also the generic
16256 transport option of the same name.
16259 .option domains routers&!? "domain list&!!" unset
16260 .cindex "router" "restricting to specific domains"
16261 .vindex "&$domain_data$&"
16262 If this option is set, the router is skipped unless the current domain matches
16263 the list. If the match is achieved by means of a file lookup, the data that the
16264 lookup returned for the domain is placed in &$domain_data$& for use in string
16265 expansions of the driver's private options. See section &<<SECTrouprecon>>& for
16266 a list of the order in which preconditions are evaluated.
16270 .option driver routers string unset
16271 This option must always be set. It specifies which of the available routers is
16276 .option errors_to routers string&!! unset
16277 .cindex "envelope sender"
16278 .cindex "router" "changing address for errors"
16279 If a router successfully handles an address, it may assign the address to a
16280 transport for delivery or it may generate child addresses. In both cases, if
16281 there is a delivery problem during later processing, the resulting bounce
16282 message is sent to the address that results from expanding this string,
16283 provided that the address verifies successfully. The &%errors_to%& option is
16284 expanded before &%headers_add%&, &%headers_remove%&, and &%transport%&.
16286 The &%errors_to%& setting associated with an address can be overridden if it
16287 subsequently passes through other routers that have their own &%errors_to%&
16288 settings, or if the message is delivered by a transport with a &%return_path%&
16291 If &%errors_to%& is unset, or the expansion is forced to fail, or the result of
16292 the expansion fails to verify, the errors address associated with the incoming
16293 address is used. At top level, this is the envelope sender. A non-forced
16294 expansion failure causes delivery to be deferred.
16296 If an address for which &%errors_to%& has been set ends up being delivered over
16297 SMTP, the envelope sender for that delivery is the &%errors_to%& value, so that
16298 any bounces that are generated by other MTAs on the delivery route are also
16299 sent there. You can set &%errors_to%& to the empty string by either of these
16305 An expansion item that yields an empty string has the same effect. If you do
16306 this, a locally detected delivery error for addresses processed by this router
16307 no longer gives rise to a bounce message; the error is discarded. If the
16308 address is delivered to a remote host, the return path is set to &`<>`&, unless
16309 overridden by the &%return_path%& option on the transport.
16311 .vindex "&$address_data$&"
16312 If for some reason you want to discard local errors, but use a non-empty
16313 MAIL command for remote delivery, you can preserve the original return
16314 path in &$address_data$& in the router, and reinstate it in the transport by
16315 setting &%return_path%&.
16317 The most common use of &%errors_to%& is to direct mailing list bounces to the
16318 manager of the list, as described in section &<<SECTmailinglists>>&, or to
16319 implement VERP (Variable Envelope Return Paths) (see section &<<SECTverp>>&).
16323 .option expn routers&!? boolean true
16324 .cindex "address" "testing"
16325 .cindex "testing" "addresses"
16326 .cindex "EXPN" "router skipping"
16327 .cindex "router" "skipping for EXPN"
16328 If this option is turned off, the router is skipped when testing an address
16329 as a result of processing an SMTP EXPN command. You might, for example,
16330 want to turn it off on a router for users' &_.forward_& files, while leaving it
16331 on for the system alias file.
16332 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
16335 The use of the SMTP EXPN command is controlled by an ACL (see chapter
16336 &<<CHAPACL>>&). When Exim is running an EXPN command, it is similar to testing
16337 an address with &%-bt%&. Compare VRFY, whose counterpart is &%-bv%&.
16341 .option fail_verify routers boolean false
16342 .cindex "router" "forcing verification failure"
16343 Setting this option has the effect of setting both &%fail_verify_sender%& and
16344 &%fail_verify_recipient%& to the same value.
16348 .option fail_verify_recipient routers boolean false
16349 If this option is true and an address is accepted by this router when
16350 verifying a recipient, verification fails.
16354 .option fail_verify_sender routers boolean false
16355 If this option is true and an address is accepted by this router when
16356 verifying a sender, verification fails.
16360 .option fallback_hosts routers "string list" unset
16361 .cindex "router" "fallback hosts"
16362 .cindex "fallback" "hosts specified on router"
16363 String expansion is not applied to this option. The argument must be a
16364 colon-separated list of host names or IP addresses. The list separator can be
16365 changed (see section &<<SECTlistconstruct>>&), and a port can be specified with
16366 each name or address. In fact, the format of each item is exactly the same as
16367 defined for the list of hosts in a &(manualroute)& router (see section
16368 &<<SECTformatonehostitem>>&).
16370 If a router queues an address for a remote transport, this host list is
16371 associated with the address, and used instead of the transport's fallback host
16372 list. If &%hosts_randomize%& is set on the transport, the order of the list is
16373 randomized for each use. See the &%fallback_hosts%& option of the &(smtp)&
16374 transport for further details.
16377 .option group routers string&!! "see below"
16378 .cindex "gid (group id)" "local delivery"
16379 .cindex "local transports" "uid and gid"
16380 .cindex "transport" "local"
16381 .cindex "router" "setting group"
16382 When a router queues an address for a transport, and the transport does not
16383 specify a group, the group given here is used when running the delivery
16385 The group may be specified numerically or by name. If expansion fails, the
16386 error is logged and delivery is deferred.
16387 The default is unset, unless &%check_local_user%& is set, when the default
16388 is taken from the password information. See also &%initgroups%& and &%user%&
16389 and the discussion in chapter &<<CHAPenvironment>>&.
16393 .option headers_add routers string&!! unset
16394 .cindex "header lines" "adding"
16395 .cindex "router" "adding header lines"
16396 This option specifies a string of text that is expanded at routing time, and
16397 associated with any addresses that are accepted by the router. However, this
16398 option has no effect when an address is just being verified. The way in which
16399 the text is used to add header lines at transport time is described in section
16400 &<<SECTheadersaddrem>>&. New header lines are not actually added until the
16401 message is in the process of being transported. This means that references to
16402 header lines in string expansions in the transport's configuration do not
16403 &"see"& the added header lines.
16405 The &%headers_add%& option is expanded after &%errors_to%&, but before
16406 &%headers_remove%& and &%transport%&. If the expanded string is empty, or if
16407 the expansion is forced to fail, the option has no effect. Other expansion
16408 failures are treated as configuration errors.
16410 &*Warning 1*&: The &%headers_add%& option cannot be used for a &(redirect)&
16411 router that has the &%one_time%& option set.
16413 .cindex "duplicate addresses"
16414 .oindex "&%unseen%&"
16415 &*Warning 2*&: If the &%unseen%& option is set on the router, all header
16416 additions are deleted when the address is passed on to subsequent routers.
16417 For a &%redirect%& router, if a generated address is the same as the incoming
16418 address, this can lead to duplicate addresses with different header
16419 modifications. Exim does not do duplicate deliveries (except, in certain
16420 circumstances, to pipes -- see section &<<SECTdupaddr>>&), but it is undefined
16421 which of the duplicates is discarded, so this ambiguous situation should be
16422 avoided. The &%repeat_use%& option of the &%redirect%& router may be of help.
16426 .option headers_remove routers string&!! unset
16427 .cindex "header lines" "removing"
16428 .cindex "router" "removing header lines"
16429 This option specifies a string of text that is expanded at routing time, and
16430 associated with any addresses that are accepted by the router. However, this
16431 option has no effect when an address is just being verified. The way in which
16432 the text is used to remove header lines at transport time is described in
16433 section &<<SECTheadersaddrem>>&. Header lines are not actually removed until
16434 the message is in the process of being transported. This means that references
16435 to header lines in string expansions in the transport's configuration still
16436 &"see"& the original header lines.
16438 The &%headers_remove%& option is expanded after &%errors_to%& and
16439 &%headers_add%&, but before &%transport%&. If the expansion is forced to fail,
16440 the option has no effect. Other expansion failures are treated as configuration
16443 &*Warning 1*&: The &%headers_remove%& option cannot be used for a &(redirect)&
16444 router that has the &%one_time%& option set.
16446 &*Warning 2*&: If the &%unseen%& option is set on the router, all header
16447 removal requests are deleted when the address is passed on to subsequent
16448 routers, and this can lead to problems with duplicates -- see the similar
16449 warning for &%headers_add%& above.
16452 .option ignore_target_hosts routers "host list&!!" unset
16453 .cindex "IP address" "discarding"
16454 .cindex "router" "discarding IP addresses"
16455 Although this option is a host list, it should normally contain IP address
16456 entries rather than names. If any host that is looked up by the router has an
16457 IP address that matches an item in this list, Exim behaves as if that IP
16458 address did not exist. This option allows you to cope with rogue DNS entries
16461 remote.domain.example. A 127.0.0.1
16465 ignore_target_hosts = 127.0.0.1
16467 on the relevant router. If all the hosts found by a &(dnslookup)& router are
16468 discarded in this way, the router declines. In a conventional configuration, an
16469 attempt to mail to such a domain would normally provoke the &"unrouteable
16470 domain"& error, and an attempt to verify an address in the domain would fail.
16471 Similarly, if &%ignore_target_hosts%& is set on an &(ipliteral)& router, the
16472 router declines if presented with one of the listed addresses.
16474 You can use this option to disable the use of IPv4 or IPv6 for mail delivery by
16475 means of the first or the second of the following settings, respectively:
16477 ignore_target_hosts = 0.0.0.0/0
16478 ignore_target_hosts = <; 0::0/0
16480 The pattern in the first line matches all IPv4 addresses, whereas the pattern
16481 in the second line matches all IPv6 addresses.
16483 This option may also be useful for ignoring link-local and site-local IPv6
16484 addresses. Because, like all host lists, the value of &%ignore_target_hosts%&
16485 is expanded before use as a list, it is possible to make it dependent on the
16486 domain that is being routed.
16488 .vindex "&$host_address$&"
16489 During its expansion, &$host_address$& is set to the IP address that is being
16492 .option initgroups routers boolean false
16493 .cindex "additional groups"
16494 .cindex "groups" "additional"
16495 .cindex "local transports" "uid and gid"
16496 .cindex "transport" "local"
16497 If the router queues an address for a transport, and this option is true, and
16498 the uid supplied by the router is not overridden by the transport, the
16499 &[initgroups()]& function is called when running the transport to ensure that
16500 any additional groups associated with the uid are set up. See also &%group%&
16501 and &%user%& and the discussion in chapter &<<CHAPenvironment>>&.
16505 .option local_part_prefix routers&!? "string list" unset
16506 .cindex "router" "prefix for local part"
16507 .cindex "prefix" "for local part, used in router"
16508 If this option is set, the router is skipped unless the local part starts with
16509 one of the given strings, or &%local_part_prefix_optional%& is true. See
16510 section &<<SECTrouprecon>>& for a list of the order in which preconditions are
16513 The list is scanned from left to right, and the first prefix that matches is
16514 used. A limited form of wildcard is available; if the prefix begins with an
16515 asterisk, it matches the longest possible sequence of arbitrary characters at
16516 the start of the local part. An asterisk should therefore always be followed by
16517 some character that does not occur in normal local parts.
16518 .cindex "multiple mailboxes"
16519 .cindex "mailbox" "multiple"
16520 Wildcarding can be used to set up multiple user mailboxes, as described in
16521 section &<<SECTmulbox>>&.
16523 .vindex "&$local_part$&"
16524 .vindex "&$local_part_prefix$&"
16525 During the testing of the &%local_parts%& option, and while the router is
16526 running, the prefix is removed from the local part, and is available in the
16527 expansion variable &$local_part_prefix$&. When a message is being delivered, if
16528 the router accepts the address, this remains true during subsequent delivery by
16529 a transport. In particular, the local part that is transmitted in the RCPT
16530 command for LMTP, SMTP, and BSMTP deliveries has the prefix removed by default.
16531 This behaviour can be overridden by setting &%rcpt_include_affixes%& true on
16532 the relevant transport.
16534 When an address is being verified, &%local_part_prefix%& affects only the
16535 behaviour of the router. If the callout feature of verification is in use, this
16536 means that the full address, including the prefix, will be used during the
16539 The prefix facility is commonly used to handle local parts of the form
16540 &%owner-something%&. Another common use is to support local parts of the form
16541 &%real-username%& to bypass a user's &_.forward_& file &-- helpful when trying
16542 to tell a user their forwarding is broken &-- by placing a router like this one
16543 immediately before the router that handles &_.forward_& files:
16547 local_part_prefix = real-
16549 transport = local_delivery
16551 For security, it would probably be a good idea to restrict the use of this
16552 router to locally-generated messages, using a condition such as this:
16554 condition = ${if match {$sender_host_address}\
16555 {\N^(|127\.0\.0\.1)$\N}}
16558 If both &%local_part_prefix%& and &%local_part_suffix%& are set for a router,
16559 both conditions must be met if not optional. Care must be taken if wildcards
16560 are used in both a prefix and a suffix on the same router. Different
16561 separator characters must be used to avoid ambiguity.
16564 .option local_part_prefix_optional routers boolean false
16565 See &%local_part_prefix%& above.
16569 .option local_part_suffix routers&!? "string list" unset
16570 .cindex "router" "suffix for local part"
16571 .cindex "suffix for local part" "used in router"
16572 This option operates in the same way as &%local_part_prefix%&, except that the
16573 local part must end (rather than start) with the given string, the
16574 &%local_part_suffix_optional%& option determines whether the suffix is
16575 mandatory, and the wildcard * character, if present, must be the last
16576 character of the suffix. This option facility is commonly used to handle local
16577 parts of the form &%something-request%& and multiple user mailboxes of the form
16581 .option local_part_suffix_optional routers boolean false
16582 See &%local_part_suffix%& above.
16586 .option local_parts routers&!? "local part list&!!" unset
16587 .cindex "router" "restricting to specific local parts"
16588 .cindex "local part" "checking in router"
16589 The router is run only if the local part of the address matches the list.
16590 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
16592 section &<<SECTlocparlis>>& for a discussion of local part lists. Because the
16593 string is expanded, it is possible to make it depend on the domain, for
16596 local_parts = dbm;/usr/local/specials/$domain
16598 .vindex "&$local_part_data$&"
16599 If the match is achieved by a lookup, the data that the lookup returned
16600 for the local part is placed in the variable &$local_part_data$& for use in
16601 expansions of the router's private options. You might use this option, for
16602 example, if you have a large number of local virtual domains, and you want to
16603 send all postmaster mail to the same place without having to set up an alias in
16604 each virtual domain:
16608 local_parts = postmaster
16609 data = postmaster@real.domain.example
16613 .option log_as_local routers boolean "see below"
16614 .cindex "log" "delivery line"
16615 .cindex "delivery" "log line format"
16616 Exim has two logging styles for delivery, the idea being to make local
16617 deliveries stand out more visibly from remote ones. In the &"local"& style, the
16618 recipient address is given just as the local part, without a domain. The use of
16619 this style is controlled by this option. It defaults to true for the &(accept)&
16620 router, and false for all the others. This option applies only when a
16621 router assigns an address to a transport. It has no effect on routers that
16622 redirect addresses.
16626 .option more routers boolean&!! true
16627 The result of string expansion for this option must be a valid boolean value,
16628 that is, one of the strings &"yes"&, &"no"&, &"true"&, or &"false"&. Any other
16629 result causes an error, and delivery is deferred. If the expansion is forced to
16630 fail, the default value for the option (true) is used. Other failures cause
16631 delivery to be deferred.
16633 If this option is set false, and the router declines to handle the address, no
16634 further routers are tried, routing fails, and the address is bounced.
16636 However, if the router explicitly passes an address to the following router by
16637 means of the setting
16641 or otherwise, the setting of &%more%& is ignored. Also, the setting of &%more%&
16642 does not affect the behaviour if one of the precondition tests fails. In that
16643 case, the address is always passed to the next router.
16645 Note that &%address_data%& is not considered to be a precondition. If its
16646 expansion is forced to fail, the router declines, and the value of &%more%&
16647 controls what happens next.
16650 .option pass_on_timeout routers boolean false
16651 .cindex "timeout" "of router"
16652 .cindex "router" "timeout"
16653 If a router times out during a host lookup, it normally causes deferral of the
16654 address. If &%pass_on_timeout%& is set, the address is passed on to the next
16655 router, overriding &%no_more%&. This may be helpful for systems that are
16656 intermittently connected to the Internet, or those that want to pass to a smart
16657 host any messages that cannot immediately be delivered.
16659 There are occasional other temporary errors that can occur while doing DNS
16660 lookups. They are treated in the same way as a timeout, and this option
16661 applies to all of them.
16665 .option pass_router routers string unset
16666 .cindex "router" "go to after &""pass""&"
16667 Routers that recognize the generic &%self%& option (&(dnslookup)&,
16668 &(ipliteral)&, and &(manualroute)&) are able to return &"pass"&, forcing
16669 routing to continue, and overriding a false setting of &%more%&. When one of
16670 these routers returns &"pass"&, the address is normally handed on to the next
16671 router in sequence. This can be changed by setting &%pass_router%& to the name
16672 of another router. However (unlike &%redirect_router%&) the named router must
16673 be below the current router, to avoid loops. Note that this option applies only
16674 to the special case of &"pass"&. It does not apply when a router returns
16675 &"decline"& because it cannot handle an address.
16679 .option redirect_router routers string unset
16680 .cindex "router" "start at after redirection"
16681 Sometimes an administrator knows that it is pointless to reprocess addresses
16682 generated from alias or forward files with the same router again. For
16683 example, if an alias file translates real names into login ids there is no
16684 point searching the alias file a second time, especially if it is a large file.
16686 The &%redirect_router%& option can be set to the name of any router instance.
16687 It causes the routing of any generated addresses to start at the named router
16688 instead of at the first router. This option has no effect if the router in
16689 which it is set does not generate new addresses.
16693 .option require_files routers&!? "string list&!!" unset
16694 .cindex "file" "requiring for router"
16695 .cindex "router" "requiring file existence"
16696 This option provides a general mechanism for predicating the running of a
16697 router on the existence or non-existence of certain files or directories.
16698 Before running a router, as one of its precondition tests, Exim works its way
16699 through the &%require_files%& list, expanding each item separately.
16701 Because the list is split before expansion, any colons in expansion items must
16702 be doubled, or the facility for using a different list separator must be used.
16703 If any expansion is forced to fail, the item is ignored. Other expansion
16704 failures cause routing of the address to be deferred.
16706 If any expanded string is empty, it is ignored. Otherwise, except as described
16707 below, each string must be a fully qualified file path, optionally preceded by
16708 &"!"&. The paths are passed to the &[stat()]& function to test for the
16709 existence of the files or directories. The router is skipped if any paths not
16710 preceded by &"!"& do not exist, or if any paths preceded by &"!"& do exist.
16713 If &[stat()]& cannot determine whether a file exists or not, delivery of
16714 the message is deferred. This can happen when NFS-mounted filesystems are
16717 This option is checked after the &%domains%&, &%local_parts%&, and &%senders%&
16718 options, so you cannot use it to check for the existence of a file in which to
16719 look up a domain, local part, or sender. (See section &<<SECTrouprecon>>& for a
16720 full list of the order in which preconditions are evaluated.) However, as
16721 these options are all expanded, you can use the &%exists%& expansion condition
16722 to make such tests. The &%require_files%& option is intended for checking files
16723 that the router may be going to use internally, or which are needed by a
16724 transport (for example &_.procmailrc_&).
16726 During delivery, the &[stat()]& function is run as root, but there is a
16727 facility for some checking of the accessibility of a file by another user.
16728 This is not a proper permissions check, but just a &"rough"& check that
16729 operates as follows:
16731 If an item in a &%require_files%& list does not contain any forward slash
16732 characters, it is taken to be the user (and optional group, separated by a
16733 comma) to be checked for subsequent files in the list. If no group is specified
16734 but the user is specified symbolically, the gid associated with the uid is
16737 require_files = mail:/some/file
16738 require_files = $local_part:$home/.procmailrc
16740 If a user or group name in a &%require_files%& list does not exist, the
16741 &%require_files%& condition fails.
16743 Exim performs the check by scanning along the components of the file path, and
16744 checking the access for the given uid and gid. It checks for &"x"& access on
16745 directories, and &"r"& access on the final file. Note that this means that file
16746 access control lists, if the operating system has them, are ignored.
16748 &*Warning 1*&: When the router is being run to verify addresses for an
16749 incoming SMTP message, Exim is not running as root, but under its own uid. This
16750 may affect the result of a &%require_files%& check. In particular, &[stat()]&
16751 may yield the error EACCES (&"Permission denied"&). This means that the Exim
16752 user is not permitted to read one of the directories on the file's path.
16754 &*Warning 2*&: Even when Exim is running as root while delivering a message,
16755 &[stat()]& can yield EACCES for a file in an NFS directory that is mounted
16756 without root access. In this case, if a check for access by a particular user
16757 is requested, Exim creates a subprocess that runs as that user, and tries the
16758 check again in that process.
16760 The default action for handling an unresolved EACCES is to consider it to
16761 be caused by a configuration error, and routing is deferred because the
16762 existence or non-existence of the file cannot be determined. However, in some
16763 circumstances it may be desirable to treat this condition as if the file did
16764 not exist. If the file name (or the exclamation mark that precedes the file
16765 name for non-existence) is preceded by a plus sign, the EACCES error is treated
16766 as if the file did not exist. For example:
16768 require_files = +/some/file
16770 If the router is not an essential part of verification (for example, it
16771 handles users' &_.forward_& files), another solution is to set the &%verify%&
16772 option false so that the router is skipped when verifying.
16776 .option retry_use_local_part routers boolean "see below"
16777 .cindex "hints database" "retry keys"
16778 .cindex "local part" "in retry keys"
16779 When a delivery suffers a temporary routing failure, a retry record is created
16780 in Exim's hints database. For addresses whose routing depends only on the
16781 domain, the key for the retry record should not involve the local part, but for
16782 other addresses, both the domain and the local part should be included.
16783 Usually, remote routing is of the former kind, and local routing is of the
16786 This option controls whether the local part is used to form the key for retry
16787 hints for addresses that suffer temporary errors while being handled by this
16788 router. The default value is true for any router that has &%check_local_user%&
16789 set, and false otherwise. Note that this option does not apply to hints keys
16790 for transport delays; they are controlled by a generic transport option of the
16793 The setting of &%retry_use_local_part%& applies only to the router on which it
16794 appears. If the router generates child addresses, they are routed
16795 independently; this setting does not become attached to them.
16799 .option router_home_directory routers string&!! unset
16800 .cindex "router" "home directory for"
16801 .cindex "home directory" "for router"
16803 This option sets a home directory for use while the router is running. (Compare
16804 &%transport_home_directory%&, which sets a home directory for later
16805 transporting.) In particular, if used on a &(redirect)& router, this option
16806 sets a value for &$home$& while a filter is running. The value is expanded;
16807 forced expansion failure causes the option to be ignored &-- other failures
16808 cause the router to defer.
16810 Expansion of &%router_home_directory%& happens immediately after the
16811 &%check_local_user%& test (if configured), before any further expansions take
16813 (See section &<<SECTrouprecon>>& for a list of the order in which preconditions
16815 While the router is running, &%router_home_directory%& overrides the value of
16816 &$home$& that came from &%check_local_user%&.
16818 When a router accepts an address and assigns it to a local transport (including
16819 the cases when a &(redirect)& router generates a pipe, file, or autoreply
16820 delivery), the home directory setting for the transport is taken from the first
16821 of these values that is set:
16824 The &%home_directory%& option on the transport;
16826 The &%transport_home_directory%& option on the router;
16828 The password data if &%check_local_user%& is set on the router;
16830 The &%router_home_directory%& option on the router.
16833 In other words, &%router_home_directory%& overrides the password data for the
16834 router, but not for the transport.
16838 .option self routers string freeze
16839 .cindex "MX record" "pointing to local host"
16840 .cindex "local host" "MX pointing to"
16841 This option applies to those routers that use a recipient address to find a
16842 list of remote hosts. Currently, these are the &(dnslookup)&, &(ipliteral)&,
16843 and &(manualroute)& routers.
16844 Certain configurations of the &(queryprogram)& router can also specify a list
16846 Usually such routers are configured to send the message to a remote host via an
16847 &(smtp)& transport. The &%self%& option specifies what happens when the first
16848 host on the list turns out to be the local host.
16849 The way in which Exim checks for the local host is described in section
16850 &<<SECTreclocipadd>>&.
16852 Normally this situation indicates either an error in Exim's configuration (for
16853 example, the router should be configured not to process this domain), or an
16854 error in the DNS (for example, the MX should not point to this host). For this
16855 reason, the default action is to log the incident, defer the address, and
16856 freeze the message. The following alternatives are provided for use in special
16861 Delivery of the message is tried again later, but the message is not frozen.
16863 .vitem "&%reroute%&: <&'domain'&>"
16864 The domain is changed to the given domain, and the address is passed back to
16865 be reprocessed by the routers. No rewriting of headers takes place. This
16866 behaviour is essentially a redirection.
16868 .vitem "&%reroute: rewrite:%& <&'domain'&>"
16869 The domain is changed to the given domain, and the address is passed back to be
16870 reprocessed by the routers. Any headers that contain the original domain are
16875 .vindex "&$self_hostname$&"
16876 The router passes the address to the next router, or to the router named in the
16877 &%pass_router%& option if it is set. This overrides &%no_more%&. During
16878 subsequent routing and delivery, the variable &$self_hostname$& contains the
16879 name of the local host that the router encountered. This can be used to
16880 distinguish between different cases for hosts with multiple names. The
16886 ensures that only those addresses that routed to the local host are passed on.
16887 Without &%no_more%&, addresses that were declined for other reasons would also
16888 be passed to the next router.
16891 Delivery fails and an error report is generated.
16894 .cindex "local host" "sending to"
16895 The anomaly is ignored and the address is queued for the transport. This
16896 setting should be used with extreme caution. For an &(smtp)& transport, it
16897 makes sense only in cases where the program that is listening on the SMTP port
16898 is not this version of Exim. That is, it must be some other MTA, or Exim with a
16899 different configuration file that handles the domain in another way.
16904 .option senders routers&!? "address list&!!" unset
16905 .cindex "router" "checking senders"
16906 If this option is set, the router is skipped unless the message's sender
16907 address matches something on the list.
16908 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
16911 There are issues concerning verification when the running of routers is
16912 dependent on the sender. When Exim is verifying the address in an &%errors_to%&
16913 setting, it sets the sender to the null string. When using the &%-bt%& option
16914 to check a configuration file, it is necessary also to use the &%-f%& option to
16915 set an appropriate sender. For incoming mail, the sender is unset when
16916 verifying the sender, but is available when verifying any recipients. If the
16917 SMTP VRFY command is enabled, it must be used after MAIL if the sender address
16921 .option translate_ip_address routers string&!! unset
16922 .cindex "IP address" "translating"
16923 .cindex "packet radio"
16924 .cindex "router" "IP address translation"
16925 There exist some rare networking situations (for example, packet radio) where
16926 it is helpful to be able to translate IP addresses generated by normal routing
16927 mechanisms into other IP addresses, thus performing a kind of manual IP
16928 routing. This should be done only if the normal IP routing of the TCP/IP stack
16929 is inadequate or broken. Because this is an extremely uncommon requirement, the
16930 code to support this option is not included in the Exim binary unless
16931 SUPPORT_TRANSLATE_IP_ADDRESS=yes is set in &_Local/Makefile_&.
16933 .vindex "&$host_address$&"
16934 The &%translate_ip_address%& string is expanded for every IP address generated
16935 by the router, with the generated address set in &$host_address$&. If the
16936 expansion is forced to fail, no action is taken.
16937 For any other expansion error, delivery of the message is deferred.
16938 If the result of the expansion is an IP address, that replaces the original
16939 address; otherwise the result is assumed to be a host name &-- this is looked
16940 up using &[gethostbyname()]& (or &[getipnodebyname()]& when available) to
16941 produce one or more replacement IP addresses. For example, to subvert all IP
16942 addresses in some specific networks, this could be added to a router:
16944 translate_ip_address = \
16945 ${lookup{${mask:$host_address/26}}lsearch{/some/file}\
16948 The file would contain lines like
16950 10.2.3.128/26 some.host
16951 10.8.4.34/26 10.44.8.15
16953 You should not make use of this facility unless you really understand what you
16958 .option transport routers string&!! unset
16959 This option specifies the transport to be used when a router accepts an address
16960 and sets it up for delivery. A transport is never needed if a router is used
16961 only for verification. The value of the option is expanded at routing time,
16962 after the expansion of &%errors_to%&, &%headers_add%&, and &%headers_remove%&,
16963 and result must be the name of one of the configured transports. If it is not,
16964 delivery is deferred.
16966 The &%transport%& option is not used by the &(redirect)& router, but it does
16967 have some private options that set up transports for pipe and file deliveries
16968 (see chapter &<<CHAPredirect>>&).
16972 .option transport_current_directory routers string&!! unset
16973 .cindex "current directory for local transport"
16974 This option associates a current directory with any address that is routed
16975 to a local transport. This can happen either because a transport is
16976 explicitly configured for the router, or because it generates a delivery to a
16977 file or a pipe. During the delivery process (that is, at transport time), this
16978 option string is expanded and is set as the current directory, unless
16979 overridden by a setting on the transport.
16980 If the expansion fails for any reason, including forced failure, an error is
16981 logged, and delivery is deferred.
16982 See chapter &<<CHAPenvironment>>& for details of the local delivery
16988 .option transport_home_directory routers string&!! "see below"
16989 .cindex "home directory" "for local transport"
16990 This option associates a home directory with any address that is routed to a
16991 local transport. This can happen either because a transport is explicitly
16992 configured for the router, or because it generates a delivery to a file or a
16993 pipe. During the delivery process (that is, at transport time), the option
16994 string is expanded and is set as the home directory, unless overridden by a
16995 setting of &%home_directory%& on the transport.
16996 If the expansion fails for any reason, including forced failure, an error is
16997 logged, and delivery is deferred.
16999 If the transport does not specify a home directory, and
17000 &%transport_home_directory%& is not set for the router, the home directory for
17001 the transport is taken from the password data if &%check_local_user%& is set for
17002 the router. Otherwise it is taken from &%router_home_directory%& if that option
17003 is set; if not, no home directory is set for the transport.
17005 See chapter &<<CHAPenvironment>>& for further details of the local delivery
17011 .option unseen routers boolean&!! false
17012 .cindex "router" "carrying on after success"
17013 The result of string expansion for this option must be a valid boolean value,
17014 that is, one of the strings &"yes"&, &"no"&, &"true"&, or &"false"&. Any other
17015 result causes an error, and delivery is deferred. If the expansion is forced to
17016 fail, the default value for the option (false) is used. Other failures cause
17017 delivery to be deferred.
17019 When this option is set true, routing does not cease if the router accepts the
17020 address. Instead, a copy of the incoming address is passed to the next router,
17021 overriding a false setting of &%more%&. There is little point in setting
17022 &%more%& false if &%unseen%& is always true, but it may be useful in cases when
17023 the value of &%unseen%& contains expansion items (and therefore, presumably, is
17024 sometimes true and sometimes false).
17026 .cindex "copy of message (&%unseen%& option)"
17027 Setting the &%unseen%& option has a similar effect to the &%unseen%& command
17028 qualifier in filter files. It can be used to cause copies of messages to be
17029 delivered to some other destination, while also carrying out a normal delivery.
17030 In effect, the current address is made into a &"parent"& that has two children
17031 &-- one that is delivered as specified by this router, and a clone that goes on
17032 to be routed further. For this reason, &%unseen%& may not be combined with the
17033 &%one_time%& option in a &(redirect)& router.
17035 &*Warning*&: Header lines added to the address (or specified for removal) by
17036 this router or by previous routers affect the &"unseen"& copy of the message
17037 only. The clone that continues to be processed by further routers starts with
17038 no added headers and none specified for removal. For a &%redirect%& router, if
17039 a generated address is the same as the incoming address, this can lead to
17040 duplicate addresses with different header modifications. Exim does not do
17041 duplicate deliveries (except, in certain circumstances, to pipes -- see section
17042 &<<SECTdupaddr>>&), but it is undefined which of the duplicates is discarded,
17043 so this ambiguous situation should be avoided. The &%repeat_use%& option of the
17044 &%redirect%& router may be of help.
17046 Unlike the handling of header modifications, any data that was set by the
17047 &%address_data%& option in the current or previous routers &'is'& passed on to
17048 subsequent routers.
17051 .option user routers string&!! "see below"
17052 .cindex "uid (user id)" "local delivery"
17053 .cindex "local transports" "uid and gid"
17054 .cindex "transport" "local"
17055 .cindex "router" "user for filter processing"
17056 .cindex "filter" "user for processing"
17057 When a router queues an address for a transport, and the transport does not
17058 specify a user, the user given here is used when running the delivery process.
17059 The user may be specified numerically or by name. If expansion fails, the
17060 error is logged and delivery is deferred.
17061 This user is also used by the &(redirect)& router when running a filter file.
17062 The default is unset, except when &%check_local_user%& is set. In this case,
17063 the default is taken from the password information. If the user is specified as
17064 a name, and &%group%& is not set, the group associated with the user is used.
17065 See also &%initgroups%& and &%group%& and the discussion in chapter
17066 &<<CHAPenvironment>>&.
17070 .option verify routers&!? boolean true
17071 Setting this option has the effect of setting &%verify_sender%& and
17072 &%verify_recipient%& to the same value.
17075 .option verify_only routers&!? boolean false
17076 .cindex "EXPN" "with &%verify_only%&"
17078 .cindex "router" "used only when verifying"
17079 If this option is set, the router is used only when verifying an address or
17080 testing with the &%-bv%& option, not when actually doing a delivery, testing
17081 with the &%-bt%& option, or running the SMTP EXPN command. It can be further
17082 restricted to verifying only senders or recipients by means of
17083 &%verify_sender%& and &%verify_recipient%&.
17085 &*Warning*&: When the router is being run to verify addresses for an incoming
17086 SMTP message, Exim is not running as root, but under its own uid. If the router
17087 accesses any files, you need to make sure that they are accessible to the Exim
17091 .option verify_recipient routers&!? boolean true
17092 If this option is false, the router is skipped when verifying recipient
17094 or testing recipient verification using &%-bv%&.
17095 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
17099 .option verify_sender routers&!? boolean true
17100 If this option is false, the router is skipped when verifying sender addresses
17101 or testing sender verification using &%-bvs%&.
17102 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
17104 .ecindex IIDgenoprou1
17105 .ecindex IIDgenoprou2
17112 . ////////////////////////////////////////////////////////////////////////////
17113 . ////////////////////////////////////////////////////////////////////////////
17115 .chapter "The accept router" "CHID4"
17116 .cindex "&(accept)& router"
17117 .cindex "routers" "&(accept)&"
17118 The &(accept)& router has no private options of its own. Unless it is being
17119 used purely for verification (see &%verify_only%&) a transport is required to
17120 be defined by the generic &%transport%& option. If the preconditions that are
17121 specified by generic options are met, the router accepts the address and queues
17122 it for the given transport. The most common use of this router is for setting
17123 up deliveries to local mailboxes. For example:
17127 domains = mydomain.example
17129 transport = local_delivery
17131 The &%domains%& condition in this example checks the domain of the address, and
17132 &%check_local_user%& checks that the local part is the login of a local user.
17133 When both preconditions are met, the &(accept)& router runs, and queues the
17134 address for the &(local_delivery)& transport.
17141 . ////////////////////////////////////////////////////////////////////////////
17142 . ////////////////////////////////////////////////////////////////////////////
17144 .chapter "The dnslookup router" "CHAPdnslookup"
17145 .scindex IIDdnsrou1 "&(dnslookup)& router"
17146 .scindex IIDdnsrou2 "routers" "&(dnslookup)&"
17147 The &(dnslookup)& router looks up the hosts that handle mail for the
17148 recipient's domain in the DNS. A transport must always be set for this router,
17149 unless &%verify_only%& is set.
17151 If SRV support is configured (see &%check_srv%& below), Exim first searches for
17152 SRV records. If none are found, or if SRV support is not configured,
17153 MX records are looked up. If no MX records exist, address records are sought.
17154 However, &%mx_domains%& can be set to disable the direct use of address
17157 MX records of equal priority are sorted by Exim into a random order. Exim then
17158 looks for address records for the host names obtained from MX or SRV records.
17159 When a host has more than one IP address, they are sorted into a random order,
17160 except that IPv6 addresses are always sorted before IPv4 addresses. If all the
17161 IP addresses found are discarded by a setting of the &%ignore_target_hosts%&
17162 generic option, the router declines.
17164 Unless they have the highest priority (lowest MX value), MX records that point
17165 to the local host, or to any host name that matches &%hosts_treat_as_local%&,
17166 are discarded, together with any other MX records of equal or lower priority.
17168 .cindex "MX record" "pointing to local host"
17169 .cindex "local host" "MX pointing to"
17170 .oindex "&%self%&" "in &(dnslookup)& router"
17171 If the host pointed to by the highest priority MX record, or looked up as an
17172 address record, is the local host, or matches &%hosts_treat_as_local%&, what
17173 happens is controlled by the generic &%self%& option.
17176 .section "Problems with DNS lookups" "SECTprowitdnsloo"
17177 There have been problems with DNS servers when SRV records are looked up.
17178 Some mis-behaving servers return a DNS error or timeout when a non-existent
17179 SRV record is sought. Similar problems have in the past been reported for
17180 MX records. The global &%dns_again_means_nonexist%& option can help with this
17181 problem, but it is heavy-handed because it is a global option.
17183 For this reason, there are two options, &%srv_fail_domains%& and
17184 &%mx_fail_domains%&, that control what happens when a DNS lookup in a
17185 &(dnslookup)& router results in a DNS failure or a &"try again"& response. If
17186 an attempt to look up an SRV or MX record causes one of these results, and the
17187 domain matches the relevant list, Exim behaves as if the DNS had responded &"no
17188 such record"&. In the case of an SRV lookup, this means that the router
17189 proceeds to look for MX records; in the case of an MX lookup, it proceeds to
17190 look for A or AAAA records, unless the domain matches &%mx_domains%&, in which
17191 case routing fails.
17194 .section "Declining addresses by dnslookup" "SECTdnslookupdecline"
17195 .cindex "&(dnslookup)& router" "declines"
17196 There are a few cases where a &(dnslookup)& router will decline to accept
17197 an address; if such a router is expected to handle "all remaining non-local
17198 domains", then it is important to set &%no_more%&.
17200 Reasons for a &(dnslookup)& router to decline currently include:
17202 The domain does not exist in DNS
17204 The domain exists but the MX record's host part is just "."; this is a common
17205 convention (borrowed from SRV) used to indicate that there is no such service
17206 for this domain and to not fall back to trying A/AAAA records.
17208 Ditto, but for SRV records, when &%check_srv%& is set on this router.
17210 MX record points to a non-existent host.
17212 MX record points to an IP address and the main section option
17213 &%allow_mx_to_ip%& is not set.
17215 MX records exist and point to valid hosts, but all hosts resolve only to
17216 addresses blocked by the &%ignore_target_hosts%& generic option on this router.
17218 The domain is not syntactically valid (see also &%allow_utf8_domains%& and
17219 &%dns_check_names_pattern%& for handling one variant of this)
17221 &%check_secondary_mx%& is set on this router but the local host can
17222 not be found in the MX records (see below)
17228 .section "Private options for dnslookup" "SECID118"
17229 .cindex "options" "&(dnslookup)& router"
17230 The private options for the &(dnslookup)& router are as follows:
17232 .option check_secondary_mx dnslookup boolean false
17233 .cindex "MX record" "checking for secondary"
17234 If this option is set, the router declines unless the local host is found in
17235 (and removed from) the list of hosts obtained by MX lookup. This can be used to
17236 process domains for which the local host is a secondary mail exchanger
17237 differently to other domains. The way in which Exim decides whether a host is
17238 the local host is described in section &<<SECTreclocipadd>>&.
17241 .option check_srv dnslookup string&!! unset
17242 .cindex "SRV record" "enabling use of"
17243 The &(dnslookup)& router supports the use of SRV records (see RFC 2782) in
17244 addition to MX and address records. The support is disabled by default. To
17245 enable SRV support, set the &%check_srv%& option to the name of the service
17246 required. For example,
17250 looks for SRV records that refer to the normal smtp service. The option is
17251 expanded, so the service name can vary from message to message or address
17252 to address. This might be helpful if SRV records are being used for a
17253 submission service. If the expansion is forced to fail, the &%check_srv%&
17254 option is ignored, and the router proceeds to look for MX records in the
17257 When the expansion succeeds, the router searches first for SRV records for
17258 the given service (it assumes TCP protocol). A single SRV record with a
17259 host name that consists of just a single dot indicates &"no such service for
17260 this domain"&; if this is encountered, the router declines. If other kinds of
17261 SRV record are found, they are used to construct a host list for delivery
17262 according to the rules of RFC 2782. MX records are not sought in this case.
17264 When no SRV records are found, MX records (and address records) are sought in
17265 the traditional way. In other words, SRV records take precedence over MX
17266 records, just as MX records take precedence over address records. Note that
17267 this behaviour is not sanctioned by RFC 2782, though a previous draft RFC
17268 defined it. It is apparently believed that MX records are sufficient for email
17269 and that SRV records should not be used for this purpose. However, SRV records
17270 have an additional &"weight"& feature which some people might find useful when
17271 trying to split an SMTP load between hosts of different power.
17273 See section &<<SECTprowitdnsloo>>& above for a discussion of Exim's behaviour
17274 when there is a DNS lookup error.
17278 .option mx_domains dnslookup "domain list&!!" unset
17279 .cindex "MX record" "required to exist"
17280 .cindex "SRV record" "required to exist"
17281 A domain that matches &%mx_domains%& is required to have either an MX or an SRV
17282 record in order to be recognized. (The name of this option could be improved.)
17283 For example, if all the mail hosts in &'fict.example'& are known to have MX
17284 records, except for those in &'discworld.fict.example'&, you could use this
17287 mx_domains = ! *.discworld.fict.example : *.fict.example
17289 This specifies that messages addressed to a domain that matches the list but
17290 has no MX record should be bounced immediately instead of being routed using
17291 the address record.
17294 .option mx_fail_domains dnslookup "domain list&!!" unset
17295 If the DNS lookup for MX records for one of the domains in this list causes a
17296 DNS lookup error, Exim behaves as if no MX records were found. See section
17297 &<<SECTprowitdnsloo>>& for more discussion.
17302 .option qualify_single dnslookup boolean true
17303 .cindex "DNS" "resolver options"
17304 .cindex "DNS" "qualifying single-component names"
17305 When this option is true, the resolver option RES_DEFNAMES is set for DNS
17306 lookups. Typically, but not standardly, this causes the resolver to qualify
17307 single-component names with the default domain. For example, on a machine
17308 called &'dictionary.ref.example'&, the domain &'thesaurus'& would be changed to
17309 &'thesaurus.ref.example'& inside the resolver. For details of what your
17310 resolver actually does, consult your man pages for &'resolver'& and
17315 .option rewrite_headers dnslookup boolean true
17316 .cindex "rewriting" "header lines"
17317 .cindex "header lines" "rewriting"
17318 If the domain name in the address that is being processed is not fully
17319 qualified, it may be expanded to its full form by a DNS lookup. For example, if
17320 an address is specified as &'dormouse@teaparty'&, the domain might be
17321 expanded to &'teaparty.wonderland.fict.example'&. Domain expansion can also
17322 occur as a result of setting the &%widen_domains%& option. If
17323 &%rewrite_headers%& is true, all occurrences of the abbreviated domain name in
17324 any &'Bcc:'&, &'Cc:'&, &'From:'&, &'Reply-to:'&, &'Sender:'&, and &'To:'&
17325 header lines of the message are rewritten with the full domain name.
17327 This option should be turned off only when it is known that no message is
17328 ever going to be sent outside an environment where the abbreviation makes
17331 When an MX record is looked up in the DNS and matches a wildcard record, name
17332 servers normally return a record containing the name that has been looked up,
17333 making it impossible to detect whether a wildcard was present or not. However,
17334 some name servers have recently been seen to return the wildcard entry. If the
17335 name returned by a DNS lookup begins with an asterisk, it is not used for
17339 .option same_domain_copy_routing dnslookup boolean false
17340 .cindex "address" "copying routing"
17341 Addresses with the same domain are normally routed by the &(dnslookup)& router
17342 to the same list of hosts. However, this cannot be presumed, because the router
17343 options and preconditions may refer to the local part of the address. By
17344 default, therefore, Exim routes each address in a message independently. DNS
17345 servers run caches, so repeated DNS lookups are not normally expensive, and in
17346 any case, personal messages rarely have more than a few recipients.
17348 If you are running mailing lists with large numbers of subscribers at the same
17349 domain, and you are using a &(dnslookup)& router which is independent of the
17350 local part, you can set &%same_domain_copy_routing%& to bypass repeated DNS
17351 lookups for identical domains in one message. In this case, when &(dnslookup)&
17352 routes an address to a remote transport, any other unrouted addresses in the
17353 message that have the same domain are automatically given the same routing
17354 without processing them independently,
17355 provided the following conditions are met:
17358 No router that processed the address specified &%headers_add%& or
17359 &%headers_remove%&.
17361 The router did not change the address in any way, for example, by &"widening"&
17368 .option search_parents dnslookup boolean false
17369 .cindex "DNS" "resolver options"
17370 When this option is true, the resolver option RES_DNSRCH is set for DNS
17371 lookups. This is different from the &%qualify_single%& option in that it
17372 applies to domains containing dots. Typically, but not standardly, it causes
17373 the resolver to search for the name in the current domain and in parent
17374 domains. For example, on a machine in the &'fict.example'& domain, if looking
17375 up &'teaparty.wonderland'& failed, the resolver would try
17376 &'teaparty.wonderland.fict.example'&. For details of what your resolver
17377 actually does, consult your man pages for &'resolver'& and &'resolv.conf'&.
17379 Setting this option true can cause problems in domains that have a wildcard MX
17380 record, because any domain that does not have its own MX record matches the
17385 .option srv_fail_domains dnslookup "domain list&!!" unset
17386 If the DNS lookup for SRV records for one of the domains in this list causes a
17387 DNS lookup error, Exim behaves as if no SRV records were found. See section
17388 &<<SECTprowitdnsloo>>& for more discussion.
17393 .option widen_domains dnslookup "string list" unset
17394 .cindex "domain" "partial; widening"
17395 If a DNS lookup fails and this option is set, each of its strings in turn is
17396 added onto the end of the domain, and the lookup is tried again. For example,
17399 widen_domains = fict.example:ref.example
17401 is set and a lookup of &'klingon.dictionary'& fails,
17402 &'klingon.dictionary.fict.example'& is looked up, and if this fails,
17403 &'klingon.dictionary.ref.example'& is tried. Note that the &%qualify_single%&
17404 and &%search_parents%& options can cause some widening to be undertaken inside
17405 the DNS resolver. &%widen_domains%& is not applied to sender addresses
17406 when verifying, unless &%rewrite_headers%& is false (not the default).
17409 .section "Effect of qualify_single and search_parents" "SECID119"
17410 When a domain from an envelope recipient is changed by the resolver as a result
17411 of the &%qualify_single%& or &%search_parents%& options, Exim rewrites the
17412 corresponding address in the message's header lines unless &%rewrite_headers%&
17413 is set false. Exim then re-routes the address, using the full domain.
17415 These two options affect only the DNS lookup that takes place inside the router
17416 for the domain of the address that is being routed. They do not affect lookups
17417 such as that implied by
17421 that may happen while processing a router precondition before the router is
17422 entered. No widening ever takes place for these lookups.
17423 .ecindex IIDdnsrou1
17424 .ecindex IIDdnsrou2
17434 . ////////////////////////////////////////////////////////////////////////////
17435 . ////////////////////////////////////////////////////////////////////////////
17437 .chapter "The ipliteral router" "CHID5"
17438 .cindex "&(ipliteral)& router"
17439 .cindex "domain literal" "routing"
17440 .cindex "routers" "&(ipliteral)&"
17441 This router has no private options. Unless it is being used purely for
17442 verification (see &%verify_only%&) a transport is required to be defined by the
17443 generic &%transport%& option. The router accepts the address if its domain part
17444 takes the form of an RFC 2822 domain literal. For example, the &(ipliteral)&
17445 router handles the address
17449 by setting up delivery to the host with that IP address. IPv4 domain literals
17450 consist of an IPv4 address enclosed in square brackets. IPv6 domain literals
17451 are similar, but the address is preceded by &`ipv6:`&. For example:
17453 postmaster@[ipv6:fe80::a00:20ff:fe86:a061.5678]
17455 Exim allows &`ipv4:`& before IPv4 addresses, for consistency, and on the
17456 grounds that sooner or later somebody will try it.
17458 .oindex "&%self%&" "in &(ipliteral)& router"
17459 If the IP address matches something in &%ignore_target_hosts%&, the router
17460 declines. If an IP literal turns out to refer to the local host, the generic
17461 &%self%& option determines what happens.
17463 The RFCs require support for domain literals; however, their use is
17464 controversial in today's Internet. If you want to use this router, you must
17465 also set the main configuration option &%allow_domain_literals%&. Otherwise,
17466 Exim will not recognize the domain literal syntax in addresses.
17470 . ////////////////////////////////////////////////////////////////////////////
17471 . ////////////////////////////////////////////////////////////////////////////
17473 .chapter "The iplookup router" "CHID6"
17474 .cindex "&(iplookup)& router"
17475 .cindex "routers" "&(iplookup)&"
17476 The &(iplookup)& router was written to fulfil a specific requirement in
17477 Cambridge University (which in fact no longer exists). For this reason, it is
17478 not included in the binary of Exim by default. If you want to include it, you
17481 ROUTER_IPLOOKUP=yes
17483 in your &_Local/Makefile_& configuration file.
17485 The &(iplookup)& router routes an address by sending it over a TCP or UDP
17486 connection to one or more specific hosts. The host can then return the same or
17487 a different address &-- in effect rewriting the recipient address in the
17488 message's envelope. The new address is then passed on to subsequent routers. If
17489 this process fails, the address can be passed on to other routers, or delivery
17490 can be deferred. Since &(iplookup)& is just a rewriting router, a transport
17491 must not be specified for it.
17493 .cindex "options" "&(iplookup)& router"
17494 .option hosts iplookup string unset
17495 This option must be supplied. Its value is a colon-separated list of host
17496 names. The hosts are looked up using &[gethostbyname()]&
17497 (or &[getipnodebyname()]& when available)
17498 and are tried in order until one responds to the query. If none respond, what
17499 happens is controlled by &%optional%&.
17502 .option optional iplookup boolean false
17503 If &%optional%& is true, if no response is obtained from any host, the address
17504 is passed to the next router, overriding &%no_more%&. If &%optional%& is false,
17505 delivery to the address is deferred.
17508 .option port iplookup integer 0
17509 .cindex "port" "&(iplookup)& router"
17510 This option must be supplied. It specifies the port number for the TCP or UDP
17514 .option protocol iplookup string udp
17515 This option can be set to &"udp"& or &"tcp"& to specify which of the two
17516 protocols is to be used.
17519 .option query iplookup string&!! "see below"
17520 This defines the content of the query that is sent to the remote hosts. The
17523 $local_part@$domain $local_part@$domain
17525 The repetition serves as a way of checking that a response is to the correct
17526 query in the default case (see &%response_pattern%& below).
17529 .option reroute iplookup string&!! unset
17530 If this option is not set, the rerouted address is precisely the byte string
17531 returned by the remote host, up to the first white space, if any. If set, the
17532 string is expanded to form the rerouted address. It can include parts matched
17533 in the response by &%response_pattern%& by means of numeric variables such as
17534 &$1$&, &$2$&, etc. The variable &$0$& refers to the entire input string,
17535 whether or not a pattern is in use. In all cases, the rerouted address must end
17536 up in the form &'local_part@domain'&.
17539 .option response_pattern iplookup string unset
17540 This option can be set to a regular expression that is applied to the string
17541 returned from the remote host. If the pattern does not match the response, the
17542 router declines. If &%response_pattern%& is not set, no checking of the
17543 response is done, unless the query was defaulted, in which case there is a
17544 check that the text returned after the first white space is the original
17545 address. This checks that the answer that has been received is in response to
17546 the correct question. For example, if the response is just a new domain, the
17547 following could be used:
17549 response_pattern = ^([^@]+)$
17550 reroute = $local_part@$1
17553 .option timeout iplookup time 5s
17554 This specifies the amount of time to wait for a response from the remote
17555 machine. The same timeout is used for the &[connect()]& function for a TCP
17556 call. It does not apply to UDP.
17561 . ////////////////////////////////////////////////////////////////////////////
17562 . ////////////////////////////////////////////////////////////////////////////
17564 .chapter "The manualroute router" "CHID7"
17565 .scindex IIDmanrou1 "&(manualroute)& router"
17566 .scindex IIDmanrou2 "routers" "&(manualroute)&"
17567 .cindex "domain" "manually routing"
17568 The &(manualroute)& router is so-called because it provides a way of manually
17569 routing an address according to its domain. It is mainly used when you want to
17570 route addresses to remote hosts according to your own rules, bypassing the
17571 normal DNS routing that looks up MX records. However, &(manualroute)& can also
17572 route to local transports, a facility that may be useful if you want to save
17573 messages for dial-in hosts in local files.
17575 The &(manualroute)& router compares a list of domain patterns with the domain
17576 it is trying to route. If there is no match, the router declines. Each pattern
17577 has associated with it a list of hosts and some other optional data, which may
17578 include a transport. The combination of a pattern and its data is called a
17579 &"routing rule"&. For patterns that do not have an associated transport, the
17580 generic &%transport%& option must specify a transport, unless the router is
17581 being used purely for verification (see &%verify_only%&).
17584 In the case of verification, matching the domain pattern is sufficient for the
17585 router to accept the address. When actually routing an address for delivery,
17586 an address that matches a domain pattern is queued for the associated
17587 transport. If the transport is not a local one, a host list must be associated
17588 with the pattern; IP addresses are looked up for the hosts, and these are
17589 passed to the transport along with the mail address. For local transports, a
17590 host list is optional. If it is present, it is passed in &$host$& as a single
17593 The list of routing rules can be provided as an inline string in
17594 &%route_list%&, or the data can be obtained by looking up the domain in a file
17595 or database by setting &%route_data%&. Only one of these settings may appear in
17596 any one instance of &(manualroute)&. The format of routing rules is described
17597 below, following the list of private options.
17600 .section "Private options for manualroute" "SECTprioptman"
17602 .cindex "options" "&(manualroute)& router"
17603 The private options for the &(manualroute)& router are as follows:
17605 .option host_all_ignored manualroute string defer
17606 See &%host_find_failed%&.
17608 .option host_find_failed manualroute string freeze
17609 This option controls what happens when &(manualroute)& tries to find an IP
17610 address for a host, and the host does not exist. The option can be set to one
17611 of the following values:
17620 The default (&"freeze"&) assumes that this state is a serious configuration
17621 error. The difference between &"pass"& and &"decline"& is that the former
17622 forces the address to be passed to the next router (or the router defined by
17625 overriding &%no_more%&, whereas the latter passes the address to the next
17626 router only if &%more%& is true.
17628 The value &"ignore"& causes Exim to completely ignore a host whose IP address
17629 cannot be found. If all the hosts in the list are ignored, the behaviour is
17630 controlled by the &%host_all_ignored%& option. This takes the same values
17631 as &%host_find_failed%&, except that it cannot be set to &"ignore"&.
17633 The &%host_find_failed%& option applies only to a definite &"does not exist"&
17634 state; if a host lookup gets a temporary error, delivery is deferred unless the
17635 generic &%pass_on_timeout%& option is set.
17638 .option hosts_randomize manualroute boolean false
17639 .cindex "randomized host list"
17640 .cindex "host" "list of; randomized"
17641 If this option is set, the order of the items in a host list in a routing rule
17642 is randomized each time the list is used, unless an option in the routing rule
17643 overrides (see below). Randomizing the order of a host list can be used to do
17644 crude load sharing. However, if more than one mail address is routed by the
17645 same router to the same host list, the host lists are considered to be the same
17646 (even though they may be randomized into different orders) for the purpose of
17647 deciding whether to batch the deliveries into a single SMTP transaction.
17649 When &%hosts_randomize%& is true, a host list may be split
17650 into groups whose order is separately randomized. This makes it possible to
17651 set up MX-like behaviour. The boundaries between groups are indicated by an
17652 item that is just &`+`& in the host list. For example:
17654 route_list = * host1:host2:host3:+:host4:host5
17656 The order of the first three hosts and the order of the last two hosts is
17657 randomized for each use, but the first three always end up before the last two.
17658 If &%hosts_randomize%& is not set, a &`+`& item in the list is ignored. If a
17659 randomized host list is passed to an &(smtp)& transport that also has
17660 &%hosts_randomize set%&, the list is not re-randomized.
17663 .option route_data manualroute string&!! unset
17664 If this option is set, it must expand to yield the data part of a routing rule.
17665 Typically, the expansion string includes a lookup based on the domain. For
17668 route_data = ${lookup{$domain}dbm{/etc/routes}}
17670 If the expansion is forced to fail, or the result is an empty string, the
17671 router declines. Other kinds of expansion failure cause delivery to be
17675 .option route_list manualroute "string list" unset
17676 This string is a list of routing rules, in the form defined below. Note that,
17677 unlike most string lists, the items are separated by semicolons. This is so
17678 that they may contain colon-separated host lists.
17681 .option same_domain_copy_routing manualroute boolean false
17682 .cindex "address" "copying routing"
17683 Addresses with the same domain are normally routed by the &(manualroute)&
17684 router to the same list of hosts. However, this cannot be presumed, because the
17685 router options and preconditions may refer to the local part of the address. By
17686 default, therefore, Exim routes each address in a message independently. DNS
17687 servers run caches, so repeated DNS lookups are not normally expensive, and in
17688 any case, personal messages rarely have more than a few recipients.
17690 If you are running mailing lists with large numbers of subscribers at the same
17691 domain, and you are using a &(manualroute)& router which is independent of the
17692 local part, you can set &%same_domain_copy_routing%& to bypass repeated DNS
17693 lookups for identical domains in one message. In this case, when
17694 &(manualroute)& routes an address to a remote transport, any other unrouted
17695 addresses in the message that have the same domain are automatically given the
17696 same routing without processing them independently. However, this is only done
17697 if &%headers_add%& and &%headers_remove%& are unset.
17702 .section "Routing rules in route_list" "SECID120"
17703 The value of &%route_list%& is a string consisting of a sequence of routing
17704 rules, separated by semicolons. If a semicolon is needed in a rule, it can be
17705 entered as two semicolons. Alternatively, the list separator can be changed as
17706 described (for colon-separated lists) in section &<<SECTlistconstruct>>&.
17707 Empty rules are ignored. The format of each rule is
17709 <&'domain pattern'&> <&'list of hosts'&> <&'options'&>
17711 The following example contains two rules, each with a simple domain pattern and
17715 dict.ref.example mail-1.ref.example:mail-2.ref.example ; \
17716 thes.ref.example mail-3.ref.example:mail-4.ref.example
17718 The three parts of a rule are separated by white space. The pattern and the
17719 list of hosts can be enclosed in quotes if necessary, and if they are, the
17720 usual quoting rules apply. Each rule in a &%route_list%& must start with a
17721 single domain pattern, which is the only mandatory item in the rule. The
17722 pattern is in the same format as one item in a domain list (see section
17723 &<<SECTdomainlist>>&),
17724 except that it may not be the name of an interpolated file.
17725 That is, it may be wildcarded, or a regular expression, or a file or database
17726 lookup (with semicolons doubled, because of the use of semicolon as a separator
17727 in a &%route_list%&).
17729 The rules in &%route_list%& are searched in order until one of the patterns
17730 matches the domain that is being routed. The list of hosts and then options are
17731 then used as described below. If there is no match, the router declines. When
17732 &%route_list%& is set, &%route_data%& must not be set.
17736 .section "Routing rules in route_data" "SECID121"
17737 The use of &%route_list%& is convenient when there are only a small number of
17738 routing rules. For larger numbers, it is easier to use a file or database to
17739 hold the routing information, and use the &%route_data%& option instead.
17740 The value of &%route_data%& is a list of hosts, followed by (optional) options.
17741 Most commonly, &%route_data%& is set as a string that contains an
17742 expansion lookup. For example, suppose we place two routing rules in a file
17745 dict.ref.example: mail-1.ref.example:mail-2.ref.example
17746 thes.ref.example: mail-3.ref.example:mail-4.ref.example
17748 This data can be accessed by setting
17750 route_data = ${lookup{$domain}lsearch{/the/file/name}}
17752 Failure of the lookup results in an empty string, causing the router to
17753 decline. However, you do not have to use a lookup in &%route_data%&. The only
17754 requirement is that the result of expanding the string is a list of hosts,
17755 possibly followed by options, separated by white space. The list of hosts must
17756 be enclosed in quotes if it contains white space.
17761 .section "Format of the list of hosts" "SECID122"
17762 A list of hosts, whether obtained via &%route_data%& or &%route_list%&, is
17763 always separately expanded before use. If the expansion fails, the router
17764 declines. The result of the expansion must be a colon-separated list of names
17765 and/or IP addresses, optionally also including ports. The format of each item
17766 in the list is described in the next section. The list separator can be changed
17767 as described in section &<<SECTlistconstruct>>&.
17769 If the list of hosts was obtained from a &%route_list%& item, the following
17770 variables are set during its expansion:
17773 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(manualroute)& router"
17774 If the domain was matched against a regular expression, the numeric variables
17775 &$1$&, &$2$&, etc. may be set. For example:
17777 route_list = ^domain(\d+) host-$1.text.example
17780 &$0$& is always set to the entire domain.
17782 &$1$& is also set when partial matching is done in a file lookup.
17785 .vindex "&$value$&"
17786 If the pattern that matched the domain was a lookup item, the data that was
17787 looked up is available in the expansion variable &$value$&. For example:
17789 route_list = lsearch;;/some/file.routes $value
17793 Note the doubling of the semicolon in the pattern that is necessary because
17794 semicolon is the default route list separator.
17798 .section "Format of one host item" "SECTformatonehostitem"
17799 Each item in the list of hosts is either a host name or an IP address,
17800 optionally with an attached port number. When no port is given, an IP address
17801 is not enclosed in brackets. When a port is specified, it overrides the port
17802 specification on the transport. The port is separated from the name or address
17803 by a colon. This leads to some complications:
17806 Because colon is the default separator for the list of hosts, either
17807 the colon that specifies a port must be doubled, or the list separator must
17808 be changed. The following two examples have the same effect:
17810 route_list = * "host1.tld::1225 : host2.tld::1226"
17811 route_list = * "<+ host1.tld:1225 + host2.tld:1226"
17814 When IPv6 addresses are involved, it gets worse, because they contain
17815 colons of their own. To make this case easier, it is permitted to
17816 enclose an IP address (either v4 or v6) in square brackets if a port
17817 number follows. For example:
17819 route_list = * "</ [10.1.1.1]:1225 / [::1]:1226"
17823 .section "How the list of hosts is used" "SECThostshowused"
17824 When an address is routed to an &(smtp)& transport by &(manualroute)&, each of
17825 the hosts is tried, in the order specified, when carrying out the SMTP
17826 delivery. However, the order can be changed by setting the &%hosts_randomize%&
17827 option, either on the router (see section &<<SECTprioptman>>& above), or on the
17830 Hosts may be listed by name or by IP address. An unadorned name in the list of
17831 hosts is interpreted as a host name. A name that is followed by &`/MX`& is
17832 interpreted as an indirection to a sublist of hosts obtained by looking up MX
17833 records in the DNS. For example:
17835 route_list = * x.y.z:p.q.r/MX:e.f.g
17837 If this feature is used with a port specifier, the port must come last. For
17840 route_list = * dom1.tld/mx::1225
17842 If the &%hosts_randomize%& option is set, the order of the items in the list is
17843 randomized before any lookups are done. Exim then scans the list; for any name
17844 that is not followed by &`/MX`& it looks up an IP address. If this turns out to
17845 be an interface on the local host and the item is not the first in the list,
17846 Exim discards it and any subsequent items. If it is the first item, what
17847 happens is controlled by the
17848 .oindex "&%self%&" "in &(manualroute)& router"
17849 &%self%& option of the router.
17851 A name on the list that is followed by &`/MX`& is replaced with the list of
17852 hosts obtained by looking up MX records for the name. This is always a DNS
17853 lookup; the &%bydns%& and &%byname%& options (see section &<<SECThowoptused>>&
17854 below) are not relevant here. The order of these hosts is determined by the
17855 preference values in the MX records, according to the usual rules. Because
17856 randomizing happens before the MX lookup, it does not affect the order that is
17857 defined by MX preferences.
17859 If the local host is present in the sublist obtained from MX records, but is
17860 not the most preferred host in that list, it and any equally or less
17861 preferred hosts are removed before the sublist is inserted into the main list.
17863 If the local host is the most preferred host in the MX list, what happens
17864 depends on where in the original list of hosts the &`/MX`& item appears. If it
17865 is not the first item (that is, there are previous hosts in the main list),
17866 Exim discards this name and any subsequent items in the main list.
17868 If the MX item is first in the list of hosts, and the local host is the
17869 most preferred host, what happens is controlled by the &%self%& option of the
17872 DNS failures when lookup up the MX records are treated in the same way as DNS
17873 failures when looking up IP addresses: &%pass_on_timeout%& and
17874 &%host_find_failed%& are used when relevant.
17876 The generic &%ignore_target_hosts%& option applies to all hosts in the list,
17877 whether obtained from an MX lookup or not.
17881 .section "How the options are used" "SECThowoptused"
17882 The options are a sequence of words; in practice no more than three are ever
17883 present. One of the words can be the name of a transport; this overrides the
17884 &%transport%& option on the router for this particular routing rule only. The
17885 other words (if present) control randomization of the list of hosts on a
17886 per-rule basis, and how the IP addresses of the hosts are to be found when
17887 routing to a remote transport. These options are as follows:
17890 &%randomize%&: randomize the order of the hosts in this list, overriding the
17891 setting of &%hosts_randomize%& for this routing rule only.
17893 &%no_randomize%&: do not randomize the order of the hosts in this list,
17894 overriding the setting of &%hosts_randomize%& for this routing rule only.
17896 &%byname%&: use &[getipnodebyname()]& (&[gethostbyname()]& on older systems) to
17897 find IP addresses. This function may ultimately cause a DNS lookup, but it may
17898 also look in &_/etc/hosts_& or other sources of information.
17900 &%bydns%&: look up address records for the hosts directly in the DNS; fail if
17901 no address records are found. If there is a temporary DNS error (such as a
17902 timeout), delivery is deferred.
17907 route_list = domain1 host1:host2:host3 randomize bydns;\
17908 domain2 host4:host5
17910 If neither &%byname%& nor &%bydns%& is given, Exim behaves as follows: First, a
17911 DNS lookup is done. If this yields anything other than HOST_NOT_FOUND, that
17912 result is used. Otherwise, Exim goes on to try a call to &[getipnodebyname()]&
17913 or &[gethostbyname()]&, and the result of the lookup is the result of that
17916 &*Warning*&: It has been discovered that on some systems, if a DNS lookup
17917 called via &[getipnodebyname()]& times out, HOST_NOT_FOUND is returned
17918 instead of TRY_AGAIN. That is why the default action is to try a DNS
17919 lookup first. Only if that gives a definite &"no such host"& is the local
17924 If no IP address for a host can be found, what happens is controlled by the
17925 &%host_find_failed%& option.
17928 When an address is routed to a local transport, IP addresses are not looked up.
17929 The host list is passed to the transport in the &$host$& variable.
17933 .section "Manualroute examples" "SECID123"
17934 In some of the examples that follow, the presence of the &%remote_smtp%&
17935 transport, as defined in the default configuration file, is assumed:
17938 .cindex "smart host" "example router"
17939 The &(manualroute)& router can be used to forward all external mail to a
17940 &'smart host'&. If you have set up, in the main part of the configuration, a
17941 named domain list that contains your local domains, for example:
17943 domainlist local_domains = my.domain.example
17945 You can arrange for all other domains to be routed to a smart host by making
17946 your first router something like this:
17949 driver = manualroute
17950 domains = !+local_domains
17951 transport = remote_smtp
17952 route_list = * smarthost.ref.example
17954 This causes all non-local addresses to be sent to the single host
17955 &'smarthost.ref.example'&. If a colon-separated list of smart hosts is given,
17956 they are tried in order
17957 (but you can use &%hosts_randomize%& to vary the order each time).
17958 Another way of configuring the same thing is this:
17961 driver = manualroute
17962 transport = remote_smtp
17963 route_list = !+local_domains smarthost.ref.example
17965 There is no difference in behaviour between these two routers as they stand.
17966 However, they behave differently if &%no_more%& is added to them. In the first
17967 example, the router is skipped if the domain does not match the &%domains%&
17968 precondition; the following router is always tried. If the router runs, it
17969 always matches the domain and so can never decline. Therefore, &%no_more%&
17970 would have no effect. In the second case, the router is never skipped; it
17971 always runs. However, if it doesn't match the domain, it declines. In this case
17972 &%no_more%& would prevent subsequent routers from running.
17975 .cindex "mail hub example"
17976 A &'mail hub'& is a host which receives mail for a number of domains via MX
17977 records in the DNS and delivers it via its own private routing mechanism. Often
17978 the final destinations are behind a firewall, with the mail hub being the one
17979 machine that can connect to machines both inside and outside the firewall. The
17980 &(manualroute)& router is usually used on a mail hub to route incoming messages
17981 to the correct hosts. For a small number of domains, the routing can be inline,
17982 using the &%route_list%& option, but for a larger number a file or database
17983 lookup is easier to manage.
17985 If the domain names are in fact the names of the machines to which the mail is
17986 to be sent by the mail hub, the configuration can be quite simple. For
17990 driver = manualroute
17991 transport = remote_smtp
17992 route_list = *.rhodes.tvs.example $domain
17994 This configuration routes domains that match &`*.rhodes.tvs.example`& to hosts
17995 whose names are the same as the mail domains. A similar approach can be taken
17996 if the host name can be obtained from the domain name by a string manipulation
17997 that the expansion facilities can handle. Otherwise, a lookup based on the
17998 domain can be used to find the host:
18001 driver = manualroute
18002 transport = remote_smtp
18003 route_data = ${lookup {$domain} cdb {/internal/host/routes}}
18005 The result of the lookup must be the name or IP address of the host (or
18006 hosts) to which the address is to be routed. If the lookup fails, the route
18007 data is empty, causing the router to decline. The address then passes to the
18011 .cindex "batched SMTP output example"
18012 .cindex "SMTP" "batched outgoing; example"
18013 You can use &(manualroute)& to deliver messages to pipes or files in batched
18014 SMTP format for onward transportation by some other means. This is one way of
18015 storing mail for a dial-up host when it is not connected. The route list entry
18016 can be as simple as a single domain name in a configuration like this:
18019 driver = manualroute
18020 transport = batchsmtp_appendfile
18021 route_list = saved.domain.example
18023 though often a pattern is used to pick up more than one domain. If there are
18024 several domains or groups of domains with different transport requirements,
18025 different transports can be listed in the routing information:
18028 driver = manualroute
18030 *.saved.domain1.example $domain batch_appendfile; \
18031 *.saved.domain2.example \
18032 ${lookup{$domain}dbm{/domain2/hosts}{$value}fail} \
18035 .vindex "&$domain$&"
18037 The first of these just passes the domain in the &$host$& variable, which
18038 doesn't achieve much (since it is also in &$domain$&), but the second does a
18039 file lookup to find a value to pass, causing the router to decline to handle
18040 the address if the lookup fails.
18043 .cindex "UUCP" "example of router for"
18044 Routing mail directly to UUCP software is a specific case of the use of
18045 &(manualroute)& in a gateway to another mail environment. This is an example of
18046 one way it can be done:
18052 command = /usr/local/bin/uux -r - \
18053 ${substr_-5:$host}!rmail ${local_part}
18054 return_fail_output = true
18059 driver = manualroute
18061 ${lookup{$domain}lsearch{/usr/local/exim/uucphosts}}
18063 The file &_/usr/local/exim/uucphosts_& contains entries like
18065 darksite.ethereal.example: darksite.UUCP
18067 It can be set up more simply without adding and removing &".UUCP"& but this way
18068 makes clear the distinction between the domain name
18069 &'darksite.ethereal.example'& and the UUCP host name &'darksite'&.
18071 .ecindex IIDmanrou1
18072 .ecindex IIDmanrou2
18081 . ////////////////////////////////////////////////////////////////////////////
18082 . ////////////////////////////////////////////////////////////////////////////
18084 .chapter "The queryprogram router" "CHAPdriverlast"
18085 .scindex IIDquerou1 "&(queryprogram)& router"
18086 .scindex IIDquerou2 "routers" "&(queryprogram)&"
18087 .cindex "routing" "by external program"
18088 The &(queryprogram)& router routes an address by running an external command
18089 and acting on its output. This is an expensive way to route, and is intended
18090 mainly for use in lightly-loaded systems, or for performing experiments.
18091 However, if it is possible to use the precondition options (&%domains%&,
18092 &%local_parts%&, etc) to skip this router for most addresses, it could sensibly
18093 be used in special cases, even on a busy host. There are the following private
18095 .cindex "options" "&(queryprogram)& router"
18097 .option command queryprogram string&!! unset
18098 This option must be set. It specifies the command that is to be run. The
18099 command is split up into a command name and arguments, and then each is
18100 expanded separately (exactly as for a &(pipe)& transport, described in chapter
18101 &<<CHAPpipetransport>>&).
18104 .option command_group queryprogram string unset
18105 .cindex "gid (group id)" "in &(queryprogram)& router"
18106 This option specifies a gid to be set when running the command while routing an
18107 address for deliver. It must be set if &%command_user%& specifies a numerical
18108 uid. If it begins with a digit, it is interpreted as the numerical value of the
18109 gid. Otherwise it is looked up using &[getgrnam()]&.
18112 .option command_user queryprogram string unset
18113 .cindex "uid (user id)" "for &(queryprogram)&"
18114 This option must be set. It specifies the uid which is set when running the
18115 command while routing an address for delivery. If the value begins with a digit,
18116 it is interpreted as the numerical value of the uid. Otherwise, it is looked up
18117 using &[getpwnam()]& to obtain a value for the uid and, if &%command_group%& is
18118 not set, a value for the gid also.
18120 &*Warning:*& Changing uid and gid is possible only when Exim is running as
18121 root, which it does during a normal delivery in a conventional configuration.
18122 However, when an address is being verified during message reception, Exim is
18123 usually running as the Exim user, not as root. If the &(queryprogram)& router
18124 is called from a non-root process, Exim cannot change uid or gid before running
18125 the command. In this circumstance the command runs under the current uid and
18129 .option current_directory queryprogram string /
18130 This option specifies an absolute path which is made the current directory
18131 before running the command.
18134 .option timeout queryprogram time 1h
18135 If the command does not complete within the timeout period, its process group
18136 is killed and the message is frozen. A value of zero time specifies no
18140 The standard output of the command is connected to a pipe, which is read when
18141 the command terminates. It should consist of a single line of output,
18142 containing up to five fields, separated by white space. The maximum length of
18143 the line is 1023 characters. Longer lines are silently truncated. The first
18144 field is one of the following words (case-insensitive):
18147 &'Accept'&: routing succeeded; the remaining fields specify what to do (see
18150 &'Decline'&: the router declines; pass the address to the next router, unless
18151 &%no_more%& is set.
18153 &'Fail'&: routing failed; do not pass the address to any more routers. Any
18154 subsequent text on the line is an error message. If the router is run as part
18155 of address verification during an incoming SMTP message, the message is
18156 included in the SMTP response.
18158 &'Defer'&: routing could not be completed at this time; try again later. Any
18159 subsequent text on the line is an error message which is logged. It is not
18160 included in any SMTP response.
18162 &'Freeze'&: the same as &'defer'&, except that the message is frozen.
18164 &'Pass'&: pass the address to the next router (or the router specified by
18165 &%pass_router%&), overriding &%no_more%&.
18167 &'Redirect'&: the message is redirected. The remainder of the line is a list of
18168 new addresses, which are routed independently, starting with the first router,
18169 or the router specified by &%redirect_router%&, if set.
18172 When the first word is &'accept'&, the remainder of the line consists of a
18173 number of keyed data values, as follows (split into two lines here, to fit on
18176 ACCEPT TRANSPORT=<transport> HOSTS=<list of hosts>
18177 LOOKUP=byname|bydns DATA=<text>
18179 The data items can be given in any order, and all are optional. If no transport
18180 is included, the transport specified by the generic &%transport%& option is
18181 used. The list of hosts and the lookup type are needed only if the transport is
18182 an &(smtp)& transport that does not itself supply a list of hosts.
18184 The format of the list of hosts is the same as for the &(manualroute)& router.
18185 As well as host names and IP addresses with optional port numbers, as described
18186 in section &<<SECTformatonehostitem>>&, it may contain names followed by
18187 &`/MX`& to specify sublists of hosts that are obtained by looking up MX records
18188 (see section &<<SECThostshowused>>&).
18190 If the lookup type is not specified, Exim behaves as follows when trying to
18191 find an IP address for each host: First, a DNS lookup is done. If this yields
18192 anything other than HOST_NOT_FOUND, that result is used. Otherwise, Exim
18193 goes on to try a call to &[getipnodebyname()]& or &[gethostbyname()]&, and the
18194 result of the lookup is the result of that call.
18196 .vindex "&$address_data$&"
18197 If the DATA field is set, its value is placed in the &$address_data$&
18198 variable. For example, this return line
18200 accept hosts=x1.y.example:x2.y.example data="rule1"
18202 routes the address to the default transport, passing a list of two hosts. When
18203 the transport runs, the string &"rule1"& is in &$address_data$&.
18204 .ecindex IIDquerou1
18205 .ecindex IIDquerou2
18210 . ////////////////////////////////////////////////////////////////////////////
18211 . ////////////////////////////////////////////////////////////////////////////
18213 .chapter "The redirect router" "CHAPredirect"
18214 .scindex IIDredrou1 "&(redirect)& router"
18215 .scindex IIDredrou2 "routers" "&(redirect)&"
18216 .cindex "alias file" "in a &(redirect)& router"
18217 .cindex "address redirection" "&(redirect)& router"
18218 The &(redirect)& router handles several kinds of address redirection. Its most
18219 common uses are for resolving local part aliases from a central alias file
18220 (usually called &_/etc/aliases_&) and for handling users' personal &_.forward_&
18221 files, but it has many other potential uses. The incoming address can be
18222 redirected in several different ways:
18225 It can be replaced by one or more new addresses which are themselves routed
18228 It can be routed to be delivered to a given file or directory.
18230 It can be routed to be delivered to a specified pipe command.
18232 It can cause an automatic reply to be generated.
18234 It can be forced to fail, optionally with a custom error message.
18236 It can be temporarily deferred, optionally with a custom message.
18238 It can be discarded.
18241 The generic &%transport%& option must not be set for &(redirect)& routers.
18242 However, there are some private options which define transports for delivery to
18243 files and pipes, and for generating autoreplies. See the &%file_transport%&,
18244 &%pipe_transport%& and &%reply_transport%& descriptions below.
18248 .section "Redirection data" "SECID124"
18249 The router operates by interpreting a text string which it obtains either by
18250 expanding the contents of the &%data%& option, or by reading the entire
18251 contents of a file whose name is given in the &%file%& option. These two
18252 options are mutually exclusive. The first is commonly used for handling system
18253 aliases, in a configuration like this:
18257 data = ${lookup{$local_part}lsearch{/etc/aliases}}
18259 If the lookup fails, the expanded string in this example is empty. When the
18260 expansion of &%data%& results in an empty string, the router declines. A forced
18261 expansion failure also causes the router to decline; other expansion failures
18262 cause delivery to be deferred.
18264 A configuration using &%file%& is commonly used for handling users'
18265 &_.forward_& files, like this:
18270 file = $home/.forward
18273 If the file does not exist, or causes no action to be taken (for example, it is
18274 empty or consists only of comments), the router declines. &*Warning*&: This
18275 is not the case when the file contains syntactically valid items that happen to
18276 yield empty addresses, for example, items containing only RFC 2822 address
18281 .section "Forward files and address verification" "SECID125"
18282 .cindex "address redirection" "while verifying"
18283 It is usual to set &%no_verify%& on &(redirect)& routers which handle users'
18284 &_.forward_& files, as in the example above. There are two reasons for this:
18287 When Exim is receiving an incoming SMTP message from a remote host, it is
18288 running under the Exim uid, not as root. Exim is unable to change uid to read
18289 the file as the user, and it may not be able to read it as the Exim user. So in
18290 practice the router may not be able to operate.
18292 However, even when the router can operate, the existence of a &_.forward_& file
18293 is unimportant when verifying an address. What should be checked is whether the
18294 local part is a valid user name or not. Cutting out the redirection processing
18295 saves some resources.
18303 .section "Interpreting redirection data" "SECID126"
18304 .cindex "Sieve filter" "specifying in redirection data"
18305 .cindex "filter" "specifying in redirection data"
18306 The contents of the data string, whether obtained from &%data%& or &%file%&,
18307 can be interpreted in two different ways:
18310 If the &%allow_filter%& option is set true, and the data begins with the text
18311 &"#Exim filter"& or &"#Sieve filter"&, it is interpreted as a list of
18312 &'filtering'& instructions in the form of an Exim or Sieve filter file,
18313 respectively. Details of the syntax and semantics of filter files are described
18314 in a separate document entitled &'Exim's interfaces to mail filtering'&; this
18315 document is intended for use by end users.
18317 Otherwise, the data must be a comma-separated list of redirection items, as
18318 described in the next section.
18321 When a message is redirected to a file (a &"mail folder"&), the file name given
18322 in a non-filter redirection list must always be an absolute path. A filter may
18323 generate a relative path &-- how this is handled depends on the transport's
18324 configuration. See section &<<SECTfildiropt>>& for a discussion of this issue
18325 for the &(appendfile)& transport.
18329 .section "Items in a non-filter redirection list" "SECTitenonfilred"
18330 .cindex "address redirection" "non-filter list items"
18331 When the redirection data is not an Exim or Sieve filter, for example, if it
18332 comes from a conventional alias or forward file, it consists of a list of
18333 addresses, file names, pipe commands, or certain special items (see section
18334 &<<SECTspecitredli>>& below). The special items can be individually enabled or
18335 disabled by means of options whose names begin with &%allow_%& or &%forbid_%&,
18336 depending on their default values. The items in the list are separated by
18337 commas or newlines.
18338 If a comma is required in an item, the entire item must be enclosed in double
18341 Lines starting with a # character are comments, and are ignored, and # may
18342 also appear following a comma, in which case everything between the # and the
18343 next newline character is ignored.
18345 If an item is entirely enclosed in double quotes, these are removed. Otherwise
18346 double quotes are retained because some forms of mail address require their use
18347 (but never to enclose the entire address). In the following description,
18348 &"item"& refers to what remains after any surrounding double quotes have been
18351 .vindex "&$local_part$&"
18352 &*Warning*&: If you use an Exim expansion to construct a redirection address,
18353 and the expansion contains a reference to &$local_part$&, you should make use
18354 of the &%quote_local_part%& expansion operator, in case the local part contains
18355 special characters. For example, to redirect all mail for the domain
18356 &'obsolete.example'&, retaining the existing local part, you could use this
18359 data = ${quote_local_part:$local_part}@newdomain.example
18363 .section "Redirecting to a local mailbox" "SECTredlocmai"
18364 .cindex "routing" "loops in"
18365 .cindex "loop" "while routing, avoidance of"
18366 .cindex "address redirection" "to local mailbox"
18367 A redirection item may safely be the same as the address currently under
18368 consideration. This does not cause a routing loop, because a router is
18369 automatically skipped if any ancestor of the address that is being processed
18370 is the same as the current address and was processed by the current router.
18371 Such an address is therefore passed to the following routers, so it is handled
18372 as if there were no redirection. When making this loop-avoidance test, the
18373 complete local part, including any prefix or suffix, is used.
18375 .cindex "address redirection" "local part without domain"
18376 Specifying the same local part without a domain is a common usage in personal
18377 filter files when the user wants to have messages delivered to the local
18378 mailbox and also forwarded elsewhere. For example, the user whose login is
18379 &'cleo'& might have a &_.forward_& file containing this:
18381 cleo, cleopatra@egypt.example
18383 .cindex "backslash in alias file"
18384 .cindex "alias file" "backslash in"
18385 For compatibility with other MTAs, such unqualified local parts may be
18386 preceded by &"\"&, but this is not a requirement for loop prevention. However,
18387 it does make a difference if more than one domain is being handled
18390 If an item begins with &"\"& and the rest of the item parses as a valid RFC
18391 2822 address that does not include a domain, the item is qualified using the
18392 domain of the incoming address. In the absence of a leading &"\"&, unqualified
18393 addresses are qualified using the value in &%qualify_recipient%&, but you can
18394 force the incoming domain to be used by setting &%qualify_preserve_domain%&.
18396 Care must be taken if there are alias names for local users.
18397 Consider an MTA handling a single local domain where the system alias file
18402 Now suppose that Sam (whose login id is &'spqr'&) wants to save copies of
18403 messages in the local mailbox, and also forward copies elsewhere. He creates
18406 Sam.Reman, spqr@reme.elsewhere.example
18408 With these settings, an incoming message addressed to &'Sam.Reman'& fails. The
18409 &(redirect)& router for system aliases does not process &'Sam.Reman'& the
18410 second time round, because it has previously routed it,
18411 and the following routers presumably cannot handle the alias. The forward file
18412 should really contain
18414 spqr, spqr@reme.elsewhere.example
18416 but because this is such a common error, the &%check_ancestor%& option (see
18417 below) exists to provide a way to get round it. This is normally set on a
18418 &(redirect)& router that is handling users' &_.forward_& files.
18422 .section "Special items in redirection lists" "SECTspecitredli"
18423 In addition to addresses, the following types of item may appear in redirection
18424 lists (that is, in non-filter redirection data):
18427 .cindex "pipe" "in redirection list"
18428 .cindex "address redirection" "to pipe"
18429 An item is treated as a pipe command if it begins with &"|"& and does not parse
18430 as a valid RFC 2822 address that includes a domain. A transport for running the
18431 command must be specified by the &%pipe_transport%& option.
18432 Normally, either the router or the transport specifies a user and a group under
18433 which to run the delivery. The default is to use the Exim user and group.
18435 Single or double quotes can be used for enclosing the individual arguments of
18436 the pipe command; no interpretation of escapes is done for single quotes. If
18437 the command contains a comma character, it is necessary to put the whole item
18438 in double quotes, for example:
18440 "|/some/command ready,steady,go"
18442 since items in redirection lists are terminated by commas. Do not, however,
18443 quote just the command. An item such as
18445 |"/some/command ready,steady,go"
18447 is interpreted as a pipe with a rather strange command name, and no arguments.
18450 Note that the above example assumes that the text comes from a lookup source
18451 of some sort, so that the quotes are part of the data. If composing a
18452 redirect router with a &%data%& option directly specifying this command, the
18453 quotes will be used by the configuration parser to define the extent of one
18454 string, but will not be passed down into the redirect router itself. There
18455 are two main approaches to get around this: escape quotes to be part of the
18456 data itself, or avoid using this mechanism and instead create a custom
18457 transport with the &%command%& option set and reference that transport from
18458 an &%accept%& router.
18462 .cindex "file" "in redirection list"
18463 .cindex "address redirection" "to file"
18464 An item is interpreted as a path name if it begins with &"/"& and does not
18465 parse as a valid RFC 2822 address that includes a domain. For example,
18467 /home/world/minbari
18469 is treated as a file name, but
18471 /s=molari/o=babylon/@x400gate.way
18473 is treated as an address. For a file name, a transport must be specified using
18474 the &%file_transport%& option. However, if the generated path name ends with a
18475 forward slash character, it is interpreted as a directory name rather than a
18476 file name, and &%directory_transport%& is used instead.
18478 Normally, either the router or the transport specifies a user and a group under
18479 which to run the delivery. The default is to use the Exim user and group.
18481 .cindex "&_/dev/null_&"
18482 However, if a redirection item is the path &_/dev/null_&, delivery to it is
18483 bypassed at a high level, and the log entry shows &"**bypassed**"&
18484 instead of a transport name. In this case the user and group are not used.
18487 .cindex "included address list"
18488 .cindex "address redirection" "included external list"
18489 If an item is of the form
18491 :include:<path name>
18493 a list of further items is taken from the given file and included at that
18494 point. &*Note*&: Such a file can not be a filter file; it is just an
18495 out-of-line addition to the list. The items in the included list are separated
18496 by commas or newlines and are not subject to expansion. If this is the first
18497 item in an alias list in an &(lsearch)& file, a colon must be used to terminate
18498 the alias name. This example is incorrect:
18500 list1 :include:/opt/lists/list1
18502 It must be given as
18504 list1: :include:/opt/lists/list1
18507 .cindex "address redirection" "to black hole"
18508 Sometimes you want to throw away mail to a particular local part. Making the
18509 &%data%& option expand to an empty string does not work, because that causes
18510 the router to decline. Instead, the alias item
18511 .cindex "black hole"
18512 .cindex "abandoning mail"
18513 &':blackhole:'& can be used. It does what its name implies. No delivery is
18514 done, and no error message is generated. This has the same effect as specifing
18515 &_/dev/null_& as a destination, but it can be independently disabled.
18517 &*Warning*&: If &':blackhole:'& appears anywhere in a redirection list, no
18518 delivery is done for the original local part, even if other redirection items
18519 are present. If you are generating a multi-item list (for example, by reading a
18520 database) and need the ability to provide a no-op item, you must use
18524 .cindex "delivery" "forcing failure"
18525 .cindex "delivery" "forcing deferral"
18526 .cindex "failing delivery" "forcing"
18527 .cindex "deferred delivery, forcing"
18528 .cindex "customizing" "failure message"
18529 An attempt to deliver a particular address can be deferred or forced to fail by
18530 redirection items of the form
18535 respectively. When a redirection list contains such an item, it applies
18536 to the entire redirection; any other items in the list are ignored. Any
18537 text following &':fail:'& or &':defer:'& is placed in the error text
18538 associated with the failure. For example, an alias file might contain:
18540 X.Employee: :fail: Gone away, no forwarding address
18542 In the case of an address that is being verified from an ACL or as the subject
18544 .cindex "VRFY" "error text, display of"
18545 VRFY command, the text is included in the SMTP error response by
18547 .cindex "EXPN" "error text, display of"
18548 The text is not included in the response to an EXPN command. In non-SMTP cases
18549 the text is included in the error message that Exim generates.
18551 .cindex "SMTP" "error codes"
18552 By default, Exim sends a 451 SMTP code for a &':defer:'&, and 550 for
18553 &':fail:'&. However, if the message starts with three digits followed by a
18554 space, optionally followed by an extended code of the form &'n.n.n'&, also
18555 followed by a space, and the very first digit is the same as the default error
18556 code, the code from the message is used instead. If the very first digit is
18557 incorrect, a panic error is logged, and the default code is used. You can
18558 suppress the use of the supplied code in a redirect router by setting the
18559 &%forbid_smtp_code%& option true. In this case, any SMTP code is quietly
18562 .vindex "&$acl_verify_message$&"
18563 In an ACL, an explicitly provided message overrides the default, but the
18564 default message is available in the variable &$acl_verify_message$& and can
18565 therefore be included in a custom message if this is desired.
18567 Normally the error text is the rest of the redirection list &-- a comma does
18568 not terminate it &-- but a newline does act as a terminator. Newlines are not
18569 normally present in alias expansions. In &(lsearch)& lookups they are removed
18570 as part of the continuation process, but they may exist in other kinds of
18571 lookup and in &':include:'& files.
18573 During routing for message delivery (as opposed to verification), a redirection
18574 containing &':fail:'& causes an immediate failure of the incoming address,
18575 whereas &':defer:'& causes the message to remain on the queue so that a
18576 subsequent delivery attempt can happen at a later time. If an address is
18577 deferred for too long, it will ultimately fail, because the normal retry
18581 .cindex "alias file" "exception to default"
18582 Sometimes it is useful to use a single-key search type with a default (see
18583 chapter &<<CHAPfdlookup>>&) to look up aliases. However, there may be a need
18584 for exceptions to the default. These can be handled by aliasing them to
18585 &':unknown:'&. This differs from &':fail:'& in that it causes the &(redirect)&
18586 router to decline, whereas &':fail:'& forces routing to fail. A lookup which
18587 results in an empty redirection list has the same effect.
18591 .section "Duplicate addresses" "SECTdupaddr"
18592 .cindex "duplicate addresses"
18593 .cindex "address duplicate, discarding"
18594 .cindex "pipe" "duplicated"
18595 Exim removes duplicate addresses from the list to which it is delivering, so as
18596 to deliver just one copy to each address. This does not apply to deliveries
18597 routed to pipes by different immediate parent addresses, but an indirect
18598 aliasing scheme of the type
18600 pipe: |/some/command $local_part
18604 does not work with a message that is addressed to both local parts, because
18605 when the second is aliased to the intermediate local part &"pipe"& it gets
18606 discarded as being the same as a previously handled address. However, a scheme
18609 localpart1: |/some/command $local_part
18610 localpart2: |/some/command $local_part
18612 does result in two different pipe deliveries, because the immediate parents of
18613 the pipes are distinct.
18617 .section "Repeated redirection expansion" "SECID128"
18618 .cindex "repeated redirection expansion"
18619 .cindex "address redirection" "repeated for each delivery attempt"
18620 When a message cannot be delivered to all of its recipients immediately,
18621 leading to two or more delivery attempts, redirection expansion is carried out
18622 afresh each time for those addresses whose children were not all previously
18623 delivered. If redirection is being used as a mailing list, this can lead to new
18624 members of the list receiving copies of old messages. The &%one_time%& option
18625 can be used to avoid this.
18628 .section "Errors in redirection lists" "SECID129"
18629 .cindex "address redirection" "errors"
18630 If &%skip_syntax_errors%& is set, a malformed address that causes a parsing
18631 error is skipped, and an entry is written to the main log. This may be useful
18632 for mailing lists that are automatically managed. Otherwise, if an error is
18633 detected while generating the list of new addresses, the original address is
18634 deferred. See also &%syntax_errors_to%&.
18638 .section "Private options for the redirect router" "SECID130"
18640 .cindex "options" "&(redirect)& router"
18641 The private options for the &(redirect)& router are as follows:
18644 .option allow_defer redirect boolean false
18645 Setting this option allows the use of &':defer:'& in non-filter redirection
18646 data, or the &%defer%& command in an Exim filter file.
18649 .option allow_fail redirect boolean false
18650 .cindex "failing delivery" "from filter"
18651 If this option is true, the &':fail:'& item can be used in a redirection list,
18652 and the &%fail%& command may be used in an Exim filter file.
18655 .option allow_filter redirect boolean false
18656 .cindex "filter" "enabling use of"
18657 .cindex "Sieve filter" "enabling use of"
18658 Setting this option allows Exim to interpret redirection data that starts with
18659 &"#Exim filter"& or &"#Sieve filter"& as a set of filtering instructions. There
18660 are some features of Exim filter files that some administrators may wish to
18661 lock out; see the &%forbid_filter_%&&'xxx'& options below.
18663 It is also possible to lock out Exim filters or Sieve filters while allowing
18664 the other type; see &%forbid_exim_filter%& and &%forbid_sieve_filter%&.
18667 The filter is run using the uid and gid set by the generic &%user%& and
18668 &%group%& options. These take their defaults from the password data if
18669 &%check_local_user%& is set, so in the normal case of users' personal filter
18670 files, the filter is run as the relevant user. When &%allow_filter%& is set
18671 true, Exim insists that either &%check_local_user%& or &%user%& is set.
18675 .option allow_freeze redirect boolean false
18676 .cindex "freezing messages" "allowing in filter"
18677 Setting this option allows the use of the &%freeze%& command in an Exim filter.
18678 This command is more normally encountered in system filters, and is disabled by
18679 default for redirection filters because it isn't something you usually want to
18680 let ordinary users do.
18684 .option check_ancestor redirect boolean false
18685 This option is concerned with handling generated addresses that are the same
18686 as some address in the list of redirection ancestors of the current address.
18687 Although it is turned off by default in the code, it is set in the default
18688 configuration file for handling users' &_.forward_& files. It is recommended
18689 for this use of the &(redirect)& router.
18691 When &%check_ancestor%& is set, if a generated address (including the domain)
18692 is the same as any ancestor of the current address, it is replaced by a copy of
18693 the current address. This helps in the case where local part A is aliased to B,
18694 and B has a &_.forward_& file pointing back to A. For example, within a single
18695 domain, the local part &"Joe.Bloggs"& is aliased to &"jb"& and
18696 &_&~jb/.forward_& contains:
18698 \Joe.Bloggs, <other item(s)>
18700 Without the &%check_ancestor%& setting, either local part (&"jb"& or
18701 &"joe.bloggs"&) gets processed once by each router and so ends up as it was
18702 originally. If &"jb"& is the real mailbox name, mail to &"jb"& gets delivered
18703 (having been turned into &"joe.bloggs"& by the &_.forward_& file and back to
18704 &"jb"& by the alias), but mail to &"joe.bloggs"& fails. Setting
18705 &%check_ancestor%& on the &(redirect)& router that handles the &_.forward_&
18706 file prevents it from turning &"jb"& back into &"joe.bloggs"& when that was the
18707 original address. See also the &%repeat_use%& option below.
18710 .option check_group redirect boolean "see below"
18711 When the &%file%& option is used, the group owner of the file is checked only
18712 when this option is set. The permitted groups are those listed in the
18713 &%owngroups%& option, together with the user's default group if
18714 &%check_local_user%& is set. If the file has the wrong group, routing is
18715 deferred. The default setting for this option is true if &%check_local_user%&
18716 is set and the &%modemask%& option permits the group write bit, or if the
18717 &%owngroups%& option is set. Otherwise it is false, and no group check occurs.
18721 .option check_owner redirect boolean "see below"
18722 When the &%file%& option is used, the owner of the file is checked only when
18723 this option is set. If &%check_local_user%& is set, the local user is
18724 permitted; otherwise the owner must be one of those listed in the &%owners%&
18725 option. The default value for this option is true if &%check_local_user%& or
18726 &%owners%& is set. Otherwise the default is false, and no owner check occurs.
18729 .option data redirect string&!! unset
18730 This option is mutually exclusive with &%file%&. One or other of them must be
18731 set, but not both. The contents of &%data%& are expanded, and then used as the
18732 list of forwarding items, or as a set of filtering instructions. If the
18733 expansion is forced to fail, or the result is an empty string or a string that
18734 has no effect (consists entirely of comments), the router declines.
18736 When filtering instructions are used, the string must begin with &"#Exim
18737 filter"&, and all comments in the string, including this initial one, must be
18738 terminated with newline characters. For example:
18740 data = #Exim filter\n\
18741 if $h_to: contains Exim then save $home/mail/exim endif
18743 If you are reading the data from a database where newlines cannot be included,
18744 you can use the &${sg}$& expansion item to turn the escape string of your
18745 choice into a newline.
18748 .option directory_transport redirect string&!! unset
18749 A &(redirect)& router sets up a direct delivery to a directory when a path name
18750 ending with a slash is specified as a new &"address"&. The transport used is
18751 specified by this option, which, after expansion, must be the name of a
18752 configured transport. This should normally be an &(appendfile)& transport.
18755 .option file redirect string&!! unset
18756 This option specifies the name of a file that contains the redirection data. It
18757 is mutually exclusive with the &%data%& option. The string is expanded before
18758 use; if the expansion is forced to fail, the router declines. Other expansion
18759 failures cause delivery to be deferred. The result of a successful expansion
18760 must be an absolute path. The entire file is read and used as the redirection
18761 data. If the data is an empty string or a string that has no effect (consists
18762 entirely of comments), the router declines.
18764 .cindex "NFS" "checking for file existence"
18765 If the attempt to open the file fails with a &"does not exist"& error, Exim
18766 runs a check on the containing directory,
18767 unless &%ignore_enotdir%& is true (see below).
18768 If the directory does not appear to exist, delivery is deferred. This can
18769 happen when users' &_.forward_& files are in NFS-mounted directories, and there
18770 is a mount problem. If the containing directory does exist, but the file does
18771 not, the router declines.
18774 .option file_transport redirect string&!! unset
18775 .vindex "&$address_file$&"
18776 A &(redirect)& router sets up a direct delivery to a file when a path name not
18777 ending in a slash is specified as a new &"address"&. The transport used is
18778 specified by this option, which, after expansion, must be the name of a
18779 configured transport. This should normally be an &(appendfile)& transport. When
18780 it is running, the file name is in &$address_file$&.
18783 .option filter_prepend_home redirect boolean true
18784 When this option is true, if a &(save)& command in an Exim filter specifies a
18785 relative path, and &$home$& is defined, it is automatically prepended to the
18786 relative path. If this option is set false, this action does not happen. The
18787 relative path is then passed to the transport unmodified.
18790 .option forbid_blackhole redirect boolean false
18791 If this option is true, the &':blackhole:'& item may not appear in a
18795 .option forbid_exim_filter redirect boolean false
18796 If this option is set true, only Sieve filters are permitted when
18797 &%allow_filter%& is true.
18802 .option forbid_file redirect boolean false
18803 .cindex "delivery" "to file; forbidding"
18804 .cindex "Sieve filter" "forbidding delivery to a file"
18805 .cindex "Sieve filter" "&""keep""& facility; disabling"
18806 If this option is true, this router may not generate a new address that
18807 specifies delivery to a local file or directory, either from a filter or from a
18808 conventional forward file. This option is forced to be true if &%one_time%& is
18809 set. It applies to Sieve filters as well as to Exim filters, but if true, it
18810 locks out the Sieve's &"keep"& facility.
18813 .option forbid_filter_dlfunc redirect boolean false
18814 .cindex "filter" "locking out certain features"
18815 If this option is true, string expansions in Exim filters are not allowed to
18816 make use of the &%dlfunc%& expansion facility to run dynamically loaded
18819 .option forbid_filter_existstest redirect boolean false
18820 .cindex "expansion" "statting a file"
18821 If this option is true, string expansions in Exim filters are not allowed to
18822 make use of the &%exists%& condition or the &%stat%& expansion item.
18824 .option forbid_filter_logwrite redirect boolean false
18825 If this option is true, use of the logging facility in Exim filters is not
18826 permitted. Logging is in any case available only if the filter is being run
18827 under some unprivileged uid (which is normally the case for ordinary users'
18828 &_.forward_& files).
18831 .option forbid_filter_lookup redirect boolean false
18832 If this option is true, string expansions in Exim filter files are not allowed
18833 to make use of &%lookup%& items.
18836 .option forbid_filter_perl redirect boolean false
18837 This option has an effect only if Exim is built with embedded Perl support. If
18838 it is true, string expansions in Exim filter files are not allowed to make use
18839 of the embedded Perl support.
18842 .option forbid_filter_readfile redirect boolean false
18843 If this option is true, string expansions in Exim filter files are not allowed
18844 to make use of &%readfile%& items.
18847 .option forbid_filter_readsocket redirect boolean false
18848 If this option is true, string expansions in Exim filter files are not allowed
18849 to make use of &%readsocket%& items.
18852 .option forbid_filter_reply redirect boolean false
18853 If this option is true, this router may not generate an automatic reply
18854 message. Automatic replies can be generated only from Exim or Sieve filter
18855 files, not from traditional forward files. This option is forced to be true if
18856 &%one_time%& is set.
18859 .option forbid_filter_run redirect boolean false
18860 If this option is true, string expansions in Exim filter files are not allowed
18861 to make use of &%run%& items.
18864 .option forbid_include redirect boolean false
18865 If this option is true, items of the form
18867 :include:<path name>
18869 are not permitted in non-filter redirection lists.
18872 .option forbid_pipe redirect boolean false
18873 .cindex "delivery" "to pipe; forbidding"
18874 If this option is true, this router may not generate a new address which
18875 specifies delivery to a pipe, either from an Exim filter or from a conventional
18876 forward file. This option is forced to be true if &%one_time%& is set.
18879 .option forbid_sieve_filter redirect boolean false
18880 If this option is set true, only Exim filters are permitted when
18881 &%allow_filter%& is true.
18884 .cindex "SMTP" "error codes"
18885 .option forbid_smtp_code redirect boolean false
18886 If this option is set true, any SMTP error codes that are present at the start
18887 of messages specified for &`:defer:`& or &`:fail:`& are quietly ignored, and
18888 the default codes (451 and 550, respectively) are always used.
18893 .option hide_child_in_errmsg redirect boolean false
18894 .cindex "bounce message" "redirection details; suppressing"
18895 If this option is true, it prevents Exim from quoting a child address if it
18896 generates a bounce or delay message for it. Instead it says &"an address
18897 generated from <&'the top level address'&>"&. Of course, this applies only to
18898 bounces generated locally. If a message is forwarded to another host, &'its'&
18899 bounce may well quote the generated address.
18902 .option ignore_eacces redirect boolean false
18904 If this option is set and an attempt to open a redirection file yields the
18905 EACCES error (permission denied), the &(redirect)& router behaves as if the
18906 file did not exist.
18909 .option ignore_enotdir redirect boolean false
18911 If this option is set and an attempt to open a redirection file yields the
18912 ENOTDIR error (something on the path is not a directory), the &(redirect)&
18913 router behaves as if the file did not exist.
18915 Setting &%ignore_enotdir%& has another effect as well: When a &(redirect)&
18916 router that has the &%file%& option set discovers that the file does not exist
18917 (the ENOENT error), it tries to &[stat()]& the parent directory, as a check
18918 against unmounted NFS directories. If the parent can not be statted, delivery
18919 is deferred. However, it seems wrong to do this check when &%ignore_enotdir%&
18920 is set, because that option tells Exim to ignore &"something on the path is not
18921 a directory"& (the ENOTDIR error). This is a confusing area, because it seems
18922 that some operating systems give ENOENT where others give ENOTDIR.
18926 .option include_directory redirect string unset
18927 If this option is set, the path names of any &':include:'& items in a
18928 redirection list must start with this directory.
18931 .option modemask redirect "octal integer" 022
18932 This specifies mode bits which must not be set for a file specified by the
18933 &%file%& option. If any of the forbidden bits are set, delivery is deferred.
18936 .option one_time redirect boolean false
18937 .cindex "one-time aliasing/forwarding expansion"
18938 .cindex "alias file" "one-time expansion"
18939 .cindex "forward file" "one-time expansion"
18940 .cindex "mailing lists" "one-time expansion"
18941 .cindex "address redirection" "one-time expansion"
18942 Sometimes the fact that Exim re-evaluates aliases and reprocesses redirection
18943 files each time it tries to deliver a message causes a problem when one or more
18944 of the generated addresses fails be delivered at the first attempt. The problem
18945 is not one of duplicate delivery &-- Exim is clever enough to handle that &--
18946 but of what happens when the redirection list changes during the time that the
18947 message is on Exim's queue. This is particularly true in the case of mailing
18948 lists, where new subscribers might receive copies of messages that were posted
18949 before they subscribed.
18951 If &%one_time%& is set and any addresses generated by the router fail to
18952 deliver at the first attempt, the failing addresses are added to the message as
18953 &"top level"& addresses, and the parent address that generated them is marked
18954 &"delivered"&. Thus, redirection does not happen again at the next delivery
18957 &*Warning 1*&: Any header line addition or removal that is specified by this
18958 router would be lost if delivery did not succeed at the first attempt. For this
18959 reason, the &%headers_add%& and &%headers_remove%& generic options are not
18960 permitted when &%one_time%& is set.
18962 &*Warning 2*&: To ensure that the router generates only addresses (as opposed
18963 to pipe or file deliveries or auto-replies) &%forbid_file%&, &%forbid_pipe%&,
18964 and &%forbid_filter_reply%& are forced to be true when &%one_time%& is set.
18966 &*Warning 3*&: The &%unseen%& generic router option may not be set with
18969 The original top-level address is remembered with each of the generated
18970 addresses, and is output in any log messages. However, any intermediate parent
18971 addresses are not recorded. This makes a difference to the log only if
18972 &%all_parents%& log selector is set. It is expected that &%one_time%& will
18973 typically be used for mailing lists, where there is normally just one level of
18977 .option owners redirect "string list" unset
18978 .cindex "ownership" "alias file"
18979 .cindex "ownership" "forward file"
18980 .cindex "alias file" "ownership"
18981 .cindex "forward file" "ownership"
18982 This specifies a list of permitted owners for the file specified by &%file%&.
18983 This list is in addition to the local user when &%check_local_user%& is set.
18984 See &%check_owner%& above.
18987 .option owngroups redirect "string list" unset
18988 This specifies a list of permitted groups for the file specified by &%file%&.
18989 The list is in addition to the local user's primary group when
18990 &%check_local_user%& is set. See &%check_group%& above.
18993 .option pipe_transport redirect string&!! unset
18994 .vindex "&$address_pipe$&"
18995 A &(redirect)& router sets up a direct delivery to a pipe when a string
18996 starting with a vertical bar character is specified as a new &"address"&. The
18997 transport used is specified by this option, which, after expansion, must be the
18998 name of a configured transport. This should normally be a &(pipe)& transport.
18999 When the transport is run, the pipe command is in &$address_pipe$&.
19002 .option qualify_domain redirect string&!! unset
19003 .vindex "&$qualify_recipient$&"
19004 If this option is set, and an unqualified address (one without a domain) is
19005 generated, and that address would normally be qualified by the global setting
19006 in &%qualify_recipient%&, it is instead qualified with the domain specified by
19007 expanding this string. If the expansion fails, the router declines. If you want
19008 to revert to the default, you can have the expansion generate
19009 &$qualify_recipient$&.
19011 This option applies to all unqualified addresses generated by Exim filters,
19012 but for traditional &_.forward_& files, it applies only to addresses that are
19013 not preceded by a backslash. Sieve filters cannot generate unqualified
19016 .option qualify_preserve_domain redirect boolean false
19017 .cindex "domain" "in redirection; preserving"
19018 .cindex "preserving domain in redirection"
19019 .cindex "address redirection" "domain; preserving"
19020 If this option is set, the router's local &%qualify_domain%& option must not be
19021 set (a configuration error occurs if it is). If an unqualified address (one
19022 without a domain) is generated, it is qualified with the domain of the parent
19023 address (the immediately preceding ancestor) instead of the global
19024 &%qualify_recipient%& value. In the case of a traditional &_.forward_& file,
19025 this applies whether or not the address is preceded by a backslash.
19028 .option repeat_use redirect boolean true
19029 If this option is set false, the router is skipped for a child address that has
19030 any ancestor that was routed by this router. This test happens before any of
19031 the other preconditions are tested. Exim's default anti-looping rules skip
19032 only when the ancestor is the same as the current address. See also
19033 &%check_ancestor%& above and the generic &%redirect_router%& option.
19036 .option reply_transport redirect string&!! unset
19037 A &(redirect)& router sets up an automatic reply when a &%mail%& or
19038 &%vacation%& command is used in a filter file. The transport used is specified
19039 by this option, which, after expansion, must be the name of a configured
19040 transport. This should normally be an &(autoreply)& transport. Other transports
19041 are unlikely to do anything sensible or useful.
19044 .option rewrite redirect boolean true
19045 .cindex "address redirection" "disabling rewriting"
19046 If this option is set false, addresses generated by the router are not
19047 subject to address rewriting. Otherwise, they are treated like new addresses
19048 and are rewritten according to the global rewriting rules.
19051 .option sieve_subaddress redirect string&!! unset
19052 The value of this option is passed to a Sieve filter to specify the
19053 :subaddress part of an address.
19055 .option sieve_useraddress redirect string&!! unset
19056 The value of this option is passed to a Sieve filter to specify the :user part
19057 of an address. However, if it is unset, the entire original local part
19058 (including any prefix or suffix) is used for :user.
19061 .option sieve_vacation_directory redirect string&!! unset
19062 .cindex "Sieve filter" "vacation directory"
19063 To enable the &"vacation"& extension for Sieve filters, you must set
19064 &%sieve_vacation_directory%& to the directory where vacation databases are held
19065 (do not put anything else in that directory), and ensure that the
19066 &%reply_transport%& option refers to an &(autoreply)& transport. Each user
19067 needs their own directory; Exim will create it if necessary.
19071 .option skip_syntax_errors redirect boolean false
19072 .cindex "forward file" "broken"
19073 .cindex "address redirection" "broken files"
19074 .cindex "alias file" "broken"
19075 .cindex "broken alias or forward files"
19076 .cindex "ignoring faulty addresses"
19077 .cindex "skipping faulty addresses"
19078 .cindex "error" "skipping bad syntax"
19079 If &%skip_syntax_errors%& is set, syntactically malformed addresses in
19080 non-filter redirection data are skipped, and each failing address is logged. If
19081 &%syntax_errors_to%& is set, a message is sent to the address it defines,
19082 giving details of the failures. If &%syntax_errors_text%& is set, its contents
19083 are expanded and placed at the head of the error message generated by
19084 &%syntax_errors_to%&. Usually it is appropriate to set &%syntax_errors_to%& to
19085 be the same address as the generic &%errors_to%& option. The
19086 &%skip_syntax_errors%& option is often used when handling mailing lists.
19088 If all the addresses in a redirection list are skipped because of syntax
19089 errors, the router declines to handle the original address, and it is passed to
19090 the following routers.
19092 If &%skip_syntax_errors%& is set when an Exim filter is interpreted, any syntax
19093 error in the filter causes filtering to be abandoned without any action being
19094 taken. The incident is logged, and the router declines to handle the address,
19095 so it is passed to the following routers.
19097 .cindex "Sieve filter" "syntax errors in"
19098 Syntax errors in a Sieve filter file cause the &"keep"& action to occur. This
19099 action is specified by RFC 3028. The values of &%skip_syntax_errors%&,
19100 &%syntax_errors_to%&, and &%syntax_errors_text%& are not used.
19102 &%skip_syntax_errors%& can be used to specify that errors in users' forward
19103 lists or filter files should not prevent delivery. The &%syntax_errors_to%&
19104 option, used with an address that does not get redirected, can be used to
19105 notify users of these errors, by means of a router like this:
19111 file = $home/.forward
19112 file_transport = address_file
19113 pipe_transport = address_pipe
19114 reply_transport = address_reply
19117 syntax_errors_to = real-$local_part@$domain
19118 syntax_errors_text = \
19119 This is an automatically generated message. An error has\n\
19120 been found in your .forward file. Details of the error are\n\
19121 reported below. While this error persists, you will receive\n\
19122 a copy of this message for every message that is addressed\n\
19123 to you. If your .forward file is a filter file, or if it is\n\
19124 a non-filter file containing no valid forwarding addresses,\n\
19125 a copy of each incoming message will be put in your normal\n\
19126 mailbox. If a non-filter file contains at least one valid\n\
19127 forwarding address, forwarding to the valid addresses will\n\
19128 happen, and those will be the only deliveries that occur.
19130 You also need a router to ensure that local addresses that are prefixed by
19131 &`real-`& are recognized, but not forwarded or filtered. For example, you could
19132 put this immediately before the &(userforward)& router:
19137 local_part_prefix = real-
19138 transport = local_delivery
19140 For security, it would probably be a good idea to restrict the use of this
19141 router to locally-generated messages, using a condition such as this:
19143 condition = ${if match {$sender_host_address}\
19144 {\N^(|127\.0\.0\.1)$\N}}
19148 .option syntax_errors_text redirect string&!! unset
19149 See &%skip_syntax_errors%& above.
19152 .option syntax_errors_to redirect string unset
19153 See &%skip_syntax_errors%& above.
19154 .ecindex IIDredrou1
19155 .ecindex IIDredrou2
19162 . ////////////////////////////////////////////////////////////////////////////
19163 . ////////////////////////////////////////////////////////////////////////////
19165 .chapter "Environment for running local transports" "CHAPenvironment" &&&
19166 "Environment for local transports"
19167 .scindex IIDenvlotra1 "local transports" "environment for"
19168 .scindex IIDenvlotra2 "environment for local transports"
19169 .scindex IIDenvlotra3 "transport" "local; environment for"
19170 Local transports handle deliveries to files and pipes. (The &(autoreply)&
19171 transport can be thought of as similar to a pipe.) Exim always runs transports
19172 in subprocesses, under specified uids and gids. Typical deliveries to local
19173 mailboxes run under the uid and gid of the local user.
19175 Exim also sets a specific current directory while running the transport; for
19176 some transports a home directory setting is also relevant. The &(pipe)&
19177 transport is the only one that sets up environment variables; see section
19178 &<<SECTpipeenv>>& for details.
19180 The values used for the uid, gid, and the directories may come from several
19181 different places. In many cases, the router that handles the address associates
19182 settings with that address as a result of its &%check_local_user%&, &%group%&,
19183 or &%user%& options. However, values may also be given in the transport's own
19184 configuration, and these override anything that comes from the router.
19188 .section "Concurrent deliveries" "SECID131"
19189 .cindex "concurrent deliveries"
19190 .cindex "simultaneous deliveries"
19191 If two different messages for the same local recipient arrive more or less
19192 simultaneously, the two delivery processes are likely to run concurrently. When
19193 the &(appendfile)& transport is used to write to a file, Exim applies locking
19194 rules to stop concurrent processes from writing to the same file at the same
19197 However, when you use a &(pipe)& transport, it is up to you to arrange any
19198 locking that is needed. Here is a silly example:
19202 command = /bin/sh -c 'cat >>/some/file'
19204 This is supposed to write the message at the end of the file. However, if two
19205 messages arrive at the same time, the file will be scrambled. You can use the
19206 &%exim_lock%& utility program (see section &<<SECTmailboxmaint>>&) to lock a
19207 file using the same algorithm that Exim itself uses.
19212 .section "Uids and gids" "SECTenvuidgid"
19213 .cindex "local transports" "uid and gid"
19214 .cindex "transport" "local; uid and gid"
19215 All transports have the options &%group%& and &%user%&. If &%group%& is set, it
19216 overrides any group that the router set in the address, even if &%user%& is not
19217 set for the transport. This makes it possible, for example, to run local mail
19218 delivery under the uid of the recipient (set by the router), but in a special
19219 group (set by the transport). For example:
19222 # User/group are set by check_local_user in this router
19226 transport = group_delivery
19229 # This transport overrides the group
19231 driver = appendfile
19232 file = /var/spool/mail/$local_part
19235 If &%user%& is set for a transport, its value overrides what is set in the
19236 address by the router. If &%user%& is non-numeric and &%group%& is not set, the
19237 gid associated with the user is used. If &%user%& is numeric, &%group%& must be
19240 .oindex "&%initgroups%&"
19241 When the uid is taken from the transport's configuration, the &[initgroups()]&
19242 function is called for the groups associated with that uid if the
19243 &%initgroups%& option is set for the transport. When the uid is not specified
19244 by the transport, but is associated with the address by a router, the option
19245 for calling &[initgroups()]& is taken from the router configuration.
19247 .cindex "&(pipe)& transport" "uid for"
19248 The &(pipe)& transport contains the special option &%pipe_as_creator%&. If this
19249 is set and &%user%& is not set, the uid of the process that called Exim to
19250 receive the message is used, and if &%group%& is not set, the corresponding
19251 original gid is also used.
19253 This is the detailed preference order for obtaining a gid; the first of the
19254 following that is set is used:
19257 A &%group%& setting of the transport;
19259 A &%group%& setting of the router;
19261 A gid associated with a user setting of the router, either as a result of
19262 &%check_local_user%& or an explicit non-numeric &%user%& setting;
19264 The group associated with a non-numeric &%user%& setting of the transport;
19266 In a &(pipe)& transport, the creator's gid if &%deliver_as_creator%& is set and
19267 the uid is the creator's uid;
19269 The Exim gid if the Exim uid is being used as a default.
19272 If, for example, the user is specified numerically on the router and there are
19273 no group settings, no gid is available. In this situation, an error occurs.
19274 This is different for the uid, for which there always is an ultimate default.
19275 The first of the following that is set is used:
19278 A &%user%& setting of the transport;
19280 In a &(pipe)& transport, the creator's uid if &%deliver_as_creator%& is set;
19282 A &%user%& setting of the router;
19284 A &%check_local_user%& setting of the router;
19289 Of course, an error will still occur if the uid that is chosen is on the
19290 &%never_users%& list.
19296 .section "Current and home directories" "SECID132"
19297 .cindex "current directory for local transport"
19298 .cindex "home directory" "for local transport"
19299 .cindex "transport" "local; home directory for"
19300 .cindex "transport" "local; current directory for"
19301 Routers may set current and home directories for local transports by means of
19302 the &%transport_current_directory%& and &%transport_home_directory%& options.
19303 However, if the transport's &%current_directory%& or &%home_directory%& options
19304 are set, they override the router's values. In detail, the home directory
19305 for a local transport is taken from the first of these values that is set:
19308 The &%home_directory%& option on the transport;
19310 The &%transport_home_directory%& option on the router;
19312 The password data if &%check_local_user%& is set on the router;
19314 The &%router_home_directory%& option on the router.
19317 The current directory is taken from the first of these values that is set:
19320 The &%current_directory%& option on the transport;
19322 The &%transport_current_directory%& option on the router.
19326 If neither the router nor the transport sets a current directory, Exim uses the
19327 value of the home directory, if it is set. Otherwise it sets the current
19328 directory to &_/_& before running a local transport.
19332 .section "Expansion variables derived from the address" "SECID133"
19333 .vindex "&$domain$&"
19334 .vindex "&$local_part$&"
19335 .vindex "&$original_domain$&"
19336 Normally a local delivery is handling a single address, and in that case the
19337 variables such as &$domain$& and &$local_part$& are set during local
19338 deliveries. However, in some circumstances more than one address may be handled
19339 at once (for example, while writing batch SMTP for onward transmission by some
19340 other means). In this case, the variables associated with the local part are
19341 never set, &$domain$& is set only if all the addresses have the same domain,
19342 and &$original_domain$& is never set.
19343 .ecindex IIDenvlotra1
19344 .ecindex IIDenvlotra2
19345 .ecindex IIDenvlotra3
19353 . ////////////////////////////////////////////////////////////////////////////
19354 . ////////////////////////////////////////////////////////////////////////////
19356 .chapter "Generic options for transports" "CHAPtransportgeneric"
19357 .scindex IIDgenoptra1 "generic options" "transport"
19358 .scindex IIDgenoptra2 "options" "generic; for transports"
19359 .scindex IIDgenoptra3 "transport" "generic options for"
19360 The following generic options apply to all transports:
19363 .option body_only transports boolean false
19364 .cindex "transport" "body only"
19365 .cindex "message" "transporting body only"
19366 .cindex "body of message" "transporting"
19367 If this option is set, the message's headers are not transported. It is
19368 mutually exclusive with &%headers_only%&. If it is used with the &(appendfile)&
19369 or &(pipe)& transports, the settings of &%message_prefix%& and
19370 &%message_suffix%& should be checked, because this option does not
19371 automatically suppress them.
19374 .option current_directory transports string&!! unset
19375 .cindex "transport" "current directory for"
19376 This specifies the current directory that is to be set while running the
19377 transport, overriding any value that may have been set by the router.
19378 If the expansion fails for any reason, including forced failure, an error is
19379 logged, and delivery is deferred.
19382 .option disable_logging transports boolean false
19383 If this option is set true, nothing is logged for any
19384 deliveries by the transport or for any
19385 transport errors. You should not set this option unless you really, really know
19386 what you are doing.
19389 .option debug_print transports string&!! unset
19390 .cindex "testing" "variables in drivers"
19391 If this option is set and debugging is enabled (see the &%-d%& command line
19392 option), the string is expanded and included in the debugging output when the
19394 If expansion of the string fails, the error message is written to the debugging
19395 output, and Exim carries on processing.
19396 This facility is provided to help with checking out the values of variables and
19397 so on when debugging driver configurations. For example, if a &%headers_add%&
19398 option is not working properly, &%debug_print%& could be used to output the
19399 variables it references. A newline is added to the text if it does not end with
19403 .option delivery_date_add transports boolean false
19404 .cindex "&'Delivery-date:'& header line"
19405 If this option is true, a &'Delivery-date:'& header is added to the message.
19406 This gives the actual time the delivery was made. As this is not a standard
19407 header, Exim has a configuration option (&%delivery_date_remove%&) which
19408 requests its removal from incoming messages, so that delivered messages can
19409 safely be resent to other recipients.
19412 .option driver transports string unset
19413 This specifies which of the available transport drivers is to be used.
19414 There is no default, and this option must be set for every transport.
19417 .option envelope_to_add transports boolean false
19418 .cindex "&'Envelope-to:'& header line"
19419 If this option is true, an &'Envelope-to:'& header is added to the message.
19420 This gives the original address(es) in the incoming envelope that caused this
19421 delivery to happen. More than one address may be present if the transport is
19422 configured to handle several addresses at once, or if more than one original
19423 address was redirected to the same final address. As this is not a standard
19424 header, Exim has a configuration option (&%envelope_to_remove%&) which requests
19425 its removal from incoming messages, so that delivered messages can safely be
19426 resent to other recipients.
19429 .option group transports string&!! "Exim group"
19430 .cindex "transport" "group; specifying"
19431 This option specifies a gid for running the transport process, overriding any
19432 value that the router supplies, and also overriding any value associated with
19433 &%user%& (see below).
19436 .option headers_add transports string&!! unset
19437 .cindex "header lines" "adding in transport"
19438 .cindex "transport" "header lines; adding"
19439 This option specifies a string of text that is expanded and added to the header
19440 portion of a message as it is transported, as described in section
19441 &<<SECTheadersaddrem>>&. Additional header lines can also be specified by
19442 routers. If the result of the expansion is an empty string, or if the expansion
19443 is forced to fail, no action is taken. Other expansion failures are treated as
19444 errors and cause the delivery to be deferred.
19448 .option headers_only transports boolean false
19449 .cindex "transport" "header lines only"
19450 .cindex "message" "transporting headers only"
19451 .cindex "header lines" "transporting"
19452 If this option is set, the message's body is not transported. It is mutually
19453 exclusive with &%body_only%&. If it is used with the &(appendfile)& or &(pipe)&
19454 transports, the settings of &%message_prefix%& and &%message_suffix%& should be
19455 checked, since this option does not automatically suppress them.
19458 .option headers_remove transports string&!! unset
19459 .cindex "header lines" "removing"
19460 .cindex "transport" "header lines; removing"
19461 This option specifies a string that is expanded into a list of header names;
19462 these headers are omitted from the message as it is transported, as described
19463 in section &<<SECTheadersaddrem>>&. Header removal can also be specified by
19464 routers. If the result of the expansion is an empty string, or if the expansion
19465 is forced to fail, no action is taken. Other expansion failures are treated as
19466 errors and cause the delivery to be deferred.
19470 .option headers_rewrite transports string unset
19471 .cindex "transport" "header lines; rewriting"
19472 .cindex "rewriting" "at transport time"
19473 This option allows addresses in header lines to be rewritten at transport time,
19474 that is, as the message is being copied to its destination. The contents of the
19475 option are a colon-separated list of rewriting rules. Each rule is in exactly
19476 the same form as one of the general rewriting rules that are applied when a
19477 message is received. These are described in chapter &<<CHAPrewrite>>&. For
19480 headers_rewrite = a@b c@d f : \
19483 changes &'a@b'& into &'c@d'& in &'From:'& header lines, and &'x@y'& into
19484 &'w@z'& in all address-bearing header lines. The rules are applied to the
19485 header lines just before they are written out at transport time, so they affect
19486 only those copies of the message that pass through the transport. However, only
19487 the message's original header lines, and any that were added by a system
19488 filter, are rewritten. If a router or transport adds header lines, they are not
19489 affected by this option. These rewriting rules are &'not'& applied to the
19490 envelope. You can change the return path using &%return_path%&, but you cannot
19491 change envelope recipients at this time.
19494 .option home_directory transports string&!! unset
19495 .cindex "transport" "home directory for"
19497 This option specifies a home directory setting for a local transport,
19498 overriding any value that may be set by the router. The home directory is
19499 placed in &$home$& while expanding the transport's private options. It is also
19500 used as the current directory if no current directory is set by the
19501 &%current_directory%& option on the transport or the
19502 &%transport_current_directory%& option on the router. If the expansion fails
19503 for any reason, including forced failure, an error is logged, and delivery is
19507 .option initgroups transports boolean false
19508 .cindex "additional groups"
19509 .cindex "groups" "additional"
19510 .cindex "transport" "group; additional"
19511 If this option is true and the uid for the delivery process is provided by the
19512 transport, the &[initgroups()]& function is called when running the transport
19513 to ensure that any additional groups associated with the uid are set up.
19516 .option message_size_limit transports string&!! 0
19517 .cindex "limit" "message size per transport"
19518 .cindex "size" "of message, limit"
19519 .cindex "transport" "message size; limiting"
19520 This option controls the size of messages passed through the transport. It is
19521 expanded before use; the result of the expansion must be a sequence of decimal
19522 digits, optionally followed by K or M. If the expansion fails for any reason,
19523 including forced failure, or if the result is not of the required form,
19524 delivery is deferred. If the value is greater than zero and the size of a
19525 message exceeds this limit, the address is failed. If there is any chance that
19526 the resulting bounce message could be routed to the same transport, you should
19527 ensure that &%return_size_limit%& is less than the transport's
19528 &%message_size_limit%&, as otherwise the bounce message will fail to get
19533 .option rcpt_include_affixes transports boolean false
19534 .cindex "prefix" "for local part, including in envelope"
19535 .cindex "suffix for local part" "including in envelope"
19536 .cindex "local part" "prefix"
19537 .cindex "local part" "suffix"
19538 When this option is false (the default), and an address that has had any
19539 affixes (prefixes or suffixes) removed from the local part is delivered by any
19540 form of SMTP or LMTP, the affixes are not included. For example, if a router
19543 local_part_prefix = *-
19545 routes the address &'abc-xyz@some.domain'& to an SMTP transport, the envelope
19548 RCPT TO:<xyz@some.domain>
19550 This is also the case when an ACL-time callout is being used to verify a
19551 recipient address. However, if &%rcpt_include_affixes%& is set true, the
19552 whole local part is included in the RCPT command. This option applies to BSMTP
19553 deliveries by the &(appendfile)& and &(pipe)& transports as well as to the
19554 &(lmtp)& and &(smtp)& transports.
19557 .option retry_use_local_part transports boolean "see below"
19558 .cindex "hints database" "retry keys"
19559 When a delivery suffers a temporary failure, a retry record is created
19560 in Exim's hints database. For remote deliveries, the key for the retry record
19561 is based on the name and/or IP address of the failing remote host. For local
19562 deliveries, the key is normally the entire address, including both the local
19563 part and the domain. This is suitable for most common cases of local delivery
19564 temporary failure &-- for example, exceeding a mailbox quota should delay only
19565 deliveries to that mailbox, not to the whole domain.
19567 However, in some special cases you may want to treat a temporary local delivery
19568 as a failure associated with the domain, and not with a particular local part.
19569 (For example, if you are storing all mail for some domain in files.) You can do
19570 this by setting &%retry_use_local_part%& false.
19572 For all the local transports, its default value is true. For remote transports,
19573 the default value is false for tidiness, but changing the value has no effect
19574 on a remote transport in the current implementation.
19577 .option return_path transports string&!! unset
19578 .cindex "envelope sender"
19579 .cindex "transport" "return path; changing"
19580 .cindex "return path" "changing in transport"
19581 If this option is set, the string is expanded at transport time and replaces
19582 the existing return path (envelope sender) value in the copy of the message
19583 that is being delivered. An empty return path is permitted. This feature is
19584 designed for remote deliveries, where the value of this option is used in the
19585 SMTP MAIL command. If you set &%return_path%& for a local transport, the
19586 only effect is to change the address that is placed in the &'Return-path:'&
19587 header line, if one is added to the message (see the next option).
19589 &*Note:*& A changed return path is not logged unless you add
19590 &%return_path_on_delivery%& to the log selector.
19592 .vindex "&$return_path$&"
19593 The expansion can refer to the existing value via &$return_path$&. This is
19594 either the message's envelope sender, or an address set by the
19595 &%errors_to%& option on a router. If the expansion is forced to fail, no
19596 replacement occurs; if it fails for another reason, delivery is deferred. This
19597 option can be used to support VERP (Variable Envelope Return Paths) &-- see
19598 section &<<SECTverp>>&.
19600 &*Note*&: If a delivery error is detected locally, including the case when a
19601 remote server rejects a message at SMTP time, the bounce message is not sent to
19602 the value of this option. It is sent to the previously set errors address.
19603 This defaults to the incoming sender address, but can be changed by setting
19604 &%errors_to%& in a router.
19608 .option return_path_add transports boolean false
19609 .cindex "&'Return-path:'& header line"
19610 If this option is true, a &'Return-path:'& header is added to the message.
19611 Although the return path is normally available in the prefix line of BSD
19612 mailboxes, this is commonly not displayed by MUAs, and so the user does not
19613 have easy access to it.
19615 RFC 2821 states that the &'Return-path:'& header is added to a message &"when
19616 the delivery SMTP server makes the final delivery"&. This implies that this
19617 header should not be present in incoming messages. Exim has a configuration
19618 option, &%return_path_remove%&, which requests removal of this header from
19619 incoming messages, so that delivered messages can safely be resent to other
19623 .option shadow_condition transports string&!! unset
19624 See &%shadow_transport%& below.
19627 .option shadow_transport transports string unset
19628 .cindex "shadow transport"
19629 .cindex "transport" "shadow"
19630 A local transport may set the &%shadow_transport%& option to the name of
19631 another local transport. Shadow remote transports are not supported.
19633 Whenever a delivery to the main transport succeeds, and either
19634 &%shadow_condition%& is unset, or its expansion does not result in the empty
19635 string or one of the strings &"0"& or &"no"& or &"false"&, the message is also
19636 passed to the shadow transport, with the same delivery address or addresses. If
19637 expansion fails, no action is taken except that non-forced expansion failures
19638 cause a log line to be written.
19640 The result of the shadow transport is discarded and does not affect the
19641 subsequent processing of the message. Only a single level of shadowing is
19642 provided; the &%shadow_transport%& option is ignored on any transport when it
19643 is running as a shadow. Options concerned with output from pipes are also
19644 ignored. The log line for the successful delivery has an item added on the end,
19647 ST=<shadow transport name>
19649 If the shadow transport did not succeed, the error message is put in
19650 parentheses afterwards. Shadow transports can be used for a number of different
19651 purposes, including keeping more detailed log information than Exim normally
19652 provides, and implementing automatic acknowledgment policies based on message
19653 headers that some sites insist on.
19656 .option transport_filter transports string&!! unset
19657 .cindex "transport" "filter"
19658 .cindex "filter" "transport filter"
19659 This option sets up a filtering (in the Unix shell sense) process for messages
19660 at transport time. It should not be confused with mail filtering as set up by
19661 individual users or via a system filter.
19663 When the message is about to be written out, the command specified by
19664 &%transport_filter%& is started up in a separate, parallel process, and
19665 the entire message, including the header lines, is passed to it on its standard
19666 input (this in fact is done from a third process, to avoid deadlock). The
19667 command must be specified as an absolute path.
19669 The lines of the message that are written to the transport filter are
19670 terminated by newline (&"\n"&). The message is passed to the filter before any
19671 SMTP-specific processing, such as turning &"\n"& into &"\r\n"& and escaping
19672 lines beginning with a dot, and also before any processing implied by the
19673 settings of &%check_string%& and &%escape_string%& in the &(appendfile)& or
19674 &(pipe)& transports.
19676 The standard error for the filter process is set to the same destination as its
19677 standard output; this is read and written to the message's ultimate
19678 destination. The process that writes the message to the filter, the
19679 filter itself, and the original process that reads the result and delivers it
19680 are all run in parallel, like a shell pipeline.
19682 The filter can perform any transformations it likes, but of course should take
19683 care not to break RFC 2822 syntax. Exim does not check the result, except to
19684 test for a final newline when SMTP is in use. All messages transmitted over
19685 SMTP must end with a newline, so Exim supplies one if it is missing.
19687 .cindex "content scanning" "per user"
19688 A transport filter can be used to provide content-scanning on a per-user basis
19689 at delivery time if the only required effect of the scan is to modify the
19690 message. For example, a content scan could insert a new header line containing
19691 a spam score. This could be interpreted by a filter in the user's MUA. It is
19692 not possible to discard a message at this stage.
19694 .cindex "SMTP" "SIZE"
19695 A problem might arise if the filter increases the size of a message that is
19696 being sent down an SMTP connection. If the receiving SMTP server has indicated
19697 support for the SIZE parameter, Exim will have sent the size of the message
19698 at the start of the SMTP session. If what is actually sent is substantially
19699 more, the server might reject the message. This can be worked round by setting
19700 the &%size_addition%& option on the &(smtp)& transport, either to allow for
19701 additions to the message, or to disable the use of SIZE altogether.
19703 .vindex "&$pipe_addresses$&"
19704 The value of the &%transport_filter%& option is the command string for starting
19705 the filter, which is run directly from Exim, not under a shell. The string is
19706 parsed by Exim in the same way as a command string for the &(pipe)& transport:
19707 Exim breaks it up into arguments and then expands each argument separately (see
19708 section &<<SECThowcommandrun>>&). Any kind of expansion failure causes delivery
19709 to be deferred. The special argument &$pipe_addresses$& is replaced by a number
19710 of arguments, one for each address that applies to this delivery. (This isn't
19711 an ideal name for this feature here, but as it was already implemented for the
19712 &(pipe)& transport, it seemed sensible not to change it.)
19715 .vindex "&$host_address$&"
19716 The expansion variables &$host$& and &$host_address$& are available when the
19717 transport is a remote one. They contain the name and IP address of the host to
19718 which the message is being sent. For example:
19720 transport_filter = /some/directory/transport-filter.pl \
19721 $host $host_address $sender_address $pipe_addresses
19724 Two problems arise if you want to use more complicated expansion items to
19725 generate transport filter commands, both of which due to the fact that the
19726 command is split up &'before'& expansion.
19728 If an expansion item contains white space, you must quote it, so that it is all
19729 part of the same command item. If the entire option setting is one such
19730 expansion item, you have to take care what kind of quoting you use. For
19733 transport_filter = '/bin/cmd${if eq{$host}{a.b.c}{1}{2}}'
19735 This runs the command &(/bin/cmd1)& if the host name is &'a.b.c'&, and
19736 &(/bin/cmd2)& otherwise. If double quotes had been used, they would have been
19737 stripped by Exim when it read the option's value. When the value is used, if
19738 the single quotes were missing, the line would be split into two items,
19739 &`/bin/cmd${if`& and &`eq{$host}{a.b.c}{1}{2}`&, and an error would occur when
19740 Exim tried to expand the first one.
19742 Except for the special case of &$pipe_addresses$& that is mentioned above, an
19743 expansion cannot generate multiple arguments, or a command name followed by
19744 arguments. Consider this example:
19746 transport_filter = ${lookup{$host}lsearch{/a/file}\
19747 {$value}{/bin/cat}}
19749 The result of the lookup is interpreted as the name of the command, even
19750 if it contains white space. The simplest way round this is to use a shell:
19752 transport_filter = /bin/sh -c ${lookup{$host}lsearch{/a/file}\
19753 {$value}{/bin/cat}}
19757 The filter process is run under the same uid and gid as the normal delivery.
19758 For remote deliveries this is the Exim uid/gid by default. The command should
19759 normally yield a zero return code. Transport filters are not supposed to fail.
19760 A non-zero code is taken to mean that the transport filter encountered some
19761 serious problem. Delivery of the message is deferred; the message remains on
19762 the queue and is tried again later. It is not possible to cause a message to be
19763 bounced from a transport filter.
19765 If a transport filter is set on an autoreply transport, the original message is
19766 passed through the filter as it is being copied into the newly generated
19767 message, which happens if the &%return_message%& option is set.
19770 .option transport_filter_timeout transports time 5m
19771 .cindex "transport" "filter, timeout"
19772 When Exim is reading the output of a transport filter, it a applies a timeout
19773 that can be set by this option. Exceeding the timeout is normally treated as a
19774 temporary delivery failure. However, if a transport filter is used with a
19775 &(pipe)& transport, a timeout in the transport filter is treated in the same
19776 way as a timeout in the pipe command itself. By default, a timeout is a hard
19777 error, but if the &(pipe)& transport's &%timeout_defer%& option is set true, it
19778 becomes a temporary error.
19781 .option user transports string&!! "Exim user"
19782 .cindex "uid (user id)" "local delivery"
19783 .cindex "transport" "user, specifying"
19784 This option specifies the user under whose uid the delivery process is to be
19785 run, overriding any uid that may have been set by the router. If the user is
19786 given as a name, the uid is looked up from the password data, and the
19787 associated group is taken as the value of the gid to be used if the &%group%&
19790 For deliveries that use local transports, a user and group are normally
19791 specified explicitly or implicitly (for example, as a result of
19792 &%check_local_user%&) by the router or transport.
19794 .cindex "hints database" "access by remote transport"
19795 For remote transports, you should leave this option unset unless you really are
19796 sure you know what you are doing. When a remote transport is running, it needs
19797 to be able to access Exim's hints databases, because each host may have its own
19799 .ecindex IIDgenoptra1
19800 .ecindex IIDgenoptra2
19801 .ecindex IIDgenoptra3
19808 . ////////////////////////////////////////////////////////////////////////////
19809 . ////////////////////////////////////////////////////////////////////////////
19811 .chapter "Address batching in local transports" "CHAPbatching" &&&
19813 .cindex "transport" "local; address batching in"
19814 The only remote transport (&(smtp)&) is normally configured to handle more than
19815 one address at a time, so that when several addresses are routed to the same
19816 remote host, just one copy of the message is sent. Local transports, however,
19817 normally handle one address at a time. That is, a separate instance of the
19818 transport is run for each address that is routed to the transport. A separate
19819 copy of the message is delivered each time.
19821 .cindex "batched local delivery"
19822 .oindex "&%batch_max%&"
19823 .oindex "&%batch_id%&"
19824 In special cases, it may be desirable to handle several addresses at once in a
19825 local transport, for example:
19828 In an &(appendfile)& transport, when storing messages in files for later
19829 delivery by some other means, a single copy of the message with multiple
19830 recipients saves space.
19832 In an &(lmtp)& transport, when delivering over &"local SMTP"& to some process,
19833 a single copy saves time, and is the normal way LMTP is expected to work.
19835 In a &(pipe)& transport, when passing the message
19836 to a scanner program or
19837 to some other delivery mechanism such as UUCP, multiple recipients may be
19841 These three local transports all have the same options for controlling multiple
19842 (&"batched"&) deliveries, namely &%batch_max%& and &%batch_id%&. To save
19843 repeating the information for each transport, these options are described here.
19845 The &%batch_max%& option specifies the maximum number of addresses that can be
19846 delivered together in a single run of the transport. Its default value is one
19847 (no batching). When more than one address is routed to a transport that has a
19848 &%batch_max%& value greater than one, the addresses are delivered in a batch
19849 (that is, in a single run of the transport with multiple recipients), subject
19850 to certain conditions:
19853 .vindex "&$local_part$&"
19854 If any of the transport's options contain a reference to &$local_part$&, no
19855 batching is possible.
19857 .vindex "&$domain$&"
19858 If any of the transport's options contain a reference to &$domain$&, only
19859 addresses with the same domain are batched.
19861 .cindex "customizing" "batching condition"
19862 If &%batch_id%& is set, it is expanded for each address, and only those
19863 addresses with the same expanded value are batched. This allows you to specify
19864 customized batching conditions. Failure of the expansion for any reason,
19865 including forced failure, disables batching, but it does not stop the delivery
19868 Batched addresses must also have the same errors address (where to send
19869 delivery errors), the same header additions and removals, the same user and
19870 group for the transport, and if a host list is present, the first host must
19874 In the case of the &(appendfile)& and &(pipe)& transports, batching applies
19875 both when the file or pipe command is specified in the transport, and when it
19876 is specified by a &(redirect)& router, but all the batched addresses must of
19877 course be routed to the same file or pipe command. These two transports have an
19878 option called &%use_bsmtp%&, which causes them to deliver the message in
19879 &"batched SMTP"& format, with the envelope represented as SMTP commands. The
19880 &%check_string%& and &%escape_string%& options are forced to the values
19883 escape_string = ".."
19885 when batched SMTP is in use. A full description of the batch SMTP mechanism is
19886 given in section &<<SECTbatchSMTP>>&. The &(lmtp)& transport does not have a
19887 &%use_bsmtp%& option, because it always delivers using the SMTP protocol.
19889 .cindex "&'Envelope-to:'& header line"
19890 If the generic &%envelope_to_add%& option is set for a batching transport, the
19891 &'Envelope-to:'& header that is added to the message contains all the addresses
19892 that are being processed together. If you are using a batching &(appendfile)&
19893 transport without &%use_bsmtp%&, the only way to preserve the recipient
19894 addresses is to set the &%envelope_to_add%& option.
19896 .cindex "&(pipe)& transport" "with multiple addresses"
19897 .vindex "&$pipe_addresses$&"
19898 If you are using a &(pipe)& transport without BSMTP, and setting the
19899 transport's &%command%& option, you can include &$pipe_addresses$& as part of
19900 the command. This is not a true variable; it is a bit of magic that causes each
19901 of the recipient addresses to be inserted into the command as a separate
19902 argument. This provides a way of accessing all the addresses that are being
19903 delivered in the batch. &*Note:*& This is not possible for pipe commands that
19904 are specified by a &(redirect)& router.
19909 . ////////////////////////////////////////////////////////////////////////////
19910 . ////////////////////////////////////////////////////////////////////////////
19912 .chapter "The appendfile transport" "CHAPappendfile"
19913 .scindex IIDapptra1 "&(appendfile)& transport"
19914 .scindex IIDapptra2 "transports" "&(appendfile)&"
19915 .cindex "directory creation"
19916 .cindex "creating directories"
19917 The &(appendfile)& transport delivers a message by appending it to an existing
19918 file, or by creating an entirely new file in a specified directory. Single
19919 files to which messages are appended can be in the traditional Unix mailbox
19920 format, or optionally in the MBX format supported by the Pine MUA and
19921 University of Washington IMAP daemon, &'inter alia'&. When each message is
19922 being delivered as a separate file, &"maildir"& format can optionally be used
19923 to give added protection against failures that happen part-way through the
19924 delivery. A third form of separate-file delivery known as &"mailstore"& is also
19925 supported. For all file formats, Exim attempts to create as many levels of
19926 directory as necessary, provided that &%create_directory%& is set.
19928 The code for the optional formats is not included in the Exim binary by
19929 default. It is necessary to set SUPPORT_MBX, SUPPORT_MAILDIR and/or
19930 SUPPORT_MAILSTORE in &_Local/Makefile_& to have the appropriate code
19933 .cindex "quota" "system"
19934 Exim recognizes system quota errors, and generates an appropriate message. Exim
19935 also supports its own quota control within the transport, for use when the
19936 system facility is unavailable or cannot be used for some reason.
19938 If there is an error while appending to a file (for example, quota exceeded or
19939 partition filled), Exim attempts to reset the file's length and last
19940 modification time back to what they were before. If there is an error while
19941 creating an entirely new file, the new file is removed.
19943 Before appending to a file, a number of security checks are made, and the
19944 file is locked. A detailed description is given below, after the list of
19947 The &(appendfile)& transport is most commonly used for local deliveries to
19948 users' mailboxes. However, it can also be used as a pseudo-remote transport for
19949 putting messages into files for remote delivery by some means other than Exim.
19950 &"Batch SMTP"& format is often used in this case (see the &%use_bsmtp%&
19955 .section "The file and directory options" "SECTfildiropt"
19956 The &%file%& option specifies a single file, to which the message is appended;
19957 the &%directory%& option specifies a directory, in which a new file containing
19958 the message is created. Only one of these two options can be set, and for
19959 normal deliveries to mailboxes, one of them &'must'& be set.
19961 .vindex "&$address_file$&"
19962 .vindex "&$local_part$&"
19963 However, &(appendfile)& is also used for delivering messages to files or
19964 directories whose names (or parts of names) are obtained from alias,
19965 forwarding, or filtering operations (for example, a &%save%& command in a
19966 user's Exim filter). When such a transport is running, &$local_part$& contains
19967 the local part that was aliased or forwarded, and &$address_file$& contains the
19968 name (or partial name) of the file or directory generated by the redirection
19969 operation. There are two cases:
19972 If neither &%file%& nor &%directory%& is set, the redirection operation
19973 must specify an absolute path (one that begins with &`/`&). This is the most
19974 common case when users with local accounts use filtering to sort mail into
19975 different folders. See for example, the &(address_file)& transport in the
19976 default configuration. If the path ends with a slash, it is assumed to be the
19977 name of a directory. A delivery to a directory can also be forced by setting
19978 &%maildir_format%& or &%mailstore_format%&.
19980 If &%file%& or &%directory%& is set for a delivery from a redirection, it is
19981 used to determine the file or directory name for the delivery. Normally, the
19982 contents of &$address_file$& are used in some way in the string expansion.
19986 .cindex "Sieve filter" "configuring &(appendfile)&"
19987 .cindex "Sieve filter" "relative mailbox path handling"
19988 As an example of the second case, consider an environment where users do not
19989 have home directories. They may be permitted to use Exim filter commands of the
19994 or Sieve filter commands of the form:
19996 require "fileinto";
19997 fileinto "folder23";
19999 In this situation, the expansion of &%file%& or &%directory%& in the transport
20000 must transform the relative path into an appropriate absolute file name. In the
20001 case of Sieve filters, the name &'inbox'& must be handled. It is the name that
20002 is used as a result of a &"keep"& action in the filter. This example shows one
20003 way of handling this requirement:
20005 file = ${if eq{$address_file}{inbox} \
20006 {/var/mail/$local_part} \
20007 {${if eq{${substr_0_1:$address_file}}{/} \
20009 {$home/mail/$address_file} \
20013 With this setting of &%file%&, &'inbox'& refers to the standard mailbox
20014 location, absolute paths are used without change, and other folders are in the
20015 &_mail_& directory within the home directory.
20017 &*Note 1*&: While processing an Exim filter, a relative path such as
20018 &_folder23_& is turned into an absolute path if a home directory is known to
20019 the router. In particular, this is the case if &%check_local_user%& is set. If
20020 you want to prevent this happening at routing time, you can set
20021 &%router_home_directory%& empty. This forces the router to pass the relative
20022 path to the transport.
20024 &*Note 2*&: An absolute path in &$address_file$& is not treated specially;
20025 the &%file%& or &%directory%& option is still used if it is set.
20030 .section "Private options for appendfile" "SECID134"
20031 .cindex "options" "&(appendfile)& transport"
20035 .option allow_fifo appendfile boolean false
20036 .cindex "fifo (named pipe)"
20037 .cindex "named pipe (fifo)"
20038 .cindex "pipe" "named (fifo)"
20039 Setting this option permits delivery to named pipes (FIFOs) as well as to
20040 regular files. If no process is reading the named pipe at delivery time, the
20041 delivery is deferred.
20044 .option allow_symlink appendfile boolean false
20045 .cindex "symbolic link" "to mailbox"
20046 .cindex "mailbox" "symbolic link"
20047 By default, &(appendfile)& will not deliver if the path name for the file is
20048 that of a symbolic link. Setting this option relaxes that constraint, but there
20049 are security issues involved in the use of symbolic links. Be sure you know
20050 what you are doing if you set this. Details of exactly what this option affects
20051 are included in the discussion which follows this list of options.
20054 .option batch_id appendfile string&!! unset
20055 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
20056 However, batching is automatically disabled for &(appendfile)& deliveries that
20057 happen as a result of forwarding or aliasing or other redirection directly to a
20061 .option batch_max appendfile integer 1
20062 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
20065 .option check_group appendfile boolean false
20066 When this option is set, the group owner of the file defined by the &%file%&
20067 option is checked to see that it is the same as the group under which the
20068 delivery process is running. The default setting is false because the default
20069 file mode is 0600, which means that the group is irrelevant.
20072 .option check_owner appendfile boolean true
20073 When this option is set, the owner of the file defined by the &%file%& option
20074 is checked to ensure that it is the same as the user under which the delivery
20075 process is running.
20078 .option check_string appendfile string "see below"
20079 .cindex "&""From""& line"
20080 As &(appendfile)& writes the message, the start of each line is tested for
20081 matching &%check_string%&, and if it does, the initial matching characters are
20082 replaced by the contents of &%escape_string%&. The value of &%check_string%& is
20083 a literal string, not a regular expression, and the case of any letters it
20084 contains is significant.
20086 If &%use_bsmtp%& is set the values of &%check_string%& and &%escape_string%&
20087 are forced to &"."& and &".."& respectively, and any settings in the
20088 configuration are ignored. Otherwise, they default to &"From&~"& and
20089 &">From&~"& when the &%file%& option is set, and unset when any of the
20090 &%directory%&, &%maildir%&, or &%mailstore%& options are set.
20092 The default settings, along with &%message_prefix%& and &%message_suffix%&, are
20093 suitable for traditional &"BSD"& mailboxes, where a line beginning with
20094 &"From&~"& indicates the start of a new message. All four options need changing
20095 if another format is used. For example, to deliver to mailboxes in MMDF format:
20096 .cindex "MMDF format mailbox"
20097 .cindex "mailbox" "MMDF format"
20099 check_string = "\1\1\1\1\n"
20100 escape_string = "\1\1\1\1 \n"
20101 message_prefix = "\1\1\1\1\n"
20102 message_suffix = "\1\1\1\1\n"
20104 .option create_directory appendfile boolean true
20105 .cindex "directory creation"
20106 When this option is true, Exim attempts to create any missing superior
20107 directories for the file that it is about to write. A created directory's mode
20108 is given by the &%directory_mode%& option.
20110 The group ownership of a newly created directory is highly dependent on the
20111 operating system (and possibly the file system) that is being used. For
20112 example, in Solaris, if the parent directory has the setgid bit set, its group
20113 is propagated to the child; if not, the currently set group is used. However,
20114 in FreeBSD, the parent's group is always used.
20118 .option create_file appendfile string anywhere
20119 This option constrains the location of files and directories that are created
20120 by this transport. It applies to files defined by the &%file%& option and
20121 directories defined by the &%directory%& option. In the case of maildir
20122 delivery, it applies to the top level directory, not the maildir directories
20125 The option must be set to one of the words &"anywhere"&, &"inhome"&, or
20126 &"belowhome"&. In the second and third cases, a home directory must have been
20127 set for the transport. This option is not useful when an explicit file name is
20128 given for normal mailbox deliveries. It is intended for the case when file
20129 names are generated from users' &_.forward_& files. These are usually handled
20130 by an &(appendfile)& transport called &%address_file%&. See also
20131 &%file_must_exist%&.
20134 .option directory appendfile string&!! unset
20135 This option is mutually exclusive with the &%file%& option, but one of &%file%&
20136 or &%directory%& must be set, unless the delivery is the direct result of a
20137 redirection (see section &<<SECTfildiropt>>&).
20139 When &%directory%& is set, the string is expanded, and the message is delivered
20140 into a new file or files in or below the given directory, instead of being
20141 appended to a single mailbox file. A number of different formats are provided
20142 (see &%maildir_format%& and &%mailstore_format%&), and see section
20143 &<<SECTopdir>>& for further details of this form of delivery.
20146 .option directory_file appendfile string&!! "see below"
20148 .vindex "&$inode$&"
20149 When &%directory%& is set, but neither &%maildir_format%& nor
20150 &%mailstore_format%& is set, &(appendfile)& delivers each message into a file
20151 whose name is obtained by expanding this string. The default value is:
20153 q${base62:$tod_epoch}-$inode
20155 This generates a unique name from the current time, in base 62 form, and the
20156 inode of the file. The variable &$inode$& is available only when expanding this
20160 .option directory_mode appendfile "octal integer" 0700
20161 If &(appendfile)& creates any directories as a result of the
20162 &%create_directory%& option, their mode is specified by this option.
20165 .option escape_string appendfile string "see description"
20166 See &%check_string%& above.
20169 .option file appendfile string&!! unset
20170 This option is mutually exclusive with the &%directory%& option, but one of
20171 &%file%& or &%directory%& must be set, unless the delivery is the direct result
20172 of a redirection (see section &<<SECTfildiropt>>&). The &%file%& option
20173 specifies a single file, to which the message is appended. One or more of
20174 &%use_fcntl_lock%&, &%use_flock_lock%&, or &%use_lockfile%& must be set with
20177 .cindex "NFS" "lock file"
20178 .cindex "locking files"
20179 .cindex "lock files"
20180 If you are using more than one host to deliver over NFS into the same
20181 mailboxes, you should always use lock files.
20183 The string value is expanded for each delivery, and must yield an absolute
20184 path. The most common settings of this option are variations on one of these
20187 file = /var/spool/mail/$local_part
20188 file = /home/$local_part/inbox
20191 .cindex "&""sticky""& bit"
20192 In the first example, all deliveries are done into the same directory. If Exim
20193 is configured to use lock files (see &%use_lockfile%& below) it must be able to
20194 create a file in the directory, so the &"sticky"& bit must be turned on for
20195 deliveries to be possible, or alternatively the &%group%& option can be used to
20196 run the delivery under a group id which has write access to the directory.
20200 .option file_format appendfile string unset
20201 .cindex "file" "mailbox; checking existing format"
20202 This option requests the transport to check the format of an existing file
20203 before adding to it. The check consists of matching a specific string at the
20204 start of the file. The value of the option consists of an even number of
20205 colon-separated strings. The first of each pair is the test string, and the
20206 second is the name of a transport. If the transport associated with a matched
20207 string is not the current transport, control is passed over to the other
20208 transport. For example, suppose the standard &(local_delivery)& transport has
20211 file_format = "From : local_delivery :\
20212 \1\1\1\1\n : local_mmdf_delivery"
20214 Mailboxes that begin with &"From"& are still handled by this transport, but if
20215 a mailbox begins with four binary ones followed by a newline, control is passed
20216 to a transport called &%local_mmdf_delivery%&, which presumably is configured
20217 to do the delivery in MMDF format. If a mailbox does not exist or is empty, it
20218 is assumed to match the current transport. If the start of a mailbox doesn't
20219 match any string, or if the transport named for a given string is not defined,
20220 delivery is deferred.
20223 .option file_must_exist appendfile boolean false
20224 If this option is true, the file specified by the &%file%& option must exist.
20225 A temporary error occurs if it does not, causing delivery to be deferred.
20226 If this option is false, the file is created if it does not exist.
20229 .option lock_fcntl_timeout appendfile time 0s
20230 .cindex "timeout" "mailbox locking"
20231 .cindex "mailbox" "locking, blocking and non-blocking"
20232 .cindex "locking files"
20233 By default, the &(appendfile)& transport uses non-blocking calls to &[fcntl()]&
20234 when locking an open mailbox file. If the call fails, the delivery process
20235 sleeps for &%lock_interval%& and tries again, up to &%lock_retries%& times.
20236 Non-blocking calls are used so that the file is not kept open during the wait
20237 for the lock; the reason for this is to make it as safe as possible for
20238 deliveries over NFS in the case when processes might be accessing an NFS
20239 mailbox without using a lock file. This should not be done, but
20240 misunderstandings and hence misconfigurations are not unknown.
20242 On a busy system, however, the performance of a non-blocking lock approach is
20243 not as good as using a blocking lock with a timeout. In this case, the waiting
20244 is done inside the system call, and Exim's delivery process acquires the lock
20245 and can proceed as soon as the previous lock holder releases it.
20247 If &%lock_fcntl_timeout%& is set to a non-zero time, blocking locks, with that
20248 timeout, are used. There may still be some retrying: the maximum number of
20251 (lock_retries * lock_interval) / lock_fcntl_timeout
20253 rounded up to the next whole number. In other words, the total time during
20254 which &(appendfile)& is trying to get a lock is roughly the same, unless
20255 &%lock_fcntl_timeout%& is set very large.
20257 You should consider setting this option if you are getting a lot of delayed
20258 local deliveries because of errors of the form
20260 failed to lock mailbox /some/file (fcntl)
20263 .option lock_flock_timeout appendfile time 0s
20264 This timeout applies to file locking when using &[flock()]& (see
20265 &%use_flock%&); the timeout operates in a similar manner to
20266 &%lock_fcntl_timeout%&.
20269 .option lock_interval appendfile time 3s
20270 This specifies the time to wait between attempts to lock the file. See below
20271 for details of locking.
20274 .option lock_retries appendfile integer 10
20275 This specifies the maximum number of attempts to lock the file. A value of zero
20276 is treated as 1. See below for details of locking.
20279 .option lockfile_mode appendfile "octal integer" 0600
20280 This specifies the mode of the created lock file, when a lock file is being
20281 used (see &%use_lockfile%& and &%use_mbx_lock%&).
20284 .option lockfile_timeout appendfile time 30m
20285 .cindex "timeout" "mailbox locking"
20286 When a lock file is being used (see &%use_lockfile%&), if a lock file already
20287 exists and is older than this value, it is assumed to have been left behind by
20288 accident, and Exim attempts to remove it.
20291 .option mailbox_filecount appendfile string&!! unset
20292 .cindex "mailbox" "specifying size of"
20293 .cindex "size" "of mailbox"
20294 If this option is set, it is expanded, and the result is taken as the current
20295 number of files in the mailbox. It must be a decimal number, optionally
20296 followed by K or M. This provides a way of obtaining this information from an
20297 external source that maintains the data.
20300 .option mailbox_size appendfile string&!! unset
20301 .cindex "mailbox" "specifying size of"
20302 .cindex "size" "of mailbox"
20303 If this option is set, it is expanded, and the result is taken as the current
20304 size the mailbox. It must be a decimal number, optionally followed by K or M.
20305 This provides a way of obtaining this information from an external source that
20306 maintains the data. This is likely to be helpful for maildir deliveries where
20307 it is computationally expensive to compute the size of a mailbox.
20311 .option maildir_format appendfile boolean false
20312 .cindex "maildir format" "specifying"
20313 If this option is set with the &%directory%& option, the delivery is into a new
20314 file, in the &"maildir"& format that is used by other mail software. When the
20315 transport is activated directly from a &(redirect)& router (for example, the
20316 &(address_file)& transport in the default configuration), setting
20317 &%maildir_format%& causes the path received from the router to be treated as a
20318 directory, whether or not it ends with &`/`&. This option is available only if
20319 SUPPORT_MAILDIR is present in &_Local/Makefile_&. See section
20320 &<<SECTmaildirdelivery>>& below for further details.
20323 .option maildir_quota_directory_regex appendfile string "See below"
20324 .cindex "maildir format" "quota; directories included in"
20325 .cindex "quota" "maildir; directories included in"
20326 This option is relevant only when &%maildir_use_size_file%& is set. It defines
20327 a regular expression for specifying directories, relative to the quota
20328 directory (see &%quota_directory%&), that should be included in the quota
20329 calculation. The default value is:
20331 maildir_quota_directory_regex = ^(?:cur|new|\..*)$
20333 This includes the &_cur_& and &_new_& directories, and any maildir++ folders
20334 (directories whose names begin with a dot). If you want to exclude the
20336 folder from the count (as some sites do), you need to change this setting to
20338 maildir_quota_directory_regex = ^(?:cur|new|\.(?!Trash).*)$
20340 This uses a negative lookahead in the regular expression to exclude the
20341 directory whose name is &_.Trash_&. When a directory is excluded from quota
20342 calculations, quota processing is bypassed for any messages that are delivered
20343 directly into that directory.
20346 .option maildir_retries appendfile integer 10
20347 This option specifies the number of times to retry when writing a file in
20348 &"maildir"& format. See section &<<SECTmaildirdelivery>>& below.
20351 .option maildir_tag appendfile string&!! unset
20352 This option applies only to deliveries in maildir format, and is described in
20353 section &<<SECTmaildirdelivery>>& below.
20356 .option maildir_use_size_file appendfile&!! boolean false
20357 .cindex "maildir format" "&_maildirsize_& file"
20358 The result of string expansion for this option must be a valid boolean value.
20359 If it is true, it enables support for &_maildirsize_& files. Exim
20360 creates a &_maildirsize_& file in a maildir if one does not exist, taking the
20361 quota from the &%quota%& option of the transport. If &%quota%& is unset, the
20362 value is zero. See &%maildir_quota_directory_regex%& above and section
20363 &<<SECTmaildirdelivery>>& below for further details.
20365 .option maildirfolder_create_regex appendfile string unset
20366 .cindex "maildir format" "&_maildirfolder_& file"
20367 .cindex "&_maildirfolder_&, creating"
20368 The value of this option is a regular expression. If it is unset, it has no
20369 effect. Otherwise, before a maildir delivery takes place, the pattern is
20370 matched against the name of the maildir directory, that is, the directory
20371 containing the &_new_& and &_tmp_& subdirectories that will be used for the
20372 delivery. If there is a match, Exim checks for the existence of a file called
20373 &_maildirfolder_& in the directory, and creates it if it does not exist.
20374 See section &<<SECTmaildirdelivery>>& for more details.
20377 .option mailstore_format appendfile boolean false
20378 .cindex "mailstore format" "specifying"
20379 If this option is set with the &%directory%& option, the delivery is into two
20380 new files in &"mailstore"& format. The option is available only if
20381 SUPPORT_MAILSTORE is present in &_Local/Makefile_&. See section &<<SECTopdir>>&
20382 below for further details.
20385 .option mailstore_prefix appendfile string&!! unset
20386 This option applies only to deliveries in mailstore format, and is described in
20387 section &<<SECTopdir>>& below.
20390 .option mailstore_suffix appendfile string&!! unset
20391 This option applies only to deliveries in mailstore format, and is described in
20392 section &<<SECTopdir>>& below.
20395 .option mbx_format appendfile boolean false
20396 .cindex "locking files"
20397 .cindex "file" "locking"
20398 .cindex "file" "MBX format"
20399 .cindex "MBX format, specifying"
20400 This option is available only if Exim has been compiled with SUPPORT_MBX
20401 set in &_Local/Makefile_&. If &%mbx_format%& is set with the &%file%& option,
20402 the message is appended to the mailbox file in MBX format instead of
20403 traditional Unix format. This format is supported by Pine4 and its associated
20404 IMAP and POP daemons, by means of the &'c-client'& library that they all use.
20406 &*Note*&: The &%message_prefix%& and &%message_suffix%& options are not
20407 automatically changed by the use of &%mbx_format%&. They should normally be set
20408 empty when using MBX format, so this option almost always appears in this
20415 If none of the locking options are mentioned in the configuration,
20416 &%use_mbx_lock%& is assumed and the other locking options default to false. It
20417 is possible to specify the other kinds of locking with &%mbx_format%&, but
20418 &%use_fcntl_lock%& and &%use_mbx_lock%& are mutually exclusive. MBX locking
20419 interworks with &'c-client'&, providing for shared access to the mailbox. It
20420 should not be used if any program that does not use this form of locking is
20421 going to access the mailbox, nor should it be used if the mailbox file is NFS
20422 mounted, because it works only when the mailbox is accessed from a single host.
20424 If you set &%use_fcntl_lock%& with an MBX-format mailbox, you cannot use
20425 the standard version of &'c-client'&, because as long as it has a mailbox open
20426 (this means for the whole of a Pine or IMAP session), Exim will not be able to
20427 append messages to it.
20430 .option message_prefix appendfile string&!! "see below"
20431 .cindex "&""From""& line"
20432 The string specified here is expanded and output at the start of every message.
20433 The default is unset unless &%file%& is specified and &%use_bsmtp%& is not set,
20434 in which case it is:
20436 message_prefix = "From ${if def:return_path{$return_path}\
20437 {MAILER-DAEMON}} $tod_bsdinbox\n"
20439 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
20440 &`\n`& to &`\r\n`& in &%message_prefix%&.
20442 .option message_suffix appendfile string&!! "see below"
20443 The string specified here is expanded and output at the end of every message.
20444 The default is unset unless &%file%& is specified and &%use_bsmtp%& is not set,
20445 in which case it is a single newline character. The suffix can be suppressed by
20450 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
20451 &`\n`& to &`\r\n`& in &%message_suffix%&.
20453 .option mode appendfile "octal integer" 0600
20454 If the output file is created, it is given this mode. If it already exists and
20455 has wider permissions, they are reduced to this mode. If it has narrower
20456 permissions, an error occurs unless &%mode_fail_narrower%& is false. However,
20457 if the delivery is the result of a &%save%& command in a filter file specifying
20458 a particular mode, the mode of the output file is always forced to take that
20459 value, and this option is ignored.
20462 .option mode_fail_narrower appendfile boolean true
20463 This option applies in the case when an existing mailbox file has a narrower
20464 mode than that specified by the &%mode%& option. If &%mode_fail_narrower%& is
20465 true, the delivery is deferred (&"mailbox has the wrong mode"&); otherwise Exim
20466 continues with the delivery attempt, using the existing mode of the file.
20469 .option notify_comsat appendfile boolean false
20470 If this option is true, the &'comsat'& daemon is notified after every
20471 successful delivery to a user mailbox. This is the daemon that notifies logged
20472 on users about incoming mail.
20475 .option quota appendfile string&!! unset
20476 .cindex "quota" "imposed by Exim"
20477 This option imposes a limit on the size of the file to which Exim is appending,
20478 or to the total space used in the directory tree when the &%directory%& option
20479 is set. In the latter case, computation of the space used is expensive, because
20480 all the files in the directory (and any sub-directories) have to be
20481 individually inspected and their sizes summed. (See &%quota_size_regex%& and
20482 &%maildir_use_size_file%& for ways to avoid this in environments where users
20483 have no shell access to their mailboxes).
20485 As there is no interlock against two simultaneous deliveries into a
20486 multi-file mailbox, it is possible for the quota to be overrun in this case.
20487 For single-file mailboxes, of course, an interlock is a necessity.
20489 A file's size is taken as its &'used'& value. Because of blocking effects, this
20490 may be a lot less than the actual amount of disk space allocated to the file.
20491 If the sizes of a number of files are being added up, the rounding effect can
20492 become quite noticeable, especially on systems that have large block sizes.
20493 Nevertheless, it seems best to stick to the &'used'& figure, because this is
20494 the obvious value which users understand most easily.
20496 The value of the option is expanded, and must then be a numerical value
20497 (decimal point allowed), optionally followed by one of the letters K, M, or G,
20498 for kilobytes, megabytes, or gigabytes. If Exim is running on a system with
20499 large file support (Linux and FreeBSD have this), mailboxes larger than 2G can
20502 &*Note*&: A value of zero is interpreted as &"no quota"&.
20504 The expansion happens while Exim is running as root, before it changes uid for
20505 the delivery. This means that files that are inaccessible to the end user can
20506 be used to hold quota values that are looked up in the expansion. When delivery
20507 fails because this quota is exceeded, the handling of the error is as for
20508 system quota failures.
20510 By default, Exim's quota checking mimics system quotas, and restricts the
20511 mailbox to the specified maximum size, though the value is not accurate to the
20512 last byte, owing to separator lines and additional headers that may get added
20513 during message delivery. When a mailbox is nearly full, large messages may get
20514 refused even though small ones are accepted, because the size of the current
20515 message is added to the quota when the check is made. This behaviour can be
20516 changed by setting &%quota_is_inclusive%& false. When this is done, the check
20517 for exceeding the quota does not include the current message. Thus, deliveries
20518 continue until the quota has been exceeded; thereafter, no further messages are
20519 delivered. See also &%quota_warn_threshold%&.
20522 .option quota_directory appendfile string&!! unset
20523 This option defines the directory to check for quota purposes when delivering
20524 into individual files. The default is the delivery directory, or, if a file
20525 called &_maildirfolder_& exists in a maildir directory, the parent of the
20526 delivery directory.
20529 .option quota_filecount appendfile string&!! 0
20530 This option applies when the &%directory%& option is set. It limits the total
20531 number of files in the directory (compare the inode limit in system quotas). It
20532 can only be used if &%quota%& is also set. The value is expanded; an expansion
20533 failure causes delivery to be deferred. A value of zero is interpreted as
20537 .option quota_is_inclusive appendfile boolean true
20538 See &%quota%& above.
20541 .option quota_size_regex appendfile string unset
20542 This option applies when one of the delivery modes that writes a separate file
20543 for each message is being used. When Exim wants to find the size of one of
20544 these files in order to test the quota, it first checks &%quota_size_regex%&.
20545 If this is set to a regular expression that matches the file name, and it
20546 captures one string, that string is interpreted as a representation of the
20547 file's size. The value of &%quota_size_regex%& is not expanded.
20549 This feature is useful only when users have no shell access to their mailboxes
20550 &-- otherwise they could defeat the quota simply by renaming the files. This
20551 facility can be used with maildir deliveries, by setting &%maildir_tag%& to add
20552 the file length to the file name. For example:
20554 maildir_tag = ,S=$message_size
20555 quota_size_regex = ,S=(\d+)
20557 An alternative to &$message_size$& is &$message_linecount$&, which contains the
20558 number of lines in the message.
20560 The regular expression should not assume that the length is at the end of the
20561 file name (even though &%maildir_tag%& puts it there) because maildir MUAs
20562 sometimes add other information onto the ends of message file names.
20564 Section &<<SECID136>>& contains further information.
20567 .option quota_warn_message appendfile string&!! "see below"
20568 See below for the use of this option. If it is not set when
20569 &%quota_warn_threshold%& is set, it defaults to
20571 quota_warn_message = "\
20572 To: $local_part@$domain\n\
20573 Subject: Your mailbox\n\n\
20574 This message is automatically created \
20575 by mail delivery software.\n\n\
20576 The size of your mailbox has exceeded \
20577 a warning threshold that is\n\
20578 set by the system administrator.\n"
20582 .option quota_warn_threshold appendfile string&!! 0
20583 .cindex "quota" "warning threshold"
20584 .cindex "mailbox" "size warning"
20585 .cindex "size" "of mailbox"
20586 This option is expanded in the same way as &%quota%& (see above). If the
20587 resulting value is greater than zero, and delivery of the message causes the
20588 size of the file or total space in the directory tree to cross the given
20589 threshold, a warning message is sent. If &%quota%& is also set, the threshold
20590 may be specified as a percentage of it by following the value with a percent
20594 quota_warn_threshold = 75%
20596 If &%quota%& is not set, a setting of &%quota_warn_threshold%& that ends with a
20597 percent sign is ignored.
20599 The warning message itself is specified by the &%quota_warn_message%& option,
20600 and it must start with a &'To:'& header line containing the recipient(s) of the
20601 warning message. These do not necessarily have to include the recipient(s) of
20602 the original message. A &'Subject:'& line should also normally be supplied. You
20603 can include any other header lines that you want. If you do not include a
20604 &'From:'& line, the default is:
20606 From: Mail Delivery System <mailer-daemon@$qualify_domain_sender>
20608 .oindex &%errors_reply_to%&
20609 If you supply a &'Reply-To:'& line, it overrides the global &%errors_reply_to%&
20612 The &%quota%& option does not have to be set in order to use this option; they
20613 are independent of one another except when the threshold is specified as a
20617 .option use_bsmtp appendfile boolean false
20618 .cindex "envelope sender"
20619 If this option is set true, &(appendfile)& writes messages in &"batch SMTP"&
20620 format, with the envelope sender and recipient(s) included as SMTP commands. If
20621 you want to include a leading HELO command with such messages, you can do
20622 so by setting the &%message_prefix%& option. See section &<<SECTbatchSMTP>>&
20623 for details of batch SMTP.
20626 .option use_crlf appendfile boolean false
20627 .cindex "carriage return"
20629 This option causes lines to be terminated with the two-character CRLF sequence
20630 (carriage return, linefeed) instead of just a linefeed character. In the case
20631 of batched SMTP, the byte sequence written to the file is then an exact image
20632 of what would be sent down a real SMTP connection.
20634 &*Note:*& The contents of the &%message_prefix%& and &%message_suffix%& options
20635 (which are used to supply the traditional &"From&~"& and blank line separators
20636 in Berkeley-style mailboxes) are written verbatim, so must contain their own
20637 carriage return characters if these are needed. In cases where these options
20638 have non-empty defaults, the values end with a single linefeed, so they must be
20639 changed to end with &`\r\n`& if &%use_crlf%& is set.
20642 .option use_fcntl_lock appendfile boolean "see below"
20643 This option controls the use of the &[fcntl()]& function to lock a file for
20644 exclusive use when a message is being appended. It is set by default unless
20645 &%use_flock_lock%& is set. Otherwise, it should be turned off only if you know
20646 that all your MUAs use lock file locking. When both &%use_fcntl_lock%& and
20647 &%use_flock_lock%& are unset, &%use_lockfile%& must be set.
20650 .option use_flock_lock appendfile boolean false
20651 This option is provided to support the use of &[flock()]& for file locking, for
20652 the few situations where it is needed. Most modern operating systems support
20653 &[fcntl()]& and &[lockf()]& locking, and these two functions interwork with
20654 each other. Exim uses &[fcntl()]& locking by default.
20656 This option is required only if you are using an operating system where
20657 &[flock()]& is used by programs that access mailboxes (typically MUAs), and
20658 where &[flock()]& does not correctly interwork with &[fcntl()]&. You can use
20659 both &[fcntl()]& and &[flock()]& locking simultaneously if you want.
20661 .cindex "Solaris" "&[flock()]& support"
20662 Not all operating systems provide &[flock()]&. Some versions of Solaris do not
20663 have it (and some, I think, provide a not quite right version built on top of
20664 &[lockf()]&). If the OS does not have &[flock()]&, Exim will be built without
20665 the ability to use it, and any attempt to do so will cause a configuration
20668 &*Warning*&: &[flock()]& locks do not work on NFS files (unless &[flock()]&
20669 is just being mapped onto &[fcntl()]& by the OS).
20672 .option use_lockfile appendfile boolean "see below"
20673 If this option is turned off, Exim does not attempt to create a lock file when
20674 appending to a mailbox file. In this situation, the only locking is by
20675 &[fcntl()]&. You should only turn &%use_lockfile%& off if you are absolutely
20676 sure that every MUA that is ever going to look at your users' mailboxes uses
20677 &[fcntl()]& rather than a lock file, and even then only when you are not
20678 delivering over NFS from more than one host.
20680 .cindex "NFS" "lock file"
20681 In order to append to an NFS file safely from more than one host, it is
20682 necessary to take out a lock &'before'& opening the file, and the lock file
20683 achieves this. Otherwise, even with &[fcntl()]& locking, there is a risk of
20686 The &%use_lockfile%& option is set by default unless &%use_mbx_lock%& is set.
20687 It is not possible to turn both &%use_lockfile%& and &%use_fcntl_lock%& off,
20688 except when &%mbx_format%& is set.
20691 .option use_mbx_lock appendfile boolean "see below"
20692 This option is available only if Exim has been compiled with SUPPORT_MBX
20693 set in &_Local/Makefile_&. Setting the option specifies that special MBX
20694 locking rules be used. It is set by default if &%mbx_format%& is set and none
20695 of the locking options are mentioned in the configuration. The locking rules
20696 are the same as are used by the &'c-client'& library that underlies Pine and
20697 the IMAP4 and POP daemons that come with it (see the discussion below). The
20698 rules allow for shared access to the mailbox. However, this kind of locking
20699 does not work when the mailbox is NFS mounted.
20701 You can set &%use_mbx_lock%& with either (or both) of &%use_fcntl_lock%& and
20702 &%use_flock_lock%& to control what kind of locking is used in implementing the
20703 MBX locking rules. The default is to use &[fcntl()]& if &%use_mbx_lock%& is set
20704 without &%use_fcntl_lock%& or &%use_flock_lock%&.
20709 .section "Operational details for appending" "SECTopappend"
20710 .cindex "appending to a file"
20711 .cindex "file" "appending"
20712 Before appending to a file, the following preparations are made:
20715 If the name of the file is &_/dev/null_&, no action is taken, and a success
20719 .cindex "directory creation"
20720 If any directories on the file's path are missing, Exim creates them if the
20721 &%create_directory%& option is set. A created directory's mode is given by the
20722 &%directory_mode%& option.
20725 If &%file_format%& is set, the format of an existing file is checked. If this
20726 indicates that a different transport should be used, control is passed to that
20730 .cindex "file" "locking"
20731 .cindex "locking files"
20732 .cindex "NFS" "lock file"
20733 If &%use_lockfile%& is set, a lock file is built in a way that will work
20734 reliably over NFS, as follows:
20737 Create a &"hitching post"& file whose name is that of the lock file with the
20738 current time, primary host name, and process id added, by opening for writing
20739 as a new file. If this fails with an access error, delivery is deferred.
20741 Close the hitching post file, and hard link it to the lock file name.
20743 If the call to &[link()]& succeeds, creation of the lock file has succeeded.
20744 Unlink the hitching post name.
20746 Otherwise, use &[stat()]& to get information about the hitching post file, and
20747 then unlink hitching post name. If the number of links is exactly two, creation
20748 of the lock file succeeded but something (for example, an NFS server crash and
20749 restart) caused this fact not to be communicated to the &[link()]& call.
20751 If creation of the lock file failed, wait for &%lock_interval%& and try again,
20752 up to &%lock_retries%& times. However, since any program that writes to a
20753 mailbox should complete its task very quickly, it is reasonable to time out old
20754 lock files that are normally the result of user agent and system crashes. If an
20755 existing lock file is older than &%lockfile_timeout%& Exim attempts to unlink
20756 it before trying again.
20760 A call is made to &[lstat()]& to discover whether the main file exists, and if
20761 so, what its characteristics are. If &[lstat()]& fails for any reason other
20762 than non-existence, delivery is deferred.
20765 .cindex "symbolic link" "to mailbox"
20766 .cindex "mailbox" "symbolic link"
20767 If the file does exist and is a symbolic link, delivery is deferred, unless the
20768 &%allow_symlink%& option is set, in which case the ownership of the link is
20769 checked, and then &[stat()]& is called to find out about the real file, which
20770 is then subjected to the checks below. The check on the top-level link
20771 ownership prevents one user creating a link for another's mailbox in a sticky
20772 directory, though allowing symbolic links in this case is definitely not a good
20773 idea. If there is a chain of symbolic links, the intermediate ones are not
20777 If the file already exists but is not a regular file, or if the file's owner
20778 and group (if the group is being checked &-- see &%check_group%& above) are
20779 different from the user and group under which the delivery is running,
20780 delivery is deferred.
20783 If the file's permissions are more generous than specified, they are reduced.
20784 If they are insufficient, delivery is deferred, unless &%mode_fail_narrower%&
20785 is set false, in which case the delivery is tried using the existing
20789 The file's inode number is saved, and the file is then opened for appending.
20790 If this fails because the file has vanished, &(appendfile)& behaves as if it
20791 hadn't existed (see below). For any other failures, delivery is deferred.
20794 If the file is opened successfully, check that the inode number hasn't
20795 changed, that it is still a regular file, and that the owner and permissions
20796 have not changed. If anything is wrong, defer delivery and freeze the message.
20799 If the file did not exist originally, defer delivery if the &%file_must_exist%&
20800 option is set. Otherwise, check that the file is being created in a permitted
20801 directory if the &%create_file%& option is set (deferring on failure), and then
20802 open for writing as a new file, with the O_EXCL and O_CREAT options,
20803 except when dealing with a symbolic link (the &%allow_symlink%& option must be
20804 set). In this case, which can happen if the link points to a non-existent file,
20805 the file is opened for writing using O_CREAT but not O_EXCL, because
20806 that prevents link following.
20809 .cindex "loop" "while file testing"
20810 If opening fails because the file exists, obey the tests given above for
20811 existing files. However, to avoid looping in a situation where the file is
20812 being continuously created and destroyed, the exists/not-exists loop is broken
20813 after 10 repetitions, and the message is then frozen.
20816 If opening fails with any other error, defer delivery.
20819 .cindex "file" "locking"
20820 .cindex "locking files"
20821 Once the file is open, unless both &%use_fcntl_lock%& and &%use_flock_lock%&
20822 are false, it is locked using &[fcntl()]& or &[flock()]& or both. If
20823 &%use_mbx_lock%& is false, an exclusive lock is requested in each case.
20824 However, if &%use_mbx_lock%& is true, Exim takes out a shared lock on the open
20825 file, and an exclusive lock on the file whose name is
20827 /tmp/.<device-number>.<inode-number>
20829 using the device and inode numbers of the open mailbox file, in accordance with
20830 the MBX locking rules. This file is created with a mode that is specified by
20831 the &%lockfile_mode%& option.
20833 If Exim fails to lock the file, there are two possible courses of action,
20834 depending on the value of the locking timeout. This is obtained from
20835 &%lock_fcntl_timeout%& or &%lock_flock_timeout%&, as appropriate.
20837 If the timeout value is zero, the file is closed, Exim waits for
20838 &%lock_interval%&, and then goes back and re-opens the file as above and tries
20839 to lock it again. This happens up to &%lock_retries%& times, after which the
20840 delivery is deferred.
20842 If the timeout has a value greater than zero, blocking calls to &[fcntl()]& or
20843 &[flock()]& are used (with the given timeout), so there has already been some
20844 waiting involved by the time locking fails. Nevertheless, Exim does not give up
20845 immediately. It retries up to
20847 (lock_retries * lock_interval) / <timeout>
20849 times (rounded up).
20852 At the end of delivery, Exim closes the file (which releases the &[fcntl()]&
20853 and/or &[flock()]& locks) and then deletes the lock file if one was created.
20856 .section "Operational details for delivery to a new file" "SECTopdir"
20857 .cindex "delivery" "to single file"
20858 .cindex "&""From""& line"
20859 When the &%directory%& option is set instead of &%file%&, each message is
20860 delivered into a newly-created file or set of files. When &(appendfile)& is
20861 activated directly from a &(redirect)& router, neither &%file%& nor
20862 &%directory%& is normally set, because the path for delivery is supplied by the
20863 router. (See for example, the &(address_file)& transport in the default
20864 configuration.) In this case, delivery is to a new file if either the path name
20865 ends in &`/`&, or the &%maildir_format%& or &%mailstore_format%& option is set.
20867 No locking is required while writing the message to a new file, so the various
20868 locking options of the transport are ignored. The &"From"& line that by default
20869 separates messages in a single file is not normally needed, nor is the escaping
20870 of message lines that start with &"From"&, and there is no need to ensure a
20871 newline at the end of each message. Consequently, the default values for
20872 &%check_string%&, &%message_prefix%&, and &%message_suffix%& are all unset when
20873 any of &%directory%&, &%maildir_format%&, or &%mailstore_format%& is set.
20875 If Exim is required to check a &%quota%& setting, it adds up the sizes of all
20876 the files in the delivery directory by default. However, you can specify a
20877 different directory by setting &%quota_directory%&. Also, for maildir
20878 deliveries (see below) the &_maildirfolder_& convention is honoured.
20881 .cindex "maildir format"
20882 .cindex "mailstore format"
20883 There are three different ways in which delivery to individual files can be
20884 done, controlled by the settings of the &%maildir_format%& and
20885 &%mailstore_format%& options. Note that code to support maildir or mailstore
20886 formats is not included in the binary unless SUPPORT_MAILDIR or
20887 SUPPORT_MAILSTORE, respectively, is set in &_Local/Makefile_&.
20889 .cindex "directory creation"
20890 In all three cases an attempt is made to create the directory and any necessary
20891 sub-directories if they do not exist, provided that the &%create_directory%&
20892 option is set (the default). The location of a created directory can be
20893 constrained by setting &%create_file%&. A created directory's mode is given by
20894 the &%directory_mode%& option. If creation fails, or if the
20895 &%create_directory%& option is not set when creation is required, delivery is
20900 .section "Maildir delivery" "SECTmaildirdelivery"
20901 .cindex "maildir format" "description of"
20902 If the &%maildir_format%& option is true, Exim delivers each message by writing
20903 it to a file whose name is &_tmp/<stime>.H<mtime>P<pid>.<host>_& in the
20904 directory that is defined by the &%directory%& option (the &"delivery
20905 directory"&). If the delivery is successful, the file is renamed into the
20906 &_new_& subdirectory.
20908 In the file name, <&'stime'&> is the current time of day in seconds, and
20909 <&'mtime'&> is the microsecond fraction of the time. After a maildir delivery,
20910 Exim checks that the time-of-day clock has moved on by at least one microsecond
20911 before terminating the delivery process. This guarantees uniqueness for the
20912 file name. However, as a precaution, Exim calls &[stat()]& for the file before
20913 opening it. If any response other than ENOENT (does not exist) is given,
20914 Exim waits 2 seconds and tries again, up to &%maildir_retries%& times.
20916 Before Exim carries out a maildir delivery, it ensures that subdirectories
20917 called &_new_&, &_cur_&, and &_tmp_& exist in the delivery directory. If they
20918 do not exist, Exim tries to create them and any superior directories in their
20919 path, subject to the &%create_directory%& and &%create_file%& options. If the
20920 &%maildirfolder_create_regex%& option is set, and the regular expression it
20921 contains matches the delivery directory, Exim also ensures that a file called
20922 &_maildirfolder_& exists in the delivery directory. If a missing directory or
20923 &_maildirfolder_& file cannot be created, delivery is deferred.
20925 These features make it possible to use Exim to create all the necessary files
20926 and directories in a maildir mailbox, including subdirectories for maildir++
20927 folders. Consider this example:
20929 maildir_format = true
20930 directory = /var/mail/$local_part\
20931 ${if eq{$local_part_suffix}{}{}\
20932 {/.${substr_1:$local_part_suffix}}}
20933 maildirfolder_create_regex = /\.[^/]+$
20935 If &$local_part_suffix$& is empty (there was no suffix for the local part),
20936 delivery is into a toplevel maildir with a name like &_/var/mail/pimbo_& (for
20937 the user called &'pimbo'&). The pattern in &%maildirfolder_create_regex%& does
20938 not match this name, so Exim will not look for or create the file
20939 &_/var/mail/pimbo/maildirfolder_&, though it will create
20940 &_/var/mail/pimbo/{cur,new,tmp}_& if necessary.
20942 However, if &$local_part_suffix$& contains &`-eximusers`& (for example),
20943 delivery is into the maildir++ folder &_/var/mail/pimbo/.eximusers_&, which
20944 does match &%maildirfolder_create_regex%&. In this case, Exim will create
20945 &_/var/mail/pimbo/.eximusers/maildirfolder_& as well as the three maildir
20946 directories &_/var/mail/pimbo/.eximusers/{cur,new,tmp}_&.
20948 &*Warning:*& Take care when setting &%maildirfolder_create_regex%& that it does
20949 not inadvertently match the toplevel maildir directory, because a
20950 &_maildirfolder_& file at top level would completely break quota calculations.
20952 .cindex "quota" "in maildir delivery"
20953 .cindex "maildir++"
20954 If Exim is required to check a &%quota%& setting before a maildir delivery, and
20955 &%quota_directory%& is not set, it looks for a file called &_maildirfolder_& in
20956 the maildir directory (alongside &_new_&, &_cur_&, &_tmp_&). If this exists,
20957 Exim assumes the directory is a maildir++ folder directory, which is one level
20958 down from the user's top level mailbox directory. This causes it to start at
20959 the parent directory instead of the current directory when calculating the
20960 amount of space used.
20962 One problem with delivering into a multi-file mailbox is that it is
20963 computationally expensive to compute the size of the mailbox for quota
20964 checking. Various approaches have been taken to reduce the amount of work
20965 needed. The next two sections describe two of them. A third alternative is to
20966 use some external process for maintaining the size data, and use the expansion
20967 of the &%mailbox_size%& option as a way of importing it into Exim.
20972 .section "Using tags to record message sizes" "SECID135"
20973 If &%maildir_tag%& is set, the string is expanded for each delivery.
20974 When the maildir file is renamed into the &_new_& sub-directory, the
20975 tag is added to its name. However, if adding the tag takes the length of the
20976 name to the point where the test &[stat()]& call fails with ENAMETOOLONG,
20977 the tag is dropped and the maildir file is created with no tag.
20980 .vindex "&$message_size$&"
20981 Tags can be used to encode the size of files in their names; see
20982 &%quota_size_regex%& above for an example. The expansion of &%maildir_tag%&
20983 happens after the message has been written. The value of the &$message_size$&
20984 variable is set to the number of bytes actually written. If the expansion is
20985 forced to fail, the tag is ignored, but a non-forced failure causes delivery to
20986 be deferred. The expanded tag may contain any printing characters except &"/"&.
20987 Non-printing characters in the string are ignored; if the resulting string is
20988 empty, it is ignored. If it starts with an alphanumeric character, a leading
20989 colon is inserted; this default has not proven to be the path that popular
20990 maildir implementations have chosen (but changing it in Exim would break
20991 backwards compatibility).
20993 For one common implementation, you might set:
20995 maildir_tag = ,S=${message_size}
20997 but you should check the documentation of the other software to be sure.
20999 It is advisable to also set &%quota_size_regex%& when setting &%maildir_tag%&
21000 as this allows Exim to extract the size from your tag, instead of having to
21001 &[stat()]& each message file.
21004 .section "Using a maildirsize file" "SECID136"
21005 .cindex "quota" "in maildir delivery"
21006 .cindex "maildir format" "&_maildirsize_& file"
21007 If &%maildir_use_size_file%& is true, Exim implements the maildir++ rules for
21008 storing quota and message size information in a file called &_maildirsize_&
21009 within the toplevel maildir directory. If this file does not exist, Exim
21010 creates it, setting the quota from the &%quota%& option of the transport. If
21011 the maildir directory itself does not exist, it is created before any attempt
21012 to write a &_maildirsize_& file.
21014 The &_maildirsize_& file is used to hold information about the sizes of
21015 messages in the maildir, thus speeding up quota calculations. The quota value
21016 in the file is just a cache; if the quota is changed in the transport, the new
21017 value overrides the cached value when the next message is delivered. The cache
21018 is maintained for the benefit of other programs that access the maildir and
21019 need to know the quota.
21021 If the &%quota%& option in the transport is unset or zero, the &_maildirsize_&
21022 file is maintained (with a zero quota setting), but no quota is imposed.
21024 A regular expression is available for controlling which directories in the
21025 maildir participate in quota calculations when a &_maildirsizefile_& is in use.
21026 See the description of the &%maildir_quota_directory_regex%& option above for
21030 .section "Mailstore delivery" "SECID137"
21031 .cindex "mailstore format" "description of"
21032 If the &%mailstore_format%& option is true, each message is written as two
21033 files in the given directory. A unique base name is constructed from the
21034 message id and the current delivery process, and the files that are written use
21035 this base name plus the suffixes &_.env_& and &_.msg_&. The &_.env_& file
21036 contains the message's envelope, and the &_.msg_& file contains the message
21037 itself. The base name is placed in the variable &$mailstore_basename$&.
21039 During delivery, the envelope is first written to a file with the suffix
21040 &_.tmp_&. The &_.msg_& file is then written, and when it is complete, the
21041 &_.tmp_& file is renamed as the &_.env_& file. Programs that access messages in
21042 mailstore format should wait for the presence of both a &_.msg_& and a &_.env_&
21043 file before accessing either of them. An alternative approach is to wait for
21044 the absence of a &_.tmp_& file.
21046 The envelope file starts with any text defined by the &%mailstore_prefix%&
21047 option, expanded and terminated by a newline if there isn't one. Then follows
21048 the sender address on one line, then all the recipient addresses, one per line.
21049 There can be more than one recipient only if the &%batch_max%& option is set
21050 greater than one. Finally, &%mailstore_suffix%& is expanded and the result
21051 appended to the file, followed by a newline if it does not end with one.
21053 If expansion of &%mailstore_prefix%& or &%mailstore_suffix%& ends with a forced
21054 failure, it is ignored. Other expansion errors are treated as serious
21055 configuration errors, and delivery is deferred. The variable
21056 &$mailstore_basename$& is available for use during these expansions.
21059 .section "Non-special new file delivery" "SECID138"
21060 If neither &%maildir_format%& nor &%mailstore_format%& is set, a single new
21061 file is created directly in the named directory. For example, when delivering
21062 messages into files in batched SMTP format for later delivery to some host (see
21063 section &<<SECTbatchSMTP>>&), a setting such as
21065 directory = /var/bsmtp/$host
21067 might be used. A message is written to a file with a temporary name, which is
21068 then renamed when the delivery is complete. The final name is obtained by
21069 expanding the contents of the &%directory_file%& option.
21070 .ecindex IIDapptra1
21071 .ecindex IIDapptra2
21078 . ////////////////////////////////////////////////////////////////////////////
21079 . ////////////////////////////////////////////////////////////////////////////
21081 .chapter "The autoreply transport" "CHID8"
21082 .scindex IIDauttra1 "transports" "&(autoreply)&"
21083 .scindex IIDauttra2 "&(autoreply)& transport"
21084 The &(autoreply)& transport is not a true transport in that it does not cause
21085 the message to be transmitted. Instead, it generates a new mail message as an
21086 automatic reply to the incoming message. &'References:'& and
21087 &'Auto-Submitted:'& header lines are included. These are constructed according
21088 to the rules in RFCs 2822 and 3834, respectively.
21090 If the router that passes the message to this transport does not have the
21091 &%unseen%& option set, the original message (for the current recipient) is not
21092 delivered anywhere. However, when the &%unseen%& option is set on the router
21093 that passes the message to this transport, routing of the address continues, so
21094 another router can set up a normal message delivery.
21097 The &(autoreply)& transport is usually run as the result of mail filtering, a
21098 &"vacation"& message being the standard example. However, it can also be run
21099 directly from a router like any other transport. To reduce the possibility of
21100 message cascades, messages created by the &(autoreply)& transport always have
21101 empty envelope sender addresses, like bounce messages.
21103 The parameters of the message to be sent can be specified in the configuration
21104 by options described below. However, these are used only when the address
21105 passed to the transport does not contain its own reply information. When the
21106 transport is run as a consequence of a
21108 or &%vacation%& command in a filter file, the parameters of the message are
21109 supplied by the filter, and passed with the address. The transport's options
21110 that define the message are then ignored (so they are not usually set in this
21111 case). The message is specified entirely by the filter or by the transport; it
21112 is never built from a mixture of options. However, the &%file_optional%&,
21113 &%mode%&, and &%return_message%& options apply in all cases.
21115 &(Autoreply)& is implemented as a local transport. When used as a result of a
21116 command in a user's filter file, &(autoreply)& normally runs under the uid and
21117 gid of the user, and with appropriate current and home directories (see chapter
21118 &<<CHAPenvironment>>&).
21120 There is a subtle difference between routing a message to a &(pipe)& transport
21121 that generates some text to be returned to the sender, and routing it to an
21122 &(autoreply)& transport. This difference is noticeable only if more than one
21123 address from the same message is so handled. In the case of a pipe, the
21124 separate outputs from the different addresses are gathered up and returned to
21125 the sender in a single message, whereas if &(autoreply)& is used, a separate
21126 message is generated for each address that is passed to it.
21128 Non-printing characters are not permitted in the header lines generated for the
21129 message that &(autoreply)& creates, with the exception of newlines that are
21130 immediately followed by white space. If any non-printing characters are found,
21131 the transport defers.
21132 Whether characters with the top bit set count as printing characters or not is
21133 controlled by the &%print_topbitchars%& global option.
21135 If any of the generic options for manipulating headers (for example,
21136 &%headers_add%&) are set on an &(autoreply)& transport, they apply to the copy
21137 of the original message that is included in the generated message when
21138 &%return_message%& is set. They do not apply to the generated message itself.
21140 .vindex "&$sender_address$&"
21141 If the &(autoreply)& transport receives return code 2 from Exim when it submits
21142 the message, indicating that there were no recipients, it does not treat this
21143 as an error. This means that autoreplies sent to &$sender_address$& when this
21144 is empty (because the incoming message is a bounce message) do not cause
21145 problems. They are just discarded.
21149 .section "Private options for autoreply" "SECID139"
21150 .cindex "options" "&(autoreply)& transport"
21152 .option bcc autoreply string&!! unset
21153 This specifies the addresses that are to receive &"blind carbon copies"& of the
21154 message when the message is specified by the transport.
21157 .option cc autoreply string&!! unset
21158 This specifies recipients of the message and the contents of the &'Cc:'& header
21159 when the message is specified by the transport.
21162 .option file autoreply string&!! unset
21163 The contents of the file are sent as the body of the message when the message
21164 is specified by the transport. If both &%file%& and &%text%& are set, the text
21165 string comes first.
21168 .option file_expand autoreply boolean false
21169 If this is set, the contents of the file named by the &%file%& option are
21170 subjected to string expansion as they are added to the message.
21173 .option file_optional autoreply boolean false
21174 If this option is true, no error is generated if the file named by the &%file%&
21175 option or passed with the address does not exist or cannot be read.
21178 .option from autoreply string&!! unset
21179 This specifies the contents of the &'From:'& header when the message is
21180 specified by the transport.
21183 .option headers autoreply string&!! unset
21184 This specifies additional RFC 2822 headers that are to be added to the message
21185 when the message is specified by the transport. Several can be given by using
21186 &"\n"& to separate them. There is no check on the format.
21189 .option log autoreply string&!! unset
21190 This option names a file in which a record of every message sent is logged when
21191 the message is specified by the transport.
21194 .option mode autoreply "octal integer" 0600
21195 If either the log file or the &"once"& file has to be created, this mode is
21199 .option never_mail autoreply "address list&!!" unset
21200 If any run of the transport creates a message with a recipient that matches any
21201 item in the list, that recipient is quietly discarded. If all recipients are
21202 discarded, no message is created. This applies both when the recipients are
21203 generated by a filter and when they are specified in the transport.
21207 .option once autoreply string&!! unset
21208 This option names a file or DBM database in which a record of each &'To:'&
21209 recipient is kept when the message is specified by the transport. &*Note*&:
21210 This does not apply to &'Cc:'& or &'Bcc:'& recipients.
21212 If &%once%& is unset, or is set to an empty string, the message is always sent.
21213 By default, if &%once%& is set to a non-empty file name, the message
21214 is not sent if a potential recipient is already listed in the database.
21215 However, if the &%once_repeat%& option specifies a time greater than zero, the
21216 message is sent if that much time has elapsed since a message was last sent to
21217 this recipient. A setting of zero time for &%once_repeat%& (the default)
21218 prevents a message from being sent a second time &-- in this case, zero means
21221 If &%once_file_size%& is zero, a DBM database is used to remember recipients,
21222 and it is allowed to grow as large as necessary. If &%once_file_size%& is set
21223 greater than zero, it changes the way Exim implements the &%once%& option.
21224 Instead of using a DBM file to record every recipient it sends to, it uses a
21225 regular file, whose size will never get larger than the given value.
21227 In the file, Exim keeps a linear list of recipient addresses and the times at
21228 which they were sent messages. If the file is full when a new address needs to
21229 be added, the oldest address is dropped. If &%once_repeat%& is not set, this
21230 means that a given recipient may receive multiple messages, but at
21231 unpredictable intervals that depend on the rate of turnover of addresses in the
21232 file. If &%once_repeat%& is set, it specifies a maximum time between repeats.
21235 .option once_file_size autoreply integer 0
21236 See &%once%& above.
21239 .option once_repeat autoreply time&!! 0s
21240 See &%once%& above.
21241 After expansion, the value of this option must be a valid time value.
21244 .option reply_to autoreply string&!! unset
21245 This specifies the contents of the &'Reply-To:'& header when the message is
21246 specified by the transport.
21249 .option return_message autoreply boolean false
21250 If this is set, a copy of the original message is returned with the new
21251 message, subject to the maximum size set in the &%return_size_limit%& global
21252 configuration option.
21255 .option subject autoreply string&!! unset
21256 This specifies the contents of the &'Subject:'& header when the message is
21257 specified by the transport. It is tempting to quote the original subject in
21258 automatic responses. For example:
21260 subject = Re: $h_subject:
21262 There is a danger in doing this, however. It may allow a third party to
21263 subscribe your users to an opt-in mailing list, provided that the list accepts
21264 bounce messages as subscription confirmations. Well-managed lists require a
21265 non-bounce message to confirm a subscription, so the danger is relatively
21270 .option text autoreply string&!! unset
21271 This specifies a single string to be used as the body of the message when the
21272 message is specified by the transport. If both &%text%& and &%file%& are set,
21273 the text comes first.
21276 .option to autoreply string&!! unset
21277 This specifies recipients of the message and the contents of the &'To:'& header
21278 when the message is specified by the transport.
21279 .ecindex IIDauttra1
21280 .ecindex IIDauttra2
21285 . ////////////////////////////////////////////////////////////////////////////
21286 . ////////////////////////////////////////////////////////////////////////////
21288 .chapter "The lmtp transport" "CHAPLMTP"
21289 .cindex "transports" "&(lmtp)&"
21290 .cindex "&(lmtp)& transport"
21291 .cindex "LMTP" "over a pipe"
21292 .cindex "LMTP" "over a socket"
21293 The &(lmtp)& transport runs the LMTP protocol (RFC 2033) over a pipe to a
21295 or by interacting with a Unix domain socket.
21296 This transport is something of a cross between the &(pipe)& and &(smtp)&
21297 transports. Exim also has support for using LMTP over TCP/IP; this is
21298 implemented as an option for the &(smtp)& transport. Because LMTP is expected
21299 to be of minority interest, the default build-time configure in &_src/EDITME_&
21300 has it commented out. You need to ensure that
21304 .cindex "options" "&(lmtp)& transport"
21305 is present in your &_Local/Makefile_& in order to have the &(lmtp)& transport
21306 included in the Exim binary. The private options of the &(lmtp)& transport are
21309 .option batch_id lmtp string&!! unset
21310 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
21313 .option batch_max lmtp integer 1
21314 This limits the number of addresses that can be handled in a single delivery.
21315 Most LMTP servers can handle several addresses at once, so it is normally a
21316 good idea to increase this value. See the description of local delivery
21317 batching in chapter &<<CHAPbatching>>&.
21320 .option command lmtp string&!! unset
21321 This option must be set if &%socket%& is not set. The string is a command which
21322 is run in a separate process. It is split up into a command name and list of
21323 arguments, each of which is separately expanded (so expansion cannot change the
21324 number of arguments). The command is run directly, not via a shell. The message
21325 is passed to the new process using the standard input and output to operate the
21328 .option ignore_quota lmtp boolean false
21329 .cindex "LMTP" "ignoring quota errors"
21330 If this option is set true, the string &`IGNOREQUOTA`& is added to RCPT
21331 commands, provided that the LMTP server has advertised support for IGNOREQUOTA
21332 in its response to the LHLO command.
21334 .option socket lmtp string&!! unset
21335 This option must be set if &%command%& is not set. The result of expansion must
21336 be the name of a Unix domain socket. The transport connects to the socket and
21337 delivers the message to it using the LMTP protocol.
21340 .option timeout lmtp time 5m
21341 The transport is aborted if the created process or Unix domain socket does not
21342 respond to LMTP commands or message input within this timeout. Delivery
21343 is deferred, and will be tried again later. Here is an example of a typical
21348 command = /some/local/lmtp/delivery/program
21352 This delivers up to 20 addresses at a time, in a mixture of domains if
21353 necessary, running as the user &'exim'&.
21357 . ////////////////////////////////////////////////////////////////////////////
21358 . ////////////////////////////////////////////////////////////////////////////
21360 .chapter "The pipe transport" "CHAPpipetransport"
21361 .scindex IIDpiptra1 "transports" "&(pipe)&"
21362 .scindex IIDpiptra2 "&(pipe)& transport"
21363 The &(pipe)& transport is used to deliver messages via a pipe to a command
21364 running in another process. One example is the use of &(pipe)& as a
21365 pseudo-remote transport for passing messages to some other delivery mechanism
21366 (such as UUCP). Another is the use by individual users to automatically process
21367 their incoming messages. The &(pipe)& transport can be used in one of the
21371 .vindex "&$local_part$&"
21372 A router routes one address to a transport in the normal way, and the
21373 transport is configured as a &(pipe)& transport. In this case, &$local_part$&
21374 contains the local part of the address (as usual), and the command that is run
21375 is specified by the &%command%& option on the transport.
21377 .vindex "&$pipe_addresses$&"
21378 If the &%batch_max%& option is set greater than 1 (the default is 1), the
21379 transport can handle more than one address in a single run. In this case, when
21380 more than one address is routed to the transport, &$local_part$& is not set
21381 (because it is not unique). However, the pseudo-variable &$pipe_addresses$&
21382 (described in section &<<SECThowcommandrun>>& below) contains all the addresses
21383 that are routed to the transport.
21385 .vindex "&$address_pipe$&"
21386 A router redirects an address directly to a pipe command (for example, from an
21387 alias or forward file). In this case, &$address_pipe$& contains the text of the
21388 pipe command, and the &%command%& option on the transport is ignored. If only
21389 one address is being transported (&%batch_max%& is not greater than one, or
21390 only one address was redirected to this pipe command), &$local_part$& contains
21391 the local part that was redirected.
21395 The &(pipe)& transport is a non-interactive delivery method. Exim can also
21396 deliver messages over pipes using the LMTP interactive protocol. This is
21397 implemented by the &(lmtp)& transport.
21399 In the case when &(pipe)& is run as a consequence of an entry in a local user's
21400 &_.forward_& file, the command runs under the uid and gid of that user. In
21401 other cases, the uid and gid have to be specified explicitly, either on the
21402 transport or on the router that handles the address. Current and &"home"&
21403 directories are also controllable. See chapter &<<CHAPenvironment>>& for
21404 details of the local delivery environment and chapter &<<CHAPbatching>>&
21405 for a discussion of local delivery batching.
21408 .section "Concurrent delivery" "SECID140"
21409 If two messages arrive at almost the same time, and both are routed to a pipe
21410 delivery, the two pipe transports may be run concurrently. You must ensure that
21411 any pipe commands you set up are robust against this happening. If the commands
21412 write to a file, the &%exim_lock%& utility might be of use.
21417 .section "Returned status and data" "SECID141"
21418 .cindex "&(pipe)& transport" "returned data"
21419 If the command exits with a non-zero return code, the delivery is deemed to
21420 have failed, unless either the &%ignore_status%& option is set (in which case
21421 the return code is treated as zero), or the return code is one of those listed
21422 in the &%temp_errors%& option, which are interpreted as meaning &"try again
21423 later"&. In this case, delivery is deferred. Details of a permanent failure are
21424 logged, but are not included in the bounce message, which merely contains
21425 &"local delivery failed"&.
21427 If the command exits on a signal and the &%freeze_signal%& option is set then
21428 the message will be frozen in the queue. If that option is not set, a bounce
21429 will be sent as normal.
21431 If the return code is greater than 128 and the command being run is a shell
21432 script, it normally means that the script was terminated by a signal whose
21433 value is the return code minus 128. The &%freeze_signal%& option does not
21434 apply in this case.
21436 If Exim is unable to run the command (that is, if &[execve()]& fails), the
21437 return code is set to 127. This is the value that a shell returns if it is
21438 asked to run a non-existent command. The wording for the log line suggests that
21439 a non-existent command may be the problem.
21441 The &%return_output%& option can affect the result of a pipe delivery. If it is
21442 set and the command produces any output on its standard output or standard
21443 error streams, the command is considered to have failed, even if it gave a zero
21444 return code or if &%ignore_status%& is set. The output from the command is
21445 included as part of the bounce message. The &%return_fail_output%& option is
21446 similar, except that output is returned only when the command exits with a
21447 failure return code, that is, a value other than zero or a code that matches
21452 .section "How the command is run" "SECThowcommandrun"
21453 .cindex "&(pipe)& transport" "path for command"
21454 The command line is (by default) broken down into a command name and arguments
21455 by the &(pipe)& transport itself. The &%allow_commands%& and
21456 &%restrict_to_path%& options can be used to restrict the commands that may be
21459 .cindex "quoting" "in pipe command"
21460 Unquoted arguments are delimited by white space. If an argument appears in
21461 double quotes, backslash is interpreted as an escape character in the usual
21462 way. If an argument appears in single quotes, no escaping is done.
21464 String expansion is applied to the command line except when it comes from a
21465 traditional &_.forward_& file (commands from a filter file are expanded). The
21466 expansion is applied to each argument in turn rather than to the whole line.
21467 For this reason, any string expansion item that contains white space must be
21468 quoted so as to be contained within a single argument. A setting such as
21470 command = /some/path ${if eq{$local_part}{postmaster}{xx}{yy}}
21472 will not work, because the expansion item gets split between several
21473 arguments. You have to write
21475 command = /some/path "${if eq{$local_part}{postmaster}{xx}{yy}}"
21477 to ensure that it is all in one argument. The expansion is done in this way,
21478 argument by argument, so that the number of arguments cannot be changed as a
21479 result of expansion, and quotes or backslashes in inserted variables do not
21480 interact with external quoting. However, this leads to problems if you want to
21481 generate multiple arguments (or the command name plus arguments) from a single
21482 expansion. In this situation, the simplest solution is to use a shell. For
21485 command = /bin/sh -c ${lookup{$local_part}lsearch{/some/file}}
21488 .cindex "transport" "filter"
21489 .cindex "filter" "transport filter"
21490 .vindex "&$pipe_addresses$&"
21491 Special handling takes place when an argument consists of precisely the text
21492 &`$pipe_addresses`&. This is not a general expansion variable; the only
21493 place this string is recognized is when it appears as an argument for a pipe or
21494 transport filter command. It causes each address that is being handled to be
21495 inserted in the argument list at that point &'as a separate argument'&. This
21496 avoids any problems with spaces or shell metacharacters, and is of use when a
21497 &(pipe)& transport is handling groups of addresses in a batch.
21499 After splitting up into arguments and expansion, the resulting command is run
21500 in a subprocess directly from the transport, &'not'& under a shell. The
21501 message that is being delivered is supplied on the standard input, and the
21502 standard output and standard error are both connected to a single pipe that is
21503 read by Exim. The &%max_output%& option controls how much output the command
21504 may produce, and the &%return_output%& and &%return_fail_output%& options
21505 control what is done with it.
21507 Not running the command under a shell (by default) lessens the security risks
21508 in cases when a command from a user's filter file is built out of data that was
21509 taken from an incoming message. If a shell is required, it can of course be
21510 explicitly specified as the command to be run. However, there are circumstances
21511 where existing commands (for example, in &_.forward_& files) expect to be run
21512 under a shell and cannot easily be modified. To allow for these cases, there is
21513 an option called &%use_shell%&, which changes the way the &(pipe)& transport
21514 works. Instead of breaking up the command line as just described, it expands it
21515 as a single string and passes the result to &_/bin/sh_&. The
21516 &%restrict_to_path%& option and the &$pipe_addresses$& facility cannot be used
21517 with &%use_shell%&, and the whole mechanism is inherently less secure.
21521 .section "Environment variables" "SECTpipeenv"
21522 .cindex "&(pipe)& transport" "environment for command"
21523 .cindex "environment for pipe transport"
21524 The environment variables listed below are set up when the command is invoked.
21525 This list is a compromise for maximum compatibility with other MTAs. Note that
21526 the &%environment%& option can be used to add additional variables to this
21529 &`DOMAIN `& the domain of the address
21530 &`HOME `& the home directory, if set
21531 &`HOST `& the host name when called from a router (see below)
21532 &`LOCAL_PART `& see below
21533 &`LOCAL_PART_PREFIX `& see below
21534 &`LOCAL_PART_SUFFIX `& see below
21535 &`LOGNAME `& see below
21536 &`MESSAGE_ID `& Exim's local ID for the message
21537 &`PATH `& as specified by the &%path%& option below
21538 &`QUALIFY_DOMAIN `& the sender qualification domain
21539 &`RECIPIENT `& the complete recipient address
21540 &`SENDER `& the sender of the message (empty if a bounce)
21541 &`SHELL `& &`/bin/sh`&
21542 &`TZ `& the value of the &%timezone%& option, if set
21543 &`USER `& see below
21545 When a &(pipe)& transport is called directly from (for example) an &(accept)&
21546 router, LOCAL_PART is set to the local part of the address. When it is
21547 called as a result of a forward or alias expansion, LOCAL_PART is set to
21548 the local part of the address that was expanded. In both cases, any affixes are
21549 removed from the local part, and made available in LOCAL_PART_PREFIX and
21550 LOCAL_PART_SUFFIX, respectively. LOGNAME and USER are set to the
21551 same value as LOCAL_PART for compatibility with other MTAs.
21554 HOST is set only when a &(pipe)& transport is called from a router that
21555 associates hosts with an address, typically when using &(pipe)& as a
21556 pseudo-remote transport. HOST is set to the first host name specified by
21560 If the transport's generic &%home_directory%& option is set, its value is used
21561 for the HOME environment variable. Otherwise, a home directory may be set
21562 by the router's &%transport_home_directory%& option, which defaults to the
21563 user's home directory if &%check_local_user%& is set.
21566 .section "Private options for pipe" "SECID142"
21567 .cindex "options" "&(pipe)& transport"
21571 .option allow_commands pipe "string list&!!" unset
21572 .cindex "&(pipe)& transport" "permitted commands"
21573 The string is expanded, and is then interpreted as a colon-separated list of
21574 permitted commands. If &%restrict_to_path%& is not set, the only commands
21575 permitted are those in the &%allow_commands%& list. They need not be absolute
21576 paths; the &%path%& option is still used for relative paths. If
21577 &%restrict_to_path%& is set with &%allow_commands%&, the command must either be
21578 in the &%allow_commands%& list, or a name without any slashes that is found on
21579 the path. In other words, if neither &%allow_commands%& nor
21580 &%restrict_to_path%& is set, there is no restriction on the command, but
21581 otherwise only commands that are permitted by one or the other are allowed. For
21584 allow_commands = /usr/bin/vacation
21586 and &%restrict_to_path%& is not set, the only permitted command is
21587 &_/usr/bin/vacation_&. The &%allow_commands%& option may not be set if
21588 &%use_shell%& is set.
21591 .option batch_id pipe string&!! unset
21592 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
21595 .option batch_max pipe integer 1
21596 This limits the number of addresses that can be handled in a single delivery.
21597 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
21600 .option check_string pipe string unset
21601 As &(pipe)& writes the message, the start of each line is tested for matching
21602 &%check_string%&, and if it does, the initial matching characters are replaced
21603 by the contents of &%escape_string%&, provided both are set. The value of
21604 &%check_string%& is a literal string, not a regular expression, and the case of
21605 any letters it contains is significant. When &%use_bsmtp%& is set, the contents
21606 of &%check_string%& and &%escape_string%& are forced to values that implement
21607 the SMTP escaping protocol. Any settings made in the configuration file are
21611 .option command pipe string&!! unset
21612 This option need not be set when &(pipe)& is being used to deliver to pipes
21613 obtained directly from address redirections. In other cases, the option must be
21614 set, to provide a command to be run. It need not yield an absolute path (see
21615 the &%path%& option below). The command is split up into separate arguments by
21616 Exim, and each argument is separately expanded, as described in section
21617 &<<SECThowcommandrun>>& above.
21620 .option environment pipe string&!! unset
21621 .cindex "&(pipe)& transport" "environment for command"
21622 .cindex "environment for &(pipe)& transport"
21623 This option is used to add additional variables to the environment in which the
21624 command runs (see section &<<SECTpipeenv>>& for the default list). Its value is
21625 a string which is expanded, and then interpreted as a colon-separated list of
21626 environment settings of the form <&'name'&>=<&'value'&>.
21629 .option escape_string pipe string unset
21630 See &%check_string%& above.
21633 .option freeze_exec_fail pipe boolean false
21634 .cindex "exec failure"
21635 .cindex "failure of exec"
21636 .cindex "&(pipe)& transport" "failure of exec"
21637 Failure to exec the command in a pipe transport is by default treated like
21638 any other failure while running the command. However, if &%freeze_exec_fail%&
21639 is set, failure to exec is treated specially, and causes the message to be
21640 frozen, whatever the setting of &%ignore_status%&.
21643 .option freeze_signal pipe boolean false
21644 .cindex "signal exit"
21645 .cindex "&(pipe)& transport", "signal exit"
21646 Normally if the process run by a command in a pipe transport exits on a signal,
21647 a bounce message is sent. If &%freeze_signal%& is set, the message will be
21648 frozen in Exim's queue instead.
21651 .option ignore_status pipe boolean false
21652 If this option is true, the status returned by the subprocess that is set up to
21653 run the command is ignored, and Exim behaves as if zero had been returned.
21654 Otherwise, a non-zero status or termination by signal causes an error return
21655 from the transport unless the status value is one of those listed in
21656 &%temp_errors%&; these cause the delivery to be deferred and tried again later.
21658 &*Note*&: This option does not apply to timeouts, which do not return a status.
21659 See the &%timeout_defer%& option for how timeouts are handled.
21661 .option log_defer_output pipe boolean false
21662 .cindex "&(pipe)& transport" "logging output"
21663 If this option is set, and the status returned by the command is
21664 one of the codes listed in &%temp_errors%& (that is, delivery was deferred),
21665 and any output was produced, the first line of it is written to the main log.
21668 .option log_fail_output pipe boolean false
21669 If this option is set, and the command returns any output, and also ends with a
21670 return code that is neither zero nor one of the return codes listed in
21671 &%temp_errors%& (that is, the delivery failed), the first line of output is
21672 written to the main log. This option and &%log_output%& are mutually exclusive.
21673 Only one of them may be set.
21677 .option log_output pipe boolean false
21678 If this option is set and the command returns any output, the first line of
21679 output is written to the main log, whatever the return code. This option and
21680 &%log_fail_output%& are mutually exclusive. Only one of them may be set.
21684 .option max_output pipe integer 20K
21685 This specifies the maximum amount of output that the command may produce on its
21686 standard output and standard error file combined. If the limit is exceeded, the
21687 process running the command is killed. This is intended as a safety measure to
21688 catch runaway processes. The limit is applied independently of the settings of
21689 the options that control what is done with such output (for example,
21690 &%return_output%&). Because of buffering effects, the amount of output may
21691 exceed the limit by a small amount before Exim notices.
21694 .option message_prefix pipe string&!! "see below"
21695 The string specified here is expanded and output at the start of every message.
21696 The default is unset if &%use_bsmtp%& is set. Otherwise it is
21699 From ${if def:return_path{$return_path}{MAILER-DAEMON}}\
21703 .cindex "&%tmail%&"
21704 .cindex "&""From""& line"
21705 This is required by the commonly used &_/usr/bin/vacation_& program.
21706 However, it must &'not'& be present if delivery is to the Cyrus IMAP server,
21707 or to the &%tmail%& local delivery agent. The prefix can be suppressed by
21712 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
21713 &`\n`& to &`\r\n`& in &%message_prefix%&.
21716 .option message_suffix pipe string&!! "see below"
21717 The string specified here is expanded and output at the end of every message.
21718 The default is unset if &%use_bsmtp%& is set. Otherwise it is a single newline.
21719 The suffix can be suppressed by setting
21723 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
21724 &`\n`& to &`\r\n`& in &%message_suffix%&.
21727 .option path pipe string "see below"
21728 This option specifies the string that is set up in the PATH environment
21729 variable of the subprocess. The default is:
21733 If the &%command%& option does not yield an absolute path name, the command is
21734 sought in the PATH directories, in the usual way. &*Warning*&: This does not
21735 apply to a command specified as a transport filter.
21738 .option permit_coredump pipe boolean false
21739 Normally Exim inhibits core-dumps during delivery. If you have a need to get
21740 a core-dump of a pipe command, enable this command. This enables core-dumps
21741 during delivery and affects both the Exim binary and the pipe command run.
21742 It is recommended that this option remain off unless and until you have a need
21743 for it and that this only be enabled when needed, as the risk of excessive
21744 resource consumption can be quite high. Note also that Exim is typically
21745 installed as a setuid binary and most operating systems will inhibit coredumps
21746 of these by default, so further OS-specific action may be required.
21749 .option pipe_as_creator pipe boolean false
21750 .cindex "uid (user id)" "local delivery"
21751 If the generic &%user%& option is not set and this option is true, the delivery
21752 process is run under the uid that was in force when Exim was originally called
21753 to accept the message. If the group id is not otherwise set (via the generic
21754 &%group%& option), the gid that was in force when Exim was originally called to
21755 accept the message is used.
21758 .option restrict_to_path pipe boolean false
21759 When this option is set, any command name not listed in &%allow_commands%& must
21760 contain no slashes. The command is searched for only in the directories listed
21761 in the &%path%& option. This option is intended for use in the case when a pipe
21762 command has been generated from a user's &_.forward_& file. This is usually
21763 handled by a &(pipe)& transport called &%address_pipe%&.
21766 .option return_fail_output pipe boolean false
21767 If this option is true, and the command produced any output and ended with a
21768 return code other than zero or one of the codes listed in &%temp_errors%& (that
21769 is, the delivery failed), the output is returned in the bounce message.
21770 However, if the message has a null sender (that is, it is itself a bounce
21771 message), output from the command is discarded. This option and
21772 &%return_output%& are mutually exclusive. Only one of them may be set.
21776 .option return_output pipe boolean false
21777 If this option is true, and the command produced any output, the delivery is
21778 deemed to have failed whatever the return code from the command, and the output
21779 is returned in the bounce message. Otherwise, the output is just discarded.
21780 However, if the message has a null sender (that is, it is a bounce message),
21781 output from the command is always discarded, whatever the setting of this
21782 option. This option and &%return_fail_output%& are mutually exclusive. Only one
21783 of them may be set.
21787 .option temp_errors pipe "string list" "see below"
21788 .cindex "&(pipe)& transport" "temporary failure"
21789 This option contains either a colon-separated list of numbers, or a single
21790 asterisk. If &%ignore_status%& is false
21791 and &%return_output%& is not set,
21792 and the command exits with a non-zero return code, the failure is treated as
21793 temporary and the delivery is deferred if the return code matches one of the
21794 numbers, or if the setting is a single asterisk. Otherwise, non-zero return
21795 codes are treated as permanent errors. The default setting contains the codes
21796 defined by EX_TEMPFAIL and EX_CANTCREAT in &_sysexits.h_&. If Exim is
21797 compiled on a system that does not define these macros, it assumes values of 75
21798 and 73, respectively.
21801 .option timeout pipe time 1h
21802 If the command fails to complete within this time, it is killed. This normally
21803 causes the delivery to fail (but see &%timeout_defer%&). A zero time interval
21804 specifies no timeout. In order to ensure that any subprocesses created by the
21805 command are also killed, Exim makes the initial process a process group leader,
21806 and kills the whole process group on a timeout. However, this can be defeated
21807 if one of the processes starts a new process group.
21809 .option timeout_defer pipe boolean false
21810 A timeout in a &(pipe)& transport, either in the command that the transport
21811 runs, or in a transport filter that is associated with it, is by default
21812 treated as a hard error, and the delivery fails. However, if &%timeout_defer%&
21813 is set true, both kinds of timeout become temporary errors, causing the
21814 delivery to be deferred.
21816 .option umask pipe "octal integer" 022
21817 This specifies the umask setting for the subprocess that runs the command.
21820 .option use_bsmtp pipe boolean false
21821 .cindex "envelope sender"
21822 If this option is set true, the &(pipe)& transport writes messages in &"batch
21823 SMTP"& format, with the envelope sender and recipient(s) included as SMTP
21824 commands. If you want to include a leading HELO command with such messages,
21825 you can do so by setting the &%message_prefix%& option. See section
21826 &<<SECTbatchSMTP>>& for details of batch SMTP.
21828 .option use_classresources pipe boolean false
21829 .cindex "class resources (BSD)"
21830 This option is available only when Exim is running on FreeBSD, NetBSD, or
21831 BSD/OS. If it is set true, the &[setclassresources()]& function is used to set
21832 resource limits when a &(pipe)& transport is run to perform a delivery. The
21833 limits for the uid under which the pipe is to run are obtained from the login
21837 .option use_crlf pipe boolean false
21838 .cindex "carriage return"
21840 This option causes lines to be terminated with the two-character CRLF sequence
21841 (carriage return, linefeed) instead of just a linefeed character. In the case
21842 of batched SMTP, the byte sequence written to the pipe is then an exact image
21843 of what would be sent down a real SMTP connection.
21845 The contents of the &%message_prefix%& and &%message_suffix%& options are
21846 written verbatim, so must contain their own carriage return characters if these
21847 are needed. When &%use_bsmtp%& is not set, the default values for both
21848 &%message_prefix%& and &%message_suffix%& end with a single linefeed, so their
21849 values must be changed to end with &`\r\n`& if &%use_crlf%& is set.
21852 .option use_shell pipe boolean false
21853 .vindex "&$pipe_addresses$&"
21854 If this option is set, it causes the command to be passed to &_/bin/sh_&
21855 instead of being run directly from the transport, as described in section
21856 &<<SECThowcommandrun>>&. This is less secure, but is needed in some situations
21857 where the command is expected to be run under a shell and cannot easily be
21858 modified. The &%allow_commands%& and &%restrict_to_path%& options, and the
21859 &`$pipe_addresses`& facility are incompatible with &%use_shell%&. The
21860 command is expanded as a single string, and handed to &_/bin/sh_& as data for
21865 .section "Using an external local delivery agent" "SECID143"
21866 .cindex "local delivery" "using an external agent"
21867 .cindex "&'procmail'&"
21868 .cindex "external local delivery"
21869 .cindex "delivery" "&'procmail'&"
21870 .cindex "delivery" "by external agent"
21871 The &(pipe)& transport can be used to pass all messages that require local
21872 delivery to a separate local delivery agent such as &%procmail%&. When doing
21873 this, care must be taken to ensure that the pipe is run under an appropriate
21874 uid and gid. In some configurations one wants this to be a uid that is trusted
21875 by the delivery agent to supply the correct sender of the message. It may be
21876 necessary to recompile or reconfigure the delivery agent so that it trusts an
21877 appropriate user. The following is an example transport and router
21878 configuration for &%procmail%&:
21883 command = /usr/local/bin/procmail -d $local_part
21887 check_string = "From "
21888 escape_string = ">From "
21897 transport = procmail_pipe
21899 In this example, the pipe is run as the local user, but with the group set to
21900 &'mail'&. An alternative is to run the pipe as a specific user such as &'mail'&
21901 or &'exim'&, but in this case you must arrange for &%procmail%& to trust that
21902 user to supply a correct sender address. If you do not specify either a
21903 &%group%& or a &%user%& option, the pipe command is run as the local user. The
21904 home directory is the user's home directory by default.
21906 &*Note*&: The command that the pipe transport runs does &'not'& begin with
21910 as shown in some &%procmail%& documentation, because Exim does not by default
21911 use a shell to run pipe commands.
21914 The next example shows a transport and a router for a system where local
21915 deliveries are handled by the Cyrus IMAP server.
21918 local_delivery_cyrus:
21920 command = /usr/cyrus/bin/deliver \
21921 -m ${substr_1:$local_part_suffix} -- $local_part
21933 local_part_suffix = .*
21934 transport = local_delivery_cyrus
21936 Note the unsetting of &%message_prefix%& and &%message_suffix%&, and the use of
21937 &%return_output%& to cause any text written by Cyrus to be returned to the
21939 .ecindex IIDpiptra1
21940 .ecindex IIDpiptra2
21943 . ////////////////////////////////////////////////////////////////////////////
21944 . ////////////////////////////////////////////////////////////////////////////
21946 .chapter "The smtp transport" "CHAPsmtptrans"
21947 .scindex IIDsmttra1 "transports" "&(smtp)&"
21948 .scindex IIDsmttra2 "&(smtp)& transport"
21949 The &(smtp)& transport delivers messages over TCP/IP connections using the SMTP
21950 or LMTP protocol. The list of hosts to try can either be taken from the address
21951 that is being processed (having been set up by the router), or specified
21952 explicitly for the transport. Timeout and retry processing (see chapter
21953 &<<CHAPretry>>&) is applied to each IP address independently.
21956 .section "Multiple messages on a single connection" "SECID144"
21957 The sending of multiple messages over a single TCP/IP connection can arise in
21961 If a message contains more than &%max_rcpt%& (see below) addresses that are
21962 routed to the same host, more than one copy of the message has to be sent to
21963 that host. In this situation, multiple copies may be sent in a single run of
21964 the &(smtp)& transport over a single TCP/IP connection. (What Exim actually
21965 does when it has too many addresses to send in one message also depends on the
21966 value of the global &%remote_max_parallel%& option. Details are given in
21967 section &<<SECToutSMTPTCP>>&.)
21969 .cindex "hints database" "remembering routing"
21970 When a message has been successfully delivered over a TCP/IP connection, Exim
21971 looks in its hints database to see if there are any other messages awaiting a
21972 connection to the same host. If there are, a new delivery process is started
21973 for one of them, and the current TCP/IP connection is passed on to it. The new
21974 process may in turn send multiple copies and possibly create yet another
21979 For each copy sent over the same TCP/IP connection, a sequence counter is
21980 incremented, and if it ever gets to the value of &%connection_max_messages%&,
21981 no further messages are sent over that connection.
21985 .section "Use of the $host and $host_address variables" "SECID145"
21987 .vindex "&$host_address$&"
21988 At the start of a run of the &(smtp)& transport, the values of &$host$& and
21989 &$host_address$& are the name and IP address of the first host on the host list
21990 passed by the router. However, when the transport is about to connect to a
21991 specific host, and while it is connected to that host, &$host$& and
21992 &$host_address$& are set to the values for that host. These are the values
21993 that are in force when the &%helo_data%&, &%hosts_try_auth%&, &%interface%&,
21994 &%serialize_hosts%&, and the various TLS options are expanded.
21997 .section "Use of $tls_cipher and $tls_peerdn" "usecippeer"
21998 .vindex &$tls_bits$&
21999 .vindex &$tls_cipher$&
22000 .vindex &$tls_peerdn$&
22001 .vindex &$tls_sni$&
22002 At the start of a run of the &(smtp)& transport, the values of &$tls_bits$&,
22003 &$tls_cipher$&, &$tls_peerdn$& and &$tls_sni$&
22004 are the values that were set when the message was received.
22005 These are the values that are used for options that are expanded before any
22006 SMTP connections are made. Just before each connection is made, these four
22007 variables are emptied. If TLS is subsequently started, they are set to the
22008 appropriate values for the outgoing connection, and these are the values that
22009 are in force when any authenticators are run and when the
22010 &%authenticated_sender%& option is expanded.
22013 .section "Private options for smtp" "SECID146"
22014 .cindex "options" "&(smtp)& transport"
22015 The private options of the &(smtp)& transport are as follows:
22018 .option address_retry_include_sender smtp boolean true
22019 .cindex "4&'xx'& responses" "retrying after"
22020 When an address is delayed because of a 4&'xx'& response to a RCPT command, it
22021 is the combination of sender and recipient that is delayed in subsequent queue
22022 runs until the retry time is reached. You can delay the recipient without
22023 reference to the sender (which is what earlier versions of Exim did), by
22024 setting &%address_retry_include_sender%& false. However, this can lead to
22025 problems with servers that regularly issue 4&'xx'& responses to RCPT commands.
22027 .option allow_localhost smtp boolean false
22028 .cindex "local host" "sending to"
22029 .cindex "fallback" "hosts specified on transport"
22030 When a host specified in &%hosts%& or &%fallback_hosts%& (see below) turns out
22031 to be the local host, or is listed in &%hosts_treat_as_local%&, delivery is
22032 deferred by default. However, if &%allow_localhost%& is set, Exim goes on to do
22033 the delivery anyway. This should be used only in special cases when the
22034 configuration ensures that no looping will result (for example, a differently
22035 configured Exim is listening on the port to which the message is sent).
22038 .option authenticated_sender smtp string&!! unset
22040 When Exim has authenticated as a client, or if &%authenticated_sender_force%&
22041 is true, this option sets a value for the AUTH= item on outgoing MAIL commands,
22042 overriding any existing authenticated sender value. If the string expansion is
22043 forced to fail, the option is ignored. Other expansion failures cause delivery
22044 to be deferred. If the result of expansion is an empty string, that is also
22047 The expansion happens after the outgoing connection has been made and TLS
22048 started, if required. This means that the &$host$&, &$host_address$&,
22049 &$tls_cipher$&, and &$tls_peerdn$& variables are set according to the
22050 particular connection.
22052 If the SMTP session is not authenticated, the expansion of
22053 &%authenticated_sender%& still happens (and can cause the delivery to be
22054 deferred if it fails), but no AUTH= item is added to MAIL commands
22055 unless &%authenticated_sender_force%& is true.
22057 This option allows you to use the &(smtp)& transport in LMTP mode to
22058 deliver mail to Cyrus IMAP and provide the proper local part as the
22059 &"authenticated sender"&, via a setting such as:
22061 authenticated_sender = $local_part
22063 This removes the need for IMAP subfolders to be assigned special ACLs to
22064 allow direct delivery to those subfolders.
22066 Because of expected uses such as that just described for Cyrus (when no
22067 domain is involved), there is no checking on the syntax of the provided
22071 .option authenticated_sender_force smtp boolean false
22072 If this option is set true, the &%authenticated_sender%& option's value
22073 is used for the AUTH= item on outgoing MAIL commands, even if Exim has not
22074 authenticated as a client.
22077 .option command_timeout smtp time 5m
22078 This sets a timeout for receiving a response to an SMTP command that has been
22079 sent out. It is also used when waiting for the initial banner line from the
22080 remote host. Its value must not be zero.
22083 .option connect_timeout smtp time 5m
22084 This sets a timeout for the &[connect()]& function, which sets up a TCP/IP call
22085 to a remote host. A setting of zero allows the system timeout (typically
22086 several minutes) to act. To have any effect, the value of this option must be
22087 less than the system timeout. However, it has been observed that on some
22088 systems there is no system timeout, which is why the default value for this
22089 option is 5 minutes, a value recommended by RFC 1123.
22092 .option connection_max_messages smtp integer 500
22093 .cindex "SMTP" "passed connection"
22094 .cindex "SMTP" "multiple deliveries"
22095 .cindex "multiple SMTP deliveries"
22096 This controls the maximum number of separate message deliveries that are sent
22097 over a single TCP/IP connection. If the value is zero, there is no limit.
22098 For testing purposes, this value can be overridden by the &%-oB%& command line
22102 .option data_timeout smtp time 5m
22103 This sets a timeout for the transmission of each block in the data portion of
22104 the message. As a result, the overall timeout for a message depends on the size
22105 of the message. Its value must not be zero. See also &%final_timeout%&.
22108 .option delay_after_cutoff smtp boolean true
22109 This option controls what happens when all remote IP addresses for a given
22110 domain have been inaccessible for so long that they have passed their retry
22113 In the default state, if the next retry time has not been reached for any of
22114 them, the address is bounced without trying any deliveries. In other words,
22115 Exim delays retrying an IP address after the final cutoff time until a new
22116 retry time is reached, and can therefore bounce an address without ever trying
22117 a delivery, when machines have been down for a long time. Some people are
22118 unhappy at this prospect, so...
22120 If &%delay_after_cutoff%& is set false, Exim behaves differently. If all IP
22121 addresses are past their final cutoff time, Exim tries to deliver to those
22122 IP addresses that have not been tried since the message arrived. If there are
22123 none, of if they all fail, the address is bounced. In other words, it does not
22124 delay when a new message arrives, but immediately tries those expired IP
22125 addresses that haven't been tried since the message arrived. If there is a
22126 continuous stream of messages for the dead hosts, unsetting
22127 &%delay_after_cutoff%& means that there will be many more attempts to deliver
22131 .option dns_qualify_single smtp boolean true
22132 If the &%hosts%& or &%fallback_hosts%& option is being used,
22133 and the &%gethostbyname%& option is false,
22134 the RES_DEFNAMES resolver option is set. See the &%qualify_single%& option
22135 in chapter &<<CHAPdnslookup>>& for more details.
22138 .option dns_search_parents smtp boolean false
22139 If the &%hosts%& or &%fallback_hosts%& option is being used, and the
22140 &%gethostbyname%& option is false, the RES_DNSRCH resolver option is set.
22141 See the &%search_parents%& option in chapter &<<CHAPdnslookup>>& for more
22146 .option dscp smtp string&!! unset
22147 .cindex "DCSP" "outbound"
22148 This option causes the DSCP value associated with a socket to be set to one
22149 of a number of fixed strings or to numeric value.
22150 The &%-bI:dscp%& option may be used to ask Exim which names it knows of.
22151 Common values include &`throughput`&, &`mincost`&, and on newer systems
22152 &`ef`&, &`af41`&, etc. Numeric values may be in the range 0 to 0x3F.
22154 The outbound packets from Exim will be marked with this value in the header
22155 (for IPv4, the TOS field; for IPv6, the TCLASS field); there is no guarantee
22156 that these values will have any effect, not be stripped by networking
22157 equipment, or do much of anything without cooperation with your Network
22158 Engineer and those of all network operators between the source and destination.
22162 .option fallback_hosts smtp "string list" unset
22163 .cindex "fallback" "hosts specified on transport"
22164 String expansion is not applied to this option. The argument must be a
22165 colon-separated list of host names or IP addresses, optionally also including
22166 port numbers, though the separator can be changed, as described in section
22167 &<<SECTlistconstruct>>&. Each individual item in the list is the same as an
22168 item in a &%route_list%& setting for the &(manualroute)& router, as described
22169 in section &<<SECTformatonehostitem>>&.
22171 Fallback hosts can also be specified on routers, which associate them with the
22172 addresses they process. As for the &%hosts%& option without &%hosts_override%&,
22173 &%fallback_hosts%& specified on the transport is used only if the address does
22174 not have its own associated fallback host list. Unlike &%hosts%&, a setting of
22175 &%fallback_hosts%& on an address is not overridden by &%hosts_override%&.
22176 However, &%hosts_randomize%& does apply to fallback host lists.
22178 If Exim is unable to deliver to any of the hosts for a particular address, and
22179 the errors are not permanent rejections, the address is put on a separate
22180 transport queue with its host list replaced by the fallback hosts, unless the
22181 address was routed via MX records and the current host was in the original MX
22182 list. In that situation, the fallback host list is not used.
22184 Once normal deliveries are complete, the fallback queue is delivered by
22185 re-running the same transports with the new host lists. If several failing
22186 addresses have the same fallback hosts (and &%max_rcpt%& permits it), a single
22187 copy of the message is sent.
22189 The resolution of the host names on the fallback list is controlled by the
22190 &%gethostbyname%& option, as for the &%hosts%& option. Fallback hosts apply
22191 both to cases when the host list comes with the address and when it is taken
22192 from &%hosts%&. This option provides a &"use a smart host only if delivery
22196 .option final_timeout smtp time 10m
22197 This is the timeout that applies while waiting for the response to the final
22198 line containing just &"."& that terminates a message. Its value must not be
22201 .option gethostbyname smtp boolean false
22202 If this option is true when the &%hosts%& and/or &%fallback_hosts%& options are
22203 being used, names are looked up using &[gethostbyname()]&
22204 (or &[getipnodebyname()]& when available)
22205 instead of using the DNS. Of course, that function may in fact use the DNS, but
22206 it may also consult other sources of information such as &_/etc/hosts_&.
22208 .option gnutls_compat_mode smtp boolean unset
22209 This option controls whether GnuTLS is used in compatibility mode in an Exim
22210 server. This reduces security slightly, but improves interworking with older
22211 implementations of TLS.
22213 .option helo_data smtp string&!! "see below"
22214 .cindex "HELO" "argument, setting"
22215 .cindex "EHLO" "argument, setting"
22216 .cindex "LHLO argument setting"
22217 The value of this option is expanded after a connection to a another host has
22218 been set up. The result is used as the argument for the EHLO, HELO, or LHLO
22219 command that starts the outgoing SMTP or LMTP session. The default value of the
22224 During the expansion, the variables &$host$& and &$host_address$& are set to
22225 the identity of the remote host, and the variables &$sending_ip_address$& and
22226 &$sending_port$& are set to the local IP address and port number that are being
22227 used. These variables can be used to generate different values for different
22228 servers or different local IP addresses. For example, if you want the string
22229 that is used for &%helo_data%& to be obtained by a DNS lookup of the outgoing
22230 interface address, you could use this:
22232 helo_data = ${lookup dnsdb{ptr=$sending_ip_address}{$value}\
22233 {$primary_hostname}}
22235 The use of &%helo_data%& applies both to sending messages and when doing
22238 .option hosts smtp "string list&!!" unset
22239 Hosts are associated with an address by a router such as &(dnslookup)&, which
22240 finds the hosts by looking up the address domain in the DNS, or by
22241 &(manualroute)&, which has lists of hosts in its configuration. However,
22242 email addresses can be passed to the &(smtp)& transport by any router, and not
22243 all of them can provide an associated list of hosts.
22245 The &%hosts%& option specifies a list of hosts to be used if the address being
22246 processed does not have any hosts associated with it. The hosts specified by
22247 &%hosts%& are also used, whether or not the address has its own hosts, if
22248 &%hosts_override%& is set.
22250 The string is first expanded, before being interpreted as a colon-separated
22251 list of host names or IP addresses, possibly including port numbers. The
22252 separator may be changed to something other than colon, as described in section
22253 &<<SECTlistconstruct>>&. Each individual item in the list is the same as an
22254 item in a &%route_list%& setting for the &(manualroute)& router, as described
22255 in section &<<SECTformatonehostitem>>&. However, note that the &`/MX`& facility
22256 of the &(manualroute)& router is not available here.
22258 If the expansion fails, delivery is deferred. Unless the failure was caused by
22259 the inability to complete a lookup, the error is logged to the panic log as
22260 well as the main log. Host names are looked up either by searching directly for
22261 address records in the DNS or by calling &[gethostbyname()]& (or
22262 &[getipnodebyname()]& when available), depending on the setting of the
22263 &%gethostbyname%& option. When Exim is compiled with IPv6 support, if a host
22264 that is looked up in the DNS has both IPv4 and IPv6 addresses, both types of
22267 During delivery, the hosts are tried in order, subject to their retry status,
22268 unless &%hosts_randomize%& is set.
22271 .option hosts_avoid_esmtp smtp "host list&!!" unset
22272 .cindex "ESMTP, avoiding use of"
22273 .cindex "HELO" "forcing use of"
22274 .cindex "EHLO" "avoiding use of"
22275 .cindex "PIPELINING" "avoiding the use of"
22276 This option is for use with broken hosts that announce ESMTP facilities (for
22277 example, PIPELINING) and then fail to implement them properly. When a host
22278 matches &%hosts_avoid_esmtp%&, Exim sends HELO rather than EHLO at the
22279 start of the SMTP session. This means that it cannot use any of the ESMTP
22280 facilities such as AUTH, PIPELINING, SIZE, and STARTTLS.
22283 .option hosts_avoid_pipelining smtp "host list&!!" unset
22284 .cindex "PIPELINING" "avoiding the use of"
22285 Exim will not use the SMTP PIPELINING extension when delivering to any host
22286 that matches this list, even if the server host advertises PIPELINING support.
22289 .option hosts_avoid_tls smtp "host list&!!" unset
22290 .cindex "TLS" "avoiding for certain hosts"
22291 Exim will not try to start a TLS session when delivering to any host that
22292 matches this list. See chapter &<<CHAPTLS>>& for details of TLS.
22295 .option hosts_max_try smtp integer 5
22296 .cindex "host" "maximum number to try"
22297 .cindex "limit" "number of hosts tried"
22298 .cindex "limit" "number of MX tried"
22299 .cindex "MX record" "maximum tried"
22300 This option limits the number of IP addresses that are tried for any one
22301 delivery in cases where there are temporary delivery errors. Section
22302 &<<SECTvalhosmax>>& describes in detail how the value of this option is used.
22305 .option hosts_max_try_hardlimit smtp integer 50
22306 This is an additional check on the maximum number of IP addresses that Exim
22307 tries for any one delivery. Section &<<SECTvalhosmax>>& describes its use and
22312 .option hosts_nopass_tls smtp "host list&!!" unset
22313 .cindex "TLS" "passing connection"
22314 .cindex "multiple SMTP deliveries"
22315 .cindex "TLS" "multiple message deliveries"
22316 For any host that matches this list, a connection on which a TLS session has
22317 been started will not be passed to a new delivery process for sending another
22318 message on the same connection. See section &<<SECTmulmessam>>& for an
22319 explanation of when this might be needed.
22322 .option hosts_override smtp boolean false
22323 If this option is set and the &%hosts%& option is also set, any hosts that are
22324 attached to the address are ignored, and instead the hosts specified by the
22325 &%hosts%& option are always used. This option does not apply to
22326 &%fallback_hosts%&.
22329 .option hosts_randomize smtp boolean false
22330 .cindex "randomized host list"
22331 .cindex "host" "list of; randomized"
22332 .cindex "fallback" "randomized hosts"
22333 If this option is set, and either the list of hosts is taken from the
22334 &%hosts%& or the &%fallback_hosts%& option, or the hosts supplied by the router
22335 were not obtained from MX records (this includes fallback hosts from the
22336 router), and were not randomized by the router, the order of trying the hosts
22337 is randomized each time the transport runs. Randomizing the order of a host
22338 list can be used to do crude load sharing.
22340 When &%hosts_randomize%& is true, a host list may be split into groups whose
22341 order is separately randomized. This makes it possible to set up MX-like
22342 behaviour. The boundaries between groups are indicated by an item that is just
22343 &`+`& in the host list. For example:
22345 hosts = host1:host2:host3:+:host4:host5
22347 The order of the first three hosts and the order of the last two hosts is
22348 randomized for each use, but the first three always end up before the last two.
22349 If &%hosts_randomize%& is not set, a &`+`& item in the list is ignored.
22351 .option hosts_require_auth smtp "host list&!!" unset
22352 .cindex "authentication" "required by client"
22353 This option provides a list of servers for which authentication must succeed
22354 before Exim will try to transfer a message. If authentication fails for
22355 servers which are not in this list, Exim tries to send unauthenticated. If
22356 authentication fails for one of these servers, delivery is deferred. This
22357 temporary error is detectable in the retry rules, so it can be turned into a
22358 hard failure if required. See also &%hosts_try_auth%&, and chapter
22359 &<<CHAPSMTPAUTH>>& for details of authentication.
22362 .option hosts_require_tls smtp "host list&!!" unset
22363 .cindex "TLS" "requiring for certain servers"
22364 Exim will insist on using a TLS session when delivering to any host that
22365 matches this list. See chapter &<<CHAPTLS>>& for details of TLS.
22366 &*Note*&: This option affects outgoing mail only. To insist on TLS for
22367 incoming messages, use an appropriate ACL.
22369 .option hosts_try_auth smtp "host list&!!" unset
22370 .cindex "authentication" "optional in client"
22371 This option provides a list of servers to which, provided they announce
22372 authentication support, Exim will attempt to authenticate as a client when it
22373 connects. If authentication fails, Exim will try to transfer the message
22374 unauthenticated. See also &%hosts_require_auth%&, and chapter
22375 &<<CHAPSMTPAUTH>>& for details of authentication.
22377 .option interface smtp "string list&!!" unset
22378 .cindex "bind IP address"
22379 .cindex "IP address" "binding"
22381 .vindex "&$host_address$&"
22382 This option specifies which interface to bind to when making an outgoing SMTP
22383 call. The value is an IP address, not an interface name such as
22384 &`eth0`&. Do not confuse this with the interface address that was used when a
22385 message was received, which is in &$received_ip_address$&, formerly known as
22386 &$interface_address$&. The name was changed to minimize confusion with the
22387 outgoing interface address. There is no variable that contains an outgoing
22388 interface address because, unless it is set by this option, its value is
22391 During the expansion of the &%interface%& option the variables &$host$& and
22392 &$host_address$& refer to the host to which a connection is about to be made
22393 during the expansion of the string. Forced expansion failure, or an empty
22394 string result causes the option to be ignored. Otherwise, after expansion, the
22395 string must be a list of IP addresses, colon-separated by default, but the
22396 separator can be changed in the usual way. For example:
22398 interface = <; 192.168.123.123 ; 3ffe:ffff:836f::fe86:a061
22400 The first interface of the correct type (IPv4 or IPv6) is used for the outgoing
22401 connection. If none of them are the correct type, the option is ignored. If
22402 &%interface%& is not set, or is ignored, the system's IP functions choose which
22403 interface to use if the host has more than one.
22406 .option keepalive smtp boolean true
22407 .cindex "keepalive" "on outgoing connection"
22408 This option controls the setting of SO_KEEPALIVE on outgoing TCP/IP socket
22409 connections. When set, it causes the kernel to probe idle connections
22410 periodically, by sending packets with &"old"& sequence numbers. The other end
22411 of the connection should send a acknowledgment if the connection is still okay
22412 or a reset if the connection has been aborted. The reason for doing this is
22413 that it has the beneficial effect of freeing up certain types of connection
22414 that can get stuck when the remote host is disconnected without tidying up the
22415 TCP/IP call properly. The keepalive mechanism takes several hours to detect
22419 .option lmtp_ignore_quota smtp boolean false
22420 .cindex "LMTP" "ignoring quota errors"
22421 If this option is set true when the &%protocol%& option is set to &"lmtp"&, the
22422 string &`IGNOREQUOTA`& is added to RCPT commands, provided that the LMTP server
22423 has advertised support for IGNOREQUOTA in its response to the LHLO command.
22425 .option max_rcpt smtp integer 100
22426 .cindex "RCPT" "maximum number of outgoing"
22427 This option limits the number of RCPT commands that are sent in a single
22428 SMTP message transaction. Each set of addresses is treated independently, and
22429 so can cause parallel connections to the same host if &%remote_max_parallel%&
22433 .option multi_domain smtp boolean true
22434 .vindex "&$domain$&"
22435 When this option is set, the &(smtp)& transport can handle a number of
22436 addresses containing a mixture of different domains provided they all resolve
22437 to the same list of hosts. Turning the option off restricts the transport to
22438 handling only one domain at a time. This is useful if you want to use
22439 &$domain$& in an expansion for the transport, because it is set only when there
22440 is a single domain involved in a remote delivery.
22443 .option port smtp string&!! "see below"
22444 .cindex "port" "sending TCP/IP"
22445 .cindex "TCP/IP" "setting outgoing port"
22446 This option specifies the TCP/IP port on the server to which Exim connects.
22447 &*Note:*& Do not confuse this with the port that was used when a message was
22448 received, which is in &$received_port$&, formerly known as &$interface_port$&.
22449 The name was changed to minimize confusion with the outgoing port. There is no
22450 variable that contains an outgoing port.
22452 If the value of this option begins with a digit it is taken as a port number;
22453 otherwise it is looked up using &[getservbyname()]&. The default value is
22454 normally &"smtp"&, but if &%protocol%& is set to &"lmtp"&, the default is
22455 &"lmtp"&. If the expansion fails, or if a port number cannot be found, delivery
22460 .option protocol smtp string smtp
22461 .cindex "LMTP" "over TCP/IP"
22462 .cindex "ssmtp protocol" "outbound"
22463 .cindex "TLS" "SSL-on-connect outbound"
22465 If this option is set to &"lmtp"& instead of &"smtp"&, the default value for
22466 the &%port%& option changes to &"lmtp"&, and the transport operates the LMTP
22467 protocol (RFC 2033) instead of SMTP. This protocol is sometimes used for local
22468 deliveries into closed message stores. Exim also has support for running LMTP
22469 over a pipe to a local process &-- see chapter &<<CHAPLMTP>>&.
22471 If this option is set to &"smtps"&, the default vaule for the &%port%& option
22472 changes to &"smtps"&, and the transport initiates TLS immediately after
22473 connecting, as an outbound SSL-on-connect, instead of using STARTTLS to upgrade.
22474 The Internet standards bodies strongly discourage use of this mode.
22477 .option retry_include_ip_address smtp boolean true
22478 Exim normally includes both the host name and the IP address in the key it
22479 constructs for indexing retry data after a temporary delivery failure. This
22480 means that when one of several IP addresses for a host is failing, it gets
22481 tried periodically (controlled by the retry rules), but use of the other IP
22482 addresses is not affected.
22484 However, in some dialup environments hosts are assigned a different IP address
22485 each time they connect. In this situation the use of the IP address as part of
22486 the retry key leads to undesirable behaviour. Setting this option false causes
22487 Exim to use only the host name. This should normally be done on a separate
22488 instance of the &(smtp)& transport, set up specially to handle the dialup
22492 .option serialize_hosts smtp "host list&!!" unset
22493 .cindex "serializing connections"
22494 .cindex "host" "serializing connections"
22495 Because Exim operates in a distributed manner, if several messages for the same
22496 host arrive at around the same time, more than one simultaneous connection to
22497 the remote host can occur. This is not usually a problem except when there is a
22498 slow link between the hosts. In that situation it may be helpful to restrict
22499 Exim to one connection at a time. This can be done by setting
22500 &%serialize_hosts%& to match the relevant hosts.
22502 .cindex "hints database" "serializing deliveries to a host"
22503 Exim implements serialization by means of a hints database in which a record is
22504 written whenever a process connects to one of the restricted hosts. The record
22505 is deleted when the connection is completed. Obviously there is scope for
22506 records to get left lying around if there is a system or program crash. To
22507 guard against this, Exim ignores any records that are more than six hours old.
22509 If you set up this kind of serialization, you should also arrange to delete the
22510 relevant hints database whenever your system reboots. The names of the files
22511 start with &_misc_& and they are kept in the &_spool/db_& directory. There
22512 may be one or two files, depending on the type of DBM in use. The same files
22513 are used for ETRN serialization.
22516 .option size_addition smtp integer 1024
22517 .cindex "SMTP" "SIZE"
22518 .cindex "message" "size issue for transport filter"
22519 .cindex "size" "of message"
22520 .cindex "transport" "filter"
22521 .cindex "filter" "transport filter"
22522 If a remote SMTP server indicates that it supports the SIZE option of the
22523 MAIL command, Exim uses this to pass over the message size at the start of
22524 an SMTP transaction. It adds the value of &%size_addition%& to the value it
22525 sends, to allow for headers and other text that may be added during delivery by
22526 configuration options or in a transport filter. It may be necessary to increase
22527 this if a lot of text is added to messages.
22529 Alternatively, if the value of &%size_addition%& is set negative, it disables
22530 the use of the SIZE option altogether.
22533 .option tls_certificate smtp string&!! unset
22534 .cindex "TLS" "client certificate, location of"
22535 .cindex "certificate" "client, location of"
22537 .vindex "&$host_address$&"
22538 The value of this option must be the absolute path to a file which contains the
22539 client's certificate, for possible use when sending a message over an encrypted
22540 connection. The values of &$host$& and &$host_address$& are set to the name and
22541 address of the server during the expansion. See chapter &<<CHAPTLS>>& for
22544 &*Note*&: This option must be set if you want Exim to be able to use a TLS
22545 certificate when sending messages as a client. The global option of the same
22546 name specifies the certificate for Exim as a server; it is not automatically
22547 assumed that the same certificate should be used when Exim is operating as a
22551 .option tls_crl smtp string&!! unset
22552 .cindex "TLS" "client certificate revocation list"
22553 .cindex "certificate" "revocation list for client"
22554 This option specifies a certificate revocation list. The expanded value must
22555 be the name of a file that contains a CRL in PEM format.
22559 .option tls_dh_min_bits smtp integer 1024
22560 .cindex "TLS" "Diffie-Hellman minimum acceptable size"
22561 When establishing a TLS session, if a ciphersuite which uses Diffie-Hellman
22562 key agreement is negotiated, the server will provide a large prime number
22563 for use. This option establishes the minimum acceptable size of that number.
22564 If the parameter offered by the server is too small, then the TLS handshake
22567 Only supported when using GnuTLS.
22571 .option tls_privatekey smtp string&!! unset
22572 .cindex "TLS" "client private key, location of"
22574 .vindex "&$host_address$&"
22575 The value of this option must be the absolute path to a file which contains the
22576 client's private key. This is used when sending a message over an encrypted
22577 connection using a client certificate. The values of &$host$& and
22578 &$host_address$& are set to the name and address of the server during the
22579 expansion. If this option is unset, or the expansion is forced to fail, or the
22580 result is an empty string, the private key is assumed to be in the same file as
22581 the certificate. See chapter &<<CHAPTLS>>& for details of TLS.
22584 .option tls_require_ciphers smtp string&!! unset
22585 .cindex "TLS" "requiring specific ciphers"
22586 .cindex "cipher" "requiring specific"
22588 .vindex "&$host_address$&"
22589 The value of this option must be a list of permitted cipher suites, for use
22590 when setting up an outgoing encrypted connection. (There is a global option of
22591 the same name for controlling incoming connections.) The values of &$host$& and
22592 &$host_address$& are set to the name and address of the server during the
22593 expansion. See chapter &<<CHAPTLS>>& for details of TLS; note that this option
22594 is used in different ways by OpenSSL and GnuTLS (see sections
22595 &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&). For GnuTLS, the order of the
22596 ciphers is a preference order.
22600 .option tls_sni smtp string&!! unset
22601 .cindex "TLS" "Server Name Indication"
22602 .vindex "&$tls_sni$&"
22603 If this option is set then it sets the $tls_sni variable and causes any
22604 TLS session to pass this value as the Server Name Indication extension to
22605 the remote side, which can be used by the remote side to select an appropriate
22606 certificate and private key for the session.
22608 See &<<SECTtlssni>>& for more information.
22610 Note that for OpenSSL, this feature requires a build of OpenSSL that supports
22616 .option tls_tempfail_tryclear smtp boolean true
22617 .cindex "4&'xx'& responses" "to STARTTLS"
22618 When the server host is not in &%hosts_require_tls%&, and there is a problem in
22619 setting up a TLS session, this option determines whether or not Exim should try
22620 to deliver the message unencrypted. If it is set false, delivery to the
22621 current host is deferred; if there are other hosts, they are tried. If this
22622 option is set true, Exim attempts to deliver unencrypted after a 4&'xx'&
22623 response to STARTTLS. Also, if STARTTLS is accepted, but the subsequent
22624 TLS negotiation fails, Exim closes the current connection (because it is in an
22625 unknown state), opens a new one to the same host, and then tries the delivery
22629 .option tls_verify_certificates smtp string&!! unset
22630 .cindex "TLS" "server certificate verification"
22631 .cindex "certificate" "verification of server"
22633 .vindex "&$host_address$&"
22634 The value of this option must be the absolute path to a file containing
22635 permitted server certificates, for use when setting up an encrypted connection.
22636 Alternatively, if you are using OpenSSL, you can set
22637 &%tls_verify_certificates%& to the name of a directory containing certificate
22638 files. This does not work with GnuTLS; the option must be set to the name of a
22639 single file if you are using GnuTLS. The values of &$host$& and
22640 &$host_address$& are set to the name and address of the server during the
22641 expansion of this option. See chapter &<<CHAPTLS>>& for details of TLS.
22646 .section "How the limits for the number of hosts to try are used" &&&
22648 .cindex "host" "maximum number to try"
22649 .cindex "limit" "hosts; maximum number tried"
22650 There are two options that are concerned with the number of hosts that are
22651 tried when an SMTP delivery takes place. They are &%hosts_max_try%& and
22652 &%hosts_max_try_hardlimit%&.
22655 The &%hosts_max_try%& option limits the number of hosts that are tried
22656 for a single delivery. However, despite the term &"host"& in its name, the
22657 option actually applies to each IP address independently. In other words, a
22658 multihomed host is treated as several independent hosts, just as it is for
22661 Many of the larger ISPs have multiple MX records which often point to
22662 multihomed hosts. As a result, a list of a dozen or more IP addresses may be
22663 created as a result of routing one of these domains.
22665 Trying every single IP address on such a long list does not seem sensible; if
22666 several at the top of the list fail, it is reasonable to assume there is some
22667 problem that is likely to affect all of them. Roughly speaking, the value of
22668 &%hosts_max_try%& is the maximum number that are tried before deferring the
22669 delivery. However, the logic cannot be quite that simple.
22671 Firstly, IP addresses that are skipped because their retry times have not
22672 arrived do not count, and in addition, addresses that are past their retry
22673 limits are also not counted, even when they are tried. This means that when
22674 some IP addresses are past their retry limits, more than the value of
22675 &%hosts_max_retry%& may be tried. The reason for this behaviour is to ensure
22676 that all IP addresses are considered before timing out an email address (but
22677 see below for an exception).
22679 Secondly, when the &%hosts_max_try%& limit is reached, Exim looks down the host
22680 list to see if there is a subsequent host with a different (higher valued) MX.
22681 If there is, that host is considered next, and the current IP address is used
22682 but not counted. This behaviour helps in the case of a domain with a retry rule
22683 that hardly ever delays any hosts, as is now explained:
22685 Consider the case of a long list of hosts with one MX value, and a few with a
22686 higher MX value. If &%hosts_max_try%& is small (the default is 5) only a few
22687 hosts at the top of the list are tried at first. With the default retry rule,
22688 which specifies increasing retry times, the higher MX hosts are eventually
22689 tried when those at the top of the list are skipped because they have not
22690 reached their retry times.
22692 However, it is common practice to put a fixed short retry time on domains for
22693 large ISPs, on the grounds that their servers are rarely down for very long.
22694 Unfortunately, these are exactly the domains that tend to resolve to long lists
22695 of hosts. The short retry time means that the lowest MX hosts are tried every
22696 time. The attempts may be in a different order because of random sorting, but
22697 without the special MX check, the higher MX hosts would never be tried until
22698 all the lower MX hosts had timed out (which might be several days), because
22699 there are always some lower MX hosts that have reached their retry times. With
22700 the special check, Exim considers at least one IP address from each MX value at
22701 every delivery attempt, even if the &%hosts_max_try%& limit has already been
22704 The above logic means that &%hosts_max_try%& is not a hard limit, and in
22705 particular, Exim normally eventually tries all the IP addresses before timing
22706 out an email address. When &%hosts_max_try%& was implemented, this seemed a
22707 reasonable thing to do. Recently, however, some lunatic DNS configurations have
22708 been set up with hundreds of IP addresses for some domains. It can
22709 take a very long time indeed for an address to time out in these cases.
22711 The &%hosts_max_try_hardlimit%& option was added to help with this problem.
22712 Exim never tries more than this number of IP addresses; if it hits this limit
22713 and they are all timed out, the email address is bounced, even though not all
22714 possible IP addresses have been tried.
22715 .ecindex IIDsmttra1
22716 .ecindex IIDsmttra2
22722 . ////////////////////////////////////////////////////////////////////////////
22723 . ////////////////////////////////////////////////////////////////////////////
22725 .chapter "Address rewriting" "CHAPrewrite"
22726 .scindex IIDaddrew "rewriting" "addresses"
22727 There are some circumstances in which Exim automatically rewrites domains in
22728 addresses. The two most common are when an address is given without a domain
22729 (referred to as an &"unqualified address"&) or when an address contains an
22730 abbreviated domain that is expanded by DNS lookup.
22732 Unqualified envelope addresses are accepted only for locally submitted
22733 messages, or for messages that are received from hosts matching
22734 &%sender_unqualified_hosts%& or &%recipient_unqualified_hosts%&, as
22735 appropriate. Unqualified addresses in header lines are qualified if they are in
22736 locally submitted messages, or messages from hosts that are permitted to send
22737 unqualified envelope addresses. Otherwise, unqualified addresses in header
22738 lines are neither qualified nor rewritten.
22740 One situation in which Exim does &'not'& automatically rewrite a domain is
22741 when it is the name of a CNAME record in the DNS. The older RFCs suggest that
22742 such a domain should be rewritten using the &"canonical"& name, and some MTAs
22743 do this. The new RFCs do not contain this suggestion.
22746 .section "Explicitly configured address rewriting" "SECID147"
22747 This chapter describes the rewriting rules that can be used in the
22748 main rewrite section of the configuration file, and also in the generic
22749 &%headers_rewrite%& option that can be set on any transport.
22751 Some people believe that configured address rewriting is a Mortal Sin.
22752 Others believe that life is not possible without it. Exim provides the
22753 facility; you do not have to use it.
22755 The main rewriting rules that appear in the &"rewrite"& section of the
22756 configuration file are applied to addresses in incoming messages, both envelope
22757 addresses and addresses in header lines. Each rule specifies the types of
22758 address to which it applies.
22760 Whether or not addresses in header lines are rewritten depends on the origin of
22761 the headers and the type of rewriting. Global rewriting, that is, rewriting
22762 rules from the rewrite section of the configuration file, is applied only to
22763 those headers that were received with the message. Header lines that are added
22764 by ACLs or by a system filter or by individual routers or transports (which
22765 are specific to individual recipient addresses) are not rewritten by the global
22768 Rewriting at transport time, by means of the &%headers_rewrite%& option,
22769 applies all headers except those added by routers and transports. That is, as
22770 well as the headers that were received with the message, it also applies to
22771 headers that were added by an ACL or a system filter.
22774 In general, rewriting addresses from your own system or domain has some
22775 legitimacy. Rewriting other addresses should be done only with great care and
22776 in special circumstances. The author of Exim believes that rewriting should be
22777 used sparingly, and mainly for &"regularizing"& addresses in your own domains.
22778 Although it can sometimes be used as a routing tool, this is very strongly
22781 There are two commonly encountered circumstances where rewriting is used, as
22782 illustrated by these examples:
22785 The company whose domain is &'hitch.fict.example'& has a number of hosts that
22786 exchange mail with each other behind a firewall, but there is only a single
22787 gateway to the outer world. The gateway rewrites &'*.hitch.fict.example'& as
22788 &'hitch.fict.example'& when sending mail off-site.
22790 A host rewrites the local parts of its own users so that, for example,
22791 &'fp42@hitch.fict.example'& becomes &'Ford.Prefect@hitch.fict.example'&.
22796 .section "When does rewriting happen?" "SECID148"
22797 .cindex "rewriting" "timing of"
22798 .cindex "&ACL;" "rewriting addresses in"
22799 Configured address rewriting can take place at several different stages of a
22800 message's processing.
22802 .vindex "&$sender_address$&"
22803 At the start of an ACL for MAIL, the sender address may have been rewritten
22804 by a special SMTP-time rewrite rule (see section &<<SECTrewriteS>>&), but no
22805 ordinary rewrite rules have yet been applied. If, however, the sender address
22806 is verified in the ACL, it is rewritten before verification, and remains
22807 rewritten thereafter. The subsequent value of &$sender_address$& is the
22808 rewritten address. This also applies if sender verification happens in a
22809 RCPT ACL. Otherwise, when the sender address is not verified, it is
22810 rewritten as soon as a message's header lines have been received.
22812 .vindex "&$domain$&"
22813 .vindex "&$local_part$&"
22814 Similarly, at the start of an ACL for RCPT, the current recipient's address
22815 may have been rewritten by a special SMTP-time rewrite rule, but no ordinary
22816 rewrite rules have yet been applied to it. However, the behaviour is different
22817 from the sender address when a recipient is verified. The address is rewritten
22818 for the verification, but the rewriting is not remembered at this stage. The
22819 value of &$local_part$& and &$domain$& after verification are always the same
22820 as they were before (that is, they contain the unrewritten &-- except for
22821 SMTP-time rewriting &-- address).
22823 As soon as a message's header lines have been received, all the envelope
22824 recipient addresses are permanently rewritten, and rewriting is also applied to
22825 the addresses in the header lines (if configured). This happens before adding
22826 any header lines that were specified in MAIL or RCPT ACLs, and
22827 .cindex "&[local_scan()]& function" "address rewriting; timing of"
22828 before the DATA ACL and &[local_scan()]& functions are run.
22830 When an address is being routed, either for delivery or for verification,
22831 rewriting is applied immediately to child addresses that are generated by
22832 redirection, unless &%no_rewrite%& is set on the router.
22834 .cindex "envelope sender" "rewriting at transport time"
22835 .cindex "rewriting" "at transport time"
22836 .cindex "header lines" "rewriting at transport time"
22837 At transport time, additional rewriting of addresses in header lines can be
22838 specified by setting the generic &%headers_rewrite%& option on a transport.
22839 This option contains rules that are identical in form to those in the rewrite
22840 section of the configuration file. They are applied to the original message
22841 header lines and any that were added by ACLs or a system filter. They are not
22842 applied to header lines that are added by routers or the transport.
22844 The outgoing envelope sender can be rewritten by means of the &%return_path%&
22845 transport option. However, it is not possible to rewrite envelope recipients at
22851 .section "Testing the rewriting rules that apply on input" "SECID149"
22852 .cindex "rewriting" "testing"
22853 .cindex "testing" "rewriting"
22854 Exim's input rewriting configuration appears in a part of the run time
22855 configuration file headed by &"begin rewrite"&. It can be tested by the
22856 &%-brw%& command line option. This takes an address (which can be a full RFC
22857 2822 address) as its argument. The output is a list of how the address would be
22858 transformed by the rewriting rules for each of the different places it might
22859 appear in an incoming message, that is, for each different header and for the
22860 envelope sender and recipient fields. For example,
22862 exim -brw ph10@exim.workshop.example
22864 might produce the output
22866 sender: Philip.Hazel@exim.workshop.example
22867 from: Philip.Hazel@exim.workshop.example
22868 to: ph10@exim.workshop.example
22869 cc: ph10@exim.workshop.example
22870 bcc: ph10@exim.workshop.example
22871 reply-to: Philip.Hazel@exim.workshop.example
22872 env-from: Philip.Hazel@exim.workshop.example
22873 env-to: ph10@exim.workshop.example
22875 which shows that rewriting has been set up for that address when used in any of
22876 the source fields, but not when it appears as a recipient address. At the
22877 present time, there is no equivalent way of testing rewriting rules that are
22878 set for a particular transport.
22881 .section "Rewriting rules" "SECID150"
22882 .cindex "rewriting" "rules"
22883 The rewrite section of the configuration file consists of lines of rewriting
22886 <&'source pattern'&> <&'replacement'&> <&'flags'&>
22888 Rewriting rules that are specified for the &%headers_rewrite%& generic
22889 transport option are given as a colon-separated list. Each item in the list
22890 takes the same form as a line in the main rewriting configuration (except that
22891 any colons must be doubled, of course).
22893 The formats of source patterns and replacement strings are described below.
22894 Each is terminated by white space, unless enclosed in double quotes, in which
22895 case normal quoting conventions apply inside the quotes. The flags are single
22896 characters which may appear in any order. Spaces and tabs between them are
22899 For each address that could potentially be rewritten, the rules are scanned in
22900 order, and replacements for the address from earlier rules can themselves be
22901 replaced by later rules (but see the &"q"& and &"R"& flags).
22903 The order in which addresses are rewritten is undefined, may change between
22904 releases, and must not be relied on, with one exception: when a message is
22905 received, the envelope sender is always rewritten first, before any header
22906 lines are rewritten. For example, the replacement string for a rewrite of an
22907 address in &'To:'& must not assume that the message's address in &'From:'& has
22908 (or has not) already been rewritten. However, a rewrite of &'From:'& may assume
22909 that the envelope sender has already been rewritten.
22911 .vindex "&$domain$&"
22912 .vindex "&$local_part$&"
22913 The variables &$local_part$& and &$domain$& can be used in the replacement
22914 string to refer to the address that is being rewritten. Note that lookup-driven
22915 rewriting can be done by a rule of the form
22919 where the lookup key uses &$1$& and &$2$& or &$local_part$& and &$domain$& to
22920 refer to the address that is being rewritten.
22923 .section "Rewriting patterns" "SECID151"
22924 .cindex "rewriting" "patterns"
22925 .cindex "address list" "in a rewriting pattern"
22926 The source pattern in a rewriting rule is any item which may appear in an
22927 address list (see section &<<SECTaddresslist>>&). It is in fact processed as a
22928 single-item address list, which means that it is expanded before being tested
22929 against the address. As always, if you use a regular expression as a pattern,
22930 you must take care to escape dollar and backslash characters, or use the &`\N`&
22931 facility to suppress string expansion within the regular expression.
22933 Domains in patterns should be given in lower case. Local parts in patterns are
22934 case-sensitive. If you want to do case-insensitive matching of local parts, you
22935 can use a regular expression that starts with &`^(?i)`&.
22937 .cindex "numerical variables (&$1$& &$2$& etc)" "in rewriting rules"
22938 After matching, the numerical variables &$1$&, &$2$&, etc. may be set,
22939 depending on the type of match which occurred. These can be used in the
22940 replacement string to insert portions of the incoming address. &$0$& always
22941 refers to the complete incoming address. When a regular expression is used, the
22942 numerical variables are set from its capturing subexpressions. For other types
22943 of pattern they are set as follows:
22946 If a local part or domain starts with an asterisk, the numerical variables
22947 refer to the character strings matched by asterisks, with &$1$& associated with
22948 the first asterisk, and &$2$& with the second, if present. For example, if the
22951 *queen@*.fict.example
22953 is matched against the address &'hearts-queen@wonderland.fict.example'& then
22955 $0 = hearts-queen@wonderland.fict.example
22959 Note that if the local part does not start with an asterisk, but the domain
22960 does, it is &$1$& that contains the wild part of the domain.
22963 If the domain part of the pattern is a partial lookup, the wild and fixed parts
22964 of the domain are placed in the next available numerical variables. Suppose,
22965 for example, that the address &'foo@bar.baz.example'& is processed by a
22966 rewriting rule of the form
22968 &`*@partial-dbm;/some/dbm/file`& <&'replacement string'&>
22970 and the key in the file that matches the domain is &`*.baz.example`&. Then
22976 If the address &'foo@baz.example'& is looked up, this matches the same
22977 wildcard file entry, and in this case &$2$& is set to the empty string, but
22978 &$3$& is still set to &'baz.example'&. If a non-wild key is matched in a
22979 partial lookup, &$2$& is again set to the empty string and &$3$& is set to the
22980 whole domain. For non-partial domain lookups, no numerical variables are set.
22984 .section "Rewriting replacements" "SECID152"
22985 .cindex "rewriting" "replacements"
22986 If the replacement string for a rule is a single asterisk, addresses that
22987 match the pattern and the flags are &'not'& rewritten, and no subsequent
22988 rewriting rules are scanned. For example,
22990 hatta@lookingglass.fict.example * f
22992 specifies that &'hatta@lookingglass.fict.example'& is never to be rewritten in
22995 .vindex "&$domain$&"
22996 .vindex "&$local_part$&"
22997 If the replacement string is not a single asterisk, it is expanded, and must
22998 yield a fully qualified address. Within the expansion, the variables
22999 &$local_part$& and &$domain$& refer to the address that is being rewritten.
23000 Any letters they contain retain their original case &-- they are not lower
23001 cased. The numerical variables are set up according to the type of pattern that
23002 matched the address, as described above. If the expansion is forced to fail by
23003 the presence of &"fail"& in a conditional or lookup item, rewriting by the
23004 current rule is abandoned, but subsequent rules may take effect. Any other
23005 expansion failure causes the entire rewriting operation to be abandoned, and an
23006 entry written to the panic log.
23010 .section "Rewriting flags" "SECID153"
23011 There are three different kinds of flag that may appear on rewriting rules:
23014 Flags that specify which headers and envelope addresses to rewrite: E, F, T, b,
23017 A flag that specifies rewriting at SMTP time: S.
23019 Flags that control the rewriting process: Q, q, R, w.
23022 For rules that are part of the &%headers_rewrite%& generic transport option,
23023 E, F, T, and S are not permitted.
23027 .section "Flags specifying which headers and envelope addresses to rewrite" &&&
23029 .cindex "rewriting" "flags"
23030 If none of the following flag letters, nor the &"S"& flag (see section
23031 &<<SECTrewriteS>>&) are present, a main rewriting rule applies to all headers
23032 and to both the sender and recipient fields of the envelope, whereas a
23033 transport-time rewriting rule just applies to all headers. Otherwise, the
23034 rewriting rule is skipped unless the relevant addresses are being processed.
23036 &`E`& rewrite all envelope fields
23037 &`F`& rewrite the envelope From field
23038 &`T`& rewrite the envelope To field
23039 &`b`& rewrite the &'Bcc:'& header
23040 &`c`& rewrite the &'Cc:'& header
23041 &`f`& rewrite the &'From:'& header
23042 &`h`& rewrite all headers
23043 &`r`& rewrite the &'Reply-To:'& header
23044 &`s`& rewrite the &'Sender:'& header
23045 &`t`& rewrite the &'To:'& header
23047 "All headers" means all of the headers listed above that can be selected
23048 individually, plus their &'Resent-'& versions. It does not include
23049 other headers such as &'Subject:'& etc.
23051 You should be particularly careful about rewriting &'Sender:'& headers, and
23052 restrict this to special known cases in your own domains.
23055 .section "The SMTP-time rewriting flag" "SECTrewriteS"
23056 .cindex "SMTP" "rewriting malformed addresses"
23057 .cindex "RCPT" "rewriting argument of"
23058 .cindex "MAIL" "rewriting argument of"
23059 The rewrite flag &"S"& specifies a rewrite of incoming envelope addresses at
23060 SMTP time, as soon as an address is received in a MAIL or RCPT command, and
23061 before any other processing; even before syntax checking. The pattern is
23062 required to be a regular expression, and it is matched against the whole of the
23063 data for the command, including any surrounding angle brackets.
23065 .vindex "&$domain$&"
23066 .vindex "&$local_part$&"
23067 This form of rewrite rule allows for the handling of addresses that are not
23068 compliant with RFCs 2821 and 2822 (for example, &"bang paths"& in batched SMTP
23069 input). Because the input is not required to be a syntactically valid address,
23070 the variables &$local_part$& and &$domain$& are not available during the
23071 expansion of the replacement string. The result of rewriting replaces the
23072 original address in the MAIL or RCPT command.
23075 .section "Flags controlling the rewriting process" "SECID155"
23076 There are four flags which control the way the rewriting process works. These
23077 take effect only when a rule is invoked, that is, when the address is of the
23078 correct type (matches the flags) and matches the pattern:
23081 If the &"Q"& flag is set on a rule, the rewritten address is permitted to be an
23082 unqualified local part. It is qualified with &%qualify_recipient%&. In the
23083 absence of &"Q"& the rewritten address must always include a domain.
23085 If the &"q"& flag is set on a rule, no further rewriting rules are considered,
23086 even if no rewriting actually takes place because of a &"fail"& in the
23087 expansion. The &"q"& flag is not effective if the address is of the wrong type
23088 (does not match the flags) or does not match the pattern.
23090 The &"R"& flag causes a successful rewriting rule to be re-applied to the new
23091 address, up to ten times. It can be combined with the &"q"& flag, to stop
23092 rewriting once it fails to match (after at least one successful rewrite).
23094 .cindex "rewriting" "whole addresses"
23095 When an address in a header is rewritten, the rewriting normally applies only
23096 to the working part of the address, with any comments and RFC 2822 &"phrase"&
23097 left unchanged. For example, rewriting might change
23099 From: Ford Prefect <fp42@restaurant.hitch.fict.example>
23103 From: Ford Prefect <prefectf@hitch.fict.example>
23106 Sometimes there is a need to replace the whole address item, and this can be
23107 done by adding the flag letter &"w"& to a rule. If this is set on a rule that
23108 causes an address in a header line to be rewritten, the entire address is
23109 replaced, not just the working part. The replacement must be a complete RFC
23110 2822 address, including the angle brackets if necessary. If text outside angle
23111 brackets contains a character whose value is greater than 126 or less than 32
23112 (except for tab), the text is encoded according to RFC 2047. The character set
23113 is taken from &%headers_charset%&, which defaults to ISO-8859-1.
23115 When the &"w"& flag is set on a rule that causes an envelope address to be
23116 rewritten, all but the working part of the replacement address is discarded.
23120 .section "Rewriting examples" "SECID156"
23121 Here is an example of the two common rewriting paradigms:
23123 *@*.hitch.fict.example $1@hitch.fict.example
23124 *@hitch.fict.example ${lookup{$1}dbm{/etc/realnames}\
23125 {$value}fail}@hitch.fict.example bctfrF
23127 Note the use of &"fail"& in the lookup expansion in the second rule, forcing
23128 the string expansion to fail if the lookup does not succeed. In this context it
23129 has the effect of leaving the original address unchanged, but Exim goes on to
23130 consider subsequent rewriting rules, if any, because the &"q"& flag is not
23131 present in that rule. An alternative to &"fail"& would be to supply &$1$&
23132 explicitly, which would cause the rewritten address to be the same as before,
23133 at the cost of a small bit of processing. Not supplying either of these is an
23134 error, since the rewritten address would then contain no local part.
23136 The first example above replaces the domain with a superior, more general
23137 domain. This may not be desirable for certain local parts. If the rule
23139 root@*.hitch.fict.example *
23141 were inserted before the first rule, rewriting would be suppressed for the
23142 local part &'root'& at any domain ending in &'hitch.fict.example'&.
23144 Rewriting can be made conditional on a number of tests, by making use of
23145 &${if$& in the expansion item. For example, to apply a rewriting rule only to
23146 messages that originate outside the local host:
23148 *@*.hitch.fict.example "${if !eq {$sender_host_address}{}\
23149 {$1@hitch.fict.example}fail}"
23151 The replacement string is quoted in this example because it contains white
23154 .cindex "rewriting" "bang paths"
23155 .cindex "bang paths" "rewriting"
23156 Exim does not handle addresses in the form of &"bang paths"&. If it sees such
23157 an address it treats it as an unqualified local part which it qualifies with
23158 the local qualification domain (if the source of the message is local or if the
23159 remote host is permitted to send unqualified addresses). Rewriting can
23160 sometimes be used to handle simple bang paths with a fixed number of
23161 components. For example, the rule
23163 \N^([^!]+)!(.*)@your.domain.example$\N $2@$1
23165 rewrites a two-component bang path &'host.name!user'& as the domain address
23166 &'user@host.name'&. However, there is a security implication in using this as
23167 a global rewriting rule for envelope addresses. It can provide a backdoor
23168 method for using your system as a relay, because the incoming addresses appear
23169 to be local. If the bang path addresses are received via SMTP, it is safer to
23170 use the &"S"& flag to rewrite them as they are received, so that relay checking
23171 can be done on the rewritten addresses.
23178 . ////////////////////////////////////////////////////////////////////////////
23179 . ////////////////////////////////////////////////////////////////////////////
23181 .chapter "Retry configuration" "CHAPretry"
23182 .scindex IIDretconf1 "retry" "configuration, description of"
23183 .scindex IIDregconf2 "configuration file" "retry section"
23184 The &"retry"& section of the runtime configuration file contains a list of
23185 retry rules that control how often Exim tries to deliver messages that cannot
23186 be delivered at the first attempt. If there are no retry rules (the section is
23187 empty or not present), there are no retries. In this situation, temporary
23188 errors are treated as permanent. The default configuration contains a single,
23189 general-purpose retry rule (see section &<<SECID57>>&). The &%-brt%& command
23190 line option can be used to test which retry rule will be used for a given
23191 address, domain and error.
23193 The most common cause of retries is temporary failure to deliver to a remote
23194 host because the host is down, or inaccessible because of a network problem.
23195 Exim's retry processing in this case is applied on a per-host (strictly, per IP
23196 address) basis, not on a per-message basis. Thus, if one message has recently
23197 been delayed, delivery of a new message to the same host is not immediately
23198 tried, but waits for the host's retry time to arrive. If the &%retry_defer%&
23199 log selector is set, the message
23200 .cindex "retry" "time not reached"
23201 &"retry time not reached"& is written to the main log whenever a delivery is
23202 skipped for this reason. Section &<<SECToutSMTPerr>>& contains more details of
23203 the handling of errors during remote deliveries.
23205 Retry processing applies to routing as well as to delivering, except as covered
23206 in the next paragraph. The retry rules do not distinguish between these
23207 actions. It is not possible, for example, to specify different behaviour for
23208 failures to route the domain &'snark.fict.example'& and failures to deliver to
23209 the host &'snark.fict.example'&. I didn't think anyone would ever need this
23210 added complication, so did not implement it. However, although they share the
23211 same retry rule, the actual retry times for routing and transporting a given
23212 domain are maintained independently.
23214 When a delivery is not part of a queue run (typically an immediate delivery on
23215 receipt of a message), the routers are always run, and local deliveries are
23216 always attempted, even if retry times are set for them. This makes for better
23217 behaviour if one particular message is causing problems (for example, causing
23218 quota overflow, or provoking an error in a filter file). If such a delivery
23219 suffers a temporary failure, the retry data is updated as normal, and
23220 subsequent delivery attempts from queue runs occur only when the retry time for
23221 the local address is reached.
23223 .section "Changing retry rules" "SECID157"
23224 If you change the retry rules in your configuration, you should consider
23225 whether or not to delete the retry data that is stored in Exim's spool area in
23226 files with names like &_db/retry_&. Deleting any of Exim's hints files is
23227 always safe; that is why they are called &"hints"&.
23229 The hints retry data contains suggested retry times based on the previous
23230 rules. In the case of a long-running problem with a remote host, it might
23231 record the fact that the host has timed out. If your new rules increase the
23232 timeout time for such a host, you should definitely remove the old retry data
23233 and let Exim recreate it, based on the new rules. Otherwise Exim might bounce
23234 messages that it should now be retaining.
23238 .section "Format of retry rules" "SECID158"
23239 .cindex "retry" "rules"
23240 Each retry rule occupies one line and consists of three or four parts,
23241 separated by white space: a pattern, an error name, an optional list of sender
23242 addresses, and a list of retry parameters. The pattern and sender lists must be
23243 enclosed in double quotes if they contain white space. The rules are searched
23244 in order until one is found where the pattern, error name, and sender list (if
23245 present) match the failing host or address, the error that occurred, and the
23246 message's sender, respectively.
23249 The pattern is any single item that may appear in an address list (see section
23250 &<<SECTaddresslist>>&). It is in fact processed as a one-item address list,
23251 which means that it is expanded before being tested against the address that
23252 has been delayed. A negated address list item is permitted. Address
23253 list processing treats a plain domain name as if it were preceded by &"*@"&,
23254 which makes it possible for many retry rules to start with just a domain. For
23257 lookingglass.fict.example * F,24h,30m;
23259 provides a rule for any address in the &'lookingglass.fict.example'& domain,
23262 alice@lookingglass.fict.example * F,24h,30m;
23264 applies only to temporary failures involving the local part &%alice%&.
23265 In practice, almost all rules start with a domain name pattern without a local
23268 .cindex "regular expressions" "in retry rules"
23269 &*Warning*&: If you use a regular expression in a routing rule pattern, it
23270 must match a complete address, not just a domain, because that is how regular
23271 expressions work in address lists.
23273 &`^\Nxyz\d+\.abc\.example$\N * G,1h,10m,2`& &%Wrong%&
23274 &`^\N[^@]+@xyz\d+\.abc\.example$\N * G,1h,10m,2`& &%Right%&
23278 .section "Choosing which retry rule to use for address errors" "SECID159"
23279 When Exim is looking for a retry rule after a routing attempt has failed (for
23280 example, after a DNS timeout), each line in the retry configuration is tested
23281 against the complete address only if &%retry_use_local_part%& is set for the
23282 router. Otherwise, only the domain is used, except when matching against a
23283 regular expression, when the local part of the address is replaced with &"*"&.
23284 A domain on its own can match a domain pattern, or a pattern that starts with
23285 &"*@"&. By default, &%retry_use_local_part%& is true for routers where
23286 &%check_local_user%& is true, and false for other routers.
23288 Similarly, when Exim is looking for a retry rule after a local delivery has
23289 failed (for example, after a mailbox full error), each line in the retry
23290 configuration is tested against the complete address only if
23291 &%retry_use_local_part%& is set for the transport (it defaults true for all
23294 .cindex "4&'xx'& responses" "retry rules for"
23295 However, when Exim is looking for a retry rule after a remote delivery attempt
23296 suffers an address error (a 4&'xx'& SMTP response for a recipient address), the
23297 whole address is always used as the key when searching the retry rules. The
23298 rule that is found is used to create a retry time for the combination of the
23299 failing address and the message's sender. It is the combination of sender and
23300 recipient that is delayed in subsequent queue runs until its retry time is
23301 reached. You can delay the recipient without regard to the sender by setting
23302 &%address_retry_include_sender%& false in the &(smtp)& transport but this can
23303 lead to problems with servers that regularly issue 4&'xx'& responses to RCPT
23308 .section "Choosing which retry rule to use for host and message errors" &&&
23310 For a temporary error that is not related to an individual address (for
23311 example, a connection timeout), each line in the retry configuration is checked
23312 twice. First, the name of the remote host is used as a domain name (preceded by
23313 &"*@"& when matching a regular expression). If this does not match the line,
23314 the domain from the email address is tried in a similar fashion. For example,
23315 suppose the MX records for &'a.b.c.example'& are
23317 a.b.c.example MX 5 x.y.z.example
23321 and the retry rules are
23323 p.q.r.example * F,24h,30m;
23324 a.b.c.example * F,4d,45m;
23326 and a delivery to the host &'x.y.z.example'& suffers a connection failure. The
23327 first rule matches neither the host nor the domain, so Exim looks at the second
23328 rule. This does not match the host, but it does match the domain, so it is used
23329 to calculate the retry time for the host &'x.y.z.example'&. Meanwhile, Exim
23330 tries to deliver to &'p.q.r.example'&. If this also suffers a host error, the
23331 first retry rule is used, because it matches the host.
23333 In other words, temporary failures to deliver to host &'p.q.r.example'& use the
23334 first rule to determine retry times, but for all the other hosts for the domain
23335 &'a.b.c.example'&, the second rule is used. The second rule is also used if
23336 routing to &'a.b.c.example'& suffers a temporary failure.
23338 &*Note*&: The host name is used when matching the patterns, not its IP address.
23339 However, if a message is routed directly to an IP address without the use of a
23340 host name, for example, if a &(manualroute)& router contains a setting such as:
23342 route_list = *.a.example 192.168.34.23
23344 then the &"host name"& that is used when searching for a retry rule is the
23345 textual form of the IP address.
23347 .section "Retry rules for specific errors" "SECID161"
23348 .cindex "retry" "specific errors; specifying"
23349 The second field in a retry rule is the name of a particular error, or an
23350 asterisk, which matches any error. The errors that can be tested for are:
23353 .vitem &%auth_failed%&
23354 Authentication failed when trying to send to a host in the
23355 &%hosts_require_auth%& list in an &(smtp)& transport.
23357 .vitem &%data_4xx%&
23358 A 4&'xx'& error was received for an outgoing DATA command, either immediately
23359 after the command, or after sending the message's data.
23361 .vitem &%mail_4xx%&
23362 A 4&'xx'& error was received for an outgoing MAIL command.
23364 .vitem &%rcpt_4xx%&
23365 A 4&'xx'& error was received for an outgoing RCPT command.
23368 For the three 4&'xx'& errors, either the first or both of the x's can be given
23369 as specific digits, for example: &`mail_45x`& or &`rcpt_436`&. For example, to
23370 recognize 452 errors given to RCPT commands for addresses in a certain domain,
23371 and have retries every ten minutes with a one-hour timeout, you could set up a
23372 retry rule of this form:
23374 the.domain.name rcpt_452 F,1h,10m
23376 These errors apply to both outgoing SMTP (the &(smtp)& transport) and outgoing
23377 LMTP (either the &(lmtp)& transport, or the &(smtp)& transport in LMTP mode).
23380 .vitem &%lost_connection%&
23381 A server unexpectedly closed the SMTP connection. There may, of course,
23382 legitimate reasons for this (host died, network died), but if it repeats a lot
23383 for the same host, it indicates something odd.
23385 .vitem &%refused_MX%&
23386 A connection to a host obtained from an MX record was refused.
23388 .vitem &%refused_A%&
23389 A connection to a host not obtained from an MX record was refused.
23392 A connection was refused.
23394 .vitem &%timeout_connect_MX%&
23395 A connection attempt to a host obtained from an MX record timed out.
23397 .vitem &%timeout_connect_A%&
23398 A connection attempt to a host not obtained from an MX record timed out.
23400 .vitem &%timeout_connect%&
23401 A connection attempt timed out.
23403 .vitem &%timeout_MX%&
23404 There was a timeout while connecting or during an SMTP session with a host
23405 obtained from an MX record.
23407 .vitem &%timeout_A%&
23408 There was a timeout while connecting or during an SMTP session with a host not
23409 obtained from an MX record.
23412 There was a timeout while connecting or during an SMTP session.
23414 .vitem &%tls_required%&
23415 The server was required to use TLS (it matched &%hosts_require_tls%& in the
23416 &(smtp)& transport), but either did not offer TLS, or it responded with 4&'xx'&
23417 to STARTTLS, or there was a problem setting up the TLS connection.
23420 A mailbox quota was exceeded in a local delivery by the &(appendfile)&
23423 .vitem &%quota_%&<&'time'&>
23424 .cindex "quota" "error testing in retry rule"
23425 .cindex "retry" "quota error testing"
23426 A mailbox quota was exceeded in a local delivery by the &(appendfile)&
23427 transport, and the mailbox has not been accessed for <&'time'&>. For example,
23428 &'quota_4d'& applies to a quota error when the mailbox has not been accessed
23432 .cindex "mailbox" "time of last read"
23433 The idea of &%quota_%&<&'time'&> is to make it possible to have shorter
23434 timeouts when the mailbox is full and is not being read by its owner. Ideally,
23435 it should be based on the last time that the user accessed the mailbox.
23436 However, it is not always possible to determine this. Exim uses the following
23440 If the mailbox is a single file, the time of last access (the &"atime"&) is
23441 used. As no new messages are being delivered (because the mailbox is over
23442 quota), Exim does not access the file, so this is the time of last user access.
23444 .cindex "maildir format" "time of last read"
23445 For a maildir delivery, the time of last modification of the &_new_&
23446 subdirectory is used. As the mailbox is over quota, no new files are created in
23447 the &_new_& subdirectory, because no new messages are being delivered. Any
23448 change to the &_new_& subdirectory is therefore assumed to be the result of an
23449 MUA moving a new message to the &_cur_& directory when it is first read. The
23450 time that is used is therefore the last time that the user read a new message.
23452 For other kinds of multi-file mailbox, the time of last access cannot be
23453 obtained, so a retry rule that uses this type of error field is never matched.
23456 The quota errors apply both to system-enforced quotas and to Exim's own quota
23457 mechanism in the &(appendfile)& transport. The &'quota'& error also applies
23458 when a local delivery is deferred because a partition is full (the ENOSPC
23463 .section "Retry rules for specified senders" "SECID162"
23464 .cindex "retry" "rules; sender-specific"
23465 You can specify retry rules that apply only when the failing message has a
23466 specific sender. In particular, this can be used to define retry rules that
23467 apply only to bounce messages. The third item in a retry rule can be of this
23470 &`senders=`&<&'address list'&>
23472 The retry timings themselves are then the fourth item. For example:
23474 * rcpt_4xx senders=: F,1h,30m
23476 matches recipient 4&'xx'& errors for bounce messages sent to any address at any
23477 host. If the address list contains white space, it must be enclosed in quotes.
23480 a.domain rcpt_452 senders="xb.dom : yc.dom" G,8h,10m,1.5
23482 &*Warning*&: This facility can be unhelpful if it is used for host errors
23483 (which do not depend on the recipient). The reason is that the sender is used
23484 only to match the retry rule. Once the rule has been found for a host error,
23485 its contents are used to set a retry time for the host, and this will apply to
23486 all messages, not just those with specific senders.
23488 When testing retry rules using &%-brt%&, you can supply a sender using the
23489 &%-f%& command line option, like this:
23491 exim -f "" -brt user@dom.ain
23493 If you do not set &%-f%& with &%-brt%&, a retry rule that contains a senders
23494 list is never matched.
23500 .section "Retry parameters" "SECID163"
23501 .cindex "retry" "parameters in rules"
23502 The third (or fourth, if a senders list is present) field in a retry rule is a
23503 sequence of retry parameter sets, separated by semicolons. Each set consists of
23505 <&'letter'&>,<&'cutoff time'&>,<&'arguments'&>
23507 The letter identifies the algorithm for computing a new retry time; the cutoff
23508 time is the time beyond which this algorithm no longer applies, and the
23509 arguments vary the algorithm's action. The cutoff time is measured from the
23510 time that the first failure for the domain (combined with the local part if
23511 relevant) was detected, not from the time the message was received.
23513 .cindex "retry" "algorithms"
23514 .cindex "retry" "fixed intervals"
23515 .cindex "retry" "increasing intervals"
23516 .cindex "retry" "random intervals"
23517 The available algorithms are:
23520 &'F'&: retry at fixed intervals. There is a single time parameter specifying
23523 &'G'&: retry at geometrically increasing intervals. The first argument
23524 specifies a starting value for the interval, and the second a multiplier, which
23525 is used to increase the size of the interval at each retry.
23527 &'H'&: retry at randomized intervals. The arguments are as for &'G'&. For each
23528 retry, the previous interval is multiplied by the factor in order to get a
23529 maximum for the next interval. The minimum interval is the first argument of
23530 the parameter, and an actual interval is chosen randomly between them. Such a
23531 rule has been found to be helpful in cluster configurations when all the
23532 members of the cluster restart at once, and may therefore synchronize their
23533 queue processing times.
23536 When computing the next retry time, the algorithm definitions are scanned in
23537 order until one whose cutoff time has not yet passed is reached. This is then
23538 used to compute a new retry time that is later than the current time. In the
23539 case of fixed interval retries, this simply means adding the interval to the
23540 current time. For geometrically increasing intervals, retry intervals are
23541 computed from the rule's parameters until one that is greater than the previous
23542 interval is found. The main configuration variable
23543 .cindex "limit" "retry interval"
23544 .cindex "retry" "interval, maximum"
23545 .oindex "&%retry_interval_max%&"
23546 &%retry_interval_max%& limits the maximum interval between retries. It
23547 cannot be set greater than &`24h`&, which is its default value.
23549 A single remote domain may have a number of hosts associated with it, and each
23550 host may have more than one IP address. Retry algorithms are selected on the
23551 basis of the domain name, but are applied to each IP address independently. If,
23552 for example, a host has two IP addresses and one is unusable, Exim will
23553 generate retry times for it and will not try to use it until its next retry
23554 time comes. Thus the good IP address is likely to be tried first most of the
23557 .cindex "hints database" "use for retrying"
23558 Retry times are hints rather than promises. Exim does not make any attempt to
23559 run deliveries exactly at the computed times. Instead, a queue runner process
23560 starts delivery processes for delayed messages periodically, and these attempt
23561 new deliveries only for those addresses that have passed their next retry time.
23562 If a new message arrives for a deferred address, an immediate delivery attempt
23563 occurs only if the address has passed its retry time. In the absence of new
23564 messages, the minimum time between retries is the interval between queue runner
23565 processes. There is not much point in setting retry times of five minutes if
23566 your queue runners happen only once an hour, unless there are a significant
23567 number of incoming messages (which might be the case on a system that is
23568 sending everything to a smart host, for example).
23570 The data in the retry hints database can be inspected by using the
23571 &'exim_dumpdb'& or &'exim_fixdb'& utility programs (see chapter
23572 &<<CHAPutils>>&). The latter utility can also be used to change the data. The
23573 &'exinext'& utility script can be used to find out what the next retry times
23574 are for the hosts associated with a particular mail domain, and also for local
23575 deliveries that have been deferred.
23578 .section "Retry rule examples" "SECID164"
23579 Here are some example retry rules:
23581 alice@wonderland.fict.example quota_5d F,7d,3h
23582 wonderland.fict.example quota_5d
23583 wonderland.fict.example * F,1h,15m; G,2d,1h,2;
23584 lookingglass.fict.example * F,24h,30m;
23585 * refused_A F,2h,20m;
23586 * * F,2h,15m; G,16h,1h,1.5; F,5d,8h
23588 The first rule sets up special handling for mail to
23589 &'alice@wonderland.fict.example'& when there is an over-quota error and the
23590 mailbox has not been read for at least 5 days. Retries continue every three
23591 hours for 7 days. The second rule handles over-quota errors for all other local
23592 parts at &'wonderland.fict.example'&; the absence of a local part has the same
23593 effect as supplying &"*@"&. As no retry algorithms are supplied, messages that
23594 fail are bounced immediately if the mailbox has not been read for at least 5
23597 The third rule handles all other errors at &'wonderland.fict.example'&; retries
23598 happen every 15 minutes for an hour, then with geometrically increasing
23599 intervals until two days have passed since a delivery first failed. After the
23600 first hour there is a delay of one hour, then two hours, then four hours, and
23601 so on (this is a rather extreme example).
23603 The fourth rule controls retries for the domain &'lookingglass.fict.example'&.
23604 They happen every 30 minutes for 24 hours only. The remaining two rules handle
23605 all other domains, with special action for connection refusal from hosts that
23606 were not obtained from an MX record.
23608 The final rule in a retry configuration should always have asterisks in the
23609 first two fields so as to provide a general catch-all for any addresses that do
23610 not have their own special handling. This example tries every 15 minutes for 2
23611 hours, then with intervals starting at one hour and increasing by a factor of
23612 1.5 up to 16 hours, then every 8 hours up to 5 days.
23616 .section "Timeout of retry data" "SECID165"
23617 .cindex "timeout" "of retry data"
23618 .oindex "&%retry_data_expire%&"
23619 .cindex "hints database" "data expiry"
23620 .cindex "retry" "timeout of data"
23621 Exim timestamps the data that it writes to its retry hints database. When it
23622 consults the data during a delivery it ignores any that is older than the value
23623 set in &%retry_data_expire%& (default 7 days). If, for example, a host hasn't
23624 been tried for 7 days, Exim will try to deliver to it immediately a message
23625 arrives, and if that fails, it will calculate a retry time as if it were
23626 failing for the first time.
23628 This improves the behaviour for messages routed to rarely-used hosts such as MX
23629 backups. If such a host was down at one time, and happens to be down again when
23630 Exim tries a month later, using the old retry data would imply that it had been
23631 down all the time, which is not a justified assumption.
23633 If a host really is permanently dead, this behaviour causes a burst of retries
23634 every now and again, but only if messages routed to it are rare. If there is a
23635 message at least once every 7 days the retry data never expires.
23640 .section "Long-term failures" "SECID166"
23641 .cindex "delivery failure, long-term"
23642 .cindex "retry" "after long-term failure"
23643 Special processing happens when an email address has been failing for so long
23644 that the cutoff time for the last algorithm is reached. For example, using the
23645 default retry rule:
23647 * * F,2h,15m; G,16h,1h,1.5; F,4d,6h
23649 the cutoff time is four days. Reaching the retry cutoff is independent of how
23650 long any specific message has been failing; it is the length of continuous
23651 failure for the recipient address that counts.
23653 When the cutoff time is reached for a local delivery, or for all the IP
23654 addresses associated with a remote delivery, a subsequent delivery failure
23655 causes Exim to give up on the address, and a bounce message is generated.
23656 In order to cater for new messages that use the failing address, a next retry
23657 time is still computed from the final algorithm, and is used as follows:
23659 For local deliveries, one delivery attempt is always made for any subsequent
23660 messages. If this delivery fails, the address fails immediately. The
23661 post-cutoff retry time is not used.
23663 If the delivery is remote, there are two possibilities, controlled by the
23664 .oindex "&%delay_after_cutoff%&"
23665 &%delay_after_cutoff%& option of the &(smtp)& transport. The option is true by
23666 default. Until the post-cutoff retry time for one of the IP addresses is
23667 reached, the failing email address is bounced immediately, without a delivery
23668 attempt taking place. After that time, one new delivery attempt is made to
23669 those IP addresses that are past their retry times, and if that still fails,
23670 the address is bounced and new retry times are computed.
23672 In other words, when all the hosts for a given email address have been failing
23673 for a long time, Exim bounces rather then defers until one of the hosts' retry
23674 times is reached. Then it tries once, and bounces if that attempt fails. This
23675 behaviour ensures that few resources are wasted in repeatedly trying to deliver
23676 to a broken destination, but if the host does recover, Exim will eventually
23679 If &%delay_after_cutoff%& is set false, Exim behaves differently. If all IP
23680 addresses are past their final cutoff time, Exim tries to deliver to those IP
23681 addresses that have not been tried since the message arrived. If there are
23682 no suitable IP addresses, or if they all fail, the address is bounced. In other
23683 words, it does not delay when a new message arrives, but tries the expired
23684 addresses immediately, unless they have been tried since the message arrived.
23685 If there is a continuous stream of messages for the failing domains, setting
23686 &%delay_after_cutoff%& false means that there will be many more attempts to
23687 deliver to permanently failing IP addresses than when &%delay_after_cutoff%& is
23690 .section "Deliveries that work intermittently" "SECID167"
23691 .cindex "retry" "intermittently working deliveries"
23692 Some additional logic is needed to cope with cases where a host is
23693 intermittently available, or when a message has some attribute that prevents
23694 its delivery when others to the same address get through. In this situation,
23695 because some messages are successfully delivered, the &"retry clock"& for the
23696 host or address keeps getting reset by the successful deliveries, and so
23697 failing messages remain on the queue for ever because the cutoff time is never
23700 Two exceptional actions are applied to prevent this happening. The first
23701 applies to errors that are related to a message rather than a remote host.
23702 Section &<<SECToutSMTPerr>>& has a discussion of the different kinds of error;
23703 examples of message-related errors are 4&'xx'& responses to MAIL or DATA
23704 commands, and quota failures. For this type of error, if a message's arrival
23705 time is earlier than the &"first failed"& time for the error, the earlier time
23706 is used when scanning the retry rules to decide when to try next and when to
23707 time out the address.
23709 The exceptional second action applies in all cases. If a message has been on
23710 the queue for longer than the cutoff time of any applicable retry rule for a
23711 given address, a delivery is attempted for that address, even if it is not yet
23712 time, and if this delivery fails, the address is timed out. A new retry time is
23713 not computed in this case, so that other messages for the same address are
23714 considered immediately.
23715 .ecindex IIDretconf1
23716 .ecindex IIDregconf2
23723 . ////////////////////////////////////////////////////////////////////////////
23724 . ////////////////////////////////////////////////////////////////////////////
23726 .chapter "SMTP authentication" "CHAPSMTPAUTH"
23727 .scindex IIDauthconf1 "SMTP" "authentication configuration"
23728 .scindex IIDauthconf2 "authentication"
23729 The &"authenticators"& section of Exim's run time configuration is concerned
23730 with SMTP authentication. This facility is an extension to the SMTP protocol,
23731 described in RFC 2554, which allows a client SMTP host to authenticate itself
23732 to a server. This is a common way for a server to recognize clients that are
23733 permitted to use it as a relay. SMTP authentication is not of relevance to the
23734 transfer of mail between servers that have no managerial connection with each
23737 .cindex "AUTH" "description of"
23738 Very briefly, the way SMTP authentication works is as follows:
23741 The server advertises a number of authentication &'mechanisms'& in response to
23742 the client's EHLO command.
23744 The client issues an AUTH command, naming a specific mechanism. The command
23745 may, optionally, contain some authentication data.
23747 The server may issue one or more &'challenges'&, to which the client must send
23748 appropriate responses. In simple authentication mechanisms, the challenges are
23749 just prompts for user names and passwords. The server does not have to issue
23750 any challenges &-- in some mechanisms the relevant data may all be transmitted
23751 with the AUTH command.
23753 The server either accepts or denies authentication.
23755 If authentication succeeds, the client may optionally make use of the AUTH
23756 option on the MAIL command to pass an authenticated sender in subsequent
23757 mail transactions. Authentication lasts for the remainder of the SMTP
23760 If authentication fails, the client may give up, or it may try a different
23761 authentication mechanism, or it may try transferring mail over the
23762 unauthenticated connection.
23765 If you are setting up a client, and want to know which authentication
23766 mechanisms the server supports, you can use Telnet to connect to port 25 (the
23767 SMTP port) on the server, and issue an EHLO command. The response to this
23768 includes the list of supported mechanisms. For example:
23770 &`$ `&&*&`telnet server.example 25`&*&
23771 &`Trying 192.168.34.25...`&
23772 &`Connected to server.example.`&
23773 &`Escape character is '^]'.`&
23774 &`220 server.example ESMTP Exim 4.20 ...`&
23775 &*&`ehlo client.example`&*&
23776 &`250-server.example Hello client.example [10.8.4.5]`&
23777 &`250-SIZE 52428800`&
23782 The second-last line of this example output shows that the server supports
23783 authentication using the PLAIN mechanism. In Exim, the different authentication
23784 mechanisms are configured by specifying &'authenticator'& drivers. Like the
23785 routers and transports, which authenticators are included in the binary is
23786 controlled by build-time definitions. The following are currently available,
23787 included by setting
23790 AUTH_CYRUS_SASL=yes
23793 AUTH_HEIMDAL_GSSAPI=yes
23797 in &_Local/Makefile_&, respectively. The first of these supports the CRAM-MD5
23798 authentication mechanism (RFC 2195), and the second provides an interface to
23799 the Cyrus SASL authentication library.
23800 The third is an interface to Dovecot's authentication system, delegating the
23801 work via a socket interface.
23802 The fourth provides an interface to the GNU SASL authentication library, which
23803 provides mechanisms but typically not data sources.
23804 The fifth provides direct access to Heimdal GSSAPI, geared for Kerberos, but
23805 supporting setting a server keytab.
23806 The sixth can be configured to support
23807 the PLAIN authentication mechanism (RFC 2595) or the LOGIN mechanism, which is
23808 not formally documented, but used by several MUAs. The seventh authenticator
23809 supports Microsoft's &'Secure Password Authentication'& mechanism.
23811 The authenticators are configured using the same syntax as other drivers (see
23812 section &<<SECTfordricon>>&). If no authenticators are required, no
23813 authentication section need be present in the configuration file. Each
23814 authenticator can in principle have both server and client functions. When Exim
23815 is receiving SMTP mail, it is acting as a server; when it is sending out
23816 messages over SMTP, it is acting as a client. Authenticator configuration
23817 options are provided for use in both these circumstances.
23819 To make it clear which options apply to which situation, the prefixes
23820 &%server_%& and &%client_%& are used on option names that are specific to
23821 either the server or the client function, respectively. Server and client
23822 functions are disabled if none of their options are set. If an authenticator is
23823 to be used for both server and client functions, a single definition, using
23824 both sets of options, is required. For example:
23828 public_name = CRAM-MD5
23829 server_secret = ${if eq{$auth1}{ph10}{secret1}fail}
23831 client_secret = secret2
23833 The &%server_%& option is used when Exim is acting as a server, and the
23834 &%client_%& options when it is acting as a client.
23836 Descriptions of the individual authenticators are given in subsequent chapters.
23837 The remainder of this chapter covers the generic options for the
23838 authenticators, followed by general discussion of the way authentication works
23841 &*Beware:*& the meaning of &$auth1$&, &$auth2$&, ... varies on a per-driver and
23842 per-mechanism basis. Please read carefully to determine which variables hold
23843 account labels such as usercodes and which hold passwords or other
23844 authenticating data.
23846 Note that some mechanisms support two different identifiers for accounts: the
23847 &'authentication id'& and the &'authorization id'&. The contractions &'authn'&
23848 and &'authz'& are commonly encountered. The American spelling is standard here.
23849 Conceptually, authentication data such as passwords are tied to the identifier
23850 used to authenticate; servers may have rules to permit one user to act as a
23851 second user, so that after login the session is treated as though that second
23852 user had logged in. That second user is the &'authorization id'&. A robust
23853 configuration might confirm that the &'authz'& field is empty or matches the
23854 &'authn'& field. Often this is just ignored. The &'authn'& can be considered
23855 as verified data, the &'authz'& as an unverified request which the server might
23858 A &'realm'& is a text string, typically a domain name, presented by a server
23859 to a client to help it select an account and credentials to use. In some
23860 mechanisms, the client and server provably agree on the realm, but clients
23861 typically can not treat the realm as secure data to be blindly trusted.
23865 .section "Generic options for authenticators" "SECID168"
23866 .cindex "authentication" "generic options"
23867 .cindex "options" "generic; for authenticators"
23869 .option client_condition authenticators string&!! unset
23870 When Exim is authenticating as a client, it skips any authenticator whose
23871 &%client_condition%& expansion yields &"0"&, &"no"&, or &"false"&. This can be
23872 used, for example, to skip plain text authenticators when the connection is not
23873 encrypted by a setting such as:
23875 client_condition = ${if !eq{$tls_cipher}{}}
23877 (Older documentation incorrectly states that &$tls_cipher$& contains the cipher
23878 used for incoming messages. In fact, during SMTP delivery, it contains the
23879 cipher used for the delivery.)
23882 .option driver authenticators string unset
23883 This option must always be set. It specifies which of the available
23884 authenticators is to be used.
23887 .option public_name authenticators string unset
23888 This option specifies the name of the authentication mechanism that the driver
23889 implements, and by which it is known to the outside world. These names should
23890 contain only upper case letters, digits, underscores, and hyphens (RFC 2222),
23891 but Exim in fact matches them caselessly. If &%public_name%& is not set, it
23892 defaults to the driver's instance name.
23895 .option server_advertise_condition authenticators string&!! unset
23896 When a server is about to advertise an authentication mechanism, the condition
23897 is expanded. If it yields the empty string, &"0"&, &"no"&, or &"false"&, the
23898 mechanism is not advertised.
23899 If the expansion fails, the mechanism is not advertised. If the failure was not
23900 forced, and was not caused by a lookup defer, the incident is logged.
23901 See section &<<SECTauthexiser>>& below for further discussion.
23904 .option server_condition authenticators string&!! unset
23905 This option must be set for a &%plaintext%& server authenticator, where it
23906 is used directly to control authentication. See section &<<SECTplainserver>>&
23909 For the &(gsasl)& authenticator, this option is required for various
23910 mechanisms; see chapter &<<CHAPgsasl>>& for details.
23912 For the other authenticators, &%server_condition%& can be used as an additional
23913 authentication or authorization mechanism that is applied after the other
23914 authenticator conditions succeed. If it is set, it is expanded when the
23915 authenticator would otherwise return a success code. If the expansion is forced
23916 to fail, authentication fails. Any other expansion failure causes a temporary
23917 error code to be returned. If the result of a successful expansion is an empty
23918 string, &"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
23919 expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds. For any
23920 other result, a temporary error code is returned, with the expanded string as
23924 .option server_debug_print authenticators string&!! unset
23925 If this option is set and authentication debugging is enabled (see the &%-d%&
23926 command line option), the string is expanded and included in the debugging
23927 output when the authenticator is run as a server. This can help with checking
23928 out the values of variables.
23929 If expansion of the string fails, the error message is written to the debugging
23930 output, and Exim carries on processing.
23933 .option server_set_id authenticators string&!! unset
23934 .vindex "&$authenticated_id$&"
23935 When an Exim server successfully authenticates a client, this string is
23936 expanded using data from the authentication, and preserved for any incoming
23937 messages in the variable &$authenticated_id$&. It is also included in the log
23938 lines for incoming messages. For example, a user/password authenticator
23939 configuration might preserve the user name that was used to authenticate, and
23940 refer to it subsequently during delivery of the message.
23941 If expansion fails, the option is ignored.
23944 .option server_mail_auth_condition authenticators string&!! unset
23945 This option allows a server to discard authenticated sender addresses supplied
23946 as part of MAIL commands in SMTP connections that are authenticated by the
23947 driver on which &%server_mail_auth_condition%& is set. The option is not used
23948 as part of the authentication process; instead its (unexpanded) value is
23949 remembered for later use.
23950 How it is used is described in the following section.
23956 .section "The AUTH parameter on MAIL commands" "SECTauthparamail"
23957 .cindex "authentication" "sender; authenticated"
23958 .cindex "AUTH" "on MAIL command"
23959 When a client supplied an AUTH= item on a MAIL command, Exim applies
23960 the following checks before accepting it as the authenticated sender of the
23964 If the connection is not using extended SMTP (that is, HELO was used rather
23965 than EHLO), the use of AUTH= is a syntax error.
23967 If the value of the AUTH= parameter is &"<>"&, it is ignored.
23969 .vindex "&$authenticated_sender$&"
23970 If &%acl_smtp_mailauth%& is defined, the ACL it specifies is run. While it is
23971 running, the value of &$authenticated_sender$& is set to the value obtained
23972 from the AUTH= parameter. If the ACL does not yield &"accept"&, the value of
23973 &$authenticated_sender$& is deleted. The &%acl_smtp_mailauth%& ACL may not
23974 return &"drop"& or &"discard"&. If it defers, a temporary error code (451) is
23975 given for the MAIL command.
23977 If &%acl_smtp_mailauth%& is not defined, the value of the AUTH= parameter
23978 is accepted and placed in &$authenticated_sender$& only if the client has
23981 If the AUTH= value was accepted by either of the two previous rules, and
23982 the client has authenticated, and the authenticator has a setting for the
23983 &%server_mail_auth_condition%&, the condition is checked at this point. The
23984 valued that was saved from the authenticator is expanded. If the expansion
23985 fails, or yields an empty string, &"0"&, &"no"&, or &"false"&, the value of
23986 &$authenticated_sender$& is deleted. If the expansion yields any other value,
23987 the value of &$authenticated_sender$& is retained and passed on with the
23992 When &$authenticated_sender$& is set for a message, it is passed on to other
23993 hosts to which Exim authenticates as a client. Do not confuse this value with
23994 &$authenticated_id$&, which is a string obtained from the authentication
23995 process, and which is not usually a complete email address.
23997 .vindex "&$sender_address$&"
23998 Whenever an AUTH= value is ignored, the incident is logged. The ACL for
23999 MAIL, if defined, is run after AUTH= is accepted or ignored. It can
24000 therefore make use of &$authenticated_sender$&. The converse is not true: the
24001 value of &$sender_address$& is not yet set up when the &%acl_smtp_mailauth%&
24006 .section "Authentication on an Exim server" "SECTauthexiser"
24007 .cindex "authentication" "on an Exim server"
24008 When Exim receives an EHLO command, it advertises the public names of those
24009 authenticators that are configured as servers, subject to the following
24013 The client host must match &%auth_advertise_hosts%& (default *).
24015 It the &%server_advertise_condition%& option is set, its expansion must not
24016 yield the empty string, &"0"&, &"no"&, or &"false"&.
24019 The order in which the authenticators are defined controls the order in which
24020 the mechanisms are advertised.
24022 Some mail clients (for example, some versions of Netscape) require the user to
24023 provide a name and password for authentication whenever AUTH is advertised,
24024 even though authentication may not in fact be needed (for example, Exim may be
24025 set up to allow unconditional relaying from the client by an IP address check).
24026 You can make such clients more friendly by not advertising AUTH to them.
24027 For example, if clients on the 10.9.8.0/24 network are permitted (by the ACL
24028 that runs for RCPT) to relay without authentication, you should set
24030 auth_advertise_hosts = ! 10.9.8.0/24
24032 so that no authentication mechanisms are advertised to them.
24034 The &%server_advertise_condition%& controls the advertisement of individual
24035 authentication mechanisms. For example, it can be used to restrict the
24036 advertisement of a particular mechanism to encrypted connections, by a setting
24039 server_advertise_condition = ${if eq{$tls_cipher}{}{no}{yes}}
24041 .vindex "&$tls_cipher$&"
24042 If the session is encrypted, &$tls_cipher$& is not empty, and so the expansion
24043 yields &"yes"&, which allows the advertisement to happen.
24045 When an Exim server receives an AUTH command from a client, it rejects it
24046 immediately if AUTH was not advertised in response to an earlier EHLO
24047 command. This is the case if
24050 The client host does not match &%auth_advertise_hosts%&; or
24052 No authenticators are configured with server options; or
24054 Expansion of &%server_advertise_condition%& blocked the advertising of all the
24055 server authenticators.
24059 Otherwise, Exim runs the ACL specified by &%acl_smtp_auth%& in order
24060 to decide whether to accept the command. If &%acl_smtp_auth%& is not set,
24061 AUTH is accepted from any client host.
24063 If AUTH is not rejected by the ACL, Exim searches its configuration for a
24064 server authentication mechanism that was advertised in response to EHLO and
24065 that matches the one named in the AUTH command. If it finds one, it runs
24066 the appropriate authentication protocol, and authentication either succeeds or
24067 fails. If there is no matching advertised mechanism, the AUTH command is
24068 rejected with a 504 error.
24070 .vindex "&$received_protocol$&"
24071 .vindex "&$sender_host_authenticated$&"
24072 When a message is received from an authenticated host, the value of
24073 &$received_protocol$& is set to &"esmtpa"& or &"esmtpsa"& instead of &"esmtp"&
24074 or &"esmtps"&, and &$sender_host_authenticated$& contains the name (not the
24075 public name) of the authenticator driver that successfully authenticated the
24076 client from which the message was received. This variable is empty if there was
24077 no successful authentication.
24082 .section "Testing server authentication" "SECID169"
24083 .cindex "authentication" "testing a server"
24084 .cindex "AUTH" "testing a server"
24085 .cindex "base64 encoding" "creating authentication test data"
24086 Exim's &%-bh%& option can be useful for testing server authentication
24087 configurations. The data for the AUTH command has to be sent using base64
24088 encoding. A quick way to produce such data for testing is the following Perl
24092 printf ("%s", encode_base64(eval "\"$ARGV[0]\""));
24094 .cindex "binary zero" "in authentication data"
24095 This interprets its argument as a Perl string, and then encodes it. The
24096 interpretation as a Perl string allows binary zeros, which are required for
24097 some kinds of authentication, to be included in the data. For example, a
24098 command line to run this script on such data might be
24100 encode '\0user\0password'
24102 Note the use of single quotes to prevent the shell interpreting the
24103 backslashes, so that they can be interpreted by Perl to specify characters
24104 whose code value is zero.
24106 &*Warning 1*&: If either of the user or password strings starts with an octal
24107 digit, you must use three zeros instead of one after the leading backslash. If
24108 you do not, the octal digit that starts your string will be incorrectly
24109 interpreted as part of the code for the first character.
24111 &*Warning 2*&: If there are characters in the strings that Perl interprets
24112 specially, you must use a Perl escape to prevent them being misinterpreted. For
24113 example, a command such as
24115 encode '\0user@domain.com\0pas$$word'
24117 gives an incorrect answer because of the unescaped &"@"& and &"$"& characters.
24119 If you have the &%mimencode%& command installed, another way to do produce
24120 base64-encoded strings is to run the command
24122 echo -e -n `\0user\0password' | mimencode
24124 The &%-e%& option of &%echo%& enables the interpretation of backslash escapes
24125 in the argument, and the &%-n%& option specifies no newline at the end of its
24126 output. However, not all versions of &%echo%& recognize these options, so you
24127 should check your version before relying on this suggestion.
24131 .section "Authentication by an Exim client" "SECID170"
24132 .cindex "authentication" "on an Exim client"
24133 The &(smtp)& transport has two options called &%hosts_require_auth%& and
24134 &%hosts_try_auth%&. When the &(smtp)& transport connects to a server that
24135 announces support for authentication, and the host matches an entry in either
24136 of these options, Exim (as a client) tries to authenticate as follows:
24139 For each authenticator that is configured as a client, in the order in which
24140 they are defined in the configuration, it searches the authentication
24141 mechanisms announced by the server for one whose name matches the public name
24142 of the authenticator.
24145 .vindex "&$host_address$&"
24146 When it finds one that matches, it runs the authenticator's client code. The
24147 variables &$host$& and &$host_address$& are available for any string expansions
24148 that the client might do. They are set to the server's name and IP address. If
24149 any expansion is forced to fail, the authentication attempt is abandoned, and
24150 Exim moves on to the next authenticator. Otherwise an expansion failure causes
24151 delivery to be deferred.
24153 If the result of the authentication attempt is a temporary error or a timeout,
24154 Exim abandons trying to send the message to the host for the moment. It will
24155 try again later. If there are any backup hosts available, they are tried in the
24158 If the response to authentication is a permanent error (5&'xx'& code), Exim
24159 carries on searching the list of authenticators and tries another one if
24160 possible. If all authentication attempts give permanent errors, or if there are
24161 no attempts because no mechanisms match (or option expansions force failure),
24162 what happens depends on whether the host matches &%hosts_require_auth%& or
24163 &%hosts_try_auth%&. In the first case, a temporary error is generated, and
24164 delivery is deferred. The error can be detected in the retry rules, and thereby
24165 turned into a permanent error if you wish. In the second case, Exim tries to
24166 deliver the message unauthenticated.
24169 .cindex "AUTH" "on MAIL command"
24170 When Exim has authenticated itself to a remote server, it adds the AUTH
24171 parameter to the MAIL commands it sends, if it has an authenticated sender for
24172 the message. If the message came from a remote host, the authenticated sender
24173 is the one that was receiving on an incoming MAIL command, provided that the
24174 incoming connection was authenticated and the &%server_mail_auth%& condition
24175 allowed the authenticated sender to be retained. If a local process calls Exim
24176 to send a message, the sender address that is built from the login name and
24177 &%qualify_domain%& is treated as authenticated. However, if the
24178 &%authenticated_sender%& option is set on the &(smtp)& transport, it overrides
24179 the authenticated sender that was received with the message.
24180 .ecindex IIDauthconf1
24181 .ecindex IIDauthconf2
24188 . ////////////////////////////////////////////////////////////////////////////
24189 . ////////////////////////////////////////////////////////////////////////////
24191 .chapter "The plaintext authenticator" "CHAPplaintext"
24192 .scindex IIDplaiauth1 "&(plaintext)& authenticator"
24193 .scindex IIDplaiauth2 "authenticators" "&(plaintext)&"
24194 The &(plaintext)& authenticator can be configured to support the PLAIN and
24195 LOGIN authentication mechanisms, both of which transfer authentication data as
24196 plain (unencrypted) text (though base64 encoded). The use of plain text is a
24197 security risk; you are strongly advised to insist on the use of SMTP encryption
24198 (see chapter &<<CHAPTLS>>&) if you use the PLAIN or LOGIN mechanisms. If you do
24199 use unencrypted plain text, you should not use the same passwords for SMTP
24200 connections as you do for login accounts.
24202 .section "Plaintext options" "SECID171"
24203 .cindex "options" "&(plaintext)& authenticator (server)"
24204 When configured as a server, &(plaintext)& uses the following options:
24206 .option server_condition authenticators string&!! unset
24207 This is actually a global authentication option, but it must be set in order to
24208 configure the &(plaintext)& driver as a server. Its use is described below.
24210 .option server_prompts plaintext string&!! unset
24211 The contents of this option, after expansion, must be a colon-separated list of
24212 prompt strings. If expansion fails, a temporary authentication rejection is
24215 .section "Using plaintext in a server" "SECTplainserver"
24216 .cindex "AUTH" "in &(plaintext)& authenticator"
24217 .cindex "binary zero" "in &(plaintext)& authenticator"
24218 .cindex "numerical variables (&$1$& &$2$& etc)" &&&
24219 "in &(plaintext)& authenticator"
24220 .vindex "&$auth1$&, &$auth2$&, etc"
24221 .cindex "base64 encoding" "in &(plaintext)& authenticator"
24223 When running as a server, &(plaintext)& performs the authentication test by
24224 expanding a string. The data sent by the client with the AUTH command, or in
24225 response to subsequent prompts, is base64 encoded, and so may contain any byte
24226 values when decoded. If any data is supplied with the command, it is treated as
24227 a list of strings, separated by NULs (binary zeros), the first three of which
24228 are placed in the expansion variables &$auth1$&, &$auth2$&, and &$auth3$&
24229 (neither LOGIN nor PLAIN uses more than three strings).
24231 For compatibility with previous releases of Exim, the values are also placed in
24232 the expansion variables &$1$&, &$2$&, and &$3$&. However, the use of these
24233 variables for this purpose is now deprecated, as it can lead to confusion in
24234 string expansions that also use them for other things.
24236 If there are more strings in &%server_prompts%& than the number of strings
24237 supplied with the AUTH command, the remaining prompts are used to obtain more
24238 data. Each response from the client may be a list of NUL-separated strings.
24240 .vindex "&$authenticated_id$&"
24241 Once a sufficient number of data strings have been received,
24242 &%server_condition%& is expanded. If the expansion is forced to fail,
24243 authentication fails. Any other expansion failure causes a temporary error code
24244 to be returned. If the result of a successful expansion is an empty string,
24245 &"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
24246 expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds and the
24247 generic &%server_set_id%& option is expanded and saved in &$authenticated_id$&.
24248 For any other result, a temporary error code is returned, with the expanded
24249 string as the error text.
24251 &*Warning*&: If you use a lookup in the expansion to find the user's
24252 password, be sure to make the authentication fail if the user is unknown.
24253 There are good and bad examples at the end of the next section.
24257 .section "The PLAIN authentication mechanism" "SECID172"
24258 .cindex "PLAIN authentication mechanism"
24259 .cindex "authentication" "PLAIN mechanism"
24260 .cindex "binary zero" "in &(plaintext)& authenticator"
24261 The PLAIN authentication mechanism (RFC 2595) specifies that three strings be
24262 sent as one item of data (that is, one combined string containing two NUL
24263 separators). The data is sent either as part of the AUTH command, or
24264 subsequently in response to an empty prompt from the server.
24266 The second and third strings are a user name and a corresponding password.
24267 Using a single fixed user name and password as an example, this could be
24268 configured as follows:
24272 public_name = PLAIN
24274 server_condition = \
24275 ${if and {{eq{$auth2}{username}}{eq{$auth3}{mysecret}}}}
24276 server_set_id = $auth2
24278 Note that the default result strings from &%if%& (&"true"& or an empty string)
24279 are exactly what we want here, so they need not be specified. Obviously, if the
24280 password contains expansion-significant characters such as dollar, backslash,
24281 or closing brace, they have to be escaped.
24283 The &%server_prompts%& setting specifies a single, empty prompt (empty items at
24284 the end of a string list are ignored). If all the data comes as part of the
24285 AUTH command, as is commonly the case, the prompt is not used. This
24286 authenticator is advertised in the response to EHLO as
24290 and a client host can authenticate itself by sending the command
24292 AUTH PLAIN AHVzZXJuYW1lAG15c2VjcmV0
24294 As this contains three strings (more than the number of prompts), no further
24295 data is required from the client. Alternatively, the client may just send
24299 to initiate authentication, in which case the server replies with an empty
24300 prompt. The client must respond with the combined data string.
24302 The data string is base64 encoded, as required by the RFC. This example,
24303 when decoded, is <&'NUL'&>&`username`&<&'NUL'&>&`mysecret`&, where <&'NUL'&>
24304 represents a zero byte. This is split up into three strings, the first of which
24305 is empty. The &%server_condition%& option in the authenticator checks that the
24306 second two are &`username`& and &`mysecret`& respectively.
24308 Having just one fixed user name and password, as in this example, is not very
24309 realistic, though for a small organization with only a handful of
24310 authenticating clients it could make sense.
24312 A more sophisticated instance of this authenticator could use the user name in
24313 &$auth2$& to look up a password in a file or database, and maybe do an encrypted
24314 comparison (see &%crypteq%& in chapter &<<CHAPexpand>>&). Here is a example of
24315 this approach, where the passwords are looked up in a DBM file. &*Warning*&:
24316 This is an incorrect example:
24318 server_condition = \
24319 ${if eq{$auth3}{${lookup{$auth2}dbm{/etc/authpwd}}}}
24321 The expansion uses the user name (&$auth2$&) as the key to look up a password,
24322 which it then compares to the supplied password (&$auth3$&). Why is this example
24323 incorrect? It works fine for existing users, but consider what happens if a
24324 non-existent user name is given. The lookup fails, but as no success/failure
24325 strings are given for the lookup, it yields an empty string. Thus, to defeat
24326 the authentication, all a client has to do is to supply a non-existent user
24327 name and an empty password. The correct way of writing this test is:
24329 server_condition = ${lookup{$auth2}dbm{/etc/authpwd}\
24330 {${if eq{$value}{$auth3}}} {false}}
24332 In this case, if the lookup succeeds, the result is checked; if the lookup
24333 fails, &"false"& is returned and authentication fails. If &%crypteq%& is being
24334 used instead of &%eq%&, the first example is in fact safe, because &%crypteq%&
24335 always fails if its second argument is empty. However, the second way of
24336 writing the test makes the logic clearer.
24339 .section "The LOGIN authentication mechanism" "SECID173"
24340 .cindex "LOGIN authentication mechanism"
24341 .cindex "authentication" "LOGIN mechanism"
24342 The LOGIN authentication mechanism is not documented in any RFC, but is in use
24343 in a number of programs. No data is sent with the AUTH command. Instead, a
24344 user name and password are supplied separately, in response to prompts. The
24345 plaintext authenticator can be configured to support this as in this example:
24349 public_name = LOGIN
24350 server_prompts = User Name : Password
24351 server_condition = \
24352 ${if and {{eq{$auth1}{username}}{eq{$auth2}{mysecret}}}}
24353 server_set_id = $auth1
24355 Because of the way plaintext operates, this authenticator accepts data supplied
24356 with the AUTH command (in contravention of the specification of LOGIN), but
24357 if the client does not supply it (as is the case for LOGIN clients), the prompt
24358 strings are used to obtain two data items.
24360 Some clients are very particular about the precise text of the prompts. For
24361 example, Outlook Express is reported to recognize only &"Username:"& and
24362 &"Password:"&. Here is an example of a LOGIN authenticator that uses those
24363 strings. It uses the &%ldapauth%& expansion condition to check the user
24364 name and password by binding to an LDAP server:
24368 public_name = LOGIN
24369 server_prompts = Username:: : Password::
24370 server_condition = ${if and{{ \
24373 user="uid=${quote_ldap_dn:$auth1},ou=people,o=example.org" \
24374 pass=${quote:$auth2} \
24375 ldap://ldap.example.org/} }} }
24376 server_set_id = uid=$auth1,ou=people,o=example.org
24378 We have to check that the username is not empty before using it, because LDAP
24379 does not permit empty DN components. We must also use the &%quote_ldap_dn%&
24380 operator to correctly quote the DN for authentication. However, the basic
24381 &%quote%& operator, rather than any of the LDAP quoting operators, is the
24382 correct one to use for the password, because quoting is needed only to make
24383 the password conform to the Exim syntax. At the LDAP level, the password is an
24384 uninterpreted string.
24387 .section "Support for different kinds of authentication" "SECID174"
24388 A number of string expansion features are provided for the purpose of
24389 interfacing to different ways of user authentication. These include checking
24390 traditionally encrypted passwords from &_/etc/passwd_& (or equivalent), PAM,
24391 Radius, &%ldapauth%&, &'pwcheck'&, and &'saslauthd'&. For details see section
24397 .section "Using plaintext in a client" "SECID175"
24398 .cindex "options" "&(plaintext)& authenticator (client)"
24399 The &(plaintext)& authenticator has two client options:
24401 .option client_ignore_invalid_base64 plaintext boolean false
24402 If the client receives a server prompt that is not a valid base64 string,
24403 authentication is abandoned by default. However, if this option is set true,
24404 the error in the challenge is ignored and the client sends the response as
24407 .option client_send plaintext string&!! unset
24408 The string is a colon-separated list of authentication data strings. Each
24409 string is independently expanded before being sent to the server. The first
24410 string is sent with the AUTH command; any more strings are sent in response
24411 to prompts from the server. Before each string is expanded, the value of the
24412 most recent prompt is placed in the next &$auth$&<&'n'&> variable, starting
24413 with &$auth1$& for the first prompt. Up to three prompts are stored in this
24414 way. Thus, the prompt that is received in response to sending the first string
24415 (with the AUTH command) can be used in the expansion of the second string, and
24416 so on. If an invalid base64 string is received when
24417 &%client_ignore_invalid_base64%& is set, an empty string is put in the
24418 &$auth$&<&'n'&> variable.
24420 &*Note*&: You cannot use expansion to create multiple strings, because
24421 splitting takes priority and happens first.
24423 Because the PLAIN authentication mechanism requires NUL (binary zero) bytes in
24424 the data, further processing is applied to each string before it is sent. If
24425 there are any single circumflex characters in the string, they are converted to
24426 NULs. Should an actual circumflex be required as data, it must be doubled in
24429 This is an example of a client configuration that implements the PLAIN
24430 authentication mechanism with a fixed user name and password:
24434 public_name = PLAIN
24435 client_send = ^username^mysecret
24437 The lack of colons means that the entire text is sent with the AUTH
24438 command, with the circumflex characters converted to NULs. A similar example
24439 that uses the LOGIN mechanism is:
24443 public_name = LOGIN
24444 client_send = : username : mysecret
24446 The initial colon means that the first string is empty, so no data is sent with
24447 the AUTH command itself. The remaining strings are sent in response to
24449 .ecindex IIDplaiauth1
24450 .ecindex IIDplaiauth2
24455 . ////////////////////////////////////////////////////////////////////////////
24456 . ////////////////////////////////////////////////////////////////////////////
24458 .chapter "The cram_md5 authenticator" "CHID9"
24459 .scindex IIDcramauth1 "&(cram_md5)& authenticator"
24460 .scindex IIDcramauth2 "authenticators" "&(cram_md5)&"
24461 .cindex "CRAM-MD5 authentication mechanism"
24462 .cindex "authentication" "CRAM-MD5 mechanism"
24463 The CRAM-MD5 authentication mechanism is described in RFC 2195. The server
24464 sends a challenge string to the client, and the response consists of a user
24465 name and the CRAM-MD5 digest of the challenge string combined with a secret
24466 string (password) which is known to both server and client. Thus, the secret
24467 is not sent over the network as plain text, which makes this authenticator more
24468 secure than &(plaintext)&. However, the downside is that the secret has to be
24469 available in plain text at either end.
24472 .section "Using cram_md5 as a server" "SECID176"
24473 .cindex "options" "&(cram_md5)& authenticator (server)"
24474 This authenticator has one server option, which must be set to configure the
24475 authenticator as a server:
24477 .option server_secret cram_md5 string&!! unset
24478 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(cram_md5)& authenticator"
24479 When the server receives the client's response, the user name is placed in
24480 the expansion variable &$auth1$&, and &%server_secret%& is expanded to
24481 obtain the password for that user. The server then computes the CRAM-MD5 digest
24482 that the client should have sent, and checks that it received the correct
24483 string. If the expansion of &%server_secret%& is forced to fail, authentication
24484 fails. If the expansion fails for some other reason, a temporary error code is
24485 returned to the client.
24487 For compatibility with previous releases of Exim, the user name is also placed
24488 in &$1$&. However, the use of this variables for this purpose is now
24489 deprecated, as it can lead to confusion in string expansions that also use
24490 numeric variables for other things.
24492 For example, the following authenticator checks that the user name given by the
24493 client is &"ph10"&, and if so, uses &"secret"& as the password. For any other
24494 user name, authentication fails.
24498 public_name = CRAM-MD5
24499 server_secret = ${if eq{$auth1}{ph10}{secret}fail}
24500 server_set_id = $auth1
24502 .vindex "&$authenticated_id$&"
24503 If authentication succeeds, the setting of &%server_set_id%& preserves the user
24504 name in &$authenticated_id$&. A more typical configuration might look up the
24505 secret string in a file, using the user name as the key. For example:
24509 public_name = CRAM-MD5
24510 server_secret = ${lookup{$auth1}lsearch{/etc/authpwd}\
24512 server_set_id = $auth1
24514 Note that this expansion explicitly forces failure if the lookup fails
24515 because &$auth1$& contains an unknown user name.
24517 As another example, if you wish to re-use a Cyrus SASL sasldb2 file without
24518 using the relevant libraries, you need to know the realm to specify in the
24519 lookup and then ask for the &"userPassword"& attribute for that user in that
24524 public_name = CRAM-MD5
24525 server_secret = ${lookup{$auth1:mail.example.org:userPassword}\
24526 dbmjz{/etc/sasldb2}}
24527 server_set_id = $auth1
24530 .section "Using cram_md5 as a client" "SECID177"
24531 .cindex "options" "&(cram_md5)& authenticator (client)"
24532 When used as a client, the &(cram_md5)& authenticator has two options:
24536 .option client_name cram_md5 string&!! "the primary host name"
24537 This string is expanded, and the result used as the user name data when
24538 computing the response to the server's challenge.
24541 .option client_secret cram_md5 string&!! unset
24542 This option must be set for the authenticator to work as a client. Its value is
24543 expanded and the result used as the secret string when computing the response.
24547 .vindex "&$host_address$&"
24548 Different user names and secrets can be used for different servers by referring
24549 to &$host$& or &$host_address$& in the options. Forced failure of either
24550 expansion string is treated as an indication that this authenticator is not
24551 prepared to handle this case. Exim moves on to the next configured client
24552 authenticator. Any other expansion failure causes Exim to give up trying to
24553 send the message to the current server.
24555 A simple example configuration of a &(cram_md5)& authenticator, using fixed
24560 public_name = CRAM-MD5
24562 client_secret = secret
24564 .ecindex IIDcramauth1
24565 .ecindex IIDcramauth2
24569 . ////////////////////////////////////////////////////////////////////////////
24570 . ////////////////////////////////////////////////////////////////////////////
24572 .chapter "The cyrus_sasl authenticator" "CHID10"
24573 .scindex IIDcyrauth1 "&(cyrus_sasl)& authenticator"
24574 .scindex IIDcyrauth2 "authenticators" "&(cyrus_sasl)&"
24575 .cindex "Cyrus" "SASL library"
24577 The code for this authenticator was provided by Matthew Byng-Maddick of A L
24578 Digital Ltd (&url(http://www.aldigital.co.uk)).
24580 The &(cyrus_sasl)& authenticator provides server support for the Cyrus SASL
24581 library implementation of the RFC 2222 (&"Simple Authentication and Security
24582 Layer"&). This library supports a number of authentication mechanisms,
24583 including PLAIN and LOGIN, but also several others that Exim does not support
24584 directly. In particular, there is support for Kerberos authentication.
24586 The &(cyrus_sasl)& authenticator provides a gatewaying mechanism directly to
24587 the Cyrus interface, so if your Cyrus library can do, for example, CRAM-MD5,
24588 then so can the &(cyrus_sasl)& authenticator. By default it uses the public
24589 name of the driver to determine which mechanism to support.
24591 Where access to some kind of secret file is required, for example in GSSAPI
24592 or CRAM-MD5, it is worth noting that the authenticator runs as the Exim
24593 user, and that the Cyrus SASL library has no way of escalating privileges
24594 by default. You may also find you need to set environment variables,
24595 depending on the driver you are using.
24597 The application name provided by Exim is &"exim"&, so various SASL options may
24598 be set in &_exim.conf_& in your SASL directory. If you are using GSSAPI for
24599 Kerberos, note that because of limitations in the GSSAPI interface,
24600 changing the server keytab might need to be communicated down to the Kerberos
24601 layer independently. The mechanism for doing so is dependent upon the Kerberos
24604 For example, for older releases of Heimdal, the environment variable KRB5_KTNAME
24605 may be set to point to an alternative keytab file. Exim will pass this
24606 variable through from its own inherited environment when started as root or the
24607 Exim user. The keytab file needs to be readable by the Exim user.
24608 With newer releases of Heimdal, a setuid Exim may cause Heimdal to discard the
24609 environment variable. In practice, for those releases, the Cyrus authenticator
24610 is not a suitable interface for GSSAPI (Kerberos) support. Instead, consider
24611 the &(heimdal_gssapi)& authenticator, described in chapter &<<CHAPheimdalgss>>&
24614 .section "Using cyrus_sasl as a server" "SECID178"
24615 The &(cyrus_sasl)& authenticator has four private options. It puts the username
24616 (on a successful authentication) into &$auth1$&. For compatibility with
24617 previous releases of Exim, the username is also placed in &$1$&. However, the
24618 use of this variable for this purpose is now deprecated, as it can lead to
24619 confusion in string expansions that also use numeric variables for other
24623 .option server_hostname cyrus_sasl string&!! "see below"
24624 This option selects the hostname that is used when communicating with the
24625 library. The default value is &`$primary_hostname`&. It is up to the underlying
24626 SASL plug-in what it does with this data.
24629 .option server_mech cyrus_sasl string "see below"
24630 This option selects the authentication mechanism this driver should use. The
24631 default is the value of the generic &%public_name%& option. This option allows
24632 you to use a different underlying mechanism from the advertised name. For
24636 driver = cyrus_sasl
24637 public_name = X-ANYTHING
24638 server_mech = CRAM-MD5
24639 server_set_id = $auth1
24642 .option server_realm cyrus_sasl string&!! unset
24643 This specifies the SASL realm that the server claims to be in.
24646 .option server_service cyrus_sasl string &`smtp`&
24647 This is the SASL service that the server claims to implement.
24650 For straightforward cases, you do not need to set any of the authenticator's
24651 private options. All you need to do is to specify an appropriate mechanism as
24652 the public name. Thus, if you have a SASL library that supports CRAM-MD5 and
24653 PLAIN, you could have two authenticators as follows:
24656 driver = cyrus_sasl
24657 public_name = CRAM-MD5
24658 server_set_id = $auth1
24661 driver = cyrus_sasl
24662 public_name = PLAIN
24663 server_set_id = $auth2
24665 Cyrus SASL does implement the LOGIN authentication method, even though it is
24666 not a standard method. It is disabled by default in the source distribution,
24667 but it is present in many binary distributions.
24668 .ecindex IIDcyrauth1
24669 .ecindex IIDcyrauth2
24674 . ////////////////////////////////////////////////////////////////////////////
24675 . ////////////////////////////////////////////////////////////////////////////
24676 .chapter "The dovecot authenticator" "CHAPdovecot"
24677 .scindex IIDdcotauth1 "&(dovecot)& authenticator"
24678 .scindex IIDdcotauth2 "authenticators" "&(dovecot)&"
24679 This authenticator is an interface to the authentication facility of the
24680 Dovecot POP/IMAP server, which can support a number of authentication methods.
24681 If you are using Dovecot to authenticate POP/IMAP clients, it might be helpful
24682 to use the same mechanisms for SMTP authentication. This is a server
24683 authenticator only. There is only one option:
24685 .option server_socket dovecot string unset
24687 This option must specify the socket that is the interface to Dovecot
24688 authentication. The &%public_name%& option must specify an authentication
24689 mechanism that Dovecot is configured to support. You can have several
24690 authenticators for different mechanisms. For example:
24694 public_name = PLAIN
24695 server_socket = /var/run/dovecot/auth-client
24696 server_set_id = $auth2
24701 server_socket = /var/run/dovecot/auth-client
24702 server_set_id = $auth1
24704 If the SMTP connection is encrypted, or if &$sender_host_address$& is equal to
24705 &$received_ip_address$& (that is, the connection is local), the &"secured"&
24706 option is passed in the Dovecot authentication command. If, for a TLS
24707 connection, a client certificate has been verified, the &"valid-client-cert"&
24708 option is passed. When authentication succeeds, the identity of the user
24709 who authenticated is placed in &$auth1$&.
24710 .ecindex IIDdcotauth1
24711 .ecindex IIDdcotauth2
24714 . ////////////////////////////////////////////////////////////////////////////
24715 . ////////////////////////////////////////////////////////////////////////////
24716 .chapter "The gsasl authenticator" "CHAPgsasl"
24717 .scindex IIDgsaslauth1 "&(gsasl)& authenticator"
24718 .scindex IIDgsaslauth2 "authenticators" "&(gsasl)&"
24719 .cindex "authentication" "GNU SASL"
24720 .cindex "authentication" "SASL"
24721 .cindex "authentication" "EXTERNAL"
24722 .cindex "authentication" "ANONYMOUS"
24723 .cindex "authentication" "PLAIN"
24724 .cindex "authentication" "LOGIN"
24725 .cindex "authentication" "DIGEST-MD5"
24726 .cindex "authentication" "CRAM-MD5"
24727 .cindex "authentication" "SCRAM-SHA-1"
24728 The &(gsasl)& authenticator provides server integration for the GNU SASL
24729 library and the mechanisms it provides. This is new as of the 4.80 release
24730 and there are a few areas where the library does not let Exim smoothly
24731 scale to handle future authentication mechanisms, so no guarantee can be
24732 made that any particular new authentication mechanism will be supported
24733 without code changes in Exim.
24736 .option server_channelbinding gsasl boolean false
24737 Some authentication mechanisms are able to use external context at both ends
24738 of the session to bind the authentication to that context, and fail the
24739 authentication process if that context differs. Specifically, some TLS
24740 ciphersuites can provide identifying information about the cryptographic
24743 This means that certificate identity and verification becomes a non-issue,
24744 as a man-in-the-middle attack will cause the correct client and server to
24745 see different identifiers and authentication will fail.
24747 This is currently only supported when using the GnuTLS library. This is
24748 only usable by mechanisms which support "channel binding"; at time of
24749 writing, that's the SCRAM family.
24751 This defaults off to ensure smooth upgrade across Exim releases, in case
24752 this option causes some clients to start failing. Some future release
24753 of Exim may switch the default to be true.
24756 .option server_hostname gsasl string&!! "see below"
24757 This option selects the hostname that is used when communicating with the
24758 library. The default value is &`$primary_hostname`&.
24759 Some mechanisms will use this data.
24762 .option server_mech gsasl string "see below"
24763 This option selects the authentication mechanism this driver should use. The
24764 default is the value of the generic &%public_name%& option. This option allows
24765 you to use a different underlying mechanism from the advertised name. For
24770 public_name = X-ANYTHING
24771 server_mech = CRAM-MD5
24772 server_set_id = $auth1
24776 .option server_password gsasl string&!! unset
24777 Various mechanisms need access to the cleartext password on the server, so
24778 that proof-of-possession can be demonstrated on the wire, without sending
24779 the password itself.
24781 The data available for lookup varies per mechanism.
24782 In all cases, &$auth1$& is set to the &'authentication id'&.
24783 The &$auth2$& variable will always be the &'authorization id'& (&'authz'&)
24784 if available, else the empty string.
24785 The &$auth3$& variable will always be the &'realm'& if available,
24786 else the empty string.
24788 A forced failure will cause authentication to defer.
24790 If using this option, it may make sense to set the &%server_condition%&
24791 option to be simply "true".
24794 .option server_realm gsasl string&!! unset
24795 This specifies the SASL realm that the server claims to be in.
24796 Some mechanisms will use this data.
24799 .option server_scram_iter gsasl string&!! unset
24800 This option provides data for the SCRAM family of mechanisms.
24801 &$auth1$& is not available at evaluation time.
24802 (This may change, as we receive feedback on use)
24805 .option server_scram_salt gsasl string&!! unset
24806 This option provides data for the SCRAM family of mechanisms.
24807 &$auth1$& is not available at evaluation time.
24808 (This may change, as we receive feedback on use)
24811 .option server_service gsasl string &`smtp`&
24812 This is the SASL service that the server claims to implement.
24813 Some mechanisms will use this data.
24816 .section "&(gsasl)& auth variables" "SECTgsaslauthvar"
24817 .vindex "&$auth1$&, &$auth2$&, etc"
24818 These may be set when evaluating specific options, as detailed above.
24819 They will also be set when evaluating &%server_condition%&.
24821 Unless otherwise stated below, the &(gsasl)& integration will use the following
24822 meanings for these variables:
24825 .vindex "&$auth1$&"
24826 &$auth1$&: the &'authentication id'&
24828 .vindex "&$auth2$&"
24829 &$auth2$&: the &'authorization id'&
24831 .vindex "&$auth3$&"
24832 &$auth3$&: the &'realm'&
24835 On a per-mechanism basis:
24838 .cindex "authentication" "EXTERNAL"
24839 EXTERNAL: only &$auth1$& is set, to the possibly empty &'authorization id'&;
24840 the &%server_condition%& option must be present.
24842 .cindex "authentication" "ANONYMOUS"
24843 ANONYMOUS: only &$auth1$& is set, to the possibly empty &'anonymous token'&;
24844 the &%server_condition%& option must be present.
24846 .cindex "authentication" "GSSAPI"
24847 GSSAPI: &$auth1$& will be set to the &'GSSAPI Display Name'&;
24848 &$auth2$& will be set to the &'authorization id'&,
24849 the &%server_condition%& option must be present.
24852 An &'anonymous token'& is something passed along as an unauthenticated
24853 identifier; this is analogous to FTP anonymous authentication passing an
24854 email address, or software-identifier@, as the "password".
24857 An example showing the password having the realm specified in the callback
24858 and demonstrating a Cyrus SASL to GSASL migration approach is:
24860 gsasl_cyrusless_crammd5:
24862 public_name = CRAM-MD5
24863 server_realm = imap.example.org
24864 server_password = ${lookup{$auth1:$auth3:userPassword}\
24865 dbmjz{/etc/sasldb2}{$value}fail}
24866 server_set_id = ${quote:$auth1}
24867 server_condition = yes
24871 . ////////////////////////////////////////////////////////////////////////////
24872 . ////////////////////////////////////////////////////////////////////////////
24874 .chapter "The heimdal_gssapi authenticator" "CHAPheimdalgss"
24875 .scindex IIDheimdalgssauth1 "&(heimdal_gssapi)& authenticator"
24876 .scindex IIDheimdalgssauth2 "authenticators" "&(heimdal_gssapi)&"
24877 .cindex "authentication" "GSSAPI"
24878 .cindex "authentication" "Kerberos"
24879 The &(heimdal_gssapi)& authenticator provides server integration for the
24880 Heimdal GSSAPI/Kerberos library, permitting Exim to set a keytab pathname
24883 .option server_hostname heimdal_gssapi string&!! "see below"
24884 This option selects the hostname that is used, with &%server_service%&,
24885 for constructing the GSS server name, as a &'GSS_C_NT_HOSTBASED_SERVICE'&
24886 identifier. The default value is &`$primary_hostname`&.
24888 .option server_keytab heimdal_gssapi string&!! unset
24889 If set, then Heimdal will not use the system default keytab (typically
24890 &_/etc/krb5.keytab_&) but instead the pathname given in this option.
24891 The value should be a pathname, with no &"file:"& prefix.
24893 .option server_service heimdal_gssapi string&!! "smtp"
24894 This option specifies the service identifier used, in conjunction with
24895 &%server_hostname%&, for building the identifer for finding credentials
24899 .section "&(heimdal_gssapi)& auth variables" "SECTheimdalgssauthvar"
24900 Beware that these variables will typically include a realm, thus will appear
24901 to be roughly like an email address already. The &'authzid'& in &$auth2$& is
24902 not verified, so a malicious client can set it to anything.
24904 The &$auth1$& field should be safely trustable as a value from the Key
24905 Distribution Center. Note that these are not quite email addresses.
24906 Each identifier is for a role, and so the left-hand-side may include a
24907 role suffix. For instance, &"joe/admin@EXAMPLE.ORG"&.
24909 .vindex "&$auth1$&, &$auth2$&, etc"
24911 .vindex "&$auth1$&"
24912 &$auth1$&: the &'authentication id'&, set to the GSS Display Name.
24914 .vindex "&$auth2$&"
24915 &$auth2$&: the &'authorization id'&, sent within SASL encapsulation after
24916 authentication. If that was empty, this will also be set to the
24921 . ////////////////////////////////////////////////////////////////////////////
24922 . ////////////////////////////////////////////////////////////////////////////
24924 .chapter "The spa authenticator" "CHAPspa"
24925 .scindex IIDspaauth1 "&(spa)& authenticator"
24926 .scindex IIDspaauth2 "authenticators" "&(spa)&"
24927 .cindex "authentication" "Microsoft Secure Password"
24928 .cindex "authentication" "NTLM"
24929 .cindex "Microsoft Secure Password Authentication"
24930 .cindex "NTLM authentication"
24931 The &(spa)& authenticator provides client support for Microsoft's &'Secure
24932 Password Authentication'& mechanism,
24933 which is also sometimes known as NTLM (NT LanMan). The code for client side of
24934 this authenticator was contributed by Marc Prud'hommeaux, and much of it is
24935 taken from the Samba project (&url(http://www.samba.org)). The code for the
24936 server side was subsequently contributed by Tom Kistner. The mechanism works as
24940 After the AUTH command has been accepted, the client sends an SPA
24941 authentication request based on the user name and optional domain.
24943 The server sends back a challenge.
24945 The client builds a challenge response which makes use of the user's password
24946 and sends it to the server, which then accepts or rejects it.
24949 Encryption is used to protect the password in transit.
24953 .section "Using spa as a server" "SECID179"
24954 .cindex "options" "&(spa)& authenticator (server)"
24955 The &(spa)& authenticator has just one server option:
24957 .option server_password spa string&!! unset
24958 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(spa)& authenticator"
24959 This option is expanded, and the result must be the cleartext password for the
24960 authenticating user, whose name is at this point in &$auth1$&. For
24961 compatibility with previous releases of Exim, the user name is also placed in
24962 &$1$&. However, the use of this variable for this purpose is now deprecated, as
24963 it can lead to confusion in string expansions that also use numeric variables
24964 for other things. For example:
24969 server_password = \
24970 ${lookup{$auth1}lsearch{/etc/exim/spa_clearpass}{$value}fail}
24972 If the expansion is forced to fail, authentication fails. Any other expansion
24973 failure causes a temporary error code to be returned.
24979 .section "Using spa as a client" "SECID180"
24980 .cindex "options" "&(spa)& authenticator (client)"
24981 The &(spa)& authenticator has the following client options:
24985 .option client_domain spa string&!! unset
24986 This option specifies an optional domain for the authentication.
24989 .option client_password spa string&!! unset
24990 This option specifies the user's password, and must be set.
24993 .option client_username spa string&!! unset
24994 This option specifies the user name, and must be set. Here is an example of a
24995 configuration of this authenticator for use with the mail servers at
25001 client_username = msn/msn_username
25002 client_password = msn_plaintext_password
25003 client_domain = DOMAIN_OR_UNSET
25005 .ecindex IIDspaauth1
25006 .ecindex IIDspaauth2
25012 . ////////////////////////////////////////////////////////////////////////////
25013 . ////////////////////////////////////////////////////////////////////////////
25015 .chapter "Encrypted SMTP connections using TLS/SSL" "CHAPTLS" &&&
25016 "Encrypted SMTP connections"
25017 .scindex IIDencsmtp1 "encryption" "on SMTP connection"
25018 .scindex IIDencsmtp2 "SMTP" "encryption"
25019 .cindex "TLS" "on SMTP connection"
25022 Support for TLS (Transport Layer Security), formerly known as SSL (Secure
25023 Sockets Layer), is implemented by making use of the OpenSSL library or the
25024 GnuTLS library (Exim requires GnuTLS release 1.0 or later). There is no
25025 cryptographic code in the Exim distribution itself for implementing TLS. In
25026 order to use this feature you must install OpenSSL or GnuTLS, and then build a
25027 version of Exim that includes TLS support (see section &<<SECTinctlsssl>>&).
25028 You also need to understand the basic concepts of encryption at a managerial
25029 level, and in particular, the way that public keys, private keys, and
25030 certificates are used.
25032 RFC 3207 defines how SMTP connections can make use of encryption. Once a
25033 connection is established, the client issues a STARTTLS command. If the
25034 server accepts this, the client and the server negotiate an encryption
25035 mechanism. If the negotiation succeeds, the data that subsequently passes
25036 between them is encrypted.
25038 Exim's ACLs can detect whether the current SMTP session is encrypted or not,
25039 and if so, what cipher suite is in use, whether the client supplied a
25040 certificate, and whether or not that certificate was verified. This makes it
25041 possible for an Exim server to deny or accept certain commands based on the
25044 &*Warning*&: Certain types of firewall and certain anti-virus products can
25045 disrupt TLS connections. You need to turn off SMTP scanning for these products
25046 in order to get TLS to work.
25050 .section "Support for the legacy &""ssmtp""& (aka &""smtps""&) protocol" &&&
25052 .cindex "ssmtp protocol"
25053 .cindex "smtps protocol"
25054 .cindex "SMTP" "ssmtp protocol"
25055 .cindex "SMTP" "smtps protocol"
25056 Early implementations of encrypted SMTP used a different TCP port from normal
25057 SMTP, and expected an encryption negotiation to start immediately, instead of
25058 waiting for a STARTTLS command from the client using the standard SMTP
25059 port. The protocol was called &"ssmtp"& or &"smtps"&, and port 465 was
25060 allocated for this purpose.
25062 This approach was abandoned when encrypted SMTP was standardized, but there are
25063 still some legacy clients that use it. Exim supports these clients by means of
25064 the &%tls_on_connect_ports%& global option. Its value must be a list of port
25065 numbers; the most common use is expected to be:
25067 tls_on_connect_ports = 465
25069 The port numbers specified by this option apply to all SMTP connections, both
25070 via the daemon and via &'inetd'&. You still need to specify all the ports that
25071 the daemon uses (by setting &%daemon_smtp_ports%& or &%local_interfaces%& or
25072 the &%-oX%& command line option) because &%tls_on_connect_ports%& does not add
25073 an extra port &-- rather, it specifies different behaviour on a port that is
25076 There is also a &%-tls-on-connect%& command line option. This overrides
25077 &%tls_on_connect_ports%&; it forces the legacy behaviour for all ports.
25084 .section "OpenSSL vs GnuTLS" "SECTopenvsgnu"
25085 .cindex "TLS" "OpenSSL &'vs'& GnuTLS"
25086 The first TLS support in Exim was implemented using OpenSSL. Support for GnuTLS
25087 followed later, when the first versions of GnuTLS were released. To build Exim
25088 to use GnuTLS, you need to set
25092 in Local/Makefile, in addition to
25096 You must also set TLS_LIBS and TLS_INCLUDE appropriately, so that the
25097 include files and libraries for GnuTLS can be found.
25099 There are some differences in usage when using GnuTLS instead of OpenSSL:
25102 The &%tls_verify_certificates%& option must contain the name of a file, not the
25103 name of a directory (for OpenSSL it can be either).
25105 The default value for &%tls_dhparam%& differs for historical reasons.
25107 .vindex "&$tls_peerdn$&"
25108 Distinguished Name (DN) strings reported by the OpenSSL library use a slash for
25109 separating fields; GnuTLS uses commas, in accordance with RFC 2253. This
25110 affects the value of the &$tls_peerdn$& variable.
25112 OpenSSL identifies cipher suites using hyphens as separators, for example:
25113 DES-CBC3-SHA. GnuTLS historically used underscores, for example:
25114 RSA_ARCFOUR_SHA. What is more, OpenSSL complains if underscores are present
25115 in a cipher list. To make life simpler, Exim changes underscores to hyphens
25116 for OpenSSL and passes the string unchanged to GnuTLS (expecting the library
25117 to handle its own older variants) when processing lists of cipher suites in the
25118 &%tls_require_ciphers%& options (the global option and the &(smtp)& transport
25121 The &%tls_require_ciphers%& options operate differently, as described in the
25122 sections &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&.
25125 The &%tls_dh_min_bits%& SMTP transport option is only honoured by GnuTLS.
25126 When using OpenSSL, this option is ignored.
25127 (If an API is found to let OpenSSL be configured in this way,
25128 let the Exim Maintainers know and we'll likely use it).
25131 Some other recently added features may only be available in one or the other.
25132 This should be documented with the feature. If the documentation does not
25133 explicitly state that the feature is infeasible in the other TLS
25134 implementation, then patches are welcome.
25138 .section "GnuTLS parameter computation" "SECTgnutlsparam"
25139 This section only applies if &%tls_dhparam%& is set to &`historic`& or to
25140 an explicit path; if the latter, then the text about generation still applies,
25141 but not the chosen filename.
25142 By default, as of Exim 4.80 a hard-coded D-H prime is used.
25143 See the documentation of &%tls_dhparam%& for more information.
25145 GnuTLS uses D-H parameters that may take a substantial amount of time
25146 to compute. It is unreasonable to re-compute them for every TLS session.
25147 Therefore, Exim keeps this data in a file in its spool directory, called
25148 &_gnutls-params-NNNN_& for some value of NNNN, corresponding to the number
25150 The file is owned by the Exim user and is readable only by
25151 its owner. Every Exim process that start up GnuTLS reads the D-H
25152 parameters from this file. If the file does not exist, the first Exim process
25153 that needs it computes the data and writes it to a temporary file which is
25154 renamed once it is complete. It does not matter if several Exim processes do
25155 this simultaneously (apart from wasting a few resources). Once a file is in
25156 place, new Exim processes immediately start using it.
25158 For maximum security, the parameters that are stored in this file should be
25159 recalculated periodically, the frequency depending on your paranoia level.
25160 If you are avoiding using the fixed D-H primes published in RFCs, then you
25161 are concerned about some advanced attacks and will wish to do this; if you do
25162 not regenerate then you might as well stick to the standard primes.
25164 Arranging this is easy in principle; just delete the file when you want new
25165 values to be computed. However, there may be a problem. The calculation of new
25166 parameters needs random numbers, and these are obtained from &_/dev/random_&.
25167 If the system is not very active, &_/dev/random_& may delay returning data
25168 until enough randomness (entropy) is available. This may cause Exim to hang for
25169 a substantial amount of time, causing timeouts on incoming connections.
25171 The solution is to generate the parameters externally to Exim. They are stored
25172 in &_gnutls-params-N_& in PEM format, which means that they can be
25173 generated externally using the &(certtool)& command that is part of GnuTLS.
25175 To replace the parameters with new ones, instead of deleting the file
25176 and letting Exim re-create it, you can generate new parameters using
25177 &(certtool)& and, when this has been done, replace Exim's cache file by
25178 renaming. The relevant commands are something like this:
25181 [ look for file; assume gnutls-params-2236 is the most recent ]
25184 # chown exim:exim new-params
25185 # chmod 0600 new-params
25186 # certtool --generate-dh-params --bits 2236 >>new-params
25187 # openssl dhparam -noout -text -in new-params | head
25188 [ check the first line, make sure it's not more than 2236;
25189 if it is, then go back to the start ("rm") and repeat
25190 until the size generated is at most the size requested ]
25191 # chmod 0400 new-params
25192 # mv new-params gnutls-params-2236
25194 If Exim never has to generate the parameters itself, the possibility of
25195 stalling is removed.
25197 The filename changed in Exim 4.80, to gain the -bits suffix. The value which
25198 Exim will choose depends upon the version of GnuTLS in use. For older GnuTLS,
25199 the value remains hard-coded in Exim as 1024. As of GnuTLS 2.12.x, there is
25200 a way for Exim to ask for the "normal" number of bits for D-H public-key usage,
25201 and Exim does so. This attempt to remove Exim from TLS policy decisions
25202 failed, as GnuTLS 2.12 returns a value higher than the current hard-coded limit
25203 of the NSS library. Thus Exim gains the &%tls_dh_max_bits%& global option,
25204 which applies to all D-H usage, client or server. If the value returned by
25205 GnuTLS is greater than &%tls_dh_max_bits%& then the value will be clamped down
25206 to &%tls_dh_max_bits%&. The default value has been set at the current NSS
25207 limit, which is still much higher than Exim historically used.
25209 The filename and bits used will change as the GnuTLS maintainers change the
25210 value for their parameter &`GNUTLS_SEC_PARAM_NORMAL`&, as clamped by
25211 &%tls_dh_max_bits%&. At the time of writing (mid 2012), GnuTLS 2.12 recommends
25212 2432 bits, while NSS is limited to 2236 bits.
25214 In fact, the requested value will be *lower* than &%tls_dh_max_bits%&, to
25215 increase the chance of the generated prime actually being within acceptable
25216 bounds, as GnuTLS has been observed to overshoot. Note the check step in the
25217 procedure above. There is no sane procedure available to Exim to double-check
25218 the size of the generated prime, so it might still be too large.
25221 .section "Requiring specific ciphers in OpenSSL" "SECTreqciphssl"
25222 .cindex "TLS" "requiring specific ciphers (OpenSSL)"
25223 .oindex "&%tls_require_ciphers%&" "OpenSSL"
25224 There is a function in the OpenSSL library that can be passed a list of cipher
25225 suites before the cipher negotiation takes place. This specifies which ciphers
25226 are acceptable. The list is colon separated and may contain names like
25227 DES-CBC3-SHA. Exim passes the expanded value of &%tls_require_ciphers%&
25228 directly to this function call.
25229 Many systems will install the OpenSSL manual-pages, so you may have
25230 &'ciphers(1)'& available to you.
25231 The following quotation from the OpenSSL
25232 documentation specifies what forms of item are allowed in the cipher string:
25235 It can consist of a single cipher suite such as RC4-SHA.
25237 It can represent a list of cipher suites containing a certain algorithm,
25238 or cipher suites of a certain type. For example SHA1 represents all
25239 ciphers suites using the digest algorithm SHA1 and SSLv3 represents all
25242 Lists of cipher suites can be combined in a single cipher string using
25243 the + character. This is used as a logical and operation. For example
25244 SHA1+DES represents all cipher suites containing the SHA1 and the DES
25248 Each cipher string can be optionally preceded by one of the characters &`!`&,
25251 If &`!`& is used, the ciphers are permanently deleted from the list. The
25252 ciphers deleted can never reappear in the list even if they are explicitly
25255 If &`-`& is used, the ciphers are deleted from the list, but some or all
25256 of the ciphers can be added again by later options.
25258 If &`+`& is used, the ciphers are moved to the end of the list. This
25259 option does not add any new ciphers; it just moves matching existing ones.
25262 If none of these characters is present, the string is interpreted as
25263 a list of ciphers to be appended to the current preference list. If the list
25264 includes any ciphers already present they will be ignored: that is, they will
25265 not be moved to the end of the list.
25268 The OpenSSL &'ciphers(1)'& command may be used to test the results of a given
25271 # note single-quotes to get ! past any shell history expansion
25272 $ openssl ciphers 'HIGH:!MD5:!SHA1'
25275 This example will let the library defaults be permitted on the MX port, where
25276 there's probably no identity verification anyway, but ups the ante on the
25277 submission ports where the administrator might have some influence on the
25278 choice of clients used:
25280 # OpenSSL variant; see man ciphers(1)
25281 tls_require_ciphers = ${if =={$received_port}{25}\
25288 .section "Requiring specific ciphers or other parameters in GnuTLS" &&&
25290 .cindex "GnuTLS" "specifying parameters for"
25291 .cindex "TLS" "specifying ciphers (GnuTLS)"
25292 .cindex "TLS" "specifying key exchange methods (GnuTLS)"
25293 .cindex "TLS" "specifying MAC algorithms (GnuTLS)"
25294 .cindex "TLS" "specifying protocols (GnuTLS)"
25295 .cindex "TLS" "specifying priority string (GnuTLS)"
25296 .oindex "&%tls_require_ciphers%&" "GnuTLS"
25297 The GnuTLS library allows the caller to provide a "priority string", documented
25298 as part of the &[gnutls_priority_init]& function. This is very similar to the
25299 ciphersuite specification in OpenSSL.
25301 The &%tls_require_ciphers%& option is treated as the GnuTLS priority string.
25303 The &%tls_require_ciphers%& option is available both as an global option,
25304 controlling how Exim behaves as a server, and also as an option of the
25305 &(smtp)& transport, controlling how Exim behaves as a client. In both cases
25306 the value is string expanded. The resulting string is not an Exim list and
25307 the string is given to the GnuTLS library, so that Exim does not need to be
25308 aware of future feature enhancements of GnuTLS.
25310 Documentation of the strings accepted may be found in the GnuTLS manual, under
25311 "Priority strings". This is online as
25312 &url(http://www.gnu.org/software/gnutls/manual/html_node/Priority-Strings.html),
25313 but beware that this relates to GnuTLS 3, which may be newer than the version
25314 installed on your system. If you are using GnuTLS 3,
25315 &url(http://www.gnu.org/software/gnutls/manual/html_node/Listing-the-ciphersuites-in-a-priority-string.html, then the example code)
25316 on that site can be used to test a given string.
25318 Prior to Exim 4.80, an older API of GnuTLS was used, and Exim supported three
25319 additional options, "&%gnutls_require_kx%&", "&%gnutls_require_mac%&" and
25320 "&%gnutls_require_protocols%&". &%tls_require_ciphers%& was an Exim list.
25322 This example will let the library defaults be permitted on the MX port, where
25323 there's probably no identity verification anyway, and lowers security further
25324 by increasing compatibility; but this ups the ante on the submission ports
25325 where the administrator might have some influence on the choice of clients
25329 tls_require_ciphers = ${if =={$received_port}{25}\
25335 .section "Configuring an Exim server to use TLS" "SECID182"
25336 .cindex "TLS" "configuring an Exim server"
25337 When Exim has been built with TLS support, it advertises the availability of
25338 the STARTTLS command to client hosts that match &%tls_advertise_hosts%&,
25339 but not to any others. The default value of this option is unset, which means
25340 that STARTTLS is not advertised at all. This default is chosen because you
25341 need to set some other options in order to make TLS available, and also it is
25342 sensible for systems that want to use TLS only as a client.
25344 If a client issues a STARTTLS command and there is some configuration
25345 problem in the server, the command is rejected with a 454 error. If the client
25346 persists in trying to issue SMTP commands, all except QUIT are rejected
25349 554 Security failure
25351 If a STARTTLS command is issued within an existing TLS session, it is
25352 rejected with a 554 error code.
25354 To enable TLS operations on a server, you must set &%tls_advertise_hosts%& to
25355 match some hosts. You can, of course, set it to * to match all hosts.
25356 However, this is not all you need to do. TLS sessions to a server won't work
25357 without some further configuration at the server end.
25359 It is rumoured that all existing clients that support TLS/SSL use RSA
25360 encryption. To make this work you need to set, in the server,
25362 tls_certificate = /some/file/name
25363 tls_privatekey = /some/file/name
25365 These options are, in fact, expanded strings, so you can make them depend on
25366 the identity of the client that is connected if you wish. The first file
25367 contains the server's X509 certificate, and the second contains the private key
25368 that goes with it. These files need to be readable by the Exim user, and must
25369 always be given as full path names. They can be the same file if both the
25370 certificate and the key are contained within it. If &%tls_privatekey%& is not
25371 set, or if its expansion is forced to fail or results in an empty string, this
25372 is assumed to be the case. The certificate file may also contain intermediate
25373 certificates that need to be sent to the client to enable it to authenticate
25374 the server's certificate.
25376 If you do not understand about certificates and keys, please try to find a
25377 source of this background information, which is not Exim-specific. (There are a
25378 few comments below in section &<<SECTcerandall>>&.)
25380 &*Note*&: These options do not apply when Exim is operating as a client &--
25381 they apply only in the case of a server. If you need to use a certificate in an
25382 Exim client, you must set the options of the same names in an &(smtp)&
25385 With just these options, an Exim server will be able to use TLS. It does not
25386 require the client to have a certificate (but see below for how to insist on
25387 this). There is one other option that may be needed in other situations. If
25389 tls_dhparam = /some/file/name
25391 is set, the SSL library is initialized for the use of Diffie-Hellman ciphers
25392 with the parameters contained in the file.
25393 Set this to &`none`& to disable use of DH entirely, by making no prime
25398 This may also be set to a string identifying a standard prime to be used for
25399 DH; if it is set to &`default`& or, for OpenSSL, is unset, then the prime
25400 used is &`ike23`&. There are a few standard primes available, see the
25401 documetnation for &%tls_dhparam%& for the complete list.
25407 for a way of generating file data.
25409 The strings supplied for these three options are expanded every time a client
25410 host connects. It is therefore possible to use different certificates and keys
25411 for different hosts, if you so wish, by making use of the client's IP address
25412 in &$sender_host_address$& to control the expansion. If a string expansion is
25413 forced to fail, Exim behaves as if the option is not set.
25415 .cindex "cipher" "logging"
25416 .cindex "log" "TLS cipher"
25417 .vindex "&$tls_cipher$&"
25418 The variable &$tls_cipher$& is set to the cipher suite that was negotiated for
25419 an incoming TLS connection. It is included in the &'Received:'& header of an
25420 incoming message (by default &-- you can, of course, change this), and it is
25421 also included in the log line that records a message's arrival, keyed by
25422 &"X="&, unless the &%tls_cipher%& log selector is turned off. The &%encrypted%&
25423 condition can be used to test for specific cipher suites in ACLs.
25424 (For outgoing SMTP deliveries, &$tls_cipher$& is reset &-- see section
25427 Once TLS has been established, the ACLs that run for subsequent SMTP commands
25428 can check the name of the cipher suite and vary their actions accordingly. The
25429 cipher suite names vary, depending on which TLS library is being used. For
25430 example, OpenSSL uses the name DES-CBC3-SHA for the cipher suite which in other
25431 contexts is known as TLS_RSA_WITH_3DES_EDE_CBC_SHA. Check the OpenSSL or GnuTLS
25432 documentation for more details.
25435 .section "Requesting and verifying client certificates" "SECID183"
25436 .cindex "certificate" "verification of client"
25437 .cindex "TLS" "client certificate verification"
25438 If you want an Exim server to request a certificate when negotiating a TLS
25439 session with a client, you must set either &%tls_verify_hosts%& or
25440 &%tls_try_verify_hosts%&. You can, of course, set either of them to * to
25441 apply to all TLS connections. For any host that matches one of these options,
25442 Exim requests a certificate as part of the setup of the TLS session. The
25443 contents of the certificate are verified by comparing it with a list of
25444 expected certificates. These must be available in a file or,
25445 for OpenSSL only (not GnuTLS), a directory, identified by
25446 &%tls_verify_certificates%&.
25448 A file can contain multiple certificates, concatenated end to end. If a
25451 each certificate must be in a separate file, with a name (or a symbolic link)
25452 of the form <&'hash'&>.0, where <&'hash'&> is a hash value constructed from the
25453 certificate. You can compute the relevant hash by running the command
25455 openssl x509 -hash -noout -in /cert/file
25457 where &_/cert/file_& contains a single certificate.
25459 The difference between &%tls_verify_hosts%& and &%tls_try_verify_hosts%& is
25460 what happens if the client does not supply a certificate, or if the certificate
25461 does not match any of the certificates in the collection named by
25462 &%tls_verify_certificates%&. If the client matches &%tls_verify_hosts%&, the
25463 attempt to set up a TLS session is aborted, and the incoming connection is
25464 dropped. If the client matches &%tls_try_verify_hosts%&, the (encrypted) SMTP
25465 session continues. ACLs that run for subsequent SMTP commands can detect the
25466 fact that no certificate was verified, and vary their actions accordingly. For
25467 example, you can insist on a certificate before accepting a message for
25468 relaying, but not when the message is destined for local delivery.
25470 .vindex "&$tls_peerdn$&"
25471 When a client supplies a certificate (whether it verifies or not), the value of
25472 the Distinguished Name of the certificate is made available in the variable
25473 &$tls_peerdn$& during subsequent processing of the message.
25475 .cindex "log" "distinguished name"
25476 Because it is often a long text string, it is not included in the log line or
25477 &'Received:'& header by default. You can arrange for it to be logged, keyed by
25478 &"DN="&, by setting the &%tls_peerdn%& log selector, and you can use
25479 &%received_header_text%& to change the &'Received:'& header. When no
25480 certificate is supplied, &$tls_peerdn$& is empty.
25483 .section "Revoked certificates" "SECID184"
25484 .cindex "TLS" "revoked certificates"
25485 .cindex "revocation list"
25486 .cindex "certificate" "revocation list"
25487 Certificate issuing authorities issue Certificate Revocation Lists (CRLs) when
25488 certificates are revoked. If you have such a list, you can pass it to an Exim
25489 server using the global option called &%tls_crl%& and to an Exim client using
25490 an identically named option for the &(smtp)& transport. In each case, the value
25491 of the option is expanded and must then be the name of a file that contains a
25495 .section "Configuring an Exim client to use TLS" "SECID185"
25496 .cindex "cipher" "logging"
25497 .cindex "log" "TLS cipher"
25498 .cindex "log" "distinguished name"
25499 .cindex "TLS" "configuring an Exim client"
25500 The &%tls_cipher%& and &%tls_peerdn%& log selectors apply to outgoing SMTP
25501 deliveries as well as to incoming, the latter one causing logging of the
25502 server certificate's DN. The remaining client configuration for TLS is all
25503 within the &(smtp)& transport.
25505 It is not necessary to set any options to have TLS work in the &(smtp)&
25506 transport. If Exim is built with TLS support, and TLS is advertised by a
25507 server, the &(smtp)& transport always tries to start a TLS session. However,
25508 this can be prevented by setting &%hosts_avoid_tls%& (an option of the
25509 transport) to a list of server hosts for which TLS should not be used.
25511 If you do not want Exim to attempt to send messages unencrypted when an attempt
25512 to set up an encrypted connection fails in any way, you can set
25513 &%hosts_require_tls%& to a list of hosts for which encryption is mandatory. For
25514 those hosts, delivery is always deferred if an encrypted connection cannot be
25515 set up. If there are any other hosts for the address, they are tried in the
25518 When the server host is not in &%hosts_require_tls%&, Exim may try to deliver
25519 the message unencrypted. It always does this if the response to STARTTLS is
25520 a 5&'xx'& code. For a temporary error code, or for a failure to negotiate a TLS
25521 session after a success response code, what happens is controlled by the
25522 &%tls_tempfail_tryclear%& option of the &(smtp)& transport. If it is false,
25523 delivery to this host is deferred, and other hosts (if available) are tried. If
25524 it is true, Exim attempts to deliver unencrypted after a 4&'xx'& response to
25525 STARTTLS, and if STARTTLS is accepted, but the subsequent TLS
25526 negotiation fails, Exim closes the current connection (because it is in an
25527 unknown state), opens a new one to the same host, and then tries the delivery
25530 The &%tls_certificate%& and &%tls_privatekey%& options of the &(smtp)&
25531 transport provide the client with a certificate, which is passed to the server
25532 if it requests it. If the server is Exim, it will request a certificate only if
25533 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& matches the client.
25535 If the &%tls_verify_certificates%& option is set on the &(smtp)& transport, it
25536 must name a file or,
25537 for OpenSSL only (not GnuTLS), a directory, that contains a collection of
25538 expected server certificates. The client verifies the server's certificate
25539 against this collection, taking into account any revoked certificates that are
25540 in the list defined by &%tls_crl%&.
25543 &%tls_require_ciphers%& is set on the &(smtp)& transport, it must contain a
25544 list of permitted cipher suites. If either of these checks fails, delivery to
25545 the current host is abandoned, and the &(smtp)& transport tries to deliver to
25546 alternative hosts, if any.
25549 These options must be set in the &(smtp)& transport for Exim to use TLS when it
25550 is operating as a client. Exim does not assume that a server certificate (set
25551 by the global options of the same name) should also be used when operating as a
25555 .vindex "&$host_address$&"
25556 All the TLS options in the &(smtp)& transport are expanded before use, with
25557 &$host$& and &$host_address$& containing the name and address of the server to
25558 which the client is connected. Forced failure of an expansion causes Exim to
25559 behave as if the relevant option were unset.
25561 .vindex &$tls_bits$&
25562 .vindex &$tls_cipher$&
25563 .vindex &$tls_peerdn$&
25564 .vindex &$tls_sni$&
25565 Before an SMTP connection is established, the
25566 &$tls_bits$&, &$tls_cipher$&, &$tls_peerdn$& and &$tls_sni$&
25567 variables are emptied. (Until the first connection, they contain the values
25568 that were set when the message was received.) If STARTTLS is subsequently
25569 successfully obeyed, these variables are set to the relevant values for the
25570 outgoing connection.
25574 .section "Use of TLS Server Name Indication" "SECTtlssni"
25575 .cindex "TLS" "Server Name Indication"
25576 .vindex "&$tls_sni$&"
25577 .oindex "&%tls_sni%&"
25578 With TLS1.0 or above, there is an extension mechanism by which extra
25579 information can be included at various points in the protocol. One of these
25580 extensions, documented in RFC 6066 (and before that RFC 4366) is
25581 &"Server Name Indication"&, commonly &"SNI"&. This extension is sent by the
25582 client in the initial handshake, so that the server can examine the servername
25583 within and possibly choose to use different certificates and keys (and more)
25586 This is analagous to HTTP's &"Host:"& header, and is the main mechanism by
25587 which HTTPS-enabled web-sites can be virtual-hosted, many sites to one IP
25590 With SMTP to MX, there are the same problems here as in choosing the identity
25591 against which to validate a certificate: you can't rely on insecure DNS to
25592 provide the identity which you then cryptographically verify. So this will
25593 be of limited use in that environment.
25595 With SMTP to Submission, there is a well-defined hostname which clients are
25596 connecting to and can validate certificates against. Thus clients &*can*&
25597 choose to include this information in the TLS negotiation. If this becomes
25598 wide-spread, then hosters can choose to present different certificates to
25599 different clients. Or even negotiate different cipher suites.
25601 The &%tls_sni%& option on an SMTP transport is an expanded string; the result,
25602 if not empty, will be sent on a TLS session as part of the handshake. There's
25603 nothing more to it. Choosing a sensible value not derived insecurely is the
25604 only point of caution. The &$tls_sni$& variable will be set to this string
25605 for the lifetime of the client connection (including during authentication).
25607 Except during SMTP client sessions, if &$tls_sni$& is set then it is a string
25608 received from a client.
25609 It can be logged with the &%log_selector%& item &`+tls_sni`&.
25611 If the string &`tls_sni`& appears in the main section's &%tls_certificate%&
25612 option (prior to expansion) then the following options will be re-expanded
25613 during TLS session handshake, to permit alternative values to be chosen:
25616 .vindex "&%tls_certificate%&"
25617 &%tls_certificate%&
25619 .vindex "&%tls_crl%&"
25622 .vindex "&%tls_privatekey%&"
25625 .vindex "&%tls_verify_certificates%&"
25626 &%tls_verify_certificates%&
25629 Great care should be taken to deal with matters of case, various injection
25630 attacks in the string (&`../`& or SQL), and ensuring that a valid filename
25631 can always be referenced; it is important to remember that &$tls_sni$& is
25632 arbitrary unverified data provided prior to authentication.
25634 The Exim developers are proceeding cautiously and so far no other TLS options
25637 When Exim is built againt OpenSSL, OpenSSL must have been built with support
25638 for TLS Extensions. This holds true for OpenSSL 1.0.0+ and 0.9.8+ with
25639 enable-tlsext in EXTRACONFIGURE. If you invoke &(openssl s_client -h)& and
25640 see &`-servername`& in the output, then OpenSSL has support.
25642 When Exim is built against GnuTLS, SNI support is available as of GnuTLS
25643 0.5.10. (Its presence predates the current API which Exim uses, so if Exim
25644 built, then you have SNI support).
25648 .section "Multiple messages on the same encrypted TCP/IP connection" &&&
25650 .cindex "multiple SMTP deliveries with TLS"
25651 .cindex "TLS" "multiple message deliveries"
25652 Exim sends multiple messages down the same TCP/IP connection by starting up
25653 an entirely new delivery process for each message, passing the socket from
25654 one process to the next. This implementation does not fit well with the use
25655 of TLS, because there is quite a lot of state information associated with a TLS
25656 connection, not just a socket identification. Passing all the state information
25657 to a new process is not feasible. Consequently, Exim shuts down an existing TLS
25658 session before passing the socket to a new process. The new process may then
25659 try to start a new TLS session, and if successful, may try to re-authenticate
25660 if AUTH is in use, before sending the next message.
25662 The RFC is not clear as to whether or not an SMTP session continues in clear
25663 after TLS has been shut down, or whether TLS may be restarted again later, as
25664 just described. However, if the server is Exim, this shutdown and
25665 reinitialization works. It is not known which (if any) other servers operate
25666 successfully if the client closes a TLS session and continues with unencrypted
25667 SMTP, but there are certainly some that do not work. For such servers, Exim
25668 should not pass the socket to another process, because the failure of the
25669 subsequent attempt to use it would cause Exim to record a temporary host error,
25670 and delay other deliveries to that host.
25672 To test for this case, Exim sends an EHLO command to the server after
25673 closing down the TLS session. If this fails in any way, the connection is
25674 closed instead of being passed to a new delivery process, but no retry
25675 information is recorded.
25677 There is also a manual override; you can set &%hosts_nopass_tls%& on the
25678 &(smtp)& transport to match those hosts for which Exim should not pass
25679 connections to new processes if TLS has been used.
25684 .section "Certificates and all that" "SECTcerandall"
25685 .cindex "certificate" "references to discussion"
25686 In order to understand fully how TLS works, you need to know about
25687 certificates, certificate signing, and certificate authorities. This is not the
25688 place to give a tutorial, especially as I do not know very much about it
25689 myself. Some helpful introduction can be found in the FAQ for the SSL addition
25690 to Apache, currently at
25692 &url(http://www.modssl.org/docs/2.7/ssl_faq.html#ToC24)
25694 Other parts of the &'modssl'& documentation are also helpful, and have
25695 links to further files.
25696 Eric Rescorla's book, &'SSL and TLS'&, published by Addison-Wesley (ISBN
25697 0-201-61598-3), contains both introductory and more in-depth descriptions.
25698 Some sample programs taken from the book are available from
25700 &url(http://www.rtfm.com/openssl-examples/)
25704 .section "Certificate chains" "SECID186"
25705 The file named by &%tls_certificate%& may contain more than one
25706 certificate. This is useful in the case where the certificate that is being
25707 sent is validated by an intermediate certificate which the other end does
25708 not have. Multiple certificates must be in the correct order in the file.
25709 First the host's certificate itself, then the first intermediate
25710 certificate to validate the issuer of the host certificate, then the next
25711 intermediate certificate to validate the issuer of the first intermediate
25712 certificate, and so on, until finally (optionally) the root certificate.
25713 The root certificate must already be trusted by the recipient for
25714 validation to succeed, of course, but if it's not preinstalled, sending the
25715 root certificate along with the rest makes it available for the user to
25716 install if the receiving end is a client MUA that can interact with a user.
25719 .section "Self-signed certificates" "SECID187"
25720 .cindex "certificate" "self-signed"
25721 You can create a self-signed certificate using the &'req'& command provided
25722 with OpenSSL, like this:
25724 openssl req -x509 -newkey rsa:1024 -keyout file1 -out file2 \
25727 &_file1_& and &_file2_& can be the same file; the key and the certificate are
25728 delimited and so can be identified independently. The &%-days%& option
25729 specifies a period for which the certificate is valid. The &%-nodes%& option is
25730 important: if you do not set it, the key is encrypted with a passphrase
25731 that you are prompted for, and any use that is made of the key causes more
25732 prompting for the passphrase. This is not helpful if you are going to use
25733 this certificate and key in an MTA, where prompting is not possible.
25735 A self-signed certificate made in this way is sufficient for testing, and
25736 may be adequate for all your requirements if you are mainly interested in
25737 encrypting transfers, and not in secure identification.
25739 However, many clients require that the certificate presented by the server be a
25740 user (also called &"leaf"& or &"site"&) certificate, and not a self-signed
25741 certificate. In this situation, the self-signed certificate described above
25742 must be installed on the client host as a trusted root &'certification
25743 authority'& (CA), and the certificate used by Exim must be a user certificate
25744 signed with that self-signed certificate.
25746 For information on creating self-signed CA certificates and using them to sign
25747 user certificates, see the &'General implementation overview'& chapter of the
25748 Open-source PKI book, available online at
25749 &url(http://ospkibook.sourceforge.net/).
25750 .ecindex IIDencsmtp1
25751 .ecindex IIDencsmtp2
25755 . ////////////////////////////////////////////////////////////////////////////
25756 . ////////////////////////////////////////////////////////////////////////////
25758 .chapter "Access control lists" "CHAPACL"
25759 .scindex IIDacl "&ACL;" "description"
25760 .cindex "control of incoming mail"
25761 .cindex "message" "controlling incoming"
25762 .cindex "policy control" "access control lists"
25763 Access Control Lists (ACLs) are defined in a separate section of the run time
25764 configuration file, headed by &"begin acl"&. Each ACL definition starts with a
25765 name, terminated by a colon. Here is a complete ACL section that contains just
25766 one very small ACL:
25770 accept hosts = one.host.only
25772 You can have as many lists as you like in the ACL section, and the order in
25773 which they appear does not matter. The lists are self-terminating.
25775 The majority of ACLs are used to control Exim's behaviour when it receives
25776 certain SMTP commands. This applies both to incoming TCP/IP connections, and
25777 when a local process submits a message using SMTP by specifying the &%-bs%&
25778 option. The most common use is for controlling which recipients are accepted
25779 in incoming messages. In addition, you can define an ACL that is used to check
25780 local non-SMTP messages. The default configuration file contains an example of
25781 a realistic ACL for checking RCPT commands. This is discussed in chapter
25782 &<<CHAPdefconfil>>&.
25785 .section "Testing ACLs" "SECID188"
25786 The &%-bh%& command line option provides a way of testing your ACL
25787 configuration locally by running a fake SMTP session with which you interact.
25788 The host &'relay-test.mail-abuse.org'& provides a service for checking your
25789 relaying configuration (see section &<<SECTcheralcon>>& for more details).
25793 .section "Specifying when ACLs are used" "SECID189"
25794 .cindex "&ACL;" "options for specifying"
25795 In order to cause an ACL to be used, you have to name it in one of the relevant
25796 options in the main part of the configuration. These options are:
25797 .cindex "AUTH" "ACL for"
25798 .cindex "DATA" "ACLs for"
25799 .cindex "ETRN" "ACL for"
25800 .cindex "EXPN" "ACL for"
25801 .cindex "HELO" "ACL for"
25802 .cindex "EHLO" "ACL for"
25803 .cindex "MAIL" "ACL for"
25804 .cindex "QUIT, ACL for"
25805 .cindex "RCPT" "ACL for"
25806 .cindex "STARTTLS, ACL for"
25807 .cindex "VRFY" "ACL for"
25808 .cindex "SMTP" "connection, ACL for"
25809 .cindex "non-SMTP messages" "ACLs for"
25810 .cindex "MIME content scanning" "ACL for"
25813 .irow &%acl_not_smtp%& "ACL for non-SMTP messages"
25814 .irow &%acl_not_smtp_mime%& "ACL for non-SMTP MIME parts"
25815 .irow &%acl_not_smtp_start%& "ACL at start of non-SMTP message"
25816 .irow &%acl_smtp_auth%& "ACL for AUTH"
25817 .irow &%acl_smtp_connect%& "ACL for start of SMTP connection"
25818 .irow &%acl_smtp_data%& "ACL after DATA is complete"
25819 .irow &%acl_smtp_etrn%& "ACL for ETRN"
25820 .irow &%acl_smtp_expn%& "ACL for EXPN"
25821 .irow &%acl_smtp_helo%& "ACL for HELO or EHLO"
25822 .irow &%acl_smtp_mail%& "ACL for MAIL"
25823 .irow &%acl_smtp_mailauth%& "ACL for the AUTH parameter of MAIL"
25824 .irow &%acl_smtp_mime%& "ACL for content-scanning MIME parts"
25825 .irow &%acl_smtp_notquit%& "ACL for non-QUIT terminations"
25826 .irow &%acl_smtp_predata%& "ACL at start of DATA command"
25827 .irow &%acl_smtp_quit%& "ACL for QUIT"
25828 .irow &%acl_smtp_rcpt%& "ACL for RCPT"
25829 .irow &%acl_smtp_starttls%& "ACL for STARTTLS"
25830 .irow &%acl_smtp_vrfy%& "ACL for VRFY"
25833 For example, if you set
25835 acl_smtp_rcpt = small_acl
25837 the little ACL defined above is used whenever Exim receives a RCPT command
25838 in an SMTP dialogue. The majority of policy tests on incoming messages can be
25839 done when RCPT commands arrive. A rejection of RCPT should cause the
25840 sending MTA to give up on the recipient address contained in the RCPT
25841 command, whereas rejection at other times may cause the client MTA to keep on
25842 trying to deliver the message. It is therefore recommended that you do as much
25843 testing as possible at RCPT time.
25846 .section "The non-SMTP ACLs" "SECID190"
25847 .cindex "non-SMTP messages" "ACLs for"
25848 The non-SMTP ACLs apply to all non-interactive incoming messages, that is, they
25849 apply to batched SMTP as well as to non-SMTP messages. (Batched SMTP is not
25850 really SMTP.) Many of the ACL conditions (for example, host tests, and tests on
25851 the state of the SMTP connection such as encryption and authentication) are not
25852 relevant and are forbidden in these ACLs. However, the sender and recipients
25853 are known, so the &%senders%& and &%sender_domains%& conditions and the
25854 &$sender_address$& and &$recipients$& variables can be used. Variables such as
25855 &$authenticated_sender$& are also available. You can specify added header lines
25856 in any of these ACLs.
25858 The &%acl_not_smtp_start%& ACL is run right at the start of receiving a
25859 non-SMTP message, before any of the message has been read. (This is the
25860 analogue of the &%acl_smtp_predata%& ACL for SMTP input.) In the case of
25861 batched SMTP input, it runs after the DATA command has been reached. The
25862 result of this ACL is ignored; it cannot be used to reject a message. If you
25863 really need to, you could set a value in an ACL variable here and reject based
25864 on that in the &%acl_not_smtp%& ACL. However, this ACL can be used to set
25865 controls, and in particular, it can be used to set
25867 control = suppress_local_fixups
25869 This cannot be used in the other non-SMTP ACLs because by the time they are
25870 run, it is too late.
25872 The &%acl_not_smtp_mime%& ACL is available only when Exim is compiled with the
25873 content-scanning extension. For details, see chapter &<<CHAPexiscan>>&.
25875 The &%acl_not_smtp%& ACL is run just before the &[local_scan()]& function. Any
25876 kind of rejection is treated as permanent, because there is no way of sending a
25877 temporary error for these kinds of message.
25880 .section "The SMTP connect ACL" "SECID191"
25881 .cindex "SMTP" "connection, ACL for"
25882 .oindex &%smtp_banner%&
25883 The ACL test specified by &%acl_smtp_connect%& happens at the start of an SMTP
25884 session, after the test specified by &%host_reject_connection%& (which is now
25885 an anomaly) and any TCP Wrappers testing (if configured). If the connection is
25886 accepted by an &%accept%& verb that has a &%message%& modifier, the contents of
25887 the message override the banner message that is otherwise specified by the
25888 &%smtp_banner%& option.
25891 .section "The EHLO/HELO ACL" "SECID192"
25892 .cindex "EHLO" "ACL for"
25893 .cindex "HELO" "ACL for"
25894 The ACL test specified by &%acl_smtp_helo%& happens when the client issues an
25895 EHLO or HELO command, after the tests specified by &%helo_accept_junk_hosts%&,
25896 &%helo_allow_chars%&, &%helo_verify_hosts%&, and &%helo_try_verify_hosts%&.
25897 Note that a client may issue more than one EHLO or HELO command in an SMTP
25898 session, and indeed is required to issue a new EHLO or HELO after successfully
25899 setting up encryption following a STARTTLS command.
25901 If the command is accepted by an &%accept%& verb that has a &%message%&
25902 modifier, the message may not contain more than one line (it will be truncated
25903 at the first newline and a panic logged if it does). Such a message cannot
25904 affect the EHLO options that are listed on the second and subsequent lines of
25908 .section "The DATA ACLs" "SECID193"
25909 .cindex "DATA" "ACLs for"
25910 Two ACLs are associated with the DATA command, because it is two-stage
25911 command, with two responses being sent to the client.
25912 When the DATA command is received, the ACL defined by &%acl_smtp_predata%&
25913 is obeyed. This gives you control after all the RCPT commands, but before
25914 the message itself is received. It offers the opportunity to give a negative
25915 response to the DATA command before the data is transmitted. Header lines
25916 added by MAIL or RCPT ACLs are not visible at this time, but any that
25917 are defined here are visible when the &%acl_smtp_data%& ACL is run.
25919 You cannot test the contents of the message, for example, to verify addresses
25920 in the headers, at RCPT time or when the DATA command is received. Such
25921 tests have to appear in the ACL that is run after the message itself has been
25922 received, before the final response to the DATA command is sent. This is
25923 the ACL specified by &%acl_smtp_data%&, which is the second ACL that is
25924 associated with the DATA command.
25926 For both of these ACLs, it is not possible to reject individual recipients. An
25927 error response rejects the entire message. Unfortunately, it is known that some
25928 MTAs do not treat hard (5&'xx'&) responses to the DATA command (either
25929 before or after the data) correctly &-- they keep the message on their queues
25930 and try again later, but that is their problem, though it does waste some of
25934 .section "The SMTP DKIM ACL" "SECTDKIMACL"
25935 The &%acl_smtp_dkim%& ACL is available only when Exim is compiled with DKIM support
25936 enabled (which is the default).
25938 The ACL test specified by &%acl_smtp_dkim%& happens after a message has been
25939 received, and is executed for each DKIM signature found in a message. If not
25940 otherwise specified, the default action is to accept.
25942 For details on the operation of DKIM, see chapter &<<CHID12>>&.
25945 .section "The SMTP MIME ACL" "SECID194"
25946 The &%acl_smtp_mime%& option is available only when Exim is compiled with the
25947 content-scanning extension. For details, see chapter &<<CHAPexiscan>>&.
25950 .section "The QUIT ACL" "SECTQUITACL"
25951 .cindex "QUIT, ACL for"
25952 The ACL for the SMTP QUIT command is anomalous, in that the outcome of the ACL
25953 does not affect the response code to QUIT, which is always 221. Thus, the ACL
25954 does not in fact control any access. For this reason, the only verbs that are
25955 permitted are &%accept%& and &%warn%&.
25957 This ACL can be used for tasks such as custom logging at the end of an SMTP
25958 session. For example, you can use ACL variables in other ACLs to count
25959 messages, recipients, etc., and log the totals at QUIT time using one or
25960 more &%logwrite%& modifiers on a &%warn%& verb.
25962 &*Warning*&: Only the &$acl_c$&&'x'& variables can be used for this, because
25963 the &$acl_m$&&'x'& variables are reset at the end of each incoming message.
25965 You do not need to have a final &%accept%&, but if you do, you can use a
25966 &%message%& modifier to specify custom text that is sent as part of the 221
25969 This ACL is run only for a &"normal"& QUIT. For certain kinds of disastrous
25970 failure (for example, failure to open a log file, or when Exim is bombing out
25971 because it has detected an unrecoverable error), all SMTP commands from the
25972 client are given temporary error responses until QUIT is received or the
25973 connection is closed. In these special cases, the QUIT ACL does not run.
25976 .section "The not-QUIT ACL" "SECTNOTQUITACL"
25977 .vindex &$acl_smtp_notquit$&
25978 The not-QUIT ACL, specified by &%acl_smtp_notquit%&, is run in most cases when
25979 an SMTP session ends without sending QUIT. However, when Exim itself is is bad
25980 trouble, such as being unable to write to its log files, this ACL is not run,
25981 because it might try to do things (such as write to log files) that make the
25982 situation even worse.
25984 Like the QUIT ACL, this ACL is provided to make it possible to do customized
25985 logging or to gather statistics, and its outcome is ignored. The &%delay%&
25986 modifier is forbidden in this ACL, and the only permitted verbs are &%accept%&
25989 .vindex &$smtp_notquit_reason$&
25990 When the not-QUIT ACL is running, the variable &$smtp_notquit_reason$& is set
25991 to a string that indicates the reason for the termination of the SMTP
25992 connection. The possible values are:
25994 .irow &`acl-drop`& "Another ACL issued a &%drop%& command"
25995 .irow &`bad-commands`& "Too many unknown or non-mail commands"
25996 .irow &`command-timeout`& "Timeout while reading SMTP commands"
25997 .irow &`connection-lost`& "The SMTP connection has been lost"
25998 .irow &`data-timeout`& "Timeout while reading message data"
25999 .irow &`local-scan-error`& "The &[local_scan()]& function crashed"
26000 .irow &`local-scan-timeout`& "The &[local_scan()]& function timed out"
26001 .irow &`signal-exit`& "SIGTERM or SIGINT"
26002 .irow &`synchronization-error`& "SMTP synchronization error"
26003 .irow &`tls-failed`& "TLS failed to start"
26005 In most cases when an SMTP connection is closed without having received QUIT,
26006 Exim sends an SMTP response message before actually closing the connection.
26007 With the exception of the &`acl-drop`& case, the default message can be
26008 overridden by the &%message%& modifier in the not-QUIT ACL. In the case of a
26009 &%drop%& verb in another ACL, it is the message from the other ACL that is
26013 .section "Finding an ACL to use" "SECID195"
26014 .cindex "&ACL;" "finding which to use"
26015 The value of an &%acl_smtp_%&&'xxx'& option is expanded before use, so
26016 you can use different ACLs in different circumstances. For example,
26018 acl_smtp_rcpt = ${if ={25}{$interface_port} \
26019 {acl_check_rcpt} {acl_check_rcpt_submit} }
26021 In the default configuration file there are some example settings for
26022 providing an RFC 4409 message submission service on port 587 and a
26023 non-standard &"smtps"& service on port 465. You can use a string
26024 expansion like this to choose an ACL for MUAs on these ports which is
26025 more appropriate for this purpose than the default ACL on port 25.
26027 The expanded string does not have to be the name of an ACL in the
26028 configuration file; there are other possibilities. Having expanded the
26029 string, Exim searches for an ACL as follows:
26032 If the string begins with a slash, Exim uses it as a file name, and reads its
26033 contents as an ACL. The lines are processed in the same way as lines in the
26034 Exim configuration file. In particular, continuation lines are supported, blank
26035 lines are ignored, as are lines whose first non-whitespace character is &"#"&.
26036 If the file does not exist or cannot be read, an error occurs (typically
26037 causing a temporary failure of whatever caused the ACL to be run). For example:
26039 acl_smtp_data = /etc/acls/\
26040 ${lookup{$sender_host_address}lsearch\
26041 {/etc/acllist}{$value}{default}}
26043 This looks up an ACL file to use on the basis of the host's IP address, falling
26044 back to a default if the lookup fails. If an ACL is successfully read from a
26045 file, it is retained in memory for the duration of the Exim process, so that it
26046 can be re-used without having to re-read the file.
26048 If the string does not start with a slash, and does not contain any spaces,
26049 Exim searches the ACL section of the configuration for an ACL whose name
26050 matches the string.
26052 If no named ACL is found, or if the string contains spaces, Exim parses
26053 the string as an inline ACL. This can save typing in cases where you just
26054 want to have something like
26056 acl_smtp_vrfy = accept
26058 in order to allow free use of the VRFY command. Such a string may contain
26059 newlines; it is processed in the same way as an ACL that is read from a file.
26065 .section "ACL return codes" "SECID196"
26066 .cindex "&ACL;" "return codes"
26067 Except for the QUIT ACL, which does not affect the SMTP return code (see
26068 section &<<SECTQUITACL>>& above), the result of running an ACL is either
26069 &"accept"& or &"deny"&, or, if some test cannot be completed (for example, if a
26070 database is down), &"defer"&. These results cause 2&'xx'&, 5&'xx'&, and 4&'xx'&
26071 return codes, respectively, to be used in the SMTP dialogue. A fourth return,
26072 &"error"&, occurs when there is an error such as invalid syntax in the ACL.
26073 This also causes a 4&'xx'& return code.
26075 For the non-SMTP ACL, &"defer"& and &"error"& are treated in the same way as
26076 &"deny"&, because there is no mechanism for passing temporary errors to the
26077 submitters of non-SMTP messages.
26080 ACLs that are relevant to message reception may also return &"discard"&. This
26081 has the effect of &"accept"&, but causes either the entire message or an
26082 individual recipient address to be discarded. In other words, it is a
26083 blackholing facility. Use it with care.
26085 If the ACL for MAIL returns &"discard"&, all recipients are discarded, and no
26086 ACL is run for subsequent RCPT commands. The effect of &"discard"& in a
26087 RCPT ACL is to discard just the one recipient address. If there are no
26088 recipients left when the message's data is received, the DATA ACL is not
26089 run. A &"discard"& return from the DATA or the non-SMTP ACL discards all the
26090 remaining recipients. The &"discard"& return is not permitted for the
26091 &%acl_smtp_predata%& ACL.
26094 .cindex "&[local_scan()]& function" "when all recipients discarded"
26095 The &[local_scan()]& function is always run, even if there are no remaining
26096 recipients; it may create new recipients.
26100 .section "Unset ACL options" "SECID197"
26101 .cindex "&ACL;" "unset options"
26102 The default actions when any of the &%acl_%&&'xxx'& options are unset are not
26103 all the same. &*Note*&: These defaults apply only when the relevant ACL is
26104 not defined at all. For any defined ACL, the default action when control
26105 reaches the end of the ACL statements is &"deny"&.
26107 For &%acl_smtp_quit%& and &%acl_not_smtp_start%& there is no default because
26108 these two are ACLs that are used only for their side effects. They cannot be
26109 used to accept or reject anything.
26111 For &%acl_not_smtp%&, &%acl_smtp_auth%&, &%acl_smtp_connect%&,
26112 &%acl_smtp_data%&, &%acl_smtp_helo%&, &%acl_smtp_mail%&, &%acl_smtp_mailauth%&,
26113 &%acl_smtp_mime%&, &%acl_smtp_predata%&, and &%acl_smtp_starttls%&, the action
26114 when the ACL is not defined is &"accept"&.
26116 For the others (&%acl_smtp_etrn%&, &%acl_smtp_expn%&, &%acl_smtp_rcpt%&, and
26117 &%acl_smtp_vrfy%&), the action when the ACL is not defined is &"deny"&.
26118 This means that &%acl_smtp_rcpt%& must be defined in order to receive any
26119 messages over an SMTP connection. For an example, see the ACL in the default
26120 configuration file.
26125 .section "Data for message ACLs" "SECID198"
26126 .cindex "&ACL;" "data for message ACL"
26128 .vindex &$local_part$&
26129 .vindex &$sender_address$&
26130 .vindex &$sender_host_address$&
26131 .vindex &$smtp_command$&
26132 When a MAIL or RCPT ACL, or either of the DATA ACLs, is running, the variables
26133 that contain information about the host and the message's sender (for example,
26134 &$sender_host_address$& and &$sender_address$&) are set, and can be used in ACL
26135 statements. In the case of RCPT (but not MAIL or DATA), &$domain$& and
26136 &$local_part$& are set from the argument address. The entire SMTP command
26137 is available in &$smtp_command$&.
26139 When an ACL for the AUTH parameter of MAIL is running, the variables that
26140 contain information about the host are set, but &$sender_address$& is not yet
26141 set. Section &<<SECTauthparamail>>& contains a discussion of this parameter and
26144 .vindex "&$message_size$&"
26145 The &$message_size$& variable is set to the value of the SIZE parameter on
26146 the MAIL command at MAIL, RCPT and pre-data time, or to -1 if
26147 that parameter is not given. The value is updated to the true message size by
26148 the time the final DATA ACL is run (after the message data has been
26151 .vindex "&$rcpt_count$&"
26152 .vindex "&$recipients_count$&"
26153 The &$rcpt_count$& variable increases by one for each RCPT command received.
26154 The &$recipients_count$& variable increases by one each time a RCPT command is
26155 accepted, so while an ACL for RCPT is being processed, it contains the number
26156 of previously accepted recipients. At DATA time (for both the DATA ACLs),
26157 &$rcpt_count$& contains the total number of RCPT commands, and
26158 &$recipients_count$& contains the total number of accepted recipients.
26164 .section "Data for non-message ACLs" "SECTdatfornon"
26165 .cindex "&ACL;" "data for non-message ACL"
26166 .vindex &$smtp_command_argument$&
26167 .vindex &$smtp_command$&
26168 When an ACL is being run for AUTH, EHLO, ETRN, EXPN, HELO, STARTTLS, or VRFY,
26169 the remainder of the SMTP command line is placed in &$smtp_command_argument$&,
26170 and the entire SMTP command is available in &$smtp_command$&.
26171 These variables can be tested using a &%condition%& condition. For example,
26172 here is an ACL for use with AUTH, which insists that either the session is
26173 encrypted, or the CRAM-MD5 authentication method is used. In other words, it
26174 does not permit authentication methods that use cleartext passwords on
26175 unencrypted connections.
26178 accept encrypted = *
26179 accept condition = ${if eq{${uc:$smtp_command_argument}}\
26181 deny message = TLS encryption or CRAM-MD5 required
26183 (Another way of applying this restriction is to arrange for the authenticators
26184 that use cleartext passwords not to be advertised when the connection is not
26185 encrypted. You can use the generic &%server_advertise_condition%& authenticator
26186 option to do this.)
26190 .section "Format of an ACL" "SECID199"
26191 .cindex "&ACL;" "format of"
26192 .cindex "&ACL;" "verbs, definition of"
26193 An individual ACL consists of a number of statements. Each statement starts
26194 with a verb, optionally followed by a number of conditions and &"modifiers"&.
26195 Modifiers can change the way the verb operates, define error and log messages,
26196 set variables, insert delays, and vary the processing of accepted messages.
26198 If all the conditions are met, the verb is obeyed. The same condition may be
26199 used (with different arguments) more than once in the same statement. This
26200 provides a means of specifying an &"and"& conjunction between conditions. For
26203 deny dnslists = list1.example
26204 dnslists = list2.example
26206 If there are no conditions, the verb is always obeyed. Exim stops evaluating
26207 the conditions and modifiers when it reaches a condition that fails. What
26208 happens then depends on the verb (and in one case, on a special modifier). Not
26209 all the conditions make sense at every testing point. For example, you cannot
26210 test a sender address in the ACL that is run for a VRFY command.
26213 .section "ACL verbs" "SECID200"
26214 The ACL verbs are as follows:
26217 .cindex "&%accept%& ACL verb"
26218 &%accept%&: If all the conditions are met, the ACL returns &"accept"&. If any
26219 of the conditions are not met, what happens depends on whether &%endpass%&
26220 appears among the conditions (for syntax see below). If the failing condition
26221 is before &%endpass%&, control is passed to the next ACL statement; if it is
26222 after &%endpass%&, the ACL returns &"deny"&. Consider this statement, used to
26223 check a RCPT command:
26225 accept domains = +local_domains
26229 If the recipient domain does not match the &%domains%& condition, control
26230 passes to the next statement. If it does match, the recipient is verified, and
26231 the command is accepted if verification succeeds. However, if verification
26232 fails, the ACL yields &"deny"&, because the failing condition is after
26235 The &%endpass%& feature has turned out to be confusing to many people, so its
26236 use is not recommended nowadays. It is always possible to rewrite an ACL so
26237 that &%endpass%& is not needed, and it is no longer used in the default
26240 .cindex "&%message%& ACL modifier" "with &%accept%&"
26241 If a &%message%& modifier appears on an &%accept%& statement, its action
26242 depends on whether or not &%endpass%& is present. In the absence of &%endpass%&
26243 (when an &%accept%& verb either accepts or passes control to the next
26244 statement), &%message%& can be used to vary the message that is sent when an
26245 SMTP command is accepted. For example, in a RCPT ACL you could have:
26247 &`accept `&<&'some conditions'&>
26248 &` message = OK, I will allow you through today`&
26250 You can specify an SMTP response code, optionally followed by an &"extended
26251 response code"& at the start of the message, but the first digit must be the
26252 same as would be sent by default, which is 2 for an &%accept%& verb.
26254 If &%endpass%& is present in an &%accept%& statement, &%message%& specifies
26255 an error message that is used when access is denied. This behaviour is retained
26256 for backward compatibility, but current &"best practice"& is to avoid the use
26261 .cindex "&%defer%& ACL verb"
26262 &%defer%&: If all the conditions are true, the ACL returns &"defer"& which, in
26263 an SMTP session, causes a 4&'xx'& response to be given. For a non-SMTP ACL,
26264 &%defer%& is the same as &%deny%&, because there is no way of sending a
26265 temporary error. For a RCPT command, &%defer%& is much the same as using a
26266 &(redirect)& router and &`:defer:`& while verifying, but the &%defer%& verb can
26267 be used in any ACL, and even for a recipient it might be a simpler approach.
26271 .cindex "&%deny%& ACL verb"
26272 &%deny%&: If all the conditions are met, the ACL returns &"deny"&. If any of
26273 the conditions are not met, control is passed to the next ACL statement. For
26276 deny dnslists = blackholes.mail-abuse.org
26278 rejects commands from hosts that are on a DNS black list.
26282 .cindex "&%discard%& ACL verb"
26283 &%discard%&: This verb behaves like &%accept%&, except that it returns
26284 &"discard"& from the ACL instead of &"accept"&. It is permitted only on ACLs
26285 that are concerned with receiving messages. When all the conditions are true,
26286 the sending entity receives a &"success"& response. However, &%discard%& causes
26287 recipients to be discarded. If it is used in an ACL for RCPT, just the one
26288 recipient is discarded; if used for MAIL, DATA or in the non-SMTP ACL, all the
26289 message's recipients are discarded. Recipients that are discarded before DATA
26290 do not appear in the log line when the &%received_recipients%& log selector is set.
26292 If the &%log_message%& modifier is set when &%discard%& operates,
26293 its contents are added to the line that is automatically written to the log.
26294 The &%message%& modifier operates exactly as it does for &%accept%&.
26298 .cindex "&%drop%& ACL verb"
26299 &%drop%&: This verb behaves like &%deny%&, except that an SMTP connection is
26300 forcibly closed after the 5&'xx'& error message has been sent. For example:
26302 drop message = I don't take more than 20 RCPTs
26303 condition = ${if > {$rcpt_count}{20}}
26305 There is no difference between &%deny%& and &%drop%& for the connect-time ACL.
26306 The connection is always dropped after sending a 550 response.
26309 .cindex "&%require%& ACL verb"
26310 &%require%&: If all the conditions are met, control is passed to the next ACL
26311 statement. If any of the conditions are not met, the ACL returns &"deny"&. For
26312 example, when checking a RCPT command,
26314 require message = Sender did not verify
26317 passes control to subsequent statements only if the message's sender can be
26318 verified. Otherwise, it rejects the command. Note the positioning of the
26319 &%message%& modifier, before the &%verify%& condition. The reason for this is
26320 discussed in section &<<SECTcondmodproc>>&.
26323 .cindex "&%warn%& ACL verb"
26324 &%warn%&: If all the conditions are true, a line specified by the
26325 &%log_message%& modifier is written to Exim's main log. Control always passes
26326 to the next ACL statement. If any condition is false, the log line is not
26327 written. If an identical log line is requested several times in the same
26328 message, only one copy is actually written to the log. If you want to force
26329 duplicates to be written, use the &%logwrite%& modifier instead.
26331 If &%log_message%& is not present, a &%warn%& verb just checks its conditions
26332 and obeys any &"immediate"& modifiers (such as &%control%&, &%set%&,
26333 &%logwrite%&, and &%add_header%&) that appear before the first failing
26334 condition. There is more about adding header lines in section
26335 &<<SECTaddheadacl>>&.
26337 If any condition on a &%warn%& statement cannot be completed (that is, there is
26338 some sort of defer), the log line specified by &%log_message%& is not written.
26339 This does not include the case of a forced failure from a lookup, which
26340 is considered to be a successful completion. After a defer, no further
26341 conditions or modifiers in the &%warn%& statement are processed. The incident
26342 is logged, and the ACL continues to be processed, from the next statement
26346 .vindex "&$acl_verify_message$&"
26347 When one of the &%warn%& conditions is an address verification that fails, the
26348 text of the verification failure message is in &$acl_verify_message$&. If you
26349 want this logged, you must set it up explicitly. For example:
26351 warn !verify = sender
26352 log_message = sender verify failed: $acl_verify_message
26356 At the end of each ACL there is an implicit unconditional &%deny%&.
26358 As you can see from the examples above, the conditions and modifiers are
26359 written one to a line, with the first one on the same line as the verb, and
26360 subsequent ones on following lines. If you have a very long condition, you can
26361 continue it onto several physical lines by the usual backslash continuation
26362 mechanism. It is conventional to align the conditions vertically.
26366 .section "ACL variables" "SECTaclvariables"
26367 .cindex "&ACL;" "variables"
26368 There are some special variables that can be set during ACL processing. They
26369 can be used to pass information between different ACLs, different invocations
26370 of the same ACL in the same SMTP connection, and between ACLs and the routers,
26371 transports, and filters that are used to deliver a message. The names of these
26372 variables must begin with &$acl_c$& or &$acl_m$&, followed either by a digit or
26373 an underscore, but the remainder of the name can be any sequence of
26374 alphanumeric characters and underscores that you choose. There is no limit on
26375 the number of ACL variables. The two sets act as follows:
26377 The values of those variables whose names begin with &$acl_c$& persist
26378 throughout an SMTP connection. They are never reset. Thus, a value that is set
26379 while receiving one message is still available when receiving the next message
26380 on the same SMTP connection.
26382 The values of those variables whose names begin with &$acl_m$& persist only
26383 while a message is being received. They are reset afterwards. They are also
26384 reset by MAIL, RSET, EHLO, HELO, and after starting up a TLS session.
26387 When a message is accepted, the current values of all the ACL variables are
26388 preserved with the message and are subsequently made available at delivery
26389 time. The ACL variables are set by a modifier called &%set%&. For example:
26391 accept hosts = whatever
26392 set acl_m4 = some value
26393 accept authenticated = *
26394 set acl_c_auth = yes
26396 &*Note*&: A leading dollar sign is not used when naming a variable that is to
26397 be set. If you want to set a variable without taking any action, you can use a
26398 &%warn%& verb without any other modifiers or conditions.
26400 .oindex &%strict_acl_vars%&
26401 What happens if a syntactically valid but undefined ACL variable is
26402 referenced depends on the setting of the &%strict_acl_vars%& option. If it is
26403 false (the default), an empty string is substituted; if it is true, an
26404 error is generated.
26406 Versions of Exim before 4.64 have a limited set of numbered variables, but
26407 their names are compatible, so there is no problem with upgrading.
26410 .section "Condition and modifier processing" "SECTcondmodproc"
26411 .cindex "&ACL;" "conditions; processing"
26412 .cindex "&ACL;" "modifiers; processing"
26413 An exclamation mark preceding a condition negates its result. For example:
26415 deny domains = *.dom.example
26416 !verify = recipient
26418 causes the ACL to return &"deny"& if the recipient domain ends in
26419 &'dom.example'& and the recipient address cannot be verified. Sometimes
26420 negation can be used on the right-hand side of a condition. For example, these
26421 two statements are equivalent:
26423 deny hosts = !192.168.3.4
26424 deny !hosts = 192.168.3.4
26426 However, for many conditions (&%verify%& being a good example), only left-hand
26427 side negation of the whole condition is possible.
26429 The arguments of conditions and modifiers are expanded. A forced failure
26430 of an expansion causes a condition to be ignored, that is, it behaves as if the
26431 condition is true. Consider these two statements:
26433 accept senders = ${lookup{$host_name}lsearch\
26434 {/some/file}{$value}fail}
26435 accept senders = ${lookup{$host_name}lsearch\
26436 {/some/file}{$value}{}}
26438 Each attempts to look up a list of acceptable senders. If the lookup succeeds,
26439 the returned list is searched, but if the lookup fails the behaviour is
26440 different in the two cases. The &%fail%& in the first statement causes the
26441 condition to be ignored, leaving no further conditions. The &%accept%& verb
26442 therefore succeeds. The second statement, however, generates an empty list when
26443 the lookup fails. No sender can match an empty list, so the condition fails,
26444 and therefore the &%accept%& also fails.
26446 ACL modifiers appear mixed in with conditions in ACL statements. Some of them
26447 specify actions that are taken as the conditions for a statement are checked;
26448 others specify text for messages that are used when access is denied or a
26449 warning is generated. The &%control%& modifier affects the way an incoming
26450 message is handled.
26452 The positioning of the modifiers in an ACL statement important, because the
26453 processing of a verb ceases as soon as its outcome is known. Only those
26454 modifiers that have already been encountered will take effect. For example,
26455 consider this use of the &%message%& modifier:
26457 require message = Can't verify sender
26459 message = Can't verify recipient
26461 message = This message cannot be used
26463 If sender verification fails, Exim knows that the result of the statement is
26464 &"deny"&, so it goes no further. The first &%message%& modifier has been seen,
26465 so its text is used as the error message. If sender verification succeeds, but
26466 recipient verification fails, the second message is used. If recipient
26467 verification succeeds, the third message becomes &"current"&, but is never used
26468 because there are no more conditions to cause failure.
26470 For the &%deny%& verb, on the other hand, it is always the last &%message%&
26471 modifier that is used, because all the conditions must be true for rejection to
26472 happen. Specifying more than one &%message%& modifier does not make sense, and
26473 the message can even be specified after all the conditions. For example:
26476 !senders = *@my.domain.example
26477 message = Invalid sender from client host
26479 The &"deny"& result does not happen until the end of the statement is reached,
26480 by which time Exim has set up the message.
26484 .section "ACL modifiers" "SECTACLmodi"
26485 .cindex "&ACL;" "modifiers; list of"
26486 The ACL modifiers are as follows:
26489 .vitem &*add_header*&&~=&~<&'text'&>
26490 This modifier specifies one or more header lines that are to be added to an
26491 incoming message, assuming, of course, that the message is ultimately
26492 accepted. For details, see section &<<SECTaddheadacl>>&.
26494 .vitem &*continue*&&~=&~<&'text'&>
26495 .cindex "&%continue%& ACL modifier"
26496 .cindex "database" "updating in ACL"
26497 This modifier does nothing of itself, and processing of the ACL always
26498 continues with the next condition or modifier. The value of &%continue%& is in
26499 the side effects of expanding its argument. Typically this could be used to
26500 update a database. It is really just a syntactic tidiness, to avoid having to
26501 write rather ugly lines like this:
26503 &`condition = ${if eq{0}{`&<&'some expansion'&>&`}{true}{true}}`&
26505 Instead, all you need is
26507 &`continue = `&<&'some expansion'&>
26510 .vitem &*control*&&~=&~<&'text'&>
26511 .cindex "&%control%& ACL modifier"
26512 This modifier affects the subsequent processing of the SMTP connection or of an
26513 incoming message that is accepted. The effect of the first type of control
26514 lasts for the duration of the connection, whereas the effect of the second type
26515 lasts only until the current message has been received. The message-specific
26516 controls always apply to the whole message, not to individual recipients,
26517 even if the &%control%& modifier appears in a RCPT ACL.
26519 As there are now quite a few controls that can be applied, they are described
26520 separately in section &<<SECTcontrols>>&. The &%control%& modifier can be used
26521 in several different ways. For example:
26523 . ==== As this is a nested list, any displays it contains must be indented
26524 . ==== as otherwise they are too far to the left. That comment applies only
26525 . ==== when xmlto and fop are used; formatting with sdop gets it right either
26529 It can be at the end of an &%accept%& statement:
26531 accept ...some conditions
26532 control = queue_only
26534 In this case, the control is applied when this statement yields &"accept"&, in
26535 other words, when the conditions are all true.
26538 It can be in the middle of an &%accept%& statement:
26540 accept ...some conditions...
26541 control = queue_only
26542 ...some more conditions...
26544 If the first set of conditions are true, the control is applied, even if the
26545 statement does not accept because one of the second set of conditions is false.
26546 In this case, some subsequent statement must yield &"accept"& for the control
26550 It can be used with &%warn%& to apply the control, leaving the
26551 decision about accepting or denying to a subsequent verb. For
26554 warn ...some conditions...
26558 This example of &%warn%& does not contain &%message%&, &%log_message%&, or
26559 &%logwrite%&, so it does not add anything to the message and does not write a
26563 If you want to apply a control unconditionally, you can use it with a
26564 &%require%& verb. For example:
26566 require control = no_multiline_responses
26570 .vitem &*delay*&&~=&~<&'time'&>
26571 .cindex "&%delay%& ACL modifier"
26573 This modifier may appear in any ACL. It causes Exim to wait for the time
26574 interval before proceeding. However, when testing Exim using the &%-bh%&
26575 option, the delay is not actually imposed (an appropriate message is output
26576 instead). The time is given in the usual Exim notation, and the delay happens
26577 as soon as the modifier is processed. In an SMTP session, pending output is
26578 flushed before the delay is imposed.
26580 Like &%control%&, &%delay%& can be used with &%accept%& or &%deny%&, for
26583 deny ...some conditions...
26586 The delay happens if all the conditions are true, before the statement returns
26587 &"deny"&. Compare this with:
26590 ...some conditions...
26592 which waits for 30s before processing the conditions. The &%delay%& modifier
26593 can also be used with &%warn%& and together with &%control%&:
26595 warn ...some conditions...
26601 If &%delay%& is encountered when the SMTP PIPELINING extension is in use,
26602 responses to several commands are no longer buffered and sent in one packet (as
26603 they would normally be) because all output is flushed before imposing the
26604 delay. This optimization is disabled so that a number of small delays do not
26605 appear to the client as one large aggregated delay that might provoke an
26606 unwanted timeout. You can, however, disable output flushing for &%delay%& by
26607 using a &%control%& modifier to set &%no_delay_flush%&.
26611 .cindex "&%endpass%& ACL modifier"
26612 This modifier, which has no argument, is recognized only in &%accept%& and
26613 &%discard%& statements. It marks the boundary between the conditions whose
26614 failure causes control to pass to the next statement, and the conditions whose
26615 failure causes the ACL to return &"deny"&. This concept has proved to be
26616 confusing to some people, so the use of &%endpass%& is no longer recommended as
26617 &"best practice"&. See the description of &%accept%& above for more details.
26620 .vitem &*log_message*&&~=&~<&'text'&>
26621 .cindex "&%log_message%& ACL modifier"
26622 This modifier sets up a message that is used as part of the log message if the
26623 ACL denies access or a &%warn%& statement's conditions are true. For example:
26625 require log_message = wrong cipher suite $tls_cipher
26626 encrypted = DES-CBC3-SHA
26628 &%log_message%& is also used when recipients are discarded by &%discard%&. For
26631 &`discard `&<&'some conditions'&>
26632 &` log_message = Discarded $local_part@$domain because...`&
26634 When access is denied, &%log_message%& adds to any underlying error message
26635 that may exist because of a condition failure. For example, while verifying a
26636 recipient address, a &':fail:'& redirection might have already set up a
26639 The message may be defined before the conditions to which it applies, because
26640 the string expansion does not happen until Exim decides that access is to be
26641 denied. This means that any variables that are set by the condition are
26642 available for inclusion in the message. For example, the &$dnslist_$&<&'xxx'&>
26643 variables are set after a DNS black list lookup succeeds. If the expansion of
26644 &%log_message%& fails, or if the result is an empty string, the modifier is
26647 .vindex "&$acl_verify_message$&"
26648 If you want to use a &%warn%& statement to log the result of an address
26649 verification, you can use &$acl_verify_message$& to include the verification
26652 If &%log_message%& is used with a &%warn%& statement, &"Warning:"& is added to
26653 the start of the logged message. If the same warning log message is requested
26654 more than once while receiving a single email message, only one copy is
26655 actually logged. If you want to log multiple copies, use &%logwrite%& instead
26656 of &%log_message%&. In the absence of &%log_message%& and &%logwrite%&, nothing
26657 is logged for a successful &%warn%& statement.
26659 If &%log_message%& is not present and there is no underlying error message (for
26660 example, from the failure of address verification), but &%message%& is present,
26661 the &%message%& text is used for logging rejections. However, if any text for
26662 logging contains newlines, only the first line is logged. In the absence of
26663 both &%log_message%& and &%message%&, a default built-in message is used for
26664 logging rejections.
26667 .vitem "&*log_reject_target*&&~=&~<&'log name list'&>"
26668 .cindex "&%log_reject_target%& ACL modifier"
26669 .cindex "logging in ACL" "specifying which log"
26670 This modifier makes it possible to specify which logs are used for messages
26671 about ACL rejections. Its argument is a colon-separated list of words that can
26672 be &"main"&, &"reject"&, or &"panic"&. The default is &`main:reject`&. The list
26673 may be empty, in which case a rejection is not logged at all. For example, this
26674 ACL fragment writes no logging information when access is denied:
26676 &`deny `&<&'some conditions'&>
26677 &` log_reject_target =`&
26679 This modifier can be used in SMTP and non-SMTP ACLs. It applies to both
26680 permanent and temporary rejections. Its effect lasts for the rest of the
26684 .vitem &*logwrite*&&~=&~<&'text'&>
26685 .cindex "&%logwrite%& ACL modifier"
26686 .cindex "logging in ACL" "immediate"
26687 This modifier writes a message to a log file as soon as it is encountered when
26688 processing an ACL. (Compare &%log_message%&, which, except in the case of
26689 &%warn%& and &%discard%&, is used only if the ACL statement denies
26690 access.) The &%logwrite%& modifier can be used to log special incidents in
26693 &`accept `&<&'some special conditions'&>
26694 &` control = freeze`&
26695 &` logwrite = froze message because ...`&
26697 By default, the message is written to the main log. However, it may begin
26698 with a colon, followed by a comma-separated list of log names, and then
26699 another colon, to specify exactly which logs are to be written. For
26702 logwrite = :main,reject: text for main and reject logs
26703 logwrite = :panic: text for panic log only
26707 .vitem &*message*&&~=&~<&'text'&>
26708 .cindex "&%message%& ACL modifier"
26709 This modifier sets up a text string that is expanded and used as a response
26710 message when an ACL statement terminates the ACL with an &"accept"&, &"deny"&,
26711 or &"defer"& response. (In the case of the &%accept%& and &%discard%& verbs,
26712 there is some complication if &%endpass%& is involved; see the description of
26713 &%accept%& for details.)
26715 The expansion of the message happens at the time Exim decides that the ACL is
26716 to end, not at the time it processes &%message%&. If the expansion fails, or
26717 generates an empty string, the modifier is ignored. Here is an example where
26718 &%message%& must be specified first, because the ACL ends with a rejection if
26719 the &%hosts%& condition fails:
26721 require message = Host not recognized
26724 (Once a condition has failed, no further conditions or modifiers are
26727 .cindex "SMTP" "error codes"
26728 .oindex "&%smtp_banner%&
26729 For ACLs that are triggered by SMTP commands, the message is returned as part
26730 of the SMTP response. The use of &%message%& with &%accept%& (or &%discard%&)
26731 is meaningful only for SMTP, as no message is returned when a non-SMTP message
26732 is accepted. In the case of the connect ACL, accepting with a message modifier
26733 overrides the value of &%smtp_banner%&. For the EHLO/HELO ACL, a customized
26734 accept message may not contain more than one line (otherwise it will be
26735 truncated at the first newline and a panic logged), and it cannot affect the
26738 When SMTP is involved, the message may begin with an overriding response code,
26739 consisting of three digits optionally followed by an &"extended response code"&
26740 of the form &'n.n.n'&, each code being followed by a space. For example:
26742 deny message = 599 1.2.3 Host not welcome
26743 hosts = 192.168.34.0/24
26745 The first digit of the supplied response code must be the same as would be sent
26746 by default. A panic occurs if it is not. Exim uses a 550 code when it denies
26747 access, but for the predata ACL, note that the default success code is 354, not
26750 Notwithstanding the previous paragraph, for the QUIT ACL, unlike the others,
26751 the message modifier cannot override the 221 response code.
26753 The text in a &%message%& modifier is literal; any quotes are taken as
26754 literals, but because the string is expanded, backslash escapes are processed
26755 anyway. If the message contains newlines, this gives rise to a multi-line SMTP
26758 .vindex "&$acl_verify_message$&"
26759 If &%message%& is used on a statement that verifies an address, the message
26760 specified overrides any message that is generated by the verification process.
26761 However, the original message is available in the variable
26762 &$acl_verify_message$&, so you can incorporate it into your message if you
26763 wish. In particular, if you want the text from &%:fail:%& items in &(redirect)&
26764 routers to be passed back as part of the SMTP response, you should either not
26765 use a &%message%& modifier, or make use of &$acl_verify_message$&.
26767 For compatibility with previous releases of Exim, a &%message%& modifier that
26768 is used with a &%warn%& verb behaves in a similar way to the &%add_header%&
26769 modifier, but this usage is now deprecated. However, &%message%& acts only when
26770 all the conditions are true, wherever it appears in an ACL command, whereas
26771 &%add_header%& acts as soon as it is encountered. If &%message%& is used with
26772 &%warn%& in an ACL that is not concerned with receiving a message, it has no
26776 .vitem &*set*&&~<&'acl_name'&>&~=&~<&'value'&>
26777 .cindex "&%set%& ACL modifier"
26778 This modifier puts a value into one of the ACL variables (see section
26779 &<<SECTaclvariables>>&).
26786 .section "Use of the control modifier" "SECTcontrols"
26787 .cindex "&%control%& ACL modifier"
26788 The &%control%& modifier supports the following settings:
26791 .vitem &*control&~=&~allow_auth_unadvertised*&
26792 This modifier allows a client host to use the SMTP AUTH command even when it
26793 has not been advertised in response to EHLO. Furthermore, because there are
26794 apparently some really broken clients that do this, Exim will accept AUTH after
26795 HELO (rather than EHLO) when this control is set. It should be used only if you
26796 really need it, and you should limit its use to those broken clients that do
26797 not work without it. For example:
26799 warn hosts = 192.168.34.25
26800 control = allow_auth_unadvertised
26802 Normally, when an Exim server receives an AUTH command, it checks the name of
26803 the authentication mechanism that is given in the command to ensure that it
26804 matches an advertised mechanism. When this control is set, the check that a
26805 mechanism has been advertised is bypassed. Any configured mechanism can be used
26806 by the client. This control is permitted only in the connection and HELO ACLs.
26809 .vitem &*control&~=&~caseful_local_part*& &&&
26810 &*control&~=&~caselower_local_part*&
26811 .cindex "&ACL;" "case of local part in"
26812 .cindex "case of local parts"
26813 .vindex "&$local_part$&"
26814 These two controls are permitted only in the ACL specified by &%acl_smtp_rcpt%&
26815 (that is, during RCPT processing). By default, the contents of &$local_part$&
26816 are lower cased before ACL processing. If &"caseful_local_part"& is specified,
26817 any uppercase letters in the original local part are restored in &$local_part$&
26818 for the rest of the ACL, or until a control that sets &"caselower_local_part"&
26821 These controls affect only the current recipient. Moreover, they apply only to
26822 local part handling that takes place directly in the ACL (for example, as a key
26823 in lookups). If a test to verify the recipient is obeyed, the case-related
26824 handling of the local part during the verification is controlled by the router
26825 configuration (see the &%caseful_local_part%& generic router option).
26827 This facility could be used, for example, to add a spam score to local parts
26828 containing upper case letters. For example, using &$acl_m4$& to accumulate the
26831 warn control = caseful_local_part
26832 set acl_m4 = ${eval:\
26834 ${if match{$local_part}{[A-Z]}{1}{0}}\
26836 control = caselower_local_part
26838 Notice that we put back the lower cased version afterwards, assuming that
26839 is what is wanted for subsequent tests.
26843 .vitem &*control&~=&~dscp/*&<&'value'&>
26844 .cindex "&ACL;" "setting DSCP value"
26845 .cindex "DSCP" "inbound"
26846 This option causes the DSCP value associated with the socket for the inbound
26847 connection to be adjusted to a given value, given as one of a number of fixed
26848 strings or to numeric value.
26849 The &%-bI:dscp%& option may be used to ask Exim which names it knows of.
26850 Common values include &`throughput`&, &`mincost`&, and on newer systems
26851 &`ef`&, &`af41`&, etc. Numeric values may be in the range 0 to 0x3F.
26853 The outbound packets from Exim will be marked with this value in the header
26854 (for IPv4, the TOS field; for IPv6, the TCLASS field); there is no guarantee
26855 that these values will have any effect, not be stripped by networking
26856 equipment, or do much of anything without cooperation with your Network
26857 Engineer and those of all network operators between the source and destination.
26861 .vitem &*control&~=&~debug/*&<&'options'&>
26862 .cindex "&ACL;" "enabling debug logging"
26863 .cindex "debugging" "enabling from an ACL"
26864 This control turns on debug logging, almost as though Exim had been invoked
26865 with &`-d`&, with the output going to a new logfile, by default called
26866 &'debuglog'&. The filename can be adjusted with the &'tag'& option, which
26867 may access any variables already defined. The logging may be adjusted with
26868 the &'opts'& option, which takes the same values as the &`-d`& command-line
26869 option. Some examples (which depend on variables that don't exist in all
26873 control = debug/tag=.$sender_host_address
26874 control = debug/opts=+expand+acl
26875 control = debug/tag=.$message_exim_id/opts=+expand
26879 .vitem &*control&~=&~enforce_sync*& &&&
26880 &*control&~=&~no_enforce_sync*&
26881 .cindex "SMTP" "synchronization checking"
26882 .cindex "synchronization checking in SMTP"
26883 These controls make it possible to be selective about when SMTP synchronization
26884 is enforced. The global option &%smtp_enforce_sync%& specifies the initial
26885 state of the switch (it is true by default). See the description of this option
26886 in chapter &<<CHAPmainconfig>>& for details of SMTP synchronization checking.
26888 The effect of these two controls lasts for the remainder of the SMTP
26889 connection. They can appear in any ACL except the one for the non-SMTP
26890 messages. The most straightforward place to put them is in the ACL defined by
26891 &%acl_smtp_connect%&, which is run at the start of an incoming SMTP connection,
26892 before the first synchronization check. The expected use is to turn off the
26893 synchronization checks for badly-behaved hosts that you nevertheless need to
26897 .vitem &*control&~=&~fakedefer/*&<&'message'&>
26898 .cindex "fake defer"
26899 .cindex "defer, fake"
26900 This control works in exactly the same way as &%fakereject%& (described below)
26901 except that it causes an SMTP 450 response after the message data instead of a
26902 550 response. You must take care when using &%fakedefer%& because it causes the
26903 messages to be duplicated when the sender retries. Therefore, you should not
26904 use &%fakedefer%& if the message is to be delivered normally.
26906 .vitem &*control&~=&~fakereject/*&<&'message'&>
26907 .cindex "fake rejection"
26908 .cindex "rejection, fake"
26909 This control is permitted only for the MAIL, RCPT, and DATA ACLs, in other
26910 words, only when an SMTP message is being received. If Exim accepts the
26911 message, instead the final 250 response, a 550 rejection message is sent.
26912 However, Exim proceeds to deliver the message as normal. The control applies
26913 only to the current message, not to any subsequent ones that may be received in
26914 the same SMTP connection.
26916 The text for the 550 response is taken from the &%control%& modifier. If no
26917 message is supplied, the following is used:
26919 550-Your message has been rejected but is being
26920 550-kept for evaluation.
26921 550-If it was a legitimate message, it may still be
26922 550 delivered to the target recipient(s).
26924 This facility should be used with extreme caution.
26926 .vitem &*control&~=&~freeze*&
26927 .cindex "frozen messages" "forcing in ACL"
26928 This control is permitted only for the MAIL, RCPT, DATA, and non-SMTP ACLs, in
26929 other words, only when a message is being received. If the message is accepted,
26930 it is placed on Exim's queue and frozen. The control applies only to the
26931 current message, not to any subsequent ones that may be received in the same
26934 This modifier can optionally be followed by &`/no_tell`&. If the global option
26935 &%freeze_tell%& is set, it is ignored for the current message (that is, nobody
26936 is told about the freezing), provided all the &*control=freeze*& modifiers that
26937 are obeyed for the current message have the &`/no_tell`& option.
26939 .vitem &*control&~=&~no_delay_flush*&
26940 .cindex "SMTP" "output flushing, disabling for delay"
26941 Exim normally flushes SMTP output before implementing a delay in an ACL, to
26942 avoid unexpected timeouts in clients when the SMTP PIPELINING extension is in
26943 use. This control, as long as it is encountered before the &%delay%& modifier,
26944 disables such output flushing.
26946 .vitem &*control&~=&~no_callout_flush*&
26947 .cindex "SMTP" "output flushing, disabling for callout"
26948 Exim normally flushes SMTP output before performing a callout in an ACL, to
26949 avoid unexpected timeouts in clients when the SMTP PIPELINING extension is in
26950 use. This control, as long as it is encountered before the &%verify%& condition
26951 that causes the callout, disables such output flushing.
26953 .vitem &*control&~=&~no_mbox_unspool*&
26954 This control is available when Exim is compiled with the content scanning
26955 extension. Content scanning may require a copy of the current message, or parts
26956 of it, to be written in &"mbox format"& to a spool file, for passing to a virus
26957 or spam scanner. Normally, such copies are deleted when they are no longer
26958 needed. If this control is set, the copies are not deleted. The control applies
26959 only to the current message, not to any subsequent ones that may be received in
26960 the same SMTP connection. It is provided for debugging purposes and is unlikely
26961 to be useful in production.
26963 .vitem &*control&~=&~no_multiline_responses*&
26964 .cindex "multiline responses, suppressing"
26965 This control is permitted for any ACL except the one for non-SMTP messages.
26966 It seems that there are broken clients in use that cannot handle multiline
26967 SMTP responses, despite the fact that RFC 821 defined them over 20 years ago.
26969 If this control is set, multiline SMTP responses from ACL rejections are
26970 suppressed. One way of doing this would have been to put out these responses as
26971 one long line. However, RFC 2821 specifies a maximum of 512 bytes per response
26972 (&"use multiline responses for more"& it says &-- ha!), and some of the
26973 responses might get close to that. So this facility, which is after all only a
26974 sop to broken clients, is implemented by doing two very easy things:
26977 Extra information that is normally output as part of a rejection caused by
26978 sender verification failure is omitted. Only the final line (typically &"sender
26979 verification failed"&) is sent.
26981 If a &%message%& modifier supplies a multiline response, only the first
26985 The setting of the switch can, of course, be made conditional on the
26986 calling host. Its effect lasts until the end of the SMTP connection.
26988 .vitem &*control&~=&~no_pipelining*&
26989 .cindex "PIPELINING" "suppressing advertising"
26990 This control turns off the advertising of the PIPELINING extension to SMTP in
26991 the current session. To be useful, it must be obeyed before Exim sends its
26992 response to an EHLO command. Therefore, it should normally appear in an ACL
26993 controlled by &%acl_smtp_connect%& or &%acl_smtp_helo%&. See also
26994 &%pipelining_advertise_hosts%&.
26996 .vitem &*control&~=&~queue_only*&
26997 .oindex "&%queue_only%&"
26998 .cindex "queueing incoming messages"
26999 This control is permitted only for the MAIL, RCPT, DATA, and non-SMTP ACLs, in
27000 other words, only when a message is being received. If the message is accepted,
27001 it is placed on Exim's queue and left there for delivery by a subsequent queue
27002 runner. No immediate delivery process is started. In other words, it has the
27003 effect as the &%queue_only%& global option. However, the control applies only
27004 to the current message, not to any subsequent ones that may be received in the
27005 same SMTP connection.
27007 .vitem &*control&~=&~submission/*&<&'options'&>
27008 .cindex "message" "submission"
27009 .cindex "submission mode"
27010 This control is permitted only for the MAIL, RCPT, and start of data ACLs (the
27011 latter is the one defined by &%acl_smtp_predata%&). Setting it tells Exim that
27012 the current message is a submission from a local MUA. In this case, Exim
27013 operates in &"submission mode"&, and applies certain fixups to the message if
27014 necessary. For example, it adds a &'Date:'& header line if one is not present.
27015 This control is not permitted in the &%acl_smtp_data%& ACL, because that is too
27016 late (the message has already been created).
27018 Chapter &<<CHAPmsgproc>>& describes the processing that Exim applies to
27019 messages. Section &<<SECTsubmodnon>>& covers the processing that happens in
27020 submission mode; the available options for this control are described there.
27021 The control applies only to the current message, not to any subsequent ones
27022 that may be received in the same SMTP connection.
27024 .vitem &*control&~=&~suppress_local_fixups*&
27025 .cindex "submission fixups, suppressing"
27026 This control applies to locally submitted (non TCP/IP) messages, and is the
27027 complement of &`control = submission`&. It disables the fixups that are
27028 normally applied to locally-submitted messages. Specifically:
27031 Any &'Sender:'& header line is left alone (in this respect, it is a
27032 dynamic version of &%local_sender_retain%&).
27034 No &'Message-ID:'&, &'From:'&, or &'Date:'& header lines are added.
27036 There is no check that &'From:'& corresponds to the actual sender.
27039 This control may be useful when a remotely-originated message is accepted,
27040 passed to some scanning program, and then re-submitted for delivery. It can be
27041 used only in the &%acl_smtp_mail%&, &%acl_smtp_rcpt%&, &%acl_smtp_predata%&,
27042 and &%acl_not_smtp_start%& ACLs, because it has to be set before the message's
27045 &*Note:*& This control applies only to the current message, not to any others
27046 that are being submitted at the same time using &%-bs%& or &%-bS%&.
27050 .section "Summary of message fixup control" "SECTsummesfix"
27051 All four possibilities for message fixups can be specified:
27054 Locally submitted, fixups applied: the default.
27056 Locally submitted, no fixups applied: use
27057 &`control = suppress_local_fixups`&.
27059 Remotely submitted, no fixups applied: the default.
27061 Remotely submitted, fixups applied: use &`control = submission`&.
27066 .section "Adding header lines in ACLs" "SECTaddheadacl"
27067 .cindex "header lines" "adding in an ACL"
27068 .cindex "header lines" "position of added lines"
27069 .cindex "&%message%& ACL modifier"
27070 The &%add_header%& modifier can be used to add one or more extra header lines
27071 to an incoming message, as in this example:
27073 warn dnslists = sbl.spamhaus.org : \
27074 dialup.mail-abuse.org
27075 add_header = X-blacklisted-at: $dnslist_domain
27077 The &%add_header%& modifier is permitted in the MAIL, RCPT, PREDATA, DATA,
27078 MIME, and non-SMTP ACLs (in other words, those that are concerned with
27079 receiving a message). The message must ultimately be accepted for
27080 &%add_header%& to have any significant effect. You can use &%add_header%& with
27081 any ACL verb, including &%deny%& (though this is potentially useful only in a
27084 If the data for the &%add_header%& modifier contains one or more newlines that
27085 are not followed by a space or a tab, it is assumed to contain multiple header
27086 lines. Each one is checked for valid syntax; &`X-ACL-Warn:`& is added to the
27087 front of any line that is not a valid header line.
27089 Added header lines are accumulated during the MAIL, RCPT, and predata ACLs.
27090 They are added to the message before processing the DATA and MIME ACLs.
27091 However, if an identical header line is requested more than once, only one copy
27092 is actually added to the message. Further header lines may be accumulated
27093 during the DATA and MIME ACLs, after which they are added to the message, again
27094 with duplicates suppressed. Thus, it is possible to add two identical header
27095 lines to an SMTP message, but only if one is added before DATA and one after.
27096 In the case of non-SMTP messages, new headers are accumulated during the
27097 non-SMTP ACLs, and are added to the message after all the ACLs have run. If a
27098 message is rejected after DATA or by the non-SMTP ACL, all added header lines
27099 are included in the entry that is written to the reject log.
27101 .cindex "header lines" "added; visibility of"
27102 Header lines are not visible in string expansions until they are added to the
27103 message. It follows that header lines defined in the MAIL, RCPT, and predata
27104 ACLs are not visible until the DATA ACL and MIME ACLs are run. Similarly,
27105 header lines that are added by the DATA or MIME ACLs are not visible in those
27106 ACLs. Because of this restriction, you cannot use header lines as a way of
27107 passing data between (for example) the MAIL and RCPT ACLs. If you want to do
27108 this, you can use ACL variables, as described in section
27109 &<<SECTaclvariables>>&.
27111 The &%add_header%& modifier acts immediately it is encountered during the
27112 processing of an ACL. Notice the difference between these two cases:
27114 &`accept add_header = ADDED: some text`&
27115 &` `&<&'some condition'&>
27117 &`accept `&<&'some condition'&>
27118 &` add_header = ADDED: some text`&
27120 In the first case, the header line is always added, whether or not the
27121 condition is true. In the second case, the header line is added only if the
27122 condition is true. Multiple occurrences of &%add_header%& may occur in the same
27123 ACL statement. All those that are encountered before a condition fails are
27126 .cindex "&%warn%& ACL verb"
27127 For compatibility with previous versions of Exim, a &%message%& modifier for a
27128 &%warn%& verb acts in the same way as &%add_header%&, except that it takes
27129 effect only if all the conditions are true, even if it appears before some of
27130 them. Furthermore, only the last occurrence of &%message%& is honoured. This
27131 usage of &%message%& is now deprecated. If both &%add_header%& and &%message%&
27132 are present on a &%warn%& verb, both are processed according to their
27135 By default, new header lines are added to a message at the end of the existing
27136 header lines. However, you can specify that any particular header line should
27137 be added right at the start (before all the &'Received:'& lines), immediately
27138 after the first block of &'Received:'& lines, or immediately before any line
27139 that is not a &'Received:'& or &'Resent-something:'& header.
27141 This is done by specifying &":at_start:"&, &":after_received:"&, or
27142 &":at_start_rfc:"& (or, for completeness, &":at_end:"&) before the text of the
27143 header line, respectively. (Header text cannot start with a colon, as there has
27144 to be a header name first.) For example:
27146 warn add_header = \
27147 :after_received:X-My-Header: something or other...
27149 If more than one header line is supplied in a single &%add_header%& modifier,
27150 each one is treated independently and can therefore be placed differently. If
27151 you add more than one line at the start, or after the Received: block, they end
27152 up in reverse order.
27154 &*Warning*&: This facility currently applies only to header lines that are
27155 added in an ACL. It does NOT work for header lines that are added in a
27156 system filter or in a router or transport.
27161 .section "ACL conditions" "SECTaclconditions"
27162 .cindex "&ACL;" "conditions; list of"
27163 Some of conditions listed in this section are available only when Exim is
27164 compiled with the content-scanning extension. They are included here briefly
27165 for completeness. More detailed descriptions can be found in the discussion on
27166 content scanning in chapter &<<CHAPexiscan>>&.
27168 Not all conditions are relevant in all circumstances. For example, testing
27169 senders and recipients does not make sense in an ACL that is being run as the
27170 result of the arrival of an ETRN command, and checks on message headers can be
27171 done only in the ACLs specified by &%acl_smtp_data%& and &%acl_not_smtp%&. You
27172 can use the same condition (with different parameters) more than once in the
27173 same ACL statement. This provides a way of specifying an &"and"& conjunction.
27174 The conditions are as follows:
27178 .vitem &*acl&~=&~*&<&'name&~of&~acl&~or&~ACL&~string&~or&~file&~name&~'&>
27179 .cindex "&ACL;" "nested"
27180 .cindex "&ACL;" "indirect"
27181 .cindex "&%acl%& ACL condition"
27182 The possible values of the argument are the same as for the
27183 &%acl_smtp_%&&'xxx'& options. The named or inline ACL is run. If it returns
27184 &"accept"& the condition is true; if it returns &"deny"& the condition is
27185 false. If it returns &"defer"&, the current ACL returns &"defer"& unless the
27186 condition is on a &%warn%& verb. In that case, a &"defer"& return makes the
27187 condition false. This means that further processing of the &%warn%& verb
27188 ceases, but processing of the ACL continues.
27190 If the nested &%acl%& returns &"drop"& and the outer condition denies access,
27191 the connection is dropped. If it returns &"discard"&, the verb must be
27192 &%accept%& or &%discard%&, and the action is taken immediately &-- no further
27193 conditions are tested.
27195 ACLs may be nested up to 20 deep; the limit exists purely to catch runaway
27196 loops. This condition allows you to use different ACLs in different
27197 circumstances. For example, different ACLs can be used to handle RCPT commands
27198 for different local users or different local domains.
27200 .vitem &*authenticated&~=&~*&<&'string&~list'&>
27201 .cindex "&%authenticated%& ACL condition"
27202 .cindex "authentication" "ACL checking"
27203 .cindex "&ACL;" "testing for authentication"
27204 If the SMTP connection is not authenticated, the condition is false. Otherwise,
27205 the name of the authenticator is tested against the list. To test for
27206 authentication by any authenticator, you can set
27211 .vitem &*condition&~=&~*&<&'string'&>
27212 .cindex "&%condition%& ACL condition"
27213 .cindex "customizing" "ACL condition"
27214 .cindex "&ACL;" "customized test"
27215 .cindex "&ACL;" "testing, customized"
27216 This feature allows you to make up custom conditions. If the result of
27217 expanding the string is an empty string, the number zero, or one of the strings
27218 &"no"& or &"false"&, the condition is false. If the result is any non-zero
27219 number, or one of the strings &"yes"& or &"true"&, the condition is true. For
27220 any other value, some error is assumed to have occurred, and the ACL returns
27221 &"defer"&. However, if the expansion is forced to fail, the condition is
27222 ignored. The effect is to treat it as true, whether it is positive or
27225 .vitem &*decode&~=&~*&<&'location'&>
27226 .cindex "&%decode%& ACL condition"
27227 This condition is available only when Exim is compiled with the
27228 content-scanning extension, and it is allowed only in the ACL defined by
27229 &%acl_smtp_mime%&. It causes the current MIME part to be decoded into a file.
27230 If all goes well, the condition is true. It is false only if there are
27231 problems such as a syntax error or a memory shortage. For more details, see
27232 chapter &<<CHAPexiscan>>&.
27234 .vitem &*demime&~=&~*&<&'extension&~list'&>
27235 .cindex "&%demime%& ACL condition"
27236 This condition is available only when Exim is compiled with the
27237 content-scanning extension. Its use is described in section
27238 &<<SECTdemimecond>>&.
27240 .vitem &*dnslists&~=&~*&<&'list&~of&~domain&~names&~and&~other&~data'&>
27241 .cindex "&%dnslists%& ACL condition"
27242 .cindex "DNS list" "in ACL"
27243 .cindex "black list (DNS)"
27244 .cindex "&ACL;" "testing a DNS list"
27245 This condition checks for entries in DNS black lists. These are also known as
27246 &"RBL lists"&, after the original Realtime Blackhole List, but note that the
27247 use of the lists at &'mail-abuse.org'& now carries a charge. There are too many
27248 different variants of this condition to describe briefly here. See sections
27249 &<<SECTmorednslists>>&&--&<<SECTmorednslistslast>>& for details.
27251 .vitem &*domains&~=&~*&<&'domain&~list'&>
27252 .cindex "&%domains%& ACL condition"
27253 .cindex "domain" "ACL checking"
27254 .cindex "&ACL;" "testing a recipient domain"
27255 .vindex "&$domain_data$&"
27256 This condition is relevant only after a RCPT command. It checks that the domain
27257 of the recipient address is in the domain list. If percent-hack processing is
27258 enabled, it is done before this test is done. If the check succeeds with a
27259 lookup, the result of the lookup is placed in &$domain_data$& until the next
27262 &*Note carefully*& (because many people seem to fall foul of this): you cannot
27263 use &%domains%& in a DATA ACL.
27266 .vitem &*encrypted&~=&~*&<&'string&~list'&>
27267 .cindex "&%encrypted%& ACL condition"
27268 .cindex "encryption" "checking in an ACL"
27269 .cindex "&ACL;" "testing for encryption"
27270 If the SMTP connection is not encrypted, the condition is false. Otherwise, the
27271 name of the cipher suite in use is tested against the list. To test for
27272 encryption without testing for any specific cipher suite(s), set
27278 .vitem &*hosts&~=&~*&<&'&~host&~list'&>
27279 .cindex "&%hosts%& ACL condition"
27280 .cindex "host" "ACL checking"
27281 .cindex "&ACL;" "testing the client host"
27282 This condition tests that the calling host matches the host list. If you have
27283 name lookups or wildcarded host names and IP addresses in the same host list,
27284 you should normally put the IP addresses first. For example, you could have:
27286 accept hosts = 10.9.8.7 : dbm;/etc/friendly/hosts
27288 The lookup in this example uses the host name for its key. This is implied by
27289 the lookup type &"dbm"&. (For a host address lookup you would use &"net-dbm"&
27290 and it wouldn't matter which way round you had these two items.)
27292 The reason for the problem with host names lies in the left-to-right way that
27293 Exim processes lists. It can test IP addresses without doing any DNS lookups,
27294 but when it reaches an item that requires a host name, it fails if it cannot
27295 find a host name to compare with the pattern. If the above list is given in the
27296 opposite order, the &%accept%& statement fails for a host whose name cannot be
27297 found, even if its IP address is 10.9.8.7.
27299 If you really do want to do the name check first, and still recognize the IP
27300 address even if the name lookup fails, you can rewrite the ACL like this:
27302 accept hosts = dbm;/etc/friendly/hosts
27303 accept hosts = 10.9.8.7
27305 The default action on failing to find the host name is to assume that the host
27306 is not in the list, so the first &%accept%& statement fails. The second
27307 statement can then check the IP address.
27309 .vindex "&$host_data$&"
27310 If a &%hosts%& condition is satisfied by means of a lookup, the result
27311 of the lookup is made available in the &$host_data$& variable. This
27312 allows you, for example, to set up a statement like this:
27314 deny hosts = net-lsearch;/some/file
27315 message = $host_data
27317 which gives a custom error message for each denied host.
27319 .vitem &*local_parts&~=&~*&<&'local&~part&~list'&>
27320 .cindex "&%local_parts%& ACL condition"
27321 .cindex "local part" "ACL checking"
27322 .cindex "&ACL;" "testing a local part"
27323 .vindex "&$local_part_data$&"
27324 This condition is relevant only after a RCPT command. It checks that the local
27325 part of the recipient address is in the list. If percent-hack processing is
27326 enabled, it is done before this test. If the check succeeds with a lookup, the
27327 result of the lookup is placed in &$local_part_data$&, which remains set until
27328 the next &%local_parts%& test.
27330 .vitem &*malware&~=&~*&<&'option'&>
27331 .cindex "&%malware%& ACL condition"
27332 .cindex "&ACL;" "virus scanning"
27333 .cindex "&ACL;" "scanning for viruses"
27334 This condition is available only when Exim is compiled with the
27335 content-scanning extension. It causes the incoming message to be scanned for
27336 viruses. For details, see chapter &<<CHAPexiscan>>&.
27338 .vitem &*mime_regex&~=&~*&<&'list&~of&~regular&~expressions'&>
27339 .cindex "&%mime_regex%& ACL condition"
27340 .cindex "&ACL;" "testing by regex matching"
27341 This condition is available only when Exim is compiled with the
27342 content-scanning extension, and it is allowed only in the ACL defined by
27343 &%acl_smtp_mime%&. It causes the current MIME part to be scanned for a match
27344 with any of the regular expressions. For details, see chapter
27347 .vitem &*ratelimit&~=&~*&<&'parameters'&>
27348 .cindex "rate limiting"
27349 This condition can be used to limit the rate at which a user or host submits
27350 messages. Details are given in section &<<SECTratelimiting>>&.
27352 .vitem &*recipients&~=&~*&<&'address&~list'&>
27353 .cindex "&%recipients%& ACL condition"
27354 .cindex "recipient" "ACL checking"
27355 .cindex "&ACL;" "testing a recipient"
27356 This condition is relevant only after a RCPT command. It checks the entire
27357 recipient address against a list of recipients.
27359 .vitem &*regex&~=&~*&<&'list&~of&~regular&~expressions'&>
27360 .cindex "&%regex%& ACL condition"
27361 .cindex "&ACL;" "testing by regex matching"
27362 This condition is available only when Exim is compiled with the
27363 content-scanning extension, and is available only in the DATA, MIME, and
27364 non-SMTP ACLs. It causes the incoming message to be scanned for a match with
27365 any of the regular expressions. For details, see chapter &<<CHAPexiscan>>&.
27367 .vitem &*sender_domains&~=&~*&<&'domain&~list'&>
27368 .cindex "&%sender_domains%& ACL condition"
27369 .cindex "sender" "ACL checking"
27370 .cindex "&ACL;" "testing a sender domain"
27371 .vindex "&$domain$&"
27372 .vindex "&$sender_address_domain$&"
27373 This condition tests the domain of the sender of the message against the given
27374 domain list. &*Note*&: The domain of the sender address is in
27375 &$sender_address_domain$&. It is &'not'& put in &$domain$& during the testing
27376 of this condition. This is an exception to the general rule for testing domain
27377 lists. It is done this way so that, if this condition is used in an ACL for a
27378 RCPT command, the recipient's domain (which is in &$domain$&) can be used to
27379 influence the sender checking.
27381 &*Warning*&: It is a bad idea to use this condition on its own as a control on
27382 relaying, because sender addresses are easily, and commonly, forged.
27384 .vitem &*senders&~=&~*&<&'address&~list'&>
27385 .cindex "&%senders%& ACL condition"
27386 .cindex "sender" "ACL checking"
27387 .cindex "&ACL;" "testing a sender"
27388 This condition tests the sender of the message against the given list. To test
27389 for a bounce message, which has an empty sender, set
27393 &*Warning*&: It is a bad idea to use this condition on its own as a control on
27394 relaying, because sender addresses are easily, and commonly, forged.
27396 .vitem &*spam&~=&~*&<&'username'&>
27397 .cindex "&%spam%& ACL condition"
27398 .cindex "&ACL;" "scanning for spam"
27399 This condition is available only when Exim is compiled with the
27400 content-scanning extension. It causes the incoming message to be scanned by
27401 SpamAssassin. For details, see chapter &<<CHAPexiscan>>&.
27403 .vitem &*verify&~=&~certificate*&
27404 .cindex "&%verify%& ACL condition"
27405 .cindex "TLS" "client certificate verification"
27406 .cindex "certificate" "verification of client"
27407 .cindex "&ACL;" "certificate verification"
27408 .cindex "&ACL;" "testing a TLS certificate"
27409 This condition is true in an SMTP session if the session is encrypted, and a
27410 certificate was received from the client, and the certificate was verified. The
27411 server requests a certificate only if the client matches &%tls_verify_hosts%&
27412 or &%tls_try_verify_hosts%& (see chapter &<<CHAPTLS>>&).
27414 .vitem &*verify&~=&~csa*&
27415 .cindex "CSA verification"
27416 This condition checks whether the sending host (the client) is authorized to
27417 send email. Details of how this works are given in section
27418 &<<SECTverifyCSA>>&.
27420 .vitem &*verify&~=&~header_sender/*&<&'options'&>
27421 .cindex "&%verify%& ACL condition"
27422 .cindex "&ACL;" "verifying sender in the header"
27423 .cindex "header lines" "verifying the sender in"
27424 .cindex "sender" "verifying in header"
27425 .cindex "verifying" "sender in header"
27426 This condition is relevant only in an ACL that is run after a message has been
27427 received, that is, in an ACL specified by &%acl_smtp_data%& or
27428 &%acl_not_smtp%&. It checks that there is a verifiable address in at least one
27429 of the &'Sender:'&, &'Reply-To:'&, or &'From:'& header lines. Such an address
27430 is loosely thought of as a &"sender"& address (hence the name of the test).
27431 However, an address that appears in one of these headers need not be an address
27432 that accepts bounce messages; only sender addresses in envelopes are required
27433 to accept bounces. Therefore, if you use the callout option on this check, you
27434 might want to arrange for a non-empty address in the MAIL command.
27436 Details of address verification and the options are given later, starting at
27437 section &<<SECTaddressverification>>& (callouts are described in section
27438 &<<SECTcallver>>&). You can combine this condition with the &%senders%&
27439 condition to restrict it to bounce messages only:
27442 message = A valid sender header is required for bounces
27443 !verify = header_sender
27446 .vitem &*verify&~=&~header_syntax*&
27447 .cindex "&%verify%& ACL condition"
27448 .cindex "&ACL;" "verifying header syntax"
27449 .cindex "header lines" "verifying syntax"
27450 .cindex "verifying" "header syntax"
27451 This condition is relevant only in an ACL that is run after a message has been
27452 received, that is, in an ACL specified by &%acl_smtp_data%& or
27453 &%acl_not_smtp%&. It checks the syntax of all header lines that can contain
27454 lists of addresses (&'Sender:'&, &'From:'&, &'Reply-To:'&, &'To:'&, &'Cc:'&,
27455 and &'Bcc:'&). Unqualified addresses (local parts without domains) are
27456 permitted only in locally generated messages and from hosts that match
27457 &%sender_unqualified_hosts%& or &%recipient_unqualified_hosts%&, as
27460 Note that this condition is a syntax check only. However, a common spamming
27461 ploy used to be to send syntactically invalid headers such as
27465 and this condition can be used to reject such messages, though they are not as
27466 common as they used to be.
27468 .vitem &*verify&~=&~helo*&
27469 .cindex "&%verify%& ACL condition"
27470 .cindex "&ACL;" "verifying HELO/EHLO"
27471 .cindex "HELO" "verifying"
27472 .cindex "EHLO" "verifying"
27473 .cindex "verifying" "EHLO"
27474 .cindex "verifying" "HELO"
27475 This condition is true if a HELO or EHLO command has been received from the
27476 client host, and its contents have been verified. If there has been no previous
27477 attempt to verify the HELO/EHLO contents, it is carried out when this
27478 condition is encountered. See the description of the &%helo_verify_hosts%& and
27479 &%helo_try_verify_hosts%& options for details of how to request verification
27480 independently of this condition.
27482 For SMTP input that does not come over TCP/IP (the &%-bs%& command line
27483 option), this condition is always true.
27486 .vitem &*verify&~=&~not_blind*&
27487 .cindex "verifying" "not blind"
27488 .cindex "bcc recipients, verifying none"
27489 This condition checks that there are no blind (bcc) recipients in the message.
27490 Every envelope recipient must appear either in a &'To:'& header line or in a
27491 &'Cc:'& header line for this condition to be true. Local parts are checked
27492 case-sensitively; domains are checked case-insensitively. If &'Resent-To:'& or
27493 &'Resent-Cc:'& header lines exist, they are also checked. This condition can be
27494 used only in a DATA or non-SMTP ACL.
27496 There are, of course, many legitimate messages that make use of blind (bcc)
27497 recipients. This check should not be used on its own for blocking messages.
27500 .vitem &*verify&~=&~recipient/*&<&'options'&>
27501 .cindex "&%verify%& ACL condition"
27502 .cindex "&ACL;" "verifying recipient"
27503 .cindex "recipient" "verifying"
27504 .cindex "verifying" "recipient"
27505 .vindex "&$address_data$&"
27506 This condition is relevant only after a RCPT command. It verifies the current
27507 recipient. Details of address verification are given later, starting at section
27508 &<<SECTaddressverification>>&. After a recipient has been verified, the value
27509 of &$address_data$& is the last value that was set while routing the address.
27510 This applies even if the verification fails. When an address that is being
27511 verified is redirected to a single address, verification continues with the new
27512 address, and in that case, the subsequent value of &$address_data$& is the
27513 value for the child address.
27515 .vitem &*verify&~=&~reverse_host_lookup*&
27516 .cindex "&%verify%& ACL condition"
27517 .cindex "&ACL;" "verifying host reverse lookup"
27518 .cindex "host" "verifying reverse lookup"
27519 This condition ensures that a verified host name has been looked up from the IP
27520 address of the client host. (This may have happened already if the host name
27521 was needed for checking a host list, or if the host matched &%host_lookup%&.)
27522 Verification ensures that the host name obtained from a reverse DNS lookup, or
27523 one of its aliases, does, when it is itself looked up in the DNS, yield the
27524 original IP address.
27526 If this condition is used for a locally generated message (that is, when there
27527 is no client host involved), it always succeeds.
27529 .vitem &*verify&~=&~sender/*&<&'options'&>
27530 .cindex "&%verify%& ACL condition"
27531 .cindex "&ACL;" "verifying sender"
27532 .cindex "sender" "verifying"
27533 .cindex "verifying" "sender"
27534 This condition is relevant only after a MAIL or RCPT command, or after a
27535 message has been received (the &%acl_smtp_data%& or &%acl_not_smtp%& ACLs). If
27536 the message's sender is empty (that is, this is a bounce message), the
27537 condition is true. Otherwise, the sender address is verified.
27539 .vindex "&$address_data$&"
27540 .vindex "&$sender_address_data$&"
27541 If there is data in the &$address_data$& variable at the end of routing, its
27542 value is placed in &$sender_address_data$& at the end of verification. This
27543 value can be used in subsequent conditions and modifiers in the same ACL
27544 statement. It does not persist after the end of the current statement. If you
27545 want to preserve the value for longer, you can save it in an ACL variable.
27547 Details of verification are given later, starting at section
27548 &<<SECTaddressverification>>&. Exim caches the result of sender verification,
27549 to avoid doing it more than once per message.
27551 .vitem &*verify&~=&~sender=*&<&'address'&>&*/*&<&'options'&>
27552 .cindex "&%verify%& ACL condition"
27553 This is a variation of the previous option, in which a modified address is
27554 verified as a sender.
27559 .section "Using DNS lists" "SECTmorednslists"
27560 .cindex "DNS list" "in ACL"
27561 .cindex "black list (DNS)"
27562 .cindex "&ACL;" "testing a DNS list"
27563 In its simplest form, the &%dnslists%& condition tests whether the calling host
27564 is on at least one of a number of DNS lists by looking up the inverted IP
27565 address in one or more DNS domains. (Note that DNS list domains are not mail
27566 domains, so the &`+`& syntax for named lists doesn't work - it is used for
27567 special options instead.) For example, if the calling host's IP
27568 address is 192.168.62.43, and the ACL statement is
27570 deny dnslists = blackholes.mail-abuse.org : \
27571 dialups.mail-abuse.org
27573 the following records are looked up:
27575 43.62.168.192.blackholes.mail-abuse.org
27576 43.62.168.192.dialups.mail-abuse.org
27578 As soon as Exim finds an existing DNS record, processing of the list stops.
27579 Thus, multiple entries on the list provide an &"or"& conjunction. If you want
27580 to test that a host is on more than one list (an &"and"& conjunction), you can
27581 use two separate conditions:
27583 deny dnslists = blackholes.mail-abuse.org
27584 dnslists = dialups.mail-abuse.org
27586 If a DNS lookup times out or otherwise fails to give a decisive answer, Exim
27587 behaves as if the host does not match the list item, that is, as if the DNS
27588 record does not exist. If there are further items in the DNS list, they are
27591 This is usually the required action when &%dnslists%& is used with &%deny%&
27592 (which is the most common usage), because it prevents a DNS failure from
27593 blocking mail. However, you can change this behaviour by putting one of the
27594 following special items in the list:
27596 &`+include_unknown `& behave as if the item is on the list
27597 &`+exclude_unknown `& behave as if the item is not on the list (default)
27598 &`+defer_unknown `& give a temporary error
27600 .cindex "&`+include_unknown`&"
27601 .cindex "&`+exclude_unknown`&"
27602 .cindex "&`+defer_unknown`&"
27603 Each of these applies to any subsequent items on the list. For example:
27605 deny dnslists = +defer_unknown : foo.bar.example
27607 Testing the list of domains stops as soon as a match is found. If you want to
27608 warn for one list and block for another, you can use two different statements:
27610 deny dnslists = blackholes.mail-abuse.org
27611 warn message = X-Warn: sending host is on dialups list
27612 dnslists = dialups.mail-abuse.org
27614 DNS list lookups are cached by Exim for the duration of the SMTP session,
27615 so a lookup based on the IP address is done at most once for any incoming
27616 connection. Exim does not share information between multiple incoming
27617 connections (but your local name server cache should be active).
27621 .section "Specifying the IP address for a DNS list lookup" "SECID201"
27622 .cindex "DNS list" "keyed by explicit IP address"
27623 By default, the IP address that is used in a DNS list lookup is the IP address
27624 of the calling host. However, you can specify another IP address by listing it
27625 after the domain name, introduced by a slash. For example:
27627 deny dnslists = black.list.tld/192.168.1.2
27629 This feature is not very helpful with explicit IP addresses; it is intended for
27630 use with IP addresses that are looked up, for example, the IP addresses of the
27631 MX hosts or nameservers of an email sender address. For an example, see section
27632 &<<SECTmulkeyfor>>& below.
27637 .section "DNS lists keyed on domain names" "SECID202"
27638 .cindex "DNS list" "keyed by domain name"
27639 There are some lists that are keyed on domain names rather than inverted IP
27640 addresses (see for example the &'domain based zones'& link at
27641 &url(http://www.rfc-ignorant.org/)). No reversing of components is used
27642 with these lists. You can change the name that is looked up in a DNS list by
27643 listing it after the domain name, introduced by a slash. For example,
27645 deny message = Sender's domain is listed at $dnslist_domain
27646 dnslists = dsn.rfc-ignorant.org/$sender_address_domain
27648 This particular example is useful only in ACLs that are obeyed after the
27649 RCPT or DATA commands, when a sender address is available. If (for
27650 example) the message's sender is &'user@tld.example'& the name that is looked
27651 up by this example is
27653 tld.example.dsn.rfc-ignorant.org
27655 A single &%dnslists%& condition can contain entries for both names and IP
27656 addresses. For example:
27658 deny dnslists = sbl.spamhaus.org : \
27659 dsn.rfc-ignorant.org/$sender_address_domain
27661 The first item checks the sending host's IP address; the second checks a domain
27662 name. The whole condition is true if either of the DNS lookups succeeds.
27667 .section "Multiple explicit keys for a DNS list" "SECTmulkeyfor"
27668 .cindex "DNS list" "multiple keys for"
27669 The syntax described above for looking up explicitly-defined values (either
27670 names or IP addresses) in a DNS blacklist is a simplification. After the domain
27671 name for the DNS list, what follows the slash can in fact be a list of items.
27672 As with all lists in Exim, the default separator is a colon. However, because
27673 this is a sublist within the list of DNS blacklist domains, it is necessary
27674 either to double the separators like this:
27676 dnslists = black.list.tld/name.1::name.2
27678 or to change the separator character, like this:
27680 dnslists = black.list.tld/<;name.1;name.2
27682 If an item in the list is an IP address, it is inverted before the DNS
27683 blacklist domain is appended. If it is not an IP address, no inversion
27684 occurs. Consider this condition:
27686 dnslists = black.list.tld/<;192.168.1.2;a.domain
27688 The DNS lookups that occur are:
27690 2.1.168.192.black.list.tld
27691 a.domain.black.list.tld
27693 Once a DNS record has been found (that matches a specific IP return
27694 address, if specified &-- see section &<<SECTaddmatcon>>&), no further lookups
27695 are done. If there is a temporary DNS error, the rest of the sublist of domains
27696 or IP addresses is tried. A temporary error for the whole dnslists item occurs
27697 only if no other DNS lookup in this sublist succeeds. In other words, a
27698 successful lookup for any of the items in the sublist overrides a temporary
27699 error for a previous item.
27701 The ability to supply a list of items after the slash is in some sense just a
27702 syntactic convenience. These two examples have the same effect:
27704 dnslists = black.list.tld/a.domain : black.list.tld/b.domain
27705 dnslists = black.list.tld/a.domain::b.domain
27707 However, when the data for the list is obtained from a lookup, the second form
27708 is usually much more convenient. Consider this example:
27710 deny message = The mail servers for the domain \
27711 $sender_address_domain \
27712 are listed at $dnslist_domain ($dnslist_value); \
27714 dnslists = sbl.spamhaus.org/<|${lookup dnsdb {>|a=<|\
27715 ${lookup dnsdb {>|mxh=\
27716 $sender_address_domain} }} }
27718 Note the use of &`>|`& in the dnsdb lookup to specify the separator for
27719 multiple DNS records. The inner dnsdb lookup produces a list of MX hosts
27720 and the outer dnsdb lookup finds the IP addresses for these hosts. The result
27721 of expanding the condition might be something like this:
27723 dnslists = sbl.spahmaus.org/<|192.168.2.3|192.168.5.6|...
27725 Thus, this example checks whether or not the IP addresses of the sender
27726 domain's mail servers are on the Spamhaus black list.
27728 The key that was used for a successful DNS list lookup is put into the variable
27729 &$dnslist_matched$& (see section &<<SECID204>>&).
27734 .section "Data returned by DNS lists" "SECID203"
27735 .cindex "DNS list" "data returned from"
27736 DNS lists are constructed using address records in the DNS. The original RBL
27737 just used the address 127.0.0.1 on the right hand side of each record, but the
27738 RBL+ list and some other lists use a number of values with different meanings.
27739 The values used on the RBL+ list are:
27743 127.1.0.3 DUL and RBL
27745 127.1.0.5 RSS and RBL
27746 127.1.0.6 RSS and DUL
27747 127.1.0.7 RSS and DUL and RBL
27749 Section &<<SECTaddmatcon>>& below describes how you can distinguish between
27750 different values. Some DNS lists may return more than one address record;
27751 see section &<<SECThanmuldnsrec>>& for details of how they are checked.
27754 .section "Variables set from DNS lists" "SECID204"
27755 .cindex "expansion" "variables, set from DNS list"
27756 .cindex "DNS list" "variables set from"
27757 .vindex "&$dnslist_domain$&"
27758 .vindex "&$dnslist_matched$&"
27759 .vindex "&$dnslist_text$&"
27760 .vindex "&$dnslist_value$&"
27761 When an entry is found in a DNS list, the variable &$dnslist_domain$& contains
27762 the name of the overall domain that matched (for example,
27763 &`spamhaus.example`&), &$dnslist_matched$& contains the key within that domain
27764 (for example, &`192.168.5.3`&), and &$dnslist_value$& contains the data from
27765 the DNS record. When the key is an IP address, it is not reversed in
27766 &$dnslist_matched$& (though it is, of course, in the actual lookup). In simple
27767 cases, for example:
27769 deny dnslists = spamhaus.example
27771 the key is also available in another variable (in this case,
27772 &$sender_host_address$&). In more complicated cases, however, this is not true.
27773 For example, using a data lookup (as described in section &<<SECTmulkeyfor>>&)
27774 might generate a dnslists lookup like this:
27776 deny dnslists = spamhaus.example/<|192.168.1.2|192.168.6.7|...
27778 If this condition succeeds, the value in &$dnslist_matched$& might be
27779 &`192.168.6.7`& (for example).
27781 If more than one address record is returned by the DNS lookup, all the IP
27782 addresses are included in &$dnslist_value$&, separated by commas and spaces.
27783 The variable &$dnslist_text$& contains the contents of any associated TXT
27784 record. For lists such as RBL+ the TXT record for a merged entry is often not
27785 very meaningful. See section &<<SECTmordetinf>>& for a way of obtaining more
27788 You can use the DNS list variables in &%message%& or &%log_message%& modifiers
27789 &-- although these appear before the condition in the ACL, they are not
27790 expanded until after it has failed. For example:
27792 deny hosts = !+local_networks
27793 message = $sender_host_address is listed \
27795 dnslists = rbl-plus.mail-abuse.example
27800 .section "Additional matching conditions for DNS lists" "SECTaddmatcon"
27801 .cindex "DNS list" "matching specific returned data"
27802 You can add an equals sign and an IP address after a &%dnslists%& domain name
27803 in order to restrict its action to DNS records with a matching right hand side.
27806 deny dnslists = rblplus.mail-abuse.org=127.0.0.2
27808 rejects only those hosts that yield 127.0.0.2. Without this additional data,
27809 any address record is considered to be a match. For the moment, we assume
27810 that the DNS lookup returns just one record. Section &<<SECThanmuldnsrec>>&
27811 describes how multiple records are handled.
27813 More than one IP address may be given for checking, using a comma as a
27814 separator. These are alternatives &-- if any one of them matches, the
27815 &%dnslists%& condition is true. For example:
27817 deny dnslists = a.b.c=127.0.0.2,127.0.0.3
27819 If you want to specify a constraining address list and also specify names or IP
27820 addresses to be looked up, the constraining address list must be specified
27821 first. For example:
27823 deny dnslists = dsn.rfc-ignorant.org\
27824 =127.0.0.2/$sender_address_domain
27827 If the character &`&&`& is used instead of &`=`&, the comparison for each
27828 listed IP address is done by a bitwise &"and"& instead of by an equality test.
27829 In other words, the listed addresses are used as bit masks. The comparison is
27830 true if all the bits in the mask are present in the address that is being
27831 tested. For example:
27833 dnslists = a.b.c&0.0.0.3
27835 matches if the address is &'x.x.x.'&3, &'x.x.x.'&7, &'x.x.x.'&11, etc. If you
27836 want to test whether one bit or another bit is present (as opposed to both
27837 being present), you must use multiple values. For example:
27839 dnslists = a.b.c&0.0.0.1,0.0.0.2
27841 matches if the final component of the address is an odd number or two times
27846 .section "Negated DNS matching conditions" "SECID205"
27847 You can supply a negative list of IP addresses as part of a &%dnslists%&
27850 deny dnslists = a.b.c=127.0.0.2,127.0.0.3
27852 means &"deny if the host is in the black list at the domain &'a.b.c'& and the
27853 IP address yielded by the list is either 127.0.0.2 or 127.0.0.3"&,
27855 deny dnslists = a.b.c!=127.0.0.2,127.0.0.3
27857 means &"deny if the host is in the black list at the domain &'a.b.c'& and the
27858 IP address yielded by the list is not 127.0.0.2 and not 127.0.0.3"&. In other
27859 words, the result of the test is inverted if an exclamation mark appears before
27860 the &`=`& (or the &`&&`&) sign.
27862 &*Note*&: This kind of negation is not the same as negation in a domain,
27863 host, or address list (which is why the syntax is different).
27865 If you are using just one list, the negation syntax does not gain you much. The
27866 previous example is precisely equivalent to
27868 deny dnslists = a.b.c
27869 !dnslists = a.b.c=127.0.0.2,127.0.0.3
27871 However, if you are using multiple lists, the negation syntax is clearer.
27872 Consider this example:
27874 deny dnslists = sbl.spamhaus.org : \
27876 dnsbl.njabl.org!=127.0.0.3 : \
27879 Using only positive lists, this would have to be:
27881 deny dnslists = sbl.spamhaus.org : \
27883 deny dnslists = dnsbl.njabl.org
27884 !dnslists = dnsbl.njabl.org=127.0.0.3
27885 deny dnslists = relays.ordb.org
27887 which is less clear, and harder to maintain.
27892 .section "Handling multiple DNS records from a DNS list" "SECThanmuldnsrec"
27893 A DNS lookup for a &%dnslists%& condition may return more than one DNS record,
27894 thereby providing more than one IP address. When an item in a &%dnslists%& list
27895 is followed by &`=`& or &`&&`& and a list of IP addresses, in order to restrict
27896 the match to specific results from the DNS lookup, there are two ways in which
27897 the checking can be handled. For example, consider the condition:
27899 dnslists = a.b.c=127.0.0.1
27901 What happens if the DNS lookup for the incoming IP address yields both
27902 127.0.0.1 and 127.0.0.2 by means of two separate DNS records? Is the
27903 condition true because at least one given value was found, or is it false
27904 because at least one of the found values was not listed? And how does this
27905 affect negated conditions? Both possibilities are provided for with the help of
27906 additional separators &`==`& and &`=&&`&.
27909 If &`=`& or &`&&`& is used, the condition is true if any one of the looked up
27910 IP addresses matches one of the listed addresses. For the example above, the
27911 condition is true because 127.0.0.1 matches.
27913 If &`==`& or &`=&&`& is used, the condition is true only if every one of the
27914 looked up IP addresses matches one of the listed addresses. If the condition is
27917 dnslists = a.b.c==127.0.0.1
27919 and the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
27920 false because 127.0.0.2 is not listed. You would need to have:
27922 dnslists = a.b.c==127.0.0.1,127.0.0.2
27924 for the condition to be true.
27927 When &`!`& is used to negate IP address matching, it inverts the result, giving
27928 the precise opposite of the behaviour above. Thus:
27930 If &`!=`& or &`!&&`& is used, the condition is true if none of the looked up IP
27931 addresses matches one of the listed addresses. Consider:
27933 dnslists = a.b.c!&0.0.0.1
27935 If the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
27936 false because 127.0.0.1 matches.
27938 If &`!==`& or &`!=&&`& is used, the condition is true there is at least one
27939 looked up IP address that does not match. Consider:
27941 dnslists = a.b.c!=&0.0.0.1
27943 If the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
27944 true, because 127.0.0.2 does not match. You would need to have:
27946 dnslists = a.b.c!=&0.0.0.1,0.0.0.2
27948 for the condition to be false.
27950 When the DNS lookup yields only a single IP address, there is no difference
27951 between &`=`& and &`==`& and between &`&&`& and &`=&&`&.
27956 .section "Detailed information from merged DNS lists" "SECTmordetinf"
27957 .cindex "DNS list" "information from merged"
27958 When the facility for restricting the matching IP values in a DNS list is used,
27959 the text from the TXT record that is set in &$dnslist_text$& may not reflect
27960 the true reason for rejection. This happens when lists are merged and the IP
27961 address in the A record is used to distinguish them; unfortunately there is
27962 only one TXT record. One way round this is not to use merged lists, but that
27963 can be inefficient because it requires multiple DNS lookups where one would do
27964 in the vast majority of cases when the host of interest is not on any of the
27967 A less inefficient way of solving this problem is available. If
27968 two domain names, comma-separated, are given, the second is used first to
27969 do an initial check, making use of any IP value restrictions that are set.
27970 If there is a match, the first domain is used, without any IP value
27971 restrictions, to get the TXT record. As a byproduct of this, there is also
27972 a check that the IP being tested is indeed on the first list. The first
27973 domain is the one that is put in &$dnslist_domain$&. For example:
27976 rejected because $sender_host_address is blacklisted \
27977 at $dnslist_domain\n$dnslist_text
27979 sbl.spamhaus.org,sbl-xbl.spamhaus.org=127.0.0.2 : \
27980 dul.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.10
27982 For the first blacklist item, this starts by doing a lookup in
27983 &'sbl-xbl.spamhaus.org'& and testing for a 127.0.0.2 return. If there is a
27984 match, it then looks in &'sbl.spamhaus.org'&, without checking the return
27985 value, and as long as something is found, it looks for the corresponding TXT
27986 record. If there is no match in &'sbl-xbl.spamhaus.org'&, nothing more is done.
27987 The second blacklist item is processed similarly.
27989 If you are interested in more than one merged list, the same list must be
27990 given several times, but because the results of the DNS lookups are cached,
27991 the DNS calls themselves are not repeated. For example:
27993 reject dnslists = \
27994 http.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.2 : \
27995 socks.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.3 : \
27996 misc.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.4 : \
27997 dul.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.10
27999 In this case there is one lookup in &'dnsbl.sorbs.net'&, and if none of the IP
28000 values matches (or if no record is found), this is the only lookup that is
28001 done. Only if there is a match is one of the more specific lists consulted.
28005 .section "DNS lists and IPv6" "SECTmorednslistslast"
28006 .cindex "IPv6" "DNS black lists"
28007 .cindex "DNS list" "IPv6 usage"
28008 If Exim is asked to do a dnslist lookup for an IPv6 address, it inverts it
28009 nibble by nibble. For example, if the calling host's IP address is
28010 3ffe:ffff:836f:0a00:000a:0800:200a:c031, Exim might look up
28012 1.3.0.c.a.0.0.2.0.0.8.0.a.0.0.0.0.0.a.0.f.6.3.8.
28013 f.f.f.f.e.f.f.3.blackholes.mail-abuse.org
28015 (split over two lines here to fit on the page). Unfortunately, some of the DNS
28016 lists contain wildcard records, intended for IPv4, that interact badly with
28017 IPv6. For example, the DNS entry
28019 *.3.some.list.example. A 127.0.0.1
28021 is probably intended to put the entire 3.0.0.0/8 IPv4 network on the list.
28022 Unfortunately, it also matches the entire 3::/4 IPv6 network.
28024 You can exclude IPv6 addresses from DNS lookups by making use of a suitable
28025 &%condition%& condition, as in this example:
28027 deny condition = ${if isip4{$sender_host_address}}
28028 dnslists = some.list.example
28031 .section "Rate limiting incoming messages" "SECTratelimiting"
28032 .cindex "rate limiting" "client sending"
28033 .cindex "limiting client sending rates"
28034 .oindex "&%smtp_ratelimit_*%&"
28035 The &%ratelimit%& ACL condition can be used to measure and control the rate at
28036 which clients can send email. This is more powerful than the
28037 &%smtp_ratelimit_*%& options, because those options control the rate of
28038 commands in a single SMTP session only, whereas the &%ratelimit%& condition
28039 works across all connections (concurrent and sequential) from the same client
28040 host. The syntax of the &%ratelimit%& condition is:
28042 &`ratelimit =`& <&'m'&> &`/`& <&'p'&> &`/`& <&'options'&> &`/`& <&'key'&>
28044 If the average client sending rate is less than &'m'& messages per time
28045 period &'p'& then the condition is false; otherwise it is true.
28047 As a side-effect, the &%ratelimit%& condition sets the expansion variable
28048 &$sender_rate$& to the client's computed rate, &$sender_rate_limit$& to the
28049 configured value of &'m'&, and &$sender_rate_period$& to the configured value
28052 The parameter &'p'& is the smoothing time constant, in the form of an Exim
28053 time interval, for example, &`8h`& for eight hours. A larger time constant
28054 means that it takes Exim longer to forget a client's past behaviour. The
28055 parameter &'m'& is the maximum number of messages that a client is permitted to
28056 send in each time interval. It also specifies the number of messages permitted
28057 in a fast burst. By increasing both &'m'& and &'p'& but keeping &'m/p'&
28058 constant, you can allow a client to send more messages in a burst without
28059 changing its long-term sending rate limit. Conversely, if &'m'& and &'p'& are
28060 both small, messages must be sent at an even rate.
28062 There is a script in &_util/ratelimit.pl_& which extracts sending rates from
28063 log files, to assist with choosing appropriate settings for &'m'& and &'p'&
28064 when deploying the &%ratelimit%& ACL condition. The script prints usage
28065 instructions when it is run with no arguments.
28067 The key is used to look up the data for calculating the client's average
28068 sending rate. This data is stored in Exim's spool directory, alongside the
28069 retry and other hints databases. The default key is &$sender_host_address$&,
28070 which means Exim computes the sending rate of each client host IP address.
28071 By changing the key you can change how Exim identifies clients for the purpose
28072 of ratelimiting. For example, to limit the sending rate of each authenticated
28073 user, independent of the computer they are sending from, set the key to
28074 &$authenticated_id$&. You must ensure that the lookup key is meaningful; for
28075 example, &$authenticated_id$& is only meaningful if the client has
28076 authenticated (which you can check with the &%authenticated%& ACL condition).
28078 The lookup key does not have to identify clients: If you want to limit the
28079 rate at which a recipient receives messages, you can use the key
28080 &`$local_part@$domain`& with the &%per_rcpt%& option (see below) in a RCPT
28083 Each &%ratelimit%& condition can have up to four options. A &%per_*%& option
28084 specifies what Exim measures the rate of, for example messages or recipients
28085 or bytes. You can adjust the measurement using the &%unique=%& and/or
28086 &%count=%& options. You can also control when Exim updates the recorded rate
28087 using a &%strict%&, &%leaky%&, or &%readonly%& option. The options are
28088 separated by a slash, like the other parameters. They may appear in any order.
28090 Internally, Exim appends the smoothing constant &'p'& onto the lookup key with
28091 any options that alter the meaning of the stored data. The limit &'m'& is not
28092 stored, so you can alter the configured maximum rate and Exim will still
28093 remember clients' past behaviour. If you change the &%per_*%& mode or add or
28094 remove the &%unique=%& option, the lookup key changes so Exim will forget past
28095 behaviour. The lookup key is not affected by changes to the update mode and
28096 the &%count=%& option.
28099 .section "Ratelimit options for what is being measured" "ratoptmea"
28100 .cindex "rate limiting" "per_* options"
28101 The &%per_conn%& option limits the client's connection rate. It is not
28102 normally used in the &%acl_not_smtp%&, &%acl_not_smtp_mime%&, or
28103 &%acl_not_smtp_start%& ACLs.
28105 The &%per_mail%& option limits the client's rate of sending messages. This is
28106 the default if none of the &%per_*%& options is specified. It can be used in
28107 &%acl_smtp_mail%&, &%acl_smtp_rcpt%&, &%acl_smtp_predata%&, &%acl_smtp_mime%&,
28108 &%acl_smtp_data%&, or &%acl_not_smtp%&.
28110 The &%per_byte%& option limits the sender's email bandwidth. It can be used in
28111 the same ACLs as the &%per_mail%& option, though it is best to use this option
28112 in the &%acl_smtp_mime%&, &%acl_smtp_data%& or &%acl_not_smtp%& ACLs; if it is
28113 used in an earlier ACL, Exim relies on the SIZE parameter given by the client
28114 in its MAIL command, which may be inaccurate or completely missing. You can
28115 follow the limit &'m'& in the configuration with K, M, or G to specify limits
28116 in kilobytes, megabytes, or gigabytes, respectively.
28118 The &%per_rcpt%& option causes Exim to limit the rate at which recipients are
28119 accepted. It can be used in the &%acl_smtp_rcpt%&, &%acl_smtp_predata%&,
28120 &%acl_smtp_mime%&, &%acl_smtp_data%&, or &%acl_smtp_rcpt%& ACLs. In
28121 &%acl_smtp_rcpt%& the rate is updated one recipient at a time; in the other
28122 ACLs the rate is updated with the total recipient count in one go. Note that
28123 in either case the rate limiting engine will see a message with many
28124 recipients as a large high-speed burst.
28126 The &%per_addr%& option is like the &%per_rcpt%& option, except it counts the
28127 number of different recipients that the client has sent messages to in the
28128 last time period. That is, if the client repeatedly sends messages to the same
28129 recipient, its measured rate is not increased. This option can only be used in
28132 The &%per_cmd%& option causes Exim to recompute the rate every time the
28133 condition is processed. This can be used to limit the rate of any SMTP
28134 command. If it is used in multiple ACLs it can limit the aggregate rate of
28135 multiple different commands.
28137 The &%count=%& option can be used to alter how much Exim adds to the client's
28138 measured rate. For example, the &%per_byte%& option is equivalent to
28139 &`per_mail/count=$message_size`&. If there is no &%count=%& option, Exim
28140 increases the measured rate by one (except for the &%per_rcpt%& option in ACLs
28141 other than &%acl_smtp_rcpt%&). The count does not have to be an integer.
28143 The &%unique=%& option is described in section &<<ratoptuniq>>& below.
28146 .section "Ratelimit update modes" "ratoptupd"
28147 .cindex "rate limiting" "reading data without updating"
28148 You can specify one of three options with the &%ratelimit%& condition to
28149 control when its database is updated. This section describes the &%readonly%&
28150 mode, and the next section describes the &%strict%& and &%leaky%& modes.
28152 If the &%ratelimit%& condition is used in &%readonly%& mode, Exim looks up a
28153 previously-computed rate to check against the limit.
28155 For example, you can test the client's sending rate and deny it access (when
28156 it is too fast) in the connect ACL. If the client passes this check then it
28157 can go on to send a message, in which case its recorded rate will be updated
28158 in the MAIL ACL. Subsequent connections from the same client will check this
28162 deny ratelimit = 100 / 5m / readonly
28163 log_message = RATE CHECK: $sender_rate/$sender_rate_period \
28164 (max $sender_rate_limit)
28167 warn ratelimit = 100 / 5m / strict
28168 log_message = RATE UPDATE: $sender_rate/$sender_rate_period \
28169 (max $sender_rate_limit)
28172 If Exim encounters multiple &%ratelimit%& conditions with the same key when
28173 processing a message then it may increase the client's measured rate more than
28174 it should. For example, this will happen if you check the &%per_rcpt%& option
28175 in both &%acl_smtp_rcpt%& and &%acl_smtp_data%&. However it's OK to check the
28176 same &%ratelimit%& condition multiple times in the same ACL. You can avoid any
28177 multiple update problems by using the &%readonly%& option on later ratelimit
28180 The &%per_*%& options described above do not make sense in some ACLs. If you
28181 use a &%per_*%& option in an ACL where it is not normally permitted then the
28182 update mode defaults to &%readonly%& and you cannot specify the &%strict%& or
28183 &%leaky%& modes. In other ACLs the default update mode is &%leaky%& (see the
28184 next section) so you must specify the &%readonly%& option explicitly.
28187 .section "Ratelimit options for handling fast clients" "ratoptfast"
28188 .cindex "rate limiting" "strict and leaky modes"
28189 If a client's average rate is greater than the maximum, the rate limiting
28190 engine can react in two possible ways, depending on the presence of the
28191 &%strict%& or &%leaky%& update modes. This is independent of the other
28192 counter-measures (such as rejecting the message) that may be specified by the
28195 The &%leaky%& (default) option means that the client's recorded rate is not
28196 updated if it is above the limit. The effect of this is that Exim measures the
28197 client's average rate of successfully sent email, which cannot be greater than
28198 the maximum allowed. If the client is over the limit it may suffer some
28199 counter-measures (as specified in the ACL), but it will still be able to send
28200 email at the configured maximum rate, whatever the rate of its attempts. This
28201 is generally the better choice if you have clients that retry automatically.
28202 For example, it does not prevent a sender with an over-aggressive retry rate
28203 from getting any email through.
28205 The &%strict%& option means that the client's recorded rate is always
28206 updated. The effect of this is that Exim measures the client's average rate
28207 of attempts to send email, which can be much higher than the maximum it is
28208 actually allowed. If the client is over the limit it may be subjected to
28209 counter-measures by the ACL. It must slow down and allow sufficient time to
28210 pass that its computed rate falls below the maximum before it can send email
28211 again. The time (the number of smoothing periods) it must wait and not
28212 attempt to send mail can be calculated with this formula:
28214 ln(peakrate/maxrate)
28218 .section "Limiting the rate of different events" "ratoptuniq"
28219 .cindex "rate limiting" "counting unique events"
28220 The &%ratelimit%& &%unique=%& option controls a mechanism for counting the
28221 rate of different events. For example, the &%per_addr%& option uses this
28222 mechanism to count the number of different recipients that the client has
28223 sent messages to in the last time period; it is equivalent to
28224 &`per_rcpt/unique=$local_part@$domain`&. You could use this feature to
28225 measure the rate that a client uses different sender addresses with the
28226 options &`per_mail/unique=$sender_address`&.
28228 For each &%ratelimit%& key Exim stores the set of &%unique=%& values that it
28229 has seen for that key. The whole set is thrown away when it is older than the
28230 rate smoothing period &'p'&, so each different event is counted at most once
28231 per period. In the &%leaky%& update mode, an event that causes the client to
28232 go over the limit is not added to the set, in the same way that the client's
28233 recorded rate is not updated in the same situation.
28235 When you combine the &%unique=%& and &%readonly%& options, the specific
28236 &%unique=%& value is ignored, and Exim just retrieves the client's stored
28239 The &%unique=%& mechanism needs more space in the ratelimit database than the
28240 other &%ratelimit%& options in order to store the event set. The number of
28241 unique values is potentially as large as the rate limit, so the extra space
28242 required increases with larger limits.
28244 The uniqueification is not perfect: there is a small probability that Exim
28245 will think a new event has happened before. If the sender's rate is less than
28246 the limit, Exim should be more than 99.9% correct. However in &%strict%& mode
28247 the measured rate can go above the limit, in which case Exim may under-count
28248 events by a significant margin. Fortunately, if the rate is high enough (2.7
28249 times the limit) that the false positive rate goes above 9%, then Exim will
28250 throw away the over-full event set before the measured rate falls below the
28251 limit. Therefore the only harm should be that exceptionally high sending rates
28252 are logged incorrectly; any countermeasures you configure will be as effective
28256 .section "Using rate limiting" "useratlim"
28257 Exim's other ACL facilities are used to define what counter-measures are taken
28258 when the rate limit is exceeded. This might be anything from logging a warning
28259 (for example, while measuring existing sending rates in order to define
28260 policy), through time delays to slow down fast senders, up to rejecting the
28261 message. For example:
28263 # Log all senders' rates
28264 warn ratelimit = 0 / 1h / strict
28265 log_message = Sender rate $sender_rate / $sender_rate_period
28267 # Slow down fast senders; note the need to truncate $sender_rate
28268 # at the decimal point.
28269 warn ratelimit = 100 / 1h / per_rcpt / strict
28270 delay = ${eval: ${sg{$sender_rate}{[.].*}{}} - \
28271 $sender_rate_limit }s
28273 # Keep authenticated users under control
28274 deny authenticated = *
28275 ratelimit = 100 / 1d / strict / $authenticated_id
28277 # System-wide rate limit
28278 defer message = Sorry, too busy. Try again later.
28279 ratelimit = 10 / 1s / $primary_hostname
28281 # Restrict incoming rate from each host, with a default
28282 # set using a macro and special cases looked up in a table.
28283 defer message = Sender rate exceeds $sender_rate_limit \
28284 messages per $sender_rate_period
28285 ratelimit = ${lookup {$sender_host_address} \
28286 cdb {DB/ratelimits.cdb} \
28287 {$value} {RATELIMIT} }
28289 &*Warning*&: If you have a busy server with a lot of &%ratelimit%& tests,
28290 especially with the &%per_rcpt%& option, you may suffer from a performance
28291 bottleneck caused by locking on the ratelimit hints database. Apart from
28292 making your ACLs less complicated, you can reduce the problem by using a
28293 RAM disk for Exim's hints directory (usually &_/var/spool/exim/db/_&). However
28294 this means that Exim will lose its hints data after a reboot (including retry
28295 hints, the callout cache, and ratelimit data).
28299 .section "Address verification" "SECTaddressverification"
28300 .cindex "verifying address" "options for"
28301 .cindex "policy control" "address verification"
28302 Several of the &%verify%& conditions described in section
28303 &<<SECTaclconditions>>& cause addresses to be verified. Section
28304 &<<SECTsenaddver>>& discusses the reporting of sender verification failures.
28305 The verification conditions can be followed by options that modify the
28306 verification process. The options are separated from the keyword and from each
28307 other by slashes, and some of them contain parameters. For example:
28309 verify = sender/callout
28310 verify = recipient/defer_ok/callout=10s,defer_ok
28312 The first stage of address verification, which always happens, is to run the
28313 address through the routers, in &"verify mode"&. Routers can detect the
28314 difference between verification and routing for delivery, and their actions can
28315 be varied by a number of generic options such as &%verify%& and &%verify_only%&
28316 (see chapter &<<CHAProutergeneric>>&). If routing fails, verification fails.
28317 The available options are as follows:
28320 If the &%callout%& option is specified, successful routing to one or more
28321 remote hosts is followed by a &"callout"& to those hosts as an additional
28322 check. Callouts and their sub-options are discussed in the next section.
28324 If there is a defer error while doing verification routing, the ACL
28325 normally returns &"defer"&. However, if you include &%defer_ok%& in the
28326 options, the condition is forced to be true instead. Note that this is a main
28327 verification option as well as a suboption for callouts.
28329 The &%no_details%& option is covered in section &<<SECTsenaddver>>&, which
28330 discusses the reporting of sender address verification failures.
28332 The &%success_on_redirect%& option causes verification always to succeed
28333 immediately after a successful redirection. By default, if a redirection
28334 generates just one address, that address is also verified. See further
28335 discussion in section &<<SECTredirwhilveri>>&.
28338 .cindex "verifying address" "differentiating failures"
28339 .vindex "&$recipient_verify_failure$&"
28340 .vindex "&$sender_verify_failure$&"
28341 .vindex "&$acl_verify_message$&"
28342 After an address verification failure, &$acl_verify_message$& contains the
28343 error message that is associated with the failure. It can be preserved by
28346 warn !verify = sender
28347 set acl_m0 = $acl_verify_message
28349 If you are writing your own custom rejection message or log message when
28350 denying access, you can use this variable to include information about the
28351 verification failure.
28353 In addition, &$sender_verify_failure$& or &$recipient_verify_failure$& (as
28354 appropriate) contains one of the following words:
28357 &%qualify%&: The address was unqualified (no domain), and the message
28358 was neither local nor came from an exempted host.
28360 &%route%&: Routing failed.
28362 &%mail%&: Routing succeeded, and a callout was attempted; rejection
28363 occurred at or before the MAIL command (that is, on initial
28364 connection, HELO, or MAIL).
28366 &%recipient%&: The RCPT command in a callout was rejected.
28368 &%postmaster%&: The postmaster check in a callout was rejected.
28371 The main use of these variables is expected to be to distinguish between
28372 rejections of MAIL and rejections of RCPT in callouts.
28377 .section "Callout verification" "SECTcallver"
28378 .cindex "verifying address" "by callout"
28379 .cindex "callout" "verification"
28380 .cindex "SMTP" "callout verification"
28381 For non-local addresses, routing verifies the domain, but is unable to do any
28382 checking of the local part. There are situations where some means of verifying
28383 the local part is desirable. One way this can be done is to make an SMTP
28384 &'callback'& to a delivery host for the sender address or a &'callforward'& to
28385 a subsequent host for a recipient address, to see if the host accepts the
28386 address. We use the term &'callout'& to cover both cases. Note that for a
28387 sender address, the callback is not to the client host that is trying to
28388 deliver the message, but to one of the hosts that accepts incoming mail for the
28391 Exim does not do callouts by default. If you want them to happen, you must
28392 request them by setting appropriate options on the &%verify%& condition, as
28393 described below. This facility should be used with care, because it can add a
28394 lot of resource usage to the cost of verifying an address. However, Exim does
28395 cache the results of callouts, which helps to reduce the cost. Details of
28396 caching are in section &<<SECTcallvercache>>&.
28398 Recipient callouts are usually used only between hosts that are controlled by
28399 the same administration. For example, a corporate gateway host could use
28400 callouts to check for valid recipients on an internal mailserver. A successful
28401 callout does not guarantee that a real delivery to the address would succeed;
28402 on the other hand, a failing callout does guarantee that a delivery would fail.
28404 If the &%callout%& option is present on a condition that verifies an address, a
28405 second stage of verification occurs if the address is successfully routed to
28406 one or more remote hosts. The usual case is routing by a &(dnslookup)& or a
28407 &(manualroute)& router, where the router specifies the hosts. However, if a
28408 router that does not set up hosts routes to an &(smtp)& transport with a
28409 &%hosts%& setting, the transport's hosts are used. If an &(smtp)& transport has
28410 &%hosts_override%& set, its hosts are always used, whether or not the router
28411 supplies a host list.
28413 The port that is used is taken from the transport, if it is specified and is a
28414 remote transport. (For routers that do verification only, no transport need be
28415 specified.) Otherwise, the default SMTP port is used. If a remote transport
28416 specifies an outgoing interface, this is used; otherwise the interface is not
28417 specified. Likewise, the text that is used for the HELO command is taken from
28418 the transport's &%helo_data%& option; if there is no transport, the value of
28419 &$smtp_active_hostname$& is used.
28421 For a sender callout check, Exim makes SMTP connections to the remote hosts, to
28422 test whether a bounce message could be delivered to the sender address. The
28423 following SMTP commands are sent:
28425 &`HELO `&<&'local host name'&>
28427 &`RCPT TO:`&<&'the address to be tested'&>
28430 LHLO is used instead of HELO if the transport's &%protocol%& option is
28433 A recipient callout check is similar. By default, it also uses an empty address
28434 for the sender. This default is chosen because most hosts do not make use of
28435 the sender address when verifying a recipient. Using the same address means
28436 that a single cache entry can be used for each recipient. Some sites, however,
28437 do make use of the sender address when verifying. These are catered for by the
28438 &%use_sender%& and &%use_postmaster%& options, described in the next section.
28440 If the response to the RCPT command is a 2&'xx'& code, the verification
28441 succeeds. If it is 5&'xx'&, the verification fails. For any other condition,
28442 Exim tries the next host, if any. If there is a problem with all the remote
28443 hosts, the ACL yields &"defer"&, unless the &%defer_ok%& parameter of the
28444 &%callout%& option is given, in which case the condition is forced to succeed.
28446 .cindex "SMTP" "output flushing, disabling for callout"
28447 A callout may take a little time. For this reason, Exim normally flushes SMTP
28448 output before performing a callout in an ACL, to avoid unexpected timeouts in
28449 clients when the SMTP PIPELINING extension is in use. The flushing can be
28450 disabled by using a &%control%& modifier to set &%no_callout_flush%&.
28455 .section "Additional parameters for callouts" "CALLaddparcall"
28456 .cindex "callout" "additional parameters for"
28457 The &%callout%& option can be followed by an equals sign and a number of
28458 optional parameters, separated by commas. For example:
28460 verify = recipient/callout=10s,defer_ok
28462 The old syntax, which had &%callout_defer_ok%& and &%check_postmaster%& as
28463 separate verify options, is retained for backwards compatibility, but is now
28464 deprecated. The additional parameters for &%callout%& are as follows:
28468 .vitem <&'a&~time&~interval'&>
28469 .cindex "callout" "timeout, specifying"
28470 This specifies the timeout that applies for the callout attempt to each host.
28473 verify = sender/callout=5s
28475 The default is 30 seconds. The timeout is used for each response from the
28476 remote host. It is also used for the initial connection, unless overridden by
28477 the &%connect%& parameter.
28480 .vitem &*connect&~=&~*&<&'time&~interval'&>
28481 .cindex "callout" "connection timeout, specifying"
28482 This parameter makes it possible to set a different (usually smaller) timeout
28483 for making the SMTP connection. For example:
28485 verify = sender/callout=5s,connect=1s
28487 If not specified, this timeout defaults to the general timeout value.
28489 .vitem &*defer_ok*&
28490 .cindex "callout" "defer, action on"
28491 When this parameter is present, failure to contact any host, or any other kind
28492 of temporary error, is treated as success by the ACL. However, the cache is not
28493 updated in this circumstance.
28495 .vitem &*fullpostmaster*&
28496 .cindex "callout" "full postmaster check"
28497 This operates like the &%postmaster%& option (see below), but if the check for
28498 &'postmaster@domain'& fails, it tries just &'postmaster'&, without a domain, in
28499 accordance with the specification in RFC 2821. The RFC states that the
28500 unqualified address &'postmaster'& should be accepted.
28503 .vitem &*mailfrom&~=&~*&<&'email&~address'&>
28504 .cindex "callout" "sender when verifying header"
28505 When verifying addresses in header lines using the &%header_sender%&
28506 verification option, Exim behaves by default as if the addresses are envelope
28507 sender addresses from a message. Callout verification therefore tests to see
28508 whether a bounce message could be delivered, by using an empty address in the
28509 MAIL command. However, it is arguable that these addresses might never be used
28510 as envelope senders, and could therefore justifiably reject bounce messages
28511 (empty senders). The &%mailfrom%& callout parameter allows you to specify what
28512 address to use in the MAIL command. For example:
28514 require verify = header_sender/callout=mailfrom=abcd@x.y.z
28516 This parameter is available only for the &%header_sender%& verification option.
28519 .vitem &*maxwait&~=&~*&<&'time&~interval'&>
28520 .cindex "callout" "overall timeout, specifying"
28521 This parameter sets an overall timeout for performing a callout verification.
28524 verify = sender/callout=5s,maxwait=30s
28526 This timeout defaults to four times the callout timeout for individual SMTP
28527 commands. The overall timeout applies when there is more than one host that can
28528 be tried. The timeout is checked before trying the next host. This prevents
28529 very long delays if there are a large number of hosts and all are timing out
28530 (for example, when network connections are timing out).
28533 .vitem &*no_cache*&
28534 .cindex "callout" "cache, suppressing"
28535 .cindex "caching callout, suppressing"
28536 When this parameter is given, the callout cache is neither read nor updated.
28538 .vitem &*postmaster*&
28539 .cindex "callout" "postmaster; checking"
28540 When this parameter is set, a successful callout check is followed by a similar
28541 check for the local part &'postmaster'& at the same domain. If this address is
28542 rejected, the callout fails (but see &%fullpostmaster%& above). The result of
28543 the postmaster check is recorded in a cache record; if it is a failure, this is
28544 used to fail subsequent callouts for the domain without a connection being
28545 made, until the cache record expires.
28547 .vitem &*postmaster_mailfrom&~=&~*&<&'email&~address'&>
28548 The postmaster check uses an empty sender in the MAIL command by default.
28549 You can use this parameter to do a postmaster check using a different address.
28552 require verify = sender/callout=postmaster_mailfrom=abc@x.y.z
28554 If both &%postmaster%& and &%postmaster_mailfrom%& are present, the rightmost
28555 one overrides. The &%postmaster%& parameter is equivalent to this example:
28557 require verify = sender/callout=postmaster_mailfrom=
28559 &*Warning*&: The caching arrangements for postmaster checking do not take
28560 account of the sender address. It is assumed that either the empty address or
28561 a fixed non-empty address will be used. All that Exim remembers is that the
28562 postmaster check for the domain succeeded or failed.
28566 .cindex "callout" "&""random""& check"
28567 When this parameter is set, before doing the normal callout check, Exim does a
28568 check for a &"random"& local part at the same domain. The local part is not
28569 really random &-- it is defined by the expansion of the option
28570 &%callout_random_local_part%&, which defaults to
28572 $primary_hostname-$tod_epoch-testing
28574 The idea here is to try to determine whether the remote host accepts all local
28575 parts without checking. If it does, there is no point in doing callouts for
28576 specific local parts. If the &"random"& check succeeds, the result is saved in
28577 a cache record, and used to force the current and subsequent callout checks to
28578 succeed without a connection being made, until the cache record expires.
28580 .vitem &*use_postmaster*&
28581 .cindex "callout" "sender for recipient check"
28582 This parameter applies to recipient callouts only. For example:
28584 deny !verify = recipient/callout=use_postmaster
28586 .vindex "&$qualify_domain$&"
28587 It causes a non-empty postmaster address to be used in the MAIL command when
28588 performing the callout for the recipient, and also for a &"random"& check if
28589 that is configured. The local part of the address is &`postmaster`& and the
28590 domain is the contents of &$qualify_domain$&.
28592 .vitem &*use_sender*&
28593 This option applies to recipient callouts only. For example:
28595 require verify = recipient/callout=use_sender
28597 It causes the message's actual sender address to be used in the MAIL
28598 command when performing the callout, instead of an empty address. There is no
28599 need to use this option unless you know that the called hosts make use of the
28600 sender when checking recipients. If used indiscriminately, it reduces the
28601 usefulness of callout caching.
28604 If you use any of the parameters that set a non-empty sender for the MAIL
28605 command (&%mailfrom%&, &%postmaster_mailfrom%&, &%use_postmaster%&, or
28606 &%use_sender%&), you should think about possible loops. Recipient checking is
28607 usually done between two hosts that are under the same management, and the host
28608 that receives the callouts is not normally configured to do callouts itself.
28609 Therefore, it is normally safe to use &%use_postmaster%& or &%use_sender%& in
28610 these circumstances.
28612 However, if you use a non-empty sender address for a callout to an arbitrary
28613 host, there is the likelihood that the remote host will itself initiate a
28614 callout check back to your host. As it is checking what appears to be a message
28615 sender, it is likely to use an empty address in MAIL, thus avoiding a
28616 callout loop. However, to be on the safe side it would be best to set up your
28617 own ACLs so that they do not do sender verification checks when the recipient
28618 is the address you use for header sender or postmaster callout checking.
28620 Another issue to think about when using non-empty senders for callouts is
28621 caching. When you set &%mailfrom%& or &%use_sender%&, the cache record is keyed
28622 by the sender/recipient combination; thus, for any given recipient, many more
28623 actual callouts are performed than when an empty sender or postmaster is used.
28628 .section "Callout caching" "SECTcallvercache"
28629 .cindex "hints database" "callout cache"
28630 .cindex "callout" "cache, description of"
28631 .cindex "caching" "callout"
28632 Exim caches the results of callouts in order to reduce the amount of resources
28633 used, unless you specify the &%no_cache%& parameter with the &%callout%&
28634 option. A hints database called &"callout"& is used for the cache. Two
28635 different record types are used: one records the result of a callout check for
28636 a specific address, and the other records information that applies to the
28637 entire domain (for example, that it accepts the local part &'postmaster'&).
28639 When an original callout fails, a detailed SMTP error message is given about
28640 the failure. However, for subsequent failures use the cache data, this message
28643 The expiry times for negative and positive address cache records are
28644 independent, and can be set by the global options &%callout_negative_expire%&
28645 (default 2h) and &%callout_positive_expire%& (default 24h), respectively.
28647 If a host gives a negative response to an SMTP connection, or rejects any
28648 commands up to and including
28652 (but not including the MAIL command with a non-empty address),
28653 any callout attempt is bound to fail. Exim remembers such failures in a
28654 domain cache record, which it uses to fail callouts for the domain without
28655 making new connections, until the domain record times out. There are two
28656 separate expiry times for domain cache records:
28657 &%callout_domain_negative_expire%& (default 3h) and
28658 &%callout_domain_positive_expire%& (default 7d).
28660 Domain records expire when the negative expiry time is reached if callouts
28661 cannot be made for the domain, or if the postmaster check failed.
28662 Otherwise, they expire when the positive expiry time is reached. This
28663 ensures that, for example, a host that stops accepting &"random"& local parts
28664 will eventually be noticed.
28666 The callout caching mechanism is based on the domain of the address that is
28667 being tested. If the domain routes to several hosts, it is assumed that their
28668 behaviour will be the same.
28672 .section "Sender address verification reporting" "SECTsenaddver"
28673 .cindex "verifying" "suppressing error details"
28674 See section &<<SECTaddressverification>>& for a general discussion of
28675 verification. When sender verification fails in an ACL, the details of the
28676 failure are given as additional output lines before the 550 response to the
28677 relevant SMTP command (RCPT or DATA). For example, if sender callout is in use,
28680 MAIL FROM:<xyz@abc.example>
28682 RCPT TO:<pqr@def.example>
28683 550-Verification failed for <xyz@abc.example>
28684 550-Called: 192.168.34.43
28685 550-Sent: RCPT TO:<xyz@abc.example>
28686 550-Response: 550 Unknown local part xyz in <xyz@abc.example>
28687 550 Sender verification failed
28689 If more than one RCPT command fails in the same way, the details are given
28690 only for the first of them. However, some administrators do not want to send
28691 out this much information. You can suppress the details by adding
28692 &`/no_details`& to the ACL statement that requests sender verification. For
28695 verify = sender/no_details
28698 .section "Redirection while verifying" "SECTredirwhilveri"
28699 .cindex "verifying" "redirection while"
28700 .cindex "address redirection" "while verifying"
28701 A dilemma arises when a local address is redirected by aliasing or forwarding
28702 during verification: should the generated addresses themselves be verified,
28703 or should the successful expansion of the original address be enough to verify
28704 it? By default, Exim takes the following pragmatic approach:
28707 When an incoming address is redirected to just one child address, verification
28708 continues with the child address, and if that fails to verify, the original
28709 verification also fails.
28711 When an incoming address is redirected to more than one child address,
28712 verification does not continue. A success result is returned.
28715 This seems the most reasonable behaviour for the common use of aliasing as a
28716 way of redirecting different local parts to the same mailbox. It means, for
28717 example, that a pair of alias entries of the form
28720 aw123: :fail: Gone away, no forwarding address
28722 work as expected, with both local parts causing verification failure. When a
28723 redirection generates more than one address, the behaviour is more like a
28724 mailing list, where the existence of the alias itself is sufficient for
28725 verification to succeed.
28727 It is possible, however, to change the default behaviour so that all successful
28728 redirections count as successful verifications, however many new addresses are
28729 generated. This is specified by the &%success_on_redirect%& verification
28730 option. For example:
28732 require verify = recipient/success_on_redirect/callout=10s
28734 In this example, verification succeeds if a router generates a new address, and
28735 the callout does not occur, because no address was routed to a remote host.
28737 When verification is being tested via the &%-bv%& option, the treatment of
28738 redirections is as just described, unless the &%-v%& or any debugging option is
28739 also specified. In that case, full verification is done for every generated
28740 address and a report is output for each of them.
28744 .section "Client SMTP authorization (CSA)" "SECTverifyCSA"
28745 .cindex "CSA" "verifying"
28746 Client SMTP Authorization is a system that allows a site to advertise
28747 which machines are and are not permitted to send email. This is done by placing
28748 special SRV records in the DNS; these are looked up using the client's HELO
28749 domain. At the time of writing, CSA is still an Internet Draft. Client SMTP
28750 Authorization checks in Exim are performed by the ACL condition:
28754 This fails if the client is not authorized. If there is a DNS problem, or if no
28755 valid CSA SRV record is found, or if the client is authorized, the condition
28756 succeeds. These three cases can be distinguished using the expansion variable
28757 &$csa_status$&, which can take one of the values &"fail"&, &"defer"&,
28758 &"unknown"&, or &"ok"&. The condition does not itself defer because that would
28759 be likely to cause problems for legitimate email.
28761 The error messages produced by the CSA code include slightly more
28762 detail. If &$csa_status$& is &"defer"&, this may be because of problems
28763 looking up the CSA SRV record, or problems looking up the CSA target
28764 address record. There are four reasons for &$csa_status$& being &"fail"&:
28767 The client's host name is explicitly not authorized.
28769 The client's IP address does not match any of the CSA target IP addresses.
28771 The client's host name is authorized but it has no valid target IP addresses
28772 (for example, the target's addresses are IPv6 and the client is using IPv4).
28774 The client's host name has no CSA SRV record but a parent domain has asserted
28775 that all subdomains must be explicitly authorized.
28778 The &%csa%& verification condition can take an argument which is the domain to
28779 use for the DNS query. The default is:
28781 verify = csa/$sender_helo_name
28783 This implementation includes an extension to CSA. If the query domain
28784 is an address literal such as [192.0.2.95], or if it is a bare IP
28785 address, Exim searches for CSA SRV records in the reverse DNS as if
28786 the HELO domain was (for example) &'95.2.0.192.in-addr.arpa'&. Therefore it is
28789 verify = csa/$sender_host_address
28791 In fact, this is the check that Exim performs if the client does not say HELO.
28792 This extension can be turned off by setting the main configuration option
28793 &%dns_csa_use_reverse%& to be false.
28795 If a CSA SRV record is not found for the domain itself, a search
28796 is performed through its parent domains for a record which might be
28797 making assertions about subdomains. The maximum depth of this search is limited
28798 using the main configuration option &%dns_csa_search_limit%&, which is 5 by
28799 default. Exim does not look for CSA SRV records in a top level domain, so the
28800 default settings handle HELO domains as long as seven
28801 (&'hostname.five.four.three.two.one.com'&). This encompasses the vast majority
28802 of legitimate HELO domains.
28804 The &'dnsdb'& lookup also has support for CSA. Although &'dnsdb'& also supports
28805 direct SRV lookups, this is not sufficient because of the extra parent domain
28806 search behaviour of CSA, and (as with PTR lookups) &'dnsdb'& also turns IP
28807 addresses into lookups in the reverse DNS space. The result of a successful
28810 ${lookup dnsdb {csa=$sender_helo_name}}
28812 has two space-separated fields: an authorization code and a target host name.
28813 The authorization code can be &"Y"& for yes, &"N"& for no, &"X"& for explicit
28814 authorization required but absent, or &"?"& for unknown.
28819 .section "Bounce address tag validation" "SECTverifyPRVS"
28820 .cindex "BATV, verifying"
28821 Bounce address tag validation (BATV) is a scheme whereby the envelope senders
28822 of outgoing messages have a cryptographic, timestamped &"tag"& added to them.
28823 Genuine incoming bounce messages should therefore always be addressed to
28824 recipients that have a valid tag. This scheme is a way of detecting unwanted
28825 bounce messages caused by sender address forgeries (often called &"collateral
28826 spam"&), because the recipients of such messages do not include valid tags.
28828 There are two expansion items to help with the implementation of the BATV
28829 &"prvs"& (private signature) scheme in an Exim configuration. This scheme signs
28830 the original envelope sender address by using a simple key to add a hash of the
28831 address and some time-based randomizing information. The &%prvs%& expansion
28832 item creates a signed address, and the &%prvscheck%& expansion item checks one.
28833 The syntax of these expansion items is described in section
28834 &<<SECTexpansionitems>>&.
28836 As an example, suppose the secret per-address keys are stored in an MySQL
28837 database. A query to look up the key for an address could be defined as a macro
28840 PRVSCHECK_SQL = ${lookup mysql{SELECT secret FROM batv_prvs \
28841 WHERE sender='${quote_mysql:$prvscheck_address}'\
28844 Suppose also that the senders who make use of BATV are defined by an address
28845 list called &%batv_senders%&. Then, in the ACL for RCPT commands, you could
28848 # Bounces: drop unsigned addresses for BATV senders
28849 deny message = This address does not send an unsigned reverse path
28851 recipients = +batv_senders
28853 # Bounces: In case of prvs-signed address, check signature.
28854 deny message = Invalid reverse path signature.
28856 condition = ${prvscheck {$local_part@$domain}\
28857 {PRVSCHECK_SQL}{1}}
28858 !condition = $prvscheck_result
28860 The first statement rejects recipients for bounce messages that are addressed
28861 to plain BATV sender addresses, because it is known that BATV senders do not
28862 send out messages with plain sender addresses. The second statement rejects
28863 recipients that are prvs-signed, but with invalid signatures (either because
28864 the key is wrong, or the signature has timed out).
28866 A non-prvs-signed address is not rejected by the second statement, because the
28867 &%prvscheck%& expansion yields an empty string if its first argument is not a
28868 prvs-signed address, thus causing the &%condition%& condition to be false. If
28869 the first argument is a syntactically valid prvs-signed address, the yield is
28870 the third string (in this case &"1"&), whether or not the cryptographic and
28871 timeout checks succeed. The &$prvscheck_result$& variable contains the result
28872 of the checks (empty for failure, &"1"& for success).
28874 There is one more issue you must consider when implementing prvs-signing:
28875 you have to ensure that the routers accept prvs-signed addresses and
28876 deliver them correctly. The easiest way to handle this is to use a &(redirect)&
28877 router to remove the signature with a configuration along these lines:
28881 data = ${prvscheck {$local_part@$domain}{PRVSCHECK_SQL}}
28883 This works because, if the third argument of &%prvscheck%& is empty, the result
28884 of the expansion of a prvs-signed address is the decoded value of the original
28885 address. This router should probably be the first of your routers that handles
28888 To create BATV-signed addresses in the first place, a transport of this form
28891 external_smtp_batv:
28893 return_path = ${prvs {$return_path} \
28894 {${lookup mysql{SELECT \
28895 secret FROM batv_prvs WHERE \
28896 sender='${quote_mysql:$sender_address}'} \
28899 If no key can be found for the existing return path, no signing takes place.
28903 .section "Using an ACL to control relaying" "SECTrelaycontrol"
28904 .cindex "&ACL;" "relay control"
28905 .cindex "relaying" "control by ACL"
28906 .cindex "policy control" "relay control"
28907 An MTA is said to &'relay'& a message if it receives it from some host and
28908 delivers it directly to another host as a result of a remote address contained
28909 within it. Redirecting a local address via an alias or forward file and then
28910 passing the message on to another host is not relaying,
28911 .cindex "&""percent hack""&"
28912 but a redirection as a result of the &"percent hack"& is.
28914 Two kinds of relaying exist, which are termed &"incoming"& and &"outgoing"&.
28915 A host which is acting as a gateway or an MX backup is concerned with incoming
28916 relaying from arbitrary hosts to a specific set of domains. On the other hand,
28917 a host which is acting as a smart host for a number of clients is concerned
28918 with outgoing relaying from those clients to the Internet at large. Often the
28919 same host is fulfilling both functions,
28921 . as illustrated in the diagram below,
28923 but in principle these two kinds of relaying are entirely independent. What is
28924 not wanted is the transmission of mail from arbitrary remote hosts through your
28925 system to arbitrary domains.
28928 You can implement relay control by means of suitable statements in the ACL that
28929 runs for each RCPT command. For convenience, it is often easiest to use
28930 Exim's named list facility to define the domains and hosts involved. For
28931 example, suppose you want to do the following:
28934 Deliver a number of domains to mailboxes on the local host (or process them
28935 locally in some other way). Let's say these are &'my.dom1.example'& and
28936 &'my.dom2.example'&.
28938 Relay mail for a number of other domains for which you are the secondary MX.
28939 These might be &'friend1.example'& and &'friend2.example'&.
28941 Relay mail from the hosts on your local LAN, to whatever domains are involved.
28942 Suppose your LAN is 192.168.45.0/24.
28946 In the main part of the configuration, you put the following definitions:
28948 domainlist local_domains = my.dom1.example : my.dom2.example
28949 domainlist relay_domains = friend1.example : friend2.example
28950 hostlist relay_hosts = 192.168.45.0/24
28952 Now you can use these definitions in the ACL that is run for every RCPT
28956 accept domains = +local_domains : +relay_domains
28957 accept hosts = +relay_hosts
28959 The first statement accepts any RCPT command that contains an address in
28960 the local or relay domains. For any other domain, control passes to the second
28961 statement, which accepts the command only if it comes from one of the relay
28962 hosts. In practice, you will probably want to make your ACL more sophisticated
28963 than this, for example, by including sender and recipient verification. The
28964 default configuration includes a more comprehensive example, which is described
28965 in chapter &<<CHAPdefconfil>>&.
28969 .section "Checking a relay configuration" "SECTcheralcon"
28970 .cindex "relaying" "checking control of"
28971 You can check the relay characteristics of your configuration in the same way
28972 that you can test any ACL behaviour for an incoming SMTP connection, by using
28973 the &%-bh%& option to run a fake SMTP session with which you interact.
28975 For specifically testing for unwanted relaying, the host
28976 &'relay-test.mail-abuse.org'& provides a useful service. If you telnet to this
28977 host from the host on which Exim is running, using the normal telnet port, you
28978 will see a normal telnet connection message and then quite a long delay. Be
28979 patient. The remote host is making an SMTP connection back to your host, and
28980 trying a number of common probes to test for open relay vulnerability. The
28981 results of the tests will eventually appear on your terminal.
28986 . ////////////////////////////////////////////////////////////////////////////
28987 . ////////////////////////////////////////////////////////////////////////////
28989 .chapter "Content scanning at ACL time" "CHAPexiscan"
28990 .scindex IIDcosca "content scanning" "at ACL time"
28991 The extension of Exim to include content scanning at ACL time, formerly known
28992 as &"exiscan"&, was originally implemented as a patch by Tom Kistner. The code
28993 was integrated into the main source for Exim release 4.50, and Tom continues to
28994 maintain it. Most of the wording of this chapter is taken from Tom's
28997 It is also possible to scan the content of messages at other times. The
28998 &[local_scan()]& function (see chapter &<<CHAPlocalscan>>&) allows for content
28999 scanning after all the ACLs have run. A transport filter can be used to scan
29000 messages at delivery time (see the &%transport_filter%& option, described in
29001 chapter &<<CHAPtransportgeneric>>&).
29003 If you want to include the ACL-time content-scanning features when you compile
29004 Exim, you need to arrange for WITH_CONTENT_SCAN to be defined in your
29005 &_Local/Makefile_&. When you do that, the Exim binary is built with:
29008 Two additional ACLs (&%acl_smtp_mime%& and &%acl_not_smtp_mime%&) that are run
29009 for all MIME parts for SMTP and non-SMTP messages, respectively.
29011 Additional ACL conditions and modifiers: &%decode%&, &%malware%&,
29012 &%mime_regex%&, &%regex%&, and &%spam%&. These can be used in the ACL that is
29013 run at the end of message reception (the &%acl_smtp_data%& ACL).
29015 An additional control feature (&"no_mbox_unspool"&) that saves spooled copies
29016 of messages, or parts of messages, for debugging purposes.
29018 Additional expansion variables that are set in the new ACL and by the new
29021 Two new main configuration options: &%av_scanner%& and &%spamd_address%&.
29024 There is another content-scanning configuration option for &_Local/Makefile_&,
29025 called WITH_OLD_DEMIME. If this is set, the old, deprecated &%demime%& ACL
29026 condition is compiled, in addition to all the other content-scanning features.
29028 Content-scanning is continually evolving, and new features are still being
29029 added. While such features are still unstable and liable to incompatible
29030 changes, they are made available in Exim by setting options whose names begin
29031 EXPERIMENTAL_ in &_Local/Makefile_&. Such features are not documented in
29032 this manual. You can find out about them by reading the file called
29033 &_doc/experimental.txt_&.
29035 All the content-scanning facilities work on a MBOX copy of the message that is
29036 temporarily created in a file called:
29038 <&'spool_directory'&>&`/scan/`&<&'message_id'&>/<&'message_id'&>&`.eml`&
29040 The &_.eml_& extension is a friendly hint to virus scanners that they can
29041 expect an MBOX-like structure inside that file. The file is created when the
29042 first content scanning facility is called. Subsequent calls to content
29043 scanning conditions open the same file again. The directory is recursively
29044 removed when the &%acl_smtp_data%& ACL has finished running, unless
29046 control = no_mbox_unspool
29048 has been encountered. When the MIME ACL decodes files, they are put into the
29049 same directory by default.
29053 .section "Scanning for viruses" "SECTscanvirus"
29054 .cindex "virus scanning"
29055 .cindex "content scanning" "for viruses"
29056 .cindex "content scanning" "the &%malware%& condition"
29057 The &%malware%& ACL condition lets you connect virus scanner software to Exim.
29058 It supports a &"generic"& interface to scanners called via the shell, and
29059 specialized interfaces for &"daemon"& type virus scanners, which are resident
29060 in memory and thus are much faster.
29063 .oindex "&%av_scanner%&"
29064 You can set the &%av_scanner%& option in first part of the Exim configuration
29065 file to specify which scanner to use, together with any additional options that
29066 are needed. The basic syntax is as follows:
29068 &`av_scanner = <`&&'scanner-type'&&`>:<`&&'option1'&&`>:<`&&'option2'&&`>:[...]`&
29070 If you do not set &%av_scanner%&, it defaults to
29072 av_scanner = sophie:/var/run/sophie
29074 If the value of &%av_scanner%& starts with a dollar character, it is expanded
29075 before use. The following scanner types are supported in this release:
29078 .vitem &%aveserver%&
29079 .cindex "virus scanners" "Kaspersky"
29080 This is the scanner daemon of Kaspersky Version 5. You can get a trial version
29081 at &url(http://www.kaspersky.com). This scanner type takes one option,
29082 which is the path to the daemon's UNIX socket. The default is shown in this
29085 av_scanner = aveserver:/var/run/aveserver
29090 .cindex "virus scanners" "clamd"
29091 This daemon-type scanner is GPL and free. You can get it at
29092 &url(http://www.clamav.net/). Some older versions of clamd do not seem to
29093 unpack MIME containers, so it used to be recommended to unpack MIME attachments
29094 in the MIME ACL. This no longer believed to be necessary. One option is
29095 required: either the path and name of a UNIX socket file, or a hostname or IP
29096 number, and a port, separated by space, as in the second of these examples:
29098 av_scanner = clamd:/opt/clamd/socket
29099 av_scanner = clamd:192.0.2.3 1234
29100 av_scanner = clamd:192.0.2.3 1234:local
29102 If the value of av_scanner points to a UNIX socket file or contains the local
29103 keyword, then the ClamAV interface will pass a filename containing the data
29104 to be scanned, which will should normally result in less I/O happening and be
29105 more efficient. Normally in the TCP case, the data is streamed to ClamAV as
29106 Exim does not assume that there is a common filesystem with the remote host.
29107 There is an option WITH_OLD_CLAMAV_STREAM in &_src/EDITME_& available, should
29108 you be running a version of ClamAV prior to 0.95.
29109 If the option is unset, the default is &_/tmp/clamd_&. Thanks to David Saez for
29110 contributing the code for this scanner.
29113 .cindex "virus scanners" "command line interface"
29114 This is the keyword for the generic command line scanner interface. It can be
29115 used to attach virus scanners that are invoked from the shell. This scanner
29116 type takes 3 mandatory options:
29119 The full path and name of the scanner binary, with all command line options,
29120 and a placeholder (&`%s`&) for the directory to scan.
29123 A regular expression to match against the STDOUT and STDERR output of the
29124 virus scanner. If the expression matches, a virus was found. You must make
29125 absolutely sure that this expression matches on &"virus found"&. This is called
29126 the &"trigger"& expression.
29129 Another regular expression, containing exactly one pair of parentheses, to
29130 match the name of the virus found in the scanners output. This is called the
29131 &"name"& expression.
29134 For example, Sophos Sweep reports a virus on a line like this:
29136 Virus 'W32/Magistr-B' found in file ./those.bat
29138 For the trigger expression, we can match the phrase &"found in file"&. For the
29139 name expression, we want to extract the W32/Magistr-B string, so we can match
29140 for the single quotes left and right of it. Altogether, this makes the
29141 configuration setting:
29143 av_scanner = cmdline:\
29144 /path/to/sweep -ss -all -rec -archive %s:\
29145 found in file:'(.+)'
29148 .cindex "virus scanners" "DrWeb"
29149 The DrWeb daemon scanner (&url(http://www.sald.com/)) interface takes one
29150 argument, either a full path to a UNIX socket, or an IP address and port
29151 separated by white space, as in these examples:
29153 av_scanner = drweb:/var/run/drwebd.sock
29154 av_scanner = drweb:192.168.2.20 31337
29156 If you omit the argument, the default path &_/usr/local/drweb/run/drwebd.sock_&
29157 is used. Thanks to Alex Miller for contributing the code for this scanner.
29160 .cindex "virus scanners" "F-Secure"
29161 The F-Secure daemon scanner (&url(http://www.f-secure.com)) takes one
29162 argument which is the path to a UNIX socket. For example:
29164 av_scanner = fsecure:/path/to/.fsav
29166 If no argument is given, the default is &_/var/run/.fsav_&. Thanks to Johan
29167 Thelmen for contributing the code for this scanner.
29169 .vitem &%kavdaemon%&
29170 .cindex "virus scanners" "Kaspersky"
29171 This is the scanner daemon of Kaspersky Version 4. This version of the
29172 Kaspersky scanner is outdated. Please upgrade (see &%aveserver%& above). This
29173 scanner type takes one option, which is the path to the daemon's UNIX socket.
29176 av_scanner = kavdaemon:/opt/AVP/AvpCtl
29178 The default path is &_/var/run/AvpCtl_&.
29181 .cindex "virus scanners" "mksd"
29182 This is a daemon type scanner that is aimed mainly at Polish users, though some
29183 parts of documentation are now available in English. You can get it at
29184 &url(http://linux.mks.com.pl/). The only option for this scanner type is
29185 the maximum number of processes used simultaneously to scan the attachments,
29186 provided that the demime facility is employed and also provided that mksd has
29187 been run with at least the same number of child processes. For example:
29189 av_scanner = mksd:2
29191 You can safely omit this option (the default value is 1).
29194 .cindex "virus scanners" "Sophos and Sophie"
29195 Sophie is a daemon that uses Sophos' &%libsavi%& library to scan for viruses.
29196 You can get Sophie at &url(http://www.clanfield.info/sophie/). The only option
29197 for this scanner type is the path to the UNIX socket that Sophie uses for
29198 client communication. For example:
29200 av_scanner = sophie:/tmp/sophie
29202 The default path is &_/var/run/sophie_&, so if you are using this, you can omit
29206 When &%av_scanner%& is correctly set, you can use the &%malware%& condition in
29207 the DATA ACL. &*Note*&: You cannot use the &%malware%& condition in the MIME
29210 The &%av_scanner%& option is expanded each time &%malware%& is called. This
29211 makes it possible to use different scanners. See further below for an example.
29212 The &%malware%& condition caches its results, so when you use it multiple times
29213 for the same message, the actual scanning process is only carried out once.
29214 However, using expandable items in &%av_scanner%& disables this caching, in
29215 which case each use of the &%malware%& condition causes a new scan of the
29218 The &%malware%& condition takes a right-hand argument that is expanded before
29219 use. It can then be one of
29222 &"true"&, &"*"&, or &"1"&, in which case the message is scanned for viruses.
29223 The condition succeeds if a virus was found, and fail otherwise. This is the
29226 &"false"& or &"0"& or an empty string, in which case no scanning is done and
29227 the condition fails immediately.
29229 A regular expression, in which case the message is scanned for viruses. The
29230 condition succeeds if a virus is found and its name matches the regular
29231 expression. This allows you to take special actions on certain types of virus.
29234 You can append &`/defer_ok`& to the &%malware%& condition to accept messages
29235 even if there is a problem with the virus scanner. Otherwise, such a problem
29236 causes the ACL to defer.
29238 .vindex "&$malware_name$&"
29239 When a virus is found, the condition sets up an expansion variable called
29240 &$malware_name$& that contains the name of the virus. You can use it in a
29241 &%message%& modifier that specifies the error returned to the sender, and/or in
29244 If your virus scanner cannot unpack MIME and TNEF containers itself, you should
29245 use the &%demime%& condition (see section &<<SECTdemimecond>>&) before the
29246 &%malware%& condition.
29248 Beware the interaction of Exim's &%message_size_limit%& with any size limits
29249 imposed by your anti-virus scanner.
29251 Here is a very simple scanning example:
29253 deny message = This message contains malware ($malware_name)
29257 The next example accepts messages when there is a problem with the scanner:
29259 deny message = This message contains malware ($malware_name)
29261 malware = */defer_ok
29263 The next example shows how to use an ACL variable to scan with both sophie and
29264 aveserver. It assumes you have set:
29266 av_scanner = $acl_m0
29268 in the main Exim configuration.
29270 deny message = This message contains malware ($malware_name)
29271 set acl_m0 = sophie
29274 deny message = This message contains malware ($malware_name)
29275 set acl_m0 = aveserver
29280 .section "Scanning with SpamAssassin" "SECTscanspamass"
29281 .cindex "content scanning" "for spam"
29282 .cindex "spam scanning"
29283 .cindex "SpamAssassin"
29284 The &%spam%& ACL condition calls SpamAssassin's &%spamd%& daemon to get a spam
29285 score and a report for the message. You can get SpamAssassin at
29286 &url(http://www.spamassassin.org), or, if you have a working Perl
29287 installation, you can use CPAN by running:
29289 perl -MCPAN -e 'install Mail::SpamAssassin'
29291 SpamAssassin has its own set of configuration files. Please review its
29292 documentation to see how you can tweak it. The default installation should work
29295 .oindex "&%spamd_address%&"
29296 After having installed and configured SpamAssassin, start the &%spamd%& daemon.
29297 By default, it listens on 127.0.0.1, TCP port 783. If you use another host or
29298 port for &%spamd%&, you must set the &%spamd_address%& option in the global
29299 part of the Exim configuration as follows (example):
29301 spamd_address = 192.168.99.45 387
29303 You do not need to set this option if you use the default. As of version 2.60,
29304 &%spamd%& also supports communication over UNIX sockets. If you want to use
29305 these, supply &%spamd_address%& with an absolute file name instead of a
29308 spamd_address = /var/run/spamd_socket
29310 You can have multiple &%spamd%& servers to improve scalability. These can
29311 reside on other hardware reachable over the network. To specify multiple
29312 &%spamd%& servers, put multiple address/port pairs in the &%spamd_address%&
29313 option, separated with colons:
29315 spamd_address = 192.168.2.10 783 : \
29316 192.168.2.11 783 : \
29319 Up to 32 &%spamd%& servers are supported. The servers are queried in a random
29320 fashion. When a server fails to respond to the connection attempt, all other
29321 servers are tried until one succeeds. If no server responds, the &%spam%&
29324 &*Warning*&: It is not possible to use the UNIX socket connection method with
29325 multiple &%spamd%& servers.
29327 The &%spamd_address%& variable is expanded before use if it starts with
29328 a dollar sign. In this case, the expansion may return a string that is
29329 used as the list so that multiple spamd servers can be the result of an
29332 .section "Calling SpamAssassin from an Exim ACL" "SECID206"
29333 Here is a simple example of the use of the &%spam%& condition in a DATA ACL:
29335 deny message = This message was classified as SPAM
29338 The right-hand side of the &%spam%& condition specifies a name. This is
29339 relevant if you have set up multiple SpamAssassin profiles. If you do not want
29340 to scan using a specific profile, but rather use the SpamAssassin system-wide
29341 default profile, you can scan for an unknown name, or simply use &"nobody"&.
29342 However, you must put something on the right-hand side.
29344 The name allows you to use per-domain or per-user antispam profiles in
29345 principle, but this is not straightforward in practice, because a message may
29346 have multiple recipients, not necessarily all in the same domain. Because the
29347 &%spam%& condition has to be called from a DATA ACL in order to be able to
29348 read the contents of the message, the variables &$local_part$& and &$domain$&
29351 The right-hand side of the &%spam%& condition is expanded before being used, so
29352 you can put lookups or conditions there. When the right-hand side evaluates to
29353 &"0"& or &"false"&, no scanning is done and the condition fails immediately.
29356 Scanning with SpamAssassin uses a lot of resources. If you scan every message,
29357 large ones may cause significant performance degradation. As most spam messages
29358 are quite small, it is recommended that you do not scan the big ones. For
29361 deny message = This message was classified as SPAM
29362 condition = ${if < {$message_size}{10K}}
29366 The &%spam%& condition returns true if the threshold specified in the user's
29367 SpamAssassin profile has been matched or exceeded. If you want to use the
29368 &%spam%& condition for its side effects (see the variables below), you can make
29369 it always return &"true"& by appending &`:true`& to the username.
29371 .cindex "spam scanning" "returned variables"
29372 When the &%spam%& condition is run, it sets up a number of expansion
29373 variables. These variables are saved with the received message, thus they are
29374 available for use at delivery time.
29377 .vitem &$spam_score$&
29378 The spam score of the message, for example &"3.4"& or &"30.5"&. This is useful
29379 for inclusion in log or reject messages.
29381 .vitem &$spam_score_int$&
29382 The spam score of the message, multiplied by ten, as an integer value. For
29383 example &"34"& or &"305"&. It may appear to disagree with &$spam_score$&
29384 because &$spam_score$& is rounded and &$spam_score_int$& is truncated.
29385 The integer value is useful for numeric comparisons in conditions.
29387 .vitem &$spam_bar$&
29388 A string consisting of a number of &"+"& or &"-"& characters, representing the
29389 integer part of the spam score value. A spam score of 4.4 would have a
29390 &$spam_bar$& value of &"++++"&. This is useful for inclusion in warning
29391 headers, since MUAs can match on such strings.
29393 .vitem &$spam_report$&
29394 A multiline text table, containing the full SpamAssassin report for the
29395 message. Useful for inclusion in headers or reject messages.
29398 The &%spam%& condition caches its results unless expansion in
29399 spamd_address was used. If you call it again with the same user name, it
29400 does not scan again, but rather returns the same values as before.
29402 The &%spam%& condition returns DEFER if there is any error while running
29403 the message through SpamAssassin or if the expansion of spamd_address
29404 failed. If you want to treat DEFER as FAIL (to pass on to the next ACL
29405 statement block), append &`/defer_ok`& to the right-hand side of the
29406 spam condition, like this:
29408 deny message = This message was classified as SPAM
29409 spam = joe/defer_ok
29411 This causes messages to be accepted even if there is a problem with &%spamd%&.
29413 Here is a longer, commented example of the use of the &%spam%&
29416 # put headers in all messages (no matter if spam or not)
29417 warn spam = nobody:true
29418 add_header = X-Spam-Score: $spam_score ($spam_bar)
29419 add_header = X-Spam-Report: $spam_report
29421 # add second subject line with *SPAM* marker when message
29422 # is over threshold
29424 add_header = Subject: *SPAM* $h_Subject:
29426 # reject spam at high scores (> 12)
29427 deny message = This message scored $spam_score spam points.
29429 condition = ${if >{$spam_score_int}{120}{1}{0}}
29434 .section "Scanning MIME parts" "SECTscanmimepart"
29435 .cindex "content scanning" "MIME parts"
29436 .cindex "MIME content scanning"
29437 .oindex "&%acl_smtp_mime%&"
29438 .oindex "&%acl_not_smtp_mime%&"
29439 The &%acl_smtp_mime%& global option specifies an ACL that is called once for
29440 each MIME part of an SMTP message, including multipart types, in the sequence
29441 of their position in the message. Similarly, the &%acl_not_smtp_mime%& option
29442 specifies an ACL that is used for the MIME parts of non-SMTP messages. These
29443 options may both refer to the same ACL if you want the same processing in both
29446 These ACLs are called (possibly many times) just before the &%acl_smtp_data%&
29447 ACL in the case of an SMTP message, or just before the &%acl_not_smtp%& ACL in
29448 the case of a non-SMTP message. However, a MIME ACL is called only if the
29449 message contains a &'Content-Type:'& header line. When a call to a MIME
29450 ACL does not yield &"accept"&, ACL processing is aborted and the appropriate
29451 result code is sent to the client. In the case of an SMTP message, the
29452 &%acl_smtp_data%& ACL is not called when this happens.
29454 You cannot use the &%malware%& or &%spam%& conditions in a MIME ACL; these can
29455 only be used in the DATA or non-SMTP ACLs. However, you can use the &%regex%&
29456 condition to match against the raw MIME part. You can also use the
29457 &%mime_regex%& condition to match against the decoded MIME part (see section
29458 &<<SECTscanregex>>&).
29460 At the start of a MIME ACL, a number of variables are set from the header
29461 information for the relevant MIME part. These are described below. The contents
29462 of the MIME part are not by default decoded into a disk file except for MIME
29463 parts whose content-type is &"message/rfc822"&. If you want to decode a MIME
29464 part into a disk file, you can use the &%decode%& condition. The general
29467 &`decode = [/`&<&'path'&>&`/]`&<&'filename'&>
29469 The right hand side is expanded before use. After expansion,
29473 &"0"& or &"false"&, in which case no decoding is done.
29475 The string &"default"&. In that case, the file is put in the temporary
29476 &"default"& directory <&'spool_directory'&>&_/scan/_&<&'message_id'&>&_/_& with
29477 a sequential file name consisting of the message id and a sequence number. The
29478 full path and name is available in &$mime_decoded_filename$& after decoding.
29480 A full path name starting with a slash. If the full name is an existing
29481 directory, it is used as a replacement for the default directory. The filename
29482 is then sequentially assigned. If the path does not exist, it is used as
29483 the full path and file name.
29485 If the string does not start with a slash, it is used as the
29486 filename, and the default path is then used.
29488 The &%decode%& condition normally succeeds. It is only false for syntax
29489 errors or unusual circumstances such as memory shortages. You can easily decode
29490 a file with its original, proposed filename using
29492 decode = $mime_filename
29494 However, you should keep in mind that &$mime_filename$& might contain
29495 anything. If you place files outside of the default path, they are not
29496 automatically unlinked.
29498 For RFC822 attachments (these are messages attached to messages, with a
29499 content-type of &"message/rfc822"&), the ACL is called again in the same manner
29500 as for the primary message, only that the &$mime_is_rfc822$& expansion
29501 variable is set (see below). Attached messages are always decoded to disk
29502 before being checked, and the files are unlinked once the check is done.
29504 The MIME ACL supports the &%regex%& and &%mime_regex%& conditions. These can be
29505 used to match regular expressions against raw and decoded MIME parts,
29506 respectively. They are described in section &<<SECTscanregex>>&.
29508 .cindex "MIME content scanning" "returned variables"
29509 The following list describes all expansion variables that are
29510 available in the MIME ACL:
29513 .vitem &$mime_boundary$&
29514 If the current part is a multipart (see &$mime_is_multipart$&) below, it should
29515 have a boundary string, which is stored in this variable. If the current part
29516 has no boundary parameter in the &'Content-Type:'& header, this variable
29517 contains the empty string.
29519 .vitem &$mime_charset$&
29520 This variable contains the character set identifier, if one was found in the
29521 &'Content-Type:'& header. Examples for charset identifiers are:
29527 Please note that this value is not normalized, so you should do matches
29528 case-insensitively.
29530 .vitem &$mime_content_description$&
29531 This variable contains the normalized content of the &'Content-Description:'&
29532 header. It can contain a human-readable description of the parts content. Some
29533 implementations repeat the filename for attachments here, but they are usually
29534 only used for display purposes.
29536 .vitem &$mime_content_disposition$&
29537 This variable contains the normalized content of the &'Content-Disposition:'&
29538 header. You can expect strings like &"attachment"& or &"inline"& here.
29540 .vitem &$mime_content_id$&
29541 This variable contains the normalized content of the &'Content-ID:'& header.
29542 This is a unique ID that can be used to reference a part from another part.
29544 .vitem &$mime_content_size$&
29545 This variable is set only after the &%decode%& modifier (see above) has been
29546 successfully run. It contains the size of the decoded part in kilobytes. The
29547 size is always rounded up to full kilobytes, so only a completely empty part
29548 has a &$mime_content_size$& of zero.
29550 .vitem &$mime_content_transfer_encoding$&
29551 This variable contains the normalized content of the
29552 &'Content-transfer-encoding:'& header. This is a symbolic name for an encoding
29553 type. Typical values are &"base64"& and &"quoted-printable"&.
29555 .vitem &$mime_content_type$&
29556 If the MIME part has a &'Content-Type:'& header, this variable contains its
29557 value, lowercased, and without any options (like &"name"& or &"charset"&). Here
29558 are some examples of popular MIME types, as they may appear in this variable:
29562 application/octet-stream
29566 If the MIME part has no &'Content-Type:'& header, this variable contains the
29569 .vitem &$mime_decoded_filename$&
29570 This variable is set only after the &%decode%& modifier (see above) has been
29571 successfully run. It contains the full path and file name of the file
29572 containing the decoded data.
29577 .vitem &$mime_filename$&
29578 This is perhaps the most important of the MIME variables. It contains a
29579 proposed filename for an attachment, if one was found in either the
29580 &'Content-Type:'& or &'Content-Disposition:'& headers. The filename will be
29581 RFC2047 decoded, but no additional sanity checks are done. If no filename was
29582 found, this variable contains the empty string.
29584 .vitem &$mime_is_coverletter$&
29585 This variable attempts to differentiate the &"cover letter"& of an e-mail from
29586 attached data. It can be used to clamp down on flashy or unnecessarily encoded
29587 content in the cover letter, while not restricting attachments at all.
29589 The variable contains 1 (true) for a MIME part believed to be part of the
29590 cover letter, and 0 (false) for an attachment. At present, the algorithm is as
29594 The outermost MIME part of a message is always a cover letter.
29597 If a multipart/alternative or multipart/related MIME part is a cover letter,
29598 so are all MIME subparts within that multipart.
29601 If any other multipart is a cover letter, the first subpart is a cover letter,
29602 and the rest are attachments.
29605 All parts contained within an attachment multipart are attachments.
29608 As an example, the following will ban &"HTML mail"& (including that sent with
29609 alternative plain text), while allowing HTML files to be attached. HTML
29610 coverletter mail attached to non-HMTL coverletter mail will also be allowed:
29612 deny message = HTML mail is not accepted here
29613 !condition = $mime_is_rfc822
29614 condition = $mime_is_coverletter
29615 condition = ${if eq{$mime_content_type}{text/html}{1}{0}}
29617 .vitem &$mime_is_multipart$&
29618 This variable has the value 1 (true) when the current part has the main type
29619 &"multipart"&, for example &"multipart/alternative"& or &"multipart/mixed"&.
29620 Since multipart entities only serve as containers for other parts, you may not
29621 want to carry out specific actions on them.
29623 .vitem &$mime_is_rfc822$&
29624 This variable has the value 1 (true) if the current part is not a part of the
29625 checked message itself, but part of an attached message. Attached message
29626 decoding is fully recursive.
29628 .vitem &$mime_part_count$&
29629 This variable is a counter that is raised for each processed MIME part. It
29630 starts at zero for the very first part (which is usually a multipart). The
29631 counter is per-message, so it is reset when processing RFC822 attachments (see
29632 &$mime_is_rfc822$&). The counter stays set after &%acl_smtp_mime%& is
29633 complete, so you can use it in the DATA ACL to determine the number of MIME
29634 parts of a message. For non-MIME messages, this variable contains the value -1.
29639 .section "Scanning with regular expressions" "SECTscanregex"
29640 .cindex "content scanning" "with regular expressions"
29641 .cindex "regular expressions" "content scanning with"
29642 You can specify your own custom regular expression matches on the full body of
29643 the message, or on individual MIME parts.
29645 The &%regex%& condition takes one or more regular expressions as arguments and
29646 matches them against the full message (when called in the DATA ACL) or a raw
29647 MIME part (when called in the MIME ACL). The &%regex%& condition matches
29648 linewise, with a maximum line length of 32K characters. That means you cannot
29649 have multiline matches with the &%regex%& condition.
29651 The &%mime_regex%& condition can be called only in the MIME ACL. It matches up
29652 to 32K of decoded content (the whole content at once, not linewise). If the
29653 part has not been decoded with the &%decode%& modifier earlier in the ACL, it
29654 is decoded automatically when &%mime_regex%& is executed (using default path
29655 and filename values). If the decoded data is larger than 32K, only the first
29656 32K characters are checked.
29658 The regular expressions are passed as a colon-separated list. To include a
29659 literal colon, you must double it. Since the whole right-hand side string is
29660 expanded before being used, you must also escape dollar signs and backslashes
29661 with more backslashes, or use the &`\N`& facility to disable expansion.
29662 Here is a simple example that contains two regular expressions:
29664 deny message = contains blacklisted regex ($regex_match_string)
29665 regex = [Mm]ortgage : URGENT BUSINESS PROPOSAL
29667 The conditions returns true if any one of the regular expressions matches. The
29668 &$regex_match_string$& expansion variable is then set up and contains the
29669 matching regular expression.
29671 &*Warning*&: With large messages, these conditions can be fairly
29677 .section "The demime condition" "SECTdemimecond"
29678 .cindex "content scanning" "MIME checking"
29679 .cindex "MIME content scanning"
29680 The &%demime%& ACL condition provides MIME unpacking, sanity checking and file
29681 extension blocking. It is usable only in the DATA and non-SMTP ACLs. The
29682 &%demime%& condition uses a simpler interface to MIME decoding than the MIME
29683 ACL functionality, but provides no additional facilities. Please note that this
29684 condition is deprecated and kept only for backward compatibility. You must set
29685 the WITH_OLD_DEMIME option in &_Local/Makefile_& at build time to be able to
29686 use the &%demime%& condition.
29688 The &%demime%& condition unpacks MIME containers in the message. It detects
29689 errors in MIME containers and can match file extensions found in the message
29690 against a list. Using this facility produces files containing the unpacked MIME
29691 parts of the message in the temporary scan directory. If you do antivirus
29692 scanning, it is recommended that you use the &%demime%& condition before the
29693 antivirus (&%malware%&) condition.
29695 On the right-hand side of the &%demime%& condition you can pass a
29696 colon-separated list of file extensions that it should match against. For
29699 deny message = Found blacklisted file attachment
29700 demime = vbs:com:bat:pif:prf:lnk
29702 If one of the file extensions is found, the condition is true, otherwise it is
29703 false. If there is a temporary error while demimeing (for example, &"disk
29704 full"&), the condition defers, and the message is temporarily rejected (unless
29705 the condition is on a &%warn%& verb).
29707 The right-hand side is expanded before being treated as a list, so you can have
29708 conditions and lookups there. If it expands to an empty string, &"false"&, or
29709 zero (&"0"&), no demimeing is done and the condition is false.
29711 The &%demime%& condition set the following variables:
29714 .vitem &$demime_errorlevel$&
29715 .vindex "&$demime_errorlevel$&"
29716 When an error is detected in a MIME container, this variable contains the
29717 severity of the error, as an integer number. The higher the value, the more
29718 severe the error (the current maximum value is 3). If this variable is unset or
29719 zero, no error occurred.
29721 .vitem &$demime_reason$&
29722 .vindex "&$demime_reason$&"
29723 When &$demime_errorlevel$& is greater than zero, this variable contains a
29724 human-readable text string describing the MIME error that occurred.
29728 .vitem &$found_extension$&
29729 .vindex "&$found_extension$&"
29730 When the &%demime%& condition is true, this variable contains the file
29731 extension it found.
29734 Both &$demime_errorlevel$& and &$demime_reason$& are set by the first call of
29735 the &%demime%& condition, and are not changed on subsequent calls.
29737 If you do not want to check for file extensions, but rather use the &%demime%&
29738 condition for unpacking or error checking purposes, pass &"*"& as the
29739 right-hand side value. Here is a more elaborate example of how to use this
29742 # Reject messages with serious MIME container errors
29743 deny message = Found MIME error ($demime_reason).
29745 condition = ${if >{$demime_errorlevel}{2}{1}{0}}
29747 # Reject known virus spreading file extensions.
29748 # Accepting these is pretty much braindead.
29749 deny message = contains $found_extension file (blacklisted).
29750 demime = com:vbs:bat:pif:scr
29752 # Freeze .exe and .doc files. Postmaster can
29753 # examine them and eventually thaw them.
29754 deny log_message = Another $found_extension file.
29763 . ////////////////////////////////////////////////////////////////////////////
29764 . ////////////////////////////////////////////////////////////////////////////
29766 .chapter "Adding a local scan function to Exim" "CHAPlocalscan" &&&
29767 "Local scan function"
29768 .scindex IIDlosca "&[local_scan()]& function" "description of"
29769 .cindex "customizing" "input scan using C function"
29770 .cindex "policy control" "by local scan function"
29771 In these days of email worms, viruses, and ever-increasing spam, some sites
29772 want to apply a lot of checking to messages before accepting them.
29774 The content scanning extension (chapter &<<CHAPexiscan>>&) has facilities for
29775 passing messages to external virus and spam scanning software. You can also do
29776 a certain amount in Exim itself through string expansions and the &%condition%&
29777 condition in the ACL that runs after the SMTP DATA command or the ACL for
29778 non-SMTP messages (see chapter &<<CHAPACL>>&), but this has its limitations.
29780 To allow for further customization to a site's own requirements, there is the
29781 possibility of linking Exim with a private message scanning function, written
29782 in C. If you want to run code that is written in something other than C, you
29783 can of course use a little C stub to call it.
29785 The local scan function is run once for every incoming message, at the point
29786 when Exim is just about to accept the message.
29787 It can therefore be used to control non-SMTP messages from local processes as
29788 well as messages arriving via SMTP.
29790 Exim applies a timeout to calls of the local scan function, and there is an
29791 option called &%local_scan_timeout%& for setting it. The default is 5 minutes.
29792 Zero means &"no timeout"&.
29793 Exim also sets up signal handlers for SIGSEGV, SIGILL, SIGFPE, and SIGBUS
29794 before calling the local scan function, so that the most common types of crash
29795 are caught. If the timeout is exceeded or one of those signals is caught, the
29796 incoming message is rejected with a temporary error if it is an SMTP message.
29797 For a non-SMTP message, the message is dropped and Exim ends with a non-zero
29798 code. The incident is logged on the main and reject logs.
29802 .section "Building Exim to use a local scan function" "SECID207"
29803 .cindex "&[local_scan()]& function" "building Exim to use"
29804 To make use of the local scan function feature, you must tell Exim where your
29805 function is before building Exim, by setting LOCAL_SCAN_SOURCE in your
29806 &_Local/Makefile_&. A recommended place to put it is in the &_Local_&
29807 directory, so you might set
29809 LOCAL_SCAN_SOURCE=Local/local_scan.c
29811 for example. The function must be called &[local_scan()]&. It is called by
29812 Exim after it has received a message, when the success return code is about to
29813 be sent. This is after all the ACLs have been run. The return code from your
29814 function controls whether the message is actually accepted or not. There is a
29815 commented template function (that just accepts the message) in the file
29816 _src/local_scan.c_.
29818 If you want to make use of Exim's run time configuration file to set options
29819 for your &[local_scan()]& function, you must also set
29821 LOCAL_SCAN_HAS_OPTIONS=yes
29823 in &_Local/Makefile_& (see section &<<SECTconoptloc>>& below).
29828 .section "API for local_scan()" "SECTapiforloc"
29829 .cindex "&[local_scan()]& function" "API description"
29830 You must include this line near the start of your code:
29832 #include "local_scan.h"
29834 This header file defines a number of variables and other values, and the
29835 prototype for the function itself. Exim is coded to use unsigned char values
29836 almost exclusively, and one of the things this header defines is a shorthand
29837 for &`unsigned char`& called &`uschar`&.
29838 It also contains the following macro definitions, to simplify casting character
29839 strings and pointers to character strings:
29841 #define CS (char *)
29842 #define CCS (const char *)
29843 #define CSS (char **)
29844 #define US (unsigned char *)
29845 #define CUS (const unsigned char *)
29846 #define USS (unsigned char **)
29848 The function prototype for &[local_scan()]& is:
29850 extern int local_scan(int fd, uschar **return_text);
29852 The arguments are as follows:
29855 &%fd%& is a file descriptor for the file that contains the body of the message
29856 (the -D file). The file is open for reading and writing, but updating it is not
29857 recommended. &*Warning*&: You must &'not'& close this file descriptor.
29859 The descriptor is positioned at character 19 of the file, which is the first
29860 character of the body itself, because the first 19 characters are the message
29861 id followed by &`-D`& and a newline. If you rewind the file, you should use the
29862 macro SPOOL_DATA_START_OFFSET to reset to the start of the data, just in
29863 case this changes in some future version.
29865 &%return_text%& is an address which you can use to return a pointer to a text
29866 string at the end of the function. The value it points to on entry is NULL.
29869 The function must return an &%int%& value which is one of the following macros:
29872 .vitem &`LOCAL_SCAN_ACCEPT`&
29873 .vindex "&$local_scan_data$&"
29874 The message is accepted. If you pass back a string of text, it is saved with
29875 the message, and made available in the variable &$local_scan_data$&. No
29876 newlines are permitted (if there are any, they are turned into spaces) and the
29877 maximum length of text is 1000 characters.
29879 .vitem &`LOCAL_SCAN_ACCEPT_FREEZE`&
29880 This behaves as LOCAL_SCAN_ACCEPT, except that the accepted message is
29881 queued without immediate delivery, and is frozen.
29883 .vitem &`LOCAL_SCAN_ACCEPT_QUEUE`&
29884 This behaves as LOCAL_SCAN_ACCEPT, except that the accepted message is
29885 queued without immediate delivery.
29887 .vitem &`LOCAL_SCAN_REJECT`&
29888 The message is rejected; the returned text is used as an error message which is
29889 passed back to the sender and which is also logged. Newlines are permitted &--
29890 they cause a multiline response for SMTP rejections, but are converted to
29891 &`\n`& in log lines. If no message is given, &"Administrative prohibition"& is
29894 .vitem &`LOCAL_SCAN_TEMPREJECT`&
29895 The message is temporarily rejected; the returned text is used as an error
29896 message as for LOCAL_SCAN_REJECT. If no message is given, &"Temporary local
29899 .vitem &`LOCAL_SCAN_REJECT_NOLOGHDR`&
29900 This behaves as LOCAL_SCAN_REJECT, except that the header of the rejected
29901 message is not written to the reject log. It has the effect of unsetting the
29902 &%rejected_header%& log selector for just this rejection. If
29903 &%rejected_header%& is already unset (see the discussion of the
29904 &%log_selection%& option in section &<<SECTlogselector>>&), this code is the
29905 same as LOCAL_SCAN_REJECT.
29907 .vitem &`LOCAL_SCAN_TEMPREJECT_NOLOGHDR`&
29908 This code is a variation of LOCAL_SCAN_TEMPREJECT in the same way that
29909 LOCAL_SCAN_REJECT_NOLOGHDR is a variation of LOCAL_SCAN_REJECT.
29912 If the message is not being received by interactive SMTP, rejections are
29913 reported by writing to &%stderr%& or by sending an email, as configured by the
29914 &%-oe%& command line options.
29918 .section "Configuration options for local_scan()" "SECTconoptloc"
29919 .cindex "&[local_scan()]& function" "configuration options"
29920 It is possible to have option settings in the main configuration file
29921 that set values in static variables in the &[local_scan()]& module. If you
29922 want to do this, you must have the line
29924 LOCAL_SCAN_HAS_OPTIONS=yes
29926 in your &_Local/Makefile_& when you build Exim. (This line is in
29927 &_OS/Makefile-Default_&, commented out). Then, in the &[local_scan()]& source
29928 file, you must define static variables to hold the option values, and a table
29931 The table must be a vector called &%local_scan_options%&, of type
29932 &`optionlist`&. Each entry is a triplet, consisting of a name, an option type,
29933 and a pointer to the variable that holds the value. The entries must appear in
29934 alphabetical order. Following &%local_scan_options%& you must also define a
29935 variable called &%local_scan_options_count%& that contains the number of
29936 entries in the table. Here is a short example, showing two kinds of option:
29938 static int my_integer_option = 42;
29939 static uschar *my_string_option = US"a default string";
29941 optionlist local_scan_options[] = {
29942 { "my_integer", opt_int, &my_integer_option },
29943 { "my_string", opt_stringptr, &my_string_option }
29946 int local_scan_options_count =
29947 sizeof(local_scan_options)/sizeof(optionlist);
29949 The values of the variables can now be changed from Exim's runtime
29950 configuration file by including a local scan section as in this example:
29954 my_string = some string of text...
29956 The available types of option data are as follows:
29959 .vitem &*opt_bool*&
29960 This specifies a boolean (true/false) option. The address should point to a
29961 variable of type &`BOOL`&, which will be set to TRUE or FALSE, which are macros
29962 that are defined as &"1"& and &"0"&, respectively. If you want to detect
29963 whether such a variable has been set at all, you can initialize it to
29964 TRUE_UNSET. (BOOL variables are integers underneath, so can hold more than two
29967 .vitem &*opt_fixed*&
29968 This specifies a fixed point number, such as is used for load averages.
29969 The address should point to a variable of type &`int`&. The value is stored
29970 multiplied by 1000, so, for example, 1.4142 is truncated and stored as 1414.
29973 This specifies an integer; the address should point to a variable of type
29974 &`int`&. The value may be specified in any of the integer formats accepted by
29977 .vitem &*opt_mkint*&
29978 This is the same as &%opt_int%&, except that when such a value is output in a
29979 &%-bP%& listing, if it is an exact number of kilobytes or megabytes, it is
29980 printed with the suffix K or M.
29982 .vitem &*opt_octint*&
29983 This also specifies an integer, but the value is always interpreted as an
29984 octal integer, whether or not it starts with the digit zero, and it is
29985 always output in octal.
29987 .vitem &*opt_stringptr*&
29988 This specifies a string value; the address must be a pointer to a
29989 variable that points to a string (for example, of type &`uschar *`&).
29991 .vitem &*opt_time*&
29992 This specifies a time interval value. The address must point to a variable of
29993 type &`int`&. The value that is placed there is a number of seconds.
29996 If the &%-bP%& command line option is followed by &`local_scan`&, Exim prints
29997 out the values of all the &[local_scan()]& options.
30001 .section "Available Exim variables" "SECID208"
30002 .cindex "&[local_scan()]& function" "available Exim variables"
30003 The header &_local_scan.h_& gives you access to a number of C variables. These
30004 are the only ones that are guaranteed to be maintained from release to release.
30005 Note, however, that you can obtain the value of any Exim expansion variable,
30006 including &$recipients$&, by calling &'expand_string()'&. The exported
30007 C variables are as follows:
30010 .vitem &*int&~body_linecount*&
30011 This variable contains the number of lines in the message's body.
30013 .vitem &*int&~body_zerocount*&
30014 This variable contains the number of binary zero bytes in the message's body.
30016 .vitem &*unsigned&~int&~debug_selector*&
30017 This variable is set to zero when no debugging is taking place. Otherwise, it
30018 is a bitmap of debugging selectors. Two bits are identified for use in
30019 &[local_scan()]&; they are defined as macros:
30022 The &`D_v`& bit is set when &%-v%& was present on the command line. This is a
30023 testing option that is not privileged &-- any caller may set it. All the
30024 other selector bits can be set only by admin users.
30027 The &`D_local_scan`& bit is provided for use by &[local_scan()]&; it is set
30028 by the &`+local_scan`& debug selector. It is not included in the default set
30032 Thus, to write to the debugging output only when &`+local_scan`& has been
30033 selected, you should use code like this:
30035 if ((debug_selector & D_local_scan) != 0)
30036 debug_printf("xxx", ...);
30038 .vitem &*uschar&~*expand_string_message*&
30039 After a failing call to &'expand_string()'& (returned value NULL), the
30040 variable &%expand_string_message%& contains the error message, zero-terminated.
30042 .vitem &*header_line&~*header_list*&
30043 A pointer to a chain of header lines. The &%header_line%& structure is
30046 .vitem &*header_line&~*header_last*&
30047 A pointer to the last of the header lines.
30049 .vitem &*uschar&~*headers_charset*&
30050 The value of the &%headers_charset%& configuration option.
30052 .vitem &*BOOL&~host_checking*&
30053 This variable is TRUE during a host checking session that is initiated by the
30054 &%-bh%& command line option.
30056 .vitem &*uschar&~*interface_address*&
30057 The IP address of the interface that received the message, as a string. This
30058 is NULL for locally submitted messages.
30060 .vitem &*int&~interface_port*&
30061 The port on which this message was received. When testing with the &%-bh%&
30062 command line option, the value of this variable is -1 unless a port has been
30063 specified via the &%-oMi%& option.
30065 .vitem &*uschar&~*message_id*&
30066 This variable contains Exim's message id for the incoming message (the value of
30067 &$message_exim_id$&) as a zero-terminated string.
30069 .vitem &*uschar&~*received_protocol*&
30070 The name of the protocol by which the message was received.
30072 .vitem &*int&~recipients_count*&
30073 The number of accepted recipients.
30075 .vitem &*recipient_item&~*recipients_list*&
30076 .cindex "recipient" "adding in local scan"
30077 .cindex "recipient" "removing in local scan"
30078 The list of accepted recipients, held in a vector of length
30079 &%recipients_count%&. The &%recipient_item%& structure is discussed below. You
30080 can add additional recipients by calling &'receive_add_recipient()'& (see
30081 below). You can delete recipients by removing them from the vector and
30082 adjusting the value in &%recipients_count%&. In particular, by setting
30083 &%recipients_count%& to zero you remove all recipients. If you then return the
30084 value &`LOCAL_SCAN_ACCEPT`&, the message is accepted, but immediately
30085 blackholed. To replace the recipients, you can set &%recipients_count%& to zero
30086 and then call &'receive_add_recipient()'& as often as needed.
30088 .vitem &*uschar&~*sender_address*&
30089 The envelope sender address. For bounce messages this is the empty string.
30091 .vitem &*uschar&~*sender_host_address*&
30092 The IP address of the sending host, as a string. This is NULL for
30093 locally-submitted messages.
30095 .vitem &*uschar&~*sender_host_authenticated*&
30096 The name of the authentication mechanism that was used, or NULL if the message
30097 was not received over an authenticated SMTP connection.
30099 .vitem &*uschar&~*sender_host_name*&
30100 The name of the sending host, if known.
30102 .vitem &*int&~sender_host_port*&
30103 The port on the sending host.
30105 .vitem &*BOOL&~smtp_input*&
30106 This variable is TRUE for all SMTP input, including BSMTP.
30108 .vitem &*BOOL&~smtp_batched_input*&
30109 This variable is TRUE for BSMTP input.
30111 .vitem &*int&~store_pool*&
30112 The contents of this variable control which pool of memory is used for new
30113 requests. See section &<<SECTmemhanloc>>& for details.
30117 .section "Structure of header lines" "SECID209"
30118 The &%header_line%& structure contains the members listed below.
30119 You can add additional header lines by calling the &'header_add()'& function
30120 (see below). You can cause header lines to be ignored (deleted) by setting
30125 .vitem &*struct&~header_line&~*next*&
30126 A pointer to the next header line, or NULL for the last line.
30128 .vitem &*int&~type*&
30129 A code identifying certain headers that Exim recognizes. The codes are printing
30130 characters, and are documented in chapter &<<CHAPspool>>& of this manual.
30131 Notice in particular that any header line whose type is * is not transmitted
30132 with the message. This flagging is used for header lines that have been
30133 rewritten, or are to be removed (for example, &'Envelope-sender:'& header
30134 lines.) Effectively, * means &"deleted"&.
30136 .vitem &*int&~slen*&
30137 The number of characters in the header line, including the terminating and any
30140 .vitem &*uschar&~*text*&
30141 A pointer to the text of the header. It always ends with a newline, followed by
30142 a zero byte. Internal newlines are preserved.
30147 .section "Structure of recipient items" "SECID210"
30148 The &%recipient_item%& structure contains these members:
30151 .vitem &*uschar&~*address*&
30152 This is a pointer to the recipient address as it was received.
30154 .vitem &*int&~pno*&
30155 This is used in later Exim processing when top level addresses are created by
30156 the &%one_time%& option. It is not relevant at the time &[local_scan()]& is run
30157 and must always contain -1 at this stage.
30159 .vitem &*uschar&~*errors_to*&
30160 If this value is not NULL, bounce messages caused by failing to deliver to the
30161 recipient are sent to the address it contains. In other words, it overrides the
30162 envelope sender for this one recipient. (Compare the &%errors_to%& generic
30163 router option.) If a &[local_scan()]& function sets an &%errors_to%& field to
30164 an unqualified address, Exim qualifies it using the domain from
30165 &%qualify_recipient%&. When &[local_scan()]& is called, the &%errors_to%& field
30166 is NULL for all recipients.
30171 .section "Available Exim functions" "SECID211"
30172 .cindex "&[local_scan()]& function" "available Exim functions"
30173 The header &_local_scan.h_& gives you access to a number of Exim functions.
30174 These are the only ones that are guaranteed to be maintained from release to
30178 .vitem "&*pid_t&~child_open(uschar&~**argv,&~uschar&~**envp,&~int&~newumask,&&&
30179 &~int&~*infdptr,&~int&~*outfdptr, &~&~BOOL&~make_leader)*&"
30181 This function creates a child process that runs the command specified by
30182 &%argv%&. The environment for the process is specified by &%envp%&, which can
30183 be NULL if no environment variables are to be passed. A new umask is supplied
30184 for the process in &%newumask%&.
30186 Pipes to the standard input and output of the new process are set up
30187 and returned to the caller via the &%infdptr%& and &%outfdptr%& arguments. The
30188 standard error is cloned to the standard output. If there are any file
30189 descriptors &"in the way"& in the new process, they are closed. If the final
30190 argument is TRUE, the new process is made into a process group leader.
30192 The function returns the pid of the new process, or -1 if things go wrong.
30194 .vitem &*int&~child_close(pid_t&~pid,&~int&~timeout)*&
30195 This function waits for a child process to terminate, or for a timeout (in
30196 seconds) to expire. A timeout value of zero means wait as long as it takes. The
30197 return value is as follows:
30202 The process terminated by a normal exit and the value is the process
30208 The process was terminated by a signal and the value is the negation of the
30214 The process timed out.
30218 The was some other error in wait(); &%errno%& is still set.
30221 .vitem &*pid_t&~child_open_exim(int&~*fd)*&
30222 This function provide you with a means of submitting a new message to
30223 Exim. (Of course, you can also call &_/usr/sbin/sendmail_& yourself if you
30224 want, but this packages it all up for you.) The function creates a pipe,
30225 forks a subprocess that is running
30227 exim -t -oem -oi -f <>
30229 and returns to you (via the &`int *`& argument) a file descriptor for the pipe
30230 that is connected to the standard input. The yield of the function is the PID
30231 of the subprocess. You can then write a message to the file descriptor, with
30232 recipients in &'To:'&, &'Cc:'&, and/or &'Bcc:'& header lines.
30234 When you have finished, call &'child_close()'& to wait for the process to
30235 finish and to collect its ending status. A timeout value of zero is usually
30236 fine in this circumstance. Unless you have made a mistake with the recipient
30237 addresses, you should get a return code of zero.
30240 .vitem &*pid_t&~child_open_exim2(int&~*fd,&~uschar&~*sender,&~uschar&~&&&
30241 *sender_authentication)*&
30242 This function is a more sophisticated version of &'child_open()'&. The command
30245 &`exim -t -oem -oi -f `&&'sender'&&` -oMas `&&'sender_authentication'&
30247 The third argument may be NULL, in which case the &%-oMas%& option is omitted.
30250 .vitem &*void&~debug_printf(char&~*,&~...)*&
30251 This is Exim's debugging function, with arguments as for &'(printf()'&. The
30252 output is written to the standard error stream. If no debugging is selected,
30253 calls to &'debug_printf()'& have no effect. Normally, you should make calls
30254 conditional on the &`local_scan`& debug selector by coding like this:
30256 if ((debug_selector & D_local_scan) != 0)
30257 debug_printf("xxx", ...);
30260 .vitem &*uschar&~*expand_string(uschar&~*string)*&
30261 This is an interface to Exim's string expansion code. The return value is the
30262 expanded string, or NULL if there was an expansion failure.
30263 The C variable &%expand_string_message%& contains an error message after an
30264 expansion failure. If expansion does not change the string, the return value is
30265 the pointer to the input string. Otherwise, the return value points to a new
30266 block of memory that was obtained by a call to &'store_get()'&. See section
30267 &<<SECTmemhanloc>>& below for a discussion of memory handling.
30269 .vitem &*void&~header_add(int&~type,&~char&~*format,&~...)*&
30270 This function allows you to an add additional header line at the end of the
30271 existing ones. The first argument is the type, and should normally be a space
30272 character. The second argument is a format string and any number of
30273 substitution arguments as for &[sprintf()]&. You may include internal newlines
30274 if you want, and you must ensure that the string ends with a newline.
30276 .vitem "&*void&~header_add_at_position(BOOL&~after,&~uschar&~*name,&~&&&
30277 BOOL&~topnot,&~int&~type,&~char&~*format, &~&~...)*&"
30278 This function adds a new header line at a specified point in the header
30279 chain. The header itself is specified as for &'header_add()'&.
30281 If &%name%& is NULL, the new header is added at the end of the chain if
30282 &%after%& is true, or at the start if &%after%& is false. If &%name%& is not
30283 NULL, the header lines are searched for the first non-deleted header that
30284 matches the name. If one is found, the new header is added before it if
30285 &%after%& is false. If &%after%& is true, the new header is added after the
30286 found header and any adjacent subsequent ones with the same name (even if
30287 marked &"deleted"&). If no matching non-deleted header is found, the &%topnot%&
30288 option controls where the header is added. If it is true, addition is at the
30289 top; otherwise at the bottom. Thus, to add a header after all the &'Received:'&
30290 headers, or at the top if there are no &'Received:'& headers, you could use
30292 header_add_at_position(TRUE, US"Received", TRUE,
30293 ' ', "X-xxx: ...");
30295 Normally, there is always at least one non-deleted &'Received:'& header, but
30296 there may not be if &%received_header_text%& expands to an empty string.
30299 .vitem &*void&~header_remove(int&~occurrence,&~uschar&~*name)*&
30300 This function removes header lines. If &%occurrence%& is zero or negative, all
30301 occurrences of the header are removed. If occurrence is greater than zero, that
30302 particular instance of the header is removed. If no header(s) can be found that
30303 match the specification, the function does nothing.
30306 .vitem "&*BOOL&~header_testname(header_line&~*hdr,&~uschar&~*name,&~&&&
30307 int&~length,&~BOOL&~notdel)*&"
30308 This function tests whether the given header has the given name. It is not just
30309 a string comparison, because white space is permitted between the name and the
30310 colon. If the &%notdel%& argument is true, a false return is forced for all
30311 &"deleted"& headers; otherwise they are not treated specially. For example:
30313 if (header_testname(h, US"X-Spam", 6, TRUE)) ...
30315 .vitem &*uschar&~*lss_b64encode(uschar&~*cleartext,&~int&~length)*&
30316 .cindex "base64 encoding" "functions for &[local_scan()]& use"
30317 This function base64-encodes a string, which is passed by address and length.
30318 The text may contain bytes of any value, including zero. The result is passed
30319 back in dynamic memory that is obtained by calling &'store_get()'&. It is
30322 .vitem &*int&~lss_b64decode(uschar&~*codetext,&~uschar&~**cleartext)*&
30323 This function decodes a base64-encoded string. Its arguments are a
30324 zero-terminated base64-encoded string and the address of a variable that is set
30325 to point to the result, which is in dynamic memory. The length of the decoded
30326 string is the yield of the function. If the input is invalid base64 data, the
30327 yield is -1. A zero byte is added to the end of the output string to make it
30328 easy to interpret as a C string (assuming it contains no zeros of its own). The
30329 added zero byte is not included in the returned count.
30331 .vitem &*int&~lss_match_domain(uschar&~*domain,&~uschar&~*list)*&
30332 This function checks for a match in a domain list. Domains are always
30333 matched caselessly. The return value is one of the following:
30335 &`OK `& match succeeded
30336 &`FAIL `& match failed
30337 &`DEFER `& match deferred
30339 DEFER is usually caused by some kind of lookup defer, such as the
30340 inability to contact a database.
30342 .vitem "&*int&~lss_match_local_part(uschar&~*localpart,&~uschar&~*list,&~&&&
30344 This function checks for a match in a local part list. The third argument
30345 controls case-sensitivity. The return values are as for
30346 &'lss_match_domain()'&.
30348 .vitem "&*int&~lss_match_address(uschar&~*address,&~uschar&~*list,&~&&&
30350 This function checks for a match in an address list. The third argument
30351 controls the case-sensitivity of the local part match. The domain is always
30352 matched caselessly. The return values are as for &'lss_match_domain()'&.
30354 .vitem "&*int&~lss_match_host(uschar&~*host_name,&~uschar&~*host_address,&~&&&
30356 This function checks for a match in a host list. The most common usage is
30359 lss_match_host(sender_host_name, sender_host_address, ...)
30361 .vindex "&$sender_host_address$&"
30362 An empty address field matches an empty item in the host list. If the host name
30363 is NULL, the name corresponding to &$sender_host_address$& is automatically
30364 looked up if a host name is required to match an item in the list. The return
30365 values are as for &'lss_match_domain()'&, but in addition, &'lss_match_host()'&
30366 returns ERROR in the case when it had to look up a host name, but the lookup
30369 .vitem "&*void&~log_write(unsigned&~int&~selector,&~int&~which,&~char&~&&&
30371 This function writes to Exim's log files. The first argument should be zero (it
30372 is concerned with &%log_selector%&). The second argument can be &`LOG_MAIN`& or
30373 &`LOG_REJECT`& or &`LOG_PANIC`& or the inclusive &"or"& of any combination of
30374 them. It specifies to which log or logs the message is written. The remaining
30375 arguments are a format and relevant insertion arguments. The string should not
30376 contain any newlines, not even at the end.
30379 .vitem &*void&~receive_add_recipient(uschar&~*address,&~int&~pno)*&
30380 This function adds an additional recipient to the message. The first argument
30381 is the recipient address. If it is unqualified (has no domain), it is qualified
30382 with the &%qualify_recipient%& domain. The second argument must always be -1.
30384 This function does not allow you to specify a private &%errors_to%& address (as
30385 described with the structure of &%recipient_item%& above), because it pre-dates
30386 the addition of that field to the structure. However, it is easy to add such a
30387 value afterwards. For example:
30389 receive_add_recipient(US"monitor@mydom.example", -1);
30390 recipients_list[recipients_count-1].errors_to =
30391 US"postmaster@mydom.example";
30394 .vitem &*BOOL&~receive_remove_recipient(uschar&~*recipient)*&
30395 This is a convenience function to remove a named recipient from the list of
30396 recipients. It returns true if a recipient was removed, and false if no
30397 matching recipient could be found. The argument must be a complete email
30404 .vitem "&*uschar&~rfc2047_decode(uschar&~*string,&~BOOL&~lencheck,&&&
30405 &~uschar&~*target,&~int&~zeroval,&~int&~*lenptr, &~&~uschar&~**error)*&"
30406 This function decodes strings that are encoded according to RFC 2047. Typically
30407 these are the contents of header lines. First, each &"encoded word"& is decoded
30408 from the Q or B encoding into a byte-string. Then, if provided with the name of
30409 a charset encoding, and if the &[iconv()]& function is available, an attempt is
30410 made to translate the result to the named character set. If this fails, the
30411 binary string is returned with an error message.
30413 The first argument is the string to be decoded. If &%lencheck%& is TRUE, the
30414 maximum MIME word length is enforced. The third argument is the target
30415 encoding, or NULL if no translation is wanted.
30417 .cindex "binary zero" "in RFC 2047 decoding"
30418 .cindex "RFC 2047" "binary zero in"
30419 If a binary zero is encountered in the decoded string, it is replaced by the
30420 contents of the &%zeroval%& argument. For use with Exim headers, the value must
30421 not be 0 because header lines are handled as zero-terminated strings.
30423 The function returns the result of processing the string, zero-terminated; if
30424 &%lenptr%& is not NULL, the length of the result is set in the variable to
30425 which it points. When &%zeroval%& is 0, &%lenptr%& should not be NULL.
30427 If an error is encountered, the function returns NULL and uses the &%error%&
30428 argument to return an error message. The variable pointed to by &%error%& is
30429 set to NULL if there is no error; it may be set non-NULL even when the function
30430 returns a non-NULL value if decoding was successful, but there was a problem
30434 .vitem &*int&~smtp_fflush(void)*&
30435 This function is used in conjunction with &'smtp_printf()'&, as described
30438 .vitem &*void&~smtp_printf(char&~*,&~...)*&
30439 The arguments of this function are like &[printf()]&; it writes to the SMTP
30440 output stream. You should use this function only when there is an SMTP output
30441 stream, that is, when the incoming message is being received via interactive
30442 SMTP. This is the case when &%smtp_input%& is TRUE and &%smtp_batched_input%&
30443 is FALSE. If you want to test for an incoming message from another host (as
30444 opposed to a local process that used the &%-bs%& command line option), you can
30445 test the value of &%sender_host_address%&, which is non-NULL when a remote host
30448 If an SMTP TLS connection is established, &'smtp_printf()'& uses the TLS
30449 output function, so it can be used for all forms of SMTP connection.
30451 Strings that are written by &'smtp_printf()'& from within &[local_scan()]&
30452 must start with an appropriate response code: 550 if you are going to return
30453 LOCAL_SCAN_REJECT, 451 if you are going to return
30454 LOCAL_SCAN_TEMPREJECT, and 250 otherwise. Because you are writing the
30455 initial lines of a multi-line response, the code must be followed by a hyphen
30456 to indicate that the line is not the final response line. You must also ensure
30457 that the lines you write terminate with CRLF. For example:
30459 smtp_printf("550-this is some extra info\r\n");
30460 return LOCAL_SCAN_REJECT;
30462 Note that you can also create multi-line responses by including newlines in
30463 the data returned via the &%return_text%& argument. The added value of using
30464 &'smtp_printf()'& is that, for instance, you could introduce delays between
30465 multiple output lines.
30467 The &'smtp_printf()'& function does not return any error indication, because it
30468 does not automatically flush pending output, and therefore does not test
30469 the state of the stream. (In the main code of Exim, flushing and error
30470 detection is done when Exim is ready for the next SMTP input command.) If
30471 you want to flush the output and check for an error (for example, the
30472 dropping of a TCP/IP connection), you can call &'smtp_fflush()'&, which has no
30473 arguments. It flushes the output stream, and returns a non-zero value if there
30476 .vitem &*void&~*store_get(int)*&
30477 This function accesses Exim's internal store (memory) manager. It gets a new
30478 chunk of memory whose size is given by the argument. Exim bombs out if it ever
30479 runs out of memory. See the next section for a discussion of memory handling.
30481 .vitem &*void&~*store_get_perm(int)*&
30482 This function is like &'store_get()'&, but it always gets memory from the
30483 permanent pool. See the next section for a discussion of memory handling.
30485 .vitem &*uschar&~*string_copy(uschar&~*string)*&
30488 .vitem &*uschar&~*string_copyn(uschar&~*string,&~int&~length)*&
30491 .vitem &*uschar&~*string_sprintf(char&~*format,&~...)*&
30492 These three functions create strings using Exim's dynamic memory facilities.
30493 The first makes a copy of an entire string. The second copies up to a maximum
30494 number of characters, indicated by the second argument. The third uses a format
30495 and insertion arguments to create a new string. In each case, the result is a
30496 pointer to a new string in the current memory pool. See the next section for
30502 .section "More about Exim's memory handling" "SECTmemhanloc"
30503 .cindex "&[local_scan()]& function" "memory handling"
30504 No function is provided for freeing memory, because that is never needed.
30505 The dynamic memory that Exim uses when receiving a message is automatically
30506 recycled if another message is received by the same process (this applies only
30507 to incoming SMTP connections &-- other input methods can supply only one
30508 message at a time). After receiving the last message, a reception process
30511 Because it is recycled, the normal dynamic memory cannot be used for holding
30512 data that must be preserved over a number of incoming messages on the same SMTP
30513 connection. However, Exim in fact uses two pools of dynamic memory; the second
30514 one is not recycled, and can be used for this purpose.
30516 If you want to allocate memory that remains available for subsequent messages
30517 in the same SMTP connection, you should set
30519 store_pool = POOL_PERM
30521 before calling the function that does the allocation. There is no need to
30522 restore the value if you do not need to; however, if you do want to revert to
30523 the normal pool, you can either restore the previous value of &%store_pool%& or
30524 set it explicitly to POOL_MAIN.
30526 The pool setting applies to all functions that get dynamic memory, including
30527 &'expand_string()'&, &'store_get()'&, and the &'string_xxx()'& functions.
30528 There is also a convenience function called &'store_get_perm()'& that gets a
30529 block of memory from the permanent pool while preserving the value of
30536 . ////////////////////////////////////////////////////////////////////////////
30537 . ////////////////////////////////////////////////////////////////////////////
30539 .chapter "System-wide message filtering" "CHAPsystemfilter"
30540 .scindex IIDsysfil1 "filter" "system filter"
30541 .scindex IIDsysfil2 "filtering all mail"
30542 .scindex IIDsysfil3 "system filter"
30543 The previous chapters (on ACLs and the local scan function) describe checks
30544 that can be applied to messages before they are accepted by a host. There is
30545 also a mechanism for checking messages once they have been received, but before
30546 they are delivered. This is called the &'system filter'&.
30548 The system filter operates in a similar manner to users' filter files, but it
30549 is run just once per message (however many recipients the message has).
30550 It should not normally be used as a substitute for routing, because &%deliver%&
30551 commands in a system router provide new envelope recipient addresses.
30552 The system filter must be an Exim filter. It cannot be a Sieve filter.
30554 The system filter is run at the start of a delivery attempt, before any routing
30555 is done. If a message fails to be completely delivered at the first attempt,
30556 the system filter is run again at the start of every retry.
30557 If you want your filter to do something only once per message, you can make use
30558 of the &%first_delivery%& condition in an &%if%& command in the filter to
30559 prevent it happening on retries.
30561 .vindex "&$domain$&"
30562 .vindex "&$local_part$&"
30563 &*Warning*&: Because the system filter runs just once, variables that are
30564 specific to individual recipient addresses, such as &$local_part$& and
30565 &$domain$&, are not set, and the &"personal"& condition is not meaningful. If
30566 you want to run a centrally-specified filter for each recipient address
30567 independently, you can do so by setting up a suitable &(redirect)& router, as
30568 described in section &<<SECTperaddfil>>& below.
30571 .section "Specifying a system filter" "SECID212"
30572 .cindex "uid (user id)" "system filter"
30573 .cindex "gid (group id)" "system filter"
30574 The name of the file that contains the system filter must be specified by
30575 setting &%system_filter%&. If you want the filter to run under a uid and gid
30576 other than root, you must also set &%system_filter_user%& and
30577 &%system_filter_group%& as appropriate. For example:
30579 system_filter = /etc/mail/exim.filter
30580 system_filter_user = exim
30582 If a system filter generates any deliveries directly to files or pipes (via the
30583 &%save%& or &%pipe%& commands), transports to handle these deliveries must be
30584 specified by setting &%system_filter_file_transport%& and
30585 &%system_filter_pipe_transport%&, respectively. Similarly,
30586 &%system_filter_reply_transport%& must be set to handle any messages generated
30587 by the &%reply%& command.
30590 .section "Testing a system filter" "SECID213"
30591 You can run simple tests of a system filter in the same way as for a user
30592 filter, but you should use &%-bF%& rather than &%-bf%&, so that features that
30593 are permitted only in system filters are recognized.
30595 If you want to test the combined effect of a system filter and a user filter,
30596 you can use both &%-bF%& and &%-bf%& on the same command line.
30600 .section "Contents of a system filter" "SECID214"
30601 The language used to specify system filters is the same as for users' filter
30602 files. It is described in the separate end-user document &'Exim's interface to
30603 mail filtering'&. However, there are some additional features that are
30604 available only in system filters; these are described in subsequent sections.
30605 If they are encountered in a user's filter file or when testing with &%-bf%&,
30608 .cindex "frozen messages" "manual thaw; testing in filter"
30609 There are two special conditions which, though available in users' filter
30610 files, are designed for use in system filters. The condition &%first_delivery%&
30611 is true only for the first attempt at delivering a message, and
30612 &%manually_thawed%& is true only if the message has been frozen, and
30613 subsequently thawed by an admin user. An explicit forced delivery counts as a
30614 manual thaw, but thawing as a result of the &%auto_thaw%& setting does not.
30616 &*Warning*&: If a system filter uses the &%first_delivery%& condition to
30617 specify an &"unseen"& (non-significant) delivery, and that delivery does not
30618 succeed, it will not be tried again.
30619 If you want Exim to retry an unseen delivery until it succeeds, you should
30620 arrange to set it up every time the filter runs.
30622 When a system filter finishes running, the values of the variables &$n0$& &--
30623 &$n9$& are copied into &$sn0$& &-- &$sn9$& and are thereby made available to
30624 users' filter files. Thus a system filter can, for example, set up &"scores"&
30625 to which users' filter files can refer.
30629 .section "Additional variable for system filters" "SECID215"
30630 .vindex "&$recipients$&"
30631 The expansion variable &$recipients$&, containing a list of all the recipients
30632 of the message (separated by commas and white space), is available in system
30633 filters. It is not available in users' filters for privacy reasons.
30637 .section "Defer, freeze, and fail commands for system filters" "SECID216"
30638 .cindex "freezing messages"
30639 .cindex "message" "freezing"
30640 .cindex "message" "forced failure"
30641 .cindex "&%fail%&" "in system filter"
30642 .cindex "&%freeze%& in system filter"
30643 .cindex "&%defer%& in system filter"
30644 There are three extra commands (&%defer%&, &%freeze%& and &%fail%&) which are
30645 always available in system filters, but are not normally enabled in users'
30646 filters. (See the &%allow_defer%&, &%allow_freeze%& and &%allow_fail%& options
30647 for the &(redirect)& router.) These commands can optionally be followed by the
30648 word &%text%& and a string containing an error message, for example:
30650 fail text "this message looks like spam to me"
30652 The keyword &%text%& is optional if the next character is a double quote.
30654 The &%defer%& command defers delivery of the original recipients of the
30655 message. The &%fail%& command causes all the original recipients to be failed,
30656 and a bounce message to be created. The &%freeze%& command suspends all
30657 delivery attempts for the original recipients. In all cases, any new deliveries
30658 that are specified by the filter are attempted as normal after the filter has
30661 The &%freeze%& command is ignored if the message has been manually unfrozen and
30662 not manually frozen since. This means that automatic freezing by a system
30663 filter can be used as a way of checking out suspicious messages. If a message
30664 is found to be all right, manually unfreezing it allows it to be delivered.
30666 .cindex "log" "&%fail%& command log line"
30667 .cindex "&%fail%&" "log line; reducing"
30668 The text given with a fail command is used as part of the bounce message as
30669 well as being written to the log. If the message is quite long, this can fill
30670 up a lot of log space when such failures are common. To reduce the size of the
30671 log message, Exim interprets the text in a special way if it starts with the
30672 two characters &`<<`& and contains &`>>`& later. The text between these two
30673 strings is written to the log, and the rest of the text is used in the bounce
30674 message. For example:
30676 fail "<<filter test 1>>Your message is rejected \
30677 because it contains attachments that we are \
30678 not prepared to receive."
30681 .cindex "loop" "caused by &%fail%&"
30682 Take great care with the &%fail%& command when basing the decision to fail on
30683 the contents of the message, because the bounce message will of course include
30684 the contents of the original message and will therefore trigger the &%fail%&
30685 command again (causing a mail loop) unless steps are taken to prevent this.
30686 Testing the &%error_message%& condition is one way to prevent this. You could
30689 if $message_body contains "this is spam" and not error_message
30690 then fail text "spam is not wanted here" endif
30692 though of course that might let through unwanted bounce messages. The
30693 alternative is clever checking of the body and/or headers to detect bounces
30694 generated by the filter.
30696 The interpretation of a system filter file ceases after a
30698 &%freeze%&, or &%fail%& command is obeyed. However, any deliveries that were
30699 set up earlier in the filter file are honoured, so you can use a sequence such
30705 to send a specified message when the system filter is freezing (or deferring or
30706 failing) a message. The normal deliveries for the message do not, of course,
30711 .section "Adding and removing headers in a system filter" "SECTaddremheasys"
30712 .cindex "header lines" "adding; in system filter"
30713 .cindex "header lines" "removing; in system filter"
30714 .cindex "filter" "header lines; adding/removing"
30715 Two filter commands that are available only in system filters are:
30717 headers add <string>
30718 headers remove <string>
30720 The argument for the &%headers add%& is a string that is expanded and then
30721 added to the end of the message's headers. It is the responsibility of the
30722 filter maintainer to make sure it conforms to RFC 2822 syntax. Leading white
30723 space is ignored, and if the string is otherwise empty, or if the expansion is
30724 forced to fail, the command has no effect.
30726 You can use &"\n"& within the string, followed by white space, to specify
30727 continued header lines. More than one header may be added in one command by
30728 including &"\n"& within the string without any following white space. For
30731 headers add "X-header-1: ....\n \
30732 continuation of X-header-1 ...\n\
30735 Note that the header line continuation white space after the first newline must
30736 be placed before the backslash that continues the input string, because white
30737 space after input continuations is ignored.
30739 The argument for &%headers remove%& is a colon-separated list of header names.
30740 This command applies only to those headers that are stored with the message;
30741 those that are added at delivery time (such as &'Envelope-To:'& and
30742 &'Return-Path:'&) cannot be removed by this means. If there is more than one
30743 header with the same name, they are all removed.
30745 The &%headers%& command in a system filter makes an immediate change to the set
30746 of header lines that was received with the message (with possible additions
30747 from ACL processing). Subsequent commands in the system filter operate on the
30748 modified set, which also forms the basis for subsequent message delivery.
30749 Unless further modified during routing or transporting, this set of headers is
30750 used for all recipients of the message.
30752 During routing and transporting, the variables that refer to the contents of
30753 header lines refer only to those lines that are in this set. Thus, header lines
30754 that are added by a system filter are visible to users' filter files and to all
30755 routers and transports. This contrasts with the manipulation of header lines by
30756 routers and transports, which is not immediate, but which instead is saved up
30757 until the message is actually being written (see section
30758 &<<SECTheadersaddrem>>&).
30760 If the message is not delivered at the first attempt, header lines that were
30761 added by the system filter are stored with the message, and so are still
30762 present at the next delivery attempt. Header lines that were removed are still
30763 present, but marked &"deleted"& so that they are not transported with the
30764 message. For this reason, it is usual to make the &%headers%& command
30765 conditional on &%first_delivery%& so that the set of header lines is not
30766 modified more than once.
30768 Because header modification in a system filter acts immediately, you have to
30769 use an indirect approach if you want to modify the contents of a header line.
30772 headers add "Old-Subject: $h_subject:"
30773 headers remove "Subject"
30774 headers add "Subject: new subject (was: $h_old-subject:)"
30775 headers remove "Old-Subject"
30780 .section "Setting an errors address in a system filter" "SECID217"
30781 .cindex "envelope sender"
30782 In a system filter, if a &%deliver%& command is followed by
30784 errors_to <some address>
30786 in order to change the envelope sender (and hence the error reporting) for that
30787 delivery, any address may be specified. (In a user filter, only the current
30788 user's address can be set.) For example, if some mail is being monitored, you
30791 unseen deliver monitor@spying.example errors_to root@local.example
30793 to take a copy which would not be sent back to the normal error reporting
30794 address if its delivery failed.
30798 .section "Per-address filtering" "SECTperaddfil"
30799 .vindex "&$domain$&"
30800 .vindex "&$local_part$&"
30801 In contrast to the system filter, which is run just once per message for each
30802 delivery attempt, it is also possible to set up a system-wide filtering
30803 operation that runs once for each recipient address. In this case, variables
30804 such as &$local_part$& and &$domain$& can be used, and indeed, the choice of
30805 filter file could be made dependent on them. This is an example of a router
30806 which implements such a filter:
30811 domains = +local_domains
30812 file = /central/filters/$local_part
30817 The filter is run in a separate process under its own uid. Therefore, either
30818 &%check_local_user%& must be set (as above), in which case the filter is run as
30819 the local user, or the &%user%& option must be used to specify which user to
30820 use. If both are set, &%user%& overrides.
30822 Care should be taken to ensure that none of the commands in the filter file
30823 specify a significant delivery if the message is to go on to be delivered to
30824 its intended recipient. The router will not then claim to have dealt with the
30825 address, so it will be passed on to subsequent routers to be delivered in the
30827 .ecindex IIDsysfil1
30828 .ecindex IIDsysfil2
30829 .ecindex IIDsysfil3
30836 . ////////////////////////////////////////////////////////////////////////////
30837 . ////////////////////////////////////////////////////////////////////////////
30839 .chapter "Message processing" "CHAPmsgproc"
30840 .scindex IIDmesproc "message" "general processing"
30841 Exim performs various transformations on the sender and recipient addresses of
30842 all messages that it handles, and also on the messages' header lines. Some of
30843 these are optional and configurable, while others always take place. All of
30844 this processing, except rewriting as a result of routing, and the addition or
30845 removal of header lines while delivering, happens when a message is received,
30846 before it is placed on Exim's queue.
30848 Some of the automatic processing takes place by default only for
30849 &"locally-originated"& messages. This adjective is used to describe messages
30850 that are not received over TCP/IP, but instead are passed to an Exim process on
30851 its standard input. This includes the interactive &"local SMTP"& case that is
30852 set up by the &%-bs%& command line option.
30854 &*Note*&: Messages received over TCP/IP on the loopback interface (127.0.0.1
30855 or ::1) are not considered to be locally-originated. Exim does not treat the
30856 loopback interface specially in any way.
30858 If you want the loopback interface to be treated specially, you must ensure
30859 that there are appropriate entries in your ACLs.
30864 .section "Submission mode for non-local messages" "SECTsubmodnon"
30865 .cindex "message" "submission"
30866 .cindex "submission mode"
30867 Processing that happens automatically for locally-originated messages (unless
30868 &%suppress_local_fixups%& is set) can also be requested for messages that are
30869 received over TCP/IP. The term &"submission mode"& is used to describe this
30870 state. Submission mode is set by the modifier
30872 control = submission
30874 in a MAIL, RCPT, or pre-data ACL for an incoming message (see sections
30875 &<<SECTACLmodi>>& and &<<SECTcontrols>>&). This makes Exim treat the message as
30876 a local submission, and is normally used when the source of the message is
30877 known to be an MUA running on a client host (as opposed to an MTA). For
30878 example, to set submission mode for messages originating on the IPv4 loopback
30879 interface, you could include the following in the MAIL ACL:
30881 warn hosts = 127.0.0.1
30882 control = submission
30884 .cindex "&%sender_retain%& submission option"
30885 There are some options that can be used when setting submission mode. A slash
30886 is used to separate options. For example:
30888 control = submission/sender_retain
30890 Specifying &%sender_retain%& has the effect of setting &%local_sender_retain%&
30891 true and &%local_from_check%& false for the current incoming message. The first
30892 of these allows an existing &'Sender:'& header in the message to remain, and
30893 the second suppresses the check to ensure that &'From:'& matches the
30894 authenticated sender. With this setting, Exim still fixes up messages by adding
30895 &'Date:'& and &'Message-ID:'& header lines if they are missing, but makes no
30896 attempt to check sender authenticity in header lines.
30898 When &%sender_retain%& is not set, a submission mode setting may specify a
30899 domain to be used when generating a &'From:'& or &'Sender:'& header line. For
30902 control = submission/domain=some.domain
30904 The domain may be empty. How this value is used is described in sections
30905 &<<SECTthefrohea>>& and &<<SECTthesenhea>>&. There is also a &%name%& option
30906 that allows you to specify the user's full name for inclusion in a created
30907 &'Sender:'& or &'From:'& header line. For example:
30909 accept authenticated = *
30910 control = submission/domain=wonderland.example/\
30911 name=${lookup {$authenticated_id} \
30912 lsearch {/etc/exim/namelist}}
30914 Because the name may contain any characters, including slashes, the &%name%&
30915 option must be given last. The remainder of the string is used as the name. For
30916 the example above, if &_/etc/exim/namelist_& contains:
30918 bigegg: Humpty Dumpty
30920 then when the sender has authenticated as &'bigegg'&, the generated &'Sender:'&
30923 Sender: Humpty Dumpty <bigegg@wonderland.example>
30925 .cindex "return path" "in submission mode"
30926 By default, submission mode forces the return path to the same address as is
30927 used to create the &'Sender:'& header. However, if &%sender_retain%& is
30928 specified, the return path is also left unchanged.
30930 &*Note*&: The changes caused by submission mode take effect after the predata
30931 ACL. This means that any sender checks performed before the fix-ups use the
30932 untrusted sender address specified by the user, not the trusted sender address
30933 specified by submission mode. Although this might be slightly unexpected, it
30934 does mean that you can configure ACL checks to spot that a user is trying to
30935 spoof another's address.
30937 .section "Line endings" "SECTlineendings"
30938 .cindex "line endings"
30939 .cindex "carriage return"
30941 RFC 2821 specifies that CRLF (two characters: carriage-return, followed by
30942 linefeed) is the line ending for messages transmitted over the Internet using
30943 SMTP over TCP/IP. However, within individual operating systems, different
30944 conventions are used. For example, Unix-like systems use just LF, but others
30945 use CRLF or just CR.
30947 Exim was designed for Unix-like systems, and internally, it stores messages
30948 using the system's convention of a single LF as a line terminator. When
30949 receiving a message, all line endings are translated to this standard format.
30950 Originally, it was thought that programs that passed messages directly to an
30951 MTA within an operating system would use that system's convention. Experience
30952 has shown that this is not the case; for example, there are Unix applications
30953 that use CRLF in this circumstance. For this reason, and for compatibility with
30954 other MTAs, the way Exim handles line endings for all messages is now as
30958 LF not preceded by CR is treated as a line ending.
30960 CR is treated as a line ending; if it is immediately followed by LF, the LF
30963 The sequence &"CR, dot, CR"& does not terminate an incoming SMTP message,
30964 nor a local message in the state where a line containing only a dot is a
30967 If a bare CR is encountered within a header line, an extra space is added after
30968 the line terminator so as not to end the header line. The reasoning behind this
30969 is that bare CRs in header lines are most likely either to be mistakes, or
30970 people trying to play silly games.
30972 If the first header line received in a message ends with CRLF, a subsequent
30973 bare LF in a header line is treated in the same way as a bare CR in a header
30981 .section "Unqualified addresses" "SECID218"
30982 .cindex "unqualified addresses"
30983 .cindex "address" "qualification"
30984 By default, Exim expects every envelope address it receives from an external
30985 host to be fully qualified. Unqualified addresses cause negative responses to
30986 SMTP commands. However, because SMTP is used as a means of transporting
30987 messages from MUAs running on personal workstations, there is sometimes a
30988 requirement to accept unqualified addresses from specific hosts or IP networks.
30990 Exim has two options that separately control which hosts may send unqualified
30991 sender or recipient addresses in SMTP commands, namely
30992 &%sender_unqualified_hosts%& and &%recipient_unqualified_hosts%&. In both
30993 cases, if an unqualified address is accepted, it is qualified by adding the
30994 value of &%qualify_domain%& or &%qualify_recipient%&, as appropriate.
30996 .oindex "&%qualify_domain%&"
30997 .oindex "&%qualify_recipient%&"
30998 Unqualified addresses in header lines are automatically qualified for messages
30999 that are locally originated, unless the &%-bnq%& option is given on the command
31000 line. For messages received over SMTP, unqualified addresses in header lines
31001 are qualified only if unqualified addresses are permitted in SMTP commands. In
31002 other words, such qualification is also controlled by
31003 &%sender_unqualified_hosts%& and &%recipient_unqualified_hosts%&,
31008 .section "The UUCP From line" "SECID219"
31009 .cindex "&""From""& line"
31010 .cindex "UUCP" "&""From""& line"
31011 .cindex "sender" "address"
31012 .oindex "&%uucp_from_pattern%&"
31013 .oindex "&%uucp_from_sender%&"
31014 .cindex "envelope sender"
31015 .cindex "Sendmail compatibility" "&""From""& line"
31016 Messages that have come from UUCP (and some other applications) often begin
31017 with a line containing the envelope sender and a timestamp, following the word
31018 &"From"&. Examples of two common formats are:
31020 From a.oakley@berlin.mus Fri Jan 5 12:35 GMT 1996
31021 From f.butler@berlin.mus Fri, 7 Jan 97 14:00:00 GMT
31023 This line precedes the RFC 2822 header lines. For compatibility with Sendmail,
31024 Exim recognizes such lines at the start of messages that are submitted to it
31025 via the command line (that is, on the standard input). It does not recognize
31026 such lines in incoming SMTP messages, unless the sending host matches
31027 &%ignore_fromline_hosts%& or the &%-bs%& option was used for a local message
31028 and &%ignore_fromline_local%& is set. The recognition is controlled by a
31029 regular expression that is defined by the &%uucp_from_pattern%& option, whose
31030 default value matches the two common cases shown above and puts the address
31031 that follows &"From"& into &$1$&.
31033 .cindex "numerical variables (&$1$& &$2$& etc)" "in &""From ""& line handling"
31034 When the caller of Exim for a non-SMTP message that contains a &"From"& line is
31035 a trusted user, the message's sender address is constructed by expanding the
31036 contents of &%uucp_sender_address%&, whose default value is &"$1"&. This is
31037 then parsed as an RFC 2822 address. If there is no domain, the local part is
31038 qualified with &%qualify_domain%& unless it is the empty string. However, if
31039 the command line &%-f%& option is used, it overrides the &"From"& line.
31041 If the caller of Exim is not trusted, the &"From"& line is recognized, but the
31042 sender address is not changed. This is also the case for incoming SMTP messages
31043 that are permitted to contain &"From"& lines.
31045 Only one &"From"& line is recognized. If there is more than one, the second is
31046 treated as a data line that starts the body of the message, as it is not valid
31047 as a header line. This also happens if a &"From"& line is present in an
31048 incoming SMTP message from a source that is not permitted to send them.
31052 .section "Resent- header lines" "SECID220"
31053 .cindex "&%Resent-%& header lines"
31054 RFC 2822 makes provision for sets of header lines starting with the string
31055 &`Resent-`& to be added to a message when it is resent by the original
31056 recipient to somebody else. These headers are &'Resent-Date:'&,
31057 &'Resent-From:'&, &'Resent-Sender:'&, &'Resent-To:'&, &'Resent-Cc:'&,
31058 &'Resent-Bcc:'& and &'Resent-Message-ID:'&. The RFC says:
31061 &'Resent fields are strictly informational. They MUST NOT be used in the normal
31062 processing of replies or other such automatic actions on messages.'&
31065 This leaves things a bit vague as far as other processing actions such as
31066 address rewriting are concerned. Exim treats &%Resent-%& header lines as
31070 A &'Resent-From:'& line that just contains the login id of the submitting user
31071 is automatically rewritten in the same way as &'From:'& (see below).
31073 If there's a rewriting rule for a particular header line, it is also applied to
31074 &%Resent-%& header lines of the same type. For example, a rule that rewrites
31075 &'From:'& also rewrites &'Resent-From:'&.
31077 For local messages, if &'Sender:'& is removed on input, &'Resent-Sender:'& is
31080 For a locally-submitted message,
31081 if there are any &%Resent-%& header lines but no &'Resent-Date:'&,
31082 &'Resent-From:'&, or &'Resent-Message-Id:'&, they are added as necessary. It is
31083 the contents of &'Resent-Message-Id:'& (rather than &'Message-Id:'&) which are
31084 included in log lines in this case.
31086 The logic for adding &'Sender:'& is duplicated for &'Resent-Sender:'& when any
31087 &%Resent-%& header lines are present.
31093 .section "The Auto-Submitted: header line" "SECID221"
31094 Whenever Exim generates an autoreply, a bounce, or a delay warning message, it
31095 includes the header line:
31097 Auto-Submitted: auto-replied
31100 .section "The Bcc: header line" "SECID222"
31101 .cindex "&'Bcc:'& header line"
31102 If Exim is called with the &%-t%& option, to take recipient addresses from a
31103 message's header, it removes any &'Bcc:'& header line that may exist (after
31104 extracting its addresses). If &%-t%& is not present on the command line, any
31105 existing &'Bcc:'& is not removed.
31108 .section "The Date: header line" "SECID223"
31109 .cindex "&'Date:'& header line"
31110 If a locally-generated or submission-mode message has no &'Date:'& header line,
31111 Exim adds one, using the current date and time, unless the
31112 &%suppress_local_fixups%& control has been specified.
31114 .section "The Delivery-date: header line" "SECID224"
31115 .cindex "&'Delivery-date:'& header line"
31116 .oindex "&%delivery_date_remove%&"
31117 &'Delivery-date:'& header lines are not part of the standard RFC 2822 header
31118 set. Exim can be configured to add them to the final delivery of messages. (See
31119 the generic &%delivery_date_add%& transport option.) They should not be present
31120 in messages in transit. If the &%delivery_date_remove%& configuration option is
31121 set (the default), Exim removes &'Delivery-date:'& header lines from incoming
31125 .section "The Envelope-to: header line" "SECID225"
31126 .cindex "&'Envelope-to:'& header line"
31127 .oindex "&%envelope_to_remove%&"
31128 &'Envelope-to:'& header lines are not part of the standard RFC 2822 header set.
31129 Exim can be configured to add them to the final delivery of messages. (See the
31130 generic &%envelope_to_add%& transport option.) They should not be present in
31131 messages in transit. If the &%envelope_to_remove%& configuration option is set
31132 (the default), Exim removes &'Envelope-to:'& header lines from incoming
31136 .section "The From: header line" "SECTthefrohea"
31137 .cindex "&'From:'& header line"
31138 .cindex "Sendmail compatibility" "&""From""& line"
31139 .cindex "message" "submission"
31140 .cindex "submission mode"
31141 If a submission-mode message does not contain a &'From:'& header line, Exim
31142 adds one if either of the following conditions is true:
31145 The envelope sender address is not empty (that is, this is not a bounce
31146 message). The added header line copies the envelope sender address.
31148 .vindex "&$authenticated_id$&"
31149 The SMTP session is authenticated and &$authenticated_id$& is not empty.
31151 .vindex "&$qualify_domain$&"
31152 If no domain is specified by the submission control, the local part is
31153 &$authenticated_id$& and the domain is &$qualify_domain$&.
31155 If a non-empty domain is specified by the submission control, the local
31156 part is &$authenticated_id$&, and the domain is the specified domain.
31158 If an empty domain is specified by the submission control,
31159 &$authenticated_id$& is assumed to be the complete address.
31163 A non-empty envelope sender takes precedence.
31165 If a locally-generated incoming message does not contain a &'From:'& header
31166 line, and the &%suppress_local_fixups%& control is not set, Exim adds one
31167 containing the sender's address. The calling user's login name and full name
31168 are used to construct the address, as described in section &<<SECTconstr>>&.
31169 They are obtained from the password data by calling &[getpwuid()]& (but see the
31170 &%unknown_login%& configuration option). The address is qualified with
31171 &%qualify_domain%&.
31173 For compatibility with Sendmail, if an incoming, non-SMTP message has a
31174 &'From:'& header line containing just the unqualified login name of the calling
31175 user, this is replaced by an address containing the user's login name and full
31176 name as described in section &<<SECTconstr>>&.
31179 .section "The Message-ID: header line" "SECID226"
31180 .cindex "&'Message-ID:'& header line"
31181 .cindex "message" "submission"
31182 .oindex "&%message_id_header_text%&"
31183 If a locally-generated or submission-mode incoming message does not contain a
31184 &'Message-ID:'& or &'Resent-Message-ID:'& header line, and the
31185 &%suppress_local_fixups%& control is not set, Exim adds a suitable header line
31186 to the message. If there are any &'Resent-:'& headers in the message, it
31187 creates &'Resent-Message-ID:'&. The id is constructed from Exim's internal
31188 message id, preceded by the letter E to ensure it starts with a letter, and
31189 followed by @ and the primary host name. Additional information can be included
31190 in this header line by setting the &%message_id_header_text%& and/or
31191 &%message_id_header_domain%& options.
31194 .section "The Received: header line" "SECID227"
31195 .cindex "&'Received:'& header line"
31196 A &'Received:'& header line is added at the start of every message. The
31197 contents are defined by the &%received_header_text%& configuration option, and
31198 Exim automatically adds a semicolon and a timestamp to the configured string.
31200 The &'Received:'& header is generated as soon as the message's header lines
31201 have been received. At this stage, the timestamp in the &'Received:'& header
31202 line is the time that the message started to be received. This is the value
31203 that is seen by the DATA ACL and by the &[local_scan()]& function.
31205 Once a message is accepted, the timestamp in the &'Received:'& header line is
31206 changed to the time of acceptance, which is (apart from a small delay while the
31207 -H spool file is written) the earliest time at which delivery could start.
31210 .section "The References: header line" "SECID228"
31211 .cindex "&'References:'& header line"
31212 Messages created by the &(autoreply)& transport include a &'References:'&
31213 header line. This is constructed according to the rules that are described in
31214 section 3.64 of RFC 2822 (which states that replies should contain such a
31215 header line), and section 3.14 of RFC 3834 (which states that automatic
31216 responses are not different in this respect). However, because some mail
31217 processing software does not cope well with very long header lines, no more
31218 than 12 message IDs are copied from the &'References:'& header line in the
31219 incoming message. If there are more than 12, the first one and then the final
31220 11 are copied, before adding the message ID of the incoming message.
31224 .section "The Return-path: header line" "SECID229"
31225 .cindex "&'Return-path:'& header line"
31226 .oindex "&%return_path_remove%&"
31227 &'Return-path:'& header lines are defined as something an MTA may insert when
31228 it does the final delivery of messages. (See the generic &%return_path_add%&
31229 transport option.) Therefore, they should not be present in messages in
31230 transit. If the &%return_path_remove%& configuration option is set (the
31231 default), Exim removes &'Return-path:'& header lines from incoming messages.
31235 .section "The Sender: header line" "SECTthesenhea"
31236 .cindex "&'Sender:'& header line"
31237 .cindex "message" "submission"
31238 For a locally-originated message from an untrusted user, Exim may remove an
31239 existing &'Sender:'& header line, and it may add a new one. You can modify
31240 these actions by setting the &%local_sender_retain%& option true, the
31241 &%local_from_check%& option false, or by using the &%suppress_local_fixups%&
31244 When a local message is received from an untrusted user and
31245 &%local_from_check%& is true (the default), and the &%suppress_local_fixups%&
31246 control has not been set, a check is made to see if the address given in the
31247 &'From:'& header line is the correct (local) sender of the message. The address
31248 that is expected has the login name as the local part and the value of
31249 &%qualify_domain%& as the domain. Prefixes and suffixes for the local part can
31250 be permitted by setting &%local_from_prefix%& and &%local_from_suffix%&
31251 appropriately. If &'From:'& does not contain the correct sender, a &'Sender:'&
31252 line is added to the message.
31254 If you set &%local_from_check%& false, this checking does not occur. However,
31255 the removal of an existing &'Sender:'& line still happens, unless you also set
31256 &%local_sender_retain%& to be true. It is not possible to set both of these
31257 options true at the same time.
31259 .cindex "submission mode"
31260 By default, no processing of &'Sender:'& header lines is done for messages
31261 received over TCP/IP or for messages submitted by trusted users. However, when
31262 a message is received over TCP/IP in submission mode, and &%sender_retain%& is
31263 not specified on the submission control, the following processing takes place:
31265 .vindex "&$authenticated_id$&"
31266 First, any existing &'Sender:'& lines are removed. Then, if the SMTP session is
31267 authenticated, and &$authenticated_id$& is not empty, a sender address is
31268 created as follows:
31271 .vindex "&$qualify_domain$&"
31272 If no domain is specified by the submission control, the local part is
31273 &$authenticated_id$& and the domain is &$qualify_domain$&.
31275 If a non-empty domain is specified by the submission control, the local part
31276 is &$authenticated_id$&, and the domain is the specified domain.
31278 If an empty domain is specified by the submission control,
31279 &$authenticated_id$& is assumed to be the complete address.
31282 This address is compared with the address in the &'From:'& header line. If they
31283 are different, a &'Sender:'& header line containing the created address is
31284 added. Prefixes and suffixes for the local part in &'From:'& can be permitted
31285 by setting &%local_from_prefix%& and &%local_from_suffix%& appropriately.
31287 .cindex "return path" "created from &'Sender:'&"
31288 &*Note*&: Whenever a &'Sender:'& header line is created, the return path for
31289 the message (the envelope sender address) is changed to be the same address,
31290 except in the case of submission mode when &%sender_retain%& is specified.
31294 .section "Adding and removing header lines in routers and transports" &&&
31295 "SECTheadersaddrem"
31296 .cindex "header lines" "adding; in router or transport"
31297 .cindex "header lines" "removing; in router or transport"
31298 When a message is delivered, the addition and removal of header lines can be
31299 specified in a system filter, or on any of the routers and transports that
31300 process the message. Section &<<SECTaddremheasys>>& contains details about
31301 modifying headers in a system filter. Header lines can also be added in an ACL
31302 as a message is received (see section &<<SECTaddheadacl>>&).
31304 In contrast to what happens in a system filter, header modifications that are
31305 specified on routers and transports apply only to the particular recipient
31306 addresses that are being processed by those routers and transports. These
31307 changes do not actually take place until a copy of the message is being
31308 transported. Therefore, they do not affect the basic set of header lines, and
31309 they do not affect the values of the variables that refer to header lines.
31311 &*Note*&: In particular, this means that any expansions in the configuration of
31312 the transport cannot refer to the modified header lines, because such
31313 expansions all occur before the message is actually transported.
31315 For both routers and transports, the result of expanding a &%headers_add%&
31316 option must be in the form of one or more RFC 2822 header lines, separated by
31317 newlines (coded as &"\n"&). For example:
31319 headers_add = X-added-header: added by $primary_hostname\n\
31320 X-added-second: another added header line
31322 Exim does not check the syntax of these added header lines.
31324 The result of expanding &%headers_remove%& must consist of a colon-separated
31325 list of header names. This is confusing, because header names themselves are
31326 often terminated by colons. In this case, the colons are the list separators,
31327 not part of the names. For example:
31329 headers_remove = return-receipt-to:acknowledge-to
31331 When &%headers_add%& or &%headers_remove%& is specified on a router, its value
31332 is expanded at routing time, and then associated with all addresses that are
31333 accepted by that router, and also with any new addresses that it generates. If
31334 an address passes through several routers as a result of aliasing or
31335 forwarding, the changes are cumulative.
31337 .oindex "&%unseen%&"
31338 However, this does not apply to multiple routers that result from the use of
31339 the &%unseen%& option. Any header modifications that were specified by the
31340 &"unseen"& router or its predecessors apply only to the &"unseen"& delivery.
31342 Addresses that end up with different &%headers_add%& or &%headers_remove%&
31343 settings cannot be delivered together in a batch, so a transport is always
31344 dealing with a set of addresses that have the same header-processing
31347 The transport starts by writing the original set of header lines that arrived
31348 with the message, possibly modified by the system filter. As it writes out
31349 these lines, it consults the list of header names that were attached to the
31350 recipient address(es) by &%headers_remove%& options in routers, and it also
31351 consults the transport's own &%headers_remove%& option. Header lines whose
31352 names are on either of these lists are not written out. If there are multiple
31353 instances of any listed header, they are all skipped.
31355 After the remaining original header lines have been written, new header
31356 lines that were specified by routers' &%headers_add%& options are written, in
31357 the order in which they were attached to the address. These are followed by any
31358 header lines specified by the transport's &%headers_add%& option.
31360 This way of handling header line modifications in routers and transports has
31361 the following consequences:
31364 The original set of header lines, possibly modified by the system filter,
31365 remains &"visible"&, in the sense that the &$header_$&&'xxx'& variables refer
31366 to it, at all times.
31368 Header lines that are added by a router's
31369 &%headers_add%& option are not accessible by means of the &$header_$&&'xxx'&
31370 expansion syntax in subsequent routers or the transport.
31372 Conversely, header lines that are specified for removal by &%headers_remove%&
31373 in a router remain visible to subsequent routers and the transport.
31375 Headers added to an address by &%headers_add%& in a router cannot be removed by
31376 a later router or by a transport.
31378 An added header can refer to the contents of an original header that is to be
31379 removed, even it has the same name as the added header. For example:
31381 headers_remove = subject
31382 headers_add = Subject: new subject (was: $h_subject:)
31386 &*Warning*&: The &%headers_add%& and &%headers_remove%& options cannot be used
31387 for a &(redirect)& router that has the &%one_time%& option set.
31393 .section "Constructed addresses" "SECTconstr"
31394 .cindex "address" "constructed"
31395 .cindex "constructed address"
31396 When Exim constructs a sender address for a locally-generated message, it uses
31399 <&'user name'&>&~&~<&'login'&&`@`&&'qualify_domain'&>
31403 Zaphod Beeblebrox <zaphod@end.univ.example>
31405 The user name is obtained from the &%-F%& command line option if set, or
31406 otherwise by looking up the calling user by &[getpwuid()]& and extracting the
31407 &"gecos"& field from the password entry. If the &"gecos"& field contains an
31408 ampersand character, this is replaced by the login name with the first letter
31409 upper cased, as is conventional in a number of operating systems. See the
31410 &%gecos_name%& option for a way to tailor the handling of the &"gecos"& field.
31411 The &%unknown_username%& option can be used to specify user names in cases when
31412 there is no password file entry.
31415 In all cases, the user name is made to conform to RFC 2822 by quoting all or
31416 parts of it if necessary. In addition, if it contains any non-printing
31417 characters, it is encoded as described in RFC 2047, which defines a way of
31418 including non-ASCII characters in header lines. The value of the
31419 &%headers_charset%& option specifies the name of the encoding that is used (the
31420 characters are assumed to be in this encoding). The setting of
31421 &%print_topbitchars%& controls whether characters with the top bit set (that
31422 is, with codes greater than 127) count as printing characters or not.
31426 .section "Case of local parts" "SECID230"
31427 .cindex "case of local parts"
31428 .cindex "local part" "case of"
31429 RFC 2822 states that the case of letters in the local parts of addresses cannot
31430 be assumed to be non-significant. Exim preserves the case of local parts of
31431 addresses, but by default it uses a lower-cased form when it is routing,
31432 because on most Unix systems, usernames are in lower case and case-insensitive
31433 routing is required. However, any particular router can be made to use the
31434 original case for local parts by setting the &%caseful_local_part%& generic
31437 .cindex "mixed-case login names"
31438 If you must have mixed-case user names on your system, the best way to proceed,
31439 assuming you want case-independent handling of incoming email, is to set up
31440 your first router to convert incoming local parts in your domains to the
31441 correct case by means of a file lookup. For example:
31445 domains = +local_domains
31446 data = ${lookup{$local_part}cdb\
31447 {/etc/usercased.cdb}{$value}fail}\
31450 For this router, the local part is forced to lower case by the default action
31451 (&%caseful_local_part%& is not set). The lower-cased local part is used to look
31452 up a new local part in the correct case. If you then set &%caseful_local_part%&
31453 on any subsequent routers which process your domains, they will operate on
31454 local parts with the correct case in a case-sensitive manner.
31458 .section "Dots in local parts" "SECID231"
31459 .cindex "dot" "in local part"
31460 .cindex "local part" "dots in"
31461 RFC 2822 forbids empty components in local parts. That is, an unquoted local
31462 part may not begin or end with a dot, nor have two consecutive dots in the
31463 middle. However, it seems that many MTAs do not enforce this, so Exim permits
31464 empty components for compatibility.
31468 .section "Rewriting addresses" "SECID232"
31469 .cindex "rewriting" "addresses"
31470 Rewriting of sender and recipient addresses, and addresses in headers, can
31471 happen automatically, or as the result of configuration options, as described
31472 in chapter &<<CHAPrewrite>>&. The headers that may be affected by this are
31473 &'Bcc:'&, &'Cc:'&, &'From:'&, &'Reply-To:'&, &'Sender:'&, and &'To:'&.
31475 Automatic rewriting includes qualification, as mentioned above. The other case
31476 in which it can happen is when an incomplete non-local domain is given. The
31477 routing process may cause this to be expanded into the full domain name. For
31478 example, a header such as
31482 might get rewritten as
31484 To: hare@teaparty.wonderland.fict.example
31486 Rewriting as a result of routing is the one kind of message processing that
31487 does not happen at input time, as it cannot be done until the address has
31490 Strictly, one should not do &'any'& deliveries of a message until all its
31491 addresses have been routed, in case any of the headers get changed as a
31492 result of routing. However, doing this in practice would hold up many
31493 deliveries for unreasonable amounts of time, just because one address could not
31494 immediately be routed. Exim therefore does not delay other deliveries when
31495 routing of one or more addresses is deferred.
31496 .ecindex IIDmesproc
31500 . ////////////////////////////////////////////////////////////////////////////
31501 . ////////////////////////////////////////////////////////////////////////////
31503 .chapter "SMTP processing" "CHAPSMTP"
31504 .scindex IIDsmtpproc1 "SMTP" "processing details"
31505 .scindex IIDsmtpproc2 "LMTP" "processing details"
31506 Exim supports a number of different ways of using the SMTP protocol, and its
31507 LMTP variant, which is an interactive protocol for transferring messages into a
31508 closed mail store application. This chapter contains details of how SMTP is
31509 processed. For incoming mail, the following are available:
31512 SMTP over TCP/IP (Exim daemon or &'inetd'&);
31514 SMTP over the standard input and output (the &%-bs%& option);
31516 Batched SMTP on the standard input (the &%-bS%& option).
31519 For mail delivery, the following are available:
31522 SMTP over TCP/IP (the &(smtp)& transport);
31524 LMTP over TCP/IP (the &(smtp)& transport with the &%protocol%& option set to
31527 LMTP over a pipe to a process running in the local host (the &(lmtp)&
31530 Batched SMTP to a file or pipe (the &(appendfile)& and &(pipe)& transports with
31531 the &%use_bsmtp%& option set).
31534 &'Batched SMTP'& is the name for a process in which batches of messages are
31535 stored in or read from files (or pipes), in a format in which SMTP commands are
31536 used to contain the envelope information.
31540 .section "Outgoing SMTP and LMTP over TCP/IP" "SECToutSMTPTCP"
31541 .cindex "SMTP" "outgoing over TCP/IP"
31542 .cindex "outgoing SMTP over TCP/IP"
31543 .cindex "LMTP" "over TCP/IP"
31544 .cindex "outgoing LMTP over TCP/IP"
31547 .cindex "SIZE option on MAIL command"
31548 Outgoing SMTP and LMTP over TCP/IP is implemented by the &(smtp)& transport.
31549 The &%protocol%& option selects which protocol is to be used, but the actual
31550 processing is the same in both cases.
31552 If, in response to its EHLO command, Exim is told that the SIZE
31553 parameter is supported, it adds SIZE=<&'n'&> to each subsequent MAIL
31554 command. The value of <&'n'&> is the message size plus the value of the
31555 &%size_addition%& option (default 1024) to allow for additions to the message
31556 such as per-transport header lines, or changes made in a
31557 .cindex "transport" "filter"
31558 .cindex "filter" "transport filter"
31559 transport filter. If &%size_addition%& is set negative, the use of SIZE is
31562 If the remote server advertises support for PIPELINING, Exim uses the
31563 pipelining extension to SMTP (RFC 2197) to reduce the number of TCP/IP packets
31564 required for the transaction.
31566 If the remote server advertises support for the STARTTLS command, and Exim
31567 was built to support TLS encryption, it tries to start a TLS session unless the
31568 server matches &%hosts_avoid_tls%&. See chapter &<<CHAPTLS>>& for more details.
31570 If the remote server advertises support for the AUTH command, Exim scans
31571 the authenticators configuration for any suitable client settings, as described
31572 in chapter &<<CHAPSMTPAUTH>>&.
31574 .cindex "carriage return"
31576 Responses from the remote host are supposed to be terminated by CR followed by
31577 LF. However, there are known to be hosts that do not send CR characters, so in
31578 order to be able to interwork with such hosts, Exim treats LF on its own as a
31581 If a message contains a number of different addresses, all those with the same
31582 characteristics (for example, the same envelope sender) that resolve to the
31583 same set of hosts, in the same order, are sent in a single SMTP transaction,
31584 even if they are for different domains, unless there are more than the setting
31585 of the &%max_rcpt%&s option in the &(smtp)& transport allows, in which case
31586 they are split into groups containing no more than &%max_rcpt%&s addresses
31587 each. If &%remote_max_parallel%& is greater than one, such groups may be sent
31588 in parallel sessions. The order of hosts with identical MX values is not
31589 significant when checking whether addresses can be batched in this way.
31591 When the &(smtp)& transport suffers a temporary failure that is not
31592 message-related, Exim updates its transport-specific database, which contains
31593 records indexed by host name that remember which messages are waiting for each
31594 particular host. It also updates the retry database with new retry times.
31596 .cindex "hints database" "retry keys"
31597 Exim's retry hints are based on host name plus IP address, so if one address of
31598 a multi-homed host is broken, it will soon be skipped most of the time.
31599 See the next section for more detail about error handling.
31601 .cindex "SMTP" "passed connection"
31602 .cindex "SMTP" "batching over TCP/IP"
31603 When a message is successfully delivered over a TCP/IP SMTP connection, Exim
31604 looks in the hints database for the transport to see if there are any queued
31605 messages waiting for the host to which it is connected. If it finds one, it
31606 creates a new Exim process using the &%-MC%& option (which can only be used by
31607 a process running as root or the Exim user) and passes the TCP/IP socket to it
31608 so that it can deliver another message using the same socket. The new process
31609 does only those deliveries that are routed to the connected host, and may in
31610 turn pass the socket on to a third process, and so on.
31612 The &%connection_max_messages%& option of the &(smtp)& transport can be used to
31613 limit the number of messages sent down a single TCP/IP connection.
31615 .cindex "asterisk" "after IP address"
31616 The second and subsequent messages delivered down an existing connection are
31617 identified in the main log by the addition of an asterisk after the closing
31618 square bracket of the IP address.
31623 .section "Errors in outgoing SMTP" "SECToutSMTPerr"
31624 .cindex "error" "in outgoing SMTP"
31625 .cindex "SMTP" "errors in outgoing"
31626 .cindex "host" "error"
31627 Three different kinds of error are recognized for outgoing SMTP: host errors,
31628 message errors, and recipient errors.
31631 .vitem "&*Host errors*&"
31632 A host error is not associated with a particular message or with a
31633 particular recipient of a message. The host errors are:
31636 Connection refused or timed out,
31638 Any error response code on connection,
31640 Any error response code to EHLO or HELO,
31642 Loss of connection at any time, except after &"."&,
31644 I/O errors at any time,
31646 Timeouts during the session, other than in response to MAIL, RCPT or
31647 the &"."& at the end of the data.
31650 For a host error, a permanent error response on connection, or in response to
31651 EHLO, causes all addresses routed to the host to be failed. Any other host
31652 error causes all addresses to be deferred, and retry data to be created for the
31653 host. It is not tried again, for any message, until its retry time arrives. If
31654 the current set of addresses are not all delivered in this run (to some
31655 alternative host), the message is added to the list of those waiting for this
31656 host, so if it is still undelivered when a subsequent successful delivery is
31657 made to the host, it will be sent down the same SMTP connection.
31659 .vitem "&*Message errors*&"
31660 .cindex "message" "error"
31661 A message error is associated with a particular message when sent to a
31662 particular host, but not with a particular recipient of the message. The
31663 message errors are:
31666 Any error response code to MAIL, DATA, or the &"."& that terminates
31669 Timeout after MAIL,
31671 Timeout or loss of connection after the &"."& that terminates the data. A
31672 timeout after the DATA command itself is treated as a host error, as is loss of
31673 connection at any other time.
31676 For a message error, a permanent error response (5&'xx'&) causes all addresses
31677 to be failed, and a delivery error report to be returned to the sender. A
31678 temporary error response (4&'xx'&), or one of the timeouts, causes all
31679 addresses to be deferred. Retry data is not created for the host, but instead,
31680 a retry record for the combination of host plus message id is created. The
31681 message is not added to the list of those waiting for this host. This ensures
31682 that the failing message will not be sent to this host again until the retry
31683 time arrives. However, other messages that are routed to the host are not
31684 affected, so if it is some property of the message that is causing the error,
31685 it will not stop the delivery of other mail.
31687 If the remote host specified support for the SIZE parameter in its response
31688 to EHLO, Exim adds SIZE=&'nnn'& to the MAIL command, so an
31689 over-large message will cause a message error because the error arrives as a
31692 .vitem "&*Recipient errors*&"
31693 .cindex "recipient" "error"
31694 A recipient error is associated with a particular recipient of a message. The
31695 recipient errors are:
31698 Any error response to RCPT,
31700 Timeout after RCPT.
31703 For a recipient error, a permanent error response (5&'xx'&) causes the
31704 recipient address to be failed, and a bounce message to be returned to the
31705 sender. A temporary error response (4&'xx'&) or a timeout causes the failing
31706 address to be deferred, and routing retry data to be created for it. This is
31707 used to delay processing of the address in subsequent queue runs, until its
31708 routing retry time arrives. This applies to all messages, but because it
31709 operates only in queue runs, one attempt will be made to deliver a new message
31710 to the failing address before the delay starts to operate. This ensures that,
31711 if the failure is really related to the message rather than the recipient
31712 (&"message too big for this recipient"& is a possible example), other messages
31713 have a chance of getting delivered. If a delivery to the address does succeed,
31714 the retry information gets cleared, so all stuck messages get tried again, and
31715 the retry clock is reset.
31717 The message is not added to the list of those waiting for this host. Use of the
31718 host for other messages is unaffected, and except in the case of a timeout,
31719 other recipients are processed independently, and may be successfully delivered
31720 in the current SMTP session. After a timeout it is of course impossible to
31721 proceed with the session, so all addresses get deferred. However, those other
31722 than the one that failed do not suffer any subsequent retry delays. Therefore,
31723 if one recipient is causing trouble, the others have a chance of getting
31724 through when a subsequent delivery attempt occurs before the failing
31725 recipient's retry time.
31728 In all cases, if there are other hosts (or IP addresses) available for the
31729 current set of addresses (for example, from multiple MX records), they are
31730 tried in this run for any undelivered addresses, subject of course to their
31731 own retry data. In other words, recipient error retry data does not take effect
31732 until the next delivery attempt.
31734 Some hosts have been observed to give temporary error responses to every
31735 MAIL command at certain times (&"insufficient space"& has been seen). It
31736 would be nice if such circumstances could be recognized, and defer data for the
31737 host itself created, but this is not possible within the current Exim design.
31738 What actually happens is that retry data for every (host, message) combination
31741 The reason that timeouts after MAIL and RCPT are treated specially is that
31742 these can sometimes arise as a result of the remote host's verification
31743 procedures. Exim makes this assumption, and treats them as if a temporary error
31744 response had been received. A timeout after &"."& is treated specially because
31745 it is known that some broken implementations fail to recognize the end of the
31746 message if the last character of the last line is a binary zero. Thus, it is
31747 helpful to treat this case as a message error.
31749 Timeouts at other times are treated as host errors, assuming a problem with the
31750 host, or the connection to it. If a timeout after MAIL, RCPT,
31751 or &"."& is really a connection problem, the assumption is that at the next try
31752 the timeout is likely to occur at some other point in the dialogue, causing it
31753 then to be treated as a host error.
31755 There is experimental evidence that some MTAs drop the connection after the
31756 terminating &"."& if they do not like the contents of the message for some
31757 reason, in contravention of the RFC, which indicates that a 5&'xx'& response
31758 should be given. That is why Exim treats this case as a message rather than a
31759 host error, in order not to delay other messages to the same host.
31764 .section "Incoming SMTP messages over TCP/IP" "SECID233"
31765 .cindex "SMTP" "incoming over TCP/IP"
31766 .cindex "incoming SMTP over TCP/IP"
31769 Incoming SMTP messages can be accepted in one of two ways: by running a
31770 listening daemon, or by using &'inetd'&. In the latter case, the entry in
31771 &_/etc/inetd.conf_& should be like this:
31773 smtp stream tcp nowait exim /opt/exim/bin/exim in.exim -bs
31775 Exim distinguishes between this case and the case of a locally running user
31776 agent using the &%-bs%& option by checking whether or not the standard input is
31777 a socket. When it is, either the port must be privileged (less than 1024), or
31778 the caller must be root or the Exim user. If any other user passes a socket
31779 with an unprivileged port number, Exim prints a message on the standard error
31780 stream and exits with an error code.
31782 By default, Exim does not make a log entry when a remote host connects or
31783 disconnects (either via the daemon or &'inetd'&), unless the disconnection is
31784 unexpected. It can be made to write such log entries by setting the
31785 &%smtp_connection%& log selector.
31787 .cindex "carriage return"
31789 Commands from the remote host are supposed to be terminated by CR followed by
31790 LF. However, there are known to be hosts that do not send CR characters. In
31791 order to be able to interwork with such hosts, Exim treats LF on its own as a
31793 Furthermore, because common code is used for receiving messages from all
31794 sources, a CR on its own is also interpreted as a line terminator. However, the
31795 sequence &"CR, dot, CR"& does not terminate incoming SMTP data.
31797 .cindex "EHLO" "invalid data"
31798 .cindex "HELO" "invalid data"
31799 One area that sometimes gives rise to problems concerns the EHLO or
31800 HELO commands. Some clients send syntactically invalid versions of these
31801 commands, which Exim rejects by default. (This is nothing to do with verifying
31802 the data that is sent, so &%helo_verify_hosts%& is not relevant.) You can tell
31803 Exim not to apply a syntax check by setting &%helo_accept_junk_hosts%& to
31804 match the broken hosts that send invalid commands.
31806 .cindex "SIZE option on MAIL command"
31807 .cindex "MAIL" "SIZE option"
31808 The amount of disk space available is checked whenever SIZE is received on
31809 a MAIL command, independently of whether &%message_size_limit%& or
31810 &%check_spool_space%& is configured, unless &%smtp_check_spool_space%& is set
31811 false. A temporary error is given if there is not enough space. If
31812 &%check_spool_space%& is set, the check is for that amount of space plus the
31813 value given with SIZE, that is, it checks that the addition of the incoming
31814 message will not reduce the space below the threshold.
31816 When a message is successfully received, Exim includes the local message id in
31817 its response to the final &"."& that terminates the data. If the remote host
31818 logs this text it can help with tracing what has happened to a message.
31820 The Exim daemon can limit the number of simultaneous incoming connections it is
31821 prepared to handle (see the &%smtp_accept_max%& option). It can also limit the
31822 number of simultaneous incoming connections from a single remote host (see the
31823 &%smtp_accept_max_per_host%& option). Additional connection attempts are
31824 rejected using the SMTP temporary error code 421.
31826 The Exim daemon does not rely on the SIGCHLD signal to detect when a
31827 subprocess has finished, as this can get lost at busy times. Instead, it looks
31828 for completed subprocesses every time it wakes up. Provided there are other
31829 things happening (new incoming calls, starts of queue runs), completed
31830 processes will be noticed and tidied away. On very quiet systems you may
31831 sometimes see a &"defunct"& Exim process hanging about. This is not a problem;
31832 it will be noticed when the daemon next wakes up.
31834 When running as a daemon, Exim can reserve some SMTP slots for specific hosts,
31835 and can also be set up to reject SMTP calls from non-reserved hosts at times of
31836 high system load &-- for details see the &%smtp_accept_reserve%&,
31837 &%smtp_load_reserve%&, and &%smtp_reserve_hosts%& options. The load check
31838 applies in both the daemon and &'inetd'& cases.
31840 Exim normally starts a delivery process for each message received, though this
31841 can be varied by means of the &%-odq%& command line option and the
31842 &%queue_only%&, &%queue_only_file%&, and &%queue_only_load%& options. The
31843 number of simultaneously running delivery processes started in this way from
31844 SMTP input can be limited by the &%smtp_accept_queue%& and
31845 &%smtp_accept_queue_per_connection%& options. When either limit is reached,
31846 subsequently received messages are just put on the input queue without starting
31847 a delivery process.
31849 The controls that involve counts of incoming SMTP calls (&%smtp_accept_max%&,
31850 &%smtp_accept_queue%&, &%smtp_accept_reserve%&) are not available when Exim is
31851 started up from the &'inetd'& daemon, because in that case each connection is
31852 handled by an entirely independent Exim process. Control by load average is,
31853 however, available with &'inetd'&.
31855 Exim can be configured to verify addresses in incoming SMTP commands as they
31856 are received. See chapter &<<CHAPACL>>& for details. It can also be configured
31857 to rewrite addresses at this time &-- before any syntax checking is done. See
31858 section &<<SECTrewriteS>>&.
31860 Exim can also be configured to limit the rate at which a client host submits
31861 MAIL and RCPT commands in a single SMTP session. See the
31862 &%smtp_ratelimit_hosts%& option.
31866 .section "Unrecognized SMTP commands" "SECID234"
31867 .cindex "SMTP" "unrecognized commands"
31868 If Exim receives more than &%smtp_max_unknown_commands%& unrecognized SMTP
31869 commands during a single SMTP connection, it drops the connection after sending
31870 the error response to the last command. The default value for
31871 &%smtp_max_unknown_commands%& is 3. This is a defence against some kinds of
31872 abuse that subvert web servers into making connections to SMTP ports; in these
31873 circumstances, a number of non-SMTP lines are sent first.
31876 .section "Syntax and protocol errors in SMTP commands" "SECID235"
31877 .cindex "SMTP" "syntax errors"
31878 .cindex "SMTP" "protocol errors"
31879 A syntax error is detected if an SMTP command is recognized, but there is
31880 something syntactically wrong with its data, for example, a malformed email
31881 address in a RCPT command. Protocol errors include invalid command
31882 sequencing such as RCPT before MAIL. If Exim receives more than
31883 &%smtp_max_synprot_errors%& such commands during a single SMTP connection, it
31884 drops the connection after sending the error response to the last command. The
31885 default value for &%smtp_max_synprot_errors%& is 3. This is a defence against
31886 broken clients that loop sending bad commands (yes, it has been seen).
31890 .section "Use of non-mail SMTP commands" "SECID236"
31891 .cindex "SMTP" "non-mail commands"
31892 The &"non-mail"& SMTP commands are those other than MAIL, RCPT, and
31893 DATA. Exim counts such commands, and drops the connection if there are too
31894 many of them in a single SMTP session. This action catches some
31895 denial-of-service attempts and things like repeated failing AUTHs, or a mad
31896 client looping sending EHLO. The global option &%smtp_accept_max_nonmail%&
31897 defines what &"too many"& means. Its default value is 10.
31899 When a new message is expected, one occurrence of RSET is not counted. This
31900 allows a client to send one RSET between messages (this is not necessary,
31901 but some clients do it). Exim also allows one uncounted occurrence of HELO
31902 or EHLO, and one occurrence of STARTTLS between messages. After
31903 starting up a TLS session, another EHLO is expected, and so it too is not
31906 The first occurrence of AUTH in a connection, or immediately following
31907 STARTTLS is also not counted. Otherwise, all commands other than MAIL,
31908 RCPT, DATA, and QUIT are counted.
31910 You can control which hosts are subject to the limit set by
31911 &%smtp_accept_max_nonmail%& by setting
31912 &%smtp_accept_max_nonmail_hosts%&. The default value is &`*`&, which makes
31913 the limit apply to all hosts. This option means that you can exclude any
31914 specific badly-behaved hosts that you have to live with.
31919 .section "The VRFY and EXPN commands" "SECID237"
31920 When Exim receives a VRFY or EXPN command on a TCP/IP connection, it
31921 runs the ACL specified by &%acl_smtp_vrfy%& or &%acl_smtp_expn%& (as
31922 appropriate) in order to decide whether the command should be accepted or not.
31923 If no ACL is defined, the command is rejected.
31925 .cindex "VRFY" "processing"
31926 When VRFY is accepted, it runs exactly the same code as when Exim is
31927 called with the &%-bv%& option.
31929 .cindex "EXPN" "processing"
31930 When EXPN is accepted, a single-level expansion of the address is done.
31931 EXPN is treated as an &"address test"& (similar to the &%-bt%& option) rather
31932 than a verification (the &%-bv%& option). If an unqualified local part is given
31933 as the argument to EXPN, it is qualified with &%qualify_domain%&. Rejections
31934 of VRFY and EXPN commands are logged on the main and reject logs, and
31935 VRFY verification failures are logged on the main log for consistency with
31940 .section "The ETRN command" "SECTETRN"
31941 .cindex "ETRN" "processing"
31942 RFC 1985 describes an SMTP command called ETRN that is designed to
31943 overcome the security problems of the TURN command (which has fallen into
31944 disuse). When Exim receives an ETRN command on a TCP/IP connection, it runs
31945 the ACL specified by &%acl_smtp_etrn%& in order to decide whether the command
31946 should be accepted or not. If no ACL is defined, the command is rejected.
31948 The ETRN command is concerned with &"releasing"& messages that are awaiting
31949 delivery to certain hosts. As Exim does not organize its message queue by host,
31950 the only form of ETRN that is supported by default is the one where the
31951 text starts with the &"#"& prefix, in which case the remainder of the text is
31952 specific to the SMTP server. A valid ETRN command causes a run of Exim with
31953 the &%-R%& option to happen, with the remainder of the ETRN text as its
31954 argument. For example,
31962 which causes a delivery attempt on all messages with undelivered addresses
31963 containing the text &"brigadoon"&. When &%smtp_etrn_serialize%& is set (the
31964 default), Exim prevents the simultaneous execution of more than one queue run
31965 for the same argument string as a result of an ETRN command. This stops
31966 a misbehaving client from starting more than one queue runner at once.
31968 .cindex "hints database" "ETRN serialization"
31969 Exim implements the serialization by means of a hints database in which a
31970 record is written whenever a process is started by ETRN, and deleted when
31971 the process completes. However, Exim does not keep the SMTP session waiting for
31972 the ETRN process to complete. Once ETRN is accepted, the client is sent
31973 a &"success"& return code. Obviously there is scope for hints records to get
31974 left lying around if there is a system or program crash. To guard against this,
31975 Exim ignores any records that are more than six hours old.
31977 .oindex "&%smtp_etrn_command%&"
31978 For more control over what ETRN does, the &%smtp_etrn_command%& option can
31979 used. This specifies a command that is run whenever ETRN is received,
31980 whatever the form of its argument. For
31983 smtp_etrn_command = /etc/etrn_command $domain \
31984 $sender_host_address
31986 .vindex "&$domain$&"
31987 The string is split up into arguments which are independently expanded. The
31988 expansion variable &$domain$& is set to the argument of the ETRN command,
31989 and no syntax checking is done on the contents of this argument. Exim does not
31990 wait for the command to complete, so its status code is not checked. Exim runs
31991 under its own uid and gid when receiving incoming SMTP, so it is not possible
31992 for it to change them before running the command.
31996 .section "Incoming local SMTP" "SECID238"
31997 .cindex "SMTP" "local incoming"
31998 Some user agents use SMTP to pass messages to their local MTA using the
31999 standard input and output, as opposed to passing the envelope on the command
32000 line and writing the message to the standard input. This is supported by the
32001 &%-bs%& option. This form of SMTP is handled in the same way as incoming
32002 messages over TCP/IP (including the use of ACLs), except that the envelope
32003 sender given in a MAIL command is ignored unless the caller is trusted. In
32004 an ACL you can detect this form of SMTP input by testing for an empty host
32005 identification. It is common to have this as the first line in the ACL that
32006 runs for RCPT commands:
32010 This accepts SMTP messages from local processes without doing any other tests.
32014 .section "Outgoing batched SMTP" "SECTbatchSMTP"
32015 .cindex "SMTP" "batched outgoing"
32016 .cindex "batched SMTP output"
32017 Both the &(appendfile)& and &(pipe)& transports can be used for handling
32018 batched SMTP. Each has an option called &%use_bsmtp%& which causes messages to
32019 be output in BSMTP format. No SMTP responses are possible for this form of
32020 delivery. All it is doing is using SMTP commands as a way of transmitting the
32021 envelope along with the message.
32023 The message is written to the file or pipe preceded by the SMTP commands
32024 MAIL and RCPT, and followed by a line containing a single dot. Lines in
32025 the message that start with a dot have an extra dot added. The SMTP command
32026 HELO is not normally used. If it is required, the &%message_prefix%& option
32027 can be used to specify it.
32029 Because &(appendfile)& and &(pipe)& are both local transports, they accept only
32030 one recipient address at a time by default. However, you can arrange for them
32031 to handle several addresses at once by setting the &%batch_max%& option. When
32032 this is done for BSMTP, messages may contain multiple RCPT commands. See
32033 chapter &<<CHAPbatching>>& for more details.
32036 When one or more addresses are routed to a BSMTP transport by a router that
32037 sets up a host list, the name of the first host on the list is available to the
32038 transport in the variable &$host$&. Here is an example of such a transport and
32043 driver = manualroute
32044 transport = smtp_appendfile
32045 route_list = domain.example batch.host.example
32049 driver = appendfile
32050 directory = /var/bsmtp/$host
32055 This causes messages addressed to &'domain.example'& to be written in BSMTP
32056 format to &_/var/bsmtp/batch.host.example_&, with only a single copy of each
32057 message (unless there are more than 1000 recipients).
32061 .section "Incoming batched SMTP" "SECTincomingbatchedSMTP"
32062 .cindex "SMTP" "batched incoming"
32063 .cindex "batched SMTP input"
32064 The &%-bS%& command line option causes Exim to accept one or more messages by
32065 reading SMTP on the standard input, but to generate no responses. If the caller
32066 is trusted, the senders in the MAIL commands are believed; otherwise the
32067 sender is always the caller of Exim. Unqualified senders and receivers are not
32068 rejected (there seems little point) but instead just get qualified. HELO
32069 and EHLO act as RSET; VRFY, EXPN, ETRN and HELP, act
32070 as NOOP; QUIT quits.
32072 Minimal policy checking is done for BSMTP input. Only the non-SMTP
32073 ACL is run in the same way as for non-SMTP local input.
32075 If an error is detected while reading a message, including a missing &"."& at
32076 the end, Exim gives up immediately. It writes details of the error to the
32077 standard output in a stylized way that the calling program should be able to
32078 make some use of automatically, for example:
32080 554 Unexpected end of file
32081 Transaction started in line 10
32082 Error detected in line 14
32084 It writes a more verbose version, for human consumption, to the standard error
32087 An error was detected while processing a file of BSMTP input.
32088 The error message was:
32090 501 '>' missing at end of address
32092 The SMTP transaction started in line 10.
32093 The error was detected in line 12.
32094 The SMTP command at fault was:
32096 rcpt to:<malformed@in.com.plete
32098 1 previous message was successfully processed.
32099 The rest of the batch was abandoned.
32101 The return code from Exim is zero only if there were no errors. It is 1 if some
32102 messages were accepted before an error was detected, and 2 if no messages were
32104 .ecindex IIDsmtpproc1
32105 .ecindex IIDsmtpproc2
32109 . ////////////////////////////////////////////////////////////////////////////
32110 . ////////////////////////////////////////////////////////////////////////////
32112 .chapter "Customizing bounce and warning messages" "CHAPemsgcust" &&&
32113 "Customizing messages"
32114 When a message fails to be delivered, or remains on the queue for more than a
32115 configured amount of time, Exim sends a message to the original sender, or
32116 to an alternative configured address. The text of these messages is built into
32117 the code of Exim, but it is possible to change it, either by adding a single
32118 string, or by replacing each of the paragraphs by text supplied in a file.
32120 The &'From:'& and &'To:'& header lines are automatically generated; you can
32121 cause a &'Reply-To:'& line to be added by setting the &%errors_reply_to%&
32122 option. Exim also adds the line
32124 Auto-Submitted: auto-generated
32126 to all warning and bounce messages,
32129 .section "Customizing bounce messages" "SECID239"
32130 .cindex "customizing" "bounce message"
32131 .cindex "bounce message" "customizing"
32132 If &%bounce_message_text%& is set, its contents are included in the default
32133 message immediately after &"This message was created automatically by mail
32134 delivery software."& The string is not expanded. It is not used if
32135 &%bounce_message_file%& is set.
32137 When &%bounce_message_file%& is set, it must point to a template file for
32138 constructing error messages. The file consists of a series of text items,
32139 separated by lines consisting of exactly four asterisks. If the file cannot be
32140 opened, default text is used and a message is written to the main and panic
32141 logs. If any text item in the file is empty, default text is used for that
32144 .vindex "&$bounce_recipient$&"
32145 .vindex "&$bounce_return_size_limit$&"
32146 Each item of text that is read from the file is expanded, and there are two
32147 expansion variables which can be of use here: &$bounce_recipient$& is set to
32148 the recipient of an error message while it is being created, and
32149 &$bounce_return_size_limit$& contains the value of the &%return_size_limit%&
32150 option, rounded to a whole number.
32152 The items must appear in the file in the following order:
32155 The first item is included in the headers, and should include at least a
32156 &'Subject:'& header. Exim does not check the syntax of these headers.
32158 The second item forms the start of the error message. After it, Exim lists the
32159 failing addresses with their error messages.
32161 The third item is used to introduce any text from pipe transports that is to be
32162 returned to the sender. It is omitted if there is no such text.
32164 The fourth item is used to introduce the copy of the message that is returned
32165 as part of the error report.
32167 The fifth item is added after the fourth one if the returned message is
32168 truncated because it is bigger than &%return_size_limit%&.
32170 The sixth item is added after the copy of the original message.
32173 The default state (&%bounce_message_file%& unset) is equivalent to the
32174 following file, in which the sixth item is empty. The &'Subject:'& and some
32175 other lines have been split in order to fit them on the page:
32177 Subject: Mail delivery failed
32178 ${if eq{$sender_address}{$bounce_recipient}
32179 {: returning message to sender}}
32181 This message was created automatically by mail delivery software.
32183 A message ${if eq{$sender_address}{$bounce_recipient}
32184 {that you sent }{sent by
32188 }}could not be delivered to all of its recipients.
32189 This is a permanent error. The following address(es) failed:
32191 The following text was generated during the delivery attempt(s):
32193 ------ This is a copy of the message, including all the headers.
32196 ------ The body of the message is $message_size characters long;
32198 ------ $bounce_return_size_limit or so are included here.
32201 .section "Customizing warning messages" "SECTcustwarn"
32202 .cindex "customizing" "warning message"
32203 .cindex "warning of delay" "customizing the message"
32204 The option &%warn_message_file%& can be pointed at a template file for use when
32205 warnings about message delays are created. In this case there are only three
32209 The first item is included in the headers, and should include at least a
32210 &'Subject:'& header. Exim does not check the syntax of these headers.
32212 The second item forms the start of the warning message. After it, Exim lists
32213 the delayed addresses.
32215 The third item then ends the message.
32218 The default state is equivalent to the following file, except that some lines
32219 have been split here, in order to fit them on the page:
32221 Subject: Warning: message $message_exim_id delayed
32222 $warn_message_delay
32224 This message was created automatically by mail delivery software.
32226 A message ${if eq{$sender_address}{$warn_message_recipients}
32227 {that you sent }{sent by
32231 }}has not been delivered to all of its recipients after
32232 more than $warn_message_delay on the queue on $primary_hostname.
32234 The message identifier is: $message_exim_id
32235 The subject of the message is: $h_subject
32236 The date of the message is: $h_date
32238 The following address(es) have not yet been delivered:
32240 No action is required on your part. Delivery attempts will
32241 continue for some time, and this warning may be repeated at
32242 intervals if the message remains undelivered. Eventually the
32243 mail delivery software will give up, and when that happens,
32244 the message will be returned to you.
32246 .vindex "&$warn_message_delay$&"
32247 .vindex "&$warn_message_recipients$&"
32248 However, in the default state the subject and date lines are omitted if no
32249 appropriate headers exist. During the expansion of this file,
32250 &$warn_message_delay$& is set to the delay time in one of the forms &"<&'n'&>
32251 minutes"& or &"<&'n'&> hours"&, and &$warn_message_recipients$& contains a list
32252 of recipients for the warning message. There may be more than one if there are
32253 multiple addresses with different &%errors_to%& settings on the routers that
32259 . ////////////////////////////////////////////////////////////////////////////
32260 . ////////////////////////////////////////////////////////////////////////////
32262 .chapter "Some common configuration settings" "CHAPcomconreq"
32263 This chapter discusses some configuration settings that seem to be fairly
32264 common. More examples and discussion can be found in the Exim book.
32268 .section "Sending mail to a smart host" "SECID240"
32269 .cindex "smart host" "example router"
32270 If you want to send all mail for non-local domains to a &"smart host"&, you
32271 should replace the default &(dnslookup)& router with a router which does the
32272 routing explicitly:
32274 send_to_smart_host:
32275 driver = manualroute
32276 route_list = !+local_domains smart.host.name
32277 transport = remote_smtp
32279 You can use the smart host's IP address instead of the name if you wish.
32280 If you are using Exim only to submit messages to a smart host, and not for
32281 receiving incoming messages, you can arrange for it to do the submission
32282 synchronously by setting the &%mua_wrapper%& option (see chapter
32283 &<<CHAPnonqueueing>>&).
32288 .section "Using Exim to handle mailing lists" "SECTmailinglists"
32289 .cindex "mailing lists"
32290 Exim can be used to run simple mailing lists, but for large and/or complicated
32291 requirements, the use of additional specialized mailing list software such as
32292 Majordomo or Mailman is recommended.
32294 The &(redirect)& router can be used to handle mailing lists where each list
32295 is maintained in a separate file, which can therefore be managed by an
32296 independent manager. The &%domains%& router option can be used to run these
32297 lists in a separate domain from normal mail. For example:
32301 domains = lists.example
32302 file = /usr/lists/$local_part
32305 errors_to = $local_part-request@lists.example
32308 This router is skipped for domains other than &'lists.example'&. For addresses
32309 in that domain, it looks for a file that matches the local part. If there is no
32310 such file, the router declines, but because &%no_more%& is set, no subsequent
32311 routers are tried, and so the whole delivery fails.
32313 The &%forbid_pipe%& and &%forbid_file%& options prevent a local part from being
32314 expanded into a file name or a pipe delivery, which is usually inappropriate in
32317 .oindex "&%errors_to%&"
32318 The &%errors_to%& option specifies that any delivery errors caused by addresses
32319 taken from a mailing list are to be sent to the given address rather than the
32320 original sender of the message. However, before acting on this, Exim verifies
32321 the error address, and ignores it if verification fails.
32323 For example, using the configuration above, mail sent to
32324 &'dicts@lists.example'& is passed on to those addresses contained in
32325 &_/usr/lists/dicts_&, with error reports directed to
32326 &'dicts-request@lists.example'&, provided that this address can be verified.
32327 There could be a file called &_/usr/lists/dicts-request_& containing
32328 the address(es) of this particular list's manager(s), but other approaches,
32329 such as setting up an earlier router (possibly using the &%local_part_prefix%&
32330 or &%local_part_suffix%& options) to handle addresses of the form
32331 &%owner-%&&'xxx'& or &%xxx-%&&'request'&, are also possible.
32335 .section "Syntax errors in mailing lists" "SECID241"
32336 .cindex "mailing lists" "syntax errors in"
32337 If an entry in redirection data contains a syntax error, Exim normally defers
32338 delivery of the original address. That means that a syntax error in a mailing
32339 list holds up all deliveries to the list. This may not be appropriate when a
32340 list is being maintained automatically from data supplied by users, and the
32341 addresses are not rigorously checked.
32343 If the &%skip_syntax_errors%& option is set, the &(redirect)& router just skips
32344 entries that fail to parse, noting the incident in the log. If in addition
32345 &%syntax_errors_to%& is set to a verifiable address, a message is sent to it
32346 whenever a broken address is skipped. It is usually appropriate to set
32347 &%syntax_errors_to%& to the same address as &%errors_to%&.
32351 .section "Re-expansion of mailing lists" "SECID242"
32352 .cindex "mailing lists" "re-expansion of"
32353 Exim remembers every individual address to which a message has been delivered,
32354 in order to avoid duplication, but it normally stores only the original
32355 recipient addresses with a message. If all the deliveries to a mailing list
32356 cannot be done at the first attempt, the mailing list is re-expanded when the
32357 delivery is next tried. This means that alterations to the list are taken into
32358 account at each delivery attempt, so addresses that have been added to
32359 the list since the message arrived will therefore receive a copy of the
32360 message, even though it pre-dates their subscription.
32362 If this behaviour is felt to be undesirable, the &%one_time%& option can be set
32363 on the &(redirect)& router. If this is done, any addresses generated by the
32364 router that fail to deliver at the first attempt are added to the message as
32365 &"top level"& addresses, and the parent address that generated them is marked
32366 &"delivered"&. Thus, expansion of the mailing list does not happen again at the
32367 subsequent delivery attempts. The disadvantage of this is that if any of the
32368 failing addresses are incorrect, correcting them in the file has no effect on
32369 pre-existing messages.
32371 The original top-level address is remembered with each of the generated
32372 addresses, and is output in any log messages. However, any intermediate parent
32373 addresses are not recorded. This makes a difference to the log only if the
32374 &%all_parents%& selector is set, but for mailing lists there is normally only
32375 one level of expansion anyway.
32379 .section "Closed mailing lists" "SECID243"
32380 .cindex "mailing lists" "closed"
32381 The examples so far have assumed open mailing lists, to which anybody may
32382 send mail. It is also possible to set up closed lists, where mail is accepted
32383 from specified senders only. This is done by making use of the generic
32384 &%senders%& option to restrict the router that handles the list.
32386 The following example uses the same file as a list of recipients and as a list
32387 of permitted senders. It requires three routers:
32391 domains = lists.example
32392 local_part_suffix = -request
32393 file = /usr/lists/$local_part$local_part_suffix
32398 domains = lists.example
32399 senders = ${if exists {/usr/lists/$local_part}\
32400 {lsearch;/usr/lists/$local_part}{*}}
32401 file = /usr/lists/$local_part
32404 errors_to = $local_part-request@lists.example
32409 domains = lists.example
32411 data = :fail: $local_part@lists.example is a closed mailing list
32413 All three routers have the same &%domains%& setting, so for any other domains,
32414 they are all skipped. The first router runs only if the local part ends in
32415 &%-request%&. It handles messages to the list manager(s) by means of an open
32418 The second router runs only if the &%senders%& precondition is satisfied. It
32419 checks for the existence of a list that corresponds to the local part, and then
32420 checks that the sender is on the list by means of a linear search. It is
32421 necessary to check for the existence of the file before trying to search it,
32422 because otherwise Exim thinks there is a configuration error. If the file does
32423 not exist, the expansion of &%senders%& is *, which matches all senders. This
32424 means that the router runs, but because there is no list, declines, and
32425 &%no_more%& ensures that no further routers are run. The address fails with an
32426 &"unrouteable address"& error.
32428 The third router runs only if the second router is skipped, which happens when
32429 a mailing list exists, but the sender is not on it. This router forcibly fails
32430 the address, giving a suitable error message.
32435 .section "Variable Envelope Return Paths (VERP)" "SECTverp"
32437 .cindex "Variable Envelope Return Paths"
32438 .cindex "envelope sender"
32439 Variable Envelope Return Paths &-- see &url(http://cr.yp.to/proto/verp.txt) &--
32440 are a way of helping mailing list administrators discover which subscription
32441 address is the cause of a particular delivery failure. The idea is to encode
32442 the original recipient address in the outgoing envelope sender address, so that
32443 if the message is forwarded by another host and then subsequently bounces, the
32444 original recipient can be extracted from the recipient address of the bounce.
32446 .oindex &%errors_to%&
32447 .oindex &%return_path%&
32448 Envelope sender addresses can be modified by Exim using two different
32449 facilities: the &%errors_to%& option on a router (as shown in previous mailing
32450 list examples), or the &%return_path%& option on a transport. The second of
32451 these is effective only if the message is successfully delivered to another
32452 host; it is not used for errors detected on the local host (see the description
32453 of &%return_path%& in chapter &<<CHAPtransportgeneric>>&). Here is an example
32454 of the use of &%return_path%& to implement VERP on an &(smtp)& transport:
32460 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}\
32461 {$1-request+$local_part=$domain@your.dom.example}fail}
32463 This has the effect of rewriting the return path (envelope sender) on outgoing
32464 SMTP messages, if the local part of the original return path ends in
32465 &"-request"&, and the domain is &'your.dom.example'&. The rewriting inserts the
32466 local part and domain of the recipient into the return path. Suppose, for
32467 example, that a message whose return path has been set to
32468 &'somelist-request@your.dom.example'& is sent to
32469 &'subscriber@other.dom.example'&. In the transport, the return path is
32472 somelist-request+subscriber=other.dom.example@your.dom.example
32474 .vindex "&$local_part$&"
32475 For this to work, you must tell Exim to send multiple copies of messages that
32476 have more than one recipient, so that each copy has just one recipient. This is
32477 achieved by setting &%max_rcpt%& to 1. Without this, a single copy of a message
32478 might be sent to several different recipients in the same domain, in which case
32479 &$local_part$& is not available in the transport, because it is not unique.
32481 Unless your host is doing nothing but mailing list deliveries, you should
32482 probably use a separate transport for the VERP deliveries, so as not to use
32483 extra resources in making one-per-recipient copies for other deliveries. This
32484 can easily be done by expanding the &%transport%& option in the router:
32488 domains = ! +local_domains
32490 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}\
32491 {verp_smtp}{remote_smtp}}
32494 If you want to change the return path using &%errors_to%& in a router instead
32495 of using &%return_path%& in the transport, you need to set &%errors_to%& on all
32496 routers that handle mailing list addresses. This will ensure that all delivery
32497 errors, including those detected on the local host, are sent to the VERP
32500 On a host that does no local deliveries and has no manual routing, only the
32501 &(dnslookup)& router needs to be changed. A special transport is not needed for
32502 SMTP deliveries. Every mailing list recipient has its own return path value,
32503 and so Exim must hand them to the transport one at a time. Here is an example
32504 of a &(dnslookup)& router that implements VERP:
32508 domains = ! +local_domains
32509 transport = remote_smtp
32511 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}}
32512 {$1-request+$local_part=$domain@your.dom.example}fail}
32515 Before you start sending out messages with VERPed return paths, you must also
32516 configure Exim to accept the bounce messages that come back to those paths.
32517 Typically this is done by setting a &%local_part_suffix%& option for a
32518 router, and using this to route the messages to wherever you want to handle
32521 The overhead incurred in using VERP depends very much on the size of the
32522 message, the number of recipient addresses that resolve to the same remote
32523 host, and the speed of the connection over which the message is being sent. If
32524 a lot of addresses resolve to the same host and the connection is slow, sending
32525 a separate copy of the message for each address may take substantially longer
32526 than sending a single copy with many recipients (for which VERP cannot be
32534 .section "Virtual domains" "SECTvirtualdomains"
32535 .cindex "virtual domains"
32536 .cindex "domain" "virtual"
32537 The phrase &'virtual domain'& is unfortunately used with two rather different
32541 A domain for which there are no real mailboxes; all valid local parts are
32542 aliases for other email addresses. Common examples are organizational
32543 top-level domains and &"vanity"& domains.
32545 One of a number of independent domains that are all handled by the same host,
32546 with mailboxes on that host, but where the mailbox owners do not necessarily
32547 have login accounts on that host.
32550 The first usage is probably more common, and does seem more &"virtual"& than
32551 the second. This kind of domain can be handled in Exim with a straightforward
32552 aliasing router. One approach is to create a separate alias file for each
32553 virtual domain. Exim can test for the existence of the alias file to determine
32554 whether the domain exists. The &(dsearch)& lookup type is useful here, leading
32555 to a router of this form:
32559 domains = dsearch;/etc/mail/virtual
32560 data = ${lookup{$local_part}lsearch{/etc/mail/virtual/$domain}}
32563 The &%domains%& option specifies that the router is to be skipped, unless there
32564 is a file in the &_/etc/mail/virtual_& directory whose name is the same as the
32565 domain that is being processed. When the router runs, it looks up the local
32566 part in the file to find a new address (or list of addresses). The &%no_more%&
32567 setting ensures that if the lookup fails (leading to &%data%& being an empty
32568 string), Exim gives up on the address without trying any subsequent routers.
32570 This one router can handle all the virtual domains because the alias file names
32571 follow a fixed pattern. Permissions can be arranged so that appropriate people
32572 can edit the different alias files. A successful aliasing operation results in
32573 a new envelope recipient address, which is then routed from scratch.
32575 The other kind of &"virtual"& domain can also be handled in a straightforward
32576 way. One approach is to create a file for each domain containing a list of
32577 valid local parts, and use it in a router like this:
32581 domains = dsearch;/etc/mail/domains
32582 local_parts = lsearch;/etc/mail/domains/$domain
32583 transport = my_mailboxes
32585 The address is accepted if there is a file for the domain, and the local part
32586 can be found in the file. The &%domains%& option is used to check for the
32587 file's existence because &%domains%& is tested before the &%local_parts%&
32588 option (see section &<<SECTrouprecon>>&). You cannot use &%require_files%&,
32589 because that option is tested after &%local_parts%&. The transport is as
32593 driver = appendfile
32594 file = /var/mail/$domain/$local_part
32597 This uses a directory of mailboxes for each domain. The &%user%& setting is
32598 required, to specify which uid is to be used for writing to the mailboxes.
32600 The configuration shown here is just one example of how you might support this
32601 requirement. There are many other ways this kind of configuration can be set
32602 up, for example, by using a database instead of separate files to hold all the
32603 information about the domains.
32607 .section "Multiple user mailboxes" "SECTmulbox"
32608 .cindex "multiple mailboxes"
32609 .cindex "mailbox" "multiple"
32610 .cindex "local part" "prefix"
32611 .cindex "local part" "suffix"
32612 Heavy email users often want to operate with multiple mailboxes, into which
32613 incoming mail is automatically sorted. A popular way of handling this is to
32614 allow users to use multiple sender addresses, so that replies can easily be
32615 identified. Users are permitted to add prefixes or suffixes to their local
32616 parts for this purpose. The wildcard facility of the generic router options
32617 &%local_part_prefix%& and &%local_part_suffix%& can be used for this. For
32618 example, consider this router:
32623 file = $home/.forward
32624 local_part_suffix = -*
32625 local_part_suffix_optional
32628 .vindex "&$local_part_suffix$&"
32629 It runs a user's &_.forward_& file for all local parts of the form
32630 &'username-*'&. Within the filter file the user can distinguish different
32631 cases by testing the variable &$local_part_suffix$&. For example:
32633 if $local_part_suffix contains -special then
32634 save /home/$local_part/Mail/special
32637 If the filter file does not exist, or does not deal with such addresses, they
32638 fall through to subsequent routers, and, assuming no subsequent use of the
32639 &%local_part_suffix%& option is made, they presumably fail. Thus, users have
32640 control over which suffixes are valid.
32642 Alternatively, a suffix can be used to trigger the use of a different
32643 &_.forward_& file &-- which is the way a similar facility is implemented in
32649 file = $home/.forward$local_part_suffix
32650 local_part_suffix = -*
32651 local_part_suffix_optional
32654 If there is no suffix, &_.forward_& is used; if the suffix is &'-special'&, for
32655 example, &_.forward-special_& is used. Once again, if the appropriate file
32656 does not exist, or does not deal with the address, it is passed on to
32657 subsequent routers, which could, if required, look for an unqualified
32658 &_.forward_& file to use as a default.
32662 .section "Simplified vacation processing" "SECID244"
32663 .cindex "vacation processing"
32664 The traditional way of running the &'vacation'& program is for a user to set up
32665 a pipe command in a &_.forward_& file
32666 (see section &<<SECTspecitredli>>& for syntax details).
32667 This is prone to error by inexperienced users. There are two features of Exim
32668 that can be used to make this process simpler for users:
32671 A local part prefix such as &"vacation-"& can be specified on a router which
32672 can cause the message to be delivered directly to the &'vacation'& program, or
32673 alternatively can use Exim's &(autoreply)& transport. The contents of a user's
32674 &_.forward_& file are then much simpler. For example:
32676 spqr, vacation-spqr
32679 The &%require_files%& generic router option can be used to trigger a
32680 vacation delivery by checking for the existence of a certain file in the
32681 user's home directory. The &%unseen%& generic option should also be used, to
32682 ensure that the original delivery also proceeds. In this case, all the user has
32683 to do is to create a file called, say, &_.vacation_&, containing a vacation
32687 Another advantage of both these methods is that they both work even when the
32688 use of arbitrary pipes by users is locked out.
32692 .section "Taking copies of mail" "SECID245"
32693 .cindex "message" "copying every"
32694 Some installations have policies that require archive copies of all messages to
32695 be made. A single copy of each message can easily be taken by an appropriate
32696 command in a system filter, which could, for example, use a different file for
32697 each day's messages.
32699 There is also a shadow transport mechanism that can be used to take copies of
32700 messages that are successfully delivered by local transports, one copy per
32701 delivery. This could be used, &'inter alia'&, to implement automatic
32702 notification of delivery by sites that insist on doing such things.
32706 .section "Intermittently connected hosts" "SECID246"
32707 .cindex "intermittently connected hosts"
32708 It has become quite common (because it is cheaper) for hosts to connect to the
32709 Internet periodically rather than remain connected all the time. The normal
32710 arrangement is that mail for such hosts accumulates on a system that is
32711 permanently connected.
32713 Exim was designed for use on permanently connected hosts, and so it is not
32714 particularly well-suited to use in an intermittently connected environment.
32715 Nevertheless there are some features that can be used.
32718 .section "Exim on the upstream server host" "SECID247"
32719 It is tempting to arrange for incoming mail for the intermittently connected
32720 host to remain on Exim's queue until the client connects. However, this
32721 approach does not scale very well. Two different kinds of waiting message are
32722 being mixed up in the same queue &-- those that cannot be delivered because of
32723 some temporary problem, and those that are waiting for their destination host
32724 to connect. This makes it hard to manage the queue, as well as wasting
32725 resources, because each queue runner scans the entire queue.
32727 A better approach is to separate off those messages that are waiting for an
32728 intermittently connected host. This can be done by delivering these messages
32729 into local files in batch SMTP, &"mailstore"&, or other envelope-preserving
32730 format, from where they are transmitted by other software when their
32731 destination connects. This makes it easy to collect all the mail for one host
32732 in a single directory, and to apply local timeout rules on a per-message basis
32735 On a very small scale, leaving the mail on Exim's queue can be made to work. If
32736 you are doing this, you should configure Exim with a long retry period for the
32737 intermittent host. For example:
32739 cheshire.wonderland.fict.example * F,5d,24h
32741 This stops a lot of failed delivery attempts from occurring, but Exim remembers
32742 which messages it has queued up for that host. Once the intermittent host comes
32743 online, forcing delivery of one message (either by using the &%-M%& or &%-R%&
32744 options, or by using the ETRN SMTP command (see section &<<SECTETRN>>&)
32745 causes all the queued up messages to be delivered, often down a single SMTP
32746 connection. While the host remains connected, any new messages get delivered
32749 If the connecting hosts do not have fixed IP addresses, that is, if a host is
32750 issued with a different IP address each time it connects, Exim's retry
32751 mechanisms on the holding host get confused, because the IP address is normally
32752 used as part of the key string for holding retry information. This can be
32753 avoided by unsetting &%retry_include_ip_address%& on the &(smtp)& transport.
32754 Since this has disadvantages for permanently connected hosts, it is best to
32755 arrange a separate transport for the intermittently connected ones.
32759 .section "Exim on the intermittently connected client host" "SECID248"
32760 The value of &%smtp_accept_queue_per_connection%& should probably be
32761 increased, or even set to zero (that is, disabled) on the intermittently
32762 connected host, so that all incoming messages down a single connection get
32763 delivered immediately.
32765 .cindex "SMTP" "passed connection"
32766 .cindex "SMTP" "multiple deliveries"
32767 .cindex "multiple SMTP deliveries"
32768 Mail waiting to be sent from an intermittently connected host will probably
32769 not have been routed, because without a connection DNS lookups are not
32770 possible. This means that if a normal queue run is done at connection time,
32771 each message is likely to be sent in a separate SMTP session. This can be
32772 avoided by starting the queue run with a command line option beginning with
32773 &%-qq%& instead of &%-q%&. In this case, the queue is scanned twice. In the
32774 first pass, routing is done but no deliveries take place. The second pass is a
32775 normal queue run; since all the messages have been previously routed, those
32776 destined for the same host are likely to get sent as multiple deliveries in a
32777 single SMTP connection.
32781 . ////////////////////////////////////////////////////////////////////////////
32782 . ////////////////////////////////////////////////////////////////////////////
32784 .chapter "Using Exim as a non-queueing client" "CHAPnonqueueing" &&&
32785 "Exim as a non-queueing client"
32786 .cindex "client, non-queueing"
32787 .cindex "smart host" "suppressing queueing"
32788 On a personal computer, it is a common requirement for all
32789 email to be sent to a &"smart host"&. There are plenty of MUAs that can be
32790 configured to operate that way, for all the popular operating systems.
32791 However, there are some MUAs for Unix-like systems that cannot be so
32792 configured: they submit messages using the command line interface of
32793 &_/usr/sbin/sendmail_&. Furthermore, utility programs such as &'cron'& submit
32796 If the personal computer runs continuously, there is no problem, because it can
32797 run a conventional MTA that handles delivery to the smart host, and deal with
32798 any delays via its queueing mechanism. However, if the computer does not run
32799 continuously or runs different operating systems at different times, queueing
32800 email is not desirable.
32802 There is therefore a requirement for something that can provide the
32803 &_/usr/sbin/sendmail_& interface but deliver messages to a smart host without
32804 any queueing or retrying facilities. Furthermore, the delivery to the smart
32805 host should be synchronous, so that if it fails, the sending MUA is immediately
32806 informed. In other words, we want something that extends an MUA that submits
32807 to a local MTA via the command line so that it behaves like one that submits
32808 to a remote smart host using TCP/SMTP.
32810 There are a number of applications (for example, there is one called &'ssmtp'&)
32811 that do this job. However, people have found them to be lacking in various
32812 ways. For instance, you might want to allow aliasing and forwarding to be done
32813 before sending a message to the smart host.
32815 Exim already had the necessary infrastructure for doing this job. Just a few
32816 tweaks were needed to make it behave as required, though it is somewhat of an
32817 overkill to use a fully-featured MTA for this purpose.
32819 .oindex "&%mua_wrapper%&"
32820 There is a Boolean global option called &%mua_wrapper%&, defaulting false.
32821 Setting &%mua_wrapper%& true causes Exim to run in a special mode where it
32822 assumes that it is being used to &"wrap"& a command-line MUA in the manner
32823 just described. As well as setting &%mua_wrapper%&, you also need to provide a
32824 compatible router and transport configuration. Typically there will be just one
32825 router and one transport, sending everything to a smart host.
32827 When run in MUA wrapping mode, the behaviour of Exim changes in the
32831 A daemon cannot be run, nor will Exim accept incoming messages from &'inetd'&.
32832 In other words, the only way to submit messages is via the command line.
32834 Each message is synchronously delivered as soon as it is received (&%-odi%& is
32835 assumed). All queueing options (&%queue_only%&, &%queue_smtp_domains%&,
32836 &%control%& in an ACL, etc.) are quietly ignored. The Exim reception process
32837 does not finish until the delivery attempt is complete. If the delivery is
32838 successful, a zero return code is given.
32840 Address redirection is permitted, but the final routing for all addresses must
32841 be to the same remote transport, and to the same list of hosts. Furthermore,
32842 the return address (envelope sender) must be the same for all recipients, as
32843 must any added or deleted header lines. In other words, it must be possible to
32844 deliver the message in a single SMTP transaction, however many recipients there
32847 If these conditions are not met, or if routing any address results in a
32848 failure or defer status, or if Exim is unable to deliver all the recipients
32849 successfully to one of the smart hosts, delivery of the entire message fails.
32851 Because no queueing is allowed, all failures are treated as permanent; there
32852 is no distinction between 4&'xx'& and 5&'xx'& SMTP response codes from the
32853 smart host. Furthermore, because only a single yes/no response can be given to
32854 the caller, it is not possible to deliver to some recipients and not others. If
32855 there is an error (temporary or permanent) for any recipient, all are failed.
32857 If more than one smart host is listed, Exim will try another host after a
32858 connection failure or a timeout, in the normal way. However, if this kind of
32859 failure happens for all the hosts, the delivery fails.
32861 When delivery fails, an error message is written to the standard error stream
32862 (as well as to Exim's log), and Exim exits to the caller with a return code
32863 value 1. The message is expunged from Exim's spool files. No bounce messages
32864 are ever generated.
32866 No retry data is maintained, and any retry rules are ignored.
32868 A number of Exim options are overridden: &%deliver_drop_privilege%& is forced
32869 true, &%max_rcpt%& in the &(smtp)& transport is forced to &"unlimited"&,
32870 &%remote_max_parallel%& is forced to one, and fallback hosts are ignored.
32873 The overall effect is that Exim makes a single synchronous attempt to deliver
32874 the message, failing if there is any kind of problem. Because no local
32875 deliveries are done and no daemon can be run, Exim does not need root
32876 privilege. It should be possible to run it setuid to &'exim'& instead of setuid
32877 to &'root'&. See section &<<SECTrunexiwitpri>>& for a general discussion about
32878 the advantages and disadvantages of running without root privilege.
32883 . ////////////////////////////////////////////////////////////////////////////
32884 . ////////////////////////////////////////////////////////////////////////////
32886 .chapter "Log files" "CHAPlog"
32887 .scindex IIDloggen "log" "general description"
32888 .cindex "log" "types of"
32889 Exim writes three different logs, referred to as the main log, the reject log,
32894 The main log records the arrival of each message and each delivery in a single
32895 line in each case. The format is as compact as possible, in an attempt to keep
32896 down the size of log files. Two-character flag sequences make it easy to pick
32897 out these lines. A number of other events are recorded in the main log. Some of
32898 them are optional, in which case the &%log_selector%& option controls whether
32899 they are included or not. A Perl script called &'eximstats'&, which does simple
32900 analysis of main log files, is provided in the Exim distribution (see section
32901 &<<SECTmailstat>>&).
32903 .cindex "reject log"
32904 The reject log records information from messages that are rejected as a result
32905 of a configuration option (that is, for policy reasons).
32906 The first line of each rejection is a copy of the line that is also written to
32907 the main log. Then, if the message's header has been read at the time the log
32908 is written, its contents are written to this log. Only the original header
32909 lines are available; header lines added by ACLs are not logged. You can use the
32910 reject log to check that your policy controls are working correctly; on a busy
32911 host this may be easier than scanning the main log for rejection messages. You
32912 can suppress the writing of the reject log by setting &%write_rejectlog%&
32915 .cindex "panic log"
32916 .cindex "system log"
32917 When certain serious errors occur, Exim writes entries to its panic log. If the
32918 error is sufficiently disastrous, Exim bombs out afterwards. Panic log entries
32919 are usually written to the main log as well, but can get lost amid the mass of
32920 other entries. The panic log should be empty under normal circumstances. It is
32921 therefore a good idea to check it (or to have a &'cron'& script check it)
32922 regularly, in order to become aware of any problems. When Exim cannot open its
32923 panic log, it tries as a last resort to write to the system log (syslog). This
32924 is opened with LOG_PID+LOG_CONS and the facility code of LOG_MAIL. The
32925 message itself is written at priority LOG_CRIT.
32928 Every log line starts with a timestamp, in the format shown in the following
32929 example. Note that many of the examples shown in this chapter are line-wrapped.
32930 In the log file, this would be all on one line:
32932 2001-09-16 16:09:47 SMTP connection from [127.0.0.1] closed
32935 By default, the timestamps are in the local timezone. There are two
32936 ways of changing this:
32939 You can set the &%timezone%& option to a different time zone; in particular, if
32944 the timestamps will be in UTC (aka GMT).
32946 If you set &%log_timezone%& true, the time zone is added to the timestamp, for
32949 2003-04-25 11:17:07 +0100 Start queue run: pid=12762
32953 .cindex "log" "process ids in"
32954 .cindex "pid (process id)" "in log lines"
32955 Exim does not include its process id in log lines by default, but you can
32956 request that it does so by specifying the &`pid`& log selector (see section
32957 &<<SECTlogselector>>&). When this is set, the process id is output, in square
32958 brackets, immediately after the time and date.
32963 .section "Where the logs are written" "SECTwhelogwri"
32964 .cindex "log" "destination"
32965 .cindex "log" "to file"
32966 .cindex "log" "to syslog"
32968 The logs may be written to local files, or to syslog, or both. However, it
32969 should be noted that many syslog implementations use UDP as a transport, and
32970 are therefore unreliable in the sense that messages are not guaranteed to
32971 arrive at the loghost, nor is the ordering of messages necessarily maintained.
32972 It has also been reported that on large log files (tens of megabytes) you may
32973 need to tweak syslog to prevent it syncing the file with each write &-- on
32974 Linux this has been seen to make syslog take 90% plus of CPU time.
32976 The destination for Exim's logs is configured by setting LOG_FILE_PATH in
32977 &_Local/Makefile_& or by setting &%log_file_path%& in the run time
32978 configuration. This latter string is expanded, so it can contain, for example,
32979 references to the host name:
32981 log_file_path = /var/log/$primary_hostname/exim_%slog
32983 It is generally advisable, however, to set the string in &_Local/Makefile_&
32984 rather than at run time, because then the setting is available right from the
32985 start of Exim's execution. Otherwise, if there's something it wants to log
32986 before it has read the configuration file (for example, an error in the
32987 configuration file) it will not use the path you want, and may not be able to
32990 The value of LOG_FILE_PATH or &%log_file_path%& is a colon-separated
32991 list, currently limited to at most two items. This is one option where the
32992 facility for changing a list separator may not be used. The list must always be
32993 colon-separated. If an item in the list is &"syslog"& then syslog is used;
32994 otherwise the item must either be an absolute path, containing &`%s`& at the
32995 point where &"main"&, &"reject"&, or &"panic"& is to be inserted, or be empty,
32996 implying the use of a default path.
32998 When Exim encounters an empty item in the list, it searches the list defined by
32999 LOG_FILE_PATH, and uses the first item it finds that is neither empty nor
33000 &"syslog"&. This means that an empty item in &%log_file_path%& can be used to
33001 mean &"use the path specified at build time"&. It no such item exists, log
33002 files are written in the &_log_& subdirectory of the spool directory. This is
33003 equivalent to the setting:
33005 log_file_path = $spool_directory/log/%slog
33007 If you do not specify anything at build time or run time, that is where the
33010 A log file path may also contain &`%D`& or &`%M`& if datestamped log file names
33011 are in use &-- see section &<<SECTdatlogfil>>& below.
33013 Here are some examples of possible settings:
33015 &`LOG_FILE_PATH=syslog `& syslog only
33016 &`LOG_FILE_PATH=:syslog `& syslog and default path
33017 &`LOG_FILE_PATH=syslog : /usr/log/exim_%s `& syslog and specified path
33018 &`LOG_FILE_PATH=/usr/log/exim_%s `& specified path only
33020 If there are more than two paths in the list, the first is used and a panic
33025 .section "Logging to local files that are periodically &""cycled""&" "SECID285"
33026 .cindex "log" "cycling local files"
33027 .cindex "cycling logs"
33028 .cindex "&'exicyclog'&"
33029 .cindex "log" "local files; writing to"
33030 Some operating systems provide centralized and standardized methods for cycling
33031 log files. For those that do not, a utility script called &'exicyclog'& is
33032 provided (see section &<<SECTcyclogfil>>&). This renames and compresses the
33033 main and reject logs each time it is called. The maximum number of old logs to
33034 keep can be set. It is suggested this script is run as a daily &'cron'& job.
33036 An Exim delivery process opens the main log when it first needs to write to it,
33037 and it keeps the file open in case subsequent entries are required &-- for
33038 example, if a number of different deliveries are being done for the same
33039 message. However, remote SMTP deliveries can take a long time, and this means
33040 that the file may be kept open long after it is renamed if &'exicyclog'& or
33041 something similar is being used to rename log files on a regular basis. To
33042 ensure that a switch of log files is noticed as soon as possible, Exim calls
33043 &[stat()]& on the main log's name before reusing an open file, and if the file
33044 does not exist, or its inode has changed, the old file is closed and Exim
33045 tries to open the main log from scratch. Thus, an old log file may remain open
33046 for quite some time, but no Exim processes should write to it once it has been
33051 .section "Datestamped log files" "SECTdatlogfil"
33052 .cindex "log" "datestamped files"
33053 Instead of cycling the main and reject log files by renaming them
33054 periodically, some sites like to use files whose names contain a datestamp,
33055 for example, &_mainlog-20031225_&. The datestamp is in the form &_yyyymmdd_& or
33056 &_yyyymm_&. Exim has support for this way of working. It is enabled by setting
33057 the &%log_file_path%& option to a path that includes &`%D`& or &`%M`& at the
33058 point where the datestamp is required. For example:
33060 log_file_path = /var/spool/exim/log/%slog-%D
33061 log_file_path = /var/log/exim-%s-%D.log
33062 log_file_path = /var/spool/exim/log/%D-%slog
33063 log_file_path = /var/log/exim/%s.%M
33065 As before, &`%s`& is replaced by &"main"& or &"reject"&; the following are
33066 examples of names generated by the above examples:
33068 /var/spool/exim/log/mainlog-20021225
33069 /var/log/exim-reject-20021225.log
33070 /var/spool/exim/log/20021225-mainlog
33071 /var/log/exim/main.200212
33073 When this form of log file is specified, Exim automatically switches to new
33074 files at midnight. It does not make any attempt to compress old logs; you
33075 will need to write your own script if you require this. You should not
33076 run &'exicyclog'& with this form of logging.
33078 The location of the panic log is also determined by &%log_file_path%&, but it
33079 is not datestamped, because rotation of the panic log does not make sense.
33080 When generating the name of the panic log, &`%D`& or &`%M`& are removed from
33081 the string. In addition, if it immediately follows a slash, a following
33082 non-alphanumeric character is removed; otherwise a preceding non-alphanumeric
33083 character is removed. Thus, the four examples above would give these panic
33086 /var/spool/exim/log/paniclog
33087 /var/log/exim-panic.log
33088 /var/spool/exim/log/paniclog
33089 /var/log/exim/panic
33093 .section "Logging to syslog" "SECID249"
33094 .cindex "log" "syslog; writing to"
33095 The use of syslog does not change what Exim logs or the format of its messages,
33096 except in one respect. If &%syslog_timestamp%& is set false, the timestamps on
33097 Exim's log lines are omitted when these lines are sent to syslog. Apart from
33098 that, the same strings are written to syslog as to log files. The syslog
33099 &"facility"& is set to LOG_MAIL, and the program name to &"exim"&
33100 by default, but you can change these by setting the &%syslog_facility%& and
33101 &%syslog_processname%& options, respectively. If Exim was compiled with
33102 SYSLOG_LOG_PID set in &_Local/Makefile_& (this is the default in
33103 &_src/EDITME_&), then, on systems that permit it (all except ULTRIX), the
33104 LOG_PID flag is set so that the &[syslog()]& call adds the pid as well as
33105 the time and host name to each line.
33106 The three log streams are mapped onto syslog priorities as follows:
33109 &'mainlog'& is mapped to LOG_INFO
33111 &'rejectlog'& is mapped to LOG_NOTICE
33113 &'paniclog'& is mapped to LOG_ALERT
33116 Many log lines are written to both &'mainlog'& and &'rejectlog'&, and some are
33117 written to both &'mainlog'& and &'paniclog'&, so there will be duplicates if
33118 these are routed by syslog to the same place. You can suppress this duplication
33119 by setting &%syslog_duplication%& false.
33121 Exim's log lines can sometimes be very long, and some of its &'rejectlog'&
33122 entries contain multiple lines when headers are included. To cope with both
33123 these cases, entries written to syslog are split into separate &[syslog()]&
33124 calls at each internal newline, and also after a maximum of
33125 870 data characters. (This allows for a total syslog line length of 1024, when
33126 additions such as timestamps are added.) If you are running a syslog
33127 replacement that can handle lines longer than the 1024 characters allowed by
33128 RFC 3164, you should set
33130 SYSLOG_LONG_LINES=yes
33132 in &_Local/Makefile_& before building Exim. That stops Exim from splitting long
33133 lines, but it still splits at internal newlines in &'reject'& log entries.
33135 To make it easy to re-assemble split lines later, each component of a split
33136 entry starts with a string of the form [<&'n'&>/<&'m'&>] or [<&'n'&>\<&'m'&>]
33137 where <&'n'&> is the component number and <&'m'&> is the total number of
33138 components in the entry. The / delimiter is used when the line was split
33139 because it was too long; if it was split because of an internal newline, the \
33140 delimiter is used. For example, supposing the length limit to be 50 instead of
33141 870, the following would be the result of a typical rejection message to
33142 &'mainlog'& (LOG_INFO), each line in addition being preceded by the time, host
33143 name, and pid as added by syslog:
33145 [1/5] 2002-09-16 16:09:43 16RdAL-0006pc-00 rejected from
33146 [2/5] [127.0.0.1] (ph10): syntax error in 'From' header
33147 [3/5] when scanning for sender: missing or malformed lo
33148 [4/5] cal part in "<>" (envelope sender is <ph10@cam.exa
33151 The same error might cause the following lines to be written to &"rejectlog"&
33154 [1/18] 2002-09-16 16:09:43 16RdAL-0006pc-00 rejected fro
33155 [2/18] m [127.0.0.1] (ph10): syntax error in 'From' head
33156 [3/18] er when scanning for sender: missing or malformed
33157 [4/18] local part in "<>" (envelope sender is <ph10@cam
33159 [6\18] Recipients: ph10@some.domain.cam.example
33160 [7\18] P Received: from [127.0.0.1] (ident=ph10)
33161 [8\18] by xxxxx.cam.example with smtp (Exim 4.00)
33162 [9\18] id 16RdAL-0006pc-00
33163 [10/18] for ph10@cam.example; Mon, 16 Sep 2002 16:
33164 [11\18] 09:43 +0100
33166 [13\18] Subject: this is a test header
33167 [18\18] X-something: this is another header
33168 [15/18] I Message-Id: <E16RdAL-0006pc-00@xxxxx.cam.examp
33171 [18/18] Date: Mon, 16 Sep 2002 16:09:43 +0100
33173 Log lines that are neither too long nor contain newlines are written to syslog
33174 without modification.
33176 If only syslog is being used, the Exim monitor is unable to provide a log tail
33177 display, unless syslog is routing &'mainlog'& to a file on the local host and
33178 the environment variable EXIMON_LOG_FILE_PATH is set to tell the monitor
33183 .section "Log line flags" "SECID250"
33184 One line is written to the main log for each message received, and for each
33185 successful, unsuccessful, and delayed delivery. These lines can readily be
33186 picked out by the distinctive two-character flags that immediately follow the
33187 timestamp. The flags are:
33189 &`<=`& message arrival
33190 &`=>`& normal message delivery
33191 &`->`& additional address in same delivery
33192 &`*>`& delivery suppressed by &%-N%&
33193 &`**`& delivery failed; address bounced
33194 &`==`& delivery deferred; temporary problem
33198 .section "Logging message reception" "SECID251"
33199 .cindex "log" "reception line"
33200 The format of the single-line entry in the main log that is written for every
33201 message received is shown in the basic example below, which is split over
33202 several lines in order to fit it on the page:
33204 2002-10-31 08:57:53 16ZCW1-0005MB-00 <= kryten@dwarf.fict.example
33205 H=mailer.fict.example [192.168.123.123] U=exim
33206 P=smtp S=5678 id=<incoming message id>
33208 The address immediately following &"<="& is the envelope sender address. A
33209 bounce message is shown with the sender address &"<>"&, and if it is locally
33210 generated, this is followed by an item of the form
33214 which is a reference to the message that caused the bounce to be sent.
33218 For messages from other hosts, the H and U fields identify the remote host and
33219 record the RFC 1413 identity of the user that sent the message, if one was
33220 received. The number given in square brackets is the IP address of the sending
33221 host. If there is a single, unparenthesized host name in the H field, as
33222 above, it has been verified to correspond to the IP address (see the
33223 &%host_lookup%& option). If the name is in parentheses, it was the name quoted
33224 by the remote host in the SMTP HELO or EHLO command, and has not been
33225 verified. If verification yields a different name to that given for HELO or
33226 EHLO, the verified name appears first, followed by the HELO or EHLO
33227 name in parentheses.
33229 Misconfigured hosts (and mail forgers) sometimes put an IP address, with or
33230 without brackets, in the HELO or EHLO command, leading to entries in
33231 the log containing text like these examples:
33233 H=(10.21.32.43) [192.168.8.34]
33234 H=([10.21.32.43]) [192.168.8.34]
33236 This can be confusing. Only the final address in square brackets can be relied
33239 For locally generated messages (that is, messages not received over TCP/IP),
33240 the H field is omitted, and the U field contains the login name of the caller
33243 .cindex "authentication" "logging"
33244 .cindex "AUTH" "logging"
33245 For all messages, the P field specifies the protocol used to receive the
33246 message. This is the value that is stored in &$received_protocol$&. In the case
33247 of incoming SMTP messages, the value indicates whether or not any SMTP
33248 extensions (ESMTP), encryption, or authentication were used. If the SMTP
33249 session was encrypted, there is an additional X field that records the cipher
33250 suite that was used.
33252 The protocol is set to &"esmtpsa"& or &"esmtpa"& for messages received from
33253 hosts that have authenticated themselves using the SMTP AUTH command. The first
33254 value is used when the SMTP connection was encrypted (&"secure"&). In this case
33255 there is an additional item A= followed by the name of the authenticator that
33256 was used. If an authenticated identification was set up by the authenticator's
33257 &%server_set_id%& option, this is logged too, separated by a colon from the
33258 authenticator name.
33260 .cindex "size" "of message"
33261 The id field records the existing message id, if present. The size of the
33262 received message is given by the S field. When the message is delivered,
33263 headers may be removed or added, so that the size of delivered copies of the
33264 message may not correspond with this value (and indeed may be different to each
33267 The &%log_selector%& option can be used to request the logging of additional
33268 data when a message is received. See section &<<SECTlogselector>>& below.
33272 .section "Logging deliveries" "SECID252"
33273 .cindex "log" "delivery line"
33274 The format of the single-line entry in the main log that is written for every
33275 delivery is shown in one of the examples below, for local and remote
33276 deliveries, respectively. Each example has been split into two lines in order
33277 to fit it on the page:
33279 2002-10-31 08:59:13 16ZCW1-0005MB-00 => marv
33280 <marv@hitch.fict.example> R=localuser T=local_delivery
33281 2002-10-31 09:00:10 16ZCW1-0005MB-00 =>
33282 monk@holistic.fict.example R=dnslookup T=remote_smtp
33283 H=holistic.fict.example [192.168.234.234]
33285 For ordinary local deliveries, the original address is given in angle brackets
33286 after the final delivery address, which might be a pipe or a file. If
33287 intermediate address(es) exist between the original and the final address, the
33288 last of these is given in parentheses after the final address. The R and T
33289 fields record the router and transport that were used to process the address.
33291 If a shadow transport was run after a successful local delivery, the log line
33292 for the successful delivery has an item added on the end, of the form
33294 &`ST=<`&&'shadow transport name'&&`>`&
33296 If the shadow transport did not succeed, the error message is put in
33297 parentheses afterwards.
33299 .cindex "asterisk" "after IP address"
33300 When more than one address is included in a single delivery (for example, two
33301 SMTP RCPT commands in one transaction) the second and subsequent addresses are
33302 flagged with &`->`& instead of &`=>`&. When two or more messages are delivered
33303 down a single SMTP connection, an asterisk follows the IP address in the log
33304 lines for the second and subsequent messages.
33306 The generation of a reply message by a filter file gets logged as a
33307 &"delivery"& to the addressee, preceded by &">"&.
33309 The &%log_selector%& option can be used to request the logging of additional
33310 data when a message is delivered. See section &<<SECTlogselector>>& below.
33313 .section "Discarded deliveries" "SECID253"
33314 .cindex "discarded messages"
33315 .cindex "message" "discarded"
33316 .cindex "delivery" "discarded; logging"
33317 When a message is discarded as a result of the command &"seen finish"& being
33318 obeyed in a filter file which generates no deliveries, a log entry of the form
33320 2002-12-10 00:50:49 16auJc-0001UB-00 => discarded
33321 <low.club@bridge.example> R=userforward
33323 is written, to record why no deliveries are logged. When a message is discarded
33324 because it is aliased to &":blackhole:"& the log line is like this:
33326 1999-03-02 09:44:33 10HmaX-0005vi-00 => :blackhole:
33327 <hole@nowhere.example> R=blackhole_router
33331 .section "Deferred deliveries" "SECID254"
33332 When a delivery is deferred, a line of the following form is logged:
33334 2002-12-19 16:20:23 16aiQz-0002Q5-00 == marvin@endrest.example
33335 R=dnslookup T=smtp defer (146): Connection refused
33337 In the case of remote deliveries, the error is the one that was given for the
33338 last IP address that was tried. Details of individual SMTP failures are also
33339 written to the log, so the above line would be preceded by something like
33341 2002-12-19 16:20:23 16aiQz-0002Q5-00 Failed to connect to
33342 mail1.endrest.example [192.168.239.239]: Connection refused
33344 When a deferred address is skipped because its retry time has not been reached,
33345 a message is written to the log, but this can be suppressed by setting an
33346 appropriate value in &%log_selector%&.
33350 .section "Delivery failures" "SECID255"
33351 .cindex "delivery" "failure; logging"
33352 If a delivery fails because an address cannot be routed, a line of the
33353 following form is logged:
33355 1995-12-19 16:20:23 0tRiQz-0002Q5-00 ** jim@trek99.example
33356 <jim@trek99.example>: unknown mail domain
33358 If a delivery fails at transport time, the router and transport are shown, and
33359 the response from the remote host is included, as in this example:
33361 2002-07-11 07:14:17 17SXDU-000189-00 ** ace400@pb.example
33362 R=dnslookup T=remote_smtp: SMTP error from remote mailer
33363 after pipelined RCPT TO:<ace400@pb.example>: host
33364 pbmail3.py.example [192.168.63.111]: 553 5.3.0
33365 <ace400@pb.example>...Addressee unknown
33367 The word &"pipelined"& indicates that the SMTP PIPELINING extension was being
33368 used. See &%hosts_avoid_esmtp%& in the &(smtp)& transport for a way of
33369 disabling PIPELINING. The log lines for all forms of delivery failure are
33370 flagged with &`**`&.
33374 .section "Fake deliveries" "SECID256"
33375 .cindex "delivery" "fake; logging"
33376 If a delivery does not actually take place because the &%-N%& option has been
33377 used to suppress it, a normal delivery line is written to the log, except that
33378 &"=>"& is replaced by &"*>"&.
33382 .section "Completion" "SECID257"
33385 2002-10-31 09:00:11 16ZCW1-0005MB-00 Completed
33387 is written to the main log when a message is about to be removed from the spool
33388 at the end of its processing.
33393 .section "Summary of Fields in Log Lines" "SECID258"
33394 .cindex "log" "summary of fields"
33395 A summary of the field identifiers that are used in log lines is shown in
33396 the following table:
33398 &`A `& authenticator name (and optional id)
33399 &`C `& SMTP confirmation on delivery
33400 &` `& command list for &"no mail in SMTP session"&
33401 &`CV `& certificate verification status
33402 &`D `& duration of &"no mail in SMTP session"&
33403 &`DN `& distinguished name from peer certificate
33404 &`DT `& on &`=>`& lines: time taken for a delivery
33405 &`F `& sender address (on delivery lines)
33406 &`H `& host name and IP address
33407 &`I `& local interface used
33408 &`id `& message id for incoming message
33409 &`P `& on &`<=`& lines: protocol used
33410 &` `& on &`=>`& and &`**`& lines: return path
33411 &`QT `& on &`=>`& lines: time spent on queue so far
33412 &` `& on &"Completed"& lines: time spent on queue
33413 &`R `& on &`<=`& lines: reference for local bounce
33414 &` `& on &`=>`& &`**`& and &`==`& lines: router name
33415 &`S `& size of message
33416 &`ST `& shadow transport name
33417 &`T `& on &`<=`& lines: message subject (topic)
33418 &` `& on &`=>`& &`**`& and &`==`& lines: transport name
33419 &`U `& local user or RFC 1413 identity
33420 &`X `& TLS cipher suite
33424 .section "Other log entries" "SECID259"
33425 Various other types of log entry are written from time to time. Most should be
33426 self-explanatory. Among the more common are:
33429 .cindex "retry" "time not reached"
33430 &'retry time not reached'&&~&~An address previously suffered a temporary error
33431 during routing or local delivery, and the time to retry has not yet arrived.
33432 This message is not written to an individual message log file unless it happens
33433 during the first delivery attempt.
33435 &'retry time not reached for any host'&&~&~An address previously suffered
33436 temporary errors during remote delivery, and the retry time has not yet arrived
33437 for any of the hosts to which it is routed.
33439 .cindex "spool directory" "file locked"
33440 &'spool file locked'&&~&~An attempt to deliver a message cannot proceed because
33441 some other Exim process is already working on the message. This can be quite
33442 common if queue running processes are started at frequent intervals. The
33443 &'exiwhat'& utility script can be used to find out what Exim processes are
33446 .cindex "error" "ignored"
33447 &'error ignored'&&~&~There are several circumstances that give rise to this
33450 Exim failed to deliver a bounce message whose age was greater than
33451 &%ignore_bounce_errors_after%&. The bounce was discarded.
33453 A filter file set up a delivery using the &"noerror"& option, and the delivery
33454 failed. The delivery was discarded.
33456 A delivery set up by a router configured with
33457 . ==== As this is a nested list, any displays it contains must be indented
33458 . ==== as otherwise they are too far to the left.
33462 failed. The delivery was discarded.
33470 .section "Reducing or increasing what is logged" "SECTlogselector"
33471 .cindex "log" "selectors"
33472 By setting the &%log_selector%& global option, you can disable some of Exim's
33473 default logging, or you can request additional logging. The value of
33474 &%log_selector%& is made up of names preceded by plus or minus characters. For
33477 log_selector = +arguments -retry_defer
33479 The list of optional log items is in the following table, with the default
33480 selection marked by asterisks:
33482 &`*acl_warn_skipped `& skipped &%warn%& statement in ACL
33483 &` address_rewrite `& address rewriting
33484 &` all_parents `& all parents in => lines
33485 &` arguments `& command line arguments
33486 &`*connection_reject `& connection rejections
33487 &`*delay_delivery `& immediate delivery delayed
33488 &` deliver_time `& time taken to perform delivery
33489 &` delivery_size `& add &`S=`&&'nnn'& to => lines
33490 &`*dnslist_defer `& defers of DNS list (aka RBL) lookups
33491 &`*etrn `& ETRN commands
33492 &`*host_lookup_failed `& as it says
33493 &` ident_timeout `& timeout for ident connection
33494 &` incoming_interface `& incoming interface on <= lines
33495 &` incoming_port `& incoming port on <= lines
33496 &`*lost_incoming_connection `& as it says (includes timeouts)
33497 &` outgoing_port `& add remote port to => lines
33498 &`*queue_run `& start and end queue runs
33499 &` queue_time `& time on queue for one recipient
33500 &` queue_time_overall `& time on queue for whole message
33501 &` pid `& Exim process id
33502 &` received_recipients `& recipients on <= lines
33503 &` received_sender `& sender on <= lines
33504 &`*rejected_header `& header contents on reject log
33505 &`*retry_defer `& &"retry time not reached"&
33506 &` return_path_on_delivery `& put return path on => and ** lines
33507 &` sender_on_delivery `& add sender to => lines
33508 &`*sender_verify_fail `& sender verification failures
33509 &`*size_reject `& rejection because too big
33510 &`*skip_delivery `& delivery skipped in a queue run
33511 &` smtp_confirmation `& SMTP confirmation on => lines
33512 &` smtp_connection `& SMTP connections
33513 &` smtp_incomplete_transaction`& incomplete SMTP transactions
33514 &` smtp_no_mail `& session with no MAIL commands
33515 &` smtp_protocol_error `& SMTP protocol errors
33516 &` smtp_syntax_error `& SMTP syntax errors
33517 &` subject `& contents of &'Subject:'& on <= lines
33518 &` tls_certificate_verified `& certificate verification status
33519 &`*tls_cipher `& TLS cipher suite on <= and => lines
33520 &` tls_peerdn `& TLS peer DN on <= and => lines
33521 &` tls_sni `& TLS SNI on <= lines
33522 &` unknown_in_list `& DNS lookup failed in list match
33524 &` all `& all of the above
33526 More details on each of these items follows:
33529 .cindex "&%warn%& ACL verb" "log when skipping"
33530 &%acl_warn_skipped%&: When an ACL &%warn%& statement is skipped because one of
33531 its conditions cannot be evaluated, a log line to this effect is written if
33532 this log selector is set.
33534 .cindex "log" "rewriting"
33535 .cindex "rewriting" "logging"
33536 &%address_rewrite%&: This applies both to global rewrites and per-transport
33537 rewrites, but not to rewrites in filters run as an unprivileged user (because
33538 such users cannot access the log).
33540 .cindex "log" "full parentage"
33541 &%all_parents%&: Normally only the original and final addresses are logged on
33542 delivery lines; with this selector, intermediate parents are given in
33543 parentheses between them.
33545 .cindex "log" "Exim arguments"
33546 .cindex "Exim arguments, logging"
33547 &%arguments%&: This causes Exim to write the arguments with which it was called
33548 to the main log, preceded by the current working directory. This is a debugging
33549 feature, added to make it easier to find out how certain MUAs call
33550 &_/usr/sbin/sendmail_&. The logging does not happen if Exim has given up root
33551 privilege because it was called with the &%-C%& or &%-D%& options. Arguments
33552 that are empty or that contain white space are quoted. Non-printing characters
33553 are shown as escape sequences. This facility cannot log unrecognized arguments,
33554 because the arguments are checked before the configuration file is read. The
33555 only way to log such cases is to interpose a script such as &_util/logargs.sh_&
33556 between the caller and Exim.
33558 .cindex "log" "connection rejections"
33559 &%connection_reject%&: A log entry is written whenever an incoming SMTP
33560 connection is rejected, for whatever reason.
33562 .cindex "log" "delayed delivery"
33563 .cindex "delayed delivery, logging"
33564 &%delay_delivery%&: A log entry is written whenever a delivery process is not
33565 started for an incoming message because the load is too high or too many
33566 messages were received on one connection. Logging does not occur if no delivery
33567 process is started because &%queue_only%& is set or &%-odq%& was used.
33569 .cindex "log" "delivery duration"
33570 &%deliver_time%&: For each delivery, the amount of real time it has taken to
33571 perform the actual delivery is logged as DT=<&'time'&>, for example, &`DT=1s`&.
33573 .cindex "log" "message size on delivery"
33574 .cindex "size" "of message"
33575 &%delivery_size%&: For each delivery, the size of message delivered is added to
33576 the &"=>"& line, tagged with S=.
33578 .cindex "log" "dnslist defer"
33579 .cindex "DNS list" "logging defer"
33580 .cindex "black list (DNS)"
33581 &%dnslist_defer%&: A log entry is written if an attempt to look up a host in a
33582 DNS black list suffers a temporary error.
33584 .cindex "log" "ETRN commands"
33585 .cindex "ETRN" "logging"
33586 &%etrn%&: Every valid ETRN command that is received is logged, before the ACL
33587 is run to determine whether or not it is actually accepted. An invalid ETRN
33588 command, or one received within a message transaction is not logged by this
33589 selector (see &%smtp_syntax_error%& and &%smtp_protocol_error%&).
33591 .cindex "log" "host lookup failure"
33592 &%host_lookup_failed%&: When a lookup of a host's IP addresses fails to find
33593 any addresses, or when a lookup of an IP address fails to find a host name, a
33594 log line is written. This logging does not apply to direct DNS lookups when
33595 routing email addresses, but it does apply to &"byname"& lookups.
33597 .cindex "log" "ident timeout"
33598 .cindex "RFC 1413" "logging timeout"
33599 &%ident_timeout%&: A log line is written whenever an attempt to connect to a
33600 client's ident port times out.
33602 .cindex "log" "incoming interface"
33603 .cindex "interface" "logging"
33604 &%incoming_interface%&: The interface on which a message was received is added
33605 to the &"<="& line as an IP address in square brackets, tagged by I= and
33606 followed by a colon and the port number. The local interface and port are also
33607 added to other SMTP log lines, for example &"SMTP connection from"&, and to
33610 .cindex "log" "incoming remote port"
33611 .cindex "port" "logging remote"
33612 .cindex "TCP/IP" "logging incoming remote port"
33613 .vindex "&$sender_fullhost$&"
33614 .vindex "&$sender_rcvhost$&"
33615 &%incoming_port%&: The remote port number from which a message was received is
33616 added to log entries and &'Received:'& header lines, following the IP address
33617 in square brackets, and separated from it by a colon. This is implemented by
33618 changing the value that is put in the &$sender_fullhost$& and
33619 &$sender_rcvhost$& variables. Recording the remote port number has become more
33620 important with the widening use of NAT (see RFC 2505).
33622 .cindex "log" "dropped connection"
33623 &%lost_incoming_connection%&: A log line is written when an incoming SMTP
33624 connection is unexpectedly dropped.
33626 .cindex "log" "outgoing remote port"
33627 .cindex "port" "logging outgoint remote"
33628 .cindex "TCP/IP" "logging ougtoing remote port"
33629 &%outgoing_port%&: The remote port number is added to delivery log lines (those
33630 containing => tags) following the IP address. This option is not included in
33631 the default setting, because for most ordinary configurations, the remote port
33632 number is always 25 (the SMTP port).
33634 .cindex "log" "process ids in"
33635 .cindex "pid (process id)" "in log lines"
33636 &%pid%&: The current process id is added to every log line, in square brackets,
33637 immediately after the time and date.
33639 .cindex "log" "queue run"
33640 .cindex "queue runner" "logging"
33641 &%queue_run%&: The start and end of every queue run are logged.
33643 .cindex "log" "queue time"
33644 &%queue_time%&: The amount of time the message has been in the queue on the
33645 local host is logged as QT=<&'time'&> on delivery (&`=>`&) lines, for example,
33646 &`QT=3m45s`&. The clock starts when Exim starts to receive the message, so it
33647 includes reception time as well as the delivery time for the current address.
33648 This means that it may be longer than the difference between the arrival and
33649 delivery log line times, because the arrival log line is not written until the
33650 message has been successfully received.
33652 &%queue_time_overall%&: The amount of time the message has been in the queue on
33653 the local host is logged as QT=<&'time'&> on &"Completed"& lines, for
33654 example, &`QT=3m45s`&. The clock starts when Exim starts to receive the
33655 message, so it includes reception time as well as the total delivery time.
33657 .cindex "log" "recipients"
33658 &%received_recipients%&: The recipients of a message are listed in the main log
33659 as soon as the message is received. The list appears at the end of the log line
33660 that is written when a message is received, preceded by the word &"for"&. The
33661 addresses are listed after they have been qualified, but before any rewriting
33663 Recipients that were discarded by an ACL for MAIL or RCPT do not appear
33666 .cindex "log" "sender reception"
33667 &%received_sender%&: The unrewritten original sender of a message is added to
33668 the end of the log line that records the message's arrival, after the word
33669 &"from"& (before the recipients if &%received_recipients%& is also set).
33671 .cindex "log" "header lines for rejection"
33672 &%rejected_header%&: If a message's header has been received at the time a
33673 rejection is written to the reject log, the complete header is added to the
33674 log. Header logging can be turned off individually for messages that are
33675 rejected by the &[local_scan()]& function (see section &<<SECTapiforloc>>&).
33677 .cindex "log" "retry defer"
33678 &%retry_defer%&: A log line is written if a delivery is deferred because a
33679 retry time has not yet been reached. However, this &"retry time not reached"&
33680 message is always omitted from individual message logs after the first delivery
33683 .cindex "log" "return path"
33684 &%return_path_on_delivery%&: The return path that is being transmitted with
33685 the message is included in delivery and bounce lines, using the tag P=.
33686 This is omitted if no delivery actually happens, for example, if routing fails,
33687 or if delivery is to &_/dev/null_& or to &`:blackhole:`&.
33689 .cindex "log" "sender on delivery"
33690 &%sender_on_delivery%&: The message's sender address is added to every delivery
33691 and bounce line, tagged by F= (for &"from"&).
33692 This is the original sender that was received with the message; it is not
33693 necessarily the same as the outgoing return path.
33695 .cindex "log" "sender verify failure"
33696 &%sender_verify_fail%&: If this selector is unset, the separate log line that
33697 gives details of a sender verification failure is not written. Log lines for
33698 the rejection of SMTP commands contain just &"sender verify failed"&, so some
33701 .cindex "log" "size rejection"
33702 &%size_reject%&: A log line is written whenever a message is rejected because
33705 .cindex "log" "frozen messages; skipped"
33706 .cindex "frozen messages" "logging skipping"
33707 &%skip_delivery%&: A log line is written whenever a message is skipped during a
33708 queue run because it is frozen or because another process is already delivering
33710 .cindex "&""spool file is locked""&"
33711 The message that is written is &"spool file is locked"&.
33713 .cindex "log" "smtp confirmation"
33714 .cindex "SMTP" "logging confirmation"
33715 &%smtp_confirmation%&: The response to the final &"."& in the SMTP dialogue for
33716 outgoing messages is added to delivery log lines in the form &`C=`&<&'text'&>.
33717 A number of MTAs (including Exim) return an identifying string in this
33720 .cindex "log" "SMTP connections"
33721 .cindex "SMTP" "logging connections"
33722 &%smtp_connection%&: A log line is written whenever an SMTP connection is
33723 established or closed, unless the connection is from a host that matches
33724 &%hosts_connection_nolog%&. (In contrast, &%lost_incoming_connection%& applies
33725 only when the closure is unexpected.) This applies to connections from local
33726 processes that use &%-bs%& as well as to TCP/IP connections. If a connection is
33727 dropped in the middle of a message, a log line is always written, whether or
33728 not this selector is set, but otherwise nothing is written at the start and end
33729 of connections unless this selector is enabled.
33731 For TCP/IP connections to an Exim daemon, the current number of connections is
33732 included in the log message for each new connection, but note that the count is
33733 reset if the daemon is restarted.
33734 Also, because connections are closed (and the closure is logged) in
33735 subprocesses, the count may not include connections that have been closed but
33736 whose termination the daemon has not yet noticed. Thus, while it is possible to
33737 match up the opening and closing of connections in the log, the value of the
33738 logged counts may not be entirely accurate.
33740 .cindex "log" "SMTP transaction; incomplete"
33741 .cindex "SMTP" "logging incomplete transactions"
33742 &%smtp_incomplete_transaction%&: When a mail transaction is aborted by
33743 RSET, QUIT, loss of connection, or otherwise, the incident is logged,
33744 and the message sender plus any accepted recipients are included in the log
33745 line. This can provide evidence of dictionary attacks.
33747 .cindex "log" "non-MAIL SMTP sessions"
33748 .cindex "MAIL" "logging session without"
33749 &%smtp_no_mail%&: A line is written to the main log whenever an accepted SMTP
33750 connection terminates without having issued a MAIL command. This includes both
33751 the case when the connection is dropped, and the case when QUIT is used. It
33752 does not include cases where the connection is rejected right at the start (by
33753 an ACL, or because there are too many connections, or whatever). These cases
33754 already have their own log lines.
33756 The log line that is written contains the identity of the client in the usual
33757 way, followed by D= and a time, which records the duration of the connection.
33758 If the connection was authenticated, this fact is logged exactly as it is for
33759 an incoming message, with an A= item. If the connection was encrypted, CV=,
33760 DN=, and X= items may appear as they do for an incoming message, controlled by
33761 the same logging options.
33763 Finally, if any SMTP commands were issued during the connection, a C= item
33764 is added to the line, listing the commands that were used. For example,
33768 shows that the client issued QUIT straight after EHLO. If there were fewer
33769 than 20 commands, they are all listed. If there were more than 20 commands,
33770 the last 20 are listed, preceded by &"..."&. However, with the default
33771 setting of 10 for &%smtp_accep_max_nonmail%&, the connection will in any case
33772 have been aborted before 20 non-mail commands are processed.
33774 .cindex "log" "SMTP protocol error"
33775 .cindex "SMTP" "logging protocol error"
33776 &%smtp_protocol_error%&: A log line is written for every SMTP protocol error
33777 encountered. Exim does not have perfect detection of all protocol errors
33778 because of transmission delays and the use of pipelining. If PIPELINING has
33779 been advertised to a client, an Exim server assumes that the client will use
33780 it, and therefore it does not count &"expected"& errors (for example, RCPT
33781 received after rejecting MAIL) as protocol errors.
33783 .cindex "SMTP" "logging syntax errors"
33784 .cindex "SMTP" "syntax errors; logging"
33785 .cindex "SMTP" "unknown command; logging"
33786 .cindex "log" "unknown SMTP command"
33787 .cindex "log" "SMTP syntax error"
33788 &%smtp_syntax_error%&: A log line is written for every SMTP syntax error
33789 encountered. An unrecognized command is treated as a syntax error. For an
33790 external connection, the host identity is given; for an internal connection
33791 using &%-bs%& the sender identification (normally the calling user) is given.
33793 .cindex "log" "subject"
33794 .cindex "subject, logging"
33795 &%subject%&: The subject of the message is added to the arrival log line,
33796 preceded by &"T="& (T for &"topic"&, since S is already used for &"size"&).
33797 Any MIME &"words"& in the subject are decoded. The &%print_topbitchars%& option
33798 specifies whether characters with values greater than 127 should be logged
33799 unchanged, or whether they should be rendered as escape sequences.
33801 .cindex "log" "certificate verification"
33802 &%tls_certificate_verified%&: An extra item is added to <= and => log lines
33803 when TLS is in use. The item is &`CV=yes`& if the peer's certificate was
33804 verified, and &`CV=no`& if not.
33806 .cindex "log" "TLS cipher"
33807 .cindex "TLS" "logging cipher"
33808 &%tls_cipher%&: When a message is sent or received over an encrypted
33809 connection, the cipher suite used is added to the log line, preceded by X=.
33811 .cindex "log" "TLS peer DN"
33812 .cindex "TLS" "logging peer DN"
33813 &%tls_peerdn%&: When a message is sent or received over an encrypted
33814 connection, and a certificate is supplied by the remote host, the peer DN is
33815 added to the log line, preceded by DN=.
33817 .cindex "log" "TLS SNI"
33818 .cindex "TLS" "logging SNI"
33819 &%tls_sni%&: When a message is received over an encrypted connection, and
33820 the remote host provided the Server Name Indication extension, the SNI is
33821 added to the log line, preceded by SNI=.
33823 .cindex "log" "DNS failure in list"
33824 &%unknown_in_list%&: This setting causes a log entry to be written when the
33825 result of a list match is failure because a DNS lookup failed.
33829 .section "Message log" "SECID260"
33830 .cindex "message" "log file for"
33831 .cindex "log" "message log; description of"
33832 .cindex "&_msglog_& directory"
33833 .oindex "&%preserve_message_logs%&"
33834 In addition to the general log files, Exim writes a log file for each message
33835 that it handles. The names of these per-message logs are the message ids, and
33836 they are kept in the &_msglog_& sub-directory of the spool directory. Each
33837 message log contains copies of the log lines that apply to the message. This
33838 makes it easier to inspect the status of an individual message without having
33839 to search the main log. A message log is deleted when processing of the message
33840 is complete, unless &%preserve_message_logs%& is set, but this should be used
33841 only with great care because they can fill up your disk very quickly.
33843 On a heavily loaded system, it may be desirable to disable the use of
33844 per-message logs, in order to reduce disk I/O. This can be done by setting the
33845 &%message_logs%& option false.
33851 . ////////////////////////////////////////////////////////////////////////////
33852 . ////////////////////////////////////////////////////////////////////////////
33854 .chapter "Exim utilities" "CHAPutils"
33855 .scindex IIDutils "utilities"
33856 A number of utility scripts and programs are supplied with Exim and are
33857 described in this chapter. There is also the Exim Monitor, which is covered in
33858 the next chapter. The utilities described here are:
33860 .itable none 0 0 3 7* left 15* left 40* left
33861 .irow &<<SECTfinoutwha>>& &'exiwhat'& &&&
33862 "list what Exim processes are doing"
33863 .irow &<<SECTgreptheque>>& &'exiqgrep'& "grep the queue"
33864 .irow &<<SECTsumtheque>>& &'exiqsumm'& "summarize the queue"
33865 .irow &<<SECTextspeinf>>& &'exigrep'& "search the main log"
33866 .irow &<<SECTexipick>>& &'exipick'& "select messages on &&&
33868 .irow &<<SECTcyclogfil>>& &'exicyclog'& "cycle (rotate) log files"
33869 .irow &<<SECTmailstat>>& &'eximstats'& &&&
33870 "extract statistics from the log"
33871 .irow &<<SECTcheckaccess>>& &'exim_checkaccess'& &&&
33872 "check address acceptance from given IP"
33873 .irow &<<SECTdbmbuild>>& &'exim_dbmbuild'& "build a DBM file"
33874 .irow &<<SECTfinindret>>& &'exinext'& "extract retry information"
33875 .irow &<<SECThindatmai>>& &'exim_dumpdb'& "dump a hints database"
33876 .irow &<<SECThindatmai>>& &'exim_tidydb'& "clean up a hints database"
33877 .irow &<<SECThindatmai>>& &'exim_fixdb'& "patch a hints database"
33878 .irow &<<SECTmailboxmaint>>& &'exim_lock'& "lock a mailbox file"
33881 Another utility that might be of use to sites with many MTAs is Tom Kistner's
33882 &'exilog'&. It provides log visualizations across multiple Exim servers. See
33883 &url(http://duncanthrax.net/exilog/) for details.
33888 .section "Finding out what Exim processes are doing (exiwhat)" "SECTfinoutwha"
33889 .cindex "&'exiwhat'&"
33890 .cindex "process, querying"
33892 On operating systems that can restart a system call after receiving a signal
33893 (most modern OS), an Exim process responds to the SIGUSR1 signal by writing
33894 a line describing what it is doing to the file &_exim-process.info_& in the
33895 Exim spool directory. The &'exiwhat'& script sends the signal to all Exim
33896 processes it can find, having first emptied the file. It then waits for one
33897 second to allow the Exim processes to react before displaying the results. In
33898 order to run &'exiwhat'& successfully you have to have sufficient privilege to
33899 send the signal to the Exim processes, so it is normally run as root.
33901 &*Warning*&: This is not an efficient process. It is intended for occasional
33902 use by system administrators. It is not sensible, for example, to set up a
33903 script that sends SIGUSR1 signals to Exim processes at short intervals.
33906 Unfortunately, the &'ps'& command that &'exiwhat'& uses to find Exim processes
33907 varies in different operating systems. Not only are different options used,
33908 but the format of the output is different. For this reason, there are some
33909 system configuration options that configure exactly how &'exiwhat'& works. If
33910 it doesn't seem to be working for you, check the following compile-time
33913 &`EXIWHAT_PS_CMD `& the command for running &'ps'&
33914 &`EXIWHAT_PS_ARG `& the argument for &'ps'&
33915 &`EXIWHAT_EGREP_ARG `& the argument for &'egrep'& to select from &'ps'& output
33916 &`EXIWHAT_KILL_ARG `& the argument for the &'kill'& command
33918 An example of typical output from &'exiwhat'& is
33920 164 daemon: -q1h, listening on port 25
33921 10483 running queue: waiting for 0tAycK-0002ij-00 (10492)
33922 10492 delivering 0tAycK-0002ij-00 to mail.ref.example
33923 [10.19.42.42] (editor@ref.example)
33924 10592 handling incoming call from [192.168.243.242]
33925 10628 accepting a local non-SMTP message
33927 The first number in the output line is the process number. The third line has
33928 been split here, in order to fit it on the page.
33932 .section "Selective queue listing (exiqgrep)" "SECTgreptheque"
33933 .cindex "&'exiqgrep'&"
33934 .cindex "queue" "grepping"
33935 This utility is a Perl script contributed by Matt Hubbard. It runs
33939 to obtain a queue listing with undelivered recipients only, and then greps the
33940 output to select messages that match given criteria. The following selection
33941 options are available:
33944 .vitem &*-f*&&~<&'regex'&>
33945 Match the sender address. The field that is tested is enclosed in angle
33946 brackets, so you can test for bounce messages with
33950 .vitem &*-r*&&~<&'regex'&>
33951 Match a recipient address. The field that is tested is not enclosed in angle
33954 .vitem &*-s*&&~<&'regex'&>
33955 Match against the size field.
33957 .vitem &*-y*&&~<&'seconds'&>
33958 Match messages that are younger than the given time.
33960 .vitem &*-o*&&~<&'seconds'&>
33961 Match messages that are older than the given time.
33964 Match only frozen messages.
33967 Match only non-frozen messages.
33970 The following options control the format of the output:
33974 Display only the count of matching messages.
33977 Long format &-- display the full message information as output by Exim. This is
33981 Display message ids only.
33984 Brief format &-- one line per message.
33987 Display messages in reverse order.
33990 There is one more option, &%-h%&, which outputs a list of options.
33994 .section "Summarizing the queue (exiqsumm)" "SECTsumtheque"
33995 .cindex "&'exiqsumm'&"
33996 .cindex "queue" "summary"
33997 The &'exiqsumm'& utility is a Perl script which reads the output of &`exim
33998 -bp`& and produces a summary of the messages on the queue. Thus, you use it by
33999 running a command such as
34001 exim -bp | exiqsumm
34003 The output consists of one line for each domain that has messages waiting for
34004 it, as in the following example:
34006 3 2322 74m 66m msn.com.example
34008 Each line lists the number of pending deliveries for a domain, their total
34009 volume, and the length of time that the oldest and the newest messages have
34010 been waiting. Note that the number of pending deliveries is greater than the
34011 number of messages when messages have more than one recipient.
34013 A summary line is output at the end. By default the output is sorted on the
34014 domain name, but &'exiqsumm'& has the options &%-a%& and &%-c%&, which cause
34015 the output to be sorted by oldest message and by count of messages,
34016 respectively. There are also three options that split the messages for each
34017 domain into two or more subcounts: &%-b%& separates bounce messages, &%-f%&
34018 separates frozen messages, and &%-s%& separates messages according to their
34021 The output of &'exim -bp'& contains the original addresses in the message, so
34022 this also applies to the output from &'exiqsumm'&. No domains from addresses
34023 generated by aliasing or forwarding are included (unless the &%one_time%&
34024 option of the &(redirect)& router has been used to convert them into &"top
34025 level"& addresses).
34030 .section "Extracting specific information from the log (exigrep)" &&&
34032 .cindex "&'exigrep'&"
34033 .cindex "log" "extracts; grepping for"
34034 The &'exigrep'& utility is a Perl script that searches one or more main log
34035 files for entries that match a given pattern. When it finds a match, it
34036 extracts all the log entries for the relevant message, not just those that
34037 match the pattern. Thus, &'exigrep'& can extract complete log entries for a
34038 given message, or all mail for a given user, or for a given host, for example.
34039 The input files can be in Exim log format or syslog format.
34040 If a matching log line is not associated with a specific message, it is
34041 included in &'exigrep'&'s output without any additional lines. The usage is:
34043 &`exigrep [-t<`&&'n'&&`>] [-I] [-l] [-v] <`&&'pattern'&&`> [<`&&'log file'&&`>] ...`&
34045 If no log file names are given on the command line, the standard input is read.
34047 The &%-t%& argument specifies a number of seconds. It adds an additional
34048 condition for message selection. Messages that are complete are shown only if
34049 they spent more than <&'n'&> seconds on the queue.
34051 By default, &'exigrep'& does case-insensitive matching. The &%-I%& option
34052 makes it case-sensitive. This may give a performance improvement when searching
34053 large log files. Without &%-I%&, the Perl pattern matches use Perl's &`/i`&
34054 option; with &%-I%& they do not. In both cases it is possible to change the
34055 case sensitivity within the pattern by using &`(?i)`& or &`(?-i)`&.
34057 The &%-l%& option means &"literal"&, that is, treat all characters in the
34058 pattern as standing for themselves. Otherwise the pattern must be a Perl
34059 regular expression.
34061 The &%-v%& option inverts the matching condition. That is, a line is selected
34062 if it does &'not'& match the pattern.
34064 If the location of a &'zcat'& command is known from the definition of
34065 ZCAT_COMMAND in &_Local/Makefile_&, &'exigrep'& automatically passes any file
34066 whose name ends in COMPRESS_SUFFIX through &'zcat'& as it searches it.
34069 .section "Selecting messages by various criteria (exipick)" "SECTexipick"
34070 .cindex "&'exipick'&"
34071 John Jetmore's &'exipick'& utility is included in the Exim distribution. It
34072 lists messages from the queue according to a variety of criteria. For details
34073 of &'exipick'&'s facilities, visit the web page at
34074 &url(http://www.exim.org/eximwiki/ToolExipickManPage) or run &'exipick'& with
34075 the &%--help%& option.
34078 .section "Cycling log files (exicyclog)" "SECTcyclogfil"
34079 .cindex "log" "cycling local files"
34080 .cindex "cycling logs"
34081 .cindex "&'exicyclog'&"
34082 The &'exicyclog'& script can be used to cycle (rotate) &'mainlog'& and
34083 &'rejectlog'& files. This is not necessary if only syslog is being used, or if
34084 you are using log files with datestamps in their names (see section
34085 &<<SECTdatlogfil>>&). Some operating systems have their own standard mechanisms
34086 for log cycling, and these can be used instead of &'exicyclog'& if preferred.
34087 There are two command line options for &'exicyclog'&:
34089 &%-k%& <&'count'&> specifies the number of log files to keep, overriding the
34090 default that is set when Exim is built. The default default is 10.
34092 &%-l%& <&'path'&> specifies the log file path, in the same format as Exim's
34093 &%log_file_path%& option (for example, &`/var/log/exim_%slog`&), again
34094 overriding the script's default, which is to find the setting from Exim's
34098 Each time &'exicyclog'& is run the file names get &"shuffled down"& by one. If
34099 the main log file name is &_mainlog_& (the default) then when &'exicyclog'& is
34100 run &_mainlog_& becomes &_mainlog.01_&, the previous &_mainlog.01_& becomes
34101 &_mainlog.02_& and so on, up to the limit that is set in the script or by the
34102 &%-k%& option. Log files whose numbers exceed the limit are discarded. Reject
34103 logs are handled similarly.
34105 If the limit is greater than 99, the script uses 3-digit numbers such as
34106 &_mainlog.001_&, &_mainlog.002_&, etc. If you change from a number less than 99
34107 to one that is greater, or &'vice versa'&, you will have to fix the names of
34108 any existing log files.
34110 If no &_mainlog_& file exists, the script does nothing. Files that &"drop off"&
34111 the end are deleted. All files with numbers greater than 01 are compressed,
34112 using a compression command which is configured by the COMPRESS_COMMAND
34113 setting in &_Local/Makefile_&. It is usual to run &'exicyclog'& daily from a
34114 root &%crontab%& entry of the form
34116 1 0 * * * su exim -c /usr/exim/bin/exicyclog
34118 assuming you have used the name &"exim"& for the Exim user. You can run
34119 &'exicyclog'& as root if you wish, but there is no need.
34123 .section "Mail statistics (eximstats)" "SECTmailstat"
34124 .cindex "statistics"
34125 .cindex "&'eximstats'&"
34126 A Perl script called &'eximstats'& is provided for extracting statistical
34127 information from log files. The output is either plain text, or HTML.
34128 Exim log files are also supported by the &'Lire'& system produced by the
34129 LogReport Foundation &url(http://www.logreport.org).
34131 The &'eximstats'& script has been hacked about quite a bit over time. The
34132 latest version is the result of some extensive revision by Steve Campbell. A
34133 lot of information is given by default, but there are options for suppressing
34134 various parts of it. Following any options, the arguments to the script are a
34135 list of files, which should be main log files. For example:
34137 eximstats -nr /var/spool/exim/log/mainlog.01
34139 By default, &'eximstats'& extracts information about the number and volume of
34140 messages received from or delivered to various hosts. The information is sorted
34141 both by message count and by volume, and the top fifty hosts in each category
34142 are listed on the standard output. Similar information, based on email
34143 addresses or domains instead of hosts can be requested by means of various
34144 options. For messages delivered and received locally, similar statistics are
34145 also produced per user.
34147 The output also includes total counts and statistics about delivery errors, and
34148 histograms showing the number of messages received and deliveries made in each
34149 hour of the day. A delivery with more than one address in its envelope (for
34150 example, an SMTP transaction with more than one RCPT command) is counted
34151 as a single delivery by &'eximstats'&.
34153 Though normally more deliveries than receipts are reported (as messages may
34154 have multiple recipients), it is possible for &'eximstats'& to report more
34155 messages received than delivered, even though the queue is empty at the start
34156 and end of the period in question. If an incoming message contains no valid
34157 recipients, no deliveries are recorded for it. A bounce message is handled as
34158 an entirely separate message.
34160 &'eximstats'& always outputs a grand total summary giving the volume and number
34161 of messages received and deliveries made, and the number of hosts involved in
34162 each case. It also outputs the number of messages that were delayed (that is,
34163 not completely delivered at the first attempt), and the number that had at
34164 least one address that failed.
34166 The remainder of the output is in sections that can be independently disabled
34167 or modified by various options. It consists of a summary of deliveries by
34168 transport, histograms of messages received and delivered per time interval
34169 (default per hour), information about the time messages spent on the queue,
34170 a list of relayed messages, lists of the top fifty sending hosts, local
34171 senders, destination hosts, and destination local users by count and by volume,
34172 and a list of delivery errors that occurred.
34174 The relay information lists messages that were actually relayed, that is, they
34175 came from a remote host and were directly delivered to some other remote host,
34176 without being processed (for example, for aliasing or forwarding) locally.
34178 There are quite a few options for &'eximstats'& to control exactly what it
34179 outputs. These are documented in the Perl script itself, and can be extracted
34180 by running the command &(perldoc)& on the script. For example:
34182 perldoc /usr/exim/bin/eximstats
34185 .section "Checking access policy (exim_checkaccess)" "SECTcheckaccess"
34186 .cindex "&'exim_checkaccess'&"
34187 .cindex "policy control" "checking access"
34188 .cindex "checking access"
34189 The &%-bh%& command line argument allows you to run a fake SMTP session with
34190 debugging output, in order to check what Exim is doing when it is applying
34191 policy controls to incoming SMTP mail. However, not everybody is sufficiently
34192 familiar with the SMTP protocol to be able to make full use of &%-bh%&, and
34193 sometimes you just want to answer the question &"Does this address have
34194 access?"& without bothering with any further details.
34196 The &'exim_checkaccess'& utility is a &"packaged"& version of &%-bh%&. It takes
34197 two arguments, an IP address and an email address:
34199 exim_checkaccess 10.9.8.7 A.User@a.domain.example
34201 The utility runs a call to Exim with the &%-bh%& option, to test whether the
34202 given email address would be accepted in a RCPT command in a TCP/IP
34203 connection from the host with the given IP address. The output of the utility
34204 is either the word &"accepted"&, or the SMTP error response, for example:
34207 550 Relay not permitted
34209 When running this test, the utility uses &`<>`& as the envelope sender address
34210 for the MAIL command, but you can change this by providing additional
34211 options. These are passed directly to the Exim command. For example, to specify
34212 that the test is to be run with the sender address &'himself@there.example'&
34215 exim_checkaccess 10.9.8.7 A.User@a.domain.example \
34216 -f himself@there.example
34218 Note that these additional Exim command line items must be given after the two
34219 mandatory arguments.
34221 Because the &%exim_checkaccess%& uses &%-bh%&, it does not perform callouts
34222 while running its checks. You can run checks that include callouts by using
34223 &%-bhc%&, but this is not yet available in a &"packaged"& form.
34227 .section "Making DBM files (exim_dbmbuild)" "SECTdbmbuild"
34228 .cindex "DBM" "building dbm files"
34229 .cindex "building DBM files"
34230 .cindex "&'exim_dbmbuild'&"
34231 .cindex "lower casing"
34232 .cindex "binary zero" "in lookup key"
34233 The &'exim_dbmbuild'& program reads an input file containing keys and data in
34234 the format used by the &(lsearch)& lookup (see section
34235 &<<SECTsinglekeylookups>>&). It writes a DBM file using the lower-cased alias
34236 names as keys and the remainder of the information as data. The lower-casing
34237 can be prevented by calling the program with the &%-nolc%& option.
34239 A terminating zero is included as part of the key string. This is expected by
34240 the &(dbm)& lookup type. However, if the option &%-nozero%& is given,
34241 &'exim_dbmbuild'& creates files without terminating zeroes in either the key
34242 strings or the data strings. The &(dbmnz)& lookup type can be used with such
34245 The program requires two arguments: the name of the input file (which can be a
34246 single hyphen to indicate the standard input), and the name of the output file.
34247 It creates the output under a temporary name, and then renames it if all went
34251 If the native DB interface is in use (USE_DB is set in a compile-time
34252 configuration file &-- this is common in free versions of Unix) the two file
34253 names must be different, because in this mode the Berkeley DB functions create
34254 a single output file using exactly the name given. For example,
34256 exim_dbmbuild /etc/aliases /etc/aliases.db
34258 reads the system alias file and creates a DBM version of it in
34259 &_/etc/aliases.db_&.
34261 In systems that use the &'ndbm'& routines (mostly proprietary versions of
34262 Unix), two files are used, with the suffixes &_.dir_& and &_.pag_&. In this
34263 environment, the suffixes are added to the second argument of
34264 &'exim_dbmbuild'&, so it can be the same as the first. This is also the case
34265 when the Berkeley functions are used in compatibility mode (though this is not
34266 recommended), because in that case it adds a &_.db_& suffix to the file name.
34268 If a duplicate key is encountered, the program outputs a warning, and when it
34269 finishes, its return code is 1 rather than zero, unless the &%-noduperr%&
34270 option is used. By default, only the first of a set of duplicates is used &--
34271 this makes it compatible with &(lsearch)& lookups. There is an option
34272 &%-lastdup%& which causes it to use the data for the last duplicate instead.
34273 There is also an option &%-nowarn%&, which stops it listing duplicate keys to
34274 &%stderr%&. For other errors, where it doesn't actually make a new file, the
34280 .section "Finding individual retry times (exinext)" "SECTfinindret"
34281 .cindex "retry" "times"
34282 .cindex "&'exinext'&"
34283 A utility called &'exinext'& (mostly a Perl script) provides the ability to
34284 fish specific information out of the retry database. Given a mail domain (or a
34285 complete address), it looks up the hosts for that domain, and outputs any retry
34286 information for the hosts or for the domain. At present, the retry information
34287 is obtained by running &'exim_dumpdb'& (see below) and post-processing the
34288 output. For example:
34290 $ exinext piglet@milne.fict.example
34291 kanga.milne.example:192.168.8.1 error 146: Connection refused
34292 first failed: 21-Feb-1996 14:57:34
34293 last tried: 21-Feb-1996 14:57:34
34294 next try at: 21-Feb-1996 15:02:34
34295 roo.milne.example:192.168.8.3 error 146: Connection refused
34296 first failed: 20-Jan-1996 13:12:08
34297 last tried: 21-Feb-1996 11:42:03
34298 next try at: 21-Feb-1996 19:42:03
34299 past final cutoff time
34301 You can also give &'exinext'& a local part, without a domain, and it
34302 will give any retry information for that local part in your default domain.
34303 A message id can be used to obtain retry information pertaining to a specific
34304 message. This exists only when an attempt to deliver a message to a remote host
34305 suffers a message-specific error (see section &<<SECToutSMTPerr>>&).
34306 &'exinext'& is not particularly efficient, but then it is not expected to be
34309 The &'exinext'& utility calls Exim to find out information such as the location
34310 of the spool directory. The utility has &%-C%& and &%-D%& options, which are
34311 passed on to the &'exim'& commands. The first specifies an alternate Exim
34312 configuration file, and the second sets macros for use within the configuration
34313 file. These features are mainly to help in testing, but might also be useful in
34314 environments where more than one configuration file is in use.
34318 .section "Hints database maintenance" "SECThindatmai"
34319 .cindex "hints database" "maintenance"
34320 .cindex "maintaining Exim's hints database"
34321 Three utility programs are provided for maintaining the DBM files that Exim
34322 uses to contain its delivery hint information. Each program requires two
34323 arguments. The first specifies the name of Exim's spool directory, and the
34324 second is the name of the database it is to operate on. These are as follows:
34327 &'retry'&: the database of retry information
34329 &'wait-'&<&'transport name'&>: databases of information about messages waiting
34332 &'callout'&: the callout cache
34334 &'ratelimit'&: the data for implementing the ratelimit ACL condition
34336 &'misc'&: other hints data
34339 The &'misc'& database is used for
34342 Serializing ETRN runs (when &%smtp_etrn_serialize%& is set)
34344 Serializing delivery to a specific host (when &%serialize_hosts%& is set in an
34345 &(smtp)& transport)
34350 .section "exim_dumpdb" "SECID261"
34351 .cindex "&'exim_dumpdb'&"
34352 The entire contents of a database are written to the standard output by the
34353 &'exim_dumpdb'& program, which has no options or arguments other than the
34354 spool and database names. For example, to dump the retry database:
34356 exim_dumpdb /var/spool/exim retry
34358 Two lines of output are produced for each entry:
34360 T:mail.ref.example:192.168.242.242 146 77 Connection refused
34361 31-Oct-1995 12:00:12 02-Nov-1995 12:21:39 02-Nov-1995 20:21:39 *
34363 The first item on the first line is the key of the record. It starts with one
34364 of the letters R, or T, depending on whether it refers to a routing or
34365 transport retry. For a local delivery, the next part is the local address; for
34366 a remote delivery it is the name of the remote host, followed by its failing IP
34367 address (unless &%retry_include_ip_address%& is set false on the &(smtp)&
34368 transport). If the remote port is not the standard one (port 25), it is added
34369 to the IP address. Then there follows an error code, an additional error code,
34370 and a textual description of the error.
34372 The three times on the second line are the time of first failure, the time of
34373 the last delivery attempt, and the computed time for the next attempt. The line
34374 ends with an asterisk if the cutoff time for the last retry rule has been
34377 Each output line from &'exim_dumpdb'& for the &'wait-xxx'& databases
34378 consists of a host name followed by a list of ids for messages that are or were
34379 waiting to be delivered to that host. If there are a very large number for any
34380 one host, continuation records, with a sequence number added to the host name,
34381 may be seen. The data in these records is often out of date, because a message
34382 may be routed to several alternative hosts, and Exim makes no effort to keep
34387 .section "exim_tidydb" "SECID262"
34388 .cindex "&'exim_tidydb'&"
34389 The &'exim_tidydb'& utility program is used to tidy up the contents of a hints
34390 database. If run with no options, it removes all records that are more than 30
34391 days old. The age is calculated from the date and time that the record was last
34392 updated. Note that, in the case of the retry database, it is &'not'& the time
34393 since the first delivery failure. Information about a host that has been down
34394 for more than 30 days will remain in the database, provided that the record is
34395 updated sufficiently often.
34397 The cutoff date can be altered by means of the &%-t%& option, which must be
34398 followed by a time. For example, to remove all records older than a week from
34399 the retry database:
34401 exim_tidydb -t 7d /var/spool/exim retry
34403 Both the &'wait-xxx'& and &'retry'& databases contain items that involve
34404 message ids. In the former these appear as data in records keyed by host &--
34405 they were messages that were waiting for that host &-- and in the latter they
34406 are the keys for retry information for messages that have suffered certain
34407 types of error. When &'exim_tidydb'& is run, a check is made to ensure that
34408 message ids in database records are those of messages that are still on the
34409 queue. Message ids for messages that no longer exist are removed from
34410 &'wait-xxx'& records, and if this leaves any records empty, they are deleted.
34411 For the &'retry'& database, records whose keys are non-existent message ids are
34412 removed. The &'exim_tidydb'& utility outputs comments on the standard output
34413 whenever it removes information from the database.
34415 Certain records are automatically removed by Exim when they are no longer
34416 needed, but others are not. For example, if all the MX hosts for a domain are
34417 down, a retry record is created for each one. If the primary MX host comes back
34418 first, its record is removed when Exim successfully delivers to it, but the
34419 records for the others remain because Exim has not tried to use those hosts.
34421 It is important, therefore, to run &'exim_tidydb'& periodically on all the
34422 hints databases. You should do this at a quiet time of day, because it requires
34423 a database to be locked (and therefore inaccessible to Exim) while it does its
34424 work. Removing records from a DBM file does not normally make the file smaller,
34425 but all the common DBM libraries are able to re-use the space that is released.
34426 After an initial phase of increasing in size, the databases normally reach a
34427 point at which they no longer get any bigger, as long as they are regularly
34430 &*Warning*&: If you never run &'exim_tidydb'&, the space used by the hints
34431 databases is likely to keep on increasing.
34436 .section "exim_fixdb" "SECID263"
34437 .cindex "&'exim_fixdb'&"
34438 The &'exim_fixdb'& program is a utility for interactively modifying databases.
34439 Its main use is for testing Exim, but it might also be occasionally useful for
34440 getting round problems in a live system. It has no options, and its interface
34441 is somewhat crude. On entry, it prompts for input with a right angle-bracket. A
34442 key of a database record can then be entered, and the data for that record is
34445 If &"d"& is typed at the next prompt, the entire record is deleted. For all
34446 except the &'retry'& database, that is the only operation that can be carried
34447 out. For the &'retry'& database, each field is output preceded by a number, and
34448 data for individual fields can be changed by typing the field number followed
34449 by new data, for example:
34453 resets the time of the next delivery attempt. Time values are given as a
34454 sequence of digit pairs for year, month, day, hour, and minute. Colons can be
34455 used as optional separators.
34460 .section "Mailbox maintenance (exim_lock)" "SECTmailboxmaint"
34461 .cindex "mailbox" "maintenance"
34462 .cindex "&'exim_lock'&"
34463 .cindex "locking mailboxes"
34464 The &'exim_lock'& utility locks a mailbox file using the same algorithm as
34465 Exim. For a discussion of locking issues, see section &<<SECTopappend>>&.
34466 &'Exim_lock'& can be used to prevent any modification of a mailbox by Exim or
34467 a user agent while investigating a problem. The utility requires the name of
34468 the file as its first argument. If the locking is successful, the second
34469 argument is run as a command (using C's &[system()]& function); if there is no
34470 second argument, the value of the SHELL environment variable is used; if this
34471 is unset or empty, &_/bin/sh_& is run. When the command finishes, the mailbox
34472 is unlocked and the utility ends. The following options are available:
34476 Use &[fcntl()]& locking on the open mailbox.
34479 Use &[flock()]& locking on the open mailbox, provided the operating system
34482 .vitem &%-interval%&
34483 This must be followed by a number, which is a number of seconds; it sets the
34484 interval to sleep between retries (default 3).
34486 .vitem &%-lockfile%&
34487 Create a lock file before opening the mailbox.
34490 Lock the mailbox using MBX rules.
34493 Suppress verification output.
34495 .vitem &%-retries%&
34496 This must be followed by a number; it sets the number of times to try to get
34497 the lock (default 10).
34499 .vitem &%-restore_time%&
34500 This option causes &%exim_lock%& to restore the modified and read times to the
34501 locked file before exiting. This allows you to access a locked mailbox (for
34502 example, to take a backup copy) without disturbing the times that the user
34505 .vitem &%-timeout%&
34506 This must be followed by a number, which is a number of seconds; it sets a
34507 timeout to be used with a blocking &[fcntl()]& lock. If it is not set (the
34508 default), a non-blocking call is used.
34511 Generate verbose output.
34514 If none of &%-fcntl%&, &%-flock%&, &%-lockfile%& or &%-mbx%& are given, the
34515 default is to create a lock file and also to use &[fcntl()]& locking on the
34516 mailbox, which is the same as Exim's default. The use of &%-flock%& or
34517 &%-fcntl%& requires that the file be writeable; the use of &%-lockfile%&
34518 requires that the directory containing the file be writeable. Locking by lock
34519 file does not last for ever; Exim assumes that a lock file is expired if it is
34520 more than 30 minutes old.
34522 The &%-mbx%& option can be used with either or both of &%-fcntl%& or
34523 &%-flock%&. It assumes &%-fcntl%& by default. MBX locking causes a shared lock
34524 to be taken out on the open mailbox, and an exclusive lock on the file
34525 &_/tmp/.n.m_& where &'n'& and &'m'& are the device number and inode
34526 number of the mailbox file. When the locking is released, if an exclusive lock
34527 can be obtained for the mailbox, the file in &_/tmp_& is deleted.
34529 The default output contains verification of the locking that takes place. The
34530 &%-v%& option causes some additional information to be given. The &%-q%& option
34531 suppresses all output except error messages.
34535 exim_lock /var/spool/mail/spqr
34537 runs an interactive shell while the file is locked, whereas
34539 &`exim_lock -q /var/spool/mail/spqr <<End`&
34540 <&'some commands'&>
34543 runs a specific non-interactive sequence of commands while the file is locked,
34544 suppressing all verification output. A single command can be run by a command
34547 exim_lock -q /var/spool/mail/spqr \
34548 "cp /var/spool/mail/spqr /some/where"
34550 Note that if a command is supplied, it must be entirely contained within the
34551 second argument &-- hence the quotes.
34555 . ////////////////////////////////////////////////////////////////////////////
34556 . ////////////////////////////////////////////////////////////////////////////
34558 .chapter "The Exim monitor" "CHAPeximon"
34559 .scindex IIDeximon "Exim monitor" "description"
34560 .cindex "X-windows"
34561 .cindex "&'eximon'&"
34562 .cindex "Local/eximon.conf"
34563 .cindex "&_exim_monitor/EDITME_&"
34564 The Exim monitor is an application which displays in an X window information
34565 about the state of Exim's queue and what Exim is doing. An admin user can
34566 perform certain operations on messages from this GUI interface; however all
34567 such facilities are also available from the command line, and indeed, the
34568 monitor itself makes use of the command line to perform any actions requested.
34572 .section "Running the monitor" "SECID264"
34573 The monitor is started by running the script called &'eximon'&. This is a shell
34574 script that sets up a number of environment variables, and then runs the
34575 binary called &_eximon.bin_&. The default appearance of the monitor window can
34576 be changed by editing the &_Local/eximon.conf_& file created by editing
34577 &_exim_monitor/EDITME_&. Comments in that file describe what the various
34578 parameters are for.
34580 The parameters that get built into the &'eximon'& script can be overridden for
34581 a particular invocation by setting up environment variables of the same names,
34582 preceded by &`EXIMON_`&. For example, a shell command such as
34584 EXIMON_LOG_DEPTH=400 eximon
34586 (in a Bourne-compatible shell) runs &'eximon'& with an overriding setting of
34587 the LOG_DEPTH parameter. If EXIMON_LOG_FILE_PATH is set in the environment, it
34588 overrides the Exim log file configuration. This makes it possible to have
34589 &'eximon'& tailing log data that is written to syslog, provided that MAIL.INFO
34590 syslog messages are routed to a file on the local host.
34592 X resources can be used to change the appearance of the window in the normal
34593 way. For example, a resource setting of the form
34595 Eximon*background: gray94
34597 changes the colour of the background to light grey rather than white. The
34598 stripcharts are drawn with both the data lines and the reference lines in
34599 black. This means that the reference lines are not visible when on top of the
34600 data. However, their colour can be changed by setting a resource called
34601 &"highlight"& (an odd name, but that's what the Athena stripchart widget uses).
34602 For example, if your X server is running Unix, you could set up lighter
34603 reference lines in the stripcharts by obeying
34606 Eximon*highlight: gray
34609 .cindex "admin user"
34610 In order to see the contents of messages on the queue, and to operate on them,
34611 &'eximon'& must either be run as root or by an admin user.
34613 The command-line parameters of &'eximon'& are passed to &_eximon.bin_& and may
34614 contain X11 resource parameters interpreted by the X11 library. In addition,
34615 if the first parameter starts with the string "gdb" then it is removed and the
34616 binary is invoked under gdb (the parameter is used as the gdb command-name, so
34617 versioned variants of gdb can be invoked).
34619 The monitor's window is divided into three parts. The first contains one or
34620 more stripcharts and two action buttons, the second contains a &"tail"& of the
34621 main log file, and the third is a display of the queue of messages awaiting
34622 delivery, with two more action buttons. The following sections describe these
34623 different parts of the display.
34628 .section "The stripcharts" "SECID265"
34629 .cindex "stripchart"
34630 The first stripchart is always a count of messages on the queue. Its name can
34631 be configured by setting QUEUE_STRIPCHART_NAME in the
34632 &_Local/eximon.conf_& file. The remaining stripcharts are defined in the
34633 configuration script by regular expression matches on log file entries, making
34634 it possible to display, for example, counts of messages delivered to certain
34635 hosts or using certain transports. The supplied defaults display counts of
34636 received and delivered messages, and of local and SMTP deliveries. The default
34637 period between stripchart updates is one minute; this can be adjusted by a
34638 parameter in the &_Local/eximon.conf_& file.
34640 The stripchart displays rescale themselves automatically as the value they are
34641 displaying changes. There are always 10 horizontal lines in each chart; the
34642 title string indicates the value of each division when it is greater than one.
34643 For example, &"x2"& means that each division represents a value of 2.
34645 It is also possible to have a stripchart which shows the percentage fullness of
34646 a particular disk partition, which is useful when local deliveries are confined
34647 to a single partition.
34649 .cindex "&%statvfs%& function"
34650 This relies on the availability of the &[statvfs()]& function or equivalent in
34651 the operating system. Most, but not all versions of Unix that support Exim have
34652 this. For this particular stripchart, the top of the chart always represents
34653 100%, and the scale is given as &"x10%"&. This chart is configured by setting
34654 SIZE_STRIPCHART and (optionally) SIZE_STRIPCHART_NAME in the
34655 &_Local/eximon.conf_& file.
34660 .section "Main action buttons" "SECID266"
34661 .cindex "size" "of monitor window"
34662 .cindex "Exim monitor" "window size"
34663 .cindex "window size"
34664 Below the stripcharts there is an action button for quitting the monitor. Next
34665 to this is another button marked &"Size"&. They are placed here so that
34666 shrinking the window to its default minimum size leaves just the queue count
34667 stripchart and these two buttons visible. Pressing the &"Size"& button causes
34668 the window to expand to its maximum size, unless it is already at the maximum,
34669 in which case it is reduced to its minimum.
34671 When expanding to the maximum, if the window cannot be fully seen where it
34672 currently is, it is moved back to where it was the last time it was at full
34673 size. When it is expanding from its minimum size, the old position is
34674 remembered, and next time it is reduced to the minimum it is moved back there.
34676 The idea is that you can keep a reduced window just showing one or two
34677 stripcharts at a convenient place on your screen, easily expand it to show
34678 the full window when required, and just as easily put it back to what it was.
34679 The idea is copied from what the &'twm'& window manager does for its
34680 &'f.fullzoom'& action. The minimum size of the window can be changed by setting
34681 the MIN_HEIGHT and MIN_WIDTH values in &_Local/eximon.conf_&.
34683 Normally, the monitor starts up with the window at its full size, but it can be
34684 built so that it starts up with the window at its smallest size, by setting
34685 START_SMALL=yes in &_Local/eximon.conf_&.
34689 .section "The log display" "SECID267"
34690 .cindex "log" "tail of; in monitor"
34691 The second section of the window is an area in which a display of the tail of
34692 the main log is maintained.
34693 To save space on the screen, the timestamp on each log line is shortened by
34694 removing the date and, if &%log_timezone%& is set, the timezone.
34695 The log tail is not available when the only destination for logging data is
34696 syslog, unless the syslog lines are routed to a local file whose name is passed
34697 to &'eximon'& via the EXIMON_LOG_FILE_PATH environment variable.
34699 The log sub-window has a scroll bar at its lefthand side which can be used to
34700 move back to look at earlier text, and the up and down arrow keys also have a
34701 scrolling effect. The amount of log that is kept depends on the setting of
34702 LOG_BUFFER in &_Local/eximon.conf_&, which specifies the amount of memory
34703 to use. When this is full, the earlier 50% of data is discarded &-- this is
34704 much more efficient than throwing it away line by line. The sub-window also has
34705 a horizontal scroll bar for accessing the ends of long log lines. This is the
34706 only means of horizontal scrolling; the right and left arrow keys are not
34707 available. Text can be cut from this part of the window using the mouse in the
34708 normal way. The size of this subwindow is controlled by parameters in the
34709 configuration file &_Local/eximon.conf_&.
34711 Searches of the text in the log window can be carried out by means of the ^R
34712 and ^S keystrokes, which default to a reverse and a forward search,
34713 respectively. The search covers only the text that is displayed in the window.
34714 It cannot go further back up the log.
34716 The point from which the search starts is indicated by a caret marker. This is
34717 normally at the end of the text in the window, but can be positioned explicitly
34718 by pointing and clicking with the left mouse button, and is moved automatically
34719 by a successful search. If new text arrives in the window when it is scrolled
34720 back, the caret remains where it is, but if the window is not scrolled back,
34721 the caret is moved to the end of the new text.
34723 Pressing ^R or ^S pops up a window into which the search text can be typed.
34724 There are buttons for selecting forward or reverse searching, for carrying out
34725 the search, and for cancelling. If the &"Search"& button is pressed, the search
34726 happens and the window remains so that further searches can be done. If the
34727 &"Return"& key is pressed, a single search is done and the window is closed. If
34728 ^C is typed the search is cancelled.
34730 The searching facility is implemented using the facilities of the Athena text
34731 widget. By default this pops up a window containing both &"search"& and
34732 &"replace"& options. In order to suppress the unwanted &"replace"& portion for
34733 eximon, a modified version of the &%TextPop%& widget is distributed with Exim.
34734 However, the linkers in BSDI and HP-UX seem unable to handle an externally
34735 provided version of &%TextPop%& when the remaining parts of the text widget
34736 come from the standard libraries. The compile-time option EXIMON_TEXTPOP can be
34737 unset to cut out the modified &%TextPop%&, making it possible to build Eximon
34738 on these systems, at the expense of having unwanted items in the search popup
34743 .section "The queue display" "SECID268"
34744 .cindex "queue" "display in monitor"
34745 The bottom section of the monitor window contains a list of all messages that
34746 are on the queue, which includes those currently being received or delivered,
34747 as well as those awaiting delivery. The size of this subwindow is controlled by
34748 parameters in the configuration file &_Local/eximon.conf_&, and the frequency
34749 at which it is updated is controlled by another parameter in the same file &--
34750 the default is 5 minutes, since queue scans can be quite expensive. However,
34751 there is an &"Update"& action button just above the display which can be used
34752 to force an update of the queue display at any time.
34754 When a host is down for some time, a lot of pending mail can build up for it,
34755 and this can make it hard to deal with other messages on the queue. To help
34756 with this situation there is a button next to &"Update"& called &"Hide"&. If
34757 pressed, a dialogue box called &"Hide addresses ending with"& is put up. If you
34758 type anything in here and press &"Return"&, the text is added to a chain of
34759 such texts, and if every undelivered address in a message matches at least one
34760 of the texts, the message is not displayed.
34762 If there is an address that does not match any of the texts, all the addresses
34763 are displayed as normal. The matching happens on the ends of addresses so, for
34764 example, &'cam.ac.uk'& specifies all addresses in Cambridge, while
34765 &'xxx@foo.com.example'& specifies just one specific address. When any hiding
34766 has been set up, a button called &"Unhide"& is displayed. If pressed, it
34767 cancels all hiding. Also, to ensure that hidden messages do not get forgotten,
34768 a hide request is automatically cancelled after one hour.
34770 While the dialogue box is displayed, you can't press any buttons or do anything
34771 else to the monitor window. For this reason, if you want to cut text from the
34772 queue display to use in the dialogue box, you have to do the cutting before
34773 pressing the &"Hide"& button.
34775 The queue display contains, for each unhidden queued message, the length of
34776 time it has been on the queue, the size of the message, the message id, the
34777 message sender, and the first undelivered recipient, all on one line. If it is
34778 a bounce message, the sender is shown as &"<>"&. If there is more than one
34779 recipient to which the message has not yet been delivered, subsequent ones are
34780 listed on additional lines, up to a maximum configured number, following which
34781 an ellipsis is displayed. Recipients that have already received the message are
34784 .cindex "frozen messages" "display"
34785 If a message is frozen, an asterisk is displayed at the left-hand side.
34787 The queue display has a vertical scroll bar, and can also be scrolled by means
34788 of the arrow keys. Text can be cut from it using the mouse in the normal way.
34789 The text searching facilities, as described above for the log window, are also
34790 available, but the caret is always moved to the end of the text when the queue
34791 display is updated.
34795 .section "The queue menu" "SECID269"
34796 .cindex "queue" "menu in monitor"
34797 If the &%shift%& key is held down and the left button is clicked when the mouse
34798 pointer is over the text for any message, an action menu pops up, and the first
34799 line of the queue display for the message is highlighted. This does not affect
34802 If you want to use some other event for popping up the menu, you can set the
34803 MENU_EVENT parameter in &_Local/eximon.conf_& to change the default, or
34804 set EXIMON_MENU_EVENT in the environment before starting the monitor. The
34805 value set in this parameter is a standard X event description. For example, to
34806 run eximon using &%ctrl%& rather than &%shift%& you could use
34808 EXIMON_MENU_EVENT='Ctrl<Btn1Down>' eximon
34810 The title of the menu is the message id, and it contains entries which act as
34814 &'message log'&: The contents of the message log for the message are displayed
34815 in a new text window.
34817 &'headers'&: Information from the spool file that contains the envelope
34818 information and headers is displayed in a new text window. See chapter
34819 &<<CHAPspool>>& for a description of the format of spool files.
34821 &'body'&: The contents of the spool file containing the body of the message are
34822 displayed in a new text window. There is a default limit of 20,000 bytes to the
34823 amount of data displayed. This can be changed by setting the BODY_MAX
34824 option at compile time, or the EXIMON_BODY_MAX option at run time.
34826 &'deliver message'&: A call to Exim is made using the &%-M%& option to request
34827 delivery of the message. This causes an automatic thaw if the message is
34828 frozen. The &%-v%& option is also set, and the output from Exim is displayed in
34829 a new text window. The delivery is run in a separate process, to avoid holding
34830 up the monitor while the delivery proceeds.
34832 &'freeze message'&: A call to Exim is made using the &%-Mf%& option to request
34833 that the message be frozen.
34835 .cindex "thawing messages"
34836 .cindex "unfreezing messages"
34837 .cindex "frozen messages" "thawing"
34838 &'thaw message'&: A call to Exim is made using the &%-Mt%& option to request
34839 that the message be thawed.
34841 .cindex "delivery" "forcing failure"
34842 &'give up on msg'&: A call to Exim is made using the &%-Mg%& option to request
34843 that Exim gives up trying to deliver the message. A bounce message is generated
34844 for any remaining undelivered addresses.
34846 &'remove message'&: A call to Exim is made using the &%-Mrm%& option to request
34847 that the message be deleted from the system without generating a bounce
34850 &'add recipient'&: A dialog box is displayed into which a recipient address can
34851 be typed. If the address is not qualified and the QUALIFY_DOMAIN parameter
34852 is set in &_Local/eximon.conf_&, the address is qualified with that domain.
34853 Otherwise it must be entered as a fully qualified address. Pressing RETURN
34854 causes a call to Exim to be made using the &%-Mar%& option to request that an
34855 additional recipient be added to the message, unless the entry box is empty, in
34856 which case no action is taken.
34858 &'mark delivered'&: A dialog box is displayed into which a recipient address
34859 can be typed. If the address is not qualified and the QUALIFY_DOMAIN parameter
34860 is set in &_Local/eximon.conf_&, the address is qualified with that domain.
34861 Otherwise it must be entered as a fully qualified address. Pressing RETURN
34862 causes a call to Exim to be made using the &%-Mmd%& option to mark the given
34863 recipient address as already delivered, unless the entry box is empty, in which
34864 case no action is taken.
34866 &'mark all delivered'&: A call to Exim is made using the &%-Mmad%& option to
34867 mark all recipient addresses as already delivered.
34869 &'edit sender'&: A dialog box is displayed initialized with the current
34870 sender's address. Pressing RETURN causes a call to Exim to be made using the
34871 &%-Mes%& option to replace the sender address, unless the entry box is empty,
34872 in which case no action is taken. If you want to set an empty sender (as in
34873 bounce messages), you must specify it as &"<>"&. Otherwise, if the address is
34874 not qualified and the QUALIFY_DOMAIN parameter is set in &_Local/eximon.conf_&,
34875 the address is qualified with that domain.
34878 When a delivery is forced, a window showing the &%-v%& output is displayed. In
34879 other cases when a call to Exim is made, if there is any output from Exim (in
34880 particular, if the command fails) a window containing the command and the
34881 output is displayed. Otherwise, the results of the action are normally apparent
34882 from the log and queue displays. However, if you set ACTION_OUTPUT=yes in
34883 &_Local/eximon.conf_&, a window showing the Exim command is always opened, even
34884 if no output is generated.
34886 The queue display is automatically updated for actions such as freezing and
34887 thawing, unless ACTION_QUEUE_UPDATE=no has been set in
34888 &_Local/eximon.conf_&. In this case the &"Update"& button has to be used to
34889 force an update of the display after one of these actions.
34891 In any text window that is displayed as result of a menu action, the normal
34892 cut-and-paste facility is available, and searching can be carried out using ^R
34893 and ^S, as described above for the log tail window.
34900 . ////////////////////////////////////////////////////////////////////////////
34901 . ////////////////////////////////////////////////////////////////////////////
34903 .chapter "Security considerations" "CHAPsecurity"
34904 .scindex IIDsecurcon "security" "discussion of"
34905 This chapter discusses a number of issues concerned with security, some of
34906 which are also covered in other parts of this manual.
34908 For reasons that this author does not understand, some people have promoted
34909 Exim as a &"particularly secure"& mailer. Perhaps it is because of the
34910 existence of this chapter in the documentation. However, the intent of the
34911 chapter is simply to describe the way Exim works in relation to certain
34912 security concerns, not to make any specific claims about the effectiveness of
34913 its security as compared with other MTAs.
34915 What follows is a description of the way Exim is supposed to be. Best efforts
34916 have been made to try to ensure that the code agrees with the theory, but an
34917 absence of bugs can never be guaranteed. Any that are reported will get fixed
34918 as soon as possible.
34921 .section "Building a more &""hardened""& Exim" "SECID286"
34922 .cindex "security" "build-time features"
34923 There are a number of build-time options that can be set in &_Local/Makefile_&
34924 to create Exim binaries that are &"harder"& to attack, in particular by a rogue
34925 Exim administrator who does not have the root password, or by someone who has
34926 penetrated the Exim (but not the root) account. These options are as follows:
34929 ALT_CONFIG_PREFIX can be set to a string that is required to match the
34930 start of any file names used with the &%-C%& option. When it is set, these file
34931 names are also not allowed to contain the sequence &"/../"&. (However, if the
34932 value of the &%-C%& option is identical to the value of CONFIGURE_FILE in
34933 &_Local/Makefile_&, Exim ignores &%-C%& and proceeds as usual.) There is no
34934 default setting for &%ALT_CONFIG_PREFIX%&.
34936 If the permitted configuration files are confined to a directory to
34937 which only root has access, this guards against someone who has broken
34938 into the Exim account from running a privileged Exim with an arbitrary
34939 configuration file, and using it to break into other accounts.
34942 If a non-trusted configuration file (i.e. not the default configuration file
34943 or one which is trusted by virtue of being listed in the TRUSTED_CONFIG_LIST
34944 file) is specified with &%-C%&, or if macros are given with &%-D%& (but see
34945 the next item), then root privilege is retained only if the caller of Exim is
34946 root. This locks out the possibility of testing a configuration using &%-C%&
34947 right through message reception and delivery, even if the caller is root. The
34948 reception works, but by that time, Exim is running as the Exim user, so when
34949 it re-execs to regain privilege for the delivery, the use of &%-C%& causes
34950 privilege to be lost. However, root can test reception and delivery using two
34954 The WHITELIST_D_MACROS build option declares some macros to be safe to override
34955 with &%-D%& if the real uid is one of root, the Exim run-time user or the
34956 CONFIGURE_OWNER, if defined. The potential impact of this option is limited by
34957 requiring the run-time value supplied to &%-D%& to match a regex that errs on
34958 the restrictive side. Requiring build-time selection of safe macros is onerous
34959 but this option is intended solely as a transition mechanism to permit
34960 previously-working configurations to continue to work after release 4.73.
34962 If DISABLE_D_OPTION is defined, the use of the &%-D%& command line option
34965 FIXED_NEVER_USERS can be set to a colon-separated list of users that are
34966 never to be used for any deliveries. This is like the &%never_users%& runtime
34967 option, but it cannot be overridden; the runtime option adds additional users
34968 to the list. The default setting is &"root"&; this prevents a non-root user who
34969 is permitted to modify the runtime file from using Exim as a way to get root.
34974 .section "Root privilege" "SECID270"
34976 .cindex "root privilege"
34977 The Exim binary is normally setuid to root, which means that it gains root
34978 privilege (runs as root) when it starts execution. In some special cases (for
34979 example, when the daemon is not in use and there are no local deliveries), it
34980 may be possible to run Exim setuid to some user other than root. This is
34981 discussed in the next section. However, in most installations, root privilege
34982 is required for two things:
34985 To set up a socket connected to the standard SMTP port (25) when initialising
34986 the listening daemon. If Exim is run from &'inetd'&, this privileged action is
34989 To be able to change uid and gid in order to read users' &_.forward_& files and
34990 perform local deliveries as the receiving user or as specified in the
34994 It is not necessary to be root to do any of the other things Exim does, such as
34995 receiving messages and delivering them externally over SMTP, and it is
34996 obviously more secure if Exim does not run as root except when necessary.
34997 For this reason, a user and group for Exim to use must be defined in
34998 &_Local/Makefile_&. These are known as &"the Exim user"& and &"the Exim
34999 group"&. Their values can be changed by the run time configuration, though this
35000 is not recommended. Often a user called &'exim'& is used, but some sites use
35001 &'mail'& or another user name altogether.
35003 Exim uses &[setuid()]& whenever it gives up root privilege. This is a permanent
35004 abdication; the process cannot regain root afterwards. Prior to release 4.00,
35005 &[seteuid()]& was used in some circumstances, but this is no longer the case.
35007 After a new Exim process has interpreted its command line options, it changes
35008 uid and gid in the following cases:
35013 If the &%-C%& option is used to specify an alternate configuration file, or if
35014 the &%-D%& option is used to define macro values for the configuration, and the
35015 calling process is not running as root, the uid and gid are changed to those of
35016 the calling process.
35017 However, if DISABLE_D_OPTION is defined in &_Local/Makefile_&, the &%-D%&
35018 option may not be used at all.
35019 If WHITELIST_D_MACROS is defined in &_Local/Makefile_&, then some macro values
35020 can be supplied if the calling process is running as root, the Exim run-time
35021 user or CONFIGURE_OWNER, if defined.
35026 If the expansion test option (&%-be%&) or one of the filter testing options
35027 (&%-bf%& or &%-bF%&) are used, the uid and gid are changed to those of the
35030 If the process is not a daemon process or a queue runner process or a delivery
35031 process or a process for testing address routing (started with &%-bt%&), the
35032 uid and gid are changed to the Exim user and group. This means that Exim always
35033 runs under its own uid and gid when receiving messages. This also applies when
35034 testing address verification
35037 (the &%-bv%& option) and testing incoming message policy controls (the &%-bh%&
35040 For a daemon, queue runner, delivery, or address testing process, the uid
35041 remains as root at this stage, but the gid is changed to the Exim group.
35044 The processes that initially retain root privilege behave as follows:
35047 A daemon process changes the gid to the Exim group and the uid to the Exim
35048 user after setting up one or more listening sockets. The &[initgroups()]&
35049 function is called, so that if the Exim user is in any additional groups, they
35050 will be used during message reception.
35052 A queue runner process retains root privilege throughout its execution. Its
35053 job is to fork a controlled sequence of delivery processes.
35055 A delivery process retains root privilege throughout most of its execution,
35056 but any actual deliveries (that is, the transports themselves) are run in
35057 subprocesses which always change to a non-root uid and gid. For local
35058 deliveries this is typically the uid and gid of the owner of the mailbox; for
35059 remote deliveries, the Exim uid and gid are used. Once all the delivery
35060 subprocesses have been run, a delivery process changes to the Exim uid and gid
35061 while doing post-delivery tidying up such as updating the retry database and
35062 generating bounce and warning messages.
35064 While the recipient addresses in a message are being routed, the delivery
35065 process runs as root. However, if a user's filter file has to be processed,
35066 this is done in a subprocess that runs under the individual user's uid and
35067 gid. A system filter is run as root unless &%system_filter_user%& is set.
35069 A process that is testing addresses (the &%-bt%& option) runs as root so that
35070 the routing is done in the same environment as a message delivery.
35076 .section "Running Exim without privilege" "SECTrunexiwitpri"
35077 .cindex "privilege, running without"
35078 .cindex "unprivileged running"
35079 .cindex "root privilege" "running without"
35080 Some installations like to run Exim in an unprivileged state for more of its
35081 operation, for added security. Support for this mode of operation is provided
35082 by the global option &%deliver_drop_privilege%&. When this is set, the uid and
35083 gid are changed to the Exim user and group at the start of a delivery process
35084 (and also queue runner and address testing processes). This means that address
35085 routing is no longer run as root, and the deliveries themselves cannot change
35089 .cindex "daemon" "restarting"
35090 Leaving the binary setuid to root, but setting &%deliver_drop_privilege%& means
35091 that the daemon can still be started in the usual way, and it can respond
35092 correctly to SIGHUP because the re-invocation regains root privilege.
35094 An alternative approach is to make Exim setuid to the Exim user and also setgid
35095 to the Exim group. If you do this, the daemon must be started from a root
35096 process. (Calling Exim from a root process makes it behave in the way it does
35097 when it is setuid root.) However, the daemon cannot restart itself after a
35098 SIGHUP signal because it cannot regain privilege.
35100 It is still useful to set &%deliver_drop_privilege%& in this case, because it
35101 stops Exim from trying to re-invoke itself to do a delivery after a message has
35102 been received. Such a re-invocation is a waste of resources because it has no
35105 If restarting the daemon is not an issue (for example, if &%mua_wrapper%& is
35106 set, or &'inetd'& is being used instead of a daemon), having the binary setuid
35107 to the Exim user seems a clean approach, but there is one complication:
35109 In this style of operation, Exim is running with the real uid and gid set to
35110 those of the calling process, and the effective uid/gid set to Exim's values.
35111 Ideally, any association with the calling process' uid/gid should be dropped,
35112 that is, the real uid/gid should be reset to the effective values so as to
35113 discard any privileges that the caller may have. While some operating systems
35114 have a function that permits this action for a non-root effective uid, quite a
35115 number of them do not. Because of this lack of standardization, Exim does not
35116 address this problem at this time.
35118 For this reason, the recommended approach for &"mostly unprivileged"& running
35119 is to keep the Exim binary setuid to root, and to set
35120 &%deliver_drop_privilege%&. This also has the advantage of allowing a daemon to
35121 be used in the most straightforward way.
35123 If you configure Exim not to run delivery processes as root, there are a
35124 number of restrictions on what you can do:
35127 You can deliver only as the Exim user/group. You should explicitly use the
35128 &%user%& and &%group%& options to override routers or local transports that
35129 normally deliver as the recipient. This makes sure that configurations that
35130 work in this mode function the same way in normal mode. Any implicit or
35131 explicit specification of another user causes an error.
35133 Use of &_.forward_& files is severely restricted, such that it is usually
35134 not worthwhile to include them in the configuration.
35136 Users who wish to use &_.forward_& would have to make their home directory and
35137 the file itself accessible to the Exim user. Pipe and append-to-file entries,
35138 and their equivalents in Exim filters, cannot be used. While they could be
35139 enabled in the Exim user's name, that would be insecure and not very useful.
35141 Unless the local user mailboxes are all owned by the Exim user (possible in
35142 some POP3 or IMAP-only environments):
35145 They must be owned by the Exim group and be writeable by that group. This
35146 implies you must set &%mode%& in the appendfile configuration, as well as the
35147 mode of the mailbox files themselves.
35149 You must set &%no_check_owner%&, since most or all of the files will not be
35150 owned by the Exim user.
35152 You must set &%file_must_exist%&, because Exim cannot set the owner correctly
35153 on a newly created mailbox when unprivileged. This also implies that new
35154 mailboxes need to be created manually.
35159 These restrictions severely restrict what can be done in local deliveries.
35160 However, there are no restrictions on remote deliveries. If you are running a
35161 gateway host that does no local deliveries, setting &%deliver_drop_privilege%&
35162 gives more security at essentially no cost.
35164 If you are using the &%mua_wrapper%& facility (see chapter
35165 &<<CHAPnonqueueing>>&), &%deliver_drop_privilege%& is forced to be true.
35170 .section "Delivering to local files" "SECID271"
35171 Full details of the checks applied by &(appendfile)& before it writes to a file
35172 are given in chapter &<<CHAPappendfile>>&.
35176 .section "IPv4 source routing" "SECID272"
35177 .cindex "source routing" "in IP packets"
35178 .cindex "IP source routing"
35179 Many operating systems suppress IP source-routed packets in the kernel, but
35180 some cannot be made to do this, so Exim does its own check. It logs incoming
35181 IPv4 source-routed TCP calls, and then drops them. Things are all different in
35182 IPv6. No special checking is currently done.
35186 .section "The VRFY, EXPN, and ETRN commands in SMTP" "SECID273"
35187 Support for these SMTP commands is disabled by default. If required, they can
35188 be enabled by defining suitable ACLs.
35193 .section "Privileged users" "SECID274"
35194 .cindex "trusted users"
35195 .cindex "admin user"
35196 .cindex "privileged user"
35197 .cindex "user" "trusted"
35198 .cindex "user" "admin"
35199 Exim recognizes two sets of users with special privileges. Trusted users are
35200 able to submit new messages to Exim locally, but supply their own sender
35201 addresses and information about a sending host. For other users submitting
35202 local messages, Exim sets up the sender address from the uid, and doesn't
35203 permit a remote host to be specified.
35206 However, an untrusted user is permitted to use the &%-f%& command line option
35207 in the special form &%-f <>%& to indicate that a delivery failure for the
35208 message should not cause an error report. This affects the message's envelope,
35209 but it does not affect the &'Sender:'& header. Untrusted users may also be
35210 permitted to use specific forms of address with the &%-f%& option by setting
35211 the &%untrusted_set_sender%& option.
35213 Trusted users are used to run processes that receive mail messages from some
35214 other mail domain and pass them on to Exim for delivery either locally, or over
35215 the Internet. Exim trusts a caller that is running as root, as the Exim user,
35216 as any user listed in the &%trusted_users%& configuration option, or under any
35217 group listed in the &%trusted_groups%& option.
35219 Admin users are permitted to do things to the messages on Exim's queue. They
35220 can freeze or thaw messages, cause them to be returned to their senders, remove
35221 them entirely, or modify them in various ways. In addition, admin users can run
35222 the Exim monitor and see all the information it is capable of providing, which
35223 includes the contents of files on the spool.
35227 By default, the use of the &%-M%& and &%-q%& options to cause Exim to attempt
35228 delivery of messages on its queue is restricted to admin users. This
35229 restriction can be relaxed by setting the &%no_prod_requires_admin%& option.
35230 Similarly, the use of &%-bp%& (and its variants) to list the contents of the
35231 queue is also restricted to admin users. This restriction can be relaxed by
35232 setting &%no_queue_list_requires_admin%&.
35234 Exim recognizes an admin user if the calling process is running as root or as
35235 the Exim user or if any of the groups associated with the calling process is
35236 the Exim group. It is not necessary actually to be running under the Exim
35237 group. However, if admin users who are not root or the Exim user are to access
35238 the contents of files on the spool via the Exim monitor (which runs
35239 unprivileged), Exim must be built to allow group read access to its spool
35244 .section "Spool files" "SECID275"
35245 .cindex "spool directory" "files"
35246 Exim's spool directory and everything it contains is owned by the Exim user and
35247 set to the Exim group. The mode for spool files is defined in the
35248 &_Local/Makefile_& configuration file, and defaults to 0640. This means that
35249 any user who is a member of the Exim group can access these files.
35253 .section "Use of argv[0]" "SECID276"
35254 Exim examines the last component of &%argv[0]%&, and if it matches one of a set
35255 of specific strings, Exim assumes certain options. For example, calling Exim
35256 with the last component of &%argv[0]%& set to &"rsmtp"& is exactly equivalent
35257 to calling it with the option &%-bS%&. There are no security implications in
35262 .section "Use of %f formatting" "SECID277"
35263 The only use made of &"%f"& by Exim is in formatting load average values. These
35264 are actually stored in integer variables as 1000 times the load average.
35265 Consequently, their range is limited and so therefore is the length of the
35270 .section "Embedded Exim path" "SECID278"
35271 Exim uses its own path name, which is embedded in the code, only when it needs
35272 to re-exec in order to regain root privilege. Therefore, it is not root when it
35273 does so. If some bug allowed the path to get overwritten, it would lead to an
35274 arbitrary program's being run as exim, not as root.
35278 .section "Dynamic module directory" "SECTdynmoddir"
35279 Any dynamically loadable modules must be installed into the directory
35280 defined in &`LOOKUP_MODULE_DIR`& in &_Local/Makefile_& for Exim to permit
35284 .section "Use of sprintf()" "SECID279"
35285 .cindex "&[sprintf()]&"
35286 A large number of occurrences of &"sprintf"& in the code are actually calls to
35287 &'string_sprintf()'&, a function that returns the result in malloc'd store.
35288 The intermediate formatting is done into a large fixed buffer by a function
35289 that runs through the format string itself, and checks the length of each
35290 conversion before performing it, thus preventing buffer overruns.
35292 The remaining uses of &[sprintf()]& happen in controlled circumstances where
35293 the output buffer is known to be sufficiently long to contain the converted
35298 .section "Use of debug_printf() and log_write()" "SECID280"
35299 Arbitrary strings are passed to both these functions, but they do their
35300 formatting by calling the function &'string_vformat()'&, which runs through
35301 the format string itself, and checks the length of each conversion.
35305 .section "Use of strcat() and strcpy()" "SECID281"
35306 These are used only in cases where the output buffer is known to be large
35307 enough to hold the result.
35308 .ecindex IIDsecurcon
35313 . ////////////////////////////////////////////////////////////////////////////
35314 . ////////////////////////////////////////////////////////////////////////////
35316 .chapter "Format of spool files" "CHAPspool"
35317 .scindex IIDforspo1 "format" "spool files"
35318 .scindex IIDforspo2 "spool directory" "format of files"
35319 .scindex IIDforspo3 "spool files" "format of"
35320 .cindex "spool files" "editing"
35321 A message on Exim's queue consists of two files, whose names are the message id
35322 followed by -D and -H, respectively. The data portion of the message is kept in
35323 the -D file on its own. The message's envelope, status, and headers are all
35324 kept in the -H file, whose format is described in this chapter. Each of these
35325 two files contains the final component of its own name as its first line. This
35326 is insurance against disk crashes where the directory is lost but the files
35327 themselves are recoverable.
35329 Some people are tempted into editing -D files in order to modify messages. You
35330 need to be extremely careful if you do this; it is not recommended and you are
35331 on your own if you do it. Here are some of the pitfalls:
35334 You must ensure that Exim does not try to deliver the message while you are
35335 fiddling with it. The safest way is to take out a write lock on the -D file,
35336 which is what Exim itself does, using &[fcntl()]&. If you update the file in
35337 place, the lock will be retained. If you write a new file and rename it, the
35338 lock will be lost at the instant of rename.
35340 .vindex "&$body_linecount$&"
35341 If you change the number of lines in the file, the value of
35342 &$body_linecount$&, which is stored in the -H file, will be incorrect. At
35343 present, this value is not used by Exim, but there is no guarantee that this
35344 will always be the case.
35346 If the message is in MIME format, you must take care not to break it.
35348 If the message is cryptographically signed, any change will invalidate the
35351 All in all, modifying -D files is fraught with danger.
35353 Files whose names end with -J may also be seen in the &_input_& directory (or
35354 its subdirectories when &%split_spool_directory%& is set). These are journal
35355 files, used to record addresses to which the message has been delivered during
35356 the course of a delivery attempt. If there are still undelivered recipients at
35357 the end, the -H file is updated, and the -J file is deleted. If, however, there
35358 is some kind of crash (for example, a power outage) before this happens, the -J
35359 file remains in existence. When Exim next processes the message, it notices the
35360 -J file and uses it to update the -H file before starting the next delivery
35363 .section "Format of the -H file" "SECID282"
35364 .cindex "uid (user id)" "in spool file"
35365 .cindex "gid (group id)" "in spool file"
35366 The second line of the -H file contains the login name for the uid of the
35367 process that called Exim to read the message, followed by the numerical uid and
35368 gid. For a locally generated message, this is normally the user who sent the
35369 message. For a message received over TCP/IP via the daemon, it is
35370 normally the Exim user.
35372 The third line of the file contains the address of the message's sender as
35373 transmitted in the envelope, contained in angle brackets. The sender address is
35374 empty for bounce messages. For incoming SMTP mail, the sender address is given
35375 in the MAIL command. For locally generated mail, the sender address is
35376 created by Exim from the login name of the current user and the configured
35377 &%qualify_domain%&. However, this can be overridden by the &%-f%& option or a
35378 leading &"From&~"& line if the caller is trusted, or if the supplied address is
35379 &"<>"& or an address that matches &%untrusted_set_senders%&.
35381 The fourth line contains two numbers. The first is the time that the message
35382 was received, in the conventional Unix form &-- the number of seconds since the
35383 start of the epoch. The second number is a count of the number of messages
35384 warning of delayed delivery that have been sent to the sender.
35386 There follow a number of lines starting with a hyphen. These can appear in any
35387 order, and are omitted when not relevant:
35390 .vitem "&%-acl%&&~<&'number'&>&~<&'length'&>"
35391 This item is obsolete, and is not generated from Exim release 4.61 onwards;
35392 &%-aclc%& and &%-aclm%& are used instead. However, &%-acl%& is still
35393 recognized, to provide backward compatibility. In the old format, a line of
35394 this form is present for every ACL variable that is not empty. The number
35395 identifies the variable; the &%acl_c%&&*x*& variables are numbered 0&--9 and
35396 the &%acl_m%&&*x*& variables are numbered 10&--19. The length is the length of
35397 the data string for the variable. The string itself starts at the beginning of
35398 the next line, and is followed by a newline character. It may contain internal
35401 .vitem "&%-aclc%&&~<&'rest-of-name'&>&~<&'length'&>"
35402 A line of this form is present for every ACL connection variable that is
35403 defined. Note that there is a space between &%-aclc%& and the rest of the name.
35404 The length is the length of the data string for the variable. The string itself
35405 starts at the beginning of the next line, and is followed by a newline
35406 character. It may contain internal newlines.
35408 .vitem "&%-aclm%&&~<&'rest-of-name'&>&~<&'length'&>"
35409 A line of this form is present for every ACL message variable that is defined.
35410 Note that there is a space between &%-aclm%& and the rest of the name. The
35411 length is the length of the data string for the variable. The string itself
35412 starts at the beginning of the next line, and is followed by a newline
35413 character. It may contain internal newlines.
35415 .vitem "&%-active_hostname%&&~<&'hostname'&>"
35416 This is present if, when the message was received over SMTP, the value of
35417 &$smtp_active_hostname$& was different to the value of &$primary_hostname$&.
35419 .vitem &%-allow_unqualified_recipient%&
35420 This is present if unqualified recipient addresses are permitted in header
35421 lines (to stop such addresses from being qualified if rewriting occurs at
35422 transport time). Local messages that were input using &%-bnq%& and remote
35423 messages from hosts that match &%recipient_unqualified_hosts%& set this flag.
35425 .vitem &%-allow_unqualified_sender%&
35426 This is present if unqualified sender addresses are permitted in header lines
35427 (to stop such addresses from being qualified if rewriting occurs at transport
35428 time). Local messages that were input using &%-bnq%& and remote messages from
35429 hosts that match &%sender_unqualified_hosts%& set this flag.
35431 .vitem "&%-auth_id%&&~<&'text'&>"
35432 The id information for a message received on an authenticated SMTP connection
35433 &-- the value of the &$authenticated_id$& variable.
35435 .vitem "&%-auth_sender%&&~<&'address'&>"
35436 The address of an authenticated sender &-- the value of the
35437 &$authenticated_sender$& variable.
35439 .vitem "&%-body_linecount%&&~<&'number'&>"
35440 This records the number of lines in the body of the message, and is always
35443 .vitem "&%-body_zerocount%&&~<&'number'&>"
35444 This records the number of binary zero bytes in the body of the message, and is
35445 present if the number is greater than zero.
35447 .vitem &%-deliver_firsttime%&
35448 This is written when a new message is first added to the spool. When the spool
35449 file is updated after a deferral, it is omitted.
35451 .vitem "&%-frozen%&&~<&'time'&>"
35452 .cindex "frozen messages" "spool data"
35453 The message is frozen, and the freezing happened at <&'time'&>.
35455 .vitem "&%-helo_name%&&~<&'text'&>"
35456 This records the host name as specified by a remote host in a HELO or EHLO
35459 .vitem "&%-host_address%&&~<&'address'&>.<&'port'&>"
35460 This records the IP address of the host from which the message was received and
35461 the remote port number that was used. It is omitted for locally generated
35464 .vitem "&%-host_auth%&&~<&'text'&>"
35465 If the message was received on an authenticated SMTP connection, this records
35466 the name of the authenticator &-- the value of the
35467 &$sender_host_authenticated$& variable.
35469 .vitem &%-host_lookup_failed%&
35470 This is present if an attempt to look up the sending host's name from its IP
35471 address failed. It corresponds to the &$host_lookup_failed$& variable.
35473 .vitem "&%-host_name%&&~<&'text'&>"
35474 .cindex "reverse DNS lookup"
35475 .cindex "DNS" "reverse lookup"
35476 This records the name of the remote host from which the message was received,
35477 if the host name was looked up from the IP address when the message was being
35478 received. It is not present if no reverse lookup was done.
35480 .vitem "&%-ident%&&~<&'text'&>"
35481 For locally submitted messages, this records the login of the originating user,
35482 unless it was a trusted user and the &%-oMt%& option was used to specify an
35483 ident value. For messages received over TCP/IP, this records the ident string
35484 supplied by the remote host, if any.
35486 .vitem "&%-interface_address%&&~<&'address'&>.<&'port'&>"
35487 This records the IP address of the local interface and the port number through
35488 which a message was received from a remote host. It is omitted for locally
35489 generated messages.
35492 The message is from a local sender.
35494 .vitem &%-localerror%&
35495 The message is a locally-generated bounce message.
35497 .vitem "&%-local_scan%&&~<&'string'&>"
35498 This records the data string that was returned by the &[local_scan()]& function
35499 when the message was received &-- the value of the &$local_scan_data$&
35500 variable. It is omitted if no data was returned.
35502 .vitem &%-manual_thaw%&
35503 The message was frozen but has been thawed manually, that is, by an explicit
35504 Exim command rather than via the auto-thaw process.
35507 A testing delivery process was started using the &%-N%& option to suppress any
35508 actual deliveries, but delivery was deferred. At any further delivery attempts,
35511 .vitem &%-received_protocol%&
35512 This records the value of the &$received_protocol$& variable, which contains
35513 the name of the protocol by which the message was received.
35515 .vitem &%-sender_set_untrusted%&
35516 The envelope sender of this message was set by an untrusted local caller (used
35517 to ensure that the caller is displayed in queue listings).
35519 .vitem "&%-spam_score_int%&&~<&'number'&>"
35520 If a message was scanned by SpamAssassin, this is present. It records the value
35521 of &$spam_score_int$&.
35523 .vitem &%-tls_certificate_verified%&
35524 A TLS certificate was received from the client that sent this message, and the
35525 certificate was verified by the server.
35527 .vitem "&%-tls_cipher%&&~<&'cipher name'&>"
35528 When the message was received over an encrypted connection, this records the
35529 name of the cipher suite that was used.
35531 .vitem "&%-tls_peerdn%&&~<&'peer DN'&>"
35532 When the message was received over an encrypted connection, and a certificate
35533 was received from the client, this records the Distinguished Name from that
35537 Following the options there is a list of those addresses to which the message
35538 is not to be delivered. This set of addresses is initialized from the command
35539 line when the &%-t%& option is used and &%extract_addresses_remove_arguments%&
35540 is set; otherwise it starts out empty. Whenever a successful delivery is made,
35541 the address is added to this set. The addresses are kept internally as a
35542 balanced binary tree, and it is a representation of that tree which is written
35543 to the spool file. If an address is expanded via an alias or forward file, the
35544 original address is added to the tree when deliveries to all its child
35545 addresses are complete.
35547 If the tree is empty, there is a single line in the spool file containing just
35548 the text &"XX"&. Otherwise, each line consists of two letters, which are either
35549 Y or N, followed by an address. The address is the value for the node of the
35550 tree, and the letters indicate whether the node has a left branch and/or a
35551 right branch attached to it, respectively. If branches exist, they immediately
35552 follow. Here is an example of a three-node tree:
35554 YY darcy@austen.fict.example
35555 NN alice@wonderland.fict.example
35556 NN editor@thesaurus.ref.example
35558 After the non-recipients tree, there is a list of the message's recipients.
35559 This is a simple list, preceded by a count. It includes all the original
35560 recipients of the message, including those to whom the message has already been
35561 delivered. In the simplest case, the list contains one address per line. For
35565 editor@thesaurus.ref.example
35566 darcy@austen.fict.example
35568 alice@wonderland.fict.example
35570 However, when a child address has been added to the top-level addresses as a
35571 result of the use of the &%one_time%& option on a &(redirect)& router, each
35572 line is of the following form:
35574 <&'top-level address'&> <&'errors_to address'&> &&&
35575 <&'length'&>,<&'parent number'&>#<&'flag bits'&>
35577 The 01 flag bit indicates the presence of the three other fields that follow
35578 the top-level address. Other bits may be used in future to support additional
35579 fields. The <&'parent number'&> is the offset in the recipients list of the
35580 original parent of the &"one time"& address. The first two fields are the
35581 envelope sender that is associated with this address and its length. If the
35582 length is zero, there is no special envelope sender (there are then two space
35583 characters in the line). A non-empty field can arise from a &(redirect)& router
35584 that has an &%errors_to%& setting.
35587 A blank line separates the envelope and status information from the headers
35588 which follow. A header may occupy several lines of the file, and to save effort
35589 when reading it in, each header is preceded by a number and an identifying
35590 character. The number is the number of characters in the header, including any
35591 embedded newlines and the terminating newline. The character is one of the
35595 .row <&'blank'&> "header in which Exim has no special interest"
35596 .row &`B`& "&'Bcc:'& header"
35597 .row &`C`& "&'Cc:'& header"
35598 .row &`F`& "&'From:'& header"
35599 .row &`I`& "&'Message-id:'& header"
35600 .row &`P`& "&'Received:'& header &-- P for &""postmark""&"
35601 .row &`R`& "&'Reply-To:'& header"
35602 .row &`S`& "&'Sender:'& header"
35603 .row &`T`& "&'To:'& header"
35604 .row &`*`& "replaced or deleted header"
35607 Deleted or replaced (rewritten) headers remain in the spool file for debugging
35608 purposes. They are not transmitted when the message is delivered. Here is a
35609 typical set of headers:
35611 111P Received: by hobbit.fict.example with local (Exim 4.00)
35612 id 14y9EI-00026G-00; Fri, 11 May 2001 10:28:59 +0100
35613 049 Message-Id: <E14y9EI-00026G-00@hobbit.fict.example>
35614 038* X-rewrote-sender: bb@hobbit.fict.example
35615 042* From: Bilbo Baggins <bb@hobbit.fict.example>
35616 049F From: Bilbo Baggins <B.Baggins@hobbit.fict.example>
35617 099* To: alice@wonderland.fict.example, rdo@foundation,
35618 darcy@austen.fict.example, editor@thesaurus.ref.example
35619 104T To: alice@wonderland.fict.example, rdo@foundation.example,
35620 darcy@austen.fict.example, editor@thesaurus.ref.example
35621 038 Date: Fri, 11 May 2001 10:28:59 +0100
35623 The asterisked headers indicate that the envelope sender, &'From:'& header, and
35624 &'To:'& header have been rewritten, the last one because routing expanded the
35625 unqualified domain &'foundation'&.
35626 .ecindex IIDforspo1
35627 .ecindex IIDforspo2
35628 .ecindex IIDforspo3
35630 . ////////////////////////////////////////////////////////////////////////////
35631 . ////////////////////////////////////////////////////////////////////////////
35633 .chapter "Support for DKIM (DomainKeys Identified Mail)" "CHID12" &&&
35637 DKIM is a mechanism by which messages sent by some entity can be provably
35638 linked to a domain which that entity controls. It permits reputation to
35639 be tracked on a per-domain basis, rather than merely upon source IP address.
35640 DKIM is documented in RFC 4871.
35642 Since version 4.70, DKIM support is compiled into Exim by default. It can be
35643 disabled by setting DISABLE_DKIM=yes in Local/Makefile.
35645 Exim's DKIM implementation allows to
35647 Sign outgoing messages: This function is implemented in the SMTP transport.
35648 It can co-exist with all other Exim features, including transport filters.
35650 Verify signatures in incoming messages: This is implemented by an additional
35651 ACL (acl_smtp_dkim), which can be called several times per message, with
35652 different signature contexts.
35655 In typical Exim style, the verification implementation does not include any
35656 default "policy". Instead it enables you to build your own policy using
35657 Exim's standard controls.
35659 Please note that verification of DKIM signatures in incoming mail is turned
35660 on by default for logging purposes. For each signature in incoming email,
35661 exim will log a line displaying the most important signature details, and the
35662 signature status. Here is an example (with line-breaks added for clarity):
35664 2009-09-09 10:22:28 1MlIRf-0003LU-U3 DKIM:
35665 d=facebookmail.com s=q1-2009b
35666 c=relaxed/relaxed a=rsa-sha1
35667 i=@facebookmail.com t=1252484542 [verification succeeded]
35669 You might want to turn off DKIM verification processing entirely for internal
35670 or relay mail sources. To do that, set the &%dkim_disable_verify%& ACL
35671 control modifier. This should typically be done in the RCPT ACL, at points
35672 where you accept mail from relay sources (internal hosts or authenticated
35676 .section "Signing outgoing messages" "SECID513"
35677 .cindex "DKIM" "signing"
35679 Signing is implemented by setting private options on the SMTP transport.
35680 These options take (expandable) strings as arguments.
35682 .option dkim_domain smtp string&!! unset
35684 The domain you want to sign with. The result of this expanded
35685 option is put into the &%$dkim_domain%& expansion variable.
35687 .option dkim_selector smtp string&!! unset
35689 This sets the key selector string. You can use the &%$dkim_domain%& expansion
35690 variable to look up a matching selector. The result is put in the expansion
35691 variable &%$dkim_selector%& which should be used in the &%dkim_private_key%&
35692 option along with &%$dkim_domain%&.
35694 .option dkim_private_key smtp string&!! unset
35696 This sets the private key to use. You can use the &%$dkim_domain%& and
35697 &%$dkim_selector%& expansion variables to determine the private key to use.
35698 The result can either
35700 be a valid RSA private key in ASCII armor, including line breaks.
35702 start with a slash, in which case it is treated as a file that contains
35705 be "0", "false" or the empty string, in which case the message will not
35706 be signed. This case will not result in an error, even if &%dkim_strict%&
35710 .option dkim_canon smtp string&!! unset
35712 This option sets the canonicalization method used when signing a message.
35713 The DKIM RFC currently supports two methods: "simple" and "relaxed".
35714 The option defaults to "relaxed" when unset. Note: the current implementation
35715 only supports using the same canonicalization method for both headers and body.
35717 .option dkim_strict smtp string&!! unset
35719 This option defines how Exim behaves when signing a message that
35720 should be signed fails for some reason. When the expansion evaluates to
35721 either "1" or "true", Exim will defer. Otherwise Exim will send the message
35722 unsigned. You can use the &%$dkim_domain%& and &%$dkim_selector%& expansion
35725 .option dkim_sign_headers smtp string&!! unset
35727 When set, this option must expand to (or be specified as) a colon-separated
35728 list of header names. Headers with these names will be included in the message
35729 signature. When unspecified, the header names recommended in RFC4871 will be
35733 .section "Verifying DKIM signatures in incoming mail" "SECID514"
35734 .cindex "DKIM" "verification"
35736 Verification of DKIM signatures in incoming email is implemented via the
35737 &%acl_smtp_dkim%& ACL. By default, this ACL is called once for each
35738 syntactically(!) correct signature in the incoming message.
35740 To evaluate the signature in the ACL a large number of expansion variables
35741 containing the signature status and its details are set up during the
35742 runtime of the ACL.
35744 Calling the ACL only for existing signatures is not sufficient to build
35745 more advanced policies. For that reason, the global option
35746 &%dkim_verify_signers%&, and a global expansion variable
35747 &%$dkim_signers%& exist.
35749 The global option &%dkim_verify_signers%& can be set to a colon-separated
35750 list of DKIM domains or identities for which the ACL &%acl_smtp_dkim%& is
35751 called. It is expanded when the message has been received. At this point,
35752 the expansion variable &%$dkim_signers%& already contains a colon-separated
35753 list of signer domains and identities for the message. When
35754 &%dkim_verify_signers%& is not specified in the main configuration,
35757 dkim_verify_signers = $dkim_signers
35759 This leads to the default behaviour of calling &%acl_smtp_dkim%& for each
35760 DKIM signature in the message. Current DKIM verifiers may want to explicitly
35761 call the ACL for known domains or identities. This would be achieved as follows:
35763 dkim_verify_signers = paypal.com:ebay.com:$dkim_signers
35765 This would result in &%acl_smtp_dkim%& always being called for "paypal.com"
35766 and "ebay.com", plus all domains and identities that have signatures in the message.
35767 You can also be more creative in constructing your policy. For example:
35769 dkim_verify_signers = $sender_address_domain:$dkim_signers
35772 If a domain or identity is listed several times in the (expanded) value of
35773 &%dkim_verify_signers%&, the ACL is only called once for that domain or identity.
35776 Inside the &%acl_smtp_dkim%&, the following expansion variables are
35777 available (from most to least important):
35781 .vitem &%$dkim_cur_signer%&
35782 The signer that is being evaluated in this ACL run. This can be a domain or
35783 an identity. This is one of the list items from the expanded main option
35784 &%dkim_verify_signers%& (see above).
35785 .vitem &%$dkim_verify_status%&
35786 A string describing the general status of the signature. One of
35788 &%none%&: There is no signature in the message for the current domain or
35789 identity (as reflected by &%$dkim_cur_signer%&).
35791 &%invalid%&: The signature could not be verified due to a processing error.
35792 More detail is available in &%$dkim_verify_reason%&.
35794 &%fail%&: Verification of the signature failed. More detail is
35795 available in &%$dkim_verify_reason%&.
35797 &%pass%&: The signature passed verification. It is valid.
35799 .vitem &%$dkim_verify_reason%&
35800 A string giving a litte bit more detail when &%$dkim_verify_status%& is either
35801 "fail" or "invalid". One of
35803 &%pubkey_unavailable%& (when &%$dkim_verify_status%&="invalid"): The public
35804 key for the domain could not be retrieved. This may be a temporary problem.
35806 &%pubkey_syntax%& (when &%$dkim_verify_status%&="invalid"): The public key
35807 record for the domain is syntactically invalid.
35809 &%bodyhash_mismatch%& (when &%$dkim_verify_status%&="fail"): The calculated
35810 body hash does not match the one specified in the signature header. This
35811 means that the message body was modified in transit.
35813 &%signature_incorrect%& (when &%$dkim_verify_status%&="fail"): The signature
35814 could not be verified. This may mean that headers were modified,
35815 re-written or otherwise changed in a way which is incompatible with
35816 DKIM verification. It may of course also mean that the signature is forged.
35818 .vitem &%$dkim_domain%&
35819 The signing domain. IMPORTANT: This variable is only populated if there is
35820 an actual signature in the message for the current domain or identity (as
35821 reflected by &%$dkim_cur_signer%&).
35822 .vitem &%$dkim_identity%&
35823 The signing identity, if present. IMPORTANT: This variable is only populated
35824 if there is an actual signature in the message for the current domain or
35825 identity (as reflected by &%$dkim_cur_signer%&).
35826 .vitem &%$dkim_selector%&
35827 The key record selector string.
35828 .vitem &%$dkim_algo%&
35829 The algorithm used. One of 'rsa-sha1' or 'rsa-sha256'.
35830 .vitem &%$dkim_canon_body%&
35831 The body canonicalization method. One of 'relaxed' or 'simple'.
35832 .vitem &%dkim_canon_headers%&
35833 The header canonicalization method. One of 'relaxed' or 'simple'.
35834 .vitem &%$dkim_copiedheaders%&
35835 A transcript of headers and their values which are included in the signature
35836 (copied from the 'z=' tag of the signature).
35837 .vitem &%$dkim_bodylength%&
35838 The number of signed body bytes. If zero ("0"), the body is unsigned. If no
35839 limit was set by the signer, "9999999999999" is returned. This makes sure
35840 that this variable always expands to an integer value.
35841 .vitem &%$dkim_created%&
35842 UNIX timestamp reflecting the date and time when the signature was created.
35843 When this was not specified by the signer, "0" is returned.
35844 .vitem &%$dkim_expires%&
35845 UNIX timestamp reflecting the date and time when the signer wants the
35846 signature to be treated as "expired". When this was not specified by the
35847 signer, "9999999999999" is returned. This makes it possible to do useful
35848 integer size comparisons against this value.
35849 .vitem &%$dkim_headernames%&
35850 A colon-separated list of names of headers included in the signature.
35851 .vitem &%$dkim_key_testing%&
35852 "1" if the key record has the "testing" flag set, "0" if not.
35853 .vitem &%$nosubdomains%&
35854 "1" if the key record forbids subdomaining, "0" otherwise.
35855 .vitem &%$dkim_key_srvtype%&
35856 Service type (tag s=) from the key record. Defaults to "*" if not specified
35858 .vitem &%$dkim_key_granularity%&
35859 Key granularity (tag g=) from the key record. Defaults to "*" if not specified
35861 .vitem &%$dkim_key_notes%&
35862 Notes from the key record (tag n=).
35865 In addition, two ACL conditions are provided:
35868 .vitem &%dkim_signers%&
35869 ACL condition that checks a colon-separated list of domains or identities
35870 for a match against the domain or identity that the ACL is currently verifying
35871 (reflected by &%$dkim_cur_signer%&). This is typically used to restrict an ACL
35872 verb to a group of domains or identities. For example:
35875 # Warn when Mail purportedly from GMail has no signature at all
35876 warn log_message = GMail sender without DKIM signature
35877 sender_domains = gmail.com
35878 dkim_signers = gmail.com
35882 .vitem &%dkim_status%&
35883 ACL condition that checks a colon-separated list of possible DKIM verification
35884 results agains the actual result of verification. This is typically used
35885 to restrict an ACL verb to a list of verification outcomes, for example:
35888 deny message = Mail from Paypal with invalid/missing signature
35889 sender_domains = paypal.com:paypal.de
35890 dkim_signers = paypal.com:paypal.de
35891 dkim_status = none:invalid:fail
35894 The possible status keywords are: 'none','invalid','fail' and 'pass'. Please
35895 see the documentation of the &%$dkim_verify_status%& expansion variable above
35896 for more information of what they mean.
35899 . ////////////////////////////////////////////////////////////////////////////
35900 . ////////////////////////////////////////////////////////////////////////////
35902 .chapter "Adding new drivers or lookup types" "CHID13" &&&
35903 "Adding drivers or lookups"
35904 .cindex "adding drivers"
35905 .cindex "new drivers, adding"
35906 .cindex "drivers" "adding new"
35907 The following actions have to be taken in order to add a new router, transport,
35908 authenticator, or lookup type to Exim:
35911 Choose a name for the driver or lookup type that does not conflict with any
35912 existing name; I will use &"newdriver"& in what follows.
35914 Add to &_src/EDITME_& the line:
35916 <&'type'&>&`_NEWDRIVER=yes`&
35918 where <&'type'&> is ROUTER, TRANSPORT, AUTH, or LOOKUP. If the
35919 code is not to be included in the binary by default, comment this line out. You
35920 should also add any relevant comments about the driver or lookup type.
35922 Add to &_src/config.h.defaults_& the line:
35924 #define <type>_NEWDRIVER
35927 Edit &_src/drtables.c_&, adding conditional code to pull in the private header
35928 and create a table entry as is done for all the other drivers and lookup types.
35930 Edit &_Makefile_& in the appropriate sub-directory (&_src/routers_&,
35931 &_src/transports_&, &_src/auths_&, or &_src/lookups_&); add a line for the new
35932 driver or lookup type and add it to the definition of OBJ.
35934 Create &_newdriver.h_& and &_newdriver.c_& in the appropriate sub-directory of
35937 Edit &_scripts/MakeLinks_& and add commands to link the &_.h_& and &_.c_& files
35938 as for other drivers and lookups.
35941 Then all you need to do is write the code! A good way to start is to make a
35942 proforma by copying an existing module of the same type, globally changing all
35943 occurrences of the name, and cutting out most of the code. Note that any
35944 options you create must be listed in alphabetical order, because the tables are
35945 searched using a binary chop procedure.
35947 There is a &_README_& file in each of the sub-directories of &_src_& describing
35948 the interface that is expected.
35953 . ////////////////////////////////////////////////////////////////////////////
35954 . ////////////////////////////////////////////////////////////////////////////
35956 . /////////////////////////////////////////////////////////////////////////////
35957 . These lines are processing instructions for the Simple DocBook Processor that
35958 . Philip Hazel has developed as a less cumbersome way of making PostScript and
35959 . PDFs than using xmlto and fop. They will be ignored by all other XML
35961 . /////////////////////////////////////////////////////////////////////////////
35966 foot_right_recto="&chaptertitle;"
35967 foot_right_verso="&chaptertitle;"
35971 .makeindex "Options index" "option"
35972 .makeindex "Variables index" "variable"
35973 .makeindex "Concept index" "concept"
35976 . /////////////////////////////////////////////////////////////////////////////
35977 . /////////////////////////////////////////////////////////////////////////////