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.
45 . Update the Copyright year (only) when changing content.
46 . /////////////////////////////////////////////////////////////////////////////
48 .set previousversion "4.80"
49 .include ./local_params
51 .set ACL "access control lists (ACLs)"
52 .set I " "
58 . /////////////////////////////////////////////////////////////////////////////
59 . Additional xfpt markup used by this document, over and above the default
60 . provided in the xfpt library.
61 . /////////////////////////////////////////////////////////////////////////////
63 . --- Override the &$ flag to automatically insert a $ with the variable name
65 .flag &$ $& "<varname>$" "</varname>"
67 . --- Short flags for daggers in option headings. They will always be inside
68 . --- an italic string, but we want the daggers to be roman.
70 .flag &!! "</emphasis>†<emphasis>"
71 .flag &!? "</emphasis>‡<emphasis>"
73 . --- A macro for an Exim option definition heading, generating a one-line
74 . --- table with four columns. For cases when the option name is given with
75 . --- a space, so that it can be split, a fifth argument is used for the
85 .itable all 0 0 4 8* left 6* center 6* center 6* right
86 .row "&%$1%&" "Use: &'$2'&" "Type: &'$3'&" "Default: &'$4'&"
90 . --- A macro for the common 2-column tables. The width of the first column
91 . --- is suitable for the many tables at the start of the main options chapter;
92 . --- the small number of other 2-column tables override it.
94 .macro table2 196pt 254pt
95 .itable none 0 0 2 $1 left $2 left
98 . --- A macro that generates .row, but puts &I; at the start of the first
99 . --- argument, thus indenting it. Assume a minimum of two arguments, and
100 . --- allow up to four arguments, which is as many as we'll ever need.
104 .row "&I;$1" "$2" "$3" "$4"
108 .row "&I;$1" "$2" "$3"
116 . --- Macros for option, variable, and concept index entries. For a "range"
117 . --- style of entry, use .scindex for the start and .ecindex for the end. The
118 . --- first argument of .scindex and the only argument of .ecindex must be the
119 . --- ID that ties them together.
122 &<indexterm role="concept">&
123 &<primary>&$1&</primary>&
125 &<secondary>&$2&</secondary>&
131 &<indexterm role="concept" id="$1" class="startofrange">&
132 &<primary>&$2&</primary>&
134 &<secondary>&$3&</secondary>&
140 &<indexterm role="concept" startref="$1" class="endofrange"/>&
144 &<indexterm role="option">&
145 &<primary>&$1&</primary>&
147 &<secondary>&$2&</secondary>&
153 &<indexterm role="variable">&
154 &<primary>&$1&</primary>&
156 &<secondary>&$2&</secondary>&
162 .echo "** Don't use .index; use .cindex or .oindex or .vindex"
164 . ////////////////////////////////////////////////////////////////////////////
167 . ////////////////////////////////////////////////////////////////////////////
168 . The <bookinfo> element is removed from the XML before processing for Ascii
170 . ////////////////////////////////////////////////////////////////////////////
174 <title>Specification of the Exim Mail Transfer Agent</title>
175 <titleabbrev>The Exim MTA</titleabbrev>
179 <author><firstname>Exim</firstname><surname>Maintainers</surname></author>
180 <authorinitials>EM</authorinitials>
181 <revhistory><revision>
183 <authorinitials>EM</authorinitials>
184 </revision></revhistory>
187 </year><holder>University of Cambridge</holder></copyright>
192 . /////////////////////////////////////////////////////////////////////////////
193 . This chunk of literal XML implements index entries of the form "x, see y" and
194 . "x, see also y". However, the DocBook DTD doesn't allow <indexterm> entries
195 . at the top level, so we have to put the .chapter directive first.
196 . /////////////////////////////////////////////////////////////////////////////
198 .chapter "Introduction" "CHID1"
201 <indexterm role="variable">
202 <primary>$1, $2, etc.</primary>
203 <see><emphasis>numerical variables</emphasis></see>
205 <indexterm role="concept">
206 <primary>address</primary>
207 <secondary>rewriting</secondary>
208 <see><emphasis>rewriting</emphasis></see>
210 <indexterm role="concept">
211 <primary>Bounce Address Tag Validation</primary>
212 <see><emphasis>BATV</emphasis></see>
214 <indexterm role="concept">
215 <primary>Client SMTP Authorization</primary>
216 <see><emphasis>CSA</emphasis></see>
218 <indexterm role="concept">
219 <primary>CR character</primary>
220 <see><emphasis>carriage return</emphasis></see>
222 <indexterm role="concept">
223 <primary>CRL</primary>
224 <see><emphasis>certificate revocation list</emphasis></see>
226 <indexterm role="concept">
227 <primary>delivery</primary>
228 <secondary>failure report</secondary>
229 <see><emphasis>bounce message</emphasis></see>
231 <indexterm role="concept">
232 <primary>dialup</primary>
233 <see><emphasis>intermittently connected hosts</emphasis></see>
235 <indexterm role="concept">
236 <primary>exiscan</primary>
237 <see><emphasis>content scanning</emphasis></see>
239 <indexterm role="concept">
240 <primary>failover</primary>
241 <see><emphasis>fallback</emphasis></see>
243 <indexterm role="concept">
244 <primary>fallover</primary>
245 <see><emphasis>fallback</emphasis></see>
247 <indexterm role="concept">
248 <primary>filter</primary>
249 <secondary>Sieve</secondary>
250 <see><emphasis>Sieve filter</emphasis></see>
252 <indexterm role="concept">
253 <primary>ident</primary>
254 <see><emphasis>RFC 1413</emphasis></see>
256 <indexterm role="concept">
257 <primary>LF character</primary>
258 <see><emphasis>linefeed</emphasis></see>
260 <indexterm role="concept">
261 <primary>maximum</primary>
262 <seealso><emphasis>limit</emphasis></seealso>
264 <indexterm role="concept">
265 <primary>monitor</primary>
266 <see><emphasis>Exim monitor</emphasis></see>
268 <indexterm role="concept">
269 <primary>no_<emphasis>xxx</emphasis></primary>
270 <see>entry for xxx</see>
272 <indexterm role="concept">
273 <primary>NUL</primary>
274 <see><emphasis>binary zero</emphasis></see>
276 <indexterm role="concept">
277 <primary>passwd file</primary>
278 <see><emphasis>/etc/passwd</emphasis></see>
280 <indexterm role="concept">
281 <primary>process id</primary>
282 <see><emphasis>pid</emphasis></see>
284 <indexterm role="concept">
285 <primary>RBL</primary>
286 <see><emphasis>DNS list</emphasis></see>
288 <indexterm role="concept">
289 <primary>redirection</primary>
290 <see><emphasis>address redirection</emphasis></see>
292 <indexterm role="concept">
293 <primary>return path</primary>
294 <seealso><emphasis>envelope sender</emphasis></seealso>
296 <indexterm role="concept">
297 <primary>scanning</primary>
298 <see><emphasis>content scanning</emphasis></see>
300 <indexterm role="concept">
301 <primary>SSL</primary>
302 <see><emphasis>TLS</emphasis></see>
304 <indexterm role="concept">
305 <primary>string</primary>
306 <secondary>expansion</secondary>
307 <see><emphasis>expansion</emphasis></see>
309 <indexterm role="concept">
310 <primary>top bit</primary>
311 <see><emphasis>8-bit characters</emphasis></see>
313 <indexterm role="concept">
314 <primary>variables</primary>
315 <see><emphasis>expansion, variables</emphasis></see>
317 <indexterm role="concept">
318 <primary>zero, binary</primary>
319 <see><emphasis>binary zero</emphasis></see>
325 . /////////////////////////////////////////////////////////////////////////////
326 . This is the real start of the first chapter. See the comment above as to why
327 . we can't have the .chapter line here.
328 . chapter "Introduction"
329 . /////////////////////////////////////////////////////////////////////////////
331 Exim is a mail transfer agent (MTA) for hosts that are running Unix or
332 Unix-like operating systems. It was designed on the assumption that it would be
333 run on hosts that are permanently connected to the Internet. However, it can be
334 used on intermittently connected hosts with suitable configuration adjustments.
336 Configuration files currently exist for the following operating systems: AIX,
337 BSD/OS (aka BSDI), Darwin (Mac OS X), DGUX, Dragonfly, FreeBSD, GNU/Hurd,
338 GNU/Linux, HI-OSF (Hitachi), HI-UX, HP-UX, IRIX, MIPS RISCOS, NetBSD, OpenBSD,
339 OpenUNIX, QNX, SCO, SCO SVR4.2 (aka UNIX-SV), Solaris (aka SunOS5), SunOS4,
340 Tru64-Unix (formerly Digital UNIX, formerly DEC-OSF1), Ultrix, and Unixware.
341 Some of these operating systems are no longer current and cannot easily be
342 tested, so the configuration files may no longer work in practice.
344 There are also configuration files for compiling Exim in the Cygwin environment
345 that can be installed on systems running Windows. However, this document does
346 not contain any information about running Exim in the Cygwin environment.
348 The terms and conditions for the use and distribution of Exim are contained in
349 the file &_NOTICE_&. Exim is distributed under the terms of the GNU General
350 Public Licence, a copy of which may be found in the file &_LICENCE_&.
352 The use, supply or promotion of Exim for the purpose of sending bulk,
353 unsolicited electronic mail is incompatible with the basic aims of the program,
354 which revolve around the free provision of a service that enhances the quality
355 of personal communications. The author of Exim regards indiscriminate
356 mass-mailing as an antisocial, irresponsible abuse of the Internet.
358 Exim owes a great deal to Smail 3 and its author, Ron Karr. Without the
359 experience of running and working on the Smail 3 code, I could never have
360 contemplated starting to write a new MTA. Many of the ideas and user interfaces
361 were originally taken from Smail 3, though the actual code of Exim is entirely
362 new, and has developed far beyond the initial concept.
364 Many people, both in Cambridge and around the world, have contributed to the
365 development and the testing of Exim, and to porting it to various operating
366 systems. I am grateful to them all. The distribution now contains a file called
367 &_ACKNOWLEDGMENTS_&, in which I have started recording the names of
371 .section "Exim documentation" "SECID1"
372 . Keep this example change bar when updating the documentation!
375 .cindex "documentation"
376 This edition of the Exim specification applies to version &version() of Exim.
377 Substantive changes from the &previousversion; edition are marked in some
378 renditions of the document; this paragraph is so marked if the rendition is
379 capable of showing a change indicator.
382 This document is very much a reference manual; it is not a tutorial. The reader
383 is expected to have some familiarity with the SMTP mail transfer protocol and
384 with general Unix system administration. Although there are some discussions
385 and examples in places, the information is mostly organized in a way that makes
386 it easy to look up, rather than in a natural order for sequential reading.
387 Furthermore, the manual aims to cover every aspect of Exim in detail, including
388 a number of rarely-used, special-purpose features that are unlikely to be of
391 .cindex "books about Exim"
392 An &"easier"& discussion of Exim which provides more in-depth explanatory,
393 introductory, and tutorial material can be found in a book entitled &'The Exim
394 SMTP Mail Server'& (second edition, 2007), published by UIT Cambridge
395 (&url(http://www.uit.co.uk/exim-book/)).
397 This book also contains a chapter that gives a general introduction to SMTP and
398 Internet mail. Inevitably, however, the book is unlikely to be fully up-to-date
399 with the latest release of Exim. (Note that the earlier book about Exim,
400 published by O'Reilly, covers Exim 3, and many things have changed in Exim 4.)
402 .cindex "Debian" "information sources"
403 If you are using a Debian distribution of Exim, you will find information about
404 Debian-specific features in the file
405 &_/usr/share/doc/exim4-base/README.Debian_&.
406 The command &(man update-exim.conf)& is another source of Debian-specific
409 .cindex "&_doc/NewStuff_&"
410 .cindex "&_doc/ChangeLog_&"
412 As the program develops, there may be features in newer versions that have not
413 yet made it into this document, which is updated only when the most significant
414 digit of the fractional part of the version number changes. Specifications of
415 new features that are not yet in this manual are placed in the file
416 &_doc/NewStuff_& in the Exim distribution.
418 Some features may be classified as &"experimental"&. These may change
419 incompatibly while they are developing, or even be withdrawn. For this reason,
420 they are not documented in this manual. Information about experimental features
421 can be found in the file &_doc/experimental.txt_&.
423 All changes to the program (whether new features, bug fixes, or other kinds of
424 change) are noted briefly in the file called &_doc/ChangeLog_&.
426 .cindex "&_doc/spec.txt_&"
427 This specification itself is available as an ASCII file in &_doc/spec.txt_& so
428 that it can easily be searched with a text editor. Other files in the &_doc_&
432 .row &_OptionLists.txt_& "list of all options in alphabetical order"
433 .row &_dbm.discuss.txt_& "discussion about DBM libraries"
434 .row &_exim.8_& "a man page of Exim's command line options"
435 .row &_experimental.txt_& "documentation of experimental features"
436 .row &_filter.txt_& "specification of the filter language"
437 .row &_Exim3.upgrade_& "upgrade notes from release 2 to release 3"
438 .row &_Exim4.upgrade_& "upgrade notes from release 3 to release 4"
441 The main specification and the specification of the filtering language are also
442 available in other formats (HTML, PostScript, PDF, and Texinfo). Section
443 &<<SECTavail>>& below tells you how to get hold of these.
447 .section "FTP and web sites" "SECID2"
450 The primary site for Exim source distributions is currently the University of
451 Cambridge's FTP site, whose contents are described in &'Where to find the Exim
452 distribution'& below. In addition, there is a web site and an FTP site at
453 &%exim.org%&. These are now also hosted at the University of Cambridge. The
454 &%exim.org%& site was previously hosted for a number of years by Energis
455 Squared, formerly Planet Online Ltd, whose support I gratefully acknowledge.
459 As well as Exim distribution tar files, the Exim web site contains a number of
460 differently formatted versions of the documentation. A recent addition to the
461 online information is the Exim wiki (&url(http://wiki.exim.org)),
462 which contains what used to be a separate FAQ, as well as various other
463 examples, tips, and know-how that have been contributed by Exim users.
466 An Exim Bugzilla exists at &url(http://bugs.exim.org). You can use
467 this to report bugs, and also to add items to the wish list. Please search
468 first to check that you are not duplicating a previous entry.
472 .section "Mailing lists" "SECID3"
473 .cindex "mailing lists" "for Exim users"
474 The following Exim mailing lists exist:
477 .row &'exim-announce@exim.org'& "Moderated, low volume announcements list"
478 .row &'exim-users@exim.org'& "General discussion list"
479 .row &'exim-dev@exim.org'& "Discussion of bugs, enhancements, etc."
480 .row &'exim-cvs@exim.org'& "Automated commit messages from the VCS"
483 You can subscribe to these lists, change your existing subscriptions, and view
484 or search the archives via the mailing lists link on the Exim home page.
485 .cindex "Debian" "mailing list for"
486 If you are using a Debian distribution of Exim, you may wish to subscribe to
487 the Debian-specific mailing list &'pkg-exim4-users@lists.alioth.debian.org'&
490 &url(http://lists.alioth.debian.org/mailman/listinfo/pkg-exim4-users)
492 Please ask Debian-specific questions on this list and not on the general Exim
495 .section "Exim training" "SECID4"
496 .cindex "training courses"
497 Training courses in Cambridge (UK) used to be run annually by the author of
498 Exim, before he retired. At the time of writing, there are no plans to run
499 further Exim courses in Cambridge. However, if that changes, relevant
500 information will be posted at &url(http://www-tus.csx.cam.ac.uk/courses/exim/).
502 .section "Bug reports" "SECID5"
503 .cindex "bug reports"
504 .cindex "reporting bugs"
505 Reports of obvious bugs can be emailed to &'bugs@exim.org'& or reported
506 via the Bugzilla (&url(http://bugs.exim.org)). However, if you are unsure
507 whether some behaviour is a bug or not, the best thing to do is to post a
508 message to the &'exim-dev'& mailing list and have it discussed.
512 .section "Where to find the Exim distribution" "SECTavail"
514 .cindex "distribution" "ftp site"
515 The master ftp site for the Exim distribution is
517 &*ftp://ftp.csx.cam.ac.uk/pub/software/email/exim*&
521 &*ftp://ftp.exim.org/pub/exim*&
523 The file references that follow are relative to the &_exim_& directories at
524 these sites. There are now quite a number of independent mirror sites around
525 the world. Those that I know about are listed in the file called &_Mirrors_&.
527 Within the &_exim_& directory there are subdirectories called &_exim3_& (for
528 previous Exim 3 distributions), &_exim4_& (for the latest Exim 4
529 distributions), and &_Testing_& for testing versions. In the &_exim4_&
530 subdirectory, the current release can always be found in files called
533 &_exim-n.nn.tar.bz2_&
535 where &'n.nn'& is the highest such version number in the directory. The two
536 files contain identical data; the only difference is the type of compression.
537 The &_.bz2_& file is usually a lot smaller than the &_.gz_& file.
539 .cindex "distribution" "signing details"
540 .cindex "distribution" "public key"
541 .cindex "public key for signed distribution"
542 The distributions will be PGP signed by an individual key of the Release
543 Coordinator. This key will have a uid containing an email address in the
544 &'exim.org'& domain and will have signatures from other people, including
545 other Exim maintainers. We expect that the key will be in the "strong set" of
546 PGP keys. There should be a trust path to that key from Nigel Metheringham's
547 PGP key, a version of which can be found in the release directory in the file
548 &_nigel-pubkey.asc_&. All keys used will be available in public keyserver pools,
549 such as &'pool.sks-keyservers.net'&.
551 At time of last update, releases were being made by Phil Pennock and signed with
552 key &'0x403043153903637F'&, although that key is expected to be replaced in 2013.
553 A trust path from Nigel's key to Phil's can be observed at
554 &url(https://www.security.spodhuis.org/exim-trustpath).
556 Releases have also been authorized to be performed by Todd Lyons who signs with
557 key &'0xC4F4F94804D29EBA'&. A direct trust path exists between previous RE Phil
558 Pennock and Todd Lyons through a common associate.
560 The signatures for the tar bundles are in:
562 &_exim-n.nn.tar.gz.asc_&
563 &_exim-n.nn.tar.bz2.asc_&
565 For each released version, the log of changes is made separately available in a
566 separate file in the directory &_ChangeLogs_& so that it is possible to
567 find out what has changed without having to download the entire distribution.
569 .cindex "documentation" "available formats"
570 The main distribution contains ASCII versions of this specification and other
571 documentation; other formats of the documents are available in separate files
572 inside the &_exim4_& directory of the FTP site:
574 &_exim-html-n.nn.tar.gz_&
575 &_exim-pdf-n.nn.tar.gz_&
576 &_exim-postscript-n.nn.tar.gz_&
577 &_exim-texinfo-n.nn.tar.gz_&
579 These tar files contain only the &_doc_& directory, not the complete
580 distribution, and are also available in &_.bz2_& as well as &_.gz_& forms.
583 .section "Limitations" "SECID6"
585 .cindex "limitations of Exim"
586 .cindex "bang paths" "not handled by Exim"
587 Exim is designed for use as an Internet MTA, and therefore handles addresses in
588 RFC 2822 domain format only. It cannot handle UUCP &"bang paths"&, though
589 simple two-component bang paths can be converted by a straightforward rewriting
590 configuration. This restriction does not prevent Exim from being interfaced to
591 UUCP as a transport mechanism, provided that domain addresses are used.
593 .cindex "domainless addresses"
594 .cindex "address" "without domain"
595 Exim insists that every address it handles has a domain attached. For incoming
596 local messages, domainless addresses are automatically qualified with a
597 configured domain value. Configuration options specify from which remote
598 systems unqualified addresses are acceptable. These are then qualified on
601 .cindex "transport" "external"
602 .cindex "external transports"
603 The only external transport mechanisms that are currently implemented are SMTP
604 and LMTP over a TCP/IP network (including support for IPv6). However, a pipe
605 transport is available, and there are facilities for writing messages to files
606 and pipes, optionally in &'batched SMTP'& format; these facilities can be used
607 to send messages to other transport mechanisms such as UUCP, provided they can
608 handle domain-style addresses. Batched SMTP input is also catered for.
610 Exim is not designed for storing mail for dial-in hosts. When the volumes of
611 such mail are large, it is better to get the messages &"delivered"& into files
612 (that is, off Exim's queue) and subsequently passed on to the dial-in hosts by
615 Although Exim does have basic facilities for scanning incoming messages, these
616 are not comprehensive enough to do full virus or spam scanning. Such operations
617 are best carried out using additional specialized software packages. If you
618 compile Exim with the content-scanning extension, straightforward interfaces to
619 a number of common scanners are provided.
623 .section "Run time configuration" "SECID7"
624 Exim's run time configuration is held in a single text file that is divided
625 into a number of sections. The entries in this file consist of keywords and
626 values, in the style of Smail 3 configuration files. A default configuration
627 file which is suitable for simple online installations is provided in the
628 distribution, and is described in chapter &<<CHAPdefconfil>>& below.
631 .section "Calling interface" "SECID8"
632 .cindex "Sendmail compatibility" "command line interface"
633 Like many MTAs, Exim has adopted the Sendmail command line interface so that it
634 can be a straight replacement for &_/usr/lib/sendmail_& or
635 &_/usr/sbin/sendmail_& when sending mail, but you do not need to know anything
636 about Sendmail in order to run Exim. For actions other than sending messages,
637 Sendmail-compatible options also exist, but those that produce output (for
638 example, &%-bp%&, which lists the messages on the queue) do so in Exim's own
639 format. There are also some additional options that are compatible with Smail
640 3, and some further options that are new to Exim. Chapter &<<CHAPcommandline>>&
641 documents all Exim's command line options. This information is automatically
642 made into the man page that forms part of the Exim distribution.
644 Control of messages on the queue can be done via certain privileged command
645 line options. There is also an optional monitor program called &'eximon'&,
646 which displays current information in an X window, and which contains a menu
647 interface to Exim's command line administration options.
651 .section "Terminology" "SECID9"
652 .cindex "terminology definitions"
653 .cindex "body of message" "definition of"
654 The &'body'& of a message is the actual data that the sender wants to transmit.
655 It is the last part of a message, and is separated from the &'header'& (see
656 below) by a blank line.
658 .cindex "bounce message" "definition of"
659 When a message cannot be delivered, it is normally returned to the sender in a
660 delivery failure message or a &"non-delivery report"& (NDR). The term
661 &'bounce'& is commonly used for this action, and the error reports are often
662 called &'bounce messages'&. This is a convenient shorthand for &"delivery
663 failure error report"&. Such messages have an empty sender address in the
664 message's &'envelope'& (see below) to ensure that they cannot themselves give
665 rise to further bounce messages.
667 The term &'default'& appears frequently in this manual. It is used to qualify a
668 value which is used in the absence of any setting in the configuration. It may
669 also qualify an action which is taken unless a configuration setting specifies
672 The term &'defer'& is used when the delivery of a message to a specific
673 destination cannot immediately take place for some reason (a remote host may be
674 down, or a user's local mailbox may be full). Such deliveries are &'deferred'&
677 The word &'domain'& is sometimes used to mean all but the first component of a
678 host's name. It is &'not'& used in that sense here, where it normally refers to
679 the part of an email address following the @ sign.
681 .cindex "envelope, definition of"
682 .cindex "sender" "definition of"
683 A message in transit has an associated &'envelope'&, as well as a header and a
684 body. The envelope contains a sender address (to which bounce messages should
685 be delivered), and any number of recipient addresses. References to the
686 sender or the recipients of a message usually mean the addresses in the
687 envelope. An MTA uses these addresses for delivery, and for returning bounce
688 messages, not the addresses that appear in the header lines.
690 .cindex "message" "header, definition of"
691 .cindex "header section" "definition of"
692 The &'header'& of a message is the first part of a message's text, consisting
693 of a number of lines, each of which has a name such as &'From:'&, &'To:'&,
694 &'Subject:'&, etc. Long header lines can be split over several text lines by
695 indenting the continuations. The header is separated from the body by a blank
698 .cindex "local part" "definition of"
699 .cindex "domain" "definition of"
700 The term &'local part'&, which is taken from RFC 2822, is used to refer to that
701 part of an email address that precedes the @ sign. The part that follows the
702 @ sign is called the &'domain'& or &'mail domain'&.
704 .cindex "local delivery" "definition of"
705 .cindex "remote delivery, definition of"
706 The terms &'local delivery'& and &'remote delivery'& are used to distinguish
707 delivery to a file or a pipe on the local host from delivery by SMTP over
708 TCP/IP to another host. As far as Exim is concerned, all hosts other than the
709 host it is running on are &'remote'&.
711 .cindex "return path" "definition of"
712 &'Return path'& is another name that is used for the sender address in a
715 .cindex "queue" "definition of"
716 The term &'queue'& is used to refer to the set of messages awaiting delivery,
717 because this term is in widespread use in the context of MTAs. However, in
718 Exim's case the reality is more like a pool than a queue, because there is
719 normally no ordering of waiting messages.
721 .cindex "queue runner" "definition of"
722 The term &'queue runner'& is used to describe a process that scans the queue
723 and attempts to deliver those messages whose retry times have come. This term
724 is used by other MTAs, and also relates to the command &%runq%&, but in Exim
725 the waiting messages are normally processed in an unpredictable order.
727 .cindex "spool directory" "definition of"
728 The term &'spool directory'& is used for a directory in which Exim keeps the
729 messages on its queue &-- that is, those that it is in the process of
730 delivering. This should not be confused with the directory in which local
731 mailboxes are stored, which is called a &"spool directory"& by some people. In
732 the Exim documentation, &"spool"& is always used in the first sense.
739 . ////////////////////////////////////////////////////////////////////////////
740 . ////////////////////////////////////////////////////////////////////////////
742 .chapter "Incorporated code" "CHID2"
743 .cindex "incorporated code"
744 .cindex "regular expressions" "library"
747 A number of pieces of external code are included in the Exim distribution.
750 Regular expressions are supported in the main Exim program and in the
751 Exim monitor using the freely-distributable PCRE library, copyright
752 © University of Cambridge. The source to PCRE is no longer shipped with
753 Exim, so you will need to use the version of PCRE shipped with your system,
754 or obtain and install the full version of the library from
755 &url(ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre).
757 .cindex "cdb" "acknowledgment"
758 Support for the cdb (Constant DataBase) lookup method is provided by code
759 contributed by Nigel Metheringham of (at the time he contributed it) Planet
760 Online Ltd. The implementation is completely contained within the code of Exim.
761 It does not link against an external cdb library. The code contains the
762 following statements:
765 Copyright © 1998 Nigel Metheringham, Planet Online Ltd
767 This program is free software; you can redistribute it and/or modify it under
768 the terms of the GNU General Public License as published by the Free Software
769 Foundation; either version 2 of the License, or (at your option) any later
771 This code implements Dan Bernstein's Constant DataBase (cdb) spec. Information,
772 the spec and sample code for cdb can be obtained from
773 &url(http://www.pobox.com/~djb/cdb.html). This implementation borrows
774 some code from Dan Bernstein's implementation (which has no license
775 restrictions applied to it).
778 .cindex "SPA authentication"
779 .cindex "Samba project"
780 .cindex "Microsoft Secure Password Authentication"
781 Client support for Microsoft's &'Secure Password Authentication'& is provided
782 by code contributed by Marc Prud'hommeaux. Server support was contributed by
783 Tom Kistner. This includes code taken from the Samba project, which is released
787 .cindex "&'pwcheck'& daemon"
788 .cindex "&'pwauthd'& daemon"
789 Support for calling the Cyrus &'pwcheck'& and &'saslauthd'& daemons is provided
790 by code taken from the Cyrus-SASL library and adapted by Alexander S.
791 Sabourenkov. The permission notice appears below, in accordance with the
792 conditions expressed therein.
795 Copyright © 2001 Carnegie Mellon University. All rights reserved.
797 Redistribution and use in source and binary forms, with or without
798 modification, are permitted provided that the following conditions
802 Redistributions of source code must retain the above copyright
803 notice, this list of conditions and the following disclaimer.
805 Redistributions in binary form must reproduce the above copyright
806 notice, this list of conditions and the following disclaimer in
807 the documentation and/or other materials provided with the
810 The name &"Carnegie Mellon University"& must not be used to
811 endorse or promote products derived from this software without
812 prior written permission. For permission or any other legal
813 details, please contact
815 Office of Technology Transfer
816 Carnegie Mellon University
818 Pittsburgh, PA 15213-3890
819 (412) 268-4387, fax: (412) 268-7395
820 tech-transfer@andrew.cmu.edu
823 Redistributions of any form whatsoever must retain the following
826 &"This product includes software developed by Computing Services
827 at Carnegie Mellon University (&url(http://www.cmu.edu/computing/)."&
829 CARNEGIE MELLON UNIVERSITY DISCLAIMS ALL WARRANTIES WITH REGARD TO
830 THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
831 AND FITNESS, IN NO EVENT SHALL CARNEGIE MELLON UNIVERSITY BE LIABLE
832 FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
833 WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN
834 AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
835 OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
840 .cindex "Exim monitor" "acknowledgment"
843 The Exim Monitor program, which is an X-Window application, includes
844 modified versions of the Athena StripChart and TextPop widgets.
845 This code is copyright by DEC and MIT, and their permission notice appears
846 below, in accordance with the conditions expressed therein.
849 Copyright 1987, 1988 by Digital Equipment Corporation, Maynard, Massachusetts,
850 and the Massachusetts Institute of Technology, Cambridge, Massachusetts.
854 Permission to use, copy, modify, and distribute this software and its
855 documentation for any purpose and without fee is hereby granted,
856 provided that the above copyright notice appear in all copies and that
857 both that copyright notice and this permission notice appear in
858 supporting documentation, and that the names of Digital or MIT not be
859 used in advertising or publicity pertaining to distribution of the
860 software without specific, written prior permission.
862 DIGITAL DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING
863 ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL
864 DIGITAL BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR
865 ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
866 WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
867 ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
872 .cindex "opendmarc" "acknowledgment"
873 The DMARC implementation uses the OpenDMARC library which is Copyrighted by
874 The Trusted Domain Project. Portions of Exim source which use OpenDMARC
875 derived code are indicated in the respective source files. The full OpenDMARC
876 license is provided in the LICENSE.opendmarc file contained in the distributed
880 Many people have contributed code fragments, some large, some small, that were
881 not covered by any specific licence requirements. It is assumed that the
882 contributors are happy to see their code incorporated into Exim under the GPL.
889 . ////////////////////////////////////////////////////////////////////////////
890 . ////////////////////////////////////////////////////////////////////////////
892 .chapter "How Exim receives and delivers mail" "CHID11" &&&
893 "Receiving and delivering mail"
896 .section "Overall philosophy" "SECID10"
897 .cindex "design philosophy"
898 Exim is designed to work efficiently on systems that are permanently connected
899 to the Internet and are handling a general mix of mail. In such circumstances,
900 most messages can be delivered immediately. Consequently, Exim does not
901 maintain independent queues of messages for specific domains or hosts, though
902 it does try to send several messages in a single SMTP connection after a host
903 has been down, and it also maintains per-host retry information.
906 .section "Policy control" "SECID11"
907 .cindex "policy control" "overview"
908 Policy controls are now an important feature of MTAs that are connected to the
909 Internet. Perhaps their most important job is to stop MTAs being abused as
910 &"open relays"& by misguided individuals who send out vast amounts of
911 unsolicited junk, and want to disguise its source. Exim provides flexible
912 facilities for specifying policy controls on incoming mail:
915 .cindex "&ACL;" "introduction"
916 Exim 4 (unlike previous versions of Exim) implements policy controls on
917 incoming mail by means of &'Access Control Lists'& (ACLs). Each list is a
918 series of statements that may either grant or deny access. ACLs can be used at
919 several places in the SMTP dialogue while receiving a message from a remote
920 host. However, the most common places are after each RCPT command, and at the
921 very end of the message. The sysadmin can specify conditions for accepting or
922 rejecting individual recipients or the entire message, respectively, at these
923 two points (see chapter &<<CHAPACL>>&). Denial of access results in an SMTP
926 An ACL is also available for locally generated, non-SMTP messages. In this
927 case, the only available actions are to accept or deny the entire message.
929 When Exim is compiled with the content-scanning extension, facilities are
930 provided in the ACL mechanism for passing the message to external virus and/or
931 spam scanning software. The result of such a scan is passed back to the ACL,
932 which can then use it to decide what to do with the message.
934 When a message has been received, either from a remote host or from the local
935 host, but before the final acknowledgment has been sent, a locally supplied C
936 function called &[local_scan()]& can be run to inspect the message and decide
937 whether to accept it or not (see chapter &<<CHAPlocalscan>>&). If the message
938 is accepted, the list of recipients can be modified by the function.
940 Using the &[local_scan()]& mechanism is another way of calling external scanner
941 software. The &%SA-Exim%& add-on package works this way. It does not require
942 Exim to be compiled with the content-scanning extension.
944 After a message has been accepted, a further checking mechanism is available in
945 the form of the &'system filter'& (see chapter &<<CHAPsystemfilter>>&). This
946 runs at the start of every delivery process.
951 .section "User filters" "SECID12"
952 .cindex "filter" "introduction"
953 .cindex "Sieve filter"
954 In a conventional Exim configuration, users are able to run private filters by
955 setting up appropriate &_.forward_& files in their home directories. See
956 chapter &<<CHAPredirect>>& (about the &(redirect)& router) for the
957 configuration needed to support this, and the separate document entitled
958 &'Exim's interfaces to mail filtering'& for user details. Two different kinds
959 of filtering are available:
962 Sieve filters are written in the standard filtering language that is defined
965 Exim filters are written in a syntax that is unique to Exim, but which is more
966 powerful than Sieve, which it pre-dates.
969 User filters are run as part of the routing process, described below.
973 .section "Message identification" "SECTmessiden"
974 .cindex "message ids" "details of format"
975 .cindex "format" "of message id"
976 .cindex "id of message"
981 Every message handled by Exim is given a &'message id'& which is sixteen
982 characters long. It is divided into three parts, separated by hyphens, for
983 example &`16VDhn-0001bo-D3`&. Each part is a sequence of letters and digits,
984 normally encoding numbers in base 62. However, in the Darwin operating
985 system (Mac OS X) and when Exim is compiled to run under Cygwin, base 36
986 (avoiding the use of lower case letters) is used instead, because the message
987 id is used to construct file names, and the names of files in those systems are
988 not always case-sensitive.
990 .cindex "pid (process id)" "re-use of"
991 The detail of the contents of the message id have changed as Exim has evolved.
992 Earlier versions relied on the operating system not re-using a process id (pid)
993 within one second. On modern operating systems, this assumption can no longer
994 be made, so the algorithm had to be changed. To retain backward compatibility,
995 the format of the message id was retained, which is why the following rules are
999 The first six characters of the message id are the time at which the message
1000 started to be received, to a granularity of one second. That is, this field
1001 contains the number of seconds since the start of the epoch (the normal Unix
1002 way of representing the date and time of day).
1004 After the first hyphen, the next six characters are the id of the process that
1005 received the message.
1007 There are two different possibilities for the final two characters:
1009 .oindex "&%localhost_number%&"
1010 If &%localhost_number%& is not set, this value is the fractional part of the
1011 time of reception, normally in units of 1/2000 of a second, but for systems
1012 that must use base 36 instead of base 62 (because of case-insensitive file
1013 systems), the units are 1/1000 of a second.
1015 If &%localhost_number%& is set, it is multiplied by 200 (100) and added to
1016 the fractional part of the time, which in this case is in units of 1/200
1017 (1/100) of a second.
1021 After a message has been received, Exim waits for the clock to tick at the
1022 appropriate resolution before proceeding, so that if another message is
1023 received by the same process, or by another process with the same (re-used)
1024 pid, it is guaranteed that the time will be different. In most cases, the clock
1025 will already have ticked while the message was being received.
1028 .section "Receiving mail" "SECID13"
1029 .cindex "receiving mail"
1030 .cindex "message" "reception"
1031 The only way Exim can receive mail from another host is using SMTP over
1032 TCP/IP, in which case the sender and recipient addresses are transferred using
1033 SMTP commands. However, from a locally running process (such as a user's MUA),
1034 there are several possibilities:
1037 If the process runs Exim with the &%-bm%& option, the message is read
1038 non-interactively (usually via a pipe), with the recipients taken from the
1039 command line, or from the body of the message if &%-t%& is also used.
1041 If the process runs Exim with the &%-bS%& option, the message is also read
1042 non-interactively, but in this case the recipients are listed at the start of
1043 the message in a series of SMTP RCPT commands, terminated by a DATA
1044 command. This is so-called &"batch SMTP"& format,
1045 but it isn't really SMTP. The SMTP commands are just another way of passing
1046 envelope addresses in a non-interactive submission.
1048 If the process runs Exim with the &%-bs%& option, the message is read
1049 interactively, using the SMTP protocol. A two-way pipe is normally used for
1050 passing data between the local process and the Exim process.
1051 This is &"real"& SMTP and is handled in the same way as SMTP over TCP/IP. For
1052 example, the ACLs for SMTP commands are used for this form of submission.
1054 A local process may also make a TCP/IP call to the host's loopback address
1055 (127.0.0.1) or any other of its IP addresses. When receiving messages, Exim
1056 does not treat the loopback address specially. It treats all such connections
1057 in the same way as connections from other hosts.
1061 .cindex "message sender, constructed by Exim"
1062 .cindex "sender" "constructed by Exim"
1063 In the three cases that do not involve TCP/IP, the sender address is
1064 constructed from the login name of the user that called Exim and a default
1065 qualification domain (which can be set by the &%qualify_domain%& configuration
1066 option). For local or batch SMTP, a sender address that is passed using the
1067 SMTP MAIL command is ignored. However, the system administrator may allow
1068 certain users (&"trusted users"&) to specify a different sender address
1069 unconditionally, or all users to specify certain forms of different sender
1070 address. The &%-f%& option or the SMTP MAIL command is used to specify these
1071 different addresses. See section &<<SECTtrustedadmin>>& for details of trusted
1072 users, and the &%untrusted_set_sender%& option for a way of allowing untrusted
1073 users to change sender addresses.
1075 Messages received by either of the non-interactive mechanisms are subject to
1076 checking by the non-SMTP ACL, if one is defined. Messages received using SMTP
1077 (either over TCP/IP, or interacting with a local process) can be checked by a
1078 number of ACLs that operate at different times during the SMTP session. Either
1079 individual recipients, or the entire message, can be rejected if local policy
1080 requirements are not met. The &[local_scan()]& function (see chapter
1081 &<<CHAPlocalscan>>&) is run for all incoming messages.
1083 Exim can be configured not to start a delivery process when a message is
1084 received; this can be unconditional, or depend on the number of incoming SMTP
1085 connections or the system load. In these situations, new messages wait on the
1086 queue until a queue runner process picks them up. However, in standard
1087 configurations under normal conditions, delivery is started as soon as a
1088 message is received.
1094 .section "Handling an incoming message" "SECID14"
1095 .cindex "spool directory" "files that hold a message"
1096 .cindex "file" "how a message is held"
1097 When Exim accepts a message, it writes two files in its spool directory. The
1098 first contains the envelope information, the current status of the message, and
1099 the header lines, and the second contains the body of the message. The names of
1100 the two spool files consist of the message id, followed by &`-H`& for the
1101 file containing the envelope and header, and &`-D`& for the data file.
1103 .cindex "spool directory" "&_input_& sub-directory"
1104 By default all these message files are held in a single directory called
1105 &_input_& inside the general Exim spool directory. Some operating systems do
1106 not perform very well if the number of files in a directory gets large; to
1107 improve performance in such cases, the &%split_spool_directory%& option can be
1108 used. This causes Exim to split up the input files into 62 sub-directories
1109 whose names are single letters or digits. When this is done, the queue is
1110 processed one sub-directory at a time instead of all at once, which can improve
1111 overall performance even when there are not enough files in each directory to
1112 affect file system performance.
1114 The envelope information consists of the address of the message's sender and
1115 the addresses of the recipients. This information is entirely separate from
1116 any addresses contained in the header lines. The status of the message includes
1117 a list of recipients who have already received the message. The format of the
1118 first spool file is described in chapter &<<CHAPspool>>&.
1120 .cindex "rewriting" "addresses"
1121 Address rewriting that is specified in the rewrite section of the configuration
1122 (see chapter &<<CHAPrewrite>>&) is done once and for all on incoming addresses,
1123 both in the header lines and the envelope, at the time the message is accepted.
1124 If during the course of delivery additional addresses are generated (for
1125 example, via aliasing), these new addresses are rewritten as soon as they are
1126 generated. At the time a message is actually delivered (transported) further
1127 rewriting can take place; because this is a transport option, it can be
1128 different for different forms of delivery. It is also possible to specify the
1129 addition or removal of certain header lines at the time the message is
1130 delivered (see chapters &<<CHAProutergeneric>>& and
1131 &<<CHAPtransportgeneric>>&).
1135 .section "Life of a message" "SECID15"
1136 .cindex "message" "life of"
1137 .cindex "message" "frozen"
1138 A message remains in the spool directory until it is completely delivered to
1139 its recipients or to an error address, or until it is deleted by an
1140 administrator or by the user who originally created it. In cases when delivery
1141 cannot proceed &-- for example, when a message can neither be delivered to its
1142 recipients nor returned to its sender, the message is marked &"frozen"& on the
1143 spool, and no more deliveries are attempted.
1145 .cindex "frozen messages" "thawing"
1146 .cindex "message" "thawing frozen"
1147 An administrator can &"thaw"& such messages when the problem has been
1148 corrected, and can also freeze individual messages by hand if necessary. In
1149 addition, an administrator can force a delivery error, causing a bounce message
1152 .oindex "&%timeout_frozen_after%&"
1153 .oindex "&%ignore_bounce_errors_after%&"
1154 There are options called &%ignore_bounce_errors_after%& and
1155 &%timeout_frozen_after%&, which discard frozen messages after a certain time.
1156 The first applies only to frozen bounces, the second to any frozen messages.
1158 .cindex "message" "log file for"
1159 .cindex "log" "file for each message"
1160 While Exim is working on a message, it writes information about each delivery
1161 attempt to its main log file. This includes successful, unsuccessful, and
1162 delayed deliveries for each recipient (see chapter &<<CHAPlog>>&). The log
1163 lines are also written to a separate &'message log'& file for each message.
1164 These logs are solely for the benefit of the administrator, and are normally
1165 deleted along with the spool files when processing of a message is complete.
1166 The use of individual message logs can be disabled by setting
1167 &%no_message_logs%&; this might give an improvement in performance on very busy
1170 .cindex "journal file"
1171 .cindex "file" "journal"
1172 All the information Exim itself needs to set up a delivery is kept in the first
1173 spool file, along with the header lines. When a successful delivery occurs, the
1174 address is immediately written at the end of a journal file, whose name is the
1175 message id followed by &`-J`&. At the end of a delivery run, if there are some
1176 addresses left to be tried again later, the first spool file (the &`-H`& file)
1177 is updated to indicate which these are, and the journal file is then deleted.
1178 Updating the spool file is done by writing a new file and renaming it, to
1179 minimize the possibility of data loss.
1181 Should the system or the program crash after a successful delivery but before
1182 the spool file has been updated, the journal is left lying around. The next
1183 time Exim attempts to deliver the message, it reads the journal file and
1184 updates the spool file before proceeding. This minimizes the chances of double
1185 deliveries caused by crashes.
1189 .section "Processing an address for delivery" "SECTprocaddress"
1190 .cindex "drivers" "definition of"
1191 .cindex "router" "definition of"
1192 .cindex "transport" "definition of"
1193 The main delivery processing elements of Exim are called &'routers'& and
1194 &'transports'&, and collectively these are known as &'drivers'&. Code for a
1195 number of them is provided in the source distribution, and compile-time options
1196 specify which ones are included in the binary. Run time options specify which
1197 ones are actually used for delivering messages.
1199 .cindex "drivers" "instance definition"
1200 Each driver that is specified in the run time configuration is an &'instance'&
1201 of that particular driver type. Multiple instances are allowed; for example,
1202 you can set up several different &(smtp)& transports, each with different
1203 option values that might specify different ports or different timeouts. Each
1204 instance has its own identifying name. In what follows we will normally use the
1205 instance name when discussing one particular instance (that is, one specific
1206 configuration of the driver), and the generic driver name when discussing
1207 the driver's features in general.
1209 A &'router'& is a driver that operates on an address, either determining how
1210 its delivery should happen, by assigning it to a specific transport, or
1211 converting the address into one or more new addresses (for example, via an
1212 alias file). A router may also explicitly choose to fail an address, causing it
1215 A &'transport'& is a driver that transmits a copy of the message from Exim's
1216 spool to some destination. There are two kinds of transport: for a &'local'&
1217 transport, the destination is a file or a pipe on the local host, whereas for a
1218 &'remote'& transport the destination is some other host. A message is passed
1219 to a specific transport as a result of successful routing. If a message has
1220 several recipients, it may be passed to a number of different transports.
1222 .cindex "preconditions" "definition of"
1223 An address is processed by passing it to each configured router instance in
1224 turn, subject to certain preconditions, until a router accepts the address or
1225 specifies that it should be bounced. We will describe this process in more
1226 detail shortly. First, as a simple example, we consider how each recipient
1227 address in a message is processed in a small configuration of three routers.
1229 To make this a more concrete example, it is described in terms of some actual
1230 routers, but remember, this is only an example. You can configure Exim's
1231 routers in many different ways, and there may be any number of routers in a
1234 The first router that is specified in a configuration is often one that handles
1235 addresses in domains that are not recognized specially by the local host. These
1236 are typically addresses for arbitrary domains on the Internet. A precondition
1237 is set up which looks for the special domains known to the host (for example,
1238 its own domain name), and the router is run for addresses that do &'not'&
1239 match. Typically, this is a router that looks up domains in the DNS in order to
1240 find the hosts to which this address routes. If it succeeds, the address is
1241 assigned to a suitable SMTP transport; if it does not succeed, the router is
1242 configured to fail the address.
1244 The second router is reached only when the domain is recognized as one that
1245 &"belongs"& to the local host. This router does redirection &-- also known as
1246 aliasing and forwarding. When it generates one or more new addresses from the
1247 original, each of them is routed independently from the start. Otherwise, the
1248 router may cause an address to fail, or it may simply decline to handle the
1249 address, in which case the address is passed to the next router.
1251 The final router in many configurations is one that checks to see if the
1252 address belongs to a local mailbox. The precondition may involve a check to
1253 see if the local part is the name of a login account, or it may look up the
1254 local part in a file or a database. If its preconditions are not met, or if
1255 the router declines, we have reached the end of the routers. When this happens,
1256 the address is bounced.
1260 .section "Processing an address for verification" "SECID16"
1261 .cindex "router" "for verification"
1262 .cindex "verifying address" "overview"
1263 As well as being used to decide how to deliver to an address, Exim's routers
1264 are also used for &'address verification'&. Verification can be requested as
1265 one of the checks to be performed in an ACL for incoming messages, on both
1266 sender and recipient addresses, and it can be tested using the &%-bv%& and
1267 &%-bvs%& command line options.
1269 When an address is being verified, the routers are run in &"verify mode"&. This
1270 does not affect the way the routers work, but it is a state that can be
1271 detected. By this means, a router can be skipped or made to behave differently
1272 when verifying. A common example is a configuration in which the first router
1273 sends all messages to a message-scanning program, unless they have been
1274 previously scanned. Thus, the first router accepts all addresses without any
1275 checking, making it useless for verifying. Normally, the &%no_verify%& option
1276 would be set for such a router, causing it to be skipped in verify mode.
1281 .section "Running an individual router" "SECTrunindrou"
1282 .cindex "router" "running details"
1283 .cindex "preconditions" "checking"
1284 .cindex "router" "result of running"
1285 As explained in the example above, a number of preconditions are checked before
1286 running a router. If any are not met, the router is skipped, and the address is
1287 passed to the next router. When all the preconditions on a router &'are'& met,
1288 the router is run. What happens next depends on the outcome, which is one of
1292 &'accept'&: The router accepts the address, and either assigns it to a
1293 transport, or generates one or more &"child"& addresses. Processing the
1294 original address ceases,
1295 .oindex "&%unseen%&"
1296 unless the &%unseen%& option is set on the router. This option
1297 can be used to set up multiple deliveries with different routing (for example,
1298 for keeping archive copies of messages). When &%unseen%& is set, the address is
1299 passed to the next router. Normally, however, an &'accept'& return marks the
1302 Any child addresses generated by the router are processed independently,
1303 starting with the first router by default. It is possible to change this by
1304 setting the &%redirect_router%& option to specify which router to start at for
1305 child addresses. Unlike &%pass_router%& (see below) the router specified by
1306 &%redirect_router%& may be anywhere in the router configuration.
1308 &'pass'&: The router recognizes the address, but cannot handle it itself. It
1309 requests that the address be passed to another router. By default the address
1310 is passed to the next router, but this can be changed by setting the
1311 &%pass_router%& option. However, (unlike &%redirect_router%&) the named router
1312 must be below the current router (to avoid loops).
1314 &'decline'&: The router declines to accept the address because it does not
1315 recognize it at all. By default, the address is passed to the next router, but
1316 this can be prevented by setting the &%no_more%& option. When &%no_more%& is
1317 set, all the remaining routers are skipped. In effect, &%no_more%& converts
1318 &'decline'& into &'fail'&.
1320 &'fail'&: The router determines that the address should fail, and queues it for
1321 the generation of a bounce message. There is no further processing of the
1322 original address unless &%unseen%& is set on the router.
1324 &'defer'&: The router cannot handle the address at the present time. (A
1325 database may be offline, or a DNS lookup may have timed out.) No further
1326 processing of the address happens in this delivery attempt. It is tried again
1327 next time the message is considered for delivery.
1329 &'error'&: There is some error in the router (for example, a syntax error in
1330 its configuration). The action is as for defer.
1333 If an address reaches the end of the routers without having been accepted by
1334 any of them, it is bounced as unrouteable. The default error message in this
1335 situation is &"unrouteable address"&, but you can set your own message by
1336 making use of the &%cannot_route_message%& option. This can be set for any
1337 router; the value from the last router that &"saw"& the address is used.
1339 Sometimes while routing you want to fail a delivery when some conditions are
1340 met but others are not, instead of passing the address on for further routing.
1341 You can do this by having a second router that explicitly fails the delivery
1342 when the relevant conditions are met. The &(redirect)& router has a &"fail"&
1343 facility for this purpose.
1346 .section "Duplicate addresses" "SECID17"
1347 .cindex "case of local parts"
1348 .cindex "address duplicate, discarding"
1349 .cindex "duplicate addresses"
1350 Once routing is complete, Exim scans the addresses that are assigned to local
1351 and remote transports, and discards any duplicates that it finds. During this
1352 check, local parts are treated as case-sensitive. This happens only when
1353 actually delivering a message; when testing routers with &%-bt%&, all the
1354 routed addresses are shown.
1358 .section "Router preconditions" "SECTrouprecon"
1359 .cindex "router" "preconditions, order of processing"
1360 .cindex "preconditions" "order of processing"
1361 The preconditions that are tested for each router are listed below, in the
1362 order in which they are tested. The individual configuration options are
1363 described in more detail in chapter &<<CHAProutergeneric>>&.
1366 The &%local_part_prefix%& and &%local_part_suffix%& options can specify that
1367 the local parts handled by the router may or must have certain prefixes and/or
1368 suffixes. If a mandatory affix (prefix or suffix) is not present, the router is
1369 skipped. These conditions are tested first. When an affix is present, it is
1370 removed from the local part before further processing, including the evaluation
1371 of any other conditions.
1373 Routers can be designated for use only when not verifying an address, that is,
1374 only when routing it for delivery (or testing its delivery routing). If the
1375 &%verify%& option is set false, the router is skipped when Exim is verifying an
1377 Setting the &%verify%& option actually sets two options, &%verify_sender%& and
1378 &%verify_recipient%&, which independently control the use of the router for
1379 sender and recipient verification. You can set these options directly if
1380 you want a router to be used for only one type of verification.
1381 Note that cutthrough delivery is classed as a recipient verification for this purpose.
1383 If the &%address_test%& option is set false, the router is skipped when Exim is
1384 run with the &%-bt%& option to test an address routing. This can be helpful
1385 when the first router sends all new messages to a scanner of some sort; it
1386 makes it possible to use &%-bt%& to test subsequent delivery routing without
1387 having to simulate the effect of the scanner.
1389 Routers can be designated for use only when verifying an address, as
1390 opposed to routing it for delivery. The &%verify_only%& option controls this.
1391 Again, cutthrough delivery counts as a verification.
1393 Individual routers can be explicitly skipped when running the routers to
1394 check an address given in the SMTP EXPN command (see the &%expn%& option).
1396 If the &%domains%& option is set, the domain of the address must be in the set
1397 of domains that it defines.
1399 .vindex "&$local_part_prefix$&"
1400 .vindex "&$local_part$&"
1401 .vindex "&$local_part_suffix$&"
1402 If the &%local_parts%& option is set, the local part of the address must be in
1403 the set of local parts that it defines. If &%local_part_prefix%& or
1404 &%local_part_suffix%& is in use, the prefix or suffix is removed from the local
1405 part before this check. If you want to do precondition tests on local parts
1406 that include affixes, you can do so by using a &%condition%& option (see below)
1407 that uses the variables &$local_part$&, &$local_part_prefix$&, and
1408 &$local_part_suffix$& as necessary.
1410 .vindex "&$local_user_uid$&"
1411 .vindex "&$local_user_gid$&"
1413 If the &%check_local_user%& option is set, the local part must be the name of
1414 an account on the local host. If this check succeeds, the uid and gid of the
1415 local user are placed in &$local_user_uid$& and &$local_user_gid$& and the
1416 user's home directory is placed in &$home$&; these values can be used in the
1417 remaining preconditions.
1419 If the &%router_home_directory%& option is set, it is expanded at this point,
1420 because it overrides the value of &$home$&. If this expansion were left till
1421 later, the value of &$home$& as set by &%check_local_user%& would be used in
1422 subsequent tests. Having two different values of &$home$& in the same router
1423 could lead to confusion.
1425 If the &%senders%& option is set, the envelope sender address must be in the
1426 set of addresses that it defines.
1428 If the &%require_files%& option is set, the existence or non-existence of
1429 specified files is tested.
1431 .cindex "customizing" "precondition"
1432 If the &%condition%& option is set, it is evaluated and tested. This option
1433 uses an expanded string to allow you to set up your own custom preconditions.
1434 Expanded strings are described in chapter &<<CHAPexpand>>&.
1438 Note that &%require_files%& comes near the end of the list, so you cannot use
1439 it to check for the existence of a file in which to lookup up a domain, local
1440 part, or sender. However, as these options are all expanded, you can use the
1441 &%exists%& expansion condition to make such tests within each condition. The
1442 &%require_files%& option is intended for checking files that the router may be
1443 going to use internally, or which are needed by a specific transport (for
1444 example, &_.procmailrc_&).
1448 .section "Delivery in detail" "SECID18"
1449 .cindex "delivery" "in detail"
1450 When a message is to be delivered, the sequence of events is as follows:
1453 If a system-wide filter file is specified, the message is passed to it. The
1454 filter may add recipients to the message, replace the recipients, discard the
1455 message, cause a new message to be generated, or cause the message delivery to
1456 fail. The format of the system filter file is the same as for Exim user filter
1457 files, described in the separate document entitled &'Exim's interfaces to mail
1459 .cindex "Sieve filter" "not available for system filter"
1460 (&*Note*&: Sieve cannot be used for system filter files.)
1462 Some additional features are available in system filters &-- see chapter
1463 &<<CHAPsystemfilter>>& for details. Note that a message is passed to the system
1464 filter only once per delivery attempt, however many recipients it has. However,
1465 if there are several delivery attempts because one or more addresses could not
1466 be immediately delivered, the system filter is run each time. The filter
1467 condition &%first_delivery%& can be used to detect the first run of the system
1470 Each recipient address is offered to each configured router in turn, subject to
1471 its preconditions, until one is able to handle it. If no router can handle the
1472 address, that is, if they all decline, the address is failed. Because routers
1473 can be targeted at particular domains, several locally handled domains can be
1474 processed entirely independently of each other.
1476 .cindex "routing" "loops in"
1477 .cindex "loop" "while routing"
1478 A router that accepts an address may assign it to a local or a remote
1479 transport. However, the transport is not run at this time. Instead, the address
1480 is placed on a list for the particular transport, which will be run later.
1481 Alternatively, the router may generate one or more new addresses (typically
1482 from alias, forward, or filter files). New addresses are fed back into this
1483 process from the top, but in order to avoid loops, a router ignores any address
1484 which has an identically-named ancestor that was processed by itself.
1486 When all the routing has been done, addresses that have been successfully
1487 handled are passed to their assigned transports. When local transports are
1488 doing real local deliveries, they handle only one address at a time, but if a
1489 local transport is being used as a pseudo-remote transport (for example, to
1490 collect batched SMTP messages for transmission by some other means) multiple
1491 addresses can be handled. Remote transports can always handle more than one
1492 address at a time, but can be configured not to do so, or to restrict multiple
1493 addresses to the same domain.
1495 Each local delivery to a file or a pipe runs in a separate process under a
1496 non-privileged uid, and these deliveries are run one at a time. Remote
1497 deliveries also run in separate processes, normally under a uid that is private
1498 to Exim (&"the Exim user"&), but in this case, several remote deliveries can be
1499 run in parallel. The maximum number of simultaneous remote deliveries for any
1500 one message is set by the &%remote_max_parallel%& option.
1501 The order in which deliveries are done is not defined, except that all local
1502 deliveries happen before any remote deliveries.
1504 .cindex "queue runner"
1505 When it encounters a local delivery during a queue run, Exim checks its retry
1506 database to see if there has been a previous temporary delivery failure for the
1507 address before running the local transport. If there was a previous failure,
1508 Exim does not attempt a new delivery until the retry time for the address is
1509 reached. However, this happens only for delivery attempts that are part of a
1510 queue run. Local deliveries are always attempted when delivery immediately
1511 follows message reception, even if retry times are set for them. This makes for
1512 better behaviour if one particular message is causing problems (for example,
1513 causing quota overflow, or provoking an error in a filter file).
1515 .cindex "delivery" "retry in remote transports"
1516 Remote transports do their own retry handling, since an address may be
1517 deliverable to one of a number of hosts, each of which may have a different
1518 retry time. If there have been previous temporary failures and no host has
1519 reached its retry time, no delivery is attempted, whether in a queue run or
1520 not. See chapter &<<CHAPretry>>& for details of retry strategies.
1522 If there were any permanent errors, a bounce message is returned to an
1523 appropriate address (the sender in the common case), with details of the error
1524 for each failing address. Exim can be configured to send copies of bounce
1525 messages to other addresses.
1527 .cindex "delivery" "deferral"
1528 If one or more addresses suffered a temporary failure, the message is left on
1529 the queue, to be tried again later. Delivery of these addresses is said to be
1532 When all the recipient addresses have either been delivered or bounced,
1533 handling of the message is complete. The spool files and message log are
1534 deleted, though the message log can optionally be preserved if required.
1540 .section "Retry mechanism" "SECID19"
1541 .cindex "delivery" "retry mechanism"
1542 .cindex "retry" "description of mechanism"
1543 .cindex "queue runner"
1544 Exim's mechanism for retrying messages that fail to get delivered at the first
1545 attempt is the queue runner process. You must either run an Exim daemon that
1546 uses the &%-q%& option with a time interval to start queue runners at regular
1547 intervals, or use some other means (such as &'cron'&) to start them. If you do
1548 not arrange for queue runners to be run, messages that fail temporarily at the
1549 first attempt will remain on your queue for ever. A queue runner process works
1550 its way through the queue, one message at a time, trying each delivery that has
1551 passed its retry time.
1552 You can run several queue runners at once.
1554 Exim uses a set of configured rules to determine when next to retry the failing
1555 address (see chapter &<<CHAPretry>>&). These rules also specify when Exim
1556 should give up trying to deliver to the address, at which point it generates a
1557 bounce message. If no retry rules are set for a particular host, address, and
1558 error combination, no retries are attempted, and temporary errors are treated
1563 .section "Temporary delivery failure" "SECID20"
1564 .cindex "delivery" "temporary failure"
1565 There are many reasons why a message may not be immediately deliverable to a
1566 particular address. Failure to connect to a remote machine (because it, or the
1567 connection to it, is down) is one of the most common. Temporary failures may be
1568 detected during routing as well as during the transport stage of delivery.
1569 Local deliveries may be delayed if NFS files are unavailable, or if a mailbox
1570 is on a file system where the user is over quota. Exim can be configured to
1571 impose its own quotas on local mailboxes; where system quotas are set they will
1574 If a host is unreachable for a period of time, a number of messages may be
1575 waiting for it by the time it recovers, and sending them in a single SMTP
1576 connection is clearly beneficial. Whenever a delivery to a remote host is
1578 .cindex "hints database"
1579 Exim makes a note in its hints database, and whenever a successful
1580 SMTP delivery has happened, it looks to see if any other messages are waiting
1581 for the same host. If any are found, they are sent over the same SMTP
1582 connection, subject to a configuration limit as to the maximum number in any
1587 .section "Permanent delivery failure" "SECID21"
1588 .cindex "delivery" "permanent failure"
1589 .cindex "bounce message" "when generated"
1590 When a message cannot be delivered to some or all of its intended recipients, a
1591 bounce message is generated. Temporary delivery failures turn into permanent
1592 errors when their timeout expires. All the addresses that fail in a given
1593 delivery attempt are listed in a single message. If the original message has
1594 many recipients, it is possible for some addresses to fail in one delivery
1595 attempt and others to fail subsequently, giving rise to more than one bounce
1596 message. The wording of bounce messages can be customized by the administrator.
1597 See chapter &<<CHAPemsgcust>>& for details.
1599 .cindex "&'X-Failed-Recipients:'& header line"
1600 Bounce messages contain an &'X-Failed-Recipients:'& header line that lists the
1601 failed addresses, for the benefit of programs that try to analyse such messages
1604 .cindex "bounce message" "recipient of"
1605 A bounce message is normally sent to the sender of the original message, as
1606 obtained from the message's envelope. For incoming SMTP messages, this is the
1607 address given in the MAIL command. However, when an address is expanded via a
1608 forward or alias file, an alternative address can be specified for delivery
1609 failures of the generated addresses. For a mailing list expansion (see section
1610 &<<SECTmailinglists>>&) it is common to direct bounce messages to the manager
1615 .section "Failures to deliver bounce messages" "SECID22"
1616 .cindex "bounce message" "failure to deliver"
1617 If a bounce message (either locally generated or received from a remote host)
1618 itself suffers a permanent delivery failure, the message is left on the queue,
1619 but it is frozen, awaiting the attention of an administrator. There are options
1620 that can be used to make Exim discard such failed messages, or to keep them
1621 for only a short time (see &%timeout_frozen_after%& and
1622 &%ignore_bounce_errors_after%&).
1628 . ////////////////////////////////////////////////////////////////////////////
1629 . ////////////////////////////////////////////////////////////////////////////
1631 .chapter "Building and installing Exim" "CHID3"
1632 .scindex IIDbuex "building Exim"
1634 .section "Unpacking" "SECID23"
1635 Exim is distributed as a gzipped or bzipped tar file which, when unpacked,
1636 creates a directory with the name of the current release (for example,
1637 &_exim-&version()_&) into which the following files are placed:
1640 .irow &_ACKNOWLEDGMENTS_& "contains some acknowledgments"
1641 .irow &_CHANGES_& "contains a reference to where changes are &&&
1643 .irow &_LICENCE_& "the GNU General Public Licence"
1644 .irow &_Makefile_& "top-level make file"
1645 .irow &_NOTICE_& "conditions for the use of Exim"
1646 .irow &_README_& "list of files, directories and simple build &&&
1650 Other files whose names begin with &_README_& may also be present. The
1651 following subdirectories are created:
1654 .irow &_Local_& "an empty directory for local configuration files"
1655 .irow &_OS_& "OS-specific files"
1656 .irow &_doc_& "documentation files"
1657 .irow &_exim_monitor_& "source files for the Exim monitor"
1658 .irow &_scripts_& "scripts used in the build process"
1659 .irow &_src_& "remaining source files"
1660 .irow &_util_& "independent utilities"
1663 The main utility programs are contained in the &_src_& directory, and are built
1664 with the Exim binary. The &_util_& directory contains a few optional scripts
1665 that may be useful to some sites.
1668 .section "Multiple machine architectures and operating systems" "SECID24"
1669 .cindex "building Exim" "multiple OS/architectures"
1670 The building process for Exim is arranged to make it easy to build binaries for
1671 a number of different architectures and operating systems from the same set of
1672 source files. Compilation does not take place in the &_src_& directory.
1673 Instead, a &'build directory'& is created for each architecture and operating
1675 .cindex "symbolic link" "to build directory"
1676 Symbolic links to the sources are installed in this directory, which is where
1677 the actual building takes place. In most cases, Exim can discover the machine
1678 architecture and operating system for itself, but the defaults can be
1679 overridden if necessary.
1682 .section "PCRE library" "SECTpcre"
1683 .cindex "PCRE library"
1684 Exim no longer has an embedded PCRE library as the vast majority of
1685 modern systems include PCRE as a system library, although you may need
1686 to install the PCRE or PCRE development package for your operating
1687 system. If your system has a normal PCRE installation the Exim build
1688 process will need no further configuration. If the library or the
1689 headers are in an unusual location you will need to either set the PCRE_LIBS
1690 and INCLUDE directives appropriately,
1691 or set PCRE_CONFIG=yes to use the installed &(pcre-config)& command.
1692 If your operating system has no
1693 PCRE support then you will need to obtain and build the current PCRE
1694 from &url(ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre/).
1695 More information on PCRE is available at &url(http://www.pcre.org/).
1697 .section "DBM libraries" "SECTdb"
1698 .cindex "DBM libraries" "discussion of"
1699 .cindex "hints database" "DBM files used for"
1700 Even if you do not use any DBM files in your configuration, Exim still needs a
1701 DBM library in order to operate, because it uses indexed files for its hints
1702 databases. Unfortunately, there are a number of DBM libraries in existence, and
1703 different operating systems often have different ones installed.
1705 .cindex "Solaris" "DBM library for"
1706 .cindex "IRIX, DBM library for"
1707 .cindex "BSD, DBM library for"
1708 .cindex "Linux, DBM library for"
1709 If you are using Solaris, IRIX, one of the modern BSD systems, or a modern
1710 Linux distribution, the DBM configuration should happen automatically, and you
1711 may be able to ignore this section. Otherwise, you may have to learn more than
1712 you would like about DBM libraries from what follows.
1714 .cindex "&'ndbm'& DBM library"
1715 Licensed versions of Unix normally contain a library of DBM functions operating
1716 via the &'ndbm'& interface, and this is what Exim expects by default. Free
1717 versions of Unix seem to vary in what they contain as standard. In particular,
1718 some early versions of Linux have no default DBM library, and different
1719 distributors have chosen to bundle different libraries with their packaged
1720 versions. However, the more recent releases seem to have standardized on the
1721 Berkeley DB library.
1723 Different DBM libraries have different conventions for naming the files they
1724 use. When a program opens a file called &_dbmfile_&, there are several
1728 A traditional &'ndbm'& implementation, such as that supplied as part of
1729 Solaris, operates on two files called &_dbmfile.dir_& and &_dbmfile.pag_&.
1731 .cindex "&'gdbm'& DBM library"
1732 The GNU library, &'gdbm'&, operates on a single file. If used via its &'ndbm'&
1733 compatibility interface it makes two different hard links to it with names
1734 &_dbmfile.dir_& and &_dbmfile.pag_&, but if used via its native interface, the
1735 file name is used unmodified.
1737 .cindex "Berkeley DB library"
1738 The Berkeley DB package, if called via its &'ndbm'& compatibility interface,
1739 operates on a single file called &_dbmfile.db_&, but otherwise looks to the
1740 programmer exactly the same as the traditional &'ndbm'& implementation.
1742 If the Berkeley package is used in its native mode, it operates on a single
1743 file called &_dbmfile_&; the programmer's interface is somewhat different to
1744 the traditional &'ndbm'& interface.
1746 To complicate things further, there are several very different versions of the
1747 Berkeley DB package. Version 1.85 was stable for a very long time, releases
1748 2.&'x'& and 3.&'x'& were current for a while, but the latest versions are now
1749 numbered 4.&'x'&. Maintenance of some of the earlier releases has ceased. All
1750 versions of Berkeley DB can be obtained from
1751 &url(http://www.sleepycat.com/).
1753 .cindex "&'tdb'& DBM library"
1754 Yet another DBM library, called &'tdb'&, is available from
1755 &url(http://download.sourceforge.net/tdb). It has its own interface, and also
1756 operates on a single file.
1760 .cindex "DBM libraries" "configuration for building"
1761 Exim and its utilities can be compiled to use any of these interfaces. In order
1762 to use any version of the Berkeley DB package in native mode, you must set
1763 USE_DB in an appropriate configuration file (typically
1764 &_Local/Makefile_&). For example:
1768 Similarly, for gdbm you set USE_GDBM, and for tdb you set USE_TDB. An
1769 error is diagnosed if you set more than one of these.
1771 At the lowest level, the build-time configuration sets none of these options,
1772 thereby assuming an interface of type (1). However, some operating system
1773 configuration files (for example, those for the BSD operating systems and
1774 Linux) assume type (4) by setting USE_DB as their default, and the
1775 configuration files for Cygwin set USE_GDBM. Anything you set in
1776 &_Local/Makefile_&, however, overrides these system defaults.
1778 As well as setting USE_DB, USE_GDBM, or USE_TDB, it may also be
1779 necessary to set DBMLIB, to cause inclusion of the appropriate library, as
1780 in one of these lines:
1785 Settings like that will work if the DBM library is installed in the standard
1786 place. Sometimes it is not, and the library's header file may also not be in
1787 the default path. You may need to set INCLUDE to specify where the header
1788 file is, and to specify the path to the library more fully in DBMLIB, as in
1791 INCLUDE=-I/usr/local/include/db-4.1
1792 DBMLIB=/usr/local/lib/db-4.1/libdb.a
1794 There is further detailed discussion about the various DBM libraries in the
1795 file &_doc/dbm.discuss.txt_& in the Exim distribution.
1799 .section "Pre-building configuration" "SECID25"
1800 .cindex "building Exim" "pre-building configuration"
1801 .cindex "configuration for building Exim"
1802 .cindex "&_Local/Makefile_&"
1803 .cindex "&_src/EDITME_&"
1804 Before building Exim, a local configuration file that specifies options
1805 independent of any operating system has to be created with the name
1806 &_Local/Makefile_&. A template for this file is supplied as the file
1807 &_src/EDITME_&, and it contains full descriptions of all the option settings
1808 therein. These descriptions are therefore not repeated here. If you are
1809 building Exim for the first time, the simplest thing to do is to copy
1810 &_src/EDITME_& to &_Local/Makefile_&, then read it and edit it appropriately.
1812 There are three settings that you must supply, because Exim will not build
1813 without them. They are the location of the run time configuration file
1814 (CONFIGURE_FILE), the directory in which Exim binaries will be installed
1815 (BIN_DIRECTORY), and the identity of the Exim user (EXIM_USER and
1816 maybe EXIM_GROUP as well). The value of CONFIGURE_FILE can in fact be
1817 a colon-separated list of file names; Exim uses the first of them that exists.
1819 There are a few other parameters that can be specified either at build time or
1820 at run time, to enable the same binary to be used on a number of different
1821 machines. However, if the locations of Exim's spool directory and log file
1822 directory (if not within the spool directory) are fixed, it is recommended that
1823 you specify them in &_Local/Makefile_& instead of at run time, so that errors
1824 detected early in Exim's execution (such as a malformed configuration file) can
1827 .cindex "content scanning" "specifying at build time"
1828 Exim's interfaces for calling virus and spam scanning software directly from
1829 access control lists are not compiled by default. If you want to include these
1830 facilities, you need to set
1832 WITH_CONTENT_SCAN=yes
1834 in your &_Local/Makefile_&. For details of the facilities themselves, see
1835 chapter &<<CHAPexiscan>>&.
1838 .cindex "&_Local/eximon.conf_&"
1839 .cindex "&_exim_monitor/EDITME_&"
1840 If you are going to build the Exim monitor, a similar configuration process is
1841 required. The file &_exim_monitor/EDITME_& must be edited appropriately for
1842 your installation and saved under the name &_Local/eximon.conf_&. If you are
1843 happy with the default settings described in &_exim_monitor/EDITME_&,
1844 &_Local/eximon.conf_& can be empty, but it must exist.
1846 This is all the configuration that is needed in straightforward cases for known
1847 operating systems. However, the building process is set up so that it is easy
1848 to override options that are set by default or by operating-system-specific
1849 configuration files, for example to change the name of the C compiler, which
1850 defaults to &%gcc%&. See section &<<SECToverride>>& below for details of how to
1855 .section "Support for iconv()" "SECID26"
1856 .cindex "&[iconv()]& support"
1858 The contents of header lines in messages may be encoded according to the rules
1859 described RFC 2047. This makes it possible to transmit characters that are not
1860 in the ASCII character set, and to label them as being in a particular
1861 character set. When Exim is inspecting header lines by means of the &%$h_%&
1862 mechanism, it decodes them, and translates them into a specified character set
1863 (default ISO-8859-1). The translation is possible only if the operating system
1864 supports the &[iconv()]& function.
1866 However, some of the operating systems that supply &[iconv()]& do not support
1867 very many conversions. The GNU &%libiconv%& library (available from
1868 &url(http://www.gnu.org/software/libiconv/)) can be installed on such
1869 systems to remedy this deficiency, as well as on systems that do not supply
1870 &[iconv()]& at all. After installing &%libiconv%&, you should add
1874 to your &_Local/Makefile_& and rebuild Exim.
1878 .section "Including TLS/SSL encryption support" "SECTinctlsssl"
1879 .cindex "TLS" "including support for TLS"
1880 .cindex "encryption" "including support for"
1881 .cindex "SUPPORT_TLS"
1882 .cindex "OpenSSL" "building Exim with"
1883 .cindex "GnuTLS" "building Exim with"
1884 Exim can be built to support encrypted SMTP connections, using the STARTTLS
1885 command as per RFC 2487. It can also support legacy clients that expect to
1886 start a TLS session immediately on connection to a non-standard port (see the
1887 &%tls_on_connect_ports%& runtime option and the &%-tls-on-connect%& command
1890 If you want to build Exim with TLS support, you must first install either the
1891 OpenSSL or GnuTLS library. There is no cryptographic code in Exim itself for
1894 If OpenSSL is installed, you should set
1897 TLS_LIBS=-lssl -lcrypto
1899 in &_Local/Makefile_&. You may also need to specify the locations of the
1900 OpenSSL library and include files. For example:
1903 TLS_LIBS=-L/usr/local/openssl/lib -lssl -lcrypto
1904 TLS_INCLUDE=-I/usr/local/openssl/include/
1906 .cindex "pkg-config" "OpenSSL"
1907 If you have &'pkg-config'& available, then instead you can just use:
1910 USE_OPENSSL_PC=openssl
1912 .cindex "USE_GNUTLS"
1913 If GnuTLS is installed, you should set
1917 TLS_LIBS=-lgnutls -ltasn1 -lgcrypt
1919 in &_Local/Makefile_&, and again you may need to specify the locations of the
1920 library and include files. For example:
1924 TLS_LIBS=-L/usr/gnu/lib -lgnutls -ltasn1 -lgcrypt
1925 TLS_INCLUDE=-I/usr/gnu/include
1927 .cindex "pkg-config" "GnuTLS"
1928 If you have &'pkg-config'& available, then instead you can just use:
1932 USE_GNUTLS_PC=gnutls
1935 You do not need to set TLS_INCLUDE if the relevant directory is already
1936 specified in INCLUDE. Details of how to configure Exim to make use of TLS are
1937 given in chapter &<<CHAPTLS>>&.
1942 .section "Use of tcpwrappers" "SECID27"
1944 .cindex "tcpwrappers, building Exim to support"
1945 .cindex "USE_TCP_WRAPPERS"
1946 .cindex "TCP_WRAPPERS_DAEMON_NAME"
1947 .cindex "tcp_wrappers_daemon_name"
1948 Exim can be linked with the &'tcpwrappers'& library in order to check incoming
1949 SMTP calls using the &'tcpwrappers'& control files. This may be a convenient
1950 alternative to Exim's own checking facilities for installations that are
1951 already making use of &'tcpwrappers'& for other purposes. To do this, you
1952 should set USE_TCP_WRAPPERS in &_Local/Makefile_&, arrange for the file
1953 &_tcpd.h_& to be available at compile time, and also ensure that the library
1954 &_libwrap.a_& is available at link time, typically by including &%-lwrap%& in
1955 EXTRALIBS_EXIM. For example, if &'tcpwrappers'& is installed in &_/usr/local_&,
1958 USE_TCP_WRAPPERS=yes
1959 CFLAGS=-O -I/usr/local/include
1960 EXTRALIBS_EXIM=-L/usr/local/lib -lwrap
1962 in &_Local/Makefile_&. The daemon name to use in the &'tcpwrappers'& control
1963 files is &"exim"&. For example, the line
1965 exim : LOCAL 192.168.1. .friendly.domain.example
1967 in your &_/etc/hosts.allow_& file allows connections from the local host, from
1968 the subnet 192.168.1.0/24, and from all hosts in &'friendly.domain.example'&.
1969 All other connections are denied. The daemon name used by &'tcpwrappers'&
1970 can be changed at build time by setting TCP_WRAPPERS_DAEMON_NAME in
1971 &_Local/Makefile_&, or by setting tcp_wrappers_daemon_name in the
1972 configure file. Consult the &'tcpwrappers'& documentation for
1976 .section "Including support for IPv6" "SECID28"
1977 .cindex "IPv6" "including support for"
1978 Exim contains code for use on systems that have IPv6 support. Setting
1979 &`HAVE_IPV6=YES`& in &_Local/Makefile_& causes the IPv6 code to be included;
1980 it may also be necessary to set IPV6_INCLUDE and IPV6_LIBS on systems
1981 where the IPv6 support is not fully integrated into the normal include and
1984 Two different types of DNS record for handling IPv6 addresses have been
1985 defined. AAAA records (analogous to A records for IPv4) are in use, and are
1986 currently seen as the mainstream. Another record type called A6 was proposed
1987 as better than AAAA because it had more flexibility. However, it was felt to be
1988 over-complex, and its status was reduced to &"experimental"&. It is not known
1989 if anyone is actually using A6 records. Exim has support for A6 records, but
1990 this is included only if you set &`SUPPORT_A6=YES`& in &_Local/Makefile_&. The
1991 support has not been tested for some time.
1995 .section "Dynamically loaded lookup module support" "SECTdynamicmodules"
1996 .cindex "lookup modules"
1997 .cindex "dynamic modules"
1998 .cindex ".so building"
1999 On some platforms, Exim supports not compiling all lookup types directly into
2000 the main binary, instead putting some into external modules which can be loaded
2002 This permits packagers to build Exim with support for lookups with extensive
2003 library dependencies without requiring all users to install all of those
2005 Most, but not all, lookup types can be built this way.
2007 Set &`LOOKUP_MODULE_DIR`& to the directory into which the modules will be
2008 installed; Exim will only load modules from that directory, as a security
2009 measure. You will need to set &`CFLAGS_DYNAMIC`& if not already defined
2010 for your OS; see &_OS/Makefile-Linux_& for an example.
2011 Some other requirements for adjusting &`EXTRALIBS`& may also be necessary,
2012 see &_src/EDITME_& for details.
2014 Then, for each module to be loaded dynamically, define the relevant
2015 &`LOOKUP_`&<&'lookup_type'&> flags to have the value "2" instead of "yes".
2016 For example, this will build in lsearch but load sqlite and mysql support
2025 .section "The building process" "SECID29"
2026 .cindex "build directory"
2027 Once &_Local/Makefile_& (and &_Local/eximon.conf_&, if required) have been
2028 created, run &'make'& at the top level. It determines the architecture and
2029 operating system types, and creates a build directory if one does not exist.
2030 For example, on a Sun system running Solaris 8, the directory
2031 &_build-SunOS5-5.8-sparc_& is created.
2032 .cindex "symbolic link" "to source files"
2033 Symbolic links to relevant source files are installed in the build directory.
2035 &*Warning*&: The &%-j%& (parallel) flag must not be used with &'make'&; the
2036 building process fails if it is set.
2038 If this is the first time &'make'& has been run, it calls a script that builds
2039 a make file inside the build directory, using the configuration files from the
2040 &_Local_& directory. The new make file is then passed to another instance of
2041 &'make'&. This does the real work, building a number of utility scripts, and
2042 then compiling and linking the binaries for the Exim monitor (if configured), a
2043 number of utility programs, and finally Exim itself. The command &`make
2044 makefile`& can be used to force a rebuild of the make file in the build
2045 directory, should this ever be necessary.
2047 If you have problems building Exim, check for any comments there may be in the
2048 &_README_& file concerning your operating system, and also take a look at the
2049 FAQ, where some common problems are covered.
2053 .section 'Output from &"make"&' "SECID283"
2054 The output produced by the &'make'& process for compile lines is often very
2055 unreadable, because these lines can be very long. For this reason, the normal
2056 output is suppressed by default, and instead output similar to that which
2057 appears when compiling the 2.6 Linux kernel is generated: just a short line for
2058 each module that is being compiled or linked. However, it is still possible to
2059 get the full output, by calling &'make'& like this:
2063 The value of FULLECHO defaults to &"@"&, the flag character that suppresses
2064 command reflection in &'make'&. When you ask for the full output, it is
2065 given in addition to the short output.
2069 .section "Overriding build-time options for Exim" "SECToverride"
2070 .cindex "build-time options, overriding"
2071 The main make file that is created at the beginning of the building process
2072 consists of the concatenation of a number of files which set configuration
2073 values, followed by a fixed set of &'make'& instructions. If a value is set
2074 more than once, the last setting overrides any previous ones. This provides a
2075 convenient way of overriding defaults. The files that are concatenated are, in
2078 &_OS/Makefile-Default_&
2079 &_OS/Makefile-_&<&'ostype'&>
2081 &_Local/Makefile-_&<&'ostype'&>
2082 &_Local/Makefile-_&<&'archtype'&>
2083 &_Local/Makefile-_&<&'ostype'&>-<&'archtype'&>
2084 &_OS/Makefile-Base_&
2086 .cindex "&_Local/Makefile_&"
2087 .cindex "building Exim" "operating system type"
2088 .cindex "building Exim" "architecture type"
2089 where <&'ostype'&> is the operating system type and <&'archtype'&> is the
2090 architecture type. &_Local/Makefile_& is required to exist, and the building
2091 process fails if it is absent. The other three &_Local_& files are optional,
2092 and are often not needed.
2094 The values used for <&'ostype'&> and <&'archtype'&> are obtained from scripts
2095 called &_scripts/os-type_& and &_scripts/arch-type_& respectively. If either of
2096 the environment variables EXIM_OSTYPE or EXIM_ARCHTYPE is set, their
2097 values are used, thereby providing a means of forcing particular settings.
2098 Otherwise, the scripts try to get values from the &%uname%& command. If this
2099 fails, the shell variables OSTYPE and ARCHTYPE are inspected. A number
2100 of &'ad hoc'& transformations are then applied, to produce the standard names
2101 that Exim expects. You can run these scripts directly from the shell in order
2102 to find out what values are being used on your system.
2105 &_OS/Makefile-Default_& contains comments about the variables that are set
2106 therein. Some (but not all) are mentioned below. If there is something that
2107 needs changing, review the contents of this file and the contents of the make
2108 file for your operating system (&_OS/Makefile-<ostype>_&) to see what the
2112 .cindex "building Exim" "overriding default settings"
2113 If you need to change any of the values that are set in &_OS/Makefile-Default_&
2114 or in &_OS/Makefile-<ostype>_&, or to add any new definitions, you do not
2115 need to change the original files. Instead, you should make the changes by
2116 putting the new values in an appropriate &_Local_& file. For example,
2117 .cindex "Tru64-Unix build-time settings"
2118 when building Exim in many releases of the Tru64-Unix (formerly Digital UNIX,
2119 formerly DEC-OSF1) operating system, it is necessary to specify that the C
2120 compiler is called &'cc'& rather than &'gcc'&. Also, the compiler must be
2121 called with the option &%-std1%&, to make it recognize some of the features of
2122 Standard C that Exim uses. (Most other compilers recognize Standard C by
2123 default.) To do this, you should create a file called &_Local/Makefile-OSF1_&
2124 containing the lines
2129 If you are compiling for just one operating system, it may be easier to put
2130 these lines directly into &_Local/Makefile_&.
2132 Keeping all your local configuration settings separate from the distributed
2133 files makes it easy to transfer them to new versions of Exim simply by copying
2134 the contents of the &_Local_& directory.
2137 .cindex "NIS lookup type" "including support for"
2138 .cindex "NIS+ lookup type" "including support for"
2139 .cindex "LDAP" "including support for"
2140 .cindex "lookup" "inclusion in binary"
2141 Exim contains support for doing LDAP, NIS, NIS+, and other kinds of file
2142 lookup, but not all systems have these components installed, so the default is
2143 not to include the relevant code in the binary. All the different kinds of file
2144 and database lookup that Exim supports are implemented as separate code modules
2145 which are included only if the relevant compile-time options are set. In the
2146 case of LDAP, NIS, and NIS+, the settings for &_Local/Makefile_& are:
2152 and similar settings apply to the other lookup types. They are all listed in
2153 &_src/EDITME_&. In many cases the relevant include files and interface
2154 libraries need to be installed before compiling Exim.
2155 .cindex "cdb" "including support for"
2156 However, there are some optional lookup types (such as cdb) for which
2157 the code is entirely contained within Exim, and no external include
2158 files or libraries are required. When a lookup type is not included in the
2159 binary, attempts to configure Exim to use it cause run time configuration
2162 .cindex "pkg-config" "lookups"
2163 .cindex "pkg-config" "authenticators"
2164 Many systems now use a tool called &'pkg-config'& to encapsulate information
2165 about how to compile against a library; Exim has some initial support for
2166 being able to use pkg-config for lookups and authenticators. For any given
2167 makefile variable which starts &`LOOKUP_`& or &`AUTH_`&, you can add a new
2168 variable with the &`_PC`& suffix in the name and assign as the value the
2169 name of the package to be queried. The results of querying via the
2170 &'pkg-config'& command will be added to the appropriate Makefile variables
2171 with &`+=`& directives, so your version of &'make'& will need to support that
2172 syntax. For instance:
2175 LOOKUP_SQLITE_PC=sqlite3
2177 AUTH_GSASL_PC=libgsasl
2178 AUTH_HEIMDAL_GSSAPI=yes
2179 AUTH_HEIMDAL_GSSAPI_PC=heimdal-gssapi
2182 .cindex "Perl" "including support for"
2183 Exim can be linked with an embedded Perl interpreter, allowing Perl
2184 subroutines to be called during string expansion. To enable this facility,
2188 must be defined in &_Local/Makefile_&. Details of this facility are given in
2189 chapter &<<CHAPperl>>&.
2191 .cindex "X11 libraries, location of"
2192 The location of the X11 libraries is something that varies a lot between
2193 operating systems, and there may be different versions of X11 to cope
2194 with. Exim itself makes no use of X11, but if you are compiling the Exim
2195 monitor, the X11 libraries must be available.
2196 The following three variables are set in &_OS/Makefile-Default_&:
2199 XINCLUDE=-I$(X11)/include
2200 XLFLAGS=-L$(X11)/lib
2202 These are overridden in some of the operating-system configuration files. For
2203 example, in &_OS/Makefile-SunOS5_& there is
2206 XINCLUDE=-I$(X11)/include
2207 XLFLAGS=-L$(X11)/lib -R$(X11)/lib
2209 If you need to override the default setting for your operating system, place a
2210 definition of all three of these variables into your
2211 &_Local/Makefile-<ostype>_& file.
2214 If you need to add any extra libraries to the link steps, these can be put in a
2215 variable called EXTRALIBS, which appears in all the link commands, but by
2216 default is not defined. In contrast, EXTRALIBS_EXIM is used only on the
2217 command for linking the main Exim binary, and not for any associated utilities.
2219 .cindex "DBM libraries" "configuration for building"
2220 There is also DBMLIB, which appears in the link commands for binaries that
2221 use DBM functions (see also section &<<SECTdb>>&). Finally, there is
2222 EXTRALIBS_EXIMON, which appears only in the link step for the Exim monitor
2223 binary, and which can be used, for example, to include additional X11
2226 .cindex "configuration file" "editing"
2227 The make file copes with rebuilding Exim correctly if any of the configuration
2228 files are edited. However, if an optional configuration file is deleted, it is
2229 necessary to touch the associated non-optional file (that is,
2230 &_Local/Makefile_& or &_Local/eximon.conf_&) before rebuilding.
2233 .section "OS-specific header files" "SECID30"
2235 .cindex "building Exim" "OS-specific C header files"
2236 The &_OS_& directory contains a number of files with names of the form
2237 &_os.h-<ostype>_&. These are system-specific C header files that should not
2238 normally need to be changed. There is a list of macro settings that are
2239 recognized in the file &_OS/os.configuring_&, which should be consulted if you
2240 are porting Exim to a new operating system.
2244 .section "Overriding build-time options for the monitor" "SECID31"
2245 .cindex "building Eximon"
2246 A similar process is used for overriding things when building the Exim monitor,
2247 where the files that are involved are
2249 &_OS/eximon.conf-Default_&
2250 &_OS/eximon.conf-_&<&'ostype'&>
2251 &_Local/eximon.conf_&
2252 &_Local/eximon.conf-_&<&'ostype'&>
2253 &_Local/eximon.conf-_&<&'archtype'&>
2254 &_Local/eximon.conf-_&<&'ostype'&>-<&'archtype'&>
2256 .cindex "&_Local/eximon.conf_&"
2257 As with Exim itself, the final three files need not exist, and in this case the
2258 &_OS/eximon.conf-<ostype>_& file is also optional. The default values in
2259 &_OS/eximon.conf-Default_& can be overridden dynamically by setting environment
2260 variables of the same name, preceded by EXIMON_. For example, setting
2261 EXIMON_LOG_DEPTH in the environment overrides the value of
2262 LOG_DEPTH at run time.
2266 .section "Installing Exim binaries and scripts" "SECID32"
2267 .cindex "installing Exim"
2268 .cindex "BIN_DIRECTORY"
2269 The command &`make install`& runs the &(exim_install)& script with no
2270 arguments. The script copies binaries and utility scripts into the directory
2271 whose name is specified by the BIN_DIRECTORY setting in &_Local/Makefile_&.
2272 .cindex "setuid" "installing Exim with"
2273 The install script copies files only if they are newer than the files they are
2274 going to replace. The Exim binary is required to be owned by root and have the
2275 &'setuid'& bit set, for normal configurations. Therefore, you must run &`make
2276 install`& as root so that it can set up the Exim binary in this way. However, in
2277 some special situations (for example, if a host is doing no local deliveries)
2278 it may be possible to run Exim without making the binary setuid root (see
2279 chapter &<<CHAPsecurity>>& for details).
2281 .cindex "CONFIGURE_FILE"
2282 Exim's run time configuration file is named by the CONFIGURE_FILE setting
2283 in &_Local/Makefile_&. If this names a single file, and the file does not
2284 exist, the default configuration file &_src/configure.default_& is copied there
2285 by the installation script. If a run time configuration file already exists, it
2286 is left alone. If CONFIGURE_FILE is a colon-separated list, naming several
2287 alternative files, no default is installed.
2289 .cindex "system aliases file"
2290 .cindex "&_/etc/aliases_&"
2291 One change is made to the default configuration file when it is installed: the
2292 default configuration contains a router that references a system aliases file.
2293 The path to this file is set to the value specified by
2294 SYSTEM_ALIASES_FILE in &_Local/Makefile_& (&_/etc/aliases_& by default).
2295 If the system aliases file does not exist, the installation script creates it,
2296 and outputs a comment to the user.
2298 The created file contains no aliases, but it does contain comments about the
2299 aliases a site should normally have. Mail aliases have traditionally been
2300 kept in &_/etc/aliases_&. However, some operating systems are now using
2301 &_/etc/mail/aliases_&. You should check if yours is one of these, and change
2302 Exim's configuration if necessary.
2304 The default configuration uses the local host's name as the only local domain,
2305 and is set up to do local deliveries into the shared directory &_/var/mail_&,
2306 running as the local user. System aliases and &_.forward_& files in users' home
2307 directories are supported, but no NIS or NIS+ support is configured. Domains
2308 other than the name of the local host are routed using the DNS, with delivery
2311 It is possible to install Exim for special purposes (such as building a binary
2312 distribution) in a private part of the file system. You can do this by a
2315 make DESTDIR=/some/directory/ install
2317 This has the effect of pre-pending the specified directory to all the file
2318 paths, except the name of the system aliases file that appears in the default
2319 configuration. (If a default alias file is created, its name &'is'& modified.)
2320 For backwards compatibility, ROOT is used if DESTDIR is not set,
2321 but this usage is deprecated.
2323 .cindex "installing Exim" "what is not installed"
2324 Running &'make install'& does not copy the Exim 4 conversion script
2325 &'convert4r4'&. You will probably run this only once if you are
2326 upgrading from Exim 3. None of the documentation files in the &_doc_&
2327 directory are copied, except for the info files when you have set
2328 INFO_DIRECTORY, as described in section &<<SECTinsinfdoc>>& below.
2330 For the utility programs, old versions are renamed by adding the suffix &_.O_&
2331 to their names. The Exim binary itself, however, is handled differently. It is
2332 installed under a name that includes the version number and the compile number,
2333 for example &_exim-&version()-1_&. The script then arranges for a symbolic link
2334 called &_exim_& to point to the binary. If you are updating a previous version
2335 of Exim, the script takes care to ensure that the name &_exim_& is never absent
2336 from the directory (as seen by other processes).
2338 .cindex "installing Exim" "testing the script"
2339 If you want to see what the &'make install'& will do before running it for
2340 real, you can pass the &%-n%& option to the installation script by this
2343 make INSTALL_ARG=-n install
2345 The contents of the variable INSTALL_ARG are passed to the installation
2346 script. You do not need to be root to run this test. Alternatively, you can run
2347 the installation script directly, but this must be from within the build
2348 directory. For example, from the top-level Exim directory you could use this
2351 (cd build-SunOS5-5.5.1-sparc; ../scripts/exim_install -n)
2353 .cindex "installing Exim" "install script options"
2354 There are two other options that can be supplied to the installation script.
2357 &%-no_chown%& bypasses the call to change the owner of the installed binary
2358 to root, and the call to make it a setuid binary.
2360 &%-no_symlink%& bypasses the setting up of the symbolic link &_exim_& to the
2364 INSTALL_ARG can be used to pass these options to the script. For example:
2366 make INSTALL_ARG=-no_symlink install
2368 The installation script can also be given arguments specifying which files are
2369 to be copied. For example, to install just the Exim binary, and nothing else,
2370 without creating the symbolic link, you could use:
2372 make INSTALL_ARG='-no_symlink exim' install
2377 .section "Installing info documentation" "SECTinsinfdoc"
2378 .cindex "installing Exim" "&'info'& documentation"
2379 Not all systems use the GNU &'info'& system for documentation, and for this
2380 reason, the Texinfo source of Exim's documentation is not included in the main
2381 distribution. Instead it is available separately from the ftp site (see section
2384 If you have defined INFO_DIRECTORY in &_Local/Makefile_& and the Texinfo
2385 source of the documentation is found in the source tree, running &`make
2386 install`& automatically builds the info files and installs them.
2390 .section "Setting up the spool directory" "SECID33"
2391 .cindex "spool directory" "creating"
2392 When it starts up, Exim tries to create its spool directory if it does not
2393 exist. The Exim uid and gid are used for the owner and group of the spool
2394 directory. Sub-directories are automatically created in the spool directory as
2400 .section "Testing" "SECID34"
2401 .cindex "testing" "installation"
2402 Having installed Exim, you can check that the run time configuration file is
2403 syntactically valid by running the following command, which assumes that the
2404 Exim binary directory is within your PATH environment variable:
2408 If there are any errors in the configuration file, Exim outputs error messages.
2409 Otherwise it outputs the version number and build date,
2410 the DBM library that is being used, and information about which drivers and
2411 other optional code modules are included in the binary.
2412 Some simple routing tests can be done by using the address testing option. For
2415 &`exim -bt`& <&'local username'&>
2417 should verify that it recognizes a local mailbox, and
2419 &`exim -bt`& <&'remote address'&>
2421 a remote one. Then try getting it to deliver mail, both locally and remotely.
2422 This can be done by passing messages directly to Exim, without going through a
2423 user agent. For example:
2425 exim -v postmaster@your.domain.example
2426 From: user@your.domain.example
2427 To: postmaster@your.domain.example
2428 Subject: Testing Exim
2430 This is a test message.
2433 The &%-v%& option causes Exim to output some verification of what it is doing.
2434 In this case you should see copies of three log lines, one for the message's
2435 arrival, one for its delivery, and one containing &"Completed"&.
2437 .cindex "delivery" "problems with"
2438 If you encounter problems, look at Exim's log files (&'mainlog'& and
2439 &'paniclog'&) to see if there is any relevant information there. Another source
2440 of information is running Exim with debugging turned on, by specifying the
2441 &%-d%& option. If a message is stuck on Exim's spool, you can force a delivery
2442 with debugging turned on by a command of the form
2444 &`exim -d -M`& <&'exim-message-id'&>
2446 You must be root or an &"admin user"& in order to do this. The &%-d%& option
2447 produces rather a lot of output, but you can cut this down to specific areas.
2448 For example, if you use &%-d-all+route%& only the debugging information
2449 relevant to routing is included. (See the &%-d%& option in chapter
2450 &<<CHAPcommandline>>& for more details.)
2452 .cindex '&"sticky"& bit'
2453 .cindex "lock files"
2454 One specific problem that has shown up on some sites is the inability to do
2455 local deliveries into a shared mailbox directory, because it does not have the
2456 &"sticky bit"& set on it. By default, Exim tries to create a lock file before
2457 writing to a mailbox file, and if it cannot create the lock file, the delivery
2458 is deferred. You can get round this either by setting the &"sticky bit"& on the
2459 directory, or by setting a specific group for local deliveries and allowing
2460 that group to create files in the directory (see the comments above the
2461 &(local_delivery)& transport in the default configuration file). Another
2462 approach is to configure Exim not to use lock files, but just to rely on
2463 &[fcntl()]& locking instead. However, you should do this only if all user
2464 agents also use &[fcntl()]& locking. For further discussion of locking issues,
2465 see chapter &<<CHAPappendfile>>&.
2467 One thing that cannot be tested on a system that is already running an MTA is
2468 the receipt of incoming SMTP mail on the standard SMTP port. However, the
2469 &%-oX%& option can be used to run an Exim daemon that listens on some other
2470 port, or &'inetd'& can be used to do this. The &%-bh%& option and the
2471 &'exim_checkaccess'& utility can be used to check out policy controls on
2474 Testing a new version on a system that is already running Exim can most easily
2475 be done by building a binary with a different CONFIGURE_FILE setting. From
2476 within the run time configuration, all other file and directory names
2477 that Exim uses can be altered, in order to keep it entirely clear of the
2481 .section "Replacing another MTA with Exim" "SECID35"
2482 .cindex "replacing another MTA"
2483 Building and installing Exim for the first time does not of itself put it in
2484 general use. The name by which the system's MTA is called by mail user agents
2485 is either &_/usr/sbin/sendmail_&, or &_/usr/lib/sendmail_& (depending on the
2486 operating system), and it is necessary to make this name point to the &'exim'&
2487 binary in order to get the user agents to pass messages to Exim. This is
2488 normally done by renaming any existing file and making &_/usr/sbin/sendmail_&
2489 or &_/usr/lib/sendmail_&
2490 .cindex "symbolic link" "to &'exim'& binary"
2491 a symbolic link to the &'exim'& binary. It is a good idea to remove any setuid
2492 privilege and executable status from the old MTA. It is then necessary to stop
2493 and restart the mailer daemon, if one is running.
2495 .cindex "FreeBSD, MTA indirection"
2496 .cindex "&_/etc/mail/mailer.conf_&"
2497 Some operating systems have introduced alternative ways of switching MTAs. For
2498 example, if you are running FreeBSD, you need to edit the file
2499 &_/etc/mail/mailer.conf_& instead of setting up a symbolic link as just
2500 described. A typical example of the contents of this file for running Exim is
2503 sendmail /usr/exim/bin/exim
2504 send-mail /usr/exim/bin/exim
2505 mailq /usr/exim/bin/exim -bp
2506 newaliases /usr/bin/true
2508 Once you have set up the symbolic link, or edited &_/etc/mail/mailer.conf_&,
2509 your Exim installation is &"live"&. Check it by sending a message from your
2510 favourite user agent.
2512 You should consider what to tell your users about the change of MTA. Exim may
2513 have different capabilities to what was previously running, and there are
2514 various operational differences such as the text of messages produced by
2515 command line options and in bounce messages. If you allow your users to make
2516 use of Exim's filtering capabilities, you should make the document entitled
2517 &'Exim's interface to mail filtering'& available to them.
2521 .section "Upgrading Exim" "SECID36"
2522 .cindex "upgrading Exim"
2523 If you are already running Exim on your host, building and installing a new
2524 version automatically makes it available to MUAs, or any other programs that
2525 call the MTA directly. However, if you are running an Exim daemon, you do need
2526 to send it a HUP signal, to make it re-execute itself, and thereby pick up the
2527 new binary. You do not need to stop processing mail in order to install a new
2528 version of Exim. The install script does not modify an existing runtime
2534 .section "Stopping the Exim daemon on Solaris" "SECID37"
2535 .cindex "Solaris" "stopping Exim on"
2536 The standard command for stopping the mailer daemon on Solaris is
2538 /etc/init.d/sendmail stop
2540 If &_/usr/lib/sendmail_& has been turned into a symbolic link, this script
2541 fails to stop Exim because it uses the command &'ps -e'& and greps the output
2542 for the text &"sendmail"&; this is not present because the actual program name
2543 (that is, &"exim"&) is given by the &'ps'& command with these options. A
2544 solution is to replace the line that finds the process id with something like
2546 pid=`cat /var/spool/exim/exim-daemon.pid`
2548 to obtain the daemon's pid directly from the file that Exim saves it in.
2550 Note, however, that stopping the daemon does not &"stop Exim"&. Messages can
2551 still be received from local processes, and if automatic delivery is configured
2552 (the normal case), deliveries will still occur.
2557 . ////////////////////////////////////////////////////////////////////////////
2558 . ////////////////////////////////////////////////////////////////////////////
2560 .chapter "The Exim command line" "CHAPcommandline"
2561 .scindex IIDclo1 "command line" "options"
2562 .scindex IIDclo2 "options" "command line"
2563 Exim's command line takes the standard Unix form of a sequence of options,
2564 each starting with a hyphen character, followed by a number of arguments. The
2565 options are compatible with the main options of Sendmail, and there are also
2566 some additional options, some of which are compatible with Smail 3. Certain
2567 combinations of options do not make sense, and provoke an error if used.
2568 The form of the arguments depends on which options are set.
2571 .section "Setting options by program name" "SECID38"
2573 If Exim is called under the name &'mailq'&, it behaves as if the option &%-bp%&
2574 were present before any other options.
2575 The &%-bp%& option requests a listing of the contents of the mail queue on the
2577 This feature is for compatibility with some systems that contain a command of
2578 that name in one of the standard libraries, symbolically linked to
2579 &_/usr/sbin/sendmail_& or &_/usr/lib/sendmail_&.
2582 If Exim is called under the name &'rsmtp'& it behaves as if the option &%-bS%&
2583 were present before any other options, for compatibility with Smail. The
2584 &%-bS%& option is used for reading in a number of messages in batched SMTP
2588 If Exim is called under the name &'rmail'& it behaves as if the &%-i%& and
2589 &%-oee%& options were present before any other options, for compatibility with
2590 Smail. The name &'rmail'& is used as an interface by some UUCP systems.
2593 .cindex "queue runner"
2594 If Exim is called under the name &'runq'& it behaves as if the option &%-q%&
2595 were present before any other options, for compatibility with Smail. The &%-q%&
2596 option causes a single queue runner process to be started.
2598 .cindex "&'newaliases'&"
2599 .cindex "alias file" "building"
2600 .cindex "Sendmail compatibility" "calling Exim as &'newaliases'&"
2601 If Exim is called under the name &'newaliases'& it behaves as if the option
2602 &%-bi%& were present before any other options, for compatibility with Sendmail.
2603 This option is used for rebuilding Sendmail's alias file. Exim does not have
2604 the concept of a single alias file, but can be configured to run a given
2605 command if called with the &%-bi%& option.
2608 .section "Trusted and admin users" "SECTtrustedadmin"
2609 Some Exim options are available only to &'trusted users'& and others are
2610 available only to &'admin users'&. In the description below, the phrases &"Exim
2611 user"& and &"Exim group"& mean the user and group defined by EXIM_USER and
2612 EXIM_GROUP in &_Local/Makefile_& or set by the &%exim_user%& and
2613 &%exim_group%& options. These do not necessarily have to use the name &"exim"&.
2616 .cindex "trusted users" "definition of"
2617 .cindex "user" "trusted definition of"
2618 The trusted users are root, the Exim user, any user listed in the
2619 &%trusted_users%& configuration option, and any user whose current group or any
2620 supplementary group is one of those listed in the &%trusted_groups%&
2621 configuration option. Note that the Exim group is not automatically trusted.
2623 .cindex '&"From"& line'
2624 .cindex "envelope sender"
2625 Trusted users are always permitted to use the &%-f%& option or a leading
2626 &"From&~"& line to specify the envelope sender of a message that is passed to
2627 Exim through the local interface (see the &%-bm%& and &%-f%& options below).
2628 See the &%untrusted_set_sender%& option for a way of permitting non-trusted
2629 users to set envelope senders.
2631 .cindex "&'From:'& header line"
2632 .cindex "&'Sender:'& header line"
2633 For a trusted user, there is never any check on the contents of the &'From:'&
2634 header line, and a &'Sender:'& line is never added. Furthermore, any existing
2635 &'Sender:'& line in incoming local (non-TCP/IP) messages is not removed.
2637 Trusted users may also specify a host name, host address, interface address,
2638 protocol name, ident value, and authentication data when submitting a message
2639 locally. Thus, they are able to insert messages into Exim's queue locally that
2640 have the characteristics of messages received from a remote host. Untrusted
2641 users may in some circumstances use &%-f%&, but can never set the other values
2642 that are available to trusted users.
2644 .cindex "user" "admin definition of"
2645 .cindex "admin user" "definition of"
2646 The admin users are root, the Exim user, and any user that is a member of the
2647 Exim group or of any group listed in the &%admin_groups%& configuration option.
2648 The current group does not have to be one of these groups.
2650 Admin users are permitted to list the queue, and to carry out certain
2651 operations on messages, for example, to force delivery failures. It is also
2652 necessary to be an admin user in order to see the full information provided by
2653 the Exim monitor, and full debugging output.
2655 By default, the use of the &%-M%&, &%-q%&, &%-R%&, and &%-S%& options to cause
2656 Exim to attempt delivery of messages on its queue is restricted to admin users.
2657 However, this restriction can be relaxed by setting the &%prod_requires_admin%&
2658 option false (that is, specifying &%no_prod_requires_admin%&).
2660 Similarly, the use of the &%-bp%& option to list all the messages in the queue
2661 is restricted to admin users unless &%queue_list_requires_admin%& is set
2666 &*Warning*&: If you configure your system so that admin users are able to
2667 edit Exim's configuration file, you are giving those users an easy way of
2668 getting root. There is further discussion of this issue at the start of chapter
2674 .section "Command line options" "SECID39"
2675 Exim's command line options are described in alphabetical order below. If none
2676 of the options that specifies a specific action (such as starting the daemon or
2677 a queue runner, or testing an address, or receiving a message in a specific
2678 format, or listing the queue) are present, and there is at least one argument
2679 on the command line, &%-bm%& (accept a local message on the standard input,
2680 with the arguments specifying the recipients) is assumed. Otherwise, Exim
2681 outputs a brief message about itself and exits.
2683 . ////////////////////////////////////////////////////////////////////////////
2684 . Insert a stylized XML comment here, to identify the start of the command line
2685 . options. This is for the benefit of the Perl script that automatically
2686 . creates a man page for the options.
2687 . ////////////////////////////////////////////////////////////////////////////
2690 <!-- === Start of command line options === -->
2697 .cindex "options" "command line; terminating"
2698 This is a pseudo-option whose only purpose is to terminate the options and
2699 therefore to cause subsequent command line items to be treated as arguments
2700 rather than options, even if they begin with hyphens.
2703 .oindex "&%--help%&"
2704 This option causes Exim to output a few sentences stating what it is.
2705 The same output is generated if the Exim binary is called with no options and
2708 .vitem &%--version%&
2709 .oindex "&%--version%&"
2710 This option is an alias for &%-bV%& and causes version information to be
2717 These options are used by Sendmail for selecting configuration files and are
2720 .vitem &%-B%&<&'type'&>
2722 .cindex "8-bit characters"
2723 .cindex "Sendmail compatibility" "8-bit characters"
2724 This is a Sendmail option for selecting 7 or 8 bit processing. Exim is 8-bit
2725 clean; it ignores this option.
2730 .cindex "SMTP" "listener"
2731 .cindex "queue runner"
2732 This option runs Exim as a daemon, awaiting incoming SMTP connections. Usually
2733 the &%-bd%& option is combined with the &%-q%&<&'time'&> option, to specify
2734 that the daemon should also initiate periodic queue runs.
2736 The &%-bd%& option can be used only by an admin user. If either of the &%-d%&
2737 (debugging) or &%-v%& (verifying) options are set, the daemon does not
2738 disconnect from the controlling terminal. When running this way, it can be
2739 stopped by pressing ctrl-C.
2741 By default, Exim listens for incoming connections to the standard SMTP port on
2742 all the host's running interfaces. However, it is possible to listen on other
2743 ports, on multiple ports, and only on specific interfaces. Chapter
2744 &<<CHAPinterfaces>>& contains a description of the options that control this.
2746 When a listening daemon
2747 .cindex "daemon" "process id (pid)"
2748 .cindex "pid (process id)" "of daemon"
2749 is started without the use of &%-oX%& (that is, without overriding the normal
2750 configuration), it writes its process id to a file called &_exim-daemon.pid_&
2751 in Exim's spool directory. This location can be overridden by setting
2752 PID_FILE_PATH in &_Local/Makefile_&. The file is written while Exim is still
2755 When &%-oX%& is used on the command line to start a listening daemon, the
2756 process id is not written to the normal pid file path. However, &%-oP%& can be
2757 used to specify a path on the command line if a pid file is required.
2761 .cindex "daemon" "restarting"
2762 can be used to cause the daemon to re-execute itself. This should be done
2763 whenever Exim's configuration file, or any file that is incorporated into it by
2764 means of the &%.include%& facility, is changed, and also whenever a new version
2765 of Exim is installed. It is not necessary to do this when other files that are
2766 referenced from the configuration (for example, alias files) are changed,
2767 because these are reread each time they are used.
2771 This option has the same effect as &%-bd%& except that it never disconnects
2772 from the controlling terminal, even when no debugging is specified.
2776 .cindex "testing" "string expansion"
2777 .cindex "expansion" "testing"
2778 Run Exim in expansion testing mode. Exim discards its root privilege, to
2779 prevent ordinary users from using this mode to read otherwise inaccessible
2780 files. If no arguments are given, Exim runs interactively, prompting for lines
2781 of data. Otherwise, it processes each argument in turn.
2783 If Exim was built with USE_READLINE=yes in &_Local/Makefile_&, it tries
2784 to load the &%libreadline%& library dynamically whenever the &%-be%& option is
2785 used without command line arguments. If successful, it uses the &[readline()]&
2786 function, which provides extensive line-editing facilities, for reading the
2787 test data. A line history is supported.
2789 Long expansion expressions can be split over several lines by using backslash
2790 continuations. As in Exim's run time configuration, white space at the start of
2791 continuation lines is ignored. Each argument or data line is passed through the
2792 string expansion mechanism, and the result is output. Variable values from the
2793 configuration file (for example, &$qualify_domain$&) are available, but no
2794 message-specific values (such as &$sender_domain$&) are set, because no message
2795 is being processed (but see &%-bem%& and &%-Mset%&).
2797 &*Note*&: If you use this mechanism to test lookups, and you change the data
2798 files or databases you are using, you must exit and restart Exim before trying
2799 the same lookup again. Otherwise, because each Exim process caches the results
2800 of lookups, you will just get the same result as before.
2802 .vitem &%-bem%&&~<&'filename'&>
2804 .cindex "testing" "string expansion"
2805 .cindex "expansion" "testing"
2806 This option operates like &%-be%& except that it must be followed by the name
2807 of a file. For example:
2809 exim -bem /tmp/testmessage
2811 The file is read as a message (as if receiving a locally-submitted non-SMTP
2812 message) before any of the test expansions are done. Thus, message-specific
2813 variables such as &$message_size$& and &$header_from:$& are available. However,
2814 no &'Received:'& header is added to the message. If the &%-t%& option is set,
2815 recipients are read from the headers in the normal way, and are shown in the
2816 &$recipients$& variable. Note that recipients cannot be given on the command
2817 line, because further arguments are taken as strings to expand (just like
2820 .vitem &%-bF%&&~<&'filename'&>
2822 .cindex "system filter" "testing"
2823 .cindex "testing" "system filter"
2824 This option is the same as &%-bf%& except that it assumes that the filter being
2825 tested is a system filter. The additional commands that are available only in
2826 system filters are recognized.
2828 .vitem &%-bf%&&~<&'filename'&>
2830 .cindex "filter" "testing"
2831 .cindex "testing" "filter file"
2832 .cindex "forward file" "testing"
2833 .cindex "testing" "forward file"
2834 .cindex "Sieve filter" "testing"
2835 This option runs Exim in user filter testing mode; the file is the filter file
2836 to be tested, and a test message must be supplied on the standard input. If
2837 there are no message-dependent tests in the filter, an empty file can be
2840 If you want to test a system filter file, use &%-bF%& instead of &%-bf%&. You
2841 can use both &%-bF%& and &%-bf%& on the same command, in order to test a system
2842 filter and a user filter in the same run. For example:
2844 exim -bF /system/filter -bf /user/filter </test/message
2846 This is helpful when the system filter adds header lines or sets filter
2847 variables that are used by the user filter.
2849 If the test filter file does not begin with one of the special lines
2854 it is taken to be a normal &_.forward_& file, and is tested for validity under
2855 that interpretation. See sections &<<SECTitenonfilred>>& to
2856 &<<SECTspecitredli>>& for a description of the possible contents of non-filter
2859 The result of an Exim command that uses &%-bf%&, provided no errors are
2860 detected, is a list of the actions that Exim would try to take if presented
2861 with the message for real. More details of filter testing are given in the
2862 separate document entitled &'Exim's interfaces to mail filtering'&.
2864 When testing a filter file,
2865 .cindex "&""From""& line"
2866 .cindex "envelope sender"
2867 .oindex "&%-f%&" "for filter testing"
2868 the envelope sender can be set by the &%-f%& option,
2869 or by a &"From&~"& line at the start of the test message. Various parameters
2870 that would normally be taken from the envelope recipient address of the message
2871 can be set by means of additional command line options (see the next four
2874 .vitem &%-bfd%&&~<&'domain'&>
2876 .vindex "&$qualify_domain$&"
2877 This sets the domain of the recipient address when a filter file is being
2878 tested by means of the &%-bf%& option. The default is the value of
2881 .vitem &%-bfl%&&~<&'local&~part'&>
2883 This sets the local part of the recipient address when a filter file is being
2884 tested by means of the &%-bf%& option. The default is the username of the
2885 process that calls Exim. A local part should be specified with any prefix or
2886 suffix stripped, because that is how it appears to the filter when a message is
2887 actually being delivered.
2889 .vitem &%-bfp%&&~<&'prefix'&>
2891 This sets the prefix of the local part of the recipient address when a filter
2892 file is being tested by means of the &%-bf%& option. The default is an empty
2895 .vitem &%-bfs%&&~<&'suffix'&>
2897 This sets the suffix of the local part of the recipient address when a filter
2898 file is being tested by means of the &%-bf%& option. The default is an empty
2901 .vitem &%-bh%&&~<&'IP&~address'&>
2903 .cindex "testing" "incoming SMTP"
2904 .cindex "SMTP" "testing incoming"
2905 .cindex "testing" "relay control"
2906 .cindex "relaying" "testing configuration"
2907 .cindex "policy control" "testing"
2908 .cindex "debugging" "&%-bh%& option"
2909 This option runs a fake SMTP session as if from the given IP address, using the
2910 standard input and output. The IP address may include a port number at the end,
2911 after a full stop. For example:
2913 exim -bh 10.9.8.7.1234
2914 exim -bh fe80::a00:20ff:fe86:a061.5678
2916 When an IPv6 address is given, it is converted into canonical form. In the case
2917 of the second example above, the value of &$sender_host_address$& after
2918 conversion to the canonical form is
2919 &`fe80:0000:0000:0a00:20ff:fe86:a061.5678`&.
2921 Comments as to what is going on are written to the standard error file. These
2922 include lines beginning with &"LOG"& for anything that would have been logged.
2923 This facility is provided for testing configuration options for incoming
2924 messages, to make sure they implement the required policy. For example, you can
2925 test your relay controls using &%-bh%&.
2929 You can test features of the configuration that rely on ident (RFC 1413)
2930 information by using the &%-oMt%& option. However, Exim cannot actually perform
2931 an ident callout when testing using &%-bh%& because there is no incoming SMTP
2934 &*Warning 2*&: Address verification callouts (see section &<<SECTcallver>>&)
2935 are also skipped when testing using &%-bh%&. If you want these callouts to
2936 occur, use &%-bhc%& instead.
2938 Messages supplied during the testing session are discarded, and nothing is
2939 written to any of the real log files. There may be pauses when DNS (and other)
2940 lookups are taking place, and of course these may time out. The &%-oMi%& option
2941 can be used to specify a specific IP interface and port if this is important,
2942 and &%-oMaa%& and &%-oMai%& can be used to set parameters as if the SMTP
2943 session were authenticated.
2945 The &'exim_checkaccess'& utility is a &"packaged"& version of &%-bh%& whose
2946 output just states whether a given recipient address from a given host is
2947 acceptable or not. See section &<<SECTcheckaccess>>&.
2949 Features such as authentication and encryption, where the client input is not
2950 plain text, cannot easily be tested with &%-bh%&. Instead, you should use a
2951 specialized SMTP test program such as
2952 &url(http://jetmore.org/john/code/#swaks,swaks).
2954 .vitem &%-bhc%&&~<&'IP&~address'&>
2956 This option operates in the same way as &%-bh%&, except that address
2957 verification callouts are performed if required. This includes consulting and
2958 updating the callout cache database.
2962 .cindex "alias file" "building"
2963 .cindex "building alias file"
2964 .cindex "Sendmail compatibility" "&%-bi%& option"
2965 Sendmail interprets the &%-bi%& option as a request to rebuild its alias file.
2966 Exim does not have the concept of a single alias file, and so it cannot mimic
2967 this behaviour. However, calls to &_/usr/lib/sendmail_& with the &%-bi%& option
2968 tend to appear in various scripts such as NIS make files, so the option must be
2971 If &%-bi%& is encountered, the command specified by the &%bi_command%&
2972 configuration option is run, under the uid and gid of the caller of Exim. If
2973 the &%-oA%& option is used, its value is passed to the command as an argument.
2974 The command set by &%bi_command%& may not contain arguments. The command can
2975 use the &'exim_dbmbuild'& utility, or some other means, to rebuild alias files
2976 if this is required. If the &%bi_command%& option is not set, calling Exim with
2979 . // Keep :help first, then the rest in alphabetical order
2981 .oindex "&%-bI:help%&"
2982 .cindex "querying exim information"
2983 We shall provide various options starting &`-bI:`& for querying Exim for
2984 information. The output of many of these will be intended for machine
2985 consumption. This one is not. The &%-bI:help%& option asks Exim for a
2986 synopsis of supported options beginning &`-bI:`&. Use of any of these
2987 options shall cause Exim to exit after producing the requested output.
2990 .oindex "&%-bI:dscp%&"
2991 .cindex "DSCP" "values"
2992 This option causes Exim to emit an alphabetically sorted list of all
2993 recognised DSCP names.
2995 .vitem &%-bI:sieve%&
2996 .oindex "&%-bI:sieve%&"
2997 .cindex "Sieve filter" "capabilities"
2998 This option causes Exim to emit an alphabetically sorted list of all supported
2999 Sieve protocol extensions on stdout, one per line. This is anticipated to be
3000 useful for ManageSieve (RFC 5804) implementations, in providing that protocol's
3001 &`SIEVE`& capability response line. As the precise list may depend upon
3002 compile-time build options, which this option will adapt to, this is the only
3003 way to guarantee a correct response.
3007 .cindex "local message reception"
3008 This option runs an Exim receiving process that accepts an incoming,
3009 locally-generated message on the standard input. The recipients are given as the
3010 command arguments (except when &%-t%& is also present &-- see below). Each
3011 argument can be a comma-separated list of RFC 2822 addresses. This is the
3012 default option for selecting the overall action of an Exim call; it is assumed
3013 if no other conflicting option is present.
3015 If any addresses in the message are unqualified (have no domain), they are
3016 qualified by the values of the &%qualify_domain%& or &%qualify_recipient%&
3017 options, as appropriate. The &%-bnq%& option (see below) provides a way of
3018 suppressing this for special cases.
3020 Policy checks on the contents of local messages can be enforced by means of
3021 the non-SMTP ACL. See chapter &<<CHAPACL>>& for details.
3023 .cindex "return code" "for &%-bm%&"
3024 The return code is zero if the message is successfully accepted. Otherwise, the
3025 action is controlled by the &%-oe%&&'x'& option setting &-- see below.
3028 .cindex "message" "format"
3029 .cindex "format" "message"
3030 .cindex "&""From""& line"
3031 .cindex "UUCP" "&""From""& line"
3032 .cindex "Sendmail compatibility" "&""From""& line"
3033 of the message must be as defined in RFC 2822, except that, for
3034 compatibility with Sendmail and Smail, a line in one of the forms
3036 From sender Fri Jan 5 12:55 GMT 1997
3037 From sender Fri, 5 Jan 97 12:55:01
3039 (with the weekday optional, and possibly with additional text after the date)
3040 is permitted to appear at the start of the message. There appears to be no
3041 authoritative specification of the format of this line. Exim recognizes it by
3042 matching against the regular expression defined by the &%uucp_from_pattern%&
3043 option, which can be changed if necessary.
3045 .oindex "&%-f%&" "overriding &""From""& line"
3046 The specified sender is treated as if it were given as the argument to the
3047 &%-f%& option, but if a &%-f%& option is also present, its argument is used in
3048 preference to the address taken from the message. The caller of Exim must be a
3049 trusted user for the sender of a message to be set in this way.
3051 .vitem &%-bmalware%&&~<&'filename'&>
3052 .oindex "&%-bmalware%&"
3053 .cindex "testing", "malware"
3054 .cindex "malware scan test"
3055 This debugging option causes Exim to scan the given file,
3056 using the malware scanning framework. The option of &%av_scanner%& influences
3057 this option, so if &%av_scanner%&'s value is dependent upon an expansion then
3058 the expansion should have defaults which apply to this invocation. ACLs are
3059 not invoked, so if &%av_scanner%& references an ACL variable then that variable
3060 will never be populated and &%-bmalware%& will fail.
3062 Exim will have changed working directory before resolving the filename, so
3063 using fully qualified pathnames is advisable. Exim will be running as the Exim
3064 user when it tries to open the file, rather than as the invoking user.
3065 This option requires admin privileges.
3067 The &%-bmalware%& option will not be extended to be more generally useful,
3068 there are better tools for file-scanning. This option exists to help
3069 administrators verify their Exim and AV scanner configuration.
3073 .cindex "address qualification, suppressing"
3074 By default, Exim automatically qualifies unqualified addresses (those
3075 without domains) that appear in messages that are submitted locally (that
3076 is, not over TCP/IP). This qualification applies both to addresses in
3077 envelopes, and addresses in header lines. Sender addresses are qualified using
3078 &%qualify_domain%&, and recipient addresses using &%qualify_recipient%& (which
3079 defaults to the value of &%qualify_domain%&).
3081 Sometimes, qualification is not wanted. For example, if &%-bS%& (batch SMTP) is
3082 being used to re-submit messages that originally came from remote hosts after
3083 content scanning, you probably do not want to qualify unqualified addresses in
3084 header lines. (Such lines will be present only if you have not enabled a header
3085 syntax check in the appropriate ACL.)
3087 The &%-bnq%& option suppresses all qualification of unqualified addresses in
3088 messages that originate on the local host. When this is used, unqualified
3089 addresses in the envelope provoke errors (causing message rejection) and
3090 unqualified addresses in header lines are left alone.
3095 .cindex "configuration options" "extracting"
3096 .cindex "options" "configuration &-- extracting"
3097 If this option is given with no arguments, it causes the values of all Exim's
3098 main configuration options to be written to the standard output. The values
3099 of one or more specific options can be requested by giving their names as
3100 arguments, for example:
3102 exim -bP qualify_domain hold_domains
3104 .cindex "hiding configuration option values"
3105 .cindex "configuration options" "hiding value of"
3106 .cindex "options" "hiding value of"
3107 However, any option setting that is preceded by the word &"hide"& in the
3108 configuration file is not shown in full, except to an admin user. For other
3109 users, the output is as in this example:
3111 mysql_servers = <value not displayable>
3113 If &%configure_file%& is given as an argument, the name of the run time
3114 configuration file is output.
3115 If a list of configuration files was supplied, the value that is output here
3116 is the name of the file that was actually used.
3118 .cindex "options" "hiding name of"
3119 If the &%-n%& flag is given, then for most modes of &%-bP%& operation the
3120 name will not be output.
3122 .cindex "daemon" "process id (pid)"
3123 .cindex "pid (process id)" "of daemon"
3124 If &%log_file_path%& or &%pid_file_path%& are given, the names of the
3125 directories where log files and daemon pid files are written are output,
3126 respectively. If these values are unset, log files are written in a
3127 sub-directory of the spool directory called &%log%&, and the pid file is
3128 written directly into the spool directory.
3130 If &%-bP%& is followed by a name preceded by &`+`&, for example,
3132 exim -bP +local_domains
3134 it searches for a matching named list of any type (domain, host, address, or
3135 local part) and outputs what it finds.
3137 .cindex "options" "router &-- extracting"
3138 .cindex "options" "transport &-- extracting"
3139 .cindex "options" "authenticator &-- extracting"
3140 If one of the words &%router%&, &%transport%&, or &%authenticator%& is given,
3141 followed by the name of an appropriate driver instance, the option settings for
3142 that driver are output. For example:
3144 exim -bP transport local_delivery
3146 The generic driver options are output first, followed by the driver's private
3147 options. A list of the names of drivers of a particular type can be obtained by
3148 using one of the words &%router_list%&, &%transport_list%&, or
3149 &%authenticator_list%&, and a complete list of all drivers with their option
3150 settings can be obtained by using &%routers%&, &%transports%&, or
3153 .cindex "options" "macro &-- extracting"
3154 If invoked by an admin user, then &%macro%&, &%macro_list%& and &%macros%&
3155 are available, similarly to the drivers. Because macros are sometimes used
3156 for storing passwords, this option is restricted.
3157 The output format is one item per line.
3161 .cindex "queue" "listing messages on"
3162 .cindex "listing" "messages on the queue"
3163 This option requests a listing of the contents of the mail queue on the
3164 standard output. If the &%-bp%& option is followed by a list of message ids,
3165 just those messages are listed. By default, this option can be used only by an
3166 admin user. However, the &%queue_list_requires_admin%& option can be set false
3167 to allow any user to see the queue.
3169 Each message on the queue is displayed as in the following example:
3171 25m 2.9K 0t5C6f-0000c8-00 <alice@wonderland.fict.example>
3172 red.king@looking-glass.fict.example
3175 .cindex "message" "size in queue listing"
3176 .cindex "size" "of message"
3177 The first line contains the length of time the message has been on the queue
3178 (in this case 25 minutes), the size of the message (2.9K), the unique local
3179 identifier for the message, and the message sender, as contained in the
3180 envelope. For bounce messages, the sender address is empty, and appears as
3181 &"<>"&. If the message was submitted locally by an untrusted user who overrode
3182 the default sender address, the user's login name is shown in parentheses
3183 before the sender address.
3185 .cindex "frozen messages" "in queue listing"
3186 If the message is frozen (attempts to deliver it are suspended) then the text
3187 &"*** frozen ***"& is displayed at the end of this line.
3189 The recipients of the message (taken from the envelope, not the headers) are
3190 displayed on subsequent lines. Those addresses to which the message has already
3191 been delivered are marked with the letter D. If an original address gets
3192 expanded into several addresses via an alias or forward file, the original is
3193 displayed with a D only when deliveries for all of its child addresses are
3199 This option operates like &%-bp%&, but in addition it shows delivered addresses
3200 that were generated from the original top level address(es) in each message by
3201 alias or forwarding operations. These addresses are flagged with &"+D"& instead
3207 .cindex "queue" "count of messages on"
3208 This option counts the number of messages on the queue, and writes the total
3209 to the standard output. It is restricted to admin users, unless
3210 &%queue_list_requires_admin%& is set false.
3215 This option operates like &%-bp%&, but the output is not sorted into
3216 chronological order of message arrival. This can speed it up when there are
3217 lots of messages on the queue, and is particularly useful if the output is
3218 going to be post-processed in a way that doesn't need the sorting.
3222 This option is a combination of &%-bpr%& and &%-bpa%&.
3226 This option is a combination of &%-bpr%& and &%-bpu%&.
3231 This option operates like &%-bp%& but shows only undelivered top-level
3232 addresses for each message displayed. Addresses generated by aliasing or
3233 forwarding are not shown, unless the message was deferred after processing by a
3234 router with the &%one_time%& option set.
3239 .cindex "testing" "retry configuration"
3240 .cindex "retry" "configuration testing"
3241 This option is for testing retry rules, and it must be followed by up to three
3242 arguments. It causes Exim to look for a retry rule that matches the values
3243 and to write it to the standard output. For example:
3245 exim -brt bach.comp.mus.example
3246 Retry rule: *.comp.mus.example F,2h,15m; F,4d,30m;
3248 See chapter &<<CHAPretry>>& for a description of Exim's retry rules. The first
3249 argument, which is required, can be a complete address in the form
3250 &'local_part@domain'&, or it can be just a domain name. If the second argument
3251 contains a dot, it is interpreted as an optional second domain name; if no
3252 retry rule is found for the first argument, the second is tried. This ties in
3253 with Exim's behaviour when looking for retry rules for remote hosts &-- if no
3254 rule is found that matches the host, one that matches the mail domain is
3255 sought. Finally, an argument that is the name of a specific delivery error, as
3256 used in setting up retry rules, can be given. For example:
3258 exim -brt haydn.comp.mus.example quota_3d
3259 Retry rule: *@haydn.comp.mus.example quota_3d F,1h,15m
3264 .cindex "testing" "rewriting"
3265 .cindex "rewriting" "testing"
3266 This option is for testing address rewriting rules, and it must be followed by
3267 a single argument, consisting of either a local part without a domain, or a
3268 complete address with a fully qualified domain. Exim outputs how this address
3269 would be rewritten for each possible place it might appear. See chapter
3270 &<<CHAPrewrite>>& for further details.
3274 .cindex "SMTP" "batched incoming"
3275 .cindex "batched SMTP input"
3276 This option is used for batched SMTP input, which is an alternative interface
3277 for non-interactive local message submission. A number of messages can be
3278 submitted in a single run. However, despite its name, this is not really SMTP
3279 input. Exim reads each message's envelope from SMTP commands on the standard
3280 input, but generates no responses. If the caller is trusted, or
3281 &%untrusted_set_sender%& is set, the senders in the SMTP MAIL commands are
3282 believed; otherwise the sender is always the caller of Exim.
3284 The message itself is read from the standard input, in SMTP format (leading
3285 dots doubled), terminated by a line containing just a single dot. An error is
3286 provoked if the terminating dot is missing. A further message may then follow.
3288 As for other local message submissions, the contents of incoming batch SMTP
3289 messages can be checked using the non-SMTP ACL (see chapter &<<CHAPACL>>&).
3290 Unqualified addresses are automatically qualified using &%qualify_domain%& and
3291 &%qualify_recipient%&, as appropriate, unless the &%-bnq%& option is used.
3293 Some other SMTP commands are recognized in the input. HELO and EHLO act
3294 as RSET; VRFY, EXPN, ETRN, and HELP act as NOOP;
3295 QUIT quits, ignoring the rest of the standard input.
3297 .cindex "return code" "for &%-bS%&"
3298 If any error is encountered, reports are written to the standard output and
3299 error streams, and Exim gives up immediately. The return code is 0 if no error
3300 was detected; it is 1 if one or more messages were accepted before the error
3301 was detected; otherwise it is 2.
3303 More details of input using batched SMTP are given in section
3304 &<<SECTincomingbatchedSMTP>>&.
3308 .cindex "SMTP" "local input"
3309 .cindex "local SMTP input"
3310 This option causes Exim to accept one or more messages by reading SMTP commands
3311 on the standard input, and producing SMTP replies on the standard output. SMTP
3312 policy controls, as defined in ACLs (see chapter &<<CHAPACL>>&) are applied.
3313 Some user agents use this interface as a way of passing locally-generated
3314 messages to the MTA.
3317 .cindex "sender" "source of"
3318 this usage, if the caller of Exim is trusted, or &%untrusted_set_sender%& is
3319 set, the senders of messages are taken from the SMTP MAIL commands.
3320 Otherwise the content of these commands is ignored and the sender is set up as
3321 the calling user. Unqualified addresses are automatically qualified using
3322 &%qualify_domain%& and &%qualify_recipient%&, as appropriate, unless the
3323 &%-bnq%& option is used.
3327 &%-bs%& option is also used to run Exim from &'inetd'&, as an alternative to
3328 using a listening daemon. Exim can distinguish the two cases by checking
3329 whether the standard input is a TCP/IP socket. When Exim is called from
3330 &'inetd'&, the source of the mail is assumed to be remote, and the comments
3331 above concerning senders and qualification do not apply. In this situation,
3332 Exim behaves in exactly the same way as it does when receiving a message via
3333 the listening daemon.
3337 .cindex "testing" "addresses"
3338 .cindex "address" "testing"
3339 This option runs Exim in address testing mode, in which each argument is taken
3340 as a recipient address to be tested for deliverability. The results are
3341 written to the standard output. If a test fails, and the caller is not an admin
3342 user, no details of the failure are output, because these might contain
3343 sensitive information such as usernames and passwords for database lookups.
3345 If no arguments are given, Exim runs in an interactive manner, prompting with a
3346 right angle bracket for addresses to be tested.
3348 Unlike the &%-be%& test option, you cannot arrange for Exim to use the
3349 &[readline()]& function, because it is running as &'root'& and there are
3352 Each address is handled as if it were the recipient address of a message
3353 (compare the &%-bv%& option). It is passed to the routers and the result is
3354 written to the standard output. However, any router that has
3355 &%no_address_test%& set is bypassed. This can make &%-bt%& easier to use for
3356 genuine routing tests if your first router passes everything to a scanner
3359 .cindex "return code" "for &%-bt%&"
3360 The return code is 2 if any address failed outright; it is 1 if no address
3361 failed outright but at least one could not be resolved for some reason. Return
3362 code 0 is given only when all addresses succeed.
3364 .cindex "duplicate addresses"
3365 &*Note*&: When actually delivering a message, Exim removes duplicate recipient
3366 addresses after routing is complete, so that only one delivery takes place.
3367 This does not happen when testing with &%-bt%&; the full results of routing are
3370 &*Warning*&: &%-bt%& can only do relatively simple testing. If any of the
3371 routers in the configuration makes any tests on the sender address of a
3373 .oindex "&%-f%&" "for address testing"
3374 you can use the &%-f%& option to set an appropriate sender when running
3375 &%-bt%& tests. Without it, the sender is assumed to be the calling user at the
3376 default qualifying domain. However, if you have set up (for example) routers
3377 whose behaviour depends on the contents of an incoming message, you cannot test
3378 those conditions using &%-bt%&. The &%-N%& option provides a possible way of
3383 .cindex "version number of Exim"
3384 This option causes Exim to write the current version number, compilation
3385 number, and compilation date of the &'exim'& binary to the standard output.
3386 It also lists the DBM library that is being used, the optional modules (such as
3387 specific lookup types), the drivers that are included in the binary, and the
3388 name of the run time configuration file that is in use.
3390 As part of its operation, &%-bV%& causes Exim to read and syntax check its
3391 configuration file. However, this is a static check only. It cannot check
3392 values that are to be expanded. For example, although a misspelt ACL verb is
3393 detected, an error in the verb's arguments is not. You cannot rely on &%-bV%&
3394 alone to discover (for example) all the typos in the configuration; some
3395 realistic testing is needed. The &%-bh%& and &%-N%& options provide more
3396 dynamic testing facilities.
3400 .cindex "verifying address" "using &%-bv%&"
3401 .cindex "address" "verification"
3402 This option runs Exim in address verification mode, in which each argument is
3403 taken as a recipient address to be verified by the routers. (This does
3404 not involve any verification callouts). During normal operation, verification
3405 happens mostly as a consequence processing a &%verify%& condition in an ACL
3406 (see chapter &<<CHAPACL>>&). If you want to test an entire ACL, possibly
3407 including callouts, see the &%-bh%& and &%-bhc%& options.
3409 If verification fails, and the caller is not an admin user, no details of the
3410 failure are output, because these might contain sensitive information such as
3411 usernames and passwords for database lookups.
3413 If no arguments are given, Exim runs in an interactive manner, prompting with a
3414 right angle bracket for addresses to be verified.
3416 Unlike the &%-be%& test option, you cannot arrange for Exim to use the
3417 &[readline()]& function, because it is running as &'exim'& and there are
3420 Verification differs from address testing (the &%-bt%& option) in that routers
3421 that have &%no_verify%& set are skipped, and if the address is accepted by a
3422 router that has &%fail_verify%& set, verification fails. The address is
3423 verified as a recipient if &%-bv%& is used; to test verification for a sender
3424 address, &%-bvs%& should be used.
3426 If the &%-v%& option is not set, the output consists of a single line for each
3427 address, stating whether it was verified or not, and giving a reason in the
3428 latter case. Without &%-v%&, generating more than one address by redirection
3429 causes verification to end successfully, without considering the generated
3430 addresses. However, if just one address is generated, processing continues,
3431 and the generated address must verify successfully for the overall verification
3434 When &%-v%& is set, more details are given of how the address has been handled,
3435 and in the case of address redirection, all the generated addresses are also
3436 considered. Verification may succeed for some and fail for others.
3439 .cindex "return code" "for &%-bv%&"
3440 return code is 2 if any address failed outright; it is 1 if no address
3441 failed outright but at least one could not be resolved for some reason. Return
3442 code 0 is given only when all addresses succeed.
3444 If any of the routers in the configuration makes any tests on the sender
3445 address of a message, you should use the &%-f%& option to set an appropriate
3446 sender when running &%-bv%& tests. Without it, the sender is assumed to be the
3447 calling user at the default qualifying domain.
3451 This option acts like &%-bv%&, but verifies the address as a sender rather
3452 than a recipient address. This affects any rewriting and qualification that
3459 .cindex "inetd" "wait mode"
3460 This option runs Exim as a daemon, awaiting incoming SMTP connections,
3461 similarly to the &%-bd%& option. All port specifications on the command-line
3462 and in the configuration file are ignored. Queue-running may not be specified.
3464 In this mode, Exim expects to be passed a socket as fd 0 (stdin) which is
3465 listening for connections. This permits the system to start up and have
3466 inetd (or equivalent) listen on the SMTP ports, starting an Exim daemon for
3467 each port only when the first connection is received.
3469 If the option is given as &%-bw%&<&'time'&> then the time is a timeout, after
3470 which the daemon will exit, which should cause inetd to listen once more.
3472 .vitem &%-C%&&~<&'filelist'&>
3474 .cindex "configuration file" "alternate"
3475 .cindex "CONFIGURE_FILE"
3476 .cindex "alternate configuration file"
3477 This option causes Exim to find the run time configuration file from the given
3478 list instead of from the list specified by the CONFIGURE_FILE
3479 compile-time setting. Usually, the list will consist of just a single file
3480 name, but it can be a colon-separated list of names. In this case, the first
3481 file that exists is used. Failure to open an existing file stops Exim from
3482 proceeding any further along the list, and an error is generated.
3484 When this option is used by a caller other than root, and the list is different
3485 from the compiled-in list, Exim gives up its root privilege immediately, and
3486 runs with the real and effective uid and gid set to those of the caller.
3487 However, if a TRUSTED_CONFIG_LIST file is defined in &_Local/Makefile_&, that
3488 file contains a list of full pathnames, one per line, for configuration files
3489 which are trusted. Root privilege is retained for any configuration file so
3490 listed, as long as the caller is the Exim user (or the user specified in the
3491 CONFIGURE_OWNER option, if any), and as long as the configuration file is
3492 not writeable by inappropriate users or groups.
3494 Leaving TRUSTED_CONFIG_LIST unset precludes the possibility of testing a
3495 configuration using &%-C%& right through message reception and delivery,
3496 even if the caller is root. The reception works, but by that time, Exim is
3497 running as the Exim user, so when it re-executes to regain privilege for the
3498 delivery, the use of &%-C%& causes privilege to be lost. However, root can
3499 test reception and delivery using two separate commands (one to put a message
3500 on the queue, using &%-odq%&, and another to do the delivery, using &%-M%&).
3502 If ALT_CONFIG_PREFIX is defined &_in Local/Makefile_&, it specifies a
3503 prefix string with which any file named in a &%-C%& command line option
3504 must start. In addition, the file name must not contain the sequence &`/../`&.
3505 However, if the value of the &%-C%& option is identical to the value of
3506 CONFIGURE_FILE in &_Local/Makefile_&, Exim ignores &%-C%& and proceeds as
3507 usual. There is no default setting for ALT_CONFIG_PREFIX; when it is
3508 unset, any file name can be used with &%-C%&.
3510 ALT_CONFIG_PREFIX can be used to confine alternative configuration files
3511 to a directory to which only root has access. This prevents someone who has
3512 broken into the Exim account from running a privileged Exim with an arbitrary
3515 The &%-C%& facility is useful for ensuring that configuration files are
3516 syntactically correct, but cannot be used for test deliveries, unless the
3517 caller is privileged, or unless it is an exotic configuration that does not
3518 require privilege. No check is made on the owner or group of the files
3519 specified by this option.
3522 .vitem &%-D%&<&'macro'&>=<&'value'&>
3524 .cindex "macro" "setting on command line"
3525 This option can be used to override macro definitions in the configuration file
3526 (see section &<<SECTmacrodefs>>&). However, like &%-C%&, if it is used by an
3527 unprivileged caller, it causes Exim to give up its root privilege.
3528 If DISABLE_D_OPTION is defined in &_Local/Makefile_&, the use of &%-D%& is
3529 completely disabled, and its use causes an immediate error exit.
3531 If WHITELIST_D_MACROS is defined in &_Local/Makefile_& then it should be a
3532 colon-separated list of macros which are considered safe and, if &%-D%& only
3533 supplies macros from this list, and the values are acceptable, then Exim will
3534 not give up root privilege if the caller is root, the Exim run-time user, or
3535 the CONFIGURE_OWNER, if set. This is a transition mechanism and is expected
3536 to be removed in the future. Acceptable values for the macros satisfy the
3537 regexp: &`^[A-Za-z0-9_/.-]*$`&
3539 The entire option (including equals sign if present) must all be within one
3540 command line item. &%-D%& can be used to set the value of a macro to the empty
3541 string, in which case the equals sign is optional. These two commands are
3547 To include spaces in a macro definition item, quotes must be used. If you use
3548 quotes, spaces are permitted around the macro name and the equals sign. For
3551 exim '-D ABC = something' ...
3553 &%-D%& may be repeated up to 10 times on a command line.
3556 .vitem &%-d%&<&'debug&~options'&>
3558 .cindex "debugging" "list of selectors"
3559 .cindex "debugging" "&%-d%& option"
3560 This option causes debugging information to be written to the standard
3561 error stream. It is restricted to admin users because debugging output may show
3562 database queries that contain password information. Also, the details of users'
3563 filter files should be protected. If a non-admin user uses &%-d%&, Exim
3564 writes an error message to the standard error stream and exits with a non-zero
3567 When &%-d%& is used, &%-v%& is assumed. If &%-d%& is given on its own, a lot of
3568 standard debugging data is output. This can be reduced, or increased to include
3569 some more rarely needed information, by directly following &%-d%& with a string
3570 made up of names preceded by plus or minus characters. These add or remove sets
3571 of debugging data, respectively. For example, &%-d+filter%& adds filter
3572 debugging, whereas &%-d-all+filter%& selects only filter debugging. Note that
3573 no spaces are allowed in the debug setting. The available debugging categories
3576 &`acl `& ACL interpretation
3577 &`auth `& authenticators
3578 &`deliver `& general delivery logic
3579 &`dns `& DNS lookups (see also resolver)
3580 &`dnsbl `& DNS black list (aka RBL) code
3581 &`exec `& arguments for &[execv()]& calls
3582 &`expand `& detailed debugging for string expansions
3583 &`filter `& filter handling
3584 &`hints_lookup `& hints data lookups
3585 &`host_lookup `& all types of name-to-IP address handling
3586 &`ident `& ident lookup
3587 &`interface `& lists of local interfaces
3588 &`lists `& matching things in lists
3589 &`load `& system load checks
3590 &`local_scan `& can be used by &[local_scan()]& (see chapter &&&
3591 &<<CHAPlocalscan>>&)
3592 &`lookup `& general lookup code and all lookups
3593 &`memory `& memory handling
3594 &`pid `& add pid to debug output lines
3595 &`process_info `& setting info for the process log
3596 &`queue_run `& queue runs
3597 &`receive `& general message reception logic
3598 &`resolver `& turn on the DNS resolver's debugging output
3599 &`retry `& retry handling
3600 &`rewrite `& address rewriting
3601 &`route `& address routing
3602 &`timestamp `& add timestamp to debug output lines
3604 &`transport `& transports
3605 &`uid `& changes of uid/gid and looking up uid/gid
3606 &`verify `& address verification logic
3607 &`all `& almost all of the above (see below), and also &%-v%&
3609 The &`all`& option excludes &`memory`& when used as &`+all`&, but includes it
3610 for &`-all`&. The reason for this is that &`+all`& is something that people
3611 tend to use when generating debug output for Exim maintainers. If &`+memory`&
3612 is included, an awful lot of output that is very rarely of interest is
3613 generated, so it now has to be explicitly requested. However, &`-all`& does
3614 turn everything off.
3616 .cindex "resolver, debugging output"
3617 .cindex "DNS resolver, debugging output"
3618 The &`resolver`& option produces output only if the DNS resolver was compiled
3619 with DEBUG enabled. This is not the case in some operating systems. Also,
3620 unfortunately, debugging output from the DNS resolver is written to stdout
3623 The default (&%-d%& with no argument) omits &`expand`&, &`filter`&,
3624 &`interface`&, &`load`&, &`memory`&, &`pid`&, &`resolver`&, and &`timestamp`&.
3625 However, the &`pid`& selector is forced when debugging is turned on for a
3626 daemon, which then passes it on to any re-executed Exims. Exim also
3627 automatically adds the pid to debug lines when several remote deliveries are
3630 The &`timestamp`& selector causes the current time to be inserted at the start
3631 of all debug output lines. This can be useful when trying to track down delays
3634 If the &%debug_print%& option is set in any driver, it produces output whenever
3635 any debugging is selected, or if &%-v%& is used.
3637 .vitem &%-dd%&<&'debug&~options'&>
3639 This option behaves exactly like &%-d%& except when used on a command that
3640 starts a daemon process. In that case, debugging is turned off for the
3641 subprocesses that the daemon creates. Thus, it is useful for monitoring the
3642 behaviour of the daemon without creating as much output as full debugging does.
3645 .oindex "&%-dropcr%&"
3646 This is an obsolete option that is now a no-op. It used to affect the way Exim
3647 handled CR and LF characters in incoming messages. What happens now is
3648 described in section &<<SECTlineendings>>&.
3652 .cindex "bounce message" "generating"
3653 This option specifies that an incoming message is a locally-generated delivery
3654 failure report. It is used internally by Exim when handling delivery failures
3655 and is not intended for external use. Its only effect is to stop Exim
3656 generating certain messages to the postmaster, as otherwise message cascades
3657 could occur in some situations. As part of the same option, a message id may
3658 follow the characters &%-E%&. If it does, the log entry for the receipt of the
3659 new message contains the id, following &"R="&, as a cross-reference.
3662 .oindex "&%-e%&&'x'&"
3663 There are a number of Sendmail options starting with &%-oe%& which seem to be
3664 called by various programs without the leading &%o%& in the option. For
3665 example, the &%vacation%& program uses &%-eq%&. Exim treats all options of the
3666 form &%-e%&&'x'& as synonymous with the corresponding &%-oe%&&'x'& options.
3668 .vitem &%-F%&&~<&'string'&>
3670 .cindex "sender" "name"
3671 .cindex "name" "of sender"
3672 This option sets the sender's full name for use when a locally-generated
3673 message is being accepted. In the absence of this option, the user's &'gecos'&
3674 entry from the password data is used. As users are generally permitted to alter
3675 their &'gecos'& entries, no security considerations are involved. White space
3676 between &%-F%& and the <&'string'&> is optional.
3678 .vitem &%-f%&&~<&'address'&>
3680 .cindex "sender" "address"
3681 .cindex "address" "sender"
3682 .cindex "trusted users"
3683 .cindex "envelope sender"
3684 .cindex "user" "trusted"
3685 This option sets the address of the envelope sender of a locally-generated
3686 message (also known as the return path). The option can normally be used only
3687 by a trusted user, but &%untrusted_set_sender%& can be set to allow untrusted
3690 Processes running as root or the Exim user are always trusted. Other
3691 trusted users are defined by the &%trusted_users%& or &%trusted_groups%&
3692 options. In the absence of &%-f%&, or if the caller is not trusted, the sender
3693 of a local message is set to the caller's login name at the default qualify
3696 There is one exception to the restriction on the use of &%-f%&: an empty sender
3697 can be specified by any user, trusted or not, to create a message that can
3698 never provoke a bounce. An empty sender can be specified either as an empty
3699 string, or as a pair of angle brackets with nothing between them, as in these
3700 examples of shell commands:
3702 exim -f '<>' user@domain
3703 exim -f "" user@domain
3705 In addition, the use of &%-f%& is not restricted when testing a filter file
3706 with &%-bf%& or when testing or verifying addresses using the &%-bt%& or
3709 Allowing untrusted users to change the sender address does not of itself make
3710 it possible to send anonymous mail. Exim still checks that the &'From:'& header
3711 refers to the local user, and if it does not, it adds a &'Sender:'& header,
3712 though this can be overridden by setting &%no_local_from_check%&.
3715 .cindex "&""From""& line"
3716 space between &%-f%& and the <&'address'&> is optional (that is, they can be
3717 given as two arguments or one combined argument). The sender of a
3718 locally-generated message can also be set (when permitted) by an initial
3719 &"From&~"& line in the message &-- see the description of &%-bm%& above &-- but
3720 if &%-f%& is also present, it overrides &"From&~"&.
3724 .cindex "submission fixups, suppressing (command-line)"
3725 This option is equivalent to an ACL applying:
3727 control = suppress_local_fixups
3729 for every message received. Note that Sendmail will complain about such
3730 bad formatting, where Exim silently just does not fix it up. This may change
3733 As this affects audit information, the caller must be a trusted user to use
3736 .vitem &%-h%&&~<&'number'&>
3738 .cindex "Sendmail compatibility" "&%-h%& option ignored"
3739 This option is accepted for compatibility with Sendmail, but has no effect. (In
3740 Sendmail it overrides the &"hop count"& obtained by counting &'Received:'&
3745 .cindex "Solaris" "&'mail'& command"
3746 .cindex "dot" "in incoming non-SMTP message"
3747 This option, which has the same effect as &%-oi%&, specifies that a dot on a
3748 line by itself should not terminate an incoming, non-SMTP message. I can find
3749 no documentation for this option in Solaris 2.4 Sendmail, but the &'mailx'&
3750 command in Solaris 2.4 uses it. See also &%-ti%&.
3752 .vitem &%-L%&&~<&'tag'&>
3754 .cindex "syslog" "process name; set with flag"
3755 This option is equivalent to setting &%syslog_processname%& in the config
3756 file and setting &%log_file_path%& to &`syslog`&.
3757 Its use is restricted to administrators. The configuration file has to be
3758 read and parsed, to determine access rights, before this is set and takes
3759 effect, so early configuration file errors will not honour this flag.
3761 The tag should not be longer than 32 characters.
3763 .vitem &%-M%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3765 .cindex "forcing delivery"
3766 .cindex "delivery" "forcing attempt"
3767 .cindex "frozen messages" "forcing delivery"
3768 This option requests Exim to run a delivery attempt on each message in turn. If
3769 any of the messages are frozen, they are automatically thawed before the
3770 delivery attempt. The settings of &%queue_domains%&, &%queue_smtp_domains%&,
3771 and &%hold_domains%& are ignored.
3774 .cindex "hints database" "overriding retry hints"
3775 hints for any of the addresses are overridden &-- Exim tries to deliver even if
3776 the normal retry time has not yet been reached. This option requires the caller
3777 to be an admin user. However, there is an option called &%prod_requires_admin%&
3778 which can be set false to relax this restriction (and also the same requirement
3779 for the &%-q%&, &%-R%&, and &%-S%& options).
3781 The deliveries happen synchronously, that is, the original Exim process does
3782 not terminate until all the delivery attempts have finished. No output is
3783 produced unless there is a serious error. If you want to see what is happening,
3784 use the &%-v%& option as well, or inspect Exim's main log.
3786 .vitem &%-Mar%&&~<&'message&~id'&>&~<&'address'&>&~<&'address'&>&~...
3788 .cindex "message" "adding recipients"
3789 .cindex "recipient" "adding"
3790 This option requests Exim to add the addresses to the list of recipients of the
3791 message (&"ar"& for &"add recipients"&). The first argument must be a message
3792 id, and the remaining ones must be email addresses. However, if the message is
3793 active (in the middle of a delivery attempt), it is not altered. This option
3794 can be used only by an admin user.
3796 .vitem "&%-MC%&&~<&'transport'&>&~<&'hostname'&>&~<&'sequence&~number'&>&&&
3797 &~<&'message&~id'&>"
3799 .cindex "SMTP" "passed connection"
3800 .cindex "SMTP" "multiple deliveries"
3801 .cindex "multiple SMTP deliveries"
3802 This option is not intended for use by external callers. It is used internally
3803 by Exim to invoke another instance of itself to deliver a waiting message using
3804 an existing SMTP connection, which is passed as the standard input. Details are
3805 given in chapter &<<CHAPSMTP>>&. This must be the final option, and the caller
3806 must be root or the Exim user in order to use it.
3810 This option is not intended for use by external callers. It is used internally
3811 by Exim in conjunction with the &%-MC%& option. It signifies that the
3812 connection to the remote host has been authenticated.
3816 This option is not intended for use by external callers. It is used internally
3817 by Exim in conjunction with the &%-MC%& option. It signifies that the server to
3818 which Exim is connected supports pipelining.
3820 .vitem &%-MCQ%&&~<&'process&~id'&>&~<&'pipe&~fd'&>
3822 This option is not intended for use by external callers. It is used internally
3823 by Exim in conjunction with the &%-MC%& option when the original delivery was
3824 started by a queue runner. It passes on the process id of the queue runner,
3825 together with the file descriptor number of an open pipe. Closure of the pipe
3826 signals the final completion of the sequence of processes that are passing
3827 messages through the same SMTP connection.
3831 This option is not intended for use by external callers. It is used internally
3832 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
3833 SMTP SIZE option should be used on messages delivered down the existing
3838 This option is not intended for use by external callers. It is used internally
3839 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
3840 host to which Exim is connected supports TLS encryption.
3842 .vitem &%-Mc%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3844 .cindex "hints database" "not overridden by &%-Mc%&"
3845 .cindex "delivery" "manually started &-- not forced"
3846 This option requests Exim to run a delivery attempt on each message in turn,
3847 but unlike the &%-M%& option, it does check for retry hints, and respects any
3848 that are found. This option is not very useful to external callers. It is
3849 provided mainly for internal use by Exim when it needs to re-invoke itself in
3850 order to regain root privilege for a delivery (see chapter &<<CHAPsecurity>>&).
3851 However, &%-Mc%& can be useful when testing, in order to run a delivery that
3852 respects retry times and other options such as &%hold_domains%& that are
3853 overridden when &%-M%& is used. Such a delivery does not count as a queue run.
3854 If you want to run a specific delivery as if in a queue run, you should use
3855 &%-q%& with a message id argument. A distinction between queue run deliveries
3856 and other deliveries is made in one or two places.
3858 .vitem &%-Mes%&&~<&'message&~id'&>&~<&'address'&>
3860 .cindex "message" "changing sender"
3861 .cindex "sender" "changing"
3862 This option requests Exim to change the sender address in the message to the
3863 given address, which must be a fully qualified address or &"<>"& (&"es"& for
3864 &"edit sender"&). There must be exactly two arguments. The first argument must
3865 be a message id, and the second one an email address. However, if the message
3866 is active (in the middle of a delivery attempt), its status is not altered.
3867 This option can be used only by an admin user.
3869 .vitem &%-Mf%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3871 .cindex "freezing messages"
3872 .cindex "message" "manually freezing"
3873 This option requests Exim to mark each listed message as &"frozen"&. This
3874 prevents any delivery attempts taking place until the message is &"thawed"&,
3875 either manually or as a result of the &%auto_thaw%& configuration option.
3876 However, if any of the messages are active (in the middle of a delivery
3877 attempt), their status is not altered. This option can be used only by an admin
3880 .vitem &%-Mg%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3882 .cindex "giving up on messages"
3883 .cindex "message" "abandoning delivery attempts"
3884 .cindex "delivery" "abandoning further attempts"
3885 This option requests Exim to give up trying to deliver the listed messages,
3886 including any that are frozen. However, if any of the messages are active,
3887 their status is not altered. For non-bounce messages, a delivery error message
3888 is sent to the sender, containing the text &"cancelled by administrator"&.
3889 Bounce messages are just discarded. This option can be used only by an admin
3892 .vitem &%-Mmad%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3894 .cindex "delivery" "cancelling all"
3895 This option requests Exim to mark all the recipient addresses in the messages
3896 as already delivered (&"mad"& for &"mark all delivered"&). However, if any
3897 message is active (in the middle of a delivery attempt), its status is not
3898 altered. This option can be used only by an admin user.
3900 .vitem &%-Mmd%&&~<&'message&~id'&>&~<&'address'&>&~<&'address'&>&~...
3902 .cindex "delivery" "cancelling by address"
3903 .cindex "recipient" "removing"
3904 .cindex "removing recipients"
3905 This option requests Exim to mark the given addresses as already delivered
3906 (&"md"& for &"mark delivered"&). The first argument must be a message id, and
3907 the remaining ones must be email addresses. These are matched to recipient
3908 addresses in the message in a case-sensitive manner. If the message is active
3909 (in the middle of a delivery attempt), its status is not altered. This option
3910 can be used only by an admin user.
3912 .vitem &%-Mrm%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3914 .cindex "removing messages"
3915 .cindex "abandoning mail"
3916 .cindex "message" "manually discarding"
3917 This option requests Exim to remove the given messages from the queue. No
3918 bounce messages are sent; each message is simply forgotten. However, if any of
3919 the messages are active, their status is not altered. This option can be used
3920 only by an admin user or by the user who originally caused the message to be
3921 placed on the queue.
3923 .vitem &%-Mset%&&~<&'message&~id'&>
3925 .cindex "testing" "string expansion"
3926 .cindex "expansion" "testing"
3927 This option is useful only in conjunction with &%-be%& (that is, when testing
3928 string expansions). Exim loads the given message from its spool before doing
3929 the test expansions, thus setting message-specific variables such as
3930 &$message_size$& and the header variables. The &$recipients$& variable is made
3931 available. This feature is provided to make it easier to test expansions that
3932 make use of these variables. However, this option can be used only by an admin
3933 user. See also &%-bem%&.
3935 .vitem &%-Mt%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3937 .cindex "thawing messages"
3938 .cindex "unfreezing messages"
3939 .cindex "frozen messages" "thawing"
3940 .cindex "message" "thawing frozen"
3941 This option requests Exim to &"thaw"& any of the listed messages that are
3942 &"frozen"&, so that delivery attempts can resume. However, if any of the
3943 messages are active, their status is not altered. This option can be used only
3946 .vitem &%-Mvb%&&~<&'message&~id'&>
3948 .cindex "listing" "message body"
3949 .cindex "message" "listing body of"
3950 This option causes the contents of the message body (-D) spool file to be
3951 written to the standard output. This option can be used only by an admin user.
3953 .vitem &%-Mvc%&&~<&'message&~id'&>
3955 .cindex "message" "listing in RFC 2822 format"
3956 .cindex "listing" "message in RFC 2822 format"
3957 This option causes a copy of the complete message (header lines plus body) to
3958 be written to the standard output in RFC 2822 format. This option can be used
3959 only by an admin user.
3961 .vitem &%-Mvh%&&~<&'message&~id'&>
3963 .cindex "listing" "message headers"
3964 .cindex "header lines" "listing"
3965 .cindex "message" "listing header lines"
3966 This option causes the contents of the message headers (-H) spool file to be
3967 written to the standard output. This option can be used only by an admin user.
3969 .vitem &%-Mvl%&&~<&'message&~id'&>
3971 .cindex "listing" "message log"
3972 .cindex "message" "listing message log"
3973 This option causes the contents of the message log spool file to be written to
3974 the standard output. This option can be used only by an admin user.
3978 This is apparently a synonym for &%-om%& that is accepted by Sendmail, so Exim
3979 treats it that way too.
3983 .cindex "debugging" "&%-N%& option"
3984 .cindex "debugging" "suppressing delivery"
3985 This is a debugging option that inhibits delivery of a message at the transport
3986 level. It implies &%-v%&. Exim goes through many of the motions of delivery &--
3987 it just doesn't actually transport the message, but instead behaves as if it
3988 had successfully done so. However, it does not make any updates to the retry
3989 database, and the log entries for deliveries are flagged with &"*>"& rather
3992 Because &%-N%& discards any message to which it applies, only root or the Exim
3993 user are allowed to use it with &%-bd%&, &%-q%&, &%-R%& or &%-M%&. In other
3994 words, an ordinary user can use it only when supplying an incoming message to
3995 which it will apply. Although transportation never fails when &%-N%& is set, an
3996 address may be deferred because of a configuration problem on a transport, or a
3997 routing problem. Once &%-N%& has been used for a delivery attempt, it sticks to
3998 the message, and applies to any subsequent delivery attempts that may happen
4003 This option is interpreted by Sendmail to mean &"no aliasing"&.
4004 For normal modes of operation, it is ignored by Exim.
4005 When combined with &%-bP%& it suppresses the name of an option from being output.
4007 .vitem &%-O%&&~<&'data'&>
4009 This option is interpreted by Sendmail to mean &`set option`&. It is ignored by
4012 .vitem &%-oA%&&~<&'file&~name'&>
4014 .cindex "Sendmail compatibility" "&%-oA%& option"
4015 This option is used by Sendmail in conjunction with &%-bi%& to specify an
4016 alternative alias file name. Exim handles &%-bi%& differently; see the
4019 .vitem &%-oB%&&~<&'n'&>
4021 .cindex "SMTP" "passed connection"
4022 .cindex "SMTP" "multiple deliveries"
4023 .cindex "multiple SMTP deliveries"
4024 This is a debugging option which limits the maximum number of messages that can
4025 be delivered down one SMTP connection, overriding the value set in any &(smtp)&
4026 transport. If <&'n'&> is omitted, the limit is set to 1.
4030 .cindex "background delivery"
4031 .cindex "delivery" "in the background"
4032 This option applies to all modes in which Exim accepts incoming messages,
4033 including the listening daemon. It requests &"background"& delivery of such
4034 messages, which means that the accepting process automatically starts a
4035 delivery process for each message received, but does not wait for the delivery
4036 processes to finish.
4038 When all the messages have been received, the reception process exits,
4039 leaving the delivery processes to finish in their own time. The standard output
4040 and error streams are closed at the start of each delivery process.
4041 This is the default action if none of the &%-od%& options are present.
4043 If one of the queueing options in the configuration file
4044 (&%queue_only%& or &%queue_only_file%&, for example) is in effect, &%-odb%&
4045 overrides it if &%queue_only_override%& is set true, which is the default
4046 setting. If &%queue_only_override%& is set false, &%-odb%& has no effect.
4050 .cindex "foreground delivery"
4051 .cindex "delivery" "in the foreground"
4052 This option requests &"foreground"& (synchronous) delivery when Exim has
4053 accepted a locally-generated message. (For the daemon it is exactly the same as
4054 &%-odb%&.) A delivery process is automatically started to deliver the message,
4055 and Exim waits for it to complete before proceeding.
4057 The original Exim reception process does not finish until the delivery
4058 process for the final message has ended. The standard error stream is left open
4061 However, like &%-odb%&, this option has no effect if &%queue_only_override%& is
4062 false and one of the queueing options in the configuration file is in effect.
4064 If there is a temporary delivery error during foreground delivery, the
4065 message is left on the queue for later delivery, and the original reception
4066 process exits. See chapter &<<CHAPnonqueueing>>& for a way of setting up a
4067 restricted configuration that never queues messages.
4072 This option is synonymous with &%-odf%&. It is provided for compatibility with
4077 .cindex "non-immediate delivery"
4078 .cindex "delivery" "suppressing immediate"
4079 .cindex "queueing incoming messages"
4080 This option applies to all modes in which Exim accepts incoming messages,
4081 including the listening daemon. It specifies that the accepting process should
4082 not automatically start a delivery process for each message received. Messages
4083 are placed on the queue, and remain there until a subsequent queue runner
4084 process encounters them. There are several configuration options (such as
4085 &%queue_only%&) that can be used to queue incoming messages under certain
4086 conditions. This option overrides all of them and also &%-odqs%&. It always
4091 .cindex "SMTP" "delaying delivery"
4092 This option is a hybrid between &%-odb%&/&%-odi%& and &%-odq%&.
4093 However, like &%-odb%& and &%-odi%&, this option has no effect if
4094 &%queue_only_override%& is false and one of the queueing options in the
4095 configuration file is in effect.
4097 When &%-odqs%& does operate, a delivery process is started for each incoming
4098 message, in the background by default, but in the foreground if &%-odi%& is
4099 also present. The recipient addresses are routed, and local deliveries are done
4100 in the normal way. However, if any SMTP deliveries are required, they are not
4101 done at this time, so the message remains on the queue until a subsequent queue
4102 runner process encounters it. Because routing was done, Exim knows which
4103 messages are waiting for which hosts, and so a number of messages for the same
4104 host can be sent in a single SMTP connection. The &%queue_smtp_domains%&
4105 configuration option has the same effect for specific domains. See also the
4110 .cindex "error" "reporting"
4111 If an error is detected while a non-SMTP message is being received (for
4112 example, a malformed address), the error is reported to the sender in a mail
4115 .cindex "return code" "for &%-oee%&"
4117 this error message is successfully sent, the Exim receiving process
4118 exits with a return code of zero. If not, the return code is 2 if the problem
4119 is that the original message has no recipients, or 1 for any other error.
4120 This is the default &%-oe%&&'x'& option if Exim is called as &'rmail'&.
4124 .cindex "error" "reporting"
4125 .cindex "return code" "for &%-oem%&"
4126 This is the same as &%-oee%&, except that Exim always exits with a non-zero
4127 return code, whether or not the error message was successfully sent.
4128 This is the default &%-oe%&&'x'& option, unless Exim is called as &'rmail'&.
4132 .cindex "error" "reporting"
4133 If an error is detected while a non-SMTP message is being received, the
4134 error is reported by writing a message to the standard error file (stderr).
4135 .cindex "return code" "for &%-oep%&"
4136 The return code is 1 for all errors.
4140 .cindex "error" "reporting"
4141 This option is supported for compatibility with Sendmail, but has the same
4146 .cindex "error" "reporting"
4147 This option is supported for compatibility with Sendmail, but has the same
4152 .cindex "dot" "in incoming non-SMTP message"
4153 This option, which has the same effect as &%-i%&, specifies that a dot on a
4154 line by itself should not terminate an incoming, non-SMTP message. Otherwise, a
4155 single dot does terminate, though Exim does no special processing for other
4156 lines that start with a dot. This option is set by default if Exim is called as
4157 &'rmail'&. See also &%-ti%&.
4160 .oindex "&%-oitrue%&"
4161 This option is treated as synonymous with &%-oi%&.
4163 .vitem &%-oMa%&&~<&'host&~address'&>
4165 .cindex "sender" "host address, specifying for local message"
4166 A number of options starting with &%-oM%& can be used to set values associated
4167 with remote hosts on locally-submitted messages (that is, messages not received
4168 over TCP/IP). These options can be used by any caller in conjunction with the
4169 &%-bh%&, &%-be%&, &%-bf%&, &%-bF%&, &%-bt%&, or &%-bv%& testing options. In
4170 other circumstances, they are ignored unless the caller is trusted.
4172 The &%-oMa%& option sets the sender host address. This may include a port
4173 number at the end, after a full stop (period). For example:
4175 exim -bs -oMa 10.9.8.7.1234
4177 An alternative syntax is to enclose the IP address in square brackets,
4178 followed by a colon and the port number:
4180 exim -bs -oMa [10.9.8.7]:1234
4182 The IP address is placed in the &$sender_host_address$& variable, and the
4183 port, if present, in &$sender_host_port$&. If both &%-oMa%& and &%-bh%&
4184 are present on the command line, the sender host IP address is taken from
4185 whichever one is last.
4187 .vitem &%-oMaa%&&~<&'name'&>
4189 .cindex "authentication" "name, specifying for local message"
4190 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMaa%&
4191 option sets the value of &$sender_host_authenticated$& (the authenticator
4192 name). See chapter &<<CHAPSMTPAUTH>>& for a discussion of SMTP authentication.
4193 This option can be used with &%-bh%& and &%-bs%& to set up an
4194 authenticated SMTP session without actually using the SMTP AUTH command.
4196 .vitem &%-oMai%&&~<&'string'&>
4198 .cindex "authentication" "id, specifying for local message"
4199 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMai%&
4200 option sets the value of &$authenticated_id$& (the id that was authenticated).
4201 This overrides the default value (the caller's login id, except with &%-bh%&,
4202 where there is no default) for messages from local sources. See chapter
4203 &<<CHAPSMTPAUTH>>& for a discussion of authenticated ids.
4205 .vitem &%-oMas%&&~<&'address'&>
4207 .cindex "authentication" "sender, specifying for local message"
4208 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMas%&
4209 option sets the authenticated sender value in &$authenticated_sender$&. It
4210 overrides the sender address that is created from the caller's login id for
4211 messages from local sources, except when &%-bh%& is used, when there is no
4212 default. For both &%-bh%& and &%-bs%&, an authenticated sender that is
4213 specified on a MAIL command overrides this value. See chapter
4214 &<<CHAPSMTPAUTH>>& for a discussion of authenticated senders.
4216 .vitem &%-oMi%&&~<&'interface&~address'&>
4218 .cindex "interface" "address, specifying for local message"
4219 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMi%&
4220 option sets the IP interface address value. A port number may be included,
4221 using the same syntax as for &%-oMa%&. The interface address is placed in
4222 &$received_ip_address$& and the port number, if present, in &$received_port$&.
4224 .vitem &%-oMm%&&~<&'message&~reference'&>
4226 .cindex "message reference" "message reference, specifying for local message"
4227 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMm%&
4228 option sets the message reference, e.g. message-id, and is logged during
4229 delivery. This is useful when some kind of audit trail is required to tie
4230 messages together. The format of the message reference is checked and will
4231 abort if the format is invalid. The option will only be accepted if exim is
4232 running in trusted mode, not as any regular user.
4234 The best example of a message reference is when Exim sends a bounce message.
4235 The message reference is the message-id of the original message for which Exim
4236 is sending the bounce.
4238 .vitem &%-oMr%&&~<&'protocol&~name'&>
4240 .cindex "protocol, specifying for local message"
4241 .vindex "&$received_protocol$&"
4242 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMr%&
4243 option sets the received protocol value that is stored in
4244 &$received_protocol$&. However, it does not apply (and is ignored) when &%-bh%&
4245 or &%-bs%& is used. For &%-bh%&, the protocol is forced to one of the standard
4246 SMTP protocol names (see the description of &$received_protocol$& in section
4247 &<<SECTexpvar>>&). For &%-bs%&, the protocol is always &"local-"& followed by
4248 one of those same names. For &%-bS%& (batched SMTP) however, the protocol can
4251 .vitem &%-oMs%&&~<&'host&~name'&>
4253 .cindex "sender" "host name, specifying for local message"
4254 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMs%&
4255 option sets the sender host name in &$sender_host_name$&. When this option is
4256 present, Exim does not attempt to look up a host name from an IP address; it
4257 uses the name it is given.
4259 .vitem &%-oMt%&&~<&'ident&~string'&>
4261 .cindex "sender" "ident string, specifying for local message"
4262 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMt%&
4263 option sets the sender ident value in &$sender_ident$&. The default setting for
4264 local callers is the login id of the calling process, except when &%-bh%& is
4265 used, when there is no default.
4269 .cindex "Sendmail compatibility" "&%-om%& option ignored"
4270 In Sendmail, this option means &"me too"&, indicating that the sender of a
4271 message should receive a copy of the message if the sender appears in an alias
4272 expansion. Exim always does this, so the option does nothing.
4276 .cindex "Sendmail compatibility" "&%-oo%& option ignored"
4277 This option is ignored. In Sendmail it specifies &"old style headers"&,
4278 whatever that means.
4280 .vitem &%-oP%&&~<&'path'&>
4282 .cindex "pid (process id)" "of daemon"
4283 .cindex "daemon" "process id (pid)"
4284 This option is useful only in conjunction with &%-bd%& or &%-q%& with a time
4285 value. The option specifies the file to which the process id of the daemon is
4286 written. When &%-oX%& is used with &%-bd%&, or when &%-q%& with a time is used
4287 without &%-bd%&, this is the only way of causing Exim to write a pid file,
4288 because in those cases, the normal pid file is not used.
4290 .vitem &%-or%&&~<&'time'&>
4292 .cindex "timeout" "for non-SMTP input"
4293 This option sets a timeout value for incoming non-SMTP messages. If it is not
4294 set, Exim will wait forever for the standard input. The value can also be set
4295 by the &%receive_timeout%& option. The format used for specifying times is
4296 described in section &<<SECTtimeformat>>&.
4298 .vitem &%-os%&&~<&'time'&>
4300 .cindex "timeout" "for SMTP input"
4301 .cindex "SMTP" "input timeout"
4302 This option sets a timeout value for incoming SMTP messages. The timeout
4303 applies to each SMTP command and block of data. The value can also be set by
4304 the &%smtp_receive_timeout%& option; it defaults to 5 minutes. The format used
4305 for specifying times is described in section &<<SECTtimeformat>>&.
4309 This option has exactly the same effect as &%-v%&.
4311 .vitem &%-oX%&&~<&'number&~or&~string'&>
4313 .cindex "TCP/IP" "setting listening ports"
4314 .cindex "TCP/IP" "setting listening interfaces"
4315 .cindex "port" "receiving TCP/IP"
4316 This option is relevant only when the &%-bd%& (start listening daemon) option
4317 is also given. It controls which ports and interfaces the daemon uses. Details
4318 of the syntax, and how it interacts with configuration file options, are given
4319 in chapter &<<CHAPinterfaces>>&. When &%-oX%& is used to start a daemon, no pid
4320 file is written unless &%-oP%& is also present to specify a pid file name.
4324 .cindex "Perl" "starting the interpreter"
4325 This option applies when an embedded Perl interpreter is linked with Exim (see
4326 chapter &<<CHAPperl>>&). It overrides the setting of the &%perl_at_start%&
4327 option, forcing the starting of the interpreter to be delayed until it is
4332 .cindex "Perl" "starting the interpreter"
4333 This option applies when an embedded Perl interpreter is linked with Exim (see
4334 chapter &<<CHAPperl>>&). It overrides the setting of the &%perl_at_start%&
4335 option, forcing the starting of the interpreter to occur as soon as Exim is
4338 .vitem &%-p%&<&'rval'&>:<&'sval'&>
4340 For compatibility with Sendmail, this option is equivalent to
4342 &`-oMr`& <&'rval'&> &`-oMs`& <&'sval'&>
4344 It sets the incoming protocol and host name (for trusted callers). The
4345 host name and its colon can be omitted when only the protocol is to be set.
4346 Note the Exim already has two private options, &%-pd%& and &%-ps%&, that refer
4347 to embedded Perl. It is therefore impossible to set a protocol value of &`d`&
4348 or &`s`& using this option (but that does not seem a real limitation).
4352 .cindex "queue runner" "starting manually"
4353 This option is normally restricted to admin users. However, there is a
4354 configuration option called &%prod_requires_admin%& which can be set false to
4355 relax this restriction (and also the same requirement for the &%-M%&, &%-R%&,
4356 and &%-S%& options).
4358 .cindex "queue runner" "description of operation"
4359 The &%-q%& option starts one queue runner process. This scans the queue of
4360 waiting messages, and runs a delivery process for each one in turn. It waits
4361 for each delivery process to finish before starting the next one. A delivery
4362 process may not actually do any deliveries if the retry times for the addresses
4363 have not been reached. Use &%-qf%& (see below) if you want to override this.
4366 .cindex "SMTP" "passed connection"
4367 .cindex "SMTP" "multiple deliveries"
4368 .cindex "multiple SMTP deliveries"
4369 the delivery process spawns other processes to deliver other messages down
4370 passed SMTP connections, the queue runner waits for these to finish before
4373 When all the queued messages have been considered, the original queue runner
4374 process terminates. In other words, a single pass is made over the waiting
4375 mail, one message at a time. Use &%-q%& with a time (see below) if you want
4376 this to be repeated periodically.
4378 Exim processes the waiting messages in an unpredictable order. It isn't very
4379 random, but it is likely to be different each time, which is all that matters.
4380 If one particular message screws up a remote MTA, other messages to the same
4381 MTA have a chance of getting through if they get tried first.
4383 It is possible to cause the messages to be processed in lexical message id
4384 order, which is essentially the order in which they arrived, by setting the
4385 &%queue_run_in_order%& option, but this is not recommended for normal use.
4387 .vitem &%-q%&<&'qflags'&>
4388 The &%-q%& option may be followed by one or more flag letters that change its
4389 behaviour. They are all optional, but if more than one is present, they must
4390 appear in the correct order. Each flag is described in a separate item below.
4394 .cindex "queue" "double scanning"
4395 .cindex "queue" "routing"
4396 .cindex "routing" "whole queue before delivery"
4397 An option starting with &%-qq%& requests a two-stage queue run. In the first
4398 stage, the queue is scanned as if the &%queue_smtp_domains%& option matched
4399 every domain. Addresses are routed, local deliveries happen, but no remote
4402 .cindex "hints database" "remembering routing"
4403 The hints database that remembers which messages are waiting for specific hosts
4404 is updated, as if delivery to those hosts had been deferred. After this is
4405 complete, a second, normal queue scan happens, with routing and delivery taking
4406 place as normal. Messages that are routed to the same host should mostly be
4407 delivered down a single SMTP
4408 .cindex "SMTP" "passed connection"
4409 .cindex "SMTP" "multiple deliveries"
4410 .cindex "multiple SMTP deliveries"
4411 connection because of the hints that were set up during the first queue scan.
4412 This option may be useful for hosts that are connected to the Internet
4415 .vitem &%-q[q]i...%&
4417 .cindex "queue" "initial delivery"
4418 If the &'i'& flag is present, the queue runner runs delivery processes only for
4419 those messages that haven't previously been tried. (&'i'& stands for &"initial
4420 delivery"&.) This can be helpful if you are putting messages on the queue using
4421 &%-odq%& and want a queue runner just to process the new messages.
4423 .vitem &%-q[q][i]f...%&
4425 .cindex "queue" "forcing delivery"
4426 .cindex "delivery" "forcing in queue run"
4427 If one &'f'& flag is present, a delivery attempt is forced for each non-frozen
4428 message, whereas without &'f'& only those non-frozen addresses that have passed
4429 their retry times are tried.
4431 .vitem &%-q[q][i]ff...%&
4433 .cindex "frozen messages" "forcing delivery"
4434 If &'ff'& is present, a delivery attempt is forced for every message, whether
4437 .vitem &%-q[q][i][f[f]]l%&
4439 .cindex "queue" "local deliveries only"
4440 The &'l'& (the letter &"ell"&) flag specifies that only local deliveries are to
4441 be done. If a message requires any remote deliveries, it remains on the queue
4444 .vitem &%-q%&<&'qflags'&>&~<&'start&~id'&>&~<&'end&~id'&>
4445 .cindex "queue" "delivering specific messages"
4446 When scanning the queue, Exim can be made to skip over messages whose ids are
4447 lexically less than a given value by following the &%-q%& option with a
4448 starting message id. For example:
4450 exim -q 0t5C6f-0000c8-00
4452 Messages that arrived earlier than &`0t5C6f-0000c8-00`& are not inspected. If a
4453 second message id is given, messages whose ids are lexically greater than it
4454 are also skipped. If the same id is given twice, for example,
4456 exim -q 0t5C6f-0000c8-00 0t5C6f-0000c8-00
4458 just one delivery process is started, for that message. This differs from
4459 &%-M%& in that retry data is respected, and it also differs from &%-Mc%& in
4460 that it counts as a delivery from a queue run. Note that the selection
4461 mechanism does not affect the order in which the messages are scanned. There
4462 are also other ways of selecting specific sets of messages for delivery in a
4463 queue run &-- see &%-R%& and &%-S%&.
4465 .vitem &%-q%&<&'qflags'&><&'time'&>
4466 .cindex "queue runner" "starting periodically"
4467 .cindex "periodic queue running"
4468 When a time value is present, the &%-q%& option causes Exim to run as a daemon,
4469 starting a queue runner process at intervals specified by the given time value
4470 (whose format is described in section &<<SECTtimeformat>>&). This form of the
4471 &%-q%& option is commonly combined with the &%-bd%& option, in which case a
4472 single daemon process handles both functions. A common way of starting up a
4473 combined daemon at system boot time is to use a command such as
4475 /usr/exim/bin/exim -bd -q30m
4477 Such a daemon listens for incoming SMTP calls, and also starts a queue runner
4478 process every 30 minutes.
4480 When a daemon is started by &%-q%& with a time value, but without &%-bd%&, no
4481 pid file is written unless one is explicitly requested by the &%-oP%& option.
4483 .vitem &%-qR%&<&'rsflags'&>&~<&'string'&>
4485 This option is synonymous with &%-R%&. It is provided for Sendmail
4488 .vitem &%-qS%&<&'rsflags'&>&~<&'string'&>
4490 This option is synonymous with &%-S%&.
4492 .vitem &%-R%&<&'rsflags'&>&~<&'string'&>
4494 .cindex "queue runner" "for specific recipients"
4495 .cindex "delivery" "to given domain"
4496 .cindex "domain" "delivery to"
4497 The <&'rsflags'&> may be empty, in which case the white space before the string
4498 is optional, unless the string is &'f'&, &'ff'&, &'r'&, &'rf'&, or &'rff'&,
4499 which are the possible values for <&'rsflags'&>. White space is required if
4500 <&'rsflags'&> is not empty.
4502 This option is similar to &%-q%& with no time value, that is, it causes Exim to
4503 perform a single queue run, except that, when scanning the messages on the
4504 queue, Exim processes only those that have at least one undelivered recipient
4505 address containing the given string, which is checked in a case-independent
4506 way. If the <&'rsflags'&> start with &'r'&, <&'string'&> is interpreted as a
4507 regular expression; otherwise it is a literal string.
4509 If you want to do periodic queue runs for messages with specific recipients,
4510 you can combine &%-R%& with &%-q%& and a time value. For example:
4512 exim -q25m -R @special.domain.example
4514 This example does a queue run for messages with recipients in the given domain
4515 every 25 minutes. Any additional flags that are specified with &%-q%& are
4516 applied to each queue run.
4518 Once a message is selected for delivery by this mechanism, all its addresses
4519 are processed. For the first selected message, Exim overrides any retry
4520 information and forces a delivery attempt for each undelivered address. This
4521 means that if delivery of any address in the first message is successful, any
4522 existing retry information is deleted, and so delivery attempts for that
4523 address in subsequently selected messages (which are processed without forcing)
4524 will run. However, if delivery of any address does not succeed, the retry
4525 information is updated, and in subsequently selected messages, the failing
4526 address will be skipped.
4528 .cindex "frozen messages" "forcing delivery"
4529 If the <&'rsflags'&> contain &'f'& or &'ff'&, the delivery forcing applies to
4530 all selected messages, not just the first; frozen messages are included when
4533 The &%-R%& option makes it straightforward to initiate delivery of all messages
4534 to a given domain after a host has been down for some time. When the SMTP
4535 command ETRN is accepted by its ACL (see chapter &<<CHAPACL>>&), its default
4536 effect is to run Exim with the &%-R%& option, but it can be configured to run
4537 an arbitrary command instead.
4541 This is a documented (for Sendmail) obsolete alternative name for &%-f%&.
4543 .vitem &%-S%&<&'rsflags'&>&~<&'string'&>
4545 .cindex "delivery" "from given sender"
4546 .cindex "queue runner" "for specific senders"
4547 This option acts like &%-R%& except that it checks the string against each
4548 message's sender instead of against the recipients. If &%-R%& is also set, both
4549 conditions must be met for a message to be selected. If either of the options
4550 has &'f'& or &'ff'& in its flags, the associated action is taken.
4552 .vitem &%-Tqt%&&~<&'times'&>
4554 This is an option that is exclusively for use by the Exim testing suite. It is not
4555 recognized when Exim is run normally. It allows for the setting up of explicit
4556 &"queue times"& so that various warning/retry features can be tested.
4560 .cindex "recipient" "extracting from header lines"
4561 .cindex "&'Bcc:'& header line"
4562 .cindex "&'Cc:'& header line"
4563 .cindex "&'To:'& header line"
4564 When Exim is receiving a locally-generated, non-SMTP message on its standard
4565 input, the &%-t%& option causes the recipients of the message to be obtained
4566 from the &'To:'&, &'Cc:'&, and &'Bcc:'& header lines in the message instead of
4567 from the command arguments. The addresses are extracted before any rewriting
4568 takes place and the &'Bcc:'& header line, if present, is then removed.
4570 .cindex "Sendmail compatibility" "&%-t%& option"
4571 If the command has any arguments, they specify addresses to which the message
4572 is &'not'& to be delivered. That is, the argument addresses are removed from
4573 the recipients list obtained from the headers. This is compatible with Smail 3
4574 and in accordance with the documented behaviour of several versions of
4575 Sendmail, as described in man pages on a number of operating systems (e.g.
4576 Solaris 8, IRIX 6.5, HP-UX 11). However, some versions of Sendmail &'add'&
4577 argument addresses to those obtained from the headers, and the O'Reilly
4578 Sendmail book documents it that way. Exim can be made to add argument addresses
4579 instead of subtracting them by setting the option
4580 &%extract_addresses_remove_arguments%& false.
4582 .cindex "&%Resent-%& header lines" "with &%-t%&"
4583 If there are any &%Resent-%& header lines in the message, Exim extracts
4584 recipients from all &'Resent-To:'&, &'Resent-Cc:'&, and &'Resent-Bcc:'& header
4585 lines instead of from &'To:'&, &'Cc:'&, and &'Bcc:'&. This is for compatibility
4586 with Sendmail and other MTAs. (Prior to release 4.20, Exim gave an error if
4587 &%-t%& was used in conjunction with &%Resent-%& header lines.)
4589 RFC 2822 talks about different sets of &%Resent-%& header lines (for when a
4590 message is resent several times). The RFC also specifies that they should be
4591 added at the front of the message, and separated by &'Received:'& lines. It is
4592 not at all clear how &%-t%& should operate in the present of multiple sets,
4593 nor indeed exactly what constitutes a &"set"&.
4594 In practice, it seems that MUAs do not follow the RFC. The &%Resent-%& lines
4595 are often added at the end of the header, and if a message is resent more than
4596 once, it is common for the original set of &%Resent-%& headers to be renamed as
4597 &%X-Resent-%& when a new set is added. This removes any possible ambiguity.
4601 This option is exactly equivalent to &%-t%& &%-i%&. It is provided for
4602 compatibility with Sendmail.
4604 .vitem &%-tls-on-connect%&
4605 .oindex "&%-tls-on-connect%&"
4606 .cindex "TLS" "use without STARTTLS"
4607 .cindex "TLS" "automatic start"
4608 This option is available when Exim is compiled with TLS support. It forces all
4609 incoming SMTP connections to behave as if the incoming port is listed in the
4610 &%tls_on_connect_ports%& option. See section &<<SECTsupobssmt>>& and chapter
4611 &<<CHAPTLS>>& for further details.
4616 .cindex "Sendmail compatibility" "&%-U%& option ignored"
4617 Sendmail uses this option for &"initial message submission"&, and its
4618 documentation states that in future releases, it may complain about
4619 syntactically invalid messages rather than fixing them when this flag is not
4620 set. Exim ignores this option.
4624 This option causes Exim to write information to the standard error stream,
4625 describing what it is doing. In particular, it shows the log lines for
4626 receiving and delivering a message, and if an SMTP connection is made, the SMTP
4627 dialogue is shown. Some of the log lines shown may not actually be written to
4628 the log if the setting of &%log_selector%& discards them. Any relevant
4629 selectors are shown with each log line. If none are shown, the logging is
4634 AIX uses &%-x%& for a private purpose (&"mail from a local mail program has
4635 National Language Support extended characters in the body of the mail item"&).
4636 It sets &%-x%& when calling the MTA from its &%mail%& command. Exim ignores
4639 .vitem &%-X%&&~<&'logfile'&>
4641 This option is interpreted by Sendmail to cause debug information to be sent
4642 to the named file. It is ignored by Exim.
4649 . ////////////////////////////////////////////////////////////////////////////
4650 . Insert a stylized DocBook comment here, to identify the end of the command
4651 . line options. This is for the benefit of the Perl script that automatically
4652 . creates a man page for the options.
4653 . ////////////////////////////////////////////////////////////////////////////
4656 <!-- === End of command line options === -->
4663 . ////////////////////////////////////////////////////////////////////////////
4664 . ////////////////////////////////////////////////////////////////////////////
4667 .chapter "The Exim run time configuration file" "CHAPconf" &&&
4668 "The runtime configuration file"
4670 .cindex "run time configuration"
4671 .cindex "configuration file" "general description"
4672 .cindex "CONFIGURE_FILE"
4673 .cindex "configuration file" "errors in"
4674 .cindex "error" "in configuration file"
4675 .cindex "return code" "for bad configuration"
4676 Exim uses a single run time configuration file that is read whenever an Exim
4677 binary is executed. Note that in normal operation, this happens frequently,
4678 because Exim is designed to operate in a distributed manner, without central
4681 If a syntax error is detected while reading the configuration file, Exim
4682 writes a message on the standard error, and exits with a non-zero return code.
4683 The message is also written to the panic log. &*Note*&: Only simple syntax
4684 errors can be detected at this time. The values of any expanded options are
4685 not checked until the expansion happens, even when the expansion does not
4686 actually alter the string.
4688 The name of the configuration file is compiled into the binary for security
4689 reasons, and is specified by the CONFIGURE_FILE compilation option. In
4690 most configurations, this specifies a single file. However, it is permitted to
4691 give a colon-separated list of file names, in which case Exim uses the first
4692 existing file in the list.
4695 .cindex "EXIM_GROUP"
4696 .cindex "CONFIGURE_OWNER"
4697 .cindex "CONFIGURE_GROUP"
4698 .cindex "configuration file" "ownership"
4699 .cindex "ownership" "configuration file"
4700 The run time configuration file must be owned by root or by the user that is
4701 specified at compile time by the CONFIGURE_OWNER option (if set). The
4702 configuration file must not be world-writeable, or group-writeable unless its
4703 group is the root group or the one specified at compile time by the
4704 CONFIGURE_GROUP option.
4706 &*Warning*&: In a conventional configuration, where the Exim binary is setuid
4707 to root, anybody who is able to edit the run time configuration file has an
4708 easy way to run commands as root. If you specify a user or group in the
4709 CONFIGURE_OWNER or CONFIGURE_GROUP options, then that user and/or any users
4710 who are members of that group will trivially be able to obtain root privileges.
4712 Up to Exim version 4.72, the run time configuration file was also permitted to
4713 be writeable by the Exim user and/or group. That has been changed in Exim 4.73
4714 since it offered a simple privilege escalation for any attacker who managed to
4715 compromise the Exim user account.
4717 A default configuration file, which will work correctly in simple situations,
4718 is provided in the file &_src/configure.default_&. If CONFIGURE_FILE
4719 defines just one file name, the installation process copies the default
4720 configuration to a new file of that name if it did not previously exist. If
4721 CONFIGURE_FILE is a list, no default is automatically installed. Chapter
4722 &<<CHAPdefconfil>>& is a &"walk-through"& discussion of the default
4727 .section "Using a different configuration file" "SECID40"
4728 .cindex "configuration file" "alternate"
4729 A one-off alternate configuration can be specified by the &%-C%& command line
4730 option, which may specify a single file or a list of files. However, when
4731 &%-C%& is used, Exim gives up its root privilege, unless called by root (or
4732 unless the argument for &%-C%& is identical to the built-in value from
4733 CONFIGURE_FILE), or is listed in the TRUSTED_CONFIG_LIST file and the caller
4734 is the Exim user or the user specified in the CONFIGURE_OWNER setting. &%-C%&
4735 is useful mainly for checking the syntax of configuration files before
4736 installing them. No owner or group checks are done on a configuration file
4737 specified by &%-C%&, if root privilege has been dropped.
4739 Even the Exim user is not trusted to specify an arbitrary configuration file
4740 with the &%-C%& option to be used with root privileges, unless that file is
4741 listed in the TRUSTED_CONFIG_LIST file. This locks out the possibility of
4742 testing a configuration using &%-C%& right through message reception and
4743 delivery, even if the caller is root. The reception works, but by that time,
4744 Exim is running as the Exim user, so when it re-execs to regain privilege for
4745 the delivery, the use of &%-C%& causes privilege to be lost. However, root
4746 can test reception and delivery using two separate commands (one to put a
4747 message on the queue, using &%-odq%&, and another to do the delivery, using
4750 If ALT_CONFIG_PREFIX is defined &_in Local/Makefile_&, it specifies a
4751 prefix string with which any file named in a &%-C%& command line option must
4752 start. In addition, the file name must not contain the sequence &"&`/../`&"&.
4753 There is no default setting for ALT_CONFIG_PREFIX; when it is unset, any file
4754 name can be used with &%-C%&.
4756 One-off changes to a configuration can be specified by the &%-D%& command line
4757 option, which defines and overrides values for macros used inside the
4758 configuration file. However, like &%-C%&, the use of this option by a
4759 non-privileged user causes Exim to discard its root privilege.
4760 If DISABLE_D_OPTION is defined in &_Local/Makefile_&, the use of &%-D%& is
4761 completely disabled, and its use causes an immediate error exit.
4763 The WHITELIST_D_MACROS option in &_Local/Makefile_& permits the binary builder
4764 to declare certain macro names trusted, such that root privilege will not
4765 necessarily be discarded.
4766 WHITELIST_D_MACROS defines a colon-separated list of macros which are
4767 considered safe and, if &%-D%& only supplies macros from this list, and the
4768 values are acceptable, then Exim will not give up root privilege if the caller
4769 is root, the Exim run-time user, or the CONFIGURE_OWNER, if set. This is a
4770 transition mechanism and is expected to be removed in the future. Acceptable
4771 values for the macros satisfy the regexp: &`^[A-Za-z0-9_/.-]*$`&
4773 Some sites may wish to use the same Exim binary on different machines that
4774 share a file system, but to use different configuration files on each machine.
4775 If CONFIGURE_FILE_USE_NODE is defined in &_Local/Makefile_&, Exim first
4776 looks for a file whose name is the configuration file name followed by a dot
4777 and the machine's node name, as obtained from the &[uname()]& function. If this
4778 file does not exist, the standard name is tried. This processing occurs for
4779 each file name in the list given by CONFIGURE_FILE or &%-C%&.
4781 In some esoteric situations different versions of Exim may be run under
4782 different effective uids and the CONFIGURE_FILE_USE_EUID is defined to
4783 help with this. See the comments in &_src/EDITME_& for details.
4787 .section "Configuration file format" "SECTconffilfor"
4788 .cindex "configuration file" "format of"
4789 .cindex "format" "configuration file"
4790 Exim's configuration file is divided into a number of different parts. General
4791 option settings must always appear at the start of the file. The other parts
4792 are all optional, and may appear in any order. Each part other than the first
4793 is introduced by the word &"begin"& followed by the name of the part. The
4797 &'ACL'&: Access control lists for controlling incoming SMTP mail (see chapter
4800 .cindex "AUTH" "configuration"
4801 &'authenticators'&: Configuration settings for the authenticator drivers. These
4802 are concerned with the SMTP AUTH command (see chapter &<<CHAPSMTPAUTH>>&).
4804 &'routers'&: Configuration settings for the router drivers. Routers process
4805 addresses and determine how the message is to be delivered (see chapters
4806 &<<CHAProutergeneric>>&&--&<<CHAPredirect>>&).
4808 &'transports'&: Configuration settings for the transport drivers. Transports
4809 define mechanisms for copying messages to destinations (see chapters
4810 &<<CHAPtransportgeneric>>&&--&<<CHAPsmtptrans>>&).
4812 &'retry'&: Retry rules, for use when a message cannot be delivered immediately.
4813 If there is no retry section, or if it is empty (that is, no retry rules are
4814 defined), Exim will not retry deliveries. In this situation, temporary errors
4815 are treated the same as permanent errors. Retry rules are discussed in chapter
4818 &'rewrite'&: Global address rewriting rules, for use when a message arrives and
4819 when new addresses are generated during delivery. Rewriting is discussed in
4820 chapter &<<CHAPrewrite>>&.
4822 &'local_scan'&: Private options for the &[local_scan()]& function. If you
4823 want to use this feature, you must set
4825 LOCAL_SCAN_HAS_OPTIONS=yes
4827 in &_Local/Makefile_& before building Exim. Details of the &[local_scan()]&
4828 facility are given in chapter &<<CHAPlocalscan>>&.
4831 .cindex "configuration file" "leading white space in"
4832 .cindex "configuration file" "trailing white space in"
4833 .cindex "white space" "in configuration file"
4834 Leading and trailing white space in configuration lines is always ignored.
4836 Blank lines in the file, and lines starting with a # character (ignoring
4837 leading white space) are treated as comments and are ignored. &*Note*&: A
4838 # character other than at the beginning of a line is not treated specially,
4839 and does not introduce a comment.
4841 Any non-comment line can be continued by ending it with a backslash. Note that
4842 the general rule for white space means that trailing white space after the
4843 backslash and leading white space at the start of continuation
4844 lines is ignored. Comment lines beginning with # (but not empty lines) may
4845 appear in the middle of a sequence of continuation lines.
4847 A convenient way to create a configuration file is to start from the
4848 default, which is supplied in &_src/configure.default_&, and add, delete, or
4849 change settings as required.
4851 The ACLs, retry rules, and rewriting rules have their own syntax which is
4852 described in chapters &<<CHAPACL>>&, &<<CHAPretry>>&, and &<<CHAPrewrite>>&,
4853 respectively. The other parts of the configuration file have some syntactic
4854 items in common, and these are described below, from section &<<SECTcos>>&
4855 onwards. Before that, the inclusion, macro, and conditional facilities are
4860 .section "File inclusions in the configuration file" "SECID41"
4861 .cindex "inclusions in configuration file"
4862 .cindex "configuration file" "including other files"
4863 .cindex "&`.include`& in configuration file"
4864 .cindex "&`.include_if_exists`& in configuration file"
4865 You can include other files inside Exim's run time configuration file by
4868 &`.include`& <&'file name'&>
4869 &`.include_if_exists`& <&'file name'&>
4871 on a line by itself. Double quotes round the file name are optional. If you use
4872 the first form, a configuration error occurs if the file does not exist; the
4873 second form does nothing for non-existent files. In all cases, an absolute file
4876 Includes may be nested to any depth, but remember that Exim reads its
4877 configuration file often, so it is a good idea to keep them to a minimum.
4878 If you change the contents of an included file, you must HUP the daemon,
4879 because an included file is read only when the configuration itself is read.
4881 The processing of inclusions happens early, at a physical line level, so, like
4882 comment lines, an inclusion can be used in the middle of an option setting,
4885 hosts_lookup = a.b.c \
4888 Include processing happens after macro processing (see below). Its effect is to
4889 process the lines of the included file as if they occurred inline where the
4894 .section "Macros in the configuration file" "SECTmacrodefs"
4895 .cindex "macro" "description of"
4896 .cindex "configuration file" "macros"
4897 If a line in the main part of the configuration (that is, before the first
4898 &"begin"& line) begins with an upper case letter, it is taken as a macro
4899 definition, and must be of the form
4901 <&'name'&> = <&'rest of line'&>
4903 The name must consist of letters, digits, and underscores, and need not all be
4904 in upper case, though that is recommended. The rest of the line, including any
4905 continuations, is the replacement text, and has leading and trailing white
4906 space removed. Quotes are not removed. The replacement text can never end with
4907 a backslash character, but this doesn't seem to be a serious limitation.
4909 Macros may also be defined between router, transport, authenticator, or ACL
4910 definitions. They may not, however, be defined within an individual driver or
4911 ACL, or in the &%local_scan%&, retry, or rewrite sections of the configuration.
4913 .section "Macro substitution" "SECID42"
4914 Once a macro is defined, all subsequent lines in the file (and any included
4915 files) are scanned for the macro name; if there are several macros, the line is
4916 scanned for each in turn, in the order in which the macros are defined. The
4917 replacement text is not re-scanned for the current macro, though it is scanned
4918 for subsequently defined macros. For this reason, a macro name may not contain
4919 the name of a previously defined macro as a substring. You could, for example,
4922 &`ABCD_XYZ = `&<&'something'&>
4923 &`ABCD = `&<&'something else'&>
4925 but putting the definitions in the opposite order would provoke a configuration
4926 error. Macro expansion is applied to individual physical lines from the file,
4927 before checking for line continuation or file inclusion (see above). If a line
4928 consists solely of a macro name, and the expansion of the macro is empty, the
4929 line is ignored. A macro at the start of a line may turn the line into a
4930 comment line or a &`.include`& line.
4933 .section "Redefining macros" "SECID43"
4934 Once defined, the value of a macro can be redefined later in the configuration
4935 (or in an included file). Redefinition is specified by using &'=='& instead of
4940 MAC == updated value
4942 Redefinition does not alter the order in which the macros are applied to the
4943 subsequent lines of the configuration file. It is still the same order in which
4944 the macros were originally defined. All that changes is the macro's value.
4945 Redefinition makes it possible to accumulate values. For example:
4949 MAC == MAC and something added
4951 This can be helpful in situations where the configuration file is built
4952 from a number of other files.
4954 .section "Overriding macro values" "SECID44"
4955 The values set for macros in the configuration file can be overridden by the
4956 &%-D%& command line option, but Exim gives up its root privilege when &%-D%& is
4957 used, unless called by root or the Exim user. A definition on the command line
4958 using the &%-D%& option causes all definitions and redefinitions within the
4963 .section "Example of macro usage" "SECID45"
4964 As an example of macro usage, consider a configuration where aliases are looked
4965 up in a MySQL database. It helps to keep the file less cluttered if long
4966 strings such as SQL statements are defined separately as macros, for example:
4968 ALIAS_QUERY = select mailbox from user where \
4969 login='${quote_mysql:$local_part}';
4971 This can then be used in a &(redirect)& router setting like this:
4973 data = ${lookup mysql{ALIAS_QUERY}}
4975 In earlier versions of Exim macros were sometimes used for domain, host, or
4976 address lists. In Exim 4 these are handled better by named lists &-- see
4977 section &<<SECTnamedlists>>&.
4980 .section "Conditional skips in the configuration file" "SECID46"
4981 .cindex "configuration file" "conditional skips"
4982 .cindex "&`.ifdef`&"
4983 You can use the directives &`.ifdef`&, &`.ifndef`&, &`.elifdef`&,
4984 &`.elifndef`&, &`.else`&, and &`.endif`& to dynamically include or exclude
4985 portions of the configuration file. The processing happens whenever the file is
4986 read (that is, when an Exim binary starts to run).
4988 The implementation is very simple. Instances of the first four directives must
4989 be followed by text that includes the names of one or macros. The condition
4990 that is tested is whether or not any macro substitution has taken place in the
4994 message_size_limit = 50M
4996 message_size_limit = 100M
4999 sets a message size limit of 50M if the macro &`AAA`& is defined, and 100M
5000 otherwise. If there is more than one macro named on the line, the condition
5001 is true if any of them are defined. That is, it is an &"or"& condition. To
5002 obtain an &"and"& condition, you need to use nested &`.ifdef`&s.
5004 Although you can use a macro expansion to generate one of these directives,
5005 it is not very useful, because the condition &"there was a macro substitution
5006 in this line"& will always be true.
5008 Text following &`.else`& and &`.endif`& is ignored, and can be used as comment
5009 to clarify complicated nestings.
5013 .section "Common option syntax" "SECTcos"
5014 .cindex "common option syntax"
5015 .cindex "syntax of common options"
5016 .cindex "configuration file" "common option syntax"
5017 For the main set of options, driver options, and &[local_scan()]& options,
5018 each setting is on a line by itself, and starts with a name consisting of
5019 lower-case letters and underscores. Many options require a data value, and in
5020 these cases the name must be followed by an equals sign (with optional white
5021 space) and then the value. For example:
5023 qualify_domain = mydomain.example.com
5025 .cindex "hiding configuration option values"
5026 .cindex "configuration options" "hiding value of"
5027 .cindex "options" "hiding value of"
5028 Some option settings may contain sensitive data, for example, passwords for
5029 accessing databases. To stop non-admin users from using the &%-bP%& command
5030 line option to read these values, you can precede the option settings with the
5031 word &"hide"&. For example:
5033 hide mysql_servers = localhost/users/admin/secret-password
5035 For non-admin users, such options are displayed like this:
5037 mysql_servers = <value not displayable>
5039 If &"hide"& is used on a driver option, it hides the value of that option on
5040 all instances of the same driver.
5042 The following sections describe the syntax used for the different data types
5043 that are found in option settings.
5046 .section "Boolean options" "SECID47"
5047 .cindex "format" "boolean"
5048 .cindex "boolean configuration values"
5049 .oindex "&%no_%&&'xxx'&"
5050 .oindex "&%not_%&&'xxx'&"
5051 Options whose type is given as boolean are on/off switches. There are two
5052 different ways of specifying such options: with and without a data value. If
5053 the option name is specified on its own without data, the switch is turned on;
5054 if it is preceded by &"no_"& or &"not_"& the switch is turned off. However,
5055 boolean options may be followed by an equals sign and one of the words
5056 &"true"&, &"false"&, &"yes"&, or &"no"&, as an alternative syntax. For example,
5057 the following two settings have exactly the same effect:
5062 The following two lines also have the same (opposite) effect:
5067 You can use whichever syntax you prefer.
5072 .section "Integer values" "SECID48"
5073 .cindex "integer configuration values"
5074 .cindex "format" "integer"
5075 If an option's type is given as &"integer"&, the value can be given in decimal,
5076 hexadecimal, or octal. If it starts with a digit greater than zero, a decimal
5077 number is assumed. Otherwise, it is treated as an octal number unless it starts
5078 with the characters &"0x"&, in which case the remainder is interpreted as a
5081 If an integer value is followed by the letter K, it is multiplied by 1024; if
5082 it is followed by the letter M, it is multiplied by 1024x1024. When the values
5083 of integer option settings are output, values which are an exact multiple of
5084 1024 or 1024x1024 are sometimes, but not always, printed using the letters K
5085 and M. The printing style is independent of the actual input format that was
5089 .section "Octal integer values" "SECID49"
5090 .cindex "integer format"
5091 .cindex "format" "octal integer"
5092 If an option's type is given as &"octal integer"&, its value is always
5093 interpreted as an octal number, whether or not it starts with the digit zero.
5094 Such options are always output in octal.
5097 .section "Fixed point numbers" "SECID50"
5098 .cindex "fixed point configuration values"
5099 .cindex "format" "fixed point"
5100 If an option's type is given as &"fixed-point"&, its value must be a decimal
5101 integer, optionally followed by a decimal point and up to three further digits.
5105 .section "Time intervals" "SECTtimeformat"
5106 .cindex "time interval" "specifying in configuration"
5107 .cindex "format" "time interval"
5108 A time interval is specified as a sequence of numbers, each followed by one of
5109 the following letters, with no intervening white space:
5119 For example, &"3h50m"& specifies 3 hours and 50 minutes. The values of time
5120 intervals are output in the same format. Exim does not restrict the values; it
5121 is perfectly acceptable, for example, to specify &"90m"& instead of &"1h30m"&.
5125 .section "String values" "SECTstrings"
5126 .cindex "string" "format of configuration values"
5127 .cindex "format" "string"
5128 If an option's type is specified as &"string"&, the value can be specified with
5129 or without double-quotes. If it does not start with a double-quote, the value
5130 consists of the remainder of the line plus any continuation lines, starting at
5131 the first character after any leading white space, with trailing white space
5132 removed, and with no interpretation of the characters in the string. Because
5133 Exim removes comment lines (those beginning with #) at an early stage, they can
5134 appear in the middle of a multi-line string. The following two settings are
5135 therefore equivalent:
5137 trusted_users = uucp:mail
5138 trusted_users = uucp:\
5139 # This comment line is ignored
5142 .cindex "string" "quoted"
5143 .cindex "escape characters in quoted strings"
5144 If a string does start with a double-quote, it must end with a closing
5145 double-quote, and any backslash characters other than those used for line
5146 continuation are interpreted as escape characters, as follows:
5149 .irow &`\\`& "single backslash"
5150 .irow &`\n`& "newline"
5151 .irow &`\r`& "carriage return"
5153 .irow "&`\`&<&'octal digits'&>" "up to 3 octal digits specify one character"
5154 .irow "&`\x`&<&'hex digits'&>" "up to 2 hexadecimal digits specify one &&&
5158 If a backslash is followed by some other character, including a double-quote
5159 character, that character replaces the pair.
5161 Quoting is necessary only if you want to make use of the backslash escapes to
5162 insert special characters, or if you need to specify a value with leading or
5163 trailing spaces. These cases are rare, so quoting is almost never needed in
5164 current versions of Exim. In versions of Exim before 3.14, quoting was required
5165 in order to continue lines, so you may come across older configuration files
5166 and examples that apparently quote unnecessarily.
5169 .section "Expanded strings" "SECID51"
5170 .cindex "expansion" "definition of"
5171 Some strings in the configuration file are subjected to &'string expansion'&,
5172 by which means various parts of the string may be changed according to the
5173 circumstances (see chapter &<<CHAPexpand>>&). The input syntax for such strings
5174 is as just described; in particular, the handling of backslashes in quoted
5175 strings is done as part of the input process, before expansion takes place.
5176 However, backslash is also an escape character for the expander, so any
5177 backslashes that are required for that reason must be doubled if they are
5178 within a quoted configuration string.
5181 .section "User and group names" "SECID52"
5182 .cindex "user name" "format of"
5183 .cindex "format" "user name"
5184 .cindex "groups" "name format"
5185 .cindex "format" "group name"
5186 User and group names are specified as strings, using the syntax described
5187 above, but the strings are interpreted specially. A user or group name must
5188 either consist entirely of digits, or be a name that can be looked up using the
5189 &[getpwnam()]& or &[getgrnam()]& function, as appropriate.
5192 .section "List construction" "SECTlistconstruct"
5193 .cindex "list" "syntax of in configuration"
5194 .cindex "format" "list item in configuration"
5195 .cindex "string" "list, definition of"
5196 The data for some configuration options is a list of items, with colon as the
5197 default separator. Many of these options are shown with type &"string list"& in
5198 the descriptions later in this document. Others are listed as &"domain list"&,
5199 &"host list"&, &"address list"&, or &"local part list"&. Syntactically, they
5200 are all the same; however, those other than &"string list"& are subject to
5201 particular kinds of interpretation, as described in chapter
5202 &<<CHAPdomhosaddlists>>&.
5204 In all these cases, the entire list is treated as a single string as far as the
5205 input syntax is concerned. The &%trusted_users%& setting in section
5206 &<<SECTstrings>>& above is an example. If a colon is actually needed in an item
5207 in a list, it must be entered as two colons. Leading and trailing white space
5208 on each item in a list is ignored. This makes it possible to include items that
5209 start with a colon, and in particular, certain forms of IPv6 address. For
5212 local_interfaces = 127.0.0.1 : ::::1
5214 contains two IP addresses, the IPv4 address 127.0.0.1 and the IPv6 address ::1.
5216 &*Note*&: Although leading and trailing white space is ignored in individual
5217 list items, it is not ignored when parsing the list. The space after the first
5218 colon in the example above is necessary. If it were not there, the list would
5219 be interpreted as the two items 127.0.0.1:: and 1.
5221 .section "Changing list separators" "SECID53"
5222 .cindex "list separator" "changing"
5223 .cindex "IPv6" "addresses in lists"
5224 Doubling colons in IPv6 addresses is an unwelcome chore, so a mechanism was
5225 introduced to allow the separator character to be changed. If a list begins
5226 with a left angle bracket, followed by any punctuation character, that
5227 character is used instead of colon as the list separator. For example, the list
5228 above can be rewritten to use a semicolon separator like this:
5230 local_interfaces = <; 127.0.0.1 ; ::1
5232 This facility applies to all lists, with the exception of the list in
5233 &%log_file_path%&. It is recommended that the use of non-colon separators be
5234 confined to circumstances where they really are needed.
5236 .cindex "list separator" "newline as"
5237 .cindex "newline" "as list separator"
5238 It is also possible to use newline and other control characters (those with
5239 code values less than 32, plus DEL) as separators in lists. Such separators
5240 must be provided literally at the time the list is processed. For options that
5241 are string-expanded, you can write the separator using a normal escape
5242 sequence. This will be processed by the expander before the string is
5243 interpreted as a list. For example, if a newline-separated list of domains is
5244 generated by a lookup, you can process it directly by a line such as this:
5246 domains = <\n ${lookup mysql{.....}}
5248 This avoids having to change the list separator in such data. You are unlikely
5249 to want to use a control character as a separator in an option that is not
5250 expanded, because the value is literal text. However, it can be done by giving
5251 the value in quotes. For example:
5253 local_interfaces = "<\n 127.0.0.1 \n ::1"
5255 Unlike printing character separators, which can be included in list items by
5256 doubling, it is not possible to include a control character as data when it is
5257 set as the separator. Two such characters in succession are interpreted as
5258 enclosing an empty list item.
5262 .section "Empty items in lists" "SECTempitelis"
5263 .cindex "list" "empty item in"
5264 An empty item at the end of a list is always ignored. In other words, trailing
5265 separator characters are ignored. Thus, the list in
5267 senders = user@domain :
5269 contains only a single item. If you want to include an empty string as one item
5270 in a list, it must not be the last item. For example, this list contains three
5271 items, the second of which is empty:
5273 senders = user1@domain : : user2@domain
5275 &*Note*&: There must be white space between the two colons, as otherwise they
5276 are interpreted as representing a single colon data character (and the list
5277 would then contain just one item). If you want to specify a list that contains
5278 just one, empty item, you can do it as in this example:
5282 In this case, the first item is empty, and the second is discarded because it
5283 is at the end of the list.
5288 .section "Format of driver configurations" "SECTfordricon"
5289 .cindex "drivers" "configuration format"
5290 There are separate parts in the configuration for defining routers, transports,
5291 and authenticators. In each part, you are defining a number of driver
5292 instances, each with its own set of options. Each driver instance is defined by
5293 a sequence of lines like this:
5295 <&'instance name'&>:
5300 In the following example, the instance name is &(localuser)&, and it is
5301 followed by three options settings:
5306 transport = local_delivery
5308 For each driver instance, you specify which Exim code module it uses &-- by the
5309 setting of the &%driver%& option &-- and (optionally) some configuration
5310 settings. For example, in the case of transports, if you want a transport to
5311 deliver with SMTP you would use the &(smtp)& driver; if you want to deliver to
5312 a local file you would use the &(appendfile)& driver. Each of the drivers is
5313 described in detail in its own separate chapter later in this manual.
5315 You can have several routers, transports, or authenticators that are based on
5316 the same underlying driver (each must have a different instance name).
5318 The order in which routers are defined is important, because addresses are
5319 passed to individual routers one by one, in order. The order in which
5320 transports are defined does not matter at all. The order in which
5321 authenticators are defined is used only when Exim, as a client, is searching
5322 them to find one that matches an authentication mechanism offered by the
5325 .cindex "generic options"
5326 .cindex "options" "generic &-- definition of"
5327 Within a driver instance definition, there are two kinds of option: &'generic'&
5328 and &'private'&. The generic options are those that apply to all drivers of the
5329 same type (that is, all routers, all transports or all authenticators). The
5330 &%driver%& option is a generic option that must appear in every definition.
5331 .cindex "private options"
5332 The private options are special for each driver, and none need appear, because
5333 they all have default values.
5335 The options may appear in any order, except that the &%driver%& option must
5336 precede any private options, since these depend on the particular driver. For
5337 this reason, it is recommended that &%driver%& always be the first option.
5339 Driver instance names, which are used for reference in log entries and
5340 elsewhere, can be any sequence of letters, digits, and underscores (starting
5341 with a letter) and must be unique among drivers of the same type. A router and
5342 a transport (for example) can each have the same name, but no two router
5343 instances can have the same name. The name of a driver instance should not be
5344 confused with the name of the underlying driver module. For example, the
5345 configuration lines:
5350 create an instance of the &(smtp)& transport driver whose name is
5351 &(remote_smtp)&. The same driver code can be used more than once, with
5352 different instance names and different option settings each time. A second
5353 instance of the &(smtp)& transport, with different options, might be defined
5359 command_timeout = 10s
5361 The names &(remote_smtp)& and &(special_smtp)& would be used to reference
5362 these transport instances from routers, and these names would appear in log
5365 Comment lines may be present in the middle of driver specifications. The full
5366 list of option settings for any particular driver instance, including all the
5367 defaulted values, can be extracted by making use of the &%-bP%& command line
5375 . ////////////////////////////////////////////////////////////////////////////
5376 . ////////////////////////////////////////////////////////////////////////////
5378 .chapter "The default configuration file" "CHAPdefconfil"
5379 .scindex IIDconfiwal "configuration file" "default &""walk through""&"
5380 .cindex "default" "configuration file &""walk through""&"
5381 The default configuration file supplied with Exim as &_src/configure.default_&
5382 is sufficient for a host with simple mail requirements. As an introduction to
5383 the way Exim is configured, this chapter &"walks through"& the default
5384 configuration, giving brief explanations of the settings. Detailed descriptions
5385 of the options are given in subsequent chapters. The default configuration file
5386 itself contains extensive comments about ways you might want to modify the
5387 initial settings. However, note that there are many options that are not
5388 mentioned at all in the default configuration.
5392 .section "Main configuration settings" "SECTdefconfmain"
5393 The main (global) configuration option settings must always come first in the
5394 file. The first thing you'll see in the file, after some initial comments, is
5397 # primary_hostname =
5399 This is a commented-out setting of the &%primary_hostname%& option. Exim needs
5400 to know the official, fully qualified name of your host, and this is where you
5401 can specify it. However, in most cases you do not need to set this option. When
5402 it is unset, Exim uses the &[uname()]& system function to obtain the host name.
5404 The first three non-comment configuration lines are as follows:
5406 domainlist local_domains = @
5407 domainlist relay_to_domains =
5408 hostlist relay_from_hosts = 127.0.0.1
5410 These are not, in fact, option settings. They are definitions of two named
5411 domain lists and one named host list. Exim allows you to give names to lists of
5412 domains, hosts, and email addresses, in order to make it easier to manage the
5413 configuration file (see section &<<SECTnamedlists>>&).
5415 The first line defines a domain list called &'local_domains'&; this is used
5416 later in the configuration to identify domains that are to be delivered
5419 .cindex "@ in a domain list"
5420 There is just one item in this list, the string &"@"&. This is a special form
5421 of entry which means &"the name of the local host"&. Thus, if the local host is
5422 called &'a.host.example'&, mail to &'any.user@a.host.example'& is expected to
5423 be delivered locally. Because the local host's name is referenced indirectly,
5424 the same configuration file can be used on different hosts.
5426 The second line defines a domain list called &'relay_to_domains'&, but the
5427 list itself is empty. Later in the configuration we will come to the part that
5428 controls mail relaying through the local host; it allows relaying to any
5429 domains in this list. By default, therefore, no relaying on the basis of a mail
5430 domain is permitted.
5432 The third line defines a host list called &'relay_from_hosts'&. This list is
5433 used later in the configuration to permit relaying from any host or IP address
5434 that matches the list. The default contains just the IP address of the IPv4
5435 loopback interface, which means that processes on the local host are able to
5436 submit mail for relaying by sending it over TCP/IP to that interface. No other
5437 hosts are permitted to submit messages for relaying.
5439 Just to be sure there's no misunderstanding: at this point in the configuration
5440 we aren't actually setting up any controls. We are just defining some domains
5441 and hosts that will be used in the controls that are specified later.
5443 The next two configuration lines are genuine option settings:
5445 acl_smtp_rcpt = acl_check_rcpt
5446 acl_smtp_data = acl_check_data
5448 These options specify &'Access Control Lists'& (ACLs) that are to be used
5449 during an incoming SMTP session for every recipient of a message (every RCPT
5450 command), and after the contents of the message have been received,
5451 respectively. The names of the lists are &'acl_check_rcpt'& and
5452 &'acl_check_data'&, and we will come to their definitions below, in the ACL
5453 section of the configuration. The RCPT ACL controls which recipients are
5454 accepted for an incoming message &-- if a configuration does not provide an ACL
5455 to check recipients, no SMTP mail can be accepted. The DATA ACL allows the
5456 contents of a message to be checked.
5458 Two commented-out option settings are next:
5460 # av_scanner = clamd:/tmp/clamd
5461 # spamd_address = 127.0.0.1 783
5463 These are example settings that can be used when Exim is compiled with the
5464 content-scanning extension. The first specifies the interface to the virus
5465 scanner, and the second specifies the interface to SpamAssassin. Further
5466 details are given in chapter &<<CHAPexiscan>>&.
5468 Three more commented-out option settings follow:
5470 # tls_advertise_hosts = *
5471 # tls_certificate = /etc/ssl/exim.crt
5472 # tls_privatekey = /etc/ssl/exim.pem
5474 These are example settings that can be used when Exim is compiled with
5475 support for TLS (aka SSL) as described in section &<<SECTinctlsssl>>&. The
5476 first one specifies the list of clients that are allowed to use TLS when
5477 connecting to this server; in this case the wildcard means all clients. The
5478 other options specify where Exim should find its TLS certificate and private
5479 key, which together prove the server's identity to any clients that connect.
5480 More details are given in chapter &<<CHAPTLS>>&.
5482 Another two commented-out option settings follow:
5484 # daemon_smtp_ports = 25 : 465 : 587
5485 # tls_on_connect_ports = 465
5487 .cindex "port" "465 and 587"
5488 .cindex "port" "for message submission"
5489 .cindex "message" "submission, ports for"
5490 .cindex "ssmtp protocol"
5491 .cindex "smtps protocol"
5492 .cindex "SMTP" "ssmtp protocol"
5493 .cindex "SMTP" "smtps protocol"
5494 These options provide better support for roaming users who wish to use this
5495 server for message submission. They are not much use unless you have turned on
5496 TLS (as described in the previous paragraph) and authentication (about which
5497 more in section &<<SECTdefconfauth>>&). The usual SMTP port 25 is often blocked
5498 on end-user networks, so RFC 4409 specifies that message submission should use
5499 port 587 instead. However some software (notably Microsoft Outlook) cannot be
5500 configured to use port 587 correctly, so these settings also enable the
5501 non-standard &"smtps"& (aka &"ssmtp"&) port 465 (see section
5502 &<<SECTsupobssmt>>&).
5504 Two more commented-out options settings follow:
5507 # qualify_recipient =
5509 The first of these specifies a domain that Exim uses when it constructs a
5510 complete email address from a local login name. This is often needed when Exim
5511 receives a message from a local process. If you do not set &%qualify_domain%&,
5512 the value of &%primary_hostname%& is used. If you set both of these options,
5513 you can have different qualification domains for sender and recipient
5514 addresses. If you set only the first one, its value is used in both cases.
5516 .cindex "domain literal" "recognizing format"
5517 The following line must be uncommented if you want Exim to recognize
5518 addresses of the form &'user@[10.11.12.13]'& that is, with a &"domain literal"&
5519 (an IP address within square brackets) instead of a named domain.
5521 # allow_domain_literals
5523 The RFCs still require this form, but many people think that in the modern
5524 Internet it makes little sense to permit mail to be sent to specific hosts by
5525 quoting their IP addresses. This ancient format has been used by people who
5526 try to abuse hosts by using them for unwanted relaying. However, some
5527 people believe there are circumstances (for example, messages addressed to
5528 &'postmaster'&) where domain literals are still useful.
5530 The next configuration line is a kind of trigger guard:
5534 It specifies that no delivery must ever be run as the root user. The normal
5535 convention is to set up &'root'& as an alias for the system administrator. This
5536 setting is a guard against slips in the configuration.
5537 The list of users specified by &%never_users%& is not, however, the complete
5538 list; the build-time configuration in &_Local/Makefile_& has an option called
5539 FIXED_NEVER_USERS specifying a list that cannot be overridden. The
5540 contents of &%never_users%& are added to this list. By default
5541 FIXED_NEVER_USERS also specifies root.
5543 When a remote host connects to Exim in order to send mail, the only information
5544 Exim has about the host's identity is its IP address. The next configuration
5549 specifies that Exim should do a reverse DNS lookup on all incoming connections,
5550 in order to get a host name. This improves the quality of the logging
5551 information, but if you feel it is too expensive, you can remove it entirely,
5552 or restrict the lookup to hosts on &"nearby"& networks.
5553 Note that it is not always possible to find a host name from an IP address,
5554 because not all DNS reverse zones are maintained, and sometimes DNS servers are
5557 The next two lines are concerned with &'ident'& callbacks, as defined by RFC
5558 1413 (hence their names):
5560 rfc1413_query_hosts = *
5561 rfc1413_query_timeout = 0s
5563 These settings cause Exim to avoid ident callbacks for all incoming SMTP calls.
5564 Few hosts offer RFC1413 service these days; calls have to be
5565 terminated by a timeout and this needlessly delays the startup
5566 of an incoming SMTP connection.
5567 If you have hosts for which you trust RFC1413 and need this
5568 information, you can change this.
5570 This line enables an efficiency SMTP option. It is negociated by clients
5571 and not expected to cause problems but can be disabled if needed.
5576 When Exim receives messages over SMTP connections, it expects all addresses to
5577 be fully qualified with a domain, as required by the SMTP definition. However,
5578 if you are running a server to which simple clients submit messages, you may
5579 find that they send unqualified addresses. The two commented-out options:
5581 # sender_unqualified_hosts =
5582 # recipient_unqualified_hosts =
5584 show how you can specify hosts that are permitted to send unqualified sender
5585 and recipient addresses, respectively.
5587 The &%percent_hack_domains%& option is also commented out:
5589 # percent_hack_domains =
5591 It provides a list of domains for which the &"percent hack"& is to operate.
5592 This is an almost obsolete form of explicit email routing. If you do not know
5593 anything about it, you can safely ignore this topic.
5595 The last two settings in the main part of the default configuration are
5596 concerned with messages that have been &"frozen"& on Exim's queue. When a
5597 message is frozen, Exim no longer continues to try to deliver it. Freezing
5598 occurs when a bounce message encounters a permanent failure because the sender
5599 address of the original message that caused the bounce is invalid, so the
5600 bounce cannot be delivered. This is probably the most common case, but there
5601 are also other conditions that cause freezing, and frozen messages are not
5602 always bounce messages.
5604 ignore_bounce_errors_after = 2d
5605 timeout_frozen_after = 7d
5607 The first of these options specifies that failing bounce messages are to be
5608 discarded after 2 days on the queue. The second specifies that any frozen
5609 message (whether a bounce message or not) is to be timed out (and discarded)
5610 after a week. In this configuration, the first setting ensures that no failing
5611 bounce message ever lasts a week.
5615 .section "ACL configuration" "SECID54"
5616 .cindex "default" "ACLs"
5617 .cindex "&ACL;" "default configuration"
5618 In the default configuration, the ACL section follows the main configuration.
5619 It starts with the line
5623 and it contains the definitions of two ACLs, called &'acl_check_rcpt'& and
5624 &'acl_check_data'&, that were referenced in the settings of &%acl_smtp_rcpt%&
5625 and &%acl_smtp_data%& above.
5627 .cindex "RCPT" "ACL for"
5628 The first ACL is used for every RCPT command in an incoming SMTP message. Each
5629 RCPT command specifies one of the message's recipients. The ACL statements
5630 are considered in order, until the recipient address is either accepted or
5631 rejected. The RCPT command is then accepted or rejected, according to the
5632 result of the ACL processing.
5636 This line, consisting of a name terminated by a colon, marks the start of the
5641 This ACL statement accepts the recipient if the sending host matches the list.
5642 But what does that strange list mean? It doesn't actually contain any host
5643 names or IP addresses. The presence of the colon puts an empty item in the
5644 list; Exim matches this only if the incoming message did not come from a remote
5645 host, because in that case, the remote hostname is empty. The colon is
5646 important. Without it, the list itself is empty, and can never match anything.
5648 What this statement is doing is to accept unconditionally all recipients in
5649 messages that are submitted by SMTP from local processes using the standard
5650 input and output (that is, not using TCP/IP). A number of MUAs operate in this
5653 deny message = Restricted characters in address
5654 domains = +local_domains
5655 local_parts = ^[.] : ^.*[@%!/|]
5657 deny message = Restricted characters in address
5658 domains = !+local_domains
5659 local_parts = ^[./|] : ^.*[@%!] : ^.*/\\.\\./
5661 These statements are concerned with local parts that contain any of the
5662 characters &"@"&, &"%"&, &"!"&, &"/"&, &"|"&, or dots in unusual places.
5663 Although these characters are entirely legal in local parts (in the case of
5664 &"@"& and leading dots, only if correctly quoted), they do not commonly occur
5665 in Internet mail addresses.
5667 The first three have in the past been associated with explicitly routed
5668 addresses (percent is still sometimes used &-- see the &%percent_hack_domains%&
5669 option). Addresses containing these characters are regularly tried by spammers
5670 in an attempt to bypass relaying restrictions, and also by open relay testing
5671 programs. Unless you really need them it is safest to reject these characters
5672 at this early stage. This configuration is heavy-handed in rejecting these
5673 characters for all messages it accepts from remote hosts. This is a deliberate
5674 policy of being as safe as possible.
5676 The first rule above is stricter, and is applied to messages that are addressed
5677 to one of the local domains handled by this host. This is implemented by the
5678 first condition, which restricts it to domains that are listed in the
5679 &'local_domains'& domain list. The &"+"& character is used to indicate a
5680 reference to a named list. In this configuration, there is just one domain in
5681 &'local_domains'&, but in general there may be many.
5683 The second condition on the first statement uses two regular expressions to
5684 block local parts that begin with a dot or contain &"@"&, &"%"&, &"!"&, &"/"&,
5685 or &"|"&. If you have local accounts that include these characters, you will
5686 have to modify this rule.
5688 Empty components (two dots in a row) are not valid in RFC 2822, but Exim
5689 allows them because they have been encountered in practice. (Consider the
5690 common convention of local parts constructed as
5691 &"&'first-initial.second-initial.family-name'&"& when applied to someone like
5692 the author of Exim, who has no second initial.) However, a local part starting
5693 with a dot or containing &"/../"& can cause trouble if it is used as part of a
5694 file name (for example, for a mailing list). This is also true for local parts
5695 that contain slashes. A pipe symbol can also be troublesome if the local part
5696 is incorporated unthinkingly into a shell command line.
5698 The second rule above applies to all other domains, and is less strict. This
5699 allows your own users to send outgoing messages to sites that use slashes
5700 and vertical bars in their local parts. It blocks local parts that begin
5701 with a dot, slash, or vertical bar, but allows these characters within the
5702 local part. However, the sequence &"/../"& is barred. The use of &"@"&, &"%"&,
5703 and &"!"& is blocked, as before. The motivation here is to prevent your users
5704 (or your users' viruses) from mounting certain kinds of attack on remote sites.
5706 accept local_parts = postmaster
5707 domains = +local_domains
5709 This statement, which has two conditions, accepts an incoming address if the
5710 local part is &'postmaster'& and the domain is one of those listed in the
5711 &'local_domains'& domain list. The &"+"& character is used to indicate a
5712 reference to a named list. In this configuration, there is just one domain in
5713 &'local_domains'&, but in general there may be many.
5715 The presence of this statement means that mail to postmaster is never blocked
5716 by any of the subsequent tests. This can be helpful while sorting out problems
5717 in cases where the subsequent tests are incorrectly denying access.
5719 require verify = sender
5721 This statement requires the sender address to be verified before any subsequent
5722 ACL statement can be used. If verification fails, the incoming recipient
5723 address is refused. Verification consists of trying to route the address, to
5724 see if a bounce message could be delivered to it. In the case of remote
5725 addresses, basic verification checks only the domain, but &'callouts'& can be
5726 used for more verification if required. Section &<<SECTaddressverification>>&
5727 discusses the details of address verification.
5729 accept hosts = +relay_from_hosts
5730 control = submission
5732 This statement accepts the address if the message is coming from one of the
5733 hosts that are defined as being allowed to relay through this host. Recipient
5734 verification is omitted here, because in many cases the clients are dumb MUAs
5735 that do not cope well with SMTP error responses. For the same reason, the
5736 second line specifies &"submission mode"& for messages that are accepted. This
5737 is described in detail in section &<<SECTsubmodnon>>&; it causes Exim to fix
5738 messages that are deficient in some way, for example, because they lack a
5739 &'Date:'& header line. If you are actually relaying out from MTAs, you should
5740 probably add recipient verification here, and disable submission mode.
5742 accept authenticated = *
5743 control = submission
5745 This statement accepts the address if the client host has authenticated itself.
5746 Submission mode is again specified, on the grounds that such messages are most
5747 likely to come from MUAs. The default configuration does not define any
5748 authenticators, though it does include some nearly complete commented-out
5749 examples described in &<<SECTdefconfauth>>&. This means that no client can in
5750 fact authenticate until you complete the authenticator definitions.
5752 require message = relay not permitted
5753 domains = +local_domains : +relay_to_domains
5755 This statement rejects the address if its domain is neither a local domain nor
5756 one of the domains for which this host is a relay.
5758 require verify = recipient
5760 This statement requires the recipient address to be verified; if verification
5761 fails, the address is rejected.
5763 # deny message = rejected because $sender_host_address \
5764 # is in a black list at $dnslist_domain\n\
5766 # dnslists = black.list.example
5768 # warn dnslists = black.list.example
5769 # add_header = X-Warning: $sender_host_address is in \
5770 # a black list at $dnslist_domain
5771 # log_message = found in $dnslist_domain
5773 These commented-out lines are examples of how you could configure Exim to check
5774 sending hosts against a DNS black list. The first statement rejects messages
5775 from blacklisted hosts, whereas the second just inserts a warning header
5778 # require verify = csa
5780 This commented-out line is an example of how you could turn on client SMTP
5781 authorization (CSA) checking. Such checks do DNS lookups for special SRV
5786 The final statement in the first ACL unconditionally accepts any recipient
5787 address that has successfully passed all the previous tests.
5791 This line marks the start of the second ACL, and names it. Most of the contents
5792 of this ACL are commented out:
5795 # message = This message contains a virus \
5798 These lines are examples of how to arrange for messages to be scanned for
5799 viruses when Exim has been compiled with the content-scanning extension, and a
5800 suitable virus scanner is installed. If the message is found to contain a
5801 virus, it is rejected with the given custom error message.
5803 # warn spam = nobody
5804 # message = X-Spam_score: $spam_score\n\
5805 # X-Spam_score_int: $spam_score_int\n\
5806 # X-Spam_bar: $spam_bar\n\
5807 # X-Spam_report: $spam_report
5809 These lines are an example of how to arrange for messages to be scanned by
5810 SpamAssassin when Exim has been compiled with the content-scanning extension,
5811 and SpamAssassin has been installed. The SpamAssassin check is run with
5812 &`nobody`& as its user parameter, and the results are added to the message as a
5813 series of extra header line. In this case, the message is not rejected,
5814 whatever the spam score.
5818 This final line in the DATA ACL accepts the message unconditionally.
5821 .section "Router configuration" "SECID55"
5822 .cindex "default" "routers"
5823 .cindex "routers" "default"
5824 The router configuration comes next in the default configuration, introduced
5829 Routers are the modules in Exim that make decisions about where to send
5830 messages. An address is passed to each router in turn, until it is either
5831 accepted, or failed. This means that the order in which you define the routers
5832 matters. Each router is fully described in its own chapter later in this
5833 manual. Here we give only brief overviews.
5836 # driver = ipliteral
5837 # domains = !+local_domains
5838 # transport = remote_smtp
5840 .cindex "domain literal" "default router"
5841 This router is commented out because the majority of sites do not want to
5842 support domain literal addresses (those of the form &'user@[10.9.8.7]'&). If
5843 you uncomment this router, you also need to uncomment the setting of
5844 &%allow_domain_literals%& in the main part of the configuration.
5848 domains = ! +local_domains
5849 transport = remote_smtp
5850 ignore_target_hosts = 0.0.0.0 : 127.0.0.0/8
5853 The first uncommented router handles addresses that do not involve any local
5854 domains. This is specified by the line
5856 domains = ! +local_domains
5858 The &%domains%& option lists the domains to which this router applies, but the
5859 exclamation mark is a negation sign, so the router is used only for domains
5860 that are not in the domain list called &'local_domains'& (which was defined at
5861 the start of the configuration). The plus sign before &'local_domains'&
5862 indicates that it is referring to a named list. Addresses in other domains are
5863 passed on to the following routers.
5865 The name of the router driver is &(dnslookup)&,
5866 and is specified by the &%driver%& option. Do not be confused by the fact that
5867 the name of this router instance is the same as the name of the driver. The
5868 instance name is arbitrary, but the name set in the &%driver%& option must be
5869 one of the driver modules that is in the Exim binary.
5871 The &(dnslookup)& router routes addresses by looking up their domains in the
5872 DNS in order to obtain a list of hosts to which the address is routed. If the
5873 router succeeds, the address is queued for the &(remote_smtp)& transport, as
5874 specified by the &%transport%& option. If the router does not find the domain
5875 in the DNS, no further routers are tried because of the &%no_more%& setting, so
5876 the address fails and is bounced.
5878 The &%ignore_target_hosts%& option specifies a list of IP addresses that are to
5879 be entirely ignored. This option is present because a number of cases have been
5880 encountered where MX records in the DNS point to host names
5881 whose IP addresses are 0.0.0.0 or are in the 127 subnet (typically 127.0.0.1).
5882 Completely ignoring these IP addresses causes Exim to fail to route the
5883 email address, so it bounces. Otherwise, Exim would log a routing problem, and
5884 continue to try to deliver the message periodically until the address timed
5891 data = ${lookup{$local_part}lsearch{/etc/aliases}}
5893 file_transport = address_file
5894 pipe_transport = address_pipe
5896 Control reaches this and subsequent routers only for addresses in the local
5897 domains. This router checks to see whether the local part is defined as an
5898 alias in the &_/etc/aliases_& file, and if so, redirects it according to the
5899 data that it looks up from that file. If no data is found for the local part,
5900 the value of the &%data%& option is empty, causing the address to be passed to
5903 &_/etc/aliases_& is a conventional name for the system aliases file that is
5904 often used. That is why it is referenced by from the default configuration
5905 file. However, you can change this by setting SYSTEM_ALIASES_FILE in
5906 &_Local/Makefile_& before building Exim.
5911 # local_part_suffix = +* : -*
5912 # local_part_suffix_optional
5913 file = $home/.forward
5918 file_transport = address_file
5919 pipe_transport = address_pipe
5920 reply_transport = address_reply
5922 This is the most complicated router in the default configuration. It is another
5923 redirection router, but this time it is looking for forwarding data set up by
5924 individual users. The &%check_local_user%& setting specifies a check that the
5925 local part of the address is the login name of a local user. If it is not, the
5926 router is skipped. The two commented options that follow &%check_local_user%&,
5929 # local_part_suffix = +* : -*
5930 # local_part_suffix_optional
5932 .vindex "&$local_part_suffix$&"
5933 show how you can specify the recognition of local part suffixes. If the first
5934 is uncommented, a suffix beginning with either a plus or a minus sign, followed
5935 by any sequence of characters, is removed from the local part and placed in the
5936 variable &$local_part_suffix$&. The second suffix option specifies that the
5937 presence of a suffix in the local part is optional. When a suffix is present,
5938 the check for a local login uses the local part with the suffix removed.
5940 When a local user account is found, the file called &_.forward_& in the user's
5941 home directory is consulted. If it does not exist, or is empty, the router
5942 declines. Otherwise, the contents of &_.forward_& are interpreted as
5943 redirection data (see chapter &<<CHAPredirect>>& for more details).
5945 .cindex "Sieve filter" "enabling in default router"
5946 Traditional &_.forward_& files contain just a list of addresses, pipes, or
5947 files. Exim supports this by default. However, if &%allow_filter%& is set (it
5948 is commented out by default), the contents of the file are interpreted as a set
5949 of Exim or Sieve filtering instructions, provided the file begins with &"#Exim
5950 filter"& or &"#Sieve filter"&, respectively. User filtering is discussed in the
5951 separate document entitled &'Exim's interfaces to mail filtering'&.
5953 The &%no_verify%& and &%no_expn%& options mean that this router is skipped when
5954 verifying addresses, or when running as a consequence of an SMTP EXPN command.
5955 There are two reasons for doing this:
5958 Whether or not a local user has a &_.forward_& file is not really relevant when
5959 checking an address for validity; it makes sense not to waste resources doing
5962 More importantly, when Exim is verifying addresses or handling an EXPN
5963 command during an SMTP session, it is running as the Exim user, not as root.
5964 The group is the Exim group, and no additional groups are set up.
5965 It may therefore not be possible for Exim to read users' &_.forward_& files at
5969 The setting of &%check_ancestor%& prevents the router from generating a new
5970 address that is the same as any previous address that was redirected. (This
5971 works round a problem concerning a bad interaction between aliasing and
5972 forwarding &-- see section &<<SECTredlocmai>>&).
5974 The final three option settings specify the transports that are to be used when
5975 forwarding generates a direct delivery to a file, or to a pipe, or sets up an
5976 auto-reply, respectively. For example, if a &_.forward_& file contains
5978 a.nother@elsewhere.example, /home/spqr/archive
5980 the delivery to &_/home/spqr/archive_& is done by running the &%address_file%&
5986 # local_part_suffix = +* : -*
5987 # local_part_suffix_optional
5988 transport = local_delivery
5990 The final router sets up delivery into local mailboxes, provided that the local
5991 part is the name of a local login, by accepting the address and assigning it to
5992 the &(local_delivery)& transport. Otherwise, we have reached the end of the
5993 routers, so the address is bounced. The commented suffix settings fulfil the
5994 same purpose as they do for the &(userforward)& router.
5997 .section "Transport configuration" "SECID56"
5998 .cindex "default" "transports"
5999 .cindex "transports" "default"
6000 Transports define mechanisms for actually delivering messages. They operate
6001 only when referenced from routers, so the order in which they are defined does
6002 not matter. The transports section of the configuration starts with
6006 One remote transport and four local transports are defined.
6012 This transport is used for delivering messages over SMTP connections.
6013 The list of remote hosts comes from the router.
6014 The &%hosts_try_prdr%& option enables an efficiency SMTP option.
6015 It is negotiated between client and server
6016 and not expected to cause problems but can be disabled if needed.
6017 All other options are defaulted.
6021 file = /var/mail/$local_part
6028 This &(appendfile)& transport is used for local delivery to user mailboxes in
6029 traditional BSD mailbox format. By default it runs under the uid and gid of the
6030 local user, which requires the sticky bit to be set on the &_/var/mail_&
6031 directory. Some systems use the alternative approach of running mail deliveries
6032 under a particular group instead of using the sticky bit. The commented options
6033 show how this can be done.
6035 Exim adds three headers to the message as it delivers it: &'Delivery-date:'&,
6036 &'Envelope-to:'& and &'Return-path:'&. This action is requested by the three
6037 similarly-named options above.
6043 This transport is used for handling deliveries to pipes that are generated by
6044 redirection (aliasing or users' &_.forward_& files). The &%return_output%&
6045 option specifies that any output generated by the pipe is to be returned to the
6054 This transport is used for handling deliveries to files that are generated by
6055 redirection. The name of the file is not specified in this instance of
6056 &(appendfile)&, because it comes from the &(redirect)& router.
6061 This transport is used for handling automatic replies generated by users'
6066 .section "Default retry rule" "SECID57"
6067 .cindex "retry" "default rule"
6068 .cindex "default" "retry rule"
6069 The retry section of the configuration file contains rules which affect the way
6070 Exim retries deliveries that cannot be completed at the first attempt. It is
6071 introduced by the line
6075 In the default configuration, there is just one rule, which applies to all
6078 * * F,2h,15m; G,16h,1h,1.5; F,4d,6h
6080 This causes any temporarily failing address to be retried every 15 minutes for
6081 2 hours, then at intervals starting at one hour and increasing by a factor of
6082 1.5 until 16 hours have passed, then every 6 hours up to 4 days. If an address
6083 is not delivered after 4 days of temporary failure, it is bounced.
6085 If the retry section is removed from the configuration, or is empty (that is,
6086 if no retry rules are defined), Exim will not retry deliveries. This turns
6087 temporary errors into permanent errors.
6090 .section "Rewriting configuration" "SECID58"
6091 The rewriting section of the configuration, introduced by
6095 contains rules for rewriting addresses in messages as they arrive. There are no
6096 rewriting rules in the default configuration file.
6100 .section "Authenticators configuration" "SECTdefconfauth"
6101 .cindex "AUTH" "configuration"
6102 The authenticators section of the configuration, introduced by
6104 begin authenticators
6106 defines mechanisms for the use of the SMTP AUTH command. The default
6107 configuration file contains two commented-out example authenticators
6108 which support plaintext username/password authentication using the
6109 standard PLAIN mechanism and the traditional but non-standard LOGIN
6110 mechanism, with Exim acting as the server. PLAIN and LOGIN are enough
6111 to support most MUA software.
6113 The example PLAIN authenticator looks like this:
6116 # driver = plaintext
6117 # server_set_id = $auth2
6118 # server_prompts = :
6119 # server_condition = Authentication is not yet configured
6120 # server_advertise_condition = ${if def:tls_in_cipher }
6122 And the example LOGIN authenticator looks like this:
6125 # driver = plaintext
6126 # server_set_id = $auth1
6127 # server_prompts = <| Username: | Password:
6128 # server_condition = Authentication is not yet configured
6129 # server_advertise_condition = ${if def:tls_in_cipher }
6132 The &%server_set_id%& option makes Exim remember the authenticated username
6133 in &$authenticated_id$&, which can be used later in ACLs or routers. The
6134 &%server_prompts%& option configures the &(plaintext)& authenticator so
6135 that it implements the details of the specific authentication mechanism,
6136 i.e. PLAIN or LOGIN. The &%server_advertise_condition%& setting controls
6137 when Exim offers authentication to clients; in the examples, this is only
6138 when TLS or SSL has been started, so to enable the authenticators you also
6139 need to add support for TLS as described in section &<<SECTdefconfmain>>&.
6141 The &%server_condition%& setting defines how to verify that the username and
6142 password are correct. In the examples it just produces an error message.
6143 To make the authenticators work, you can use a string expansion
6144 expression like one of the examples in chapter &<<CHAPplaintext>>&.
6146 Beware that the sequence of the parameters to PLAIN and LOGIN differ; the
6147 usercode and password are in different positions.
6148 Chapter &<<CHAPplaintext>>& covers both.
6150 .ecindex IIDconfiwal
6154 . ////////////////////////////////////////////////////////////////////////////
6155 . ////////////////////////////////////////////////////////////////////////////
6157 .chapter "Regular expressions" "CHAPregexp"
6159 .cindex "regular expressions" "library"
6161 Exim supports the use of regular expressions in many of its options. It
6162 uses the PCRE regular expression library; this provides regular expression
6163 matching that is compatible with Perl 5. The syntax and semantics of
6164 regular expressions is discussed in many Perl reference books, and also in
6165 Jeffrey Friedl's &'Mastering Regular Expressions'&, which is published by
6166 O'Reilly (see &url(http://www.oreilly.com/catalog/regex2/)).
6168 The documentation for the syntax and semantics of the regular expressions that
6169 are supported by PCRE is included in the PCRE distribution, and no further
6170 description is included here. The PCRE functions are called from Exim using
6171 the default option settings (that is, with no PCRE options set), except that
6172 the PCRE_CASELESS option is set when the matching is required to be
6175 In most cases, when a regular expression is required in an Exim configuration,
6176 it has to start with a circumflex, in order to distinguish it from plain text
6177 or an &"ends with"& wildcard. In this example of a configuration setting, the
6178 second item in the colon-separated list is a regular expression.
6180 domains = a.b.c : ^\\d{3} : *.y.z : ...
6182 The doubling of the backslash is required because of string expansion that
6183 precedes interpretation &-- see section &<<SECTlittext>>& for more discussion
6184 of this issue, and a way of avoiding the need for doubling backslashes. The
6185 regular expression that is eventually used in this example contains just one
6186 backslash. The circumflex is included in the regular expression, and has the
6187 normal effect of &"anchoring"& it to the start of the string that is being
6190 There are, however, two cases where a circumflex is not required for the
6191 recognition of a regular expression: these are the &%match%& condition in a
6192 string expansion, and the &%matches%& condition in an Exim filter file. In
6193 these cases, the relevant string is always treated as a regular expression; if
6194 it does not start with a circumflex, the expression is not anchored, and can
6195 match anywhere in the subject string.
6197 In all cases, if you want a regular expression to match at the end of a string,
6198 you must code the $ metacharacter to indicate this. For example:
6200 domains = ^\\d{3}\\.example
6202 matches the domain &'123.example'&, but it also matches &'123.example.com'&.
6205 domains = ^\\d{3}\\.example\$
6207 if you want &'example'& to be the top-level domain. The backslash before the
6208 $ is needed because string expansion also interprets dollar characters.
6212 . ////////////////////////////////////////////////////////////////////////////
6213 . ////////////////////////////////////////////////////////////////////////////
6215 .chapter "File and database lookups" "CHAPfdlookup"
6216 .scindex IIDfidalo1 "file" "lookups"
6217 .scindex IIDfidalo2 "database" "lookups"
6218 .cindex "lookup" "description of"
6219 Exim can be configured to look up data in files or databases as it processes
6220 messages. Two different kinds of syntax are used:
6223 A string that is to be expanded may contain explicit lookup requests. These
6224 cause parts of the string to be replaced by data that is obtained from the
6225 lookup. Lookups of this type are conditional expansion items. Different results
6226 can be defined for the cases of lookup success and failure. See chapter
6227 &<<CHAPexpand>>&, where string expansions are described in detail.
6229 Lists of domains, hosts, and email addresses can contain lookup requests as a
6230 way of avoiding excessively long linear lists. In this case, the data that is
6231 returned by the lookup is often (but not always) discarded; whether the lookup
6232 succeeds or fails is what really counts. These kinds of list are described in
6233 chapter &<<CHAPdomhosaddlists>>&.
6236 String expansions, lists, and lookups interact with each other in such a way
6237 that there is no order in which to describe any one of them that does not
6238 involve references to the others. Each of these three chapters makes more sense
6239 if you have read the other two first. If you are reading this for the first
6240 time, be aware that some of it will make a lot more sense after you have read
6241 chapters &<<CHAPdomhosaddlists>>& and &<<CHAPexpand>>&.
6243 .section "Examples of different lookup syntax" "SECID60"
6244 It is easy to confuse the two different kinds of lookup, especially as the
6245 lists that may contain the second kind are always expanded before being
6246 processed as lists. Therefore, they may also contain lookups of the first kind.
6247 Be careful to distinguish between the following two examples:
6249 domains = ${lookup{$sender_host_address}lsearch{/some/file}}
6250 domains = lsearch;/some/file
6252 The first uses a string expansion, the result of which must be a domain list.
6253 No strings have been specified for a successful or a failing lookup; the
6254 defaults in this case are the looked-up data and an empty string, respectively.
6255 The expansion takes place before the string is processed as a list, and the
6256 file that is searched could contain lines like this:
6258 192.168.3.4: domain1:domain2:...
6259 192.168.1.9: domain3:domain4:...
6261 When the lookup succeeds, the result of the expansion is a list of domains (and
6262 possibly other types of item that are allowed in domain lists).
6264 In the second example, the lookup is a single item in a domain list. It causes
6265 Exim to use a lookup to see if the domain that is being processed can be found
6266 in the file. The file could contains lines like this:
6271 Any data that follows the keys is not relevant when checking that the domain
6272 matches the list item.
6274 It is possible, though no doubt confusing, to use both kinds of lookup at once.
6275 Consider a file containing lines like this:
6277 192.168.5.6: lsearch;/another/file
6279 If the value of &$sender_host_address$& is 192.168.5.6, expansion of the
6280 first &%domains%& setting above generates the second setting, which therefore
6281 causes a second lookup to occur.
6283 The rest of this chapter describes the different lookup types that are
6284 available. Any of them can be used in any part of the configuration where a
6285 lookup is permitted.
6288 .section "Lookup types" "SECID61"
6289 .cindex "lookup" "types of"
6290 .cindex "single-key lookup" "definition of"
6291 Two different types of data lookup are implemented:
6294 The &'single-key'& type requires the specification of a file in which to look,
6295 and a single key to search for. The key must be a non-empty string for the
6296 lookup to succeed. The lookup type determines how the file is searched.
6298 .cindex "query-style lookup" "definition of"
6299 The &'query-style'& type accepts a generalized database query. No particular
6300 key value is assumed by Exim for query-style lookups. You can use whichever
6301 Exim variables you need to construct the database query.
6304 The code for each lookup type is in a separate source file that is included in
6305 the binary of Exim only if the corresponding compile-time option is set. The
6306 default settings in &_src/EDITME_& are:
6311 which means that only linear searching and DBM lookups are included by default.
6312 For some types of lookup (e.g. SQL databases), you need to install appropriate
6313 libraries and header files before building Exim.
6318 .section "Single-key lookup types" "SECTsinglekeylookups"
6319 .cindex "lookup" "single-key types"
6320 .cindex "single-key lookup" "list of types"
6321 The following single-key lookup types are implemented:
6324 .cindex "cdb" "description of"
6325 .cindex "lookup" "cdb"
6326 .cindex "binary zero" "in lookup key"
6327 &(cdb)&: The given file is searched as a Constant DataBase file, using the key
6328 string without a terminating binary zero. The cdb format is designed for
6329 indexed files that are read frequently and never updated, except by total
6330 re-creation. As such, it is particularly suitable for large files containing
6331 aliases or other indexed data referenced by an MTA. Information about cdb can
6332 be found in several places:
6334 &url(http://www.pobox.com/~djb/cdb.html)
6335 &url(ftp://ftp.corpit.ru/pub/tinycdb/)
6336 &url(http://packages.debian.org/stable/utils/freecdb.html)
6338 A cdb distribution is not needed in order to build Exim with cdb support,
6339 because the code for reading cdb files is included directly in Exim itself.
6340 However, no means of building or testing cdb files is provided with Exim, so
6341 you need to obtain a cdb distribution in order to do this.
6343 .cindex "DBM" "lookup type"
6344 .cindex "lookup" "dbm"
6345 .cindex "binary zero" "in lookup key"
6346 &(dbm)&: Calls to DBM library functions are used to extract data from the given
6347 DBM file by looking up the record with the given key. A terminating binary
6348 zero is included in the key that is passed to the DBM library. See section
6349 &<<SECTdb>>& for a discussion of DBM libraries.
6351 .cindex "Berkeley DB library" "file format"
6352 For all versions of Berkeley DB, Exim uses the DB_HASH style of database
6353 when building DBM files using the &%exim_dbmbuild%& utility. However, when
6354 using Berkeley DB versions 3 or 4, it opens existing databases for reading with
6355 the DB_UNKNOWN option. This enables it to handle any of the types of database
6356 that the library supports, and can be useful for accessing DBM files created by
6357 other applications. (For earlier DB versions, DB_HASH is always used.)
6359 .cindex "lookup" "dbmjz"
6360 .cindex "lookup" "dbm &-- embedded NULs"
6362 .cindex "dbmjz lookup type"
6363 &(dbmjz)&: This is the same as &(dbm)&, except that the lookup key is
6364 interpreted as an Exim list; the elements of the list are joined together with
6365 ASCII NUL characters to form the lookup key. An example usage would be to
6366 authenticate incoming SMTP calls using the passwords from Cyrus SASL's
6367 &_/etc/sasldb2_& file with the &(gsasl)& authenticator or Exim's own
6368 &(cram_md5)& authenticator.
6370 .cindex "lookup" "dbmnz"
6371 .cindex "lookup" "dbm &-- terminating zero"
6372 .cindex "binary zero" "in lookup key"
6374 .cindex "&_/etc/userdbshadow.dat_&"
6375 .cindex "dbmnz lookup type"
6376 &(dbmnz)&: This is the same as &(dbm)&, except that a terminating binary zero
6377 is not included in the key that is passed to the DBM library. You may need this
6378 if you want to look up data in files that are created by or shared with some
6379 other application that does not use terminating zeros. For example, you need to
6380 use &(dbmnz)& rather than &(dbm)& if you want to authenticate incoming SMTP
6381 calls using the passwords from Courier's &_/etc/userdbshadow.dat_& file. Exim's
6382 utility program for creating DBM files (&'exim_dbmbuild'&) includes the zeros
6383 by default, but has an option to omit them (see section &<<SECTdbmbuild>>&).
6385 .cindex "lookup" "dsearch"
6386 .cindex "dsearch lookup type"
6387 &(dsearch)&: The given file must be a directory; this is searched for an entry
6388 whose name is the key by calling the &[lstat()]& function. The key may not
6389 contain any forward slash characters. If &[lstat()]& succeeds, the result of
6390 the lookup is the name of the entry, which may be a file, directory,
6391 symbolic link, or any other kind of directory entry. An example of how this
6392 lookup can be used to support virtual domains is given in section
6393 &<<SECTvirtualdomains>>&.
6395 .cindex "lookup" "iplsearch"
6396 .cindex "iplsearch lookup type"
6397 &(iplsearch)&: The given file is a text file containing keys and data. A key is
6398 terminated by a colon or white space or the end of the line. The keys in the
6399 file must be IP addresses, or IP addresses with CIDR masks. Keys that involve
6400 IPv6 addresses must be enclosed in quotes to prevent the first internal colon
6401 being interpreted as a key terminator. For example:
6403 1.2.3.4: data for 1.2.3.4
6404 192.168.0.0/16: data for 192.168.0.0/16
6405 "abcd::cdab": data for abcd::cdab
6406 "abcd:abcd::/32" data for abcd:abcd::/32
6408 The key for an &(iplsearch)& lookup must be an IP address (without a mask). The
6409 file is searched linearly, using the CIDR masks where present, until a matching
6410 key is found. The first key that matches is used; there is no attempt to find a
6411 &"best"& match. Apart from the way the keys are matched, the processing for
6412 &(iplsearch)& is the same as for &(lsearch)&.
6414 &*Warning 1*&: Unlike most other single-key lookup types, a file of data for
6415 &(iplsearch)& can &'not'& be turned into a DBM or cdb file, because those
6416 lookup types support only literal keys.
6418 &*Warning 2*&: In a host list, you must always use &(net-iplsearch)& so that
6419 the implicit key is the host's IP address rather than its name (see section
6420 &<<SECThoslispatsikey>>&).
6422 .cindex "linear search"
6423 .cindex "lookup" "lsearch"
6424 .cindex "lsearch lookup type"
6425 .cindex "case sensitivity" "in lsearch lookup"
6426 &(lsearch)&: The given file is a text file that is searched linearly for a
6427 line beginning with the search key, terminated by a colon or white space or the
6428 end of the line. The search is case-insensitive; that is, upper and lower case
6429 letters are treated as the same. The first occurrence of the key that is found
6430 in the file is used.
6432 White space between the key and the colon is permitted. The remainder of the
6433 line, with leading and trailing white space removed, is the data. This can be
6434 continued onto subsequent lines by starting them with any amount of white
6435 space, but only a single space character is included in the data at such a
6436 junction. If the data begins with a colon, the key must be terminated by a
6441 Empty lines and lines beginning with # are ignored, even if they occur in the
6442 middle of an item. This is the traditional textual format of alias files. Note
6443 that the keys in an &(lsearch)& file are literal strings. There is no
6444 wildcarding of any kind.
6446 .cindex "lookup" "lsearch &-- colons in keys"
6447 .cindex "white space" "in lsearch key"
6448 In most &(lsearch)& files, keys are not required to contain colons or #
6449 characters, or white space. However, if you need this feature, it is available.
6450 If a key begins with a doublequote character, it is terminated only by a
6451 matching quote (or end of line), and the normal escaping rules apply to its
6452 contents (see section &<<SECTstrings>>&). An optional colon is permitted after
6453 quoted keys (exactly as for unquoted keys). There is no special handling of
6454 quotes for the data part of an &(lsearch)& line.
6457 .cindex "NIS lookup type"
6458 .cindex "lookup" "NIS"
6459 .cindex "binary zero" "in lookup key"
6460 &(nis)&: The given file is the name of a NIS map, and a NIS lookup is done with
6461 the given key, without a terminating binary zero. There is a variant called
6462 &(nis0)& which does include the terminating binary zero in the key. This is
6463 reportedly needed for Sun-style alias files. Exim does not recognize NIS
6464 aliases; the full map names must be used.
6467 .cindex "wildlsearch lookup type"
6468 .cindex "lookup" "wildlsearch"
6469 .cindex "nwildlsearch lookup type"
6470 .cindex "lookup" "nwildlsearch"
6471 &(wildlsearch)& or &(nwildlsearch)&: These search a file linearly, like
6472 &(lsearch)&, but instead of being interpreted as a literal string, each key in
6473 the file may be wildcarded. The difference between these two lookup types is
6474 that for &(wildlsearch)&, each key in the file is string-expanded before being
6475 used, whereas for &(nwildlsearch)&, no expansion takes place.
6477 .cindex "case sensitivity" "in (n)wildlsearch lookup"
6478 Like &(lsearch)&, the testing is done case-insensitively. However, keys in the
6479 file that are regular expressions can be made case-sensitive by the use of
6480 &`(-i)`& within the pattern. The following forms of wildcard are recognized:
6482 . ==== As this is a nested list, any displays it contains must be indented
6483 . ==== as otherwise they are too far to the left.
6486 The string may begin with an asterisk to mean &"ends with"&. For example:
6488 *.a.b.c data for anything.a.b.c
6489 *fish data for anythingfish
6492 The string may begin with a circumflex to indicate a regular expression. For
6493 example, for &(wildlsearch)&:
6495 ^\N\d+\.a\.b\N data for <digits>.a.b
6497 Note the use of &`\N`& to disable expansion of the contents of the regular
6498 expression. If you are using &(nwildlsearch)&, where the keys are not
6499 string-expanded, the equivalent entry is:
6501 ^\d+\.a\.b data for <digits>.a.b
6503 The case-insensitive flag is set at the start of compiling the regular
6504 expression, but it can be turned off by using &`(-i)`& at an appropriate point.
6505 For example, to make the entire pattern case-sensitive:
6507 ^(?-i)\d+\.a\.b data for <digits>.a.b
6510 If the regular expression contains white space or colon characters, you must
6511 either quote it (see &(lsearch)& above), or represent these characters in other
6512 ways. For example, &`\s`& can be used for white space and &`\x3A`& for a
6513 colon. This may be easier than quoting, because if you quote, you have to
6514 escape all the backslashes inside the quotes.
6516 &*Note*&: It is not possible to capture substrings in a regular expression
6517 match for later use, because the results of all lookups are cached. If a lookup
6518 is repeated, the result is taken from the cache, and no actual pattern matching
6519 takes place. The values of all the numeric variables are unset after a
6520 &((n)wildlsearch)& match.
6523 Although I cannot see it being of much use, the general matching function that
6524 is used to implement &((n)wildlsearch)& means that the string may begin with a
6525 lookup name terminated by a semicolon, and followed by lookup data. For
6528 cdb;/some/file data for keys that match the file
6530 The data that is obtained from the nested lookup is discarded.
6533 Keys that do not match any of these patterns are interpreted literally. The
6534 continuation rules for the data are the same as for &(lsearch)&, and keys may
6535 be followed by optional colons.
6537 &*Warning*&: Unlike most other single-key lookup types, a file of data for
6538 &((n)wildlsearch)& can &'not'& be turned into a DBM or cdb file, because those
6539 lookup types support only literal keys.
6543 .section "Query-style lookup types" "SECID62"
6544 .cindex "lookup" "query-style types"
6545 .cindex "query-style lookup" "list of types"
6546 The supported query-style lookup types are listed below. Further details about
6547 many of them are given in later sections.
6550 .cindex "DNS" "as a lookup type"
6551 .cindex "lookup" "DNS"
6552 &(dnsdb)&: This does a DNS search for one or more records whose domain names
6553 are given in the supplied query. The resulting data is the contents of the
6554 records. See section &<<SECTdnsdb>>&.
6556 .cindex "InterBase lookup type"
6557 .cindex "lookup" "InterBase"
6558 &(ibase)&: This does a lookup in an InterBase database.
6560 .cindex "LDAP" "lookup type"
6561 .cindex "lookup" "LDAP"
6562 &(ldap)&: This does an LDAP lookup using a query in the form of a URL, and
6563 returns attributes from a single entry. There is a variant called &(ldapm)&
6564 that permits values from multiple entries to be returned. A third variant
6565 called &(ldapdn)& returns the Distinguished Name of a single entry instead of
6566 any attribute values. See section &<<SECTldap>>&.
6568 .cindex "MySQL" "lookup type"
6569 .cindex "lookup" "MySQL"
6570 &(mysql)&: The format of the query is an SQL statement that is passed to a
6571 MySQL database. See section &<<SECTsql>>&.
6573 .cindex "NIS+ lookup type"
6574 .cindex "lookup" "NIS+"
6575 &(nisplus)&: This does a NIS+ lookup using a query that can specify the name of
6576 the field to be returned. See section &<<SECTnisplus>>&.
6578 .cindex "Oracle" "lookup type"
6579 .cindex "lookup" "Oracle"
6580 &(oracle)&: The format of the query is an SQL statement that is passed to an
6581 Oracle database. See section &<<SECTsql>>&.
6583 .cindex "lookup" "passwd"
6584 .cindex "passwd lookup type"
6585 .cindex "&_/etc/passwd_&"
6586 &(passwd)& is a query-style lookup with queries that are just user names. The
6587 lookup calls &[getpwnam()]& to interrogate the system password data, and on
6588 success, the result string is the same as you would get from an &(lsearch)&
6589 lookup on a traditional &_/etc/passwd file_&, though with &`*`& for the
6590 password value. For example:
6592 *:42:42:King Rat:/home/kr:/bin/bash
6595 .cindex "PostgreSQL lookup type"
6596 .cindex "lookup" "PostgreSQL"
6597 &(pgsql)&: The format of the query is an SQL statement that is passed to a
6598 PostgreSQL database. See section &<<SECTsql>>&.
6601 .cindex "sqlite lookup type"
6602 .cindex "lookup" "sqlite"
6603 &(sqlite)&: The format of the query is a file name followed by an SQL statement
6604 that is passed to an SQLite database. See section &<<SECTsqlite>>&.
6607 &(testdb)&: This is a lookup type that is used for testing Exim. It is
6608 not likely to be useful in normal operation.
6610 .cindex "whoson lookup type"
6611 .cindex "lookup" "whoson"
6612 &(whoson)&: &'Whoson'& (&url(http://whoson.sourceforge.net)) is a protocol that
6613 allows a server to check whether a particular (dynamically allocated) IP
6614 address is currently allocated to a known (trusted) user and, optionally, to
6615 obtain the identity of the said user. For SMTP servers, &'Whoson'& was popular
6616 at one time for &"POP before SMTP"& authentication, but that approach has been
6617 superseded by SMTP authentication. In Exim, &'Whoson'& can be used to implement
6618 &"POP before SMTP"& checking using ACL statements such as
6620 require condition = \
6621 ${lookup whoson {$sender_host_address}{yes}{no}}
6623 The query consists of a single IP address. The value returned is the name of
6624 the authenticated user, which is stored in the variable &$value$&. However, in
6625 this example, the data in &$value$& is not used; the result of the lookup is
6626 one of the fixed strings &"yes"& or &"no"&.
6631 .section "Temporary errors in lookups" "SECID63"
6632 .cindex "lookup" "temporary error in"
6633 Lookup functions can return temporary error codes if the lookup cannot be
6634 completed. For example, an SQL or LDAP database might be unavailable. For this
6635 reason, it is not advisable to use a lookup that might do this for critical
6636 options such as a list of local domains.
6638 When a lookup cannot be completed in a router or transport, delivery
6639 of the message (to the relevant address) is deferred, as for any other
6640 temporary error. In other circumstances Exim may assume the lookup has failed,
6641 or may give up altogether.
6645 .section "Default values in single-key lookups" "SECTdefaultvaluelookups"
6646 .cindex "wildcard lookups"
6647 .cindex "lookup" "default values"
6648 .cindex "lookup" "wildcard"
6649 .cindex "lookup" "* added to type"
6650 .cindex "default" "in single-key lookups"
6651 In this context, a &"default value"& is a value specified by the administrator
6652 that is to be used if a lookup fails.
6654 &*Note:*& This section applies only to single-key lookups. For query-style
6655 lookups, the facilities of the query language must be used. An attempt to
6656 specify a default for a query-style lookup provokes an error.
6658 If &"*"& is added to a single-key lookup type (for example, &%lsearch*%&)
6659 and the initial lookup fails, the key &"*"& is looked up in the file to
6660 provide a default value. See also the section on partial matching below.
6662 .cindex "*@ with single-key lookup"
6663 .cindex "lookup" "*@ added to type"
6664 .cindex "alias file" "per-domain default"
6665 Alternatively, if &"*@"& is added to a single-key lookup type (for example
6666 &%dbm*@%&) then, if the initial lookup fails and the key contains an @
6667 character, a second lookup is done with everything before the last @ replaced
6668 by *. This makes it possible to provide per-domain defaults in alias files
6669 that include the domains in the keys. If the second lookup fails (or doesn't
6670 take place because there is no @ in the key), &"*"& is looked up.
6671 For example, a &(redirect)& router might contain:
6673 data = ${lookup{$local_part@$domain}lsearch*@{/etc/mix-aliases}}
6675 Suppose the address that is being processed is &'jane@eyre.example'&. Exim
6676 looks up these keys, in this order:
6682 The data is taken from whichever key it finds first. &*Note*&: In an
6683 &(lsearch)& file, this does not mean the first of these keys in the file. A
6684 complete scan is done for each key, and only if it is not found at all does
6685 Exim move on to try the next key.
6689 .section "Partial matching in single-key lookups" "SECTpartiallookup"
6690 .cindex "partial matching"
6691 .cindex "wildcard lookups"
6692 .cindex "lookup" "partial matching"
6693 .cindex "lookup" "wildcard"
6694 .cindex "asterisk" "in search type"
6695 The normal operation of a single-key lookup is to search the file for an exact
6696 match with the given key. However, in a number of situations where domains are
6697 being looked up, it is useful to be able to do partial matching. In this case,
6698 information in the file that has a key starting with &"*."& is matched by any
6699 domain that ends with the components that follow the full stop. For example, if
6700 a key in a DBM file is
6702 *.dates.fict.example
6704 then when partial matching is enabled this is matched by (amongst others)
6705 &'2001.dates.fict.example'& and &'1984.dates.fict.example'&. It is also matched
6706 by &'dates.fict.example'&, if that does not appear as a separate key in the
6709 &*Note*&: Partial matching is not available for query-style lookups. It is
6710 also not available for any lookup items in address lists (see section
6711 &<<SECTaddresslist>>&).
6713 Partial matching is implemented by doing a series of separate lookups using
6714 keys constructed by modifying the original subject key. This means that it can
6715 be used with any of the single-key lookup types, provided that
6716 partial matching keys
6717 beginning with a special prefix (default &"*."&) are included in the data file.
6718 Keys in the file that do not begin with the prefix are matched only by
6719 unmodified subject keys when partial matching is in use.
6721 Partial matching is requested by adding the string &"partial-"& to the front of
6722 the name of a single-key lookup type, for example, &%partial-dbm%&. When this
6723 is done, the subject key is first looked up unmodified; if that fails, &"*."&
6724 is added at the start of the subject key, and it is looked up again. If that
6725 fails, further lookups are tried with dot-separated components removed from the
6726 start of the subject key, one-by-one, and &"*."& added on the front of what
6729 A minimum number of two non-* components are required. This can be adjusted
6730 by including a number before the hyphen in the search type. For example,
6731 &%partial3-lsearch%& specifies a minimum of three non-* components in the
6732 modified keys. Omitting the number is equivalent to &"partial2-"&. If the
6733 subject key is &'2250.dates.fict.example'& then the following keys are looked
6734 up when the minimum number of non-* components is two:
6736 2250.dates.fict.example
6737 *.2250.dates.fict.example
6738 *.dates.fict.example
6741 As soon as one key in the sequence is successfully looked up, the lookup
6744 .cindex "lookup" "partial matching &-- changing prefix"
6745 .cindex "prefix" "for partial matching"
6746 The use of &"*."& as the partial matching prefix is a default that can be
6747 changed. The motivation for this feature is to allow Exim to operate with file
6748 formats that are used by other MTAs. A different prefix can be supplied in
6749 parentheses instead of the hyphen after &"partial"&. For example:
6751 domains = partial(.)lsearch;/some/file
6753 In this example, if the domain is &'a.b.c'&, the sequence of lookups is
6754 &`a.b.c`&, &`.a.b.c`&, and &`.b.c`& (the default minimum of 2 non-wild
6755 components is unchanged). The prefix may consist of any punctuation characters
6756 other than a closing parenthesis. It may be empty, for example:
6758 domains = partial1()cdb;/some/file
6760 For this example, if the domain is &'a.b.c'&, the sequence of lookups is
6761 &`a.b.c`&, &`b.c`&, and &`c`&.
6763 If &"partial0"& is specified, what happens at the end (when the lookup with
6764 just one non-wild component has failed, and the original key is shortened right
6765 down to the null string) depends on the prefix:
6768 If the prefix has zero length, the whole lookup fails.
6770 If the prefix has length 1, a lookup for just the prefix is done. For
6771 example, the final lookup for &"partial0(.)"& is for &`.`& alone.
6773 Otherwise, if the prefix ends in a dot, the dot is removed, and the
6774 remainder is looked up. With the default prefix, therefore, the final lookup is
6775 for &"*"& on its own.
6777 Otherwise, the whole prefix is looked up.
6781 If the search type ends in &"*"& or &"*@"& (see section
6782 &<<SECTdefaultvaluelookups>>& above), the search for an ultimate default that
6783 this implies happens after all partial lookups have failed. If &"partial0"& is
6784 specified, adding &"*"& to the search type has no effect with the default
6785 prefix, because the &"*"& key is already included in the sequence of partial
6786 lookups. However, there might be a use for lookup types such as
6787 &"partial0(.)lsearch*"&.
6789 The use of &"*"& in lookup partial matching differs from its use as a wildcard
6790 in domain lists and the like. Partial matching works only in terms of
6791 dot-separated components; a key such as &`*fict.example`&
6792 in a database file is useless, because the asterisk in a partial matching
6793 subject key is always followed by a dot.
6798 .section "Lookup caching" "SECID64"
6799 .cindex "lookup" "caching"
6800 .cindex "caching" "lookup data"
6801 Exim caches all lookup results in order to avoid needless repetition of
6802 lookups. However, because (apart from the daemon) Exim operates as a collection
6803 of independent, short-lived processes, this caching applies only within a
6804 single Exim process. There is no inter-process lookup caching facility.
6806 For single-key lookups, Exim keeps the relevant files open in case there is
6807 another lookup that needs them. In some types of configuration this can lead to
6808 many files being kept open for messages with many recipients. To avoid hitting
6809 the operating system limit on the number of simultaneously open files, Exim
6810 closes the least recently used file when it needs to open more files than its
6811 own internal limit, which can be changed via the &%lookup_open_max%& option.
6813 The single-key lookup files are closed and the lookup caches are flushed at
6814 strategic points during delivery &-- for example, after all routing is
6820 .section "Quoting lookup data" "SECID65"
6821 .cindex "lookup" "quoting"
6822 .cindex "quoting" "in lookups"
6823 When data from an incoming message is included in a query-style lookup, there
6824 is the possibility of special characters in the data messing up the syntax of
6825 the query. For example, a NIS+ query that contains
6829 will be broken if the local part happens to contain a closing square bracket.
6830 For NIS+, data can be enclosed in double quotes like this:
6832 [name="$local_part"]
6834 but this still leaves the problem of a double quote in the data. The rule for
6835 NIS+ is that double quotes must be doubled. Other lookup types have different
6836 rules, and to cope with the differing requirements, an expansion operator
6837 of the following form is provided:
6839 ${quote_<lookup-type>:<string>}
6841 For example, the safest way to write the NIS+ query is
6843 [name="${quote_nisplus:$local_part}"]
6845 See chapter &<<CHAPexpand>>& for full coverage of string expansions. The quote
6846 operator can be used for all lookup types, but has no effect for single-key
6847 lookups, since no quoting is ever needed in their key strings.
6852 .section "More about dnsdb" "SECTdnsdb"
6853 .cindex "dnsdb lookup"
6854 .cindex "lookup" "dnsdb"
6855 .cindex "DNS" "as a lookup type"
6856 The &(dnsdb)& lookup type uses the DNS as its database. A simple query consists
6857 of a record type and a domain name, separated by an equals sign. For example,
6858 an expansion string could contain:
6860 ${lookup dnsdb{mx=a.b.example}{$value}fail}
6862 If the lookup succeeds, the result is placed in &$value$&, which in this case
6863 is used on its own as the result. If the lookup does not succeed, the
6864 &`fail`& keyword causes a &'forced expansion failure'& &-- see section
6865 &<<SECTforexpfai>>& for an explanation of what this means.
6867 The supported DNS record types are A, CNAME, MX, NS, PTR, SPF, SRV, TLSA and TXT,
6868 and, when Exim is compiled with IPv6 support, AAAA (and A6 if that is also
6869 configured). If no type is given, TXT is assumed. When the type is PTR,
6870 the data can be an IP address, written as normal; inversion and the addition of
6871 &%in-addr.arpa%& or &%ip6.arpa%& happens automatically. For example:
6873 ${lookup dnsdb{ptr=192.168.4.5}{$value}fail}
6875 If the data for a PTR record is not a syntactically valid IP address, it is not
6876 altered and nothing is added.
6878 .cindex "MX record" "in &(dnsdb)& lookup"
6879 .cindex "SRV record" "in &(dnsdb)& lookup"
6880 For an MX lookup, both the preference value and the host name are returned for
6881 each record, separated by a space. For an SRV lookup, the priority, weight,
6882 port, and host name are returned for each record, separated by spaces.
6884 For any record type, if multiple records are found (or, for A6 lookups, if a
6885 single record leads to multiple addresses), the data is returned as a
6886 concatenation, with newline as the default separator. The order, of course,
6887 depends on the DNS resolver. You can specify a different separator character
6888 between multiple records by putting a right angle-bracket followed immediately
6889 by the new separator at the start of the query. For example:
6891 ${lookup dnsdb{>: a=host1.example}}
6893 It is permitted to specify a space as the separator character. Further
6894 white space is ignored.
6896 .cindex "TXT record" "in &(dnsdb)& lookup"
6897 .cindex "SPF record" "in &(dnsdb)& lookup"
6898 For TXT records with multiple items of data, only the first item is returned,
6899 unless a separator for them is specified using a comma after the separator
6900 character followed immediately by the TXT record item separator. To concatenate
6901 items without a separator, use a semicolon instead. For SPF records the
6902 default behaviour is to concatenate multiple items without using a separator.
6904 ${lookup dnsdb{>\n,: txt=a.b.example}}
6905 ${lookup dnsdb{>\n; txt=a.b.example}}
6906 ${lookup dnsdb{spf=example.org}}
6908 It is permitted to specify a space as the separator character. Further
6909 white space is ignored.
6911 .section "Pseudo dnsdb record types" "SECID66"
6912 .cindex "MX record" "in &(dnsdb)& lookup"
6913 By default, both the preference value and the host name are returned for
6914 each MX record, separated by a space. If you want only host names, you can use
6915 the pseudo-type MXH:
6917 ${lookup dnsdb{mxh=a.b.example}}
6919 In this case, the preference values are omitted, and just the host names are
6922 .cindex "name server for enclosing domain"
6923 Another pseudo-type is ZNS (for &"zone NS"&). It performs a lookup for NS
6924 records on the given domain, but if none are found, it removes the first
6925 component of the domain name, and tries again. This process continues until NS
6926 records are found or there are no more components left (or there is a DNS
6927 error). In other words, it may return the name servers for a top-level domain,
6928 but it never returns the root name servers. If there are no NS records for the
6929 top-level domain, the lookup fails. Consider these examples:
6931 ${lookup dnsdb{zns=xxx.quercite.com}}
6932 ${lookup dnsdb{zns=xxx.edu}}
6934 Assuming that in each case there are no NS records for the full domain name,
6935 the first returns the name servers for &%quercite.com%&, and the second returns
6936 the name servers for &%edu%&.
6938 You should be careful about how you use this lookup because, unless the
6939 top-level domain does not exist, the lookup always returns some host names. The
6940 sort of use to which this might be put is for seeing if the name servers for a
6941 given domain are on a blacklist. You can probably assume that the name servers
6942 for the high-level domains such as &%com%& or &%co.uk%& are not going to be on
6945 .cindex "CSA" "in &(dnsdb)& lookup"
6946 A third pseudo-type is CSA (Client SMTP Authorization). This looks up SRV
6947 records according to the CSA rules, which are described in section
6948 &<<SECTverifyCSA>>&. Although &(dnsdb)& supports SRV lookups directly, this is
6949 not sufficient because of the extra parent domain search behaviour of CSA. The
6950 result of a successful lookup such as:
6952 ${lookup dnsdb {csa=$sender_helo_name}}
6954 has two space-separated fields: an authorization code and a target host name.
6955 The authorization code can be &"Y"& for yes, &"N"& for no, &"X"& for explicit
6956 authorization required but absent, or &"?"& for unknown.
6958 .cindex "A+" "in &(dnsdb)& lookup"
6959 The pseudo-type A+ performs an A6 lookup (if configured) followed by an AAAA
6960 and then an A lookup. All results are returned; defer processing
6961 (see below) is handled separately for each lookup. Example:
6963 ${lookup dnsdb {>; a+=$sender_helo_name}}
6967 .section "Multiple dnsdb lookups" "SECID67"
6968 In the previous sections, &(dnsdb)& lookups for a single domain are described.
6969 However, you can specify a list of domains or IP addresses in a single
6970 &(dnsdb)& lookup. The list is specified in the normal Exim way, with colon as
6971 the default separator, but with the ability to change this. For example:
6973 ${lookup dnsdb{one.domain.com:two.domain.com}}
6974 ${lookup dnsdb{a=one.host.com:two.host.com}}
6975 ${lookup dnsdb{ptr = <; 1.2.3.4 ; 4.5.6.8}}
6977 In order to retain backwards compatibility, there is one special case: if
6978 the lookup type is PTR and no change of separator is specified, Exim looks
6979 to see if the rest of the string is precisely one IPv6 address. In this
6980 case, it does not treat it as a list.
6982 The data from each lookup is concatenated, with newline separators by default,
6983 in the same way that multiple DNS records for a single item are handled. A
6984 different separator can be specified, as described above.
6986 Modifiers for &(dnsdb)& lookups are givien by optional keywords,
6987 each followed by a comma,
6988 that may appear before the record type.
6990 The &(dnsdb)& lookup fails only if all the DNS lookups fail. If there is a
6991 temporary DNS error for any of them, the behaviour is controlled by
6992 a defer-option modifier.
6993 The possible keywords are
6994 &"defer_strict"&, &"defer_never"&, and &"defer_lax"&.
6995 With &"strict"& behaviour, any temporary DNS error causes the
6996 whole lookup to defer. With &"never"& behaviour, a temporary DNS error is
6997 ignored, and the behaviour is as if the DNS lookup failed to find anything.
6998 With &"lax"& behaviour, all the queries are attempted, but a temporary DNS
6999 error causes the whole lookup to defer only if none of the other lookups
7000 succeed. The default is &"lax"&, so the following lookups are equivalent:
7002 ${lookup dnsdb{defer_lax,a=one.host.com:two.host.com}}
7003 ${lookup dnsdb{a=one.host.com:two.host.com}}
7005 Thus, in the default case, as long as at least one of the DNS lookups
7006 yields some data, the lookup succeeds.
7009 .cindex "DNSSEC" "dns lookup"
7010 Use of &(DNSSEC)& is controlled by a dnssec modifier.
7011 The possible keywords are
7012 &"dnssec_strict"&, &"dnssec_lax"&, and &"dnssec_never"&.
7013 With &"strict"& or &"lax"& DNSSEC information is requested
7015 With &"strict"& a response from the DNS resolver that
7016 is not labelled as authenticated data
7017 is treated as equivalent to a temporary DNS error.
7018 The default is &"never"&.
7020 See also the &$lookup_dnssec_authenticated$& variable.
7026 .section "More about LDAP" "SECTldap"
7027 .cindex "LDAP" "lookup, more about"
7028 .cindex "lookup" "LDAP"
7029 .cindex "Solaris" "LDAP"
7030 The original LDAP implementation came from the University of Michigan; this has
7031 become &"Open LDAP"&, and there are now two different releases. Another
7032 implementation comes from Netscape, and Solaris 7 and subsequent releases
7033 contain inbuilt LDAP support. Unfortunately, though these are all compatible at
7034 the lookup function level, their error handling is different. For this reason
7035 it is necessary to set a compile-time variable when building Exim with LDAP, to
7036 indicate which LDAP library is in use. One of the following should appear in
7037 your &_Local/Makefile_&:
7039 LDAP_LIB_TYPE=UMICHIGAN
7040 LDAP_LIB_TYPE=OPENLDAP1
7041 LDAP_LIB_TYPE=OPENLDAP2
7042 LDAP_LIB_TYPE=NETSCAPE
7043 LDAP_LIB_TYPE=SOLARIS
7045 If LDAP_LIB_TYPE is not set, Exim assumes &`OPENLDAP1`&, which has the
7046 same interface as the University of Michigan version.
7048 There are three LDAP lookup types in Exim. These behave slightly differently in
7049 the way they handle the results of a query:
7052 &(ldap)& requires the result to contain just one entry; if there are more, it
7055 &(ldapdn)& also requires the result to contain just one entry, but it is the
7056 Distinguished Name that is returned rather than any attribute values.
7058 &(ldapm)& permits the result to contain more than one entry; the attributes
7059 from all of them are returned.
7063 For &(ldap)& and &(ldapm)&, if a query finds only entries with no attributes,
7064 Exim behaves as if the entry did not exist, and the lookup fails. The format of
7065 the data returned by a successful lookup is described in the next section.
7066 First we explain how LDAP queries are coded.
7069 .section "Format of LDAP queries" "SECTforldaque"
7070 .cindex "LDAP" "query format"
7071 An LDAP query takes the form of a URL as defined in RFC 2255. For example, in
7072 the configuration of a &(redirect)& router one might have this setting:
7074 data = ${lookup ldap \
7075 {ldap:///cn=$local_part,o=University%20of%20Cambridge,\
7076 c=UK?mailbox?base?}}
7078 .cindex "LDAP" "with TLS"
7079 The URL may begin with &`ldap`& or &`ldaps`& if your LDAP library supports
7080 secure (encrypted) LDAP connections. The second of these ensures that an
7081 encrypted TLS connection is used.
7083 With sufficiently modern LDAP libraries, Exim supports forcing TLS over regular
7084 LDAP connections, rather than the SSL-on-connect &`ldaps`&.
7085 See the &%ldap_start_tls%& option.
7088 Starting with Exim 4.83, the initialization of LDAP with TLS is more tightly
7089 controlled. Every part of the TLS configuration can be configured by settings in
7090 &_exim.conf_&. Depending on the version of the client libraries installed on
7091 your system, some of the initialization may have required setting options in
7092 &_/etc/ldap.conf_& or &_~/.ldaprc_& to get TLS working with self-signed
7093 certificates. This revealed a nuance where the current UID that exim was
7094 running as could affect which config files it read. With Exim 4.83, these
7095 methods become optional, only taking effect if not specifically set in
7100 .section "LDAP quoting" "SECID68"
7101 .cindex "LDAP" "quoting"
7102 Two levels of quoting are required in LDAP queries, the first for LDAP itself
7103 and the second because the LDAP query is represented as a URL. Furthermore,
7104 within an LDAP query, two different kinds of quoting are required. For this
7105 reason, there are two different LDAP-specific quoting operators.
7107 The &%quote_ldap%& operator is designed for use on strings that are part of
7108 filter specifications. Conceptually, it first does the following conversions on
7116 in accordance with RFC 2254. The resulting string is then quoted according
7117 to the rules for URLs, that is, all non-alphanumeric characters except
7121 are converted to their hex values, preceded by a percent sign. For example:
7123 ${quote_ldap: a(bc)*, a<yz>; }
7127 %20a%5C28bc%5C29%5C2A%2C%20a%3Cyz%3E%3B%20
7129 Removing the URL quoting, this is (with a leading and a trailing space):
7131 a\28bc\29\2A, a<yz>;
7133 The &%quote_ldap_dn%& operator is designed for use on strings that are part of
7134 base DN specifications in queries. Conceptually, it first converts the string
7135 by inserting a backslash in front of any of the following characters:
7139 It also inserts a backslash before any leading spaces or # characters, and
7140 before any trailing spaces. (These rules are in RFC 2253.) The resulting string
7141 is then quoted according to the rules for URLs. For example:
7143 ${quote_ldap_dn: a(bc)*, a<yz>; }
7147 %5C%20a(bc)*%5C%2C%20a%5C%3Cyz%5C%3E%5C%3B%5C%20
7149 Removing the URL quoting, this is (with a trailing space):
7151 \ a(bc)*\, a\<yz\>\;\
7153 There are some further comments about quoting in the section on LDAP
7154 authentication below.
7157 .section "LDAP connections" "SECID69"
7158 .cindex "LDAP" "connections"
7159 The connection to an LDAP server may either be over TCP/IP, or, when OpenLDAP
7160 is in use, via a Unix domain socket. The example given above does not specify
7161 an LDAP server. A server that is reached by TCP/IP can be specified in a query
7164 ldap://<hostname>:<port>/...
7166 If the port (and preceding colon) are omitted, the standard LDAP port (389) is
7167 used. When no server is specified in a query, a list of default servers is
7168 taken from the &%ldap_default_servers%& configuration option. This supplies a
7169 colon-separated list of servers which are tried in turn until one successfully
7170 handles a query, or there is a serious error. Successful handling either
7171 returns the requested data, or indicates that it does not exist. Serious errors
7172 are syntactical, or multiple values when only a single value is expected.
7173 Errors which cause the next server to be tried are connection failures, bind
7174 failures, and timeouts.
7176 For each server name in the list, a port number can be given. The standard way
7177 of specifying a host and port is to use a colon separator (RFC 1738). Because
7178 &%ldap_default_servers%& is a colon-separated list, such colons have to be
7179 doubled. For example
7181 ldap_default_servers = ldap1.example.com::145:ldap2.example.com
7183 If &%ldap_default_servers%& is unset, a URL with no server name is passed
7184 to the LDAP library with no server name, and the library's default (normally
7185 the local host) is used.
7187 If you are using the OpenLDAP library, you can connect to an LDAP server using
7188 a Unix domain socket instead of a TCP/IP connection. This is specified by using
7189 &`ldapi`& instead of &`ldap`& in LDAP queries. What follows here applies only
7190 to OpenLDAP. If Exim is compiled with a different LDAP library, this feature is
7193 For this type of connection, instead of a host name for the server, a pathname
7194 for the socket is required, and the port number is not relevant. The pathname
7195 can be specified either as an item in &%ldap_default_servers%&, or inline in
7196 the query. In the former case, you can have settings such as
7198 ldap_default_servers = /tmp/ldap.sock : backup.ldap.your.domain
7200 When the pathname is given in the query, you have to escape the slashes as
7201 &`%2F`& to fit in with the LDAP URL syntax. For example:
7203 ${lookup ldap {ldapi://%2Ftmp%2Fldap.sock/o=...
7205 When Exim processes an LDAP lookup and finds that the &"hostname"& is really
7206 a pathname, it uses the Unix domain socket code, even if the query actually
7207 specifies &`ldap`& or &`ldaps`&. In particular, no encryption is used for a
7208 socket connection. This behaviour means that you can use a setting of
7209 &%ldap_default_servers%& such as in the example above with traditional &`ldap`&
7210 or &`ldaps`& queries, and it will work. First, Exim tries a connection via
7211 the Unix domain socket; if that fails, it tries a TCP/IP connection to the
7214 If an explicit &`ldapi`& type is given in a query when a host name is
7215 specified, an error is diagnosed. However, if there are more items in
7216 &%ldap_default_servers%&, they are tried. In other words:
7219 Using a pathname with &`ldap`& or &`ldaps`& forces the use of the Unix domain
7222 Using &`ldapi`& with a host name causes an error.
7226 Using &`ldapi`& with no host or path in the query, and no setting of
7227 &%ldap_default_servers%&, does whatever the library does by default.
7231 .section "LDAP authentication and control information" "SECID70"
7232 .cindex "LDAP" "authentication"
7233 The LDAP URL syntax provides no way of passing authentication and other control
7234 information to the server. To make this possible, the URL in an LDAP query may
7235 be preceded by any number of <&'name'&>=<&'value'&> settings, separated by
7236 spaces. If a value contains spaces it must be enclosed in double quotes, and
7237 when double quotes are used, backslash is interpreted in the usual way inside
7238 them. The following names are recognized:
7240 &`DEREFERENCE`& set the dereferencing parameter
7241 &`NETTIME `& set a timeout for a network operation
7242 &`USER `& set the DN, for authenticating the LDAP bind
7243 &`PASS `& set the password, likewise
7244 &`REFERRALS `& set the referrals parameter
7246 &`SERVERS `& set alternate server list for this query only
7248 &`SIZE `& set the limit for the number of entries returned
7249 &`TIME `& set the maximum waiting time for a query
7251 The value of the DEREFERENCE parameter must be one of the words &"never"&,
7252 &"searching"&, &"finding"&, or &"always"&. The value of the REFERRALS parameter
7253 must be &"follow"& (the default) or &"nofollow"&. The latter stops the LDAP
7254 library from trying to follow referrals issued by the LDAP server.
7256 The name CONNECT is an obsolete name for NETTIME, retained for
7257 backwards compatibility. This timeout (specified as a number of seconds) is
7258 enforced from the client end for operations that can be carried out over a
7259 network. Specifically, it applies to network connections and calls to the
7260 &'ldap_result()'& function. If the value is greater than zero, it is used if
7261 LDAP_OPT_NETWORK_TIMEOUT is defined in the LDAP headers (OpenLDAP), or
7262 if LDAP_X_OPT_CONNECT_TIMEOUT is defined in the LDAP headers (Netscape
7263 SDK 4.1). A value of zero forces an explicit setting of &"no timeout"& for
7264 Netscape SDK; for OpenLDAP no action is taken.
7266 The TIME parameter (also a number of seconds) is passed to the server to
7267 set a server-side limit on the time taken to complete a search.
7270 The SERVERS parameter allows you to specify an alternate list of ldap servers
7271 to use for an individual lookup. The global ldap_servers option provides a
7272 default list of ldap servers, and a single lookup can specify a single ldap
7273 server to use. But when you need to do a lookup with a list of servers that is
7274 different than the default list (maybe different order, maybe a completely
7275 different set of servers), the SERVERS parameter allows you to specify this
7279 Here is an example of an LDAP query in an Exim lookup that uses some of these
7280 values. This is a single line, folded to fit on the page:
7283 {user="cn=manager,o=University of Cambridge,c=UK" pass=secret
7284 ldap:///o=University%20of%20Cambridge,c=UK?sn?sub?(cn=foo)}
7287 The encoding of spaces as &`%20`& is a URL thing which should not be done for
7288 any of the auxiliary data. Exim configuration settings that include lookups
7289 which contain password information should be preceded by &"hide"& to prevent
7290 non-admin users from using the &%-bP%& option to see their values.
7292 The auxiliary data items may be given in any order. The default is no
7293 connection timeout (the system timeout is used), no user or password, no limit
7294 on the number of entries returned, and no time limit on queries.
7296 When a DN is quoted in the USER= setting for LDAP authentication, Exim
7297 removes any URL quoting that it may contain before passing it LDAP. Apparently
7298 some libraries do this for themselves, but some do not. Removing the URL
7299 quoting has two advantages:
7302 It makes it possible to use the same &%quote_ldap_dn%& expansion for USER=
7303 DNs as with DNs inside actual queries.
7305 It permits spaces inside USER= DNs.
7308 For example, a setting such as
7310 USER=cn=${quote_ldap_dn:$1}
7312 should work even if &$1$& contains spaces.
7314 Expanded data for the PASS= value should be quoted using the &%quote%&
7315 expansion operator, rather than the LDAP quote operators. The only reason this
7316 field needs quoting is to ensure that it conforms to the Exim syntax, which
7317 does not allow unquoted spaces. For example:
7321 The LDAP authentication mechanism can be used to check passwords as part of
7322 SMTP authentication. See the &%ldapauth%& expansion string condition in chapter
7327 .section "Format of data returned by LDAP" "SECID71"
7328 .cindex "LDAP" "returned data formats"
7329 The &(ldapdn)& lookup type returns the Distinguished Name from a single entry
7330 as a sequence of values, for example
7332 cn=manager, o=University of Cambridge, c=UK
7334 The &(ldap)& lookup type generates an error if more than one entry matches the
7335 search filter, whereas &(ldapm)& permits this case, and inserts a newline in
7336 the result between the data from different entries. It is possible for multiple
7337 values to be returned for both &(ldap)& and &(ldapm)&, but in the former case
7338 you know that whatever values are returned all came from a single entry in the
7341 In the common case where you specify a single attribute in your LDAP query, the
7342 result is not quoted, and does not contain the attribute name. If the attribute
7343 has multiple values, they are separated by commas.
7345 If you specify multiple attributes, the result contains space-separated, quoted
7346 strings, each preceded by the attribute name and an equals sign. Within the
7347 quotes, the quote character, backslash, and newline are escaped with
7348 backslashes, and commas are used to separate multiple values for the attribute.
7349 Apart from the escaping, the string within quotes takes the same form as the
7350 output when a single attribute is requested. Specifying no attributes is the
7351 same as specifying all of an entry's attributes.
7353 Here are some examples of the output format. The first line of each pair is an
7354 LDAP query, and the second is the data that is returned. The attribute called
7355 &%attr1%& has two values, whereas &%attr2%& has only one value:
7357 ldap:///o=base?attr1?sub?(uid=fred)
7360 ldap:///o=base?attr2?sub?(uid=fred)
7363 ldap:///o=base?attr1,attr2?sub?(uid=fred)
7364 attr1="value1.1, value1.2" attr2="value two"
7366 ldap:///o=base??sub?(uid=fred)
7367 objectClass="top" attr1="value1.1, value1.2" attr2="value two"
7369 The &%extract%& operator in string expansions can be used to pick out
7370 individual fields from data that consists of &'key'&=&'value'& pairs. You can
7371 make use of Exim's &%-be%& option to run expansion tests and thereby check the
7372 results of LDAP lookups.
7377 .section "More about NIS+" "SECTnisplus"
7378 .cindex "NIS+ lookup type"
7379 .cindex "lookup" "NIS+"
7380 NIS+ queries consist of a NIS+ &'indexed name'& followed by an optional colon
7381 and field name. If this is given, the result of a successful query is the
7382 contents of the named field; otherwise the result consists of a concatenation
7383 of &'field-name=field-value'& pairs, separated by spaces. Empty values and
7384 values containing spaces are quoted. For example, the query
7386 [name=mg1456],passwd.org_dir
7388 might return the string
7390 name=mg1456 passwd="" uid=999 gid=999 gcos="Martin Guerre"
7391 home=/home/mg1456 shell=/bin/bash shadow=""
7393 (split over two lines here to fit on the page), whereas
7395 [name=mg1456],passwd.org_dir:gcos
7401 with no quotes. A NIS+ lookup fails if NIS+ returns more than one table entry
7402 for the given indexed key. The effect of the &%quote_nisplus%& expansion
7403 operator is to double any quote characters within the text.
7407 .section "SQL lookups" "SECTsql"
7408 .cindex "SQL lookup types"
7409 .cindex "MySQL" "lookup type"
7410 .cindex "PostgreSQL lookup type"
7411 .cindex "lookup" "MySQL"
7412 .cindex "lookup" "PostgreSQL"
7413 .cindex "Oracle" "lookup type"
7414 .cindex "lookup" "Oracle"
7415 .cindex "InterBase lookup type"
7416 .cindex "lookup" "InterBase"
7417 Exim can support lookups in InterBase, MySQL, Oracle, PostgreSQL, and SQLite
7418 databases. Queries for these databases contain SQL statements, so an example
7421 ${lookup mysql{select mailbox from users where id='userx'}\
7424 If the result of the query contains more than one field, the data for each
7425 field in the row is returned, preceded by its name, so the result of
7427 ${lookup pgsql{select home,name from users where id='userx'}\
7432 home=/home/userx name="Mister X"
7434 Empty values and values containing spaces are double quoted, with embedded
7435 quotes escaped by a backslash. If the result of the query contains just one
7436 field, the value is passed back verbatim, without a field name, for example:
7440 If the result of the query yields more than one row, it is all concatenated,
7441 with a newline between the data for each row.
7444 .section "More about MySQL, PostgreSQL, Oracle, and InterBase" "SECID72"
7445 .cindex "MySQL" "lookup type"
7446 .cindex "PostgreSQL lookup type"
7447 .cindex "lookup" "MySQL"
7448 .cindex "lookup" "PostgreSQL"
7449 .cindex "Oracle" "lookup type"
7450 .cindex "lookup" "Oracle"
7451 .cindex "InterBase lookup type"
7452 .cindex "lookup" "InterBase"
7453 If any MySQL, PostgreSQL, Oracle, or InterBase lookups are used, the
7454 &%mysql_servers%&, &%pgsql_servers%&, &%oracle_servers%&, or &%ibase_servers%&
7455 option (as appropriate) must be set to a colon-separated list of server
7457 (For MySQL and PostgreSQL only, the global option need not be set if all
7458 queries contain their own server information &-- see section
7459 &<<SECTspeserque>>&.) Each item in the list is a slash-separated list of four
7460 items: host name, database name, user name, and password. In the case of
7461 Oracle, the host name field is used for the &"service name"&, and the database
7462 name field is not used and should be empty. For example:
7464 hide oracle_servers = oracle.plc.example//userx/abcdwxyz
7466 Because password data is sensitive, you should always precede the setting with
7467 &"hide"&, to prevent non-admin users from obtaining the setting via the &%-bP%&
7468 option. Here is an example where two MySQL servers are listed:
7470 hide mysql_servers = localhost/users/root/secret:\
7471 otherhost/users/root/othersecret
7473 For MySQL and PostgreSQL, a host may be specified as <&'name'&>:<&'port'&> but
7474 because this is a colon-separated list, the colon has to be doubled. For each
7475 query, these parameter groups are tried in order until a connection is made and
7476 a query is successfully processed. The result of a query may be that no data is
7477 found, but that is still a successful query. In other words, the list of
7478 servers provides a backup facility, not a list of different places to look.
7480 The &%quote_mysql%&, &%quote_pgsql%&, and &%quote_oracle%& expansion operators
7481 convert newline, tab, carriage return, and backspace to \n, \t, \r, and \b
7482 respectively, and the characters single-quote, double-quote, and backslash
7483 itself are escaped with backslashes. The &%quote_pgsql%& expansion operator, in
7484 addition, escapes the percent and underscore characters. This cannot be done
7485 for MySQL because these escapes are not recognized in contexts where these
7486 characters are not special.
7488 .section "Specifying the server in the query" "SECTspeserque"
7489 For MySQL and PostgreSQL lookups (but not currently for Oracle and InterBase),
7490 it is possible to specify a list of servers with an individual query. This is
7491 done by starting the query with
7493 &`servers=`&&'server1:server2:server3:...'&&`;`&
7495 Each item in the list may take one of two forms:
7497 If it contains no slashes it is assumed to be just a host name. The appropriate
7498 global option (&%mysql_servers%& or &%pgsql_servers%&) is searched for a host
7499 of the same name, and the remaining parameters (database, user, password) are
7502 If it contains any slashes, it is taken as a complete parameter set.
7504 The list of servers is used in exactly the same way as the global list.
7505 Once a connection to a server has happened and a query has been
7506 successfully executed, processing of the lookup ceases.
7508 This feature is intended for use in master/slave situations where updates
7509 are occurring and you want to update the master rather than a slave. If the
7510 master is in the list as a backup for reading, you might have a global setting
7513 mysql_servers = slave1/db/name/pw:\
7517 In an updating lookup, you could then write:
7519 ${lookup mysql{servers=master; UPDATE ...} }
7521 That query would then be sent only to the master server. If, on the other hand,
7522 the master is not to be used for reading, and so is not present in the global
7523 option, you can still update it by a query of this form:
7525 ${lookup pgsql{servers=master/db/name/pw; UPDATE ...} }
7529 .section "Special MySQL features" "SECID73"
7530 For MySQL, an empty host name or the use of &"localhost"& in &%mysql_servers%&
7531 causes a connection to the server on the local host by means of a Unix domain
7532 socket. An alternate socket can be specified in parentheses. The full syntax of
7533 each item in &%mysql_servers%& is:
7535 <&'hostname'&>::<&'port'&>(<&'socket name'&>)/<&'database'&>/&&&
7536 <&'user'&>/<&'password'&>
7538 Any of the three sub-parts of the first field can be omitted. For normal use on
7539 the local host it can be left blank or set to just &"localhost"&.
7541 No database need be supplied &-- but if it is absent here, it must be given in
7544 If a MySQL query is issued that does not request any data (an insert, update,
7545 or delete command), the result of the lookup is the number of rows affected.
7547 &*Warning*&: This can be misleading. If an update does not actually change
7548 anything (for example, setting a field to the value it already has), the result
7549 is zero because no rows are affected.
7552 .section "Special PostgreSQL features" "SECID74"
7553 PostgreSQL lookups can also use Unix domain socket connections to the database.
7554 This is usually faster and costs less CPU time than a TCP/IP connection.
7555 However it can be used only if the mail server runs on the same machine as the
7556 database server. A configuration line for PostgreSQL via Unix domain sockets
7559 hide pgsql_servers = (/tmp/.s.PGSQL.5432)/db/user/password : ...
7561 In other words, instead of supplying a host name, a path to the socket is
7562 given. The path name is enclosed in parentheses so that its slashes aren't
7563 visually confused with the delimiters for the other server parameters.
7565 If a PostgreSQL query is issued that does not request any data (an insert,
7566 update, or delete command), the result of the lookup is the number of rows
7569 .section "More about SQLite" "SECTsqlite"
7570 .cindex "lookup" "SQLite"
7571 .cindex "sqlite lookup type"
7572 SQLite is different to the other SQL lookups because a file name is required in
7573 addition to the SQL query. An SQLite database is a single file, and there is no
7574 daemon as in the other SQL databases. The interface to Exim requires the name
7575 of the file, as an absolute path, to be given at the start of the query. It is
7576 separated from the query by white space. This means that the path name cannot
7577 contain white space. Here is a lookup expansion example:
7579 ${lookup sqlite {/some/thing/sqlitedb \
7580 select name from aliases where id='userx';}}
7582 In a list, the syntax is similar. For example:
7584 domainlist relay_to_domains = sqlite;/some/thing/sqlitedb \
7585 select * from relays where ip='$sender_host_address';
7587 The only character affected by the &%quote_sqlite%& operator is a single
7588 quote, which it doubles.
7590 The SQLite library handles multiple simultaneous accesses to the database
7591 internally. Multiple readers are permitted, but only one process can
7592 update at once. Attempts to access the database while it is being updated
7593 are rejected after a timeout period, during which the SQLite library
7594 waits for the lock to be released. In Exim, the default timeout is set
7595 to 5 seconds, but it can be changed by means of the &%sqlite_lock_timeout%&
7601 . ////////////////////////////////////////////////////////////////////////////
7602 . ////////////////////////////////////////////////////////////////////////////
7604 .chapter "Domain, host, address, and local part lists" &&&
7605 "CHAPdomhosaddlists" &&&
7606 "Domain, host, and address lists"
7607 .scindex IIDdohoadli "lists of domains; hosts; etc."
7608 A number of Exim configuration options contain lists of domains, hosts,
7609 email addresses, or local parts. For example, the &%hold_domains%& option
7610 contains a list of domains whose delivery is currently suspended. These lists
7611 are also used as data in ACL statements (see chapter &<<CHAPACL>>&), and as
7612 arguments to expansion conditions such as &%match_domain%&.
7614 Each item in one of these lists is a pattern to be matched against a domain,
7615 host, email address, or local part, respectively. In the sections below, the
7616 different types of pattern for each case are described, but first we cover some
7617 general facilities that apply to all four kinds of list.
7621 .section "Expansion of lists" "SECID75"
7622 .cindex "expansion" "of lists"
7623 Each list is expanded as a single string before it is used. The result of
7624 expansion must be a list, possibly containing empty items, which is split up
7625 into separate items for matching. By default, colon is the separator character,
7626 but this can be varied if necessary. See sections &<<SECTlistconstruct>>& and
7627 &<<SECTempitelis>>& for details of the list syntax; the second of these
7628 discusses the way to specify empty list items.
7631 If the string expansion is forced to fail, Exim behaves as if the item it is
7632 testing (domain, host, address, or local part) is not in the list. Other
7633 expansion failures cause temporary errors.
7635 If an item in a list is a regular expression, backslashes, dollars and possibly
7636 other special characters in the expression must be protected against
7637 misinterpretation by the string expander. The easiest way to do this is to use
7638 the &`\N`& expansion feature to indicate that the contents of the regular
7639 expression should not be expanded. For example, in an ACL you might have:
7641 deny senders = \N^\d{8}\w@.*\.baddomain\.example$\N : \
7642 ${lookup{$domain}lsearch{/badsenders/bydomain}}
7644 The first item is a regular expression that is protected from expansion by
7645 &`\N`&, whereas the second uses the expansion to obtain a list of unwanted
7646 senders based on the receiving domain.
7651 .section "Negated items in lists" "SECID76"
7652 .cindex "list" "negation"
7653 .cindex "negation" "in lists"
7654 Items in a list may be positive or negative. Negative items are indicated by a
7655 leading exclamation mark, which may be followed by optional white space. A list
7656 defines a set of items (domains, etc). When Exim processes one of these lists,
7657 it is trying to find out whether a domain, host, address, or local part
7658 (respectively) is in the set that is defined by the list. It works like this:
7660 The list is scanned from left to right. If a positive item is matched, the
7661 subject that is being checked is in the set; if a negative item is matched, the
7662 subject is not in the set. If the end of the list is reached without the
7663 subject having matched any of the patterns, it is in the set if the last item
7664 was a negative one, but not if it was a positive one. For example, the list in
7666 domainlist relay_to_domains = !a.b.c : *.b.c
7668 matches any domain ending in &'.b.c'& except for &'a.b.c'&. Domains that match
7669 neither &'a.b.c'& nor &'*.b.c'& do not match, because the last item in the
7670 list is positive. However, if the setting were
7672 domainlist relay_to_domains = !a.b.c
7674 then all domains other than &'a.b.c'& would match because the last item in the
7675 list is negative. In other words, a list that ends with a negative item behaves
7676 as if it had an extra item &`:*`& on the end.
7678 Another way of thinking about positive and negative items in lists is to read
7679 the connector as &"or"& after a positive item and as &"and"& after a negative
7684 .section "File names in lists" "SECTfilnamlis"
7685 .cindex "list" "file name in"
7686 If an item in a domain, host, address, or local part list is an absolute file
7687 name (beginning with a slash character), each line of the file is read and
7688 processed as if it were an independent item in the list, except that further
7689 file names are not allowed,
7690 and no expansion of the data from the file takes place.
7691 Empty lines in the file are ignored, and the file may also contain comment
7695 For domain and host lists, if a # character appears anywhere in a line of the
7696 file, it and all following characters are ignored.
7698 Because local parts may legitimately contain # characters, a comment in an
7699 address list or local part list file is recognized only if # is preceded by
7700 white space or the start of the line. For example:
7702 not#comment@x.y.z # but this is a comment
7706 Putting a file name in a list has the same effect as inserting each line of the
7707 file as an item in the list (blank lines and comments excepted). However, there
7708 is one important difference: the file is read each time the list is processed,
7709 so if its contents vary over time, Exim's behaviour changes.
7711 If a file name is preceded by an exclamation mark, the sense of any match
7712 within the file is inverted. For example, if
7714 hold_domains = !/etc/nohold-domains
7716 and the file contains the lines
7721 then &'a.b.c'& is in the set of domains defined by &%hold_domains%&, whereas
7722 any domain matching &`*.b.c`& is not.
7726 .section "An lsearch file is not an out-of-line list" "SECID77"
7727 As will be described in the sections that follow, lookups can be used in lists
7728 to provide indexed methods of checking list membership. There has been some
7729 confusion about the way &(lsearch)& lookups work in lists. Because
7730 an &(lsearch)& file contains plain text and is scanned sequentially, it is
7731 sometimes thought that it is allowed to contain wild cards and other kinds of
7732 non-constant pattern. This is not the case. The keys in an &(lsearch)& file are
7733 always fixed strings, just as for any other single-key lookup type.
7735 If you want to use a file to contain wild-card patterns that form part of a
7736 list, just give the file name on its own, without a search type, as described
7737 in the previous section. You could also use the &(wildlsearch)& or
7738 &(nwildlsearch)&, but there is no advantage in doing this.
7743 .section "Named lists" "SECTnamedlists"
7744 .cindex "named lists"
7745 .cindex "list" "named"
7746 A list of domains, hosts, email addresses, or local parts can be given a name
7747 which is then used to refer to the list elsewhere in the configuration. This is
7748 particularly convenient if the same list is required in several different
7749 places. It also allows lists to be given meaningful names, which can improve
7750 the readability of the configuration. For example, it is conventional to define
7751 a domain list called &'local_domains'& for all the domains that are handled
7752 locally on a host, using a configuration line such as
7754 domainlist local_domains = localhost:my.dom.example
7756 Named lists are referenced by giving their name preceded by a plus sign, so,
7757 for example, a router that is intended to handle local domains would be
7758 configured with the line
7760 domains = +local_domains
7762 The first router in a configuration is often one that handles all domains
7763 except the local ones, using a configuration with a negated item like this:
7767 domains = ! +local_domains
7768 transport = remote_smtp
7771 The four kinds of named list are created by configuration lines starting with
7772 the words &%domainlist%&, &%hostlist%&, &%addresslist%&, or &%localpartlist%&,
7773 respectively. Then there follows the name that you are defining, followed by an
7774 equals sign and the list itself. For example:
7776 hostlist relay_from_hosts = 192.168.23.0/24 : my.friend.example
7777 addresslist bad_senders = cdb;/etc/badsenders
7779 A named list may refer to other named lists:
7781 domainlist dom1 = first.example : second.example
7782 domainlist dom2 = +dom1 : third.example
7783 domainlist dom3 = fourth.example : +dom2 : fifth.example
7785 &*Warning*&: If the last item in a referenced list is a negative one, the
7786 effect may not be what you intended, because the negation does not propagate
7787 out to the higher level. For example, consider:
7789 domainlist dom1 = !a.b
7790 domainlist dom2 = +dom1 : *.b
7792 The second list specifies &"either in the &%dom1%& list or &'*.b'&"&. The first
7793 list specifies just &"not &'a.b'&"&, so the domain &'x.y'& matches it. That
7794 means it matches the second list as well. The effect is not the same as
7796 domainlist dom2 = !a.b : *.b
7798 where &'x.y'& does not match. It's best to avoid negation altogether in
7799 referenced lists if you can.
7801 Named lists may have a performance advantage. When Exim is routing an
7802 address or checking an incoming message, it caches the result of tests on named
7803 lists. So, if you have a setting such as
7805 domains = +local_domains
7807 on several of your routers
7808 or in several ACL statements,
7809 the actual test is done only for the first one. However, the caching works only
7810 if there are no expansions within the list itself or any sublists that it
7811 references. In other words, caching happens only for lists that are known to be
7812 the same each time they are referenced.
7814 By default, there may be up to 16 named lists of each type. This limit can be
7815 extended by changing a compile-time variable. The use of domain and host lists
7816 is recommended for concepts such as local domains, relay domains, and relay
7817 hosts. The default configuration is set up like this.
7821 .section "Named lists compared with macros" "SECID78"
7822 .cindex "list" "named compared with macro"
7823 .cindex "macro" "compared with named list"
7824 At first sight, named lists might seem to be no different from macros in the
7825 configuration file. However, macros are just textual substitutions. If you
7828 ALIST = host1 : host2
7829 auth_advertise_hosts = !ALIST
7831 it probably won't do what you want, because that is exactly the same as
7833 auth_advertise_hosts = !host1 : host2
7835 Notice that the second host name is not negated. However, if you use a host
7838 hostlist alist = host1 : host2
7839 auth_advertise_hosts = ! +alist
7841 the negation applies to the whole list, and so that is equivalent to
7843 auth_advertise_hosts = !host1 : !host2
7847 .section "Named list caching" "SECID79"
7848 .cindex "list" "caching of named"
7849 .cindex "caching" "named lists"
7850 While processing a message, Exim caches the result of checking a named list if
7851 it is sure that the list is the same each time. In practice, this means that
7852 the cache operates only if the list contains no $ characters, which guarantees
7853 that it will not change when it is expanded. Sometimes, however, you may have
7854 an expanded list that you know will be the same each time within a given
7855 message. For example:
7857 domainlist special_domains = \
7858 ${lookup{$sender_host_address}cdb{/some/file}}
7860 This provides a list of domains that depends only on the sending host's IP
7861 address. If this domain list is referenced a number of times (for example,
7862 in several ACL lines, or in several routers) the result of the check is not
7863 cached by default, because Exim does not know that it is going to be the
7864 same list each time.
7866 By appending &`_cache`& to &`domainlist`& you can tell Exim to go ahead and
7867 cache the result anyway. For example:
7869 domainlist_cache special_domains = ${lookup{...
7871 If you do this, you should be absolutely sure that caching is going to do
7872 the right thing in all cases. When in doubt, leave it out.
7876 .section "Domain lists" "SECTdomainlist"
7877 .cindex "domain list" "patterns for"
7878 .cindex "list" "domain list"
7879 Domain lists contain patterns that are to be matched against a mail domain.
7880 The following types of item may appear in domain lists:
7883 .cindex "primary host name"
7884 .cindex "host name" "matched in domain list"
7885 .oindex "&%primary_hostname%&"
7886 .cindex "domain list" "matching primary host name"
7887 .cindex "@ in a domain list"
7888 If a pattern consists of a single @ character, it matches the local host name,
7889 as set by the &%primary_hostname%& option (or defaulted). This makes it
7890 possible to use the same configuration file on several different hosts that
7891 differ only in their names.
7893 .cindex "@[] in a domain list"
7894 .cindex "domain list" "matching local IP interfaces"
7895 .cindex "domain literal"
7896 If a pattern consists of the string &`@[]`& it matches an IP address enclosed
7897 in square brackets (as in an email address that contains a domain literal), but
7898 only if that IP address is recognized as local for email routing purposes. The
7899 &%local_interfaces%& and &%extra_local_interfaces%& options can be used to
7900 control which of a host's several IP addresses are treated as local.
7901 In today's Internet, the use of domain literals is controversial.
7904 .cindex "@mx_primary"
7905 .cindex "@mx_secondary"
7906 .cindex "domain list" "matching MX pointers to local host"
7907 If a pattern consists of the string &`@mx_any`& it matches any domain that
7908 has an MX record pointing to the local host or to any host that is listed in
7909 .oindex "&%hosts_treat_as_local%&"
7910 &%hosts_treat_as_local%&. The items &`@mx_primary`& and &`@mx_secondary`&
7911 are similar, except that the first matches only when a primary MX target is the
7912 local host, and the second only when no primary MX target is the local host,
7913 but a secondary MX target is. &"Primary"& means an MX record with the lowest
7914 preference value &-- there may of course be more than one of them.
7916 The MX lookup that takes place when matching a pattern of this type is
7917 performed with the resolver options for widening names turned off. Thus, for
7918 example, a single-component domain will &'not'& be expanded by adding the
7919 resolver's default domain. See the &%qualify_single%& and &%search_parents%&
7920 options of the &(dnslookup)& router for a discussion of domain widening.
7922 Sometimes you may want to ignore certain IP addresses when using one of these
7923 patterns. You can specify this by following the pattern with &`/ignore=`&<&'ip
7924 list'&>, where <&'ip list'&> is a list of IP addresses. These addresses are
7925 ignored when processing the pattern (compare the &%ignore_target_hosts%& option
7926 on a router). For example:
7928 domains = @mx_any/ignore=127.0.0.1
7930 This example matches any domain that has an MX record pointing to one of
7931 the local host's IP addresses other than 127.0.0.1.
7933 The list of IP addresses is in fact processed by the same code that processes
7934 host lists, so it may contain CIDR-coded network specifications and it may also
7935 contain negative items.
7937 Because the list of IP addresses is a sublist within a domain list, you have to
7938 be careful about delimiters if there is more than one address. Like any other
7939 list, the default delimiter can be changed. Thus, you might have:
7941 domains = @mx_any/ignore=<;127.0.0.1;0.0.0.0 : \
7942 an.other.domain : ...
7944 so that the sublist uses semicolons for delimiters. When IPv6 addresses are
7945 involved, it is easiest to change the delimiter for the main list as well:
7947 domains = <? @mx_any/ignore=<;127.0.0.1;::1 ? \
7948 an.other.domain ? ...
7951 .cindex "asterisk" "in domain list"
7952 .cindex "domain list" "asterisk in"
7953 .cindex "domain list" "matching &""ends with""&"
7954 If a pattern starts with an asterisk, the remaining characters of the pattern
7955 are compared with the terminating characters of the domain. The use of &"*"& in
7956 domain lists differs from its use in partial matching lookups. In a domain
7957 list, the character following the asterisk need not be a dot, whereas partial
7958 matching works only in terms of dot-separated components. For example, a domain
7959 list item such as &`*key.ex`& matches &'donkey.ex'& as well as
7963 .cindex "regular expressions" "in domain list"
7964 .cindex "domain list" "matching regular expression"
7965 If a pattern starts with a circumflex character, it is treated as a regular
7966 expression, and matched against the domain using a regular expression matching
7967 function. The circumflex is treated as part of the regular expression.
7968 Email domains are case-independent, so this regular expression match is by
7969 default case-independent, but you can make it case-dependent by starting it
7970 with &`(?-i)`&. References to descriptions of the syntax of regular expressions
7971 are given in chapter &<<CHAPregexp>>&.
7973 &*Warning*&: Because domain lists are expanded before being processed, you
7974 must escape any backslash and dollar characters in the regular expression, or
7975 use the special &`\N`& sequence (see chapter &<<CHAPexpand>>&) to specify that
7976 it is not to be expanded (unless you really do want to build a regular
7977 expression by expansion, of course).
7979 .cindex "lookup" "in domain list"
7980 .cindex "domain list" "matching by lookup"
7981 If a pattern starts with the name of a single-key lookup type followed by a
7982 semicolon (for example, &"dbm;"& or &"lsearch;"&), the remainder of the pattern
7983 must be a file name in a suitable format for the lookup type. For example, for
7984 &"cdb;"& it must be an absolute path:
7986 domains = cdb;/etc/mail/local_domains.cdb
7988 The appropriate type of lookup is done on the file using the domain name as the
7989 key. In most cases, the data that is looked up is not used; Exim is interested
7990 only in whether or not the key is present in the file. However, when a lookup
7991 is used for the &%domains%& option on a router
7992 or a &%domains%& condition in an ACL statement, the data is preserved in the
7993 &$domain_data$& variable and can be referred to in other router options or
7994 other statements in the same ACL.
7997 Any of the single-key lookup type names may be preceded by
7998 &`partial`&<&'n'&>&`-`&, where the <&'n'&> is optional, for example,
8000 domains = partial-dbm;/partial/domains
8002 This causes partial matching logic to be invoked; a description of how this
8003 works is given in section &<<SECTpartiallookup>>&.
8006 .cindex "asterisk" "in lookup type"
8007 Any of the single-key lookup types may be followed by an asterisk. This causes
8008 a default lookup for a key consisting of a single asterisk to be done if the
8009 original lookup fails. This is not a useful feature when using a domain list to
8010 select particular domains (because any domain would match), but it might have
8011 value if the result of the lookup is being used via the &$domain_data$&
8014 If the pattern starts with the name of a query-style lookup type followed by a
8015 semicolon (for example, &"nisplus;"& or &"ldap;"&), the remainder of the
8016 pattern must be an appropriate query for the lookup type, as described in
8017 chapter &<<CHAPfdlookup>>&. For example:
8019 hold_domains = mysql;select domain from holdlist \
8020 where domain = '${quote_mysql:$domain}';
8022 In most cases, the data that is looked up is not used (so for an SQL query, for
8023 example, it doesn't matter what field you select). Exim is interested only in
8024 whether or not the query succeeds. However, when a lookup is used for the
8025 &%domains%& option on a router, the data is preserved in the &$domain_data$&
8026 variable and can be referred to in other options.
8028 .cindex "domain list" "matching literal domain name"
8029 If none of the above cases apply, a caseless textual comparison is made
8030 between the pattern and the domain.
8033 Here is an example that uses several different kinds of pattern:
8035 domainlist funny_domains = \
8038 *.foundation.fict.example : \
8039 \N^[1-2]\d{3}\.fict\.example$\N : \
8040 partial-dbm;/opt/data/penguin/book : \
8041 nis;domains.byname : \
8042 nisplus;[name=$domain,status=local],domains.org_dir
8044 There are obvious processing trade-offs among the various matching modes. Using
8045 an asterisk is faster than a regular expression, and listing a few names
8046 explicitly probably is too. The use of a file or database lookup is expensive,
8047 but may be the only option if hundreds of names are required. Because the
8048 patterns are tested in order, it makes sense to put the most commonly matched
8053 .section "Host lists" "SECThostlist"
8054 .cindex "host list" "patterns in"
8055 .cindex "list" "host list"
8056 Host lists are used to control what remote hosts are allowed to do. For
8057 example, some hosts may be allowed to use the local host as a relay, and some
8058 may be permitted to use the SMTP ETRN command. Hosts can be identified in
8059 two different ways, by name or by IP address. In a host list, some types of
8060 pattern are matched to a host name, and some are matched to an IP address.
8061 You need to be particularly careful with this when single-key lookups are
8062 involved, to ensure that the right value is being used as the key.
8065 .section "Special host list patterns" "SECID80"
8066 .cindex "empty item in hosts list"
8067 .cindex "host list" "empty string in"
8068 If a host list item is the empty string, it matches only when no remote host is
8069 involved. This is the case when a message is being received from a local
8070 process using SMTP on the standard input, that is, when a TCP/IP connection is
8073 .cindex "asterisk" "in host list"
8074 The special pattern &"*"& in a host list matches any host or no host. Neither
8075 the IP address nor the name is actually inspected.
8079 .section "Host list patterns that match by IP address" "SECThoslispatip"
8080 .cindex "host list" "matching IP addresses"
8081 If an IPv4 host calls an IPv6 host and the call is accepted on an IPv6 socket,
8082 the incoming address actually appears in the IPv6 host as
8083 &`::ffff:`&<&'v4address'&>. When such an address is tested against a host
8084 list, it is converted into a traditional IPv4 address first. (Not all operating
8085 systems accept IPv4 calls on IPv6 sockets, as there have been some security
8088 The following types of pattern in a host list check the remote host by
8089 inspecting its IP address:
8092 If the pattern is a plain domain name (not a regular expression, not starting
8093 with *, not a lookup of any kind), Exim calls the operating system function
8094 to find the associated IP address(es). Exim uses the newer
8095 &[getipnodebyname()]& function when available, otherwise &[gethostbyname()]&.
8096 This typically causes a forward DNS lookup of the name. The result is compared
8097 with the IP address of the subject host.
8099 If there is a temporary problem (such as a DNS timeout) with the host name
8100 lookup, a temporary error occurs. For example, if the list is being used in an
8101 ACL condition, the ACL gives a &"defer"& response, usually leading to a
8102 temporary SMTP error code. If no IP address can be found for the host name,
8103 what happens is described in section &<<SECTbehipnot>>& below.
8106 .cindex "@ in a host list"
8107 If the pattern is &"@"&, the primary host name is substituted and used as a
8108 domain name, as just described.
8111 If the pattern is an IP address, it is matched against the IP address of the
8112 subject host. IPv4 addresses are given in the normal &"dotted-quad"& notation.
8113 IPv6 addresses can be given in colon-separated format, but the colons have to
8114 be doubled so as not to be taken as item separators when the default list
8115 separator is used. IPv6 addresses are recognized even when Exim is compiled
8116 without IPv6 support. This means that if they appear in a host list on an
8117 IPv4-only host, Exim will not treat them as host names. They are just addresses
8118 that can never match a client host.
8121 .cindex "@[] in a host list"
8122 If the pattern is &"@[]"&, it matches the IP address of any IP interface on
8123 the local host. For example, if the local host is an IPv4 host with one
8124 interface address 10.45.23.56, these two ACL statements have the same effect:
8126 accept hosts = 127.0.0.1 : 10.45.23.56
8130 .cindex "CIDR notation"
8131 If the pattern is an IP address followed by a slash and a mask length (for
8132 example 10.11.42.0/24), it is matched against the IP address of the subject
8133 host under the given mask. This allows, an entire network of hosts to be
8134 included (or excluded) by a single item. The mask uses CIDR notation; it
8135 specifies the number of address bits that must match, starting from the most
8136 significant end of the address.
8138 &*Note*&: The mask is &'not'& a count of addresses, nor is it the high number
8139 of a range of addresses. It is the number of bits in the network portion of the
8140 address. The above example specifies a 24-bit netmask, so it matches all 256
8141 addresses in the 10.11.42.0 network. An item such as
8145 matches just two addresses, 192.168.23.236 and 192.168.23.237. A mask value of
8146 32 for an IPv4 address is the same as no mask at all; just a single address
8149 Here is another example which shows an IPv4 and an IPv6 network:
8151 recipient_unqualified_hosts = 192.168.0.0/16: \
8152 3ffe::ffff::836f::::/48
8154 The doubling of list separator characters applies only when these items
8155 appear inline in a host list. It is not required when indirecting via a file.
8158 recipient_unqualified_hosts = /opt/exim/unqualnets
8160 could make use of a file containing
8165 to have exactly the same effect as the previous example. When listing IPv6
8166 addresses inline, it is usually more convenient to use the facility for
8167 changing separator characters. This list contains the same two networks:
8169 recipient_unqualified_hosts = <; 172.16.0.0/12; \
8172 The separator is changed to semicolon by the leading &"<;"& at the start of the
8178 .section "Host list patterns for single-key lookups by host address" &&&
8179 "SECThoslispatsikey"
8180 .cindex "host list" "lookup of IP address"
8181 When a host is to be identified by a single-key lookup of its complete IP
8182 address, the pattern takes this form:
8184 &`net-<`&&'single-key-search-type'&&`>;<`&&'search-data'&&`>`&
8188 hosts_lookup = net-cdb;/hosts-by-ip.db
8190 The text form of the IP address of the subject host is used as the lookup key.
8191 IPv6 addresses are converted to an unabbreviated form, using lower case
8192 letters, with dots as separators because colon is the key terminator in
8193 &(lsearch)& files. [Colons can in fact be used in keys in &(lsearch)& files by
8194 quoting the keys, but this is a facility that was added later.] The data
8195 returned by the lookup is not used.
8197 .cindex "IP address" "masking"
8198 .cindex "host list" "masked IP address"
8199 Single-key lookups can also be performed using masked IP addresses, using
8200 patterns of this form:
8202 &`net<`&&'number'&&`>-<`&&'single-key-search-type'&&`>;<`&&'search-data'&&`>`&
8206 net24-dbm;/networks.db
8208 The IP address of the subject host is masked using <&'number'&> as the mask
8209 length. A textual string is constructed from the masked value, followed by the
8210 mask, and this is used as the lookup key. For example, if the host's IP address
8211 is 192.168.34.6, the key that is looked up for the above example is
8212 &"192.168.34.0/24"&.
8214 When an IPv6 address is converted to a string, dots are normally used instead
8215 of colons, so that keys in &(lsearch)& files need not contain colons (which
8216 terminate &(lsearch)& keys). This was implemented some time before the ability
8217 to quote keys was made available in &(lsearch)& files. However, the more
8218 recently implemented &(iplsearch)& files do require colons in IPv6 keys
8219 (notated using the quoting facility) so as to distinguish them from IPv4 keys.
8220 For this reason, when the lookup type is &(iplsearch)&, IPv6 addresses are
8221 converted using colons and not dots. In all cases, full, unabbreviated IPv6
8222 addresses are always used.
8224 Ideally, it would be nice to tidy up this anomalous situation by changing to
8225 colons in all cases, given that quoting is now available for &(lsearch)&.
8226 However, this would be an incompatible change that might break some existing
8229 &*Warning*&: Specifying &%net32-%& (for an IPv4 address) or &%net128-%& (for an
8230 IPv6 address) is not the same as specifying just &%net-%& without a number. In
8231 the former case the key strings include the mask value, whereas in the latter
8232 case the IP address is used on its own.
8236 .section "Host list patterns that match by host name" "SECThoslispatnam"
8237 .cindex "host" "lookup failures"
8238 .cindex "unknown host name"
8239 .cindex "host list" "matching host name"
8240 There are several types of pattern that require Exim to know the name of the
8241 remote host. These are either wildcard patterns or lookups by name. (If a
8242 complete hostname is given without any wildcarding, it is used to find an IP
8243 address to match against, as described in section &<<SECThoslispatip>>&
8246 If the remote host name is not already known when Exim encounters one of these
8247 patterns, it has to be found from the IP address.
8248 Although many sites on the Internet are conscientious about maintaining reverse
8249 DNS data for their hosts, there are also many that do not do this.
8250 Consequently, a name cannot always be found, and this may lead to unwanted
8251 effects. Take care when configuring host lists with wildcarded name patterns.
8252 Consider what will happen if a name cannot be found.
8254 Because of the problems of determining host names from IP addresses, matching
8255 against host names is not as common as matching against IP addresses.
8257 By default, in order to find a host name, Exim first does a reverse DNS lookup;
8258 if no name is found in the DNS, the system function (&[gethostbyaddr()]& or
8259 &[getipnodebyaddr()]& if available) is tried. The order in which these lookups
8260 are done can be changed by setting the &%host_lookup_order%& option. For
8261 security, once Exim has found one or more names, it looks up the IP addresses
8262 for these names and compares them with the IP address that it started with.
8263 Only those names whose IP addresses match are accepted. Any other names are
8264 discarded. If no names are left, Exim behaves as if the host name cannot be
8265 found. In the most common case there is only one name and one IP address.
8267 There are some options that control what happens if a host name cannot be
8268 found. These are described in section &<<SECTbehipnot>>& below.
8270 .cindex "host" "alias for"
8271 .cindex "alias for host"
8272 As a result of aliasing, hosts may have more than one name. When processing any
8273 of the following types of pattern, all the host's names are checked:
8276 .cindex "asterisk" "in host list"
8277 If a pattern starts with &"*"& the remainder of the item must match the end of
8278 the host name. For example, &`*.b.c`& matches all hosts whose names end in
8279 &'.b.c'&. This special simple form is provided because this is a very common
8280 requirement. Other kinds of wildcarding require the use of a regular
8283 .cindex "regular expressions" "in host list"
8284 .cindex "host list" "regular expression in"
8285 If the item starts with &"^"& it is taken to be a regular expression which is
8286 matched against the host name. Host names are case-independent, so this regular
8287 expression match is by default case-independent, but you can make it
8288 case-dependent by starting it with &`(?-i)`&. References to descriptions of the
8289 syntax of regular expressions are given in chapter &<<CHAPregexp>>&. For
8294 is a regular expression that matches either of the two hosts &'a.c.d'& or
8295 &'b.c.d'&. When a regular expression is used in a host list, you must take care
8296 that backslash and dollar characters are not misinterpreted as part of the
8297 string expansion. The simplest way to do this is to use &`\N`& to mark that
8298 part of the string as non-expandable. For example:
8300 sender_unqualified_hosts = \N^(a|b)\.c\.d$\N : ....
8302 &*Warning*&: If you want to match a complete host name, you must include the
8303 &`$`& terminating metacharacter in the regular expression, as in the above
8304 example. Without it, a match at the start of the host name is all that is
8311 .section "Behaviour when an IP address or name cannot be found" "SECTbehipnot"
8312 .cindex "host" "lookup failures, permanent"
8313 While processing a host list, Exim may need to look up an IP address from a
8314 name (see section &<<SECThoslispatip>>&), or it may need to look up a host name
8315 from an IP address (see section &<<SECThoslispatnam>>&). In either case, the
8316 behaviour when it fails to find the information it is seeking is the same.
8318 &*Note*&: This section applies to permanent lookup failures. It does &'not'&
8319 apply to temporary DNS errors, whose handling is described in the next section.
8321 .cindex "&`+include_unknown`&"
8322 .cindex "&`+ignore_unknown`&"
8323 Exim parses a host list from left to right. If it encounters a permanent
8324 lookup failure in any item in the host list before it has found a match,
8325 Exim treats it as a failure and the default behavior is as if the host
8326 does not match the list. This may not always be what you want to happen.
8327 To change Exim's behaviour, the special items &`+include_unknown`& or
8328 &`+ignore_unknown`& may appear in the list (at top level &-- they are
8329 not recognized in an indirected file).
8332 If any item that follows &`+include_unknown`& requires information that
8333 cannot found, Exim behaves as if the host does match the list. For example,
8335 host_reject_connection = +include_unknown:*.enemy.ex
8337 rejects connections from any host whose name matches &`*.enemy.ex`&, and also
8338 any hosts whose name it cannot find.
8341 If any item that follows &`+ignore_unknown`& requires information that cannot
8342 be found, Exim ignores that item and proceeds to the rest of the list. For
8345 accept hosts = +ignore_unknown : friend.example : \
8348 accepts from any host whose name is &'friend.example'& and from 192.168.4.5,
8349 whether or not its host name can be found. Without &`+ignore_unknown`&, if no
8350 name can be found for 192.168.4.5, it is rejected.
8353 Both &`+include_unknown`& and &`+ignore_unknown`& may appear in the same
8354 list. The effect of each one lasts until the next, or until the end of the
8358 .section "Mixing wildcarded host names and addresses in host lists" &&&
8360 .cindex "host list" "mixing names and addresses in"
8362 This section explains the host/ip processing logic with the same concepts
8363 as the previous section, but specifically addresses what happens when a
8364 wildcarded hostname is one of the items in the hostlist.
8367 If you have name lookups or wildcarded host names and
8368 IP addresses in the same host list, you should normally put the IP
8369 addresses first. For example, in an ACL you could have:
8371 accept hosts = 10.9.8.7 : *.friend.example
8373 The reason you normally would order it this way lies in the
8374 left-to-right way that Exim processes lists. It can test IP addresses
8375 without doing any DNS lookups, but when it reaches an item that requires
8376 a host name, it fails if it cannot find a host name to compare with the
8377 pattern. If the above list is given in the opposite order, the
8378 &%accept%& statement fails for a host whose name cannot be found, even
8379 if its IP address is 10.9.8.7.
8382 If you really do want to do the name check first, and still recognize the IP
8383 address, you can rewrite the ACL like this:
8385 accept hosts = *.friend.example
8386 accept hosts = 10.9.8.7
8388 If the first &%accept%& fails, Exim goes on to try the second one. See chapter
8389 &<<CHAPACL>>& for details of ACLs. Alternatively, you can use
8390 &`+ignore_unknown`&, which was discussed in depth in the first example in
8396 .section "Temporary DNS errors when looking up host information" &&&
8398 .cindex "host" "lookup failures, temporary"
8399 .cindex "&`+include_defer`&"
8400 .cindex "&`+ignore_defer`&"
8401 A temporary DNS lookup failure normally causes a defer action (except when
8402 &%dns_again_means_nonexist%& converts it into a permanent error). However,
8403 host lists can include &`+ignore_defer`& and &`+include_defer`&, analagous to
8404 &`+ignore_unknown`& and &`+include_unknown`&, as described in the previous
8405 section. These options should be used with care, probably only in non-critical
8406 host lists such as whitelists.
8410 .section "Host list patterns for single-key lookups by host name" &&&
8411 "SECThoslispatnamsk"
8412 .cindex "unknown host name"
8413 .cindex "host list" "matching host name"
8414 If a pattern is of the form
8416 <&'single-key-search-type'&>;<&'search-data'&>
8420 dbm;/host/accept/list
8422 a single-key lookup is performed, using the host name as its key. If the
8423 lookup succeeds, the host matches the item. The actual data that is looked up
8426 &*Reminder*&: With this kind of pattern, you must have host &'names'& as
8427 keys in the file, not IP addresses. If you want to do lookups based on IP
8428 addresses, you must precede the search type with &"net-"& (see section
8429 &<<SECThoslispatsikey>>&). There is, however, no reason why you could not use
8430 two items in the same list, one doing an address lookup and one doing a name
8431 lookup, both using the same file.
8435 .section "Host list patterns for query-style lookups" "SECID81"
8436 If a pattern is of the form
8438 <&'query-style-search-type'&>;<&'query'&>
8440 the query is obeyed, and if it succeeds, the host matches the item. The actual
8441 data that is looked up is not used. The variables &$sender_host_address$& and
8442 &$sender_host_name$& can be used in the query. For example:
8444 hosts_lookup = pgsql;\
8445 select ip from hostlist where ip='$sender_host_address'
8447 The value of &$sender_host_address$& for an IPv6 address contains colons. You
8448 can use the &%sg%& expansion item to change this if you need to. If you want to
8449 use masked IP addresses in database queries, you can use the &%mask%& expansion
8452 If the query contains a reference to &$sender_host_name$&, Exim automatically
8453 looks up the host name if it has not already done so. (See section
8454 &<<SECThoslispatnam>>& for comments on finding host names.)
8456 Historical note: prior to release 4.30, Exim would always attempt to find a
8457 host name before running the query, unless the search type was preceded by
8458 &`net-`&. This is no longer the case. For backwards compatibility, &`net-`& is
8459 still recognized for query-style lookups, but its presence or absence has no
8460 effect. (Of course, for single-key lookups, &`net-`& &'is'& important.
8461 See section &<<SECThoslispatsikey>>&.)
8467 .section "Address lists" "SECTaddresslist"
8468 .cindex "list" "address list"
8469 .cindex "address list" "empty item"
8470 .cindex "address list" "patterns"
8471 Address lists contain patterns that are matched against mail addresses. There
8472 is one special case to be considered: the sender address of a bounce message is
8473 always empty. You can test for this by providing an empty item in an address
8474 list. For example, you can set up a router to process bounce messages by
8475 using this option setting:
8479 The presence of the colon creates an empty item. If you do not provide any
8480 data, the list is empty and matches nothing. The empty sender can also be
8481 detected by a regular expression that matches an empty string,
8482 and by a query-style lookup that succeeds when &$sender_address$& is empty.
8484 Non-empty items in an address list can be straightforward email addresses. For
8487 senders = jbc@askone.example : hs@anacreon.example
8489 A certain amount of wildcarding is permitted. If a pattern contains an @
8490 character, but is not a regular expression and does not begin with a
8491 semicolon-terminated lookup type (described below), the local part of the
8492 subject address is compared with the local part of the pattern, which may start
8493 with an asterisk. If the local parts match, the domain is checked in exactly
8494 the same way as for a pattern in a domain list. For example, the domain can be
8495 wildcarded, refer to a named list, or be a lookup:
8497 deny senders = *@*.spamming.site:\
8498 *@+hostile_domains:\
8499 bozo@partial-lsearch;/list/of/dodgy/sites:\
8500 *@dbm;/bad/domains.db
8502 .cindex "local part" "starting with !"
8503 .cindex "address list" "local part starting with !"
8504 If a local part that begins with an exclamation mark is required, it has to be
8505 specified using a regular expression, because otherwise the exclamation mark is
8506 treated as a sign of negation, as is standard in lists.
8508 If a non-empty pattern that is not a regular expression or a lookup does not
8509 contain an @ character, it is matched against the domain part of the subject
8510 address. The only two formats that are recognized this way are a literal
8511 domain, or a domain pattern that starts with *. In both these cases, the effect
8512 is the same as if &`*@`& preceded the pattern. For example:
8514 deny senders = enemy.domain : *.enemy.domain
8517 The following kinds of more complicated address list pattern can match any
8518 address, including the empty address that is characteristic of bounce message
8522 .cindex "regular expressions" "in address list"
8523 .cindex "address list" "regular expression in"
8524 If (after expansion) a pattern starts with &"^"&, a regular expression match is
8525 done against the complete address, with the pattern as the regular expression.
8526 You must take care that backslash and dollar characters are not misinterpreted
8527 as part of the string expansion. The simplest way to do this is to use &`\N`&
8528 to mark that part of the string as non-expandable. For example:
8530 deny senders = \N^.*this.*@example\.com$\N : \
8531 \N^\d{8}.+@spamhaus.example$\N : ...
8533 The &`\N`& sequences are removed by the expansion, so these items do indeed
8534 start with &"^"& by the time they are being interpreted as address patterns.
8537 .cindex "address list" "lookup for complete address"
8538 Complete addresses can be looked up by using a pattern that starts with a
8539 lookup type terminated by a semicolon, followed by the data for the lookup. For
8542 deny senders = cdb;/etc/blocked.senders : \
8543 mysql;select address from blocked where \
8544 address='${quote_mysql:$sender_address}'
8546 Both query-style and single-key lookup types can be used. For a single-key
8547 lookup type, Exim uses the complete address as the key. However, empty keys are
8548 not supported for single-key lookups, so a match against the empty address
8549 always fails. This restriction does not apply to query-style lookups.
8551 Partial matching for single-key lookups (section &<<SECTpartiallookup>>&)
8552 cannot be used, and is ignored if specified, with an entry being written to the
8554 .cindex "*@ with single-key lookup"
8555 However, you can configure lookup defaults, as described in section
8556 &<<SECTdefaultvaluelookups>>&, but this is useful only for the &"*@"& type of
8557 default. For example, with this lookup:
8559 accept senders = lsearch*@;/some/file
8561 the file could contains lines like this:
8563 user1@domain1.example
8566 and for the sender address &'nimrod@jaeger.example'&, the sequence of keys
8569 nimrod@jaeger.example
8573 &*Warning 1*&: Do not include a line keyed by &"*"& in the file, because that
8574 would mean that every address matches, thus rendering the test useless.
8576 &*Warning 2*&: Do not confuse these two kinds of item:
8578 deny recipients = dbm*@;/some/file
8579 deny recipients = *@dbm;/some/file
8581 The first does a whole address lookup, with defaulting, as just described,
8582 because it starts with a lookup type. The second matches the local part and
8583 domain independently, as described in a bullet point below.
8587 The following kinds of address list pattern can match only non-empty addresses.
8588 If the subject address is empty, a match against any of these pattern types
8593 .cindex "@@ with single-key lookup"
8594 .cindex "address list" "@@ lookup type"
8595 .cindex "address list" "split local part and domain"
8596 If a pattern starts with &"@@"& followed by a single-key lookup item
8597 (for example, &`@@lsearch;/some/file`&), the address that is being checked is
8598 split into a local part and a domain. The domain is looked up in the file. If
8599 it is not found, there is no match. If it is found, the data that is looked up
8600 from the file is treated as a colon-separated list of local part patterns, each
8601 of which is matched against the subject local part in turn.
8603 .cindex "asterisk" "in address list"
8604 The lookup may be a partial one, and/or one involving a search for a default
8605 keyed by &"*"& (see section &<<SECTdefaultvaluelookups>>&). The local part
8606 patterns that are looked up can be regular expressions or begin with &"*"&, or
8607 even be further lookups. They may also be independently negated. For example,
8610 deny senders = @@dbm;/etc/reject-by-domain
8612 the data from which the DBM file is built could contain lines like
8614 baddomain.com: !postmaster : *
8616 to reject all senders except &%postmaster%& from that domain.
8618 .cindex "local part" "starting with !"
8619 If a local part that actually begins with an exclamation mark is required, it
8620 has to be specified using a regular expression. In &(lsearch)& files, an entry
8621 may be split over several lines by indenting the second and subsequent lines,
8622 but the separating colon must still be included at line breaks. White space
8623 surrounding the colons is ignored. For example:
8625 aol.com: spammer1 : spammer2 : ^[0-9]+$ :
8628 As in all colon-separated lists in Exim, a colon can be included in an item by
8631 If the last item in the list starts with a right angle-bracket, the remainder
8632 of the item is taken as a new key to look up in order to obtain a continuation
8633 list of local parts. The new key can be any sequence of characters. Thus one
8634 might have entries like
8636 aol.com: spammer1 : spammer 2 : >*
8637 xyz.com: spammer3 : >*
8640 in a file that was searched with &%@@dbm*%&, to specify a match for 8-digit
8641 local parts for all domains, in addition to the specific local parts listed for
8642 each domain. Of course, using this feature costs another lookup each time a
8643 chain is followed, but the effort needed to maintain the data is reduced.
8645 .cindex "loop" "in lookups"
8646 It is possible to construct loops using this facility, and in order to catch
8647 them, the chains may be no more than fifty items long.
8650 The @@<&'lookup'&> style of item can also be used with a query-style
8651 lookup, but in this case, the chaining facility is not available. The lookup
8652 can only return a single list of local parts.
8655 &*Warning*&: There is an important difference between the address list items
8656 in these two examples:
8659 senders = *@+my_list
8661 In the first one, &`my_list`& is a named address list, whereas in the second
8662 example it is a named domain list.
8667 .section "Case of letters in address lists" "SECTcasletadd"
8668 .cindex "case of local parts"
8669 .cindex "address list" "case forcing"
8670 .cindex "case forcing in address lists"
8671 Domains in email addresses are always handled caselessly, but for local parts
8672 case may be significant on some systems (see &%caseful_local_part%& for how
8673 Exim deals with this when routing addresses). However, RFC 2505 (&'Anti-Spam
8674 Recommendations for SMTP MTAs'&) suggests that matching of addresses to
8675 blocking lists should be done in a case-independent manner. Since most address
8676 lists in Exim are used for this kind of control, Exim attempts to do this by
8679 The domain portion of an address is always lowercased before matching it to an
8680 address list. The local part is lowercased by default, and any string
8681 comparisons that take place are done caselessly. This means that the data in
8682 the address list itself, in files included as plain file names, and in any file
8683 that is looked up using the &"@@"& mechanism, can be in any case. However, the
8684 keys in files that are looked up by a search type other than &(lsearch)& (which
8685 works caselessly) must be in lower case, because these lookups are not
8688 .cindex "&`+caseful`&"
8689 To allow for the possibility of caseful address list matching, if an item in
8690 an address list is the string &"+caseful"&, the original case of the local
8691 part is restored for any comparisons that follow, and string comparisons are no
8692 longer case-independent. This does not affect the domain, which remains in
8693 lower case. However, although independent matches on the domain alone are still
8694 performed caselessly, regular expressions that match against an entire address
8695 become case-sensitive after &"+caseful"& has been seen.
8699 .section "Local part lists" "SECTlocparlis"
8700 .cindex "list" "local part list"
8701 .cindex "local part" "list"
8702 Case-sensitivity in local part lists is handled in the same way as for address
8703 lists, as just described. The &"+caseful"& item can be used if required. In a
8704 setting of the &%local_parts%& option in a router with &%caseful_local_part%&
8705 set false, the subject is lowercased and the matching is initially
8706 case-insensitive. In this case, &"+caseful"& will restore case-sensitive
8707 matching in the local part list, but not elsewhere in the router. If
8708 &%caseful_local_part%& is set true in a router, matching in the &%local_parts%&
8709 option is case-sensitive from the start.
8711 If a local part list is indirected to a file (see section &<<SECTfilnamlis>>&),
8712 comments are handled in the same way as address lists &-- they are recognized
8713 only if the # is preceded by white space or the start of the line.
8714 Otherwise, local part lists are matched in the same way as domain lists, except
8715 that the special items that refer to the local host (&`@`&, &`@[]`&,
8716 &`@mx_any`&, &`@mx_primary`&, and &`@mx_secondary`&) are not recognized.
8717 Refer to section &<<SECTdomainlist>>& for details of the other available item
8719 .ecindex IIDdohoadli
8724 . ////////////////////////////////////////////////////////////////////////////
8725 . ////////////////////////////////////////////////////////////////////////////
8727 .chapter "String expansions" "CHAPexpand"
8728 .scindex IIDstrexp "expansion" "of strings"
8729 Many strings in Exim's run time configuration are expanded before use. Some of
8730 them are expanded every time they are used; others are expanded only once.
8732 When a string is being expanded it is copied verbatim from left to right except
8733 when a dollar or backslash character is encountered. A dollar specifies the
8734 start of a portion of the string that is interpreted and replaced as described
8735 below in section &<<SECTexpansionitems>>& onwards. Backslash is used as an
8736 escape character, as described in the following section.
8738 Whether a string is expanded depends upon the context. Usually this is solely
8739 dependent upon the option for which a value is sought; in this documentation,
8740 options for which string expansion is performed are marked with † after
8741 the data type. ACL rules always expand strings. A couple of expansion
8742 conditions do not expand some of the brace-delimited branches, for security
8747 .section "Literal text in expanded strings" "SECTlittext"
8748 .cindex "expansion" "including literal text"
8749 An uninterpreted dollar can be included in an expanded string by putting a
8750 backslash in front of it. A backslash can be used to prevent any special
8751 character being treated specially in an expansion, including backslash itself.
8752 If the string appears in quotes in the configuration file, two backslashes are
8753 required because the quotes themselves cause interpretation of backslashes when
8754 the string is read in (see section &<<SECTstrings>>&).
8756 .cindex "expansion" "non-expandable substrings"
8757 A portion of the string can specified as non-expandable by placing it between
8758 two occurrences of &`\N`&. This is particularly useful for protecting regular
8759 expressions, which often contain backslashes and dollar signs. For example:
8761 deny senders = \N^\d{8}[a-z]@some\.site\.example$\N
8763 On encountering the first &`\N`&, the expander copies subsequent characters
8764 without interpretation until it reaches the next &`\N`& or the end of the
8769 .section "Character escape sequences in expanded strings" "SECID82"
8770 .cindex "expansion" "escape sequences"
8771 A backslash followed by one of the letters &"n"&, &"r"&, or &"t"& in an
8772 expanded string is recognized as an escape sequence for the character newline,
8773 carriage return, or tab, respectively. A backslash followed by up to three
8774 octal digits is recognized as an octal encoding for a single character, and a
8775 backslash followed by &"x"& and up to two hexadecimal digits is a hexadecimal
8778 These escape sequences are also recognized in quoted strings when they are read
8779 in. Their interpretation in expansions as well is useful for unquoted strings,
8780 and for other cases such as looked-up strings that are then expanded.
8783 .section "Testing string expansions" "SECID83"
8784 .cindex "expansion" "testing"
8785 .cindex "testing" "string expansion"
8787 Many expansions can be tested by calling Exim with the &%-be%& option. This
8788 takes the command arguments, or lines from the standard input if there are no
8789 arguments, runs them through the string expansion code, and writes the results
8790 to the standard output. Variables based on configuration values are set up, but
8791 since no message is being processed, variables such as &$local_part$& have no
8792 value. Nevertheless the &%-be%& option can be useful for checking out file and
8793 database lookups, and the use of expansion operators such as &%sg%&, &%substr%&
8796 Exim gives up its root privilege when it is called with the &%-be%& option, and
8797 instead runs under the uid and gid it was called with, to prevent users from
8798 using &%-be%& for reading files to which they do not have access.
8801 If you want to test expansions that include variables whose values are taken
8802 from a message, there are two other options that can be used. The &%-bem%&
8803 option is like &%-be%& except that it is followed by a file name. The file is
8804 read as a message before doing the test expansions. For example:
8806 exim -bem /tmp/test.message '$h_subject:'
8808 The &%-Mset%& option is used in conjunction with &%-be%& and is followed by an
8809 Exim message identifier. For example:
8811 exim -be -Mset 1GrA8W-0004WS-LQ '$recipients'
8813 This loads the message from Exim's spool before doing the test expansions, and
8814 is therefore restricted to admin users.
8817 .section "Forced expansion failure" "SECTforexpfai"
8818 .cindex "expansion" "forced failure"
8819 A number of expansions that are described in the following section have
8820 alternative &"true"& and &"false"& substrings, enclosed in brace characters
8821 (which are sometimes called &"curly brackets"&). Which of the two strings is
8822 used depends on some condition that is evaluated as part of the expansion. If,
8823 instead of a &"false"& substring, the word &"fail"& is used (not in braces),
8824 the entire string expansion fails in a way that can be detected by the code
8825 that requested the expansion. This is called &"forced expansion failure"&, and
8826 its consequences depend on the circumstances. In some cases it is no different
8827 from any other expansion failure, but in others a different action may be
8828 taken. Such variations are mentioned in the documentation of the option that is
8834 .section "Expansion items" "SECTexpansionitems"
8835 The following items are recognized in expanded strings. White space may be used
8836 between sub-items that are keywords or substrings enclosed in braces inside an
8837 outer set of braces, to improve readability. &*Warning*&: Within braces,
8838 white space is significant.
8841 .vitem &*$*&<&'variable&~name'&>&~or&~&*${*&<&'variable&~name'&>&*}*&
8842 .cindex "expansion" "variables"
8843 Substitute the contents of the named variable, for example:
8848 The second form can be used to separate the name from subsequent alphanumeric
8849 characters. This form (using braces) is available only for variables; it does
8850 &'not'& apply to message headers. The names of the variables are given in
8851 section &<<SECTexpvar>>& below. If the name of a non-existent variable is
8852 given, the expansion fails.
8854 .vitem &*${*&<&'op'&>&*:*&<&'string'&>&*}*&
8855 .cindex "expansion" "operators"
8856 The string is first itself expanded, and then the operation specified by
8857 <&'op'&> is applied to it. For example:
8861 The string starts with the first character after the colon, which may be
8862 leading white space. A list of operators is given in section &<<SECTexpop>>&
8863 below. The operator notation is used for simple expansion items that have just
8864 one argument, because it reduces the number of braces and therefore makes the
8865 string easier to understand.
8867 .vitem &*$bheader_*&<&'header&~name'&>&*:*&&~or&~&*$bh_*&<&'header&~name'&>&*:*&
8868 This item inserts &"basic"& header lines. It is described with the &%header%&
8869 expansion item below.
8872 .vitem "&*${acl{*&<&'name'&>&*}{*&<&'arg'&>&*}...}*&"
8873 .cindex "expansion" "calling an acl"
8874 .cindex "&%acl%&" "call from expansion"
8875 The name and zero to nine argument strings are first expanded separately. The expanded
8876 arguments are assigned to the variables &$acl_arg1$& to &$acl_arg9$& in order.
8877 Any unused are made empty. The variable &$acl_narg$& is set to the number of
8878 arguments. The named ACL (see chapter &<<CHAPACL>>&) is called
8879 and may use the variables; if another acl expansion is used the values
8880 are restored after it returns. If the ACL sets
8881 a value using a "message =" modifier and returns accept or deny, the value becomes
8882 the result of the expansion.
8883 If no message is set and the ACL returns accept or deny
8884 the expansion result is an empty string.
8885 If the ACL returns defer the result is a forced-fail. Otherwise the expansion fails.
8889 .vitem "&*${certextract{*&<&'field'&>&*}{*&<&'certificate'&>&*}&&&
8890 {*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
8891 .cindex "expansion" "extracting cerificate fields"
8892 .cindex "&%certextract%&" "certificate fields"
8893 .cindex "certificate" "extracting fields"
8894 The <&'certificate'&> must be a variable of type certificate.
8895 The field name is expanded and used to retrive the relevant field from
8896 the certificate. Supported fields are:
8900 &`subject `& RFC4514 DN
8901 &`issuer `& RFC4514 DN
8906 &`subj_altname `& tagged list
8910 If the field is found,
8911 <&'string2'&> is expanded, and replaces the whole item;
8912 otherwise <&'string3'&> is used. During the expansion of <&'string2'&> the
8913 variable &$value$& contains the value that has been extracted. Afterwards, it
8914 is restored to any previous value it might have had.
8916 If {<&'string3'&>} is omitted, the item is replaced by an empty string if the
8917 key is not found. If {<&'string2'&>} is also omitted, the value that was
8920 Some field names take optional modifiers, appended and separated by commas.
8922 The field selectors marked as "RFC4514" above
8923 output a Distinguished Name string which is
8925 parseable by Exim as a comma-separated tagged list
8926 (the exceptions being elements containin commas).
8927 RDN elements of a single type may be selected by
8928 a modifier of the type label; if so the expansion
8929 result is a list (newline-separated by default).
8930 The separator may be changed by another modifer of
8931 a right angle-bracket followed immediately by the new separator.
8932 Recognised RDN type labels include "CN", "O", "OU" and "DC".
8934 The field selectors marked as "time" above
8935 may output a number of seconds since epoch
8936 if the modifier "int" is used.
8938 The field selectors marked as "list" above return a list,
8939 newline-separated by default,
8940 (embedded separator characters in elements are doubled).
8941 The separator may be changed by a modifier of
8942 a right angle-bracket followed immediately by the new separator.
8944 The field selectors marked as "tagged" above
8945 prefix each list element with a type string and an equals sign.
8946 Elements of only one type may be selected by a modifier
8947 which is one of "dns", "uri" or "mail";
8948 if so the elenment tags are omitted.
8950 If not otherwise noted field values are presented in human-readable form.
8953 .vitem "&*${dlfunc{*&<&'file'&>&*}{*&<&'function'&>&*}{*&<&'arg'&>&*}&&&
8954 {*&<&'arg'&>&*}...}*&"
8956 This expansion dynamically loads and then calls a locally-written C function.
8957 This functionality is available only if Exim is compiled with
8961 set in &_Local/Makefile_&. Once loaded, Exim remembers the dynamically loaded
8962 object so that it doesn't reload the same object file in the same Exim process
8963 (but of course Exim does start new processes frequently).
8965 There may be from zero to eight arguments to the function. When compiling
8966 a local function that is to be called in this way, &_local_scan.h_& should be
8967 included. The Exim variables and functions that are defined by that API
8968 are also available for dynamically loaded functions. The function itself
8969 must have the following type:
8971 int dlfunction(uschar **yield, int argc, uschar *argv[])
8973 Where &`uschar`& is a typedef for &`unsigned char`& in &_local_scan.h_&. The
8974 function should return one of the following values:
8976 &`OK`&: Success. The string that is placed in the variable &'yield'& is put
8977 into the expanded string that is being built.
8979 &`FAIL`&: A non-forced expansion failure occurs, with the error message taken
8980 from &'yield'&, if it is set.
8982 &`FAIL_FORCED`&: A forced expansion failure occurs, with the error message
8983 taken from &'yield'& if it is set.
8985 &`ERROR`&: Same as &`FAIL`&, except that a panic log entry is written.
8987 When compiling a function that is to be used in this way with gcc,
8988 you need to add &%-shared%& to the gcc command. Also, in the Exim build-time
8989 configuration, you must add &%-export-dynamic%& to EXTRALIBS.
8991 .vitem "&*${extract{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}&&&
8992 {*&<&'string3'&>&*}}*&"
8993 .cindex "expansion" "extracting substrings by key"
8994 .cindex "&%extract%&" "substrings by key"
8995 The key and <&'string1'&> are first expanded separately. Leading and trailing
8996 white space is removed from the key (but not from any of the strings). The key
8997 must not consist entirely of digits. The expanded <&'string1'&> must be of the
9000 <&'key1'&> = <&'value1'&> <&'key2'&> = <&'value2'&> ...
9003 where the equals signs and spaces (but not both) are optional. If any of the
9004 values contain white space, they must be enclosed in double quotes, and any
9005 values that are enclosed in double quotes are subject to escape processing as
9006 described in section &<<SECTstrings>>&. The expanded <&'string1'&> is searched
9007 for the value that corresponds to the key. The search is case-insensitive. If
9008 the key is found, <&'string2'&> is expanded, and replaces the whole item;
9009 otherwise <&'string3'&> is used. During the expansion of <&'string2'&> the
9010 variable &$value$& contains the value that has been extracted. Afterwards, it
9011 is restored to any previous value it might have had.
9013 If {<&'string3'&>} is omitted, the item is replaced by an empty string if the
9014 key is not found. If {<&'string2'&>} is also omitted, the value that was
9015 extracted is used. Thus, for example, these two expansions are identical, and
9018 ${extract{gid}{uid=1984 gid=2001}}
9019 ${extract{gid}{uid=1984 gid=2001}{$value}}
9021 Instead of {<&'string3'&>} the word &"fail"& (not in curly brackets) can
9022 appear, for example:
9024 ${extract{Z}{A=... B=...}{$value} fail }
9026 This forces an expansion failure (see section &<<SECTforexpfai>>&);
9027 {<&'string2'&>} must be present for &"fail"& to be recognized.
9030 .vitem "&*${extract{*&<&'number'&>&*}{*&<&'separators'&>&*}&&&
9031 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
9032 .cindex "expansion" "extracting substrings by number"
9033 .cindex "&%extract%&" "substrings by number"
9034 The <&'number'&> argument must consist entirely of decimal digits,
9035 apart from leading and trailing white space, which is ignored.
9036 This is what distinguishes this form of &%extract%& from the previous kind. It
9037 behaves in the same way, except that, instead of extracting a named field, it
9038 extracts from <&'string1'&> the field whose number is given as the first
9039 argument. You can use &$value$& in <&'string2'&> or &`fail`& instead of
9040 <&'string3'&> as before.
9042 The fields in the string are separated by any one of the characters in the
9043 separator string. These may include space or tab characters.
9044 The first field is numbered one. If the number is negative, the fields are
9045 counted from the end of the string, with the rightmost one numbered -1. If the
9046 number given is zero, the entire string is returned. If the modulus of the
9047 number is greater than the number of fields in the string, the result is the
9048 expansion of <&'string3'&>, or the empty string if <&'string3'&> is not
9049 provided. For example:
9051 ${extract{2}{:}{x:42:99:& Mailer::/bin/bash}}
9055 ${extract{-4}{:}{x:42:99:& Mailer::/bin/bash}}
9057 yields &"99"&. Two successive separators mean that the field between them is
9058 empty (for example, the fifth field above).
9061 .vitem &*${filter{*&<&'string'&>&*}{*&<&'condition'&>&*}}*&
9062 .cindex "list" "selecting by condition"
9063 .cindex "expansion" "selecting from list by condition"
9065 After expansion, <&'string'&> is interpreted as a list, colon-separated by
9066 default, but the separator can be changed in the usual way. For each item
9067 in this list, its value is place in &$item$&, and then the condition is
9068 evaluated. If the condition is true, &$item$& is added to the output as an
9069 item in a new list; if the condition is false, the item is discarded. The
9070 separator used for the output list is the same as the one used for the
9071 input, but a separator setting is not included in the output. For example:
9073 ${filter{a:b:c}{!eq{$item}{b}}
9075 yields &`a:c`&. At the end of the expansion, the value of &$item$& is restored
9076 to what it was before. See also the &*map*& and &*reduce*& expansion items.
9079 .vitem &*${hash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
9080 .cindex "hash function" "textual"
9081 .cindex "expansion" "textual hash"
9082 This is a textual hashing function, and was the first to be implemented in
9083 early versions of Exim. In current releases, there are other hashing functions
9084 (numeric, MD5, and SHA-1), which are described below.
9086 The first two strings, after expansion, must be numbers. Call them <&'m'&> and
9087 <&'n'&>. If you are using fixed values for these numbers, that is, if
9088 <&'string1'&> and <&'string2'&> do not change when they are expanded, you can
9089 use the simpler operator notation that avoids some of the braces:
9091 ${hash_<n>_<m>:<string>}
9093 The second number is optional (in both notations). If <&'n'&> is greater than
9094 or equal to the length of the string, the expansion item returns the string.
9095 Otherwise it computes a new string of length <&'n'&> by applying a hashing
9096 function to the string. The new string consists of characters taken from the
9097 first <&'m'&> characters of the string
9099 abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQWRSTUVWXYZ0123456789
9101 If <&'m'&> is not present the value 26 is used, so that only lower case
9102 letters appear. For example:
9104 &`$hash{3}{monty}} `& yields &`jmg`&
9105 &`$hash{5}{monty}} `& yields &`monty`&
9106 &`$hash{4}{62}{monty python}}`& yields &`fbWx`&
9109 .vitem "&*$header_*&<&'header&~name'&>&*:*&&~or&~&&&
9110 &*$h_*&<&'header&~name'&>&*:*&" &&&
9111 "&*$bheader_*&<&'header&~name'&>&*:*&&~or&~&&&
9112 &*$bh_*&<&'header&~name'&>&*:*&" &&&
9113 "&*$rheader_*&<&'header&~name'&>&*:*&&~or&~&&&
9114 &*$rh_*&<&'header&~name'&>&*:*&"
9115 .cindex "expansion" "header insertion"
9116 .vindex "&$header_$&"
9117 .vindex "&$bheader_$&"
9118 .vindex "&$rheader_$&"
9119 .cindex "header lines" "in expansion strings"
9120 .cindex "header lines" "character sets"
9121 .cindex "header lines" "decoding"
9122 Substitute the contents of the named message header line, for example
9126 The newline that terminates a header line is not included in the expansion, but
9127 internal newlines (caused by splitting the header line over several physical
9128 lines) may be present.
9130 The difference between &%rheader%&, &%bheader%&, and &%header%& is in the way
9131 the data in the header line is interpreted.
9134 .cindex "white space" "in header lines"
9135 &%rheader%& gives the original &"raw"& content of the header line, with no
9136 processing at all, and without the removal of leading and trailing white space.
9139 .cindex "base64 encoding" "in header lines"
9140 &%bheader%& removes leading and trailing white space, and then decodes base64
9141 or quoted-printable MIME &"words"& within the header text, but does no
9142 character set translation. If decoding of what looks superficially like a MIME
9143 &"word"& fails, the raw string is returned. If decoding
9144 .cindex "binary zero" "in header line"
9145 produces a binary zero character, it is replaced by a question mark &-- this is
9146 what Exim does for binary zeros that are actually received in header lines.
9149 &%header%& tries to translate the string as decoded by &%bheader%& to a
9150 standard character set. This is an attempt to produce the same string as would
9151 be displayed on a user's MUA. If translation fails, the &%bheader%& string is
9152 returned. Translation is attempted only on operating systems that support the
9153 &[iconv()]& function. This is indicated by the compile-time macro HAVE_ICONV in
9154 a system Makefile or in &_Local/Makefile_&.
9157 In a filter file, the target character set for &%header%& can be specified by a
9158 command of the following form:
9160 headers charset "UTF-8"
9162 This command affects all references to &$h_$& (or &$header_$&) expansions in
9163 subsequently obeyed filter commands. In the absence of this command, the target
9164 character set in a filter is taken from the setting of the &%headers_charset%&
9165 option in the runtime configuration. The value of this option defaults to the
9166 value of HEADERS_CHARSET in &_Local/Makefile_&. The ultimate default is
9169 Header names follow the syntax of RFC 2822, which states that they may contain
9170 any printing characters except space and colon. Consequently, curly brackets
9171 &'do not'& terminate header names, and should not be used to enclose them as
9172 if they were variables. Attempting to do so causes a syntax error.
9174 Only header lines that are common to all copies of a message are visible to
9175 this mechanism. These are the original header lines that are received with the
9176 message, and any that are added by an ACL statement or by a system
9177 filter. Header lines that are added to a particular copy of a message by a
9178 router or transport are not accessible.
9180 For incoming SMTP messages, no header lines are visible in ACLs that are obeyed
9181 before the DATA ACL, because the header structure is not set up until the
9182 message is received. Header lines that are added in a RCPT ACL (for example)
9183 are saved until the message's incoming header lines are available, at which
9184 point they are added. When a DATA ACL is running, however, header lines added
9185 by earlier ACLs are visible.
9187 Upper case and lower case letters are synonymous in header names. If the
9188 following character is white space, the terminating colon may be omitted, but
9189 this is not recommended, because you may then forget it when it is needed. When
9190 white space terminates the header name, it is included in the expanded string.
9191 If the message does not contain the given header, the expansion item is
9192 replaced by an empty string. (See the &%def%& condition in section
9193 &<<SECTexpcond>>& for a means of testing for the existence of a header.)
9195 If there is more than one header with the same name, they are all concatenated
9196 to form the substitution string, up to a maximum length of 64K. Unless
9197 &%rheader%& is being used, leading and trailing white space is removed from
9198 each header before concatenation, and a completely empty header is ignored. A
9199 newline character is then inserted between non-empty headers, but there is no
9200 newline at the very end. For the &%header%& and &%bheader%& expansion, for
9201 those headers that contain lists of addresses, a comma is also inserted at the
9202 junctions between headers. This does not happen for the &%rheader%& expansion.
9205 .vitem &*${hmac{*&<&'hashname'&>&*}{*&<&'secret'&>&*}{*&<&'string'&>&*}}*&
9206 .cindex "expansion" "hmac hashing"
9208 This function uses cryptographic hashing (either MD5 or SHA-1) to convert a
9209 shared secret and some text into a message authentication code, as specified in
9210 RFC 2104. This differs from &`${md5:secret_text...}`& or
9211 &`${sha1:secret_text...}`& in that the hmac step adds a signature to the
9212 cryptographic hash, allowing for authentication that is not possible with MD5
9213 or SHA-1 alone. The hash name must expand to either &`md5`& or &`sha1`& at
9214 present. For example:
9216 ${hmac{md5}{somesecret}{$primary_hostname $tod_log}}
9218 For the hostname &'mail.example.com'& and time 2002-10-17 11:30:59, this
9221 dd97e3ba5d1a61b5006108f8c8252953
9223 As an example of how this might be used, you might put in the main part of
9224 an Exim configuration:
9226 SPAMSCAN_SECRET=cohgheeLei2thahw
9228 In a router or a transport you could then have:
9231 X-Spam-Scanned: ${primary_hostname} ${message_exim_id} \
9232 ${hmac{md5}{SPAMSCAN_SECRET}\
9233 {${primary_hostname},${message_exim_id},$h_message-id:}}
9235 Then given a message, you can check where it was scanned by looking at the
9236 &'X-Spam-Scanned:'& header line. If you know the secret, you can check that
9237 this header line is authentic by recomputing the authentication code from the
9238 host name, message ID and the &'Message-id:'& header line. This can be done
9239 using Exim's &%-be%& option, or by other means, for example by using the
9240 &'hmac_md5_hex()'& function in Perl.
9243 .vitem &*${if&~*&<&'condition'&>&*&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
9244 .cindex "expansion" "conditional"
9245 .cindex "&%if%&, expansion item"
9246 If <&'condition'&> is true, <&'string1'&> is expanded and replaces the whole
9247 item; otherwise <&'string2'&> is used. The available conditions are described
9248 in section &<<SECTexpcond>>& below. For example:
9250 ${if eq {$local_part}{postmaster} {yes}{no} }
9252 The second string need not be present; if it is not and the condition is not
9253 true, the item is replaced with nothing. Alternatively, the word &"fail"& may
9254 be present instead of the second string (without any curly brackets). In this
9255 case, the expansion is forced to fail if the condition is not true (see section
9256 &<<SECTforexpfai>>&).
9258 If both strings are omitted, the result is the string &`true`& if the condition
9259 is true, and the empty string if the condition is false. This makes it less
9260 cumbersome to write custom ACL and router conditions. For example, instead of
9262 condition = ${if >{$acl_m4}{3}{true}{false}}
9266 condition = ${if >{$acl_m4}{3}}
9269 .vitem &*${length{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
9270 .cindex "expansion" "string truncation"
9271 .cindex "&%length%& expansion item"
9272 The &%length%& item is used to extract the initial portion of a string. Both
9273 strings are expanded, and the first one must yield a number, <&'n'&>, say. If
9274 you are using a fixed value for the number, that is, if <&'string1'&> does not
9275 change when expanded, you can use the simpler operator notation that avoids
9278 ${length_<n>:<string>}
9280 The result of this item is either the first <&'n'&> characters or the whole
9281 of <&'string2'&>, whichever is the shorter. Do not confuse &%length%& with
9282 &%strlen%&, which gives the length of a string.
9285 .vitem "&*${listextract{*&<&'number'&>&*}&&&
9286 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
9287 .cindex "expansion" "extracting list elements by number"
9288 .cindex "&%listextract%&" "extract list elements by number"
9289 .cindex "list" "extracting elements by number"
9290 The <&'number'&> argument must consist entirely of decimal digits,
9291 apart from an optional leading minus,
9292 and leading and trailing white space (which is ignored).
9294 After expansion, <&'string1'&> is interpreted as a list, colon-separated by
9295 default, but the separator can be changed in the usual way.
9297 The first field of the list is numbered one.
9298 If the number is negative, the fields are
9299 counted from the end of the list, with the rightmost one numbered -1.
9300 The numbered element of the list is extracted and placed in &$value$&,
9301 then <&'string2'&> is expanded as the result.
9303 If the modulus of the
9304 number is zero or greater than the number of fields in the string,
9305 the result is the expansion of <&'string3'&>.
9309 ${listextract{2}{x:42:99}}
9313 ${listextract{-3}{<, x,42,99,& Mailer,,/bin/bash}{result: $value}}
9315 yields &"result: 99"&.
9317 If {<&'string3'&>} is omitted, an empty string is used for string3.
9318 If {<&'string2'&>} is also omitted, the value that was
9320 You can use &`fail`& instead of {<&'string3'&>} as in a string extract.
9323 .vitem "&*${lookup{*&<&'key'&>&*}&~*&<&'search&~type'&>&*&~&&&
9324 {*&<&'file'&>&*}&~{*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&"
9325 This is the first of one of two different types of lookup item, which are both
9326 described in the next item.
9328 .vitem "&*${lookup&~*&<&'search&~type'&>&*&~{*&<&'query'&>&*}&~&&&
9329 {*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&"
9330 .cindex "expansion" "lookup in"
9331 .cindex "file" "lookups"
9332 .cindex "lookup" "in expanded string"
9333 The two forms of lookup item specify data lookups in files and databases, as
9334 discussed in chapter &<<CHAPfdlookup>>&. The first form is used for single-key
9335 lookups, and the second is used for query-style lookups. The <&'key'&>,
9336 <&'file'&>, and <&'query'&> strings are expanded before use.
9338 If there is any white space in a lookup item which is part of a filter command,
9339 a retry or rewrite rule, a routing rule for the &(manualroute)& router, or any
9340 other place where white space is significant, the lookup item must be enclosed
9341 in double quotes. The use of data lookups in users' filter files may be locked
9342 out by the system administrator.
9345 If the lookup succeeds, <&'string1'&> is expanded and replaces the entire item.
9346 During its expansion, the variable &$value$& contains the data returned by the
9347 lookup. Afterwards it reverts to the value it had previously (at the outer
9348 level it is empty). If the lookup fails, <&'string2'&> is expanded and replaces
9349 the entire item. If {<&'string2'&>} is omitted, the replacement is the empty
9350 string on failure. If <&'string2'&> is provided, it can itself be a nested
9351 lookup, thus providing a mechanism for looking up a default value when the
9352 original lookup fails.
9354 If a nested lookup is used as part of <&'string1'&>, &$value$& contains the
9355 data for the outer lookup while the parameters of the second lookup are
9356 expanded, and also while <&'string2'&> of the second lookup is expanded, should
9357 the second lookup fail. Instead of {<&'string2'&>} the word &"fail"& can
9358 appear, and in this case, if the lookup fails, the entire expansion is forced
9359 to fail (see section &<<SECTforexpfai>>&). If both {<&'string1'&>} and
9360 {<&'string2'&>} are omitted, the result is the looked up value in the case of a
9361 successful lookup, and nothing in the case of failure.
9363 For single-key lookups, the string &"partial"& is permitted to precede the
9364 search type in order to do partial matching, and * or *@ may follow a search
9365 type to request default lookups if the key does not match (see sections
9366 &<<SECTdefaultvaluelookups>>& and &<<SECTpartiallookup>>& for details).
9368 .cindex "numerical variables (&$1$& &$2$& etc)" "in lookup expansion"
9369 If a partial search is used, the variables &$1$& and &$2$& contain the wild
9370 and non-wild parts of the key during the expansion of the replacement text.
9371 They return to their previous values at the end of the lookup item.
9373 This example looks up the postmaster alias in the conventional alias file:
9375 ${lookup {postmaster} lsearch {/etc/aliases} {$value}}
9377 This example uses NIS+ to look up the full name of the user corresponding to
9378 the local part of an address, forcing the expansion to fail if it is not found:
9380 ${lookup nisplus {[name=$local_part],passwd.org_dir:gcos} \
9385 .vitem &*${map{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
9386 .cindex "expansion" "list creation"
9388 After expansion, <&'string1'&> is interpreted as a list, colon-separated by
9389 default, but the separator can be changed in the usual way. For each item
9390 in this list, its value is place in &$item$&, and then <&'string2'&> is
9391 expanded and added to the output as an item in a new list. The separator used
9392 for the output list is the same as the one used for the input, but a separator
9393 setting is not included in the output. For example:
9395 ${map{a:b:c}{[$item]}} ${map{<- x-y-z}{($item)}}
9397 expands to &`[a]:[b]:[c] (x)-(y)-(z)`&. At the end of the expansion, the
9398 value of &$item$& is restored to what it was before. See also the &*filter*&
9399 and &*reduce*& expansion items.
9401 .vitem &*${nhash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
9402 .cindex "expansion" "numeric hash"
9403 .cindex "hash function" "numeric"
9404 The three strings are expanded; the first two must yield numbers. Call them
9405 <&'n'&> and <&'m'&>. If you are using fixed values for these numbers, that is,
9406 if <&'string1'&> and <&'string2'&> do not change when they are expanded, you
9407 can use the simpler operator notation that avoids some of the braces:
9409 ${nhash_<n>_<m>:<string>}
9411 The second number is optional (in both notations). If there is only one number,
9412 the result is a number in the range 0&--<&'n'&>-1. Otherwise, the string is
9413 processed by a div/mod hash function that returns two numbers, separated by a
9414 slash, in the ranges 0 to <&'n'&>-1 and 0 to <&'m'&>-1, respectively. For
9417 ${nhash{8}{64}{supercalifragilisticexpialidocious}}
9419 returns the string &"6/33"&.
9423 .vitem &*${perl{*&<&'subroutine'&>&*}{*&<&'arg'&>&*}{*&<&'arg'&>&*}...}*&
9424 .cindex "Perl" "use in expanded string"
9425 .cindex "expansion" "calling Perl from"
9426 This item is available only if Exim has been built to include an embedded Perl
9427 interpreter. The subroutine name and the arguments are first separately
9428 expanded, and then the Perl subroutine is called with those arguments. No
9429 additional arguments need be given; the maximum number permitted, including the
9430 name of the subroutine, is nine.
9432 The return value of the subroutine is inserted into the expanded string, unless
9433 the return value is &%undef%&. In that case, the expansion fails in the same
9434 way as an explicit &"fail"& on a lookup item. The return value is a scalar.
9435 Whatever you return is evaluated in a scalar context. For example, if you
9436 return the name of a Perl vector, the return value is the size of the vector,
9439 If the subroutine exits by calling Perl's &%die%& function, the expansion fails
9440 with the error message that was passed to &%die%&. More details of the embedded
9441 Perl facility are given in chapter &<<CHAPperl>>&.
9443 The &(redirect)& router has an option called &%forbid_filter_perl%& which locks
9444 out the use of this expansion item in filter files.
9447 .vitem &*${prvs{*&<&'address'&>&*}{*&<&'secret'&>&*}{*&<&'keynumber'&>&*}}*&
9448 .cindex "&%prvs%& expansion item"
9449 The first argument is a complete email address and the second is secret
9450 keystring. The third argument, specifying a key number, is optional. If absent,
9451 it defaults to 0. The result of the expansion is a prvs-signed email address,
9452 to be typically used with the &%return_path%& option on an &(smtp)& transport
9453 as part of a bounce address tag validation (BATV) scheme. For more discussion
9454 and an example, see section &<<SECTverifyPRVS>>&.
9456 .vitem "&*${prvscheck{*&<&'address'&>&*}{*&<&'secret'&>&*}&&&
9457 {*&<&'string'&>&*}}*&"
9458 .cindex "&%prvscheck%& expansion item"
9459 This expansion item is the complement of the &%prvs%& item. It is used for
9460 checking prvs-signed addresses. If the expansion of the first argument does not
9461 yield a syntactically valid prvs-signed address, the whole item expands to the
9462 empty string. When the first argument does expand to a syntactically valid
9463 prvs-signed address, the second argument is expanded, with the prvs-decoded
9464 version of the address and the key number extracted from the address in the
9465 variables &$prvscheck_address$& and &$prvscheck_keynum$&, respectively.
9467 These two variables can be used in the expansion of the second argument to
9468 retrieve the secret. The validity of the prvs-signed address is then checked
9469 against the secret. The result is stored in the variable &$prvscheck_result$&,
9470 which is empty for failure or &"1"& for success.
9472 The third argument is optional; if it is missing, it defaults to an empty
9473 string. This argument is now expanded. If the result is an empty string, the
9474 result of the expansion is the decoded version of the address. This is the case
9475 whether or not the signature was valid. Otherwise, the result of the expansion
9476 is the expansion of the third argument.
9478 All three variables can be used in the expansion of the third argument.
9479 However, once the expansion is complete, only &$prvscheck_result$& remains set.
9480 For more discussion and an example, see section &<<SECTverifyPRVS>>&.
9482 .vitem &*${readfile{*&<&'file&~name'&>&*}{*&<&'eol&~string'&>&*}}*&
9483 .cindex "expansion" "inserting an entire file"
9484 .cindex "file" "inserting into expansion"
9485 .cindex "&%readfile%& expansion item"
9486 The file name and end-of-line string are first expanded separately. The file is
9487 then read, and its contents replace the entire item. All newline characters in
9488 the file are replaced by the end-of-line string if it is present. Otherwise,
9489 newlines are left in the string.
9490 String expansion is not applied to the contents of the file. If you want this,
9491 you must wrap the item in an &%expand%& operator. If the file cannot be read,
9492 the string expansion fails.
9494 The &(redirect)& router has an option called &%forbid_filter_readfile%& which
9495 locks out the use of this expansion item in filter files.
9499 .vitem "&*${readsocket{*&<&'name'&>&*}{*&<&'request'&>&*}&&&
9500 {*&<&'timeout'&>&*}{*&<&'eol&~string'&>&*}{*&<&'fail&~string'&>&*}}*&"
9501 .cindex "expansion" "inserting from a socket"
9502 .cindex "socket, use of in expansion"
9503 .cindex "&%readsocket%& expansion item"
9504 This item inserts data from a Unix domain or Internet socket into the expanded
9505 string. The minimal way of using it uses just two arguments, as in these
9508 ${readsocket{/socket/name}{request string}}
9509 ${readsocket{inet:some.host:1234}{request string}}
9511 For a Unix domain socket, the first substring must be the path to the socket.
9512 For an Internet socket, the first substring must contain &`inet:`& followed by
9513 a host name or IP address, followed by a colon and a port, which can be a
9514 number or the name of a TCP port in &_/etc/services_&. An IP address may
9515 optionally be enclosed in square brackets. This is best for IPv6 addresses. For
9518 ${readsocket{inet:[::1]:1234}{request string}}
9520 Only a single host name may be given, but if looking it up yields more than
9521 one IP address, they are each tried in turn until a connection is made. For
9522 both kinds of socket, Exim makes a connection, writes the request string
9523 (unless it is an empty string) and reads from the socket until an end-of-file
9524 is read. A timeout of 5 seconds is applied. Additional, optional arguments
9525 extend what can be done. Firstly, you can vary the timeout. For example:
9527 ${readsocket{/socket/name}{request string}{3s}}
9529 A fourth argument allows you to change any newlines that are in the data
9530 that is read, in the same way as for &%readfile%& (see above). This example
9531 turns them into spaces:
9533 ${readsocket{inet:127.0.0.1:3294}{request string}{3s}{ }}
9535 As with all expansions, the substrings are expanded before the processing
9536 happens. Errors in these sub-expansions cause the expansion to fail. In
9537 addition, the following errors can occur:
9540 Failure to create a socket file descriptor;
9542 Failure to connect the socket;
9544 Failure to write the request string;
9546 Timeout on reading from the socket.
9549 By default, any of these errors causes the expansion to fail. However, if
9550 you supply a fifth substring, it is expanded and used when any of the above
9551 errors occurs. For example:
9553 ${readsocket{/socket/name}{request string}{3s}{\n}\
9556 You can test for the existence of a Unix domain socket by wrapping this
9557 expansion in &`${if exists`&, but there is a race condition between that test
9558 and the actual opening of the socket, so it is safer to use the fifth argument
9559 if you want to be absolutely sure of avoiding an expansion error for a
9560 non-existent Unix domain socket, or a failure to connect to an Internet socket.
9562 The &(redirect)& router has an option called &%forbid_filter_readsocket%& which
9563 locks out the use of this expansion item in filter files.
9566 .vitem &*${reduce{*&<&'string1'&>}{<&'string2'&>&*}{*&<&'string3'&>&*}}*&
9567 .cindex "expansion" "reducing a list to a scalar"
9568 .cindex "list" "reducing to a scalar"
9571 This operation reduces a list to a single, scalar string. After expansion,
9572 <&'string1'&> is interpreted as a list, colon-separated by default, but the
9573 separator can be changed in the usual way. Then <&'string2'&> is expanded and
9574 assigned to the &$value$& variable. After this, each item in the <&'string1'&>
9575 list is assigned to &$item$& in turn, and <&'string3'&> is expanded for each of
9576 them. The result of that expansion is assigned to &$value$& before the next
9577 iteration. When the end of the list is reached, the final value of &$value$& is
9578 added to the expansion output. The &*reduce*& expansion item can be used in a
9579 number of ways. For example, to add up a list of numbers:
9581 ${reduce {<, 1,2,3}{0}{${eval:$value+$item}}}
9583 The result of that expansion would be &`6`&. The maximum of a list of numbers
9586 ${reduce {3:0:9:4:6}{0}{${if >{$item}{$value}{$item}{$value}}}}
9588 At the end of a &*reduce*& expansion, the values of &$item$& and &$value$& are
9589 restored to what they were before. See also the &*filter*& and &*map*&
9592 .vitem &*$rheader_*&<&'header&~name'&>&*:*&&~or&~&*$rh_*&<&'header&~name'&>&*:*&
9593 This item inserts &"raw"& header lines. It is described with the &%header%&
9594 expansion item above.
9596 .vitem "&*${run{*&<&'command'&>&*&~*&<&'args'&>&*}{*&<&'string1'&>&*}&&&
9597 {*&<&'string2'&>&*}}*&"
9598 .cindex "expansion" "running a command"
9599 .cindex "&%run%& expansion item"
9600 The command and its arguments are first expanded separately, and then the
9601 command is run in a separate process, but under the same uid and gid. As in
9602 other command executions from Exim, a shell is not used by default. If you want
9603 a shell, you must explicitly code it.
9605 The standard input for the command exists, but is empty. The standard output
9606 and standard error are set to the same file descriptor.
9607 .cindex "return code" "from &%run%& expansion"
9609 If the command succeeds (gives a zero return code) <&'string1'&> is expanded
9610 and replaces the entire item; during this expansion, the standard output/error
9611 from the command is in the variable &$value$&. If the command fails,
9612 <&'string2'&>, if present, is expanded and used. Once again, during the
9613 expansion, the standard output/error from the command is in the variable
9616 If <&'string2'&> is absent, the result is empty. Alternatively, <&'string2'&>
9617 can be the word &"fail"& (not in braces) to force expansion failure if the
9618 command does not succeed. If both strings are omitted, the result is contents
9619 of the standard output/error on success, and nothing on failure.
9621 .vindex "&$run_in_acl$&"
9622 The standard output/error of the command is put in the variable &$value$&.
9623 In this ACL example, the output of a command is logged for the admin to
9626 warn condition = ${run{/usr/bin/id}{yes}{no}}
9627 log_message = Output of id: $value
9629 If the command requires shell idioms, such as the > redirect operator, the
9630 shell must be invoked directly, such as with:
9632 ${run{/bin/bash -c "/usr/bin/id >/tmp/id"}{yes}{yes}}
9636 The return code from the command is put in the variable &$runrc$&, and this
9637 remains set afterwards, so in a filter file you can do things like this:
9639 if "${run{x y z}{}}$runrc" is 1 then ...
9640 elif $runrc is 2 then ...
9644 If execution of the command fails (for example, the command does not exist),
9645 the return code is 127 &-- the same code that shells use for non-existent
9648 &*Warning*&: In a router or transport, you cannot assume the order in which
9649 option values are expanded, except for those preconditions whose order of
9650 testing is documented. Therefore, you cannot reliably expect to set &$runrc$&
9651 by the expansion of one option, and use it in another.
9653 The &(redirect)& router has an option called &%forbid_filter_run%& which locks
9654 out the use of this expansion item in filter files.
9657 .vitem &*${sg{*&<&'subject'&>&*}{*&<&'regex'&>&*}{*&<&'replacement'&>&*}}*&
9658 .cindex "expansion" "string substitution"
9659 .cindex "&%sg%& expansion item"
9660 This item works like Perl's substitution operator (s) with the global (/g)
9661 option; hence its name. However, unlike the Perl equivalent, Exim does not
9662 modify the subject string; instead it returns the modified string for insertion
9663 into the overall expansion. The item takes three arguments: the subject string,
9664 a regular expression, and a substitution string. For example:
9666 ${sg{abcdefabcdef}{abc}{xyz}}
9668 yields &"xyzdefxyzdef"&. Because all three arguments are expanded before use,
9669 if any $ or \ characters are required in the regular expression or in the
9670 substitution string, they have to be escaped. For example:
9672 ${sg{abcdef}{^(...)(...)\$}{\$2\$1}}
9674 yields &"defabc"&, and
9676 ${sg{1=A 4=D 3=C}{\N(\d+)=\N}{K\$1=}}
9678 yields &"K1=A K4=D K3=C"&. Note the use of &`\N`& to protect the contents of
9679 the regular expression from string expansion.
9683 .vitem &*${substr{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
9684 .cindex "&%substr%& expansion item"
9685 .cindex "substring extraction"
9686 .cindex "expansion" "substring extraction"
9687 The three strings are expanded; the first two must yield numbers. Call them
9688 <&'n'&> and <&'m'&>. If you are using fixed values for these numbers, that is,
9689 if <&'string1'&> and <&'string2'&> do not change when they are expanded, you
9690 can use the simpler operator notation that avoids some of the braces:
9692 ${substr_<n>_<m>:<string>}
9694 The second number is optional (in both notations).
9695 If it is absent in the simpler format, the preceding underscore must also be
9698 The &%substr%& item can be used to extract more general substrings than
9699 &%length%&. The first number, <&'n'&>, is a starting offset, and <&'m'&> is the
9700 length required. For example
9702 ${substr{3}{2}{$local_part}}
9704 If the starting offset is greater than the string length the result is the
9705 null string; if the length plus starting offset is greater than the string
9706 length, the result is the right-hand part of the string, starting from the
9707 given offset. The first character in the string has offset zero.
9709 The &%substr%& expansion item can take negative offset values to count
9710 from the right-hand end of its operand. The last character is offset -1, the
9711 second-last is offset -2, and so on. Thus, for example,
9713 ${substr{-5}{2}{1234567}}
9715 yields &"34"&. If the absolute value of a negative offset is greater than the
9716 length of the string, the substring starts at the beginning of the string, and
9717 the length is reduced by the amount of overshoot. Thus, for example,
9719 ${substr{-5}{2}{12}}
9721 yields an empty string, but
9723 ${substr{-3}{2}{12}}
9727 When the second number is omitted from &%substr%&, the remainder of the string
9728 is taken if the offset is positive. If it is negative, all characters in the
9729 string preceding the offset point are taken. For example, an offset of -1 and
9730 no length, as in these semantically identical examples:
9733 ${substr{-1}{abcde}}
9735 yields all but the last character of the string, that is, &"abcd"&.
9739 .vitem "&*${tr{*&<&'subject'&>&*}{*&<&'characters'&>&*}&&&
9740 {*&<&'replacements'&>&*}}*&"
9741 .cindex "expansion" "character translation"
9742 .cindex "&%tr%& expansion item"
9743 This item does single-character translation on its subject string. The second
9744 argument is a list of characters to be translated in the subject string. Each
9745 matching character is replaced by the corresponding character from the
9746 replacement list. For example
9748 ${tr{abcdea}{ac}{13}}
9750 yields &`1b3de1`&. If there are duplicates in the second character string, the
9751 last occurrence is used. If the third string is shorter than the second, its
9752 last character is replicated. However, if it is empty, no translation takes
9758 .section "Expansion operators" "SECTexpop"
9759 .cindex "expansion" "operators"
9760 For expansion items that perform transformations on a single argument string,
9761 the &"operator"& notation is used because it is simpler and uses fewer braces.
9762 The substring is first expanded before the operation is applied to it. The
9763 following operations can be performed:
9766 .vitem &*${address:*&<&'string'&>&*}*&
9767 .cindex "expansion" "RFC 2822 address handling"
9768 .cindex "&%address%& expansion item"
9769 The string is interpreted as an RFC 2822 address, as it might appear in a
9770 header line, and the effective address is extracted from it. If the string does
9771 not parse successfully, the result is empty.
9774 .vitem &*${addresses:*&<&'string'&>&*}*&
9775 .cindex "expansion" "RFC 2822 address handling"
9776 .cindex "&%addresses%& expansion item"
9777 The string (after expansion) is interpreted as a list of addresses in RFC
9778 2822 format, such as can be found in a &'To:'& or &'Cc:'& header line. The
9779 operative address (&'local-part@domain'&) is extracted from each item, and the
9780 result of the expansion is a colon-separated list, with appropriate
9781 doubling of colons should any happen to be present in the email addresses.
9782 Syntactically invalid RFC2822 address items are omitted from the output.
9784 It is possible to specify a character other than colon for the output
9785 separator by starting the string with > followed by the new separator
9786 character. For example:
9788 ${addresses:>& Chief <ceo@up.stairs>, sec@base.ment (dogsbody)}
9790 expands to &`ceo@up.stairs&&sec@base.ment`&. Compare the &*address*& (singular)
9791 expansion item, which extracts the working address from a single RFC2822
9792 address. See the &*filter*&, &*map*&, and &*reduce*& items for ways of
9795 To clarify "list of addresses in RFC 2822 format" mentioned above, Exim follows
9796 a strict interpretation of header line formatting. Exim parses the bare,
9797 unquoted portion of an email address and if it finds a comma, treats it as an
9798 email address seperator. For the example header line:
9800 From: =?iso-8859-2?Q?Last=2C_First?= <user@example.com>
9802 The first example below demonstrates that Q-encoded email addresses are parsed
9803 properly if it is given the raw header (in this example, &`$rheader_from:`&).
9804 It does not see the comma because it's still encoded as "=2C". The second
9805 example below is passed the contents of &`$header_from:`&, meaning it gets
9806 de-mimed. Exim sees the decoded "," so it treats it as &*two*& email addresses.
9807 The third example shows that the presence of a comma is skipped when it is
9810 # exim -be '${addresses:From: \
9811 =?iso-8859-2?Q?Last=2C_First?= <user@example.com>}'
9813 # exim -be '${addresses:From: Last, First <user@example.com>}'
9814 Last:user@example.com
9815 # exim -be '${addresses:From: "Last, First" <user@example.com>}'
9819 .vitem &*${base62:*&<&'digits'&>&*}*&
9820 .cindex "&%base62%& expansion item"
9821 .cindex "expansion" "conversion to base 62"
9822 The string must consist entirely of decimal digits. The number is converted to
9823 base 62 and output as a string of six characters, including leading zeros. In
9824 the few operating environments where Exim uses base 36 instead of base 62 for
9825 its message identifiers (because those systems do not have case-sensitive file
9826 names), base 36 is used by this operator, despite its name. &*Note*&: Just to
9827 be absolutely clear: this is &'not'& base64 encoding.
9829 .vitem &*${base62d:*&<&'base-62&~digits'&>&*}*&
9830 .cindex "&%base62d%& expansion item"
9831 .cindex "expansion" "conversion to base 62"
9832 The string must consist entirely of base-62 digits, or, in operating
9833 environments where Exim uses base 36 instead of base 62 for its message
9834 identifiers, base-36 digits. The number is converted to decimal and output as a
9838 .vitem &*${domain:*&<&'string'&>&*}*&
9839 .cindex "domain" "extraction"
9840 .cindex "expansion" "domain extraction"
9841 The string is interpreted as an RFC 2822 address and the domain is extracted
9842 from it. If the string does not parse successfully, the result is empty.
9845 .vitem &*${escape:*&<&'string'&>&*}*&
9846 .cindex "expansion" "escaping non-printing characters"
9847 .cindex "&%escape%& expansion item"
9848 If the string contains any non-printing characters, they are converted to
9849 escape sequences starting with a backslash. Whether characters with the most
9850 significant bit set (so-called &"8-bit characters"&) count as printing or not
9851 is controlled by the &%print_topbitchars%& option.
9854 .vitem &*${eval:*&<&'string'&>&*}*&&~and&~&*${eval10:*&<&'string'&>&*}*&
9855 .cindex "expansion" "expression evaluation"
9856 .cindex "expansion" "arithmetic expression"
9857 .cindex "&%eval%& expansion item"
9858 These items supports simple arithmetic and bitwise logical operations in
9859 expansion strings. The string (after expansion) must be a conventional
9860 arithmetic expression, but it is limited to basic arithmetic operators, bitwise
9861 logical operators, and parentheses. All operations are carried out using
9862 integer arithmetic. The operator priorities are as follows (the same as in the
9863 C programming language):
9865 .irow &'highest:'& "not (~), negate (-)"
9866 .irow "" "multiply (*), divide (/), remainder (%)"
9867 .irow "" "plus (+), minus (-)"
9868 .irow "" "shift-left (<<), shift-right (>>)"
9871 .irow &'lowest:'& "or (|)"
9873 Binary operators with the same priority are evaluated from left to right. White
9874 space is permitted before or after operators.
9876 For &%eval%&, numbers may be decimal, octal (starting with &"0"&) or
9877 hexadecimal (starting with &"0x"&). For &%eval10%&, all numbers are taken as
9878 decimal, even if they start with a leading zero; hexadecimal numbers are not
9879 permitted. This can be useful when processing numbers extracted from dates or
9880 times, which often do have leading zeros.
9882 A number may be followed by &"K"&, &"M"& or &"G"& to multiply it by 1024, 1024*1024
9884 respectively. Negative numbers are supported. The result of the computation is
9885 a decimal representation of the answer (without &"K"&, &"M"& or &"G"&). For example:
9888 &`${eval:1+1} `& yields 2
9889 &`${eval:1+2*3} `& yields 7
9890 &`${eval:(1+2)*3} `& yields 9
9891 &`${eval:2+42%5} `& yields 4
9892 &`${eval:0xc&5} `& yields 4
9893 &`${eval:0xc|5} `& yields 13
9894 &`${eval:0xc^5} `& yields 9
9895 &`${eval:0xc>>1} `& yields 6
9896 &`${eval:0xc<<1} `& yields 24
9897 &`${eval:~255&0x1234} `& yields 4608
9898 &`${eval:-(~255&0x1234)} `& yields -4608
9901 As a more realistic example, in an ACL you might have
9903 deny message = Too many bad recipients
9906 {>{$rcpt_count}{10}} \
9909 {$recipients_count} \
9910 {${eval:$rcpt_count/2}} \
9914 The condition is true if there have been more than 10 RCPT commands and
9915 fewer than half of them have resulted in a valid recipient.
9918 .vitem &*${expand:*&<&'string'&>&*}*&
9919 .cindex "expansion" "re-expansion of substring"
9920 The &%expand%& operator causes a string to be expanded for a second time. For
9923 ${expand:${lookup{$domain}dbm{/some/file}{$value}}}
9925 first looks up a string in a file while expanding the operand for &%expand%&,
9926 and then re-expands what it has found.
9929 .vitem &*${from_utf8:*&<&'string'&>&*}*&
9931 .cindex "UTF-8" "conversion from"
9932 .cindex "expansion" "UTF-8 conversion"
9933 .cindex "&%from_utf8%& expansion item"
9934 The world is slowly moving towards Unicode, although there are no standards for
9935 email yet. However, other applications (including some databases) are starting
9936 to store data in Unicode, using UTF-8 encoding. This operator converts from a
9937 UTF-8 string to an ISO-8859-1 string. UTF-8 code values greater than 255 are
9938 converted to underscores. The input must be a valid UTF-8 string. If it is not,
9939 the result is an undefined sequence of bytes.
9941 Unicode code points with values less than 256 are compatible with ASCII and
9942 ISO-8859-1 (also known as Latin-1).
9943 For example, character 169 is the copyright symbol in both cases, though the
9944 way it is encoded is different. In UTF-8, more than one byte is needed for
9945 characters with code values greater than 127, whereas ISO-8859-1 is a
9946 single-byte encoding (but thereby limited to 256 characters). This makes
9947 translation from UTF-8 to ISO-8859-1 straightforward.
9950 .vitem &*${hash_*&<&'n'&>&*_*&<&'m'&>&*:*&<&'string'&>&*}*&
9951 .cindex "hash function" "textual"
9952 .cindex "expansion" "textual hash"
9953 The &%hash%& operator is a simpler interface to the hashing function that can
9954 be used when the two parameters are fixed numbers (as opposed to strings that
9955 change when expanded). The effect is the same as
9957 ${hash{<n>}{<m>}{<string>}}
9959 See the description of the general &%hash%& item above for details. The
9960 abbreviation &%h%& can be used when &%hash%& is used as an operator.
9964 .vitem &*${hex2b64:*&<&'hexstring'&>&*}*&
9965 .cindex "base64 encoding" "conversion from hex"
9966 .cindex "expansion" "hex to base64"
9967 .cindex "&%hex2b64%& expansion item"
9968 This operator converts a hex string into one that is base64 encoded. This can
9969 be useful for processing the output of the MD5 and SHA-1 hashing functions.
9973 .vitem &*${hexquote:*&<&'string'&>&*}*&
9974 .cindex "quoting" "hex-encoded unprintable characters"
9975 .cindex "&%hexquote%& expansion item"
9976 This operator converts non-printable characters in a string into a hex
9977 escape form. Byte values between 33 (!) and 126 (~) inclusive are left
9978 as is, and other byte values are converted to &`\xNN`&, for example a
9979 byte value 127 is converted to &`\x7f`&.
9982 .vitem &*${lc:*&<&'string'&>&*}*&
9983 .cindex "case forcing in strings"
9984 .cindex "string" "case forcing"
9985 .cindex "lower casing"
9986 .cindex "expansion" "case forcing"
9987 .cindex "&%lc%& expansion item"
9988 This forces the letters in the string into lower-case, for example:
9993 .vitem &*${length_*&<&'number'&>&*:*&<&'string'&>&*}*&
9994 .cindex "expansion" "string truncation"
9995 .cindex "&%length%& expansion item"
9996 The &%length%& operator is a simpler interface to the &%length%& function that
9997 can be used when the parameter is a fixed number (as opposed to a string that
9998 changes when expanded). The effect is the same as
10000 ${length{<number>}{<string>}}
10002 See the description of the general &%length%& item above for details. Note that
10003 &%length%& is not the same as &%strlen%&. The abbreviation &%l%& can be used
10004 when &%length%& is used as an operator.
10007 .vitem &*${listcount:*&<&'string'&>&*}*&
10008 .cindex "expansion" "list item count"
10009 .cindex "list" "item count"
10010 .cindex "list" "count of items"
10011 .cindex "&%listcount%& expansion item"
10012 The string is interpreted as a list and the number of items is returned.
10015 .vitem &*${listnamed:*&<&'name'&>&*}*&&~and&~&*${listnamed_*&<&'type'&>&*:*&<&'name'&>&*}*&
10016 .cindex "expansion" "named list"
10017 .cindex "&%listnamed%& expansion item"
10018 The name is interpreted as a named list and the content of the list is returned,
10019 expanding any referenced lists, re-quoting as needed for colon-separation.
10020 If the optional type is given it must be one of "a", "d", "h" or "l"
10021 and selects address-, domain-, host- or localpart- lists to search among respectively.
10022 Otherwise all types are searched in an undefined order and the first
10023 matching list is returned.
10026 .vitem &*${local_part:*&<&'string'&>&*}*&
10027 .cindex "expansion" "local part extraction"
10028 .cindex "&%local_part%& expansion item"
10029 The string is interpreted as an RFC 2822 address and the local part is
10030 extracted from it. If the string does not parse successfully, the result is
10034 .vitem &*${mask:*&<&'IP&~address'&>&*/*&<&'bit&~count'&>&*}*&
10035 .cindex "masked IP address"
10036 .cindex "IP address" "masking"
10037 .cindex "CIDR notation"
10038 .cindex "expansion" "IP address masking"
10039 .cindex "&%mask%& expansion item"
10040 If the form of the string to be operated on is not an IP address followed by a
10041 slash and an integer (that is, a network address in CIDR notation), the
10042 expansion fails. Otherwise, this operator converts the IP address to binary,
10043 masks off the least significant bits according to the bit count, and converts
10044 the result back to text, with mask appended. For example,
10046 ${mask:10.111.131.206/28}
10048 returns the string &"10.111.131.192/28"&. Since this operation is expected to
10049 be mostly used for looking up masked addresses in files, the result for an IPv6
10050 address uses dots to separate components instead of colons, because colon
10051 terminates a key string in lsearch files. So, for example,
10053 ${mask:3ffe:ffff:836f:0a00:000a:0800:200a:c031/99}
10057 3ffe.ffff.836f.0a00.000a.0800.2000.0000/99
10059 Letters in IPv6 addresses are always output in lower case.
10062 .vitem &*${md5:*&<&'string'&>&*}*&
10064 .cindex "expansion" "MD5 hash"
10065 .cindex "certificate fingerprint"
10066 .cindex "&%md5%& expansion item"
10067 The &%md5%& operator computes the MD5 hash value of the string, and returns it
10068 as a 32-digit hexadecimal number, in which any letters are in lower case.
10071 .vitem &*${nhash_*&<&'n'&>&*_*&<&'m'&>&*:*&<&'string'&>&*}*&
10072 .cindex "expansion" "numeric hash"
10073 .cindex "hash function" "numeric"
10074 The &%nhash%& operator is a simpler interface to the numeric hashing function
10075 that can be used when the two parameters are fixed numbers (as opposed to
10076 strings that change when expanded). The effect is the same as
10078 ${nhash{<n>}{<m>}{<string>}}
10080 See the description of the general &%nhash%& item above for details.
10083 .vitem &*${quote:*&<&'string'&>&*}*&
10084 .cindex "quoting" "in string expansions"
10085 .cindex "expansion" "quoting"
10086 .cindex "&%quote%& expansion item"
10087 The &%quote%& operator puts its argument into double quotes if it
10088 is an empty string or
10089 contains anything other than letters, digits, underscores, dots, and hyphens.
10090 Any occurrences of double quotes and backslashes are escaped with a backslash.
10091 Newlines and carriage returns are converted to &`\n`& and &`\r`&,
10092 respectively For example,
10100 The place where this is useful is when the argument is a substitution from a
10101 variable or a message header.
10103 .vitem &*${quote_local_part:*&<&'string'&>&*}*&
10104 .cindex "&%quote_local_part%& expansion item"
10105 This operator is like &%quote%&, except that it quotes the string only if
10106 required to do so by the rules of RFC 2822 for quoting local parts. For
10107 example, a plus sign would not cause quoting (but it would for &%quote%&).
10108 If you are creating a new email address from the contents of &$local_part$&
10109 (or any other unknown data), you should always use this operator.
10112 .vitem &*${quote_*&<&'lookup-type'&>&*:*&<&'string'&>&*}*&
10113 .cindex "quoting" "lookup-specific"
10114 This operator applies lookup-specific quoting rules to the string. Each
10115 query-style lookup type has its own quoting rules which are described with
10116 the lookups in chapter &<<CHAPfdlookup>>&. For example,
10118 ${quote_ldap:two * two}
10124 For single-key lookup types, no quoting is ever necessary and this operator
10125 yields an unchanged string.
10128 .vitem &*${randint:*&<&'n'&>&*}*&
10129 .cindex "random number"
10130 This operator returns a somewhat random number which is less than the
10131 supplied number and is at least 0. The quality of this randomness depends
10132 on how Exim was built; the values are not suitable for keying material.
10133 If Exim is linked against OpenSSL then RAND_pseudo_bytes() is used.
10134 If Exim is linked against GnuTLS then gnutls_rnd(GNUTLS_RND_NONCE) is used,
10135 for versions of GnuTLS with that function.
10136 Otherwise, the implementation may be arc4random(), random() seeded by
10137 srandomdev() or srandom(), or a custom implementation even weaker than
10141 .vitem &*${reverse_ip:*&<&'ipaddr'&>&*}*&
10142 .cindex "expansion" "IP address"
10143 This operator reverses an IP address; for IPv4 addresses, the result is in
10144 dotted-quad decimal form, while for IPv6 addreses the result is in
10145 dotted-nibble hexadecimal form. In both cases, this is the "natural" form
10146 for DNS. For example,
10148 ${reverse_ip:192.0.2.4}
10149 ${reverse_ip:2001:0db8:c42:9:1:abcd:192.0.2.127}
10154 f.7.2.0.0.0.0.c.d.c.b.a.1.0.0.0.9.0.0.0.2.4.c.0.8.b.d.0.1.0.0.2
10158 .vitem &*${rfc2047:*&<&'string'&>&*}*&
10159 .cindex "expansion" "RFC 2047"
10160 .cindex "RFC 2047" "expansion operator"
10161 .cindex "&%rfc2047%& expansion item"
10162 This operator encodes text according to the rules of RFC 2047. This is an
10163 encoding that is used in header lines to encode non-ASCII characters. It is
10164 assumed that the input string is in the encoding specified by the
10165 &%headers_charset%& option, which defaults to ISO-8859-1. If the string
10166 contains only characters in the range 33&--126, and no instances of the
10169 ? = ( ) < > @ , ; : \ " . [ ] _
10171 it is not modified. Otherwise, the result is the RFC 2047 encoding of the
10172 string, using as many &"encoded words"& as necessary to encode all the
10176 .vitem &*${rfc2047d:*&<&'string'&>&*}*&
10177 .cindex "expansion" "RFC 2047"
10178 .cindex "RFC 2047" "decoding"
10179 .cindex "&%rfc2047d%& expansion item"
10180 This operator decodes strings that are encoded as per RFC 2047. Binary zero
10181 bytes are replaced by question marks. Characters are converted into the
10182 character set defined by &%headers_charset%&. Overlong RFC 2047 &"words"& are
10183 not recognized unless &%check_rfc2047_length%& is set false.
10185 &*Note*&: If you use &%$header%&_&'xxx'&&*:*& (or &%$h%&_&'xxx'&&*:*&) to
10186 access a header line, RFC 2047 decoding is done automatically. You do not need
10187 to use this operator as well.
10191 .vitem &*${rxquote:*&<&'string'&>&*}*&
10192 .cindex "quoting" "in regular expressions"
10193 .cindex "regular expressions" "quoting"
10194 .cindex "&%rxquote%& expansion item"
10195 The &%rxquote%& operator inserts a backslash before any non-alphanumeric
10196 characters in its argument. This is useful when substituting the values of
10197 variables or headers inside regular expressions.
10200 .vitem &*${sha1:*&<&'string'&>&*}*&
10201 .cindex "SHA-1 hash"
10202 .cindex "expansion" "SHA-1 hashing"
10203 .cindex "certificate fingerprint"
10204 .cindex "&%sha2%& expansion item"
10205 The &%sha1%& operator computes the SHA-1 hash value of the string, and returns
10206 it as a 40-digit hexadecimal number, in which any letters are in upper case.
10209 .vitem &*${sha256:*&<&'certificate'&>&*}*&
10210 .cindex "SHA-256 hash"
10211 .cindex "certificate fingerprint"
10212 .cindex "expansion" "SHA-256 hashing"
10213 .cindex "&%sha256%& expansion item"
10214 The &%sha256%& operator computes the SHA-256 hash fingerprint of the
10217 it as a 64-digit hexadecimal number, in which any letters are in upper case.
10218 Only arguments which are a single variable of certificate type are supported.
10221 .vitem &*${stat:*&<&'string'&>&*}*&
10222 .cindex "expansion" "statting a file"
10223 .cindex "file" "extracting characteristics"
10224 .cindex "&%stat%& expansion item"
10225 The string, after expansion, must be a file path. A call to the &[stat()]&
10226 function is made for this path. If &[stat()]& fails, an error occurs and the
10227 expansion fails. If it succeeds, the data from the stat replaces the item, as a
10228 series of <&'name'&>=<&'value'&> pairs, where the values are all numerical,
10229 except for the value of &"smode"&. The names are: &"mode"& (giving the mode as
10230 a 4-digit octal number), &"smode"& (giving the mode in symbolic format as a
10231 10-character string, as for the &'ls'& command), &"inode"&, &"device"&,
10232 &"links"&, &"uid"&, &"gid"&, &"size"&, &"atime"&, &"mtime"&, and &"ctime"&. You
10233 can extract individual fields using the &%extract%& expansion item.
10235 The use of the &%stat%& expansion in users' filter files can be locked out by
10236 the system administrator. &*Warning*&: The file size may be incorrect on 32-bit
10237 systems for files larger than 2GB.
10239 .vitem &*${str2b64:*&<&'string'&>&*}*&
10240 .cindex "expansion" "base64 encoding"
10241 .cindex "base64 encoding" "in string expansion"
10242 .cindex "&%str2b64%& expansion item"
10243 This operator converts a string into one that is base64 encoded.
10247 .vitem &*${strlen:*&<&'string'&>&*}*&
10248 .cindex "expansion" "string length"
10249 .cindex "string" "length in expansion"
10250 .cindex "&%strlen%& expansion item"
10251 The item is replace by the length of the expanded string, expressed as a
10252 decimal number. &*Note*&: Do not confuse &%strlen%& with &%length%&.
10255 .vitem &*${substr_*&<&'start'&>&*_*&<&'length'&>&*:*&<&'string'&>&*}*&
10256 .cindex "&%substr%& expansion item"
10257 .cindex "substring extraction"
10258 .cindex "expansion" "substring expansion"
10259 The &%substr%& operator is a simpler interface to the &%substr%& function that
10260 can be used when the two parameters are fixed numbers (as opposed to strings
10261 that change when expanded). The effect is the same as
10263 ${substr{<start>}{<length>}{<string>}}
10265 See the description of the general &%substr%& item above for details. The
10266 abbreviation &%s%& can be used when &%substr%& is used as an operator.
10268 .vitem &*${time_eval:*&<&'string'&>&*}*&
10269 .cindex "&%time_eval%& expansion item"
10270 .cindex "time interval" "decoding"
10271 This item converts an Exim time interval such as &`2d4h5m`& into a number of
10274 .vitem &*${time_interval:*&<&'string'&>&*}*&
10275 .cindex "&%time_interval%& expansion item"
10276 .cindex "time interval" "formatting"
10277 The argument (after sub-expansion) must be a sequence of decimal digits that
10278 represents an interval of time as a number of seconds. It is converted into a
10279 number of larger units and output in Exim's normal time format, for example,
10282 .vitem &*${uc:*&<&'string'&>&*}*&
10283 .cindex "case forcing in strings"
10284 .cindex "string" "case forcing"
10285 .cindex "upper casing"
10286 .cindex "expansion" "case forcing"
10287 .cindex "&%uc%& expansion item"
10288 This forces the letters in the string into upper-case.
10290 .vitem &*${utf8clean:*&<&'string'&>&*}*&
10291 .cindex "correction of invalid utf-8 sequences in strings"
10292 .cindex "utf-8" "utf-8 sequences"
10293 .cindex "incorrect utf-8"
10294 .cindex "expansion" "utf-8 forcing"
10295 .cindex "&%utf8clean%& expansion item"
10296 This replaces any invalid utf-8 sequence in the string by the character &`?`&.
10304 .section "Expansion conditions" "SECTexpcond"
10305 .scindex IIDexpcond "expansion" "conditions"
10306 The following conditions are available for testing by the &%${if%& construct
10307 while expanding strings:
10310 .vitem &*!*&<&'condition'&>
10311 .cindex "expansion" "negating a condition"
10312 .cindex "negation" "in expansion condition"
10313 Preceding any condition with an exclamation mark negates the result of the
10316 .vitem <&'symbolic&~operator'&>&~&*{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10317 .cindex "numeric comparison"
10318 .cindex "expansion" "numeric comparison"
10319 There are a number of symbolic operators for doing numeric comparisons. They
10325 &`>= `& greater or equal
10327 &`<= `& less or equal
10331 ${if >{$message_size}{10M} ...
10333 Note that the general negation operator provides for inequality testing. The
10334 two strings must take the form of optionally signed decimal integers,
10335 optionally followed by one of the letters &"K"&, &"M"& or &"G"& (in either upper or
10336 lower case), signifying multiplication by 1024, 1024*1024 or 1024*1024*1024, respectively.
10337 As a special case, the numerical value of an empty string is taken as
10340 In all cases, a relative comparator OP is testing if <&'string1'&> OP
10341 <&'string2'&>; the above example is checking if &$message_size$& is larger than
10342 10M, not if 10M is larger than &$message_size$&.
10345 .vitem &*acl&~{{*&<&'name'&>&*}{*&<&'arg1'&>&*}&&&
10346 {*&<&'arg2'&>&*}...}*&
10347 .cindex "expansion" "calling an acl"
10348 .cindex "&%acl%&" "expansion condition"
10349 The name and zero to nine argument strings are first expanded separately. The expanded
10350 arguments are assigned to the variables &$acl_arg1$& to &$acl_arg9$& in order.
10351 Any unused are made empty. The variable &$acl_narg$& is set to the number of
10352 arguments. The named ACL (see chapter &<<CHAPACL>>&) is called
10353 and may use the variables; if another acl expansion is used the values
10354 are restored after it returns. If the ACL sets
10355 a value using a "message =" modifier the variable $value becomes
10356 the result of the expansion, otherwise it is empty.
10357 If the ACL returns accept the condition is true; if deny, false.
10358 If the ACL returns defer the result is a forced-fail.
10360 .vitem &*bool&~{*&<&'string'&>&*}*&
10361 .cindex "expansion" "boolean parsing"
10362 .cindex "&%bool%& expansion condition"
10363 This condition turns a string holding a true or false representation into
10364 a boolean state. It parses &"true"&, &"false"&, &"yes"& and &"no"&
10365 (case-insensitively); also integer numbers map to true if non-zero,
10367 An empty string is treated as false.
10368 Leading and trailing whitespace is ignored;
10369 thus a string consisting only of whitespace is false.
10370 All other string values will result in expansion failure.
10372 When combined with ACL variables, this expansion condition will let you
10373 make decisions in one place and act on those decisions in another place.
10376 ${if bool{$acl_m_privileged_sender} ...
10380 .vitem &*bool_lax&~{*&<&'string'&>&*}*&
10381 .cindex "expansion" "boolean parsing"
10382 .cindex "&%bool_lax%& expansion condition"
10383 Like &%bool%&, this condition turns a string into a boolean state. But
10384 where &%bool%& accepts a strict set of strings, &%bool_lax%& uses the same
10385 loose definition that the Router &%condition%& option uses. The empty string
10386 and the values &"false"&, &"no"& and &"0"& map to false, all others map to
10387 true. Leading and trailing whitespace is ignored.
10389 Note that where &"bool{00}"& is false, &"bool_lax{00}"& is true.
10391 .vitem &*crypteq&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10392 .cindex "expansion" "encrypted comparison"
10393 .cindex "encrypted strings, comparing"
10394 .cindex "&%crypteq%& expansion condition"
10395 This condition is included in the Exim binary if it is built to support any
10396 authentication mechanisms (see chapter &<<CHAPSMTPAUTH>>&). Otherwise, it is
10397 necessary to define SUPPORT_CRYPTEQ in &_Local/Makefile_& to get &%crypteq%&
10398 included in the binary.
10400 The &%crypteq%& condition has two arguments. The first is encrypted and
10401 compared against the second, which is already encrypted. The second string may
10402 be in the LDAP form for storing encrypted strings, which starts with the
10403 encryption type in curly brackets, followed by the data. If the second string
10404 does not begin with &"{"& it is assumed to be encrypted with &[crypt()]& or
10405 &[crypt16()]& (see below), since such strings cannot begin with &"{"&.
10406 Typically this will be a field from a password file. An example of an encrypted
10407 string in LDAP form is:
10409 {md5}CY9rzUYh03PK3k6DJie09g==
10411 If such a string appears directly in an expansion, the curly brackets have to
10412 be quoted, because they are part of the expansion syntax. For example:
10414 ${if crypteq {test}{\{md5\}CY9rzUYh03PK3k6DJie09g==}{yes}{no}}
10416 The following encryption types (whose names are matched case-independently) are
10421 .cindex "base64 encoding" "in encrypted password"
10422 &%{md5}%& computes the MD5 digest of the first string, and expresses this as
10423 printable characters to compare with the remainder of the second string. If the
10424 length of the comparison string is 24, Exim assumes that it is base64 encoded
10425 (as in the above example). If the length is 32, Exim assumes that it is a
10426 hexadecimal encoding of the MD5 digest. If the length not 24 or 32, the
10430 .cindex "SHA-1 hash"
10431 &%{sha1}%& computes the SHA-1 digest of the first string, and expresses this as
10432 printable characters to compare with the remainder of the second string. If the
10433 length of the comparison string is 28, Exim assumes that it is base64 encoded.
10434 If the length is 40, Exim assumes that it is a hexadecimal encoding of the
10435 SHA-1 digest. If the length is not 28 or 40, the comparison fails.
10438 .cindex "&[crypt()]&"
10439 &%{crypt}%& calls the &[crypt()]& function, which traditionally used to use
10440 only the first eight characters of the password. However, in modern operating
10441 systems this is no longer true, and in many cases the entire password is used,
10442 whatever its length.
10445 .cindex "&[crypt16()]&"
10446 &%{crypt16}%& calls the &[crypt16()]& function, which was originally created to
10447 use up to 16 characters of the password in some operating systems. Again, in
10448 modern operating systems, more characters may be used.
10450 Exim has its own version of &[crypt16()]&, which is just a double call to
10451 &[crypt()]&. For operating systems that have their own version, setting
10452 HAVE_CRYPT16 in &_Local/Makefile_& when building Exim causes it to use the
10453 operating system version instead of its own. This option is set by default in
10454 the OS-dependent &_Makefile_& for those operating systems that are known to
10455 support &[crypt16()]&.
10457 Some years after Exim's &[crypt16()]& was implemented, a user discovered that
10458 it was not using the same algorithm as some operating systems' versions. It
10459 turns out that as well as &[crypt16()]& there is a function called
10460 &[bigcrypt()]& in some operating systems. This may or may not use the same
10461 algorithm, and both of them may be different to Exim's built-in &[crypt16()]&.
10463 However, since there is now a move away from the traditional &[crypt()]&
10464 functions towards using SHA1 and other algorithms, tidying up this area of
10465 Exim is seen as very low priority.
10467 If you do not put a encryption type (in curly brackets) in a &%crypteq%&
10468 comparison, the default is usually either &`{crypt}`& or &`{crypt16}`&, as
10469 determined by the setting of DEFAULT_CRYPT in &_Local/Makefile_&. The default
10470 default is &`{crypt}`&. Whatever the default, you can always use either
10471 function by specifying it explicitly in curly brackets.
10473 .vitem &*def:*&<&'variable&~name'&>
10474 .cindex "expansion" "checking for empty variable"
10475 .cindex "&%def%& expansion condition"
10476 The &%def%& condition must be followed by the name of one of the expansion
10477 variables defined in section &<<SECTexpvar>>&. The condition is true if the
10478 variable does not contain the empty string. For example:
10480 ${if def:sender_ident {from $sender_ident}}
10482 Note that the variable name is given without a leading &%$%& character. If the
10483 variable does not exist, the expansion fails.
10485 .vitem "&*def:header_*&<&'header&~name'&>&*:*&&~&~or&~&&&
10486 &~&*def:h_*&<&'header&~name'&>&*:*&"
10487 .cindex "expansion" "checking header line existence"
10488 This condition is true if a message is being processed and the named header
10489 exists in the message. For example,
10491 ${if def:header_reply-to:{$h_reply-to:}{$h_from:}}
10493 &*Note*&: No &%$%& appears before &%header_%& or &%h_%& in the condition, and
10494 the header name must be terminated by a colon if white space does not follow.
10496 .vitem &*eq&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
10497 &*eqi&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10498 .cindex "string" "comparison"
10499 .cindex "expansion" "string comparison"
10500 .cindex "&%eq%& expansion condition"
10501 .cindex "&%eqi%& expansion condition"
10502 The two substrings are first expanded. The condition is true if the two
10503 resulting strings are identical. For &%eq%& the comparison includes the case of
10504 letters, whereas for &%eqi%& the comparison is case-independent.
10506 .vitem &*exists&~{*&<&'file&~name'&>&*}*&
10507 .cindex "expansion" "file existence test"
10508 .cindex "file" "existence test"
10509 .cindex "&%exists%&, expansion condition"
10510 The substring is first expanded and then interpreted as an absolute path. The
10511 condition is true if the named file (or directory) exists. The existence test
10512 is done by calling the &[stat()]& function. The use of the &%exists%& test in
10513 users' filter files may be locked out by the system administrator.
10515 .vitem &*first_delivery*&
10516 .cindex "delivery" "first"
10517 .cindex "first delivery"
10518 .cindex "expansion" "first delivery test"
10519 .cindex "&%first_delivery%& expansion condition"
10520 This condition, which has no data, is true during a message's first delivery
10521 attempt. It is false during any subsequent delivery attempts.
10524 .vitem "&*forall{*&<&'a list'&>&*}{*&<&'a condition'&>&*}*&" &&&
10525 "&*forany{*&<&'a list'&>&*}{*&<&'a condition'&>&*}*&"
10526 .cindex "list" "iterative conditions"
10527 .cindex "expansion" "&*forall*& condition"
10528 .cindex "expansion" "&*forany*& condition"
10530 These conditions iterate over a list. The first argument is expanded to form
10531 the list. By default, the list separator is a colon, but it can be changed by
10532 the normal method. The second argument is interpreted as a condition that is to
10533 be applied to each item in the list in turn. During the interpretation of the
10534 condition, the current list item is placed in a variable called &$item$&.
10536 For &*forany*&, interpretation stops if the condition is true for any item, and
10537 the result of the whole condition is true. If the condition is false for all
10538 items in the list, the overall condition is false.
10540 For &*forall*&, interpretation stops if the condition is false for any item,
10541 and the result of the whole condition is false. If the condition is true for
10542 all items in the list, the overall condition is true.
10544 Note that negation of &*forany*& means that the condition must be false for all
10545 items for the overall condition to succeed, and negation of &*forall*& means
10546 that the condition must be false for at least one item. In this example, the
10547 list separator is changed to a comma:
10549 ${if forany{<, $recipients}{match{$item}{^user3@}}{yes}{no}}
10551 The value of &$item$& is saved and restored while &*forany*& or &*forall*& is
10552 being processed, to enable these expansion items to be nested.
10554 To scan a named list, expand it with the &*listnamed*& operator.
10557 .vitem &*ge&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
10558 &*gei&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10559 .cindex "string" "comparison"
10560 .cindex "expansion" "string comparison"
10561 .cindex "&%ge%& expansion condition"
10562 .cindex "&%gei%& expansion condition"
10563 The two substrings are first expanded. The condition is true if the first
10564 string is lexically greater than or equal to the second string. For &%ge%& the
10565 comparison includes the case of letters, whereas for &%gei%& the comparison is
10568 .vitem &*gt&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
10569 &*gti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10570 .cindex "string" "comparison"
10571 .cindex "expansion" "string comparison"
10572 .cindex "&%gt%& expansion condition"
10573 .cindex "&%gti%& expansion condition"
10574 The two substrings are first expanded. The condition is true if the first
10575 string is lexically greater than the second string. For &%gt%& the comparison
10576 includes the case of letters, whereas for &%gti%& the comparison is
10579 .vitem &*inlist&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
10580 &*inlisti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10581 .cindex "string" "comparison"
10582 .cindex "list" "iterative conditions"
10583 Both strings are expanded; the second string is treated as a list of simple
10584 strings; if the first string is a member of the second, then the condition
10587 These are simpler to use versions of the more powerful &*forany*& condition.
10588 Examples, and the &*forany*& equivalents:
10590 ${if inlist{needle}{foo:needle:bar}}
10591 ${if forany{foo:needle:bar}{eq{$item}{needle}}}
10592 ${if inlisti{Needle}{fOo:NeeDLE:bAr}}
10593 ${if forany{fOo:NeeDLE:bAr}{eqi{$item}{Needle}}}
10596 .vitem &*isip&~{*&<&'string'&>&*}*& &&&
10597 &*isip4&~{*&<&'string'&>&*}*& &&&
10598 &*isip6&~{*&<&'string'&>&*}*&
10599 .cindex "IP address" "testing string format"
10600 .cindex "string" "testing for IP address"
10601 .cindex "&%isip%& expansion condition"
10602 .cindex "&%isip4%& expansion condition"
10603 .cindex "&%isip6%& expansion condition"
10604 The substring is first expanded, and then tested to see if it has the form of
10605 an IP address. Both IPv4 and IPv6 addresses are valid for &%isip%&, whereas
10606 &%isip4%& and &%isip6%& test specifically for IPv4 or IPv6 addresses.
10608 For an IPv4 address, the test is for four dot-separated components, each of
10609 which consists of from one to three digits. For an IPv6 address, up to eight
10610 colon-separated components are permitted, each containing from one to four
10611 hexadecimal digits. There may be fewer than eight components if an empty
10612 component (adjacent colons) is present. Only one empty component is permitted.
10614 &*Note*&: The checks are just on the form of the address; actual numerical
10615 values are not considered. Thus, for example, 999.999.999.999 passes the IPv4
10616 check. The main use of these tests is to distinguish between IP addresses and
10617 host names, or between IPv4 and IPv6 addresses. For example, you could use
10619 ${if isip4{$sender_host_address}...
10621 to test which IP version an incoming SMTP connection is using.
10623 .vitem &*ldapauth&~{*&<&'ldap&~query'&>&*}*&
10624 .cindex "LDAP" "use for authentication"
10625 .cindex "expansion" "LDAP authentication test"
10626 .cindex "&%ldapauth%& expansion condition"
10627 This condition supports user authentication using LDAP. See section
10628 &<<SECTldap>>& for details of how to use LDAP in lookups and the syntax of
10629 queries. For this use, the query must contain a user name and password. The
10630 query itself is not used, and can be empty. The condition is true if the
10631 password is not empty, and the user name and password are accepted by the LDAP
10632 server. An empty password is rejected without calling LDAP because LDAP binds
10633 with an empty password are considered anonymous regardless of the username, and
10634 will succeed in most configurations. See chapter &<<CHAPSMTPAUTH>>& for details
10635 of SMTP authentication, and chapter &<<CHAPplaintext>>& for an example of how
10639 .vitem &*le&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
10640 &*lei&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10641 .cindex "string" "comparison"
10642 .cindex "expansion" "string comparison"
10643 .cindex "&%le%& expansion condition"
10644 .cindex "&%lei%& expansion condition"
10645 The two substrings are first expanded. The condition is true if the first
10646 string is lexically less than or equal to the second string. For &%le%& the
10647 comparison includes the case of letters, whereas for &%lei%& the comparison is
10650 .vitem &*lt&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
10651 &*lti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10652 .cindex "string" "comparison"
10653 .cindex "expansion" "string comparison"
10654 .cindex "&%lt%& expansion condition"
10655 .cindex "&%lti%& expansion condition"
10656 The two substrings are first expanded. The condition is true if the first
10657 string is lexically less than the second string. For &%lt%& the comparison
10658 includes the case of letters, whereas for &%lti%& the comparison is
10662 .vitem &*match&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10663 .cindex "expansion" "regular expression comparison"
10664 .cindex "regular expressions" "match in expanded string"
10665 .cindex "&%match%& expansion condition"
10666 The two substrings are first expanded. The second is then treated as a regular
10667 expression and applied to the first. Because of the pre-expansion, if the
10668 regular expression contains dollar, or backslash characters, they must be
10669 escaped. Care must also be taken if the regular expression contains braces
10670 (curly brackets). A closing brace must be escaped so that it is not taken as a
10671 premature termination of <&'string2'&>. The easiest approach is to use the
10672 &`\N`& feature to disable expansion of the regular expression.
10675 ${if match {$local_part}{\N^\d{3}\N} ...
10677 If the whole expansion string is in double quotes, further escaping of
10678 backslashes is also required.
10680 The condition is true if the regular expression match succeeds.
10681 The regular expression is not required to begin with a circumflex
10682 metacharacter, but if there is no circumflex, the expression is not anchored,
10683 and it may match anywhere in the subject, not just at the start. If you want
10684 the pattern to match at the end of the subject, you must include the &`$`&
10685 metacharacter at an appropriate point.
10687 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%if%& expansion"
10688 At the start of an &%if%& expansion the values of the numeric variable
10689 substitutions &$1$& etc. are remembered. Obeying a &%match%& condition that
10690 succeeds causes them to be reset to the substrings of that condition and they
10691 will have these values during the expansion of the success string. At the end
10692 of the &%if%& expansion, the previous values are restored. After testing a
10693 combination of conditions using &%or%&, the subsequent values of the numeric
10694 variables are those of the condition that succeeded.
10696 .vitem &*match_address&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10697 .cindex "&%match_address%& expansion condition"
10698 See &*match_local_part*&.
10700 .vitem &*match_domain&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10701 .cindex "&%match_domain%& expansion condition"
10702 See &*match_local_part*&.
10704 .vitem &*match_ip&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10705 .cindex "&%match_ip%& expansion condition"
10706 This condition matches an IP address to a list of IP address patterns. It must
10707 be followed by two argument strings. The first (after expansion) must be an IP
10708 address or an empty string. The second (not expanded) is a restricted host
10709 list that can match only an IP address, not a host name. For example:
10711 ${if match_ip{$sender_host_address}{1.2.3.4:5.6.7.8}{...}{...}}
10713 The specific types of host list item that are permitted in the list are:
10716 An IP address, optionally with a CIDR mask.
10718 A single asterisk, which matches any IP address.
10720 An empty item, which matches only if the IP address is empty. This could be
10721 useful for testing for a locally submitted message or one from specific hosts
10722 in a single test such as
10723 . ==== As this is a nested list, any displays it contains must be indented
10724 . ==== as otherwise they are too far to the left. This comment applies to
10725 . ==== the use of xmlto plus fop. There's no problem when formatting with
10726 . ==== sdop, with or without the extra indent.
10728 ${if match_ip{$sender_host_address}{:4.3.2.1:...}{...}{...}}
10730 where the first item in the list is the empty string.
10732 The item @[] matches any of the local host's interface addresses.
10734 Single-key lookups are assumed to be like &"net-"& style lookups in host lists,
10735 even if &`net-`& is not specified. There is never any attempt to turn the IP
10736 address into a host name. The most common type of linear search for
10737 &*match_ip*& is likely to be &*iplsearch*&, in which the file can contain CIDR
10738 masks. For example:
10740 ${if match_ip{$sender_host_address}{iplsearch;/some/file}...
10742 It is of course possible to use other kinds of lookup, and in such a case, you
10743 do need to specify the &`net-`& prefix if you want to specify a specific
10744 address mask, for example:
10746 ${if match_ip{$sender_host_address}{net24-dbm;/some/file}...
10748 However, unless you are combining a &%match_ip%& condition with others, it is
10749 just as easy to use the fact that a lookup is itself a condition, and write:
10751 ${lookup{${mask:$sender_host_address/24}}dbm{/a/file}...
10755 Note that <&'string2'&> is not itself subject to string expansion, unless
10756 Exim was built with the EXPAND_LISTMATCH_RHS option.
10758 Consult section &<<SECThoslispatip>>& for further details of these patterns.
10760 .vitem &*match_local_part&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10761 .cindex "domain list" "in expansion condition"
10762 .cindex "address list" "in expansion condition"
10763 .cindex "local part" "list, in expansion condition"
10764 .cindex "&%match_local_part%& expansion condition"
10765 This condition, together with &%match_address%& and &%match_domain%&, make it
10766 possible to test domain, address, and local part lists within expansions. Each
10767 condition requires two arguments: an item and a list to match. A trivial
10770 ${if match_domain{a.b.c}{x.y.z:a.b.c:p.q.r}{yes}{no}}
10772 In each case, the second argument may contain any of the allowable items for a
10773 list of the appropriate type. Also, because the second argument (after
10774 expansion) is a standard form of list, it is possible to refer to a named list.
10775 Thus, you can use conditions like this:
10777 ${if match_domain{$domain}{+local_domains}{...
10779 .cindex "&`+caseful`&"
10780 For address lists, the matching starts off caselessly, but the &`+caseful`&
10781 item can be used, as in all address lists, to cause subsequent items to
10782 have their local parts matched casefully. Domains are always matched
10785 Note that <&'string2'&> is not itself subject to string expansion, unless
10786 Exim was built with the EXPAND_LISTMATCH_RHS option.
10788 &*Note*&: Host lists are &'not'& supported in this way. This is because
10789 hosts have two identities: a name and an IP address, and it is not clear
10790 how to specify cleanly how such a test would work. However, IP addresses can be
10791 matched using &%match_ip%&.
10793 .vitem &*pam&~{*&<&'string1'&>&*:*&<&'string2'&>&*:...}*&
10794 .cindex "PAM authentication"
10795 .cindex "AUTH" "with PAM"
10796 .cindex "Solaris" "PAM support"
10797 .cindex "expansion" "PAM authentication test"
10798 .cindex "&%pam%& expansion condition"
10799 &'Pluggable Authentication Modules'&
10800 (&url(http://www.kernel.org/pub/linux/libs/pam/)) are a facility that is
10801 available in the latest releases of Solaris and in some GNU/Linux
10802 distributions. The Exim support, which is intended for use in conjunction with
10803 the SMTP AUTH command, is available only if Exim is compiled with
10807 in &_Local/Makefile_&. You probably need to add &%-lpam%& to EXTRALIBS, and
10808 in some releases of GNU/Linux &%-ldl%& is also needed.
10810 The argument string is first expanded, and the result must be a
10811 colon-separated list of strings. Leading and trailing white space is ignored.
10812 The PAM module is initialized with the service name &"exim"& and the user name
10813 taken from the first item in the colon-separated data string (<&'string1'&>).
10814 The remaining items in the data string are passed over in response to requests
10815 from the authentication function. In the simple case there will only be one
10816 request, for a password, so the data consists of just two strings.
10818 There can be problems if any of the strings are permitted to contain colon
10819 characters. In the usual way, these have to be doubled to avoid being taken as
10820 separators. If the data is being inserted from a variable, the &%sg%& expansion
10821 item can be used to double any existing colons. For example, the configuration
10822 of a LOGIN authenticator might contain this setting:
10824 server_condition = ${if pam{$auth1:${sg{$auth2}{:}{::}}}}
10826 For a PLAIN authenticator you could use:
10828 server_condition = ${if pam{$auth2:${sg{$auth3}{:}{::}}}}
10830 In some operating systems, PAM authentication can be done only from a process
10831 running as root. Since Exim is running as the Exim user when receiving
10832 messages, this means that PAM cannot be used directly in those systems.
10833 A patched version of the &'pam_unix'& module that comes with the
10834 Linux PAM package is available from &url(http://www.e-admin.de/pam_exim/).
10835 The patched module allows one special uid/gid combination, in addition to root,
10836 to authenticate. If you build the patched module to allow the Exim user and
10837 group, PAM can then be used from an Exim authenticator.
10840 .vitem &*pwcheck&~{*&<&'string1'&>&*:*&<&'string2'&>&*}*&
10841 .cindex "&'pwcheck'& daemon"
10843 .cindex "expansion" "&'pwcheck'& authentication test"
10844 .cindex "&%pwcheck%& expansion condition"
10845 This condition supports user authentication using the Cyrus &'pwcheck'& daemon.
10846 This is one way of making it possible for passwords to be checked by a process
10847 that is not running as root. &*Note*&: The use of &'pwcheck'& is now
10848 deprecated. Its replacement is &'saslauthd'& (see below).
10850 The pwcheck support is not included in Exim by default. You need to specify
10851 the location of the pwcheck daemon's socket in &_Local/Makefile_& before
10852 building Exim. For example:
10854 CYRUS_PWCHECK_SOCKET=/var/pwcheck/pwcheck
10856 You do not need to install the full Cyrus software suite in order to use
10857 the pwcheck daemon. You can compile and install just the daemon alone
10858 from the Cyrus SASL library. Ensure that &'exim'& is the only user that has
10859 access to the &_/var/pwcheck_& directory.
10861 The &%pwcheck%& condition takes one argument, which must be the user name and
10862 password, separated by a colon. For example, in a LOGIN authenticator
10863 configuration, you might have this:
10865 server_condition = ${if pwcheck{$auth1:$auth2}}
10867 Again, for a PLAIN authenticator configuration, this would be:
10869 server_condition = ${if pwcheck{$auth2:$auth3}}
10871 .vitem &*queue_running*&
10872 .cindex "queue runner" "detecting when delivering from"
10873 .cindex "expansion" "queue runner test"
10874 .cindex "&%queue_running%& expansion condition"
10875 This condition, which has no data, is true during delivery attempts that are
10876 initiated by queue runner processes, and false otherwise.
10879 .vitem &*radius&~{*&<&'authentication&~string'&>&*}*&
10881 .cindex "expansion" "Radius authentication"
10882 .cindex "&%radius%& expansion condition"
10883 Radius authentication (RFC 2865) is supported in a similar way to PAM. You must
10884 set RADIUS_CONFIG_FILE in &_Local/Makefile_& to specify the location of
10885 the Radius client configuration file in order to build Exim with Radius
10888 With just that one setting, Exim expects to be linked with the &%radiusclient%&
10889 library, using the original API. If you are using release 0.4.0 or later of
10890 this library, you need to set
10892 RADIUS_LIB_TYPE=RADIUSCLIENTNEW
10894 in &_Local/Makefile_& when building Exim. You can also link Exim with the
10895 &%libradius%& library that comes with FreeBSD. To do this, set
10897 RADIUS_LIB_TYPE=RADLIB
10899 in &_Local/Makefile_&, in addition to setting RADIUS_CONFIGURE_FILE.
10900 You may also have to supply a suitable setting in EXTRALIBS so that the
10901 Radius library can be found when Exim is linked.
10903 The string specified by RADIUS_CONFIG_FILE is expanded and passed to the
10904 Radius client library, which calls the Radius server. The condition is true if
10905 the authentication is successful. For example:
10907 server_condition = ${if radius{<arguments>}}
10911 .vitem "&*saslauthd&~{{*&<&'user'&>&*}{*&<&'password'&>&*}&&&
10912 {*&<&'service'&>&*}{*&<&'realm'&>&*}}*&"
10913 .cindex "&'saslauthd'& daemon"
10915 .cindex "expansion" "&'saslauthd'& authentication test"
10916 .cindex "&%saslauthd%& expansion condition"
10917 This condition supports user authentication using the Cyrus &'saslauthd'&
10918 daemon. This replaces the older &'pwcheck'& daemon, which is now deprecated.
10919 Using this daemon is one way of making it possible for passwords to be checked
10920 by a process that is not running as root.
10922 The saslauthd support is not included in Exim by default. You need to specify
10923 the location of the saslauthd daemon's socket in &_Local/Makefile_& before
10924 building Exim. For example:
10926 CYRUS_SASLAUTHD_SOCKET=/var/state/saslauthd/mux
10928 You do not need to install the full Cyrus software suite in order to use
10929 the saslauthd daemon. You can compile and install just the daemon alone
10930 from the Cyrus SASL library.
10932 Up to four arguments can be supplied to the &%saslauthd%& condition, but only
10933 two are mandatory. For example:
10935 server_condition = ${if saslauthd{{$auth1}{$auth2}}}
10937 The service and the realm are optional (which is why the arguments are enclosed
10938 in their own set of braces). For details of the meaning of the service and
10939 realm, and how to run the daemon, consult the Cyrus documentation.
10944 .section "Combining expansion conditions" "SECID84"
10945 .cindex "expansion" "combining conditions"
10946 Several conditions can be tested at once by combining them using the &%and%&
10947 and &%or%& combination conditions. Note that &%and%& and &%or%& are complete
10948 conditions on their own, and precede their lists of sub-conditions. Each
10949 sub-condition must be enclosed in braces within the overall braces that contain
10950 the list. No repetition of &%if%& is used.
10954 .vitem &*or&~{{*&<&'cond1'&>&*}{*&<&'cond2'&>&*}...}*&
10955 .cindex "&""or""& expansion condition"
10956 .cindex "expansion" "&""or""& of conditions"
10957 The sub-conditions are evaluated from left to right. The condition is true if
10958 any one of the sub-conditions is true.
10961 ${if or {{eq{$local_part}{spqr}}{eq{$domain}{testing.com}}}...
10963 When a true sub-condition is found, the following ones are parsed but not
10964 evaluated. If there are several &"match"& sub-conditions the values of the
10965 numeric variables afterwards are taken from the first one that succeeds.
10967 .vitem &*and&~{{*&<&'cond1'&>&*}{*&<&'cond2'&>&*}...}*&
10968 .cindex "&""and""& expansion condition"
10969 .cindex "expansion" "&""and""& of conditions"
10970 The sub-conditions are evaluated from left to right. The condition is true if
10971 all of the sub-conditions are true. If there are several &"match"&
10972 sub-conditions, the values of the numeric variables afterwards are taken from
10973 the last one. When a false sub-condition is found, the following ones are
10974 parsed but not evaluated.
10976 .ecindex IIDexpcond
10981 .section "Expansion variables" "SECTexpvar"
10982 .cindex "expansion" "variables, list of"
10983 This section contains an alphabetical list of all the expansion variables. Some
10984 of them are available only when Exim is compiled with specific options such as
10985 support for TLS or the content scanning extension.
10988 .vitem "&$0$&, &$1$&, etc"
10989 .cindex "numerical variables (&$1$& &$2$& etc)"
10990 When a &%match%& expansion condition succeeds, these variables contain the
10991 captured substrings identified by the regular expression during subsequent
10992 processing of the success string of the containing &%if%& expansion item.
10993 However, they do not retain their values afterwards; in fact, their previous
10994 values are restored at the end of processing an &%if%& item. The numerical
10995 variables may also be set externally by some other matching process which
10996 precedes the expansion of the string. For example, the commands available in
10997 Exim filter files include an &%if%& command with its own regular expression
10998 matching condition.
11000 .vitem "&$acl_c...$&"
11001 Values can be placed in these variables by the &%set%& modifier in an ACL. They
11002 can be given any name that starts with &$acl_c$& and is at least six characters
11003 long, but the sixth character must be either a digit or an underscore. For
11004 example: &$acl_c5$&, &$acl_c_mycount$&. The values of the &$acl_c...$&
11005 variables persist throughout the lifetime of an SMTP connection. They can be
11006 used to pass information between ACLs and between different invocations of the
11007 same ACL. When a message is received, the values of these variables are saved
11008 with the message, and can be accessed by filters, routers, and transports
11009 during subsequent delivery.
11011 .vitem "&$acl_m...$&"
11012 These variables are like the &$acl_c...$& variables, except that their values
11013 are reset after a message has been received. Thus, if several messages are
11014 received in one SMTP connection, &$acl_m...$& values are not passed on from one
11015 message to the next, as &$acl_c...$& values are. The &$acl_m...$& variables are
11016 also reset by MAIL, RSET, EHLO, HELO, and after starting a TLS session. When a
11017 message is received, the values of these variables are saved with the message,
11018 and can be accessed by filters, routers, and transports during subsequent
11021 .vitem &$acl_verify_message$&
11022 .vindex "&$acl_verify_message$&"
11023 After an address verification has failed, this variable contains the failure
11024 message. It retains its value for use in subsequent modifiers. The message can
11025 be preserved by coding like this:
11027 warn !verify = sender
11028 set acl_m0 = $acl_verify_message
11030 You can use &$acl_verify_message$& during the expansion of the &%message%& or
11031 &%log_message%& modifiers, to include information about the verification
11034 .vitem &$address_data$&
11035 .vindex "&$address_data$&"
11036 This variable is set by means of the &%address_data%& option in routers. The
11037 value then remains with the address while it is processed by subsequent routers
11038 and eventually a transport. If the transport is handling multiple addresses,
11039 the value from the first address is used. See chapter &<<CHAProutergeneric>>&
11040 for more details. &*Note*&: The contents of &$address_data$& are visible in
11043 If &$address_data$& is set when the routers are called from an ACL to verify
11044 a recipient address, the final value is still in the variable for subsequent
11045 conditions and modifiers of the ACL statement. If routing the address caused it
11046 to be redirected to just one address, the child address is also routed as part
11047 of the verification, and in this case the final value of &$address_data$& is
11048 from the child's routing.
11050 If &$address_data$& is set when the routers are called from an ACL to verify a
11051 sender address, the final value is also preserved, but this time in
11052 &$sender_address_data$&, to distinguish it from data from a recipient
11055 In both cases (recipient and sender verification), the value does not persist
11056 after the end of the current ACL statement. If you want to preserve
11057 these values for longer, you can save them in ACL variables.
11059 .vitem &$address_file$&
11060 .vindex "&$address_file$&"
11061 When, as a result of aliasing, forwarding, or filtering, a message is directed
11062 to a specific file, this variable holds the name of the file when the transport
11063 is running. At other times, the variable is empty. For example, using the
11064 default configuration, if user &%r2d2%& has a &_.forward_& file containing
11066 /home/r2d2/savemail
11068 then when the &(address_file)& transport is running, &$address_file$&
11069 contains the text string &`/home/r2d2/savemail`&.
11070 .cindex "Sieve filter" "value of &$address_file$&"
11071 For Sieve filters, the value may be &"inbox"& or a relative folder name. It is
11072 then up to the transport configuration to generate an appropriate absolute path
11073 to the relevant file.
11075 .vitem &$address_pipe$&
11076 .vindex "&$address_pipe$&"
11077 When, as a result of aliasing or forwarding, a message is directed to a pipe,
11078 this variable holds the pipe command when the transport is running.
11080 .vitem "&$auth1$& &-- &$auth3$&"
11081 .vindex "&$auth1$&, &$auth2$&, etc"
11082 These variables are used in SMTP authenticators (see chapters
11083 &<<CHAPplaintext>>&&--&<<CHAPspa>>&). Elsewhere, they are empty.
11085 .vitem &$authenticated_id$&
11086 .cindex "authentication" "id"
11087 .vindex "&$authenticated_id$&"
11088 When a server successfully authenticates a client it may be configured to
11089 preserve some of the authentication information in the variable
11090 &$authenticated_id$& (see chapter &<<CHAPSMTPAUTH>>&). For example, a
11091 user/password authenticator configuration might preserve the user name for use
11092 in the routers. Note that this is not the same information that is saved in
11093 &$sender_host_authenticated$&.
11094 When a message is submitted locally (that is, not over a TCP connection)
11095 the value of &$authenticated_id$& is normally the login name of the calling
11096 process. However, a trusted user can override this by means of the &%-oMai%&
11097 command line option.
11099 .vitem &$authenticated_fail_id$&
11100 .cindex "authentication" "fail" "id"
11101 .vindex "&$authenticated_fail_id$&"
11102 When an authentication attempt fails, the variable &$authenticated_fail_id$&
11103 will contain the failed authentication id. If more than one authentication
11104 id is attempted, it will contain only the last one. The variable is
11105 available for processing in the ACL's, generally the quit or notquit ACL.
11106 A message to a local recipient could still be accepted without requiring
11107 authentication, which means this variable could also be visible in all of
11111 .vitem &$authenticated_sender$&
11112 .cindex "sender" "authenticated"
11113 .cindex "authentication" "sender"
11114 .cindex "AUTH" "on MAIL command"
11115 .vindex "&$authenticated_sender$&"
11116 When acting as a server, Exim takes note of the AUTH= parameter on an incoming
11117 SMTP MAIL command if it believes the sender is sufficiently trusted, as
11118 described in section &<<SECTauthparamail>>&. Unless the data is the string
11119 &"<>"&, it is set as the authenticated sender of the message, and the value is
11120 available during delivery in the &$authenticated_sender$& variable. If the
11121 sender is not trusted, Exim accepts the syntax of AUTH=, but ignores the data.
11123 .vindex "&$qualify_domain$&"
11124 When a message is submitted locally (that is, not over a TCP connection), the
11125 value of &$authenticated_sender$& is an address constructed from the login
11126 name of the calling process and &$qualify_domain$&, except that a trusted user
11127 can override this by means of the &%-oMas%& command line option.
11130 .vitem &$authentication_failed$&
11131 .cindex "authentication" "failure"
11132 .vindex "&$authentication_failed$&"
11133 This variable is set to &"1"& in an Exim server if a client issues an AUTH
11134 command that does not succeed. Otherwise it is set to &"0"&. This makes it
11135 possible to distinguish between &"did not try to authenticate"&
11136 (&$sender_host_authenticated$& is empty and &$authentication_failed$& is set to
11137 &"0"&) and &"tried to authenticate but failed"& (&$sender_host_authenticated$&
11138 is empty and &$authentication_failed$& is set to &"1"&). Failure includes any
11139 negative response to an AUTH command, including (for example) an attempt to use
11140 an undefined mechanism.
11142 .vitem &$av_failed$&
11143 .cindex "content scanning" "AV scanner failure"
11144 This variable is available when Exim is compiled with the content-scanning
11145 extension. It is set to &"0"& by default, but will be set to &"1"& if any
11146 problem occurs with the virus scanner (specified by &%av_scanner%&) during
11147 the ACL malware condition.
11149 .vitem &$body_linecount$&
11150 .cindex "message body" "line count"
11151 .cindex "body of message" "line count"
11152 .vindex "&$body_linecount$&"
11153 When a message is being received or delivered, this variable contains the
11154 number of lines in the message's body. See also &$message_linecount$&.
11156 .vitem &$body_zerocount$&
11157 .cindex "message body" "binary zero count"
11158 .cindex "body of message" "binary zero count"
11159 .cindex "binary zero" "in message body"
11160 .vindex "&$body_zerocount$&"
11161 When a message is being received or delivered, this variable contains the
11162 number of binary zero bytes (ASCII NULs) in the message's body.
11164 .vitem &$bounce_recipient$&
11165 .vindex "&$bounce_recipient$&"
11166 This is set to the recipient address of a bounce message while Exim is creating
11167 it. It is useful if a customized bounce message text file is in use (see
11168 chapter &<<CHAPemsgcust>>&).
11170 .vitem &$bounce_return_size_limit$&
11171 .vindex "&$bounce_return_size_limit$&"
11172 This contains the value set in the &%bounce_return_size_limit%& option, rounded
11173 up to a multiple of 1000. It is useful when a customized error message text
11174 file is in use (see chapter &<<CHAPemsgcust>>&).
11176 .vitem &$caller_gid$&
11177 .cindex "gid (group id)" "caller"
11178 .vindex "&$caller_gid$&"
11179 The real group id under which the process that called Exim was running. This is
11180 not the same as the group id of the originator of a message (see
11181 &$originator_gid$&). If Exim re-execs itself, this variable in the new
11182 incarnation normally contains the Exim gid.
11184 .vitem &$caller_uid$&
11185 .cindex "uid (user id)" "caller"
11186 .vindex "&$caller_uid$&"
11187 The real user id under which the process that called Exim was running. This is
11188 not the same as the user id of the originator of a message (see
11189 &$originator_uid$&). If Exim re-execs itself, this variable in the new
11190 incarnation normally contains the Exim uid.
11192 .vitem &$compile_date$&
11193 .vindex "&$compile_date$&"
11194 The date on which the Exim binary was compiled.
11196 .vitem &$compile_number$&
11197 .vindex "&$compile_number$&"
11198 The building process for Exim keeps a count of the number
11199 of times it has been compiled. This serves to distinguish different
11200 compilations of the same version of the program.
11202 .vitem &$demime_errorlevel$&
11203 .vindex "&$demime_errorlevel$&"
11204 This variable is available when Exim is compiled with
11205 the content-scanning extension and the obsolete &%demime%& condition. For
11206 details, see section &<<SECTdemimecond>>&.
11208 .vitem &$demime_reason$&
11209 .vindex "&$demime_reason$&"
11210 This variable is available when Exim is compiled with the
11211 content-scanning extension and the obsolete &%demime%& condition. For details,
11212 see section &<<SECTdemimecond>>&.
11214 .vitem &$dnslist_domain$& &&&
11215 &$dnslist_matched$& &&&
11216 &$dnslist_text$& &&&
11218 .vindex "&$dnslist_domain$&"
11219 .vindex "&$dnslist_matched$&"
11220 .vindex "&$dnslist_text$&"
11221 .vindex "&$dnslist_value$&"
11222 .cindex "black list (DNS)"
11223 When a DNS (black) list lookup succeeds, these variables are set to contain
11224 the following data from the lookup: the list's domain name, the key that was
11225 looked up, the contents of any associated TXT record, and the value from the
11226 main A record. See section &<<SECID204>>& for more details.
11229 .vindex "&$domain$&"
11230 When an address is being routed, or delivered on its own, this variable
11231 contains the domain. Uppercase letters in the domain are converted into lower
11232 case for &$domain$&.
11234 Global address rewriting happens when a message is received, so the value of
11235 &$domain$& during routing and delivery is the value after rewriting. &$domain$&
11236 is set during user filtering, but not during system filtering, because a
11237 message may have many recipients and the system filter is called just once.
11239 When more than one address is being delivered at once (for example, several
11240 RCPT commands in one SMTP delivery), &$domain$& is set only if they all
11241 have the same domain. Transports can be restricted to handling only one domain
11242 at a time if the value of &$domain$& is required at transport time &-- this is
11243 the default for local transports. For further details of the environment in
11244 which local transports are run, see chapter &<<CHAPenvironment>>&.
11246 .oindex "&%delay_warning_condition%&"
11247 At the end of a delivery, if all deferred addresses have the same domain, it is
11248 set in &$domain$& during the expansion of &%delay_warning_condition%&.
11250 The &$domain$& variable is also used in some other circumstances:
11253 When an ACL is running for a RCPT command, &$domain$& contains the domain of
11254 the recipient address. The domain of the &'sender'& address is in
11255 &$sender_address_domain$& at both MAIL time and at RCPT time. &$domain$& is not
11256 normally set during the running of the MAIL ACL. However, if the sender address
11257 is verified with a callout during the MAIL ACL, the sender domain is placed in
11258 &$domain$& during the expansions of &%hosts%&, &%interface%&, and &%port%& in
11259 the &(smtp)& transport.
11262 When a rewrite item is being processed (see chapter &<<CHAPrewrite>>&),
11263 &$domain$& contains the domain portion of the address that is being rewritten;
11264 it can be used in the expansion of the replacement address, for example, to
11265 rewrite domains by file lookup.
11268 With one important exception, whenever a domain list is being scanned,
11269 &$domain$& contains the subject domain. &*Exception*&: When a domain list in
11270 a &%sender_domains%& condition in an ACL is being processed, the subject domain
11271 is in &$sender_address_domain$& and not in &$domain$&. It works this way so
11272 that, in a RCPT ACL, the sender domain list can be dependent on the
11273 recipient domain (which is what is in &$domain$& at this time).
11276 .cindex "ETRN" "value of &$domain$&"
11277 .oindex "&%smtp_etrn_command%&"
11278 When the &%smtp_etrn_command%& option is being expanded, &$domain$& contains
11279 the complete argument of the ETRN command (see section &<<SECTETRN>>&).
11283 .vitem &$domain_data$&
11284 .vindex "&$domain_data$&"
11285 When the &%domains%& option on a router matches a domain by
11286 means of a lookup, the data read by the lookup is available during the running
11287 of the router as &$domain_data$&. In addition, if the driver routes the
11288 address to a transport, the value is available in that transport. If the
11289 transport is handling multiple addresses, the value from the first address is
11292 &$domain_data$& is also set when the &%domains%& condition in an ACL matches a
11293 domain by means of a lookup. The data read by the lookup is available during
11294 the rest of the ACL statement. In all other situations, this variable expands
11297 .vitem &$exim_gid$&
11298 .vindex "&$exim_gid$&"
11299 This variable contains the numerical value of the Exim group id.
11301 .vitem &$exim_path$&
11302 .vindex "&$exim_path$&"
11303 This variable contains the path to the Exim binary.
11305 .vitem &$exim_uid$&
11306 .vindex "&$exim_uid$&"
11307 This variable contains the numerical value of the Exim user id.
11309 .vitem &$found_extension$&
11310 .vindex "&$found_extension$&"
11311 This variable is available when Exim is compiled with the
11312 content-scanning extension and the obsolete &%demime%& condition. For details,
11313 see section &<<SECTdemimecond>>&.
11315 .vitem &$header_$&<&'name'&>
11316 This is not strictly an expansion variable. It is expansion syntax for
11317 inserting the message header line with the given name. Note that the name must
11318 be terminated by colon or white space, because it may contain a wide variety of
11319 characters. Note also that braces must &'not'& be used.
11321 .vitem &$headers_added$&
11322 .vindex "&$headers_added$&"
11323 Within an ACL this variable contains the headers added so far by
11324 the ACL modifier add_header (section &<<SECTaddheadacl>>&).
11325 The headers are a newline-separated list.
11329 When the &%check_local_user%& option is set for a router, the user's home
11330 directory is placed in &$home$& when the check succeeds. In particular, this
11331 means it is set during the running of users' filter files. A router may also
11332 explicitly set a home directory for use by a transport; this can be overridden
11333 by a setting on the transport itself.
11335 When running a filter test via the &%-bf%& option, &$home$& is set to the value
11336 of the environment variable HOME.
11340 If a router assigns an address to a transport (any transport), and passes a
11341 list of hosts with the address, the value of &$host$& when the transport starts
11342 to run is the name of the first host on the list. Note that this applies both
11343 to local and remote transports.
11345 .cindex "transport" "filter"
11346 .cindex "filter" "transport filter"
11347 For the &(smtp)& transport, if there is more than one host, the value of
11348 &$host$& changes as the transport works its way through the list. In
11349 particular, when the &(smtp)& transport is expanding its options for encryption
11350 using TLS, or for specifying a transport filter (see chapter
11351 &<<CHAPtransportgeneric>>&), &$host$& contains the name of the host to which it
11354 When used in the client part of an authenticator configuration (see chapter
11355 &<<CHAPSMTPAUTH>>&), &$host$& contains the name of the server to which the
11356 client is connected.
11359 .vitem &$host_address$&
11360 .vindex "&$host_address$&"
11361 This variable is set to the remote host's IP address whenever &$host$& is set
11362 for a remote connection. It is also set to the IP address that is being checked
11363 when the &%ignore_target_hosts%& option is being processed.
11365 .vitem &$host_data$&
11366 .vindex "&$host_data$&"
11367 If a &%hosts%& condition in an ACL is satisfied by means of a lookup, the
11368 result of the lookup is made available in the &$host_data$& variable. This
11369 allows you, for example, to do things like this:
11371 deny hosts = net-lsearch;/some/file
11372 message = $host_data
11374 .vitem &$host_lookup_deferred$&
11375 .cindex "host name" "lookup, failure of"
11376 .vindex "&$host_lookup_deferred$&"
11377 This variable normally contains &"0"&, as does &$host_lookup_failed$&. When a
11378 message comes from a remote host and there is an attempt to look up the host's
11379 name from its IP address, and the attempt is not successful, one of these
11380 variables is set to &"1"&.
11383 If the lookup receives a definite negative response (for example, a DNS lookup
11384 succeeded, but no records were found), &$host_lookup_failed$& is set to &"1"&.
11387 If there is any kind of problem during the lookup, such that Exim cannot
11388 tell whether or not the host name is defined (for example, a timeout for a DNS
11389 lookup), &$host_lookup_deferred$& is set to &"1"&.
11392 Looking up a host's name from its IP address consists of more than just a
11393 single reverse lookup. Exim checks that a forward lookup of at least one of the
11394 names it receives from a reverse lookup yields the original IP address. If this
11395 is not the case, Exim does not accept the looked up name(s), and
11396 &$host_lookup_failed$& is set to &"1"&. Thus, being able to find a name from an
11397 IP address (for example, the existence of a PTR record in the DNS) is not
11398 sufficient on its own for the success of a host name lookup. If the reverse
11399 lookup succeeds, but there is a lookup problem such as a timeout when checking
11400 the result, the name is not accepted, and &$host_lookup_deferred$& is set to
11401 &"1"&. See also &$sender_host_name$&.
11403 .vitem &$host_lookup_failed$&
11404 .vindex "&$host_lookup_failed$&"
11405 See &$host_lookup_deferred$&.
11409 .vindex "&$inode$&"
11410 The only time this variable is set is while expanding the &%directory_file%&
11411 option in the &(appendfile)& transport. The variable contains the inode number
11412 of the temporary file which is about to be renamed. It can be used to construct
11413 a unique name for the file.
11415 .vitem &$interface_address$&
11416 .vindex "&$interface_address$&"
11417 This is an obsolete name for &$received_ip_address$&.
11419 .vitem &$interface_port$&
11420 .vindex "&$interface_port$&"
11421 This is an obsolete name for &$received_port$&.
11425 This variable is used during the expansion of &*forall*& and &*forany*&
11426 conditions (see section &<<SECTexpcond>>&), and &*filter*&, &*map*&, and
11427 &*reduce*& items (see section &<<SECTexpcond>>&). In other circumstances, it is
11431 .vindex "&$ldap_dn$&"
11432 This variable, which is available only when Exim is compiled with LDAP support,
11433 contains the DN from the last entry in the most recently successful LDAP
11436 .vitem &$load_average$&
11437 .vindex "&$load_average$&"
11438 This variable contains the system load average, multiplied by 1000 so that it
11439 is an integer. For example, if the load average is 0.21, the value of the
11440 variable is 210. The value is recomputed every time the variable is referenced.
11442 .vitem &$local_part$&
11443 .vindex "&$local_part$&"
11444 When an address is being routed, or delivered on its own, this
11445 variable contains the local part. When a number of addresses are being
11446 delivered together (for example, multiple RCPT commands in an SMTP
11447 session), &$local_part$& is not set.
11449 Global address rewriting happens when a message is received, so the value of
11450 &$local_part$& during routing and delivery is the value after rewriting.
11451 &$local_part$& is set during user filtering, but not during system filtering,
11452 because a message may have many recipients and the system filter is called just
11455 .vindex "&$local_part_prefix$&"
11456 .vindex "&$local_part_suffix$&"
11457 If a local part prefix or suffix has been recognized, it is not included in the
11458 value of &$local_part$& during routing and subsequent delivery. The values of
11459 any prefix or suffix are in &$local_part_prefix$& and
11460 &$local_part_suffix$&, respectively.
11462 When a message is being delivered to a file, pipe, or autoreply transport as a
11463 result of aliasing or forwarding, &$local_part$& is set to the local part of
11464 the parent address, not to the file name or command (see &$address_file$& and
11467 When an ACL is running for a RCPT command, &$local_part$& contains the
11468 local part of the recipient address.
11470 When a rewrite item is being processed (see chapter &<<CHAPrewrite>>&),
11471 &$local_part$& contains the local part of the address that is being rewritten;
11472 it can be used in the expansion of the replacement address, for example.
11474 In all cases, all quoting is removed from the local part. For example, for both
11477 "abc:xyz"@test.example
11478 abc\:xyz@test.example
11480 the value of &$local_part$& is
11484 If you use &$local_part$& to create another address, you should always wrap it
11485 inside a quoting operator. For example, in a &(redirect)& router you could
11488 data = ${quote_local_part:$local_part}@new.domain.example
11490 &*Note*&: The value of &$local_part$& is normally lower cased. If you want
11491 to process local parts in a case-dependent manner in a router, you can set the
11492 &%caseful_local_part%& option (see chapter &<<CHAProutergeneric>>&).
11494 .vitem &$local_part_data$&
11495 .vindex "&$local_part_data$&"
11496 When the &%local_parts%& option on a router matches a local part by means of a
11497 lookup, the data read by the lookup is available during the running of the
11498 router as &$local_part_data$&. In addition, if the driver routes the address
11499 to a transport, the value is available in that transport. If the transport is
11500 handling multiple addresses, the value from the first address is used.
11502 &$local_part_data$& is also set when the &%local_parts%& condition in an ACL
11503 matches a local part by means of a lookup. The data read by the lookup is
11504 available during the rest of the ACL statement. In all other situations, this
11505 variable expands to nothing.
11507 .vitem &$local_part_prefix$&
11508 .vindex "&$local_part_prefix$&"
11509 When an address is being routed or delivered, and a
11510 specific prefix for the local part was recognized, it is available in this
11511 variable, having been removed from &$local_part$&.
11513 .vitem &$local_part_suffix$&
11514 .vindex "&$local_part_suffix$&"
11515 When an address is being routed or delivered, and a
11516 specific suffix for the local part was recognized, it is available in this
11517 variable, having been removed from &$local_part$&.
11519 .vitem &$local_scan_data$&
11520 .vindex "&$local_scan_data$&"
11521 This variable contains the text returned by the &[local_scan()]& function when
11522 a message is received. See chapter &<<CHAPlocalscan>>& for more details.
11524 .vitem &$local_user_gid$&
11525 .vindex "&$local_user_gid$&"
11526 See &$local_user_uid$&.
11528 .vitem &$local_user_uid$&
11529 .vindex "&$local_user_uid$&"
11530 This variable and &$local_user_gid$& are set to the uid and gid after the
11531 &%check_local_user%& router precondition succeeds. This means that their values
11532 are available for the remaining preconditions (&%senders%&, &%require_files%&,
11533 and &%condition%&), for the &%address_data%& expansion, and for any
11534 router-specific expansions. At all other times, the values in these variables
11535 are &`(uid_t)(-1)`& and &`(gid_t)(-1)`&, respectively.
11537 .vitem &$localhost_number$&
11538 .vindex "&$localhost_number$&"
11539 This contains the expanded value of the
11540 &%localhost_number%& option. The expansion happens after the main options have
11543 .vitem &$log_inodes$&
11544 .vindex "&$log_inodes$&"
11545 The number of free inodes in the disk partition where Exim's
11546 log files are being written. The value is recalculated whenever the variable is
11547 referenced. If the relevant file system does not have the concept of inodes,
11548 the value of is -1. See also the &%check_log_inodes%& option.
11550 .vitem &$log_space$&
11551 .vindex "&$log_space$&"
11552 The amount of free space (as a number of kilobytes) in the disk
11553 partition where Exim's log files are being written. The value is recalculated
11554 whenever the variable is referenced. If the operating system does not have the
11555 ability to find the amount of free space (only true for experimental systems),
11556 the space value is -1. See also the &%check_log_space%& option.
11560 .vitem &$lookup_dnssec_authenticated$&
11561 .vindex "&$lookup_dnssec_authenticated$&"
11562 This variable is set after a DNS lookup done by
11563 a dnsdb lookup expansion, dnslookup router or smtp transport.
11564 It will be empty if &(DNSSEC)& was not requested,
11565 &"no"& if the result was not labelled as authenticated data
11566 and &"yes"& if it was.
11569 .vitem &$mailstore_basename$&
11570 .vindex "&$mailstore_basename$&"
11571 This variable is set only when doing deliveries in &"mailstore"& format in the
11572 &(appendfile)& transport. During the expansion of the &%mailstore_prefix%&,
11573 &%mailstore_suffix%&, &%message_prefix%&, and &%message_suffix%& options, it
11574 contains the basename of the files that are being written, that is, the name
11575 without the &".tmp"&, &".env"&, or &".msg"& suffix. At all other times, this
11578 .vitem &$malware_name$&
11579 .vindex "&$malware_name$&"
11580 This variable is available when Exim is compiled with the
11581 content-scanning extension. It is set to the name of the virus that was found
11582 when the ACL &%malware%& condition is true (see section &<<SECTscanvirus>>&).
11584 .vitem &$max_received_linelength$&
11585 .vindex "&$max_received_linelength$&"
11586 .cindex "maximum" "line length"
11587 .cindex "line length" "maximum"
11588 This variable contains the number of bytes in the longest line that was
11589 received as part of the message, not counting the line termination
11592 .vitem &$message_age$&
11593 .cindex "message" "age of"
11594 .vindex "&$message_age$&"
11595 This variable is set at the start of a delivery attempt to contain the number
11596 of seconds since the message was received. It does not change during a single
11599 .vitem &$message_body$&
11600 .cindex "body of message" "expansion variable"
11601 .cindex "message body" "in expansion"
11602 .cindex "binary zero" "in message body"
11603 .vindex "&$message_body$&"
11604 .oindex "&%message_body_visible%&"
11605 This variable contains the initial portion of a message's body while it is
11606 being delivered, and is intended mainly for use in filter files. The maximum
11607 number of characters of the body that are put into the variable is set by the
11608 &%message_body_visible%& configuration option; the default is 500.
11610 .oindex "&%message_body_newlines%&"
11611 By default, newlines are converted into spaces in &$message_body$&, to make it
11612 easier to search for phrases that might be split over a line break. However,
11613 this can be disabled by setting &%message_body_newlines%& to be true. Binary
11614 zeros are always converted into spaces.
11616 .vitem &$message_body_end$&
11617 .cindex "body of message" "expansion variable"
11618 .cindex "message body" "in expansion"
11619 .vindex "&$message_body_end$&"
11620 This variable contains the final portion of a message's
11621 body while it is being delivered. The format and maximum size are as for
11624 .vitem &$message_body_size$&
11625 .cindex "body of message" "size"
11626 .cindex "message body" "size"
11627 .vindex "&$message_body_size$&"
11628 When a message is being delivered, this variable contains the size of the body
11629 in bytes. The count starts from the character after the blank line that
11630 separates the body from the header. Newlines are included in the count. See
11631 also &$message_size$&, &$body_linecount$&, and &$body_zerocount$&.
11633 .vitem &$message_exim_id$&
11634 .vindex "&$message_exim_id$&"
11635 When a message is being received or delivered, this variable contains the
11636 unique message id that is generated and used by Exim to identify the message.
11637 An id is not created for a message until after its header has been successfully
11638 received. &*Note*&: This is &'not'& the contents of the &'Message-ID:'& header
11639 line; it is the local id that Exim assigns to the message, for example:
11640 &`1BXTIK-0001yO-VA`&.
11642 .vitem &$message_headers$&
11643 .vindex &$message_headers$&
11644 This variable contains a concatenation of all the header lines when a message
11645 is being processed, except for lines added by routers or transports. The header
11646 lines are separated by newline characters. Their contents are decoded in the
11647 same way as a header line that is inserted by &%bheader%&.
11649 .vitem &$message_headers_raw$&
11650 .vindex &$message_headers_raw$&
11651 This variable is like &$message_headers$& except that no processing of the
11652 contents of header lines is done.
11654 .vitem &$message_id$&
11655 This is an old name for &$message_exim_id$&, which is now deprecated.
11657 .vitem &$message_linecount$&
11658 .vindex "&$message_linecount$&"
11659 This variable contains the total number of lines in the header and body of the
11660 message. Compare &$body_linecount$&, which is the count for the body only.
11661 During the DATA and content-scanning ACLs, &$message_linecount$& contains the
11662 number of lines received. Before delivery happens (that is, before filters,
11663 routers, and transports run) the count is increased to include the
11664 &'Received:'& header line that Exim standardly adds, and also any other header
11665 lines that are added by ACLs. The blank line that separates the message header
11666 from the body is not counted.
11668 As with the special case of &$message_size$&, during the expansion of the
11669 appendfile transport's maildir_tag option in maildir format, the value of
11670 &$message_linecount$& is the precise size of the number of newlines in the
11671 file that has been written (minus one for the blank line between the
11672 header and the body).
11674 Here is an example of the use of this variable in a DATA ACL:
11676 deny message = Too many lines in message header
11678 ${if <{250}{${eval:$message_linecount - $body_linecount}}}
11680 In the MAIL and RCPT ACLs, the value is zero because at that stage the
11681 message has not yet been received.
11683 .vitem &$message_size$&
11684 .cindex "size" "of message"
11685 .cindex "message" "size"
11686 .vindex "&$message_size$&"
11687 When a message is being processed, this variable contains its size in bytes. In
11688 most cases, the size includes those headers that were received with the
11689 message, but not those (such as &'Envelope-to:'&) that are added to individual
11690 deliveries as they are written. However, there is one special case: during the
11691 expansion of the &%maildir_tag%& option in the &(appendfile)& transport while
11692 doing a delivery in maildir format, the value of &$message_size$& is the
11693 precise size of the file that has been written. See also
11694 &$message_body_size$&, &$body_linecount$&, and &$body_zerocount$&.
11696 .cindex "RCPT" "value of &$message_size$&"
11697 While running a per message ACL (mail/rcpt/predata), &$message_size$&
11698 contains the size supplied on the MAIL command, or -1 if no size was given. The
11699 value may not, of course, be truthful.
11701 .vitem &$mime_$&&'xxx'&
11702 A number of variables whose names start with &$mime$& are
11703 available when Exim is compiled with the content-scanning extension. For
11704 details, see section &<<SECTscanmimepart>>&.
11706 .vitem "&$n0$& &-- &$n9$&"
11707 These variables are counters that can be incremented by means
11708 of the &%add%& command in filter files.
11710 .vitem &$original_domain$&
11711 .vindex "&$domain$&"
11712 .vindex "&$original_domain$&"
11713 When a top-level address is being processed for delivery, this contains the
11714 same value as &$domain$&. However, if a &"child"& address (for example,
11715 generated by an alias, forward, or filter file) is being processed, this
11716 variable contains the domain of the original address (lower cased). This
11717 differs from &$parent_domain$& only when there is more than one level of
11718 aliasing or forwarding. When more than one address is being delivered in a
11719 single transport run, &$original_domain$& is not set.
11721 If a new address is created by means of a &%deliver%& command in a system
11722 filter, it is set up with an artificial &"parent"& address. This has the local
11723 part &'system-filter'& and the default qualify domain.
11725 .vitem &$original_local_part$&
11726 .vindex "&$local_part$&"
11727 .vindex "&$original_local_part$&"
11728 When a top-level address is being processed for delivery, this contains the
11729 same value as &$local_part$&, unless a prefix or suffix was removed from the
11730 local part, because &$original_local_part$& always contains the full local
11731 part. When a &"child"& address (for example, generated by an alias, forward, or
11732 filter file) is being processed, this variable contains the full local part of
11733 the original address.
11735 If the router that did the redirection processed the local part
11736 case-insensitively, the value in &$original_local_part$& is in lower case.
11737 This variable differs from &$parent_local_part$& only when there is more than
11738 one level of aliasing or forwarding. When more than one address is being
11739 delivered in a single transport run, &$original_local_part$& is not set.
11741 If a new address is created by means of a &%deliver%& command in a system
11742 filter, it is set up with an artificial &"parent"& address. This has the local
11743 part &'system-filter'& and the default qualify domain.
11745 .vitem &$originator_gid$&
11746 .cindex "gid (group id)" "of originating user"
11747 .cindex "sender" "gid"
11748 .vindex "&$caller_gid$&"
11749 .vindex "&$originator_gid$&"
11750 This variable contains the value of &$caller_gid$& that was set when the
11751 message was received. For messages received via the command line, this is the
11752 gid of the sending user. For messages received by SMTP over TCP/IP, this is
11753 normally the gid of the Exim user.
11755 .vitem &$originator_uid$&
11756 .cindex "uid (user id)" "of originating user"
11757 .cindex "sender" "uid"
11758 .vindex "&$caller_uid$&"
11759 .vindex "&$originaltor_uid$&"
11760 The value of &$caller_uid$& that was set when the message was received. For
11761 messages received via the command line, this is the uid of the sending user.
11762 For messages received by SMTP over TCP/IP, this is normally the uid of the Exim
11765 .vitem &$parent_domain$&
11766 .vindex "&$parent_domain$&"
11767 This variable is similar to &$original_domain$& (see
11768 above), except that it refers to the immediately preceding parent address.
11770 .vitem &$parent_local_part$&
11771 .vindex "&$parent_local_part$&"
11772 This variable is similar to &$original_local_part$&
11773 (see above), except that it refers to the immediately preceding parent address.
11776 .cindex "pid (process id)" "of current process"
11778 This variable contains the current process id.
11780 .vitem &$pipe_addresses$&
11781 .cindex "filter" "transport filter"
11782 .cindex "transport" "filter"
11783 .vindex "&$pipe_addresses$&"
11784 This is not an expansion variable, but is mentioned here because the string
11785 &`$pipe_addresses`& is handled specially in the command specification for the
11786 &(pipe)& transport (chapter &<<CHAPpipetransport>>&) and in transport filters
11787 (described under &%transport_filter%& in chapter &<<CHAPtransportgeneric>>&).
11788 It cannot be used in general expansion strings, and provokes an &"unknown
11789 variable"& error if encountered.
11791 .vitem &$primary_hostname$&
11792 .vindex "&$primary_hostname$&"
11793 This variable contains the value set by &%primary_hostname%& in the
11794 configuration file, or read by the &[uname()]& function. If &[uname()]& returns
11795 a single-component name, Exim calls &[gethostbyname()]& (or
11796 &[getipnodebyname()]& where available) in an attempt to acquire a fully
11797 qualified host name. See also &$smtp_active_hostname$&.
11800 .vitem &$prvscheck_address$&
11801 This variable is used in conjunction with the &%prvscheck%& expansion item,
11802 which is described in sections &<<SECTexpansionitems>>& and
11803 &<<SECTverifyPRVS>>&.
11805 .vitem &$prvscheck_keynum$&
11806 This variable is used in conjunction with the &%prvscheck%& expansion item,
11807 which is described in sections &<<SECTexpansionitems>>& and
11808 &<<SECTverifyPRVS>>&.
11810 .vitem &$prvscheck_result$&
11811 This variable is used in conjunction with the &%prvscheck%& expansion item,
11812 which is described in sections &<<SECTexpansionitems>>& and
11813 &<<SECTverifyPRVS>>&.
11815 .vitem &$qualify_domain$&
11816 .vindex "&$qualify_domain$&"
11817 The value set for the &%qualify_domain%& option in the configuration file.
11819 .vitem &$qualify_recipient$&
11820 .vindex "&$qualify_recipient$&"
11821 The value set for the &%qualify_recipient%& option in the configuration file,
11822 or if not set, the value of &$qualify_domain$&.
11824 .vitem &$rcpt_count$&
11825 .vindex "&$rcpt_count$&"
11826 When a message is being received by SMTP, this variable contains the number of
11827 RCPT commands received for the current message. If this variable is used in a
11828 RCPT ACL, its value includes the current command.
11830 .vitem &$rcpt_defer_count$&
11831 .vindex "&$rcpt_defer_count$&"
11832 .cindex "4&'xx'& responses" "count of"
11833 When a message is being received by SMTP, this variable contains the number of
11834 RCPT commands in the current message that have previously been rejected with a
11835 temporary (4&'xx'&) response.
11837 .vitem &$rcpt_fail_count$&
11838 .vindex "&$rcpt_fail_count$&"
11839 When a message is being received by SMTP, this variable contains the number of
11840 RCPT commands in the current message that have previously been rejected with a
11841 permanent (5&'xx'&) response.
11843 .vitem &$received_count$&
11844 .vindex "&$received_count$&"
11845 This variable contains the number of &'Received:'& header lines in the message,
11846 including the one added by Exim (so its value is always greater than zero). It
11847 is available in the DATA ACL, the non-SMTP ACL, and while routing and
11850 .vitem &$received_for$&
11851 .vindex "&$received_for$&"
11852 If there is only a single recipient address in an incoming message, this
11853 variable contains that address when the &'Received:'& header line is being
11854 built. The value is copied after recipient rewriting has happened, but before
11855 the &[local_scan()]& function is run.
11857 .vitem &$received_ip_address$&
11858 .vindex "&$received_ip_address$&"
11859 As soon as an Exim server starts processing an incoming TCP/IP connection, this
11860 variable is set to the address of the local IP interface, and &$received_port$&
11861 is set to the local port number. (The remote IP address and port are in
11862 &$sender_host_address$& and &$sender_host_port$&.) When testing with &%-bh%&,
11863 the port value is -1 unless it has been set using the &%-oMi%& command line
11866 As well as being useful in ACLs (including the &"connect"& ACL), these variable
11867 could be used, for example, to make the file name for a TLS certificate depend
11868 on which interface and/or port is being used for the incoming connection. The
11869 values of &$received_ip_address$& and &$received_port$& are saved with any
11870 messages that are received, thus making these variables available at delivery
11873 &*Note:*& There are no equivalent variables for outgoing connections, because
11874 the values are unknown (unless they are explicitly set by options of the
11875 &(smtp)& transport).
11877 .vitem &$received_port$&
11878 .vindex "&$received_port$&"
11879 See &$received_ip_address$&.
11881 .vitem &$received_protocol$&
11882 .vindex "&$received_protocol$&"
11883 When a message is being processed, this variable contains the name of the
11884 protocol by which it was received. Most of the names used by Exim are defined
11885 by RFCs 821, 2821, and 3848. They start with &"smtp"& (the client used HELO) or
11886 &"esmtp"& (the client used EHLO). This can be followed by &"s"& for secure
11887 (encrypted) and/or &"a"& for authenticated. Thus, for example, if the protocol
11888 is set to &"esmtpsa"&, the message was received over an encrypted SMTP
11889 connection and the client was successfully authenticated.
11891 Exim uses the protocol name &"smtps"& for the case when encryption is
11892 automatically set up on connection without the use of STARTTLS (see
11893 &%tls_on_connect_ports%&), and the client uses HELO to initiate the
11894 encrypted SMTP session. The name &"smtps"& is also used for the rare situation
11895 where the client initially uses EHLO, sets up an encrypted connection using
11896 STARTTLS, and then uses HELO afterwards.
11898 The &%-oMr%& option provides a way of specifying a custom protocol name for
11899 messages that are injected locally by trusted callers. This is commonly used to
11900 identify messages that are being re-injected after some kind of scanning.
11902 .vitem &$received_time$&
11903 .vindex "&$received_time$&"
11904 This variable contains the date and time when the current message was received,
11905 as a number of seconds since the start of the Unix epoch.
11907 .vitem &$recipient_data$&
11908 .vindex "&$recipient_data$&"
11909 This variable is set after an indexing lookup success in an ACL &%recipients%&
11910 condition. It contains the data from the lookup, and the value remains set
11911 until the next &%recipients%& test. Thus, you can do things like this:
11913 &`require recipients = cdb*@;/some/file`&
11914 &`deny `&&'some further test involving'& &`$recipient_data`&
11916 &*Warning*&: This variable is set only when a lookup is used as an indexing
11917 method in the address list, using the semicolon syntax as in the example above.
11918 The variable is not set for a lookup that is used as part of the string
11919 expansion that all such lists undergo before being interpreted.
11921 .vitem &$recipient_verify_failure$&
11922 .vindex "&$recipient_verify_failure$&"
11923 In an ACL, when a recipient verification fails, this variable contains
11924 information about the failure. It is set to one of the following words:
11927 &"qualify"&: The address was unqualified (no domain), and the message
11928 was neither local nor came from an exempted host.
11931 &"route"&: Routing failed.
11934 &"mail"&: Routing succeeded, and a callout was attempted; rejection occurred at
11935 or before the MAIL command (that is, on initial connection, HELO, or
11939 &"recipient"&: The RCPT command in a callout was rejected.
11942 &"postmaster"&: The postmaster check in a callout was rejected.
11945 The main use of this variable is expected to be to distinguish between
11946 rejections of MAIL and rejections of RCPT.
11948 .vitem &$recipients$&
11949 .vindex "&$recipients$&"
11950 This variable contains a list of envelope recipients for a message. A comma and
11951 a space separate the addresses in the replacement text. However, the variable
11952 is not generally available, to prevent exposure of Bcc recipients in
11953 unprivileged users' filter files. You can use &$recipients$& only in these
11957 In a system filter file.
11959 In the ACLs associated with the DATA command and with non-SMTP messages, that
11960 is, the ACLs defined by &%acl_smtp_predata%&, &%acl_smtp_data%&,
11961 &%acl_smtp_mime%&, &%acl_not_smtp_start%&, &%acl_not_smtp%&, and
11962 &%acl_not_smtp_mime%&.
11964 From within a &[local_scan()]& function.
11968 .vitem &$recipients_count$&
11969 .vindex "&$recipients_count$&"
11970 When a message is being processed, this variable contains the number of
11971 envelope recipients that came with the message. Duplicates are not excluded
11972 from the count. While a message is being received over SMTP, the number
11973 increases for each accepted recipient. It can be referenced in an ACL.
11976 .vitem &$regex_match_string$&
11977 .vindex "&$regex_match_string$&"
11978 This variable is set to contain the matching regular expression after a
11979 &%regex%& ACL condition has matched (see section &<<SECTscanregex>>&).
11982 .vitem &$reply_address$&
11983 .vindex "&$reply_address$&"
11984 When a message is being processed, this variable contains the contents of the
11985 &'Reply-To:'& header line if one exists and it is not empty, or otherwise the
11986 contents of the &'From:'& header line. Apart from the removal of leading
11987 white space, the value is not processed in any way. In particular, no RFC 2047
11988 decoding or character code translation takes place.
11990 .vitem &$return_path$&
11991 .vindex "&$return_path$&"
11992 When a message is being delivered, this variable contains the return path &--
11993 the sender field that will be sent as part of the envelope. It is not enclosed
11994 in <> characters. At the start of routing an address, &$return_path$& has the
11995 same value as &$sender_address$&, but if, for example, an incoming message to a
11996 mailing list has been expanded by a router which specifies a different address
11997 for bounce messages, &$return_path$& subsequently contains the new bounce
11998 address, whereas &$sender_address$& always contains the original sender address
11999 that was received with the message. In other words, &$sender_address$& contains
12000 the incoming envelope sender, and &$return_path$& contains the outgoing
12003 .vitem &$return_size_limit$&
12004 .vindex "&$return_size_limit$&"
12005 This is an obsolete name for &$bounce_return_size_limit$&.
12007 .vitem &$router_name$&
12008 .cindex "router" "name"
12009 .cindex "name" "of router"
12010 .vindex "&$router_name$&"
12011 During the running of a router this variable contains its name.
12014 .cindex "return code" "from &%run%& expansion"
12015 .vindex "&$runrc$&"
12016 This variable contains the return code from a command that is run by the
12017 &%${run...}%& expansion item. &*Warning*&: In a router or transport, you cannot
12018 assume the order in which option values are expanded, except for those
12019 preconditions whose order of testing is documented. Therefore, you cannot
12020 reliably expect to set &$runrc$& by the expansion of one option, and use it in
12023 .vitem &$self_hostname$&
12024 .oindex "&%self%&" "value of host name"
12025 .vindex "&$self_hostname$&"
12026 When an address is routed to a supposedly remote host that turns out to be the
12027 local host, what happens is controlled by the &%self%& generic router option.
12028 One of its values causes the address to be passed to another router. When this
12029 happens, &$self_hostname$& is set to the name of the local host that the
12030 original router encountered. In other circumstances its contents are null.
12032 .vitem &$sender_address$&
12033 .vindex "&$sender_address$&"
12034 When a message is being processed, this variable contains the sender's address
12035 that was received in the message's envelope. The case of letters in the address
12036 is retained, in both the local part and the domain. For bounce messages, the
12037 value of this variable is the empty string. See also &$return_path$&.
12039 .vitem &$sender_address_data$&
12040 .vindex "&$address_data$&"
12041 .vindex "&$sender_address_data$&"
12042 If &$address_data$& is set when the routers are called from an ACL to verify a
12043 sender address, the final value is preserved in &$sender_address_data$&, to
12044 distinguish it from data from a recipient address. The value does not persist
12045 after the end of the current ACL statement. If you want to preserve it for
12046 longer, you can save it in an ACL variable.
12048 .vitem &$sender_address_domain$&
12049 .vindex "&$sender_address_domain$&"
12050 The domain portion of &$sender_address$&.
12052 .vitem &$sender_address_local_part$&
12053 .vindex "&$sender_address_local_part$&"
12054 The local part portion of &$sender_address$&.
12056 .vitem &$sender_data$&
12057 .vindex "&$sender_data$&"
12058 This variable is set after a lookup success in an ACL &%senders%& condition or
12059 in a router &%senders%& option. It contains the data from the lookup, and the
12060 value remains set until the next &%senders%& test. Thus, you can do things like
12063 &`require senders = cdb*@;/some/file`&
12064 &`deny `&&'some further test involving'& &`$sender_data`&
12066 &*Warning*&: This variable is set only when a lookup is used as an indexing
12067 method in the address list, using the semicolon syntax as in the example above.
12068 The variable is not set for a lookup that is used as part of the string
12069 expansion that all such lists undergo before being interpreted.
12071 .vitem &$sender_fullhost$&
12072 .vindex "&$sender_fullhost$&"
12073 When a message is received from a remote host, this variable contains the host
12074 name and IP address in a single string. It ends with the IP address in square
12075 brackets, followed by a colon and a port number if the logging of ports is
12076 enabled. The format of the rest of the string depends on whether the host
12077 issued a HELO or EHLO SMTP command, and whether the host name was verified by
12078 looking up its IP address. (Looking up the IP address can be forced by the
12079 &%host_lookup%& option, independent of verification.) A plain host name at the
12080 start of the string is a verified host name; if this is not present,
12081 verification either failed or was not requested. A host name in parentheses is
12082 the argument of a HELO or EHLO command. This is omitted if it is identical to
12083 the verified host name or to the host's IP address in square brackets.
12085 .vitem &$sender_helo_name$&
12086 .vindex "&$sender_helo_name$&"
12087 When a message is received from a remote host that has issued a HELO or EHLO
12088 command, the argument of that command is placed in this variable. It is also
12089 set if HELO or EHLO is used when a message is received using SMTP locally via
12090 the &%-bs%& or &%-bS%& options.
12092 .vitem &$sender_host_address$&
12093 .vindex "&$sender_host_address$&"
12094 When a message is received from a remote host, this variable contains that
12095 host's IP address. For locally submitted messages, it is empty.
12097 .vitem &$sender_host_authenticated$&
12098 .vindex "&$sender_host_authenticated$&"
12099 This variable contains the name (not the public name) of the authenticator
12100 driver that successfully authenticated the client from which the message was
12101 received. It is empty if there was no successful authentication. See also
12102 &$authenticated_id$&.
12104 .vitem &$sender_host_dnssec$&
12105 .vindex "&$sender_host_dnssec$&"
12106 If &$sender_host_name$& has been populated (by reference, &%hosts_lookup%& or
12107 otherwise) then this boolean will have been set true if, and only if, the
12108 resolver library states that the reverse DNS was authenticated data. At all
12109 other times, this variable is false.
12111 It is likely that you will need to coerce DNSSEC support on in the resolver
12112 library, by setting:
12117 Exim does not perform DNSSEC validation itself, instead leaving that to a
12118 validating resolver (eg, unbound, or bind with suitable configuration).
12120 Exim does not (currently) check to see if the forward DNS was also secured
12121 with DNSSEC, only the reverse DNS.
12123 If you have changed &%host_lookup_order%& so that &`bydns`& is not the first
12124 mechanism in the list, then this variable will be false.
12127 .vitem &$sender_host_name$&
12128 .vindex "&$sender_host_name$&"
12129 When a message is received from a remote host, this variable contains the
12130 host's name as obtained by looking up its IP address. For messages received by
12131 other means, this variable is empty.
12133 .vindex "&$host_lookup_failed$&"
12134 If the host name has not previously been looked up, a reference to
12135 &$sender_host_name$& triggers a lookup (for messages from remote hosts).
12136 A looked up name is accepted only if it leads back to the original IP address
12137 via a forward lookup. If either the reverse or the forward lookup fails to find
12138 any data, or if the forward lookup does not yield the original IP address,
12139 &$sender_host_name$& remains empty, and &$host_lookup_failed$& is set to &"1"&.
12141 .vindex "&$host_lookup_deferred$&"
12142 However, if either of the lookups cannot be completed (for example, there is a
12143 DNS timeout), &$host_lookup_deferred$& is set to &"1"&, and
12144 &$host_lookup_failed$& remains set to &"0"&.
12146 Once &$host_lookup_failed$& is set to &"1"&, Exim does not try to look up the
12147 host name again if there is a subsequent reference to &$sender_host_name$&
12148 in the same Exim process, but it does try again if &$host_lookup_deferred$&
12151 Exim does not automatically look up every calling host's name. If you want
12152 maximum efficiency, you should arrange your configuration so that it avoids
12153 these lookups altogether. The lookup happens only if one or more of the
12154 following are true:
12157 A string containing &$sender_host_name$& is expanded.
12159 The calling host matches the list in &%host_lookup%&. In the default
12160 configuration, this option is set to *, so it must be changed if lookups are
12161 to be avoided. (In the code, the default for &%host_lookup%& is unset.)
12163 Exim needs the host name in order to test an item in a host list. The items
12164 that require this are described in sections &<<SECThoslispatnam>>& and
12165 &<<SECThoslispatnamsk>>&.
12167 The calling host matches &%helo_try_verify_hosts%& or &%helo_verify_hosts%&.
12168 In this case, the host name is required to compare with the name quoted in any
12169 EHLO or HELO commands that the client issues.
12171 The remote host issues a EHLO or HELO command that quotes one of the
12172 domains in &%helo_lookup_domains%&. The default value of this option is
12173 . ==== As this is a nested list, any displays it contains must be indented
12174 . ==== as otherwise they are too far to the left.
12176 helo_lookup_domains = @ : @[]
12178 which causes a lookup if a remote host (incorrectly) gives the server's name or
12179 IP address in an EHLO or HELO command.
12183 .vitem &$sender_host_port$&
12184 .vindex "&$sender_host_port$&"
12185 When a message is received from a remote host, this variable contains the port
12186 number that was used on the remote host.
12188 .vitem &$sender_ident$&
12189 .vindex "&$sender_ident$&"
12190 When a message is received from a remote host, this variable contains the
12191 identification received in response to an RFC 1413 request. When a message has
12192 been received locally, this variable contains the login name of the user that
12195 .vitem &$sender_rate_$&&'xxx'&
12196 A number of variables whose names begin &$sender_rate_$& are set as part of the
12197 &%ratelimit%& ACL condition. Details are given in section
12198 &<<SECTratelimiting>>&.
12200 .vitem &$sender_rcvhost$&
12201 .cindex "DNS" "reverse lookup"
12202 .cindex "reverse DNS lookup"
12203 .vindex "&$sender_rcvhost$&"
12204 This is provided specifically for use in &'Received:'& headers. It starts with
12205 either the verified host name (as obtained from a reverse DNS lookup) or, if
12206 there is no verified host name, the IP address in square brackets. After that
12207 there may be text in parentheses. When the first item is a verified host name,
12208 the first thing in the parentheses is the IP address in square brackets,
12209 followed by a colon and a port number if port logging is enabled. When the
12210 first item is an IP address, the port is recorded as &"port=&'xxxx'&"& inside
12213 There may also be items of the form &"helo=&'xxxx'&"& if HELO or EHLO
12214 was used and its argument was not identical to the real host name or IP
12215 address, and &"ident=&'xxxx'&"& if an RFC 1413 ident string is available. If
12216 all three items are present in the parentheses, a newline and tab are inserted
12217 into the string, to improve the formatting of the &'Received:'& header.
12219 .vitem &$sender_verify_failure$&
12220 .vindex "&$sender_verify_failure$&"
12221 In an ACL, when a sender verification fails, this variable contains information
12222 about the failure. The details are the same as for
12223 &$recipient_verify_failure$&.
12225 .vitem &$sending_ip_address$&
12226 .vindex "&$sending_ip_address$&"
12227 This variable is set whenever an outgoing SMTP connection to another host has
12228 been set up. It contains the IP address of the local interface that is being
12229 used. This is useful if a host that has more than one IP address wants to take
12230 on different personalities depending on which one is being used. For incoming
12231 connections, see &$received_ip_address$&.
12233 .vitem &$sending_port$&
12234 .vindex "&$sending_port$&"
12235 This variable is set whenever an outgoing SMTP connection to another host has
12236 been set up. It contains the local port that is being used. For incoming
12237 connections, see &$received_port$&.
12239 .vitem &$smtp_active_hostname$&
12240 .vindex "&$smtp_active_hostname$&"
12241 During an incoming SMTP session, this variable contains the value of the active
12242 host name, as specified by the &%smtp_active_hostname%& option. The value of
12243 &$smtp_active_hostname$& is saved with any message that is received, so its
12244 value can be consulted during routing and delivery.
12246 .vitem &$smtp_command$&
12247 .vindex "&$smtp_command$&"
12248 During the processing of an incoming SMTP command, this variable contains the
12249 entire command. This makes it possible to distinguish between HELO and EHLO in
12250 the HELO ACL, and also to distinguish between commands such as these:
12255 For a MAIL command, extra parameters such as SIZE can be inspected. For a RCPT
12256 command, the address in &$smtp_command$& is the original address before any
12257 rewriting, whereas the values in &$local_part$& and &$domain$& are taken from
12258 the address after SMTP-time rewriting.
12260 .vitem &$smtp_command_argument$&
12261 .cindex "SMTP" "command, argument for"
12262 .vindex "&$smtp_command_argument$&"
12263 While an ACL is running to check an SMTP command, this variable contains the
12264 argument, that is, the text that follows the command name, with leading white
12265 space removed. Following the introduction of &$smtp_command$&, this variable is
12266 somewhat redundant, but is retained for backwards compatibility.
12268 .vitem &$smtp_count_at_connection_start$&
12269 .vindex "&$smtp_count_at_connection_start$&"
12270 This variable is set greater than zero only in processes spawned by the Exim
12271 daemon for handling incoming SMTP connections. The name is deliberately long,
12272 in order to emphasize what the contents are. When the daemon accepts a new
12273 connection, it increments this variable. A copy of the variable is passed to
12274 the child process that handles the connection, but its value is fixed, and
12275 never changes. It is only an approximation of how many incoming connections
12276 there actually are, because many other connections may come and go while a
12277 single connection is being processed. When a child process terminates, the
12278 daemon decrements its copy of the variable.
12280 .vitem "&$sn0$& &-- &$sn9$&"
12281 These variables are copies of the values of the &$n0$& &-- &$n9$& accumulators
12282 that were current at the end of the system filter file. This allows a system
12283 filter file to set values that can be tested in users' filter files. For
12284 example, a system filter could set a value indicating how likely it is that a
12285 message is junk mail.
12287 .vitem &$spam_$&&'xxx'&
12288 A number of variables whose names start with &$spam$& are available when Exim
12289 is compiled with the content-scanning extension. For details, see section
12290 &<<SECTscanspamass>>&.
12293 .vitem &$spool_directory$&
12294 .vindex "&$spool_directory$&"
12295 The name of Exim's spool directory.
12297 .vitem &$spool_inodes$&
12298 .vindex "&$spool_inodes$&"
12299 The number of free inodes in the disk partition where Exim's spool files are
12300 being written. The value is recalculated whenever the variable is referenced.
12301 If the relevant file system does not have the concept of inodes, the value of
12302 is -1. See also the &%check_spool_inodes%& option.
12304 .vitem &$spool_space$&
12305 .vindex "&$spool_space$&"
12306 The amount of free space (as a number of kilobytes) in the disk partition where
12307 Exim's spool files are being written. The value is recalculated whenever the
12308 variable is referenced. If the operating system does not have the ability to
12309 find the amount of free space (only true for experimental systems), the space
12310 value is -1. For example, to check in an ACL that there is at least 50
12311 megabytes free on the spool, you could write:
12313 condition = ${if > {$spool_space}{50000}}
12315 See also the &%check_spool_space%& option.
12318 .vitem &$thisaddress$&
12319 .vindex "&$thisaddress$&"
12320 This variable is set only during the processing of the &%foranyaddress%&
12321 command in a filter file. Its use is explained in the description of that
12322 command, which can be found in the separate document entitled &'Exim's
12323 interfaces to mail filtering'&.
12325 .vitem &$tls_in_bits$&
12326 .vindex "&$tls_in_bits$&"
12327 Contains an approximation of the TLS cipher's bit-strength
12328 on the inbound connection; the meaning of
12329 this depends upon the TLS implementation used.
12330 If TLS has not been negotiated, the value will be 0.
12331 The value of this is automatically fed into the Cyrus SASL authenticator
12332 when acting as a server, to specify the "external SSF" (a SASL term).
12334 The deprecated &$tls_bits$& variable refers to the inbound side
12335 except when used in the context of an outbound SMTP delivery, when it refers to
12338 .vitem &$tls_out_bits$&
12339 .vindex "&$tls_out_bits$&"
12340 Contains an approximation of the TLS cipher's bit-strength
12341 on an outbound SMTP connection; the meaning of
12342 this depends upon the TLS implementation used.
12343 If TLS has not been negotiated, the value will be 0.
12346 .vitem &$tls_in_ourcert$&
12347 .vindex "&$tls_in_ourcert$&"
12348 This variable refers to the certificate presented to the peer of an
12349 inbound connection when the message was received.
12350 It is only useful as the argument of a
12351 &%certextract%& expansion item, &%md5%& or &%sha1%& operator,
12352 or a &%def%& condition.
12356 .vitem &$tls_in_peercert$&
12357 .vindex "&$tls_in_peercert$&"
12358 This variable refers to the certificate presented by the peer of an
12359 inbound connection when the message was received.
12360 It is only useful as the argument of a
12361 &%certextract%& expansion item, &%md5%& or &%sha1%& operator,
12362 or a &%def%& condition.
12366 .vitem &$tls_out_ourcert$&
12367 .vindex "&$tls_out_ourcert$&"
12368 This variable refers to the certificate presented to the peer of an
12369 outbound connection. It is only useful as the argument of a
12370 &%certextract%& expansion item, &%md5%& or &%sha1%& operator,
12371 or a &%def%& condition.
12375 .vitem &$tls_out_peercert$&
12376 .vindex "&$tls_out_peercert$&"
12377 This variable refers to the certificate presented by the peer of an
12378 outbound connection. It is only useful as the argument of a
12379 &%certextract%& expansion item, &%md5%& or &%sha1%& operator,
12380 or a &%def%& condition.
12383 .vitem &$tls_in_certificate_verified$&
12384 .vindex "&$tls_in_certificate_verified$&"
12385 This variable is set to &"1"& if a TLS certificate was verified when the
12386 message was received, and &"0"& otherwise.
12388 The deprecated &$tls_certificate_verfied$& variable refers to the inbound side
12389 except when used in the context of an outbound SMTP delivery, when it refers to
12392 .vitem &$tls_out_certificate_verified$&
12393 .vindex "&$tls_out_certificate_verified$&"
12394 This variable is set to &"1"& if a TLS certificate was verified when an
12395 outbound SMTP connection was made,
12396 and &"0"& otherwise.
12398 .vitem &$tls_in_cipher$&
12399 .vindex "&$tls_in_cipher$&"
12400 .vindex "&$tls_cipher$&"
12401 When a message is received from a remote host over an encrypted SMTP
12402 connection, this variable is set to the cipher suite that was negotiated, for
12403 example DES-CBC3-SHA. In other circumstances, in particular, for message
12404 received over unencrypted connections, the variable is empty. Testing
12405 &$tls_cipher$& for emptiness is one way of distinguishing between encrypted and
12406 non-encrypted connections during ACL processing.
12408 The deprecated &$tls_cipher$& variable is the same as &$tls_in_cipher$& during message reception,
12409 but in the context of an outward SMTP delivery taking place via the &(smtp)& transport
12410 becomes the same as &$tls_out_cipher$&.
12412 .vitem &$tls_out_cipher$&
12413 .vindex "&$tls_out_cipher$&"
12415 cleared before any outgoing SMTP connection is made,
12416 and then set to the outgoing cipher suite if one is negotiated. See chapter
12417 &<<CHAPTLS>>& for details of TLS support and chapter &<<CHAPsmtptrans>>& for
12418 details of the &(smtp)& transport.
12420 .vitem &$tls_in_peerdn$&
12421 .vindex "&$tls_in_peerdn$&"
12422 .vindex "&$tls_peerdn$&"
12423 When a message is received from a remote host over an encrypted SMTP
12424 connection, and Exim is configured to request a certificate from the client,
12425 the value of the Distinguished Name of the certificate is made available in the
12426 &$tls_in_peerdn$& during subsequent processing.
12428 The deprecated &$tls_peerdn$& variable refers to the inbound side
12429 except when used in the context of an outbound SMTP delivery, when it refers to
12432 .vitem &$tls_out_peerdn$&
12433 .vindex "&$tls_out_peerdn$&"
12434 When a message is being delivered to a remote host over an encrypted SMTP
12435 connection, and Exim is configured to request a certificate from the server,
12436 the value of the Distinguished Name of the certificate is made available in the
12437 &$tls_out_peerdn$& during subsequent processing.
12439 .vitem &$tls_in_sni$&
12440 .vindex "&$tls_in_sni$&"
12441 .vindex "&$tls_sni$&"
12442 .cindex "TLS" "Server Name Indication"
12443 When a TLS session is being established, if the client sends the Server
12444 Name Indication extension, the value will be placed in this variable.
12445 If the variable appears in &%tls_certificate%& then this option and
12446 some others, described in &<<SECTtlssni>>&,
12447 will be re-expanded early in the TLS session, to permit
12448 a different certificate to be presented (and optionally a different key to be
12449 used) to the client, based upon the value of the SNI extension.
12451 The deprecated &$tls_sni$& variable refers to the inbound side
12452 except when used in the context of an outbound SMTP delivery, when it refers to
12455 .vitem &$tls_out_sni$&
12456 .vindex "&$tls_out_sni$&"
12457 .cindex "TLS" "Server Name Indication"
12459 SMTP deliveries, this variable reflects the value of the &%tls_sni%& option on
12462 .vitem &$tod_bsdinbox$&
12463 .vindex "&$tod_bsdinbox$&"
12464 The time of day and the date, in the format required for BSD-style mailbox
12465 files, for example: Thu Oct 17 17:14:09 1995.
12467 .vitem &$tod_epoch$&
12468 .vindex "&$tod_epoch$&"
12469 The time and date as a number of seconds since the start of the Unix epoch.
12471 .vitem &$tod_epoch_l$&
12472 .vindex "&$tod_epoch_l$&"
12473 The time and date as a number of microseconds since the start of the Unix epoch.
12475 .vitem &$tod_full$&
12476 .vindex "&$tod_full$&"
12477 A full version of the time and date, for example: Wed, 16 Oct 1995 09:51:40
12478 +0100. The timezone is always given as a numerical offset from UTC, with
12479 positive values used for timezones that are ahead (east) of UTC, and negative
12480 values for those that are behind (west).
12483 .vindex "&$tod_log$&"
12484 The time and date in the format used for writing Exim's log files, for example:
12485 1995-10-12 15:32:29, but without a timezone.
12487 .vitem &$tod_logfile$&
12488 .vindex "&$tod_logfile$&"
12489 This variable contains the date in the format yyyymmdd. This is the format that
12490 is used for datestamping log files when &%log_file_path%& contains the &`%D`&
12493 .vitem &$tod_zone$&
12494 .vindex "&$tod_zone$&"
12495 This variable contains the numerical value of the local timezone, for example:
12498 .vitem &$tod_zulu$&
12499 .vindex "&$tod_zulu$&"
12500 This variable contains the UTC date and time in &"Zulu"& format, as specified
12501 by ISO 8601, for example: 20030221154023Z.
12503 .vitem &$transport_name$&
12504 .cindex "transport" "name"
12505 .cindex "name" "of transport"
12506 .vindex "&$transport_name$&"
12507 During the running of a transport, this variable contains its name.
12510 .vindex "&$value$&"
12511 This variable contains the result of an expansion lookup, extraction operation,
12512 or external command, as described above. It is also used during a
12513 &*reduce*& expansion.
12515 .vitem &$version_number$&
12516 .vindex "&$version_number$&"
12517 The version number of Exim.
12519 .vitem &$warn_message_delay$&
12520 .vindex "&$warn_message_delay$&"
12521 This variable is set only during the creation of a message warning about a
12522 delivery delay. Details of its use are explained in section &<<SECTcustwarn>>&.
12524 .vitem &$warn_message_recipients$&
12525 .vindex "&$warn_message_recipients$&"
12526 This variable is set only during the creation of a message warning about a
12527 delivery delay. Details of its use are explained in section &<<SECTcustwarn>>&.
12533 . ////////////////////////////////////////////////////////////////////////////
12534 . ////////////////////////////////////////////////////////////////////////////
12536 .chapter "Embedded Perl" "CHAPperl"
12537 .scindex IIDperl "Perl" "calling from Exim"
12538 Exim can be built to include an embedded Perl interpreter. When this is done,
12539 Perl subroutines can be called as part of the string expansion process. To make
12540 use of the Perl support, you need version 5.004 or later of Perl installed on
12541 your system. To include the embedded interpreter in the Exim binary, include
12546 in your &_Local/Makefile_& and then build Exim in the normal way.
12549 .section "Setting up so Perl can be used" "SECID85"
12550 .oindex "&%perl_startup%&"
12551 Access to Perl subroutines is via a global configuration option called
12552 &%perl_startup%& and an expansion string operator &%${perl ...}%&. If there is
12553 no &%perl_startup%& option in the Exim configuration file then no Perl
12554 interpreter is started and there is almost no overhead for Exim (since none of
12555 the Perl library will be paged in unless used). If there is a &%perl_startup%&
12556 option then the associated value is taken to be Perl code which is executed in
12557 a newly created Perl interpreter.
12559 The value of &%perl_startup%& is not expanded in the Exim sense, so you do not
12560 need backslashes before any characters to escape special meanings. The option
12561 should usually be something like
12563 perl_startup = do '/etc/exim.pl'
12565 where &_/etc/exim.pl_& is Perl code which defines any subroutines you want to
12566 use from Exim. Exim can be configured either to start up a Perl interpreter as
12567 soon as it is entered, or to wait until the first time it is needed. Starting
12568 the interpreter at the beginning ensures that it is done while Exim still has
12569 its setuid privilege, but can impose an unnecessary overhead if Perl is not in
12570 fact used in a particular run. Also, note that this does not mean that Exim is
12571 necessarily running as root when Perl is called at a later time. By default,
12572 the interpreter is started only when it is needed, but this can be changed in
12576 .oindex "&%perl_at_start%&"
12577 Setting &%perl_at_start%& (a boolean option) in the configuration requests
12578 a startup when Exim is entered.
12580 The command line option &%-ps%& also requests a startup when Exim is entered,
12581 overriding the setting of &%perl_at_start%&.
12584 There is also a command line option &%-pd%& (for delay) which suppresses the
12585 initial startup, even if &%perl_at_start%& is set.
12588 .section "Calling Perl subroutines" "SECID86"
12589 When the configuration file includes a &%perl_startup%& option you can make use
12590 of the string expansion item to call the Perl subroutines that are defined
12591 by the &%perl_startup%& code. The operator is used in any of the following
12595 ${perl{foo}{argument}}
12596 ${perl{foo}{argument1}{argument2} ... }
12598 which calls the subroutine &%foo%& with the given arguments. A maximum of eight
12599 arguments may be passed. Passing more than this results in an expansion failure
12600 with an error message of the form
12602 Too many arguments passed to Perl subroutine "foo" (max is 8)
12604 The return value of the Perl subroutine is evaluated in a scalar context before
12605 it is passed back to Exim to be inserted into the expanded string. If the
12606 return value is &'undef'&, the expansion is forced to fail in the same way as
12607 an explicit &"fail"& on an &%if%& or &%lookup%& item. If the subroutine aborts
12608 by obeying Perl's &%die%& function, the expansion fails with the error message
12609 that was passed to &%die%&.
12612 .section "Calling Exim functions from Perl" "SECID87"
12613 Within any Perl code called from Exim, the function &'Exim::expand_string()'&
12614 is available to call back into Exim's string expansion function. For example,
12617 my $lp = Exim::expand_string('$local_part');
12619 makes the current Exim &$local_part$& available in the Perl variable &$lp$&.
12620 Note those are single quotes and not double quotes to protect against
12621 &$local_part$& being interpolated as a Perl variable.
12623 If the string expansion is forced to fail by a &"fail"& item, the result of
12624 &'Exim::expand_string()'& is &%undef%&. If there is a syntax error in the
12625 expansion string, the Perl call from the original expansion string fails with
12626 an appropriate error message, in the same way as if &%die%& were used.
12628 .cindex "debugging" "from embedded Perl"
12629 .cindex "log" "writing from embedded Perl"
12630 Two other Exim functions are available for use from within Perl code.
12631 &'Exim::debug_write()'& writes a string to the standard error stream if Exim's
12632 debugging is enabled. If you want a newline at the end, you must supply it.
12633 &'Exim::log_write()'& writes a string to Exim's main log, adding a leading
12634 timestamp. In this case, you should not supply a terminating newline.
12637 .section "Use of standard output and error by Perl" "SECID88"
12638 .cindex "Perl" "standard output and error"
12639 You should not write to the standard error or output streams from within your
12640 Perl code, as it is not defined how these are set up. In versions of Exim
12641 before 4.50, it is possible for the standard output or error to refer to the
12642 SMTP connection during message reception via the daemon. Writing to this stream
12643 is certain to cause chaos. From Exim 4.50 onwards, the standard output and
12644 error streams are connected to &_/dev/null_& in the daemon. The chaos is
12645 avoided, but the output is lost.
12647 .cindex "Perl" "use of &%warn%&"
12648 The Perl &%warn%& statement writes to the standard error stream by default.
12649 Calls to &%warn%& may be embedded in Perl modules that you use, but over which
12650 you have no control. When Exim starts up the Perl interpreter, it arranges for
12651 output from the &%warn%& statement to be written to the Exim main log. You can
12652 change this by including appropriate Perl magic somewhere in your Perl code.
12653 For example, to discard &%warn%& output completely, you need this:
12655 $SIG{__WARN__} = sub { };
12657 Whenever a &%warn%& is obeyed, the anonymous subroutine is called. In this
12658 example, the code for the subroutine is empty, so it does nothing, but you can
12659 include any Perl code that you like. The text of the &%warn%& message is passed
12660 as the first subroutine argument.
12664 . ////////////////////////////////////////////////////////////////////////////
12665 . ////////////////////////////////////////////////////////////////////////////
12667 .chapter "Starting the daemon and the use of network interfaces" &&&
12668 "CHAPinterfaces" &&&
12669 "Starting the daemon"
12670 .cindex "daemon" "starting"
12671 .cindex "interface" "listening"
12672 .cindex "network interface"
12673 .cindex "interface" "network"
12674 .cindex "IP address" "for listening"
12675 .cindex "daemon" "listening IP addresses"
12676 .cindex "TCP/IP" "setting listening interfaces"
12677 .cindex "TCP/IP" "setting listening ports"
12678 A host that is connected to a TCP/IP network may have one or more physical
12679 hardware network interfaces. Each of these interfaces may be configured as one
12680 or more &"logical"& interfaces, which are the entities that a program actually
12681 works with. Each of these logical interfaces is associated with an IP address.
12682 In addition, TCP/IP software supports &"loopback"& interfaces (127.0.0.1 in
12683 IPv4 and ::1 in IPv6), which do not use any physical hardware. Exim requires
12684 knowledge about the host's interfaces for use in three different circumstances:
12687 When a listening daemon is started, Exim needs to know which interfaces
12688 and ports to listen on.
12690 When Exim is routing an address, it needs to know which IP addresses
12691 are associated with local interfaces. This is required for the correct
12692 processing of MX lists by removing the local host and others with the
12693 same or higher priority values. Also, Exim needs to detect cases
12694 when an address is routed to an IP address that in fact belongs to the
12695 local host. Unless the &%self%& router option or the &%allow_localhost%&
12696 option of the smtp transport is set (as appropriate), this is treated
12697 as an error situation.
12699 When Exim connects to a remote host, it may need to know which interface to use
12700 for the outgoing connection.
12704 Exim's default behaviour is likely to be appropriate in the vast majority
12705 of cases. If your host has only one interface, and you want all its IP
12706 addresses to be treated in the same way, and you are using only the
12707 standard SMTP port, you should not need to take any special action. The
12708 rest of this chapter does not apply to you.
12710 In a more complicated situation you may want to listen only on certain
12711 interfaces, or on different ports, and for this reason there are a number of
12712 options that can be used to influence Exim's behaviour. The rest of this
12713 chapter describes how they operate.
12715 When a message is received over TCP/IP, the interface and port that were
12716 actually used are set in &$received_ip_address$& and &$received_port$&.
12720 .section "Starting a listening daemon" "SECID89"
12721 When a listening daemon is started (by means of the &%-bd%& command line
12722 option), the interfaces and ports on which it listens are controlled by the
12726 &%daemon_smtp_ports%& contains a list of default ports. (For backward
12727 compatibility, this option can also be specified in the singular.)
12729 &%local_interfaces%& contains list of interface IP addresses on which to
12730 listen. Each item may optionally also specify a port.
12733 The default list separator in both cases is a colon, but this can be changed as
12734 described in section &<<SECTlistconstruct>>&. When IPv6 addresses are involved,
12735 it is usually best to change the separator to avoid having to double all the
12736 colons. For example:
12738 local_interfaces = <; 127.0.0.1 ; \
12741 3ffe:ffff:836f::fe86:a061
12743 There are two different formats for specifying a port along with an IP address
12744 in &%local_interfaces%&:
12747 The port is added onto the address with a dot separator. For example, to listen
12748 on port 1234 on two different IP addresses:
12750 local_interfaces = <; 192.168.23.65.1234 ; \
12751 3ffe:ffff:836f::fe86:a061.1234
12754 The IP address is enclosed in square brackets, and the port is added
12755 with a colon separator, for example:
12757 local_interfaces = <; [192.168.23.65]:1234 ; \
12758 [3ffe:ffff:836f::fe86:a061]:1234
12762 When a port is not specified, the value of &%daemon_smtp_ports%& is used. The
12763 default setting contains just one port:
12765 daemon_smtp_ports = smtp
12767 If more than one port is listed, each interface that does not have its own port
12768 specified listens on all of them. Ports that are listed in
12769 &%daemon_smtp_ports%& can be identified either by name (defined in
12770 &_/etc/services_&) or by number. However, when ports are given with individual
12771 IP addresses in &%local_interfaces%&, only numbers (not names) can be used.
12775 .section "Special IP listening addresses" "SECID90"
12776 The addresses 0.0.0.0 and ::0 are treated specially. They are interpreted
12777 as &"all IPv4 interfaces"& and &"all IPv6 interfaces"&, respectively. In each
12778 case, Exim tells the TCP/IP stack to &"listen on all IPv&'x'& interfaces"&
12779 instead of setting up separate listening sockets for each interface. The
12780 default value of &%local_interfaces%& is
12782 local_interfaces = 0.0.0.0
12784 when Exim is built without IPv6 support; otherwise it is:
12786 local_interfaces = <; ::0 ; 0.0.0.0
12788 Thus, by default, Exim listens on all available interfaces, on the SMTP port.
12792 .section "Overriding local_interfaces and daemon_smtp_ports" "SECID91"
12793 The &%-oX%& command line option can be used to override the values of
12794 &%daemon_smtp_ports%& and/or &%local_interfaces%& for a particular daemon
12795 instance. Another way of doing this would be to use macros and the &%-D%&
12796 option. However, &%-oX%& can be used by any admin user, whereas modification of
12797 the runtime configuration by &%-D%& is allowed only when the caller is root or
12800 The value of &%-oX%& is a list of items. The default colon separator can be
12801 changed in the usual way if required. If there are any items that do not
12802 contain dots or colons (that is, are not IP addresses), the value of
12803 &%daemon_smtp_ports%& is replaced by the list of those items. If there are any
12804 items that do contain dots or colons, the value of &%local_interfaces%& is
12805 replaced by those items. Thus, for example,
12809 overrides &%daemon_smtp_ports%&, but leaves &%local_interfaces%& unchanged,
12812 -oX 192.168.34.5.1125
12814 overrides &%local_interfaces%&, leaving &%daemon_smtp_ports%& unchanged.
12815 (However, since &%local_interfaces%& now contains no items without ports, the
12816 value of &%daemon_smtp_ports%& is no longer relevant in this example.)
12820 .section "Support for the obsolete SSMTP (or SMTPS) protocol" "SECTsupobssmt"
12821 .cindex "ssmtp protocol"
12822 .cindex "smtps protocol"
12823 .cindex "SMTP" "ssmtp protocol"
12824 .cindex "SMTP" "smtps protocol"
12825 Exim supports the obsolete SSMTP protocol (also known as SMTPS) that was used
12826 before the STARTTLS command was standardized for SMTP. Some legacy clients
12827 still use this protocol. If the &%tls_on_connect_ports%& option is set to a
12828 list of port numbers, connections to those ports must use SSMTP. The most
12829 common use of this option is expected to be
12831 tls_on_connect_ports = 465
12833 because 465 is the usual port number used by the legacy clients. There is also
12834 a command line option &%-tls-on-connect%&, which forces all ports to behave in
12835 this way when a daemon is started.
12837 &*Warning*&: Setting &%tls_on_connect_ports%& does not of itself cause the
12838 daemon to listen on those ports. You must still specify them in
12839 &%daemon_smtp_ports%&, &%local_interfaces%&, or the &%-oX%& option. (This is
12840 because &%tls_on_connect_ports%& applies to &%inetd%& connections as well as to
12841 connections via the daemon.)
12846 .section "IPv6 address scopes" "SECID92"
12847 .cindex "IPv6" "address scopes"
12848 IPv6 addresses have &"scopes"&, and a host with multiple hardware interfaces
12849 can, in principle, have the same link-local IPv6 address on different
12850 interfaces. Thus, additional information is needed, over and above the IP
12851 address, to distinguish individual interfaces. A convention of using a
12852 percent sign followed by something (often the interface name) has been
12853 adopted in some cases, leading to addresses like this:
12855 fe80::202:b3ff:fe03:45c1%eth0
12857 To accommodate this usage, a percent sign followed by an arbitrary string is
12858 allowed at the end of an IPv6 address. By default, Exim calls &[getaddrinfo()]&
12859 to convert a textual IPv6 address for actual use. This function recognizes the
12860 percent convention in operating systems that support it, and it processes the
12861 address appropriately. Unfortunately, some older libraries have problems with
12862 &[getaddrinfo()]&. If
12864 IPV6_USE_INET_PTON=yes
12866 is set in &_Local/Makefile_& (or an OS-dependent Makefile) when Exim is built,
12867 Exim uses &'inet_pton()'& to convert a textual IPv6 address for actual use,
12868 instead of &[getaddrinfo()]&. (Before version 4.14, it always used this
12869 function.) Of course, this means that the additional functionality of
12870 &[getaddrinfo()]& &-- recognizing scoped addresses &-- is lost.
12872 .section "Disabling IPv6" "SECID93"
12873 .cindex "IPv6" "disabling"
12874 Sometimes it happens that an Exim binary that was compiled with IPv6 support is
12875 run on a host whose kernel does not support IPv6. The binary will fall back to
12876 using IPv4, but it may waste resources looking up AAAA records, and trying to
12877 connect to IPv6 addresses, causing delays to mail delivery. If you set the
12878 .oindex "&%disable_ipv6%&"
12879 &%disable_ipv6%& option true, even if the Exim binary has IPv6 support, no IPv6
12880 activities take place. AAAA records are never looked up, and any IPv6 addresses
12881 that are listed in &%local_interfaces%&, data for the &(manualroute)& router,
12882 etc. are ignored. If IP literals are enabled, the &(ipliteral)& router declines
12883 to handle IPv6 literal addresses.
12885 On the other hand, when IPv6 is in use, there may be times when you want to
12886 disable it for certain hosts or domains. You can use the &%dns_ipv4_lookup%&
12887 option to globally suppress the lookup of AAAA records for specified domains,
12888 and you can use the &%ignore_target_hosts%& generic router option to ignore
12889 IPv6 addresses in an individual router.
12893 .section "Examples of starting a listening daemon" "SECID94"
12894 The default case in an IPv6 environment is
12896 daemon_smtp_ports = smtp
12897 local_interfaces = <; ::0 ; 0.0.0.0
12899 This specifies listening on the smtp port on all IPv6 and IPv4 interfaces.
12900 Either one or two sockets may be used, depending on the characteristics of
12901 the TCP/IP stack. (This is complicated and messy; for more information,
12902 read the comments in the &_daemon.c_& source file.)
12904 To specify listening on ports 25 and 26 on all interfaces:
12906 daemon_smtp_ports = 25 : 26
12908 (leaving &%local_interfaces%& at the default setting) or, more explicitly:
12910 local_interfaces = <; ::0.25 ; ::0.26 \
12911 0.0.0.0.25 ; 0.0.0.0.26
12913 To listen on the default port on all IPv4 interfaces, and on port 26 on the
12914 IPv4 loopback address only:
12916 local_interfaces = 0.0.0.0 : 127.0.0.1.26
12918 To specify listening on the default port on specific interfaces only:
12920 local_interfaces = 10.0.0.67 : 192.168.34.67
12922 &*Warning*&: Such a setting excludes listening on the loopback interfaces.
12926 .section "Recognizing the local host" "SECTreclocipadd"
12927 The &%local_interfaces%& option is also used when Exim needs to determine
12928 whether or not an IP address refers to the local host. That is, the IP
12929 addresses of all the interfaces on which a daemon is listening are always
12932 For this usage, port numbers in &%local_interfaces%& are ignored. If either of
12933 the items 0.0.0.0 or ::0 are encountered, Exim gets a complete list of
12934 available interfaces from the operating system, and extracts the relevant
12935 (that is, IPv4 or IPv6) addresses to use for checking.
12937 Some systems set up large numbers of virtual interfaces in order to provide
12938 many virtual web servers. In this situation, you may want to listen for
12939 email on only a few of the available interfaces, but nevertheless treat all
12940 interfaces as local when routing. You can do this by setting
12941 &%extra_local_interfaces%& to a list of IP addresses, possibly including the
12942 &"all"& wildcard values. These addresses are recognized as local, but are not
12943 used for listening. Consider this example:
12945 local_interfaces = <; 127.0.0.1 ; ::1 ; \
12947 3ffe:2101:12:1:a00:20ff:fe86:a061
12949 extra_local_interfaces = <; ::0 ; 0.0.0.0
12951 The daemon listens on the loopback interfaces and just one IPv4 and one IPv6
12952 address, but all available interface addresses are treated as local when
12955 In some environments the local host name may be in an MX list, but with an IP
12956 address that is not assigned to any local interface. In other cases it may be
12957 desirable to treat other host names as if they referred to the local host. Both
12958 these cases can be handled by setting the &%hosts_treat_as_local%& option.
12959 This contains host names rather than IP addresses. When a host is referenced
12960 during routing, either via an MX record or directly, it is treated as the local
12961 host if its name matches &%hosts_treat_as_local%&, or if any of its IP
12962 addresses match &%local_interfaces%& or &%extra_local_interfaces%&.
12966 .section "Delivering to a remote host" "SECID95"
12967 Delivery to a remote host is handled by the smtp transport. By default, it
12968 allows the system's TCP/IP functions to choose which interface to use (if
12969 there is more than one) when connecting to a remote host. However, the
12970 &%interface%& option can be set to specify which interface is used. See the
12971 description of the smtp transport in chapter &<<CHAPsmtptrans>>& for more
12977 . ////////////////////////////////////////////////////////////////////////////
12978 . ////////////////////////////////////////////////////////////////////////////
12980 .chapter "Main configuration" "CHAPmainconfig"
12981 .scindex IIDconfima "configuration file" "main section"
12982 .scindex IIDmaiconf "main configuration"
12983 The first part of the run time configuration file contains three types of item:
12986 Macro definitions: These lines start with an upper case letter. See section
12987 &<<SECTmacrodefs>>& for details of macro processing.
12989 Named list definitions: These lines start with one of the words &"domainlist"&,
12990 &"hostlist"&, &"addresslist"&, or &"localpartlist"&. Their use is described in
12991 section &<<SECTnamedlists>>&.
12993 Main configuration settings: Each setting occupies one line of the file
12994 (with possible continuations). If any setting is preceded by the word
12995 &"hide"&, the &%-bP%& command line option displays its value to admin users
12996 only. See section &<<SECTcos>>& for a description of the syntax of these option
13000 This chapter specifies all the main configuration options, along with their
13001 types and default values. For ease of finding a particular option, they appear
13002 in alphabetical order in section &<<SECTalomo>>& below. However, because there
13003 are now so many options, they are first listed briefly in functional groups, as
13004 an aid to finding the name of the option you are looking for. Some options are
13005 listed in more than one group.
13007 .section "Miscellaneous" "SECID96"
13009 .row &%bi_command%& "to run for &%-bi%& command line option"
13010 .row &%disable_ipv6%& "do no IPv6 processing"
13011 .row &%keep_malformed%& "for broken files &-- should not happen"
13012 .row &%localhost_number%& "for unique message ids in clusters"
13013 .row &%message_body_newlines%& "retain newlines in &$message_body$&"
13014 .row &%message_body_visible%& "how much to show in &$message_body$&"
13015 .row &%mua_wrapper%& "run in &""MUA wrapper""& mode"
13016 .row &%print_topbitchars%& "top-bit characters are printing"
13017 .row &%timezone%& "force time zone"
13021 .section "Exim parameters" "SECID97"
13023 .row &%exim_group%& "override compiled-in value"
13024 .row &%exim_path%& "override compiled-in value"
13025 .row &%exim_user%& "override compiled-in value"
13026 .row &%primary_hostname%& "default from &[uname()]&"
13027 .row &%split_spool_directory%& "use multiple directories"
13028 .row &%spool_directory%& "override compiled-in value"
13033 .section "Privilege controls" "SECID98"
13035 .row &%admin_groups%& "groups that are Exim admin users"
13036 .row &%deliver_drop_privilege%& "drop root for delivery processes"
13037 .row &%local_from_check%& "insert &'Sender:'& if necessary"
13038 .row &%local_from_prefix%& "for testing &'From:'& for local sender"
13039 .row &%local_from_suffix%& "for testing &'From:'& for local sender"
13040 .row &%local_sender_retain%& "keep &'Sender:'& from untrusted user"
13041 .row &%never_users%& "do not run deliveries as these"
13042 .row &%prod_requires_admin%& "forced delivery requires admin user"
13043 .row &%queue_list_requires_admin%& "queue listing requires admin user"
13044 .row &%trusted_groups%& "groups that are trusted"
13045 .row &%trusted_users%& "users that are trusted"
13050 .section "Logging" "SECID99"
13052 .row &%hosts_connection_nolog%& "exemption from connect logging"
13053 .row &%log_file_path%& "override compiled-in value"
13054 .row &%log_selector%& "set/unset optional logging"
13055 .row &%log_timezone%& "add timezone to log lines"
13056 .row &%message_logs%& "create per-message logs"
13057 .row &%preserve_message_logs%& "after message completion"
13058 .row &%process_log_path%& "for SIGUSR1 and &'exiwhat'&"
13059 .row &%syslog_duplication%& "controls duplicate log lines on syslog"
13060 .row &%syslog_facility%& "set syslog &""facility""& field"
13061 .row &%syslog_processname%& "set syslog &""ident""& field"
13062 .row &%syslog_timestamp%& "timestamp syslog lines"
13063 .row &%write_rejectlog%& "control use of message log"
13068 .section "Frozen messages" "SECID100"
13070 .row &%auto_thaw%& "sets time for retrying frozen messages"
13071 .row &%freeze_tell%& "send message when freezing"
13072 .row &%move_frozen_messages%& "to another directory"
13073 .row &%timeout_frozen_after%& "keep frozen messages only so long"
13078 .section "Data lookups" "SECID101"
13080 .row &%ibase_servers%& "InterBase servers"
13081 .row &%ldap_ca_cert_dir%& "dir of CA certs to verify LDAP server's"
13082 .row &%ldap_ca_cert_file%& "file of CA certs to verify LDAP server's"
13083 .row &%ldap_cert_file%& "client cert file for LDAP"
13084 .row &%ldap_cert_key%& "client key file for LDAP"
13085 .row &%ldap_cipher_suite%& "TLS negotiation preference control"
13086 .row &%ldap_default_servers%& "used if no server in query"
13087 .row &%ldap_require_cert%& "action to take without LDAP server cert"
13088 .row &%ldap_start_tls%& "require TLS within LDAP"
13089 .row &%ldap_version%& "set protocol version"
13090 .row &%lookup_open_max%& "lookup files held open"
13091 .row &%mysql_servers%& "default MySQL servers"
13092 .row &%oracle_servers%& "Oracle servers"
13093 .row &%pgsql_servers%& "default PostgreSQL servers"
13094 .row &%sqlite_lock_timeout%& "as it says"
13099 .section "Message ids" "SECID102"
13101 .row &%message_id_header_domain%& "used to build &'Message-ID:'& header"
13102 .row &%message_id_header_text%& "ditto"
13107 .section "Embedded Perl Startup" "SECID103"
13109 .row &%perl_at_start%& "always start the interpreter"
13110 .row &%perl_startup%& "code to obey when starting Perl"
13115 .section "Daemon" "SECID104"
13117 .row &%daemon_smtp_ports%& "default ports"
13118 .row &%daemon_startup_retries%& "number of times to retry"
13119 .row &%daemon_startup_sleep%& "time to sleep between tries"
13120 .row &%extra_local_interfaces%& "not necessarily listened on"
13121 .row &%local_interfaces%& "on which to listen, with optional ports"
13122 .row &%pid_file_path%& "override compiled-in value"
13123 .row &%queue_run_max%& "maximum simultaneous queue runners"
13128 .section "Resource control" "SECID105"
13130 .row &%check_log_inodes%& "before accepting a message"
13131 .row &%check_log_space%& "before accepting a message"
13132 .row &%check_spool_inodes%& "before accepting a message"
13133 .row &%check_spool_space%& "before accepting a message"
13134 .row &%deliver_queue_load_max%& "no queue deliveries if load high"
13135 .row &%queue_only_load%& "queue incoming if load high"
13136 .row &%queue_only_load_latch%& "don't re-evaluate load for each message"
13137 .row &%queue_run_max%& "maximum simultaneous queue runners"
13138 .row &%remote_max_parallel%& "parallel SMTP delivery per message"
13139 .row &%smtp_accept_max%& "simultaneous incoming connections"
13140 .row &%smtp_accept_max_nonmail%& "non-mail commands"
13141 .row &%smtp_accept_max_nonmail_hosts%& "hosts to which the limit applies"
13142 .row &%smtp_accept_max_per_connection%& "messages per connection"
13143 .row &%smtp_accept_max_per_host%& "connections from one host"
13144 .row &%smtp_accept_queue%& "queue mail if more connections"
13145 .row &%smtp_accept_queue_per_connection%& "queue if more messages per &&&
13147 .row &%smtp_accept_reserve%& "only reserve hosts if more connections"
13148 .row &%smtp_check_spool_space%& "from SIZE on MAIL command"
13149 .row &%smtp_connect_backlog%& "passed to TCP/IP stack"
13150 .row &%smtp_load_reserve%& "SMTP from reserved hosts if load high"
13151 .row &%smtp_reserve_hosts%& "these are the reserve hosts"
13156 .section "Policy controls" "SECID106"
13158 .row &%acl_not_smtp%& "ACL for non-SMTP messages"
13159 .row &%acl_not_smtp_mime%& "ACL for non-SMTP MIME parts"
13160 .row &%acl_not_smtp_start%& "ACL for start of non-SMTP message"
13161 .row &%acl_smtp_auth%& "ACL for AUTH"
13162 .row &%acl_smtp_connect%& "ACL for connection"
13163 .row &%acl_smtp_data%& "ACL for DATA"
13164 .row &%acl_smtp_data_prdr%& "ACL for DATA, per-recipient"
13165 .row &%acl_smtp_dkim%& "ACL for DKIM verification"
13166 .row &%acl_smtp_etrn%& "ACL for ETRN"
13167 .row &%acl_smtp_expn%& "ACL for EXPN"
13168 .row &%acl_smtp_helo%& "ACL for EHLO or HELO"
13169 .row &%acl_smtp_mail%& "ACL for MAIL"
13170 .row &%acl_smtp_mailauth%& "ACL for AUTH on MAIL command"
13171 .row &%acl_smtp_mime%& "ACL for MIME parts"
13172 .row &%acl_smtp_predata%& "ACL for start of data"
13173 .row &%acl_smtp_quit%& "ACL for QUIT"
13174 .row &%acl_smtp_rcpt%& "ACL for RCPT"
13175 .row &%acl_smtp_starttls%& "ACL for STARTTLS"
13176 .row &%acl_smtp_vrfy%& "ACL for VRFY"
13177 .row &%av_scanner%& "specify virus scanner"
13178 .row &%check_rfc2047_length%& "check length of RFC 2047 &""encoded &&&
13180 .row &%dns_csa_search_limit%& "control CSA parent search depth"
13181 .row &%dns_csa_use_reverse%& "en/disable CSA IP reverse search"
13182 .row &%header_maxsize%& "total size of message header"
13183 .row &%header_line_maxsize%& "individual header line limit"
13184 .row &%helo_accept_junk_hosts%& "allow syntactic junk from these hosts"
13185 .row &%helo_allow_chars%& "allow illegal chars in HELO names"
13186 .row &%helo_lookup_domains%& "lookup hostname for these HELO names"
13187 .row &%helo_try_verify_hosts%& "HELO soft-checked for these hosts"
13188 .row &%helo_verify_hosts%& "HELO hard-checked for these hosts"
13189 .row &%host_lookup%& "host name looked up for these hosts"
13190 .row &%host_lookup_order%& "order of DNS and local name lookups"
13191 .row &%host_reject_connection%& "reject connection from these hosts"
13192 .row &%hosts_treat_as_local%& "useful in some cluster configurations"
13193 .row &%local_scan_timeout%& "timeout for &[local_scan()]&"
13194 .row &%message_size_limit%& "for all messages"
13195 .row &%percent_hack_domains%& "recognize %-hack for these domains"
13196 .row &%spamd_address%& "set interface to SpamAssassin"
13197 .row &%strict_acl_vars%& "object to unset ACL variables"
13202 .section "Callout cache" "SECID107"
13204 .row &%callout_domain_negative_expire%& "timeout for negative domain cache &&&
13206 .row &%callout_domain_positive_expire%& "timeout for positive domain cache &&&
13208 .row &%callout_negative_expire%& "timeout for negative address cache item"
13209 .row &%callout_positive_expire%& "timeout for positive address cache item"
13210 .row &%callout_random_local_part%& "string to use for &""random""& testing"
13215 .section "TLS" "SECID108"
13217 .row &%gnutls_compat_mode%& "use GnuTLS compatibility mode"
13218 .row &%gnutls_allow_auto_pkcs11%& "allow GnuTLS to autoload PKCS11 modules"
13219 .row &%openssl_options%& "adjust OpenSSL compatibility options"
13220 .row &%tls_advertise_hosts%& "advertise TLS to these hosts"
13221 .row &%tls_certificate%& "location of server certificate"
13222 .row &%tls_crl%& "certificate revocation list"
13223 .row &%tls_dh_max_bits%& "clamp D-H bit count suggestion"
13224 .row &%tls_dhparam%& "DH parameters for server"
13225 .row &%tls_on_connect_ports%& "specify SSMTP (SMTPS) ports"
13226 .row &%tls_privatekey%& "location of server private key"
13227 .row &%tls_remember_esmtp%& "don't reset after starting TLS"
13228 .row &%tls_require_ciphers%& "specify acceptable ciphers"
13229 .row &%tls_try_verify_hosts%& "try to verify client certificate"
13230 .row &%tls_verify_certificates%& "expected client certificates"
13231 .row &%tls_verify_hosts%& "insist on client certificate verify"
13236 .section "Local user handling" "SECID109"
13238 .row &%finduser_retries%& "useful in NIS environments"
13239 .row &%gecos_name%& "used when creating &'Sender:'&"
13240 .row &%gecos_pattern%& "ditto"
13241 .row &%max_username_length%& "for systems that truncate"
13242 .row &%unknown_login%& "used when no login name found"
13243 .row &%unknown_username%& "ditto"
13244 .row &%uucp_from_pattern%& "for recognizing &""From ""& lines"
13245 .row &%uucp_from_sender%& "ditto"
13250 .section "All incoming messages (SMTP and non-SMTP)" "SECID110"
13252 .row &%header_maxsize%& "total size of message header"
13253 .row &%header_line_maxsize%& "individual header line limit"
13254 .row &%message_size_limit%& "applies to all messages"
13255 .row &%percent_hack_domains%& "recognize %-hack for these domains"
13256 .row &%received_header_text%& "expanded to make &'Received:'&"
13257 .row &%received_headers_max%& "for mail loop detection"
13258 .row &%recipients_max%& "limit per message"
13259 .row &%recipients_max_reject%& "permanently reject excess recipients"
13265 .section "Non-SMTP incoming messages" "SECID111"
13267 .row &%receive_timeout%& "for non-SMTP messages"
13274 .section "Incoming SMTP messages" "SECID112"
13275 See also the &'Policy controls'& section above.
13278 .row &%host_lookup%& "host name looked up for these hosts"
13279 .row &%host_lookup_order%& "order of DNS and local name lookups"
13280 .row &%recipient_unqualified_hosts%& "may send unqualified recipients"
13281 .row &%rfc1413_hosts%& "make ident calls to these hosts"
13282 .row &%rfc1413_query_timeout%& "zero disables ident calls"
13283 .row &%sender_unqualified_hosts%& "may send unqualified senders"
13284 .row &%smtp_accept_keepalive%& "some TCP/IP magic"
13285 .row &%smtp_accept_max%& "simultaneous incoming connections"
13286 .row &%smtp_accept_max_nonmail%& "non-mail commands"
13287 .row &%smtp_accept_max_nonmail_hosts%& "hosts to which the limit applies"
13288 .row &%smtp_accept_max_per_connection%& "messages per connection"
13289 .row &%smtp_accept_max_per_host%& "connections from one host"
13290 .row &%smtp_accept_queue%& "queue mail if more connections"
13291 .row &%smtp_accept_queue_per_connection%& "queue if more messages per &&&
13293 .row &%smtp_accept_reserve%& "only reserve hosts if more connections"
13294 .row &%smtp_active_hostname%& "host name to use in messages"
13295 .row &%smtp_banner%& "text for welcome banner"
13296 .row &%smtp_check_spool_space%& "from SIZE on MAIL command"
13297 .row &%smtp_connect_backlog%& "passed to TCP/IP stack"
13298 .row &%smtp_enforce_sync%& "of SMTP command/responses"
13299 .row &%smtp_etrn_command%& "what to run for ETRN"
13300 .row &%smtp_etrn_serialize%& "only one at once"
13301 .row &%smtp_load_reserve%& "only reserve hosts if this load"
13302 .row &%smtp_max_unknown_commands%& "before dropping connection"
13303 .row &%smtp_ratelimit_hosts%& "apply ratelimiting to these hosts"
13304 .row &%smtp_ratelimit_mail%& "ratelimit for MAIL commands"
13305 .row &%smtp_ratelimit_rcpt%& "ratelimit for RCPT commands"
13306 .row &%smtp_receive_timeout%& "per command or data line"
13307 .row &%smtp_reserve_hosts%& "these are the reserve hosts"
13308 .row &%smtp_return_error_details%& "give detail on rejections"
13313 .section "SMTP extensions" "SECID113"
13315 .row &%accept_8bitmime%& "advertise 8BITMIME"
13316 .row &%auth_advertise_hosts%& "advertise AUTH to these hosts"
13317 .row &%ignore_fromline_hosts%& "allow &""From ""& from these hosts"
13318 .row &%ignore_fromline_local%& "allow &""From ""& from local SMTP"
13319 .row &%pipelining_advertise_hosts%& "advertise pipelining to these hosts"
13320 .row &%prdr_enable%& "advertise PRDR to all hosts"
13321 .row &%tls_advertise_hosts%& "advertise TLS to these hosts"
13326 .section "Processing messages" "SECID114"
13328 .row &%allow_domain_literals%& "recognize domain literal syntax"
13329 .row &%allow_mx_to_ip%& "allow MX to point to IP address"
13330 .row &%allow_utf8_domains%& "in addresses"
13331 .row &%check_rfc2047_length%& "check length of RFC 2047 &""encoded &&&
13333 .row &%delivery_date_remove%& "from incoming messages"
13334 .row &%envelope_to_remove%& "from incoming messages"
13335 .row &%extract_addresses_remove_arguments%& "affects &%-t%& processing"
13336 .row &%headers_charset%& "default for translations"
13337 .row &%qualify_domain%& "default for senders"
13338 .row &%qualify_recipient%& "default for recipients"
13339 .row &%return_path_remove%& "from incoming messages"
13340 .row &%strip_excess_angle_brackets%& "in addresses"
13341 .row &%strip_trailing_dot%& "at end of addresses"
13342 .row &%untrusted_set_sender%& "untrusted can set envelope sender"
13347 .section "System filter" "SECID115"
13349 .row &%system_filter%& "locate system filter"
13350 .row &%system_filter_directory_transport%& "transport for delivery to a &&&
13352 .row &%system_filter_file_transport%& "transport for delivery to a file"
13353 .row &%system_filter_group%& "group for filter running"
13354 .row &%system_filter_pipe_transport%& "transport for delivery to a pipe"
13355 .row &%system_filter_reply_transport%& "transport for autoreply delivery"
13356 .row &%system_filter_user%& "user for filter running"
13361 .section "Routing and delivery" "SECID116"
13363 .row &%disable_ipv6%& "do no IPv6 processing"
13364 .row &%dns_again_means_nonexist%& "for broken domains"
13365 .row &%dns_check_names_pattern%& "pre-DNS syntax check"
13366 .row &%dns_dnssec_ok%& "parameter for resolver"
13367 .row &%dns_ipv4_lookup%& "only v4 lookup for these domains"
13368 .row &%dns_retrans%& "parameter for resolver"
13369 .row &%dns_retry%& "parameter for resolver"
13370 .row &%dns_use_edns0%& "parameter for resolver"
13371 .row &%hold_domains%& "hold delivery for these domains"
13372 .row &%local_interfaces%& "for routing checks"
13373 .row &%queue_domains%& "no immediate delivery for these"
13374 .row &%queue_only%& "no immediate delivery at all"
13375 .row &%queue_only_file%& "no immediate delivery if file exists"
13376 .row &%queue_only_load%& "no immediate delivery if load is high"
13377 .row &%queue_only_load_latch%& "don't re-evaluate load for each message"
13378 .row &%queue_only_override%& "allow command line to override"
13379 .row &%queue_run_in_order%& "order of arrival"
13380 .row &%queue_run_max%& "of simultaneous queue runners"
13381 .row &%queue_smtp_domains%& "no immediate SMTP delivery for these"
13382 .row &%remote_max_parallel%& "parallel SMTP delivery per message"
13383 .row &%remote_sort_domains%& "order of remote deliveries"
13384 .row &%retry_data_expire%& "timeout for retry data"
13385 .row &%retry_interval_max%& "safety net for retry rules"
13390 .section "Bounce and warning messages" "SECID117"
13392 .row &%bounce_message_file%& "content of bounce"
13393 .row &%bounce_message_text%& "content of bounce"
13394 .row &%bounce_return_body%& "include body if returning message"
13395 .row &%bounce_return_message%& "include original message in bounce"
13396 .row &%bounce_return_size_limit%& "limit on returned message"
13397 .row &%bounce_sender_authentication%& "send authenticated sender with bounce"
13398 .row &%dsn_from%& "set &'From:'& contents in bounces"
13399 .row &%errors_copy%& "copy bounce messages"
13400 .row &%errors_reply_to%& "&'Reply-to:'& in bounces"
13401 .row &%delay_warning%& "time schedule"
13402 .row &%delay_warning_condition%& "condition for warning messages"
13403 .row &%ignore_bounce_errors_after%& "discard undeliverable bounces"
13404 .row &%smtp_return_error_details%& "give detail on rejections"
13405 .row &%warn_message_file%& "content of warning message"
13410 .section "Alphabetical list of main options" "SECTalomo"
13411 Those options that undergo string expansion before use are marked with
13414 .option accept_8bitmime main boolean true
13416 .cindex "8-bit characters"
13417 .cindex "log" "selectors"
13418 .cindex "log" "8BITMIME"
13419 This option causes Exim to send 8BITMIME in its response to an SMTP
13420 EHLO command, and to accept the BODY= parameter on MAIL commands.
13421 However, though Exim is 8-bit clean, it is not a protocol converter, and it
13422 takes no steps to do anything special with messages received by this route.
13424 Historically Exim kept this option off by default, but the maintainers
13425 feel that in today's Internet, this causes more problems than it solves.
13426 It now defaults to true.
13427 A more detailed analysis of the issues is provided by Dan Bernstein:
13429 &url(http://cr.yp.to/smtp/8bitmime.html)
13432 To log received 8BITMIME status use
13434 log_selector = +8bitmime
13437 .option acl_not_smtp main string&!! unset
13438 .cindex "&ACL;" "for non-SMTP messages"
13439 .cindex "non-SMTP messages" "ACLs for"
13440 This option defines the ACL that is run when a non-SMTP message has been
13441 read and is on the point of being accepted. See chapter &<<CHAPACL>>& for
13444 .option acl_not_smtp_mime main string&!! unset
13445 This option defines the ACL that is run for individual MIME parts of non-SMTP
13446 messages. It operates in exactly the same way as &%acl_smtp_mime%& operates for
13449 .option acl_not_smtp_start main string&!! unset
13450 .cindex "&ACL;" "at start of non-SMTP message"
13451 .cindex "non-SMTP messages" "ACLs for"
13452 This option defines the ACL that is run before Exim starts reading a
13453 non-SMTP message. See chapter &<<CHAPACL>>& for further details.
13455 .option acl_smtp_auth main string&!! unset
13456 .cindex "&ACL;" "setting up for SMTP commands"
13457 .cindex "AUTH" "ACL for"
13458 This option defines the ACL that is run when an SMTP AUTH command is
13459 received. See chapter &<<CHAPACL>>& for further details.
13461 .option acl_smtp_connect main string&!! unset
13462 .cindex "&ACL;" "on SMTP connection"
13463 This option defines the ACL that is run when an SMTP connection is received.
13464 See chapter &<<CHAPACL>>& for further details.
13466 .option acl_smtp_data main string&!! unset
13467 .cindex "DATA" "ACL for"
13468 This option defines the ACL that is run after an SMTP DATA command has been
13469 processed and the message itself has been received, but before the final
13470 acknowledgment is sent. See chapter &<<CHAPACL>>& for further details.
13472 .option acl_smtp_data_prdr main string&!! unset
13473 .cindex "DATA" "ACL for"
13474 .cindex "&ACL;" "PRDR-related"
13475 .cindex "&ACL;" "per-user data processing"
13476 This option defines the ACL that,
13477 if the PRDR feature has been negotiated,
13478 is run for each recipient after an SMTP DATA command has been
13479 processed and the message itself has been received, but before the
13480 acknowledgment is sent. See chapter &<<CHAPACL>>& for further details.
13482 .option acl_smtp_etrn main string&!! unset
13483 .cindex "ETRN" "ACL for"
13484 This option defines the ACL that is run when an SMTP ETRN command is
13485 received. See chapter &<<CHAPACL>>& for further details.
13487 .option acl_smtp_expn main string&!! unset
13488 .cindex "EXPN" "ACL for"
13489 This option defines the ACL that is run when an SMTP EXPN command is
13490 received. See chapter &<<CHAPACL>>& for further details.
13492 .option acl_smtp_helo main string&!! unset
13493 .cindex "EHLO" "ACL for"
13494 .cindex "HELO" "ACL for"
13495 This option defines the ACL that is run when an SMTP EHLO or HELO
13496 command is received. See chapter &<<CHAPACL>>& for further details.
13499 .option acl_smtp_mail main string&!! unset
13500 .cindex "MAIL" "ACL for"
13501 This option defines the ACL that is run when an SMTP MAIL command is
13502 received. See chapter &<<CHAPACL>>& for further details.
13504 .option acl_smtp_mailauth main string&!! unset
13505 .cindex "AUTH" "on MAIL command"
13506 This option defines the ACL that is run when there is an AUTH parameter on
13507 a MAIL command. See chapter &<<CHAPACL>>& for details of ACLs, and chapter
13508 &<<CHAPSMTPAUTH>>& for details of authentication.
13510 .option acl_smtp_mime main string&!! unset
13511 .cindex "MIME content scanning" "ACL for"
13512 This option is available when Exim is built with the content-scanning
13513 extension. It defines the ACL that is run for each MIME part in a message. See
13514 section &<<SECTscanmimepart>>& for details.
13516 .option acl_smtp_predata main string&!! unset
13517 This option defines the ACL that is run when an SMTP DATA command is
13518 received, before the message itself is received. See chapter &<<CHAPACL>>& for
13521 .option acl_smtp_quit main string&!! unset
13522 .cindex "QUIT, ACL for"
13523 This option defines the ACL that is run when an SMTP QUIT command is
13524 received. See chapter &<<CHAPACL>>& for further details.
13526 .option acl_smtp_rcpt main string&!! unset
13527 .cindex "RCPT" "ACL for"
13528 This option defines the ACL that is run when an SMTP RCPT command is
13529 received. See chapter &<<CHAPACL>>& for further details.
13531 .option acl_smtp_starttls main string&!! unset
13532 .cindex "STARTTLS, ACL for"
13533 This option defines the ACL that is run when an SMTP STARTTLS command is
13534 received. See chapter &<<CHAPACL>>& for further details.
13536 .option acl_smtp_vrfy main string&!! unset
13537 .cindex "VRFY" "ACL for"
13538 This option defines the ACL that is run when an SMTP VRFY command is
13539 received. See chapter &<<CHAPACL>>& for further details.
13541 .option admin_groups main "string list&!!" unset
13542 .cindex "admin user"
13543 This option is expanded just once, at the start of Exim's processing. If the
13544 current group or any of the supplementary groups of an Exim caller is in this
13545 colon-separated list, the caller has admin privileges. If all your system
13546 programmers are in a specific group, for example, you can give them all Exim
13547 admin privileges by putting that group in &%admin_groups%&. However, this does
13548 not permit them to read Exim's spool files (whose group owner is the Exim gid).
13549 To permit this, you have to add individuals to the Exim group.
13551 .option allow_domain_literals main boolean false
13552 .cindex "domain literal"
13553 If this option is set, the RFC 2822 domain literal format is permitted in
13554 email addresses. The option is not set by default, because the domain literal
13555 format is not normally required these days, and few people know about it. It
13556 has, however, been exploited by mail abusers.
13558 Unfortunately, it seems that some DNS black list maintainers are using this
13559 format to report black listing to postmasters. If you want to accept messages
13560 addressed to your hosts by IP address, you need to set
13561 &%allow_domain_literals%& true, and also to add &`@[]`& to the list of local
13562 domains (defined in the named domain list &%local_domains%& in the default
13563 configuration). This &"magic string"& matches the domain literal form of all
13564 the local host's IP addresses.
13567 .option allow_mx_to_ip main boolean false
13568 .cindex "MX record" "pointing to IP address"
13569 It appears that more and more DNS zone administrators are breaking the rules
13570 and putting domain names that look like IP addresses on the right hand side of
13571 MX records. Exim follows the rules and rejects this, giving an error message
13572 that explains the mis-configuration. However, some other MTAs support this
13573 practice, so to avoid &"Why can't Exim do this?"& complaints,
13574 &%allow_mx_to_ip%& exists, in order to enable this heinous activity. It is not
13575 recommended, except when you have no other choice.
13577 .option allow_utf8_domains main boolean false
13578 .cindex "domain" "UTF-8 characters in"
13579 .cindex "UTF-8" "in domain name"
13580 Lots of discussion is going on about internationalized domain names. One
13581 camp is strongly in favour of just using UTF-8 characters, and it seems
13582 that at least two other MTAs permit this. This option allows Exim users to
13583 experiment if they wish.
13585 If it is set true, Exim's domain parsing function allows valid
13586 UTF-8 multicharacters to appear in domain name components, in addition to
13587 letters, digits, and hyphens. However, just setting this option is not
13588 enough; if you want to look up these domain names in the DNS, you must also
13589 adjust the value of &%dns_check_names_pattern%& to match the extended form. A
13590 suitable setting is:
13592 dns_check_names_pattern = (?i)^(?>(?(1)\.|())[a-z0-9\xc0-\xff]\
13593 (?>[-a-z0-9\x80-\xff]*[a-z0-9\x80-\xbf])?)+$
13595 Alternatively, you can just disable this feature by setting
13597 dns_check_names_pattern =
13599 That is, set the option to an empty string so that no check is done.
13602 .option auth_advertise_hosts main "host list&!!" *
13603 .cindex "authentication" "advertising"
13604 .cindex "AUTH" "advertising"
13605 If any server authentication mechanisms are configured, Exim advertises them in
13606 response to an EHLO command only if the calling host matches this list.
13607 Otherwise, Exim does not advertise AUTH.
13608 Exim does not accept AUTH commands from clients to which it has not
13609 advertised the availability of AUTH. The advertising of individual
13610 authentication mechanisms can be controlled by the use of the
13611 &%server_advertise_condition%& generic authenticator option on the individual
13612 authenticators. See chapter &<<CHAPSMTPAUTH>>& for further details.
13614 Certain mail clients (for example, Netscape) require the user to provide a name
13615 and password for authentication if AUTH is advertised, even though it may
13616 not be needed (the host may accept messages from hosts on its local LAN without
13617 authentication, for example). The &%auth_advertise_hosts%& option can be used
13618 to make these clients more friendly by excluding them from the set of hosts to
13619 which Exim advertises AUTH.
13621 .cindex "AUTH" "advertising when encrypted"
13622 If you want to advertise the availability of AUTH only when the connection
13623 is encrypted using TLS, you can make use of the fact that the value of this
13624 option is expanded, with a setting like this:
13626 auth_advertise_hosts = ${if eq{$tls_in_cipher}{}{}{*}}
13628 .vindex "&$tls_in_cipher$&"
13629 If &$tls_in_cipher$& is empty, the session is not encrypted, and the result of
13630 the expansion is empty, thus matching no hosts. Otherwise, the result of the
13631 expansion is *, which matches all hosts.
13634 .option auto_thaw main time 0s
13635 .cindex "thawing messages"
13636 .cindex "unfreezing messages"
13637 If this option is set to a time greater than zero, a queue runner will try a
13638 new delivery attempt on any frozen message, other than a bounce message, if
13639 this much time has passed since it was frozen. This may result in the message
13640 being re-frozen if nothing has changed since the last attempt. It is a way of
13641 saying &"keep on trying, even though there are big problems"&.
13643 &*Note*&: This is an old option, which predates &%timeout_frozen_after%& and
13644 &%ignore_bounce_errors_after%&. It is retained for compatibility, but it is not
13645 thought to be very useful any more, and its use should probably be avoided.
13648 .option av_scanner main string "see below"
13649 This option is available if Exim is built with the content-scanning extension.
13650 It specifies which anti-virus scanner to use. The default value is:
13652 sophie:/var/run/sophie
13654 If the value of &%av_scanner%& starts with a dollar character, it is expanded
13655 before use. See section &<<SECTscanvirus>>& for further details.
13658 .option bi_command main string unset
13660 This option supplies the name of a command that is run when Exim is called with
13661 the &%-bi%& option (see chapter &<<CHAPcommandline>>&). The string value is
13662 just the command name, it is not a complete command line. If an argument is
13663 required, it must come from the &%-oA%& command line option.
13666 .option bounce_message_file main string unset
13667 .cindex "bounce message" "customizing"
13668 .cindex "customizing" "bounce message"
13669 This option defines a template file containing paragraphs of text to be used
13670 for constructing bounce messages. Details of the file's contents are given in
13671 chapter &<<CHAPemsgcust>>&. See also &%warn_message_file%&.
13674 .option bounce_message_text main string unset
13675 When this option is set, its contents are included in the default bounce
13676 message immediately after &"This message was created automatically by mail
13677 delivery software."& It is not used if &%bounce_message_file%& is set.
13679 .option bounce_return_body main boolean true
13680 .cindex "bounce message" "including body"
13681 This option controls whether the body of an incoming message is included in a
13682 bounce message when &%bounce_return_message%& is true. The default setting
13683 causes the entire message, both header and body, to be returned (subject to the
13684 value of &%bounce_return_size_limit%&). If this option is false, only the
13685 message header is included. In the case of a non-SMTP message containing an
13686 error that is detected during reception, only those header lines preceding the
13687 point at which the error was detected are returned.
13688 .cindex "bounce message" "including original"
13690 .option bounce_return_message main boolean true
13691 If this option is set false, none of the original message is included in
13692 bounce messages generated by Exim. See also &%bounce_return_size_limit%& and
13693 &%bounce_return_body%&.
13696 .option bounce_return_size_limit main integer 100K
13697 .cindex "size" "of bounce, limit"
13698 .cindex "bounce message" "size limit"
13699 .cindex "limit" "bounce message size"
13700 This option sets a limit in bytes on the size of messages that are returned to
13701 senders as part of bounce messages when &%bounce_return_message%& is true. The
13702 limit should be less than the value of the global &%message_size_limit%& and of
13703 any &%message_size_limit%& settings on transports, to allow for the bounce text
13704 that Exim generates. If this option is set to zero there is no limit.
13706 When the body of any message that is to be included in a bounce message is
13707 greater than the limit, it is truncated, and a comment pointing this out is
13708 added at the top. The actual cutoff may be greater than the value given, owing
13709 to the use of buffering for transferring the message in chunks (typically 8K in
13710 size). The idea is to save bandwidth on those undeliverable 15-megabyte
13713 .option bounce_sender_authentication main string unset
13714 .cindex "bounce message" "sender authentication"
13715 .cindex "authentication" "bounce message"
13716 .cindex "AUTH" "on bounce message"
13717 This option provides an authenticated sender address that is sent with any
13718 bounce messages generated by Exim that are sent over an authenticated SMTP
13719 connection. A typical setting might be:
13721 bounce_sender_authentication = mailer-daemon@my.domain.example
13723 which would cause bounce messages to be sent using the SMTP command:
13725 MAIL FROM:<> AUTH=mailer-daemon@my.domain.example
13727 The value of &%bounce_sender_authentication%& must always be a complete email
13730 .option callout_domain_negative_expire main time 3h
13731 .cindex "caching" "callout timeouts"
13732 .cindex "callout" "caching timeouts"
13733 This option specifies the expiry time for negative callout cache data for a
13734 domain. See section &<<SECTcallver>>& for details of callout verification, and
13735 section &<<SECTcallvercache>>& for details of the caching.
13738 .option callout_domain_positive_expire main time 7d
13739 This option specifies the expiry time for positive callout cache data for a
13740 domain. See section &<<SECTcallver>>& for details of callout verification, and
13741 section &<<SECTcallvercache>>& for details of the caching.
13744 .option callout_negative_expire main time 2h
13745 This option specifies the expiry time for negative callout cache data for an
13746 address. See section &<<SECTcallver>>& for details of callout verification, and
13747 section &<<SECTcallvercache>>& for details of the caching.
13750 .option callout_positive_expire main time 24h
13751 This option specifies the expiry time for positive callout cache data for an
13752 address. See section &<<SECTcallver>>& for details of callout verification, and
13753 section &<<SECTcallvercache>>& for details of the caching.
13756 .option callout_random_local_part main string&!! "see below"
13757 This option defines the &"random"& local part that can be used as part of
13758 callout verification. The default value is
13760 $primary_hostname-$tod_epoch-testing
13762 See section &<<CALLaddparcall>>& for details of how this value is used.
13765 .option check_log_inodes main integer 0
13766 See &%check_spool_space%& below.
13769 .option check_log_space main integer 0
13770 See &%check_spool_space%& below.
13772 .oindex "&%check_rfc2047_length%&"
13773 .cindex "RFC 2047" "disabling length check"
13774 .option check_rfc2047_length main boolean true
13775 RFC 2047 defines a way of encoding non-ASCII characters in headers using a
13776 system of &"encoded words"&. The RFC specifies a maximum length for an encoded
13777 word; strings to be encoded that exceed this length are supposed to use
13778 multiple encoded words. By default, Exim does not recognize encoded words that
13779 exceed the maximum length. However, it seems that some software, in violation
13780 of the RFC, generates overlong encoded words. If &%check_rfc2047_length%& is
13781 set false, Exim recognizes encoded words of any length.
13784 .option check_spool_inodes main integer 0
13785 See &%check_spool_space%& below.
13788 .option check_spool_space main integer 0
13789 .cindex "checking disk space"
13790 .cindex "disk space, checking"
13791 .cindex "spool directory" "checking space"
13792 The four &%check_...%& options allow for checking of disk resources before a
13793 message is accepted.
13795 .vindex "&$log_inodes$&"
13796 .vindex "&$log_space$&"
13797 .vindex "&$spool_inodes$&"
13798 .vindex "&$spool_space$&"
13799 When any of these options are set, they apply to all incoming messages. If you
13800 want to apply different checks to different kinds of message, you can do so by
13801 testing the variables &$log_inodes$&, &$log_space$&, &$spool_inodes$&, and
13802 &$spool_space$& in an ACL with appropriate additional conditions.
13805 &%check_spool_space%& and &%check_spool_inodes%& check the spool partition if
13806 either value is greater than zero, for example:
13808 check_spool_space = 10M
13809 check_spool_inodes = 100
13811 The spool partition is the one that contains the directory defined by
13812 SPOOL_DIRECTORY in &_Local/Makefile_&. It is used for holding messages in
13815 &%check_log_space%& and &%check_log_inodes%& check the partition in which log
13816 files are written if either is greater than zero. These should be set only if
13817 &%log_file_path%& and &%spool_directory%& refer to different partitions.
13819 If there is less space or fewer inodes than requested, Exim refuses to accept
13820 incoming mail. In the case of SMTP input this is done by giving a 452 temporary
13821 error response to the MAIL command. If ESMTP is in use and there was a
13822 SIZE parameter on the MAIL command, its value is added to the
13823 &%check_spool_space%& value, and the check is performed even if
13824 &%check_spool_space%& is zero, unless &%no_smtp_check_spool_space%& is set.
13826 The values for &%check_spool_space%& and &%check_log_space%& are held as a
13827 number of kilobytes. If a non-multiple of 1024 is specified, it is rounded up.
13829 For non-SMTP input and for batched SMTP input, the test is done at start-up; on
13830 failure a message is written to stderr and Exim exits with a non-zero code, as
13831 it obviously cannot send an error message of any kind.
13833 .option daemon_smtp_ports main string &`smtp`&
13834 .cindex "port" "for daemon"
13835 .cindex "TCP/IP" "setting listening ports"
13836 This option specifies one or more default SMTP ports on which the Exim daemon
13837 listens. See chapter &<<CHAPinterfaces>>& for details of how it is used. For
13838 backward compatibility, &%daemon_smtp_port%& (singular) is a synonym.
13840 .option daemon_startup_retries main integer 9
13841 .cindex "daemon startup, retrying"
13842 This option, along with &%daemon_startup_sleep%&, controls the retrying done by
13843 the daemon at startup when it cannot immediately bind a listening socket
13844 (typically because the socket is already in use): &%daemon_startup_retries%&
13845 defines the number of retries after the first failure, and
13846 &%daemon_startup_sleep%& defines the length of time to wait between retries.
13848 .option daemon_startup_sleep main time 30s
13849 See &%daemon_startup_retries%&.
13851 .option delay_warning main "time list" 24h
13852 .cindex "warning of delay"
13853 .cindex "delay warning, specifying"
13854 When a message is delayed, Exim sends a warning message to the sender at
13855 intervals specified by this option. The data is a colon-separated list of times
13856 after which to send warning messages. If the value of the option is an empty
13857 string or a zero time, no warnings are sent. Up to 10 times may be given. If a
13858 message has been on the queue for longer than the last time, the last interval
13859 between the times is used to compute subsequent warning times. For example,
13862 delay_warning = 4h:8h:24h
13864 the first message is sent after 4 hours, the second after 8 hours, and
13865 the third one after 24 hours. After that, messages are sent every 16 hours,
13866 because that is the interval between the last two times on the list. If you set
13867 just one time, it specifies the repeat interval. For example, with:
13871 messages are repeated every six hours. To stop warnings after a given time, set
13872 a very large time at the end of the list. For example:
13874 delay_warning = 2h:12h:99d
13876 Note that the option is only evaluated at the time a delivery attempt fails,
13877 which depends on retry and queue-runner configuration.
13878 Typically retries will be configured more frequently than warning messages.
13880 .option delay_warning_condition main string&!! "see below"
13881 .vindex "&$domain$&"
13882 The string is expanded at the time a warning message might be sent. If all the
13883 deferred addresses have the same domain, it is set in &$domain$& during the
13884 expansion. Otherwise &$domain$& is empty. If the result of the expansion is a
13885 forced failure, an empty string, or a string matching any of &"0"&, &"no"& or
13886 &"false"& (the comparison being done caselessly) then the warning message is
13887 not sent. The default is:
13889 delay_warning_condition = ${if or {\
13890 { !eq{$h_list-id:$h_list-post:$h_list-subscribe:}{} }\
13891 { match{$h_precedence:}{(?i)bulk|list|junk} }\
13892 { match{$h_auto-submitted:}{(?i)auto-generated|auto-replied} }\
13895 This suppresses the sending of warnings for messages that contain &'List-ID:'&,
13896 &'List-Post:'&, or &'List-Subscribe:'& headers, or have &"bulk"&, &"list"& or
13897 &"junk"& in a &'Precedence:'& header, or have &"auto-generated"& or
13898 &"auto-replied"& in an &'Auto-Submitted:'& header.
13900 .option deliver_drop_privilege main boolean false
13901 .cindex "unprivileged delivery"
13902 .cindex "delivery" "unprivileged"
13903 If this option is set true, Exim drops its root privilege at the start of a
13904 delivery process, and runs as the Exim user throughout. This severely restricts
13905 the kinds of local delivery that are possible, but is viable in certain types
13906 of configuration. There is a discussion about the use of root privilege in
13907 chapter &<<CHAPsecurity>>&.
13909 .option deliver_queue_load_max main fixed-point unset
13910 .cindex "load average"
13911 .cindex "queue runner" "abandoning"
13912 When this option is set, a queue run is abandoned if the system load average
13913 becomes greater than the value of the option. The option has no effect on
13914 ancient operating systems on which Exim cannot determine the load average.
13915 See also &%queue_only_load%& and &%smtp_load_reserve%&.
13918 .option delivery_date_remove main boolean true
13919 .cindex "&'Delivery-date:'& header line"
13920 Exim's transports have an option for adding a &'Delivery-date:'& header to a
13921 message when it is delivered, in exactly the same way as &'Return-path:'& is
13922 handled. &'Delivery-date:'& records the actual time of delivery. Such headers
13923 should not be present in incoming messages, and this option causes them to be
13924 removed at the time the message is received, to avoid any problems that might
13925 occur when a delivered message is subsequently sent on to some other recipient.
13927 .option disable_fsync main boolean false
13928 .cindex "&[fsync()]&, disabling"
13929 This option is available only if Exim was built with the compile-time option
13930 ENABLE_DISABLE_FSYNC. When this is not set, a reference to &%disable_fsync%& in
13931 a runtime configuration generates an &"unknown option"& error. You should not
13932 build Exim with ENABLE_DISABLE_FSYNC or set &%disable_fsync%& unless you
13933 really, really, really understand what you are doing. &'No pre-compiled
13934 distributions of Exim should ever make this option available.'&
13936 When &%disable_fsync%& is set true, Exim no longer calls &[fsync()]& to force
13937 updated files' data to be written to disc before continuing. Unexpected events
13938 such as crashes and power outages may cause data to be lost or scrambled.
13939 Here be Dragons. &*Beware.*&
13942 .option disable_ipv6 main boolean false
13943 .cindex "IPv6" "disabling"
13944 If this option is set true, even if the Exim binary has IPv6 support, no IPv6
13945 activities take place. AAAA records are never looked up, and any IPv6 addresses
13946 that are listed in &%local_interfaces%&, data for the &%manualroute%& router,
13947 etc. are ignored. If IP literals are enabled, the &(ipliteral)& router declines
13948 to handle IPv6 literal addresses.
13951 .option dns_again_means_nonexist main "domain list&!!" unset
13952 .cindex "DNS" "&""try again""& response; overriding"
13953 DNS lookups give a &"try again"& response for the DNS errors
13954 &"non-authoritative host not found"& and &"SERVERFAIL"&. This can cause Exim to
13955 keep trying to deliver a message, or to give repeated temporary errors to
13956 incoming mail. Sometimes the effect is caused by a badly set up name server and
13957 may persist for a long time. If a domain which exhibits this problem matches
13958 anything in &%dns_again_means_nonexist%&, it is treated as if it did not exist.
13959 This option should be used with care. You can make it apply to reverse lookups
13960 by a setting such as this:
13962 dns_again_means_nonexist = *.in-addr.arpa
13964 This option applies to all DNS lookups that Exim does. It also applies when the
13965 &[gethostbyname()]& or &[getipnodebyname()]& functions give temporary errors,
13966 since these are most likely to be caused by DNS lookup problems. The
13967 &(dnslookup)& router has some options of its own for controlling what happens
13968 when lookups for MX or SRV records give temporary errors. These more specific
13969 options are applied after this global option.
13971 .option dns_check_names_pattern main string "see below"
13972 .cindex "DNS" "pre-check of name syntax"
13973 When this option is set to a non-empty string, it causes Exim to check domain
13974 names for characters that are not allowed in host names before handing them to
13975 the DNS resolver, because some resolvers give temporary errors for names that
13976 contain unusual characters. If a domain name contains any unwanted characters,
13977 a &"not found"& result is forced, and the resolver is not called. The check is
13978 done by matching the domain name against a regular expression, which is the
13979 value of this option. The default pattern is
13981 dns_check_names_pattern = \
13982 (?i)^(?>(?(1)\.|())[^\W_](?>[a-z0-9/-]*[^\W_])?)+$
13984 which permits only letters, digits, slashes, and hyphens in components, but
13985 they must start and end with a letter or digit. Slashes are not, in fact,
13986 permitted in host names, but they are found in certain NS records (which can be
13987 accessed in Exim by using a &%dnsdb%& lookup). If you set
13988 &%allow_utf8_domains%&, you must modify this pattern, or set the option to an
13991 .option dns_csa_search_limit main integer 5
13992 This option controls the depth of parental searching for CSA SRV records in the
13993 DNS, as described in more detail in section &<<SECTverifyCSA>>&.
13995 .option dns_csa_use_reverse main boolean true
13996 This option controls whether or not an IP address, given as a CSA domain, is
13997 reversed and looked up in the reverse DNS, as described in more detail in
13998 section &<<SECTverifyCSA>>&.
14001 .option dns_dnssec_ok main integer -1
14002 .cindex "DNS" "resolver options"
14003 .cindex "DNS" "DNSSEC"
14004 If this option is set to a non-negative number then Exim will initialise the
14005 DNS resolver library to either use or not use DNSSEC, overriding the system
14006 default. A value of 0 coerces DNSSEC off, a value of 1 coerces DNSSEC on.
14008 If the resolver library does not support DNSSEC then this option has no effect.
14011 .option dns_ipv4_lookup main "domain list&!!" unset
14012 .cindex "IPv6" "DNS lookup for AAAA records"
14013 .cindex "DNS" "IPv6 lookup for AAAA records"
14014 When Exim is compiled with IPv6 support and &%disable_ipv6%& is not set, it
14015 looks for IPv6 address records (AAAA records) as well as IPv4 address records
14016 (A records) when trying to find IP addresses for hosts, unless the host's
14017 domain matches this list.
14019 This is a fudge to help with name servers that give big delays or otherwise do
14020 not work for the AAAA record type. In due course, when the world's name
14021 servers have all been upgraded, there should be no need for this option.
14024 .option dns_retrans main time 0s
14025 .cindex "DNS" "resolver options"
14026 The options &%dns_retrans%& and &%dns_retry%& can be used to set the
14027 retransmission and retry parameters for DNS lookups. Values of zero (the
14028 defaults) leave the system default settings unchanged. The first value is the
14029 time between retries, and the second is the number of retries. It isn't
14030 totally clear exactly how these settings affect the total time a DNS lookup may
14031 take. I haven't found any documentation about timeouts on DNS lookups; these
14032 parameter values are available in the external resolver interface structure,
14033 but nowhere does it seem to describe how they are used or what you might want
14037 .option dns_retry main integer 0
14038 See &%dns_retrans%& above.
14041 .option dns_use_edns0 main integer -1
14042 .cindex "DNS" "resolver options"
14043 .cindex "DNS" "EDNS0"
14044 If this option is set to a non-negative number then Exim will initialise the
14045 DNS resolver library to either use or not use EDNS0 extensions, overriding
14046 the system default. A value of 0 coerces EDNS0 off, a value of 1 coerces EDNS0
14049 If the resolver library does not support EDNS0 then this option has no effect.
14052 .option drop_cr main boolean false
14053 This is an obsolete option that is now a no-op. It used to affect the way Exim
14054 handled CR and LF characters in incoming messages. What happens now is
14055 described in section &<<SECTlineendings>>&.
14057 .option dsn_from main "string&!!" "see below"
14058 .cindex "&'From:'& header line" "in bounces"
14059 .cindex "bounce messages" "&'From:'& line, specifying"
14060 This option can be used to vary the contents of &'From:'& header lines in
14061 bounces and other automatically generated messages (&"Delivery Status
14062 Notifications"& &-- hence the name of the option). The default setting is:
14064 dsn_from = Mail Delivery System <Mailer-Daemon@$qualify_domain>
14066 The value is expanded every time it is needed. If the expansion fails, a
14067 panic is logged, and the default value is used.
14069 .option envelope_to_remove main boolean true
14070 .cindex "&'Envelope-to:'& header line"
14071 Exim's transports have an option for adding an &'Envelope-to:'& header to a
14072 message when it is delivered, in exactly the same way as &'Return-path:'& is
14073 handled. &'Envelope-to:'& records the original recipient address from the
14074 messages's envelope that caused the delivery to happen. Such headers should not
14075 be present in incoming messages, and this option causes them to be removed at
14076 the time the message is received, to avoid any problems that might occur when a
14077 delivered message is subsequently sent on to some other recipient.
14080 .option errors_copy main "string list&!!" unset
14081 .cindex "bounce message" "copy to other address"
14082 .cindex "copy of bounce message"
14083 Setting this option causes Exim to send bcc copies of bounce messages that it
14084 generates to other addresses. &*Note*&: This does not apply to bounce messages
14085 coming from elsewhere. The value of the option is a colon-separated list of
14086 items. Each item consists of a pattern, terminated by white space, followed by
14087 a comma-separated list of email addresses. If a pattern contains spaces, it
14088 must be enclosed in double quotes.
14090 Each pattern is processed in the same way as a single item in an address list
14091 (see section &<<SECTaddresslist>>&). When a pattern matches the recipient of
14092 the bounce message, the message is copied to the addresses on the list. The
14093 items are scanned in order, and once a matching one is found, no further items
14094 are examined. For example:
14096 errors_copy = spqr@mydomain postmaster@mydomain.example :\
14097 rqps@mydomain hostmaster@mydomain.example,\
14098 postmaster@mydomain.example
14100 .vindex "&$domain$&"
14101 .vindex "&$local_part$&"
14102 The address list is expanded before use. The expansion variables &$local_part$&
14103 and &$domain$& are set from the original recipient of the error message, and if
14104 there was any wildcard matching in the pattern, the expansion
14105 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%errors_copy%&"
14106 variables &$0$&, &$1$&, etc. are set in the normal way.
14109 .option errors_reply_to main string unset
14110 .cindex "bounce message" "&'Reply-to:'& in"
14111 By default, Exim's bounce and delivery warning messages contain the header line
14113 &`From: Mail Delivery System <Mailer-Daemon@`&&'qualify-domain'&&`>`&
14115 .oindex &%quota_warn_message%&
14116 where &'qualify-domain'& is the value of the &%qualify_domain%& option.
14117 A warning message that is generated by the &%quota_warn_message%& option in an
14118 &(appendfile)& transport may contain its own &'From:'& header line that
14119 overrides the default.
14121 Experience shows that people reply to bounce messages. If the
14122 &%errors_reply_to%& option is set, a &'Reply-To:'& header is added to bounce
14123 and warning messages. For example:
14125 errors_reply_to = postmaster@my.domain.example
14127 The value of the option is not expanded. It must specify a valid RFC 2822
14128 address. However, if a warning message that is generated by the
14129 &%quota_warn_message%& option in an &(appendfile)& transport contain its
14130 own &'Reply-To:'& header line, the value of the &%errors_reply_to%& option is
14134 .option exim_group main string "compile-time configured"
14135 .cindex "gid (group id)" "Exim's own"
14136 .cindex "Exim group"
14137 This option changes the gid under which Exim runs when it gives up root
14138 privilege. The default value is compiled into the binary. The value of this
14139 option is used only when &%exim_user%& is also set. Unless it consists entirely
14140 of digits, the string is looked up using &[getgrnam()]&, and failure causes a
14141 configuration error. See chapter &<<CHAPsecurity>>& for a discussion of
14145 .option exim_path main string "see below"
14146 .cindex "Exim binary, path name"
14147 This option specifies the path name of the Exim binary, which is used when Exim
14148 needs to re-exec itself. The default is set up to point to the file &'exim'& in
14149 the directory configured at compile time by the BIN_DIRECTORY setting. It
14150 is necessary to change &%exim_path%& if, exceptionally, Exim is run from some
14152 &*Warning*&: Do not use a macro to define the value of this option, because
14153 you will break those Exim utilities that scan the configuration file to find
14154 where the binary is. (They then use the &%-bP%& option to extract option
14155 settings such as the value of &%spool_directory%&.)
14158 .option exim_user main string "compile-time configured"
14159 .cindex "uid (user id)" "Exim's own"
14160 .cindex "Exim user"
14161 This option changes the uid under which Exim runs when it gives up root
14162 privilege. The default value is compiled into the binary. Ownership of the run
14163 time configuration file and the use of the &%-C%& and &%-D%& command line
14164 options is checked against the values in the binary, not what is set here.
14166 Unless it consists entirely of digits, the string is looked up using
14167 &[getpwnam()]&, and failure causes a configuration error. If &%exim_group%& is
14168 not also supplied, the gid is taken from the result of &[getpwnam()]& if it is
14169 used. See chapter &<<CHAPsecurity>>& for a discussion of security issues.
14172 .option extra_local_interfaces main "string list" unset
14173 This option defines network interfaces that are to be considered local when
14174 routing, but which are not used for listening by the daemon. See section
14175 &<<SECTreclocipadd>>& for details.
14178 . Allow this long option name to split; give it unsplit as a fifth argument
14179 . for the automatic .oindex that is generated by .option.
14181 .option "extract_addresses_remove_ &~&~arguments" main boolean true &&&
14182 extract_addresses_remove_arguments
14184 .cindex "command line" "addresses with &%-t%&"
14185 .cindex "Sendmail compatibility" "&%-t%& option"
14186 According to some Sendmail documentation (Sun, IRIX, HP-UX), if any addresses
14187 are present on the command line when the &%-t%& option is used to build an
14188 envelope from a message's &'To:'&, &'Cc:'& and &'Bcc:'& headers, the command
14189 line addresses are removed from the recipients list. This is also how Smail
14190 behaves. However, other Sendmail documentation (the O'Reilly book) states that
14191 command line addresses are added to those obtained from the header lines. When
14192 &%extract_addresses_remove_arguments%& is true (the default), Exim subtracts
14193 argument headers. If it is set false, Exim adds rather than removes argument
14197 .option finduser_retries main integer 0
14198 .cindex "NIS, retrying user lookups"
14199 On systems running NIS or other schemes in which user and group information is
14200 distributed from a remote system, there can be times when &[getpwnam()]& and
14201 related functions fail, even when given valid data, because things time out.
14202 Unfortunately these failures cannot be distinguished from genuine &"not found"&
14203 errors. If &%finduser_retries%& is set greater than zero, Exim will try that
14204 many extra times to find a user or a group, waiting for one second between
14207 .cindex "&_/etc/passwd_&" "multiple reading of"
14208 You should not set this option greater than zero if your user information is in
14209 a traditional &_/etc/passwd_& file, because it will cause Exim needlessly to
14210 search the file multiple times for non-existent users, and also cause delay.
14214 .option freeze_tell main "string list, comma separated" unset
14215 .cindex "freezing messages" "sending a message when freezing"
14216 On encountering certain errors, or when configured to do so in a system filter,
14217 ACL, or special router, Exim freezes a message. This means that no further
14218 delivery attempts take place until an administrator thaws the message, or the
14219 &%auto_thaw%&, &%ignore_bounce_errors_after%&, or &%timeout_frozen_after%&
14220 feature cause it to be processed. If &%freeze_tell%& is set, Exim generates a
14221 warning message whenever it freezes something, unless the message it is
14222 freezing is a locally-generated bounce message. (Without this exception there
14223 is the possibility of looping.) The warning message is sent to the addresses
14224 supplied as the comma-separated value of this option. If several of the
14225 message's addresses cause freezing, only a single message is sent. If the
14226 freezing was automatic, the reason(s) for freezing can be found in the message
14227 log. If you configure freezing in a filter or ACL, you must arrange for any
14228 logging that you require.
14231 .option gecos_name main string&!! unset
14233 .cindex "&""gecos""& field, parsing"
14234 Some operating systems, notably HP-UX, use the &"gecos"& field in the system
14235 password file to hold other information in addition to users' real names. Exim
14236 looks up this field for use when it is creating &'Sender:'& or &'From:'&
14237 headers. If either &%gecos_pattern%& or &%gecos_name%& are unset, the contents
14238 of the field are used unchanged, except that, if an ampersand is encountered,
14239 it is replaced by the user's login name with the first character forced to
14240 upper case, since this is a convention that is observed on many systems.
14242 When these options are set, &%gecos_pattern%& is treated as a regular
14243 expression that is to be applied to the field (again with && replaced by the
14244 login name), and if it matches, &%gecos_name%& is expanded and used as the
14247 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%gecos_name%&"
14248 Numeric variables such as &$1$&, &$2$&, etc. can be used in the expansion to
14249 pick up sub-fields that were matched by the pattern. In HP-UX, where the user's
14250 name terminates at the first comma, the following can be used:
14252 gecos_pattern = ([^,]*)
14256 .option gecos_pattern main string unset
14257 See &%gecos_name%& above.
14260 .option gnutls_compat_mode main boolean unset
14261 This option controls whether GnuTLS is used in compatibility mode in an Exim
14262 server. This reduces security slightly, but improves interworking with older
14263 implementations of TLS.
14266 option gnutls_allow_auto_pkcs11 main boolean unset
14267 This option will let GnuTLS (2.12.0 or later) autoload PKCS11 modules with
14268 the p11-kit configuration files in &_/etc/pkcs11/modules/_&.
14271 &url(http://www.gnutls.org/manual/gnutls.html#Smart-cards-and-HSMs)
14276 .option headers_charset main string "see below"
14277 This option sets a default character set for translating from encoded MIME
14278 &"words"& in header lines, when referenced by an &$h_xxx$& expansion item. The
14279 default is the value of HEADERS_CHARSET in &_Local/Makefile_&. The
14280 ultimate default is ISO-8859-1. For more details see the description of header
14281 insertions in section &<<SECTexpansionitems>>&.
14285 .option header_maxsize main integer "see below"
14286 .cindex "header section" "maximum size of"
14287 .cindex "limit" "size of message header section"
14288 This option controls the overall maximum size of a message's header
14289 section. The default is the value of HEADER_MAXSIZE in
14290 &_Local/Makefile_&; the default for that is 1M. Messages with larger header
14291 sections are rejected.
14294 .option header_line_maxsize main integer 0
14295 .cindex "header lines" "maximum size of"
14296 .cindex "limit" "size of one header line"
14297 This option limits the length of any individual header line in a message, after
14298 all the continuations have been joined together. Messages with individual
14299 header lines that are longer than the limit are rejected. The default value of
14300 zero means &"no limit"&.
14305 .option helo_accept_junk_hosts main "host list&!!" unset
14306 .cindex "HELO" "accepting junk data"
14307 .cindex "EHLO" "accepting junk data"
14308 Exim checks the syntax of HELO and EHLO commands for incoming SMTP
14309 mail, and gives an error response for invalid data. Unfortunately, there are
14310 some SMTP clients that send syntactic junk. They can be accommodated by setting
14311 this option. Note that this is a syntax check only. See &%helo_verify_hosts%&
14312 if you want to do semantic checking.
14313 See also &%helo_allow_chars%& for a way of extending the permitted character
14317 .option helo_allow_chars main string unset
14318 .cindex "HELO" "underscores in"
14319 .cindex "EHLO" "underscores in"
14320 .cindex "underscore in EHLO/HELO"
14321 This option can be set to a string of rogue characters that are permitted in
14322 all EHLO and HELO names in addition to the standard letters, digits,
14323 hyphens, and dots. If you really must allow underscores, you can set
14325 helo_allow_chars = _
14327 Note that the value is one string, not a list.
14330 .option helo_lookup_domains main "domain list&!!" &`@:@[]`&
14331 .cindex "HELO" "forcing reverse lookup"
14332 .cindex "EHLO" "forcing reverse lookup"
14333 If the domain given by a client in a HELO or EHLO command matches this
14334 list, a reverse lookup is done in order to establish the host's true name. The
14335 default forces a lookup if the client host gives the server's name or any of
14336 its IP addresses (in brackets), something that broken clients have been seen to
14340 .option helo_try_verify_hosts main "host list&!!" unset
14341 .cindex "HELO verifying" "optional"
14342 .cindex "EHLO" "verifying, optional"
14343 By default, Exim just checks the syntax of HELO and EHLO commands (see
14344 &%helo_accept_junk_hosts%& and &%helo_allow_chars%&). However, some sites like
14345 to do more extensive checking of the data supplied by these commands. The ACL
14346 condition &`verify = helo`& is provided to make this possible.
14347 Formerly, it was necessary also to set this option (&%helo_try_verify_hosts%&)
14348 to force the check to occur. From release 4.53 onwards, this is no longer
14349 necessary. If the check has not been done before &`verify = helo`& is
14350 encountered, it is done at that time. Consequently, this option is obsolete.
14351 Its specification is retained here for backwards compatibility.
14353 When an EHLO or HELO command is received, if the calling host matches
14354 &%helo_try_verify_hosts%&, Exim checks that the host name given in the HELO or
14355 EHLO command either:
14358 is an IP literal matching the calling address of the host, or
14360 .cindex "DNS" "reverse lookup"
14361 .cindex "reverse DNS lookup"
14362 matches the host name that Exim obtains by doing a reverse lookup of the
14363 calling host address, or
14365 when looked up using &[gethostbyname()]& (or &[getipnodebyname()]& when
14366 available) yields the calling host address.
14369 However, the EHLO or HELO command is not rejected if any of the checks
14370 fail. Processing continues, but the result of the check is remembered, and can
14371 be detected later in an ACL by the &`verify = helo`& condition.
14373 .option helo_verify_hosts main "host list&!!" unset
14374 .cindex "HELO verifying" "mandatory"
14375 .cindex "EHLO" "verifying, mandatory"
14376 Like &%helo_try_verify_hosts%&, this option is obsolete, and retained only for
14377 backwards compatibility. For hosts that match this option, Exim checks the host
14378 name given in the HELO or EHLO in the same way as for
14379 &%helo_try_verify_hosts%&. If the check fails, the HELO or EHLO command is
14380 rejected with a 550 error, and entries are written to the main and reject logs.
14381 If a MAIL command is received before EHLO or HELO, it is rejected with a 503
14384 .option hold_domains main "domain list&!!" unset
14385 .cindex "domain" "delaying delivery"
14386 .cindex "delivery" "delaying certain domains"
14387 This option allows mail for particular domains to be held on the queue
14388 manually. The option is overridden if a message delivery is forced with the
14389 &%-M%&, &%-qf%&, &%-Rf%& or &%-Sf%& options, and also while testing or
14390 verifying addresses using &%-bt%& or &%-bv%&. Otherwise, if a domain matches an
14391 item in &%hold_domains%&, no routing or delivery for that address is done, and
14392 it is deferred every time the message is looked at.
14394 This option is intended as a temporary operational measure for delaying the
14395 delivery of mail while some problem is being sorted out, or some new
14396 configuration tested. If you just want to delay the processing of some
14397 domains until a queue run occurs, you should use &%queue_domains%& or
14398 &%queue_smtp_domains%&, not &%hold_domains%&.
14400 A setting of &%hold_domains%& does not override Exim's code for removing
14401 messages from the queue if they have been there longer than the longest retry
14402 time in any retry rule. If you want to hold messages for longer than the normal
14403 retry times, insert a dummy retry rule with a long retry time.
14406 .option host_lookup main "host list&!!" unset
14407 .cindex "host name" "lookup, forcing"
14408 Exim does not look up the name of a calling host from its IP address unless it
14409 is required to compare against some host list, or the host matches
14410 &%helo_try_verify_hosts%& or &%helo_verify_hosts%&, or the host matches this
14411 option (which normally contains IP addresses rather than host names). The
14412 default configuration file contains
14416 which causes a lookup to happen for all hosts. If the expense of these lookups
14417 is felt to be too great, the setting can be changed or removed.
14419 After a successful reverse lookup, Exim does a forward lookup on the name it
14420 has obtained, to verify that it yields the IP address that it started with. If
14421 this check fails, Exim behaves as if the name lookup failed.
14423 .vindex "&$host_lookup_failed$&"
14424 .vindex "&$sender_host_name$&"
14425 After any kind of failure, the host name (in &$sender_host_name$&) remains
14426 unset, and &$host_lookup_failed$& is set to the string &"1"&. See also
14427 &%dns_again_means_nonexist%&, &%helo_lookup_domains%&, and
14428 &`verify = reverse_host_lookup`& in ACLs.
14431 .option host_lookup_order main "string list" &`bydns:byaddr`&
14432 This option specifies the order of different lookup methods when Exim is trying
14433 to find a host name from an IP address. The default is to do a DNS lookup
14434 first, and then to try a local lookup (using &[gethostbyaddr()]& or equivalent)
14435 if that fails. You can change the order of these lookups, or omit one entirely,
14438 &*Warning*&: The &"byaddr"& method does not always yield aliases when there are
14439 multiple PTR records in the DNS and the IP address is not listed in
14440 &_/etc/hosts_&. Different operating systems give different results in this
14441 case. That is why the default tries a DNS lookup first.
14445 .option host_reject_connection main "host list&!!" unset
14446 .cindex "host" "rejecting connections from"
14447 If this option is set, incoming SMTP calls from the hosts listed are rejected
14448 as soon as the connection is made.
14449 This option is obsolete, and retained only for backward compatibility, because
14450 nowadays the ACL specified by &%acl_smtp_connect%& can also reject incoming
14451 connections immediately.
14453 The ability to give an immediate rejection (either by this option or using an
14454 ACL) is provided for use in unusual cases. Many hosts will just try again,
14455 sometimes without much delay. Normally, it is better to use an ACL to reject
14456 incoming messages at a later stage, such as after RCPT commands. See
14457 chapter &<<CHAPACL>>&.
14460 .option hosts_connection_nolog main "host list&!!" unset
14461 .cindex "host" "not logging connections from"
14462 This option defines a list of hosts for which connection logging does not
14463 happen, even though the &%smtp_connection%& log selector is set. For example,
14464 you might want not to log SMTP connections from local processes, or from
14465 127.0.0.1, or from your local LAN. This option is consulted in the main loop of
14466 the daemon; you should therefore strive to restrict its value to a short inline
14467 list of IP addresses and networks. To disable logging SMTP connections from
14468 local processes, you must create a host list with an empty item. For example:
14470 hosts_connection_nolog = :
14472 If the &%smtp_connection%& log selector is not set, this option has no effect.
14476 .option hosts_treat_as_local main "domain list&!!" unset
14477 .cindex "local host" "domains treated as"
14478 .cindex "host" "treated as local"
14479 If this option is set, any host names that match the domain list are treated as
14480 if they were the local host when Exim is scanning host lists obtained from MX
14482 or other sources. Note that the value of this option is a domain list, not a
14483 host list, because it is always used to check host names, not IP addresses.
14485 This option also applies when Exim is matching the special items
14486 &`@mx_any`&, &`@mx_primary`&, and &`@mx_secondary`& in a domain list (see
14487 section &<<SECTdomainlist>>&), and when checking the &%hosts%& option in the
14488 &(smtp)& transport for the local host (see the &%allow_localhost%& option in
14489 that transport). See also &%local_interfaces%&, &%extra_local_interfaces%&, and
14490 chapter &<<CHAPinterfaces>>&, which contains a discussion about local network
14491 interfaces and recognizing the local host.
14494 .option ibase_servers main "string list" unset
14495 .cindex "InterBase" "server list"
14496 This option provides a list of InterBase servers and associated connection data,
14497 to be used in conjunction with &(ibase)& lookups (see section &<<SECID72>>&).
14498 The option is available only if Exim has been built with InterBase support.
14502 .option ignore_bounce_errors_after main time 10w
14503 .cindex "bounce message" "discarding"
14504 .cindex "discarding bounce message"
14505 This option affects the processing of bounce messages that cannot be delivered,
14506 that is, those that suffer a permanent delivery failure. (Bounce messages that
14507 suffer temporary delivery failures are of course retried in the usual way.)
14509 After a permanent delivery failure, bounce messages are frozen,
14510 because there is no sender to whom they can be returned. When a frozen bounce
14511 message has been on the queue for more than the given time, it is unfrozen at
14512 the next queue run, and a further delivery is attempted. If delivery fails
14513 again, the bounce message is discarded. This makes it possible to keep failed
14514 bounce messages around for a shorter time than the normal maximum retry time
14515 for frozen messages. For example,
14517 ignore_bounce_errors_after = 12h
14519 retries failed bounce message deliveries after 12 hours, discarding any further
14520 failures. If the value of this option is set to a zero time period, bounce
14521 failures are discarded immediately. Setting a very long time (as in the default
14522 value) has the effect of disabling this option. For ways of automatically
14523 dealing with other kinds of frozen message, see &%auto_thaw%& and
14524 &%timeout_frozen_after%&.
14527 .option ignore_fromline_hosts main "host list&!!" unset
14528 .cindex "&""From""& line"
14529 .cindex "UUCP" "&""From""& line"
14530 Some broken SMTP clients insist on sending a UUCP-like &"From&~"& line before
14531 the headers of a message. By default this is treated as the start of the
14532 message's body, which means that any following headers are not recognized as
14533 such. Exim can be made to ignore it by setting &%ignore_fromline_hosts%& to
14534 match those hosts that insist on sending it. If the sender is actually a local
14535 process rather than a remote host, and is using &%-bs%& to inject the messages,
14536 &%ignore_fromline_local%& must be set to achieve this effect.
14539 .option ignore_fromline_local main boolean false
14540 See &%ignore_fromline_hosts%& above.
14543 .option keep_malformed main time 4d
14544 This option specifies the length of time to keep messages whose spool files
14545 have been corrupted in some way. This should, of course, never happen. At the
14546 next attempt to deliver such a message, it gets removed. The incident is
14550 .option ldap_ca_cert_dir main string unset
14551 .cindex "LDAP", "TLS CA certificate directory"
14552 This option indicates which directory contains CA certificates for verifying
14553 a TLS certificate presented by an LDAP server.
14554 While Exim does not provide a default value, your SSL library may.
14555 Analogous to &%tls_verify_certificates%& but as a client-side option for LDAP
14556 and constrained to be a directory.
14559 .option ldap_ca_cert_file main string unset
14560 .cindex "LDAP", "TLS CA certificate file"
14561 This option indicates which file contains CA certificates for verifying
14562 a TLS certificate presented by an LDAP server.
14563 While Exim does not provide a default value, your SSL library may.
14564 Analogous to &%tls_verify_certificates%& but as a client-side option for LDAP
14565 and constrained to be a file.
14568 .option ldap_cert_file main string unset
14569 .cindex "LDAP" "TLS client certificate file"
14570 This option indicates which file contains an TLS client certificate which
14571 Exim should present to the LDAP server during TLS negotiation.
14572 Should be used together with &%ldap_cert_key%&.
14575 .option ldap_cert_key main string unset
14576 .cindex "LDAP" "TLS client key file"
14577 This option indicates which file contains the secret/private key to use
14578 to prove identity to the LDAP server during TLS negotiation.
14579 Should be used together with &%ldap_cert_file%&, which contains the
14580 identity to be proven.
14583 .option ldap_cipher_suite main string unset
14584 .cindex "LDAP" "TLS cipher suite"
14585 This controls the TLS cipher-suite negotiation during TLS negotiation with
14586 the LDAP server. See &<<SECTreqciphssl>>& for more details of the format of
14587 cipher-suite options with OpenSSL (as used by LDAP client libraries).
14590 .option ldap_default_servers main "string list" unset
14591 .cindex "LDAP" "default servers"
14592 This option provides a list of LDAP servers which are tried in turn when an
14593 LDAP query does not contain a server. See section &<<SECTforldaque>>& for
14594 details of LDAP queries. This option is available only when Exim has been built
14598 .option ldap_require_cert main string unset.
14599 .cindex "LDAP" "policy for LDAP server TLS cert presentation"
14600 This should be one of the values "hard", "demand", "allow", "try" or "never".
14601 A value other than one of these is interpreted as "never".
14602 See the entry "TLS_REQCERT" in your system man page for ldap.conf(5).
14603 Although Exim does not set a default, the LDAP library probably defaults
14607 .option ldap_start_tls main boolean false
14608 .cindex "LDAP" "whether or not to negotiate TLS"
14609 If set, Exim will attempt to negotiate TLS with the LDAP server when
14610 connecting on a regular LDAP port. This is the LDAP equivalent of SMTP's
14611 "STARTTLS". This is distinct from using "ldaps", which is the LDAP form
14613 In the event of failure to negotiate TLS, the action taken is controlled
14614 by &%ldap_require_cert%&.
14617 .option ldap_version main integer unset
14618 .cindex "LDAP" "protocol version, forcing"
14619 This option can be used to force Exim to set a specific protocol version for
14620 LDAP. If it option is unset, it is shown by the &%-bP%& command line option as
14621 -1. When this is the case, the default is 3 if LDAP_VERSION3 is defined in
14622 the LDAP headers; otherwise it is 2. This option is available only when Exim
14623 has been built with LDAP support.
14627 .option local_from_check main boolean true
14628 .cindex "&'Sender:'& header line" "disabling addition of"
14629 .cindex "&'From:'& header line" "disabling checking of"
14630 When a message is submitted locally (that is, not over a TCP/IP connection) by
14631 an untrusted user, Exim removes any existing &'Sender:'& header line, and
14632 checks that the &'From:'& header line matches the login of the calling user and
14633 the domain specified by &%qualify_domain%&.
14635 &*Note*&: An unqualified address (no domain) in the &'From:'& header in a
14636 locally submitted message is automatically qualified by Exim, unless the
14637 &%-bnq%& command line option is used.
14639 You can use &%local_from_prefix%& and &%local_from_suffix%& to permit affixes
14640 on the local part. If the &'From:'& header line does not match, Exim adds a
14641 &'Sender:'& header with an address constructed from the calling user's login
14642 and the default qualify domain.
14644 If &%local_from_check%& is set false, the &'From:'& header check is disabled,
14645 and no &'Sender:'& header is ever added. If, in addition, you want to retain
14646 &'Sender:'& header lines supplied by untrusted users, you must also set
14647 &%local_sender_retain%& to be true.
14649 .cindex "envelope sender"
14650 These options affect only the header lines in the message. The envelope sender
14651 is still forced to be the login id at the qualify domain unless
14652 &%untrusted_set_sender%& permits the user to supply an envelope sender.
14654 For messages received over TCP/IP, an ACL can specify &"submission mode"& to
14655 request similar header line checking. See section &<<SECTthesenhea>>&, which
14656 has more details about &'Sender:'& processing.
14661 .option local_from_prefix main string unset
14662 When Exim checks the &'From:'& header line of locally submitted messages for
14663 matching the login id (see &%local_from_check%& above), it can be configured to
14664 ignore certain prefixes and suffixes in the local part of the address. This is
14665 done by setting &%local_from_prefix%& and/or &%local_from_suffix%& to
14666 appropriate lists, in the same form as the &%local_part_prefix%& and
14667 &%local_part_suffix%& router options (see chapter &<<CHAProutergeneric>>&). For
14670 local_from_prefix = *-
14672 is set, a &'From:'& line containing
14674 From: anything-user@your.domain.example
14676 will not cause a &'Sender:'& header to be added if &'user@your.domain.example'&
14677 matches the actual sender address that is constructed from the login name and
14681 .option local_from_suffix main string unset
14682 See &%local_from_prefix%& above.
14685 .option local_interfaces main "string list" "see below"
14686 This option controls which network interfaces are used by the daemon for
14687 listening; they are also used to identify the local host when routing. Chapter
14688 &<<CHAPinterfaces>>& contains a full description of this option and the related
14689 options &%daemon_smtp_ports%&, &%extra_local_interfaces%&,
14690 &%hosts_treat_as_local%&, and &%tls_on_connect_ports%&. The default value for
14691 &%local_interfaces%& is
14693 local_interfaces = 0.0.0.0
14695 when Exim is built without IPv6 support; otherwise it is
14697 local_interfaces = <; ::0 ; 0.0.0.0
14700 .option local_scan_timeout main time 5m
14701 .cindex "timeout" "for &[local_scan()]& function"
14702 .cindex "&[local_scan()]& function" "timeout"
14703 This timeout applies to the &[local_scan()]& function (see chapter
14704 &<<CHAPlocalscan>>&). Zero means &"no timeout"&. If the timeout is exceeded,
14705 the incoming message is rejected with a temporary error if it is an SMTP
14706 message. For a non-SMTP message, the message is dropped and Exim ends with a
14707 non-zero code. The incident is logged on the main and reject logs.
14711 .option local_sender_retain main boolean false
14712 .cindex "&'Sender:'& header line" "retaining from local submission"
14713 When a message is submitted locally (that is, not over a TCP/IP connection) by
14714 an untrusted user, Exim removes any existing &'Sender:'& header line. If you
14715 do not want this to happen, you must set &%local_sender_retain%&, and you must
14716 also set &%local_from_check%& to be false (Exim will complain if you do not).
14717 See also the ACL modifier &`control = suppress_local_fixups`&. Section
14718 &<<SECTthesenhea>>& has more details about &'Sender:'& processing.
14723 .option localhost_number main string&!! unset
14724 .cindex "host" "locally unique number for"
14725 .cindex "message ids" "with multiple hosts"
14726 .vindex "&$localhost_number$&"
14727 Exim's message ids are normally unique only within the local host. If
14728 uniqueness among a set of hosts is required, each host must set a different
14729 value for the &%localhost_number%& option. The string is expanded immediately
14730 after reading the configuration file (so that a number can be computed from the
14731 host name, for example) and the result of the expansion must be a number in the
14732 range 0&--16 (or 0&--10 on operating systems with case-insensitive file
14733 systems). This is available in subsequent string expansions via the variable
14734 &$localhost_number$&. When &%localhost_number is set%&, the final two
14735 characters of the message id, instead of just being a fractional part of the
14736 time, are computed from the time and the local host number as described in
14737 section &<<SECTmessiden>>&.
14741 .option log_file_path main "string list&!!" "set at compile time"
14742 .cindex "log" "file path for"
14743 This option sets the path which is used to determine the names of Exim's log
14744 files, or indicates that logging is to be to syslog, or both. It is expanded
14745 when Exim is entered, so it can, for example, contain a reference to the host
14746 name. If no specific path is set for the log files at compile or run time, they
14747 are written in a sub-directory called &_log_& in Exim's spool directory.
14748 Chapter &<<CHAPlog>>& contains further details about Exim's logging, and
14749 section &<<SECTwhelogwri>>& describes how the contents of &%log_file_path%& are
14750 used. If this string is fixed at your installation (contains no expansion
14751 variables) it is recommended that you do not set this option in the
14752 configuration file, but instead supply the path using LOG_FILE_PATH in
14753 &_Local/Makefile_& so that it is available to Exim for logging errors detected
14754 early on &-- in particular, failure to read the configuration file.
14757 .option log_selector main string unset
14758 .cindex "log" "selectors"
14759 This option can be used to reduce or increase the number of things that Exim
14760 writes to its log files. Its argument is made up of names preceded by plus or
14761 minus characters. For example:
14763 log_selector = +arguments -retry_defer
14765 A list of possible names and what they control is given in the chapter on
14766 logging, in section &<<SECTlogselector>>&.
14769 .option log_timezone main boolean false
14770 .cindex "log" "timezone for entries"
14771 .vindex "&$tod_log$&"
14772 .vindex "&$tod_zone$&"
14773 By default, the timestamps on log lines are in local time without the
14774 timezone. This means that if your timezone changes twice a year, the timestamps
14775 in log lines are ambiguous for an hour when the clocks go back. One way of
14776 avoiding this problem is to set the timezone to UTC. An alternative is to set
14777 &%log_timezone%& true. This turns on the addition of the timezone offset to
14778 timestamps in log lines. Turning on this option can add quite a lot to the size
14779 of log files because each line is extended by 6 characters. Note that the
14780 &$tod_log$& variable contains the log timestamp without the zone, but there is
14781 another variable called &$tod_zone$& that contains just the timezone offset.
14784 .option lookup_open_max main integer 25
14785 .cindex "too many open files"
14786 .cindex "open files, too many"
14787 .cindex "file" "too many open"
14788 .cindex "lookup" "maximum open files"
14789 .cindex "limit" "open files for lookups"
14790 This option limits the number of simultaneously open files for single-key
14791 lookups that use regular files (that is, &(lsearch)&, &(dbm)&, and &(cdb)&).
14792 Exim normally keeps these files open during routing, because often the same
14793 file is required several times. If the limit is reached, Exim closes the least
14794 recently used file. Note that if you are using the &'ndbm'& library, it
14795 actually opens two files for each logical DBM database, though it still counts
14796 as one for the purposes of &%lookup_open_max%&. If you are getting &"too many
14797 open files"& errors with NDBM, you need to reduce the value of
14798 &%lookup_open_max%&.
14801 .option max_username_length main integer 0
14802 .cindex "length of login name"
14803 .cindex "user name" "maximum length"
14804 .cindex "limit" "user name length"
14805 Some operating systems are broken in that they truncate long arguments to
14806 &[getpwnam()]& to eight characters, instead of returning &"no such user"&. If
14807 this option is set greater than zero, any attempt to call &[getpwnam()]& with
14808 an argument that is longer behaves as if &[getpwnam()]& failed.
14811 .option message_body_newlines main bool false
14812 .cindex "message body" "newlines in variables"
14813 .cindex "newline" "in message body variables"
14814 .vindex "&$message_body$&"
14815 .vindex "&$message_body_end$&"
14816 By default, newlines in the message body are replaced by spaces when setting
14817 the &$message_body$& and &$message_body_end$& expansion variables. If this
14818 option is set true, this no longer happens.
14821 .option message_body_visible main integer 500
14822 .cindex "body of message" "visible size"
14823 .cindex "message body" "visible size"
14824 .vindex "&$message_body$&"
14825 .vindex "&$message_body_end$&"
14826 This option specifies how much of a message's body is to be included in the
14827 &$message_body$& and &$message_body_end$& expansion variables.
14830 .option message_id_header_domain main string&!! unset
14831 .cindex "&'Message-ID:'& header line"
14832 If this option is set, the string is expanded and used as the right hand side
14833 (domain) of the &'Message-ID:'& header that Exim creates if a
14834 locally-originated incoming message does not have one. &"Locally-originated"&
14835 means &"not received over TCP/IP."&
14836 Otherwise, the primary host name is used.
14837 Only letters, digits, dot and hyphen are accepted; any other characters are
14838 replaced by hyphens. If the expansion is forced to fail, or if the result is an
14839 empty string, the option is ignored.
14842 .option message_id_header_text main string&!! unset
14843 If this variable is set, the string is expanded and used to augment the text of
14844 the &'Message-id:'& header that Exim creates if a locally-originated incoming
14845 message does not have one. The text of this header is required by RFC 2822 to
14846 take the form of an address. By default, Exim uses its internal message id as
14847 the local part, and the primary host name as the domain. If this option is set,
14848 it is expanded, and provided the expansion is not forced to fail, and does not
14849 yield an empty string, the result is inserted into the header immediately
14850 before the @, separated from the internal message id by a dot. Any characters
14851 that are illegal in an address are automatically converted into hyphens. This
14852 means that variables such as &$tod_log$& can be used, because the spaces and
14853 colons will become hyphens.
14856 .option message_logs main boolean true
14857 .cindex "message logs" "disabling"
14858 .cindex "log" "message log; disabling"
14859 If this option is turned off, per-message log files are not created in the
14860 &_msglog_& spool sub-directory. This reduces the amount of disk I/O required by
14861 Exim, by reducing the number of files involved in handling a message from a
14862 minimum of four (header spool file, body spool file, delivery journal, and
14863 per-message log) to three. The other major I/O activity is Exim's main log,
14864 which is not affected by this option.
14867 .option message_size_limit main string&!! 50M
14868 .cindex "message" "size limit"
14869 .cindex "limit" "message size"
14870 .cindex "size" "of message, limit"
14871 This option limits the maximum size of message that Exim will process. The
14872 value is expanded for each incoming connection so, for example, it can be made
14873 to depend on the IP address of the remote host for messages arriving via
14874 TCP/IP. After expansion, the value must be a sequence of decimal digits,
14875 optionally followed by K or M.
14877 &*Note*&: This limit cannot be made to depend on a message's sender or any
14878 other properties of an individual message, because it has to be advertised in
14879 the server's response to EHLO. String expansion failure causes a temporary
14880 error. A value of zero means no limit, but its use is not recommended. See also
14881 &%bounce_return_size_limit%&.
14883 Incoming SMTP messages are failed with a 552 error if the limit is
14884 exceeded; locally-generated messages either get a stderr message or a delivery
14885 failure message to the sender, depending on the &%-oe%& setting. Rejection of
14886 an oversized message is logged in both the main and the reject logs. See also
14887 the generic transport option &%message_size_limit%&, which limits the size of
14888 message that an individual transport can process.
14890 If you use a virus-scanner and set this option to to a value larger than the
14891 maximum size that your virus-scanner is configured to support, you may get
14892 failures triggered by large mails. The right size to configure for the
14893 virus-scanner depends upon what data is passed and the options in use but it's
14894 probably safest to just set it to a little larger than this value. Eg, with a
14895 default Exim message size of 50M and a default ClamAV StreamMaxLength of 10M,
14896 some problems may result.
14898 A value of 0 will disable size limit checking; Exim will still advertise the
14899 SIZE extension in an EHLO response, but without a limit, so as to permit
14900 SMTP clients to still indicate the message size along with the MAIL verb.
14903 .option move_frozen_messages main boolean false
14904 .cindex "frozen messages" "moving"
14905 This option, which is available only if Exim has been built with the setting
14907 SUPPORT_MOVE_FROZEN_MESSAGES=yes
14909 in &_Local/Makefile_&, causes frozen messages and their message logs to be
14910 moved from the &_input_& and &_msglog_& directories on the spool to &_Finput_&
14911 and &_Fmsglog_&, respectively. There is currently no support in Exim or the
14912 standard utilities for handling such moved messages, and they do not show up in
14913 lists generated by &%-bp%& or by the Exim monitor.
14916 .option mua_wrapper main boolean false
14917 Setting this option true causes Exim to run in a very restrictive mode in which
14918 it passes messages synchronously to a smart host. Chapter &<<CHAPnonqueueing>>&
14919 contains a full description of this facility.
14923 .option mysql_servers main "string list" unset
14924 .cindex "MySQL" "server list"
14925 This option provides a list of MySQL servers and associated connection data, to
14926 be used in conjunction with &(mysql)& lookups (see section &<<SECID72>>&). The
14927 option is available only if Exim has been built with MySQL support.
14930 .option never_users main "string list&!!" unset
14931 This option is expanded just once, at the start of Exim's processing. Local
14932 message deliveries are normally run in processes that are setuid to the
14933 recipient, and remote deliveries are normally run under Exim's own uid and gid.
14934 It is usually desirable to prevent any deliveries from running as root, as a
14937 When Exim is built, an option called FIXED_NEVER_USERS can be set to a
14938 list of users that must not be used for local deliveries. This list is fixed in
14939 the binary and cannot be overridden by the configuration file. By default, it
14940 contains just the single user name &"root"&. The &%never_users%& runtime option
14941 can be used to add more users to the fixed list.
14943 If a message is to be delivered as one of the users on the fixed list or the
14944 &%never_users%& list, an error occurs, and delivery is deferred. A common
14947 never_users = root:daemon:bin
14949 Including root is redundant if it is also on the fixed list, but it does no
14950 harm. This option overrides the &%pipe_as_creator%& option of the &(pipe)&
14954 .option openssl_options main "string list" "+no_sslv2"
14955 .cindex "OpenSSL "compatibility options"
14956 This option allows an administrator to adjust the SSL options applied
14957 by OpenSSL to connections. It is given as a space-separated list of items,
14958 each one to be +added or -subtracted from the current value.
14960 This option is only available if Exim is built against OpenSSL. The values
14961 available for this option vary according to the age of your OpenSSL install.
14962 The &"all"& value controls a subset of flags which are available, typically
14963 the bug workaround options. The &'SSL_CTX_set_options'& man page will
14964 list the values known on your system and Exim should support all the
14965 &"bug workaround"& options and many of the &"modifying"& options. The Exim
14966 names lose the leading &"SSL_OP_"& and are lower-cased.
14968 Note that adjusting the options can have severe impact upon the security of
14969 SSL as used by Exim. It is possible to disable safety checks and shoot
14970 yourself in the foot in various unpleasant ways. This option should not be
14971 adjusted lightly. An unrecognised item will be detected at startup, by
14972 invoking Exim with the &%-bV%& flag.
14974 Historical note: prior to release 4.80, Exim defaulted this value to
14975 "+dont_insert_empty_fragments", which may still be needed for compatibility
14976 with some clients, but which lowers security by increasing exposure to
14977 some now infamous attacks.
14981 # Make both old MS and old Eudora happy:
14982 openssl_options = -all +microsoft_big_sslv3_buffer \
14983 +dont_insert_empty_fragments
14986 Possible options may include:
14990 &`allow_unsafe_legacy_renegotiation`&
14992 &`cipher_server_preference`&
14994 &`dont_insert_empty_fragments`&
14998 &`legacy_server_connect`&
15000 &`microsoft_big_sslv3_buffer`&
15002 &`microsoft_sess_id_bug`&
15004 &`msie_sslv2_rsa_padding`&
15006 &`netscape_challenge_bug`&
15008 &`netscape_reuse_cipher_change_bug`&
15012 &`no_session_resumption_on_renegotiation`&
15026 &`safari_ecdhe_ecdsa_bug`&
15030 &`single_ecdh_use`&
15032 &`ssleay_080_client_dh_bug`&
15034 &`sslref2_reuse_cert_type_bug`&
15036 &`tls_block_padding_bug`&
15040 &`tls_rollback_bug`&
15043 As an aside, the &`safari_ecdhe_ecdsa_bug`& item is a misnomer and affects
15044 all clients connecting using the MacOS SecureTransport TLS facility prior
15045 to MacOS 10.8.4, including email clients. If you see old MacOS clients failing
15046 to negotiate TLS then this option value might help, provided that your OpenSSL
15047 release is new enough to contain this work-around. This may be a situation
15048 where you have to upgrade OpenSSL to get buggy clients working.
15051 .option oracle_servers main "string list" unset
15052 .cindex "Oracle" "server list"
15053 This option provides a list of Oracle servers and associated connection data,
15054 to be used in conjunction with &(oracle)& lookups (see section &<<SECID72>>&).
15055 The option is available only if Exim has been built with Oracle support.
15058 .option percent_hack_domains main "domain list&!!" unset
15059 .cindex "&""percent hack""&"
15060 .cindex "source routing" "in email address"
15061 .cindex "address" "source-routed"
15062 The &"percent hack"& is the convention whereby a local part containing a
15063 percent sign is re-interpreted as a new email address, with the percent
15064 replaced by @. This is sometimes called &"source routing"&, though that term is
15065 also applied to RFC 2822 addresses that begin with an @ character. If this
15066 option is set, Exim implements the percent facility for those domains listed,
15067 but no others. This happens before an incoming SMTP address is tested against
15070 &*Warning*&: The &"percent hack"& has often been abused by people who are
15071 trying to get round relaying restrictions. For this reason, it is best avoided
15072 if at all possible. Unfortunately, a number of less security-conscious MTAs
15073 implement it unconditionally. If you are running Exim on a gateway host, and
15074 routing mail through to internal MTAs without processing the local parts, it is
15075 a good idea to reject recipient addresses with percent characters in their
15076 local parts. Exim's default configuration does this.
15079 .option perl_at_start main boolean false
15080 This option is available only when Exim is built with an embedded Perl
15081 interpreter. See chapter &<<CHAPperl>>& for details of its use.
15084 .option perl_startup main string unset
15085 This option is available only when Exim is built with an embedded Perl
15086 interpreter. See chapter &<<CHAPperl>>& for details of its use.
15089 .option pgsql_servers main "string list" unset
15090 .cindex "PostgreSQL lookup type" "server list"
15091 This option provides a list of PostgreSQL servers and associated connection
15092 data, to be used in conjunction with &(pgsql)& lookups (see section
15093 &<<SECID72>>&). The option is available only if Exim has been built with
15094 PostgreSQL support.
15097 .option pid_file_path main string&!! "set at compile time"
15098 .cindex "daemon" "pid file path"
15099 .cindex "pid file, path for"
15100 This option sets the name of the file to which the Exim daemon writes its
15101 process id. The string is expanded, so it can contain, for example, references
15104 pid_file_path = /var/log/$primary_hostname/exim.pid
15106 If no path is set, the pid is written to the file &_exim-daemon.pid_& in Exim's
15108 The value set by the option can be overridden by the &%-oP%& command line
15109 option. A pid file is not written if a &"non-standard"& daemon is run by means
15110 of the &%-oX%& option, unless a path is explicitly supplied by &%-oP%&.
15113 .option pipelining_advertise_hosts main "host list&!!" *
15114 .cindex "PIPELINING" "suppressing advertising"
15115 This option can be used to suppress the advertisement of the SMTP
15116 PIPELINING extension to specific hosts. See also the &*no_pipelining*&
15117 control in section &<<SECTcontrols>>&. When PIPELINING is not advertised and
15118 &%smtp_enforce_sync%& is true, an Exim server enforces strict synchronization
15119 for each SMTP command and response. When PIPELINING is advertised, Exim assumes
15120 that clients will use it; &"out of order"& commands that are &"expected"& do
15121 not count as protocol errors (see &%smtp_max_synprot_errors%&).
15124 .option prdr_enable main boolean false
15125 .cindex "PRDR" "enabling on server"
15126 This option can be used to enable the Per-Recipient Data Response extension
15127 to SMTP, defined by Eric Hall.
15128 If the option is set, PRDR is advertised by Exim when operating as a server.
15129 If the client requests PRDR, and more than one recipient, for a message
15130 an additional ACL is called for each recipient after the message content
15131 is recieved. See section &<<SECTPRDRACL>>&.
15133 .option preserve_message_logs main boolean false
15134 .cindex "message logs" "preserving"
15135 If this option is set, message log files are not deleted when messages are
15136 completed. Instead, they are moved to a sub-directory of the spool directory
15137 called &_msglog.OLD_&, where they remain available for statistical or debugging
15138 purposes. This is a dangerous option to set on systems with any appreciable
15139 volume of mail. Use with care!
15142 .option primary_hostname main string "see below"
15143 .cindex "name" "of local host"
15144 .cindex "host" "name of local"
15145 .cindex "local host" "name of"
15146 .vindex "&$primary_hostname$&"
15147 This specifies the name of the current host. It is used in the default EHLO or
15148 HELO command for outgoing SMTP messages (changeable via the &%helo_data%&
15149 option in the &(smtp)& transport), and as the default for &%qualify_domain%&.
15150 The value is also used by default in some SMTP response messages from an Exim
15151 server. This can be changed dynamically by setting &%smtp_active_hostname%&.
15153 If &%primary_hostname%& is not set, Exim calls &[uname()]& to find the host
15154 name. If this fails, Exim panics and dies. If the name returned by &[uname()]&
15155 contains only one component, Exim passes it to &[gethostbyname()]& (or
15156 &[getipnodebyname()]& when available) in order to obtain the fully qualified
15157 version. The variable &$primary_hostname$& contains the host name, whether set
15158 explicitly by this option, or defaulted.
15161 .option print_topbitchars main boolean false
15162 .cindex "printing characters"
15163 .cindex "8-bit characters"
15164 By default, Exim considers only those characters whose codes lie in the range
15165 32&--126 to be printing characters. In a number of circumstances (for example,
15166 when writing log entries) non-printing characters are converted into escape
15167 sequences, primarily to avoid messing up the layout. If &%print_topbitchars%&
15168 is set, code values of 128 and above are also considered to be printing
15171 This option also affects the header syntax checks performed by the
15172 &(autoreply)& transport, and whether Exim uses RFC 2047 encoding of
15173 the user's full name when constructing From: and Sender: addresses (as
15174 described in section &<<SECTconstr>>&). Setting this option can cause
15175 Exim to generate eight bit message headers that do not conform to the
15179 .option process_log_path main string unset
15180 .cindex "process log path"
15181 .cindex "log" "process log"
15182 .cindex "&'exiwhat'&"
15183 This option sets the name of the file to which an Exim process writes its
15184 &"process log"& when sent a USR1 signal. This is used by the &'exiwhat'&
15185 utility script. If this option is unset, the file called &_exim-process.info_&
15186 in Exim's spool directory is used. The ability to specify the name explicitly
15187 can be useful in environments where two different Exims are running, using
15188 different spool directories.
15191 .option prod_requires_admin main boolean true
15195 The &%-M%&, &%-R%&, and &%-q%& command-line options require the caller to be an
15196 admin user unless &%prod_requires_admin%& is set false. See also
15197 &%queue_list_requires_admin%&.
15200 .option qualify_domain main string "see below"
15201 .cindex "domain" "for qualifying addresses"
15202 .cindex "address" "qualification"
15203 This option specifies the domain name that is added to any envelope sender
15204 addresses that do not have a domain qualification. It also applies to
15205 recipient addresses if &%qualify_recipient%& is not set. Unqualified addresses
15206 are accepted by default only for locally-generated messages. Qualification is
15207 also applied to addresses in header lines such as &'From:'& and &'To:'& for
15208 locally-generated messages, unless the &%-bnq%& command line option is used.
15210 Messages from external sources must always contain fully qualified addresses,
15211 unless the sending host matches &%sender_unqualified_hosts%& or
15212 &%recipient_unqualified_hosts%& (as appropriate), in which case incoming
15213 addresses are qualified with &%qualify_domain%& or &%qualify_recipient%& as
15214 necessary. Internally, Exim always works with fully qualified envelope
15215 addresses. If &%qualify_domain%& is not set, it defaults to the
15216 &%primary_hostname%& value.
15219 .option qualify_recipient main string "see below"
15220 This option allows you to specify a different domain for qualifying recipient
15221 addresses to the one that is used for senders. See &%qualify_domain%& above.
15225 .option queue_domains main "domain list&!!" unset
15226 .cindex "domain" "specifying non-immediate delivery"
15227 .cindex "queueing incoming messages"
15228 .cindex "message" "queueing certain domains"
15229 This option lists domains for which immediate delivery is not required.
15230 A delivery process is started whenever a message is received, but only those
15231 domains that do not match are processed. All other deliveries wait until the
15232 next queue run. See also &%hold_domains%& and &%queue_smtp_domains%&.
15235 .option queue_list_requires_admin main boolean true
15237 The &%-bp%& command-line option, which lists the messages that are on the
15238 queue, requires the caller to be an admin user unless
15239 &%queue_list_requires_admin%& is set false. See also &%prod_requires_admin%&.
15242 .option queue_only main boolean false
15243 .cindex "queueing incoming messages"
15244 .cindex "message" "queueing unconditionally"
15245 If &%queue_only%& is set, a delivery process is not automatically started
15246 whenever a message is received. Instead, the message waits on the queue for the
15247 next queue run. Even if &%queue_only%& is false, incoming messages may not get
15248 delivered immediately when certain conditions (such as heavy load) occur.
15250 The &%-odq%& command line has the same effect as &%queue_only%&. The &%-odb%&
15251 and &%-odi%& command line options override &%queue_only%& unless
15252 &%queue_only_override%& is set false. See also &%queue_only_file%&,
15253 &%queue_only_load%&, and &%smtp_accept_queue%&.
15256 .option queue_only_file main string unset
15257 .cindex "queueing incoming messages"
15258 .cindex "message" "queueing by file existence"
15259 This option can be set to a colon-separated list of absolute path names, each
15260 one optionally preceded by &"smtp"&. When Exim is receiving a message,
15261 it tests for the existence of each listed path using a call to &[stat()]&. For
15262 each path that exists, the corresponding queueing option is set.
15263 For paths with no prefix, &%queue_only%& is set; for paths prefixed by
15264 &"smtp"&, &%queue_smtp_domains%& is set to match all domains. So, for example,
15266 queue_only_file = smtp/some/file
15268 causes Exim to behave as if &%queue_smtp_domains%& were set to &"*"& whenever
15269 &_/some/file_& exists.
15272 .option queue_only_load main fixed-point unset
15273 .cindex "load average"
15274 .cindex "queueing incoming messages"
15275 .cindex "message" "queueing by load"
15276 If the system load average is higher than this value, incoming messages from
15277 all sources are queued, and no automatic deliveries are started. If this
15278 happens during local or remote SMTP input, all subsequent messages received on
15279 the same SMTP connection are queued by default, whatever happens to the load in
15280 the meantime, but this can be changed by setting &%queue_only_load_latch%&
15283 Deliveries will subsequently be performed by queue runner processes. This
15284 option has no effect on ancient operating systems on which Exim cannot
15285 determine the load average. See also &%deliver_queue_load_max%& and
15286 &%smtp_load_reserve%&.
15289 .option queue_only_load_latch main boolean true
15290 .cindex "load average" "re-evaluating per message"
15291 When this option is true (the default), once one message has been queued
15292 because the load average is higher than the value set by &%queue_only_load%&,
15293 all subsequent messages received on the same SMTP connection are also queued.
15294 This is a deliberate choice; even though the load average may fall below the
15295 threshold, it doesn't seem right to deliver later messages on the same
15296 connection when not delivering earlier ones. However, there are special
15297 circumstances such as very long-lived connections from scanning appliances
15298 where this is not the best strategy. In such cases, &%queue_only_load_latch%&
15299 should be set false. This causes the value of the load average to be
15300 re-evaluated for each message.
15303 .option queue_only_override main boolean true
15304 .cindex "queueing incoming messages"
15305 When this option is true, the &%-od%&&'x'& command line options override the
15306 setting of &%queue_only%& or &%queue_only_file%& in the configuration file. If
15307 &%queue_only_override%& is set false, the &%-od%&&'x'& options cannot be used
15308 to override; they are accepted, but ignored.
15311 .option queue_run_in_order main boolean false
15312 .cindex "queue runner" "processing messages in order"
15313 If this option is set, queue runs happen in order of message arrival instead of
15314 in an arbitrary order. For this to happen, a complete list of the entire queue
15315 must be set up before the deliveries start. When the queue is all held in a
15316 single directory (the default), a single list is created for both the ordered
15317 and the non-ordered cases. However, if &%split_spool_directory%& is set, a
15318 single list is not created when &%queue_run_in_order%& is false. In this case,
15319 the sub-directories are processed one at a time (in a random order), and this
15320 avoids setting up one huge list for the whole queue. Thus, setting
15321 &%queue_run_in_order%& with &%split_spool_directory%& may degrade performance
15322 when the queue is large, because of the extra work in setting up the single,
15323 large list. In most situations, &%queue_run_in_order%& should not be set.
15327 .option queue_run_max main integer 5
15328 .cindex "queue runner" "maximum number of"
15329 This controls the maximum number of queue runner processes that an Exim daemon
15330 can run simultaneously. This does not mean that it starts them all at once,
15331 but rather that if the maximum number are still running when the time comes to
15332 start another one, it refrains from starting another one. This can happen with
15333 very large queues and/or very sluggish deliveries. This option does not,
15334 however, interlock with other processes, so additional queue runners can be
15335 started by other means, or by killing and restarting the daemon.
15337 Setting this option to zero does not suppress queue runs; rather, it disables
15338 the limit, allowing any number of simultaneous queue runner processes to be
15339 run. If you do not want queue runs to occur, omit the &%-q%&&'xx'& setting on
15340 the daemon's command line.
15342 .option queue_smtp_domains main "domain list&!!" unset
15343 .cindex "queueing incoming messages"
15344 .cindex "message" "queueing remote deliveries"
15345 When this option is set, a delivery process is started whenever a message is
15346 received, routing is performed, and local deliveries take place.
15347 However, if any SMTP deliveries are required for domains that match
15348 &%queue_smtp_domains%&, they are not immediately delivered, but instead the
15349 message waits on the queue for the next queue run. Since routing of the message
15350 has taken place, Exim knows to which remote hosts it must be delivered, and so
15351 when the queue run happens, multiple messages for the same host are delivered
15352 over a single SMTP connection. The &%-odqs%& command line option causes all
15353 SMTP deliveries to be queued in this way, and is equivalent to setting
15354 &%queue_smtp_domains%& to &"*"&. See also &%hold_domains%& and
15358 .option receive_timeout main time 0s
15359 .cindex "timeout" "for non-SMTP input"
15360 This option sets the timeout for accepting a non-SMTP message, that is, the
15361 maximum time that Exim waits when reading a message on the standard input. If
15362 the value is zero, it will wait for ever. This setting is overridden by the
15363 &%-or%& command line option. The timeout for incoming SMTP messages is
15364 controlled by &%smtp_receive_timeout%&.
15366 .option received_header_text main string&!! "see below"
15367 .cindex "customizing" "&'Received:'& header"
15368 .cindex "&'Received:'& header line" "customizing"
15369 This string defines the contents of the &'Received:'& message header that is
15370 added to each message, except for the timestamp, which is automatically added
15371 on at the end (preceded by a semicolon). The string is expanded each time it is
15372 used. If the expansion yields an empty string, no &'Received:'& header line is
15373 added to the message. Otherwise, the string should start with the text
15374 &"Received:"& and conform to the RFC 2822 specification for &'Received:'&
15375 header lines. The default setting is:
15378 received_header_text = Received: \
15379 ${if def:sender_rcvhost {from $sender_rcvhost\n\t}\
15380 {${if def:sender_ident \
15381 {from ${quote_local_part:$sender_ident} }}\
15382 ${if def:sender_helo_name {(helo=$sender_helo_name)\n\t}}}}\
15383 by $primary_hostname \
15384 ${if def:received_protocol {with $received_protocol}} \
15385 ${if def:tls_in_cipher {($tls_in_cipher)\n\t}}\
15386 (Exim $version_number)\n\t\
15387 ${if def:sender_address \
15388 {(envelope-from <$sender_address>)\n\t}}\
15389 id $message_exim_id\
15390 ${if def:received_for {\n\tfor $received_for}}
15393 The reference to the TLS cipher is omitted when Exim is built without TLS
15394 support. The use of conditional expansions ensures that this works for both
15395 locally generated messages and messages received from remote hosts, giving
15396 header lines such as the following:
15398 Received: from scrooge.carol.example ([192.168.12.25] ident=root)
15399 by marley.carol.example with esmtp (Exim 4.00)
15400 (envelope-from <bob@carol.example>)
15401 id 16IOWa-00019l-00
15402 for chas@dickens.example; Tue, 25 Dec 2001 14:43:44 +0000
15403 Received: by scrooge.carol.example with local (Exim 4.00)
15404 id 16IOWW-000083-00; Tue, 25 Dec 2001 14:43:41 +0000
15406 Until the body of the message has been received, the timestamp is the time when
15407 the message started to be received. Once the body has arrived, and all policy
15408 checks have taken place, the timestamp is updated to the time at which the
15409 message was accepted.
15412 .option received_headers_max main integer 30
15413 .cindex "loop" "prevention"
15414 .cindex "mail loop prevention"
15415 .cindex "&'Received:'& header line" "counting"
15416 When a message is to be delivered, the number of &'Received:'& headers is
15417 counted, and if it is greater than this parameter, a mail loop is assumed to
15418 have occurred, the delivery is abandoned, and an error message is generated.
15419 This applies to both local and remote deliveries.
15422 .option recipient_unqualified_hosts main "host list&!!" unset
15423 .cindex "unqualified addresses"
15424 .cindex "host" "unqualified addresses from"
15425 This option lists those hosts from which Exim is prepared to accept unqualified
15426 recipient addresses in message envelopes. The addresses are made fully
15427 qualified by the addition of the &%qualify_recipient%& value. This option also
15428 affects message header lines. Exim does not reject unqualified recipient
15429 addresses in headers, but it qualifies them only if the message came from a
15430 host that matches &%recipient_unqualified_hosts%&,
15431 or if the message was submitted locally (not using TCP/IP), and the &%-bnq%&
15432 option was not set.
15435 .option recipients_max main integer 0
15436 .cindex "limit" "number of recipients"
15437 .cindex "recipient" "maximum number"
15438 If this option is set greater than zero, it specifies the maximum number of
15439 original recipients for any message. Additional recipients that are generated
15440 by aliasing or forwarding do not count. SMTP messages get a 452 response for
15441 all recipients over the limit; earlier recipients are delivered as normal.
15442 Non-SMTP messages with too many recipients are failed, and no deliveries are
15445 .cindex "RCPT" "maximum number of incoming"
15446 &*Note*&: The RFCs specify that an SMTP server should accept at least 100
15447 RCPT commands in a single message.
15450 .option recipients_max_reject main boolean false
15451 If this option is set true, Exim rejects SMTP messages containing too many
15452 recipients by giving 552 errors to the surplus RCPT commands, and a 554
15453 error to the eventual DATA command. Otherwise (the default) it gives a 452
15454 error to the surplus RCPT commands and accepts the message on behalf of the
15455 initial set of recipients. The remote server should then re-send the message
15456 for the remaining recipients at a later time.
15459 .option remote_max_parallel main integer 2
15460 .cindex "delivery" "parallelism for remote"
15461 This option controls parallel delivery of one message to a number of remote
15462 hosts. If the value is less than 2, parallel delivery is disabled, and Exim
15463 does all the remote deliveries for a message one by one. Otherwise, if a single
15464 message has to be delivered to more than one remote host, or if several copies
15465 have to be sent to the same remote host, up to &%remote_max_parallel%&
15466 deliveries are done simultaneously. If more than &%remote_max_parallel%&
15467 deliveries are required, the maximum number of processes are started, and as
15468 each one finishes, another is begun. The order of starting processes is the
15469 same as if sequential delivery were being done, and can be controlled by the
15470 &%remote_sort_domains%& option. If parallel delivery takes place while running
15471 with debugging turned on, the debugging output from each delivery process is
15472 tagged with its process id.
15474 This option controls only the maximum number of parallel deliveries for one
15475 message in one Exim delivery process. Because Exim has no central queue
15476 manager, there is no way of controlling the total number of simultaneous
15477 deliveries if the configuration allows a delivery attempt as soon as a message
15480 .cindex "number of deliveries"
15481 .cindex "delivery" "maximum number of"
15482 If you want to control the total number of deliveries on the system, you
15483 need to set the &%queue_only%& option. This ensures that all incoming messages
15484 are added to the queue without starting a delivery process. Then set up an Exim
15485 daemon to start queue runner processes at appropriate intervals (probably
15486 fairly often, for example, every minute), and limit the total number of queue
15487 runners by setting the &%queue_run_max%& parameter. Because each queue runner
15488 delivers only one message at a time, the maximum number of deliveries that can
15489 then take place at once is &%queue_run_max%& multiplied by
15490 &%remote_max_parallel%&.
15492 If it is purely remote deliveries you want to control, use
15493 &%queue_smtp_domains%& instead of &%queue_only%&. This has the added benefit of
15494 doing the SMTP routing before queueing, so that several messages for the same
15495 host will eventually get delivered down the same connection.
15498 .option remote_sort_domains main "domain list&!!" unset
15499 .cindex "sorting remote deliveries"
15500 .cindex "delivery" "sorting remote"
15501 When there are a number of remote deliveries for a message, they are sorted by
15502 domain into the order given by this list. For example,
15504 remote_sort_domains = *.cam.ac.uk:*.uk
15506 would attempt to deliver to all addresses in the &'cam.ac.uk'& domain first,
15507 then to those in the &%uk%& domain, then to any others.
15510 .option retry_data_expire main time 7d
15511 .cindex "hints database" "data expiry"
15512 This option sets a &"use before"& time on retry information in Exim's hints
15513 database. Any older retry data is ignored. This means that, for example, once a
15514 host has not been tried for 7 days, Exim behaves as if it has no knowledge of
15518 .option retry_interval_max main time 24h
15519 .cindex "retry" "limit on interval"
15520 .cindex "limit" "on retry interval"
15521 Chapter &<<CHAPretry>>& describes Exim's mechanisms for controlling the
15522 intervals between delivery attempts for messages that cannot be delivered
15523 straight away. This option sets an overall limit to the length of time between
15524 retries. It cannot be set greater than 24 hours; any attempt to do so forces
15528 .option return_path_remove main boolean true
15529 .cindex "&'Return-path:'& header line" "removing"
15530 RFC 2821, section 4.4, states that an SMTP server must insert a
15531 &'Return-path:'& header line into a message when it makes a &"final delivery"&.
15532 The &'Return-path:'& header preserves the sender address as received in the
15533 MAIL command. This description implies that this header should not be present
15534 in an incoming message. If &%return_path_remove%& is true, any existing
15535 &'Return-path:'& headers are removed from messages at the time they are
15536 received. Exim's transports have options for adding &'Return-path:'& headers at
15537 the time of delivery. They are normally used only for final local deliveries.
15540 .option return_size_limit main integer 100K
15541 This option is an obsolete synonym for &%bounce_return_size_limit%&.
15544 .option rfc1413_hosts main "host list&!!" *
15546 .cindex "host" "for RFC 1413 calls"
15547 RFC 1413 identification calls are made to any client host which matches an item
15550 .option rfc1413_query_timeout main time 5s
15551 .cindex "RFC 1413" "query timeout"
15552 .cindex "timeout" "for RFC 1413 call"
15553 This sets the timeout on RFC 1413 identification calls. If it is set to zero,
15554 no RFC 1413 calls are ever made.
15557 .option sender_unqualified_hosts main "host list&!!" unset
15558 .cindex "unqualified addresses"
15559 .cindex "host" "unqualified addresses from"
15560 This option lists those hosts from which Exim is prepared to accept unqualified
15561 sender addresses. The addresses are made fully qualified by the addition of
15562 &%qualify_domain%&. This option also affects message header lines. Exim does
15563 not reject unqualified addresses in headers that contain sender addresses, but
15564 it qualifies them only if the message came from a host that matches
15565 &%sender_unqualified_hosts%&, or if the message was submitted locally (not
15566 using TCP/IP), and the &%-bnq%& option was not set.
15569 .option smtp_accept_keepalive main boolean true
15570 .cindex "keepalive" "on incoming connection"
15571 This option controls the setting of the SO_KEEPALIVE option on incoming
15572 TCP/IP socket connections. When set, it causes the kernel to probe idle
15573 connections periodically, by sending packets with &"old"& sequence numbers. The
15574 other end of the connection should send an acknowledgment if the connection is
15575 still okay or a reset if the connection has been aborted. The reason for doing
15576 this is that it has the beneficial effect of freeing up certain types of
15577 connection that can get stuck when the remote host is disconnected without
15578 tidying up the TCP/IP call properly. The keepalive mechanism takes several
15579 hours to detect unreachable hosts.
15583 .option smtp_accept_max main integer 20
15584 .cindex "limit" "incoming SMTP connections"
15585 .cindex "SMTP" "incoming connection count"
15587 This option specifies the maximum number of simultaneous incoming SMTP calls
15588 that Exim will accept. It applies only to the listening daemon; there is no
15589 control (in Exim) when incoming SMTP is being handled by &'inetd'&. If the
15590 value is set to zero, no limit is applied. However, it is required to be
15591 non-zero if either &%smtp_accept_max_per_host%& or &%smtp_accept_queue%& is
15592 set. See also &%smtp_accept_reserve%& and &%smtp_load_reserve%&.
15594 A new SMTP connection is immediately rejected if the &%smtp_accept_max%& limit
15595 has been reached. If not, Exim first checks &%smtp_accept_max_per_host%&. If
15596 that limit has not been reached for the client host, &%smtp_accept_reserve%&
15597 and &%smtp_load_reserve%& are then checked before accepting the connection.
15600 .option smtp_accept_max_nonmail main integer 10
15601 .cindex "limit" "non-mail SMTP commands"
15602 .cindex "SMTP" "limiting non-mail commands"
15603 Exim counts the number of &"non-mail"& commands in an SMTP session, and drops
15604 the connection if there are too many. This option defines &"too many"&. The
15605 check catches some denial-of-service attacks, repeated failing AUTHs, or a mad
15606 client looping sending EHLO, for example. The check is applied only if the
15607 client host matches &%smtp_accept_max_nonmail_hosts%&.
15609 When a new message is expected, one occurrence of RSET is not counted. This
15610 allows a client to send one RSET between messages (this is not necessary,
15611 but some clients do it). Exim also allows one uncounted occurrence of HELO
15612 or EHLO, and one occurrence of STARTTLS between messages. After
15613 starting up a TLS session, another EHLO is expected, and so it too is not
15614 counted. The first occurrence of AUTH in a connection, or immediately
15615 following STARTTLS is not counted. Otherwise, all commands other than
15616 MAIL, RCPT, DATA, and QUIT are counted.
15619 .option smtp_accept_max_nonmail_hosts main "host list&!!" *
15620 You can control which hosts are subject to the &%smtp_accept_max_nonmail%&
15621 check by setting this option. The default value makes it apply to all hosts. By
15622 changing the value, you can exclude any badly-behaved hosts that you have to
15626 . Allow this long option name to split; give it unsplit as a fifth argument
15627 . for the automatic .oindex that is generated by .option.
15628 . We insert " &~&~" which is both pretty nasty visually and results in
15629 . non-searchable text. HowItWorks.txt mentions an option for inserting
15630 . zero-width-space, which would be nicer visually and results in (at least)
15631 . html that Firefox will split on when it's forced to reflow (rather than
15632 . inserting a horizontal scrollbar). However, the text is still not
15633 . searchable. NM changed this occurrence for bug 1197 to no longer allow
15634 . the option name to split.
15636 .option "smtp_accept_max_per_connection" main integer 1000 &&&
15637 smtp_accept_max_per_connection
15638 .cindex "SMTP" "limiting incoming message count"
15639 .cindex "limit" "messages per SMTP connection"
15640 The value of this option limits the number of MAIL commands that Exim is
15641 prepared to accept over a single SMTP connection, whether or not each command
15642 results in the transfer of a message. After the limit is reached, a 421
15643 response is given to subsequent MAIL commands. This limit is a safety
15644 precaution against a client that goes mad (incidents of this type have been
15648 .option smtp_accept_max_per_host main string&!! unset
15649 .cindex "limit" "SMTP connections from one host"
15650 .cindex "host" "limiting SMTP connections from"
15651 This option restricts the number of simultaneous IP connections from a single
15652 host (strictly, from a single IP address) to the Exim daemon. The option is
15653 expanded, to enable different limits to be applied to different hosts by
15654 reference to &$sender_host_address$&. Once the limit is reached, additional
15655 connection attempts from the same host are rejected with error code 421. This
15656 is entirely independent of &%smtp_accept_reserve%&. The option's default value
15657 of zero imposes no limit. If this option is set greater than zero, it is
15658 required that &%smtp_accept_max%& be non-zero.
15660 &*Warning*&: When setting this option you should not use any expansion
15661 constructions that take an appreciable amount of time. The expansion and test
15662 happen in the main daemon loop, in order to reject additional connections
15663 without forking additional processes (otherwise a denial-of-service attack
15664 could cause a vast number or processes to be created). While the daemon is
15665 doing this processing, it cannot accept any other incoming connections.
15669 .option smtp_accept_queue main integer 0
15670 .cindex "SMTP" "incoming connection count"
15671 .cindex "queueing incoming messages"
15672 .cindex "message" "queueing by SMTP connection count"
15673 If the number of simultaneous incoming SMTP connections being handled via the
15674 listening daemon exceeds this value, messages received by SMTP are just placed
15675 on the queue; no delivery processes are started automatically. The count is
15676 fixed at the start of an SMTP connection. It cannot be updated in the
15677 subprocess that receives messages, and so the queueing or not queueing applies
15678 to all messages received in the same connection.
15680 A value of zero implies no limit, and clearly any non-zero value is useful only
15681 if it is less than the &%smtp_accept_max%& value (unless that is zero). See
15682 also &%queue_only%&, &%queue_only_load%&, &%queue_smtp_domains%&, and the
15683 various &%-od%&&'x'& command line options.
15686 . See the comment on smtp_accept_max_per_connection
15688 .option "smtp_accept_queue_per_connection" main integer 10 &&&
15689 smtp_accept_queue_per_connection
15690 .cindex "queueing incoming messages"
15691 .cindex "message" "queueing by message count"
15692 This option limits the number of delivery processes that Exim starts
15693 automatically when receiving messages via SMTP, whether via the daemon or by
15694 the use of &%-bs%& or &%-bS%&. If the value of the option is greater than zero,
15695 and the number of messages received in a single SMTP session exceeds this
15696 number, subsequent messages are placed on the queue, but no delivery processes
15697 are started. This helps to limit the number of Exim processes when a server
15698 restarts after downtime and there is a lot of mail waiting for it on other
15699 systems. On large systems, the default should probably be increased, and on
15700 dial-in client systems it should probably be set to zero (that is, disabled).
15703 .option smtp_accept_reserve main integer 0
15704 .cindex "SMTP" "incoming call count"
15705 .cindex "host" "reserved"
15706 When &%smtp_accept_max%& is set greater than zero, this option specifies a
15707 number of SMTP connections that are reserved for connections from the hosts
15708 that are specified in &%smtp_reserve_hosts%&. The value set in
15709 &%smtp_accept_max%& includes this reserve pool. The specified hosts are not
15710 restricted to this number of connections; the option specifies a minimum number
15711 of connection slots for them, not a maximum. It is a guarantee that this group
15712 of hosts can always get at least &%smtp_accept_reserve%& connections. However,
15713 the limit specified by &%smtp_accept_max_per_host%& is still applied to each
15716 For example, if &%smtp_accept_max%& is set to 50 and &%smtp_accept_reserve%& is
15717 set to 5, once there are 45 active connections (from any hosts), new
15718 connections are accepted only from hosts listed in &%smtp_reserve_hosts%&,
15719 provided the other criteria for acceptance are met.
15722 .option smtp_active_hostname main string&!! unset
15723 .cindex "host" "name in SMTP responses"
15724 .cindex "SMTP" "host name in responses"
15725 .vindex "&$primary_hostname$&"
15726 This option is provided for multi-homed servers that want to masquerade as
15727 several different hosts. At the start of an incoming SMTP connection, its value
15728 is expanded and used instead of the value of &$primary_hostname$& in SMTP
15729 responses. For example, it is used as domain name in the response to an
15730 incoming HELO or EHLO command.
15732 .vindex "&$smtp_active_hostname$&"
15733 The active hostname is placed in the &$smtp_active_hostname$& variable, which
15734 is saved with any messages that are received. It is therefore available for use
15735 in routers and transports when the message is later delivered.
15737 If this option is unset, or if its expansion is forced to fail, or if the
15738 expansion results in an empty string, the value of &$primary_hostname$& is
15739 used. Other expansion failures cause a message to be written to the main and
15740 panic logs, and the SMTP command receives a temporary error. Typically, the
15741 value of &%smtp_active_hostname%& depends on the incoming interface address.
15744 smtp_active_hostname = ${if eq{$received_ip_address}{10.0.0.1}\
15745 {cox.mydomain}{box.mydomain}}
15748 Although &$smtp_active_hostname$& is primarily concerned with incoming
15749 messages, it is also used as the default for HELO commands in callout
15750 verification if there is no remote transport from which to obtain a
15751 &%helo_data%& value.
15753 .option smtp_banner main string&!! "see below"
15754 .cindex "SMTP" "welcome banner"
15755 .cindex "banner for SMTP"
15756 .cindex "welcome banner for SMTP"
15757 .cindex "customizing" "SMTP banner"
15758 This string, which is expanded every time it is used, is output as the initial
15759 positive response to an SMTP connection. The default setting is:
15761 smtp_banner = $smtp_active_hostname ESMTP Exim \
15762 $version_number $tod_full
15764 Failure to expand the string causes a panic error. If you want to create a
15765 multiline response to the initial SMTP connection, use &"\n"& in the string at
15766 appropriate points, but not at the end. Note that the 220 code is not included
15767 in this string. Exim adds it automatically (several times in the case of a
15768 multiline response).
15771 .option smtp_check_spool_space main boolean true
15772 .cindex "checking disk space"
15773 .cindex "disk space, checking"
15774 .cindex "spool directory" "checking space"
15775 When this option is set, if an incoming SMTP session encounters the SIZE
15776 option on a MAIL command, it checks that there is enough space in the
15777 spool directory's partition to accept a message of that size, while still
15778 leaving free the amount specified by &%check_spool_space%& (even if that value
15779 is zero). If there isn't enough space, a temporary error code is returned.
15782 .option smtp_connect_backlog main integer 20
15783 .cindex "connection backlog"
15784 .cindex "SMTP" "connection backlog"
15785 .cindex "backlog of connections"
15786 This option specifies a maximum number of waiting SMTP connections. Exim passes
15787 this value to the TCP/IP system when it sets up its listener. Once this number
15788 of connections are waiting for the daemon's attention, subsequent connection
15789 attempts are refused at the TCP/IP level. At least, that is what the manuals
15790 say; in some circumstances such connection attempts have been observed to time
15791 out instead. For large systems it is probably a good idea to increase the
15792 value (to 50, say). It also gives some protection against denial-of-service
15793 attacks by SYN flooding.
15796 .option smtp_enforce_sync main boolean true
15797 .cindex "SMTP" "synchronization checking"
15798 .cindex "synchronization checking in SMTP"
15799 The SMTP protocol specification requires the client to wait for a response from
15800 the server at certain points in the dialogue. Without PIPELINING these
15801 synchronization points are after every command; with PIPELINING they are
15802 fewer, but they still exist.
15804 Some spamming sites send out a complete set of SMTP commands without waiting
15805 for any response. Exim protects against this by rejecting a message if the
15806 client has sent further input when it should not have. The error response &"554
15807 SMTP synchronization error"& is sent, and the connection is dropped. Testing
15808 for this error cannot be perfect because of transmission delays (unexpected
15809 input may be on its way but not yet received when Exim checks). However, it
15810 does detect many instances.
15812 The check can be globally disabled by setting &%smtp_enforce_sync%& false.
15813 If you want to disable the check selectively (for example, only for certain
15814 hosts), you can do so by an appropriate use of a &%control%& modifier in an ACL
15815 (see section &<<SECTcontrols>>&). See also &%pipelining_advertise_hosts%&.
15819 .option smtp_etrn_command main string&!! unset
15820 .cindex "ETRN" "command to be run"
15821 .vindex "&$domain$&"
15822 If this option is set, the given command is run whenever an SMTP ETRN
15823 command is received from a host that is permitted to issue such commands (see
15824 chapter &<<CHAPACL>>&). The string is split up into separate arguments which
15825 are independently expanded. The expansion variable &$domain$& is set to the
15826 argument of the ETRN command, and no syntax checking is done on it. For
15829 smtp_etrn_command = /etc/etrn_command $domain \
15830 $sender_host_address
15832 A new process is created to run the command, but Exim does not wait for it to
15833 complete. Consequently, its status cannot be checked. If the command cannot be
15834 run, a line is written to the panic log, but the ETRN caller still receives
15835 a 250 success response. Exim is normally running under its own uid when
15836 receiving SMTP, so it is not possible for it to change the uid before running
15840 .option smtp_etrn_serialize main boolean true
15841 .cindex "ETRN" "serializing"
15842 When this option is set, it prevents the simultaneous execution of more than
15843 one identical command as a result of ETRN in an SMTP connection. See
15844 section &<<SECTETRN>>& for details.
15847 .option smtp_load_reserve main fixed-point unset
15848 .cindex "load average"
15849 If the system load average ever gets higher than this, incoming SMTP calls are
15850 accepted only from those hosts that match an entry in &%smtp_reserve_hosts%&.
15851 If &%smtp_reserve_hosts%& is not set, no incoming SMTP calls are accepted when
15852 the load is over the limit. The option has no effect on ancient operating
15853 systems on which Exim cannot determine the load average. See also
15854 &%deliver_queue_load_max%& and &%queue_only_load%&.
15858 .option smtp_max_synprot_errors main integer 3
15859 .cindex "SMTP" "limiting syntax and protocol errors"
15860 .cindex "limit" "SMTP syntax and protocol errors"
15861 Exim rejects SMTP commands that contain syntax or protocol errors. In
15862 particular, a syntactically invalid email address, as in this command:
15864 RCPT TO:<abc xyz@a.b.c>
15866 causes immediate rejection of the command, before any other tests are done.
15867 (The ACL cannot be run if there is no valid address to set up for it.) An
15868 example of a protocol error is receiving RCPT before MAIL. If there are
15869 too many syntax or protocol errors in one SMTP session, the connection is
15870 dropped. The limit is set by this option.
15872 .cindex "PIPELINING" "expected errors"
15873 When the PIPELINING extension to SMTP is in use, some protocol errors are
15874 &"expected"&, for instance, a RCPT command after a rejected MAIL command.
15875 Exim assumes that PIPELINING will be used if it advertises it (see
15876 &%pipelining_advertise_hosts%&), and in this situation, &"expected"& errors do
15877 not count towards the limit.
15881 .option smtp_max_unknown_commands main integer 3
15882 .cindex "SMTP" "limiting unknown commands"
15883 .cindex "limit" "unknown SMTP commands"
15884 If there are too many unrecognized commands in an incoming SMTP session, an
15885 Exim server drops the connection. This is a defence against some kinds of abuse
15888 into making connections to SMTP ports; in these circumstances, a number of
15889 non-SMTP command lines are sent first.
15893 .option smtp_ratelimit_hosts main "host list&!!" unset
15894 .cindex "SMTP" "rate limiting"
15895 .cindex "limit" "rate of message arrival"
15896 .cindex "RCPT" "rate limiting"
15897 Some sites find it helpful to be able to limit the rate at which certain hosts
15898 can send them messages, and the rate at which an individual message can specify
15901 Exim has two rate-limiting facilities. This section describes the older
15902 facility, which can limit rates within a single connection. The newer
15903 &%ratelimit%& ACL condition can limit rates across all connections. See section
15904 &<<SECTratelimiting>>& for details of the newer facility.
15906 When a host matches &%smtp_ratelimit_hosts%&, the values of
15907 &%smtp_ratelimit_mail%& and &%smtp_ratelimit_rcpt%& are used to control the
15908 rate of acceptance of MAIL and RCPT commands in a single SMTP session,
15909 respectively. Each option, if set, must contain a set of four comma-separated
15913 A threshold, before which there is no rate limiting.
15915 An initial time delay. Unlike other times in Exim, numbers with decimal
15916 fractional parts are allowed here.
15918 A factor by which to increase the delay each time.
15920 A maximum value for the delay. This should normally be less than 5 minutes,
15921 because after that time, the client is liable to timeout the SMTP command.
15924 For example, these settings have been used successfully at the site which
15925 first suggested this feature, for controlling mail from their customers:
15927 smtp_ratelimit_mail = 2,0.5s,1.05,4m
15928 smtp_ratelimit_rcpt = 4,0.25s,1.015,4m
15930 The first setting specifies delays that are applied to MAIL commands after
15931 two have been received over a single connection. The initial delay is 0.5
15932 seconds, increasing by a factor of 1.05 each time. The second setting applies
15933 delays to RCPT commands when more than four occur in a single message.
15936 .option smtp_ratelimit_mail main string unset
15937 See &%smtp_ratelimit_hosts%& above.
15940 .option smtp_ratelimit_rcpt main string unset
15941 See &%smtp_ratelimit_hosts%& above.
15944 .option smtp_receive_timeout main time 5m
15945 .cindex "timeout" "for SMTP input"
15946 .cindex "SMTP" "input timeout"
15947 This sets a timeout value for SMTP reception. It applies to all forms of SMTP
15948 input, including batch SMTP. If a line of input (either an SMTP command or a
15949 data line) is not received within this time, the SMTP connection is dropped and
15950 the message is abandoned.
15951 A line is written to the log containing one of the following messages:
15953 SMTP command timeout on connection from...
15954 SMTP data timeout on connection from...
15956 The former means that Exim was expecting to read an SMTP command; the latter
15957 means that it was in the DATA phase, reading the contents of a message.
15961 The value set by this option can be overridden by the
15962 &%-os%& command-line option. A setting of zero time disables the timeout, but
15963 this should never be used for SMTP over TCP/IP. (It can be useful in some cases
15964 of local input using &%-bs%& or &%-bS%&.) For non-SMTP input, the reception
15965 timeout is controlled by &%receive_timeout%& and &%-or%&.
15968 .option smtp_reserve_hosts main "host list&!!" unset
15969 This option defines hosts for which SMTP connections are reserved; see
15970 &%smtp_accept_reserve%& and &%smtp_load_reserve%& above.
15973 .option smtp_return_error_details main boolean false
15974 .cindex "SMTP" "details policy failures"
15975 .cindex "policy control" "rejection, returning details"
15976 In the default state, Exim uses bland messages such as
15977 &"Administrative prohibition"& when it rejects SMTP commands for policy
15978 reasons. Many sysadmins like this because it gives away little information
15979 to spammers. However, some other sysadmins who are applying strict checking
15980 policies want to give out much fuller information about failures. Setting
15981 &%smtp_return_error_details%& true causes Exim to be more forthcoming. For
15982 example, instead of &"Administrative prohibition"&, it might give:
15984 550-Rejected after DATA: '>' missing at end of address:
15985 550 failing address in "From" header is: <user@dom.ain
15988 .option spamd_address main string "see below"
15989 This option is available when Exim is compiled with the content-scanning
15990 extension. It specifies how Exim connects to SpamAssassin's &%spamd%& daemon.
15991 The default value is
15995 See section &<<SECTscanspamass>>& for more details.
15999 .option split_spool_directory main boolean false
16000 .cindex "multiple spool directories"
16001 .cindex "spool directory" "split"
16002 .cindex "directories, multiple"
16003 If this option is set, it causes Exim to split its input directory into 62
16004 subdirectories, each with a single alphanumeric character as its name. The
16005 sixth character of the message id is used to allocate messages to
16006 subdirectories; this is the least significant base-62 digit of the time of
16007 arrival of the message.
16009 Splitting up the spool in this way may provide better performance on systems
16010 where there are long mail queues, by reducing the number of files in any one
16011 directory. The msglog directory is also split up in a similar way to the input
16012 directory; however, if &%preserve_message_logs%& is set, all old msglog files
16013 are still placed in the single directory &_msglog.OLD_&.
16015 It is not necessary to take any special action for existing messages when
16016 changing &%split_spool_directory%&. Exim notices messages that are in the
16017 &"wrong"& place, and continues to process them. If the option is turned off
16018 after a period of being on, the subdirectories will eventually empty and be
16019 automatically deleted.
16021 When &%split_spool_directory%& is set, the behaviour of queue runner processes
16022 changes. Instead of creating a list of all messages in the queue, and then
16023 trying to deliver each one in turn, it constructs a list of those in one
16024 sub-directory and tries to deliver them, before moving on to the next
16025 sub-directory. The sub-directories are processed in a random order. This
16026 spreads out the scanning of the input directories, and uses less memory. It is
16027 particularly beneficial when there are lots of messages on the queue. However,
16028 if &%queue_run_in_order%& is set, none of this new processing happens. The
16029 entire queue has to be scanned and sorted before any deliveries can start.
16032 .option spool_directory main string&!! "set at compile time"
16033 .cindex "spool directory" "path to"
16034 This defines the directory in which Exim keeps its spool, that is, the messages
16035 it is waiting to deliver. The default value is taken from the compile-time
16036 configuration setting, if there is one. If not, this option must be set. The
16037 string is expanded, so it can contain, for example, a reference to
16038 &$primary_hostname$&.
16040 If the spool directory name is fixed on your installation, it is recommended
16041 that you set it at build time rather than from this option, particularly if the
16042 log files are being written to the spool directory (see &%log_file_path%&).
16043 Otherwise log files cannot be used for errors that are detected early on, such
16044 as failures in the configuration file.
16046 By using this option to override the compiled-in path, it is possible to run
16047 tests of Exim without using the standard spool.
16049 .option sqlite_lock_timeout main time 5s
16050 .cindex "sqlite lookup type" "lock timeout"
16051 This option controls the timeout that the &(sqlite)& lookup uses when trying to
16052 access an SQLite database. See section &<<SECTsqlite>>& for more details.
16054 .option strict_acl_vars main boolean false
16055 .cindex "&ACL;" "variables, handling unset"
16056 This option controls what happens if a syntactically valid but undefined ACL
16057 variable is referenced. If it is false (the default), an empty string
16058 is substituted; if it is true, an error is generated. See section
16059 &<<SECTaclvariables>>& for details of ACL variables.
16061 .option strip_excess_angle_brackets main boolean false
16062 .cindex "angle brackets, excess"
16063 If this option is set, redundant pairs of angle brackets round &"route-addr"&
16064 items in addresses are stripped. For example, &'<<xxx@a.b.c.d>>'& is
16065 treated as &'<xxx@a.b.c.d>'&. If this is in the envelope and the message is
16066 passed on to another MTA, the excess angle brackets are not passed on. If this
16067 option is not set, multiple pairs of angle brackets cause a syntax error.
16070 .option strip_trailing_dot main boolean false
16071 .cindex "trailing dot on domain"
16072 .cindex "dot" "trailing on domain"
16073 If this option is set, a trailing dot at the end of a domain in an address is
16074 ignored. If this is in the envelope and the message is passed on to another
16075 MTA, the dot is not passed on. If this option is not set, a dot at the end of a
16076 domain causes a syntax error.
16077 However, addresses in header lines are checked only when an ACL requests header
16081 .option syslog_duplication main boolean true
16082 .cindex "syslog" "duplicate log lines; suppressing"
16083 When Exim is logging to syslog, it writes the log lines for its three
16084 separate logs at different syslog priorities so that they can in principle
16085 be separated on the logging hosts. Some installations do not require this
16086 separation, and in those cases, the duplication of certain log lines is a
16087 nuisance. If &%syslog_duplication%& is set false, only one copy of any
16088 particular log line is written to syslog. For lines that normally go to
16089 both the main log and the reject log, the reject log version (possibly
16090 containing message header lines) is written, at LOG_NOTICE priority.
16091 Lines that normally go to both the main and the panic log are written at
16092 the LOG_ALERT priority.
16095 .option syslog_facility main string unset
16096 .cindex "syslog" "facility; setting"
16097 This option sets the syslog &"facility"& name, used when Exim is logging to
16098 syslog. The value must be one of the strings &"mail"&, &"user"&, &"news"&,
16099 &"uucp"&, &"daemon"&, or &"local&'x'&"& where &'x'& is a digit between 0 and 7.
16100 If this option is unset, &"mail"& is used. See chapter &<<CHAPlog>>& for
16101 details of Exim's logging.
16105 .option syslog_processname main string &`exim`&
16106 .cindex "syslog" "process name; setting"
16107 This option sets the syslog &"ident"& name, used when Exim is logging to
16108 syslog. The value must be no longer than 32 characters. See chapter
16109 &<<CHAPlog>>& for details of Exim's logging.
16113 .option syslog_timestamp main boolean true
16114 .cindex "syslog" "timestamps"
16115 If &%syslog_timestamp%& is set false, the timestamps on Exim's log lines are
16116 omitted when these lines are sent to syslog. See chapter &<<CHAPlog>>& for
16117 details of Exim's logging.
16120 .option system_filter main string&!! unset
16121 .cindex "filter" "system filter"
16122 .cindex "system filter" "specifying"
16123 .cindex "Sieve filter" "not available for system filter"
16124 This option specifies an Exim filter file that is applied to all messages at
16125 the start of each delivery attempt, before any routing is done. System filters
16126 must be Exim filters; they cannot be Sieve filters. If the system filter
16127 generates any deliveries to files or pipes, or any new mail messages, the
16128 appropriate &%system_filter_..._transport%& option(s) must be set, to define
16129 which transports are to be used. Details of this facility are given in chapter
16130 &<<CHAPsystemfilter>>&.
16133 .option system_filter_directory_transport main string&!! unset
16134 .vindex "&$address_file$&"
16135 This sets the name of the transport driver that is to be used when the
16136 &%save%& command in a system message filter specifies a path ending in &"/"&,
16137 implying delivery of each message into a separate file in some directory.
16138 During the delivery, the variable &$address_file$& contains the path name.
16141 .option system_filter_file_transport main string&!! unset
16142 .cindex "file" "transport for system filter"
16143 This sets the name of the transport driver that is to be used when the &%save%&
16144 command in a system message filter specifies a path not ending in &"/"&. During
16145 the delivery, the variable &$address_file$& contains the path name.
16147 .option system_filter_group main string unset
16148 .cindex "gid (group id)" "system filter"
16149 This option is used only when &%system_filter_user%& is also set. It sets the
16150 gid under which the system filter is run, overriding any gid that is associated
16151 with the user. The value may be numerical or symbolic.
16153 .option system_filter_pipe_transport main string&!! unset
16154 .cindex "&(pipe)& transport" "for system filter"
16155 .vindex "&$address_pipe$&"
16156 This specifies the transport driver that is to be used when a &%pipe%& command
16157 is used in a system filter. During the delivery, the variable &$address_pipe$&
16158 contains the pipe command.
16161 .option system_filter_reply_transport main string&!! unset
16162 .cindex "&(autoreply)& transport" "for system filter"
16163 This specifies the transport driver that is to be used when a &%mail%& command
16164 is used in a system filter.
16167 .option system_filter_user main string unset
16168 .cindex "uid (user id)" "system filter"
16169 If this option is set to root, the system filter is run in the main Exim
16170 delivery process, as root. Otherwise, the system filter runs in a separate
16171 process, as the given user, defaulting to the Exim run-time user.
16172 Unless the string consists entirely of digits, it
16173 is looked up in the password data. Failure to find the named user causes a
16174 configuration error. The gid is either taken from the password data, or
16175 specified by &%system_filter_group%&. When the uid is specified numerically,
16176 &%system_filter_group%& is required to be set.
16178 If the system filter generates any pipe, file, or reply deliveries, the uid
16179 under which the filter is run is used when transporting them, unless a
16180 transport option overrides.
16183 .option tcp_nodelay main boolean true
16184 .cindex "daemon" "TCP_NODELAY on sockets"
16185 .cindex "Nagle algorithm"
16186 .cindex "TCP_NODELAY on listening sockets"
16187 If this option is set false, it stops the Exim daemon setting the
16188 TCP_NODELAY option on its listening sockets. Setting TCP_NODELAY
16189 turns off the &"Nagle algorithm"&, which is a way of improving network
16190 performance in interactive (character-by-character) situations. Turning it off
16191 should improve Exim's performance a bit, so that is what happens by default.
16192 However, it appears that some broken clients cannot cope, and time out. Hence
16193 this option. It affects only those sockets that are set up for listening by the
16194 daemon. Sockets created by the smtp transport for delivering mail always set
16198 .option timeout_frozen_after main time 0s
16199 .cindex "frozen messages" "timing out"
16200 .cindex "timeout" "frozen messages"
16201 If &%timeout_frozen_after%& is set to a time greater than zero, a frozen
16202 message of any kind that has been on the queue for longer than the given time
16203 is automatically cancelled at the next queue run. If the frozen message is a
16204 bounce message, it is just discarded; otherwise, a bounce is sent to the
16205 sender, in a similar manner to cancellation by the &%-Mg%& command line option.
16206 If you want to timeout frozen bounce messages earlier than other kinds of
16207 frozen message, see &%ignore_bounce_errors_after%&.
16209 &*Note:*& the default value of zero means no timeouts; with this setting,
16210 frozen messages remain on the queue forever (except for any frozen bounce
16211 messages that are released by &%ignore_bounce_errors_after%&).
16214 .option timezone main string unset
16215 .cindex "timezone, setting"
16216 The value of &%timezone%& is used to set the environment variable TZ while
16217 running Exim (if it is different on entry). This ensures that all timestamps
16218 created by Exim are in the required timezone. If you want all your timestamps
16219 to be in UTC (aka GMT) you should set
16223 The default value is taken from TIMEZONE_DEFAULT in &_Local/Makefile_&,
16224 or, if that is not set, from the value of the TZ environment variable when Exim
16225 is built. If &%timezone%& is set to the empty string, either at build or run
16226 time, any existing TZ variable is removed from the environment when Exim
16227 runs. This is appropriate behaviour for obtaining wall-clock time on some, but
16228 unfortunately not all, operating systems.
16231 .option tls_advertise_hosts main "host list&!!" unset
16232 .cindex "TLS" "advertising"
16233 .cindex "encryption" "on SMTP connection"
16234 .cindex "SMTP" "encrypted connection"
16235 When Exim is built with support for TLS encrypted connections, the availability
16236 of the STARTTLS command to set up an encrypted session is advertised in
16237 response to EHLO only to those client hosts that match this option. See
16238 chapter &<<CHAPTLS>>& for details of Exim's support for TLS.
16241 .option tls_certificate main string&!! unset
16242 .cindex "TLS" "server certificate; location of"
16243 .cindex "certificate" "server, location of"
16244 The value of this option is expanded, and must then be the absolute path to a
16245 file which contains the server's certificates. The server's private key is also
16246 assumed to be in this file if &%tls_privatekey%& is unset. See chapter
16247 &<<CHAPTLS>>& for further details.
16249 &*Note*&: The certificates defined by this option are used only when Exim is
16250 receiving incoming messages as a server. If you want to supply certificates for
16251 use when sending messages as a client, you must set the &%tls_certificate%&
16252 option in the relevant &(smtp)& transport.
16254 If the option contains &$tls_out_sni$& and Exim is built against OpenSSL, then
16255 if the OpenSSL build supports TLS extensions and the TLS client sends the
16256 Server Name Indication extension, then this option and others documented in
16257 &<<SECTtlssni>>& will be re-expanded.
16259 .option tls_crl main string&!! unset
16260 .cindex "TLS" "server certificate revocation list"
16261 .cindex "certificate" "revocation list for server"
16262 This option specifies a certificate revocation list. The expanded value must
16263 be the name of a file that contains a CRL in PEM format.
16265 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
16268 .option tls_dh_max_bits main integer 2236
16269 .cindex "TLS" "D-H bit count"
16270 The number of bits used for Diffie-Hellman key-exchange may be suggested by
16271 the chosen TLS library. That value might prove to be too high for
16272 interoperability. This option provides a maximum clamp on the value
16273 suggested, trading off security for interoperability.
16275 The value must be at least 1024.
16277 The value 2236 was chosen because, at time of adding the option, it was the
16278 hard-coded maximum value supported by the NSS cryptographic library, as used
16279 by Thunderbird, while GnuTLS was suggesting 2432 bits as normal.
16281 If you prefer more security and are willing to break some clients, raise this
16284 Note that the value passed to GnuTLS for *generating* a new prime may be a
16285 little less than this figure, because GnuTLS is inexact and may produce a
16286 larger prime than requested.
16289 .option tls_dhparam main string&!! unset
16290 .cindex "TLS" "D-H parameters for server"
16291 The value of this option is expanded and indicates the source of DH parameters
16292 to be used by Exim.
16294 If it is a filename starting with a &`/`&, then it names a file from which DH
16295 parameters should be loaded. If the file exists, it should hold a PEM-encoded
16296 PKCS#3 representation of the DH prime. If the file does not exist, for
16297 OpenSSL it is an error. For GnuTLS, Exim will attempt to create the file and
16298 fill it with a generated DH prime. For OpenSSL, if the DH bit-count from
16299 loading the file is greater than &%tls_dh_max_bits%& then it will be ignored,
16300 and treated as though the &%tls_dhparam%& were set to "none".
16302 If this option expands to the string "none", then no DH parameters will be
16305 If this option expands to the string "historic" and Exim is using GnuTLS, then
16306 Exim will attempt to load a file from inside the spool directory. If the file
16307 does not exist, Exim will attempt to create it.
16308 See section &<<SECTgnutlsparam>>& for further details.
16310 If Exim is using OpenSSL and this option is empty or unset, then Exim will load
16311 a default DH prime; the default is the 2048 bit prime described in section
16312 2.2 of RFC 5114, "2048-bit MODP Group with 224-bit Prime Order Subgroup", which
16313 in IKE is assigned number 23.
16315 Otherwise, the option must expand to the name used by Exim for any of a number
16316 of DH primes specified in RFC 2409, RFC 3526 and RFC 5114. As names, Exim uses
16317 "ike" followed by the number used by IKE, of "default" which corresponds to
16320 The available primes are:
16321 &`ike1`&, &`ike2`&, &`ike5`&,
16322 &`ike14`&, &`ike15`&, &`ike16`&, &`ike17`&, &`ike18`&,
16323 &`ike22`&, &`ike23`& (aka &`default`&) and &`ike24`&.
16325 Some of these will be too small to be accepted by clients.
16326 Some may be too large to be accepted by clients.
16328 The TLS protocol does not negotiate an acceptable size for this; clients tend
16329 to hard-drop connections if what is offered by the server is unacceptable,
16330 whether too large or too small, and there's no provision for the client to
16331 tell the server what these constraints are. Thus, as a server operator, you
16332 need to make an educated guess as to what is most likely to work for your
16335 Some known size constraints suggest that a bit-size in the range 2048 to 2236
16336 is most likely to maximise interoperability. The upper bound comes from
16337 applications using the Mozilla Network Security Services (NSS) library, which
16338 used to set its &`DH_MAX_P_BITS`& upper-bound to 2236. This affects many
16339 mail user agents (MUAs). The lower bound comes from Debian installs of Exim4
16340 prior to the 4.80 release, as Debian used to patch Exim to raise the minimum
16341 acceptable bound from 1024 to 2048.
16344 .option tls_on_connect_ports main "string list" unset
16345 This option specifies a list of incoming SSMTP (aka SMTPS) ports that should
16346 operate the obsolete SSMTP (SMTPS) protocol, where a TLS session is immediately
16347 set up without waiting for the client to issue a STARTTLS command. For
16348 further details, see section &<<SECTsupobssmt>>&.
16352 .option tls_privatekey main string&!! unset
16353 .cindex "TLS" "server private key; location of"
16354 The value of this option is expanded, and must then be the absolute path to a
16355 file which contains the server's private key. If this option is unset, or if
16356 the expansion is forced to fail, or the result is an empty string, the private
16357 key is assumed to be in the same file as the server's certificates. See chapter
16358 &<<CHAPTLS>>& for further details.
16360 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
16363 .option tls_remember_esmtp main boolean false
16364 .cindex "TLS" "esmtp state; remembering"
16365 .cindex "TLS" "broken clients"
16366 If this option is set true, Exim violates the RFCs by remembering that it is in
16367 &"esmtp"& state after successfully negotiating a TLS session. This provides
16368 support for broken clients that fail to send a new EHLO after starting a
16372 .option tls_require_ciphers main string&!! unset
16373 .cindex "TLS" "requiring specific ciphers"
16374 .cindex "cipher" "requiring specific"
16375 This option controls which ciphers can be used for incoming TLS connections.
16376 The &(smtp)& transport has an option of the same name for controlling outgoing
16377 connections. This option is expanded for each connection, so can be varied for
16378 different clients if required. The value of this option must be a list of
16379 permitted cipher suites. The OpenSSL and GnuTLS libraries handle cipher control
16380 in somewhat different ways. If GnuTLS is being used, the client controls the
16381 preference order of the available ciphers. Details are given in sections
16382 &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&.
16385 .option tls_try_verify_hosts main "host list&!!" unset
16386 .cindex "TLS" "client certificate verification"
16387 .cindex "certificate" "verification of client"
16388 See &%tls_verify_hosts%& below.
16391 .option tls_verify_certificates main string&!! unset
16392 .cindex "TLS" "client certificate verification"
16393 .cindex "certificate" "verification of client"
16394 The value of this option is expanded, and must then be the absolute path to
16395 a file containing permitted certificates for clients that
16396 match &%tls_verify_hosts%& or &%tls_try_verify_hosts%&. Alternatively, if you
16397 are using OpenSSL, you can set &%tls_verify_certificates%& to the name of a
16398 directory containing certificate files. This does not work with GnuTLS; the
16399 option must be set to the name of a single file if you are using GnuTLS.
16401 These certificates should be for the certificate authorities trusted, rather
16402 than the public cert of individual clients. With both OpenSSL and GnuTLS, if
16403 the value is a file then the certificates are sent by Exim as a server to
16404 connecting clients, defining the list of accepted certificate authorities.
16405 Thus the values defined should be considered public data. To avoid this,
16406 use OpenSSL with a directory.
16408 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
16410 A forced expansion failure or setting to an empty string is equivalent to
16414 .option tls_verify_hosts main "host list&!!" unset
16415 .cindex "TLS" "client certificate verification"
16416 .cindex "certificate" "verification of client"
16417 This option, along with &%tls_try_verify_hosts%&, controls the checking of
16418 certificates from clients. The expected certificates are defined by
16419 &%tls_verify_certificates%&, which must be set. A configuration error occurs if
16420 either &%tls_verify_hosts%& or &%tls_try_verify_hosts%& is set and
16421 &%tls_verify_certificates%& is not set.
16423 Any client that matches &%tls_verify_hosts%& is constrained by
16424 &%tls_verify_certificates%&. When the client initiates a TLS session, it must
16425 present one of the listed certificates. If it does not, the connection is
16426 aborted. &*Warning*&: Including a host in &%tls_verify_hosts%& does not require
16427 the host to use TLS. It can still send SMTP commands through unencrypted
16428 connections. Forcing a client to use TLS has to be done separately using an
16429 ACL to reject inappropriate commands when the connection is not encrypted.
16431 A weaker form of checking is provided by &%tls_try_verify_hosts%&. If a client
16432 matches this option (but not &%tls_verify_hosts%&), Exim requests a
16433 certificate and checks it against &%tls_verify_certificates%&, but does not
16434 abort the connection if there is no certificate or if it does not match. This
16435 state can be detected in an ACL, which makes it possible to implement policies
16436 such as &"accept for relay only if a verified certificate has been received,
16437 but accept for local delivery if encrypted, even without a verified
16440 Client hosts that match neither of these lists are not asked to present
16444 .option trusted_groups main "string list&!!" unset
16445 .cindex "trusted groups"
16446 .cindex "groups" "trusted"
16447 This option is expanded just once, at the start of Exim's processing. If this
16448 option is set, any process that is running in one of the listed groups, or
16449 which has one of them as a supplementary group, is trusted. The groups can be
16450 specified numerically or by name. See section &<<SECTtrustedadmin>>& for
16451 details of what trusted callers are permitted to do. If neither
16452 &%trusted_groups%& nor &%trusted_users%& is set, only root and the Exim user
16455 .option trusted_users main "string list&!!" unset
16456 .cindex "trusted users"
16457 .cindex "user" "trusted"
16458 This option is expanded just once, at the start of Exim's processing. If this
16459 option is set, any process that is running as one of the listed users is
16460 trusted. The users can be specified numerically or by name. See section
16461 &<<SECTtrustedadmin>>& for details of what trusted callers are permitted to do.
16462 If neither &%trusted_groups%& nor &%trusted_users%& is set, only root and the
16463 Exim user are trusted.
16465 .option unknown_login main string&!! unset
16466 .cindex "uid (user id)" "unknown caller"
16467 .vindex "&$caller_uid$&"
16468 This is a specialized feature for use in unusual configurations. By default, if
16469 the uid of the caller of Exim cannot be looked up using &[getpwuid()]&, Exim
16470 gives up. The &%unknown_login%& option can be used to set a login name to be
16471 used in this circumstance. It is expanded, so values like &%user$caller_uid%&
16472 can be set. When &%unknown_login%& is used, the value of &%unknown_username%&
16473 is used for the user's real name (gecos field), unless this has been set by the
16476 .option unknown_username main string unset
16477 See &%unknown_login%&.
16479 .option untrusted_set_sender main "address list&!!" unset
16480 .cindex "trusted users"
16481 .cindex "sender" "setting by untrusted user"
16482 .cindex "untrusted user setting sender"
16483 .cindex "user" "untrusted setting sender"
16484 .cindex "envelope sender"
16485 When an untrusted user submits a message to Exim using the standard input, Exim
16486 normally creates an envelope sender address from the user's login and the
16487 default qualification domain. Data from the &%-f%& option (for setting envelope
16488 senders on non-SMTP messages) or the SMTP MAIL command (if &%-bs%& or &%-bS%&
16489 is used) is ignored.
16491 However, untrusted users are permitted to set an empty envelope sender address,
16492 to declare that a message should never generate any bounces. For example:
16494 exim -f '<>' user@domain.example
16496 .vindex "&$sender_ident$&"
16497 The &%untrusted_set_sender%& option allows you to permit untrusted users to set
16498 other envelope sender addresses in a controlled way. When it is set, untrusted
16499 users are allowed to set envelope sender addresses that match any of the
16500 patterns in the list. Like all address lists, the string is expanded. The
16501 identity of the user is in &$sender_ident$&, so you can, for example, restrict
16502 users to setting senders that start with their login ids
16503 followed by a hyphen
16504 by a setting like this:
16506 untrusted_set_sender = ^$sender_ident-
16508 If you want to allow untrusted users to set envelope sender addresses without
16509 restriction, you can use
16511 untrusted_set_sender = *
16513 The &%untrusted_set_sender%& option applies to all forms of local input, but
16514 only to the setting of the envelope sender. It does not permit untrusted users
16515 to use the other options which trusted user can use to override message
16516 parameters. Furthermore, it does not stop Exim from removing an existing
16517 &'Sender:'& header in the message, or from adding a &'Sender:'& header if
16518 necessary. See &%local_sender_retain%& and &%local_from_check%& for ways of
16519 overriding these actions. The handling of the &'Sender:'& header is also
16520 described in section &<<SECTthesenhea>>&.
16522 The log line for a message's arrival shows the envelope sender following
16523 &"<="&. For local messages, the user's login always follows, after &"U="&. In
16524 &%-bp%& displays, and in the Exim monitor, if an untrusted user sets an
16525 envelope sender address, the user's login is shown in parentheses after the
16529 .option uucp_from_pattern main string "see below"
16530 .cindex "&""From""& line"
16531 .cindex "UUCP" "&""From""& line"
16532 Some applications that pass messages to an MTA via a command line interface use
16533 an initial line starting with &"From&~"& to pass the envelope sender. In
16534 particular, this is used by UUCP software. Exim recognizes such a line by means
16535 of a regular expression that is set in &%uucp_from_pattern%&. When the pattern
16536 matches, the sender address is constructed by expanding the contents of
16537 &%uucp_from_sender%&, provided that the caller of Exim is a trusted user. The
16538 default pattern recognizes lines in the following two forms:
16540 From ph10 Fri Jan 5 12:35 GMT 1996
16541 From ph10 Fri, 7 Jan 97 14:00:00 GMT
16543 The pattern can be seen by running
16545 exim -bP uucp_from_pattern
16547 It checks only up to the hours and minutes, and allows for a 2-digit or 4-digit
16548 year in the second case. The first word after &"From&~"& is matched in the
16549 regular expression by a parenthesized subpattern. The default value for
16550 &%uucp_from_sender%& is &"$1"&, which therefore just uses this first word
16551 (&"ph10"& in the example above) as the message's sender. See also
16552 &%ignore_fromline_hosts%&.
16555 .option uucp_from_sender main string&!! &`$1`&
16556 See &%uucp_from_pattern%& above.
16559 .option warn_message_file main string unset
16560 .cindex "warning of delay" "customizing the message"
16561 .cindex "customizing" "warning message"
16562 This option defines a template file containing paragraphs of text to be used
16563 for constructing the warning message which is sent by Exim when a message has
16564 been on the queue for a specified amount of time, as specified by
16565 &%delay_warning%&. Details of the file's contents are given in chapter
16566 &<<CHAPemsgcust>>&. See also &%bounce_message_file%&.
16569 .option write_rejectlog main boolean true
16570 .cindex "reject log" "disabling"
16571 If this option is set false, Exim no longer writes anything to the reject log.
16572 See chapter &<<CHAPlog>>& for details of what Exim writes to its logs.
16573 .ecindex IIDconfima
16574 .ecindex IIDmaiconf
16579 . ////////////////////////////////////////////////////////////////////////////
16580 . ////////////////////////////////////////////////////////////////////////////
16582 .chapter "Generic options for routers" "CHAProutergeneric"
16583 .scindex IIDgenoprou1 "options" "generic; for routers"
16584 .scindex IIDgenoprou2 "generic options" "router"
16585 This chapter describes the generic options that apply to all routers.
16586 Those that are preconditions are marked with ‡ in the &"use"& field.
16588 For a general description of how a router operates, see sections
16589 &<<SECTrunindrou>>& and &<<SECTrouprecon>>&. The latter specifies the order in
16590 which the preconditions are tested. The order of expansion of the options that
16591 provide data for a transport is: &%errors_to%&, &%headers_add%&,
16592 &%headers_remove%&, &%transport%&.
16596 .option address_data routers string&!! unset
16597 .cindex "router" "data attached to address"
16598 The string is expanded just before the router is run, that is, after all the
16599 precondition tests have succeeded. If the expansion is forced to fail, the
16600 router declines, the value of &%address_data%& remains unchanged, and the
16601 &%more%& option controls what happens next. Other expansion failures cause
16602 delivery of the address to be deferred.
16604 .vindex "&$address_data$&"
16605 When the expansion succeeds, the value is retained with the address, and can be
16606 accessed using the variable &$address_data$& in the current router, subsequent
16607 routers, and the eventual transport.
16609 &*Warning*&: If the current or any subsequent router is a &(redirect)& router
16610 that runs a user's filter file, the contents of &$address_data$& are accessible
16611 in the filter. This is not normally a problem, because such data is usually
16612 either not confidential or it &"belongs"& to the current user, but if you do
16613 put confidential data into &$address_data$& you need to remember this point.
16615 Even if the router declines or passes, the value of &$address_data$& remains
16616 with the address, though it can be changed by another &%address_data%& setting
16617 on a subsequent router. If a router generates child addresses, the value of
16618 &$address_data$& propagates to them. This also applies to the special kind of
16619 &"child"& that is generated by a router with the &%unseen%& option.
16621 The idea of &%address_data%& is that you can use it to look up a lot of data
16622 for the address once, and then pick out parts of the data later. For example,
16623 you could use a single LDAP lookup to return a string of the form
16625 uid=1234 gid=5678 mailbox=/mail/xyz forward=/home/xyz/.forward
16627 In the transport you could pick out the mailbox by a setting such as
16629 file = ${extract{mailbox}{$address_data}}
16631 This makes the configuration file less messy, and also reduces the number of
16632 lookups (though Exim does cache lookups).
16634 .vindex "&$sender_address_data$&"
16635 .vindex "&$address_data$&"
16636 The &%address_data%& facility is also useful as a means of passing information
16637 from one router to another, and from a router to a transport. In addition, if
16638 &$address_data$& is set by a router when verifying a recipient address from an
16639 ACL, it remains available for use in the rest of the ACL statement. After
16640 verifying a sender, the value is transferred to &$sender_address_data$&.
16644 .option address_test routers&!? boolean true
16646 .cindex "router" "skipping when address testing"
16647 If this option is set false, the router is skipped when routing is being tested
16648 by means of the &%-bt%& command line option. This can be a convenience when
16649 your first router sends messages to an external scanner, because it saves you
16650 having to set the &"already scanned"& indicator when testing real address
16655 .option cannot_route_message routers string&!! unset
16656 .cindex "router" "customizing &""cannot route""& message"
16657 .cindex "customizing" "&""cannot route""& message"
16658 This option specifies a text message that is used when an address cannot be
16659 routed because Exim has run out of routers. The default message is
16660 &"Unrouteable address"&. This option is useful only on routers that have
16661 &%more%& set false, or on the very last router in a configuration, because the
16662 value that is used is taken from the last router that is considered. This
16663 includes a router that is skipped because its preconditions are not met, as
16664 well as a router that declines. For example, using the default configuration,
16667 cannot_route_message = Remote domain not found in DNS
16669 on the first router, which is a &(dnslookup)& router with &%more%& set false,
16672 cannot_route_message = Unknown local user
16674 on the final router that checks for local users. If string expansion fails for
16675 this option, the default message is used. Unless the expansion failure was
16676 explicitly forced, a message about the failure is written to the main and panic
16677 logs, in addition to the normal message about the routing failure.
16680 .option caseful_local_part routers boolean false
16681 .cindex "case of local parts"
16682 .cindex "router" "case of local parts"
16683 By default, routers handle the local parts of addresses in a case-insensitive
16684 manner, though the actual case is preserved for transmission with the message.
16685 If you want the case of letters to be significant in a router, you must set
16686 this option true. For individual router options that contain address or local
16687 part lists (for example, &%local_parts%&), case-sensitive matching can be
16688 turned on by &"+caseful"& as a list item. See section &<<SECTcasletadd>>& for
16691 .vindex "&$local_part$&"
16692 .vindex "&$original_local_part$&"
16693 .vindex "&$parent_local_part$&"
16694 The value of the &$local_part$& variable is forced to lower case while a
16695 router is running unless &%caseful_local_part%& is set. When a router assigns
16696 an address to a transport, the value of &$local_part$& when the transport runs
16697 is the same as it was in the router. Similarly, when a router generates child
16698 addresses by aliasing or forwarding, the values of &$original_local_part$&
16699 and &$parent_local_part$& are those that were used by the redirecting router.
16701 This option applies to the processing of an address by a router. When a
16702 recipient address is being processed in an ACL, there is a separate &%control%&
16703 modifier that can be used to specify case-sensitive processing within the ACL
16704 (see section &<<SECTcontrols>>&).
16708 .option check_local_user routers&!? boolean false
16709 .cindex "local user, checking in router"
16710 .cindex "router" "checking for local user"
16711 .cindex "&_/etc/passwd_&"
16713 When this option is true, Exim checks that the local part of the recipient
16714 address (with affixes removed if relevant) is the name of an account on the
16715 local system. The check is done by calling the &[getpwnam()]& function rather
16716 than trying to read &_/etc/passwd_& directly. This means that other methods of
16717 holding password data (such as NIS) are supported. If the local part is a local
16718 user, &$home$& is set from the password data, and can be tested in other
16719 preconditions that are evaluated after this one (the order of evaluation is
16720 given in section &<<SECTrouprecon>>&). However, the value of &$home$& can be
16721 overridden by &%router_home_directory%&. If the local part is not a local user,
16722 the router is skipped.
16724 If you want to check that the local part is either the name of a local user
16725 or matches something else, you cannot combine &%check_local_user%& with a
16726 setting of &%local_parts%&, because that specifies the logical &'and'& of the
16727 two conditions. However, you can use a &(passwd)& lookup in a &%local_parts%&
16728 setting to achieve this. For example:
16730 local_parts = passwd;$local_part : lsearch;/etc/other/users
16732 Note, however, that the side effects of &%check_local_user%& (such as setting
16733 up a home directory) do not occur when a &(passwd)& lookup is used in a
16734 &%local_parts%& (or any other) precondition.
16738 .option condition routers&!? string&!! unset
16739 .cindex "router" "customized precondition"
16740 This option specifies a general precondition test that has to succeed for the
16741 router to be called. The &%condition%& option is the last precondition to be
16742 evaluated (see section &<<SECTrouprecon>>&). The string is expanded, and if the
16743 result is a forced failure, or an empty string, or one of the strings &"0"& or
16744 &"no"& or &"false"& (checked without regard to the case of the letters), the
16745 router is skipped, and the address is offered to the next one.
16747 If the result is any other value, the router is run (as this is the last
16748 precondition to be evaluated, all the other preconditions must be true).
16750 This option is unusual in that multiple &%condition%& options may be present.
16751 All &%condition%& options must succeed.
16753 The &%condition%& option provides a means of applying custom conditions to the
16754 running of routers. Note that in the case of a simple conditional expansion,
16755 the default expansion values are exactly what is wanted. For example:
16757 condition = ${if >{$message_age}{600}}
16759 Because of the default behaviour of the string expansion, this is equivalent to
16761 condition = ${if >{$message_age}{600}{true}{}}
16764 A multiple condition example, which succeeds:
16766 condition = ${if >{$message_age}{600}}
16767 condition = ${if !eq{${lc:$local_part}}{postmaster}}
16771 If the expansion fails (other than forced failure) delivery is deferred. Some
16772 of the other precondition options are common special cases that could in fact
16773 be specified using &%condition%&.
16776 .option debug_print routers string&!! unset
16777 .cindex "testing" "variables in drivers"
16778 If this option is set and debugging is enabled (see the &%-d%& command line
16779 option) or in address-testing mode (see the &%-bt%& command line option),
16780 the string is expanded and included in the debugging output.
16781 If expansion of the string fails, the error message is written to the debugging
16782 output, and Exim carries on processing.
16783 This option is provided to help with checking out the values of variables and
16784 so on when debugging router configurations. For example, if a &%condition%&
16785 option appears not to be working, &%debug_print%& can be used to output the
16786 variables it references. The output happens after checks for &%domains%&,
16787 &%local_parts%&, and &%check_local_user%& but before any other preconditions
16788 are tested. A newline is added to the text if it does not end with one.
16789 The variable &$router_name$& contains the name of the router.
16793 .option disable_logging routers boolean false
16794 If this option is set true, nothing is logged for any routing errors
16795 or for any deliveries caused by this router. You should not set this option
16796 unless you really, really know what you are doing. See also the generic
16797 transport option of the same name.
16800 .option domains routers&!? "domain list&!!" unset
16801 .cindex "router" "restricting to specific domains"
16802 .vindex "&$domain_data$&"
16803 If this option is set, the router is skipped unless the current domain matches
16804 the list. If the match is achieved by means of a file lookup, the data that the
16805 lookup returned for the domain is placed in &$domain_data$& for use in string
16806 expansions of the driver's private options. See section &<<SECTrouprecon>>& for
16807 a list of the order in which preconditions are evaluated.
16811 .option driver routers string unset
16812 This option must always be set. It specifies which of the available routers is
16817 .option errors_to routers string&!! unset
16818 .cindex "envelope sender"
16819 .cindex "router" "changing address for errors"
16820 If a router successfully handles an address, it may assign the address to a
16821 transport for delivery or it may generate child addresses. In both cases, if
16822 there is a delivery problem during later processing, the resulting bounce
16823 message is sent to the address that results from expanding this string,
16824 provided that the address verifies successfully. The &%errors_to%& option is
16825 expanded before &%headers_add%&, &%headers_remove%&, and &%transport%&.
16827 The &%errors_to%& setting associated with an address can be overridden if it
16828 subsequently passes through other routers that have their own &%errors_to%&
16829 settings, or if the message is delivered by a transport with a &%return_path%&
16832 If &%errors_to%& is unset, or the expansion is forced to fail, or the result of
16833 the expansion fails to verify, the errors address associated with the incoming
16834 address is used. At top level, this is the envelope sender. A non-forced
16835 expansion failure causes delivery to be deferred.
16837 If an address for which &%errors_to%& has been set ends up being delivered over
16838 SMTP, the envelope sender for that delivery is the &%errors_to%& value, so that
16839 any bounces that are generated by other MTAs on the delivery route are also
16840 sent there. You can set &%errors_to%& to the empty string by either of these
16846 An expansion item that yields an empty string has the same effect. If you do
16847 this, a locally detected delivery error for addresses processed by this router
16848 no longer gives rise to a bounce message; the error is discarded. If the
16849 address is delivered to a remote host, the return path is set to &`<>`&, unless
16850 overridden by the &%return_path%& option on the transport.
16852 .vindex "&$address_data$&"
16853 If for some reason you want to discard local errors, but use a non-empty
16854 MAIL command for remote delivery, you can preserve the original return
16855 path in &$address_data$& in the router, and reinstate it in the transport by
16856 setting &%return_path%&.
16858 The most common use of &%errors_to%& is to direct mailing list bounces to the
16859 manager of the list, as described in section &<<SECTmailinglists>>&, or to
16860 implement VERP (Variable Envelope Return Paths) (see section &<<SECTverp>>&).
16864 .option expn routers&!? boolean true
16865 .cindex "address" "testing"
16866 .cindex "testing" "addresses"
16867 .cindex "EXPN" "router skipping"
16868 .cindex "router" "skipping for EXPN"
16869 If this option is turned off, the router is skipped when testing an address
16870 as a result of processing an SMTP EXPN command. You might, for example,
16871 want to turn it off on a router for users' &_.forward_& files, while leaving it
16872 on for the system alias file.
16873 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
16876 The use of the SMTP EXPN command is controlled by an ACL (see chapter
16877 &<<CHAPACL>>&). When Exim is running an EXPN command, it is similar to testing
16878 an address with &%-bt%&. Compare VRFY, whose counterpart is &%-bv%&.
16882 .option fail_verify routers boolean false
16883 .cindex "router" "forcing verification failure"
16884 Setting this option has the effect of setting both &%fail_verify_sender%& and
16885 &%fail_verify_recipient%& to the same value.
16889 .option fail_verify_recipient routers boolean false
16890 If this option is true and an address is accepted by this router when
16891 verifying a recipient, verification fails.
16895 .option fail_verify_sender routers boolean false
16896 If this option is true and an address is accepted by this router when
16897 verifying a sender, verification fails.
16901 .option fallback_hosts routers "string list" unset
16902 .cindex "router" "fallback hosts"
16903 .cindex "fallback" "hosts specified on router"
16904 String expansion is not applied to this option. The argument must be a
16905 colon-separated list of host names or IP addresses. The list separator can be
16906 changed (see section &<<SECTlistconstruct>>&), and a port can be specified with
16907 each name or address. In fact, the format of each item is exactly the same as
16908 defined for the list of hosts in a &(manualroute)& router (see section
16909 &<<SECTformatonehostitem>>&).
16911 If a router queues an address for a remote transport, this host list is
16912 associated with the address, and used instead of the transport's fallback host
16913 list. If &%hosts_randomize%& is set on the transport, the order of the list is
16914 randomized for each use. See the &%fallback_hosts%& option of the &(smtp)&
16915 transport for further details.
16918 .option group routers string&!! "see below"
16919 .cindex "gid (group id)" "local delivery"
16920 .cindex "local transports" "uid and gid"
16921 .cindex "transport" "local"
16922 .cindex "router" "setting group"
16923 When a router queues an address for a transport, and the transport does not
16924 specify a group, the group given here is used when running the delivery
16926 The group may be specified numerically or by name. If expansion fails, the
16927 error is logged and delivery is deferred.
16928 The default is unset, unless &%check_local_user%& is set, when the default
16929 is taken from the password information. See also &%initgroups%& and &%user%&
16930 and the discussion in chapter &<<CHAPenvironment>>&.
16934 .option headers_add routers list&!! unset
16935 .cindex "header lines" "adding"
16936 .cindex "router" "adding header lines"
16937 This option specifies a list of text headers, newline-separated,
16938 that is associated with any addresses that are accepted by the router.
16939 Each item is separately expanded, at routing time. However, this
16940 option has no effect when an address is just being verified. The way in which
16941 the text is used to add header lines at transport time is described in section
16942 &<<SECTheadersaddrem>>&. New header lines are not actually added until the
16943 message is in the process of being transported. This means that references to
16944 header lines in string expansions in the transport's configuration do not
16945 &"see"& the added header lines.
16947 The &%headers_add%& option is expanded after &%errors_to%&, but before
16948 &%headers_remove%& and &%transport%&. If an item is empty, or if
16949 an item expansion is forced to fail, the item has no effect. Other expansion
16950 failures are treated as configuration errors.
16952 Unlike most options, &%headers_add%& can be specified multiple times
16953 for a router; all listed headers are added.
16955 &*Warning 1*&: The &%headers_add%& option cannot be used for a &(redirect)&
16956 router that has the &%one_time%& option set.
16958 .cindex "duplicate addresses"
16959 .oindex "&%unseen%&"
16960 &*Warning 2*&: If the &%unseen%& option is set on the router, all header
16961 additions are deleted when the address is passed on to subsequent routers.
16962 For a &%redirect%& router, if a generated address is the same as the incoming
16963 address, this can lead to duplicate addresses with different header
16964 modifications. Exim does not do duplicate deliveries (except, in certain
16965 circumstances, to pipes -- see section &<<SECTdupaddr>>&), but it is undefined
16966 which of the duplicates is discarded, so this ambiguous situation should be
16967 avoided. The &%repeat_use%& option of the &%redirect%& router may be of help.
16971 .option headers_remove routers list&!! unset
16972 .cindex "header lines" "removing"
16973 .cindex "router" "removing header lines"
16974 This option specifies a list of text headers, colon-separated,
16975 that is associated with any addresses that are accepted by the router.
16976 Each item is separately expanded, at routing time. However, this
16977 option has no effect when an address is just being verified. The way in which
16978 the text is used to remove header lines at transport time is described in
16979 section &<<SECTheadersaddrem>>&. Header lines are not actually removed until
16980 the message is in the process of being transported. This means that references
16981 to header lines in string expansions in the transport's configuration still
16982 &"see"& the original header lines.
16984 The &%headers_remove%& option is expanded after &%errors_to%& and
16985 &%headers_add%&, but before &%transport%&. If an item expansion is forced to fail,
16986 the item has no effect. Other expansion failures are treated as configuration
16989 Unlike most options, &%headers_remove%& can be specified multiple times
16990 for a router; all listed headers are removed.
16992 &*Warning 1*&: The &%headers_remove%& option cannot be used for a &(redirect)&
16993 router that has the &%one_time%& option set.
16995 &*Warning 2*&: If the &%unseen%& option is set on the router, all header
16996 removal requests are deleted when the address is passed on to subsequent
16997 routers, and this can lead to problems with duplicates -- see the similar
16998 warning for &%headers_add%& above.
17001 .option ignore_target_hosts routers "host list&!!" unset
17002 .cindex "IP address" "discarding"
17003 .cindex "router" "discarding IP addresses"
17004 Although this option is a host list, it should normally contain IP address
17005 entries rather than names. If any host that is looked up by the router has an
17006 IP address that matches an item in this list, Exim behaves as if that IP
17007 address did not exist. This option allows you to cope with rogue DNS entries
17010 remote.domain.example. A 127.0.0.1
17014 ignore_target_hosts = 127.0.0.1
17016 on the relevant router. If all the hosts found by a &(dnslookup)& router are
17017 discarded in this way, the router declines. In a conventional configuration, an
17018 attempt to mail to such a domain would normally provoke the &"unrouteable
17019 domain"& error, and an attempt to verify an address in the domain would fail.
17020 Similarly, if &%ignore_target_hosts%& is set on an &(ipliteral)& router, the
17021 router declines if presented with one of the listed addresses.
17023 You can use this option to disable the use of IPv4 or IPv6 for mail delivery by
17024 means of the first or the second of the following settings, respectively:
17026 ignore_target_hosts = 0.0.0.0/0
17027 ignore_target_hosts = <; 0::0/0
17029 The pattern in the first line matches all IPv4 addresses, whereas the pattern
17030 in the second line matches all IPv6 addresses.
17032 This option may also be useful for ignoring link-local and site-local IPv6
17033 addresses. Because, like all host lists, the value of &%ignore_target_hosts%&
17034 is expanded before use as a list, it is possible to make it dependent on the
17035 domain that is being routed.
17037 .vindex "&$host_address$&"
17038 During its expansion, &$host_address$& is set to the IP address that is being
17041 .option initgroups routers boolean false
17042 .cindex "additional groups"
17043 .cindex "groups" "additional"
17044 .cindex "local transports" "uid and gid"
17045 .cindex "transport" "local"
17046 If the router queues an address for a transport, and this option is true, and
17047 the uid supplied by the router is not overridden by the transport, the
17048 &[initgroups()]& function is called when running the transport to ensure that
17049 any additional groups associated with the uid are set up. See also &%group%&
17050 and &%user%& and the discussion in chapter &<<CHAPenvironment>>&.
17054 .option local_part_prefix routers&!? "string list" unset
17055 .cindex "router" "prefix for local part"
17056 .cindex "prefix" "for local part, used in router"
17057 If this option is set, the router is skipped unless the local part starts with
17058 one of the given strings, or &%local_part_prefix_optional%& is true. See
17059 section &<<SECTrouprecon>>& for a list of the order in which preconditions are
17062 The list is scanned from left to right, and the first prefix that matches is
17063 used. A limited form of wildcard is available; if the prefix begins with an
17064 asterisk, it matches the longest possible sequence of arbitrary characters at
17065 the start of the local part. An asterisk should therefore always be followed by
17066 some character that does not occur in normal local parts.
17067 .cindex "multiple mailboxes"
17068 .cindex "mailbox" "multiple"
17069 Wildcarding can be used to set up multiple user mailboxes, as described in
17070 section &<<SECTmulbox>>&.
17072 .vindex "&$local_part$&"
17073 .vindex "&$local_part_prefix$&"
17074 During the testing of the &%local_parts%& option, and while the router is
17075 running, the prefix is removed from the local part, and is available in the
17076 expansion variable &$local_part_prefix$&. When a message is being delivered, if
17077 the router accepts the address, this remains true during subsequent delivery by
17078 a transport. In particular, the local part that is transmitted in the RCPT
17079 command for LMTP, SMTP, and BSMTP deliveries has the prefix removed by default.
17080 This behaviour can be overridden by setting &%rcpt_include_affixes%& true on
17081 the relevant transport.
17083 When an address is being verified, &%local_part_prefix%& affects only the
17084 behaviour of the router. If the callout feature of verification is in use, this
17085 means that the full address, including the prefix, will be used during the
17088 The prefix facility is commonly used to handle local parts of the form
17089 &%owner-something%&. Another common use is to support local parts of the form
17090 &%real-username%& to bypass a user's &_.forward_& file &-- helpful when trying
17091 to tell a user their forwarding is broken &-- by placing a router like this one
17092 immediately before the router that handles &_.forward_& files:
17096 local_part_prefix = real-
17098 transport = local_delivery
17100 For security, it would probably be a good idea to restrict the use of this
17101 router to locally-generated messages, using a condition such as this:
17103 condition = ${if match {$sender_host_address}\
17104 {\N^(|127\.0\.0\.1)$\N}}
17107 If both &%local_part_prefix%& and &%local_part_suffix%& are set for a router,
17108 both conditions must be met if not optional. Care must be taken if wildcards
17109 are used in both a prefix and a suffix on the same router. Different
17110 separator characters must be used to avoid ambiguity.
17113 .option local_part_prefix_optional routers boolean false
17114 See &%local_part_prefix%& above.
17118 .option local_part_suffix routers&!? "string list" unset
17119 .cindex "router" "suffix for local part"
17120 .cindex "suffix for local part" "used in router"
17121 This option operates in the same way as &%local_part_prefix%&, except that the
17122 local part must end (rather than start) with the given string, the
17123 &%local_part_suffix_optional%& option determines whether the suffix is
17124 mandatory, and the wildcard * character, if present, must be the last
17125 character of the suffix. This option facility is commonly used to handle local
17126 parts of the form &%something-request%& and multiple user mailboxes of the form
17130 .option local_part_suffix_optional routers boolean false
17131 See &%local_part_suffix%& above.
17135 .option local_parts routers&!? "local part list&!!" unset
17136 .cindex "router" "restricting to specific local parts"
17137 .cindex "local part" "checking in router"
17138 The router is run only if the local part of the address matches the list.
17139 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
17141 section &<<SECTlocparlis>>& for a discussion of local part lists. Because the
17142 string is expanded, it is possible to make it depend on the domain, for
17145 local_parts = dbm;/usr/local/specials/$domain
17147 .vindex "&$local_part_data$&"
17148 If the match is achieved by a lookup, the data that the lookup returned
17149 for the local part is placed in the variable &$local_part_data$& for use in
17150 expansions of the router's private options. You might use this option, for
17151 example, if you have a large number of local virtual domains, and you want to
17152 send all postmaster mail to the same place without having to set up an alias in
17153 each virtual domain:
17157 local_parts = postmaster
17158 data = postmaster@real.domain.example
17162 .option log_as_local routers boolean "see below"
17163 .cindex "log" "delivery line"
17164 .cindex "delivery" "log line format"
17165 Exim has two logging styles for delivery, the idea being to make local
17166 deliveries stand out more visibly from remote ones. In the &"local"& style, the
17167 recipient address is given just as the local part, without a domain. The use of
17168 this style is controlled by this option. It defaults to true for the &(accept)&
17169 router, and false for all the others. This option applies only when a
17170 router assigns an address to a transport. It has no effect on routers that
17171 redirect addresses.
17175 .option more routers boolean&!! true
17176 The result of string expansion for this option must be a valid boolean value,
17177 that is, one of the strings &"yes"&, &"no"&, &"true"&, or &"false"&. Any other
17178 result causes an error, and delivery is deferred. If the expansion is forced to
17179 fail, the default value for the option (true) is used. Other failures cause
17180 delivery to be deferred.
17182 If this option is set false, and the router declines to handle the address, no
17183 further routers are tried, routing fails, and the address is bounced.
17185 However, if the router explicitly passes an address to the following router by
17186 means of the setting
17190 or otherwise, the setting of &%more%& is ignored. Also, the setting of &%more%&
17191 does not affect the behaviour if one of the precondition tests fails. In that
17192 case, the address is always passed to the next router.
17194 Note that &%address_data%& is not considered to be a precondition. If its
17195 expansion is forced to fail, the router declines, and the value of &%more%&
17196 controls what happens next.
17199 .option pass_on_timeout routers boolean false
17200 .cindex "timeout" "of router"
17201 .cindex "router" "timeout"
17202 If a router times out during a host lookup, it normally causes deferral of the
17203 address. If &%pass_on_timeout%& is set, the address is passed on to the next
17204 router, overriding &%no_more%&. This may be helpful for systems that are
17205 intermittently connected to the Internet, or those that want to pass to a smart
17206 host any messages that cannot immediately be delivered.
17208 There are occasional other temporary errors that can occur while doing DNS
17209 lookups. They are treated in the same way as a timeout, and this option
17210 applies to all of them.
17214 .option pass_router routers string unset
17215 .cindex "router" "go to after &""pass""&"
17216 Routers that recognize the generic &%self%& option (&(dnslookup)&,
17217 &(ipliteral)&, and &(manualroute)&) are able to return &"pass"&, forcing
17218 routing to continue, and overriding a false setting of &%more%&. When one of
17219 these routers returns &"pass"&, the address is normally handed on to the next
17220 router in sequence. This can be changed by setting &%pass_router%& to the name
17221 of another router. However (unlike &%redirect_router%&) the named router must
17222 be below the current router, to avoid loops. Note that this option applies only
17223 to the special case of &"pass"&. It does not apply when a router returns
17224 &"decline"& because it cannot handle an address.
17228 .option redirect_router routers string unset
17229 .cindex "router" "start at after redirection"
17230 Sometimes an administrator knows that it is pointless to reprocess addresses
17231 generated from alias or forward files with the same router again. For
17232 example, if an alias file translates real names into login ids there is no
17233 point searching the alias file a second time, especially if it is a large file.
17235 The &%redirect_router%& option can be set to the name of any router instance.
17236 It causes the routing of any generated addresses to start at the named router
17237 instead of at the first router. This option has no effect if the router in
17238 which it is set does not generate new addresses.
17242 .option require_files routers&!? "string list&!!" unset
17243 .cindex "file" "requiring for router"
17244 .cindex "router" "requiring file existence"
17245 This option provides a general mechanism for predicating the running of a
17246 router on the existence or non-existence of certain files or directories.
17247 Before running a router, as one of its precondition tests, Exim works its way
17248 through the &%require_files%& list, expanding each item separately.
17250 Because the list is split before expansion, any colons in expansion items must
17251 be doubled, or the facility for using a different list separator must be used.
17252 If any expansion is forced to fail, the item is ignored. Other expansion
17253 failures cause routing of the address to be deferred.
17255 If any expanded string is empty, it is ignored. Otherwise, except as described
17256 below, each string must be a fully qualified file path, optionally preceded by
17257 &"!"&. The paths are passed to the &[stat()]& function to test for the
17258 existence of the files or directories. The router is skipped if any paths not
17259 preceded by &"!"& do not exist, or if any paths preceded by &"!"& do exist.
17262 If &[stat()]& cannot determine whether a file exists or not, delivery of
17263 the message is deferred. This can happen when NFS-mounted filesystems are
17266 This option is checked after the &%domains%&, &%local_parts%&, and &%senders%&
17267 options, so you cannot use it to check for the existence of a file in which to
17268 look up a domain, local part, or sender. (See section &<<SECTrouprecon>>& for a
17269 full list of the order in which preconditions are evaluated.) However, as
17270 these options are all expanded, you can use the &%exists%& expansion condition
17271 to make such tests. The &%require_files%& option is intended for checking files
17272 that the router may be going to use internally, or which are needed by a
17273 transport (for example &_.procmailrc_&).
17275 During delivery, the &[stat()]& function is run as root, but there is a
17276 facility for some checking of the accessibility of a file by another user.
17277 This is not a proper permissions check, but just a &"rough"& check that
17278 operates as follows:
17280 If an item in a &%require_files%& list does not contain any forward slash
17281 characters, it is taken to be the user (and optional group, separated by a
17282 comma) to be checked for subsequent files in the list. If no group is specified
17283 but the user is specified symbolically, the gid associated with the uid is
17286 require_files = mail:/some/file
17287 require_files = $local_part:$home/.procmailrc
17289 If a user or group name in a &%require_files%& list does not exist, the
17290 &%require_files%& condition fails.
17292 Exim performs the check by scanning along the components of the file path, and
17293 checking the access for the given uid and gid. It checks for &"x"& access on
17294 directories, and &"r"& access on the final file. Note that this means that file
17295 access control lists, if the operating system has them, are ignored.
17297 &*Warning 1*&: When the router is being run to verify addresses for an
17298 incoming SMTP message, Exim is not running as root, but under its own uid. This
17299 may affect the result of a &%require_files%& check. In particular, &[stat()]&
17300 may yield the error EACCES (&"Permission denied"&). This means that the Exim
17301 user is not permitted to read one of the directories on the file's path.
17303 &*Warning 2*&: Even when Exim is running as root while delivering a message,
17304 &[stat()]& can yield EACCES for a file in an NFS directory that is mounted
17305 without root access. In this case, if a check for access by a particular user
17306 is requested, Exim creates a subprocess that runs as that user, and tries the
17307 check again in that process.
17309 The default action for handling an unresolved EACCES is to consider it to
17310 be caused by a configuration error, and routing is deferred because the
17311 existence or non-existence of the file cannot be determined. However, in some
17312 circumstances it may be desirable to treat this condition as if the file did
17313 not exist. If the file name (or the exclamation mark that precedes the file
17314 name for non-existence) is preceded by a plus sign, the EACCES error is treated
17315 as if the file did not exist. For example:
17317 require_files = +/some/file
17319 If the router is not an essential part of verification (for example, it
17320 handles users' &_.forward_& files), another solution is to set the &%verify%&
17321 option false so that the router is skipped when verifying.
17325 .option retry_use_local_part routers boolean "see below"
17326 .cindex "hints database" "retry keys"
17327 .cindex "local part" "in retry keys"
17328 When a delivery suffers a temporary routing failure, a retry record is created
17329 in Exim's hints database. For addresses whose routing depends only on the
17330 domain, the key for the retry record should not involve the local part, but for
17331 other addresses, both the domain and the local part should be included.
17332 Usually, remote routing is of the former kind, and local routing is of the
17335 This option controls whether the local part is used to form the key for retry
17336 hints for addresses that suffer temporary errors while being handled by this
17337 router. The default value is true for any router that has &%check_local_user%&
17338 set, and false otherwise. Note that this option does not apply to hints keys
17339 for transport delays; they are controlled by a generic transport option of the
17342 The setting of &%retry_use_local_part%& applies only to the router on which it
17343 appears. If the router generates child addresses, they are routed
17344 independently; this setting does not become attached to them.
17348 .option router_home_directory routers string&!! unset
17349 .cindex "router" "home directory for"
17350 .cindex "home directory" "for router"
17352 This option sets a home directory for use while the router is running. (Compare
17353 &%transport_home_directory%&, which sets a home directory for later
17354 transporting.) In particular, if used on a &(redirect)& router, this option
17355 sets a value for &$home$& while a filter is running. The value is expanded;
17356 forced expansion failure causes the option to be ignored &-- other failures
17357 cause the router to defer.
17359 Expansion of &%router_home_directory%& happens immediately after the
17360 &%check_local_user%& test (if configured), before any further expansions take
17362 (See section &<<SECTrouprecon>>& for a list of the order in which preconditions
17364 While the router is running, &%router_home_directory%& overrides the value of
17365 &$home$& that came from &%check_local_user%&.
17367 When a router accepts an address and assigns it to a local transport (including
17368 the cases when a &(redirect)& router generates a pipe, file, or autoreply
17369 delivery), the home directory setting for the transport is taken from the first
17370 of these values that is set:
17373 The &%home_directory%& option on the transport;
17375 The &%transport_home_directory%& option on the router;
17377 The password data if &%check_local_user%& is set on the router;
17379 The &%router_home_directory%& option on the router.
17382 In other words, &%router_home_directory%& overrides the password data for the
17383 router, but not for the transport.
17387 .option self routers string freeze
17388 .cindex "MX record" "pointing to local host"
17389 .cindex "local host" "MX pointing to"
17390 This option applies to those routers that use a recipient address to find a
17391 list of remote hosts. Currently, these are the &(dnslookup)&, &(ipliteral)&,
17392 and &(manualroute)& routers.
17393 Certain configurations of the &(queryprogram)& router can also specify a list
17395 Usually such routers are configured to send the message to a remote host via an
17396 &(smtp)& transport. The &%self%& option specifies what happens when the first
17397 host on the list turns out to be the local host.
17398 The way in which Exim checks for the local host is described in section
17399 &<<SECTreclocipadd>>&.
17401 Normally this situation indicates either an error in Exim's configuration (for
17402 example, the router should be configured not to process this domain), or an
17403 error in the DNS (for example, the MX should not point to this host). For this
17404 reason, the default action is to log the incident, defer the address, and
17405 freeze the message. The following alternatives are provided for use in special
17410 Delivery of the message is tried again later, but the message is not frozen.
17412 .vitem "&%reroute%&: <&'domain'&>"
17413 The domain is changed to the given domain, and the address is passed back to
17414 be reprocessed by the routers. No rewriting of headers takes place. This
17415 behaviour is essentially a redirection.
17417 .vitem "&%reroute: rewrite:%& <&'domain'&>"
17418 The domain is changed to the given domain, and the address is passed back to be
17419 reprocessed by the routers. Any headers that contain the original domain are
17424 .vindex "&$self_hostname$&"
17425 The router passes the address to the next router, or to the router named in the
17426 &%pass_router%& option if it is set. This overrides &%no_more%&. During
17427 subsequent routing and delivery, the variable &$self_hostname$& contains the
17428 name of the local host that the router encountered. This can be used to
17429 distinguish between different cases for hosts with multiple names. The
17435 ensures that only those addresses that routed to the local host are passed on.
17436 Without &%no_more%&, addresses that were declined for other reasons would also
17437 be passed to the next router.
17440 Delivery fails and an error report is generated.
17443 .cindex "local host" "sending to"
17444 The anomaly is ignored and the address is queued for the transport. This
17445 setting should be used with extreme caution. For an &(smtp)& transport, it
17446 makes sense only in cases where the program that is listening on the SMTP port
17447 is not this version of Exim. That is, it must be some other MTA, or Exim with a
17448 different configuration file that handles the domain in another way.
17453 .option senders routers&!? "address list&!!" unset
17454 .cindex "router" "checking senders"
17455 If this option is set, the router is skipped unless the message's sender
17456 address matches something on the list.
17457 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
17460 There are issues concerning verification when the running of routers is
17461 dependent on the sender. When Exim is verifying the address in an &%errors_to%&
17462 setting, it sets the sender to the null string. When using the &%-bt%& option
17463 to check a configuration file, it is necessary also to use the &%-f%& option to
17464 set an appropriate sender. For incoming mail, the sender is unset when
17465 verifying the sender, but is available when verifying any recipients. If the
17466 SMTP VRFY command is enabled, it must be used after MAIL if the sender address
17470 .option translate_ip_address routers string&!! unset
17471 .cindex "IP address" "translating"
17472 .cindex "packet radio"
17473 .cindex "router" "IP address translation"
17474 There exist some rare networking situations (for example, packet radio) where
17475 it is helpful to be able to translate IP addresses generated by normal routing
17476 mechanisms into other IP addresses, thus performing a kind of manual IP
17477 routing. This should be done only if the normal IP routing of the TCP/IP stack
17478 is inadequate or broken. Because this is an extremely uncommon requirement, the
17479 code to support this option is not included in the Exim binary unless
17480 SUPPORT_TRANSLATE_IP_ADDRESS=yes is set in &_Local/Makefile_&.
17482 .vindex "&$host_address$&"
17483 The &%translate_ip_address%& string is expanded for every IP address generated
17484 by the router, with the generated address set in &$host_address$&. If the
17485 expansion is forced to fail, no action is taken.
17486 For any other expansion error, delivery of the message is deferred.
17487 If the result of the expansion is an IP address, that replaces the original
17488 address; otherwise the result is assumed to be a host name &-- this is looked
17489 up using &[gethostbyname()]& (or &[getipnodebyname()]& when available) to
17490 produce one or more replacement IP addresses. For example, to subvert all IP
17491 addresses in some specific networks, this could be added to a router:
17493 translate_ip_address = \
17494 ${lookup{${mask:$host_address/26}}lsearch{/some/file}\
17497 The file would contain lines like
17499 10.2.3.128/26 some.host
17500 10.8.4.34/26 10.44.8.15
17502 You should not make use of this facility unless you really understand what you
17507 .option transport routers string&!! unset
17508 This option specifies the transport to be used when a router accepts an address
17509 and sets it up for delivery. A transport is never needed if a router is used
17510 only for verification. The value of the option is expanded at routing time,
17511 after the expansion of &%errors_to%&, &%headers_add%&, and &%headers_remove%&,
17512 and result must be the name of one of the configured transports. If it is not,
17513 delivery is deferred.
17515 The &%transport%& option is not used by the &(redirect)& router, but it does
17516 have some private options that set up transports for pipe and file deliveries
17517 (see chapter &<<CHAPredirect>>&).
17521 .option transport_current_directory routers string&!! unset
17522 .cindex "current directory for local transport"
17523 This option associates a current directory with any address that is routed
17524 to a local transport. This can happen either because a transport is
17525 explicitly configured for the router, or because it generates a delivery to a
17526 file or a pipe. During the delivery process (that is, at transport time), this
17527 option string is expanded and is set as the current directory, unless
17528 overridden by a setting on the transport.
17529 If the expansion fails for any reason, including forced failure, an error is
17530 logged, and delivery is deferred.
17531 See chapter &<<CHAPenvironment>>& for details of the local delivery
17537 .option transport_home_directory routers string&!! "see below"
17538 .cindex "home directory" "for local transport"
17539 This option associates a home directory with any address that is routed to a
17540 local transport. This can happen either because a transport is explicitly
17541 configured for the router, or because it generates a delivery to a file or a
17542 pipe. During the delivery process (that is, at transport time), the option
17543 string is expanded and is set as the home directory, unless overridden by a
17544 setting of &%home_directory%& on the transport.
17545 If the expansion fails for any reason, including forced failure, an error is
17546 logged, and delivery is deferred.
17548 If the transport does not specify a home directory, and
17549 &%transport_home_directory%& is not set for the router, the home directory for
17550 the transport is taken from the password data if &%check_local_user%& is set for
17551 the router. Otherwise it is taken from &%router_home_directory%& if that option
17552 is set; if not, no home directory is set for the transport.
17554 See chapter &<<CHAPenvironment>>& for further details of the local delivery
17560 .option unseen routers boolean&!! false
17561 .cindex "router" "carrying on after success"
17562 The result of string expansion for this option must be a valid boolean value,
17563 that is, one of the strings &"yes"&, &"no"&, &"true"&, or &"false"&. Any other
17564 result causes an error, and delivery is deferred. If the expansion is forced to
17565 fail, the default value for the option (false) is used. Other failures cause
17566 delivery to be deferred.
17568 When this option is set true, routing does not cease if the router accepts the
17569 address. Instead, a copy of the incoming address is passed to the next router,
17570 overriding a false setting of &%more%&. There is little point in setting
17571 &%more%& false if &%unseen%& is always true, but it may be useful in cases when
17572 the value of &%unseen%& contains expansion items (and therefore, presumably, is
17573 sometimes true and sometimes false).
17575 .cindex "copy of message (&%unseen%& option)"
17576 Setting the &%unseen%& option has a similar effect to the &%unseen%& command
17577 qualifier in filter files. It can be used to cause copies of messages to be
17578 delivered to some other destination, while also carrying out a normal delivery.
17579 In effect, the current address is made into a &"parent"& that has two children
17580 &-- one that is delivered as specified by this router, and a clone that goes on
17581 to be routed further. For this reason, &%unseen%& may not be combined with the
17582 &%one_time%& option in a &(redirect)& router.
17584 &*Warning*&: Header lines added to the address (or specified for removal) by
17585 this router or by previous routers affect the &"unseen"& copy of the message
17586 only. The clone that continues to be processed by further routers starts with
17587 no added headers and none specified for removal. For a &%redirect%& router, if
17588 a generated address is the same as the incoming address, this can lead to
17589 duplicate addresses with different header modifications. Exim does not do
17590 duplicate deliveries (except, in certain circumstances, to pipes -- see section
17591 &<<SECTdupaddr>>&), but it is undefined which of the duplicates is discarded,
17592 so this ambiguous situation should be avoided. The &%repeat_use%& option of the
17593 &%redirect%& router may be of help.
17595 Unlike the handling of header modifications, any data that was set by the
17596 &%address_data%& option in the current or previous routers &'is'& passed on to
17597 subsequent routers.
17600 .option user routers string&!! "see below"
17601 .cindex "uid (user id)" "local delivery"
17602 .cindex "local transports" "uid and gid"
17603 .cindex "transport" "local"
17604 .cindex "router" "user for filter processing"
17605 .cindex "filter" "user for processing"
17606 When a router queues an address for a transport, and the transport does not
17607 specify a user, the user given here is used when running the delivery process.
17608 The user may be specified numerically or by name. If expansion fails, the
17609 error is logged and delivery is deferred.
17610 This user is also used by the &(redirect)& router when running a filter file.
17611 The default is unset, except when &%check_local_user%& is set. In this case,
17612 the default is taken from the password information. If the user is specified as
17613 a name, and &%group%& is not set, the group associated with the user is used.
17614 See also &%initgroups%& and &%group%& and the discussion in chapter
17615 &<<CHAPenvironment>>&.
17619 .option verify routers&!? boolean true
17620 Setting this option has the effect of setting &%verify_sender%& and
17621 &%verify_recipient%& to the same value.
17624 .option verify_only routers&!? boolean false
17625 .cindex "EXPN" "with &%verify_only%&"
17627 .cindex "router" "used only when verifying"
17628 If this option is set, the router is used only when verifying an address,
17629 delivering in cutthrough mode or
17630 testing with the &%-bv%& option, not when actually doing a delivery, testing
17631 with the &%-bt%& option, or running the SMTP EXPN command. It can be further
17632 restricted to verifying only senders or recipients by means of
17633 &%verify_sender%& and &%verify_recipient%&.
17635 &*Warning*&: When the router is being run to verify addresses for an incoming
17636 SMTP message, Exim is not running as root, but under its own uid. If the router
17637 accesses any files, you need to make sure that they are accessible to the Exim
17641 .option verify_recipient routers&!? boolean true
17642 If this option is false, the router is skipped when verifying recipient
17644 delivering in cutthrough mode
17645 or testing recipient verification using &%-bv%&.
17646 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
17650 .option verify_sender routers&!? boolean true
17651 If this option is false, the router is skipped when verifying sender addresses
17652 or testing sender verification using &%-bvs%&.
17653 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
17655 .ecindex IIDgenoprou1
17656 .ecindex IIDgenoprou2
17663 . ////////////////////////////////////////////////////////////////////////////
17664 . ////////////////////////////////////////////////////////////////////////////
17666 .chapter "The accept router" "CHID4"
17667 .cindex "&(accept)& router"
17668 .cindex "routers" "&(accept)&"
17669 The &(accept)& router has no private options of its own. Unless it is being
17670 used purely for verification (see &%verify_only%&) a transport is required to
17671 be defined by the generic &%transport%& option. If the preconditions that are
17672 specified by generic options are met, the router accepts the address and queues
17673 it for the given transport. The most common use of this router is for setting
17674 up deliveries to local mailboxes. For example:
17678 domains = mydomain.example
17680 transport = local_delivery
17682 The &%domains%& condition in this example checks the domain of the address, and
17683 &%check_local_user%& checks that the local part is the login of a local user.
17684 When both preconditions are met, the &(accept)& router runs, and queues the
17685 address for the &(local_delivery)& transport.
17692 . ////////////////////////////////////////////////////////////////////////////
17693 . ////////////////////////////////////////////////////////////////////////////
17695 .chapter "The dnslookup router" "CHAPdnslookup"
17696 .scindex IIDdnsrou1 "&(dnslookup)& router"
17697 .scindex IIDdnsrou2 "routers" "&(dnslookup)&"
17698 The &(dnslookup)& router looks up the hosts that handle mail for the
17699 recipient's domain in the DNS. A transport must always be set for this router,
17700 unless &%verify_only%& is set.
17702 If SRV support is configured (see &%check_srv%& below), Exim first searches for
17703 SRV records. If none are found, or if SRV support is not configured,
17704 MX records are looked up. If no MX records exist, address records are sought.
17705 However, &%mx_domains%& can be set to disable the direct use of address
17708 MX records of equal priority are sorted by Exim into a random order. Exim then
17709 looks for address records for the host names obtained from MX or SRV records.
17710 When a host has more than one IP address, they are sorted into a random order,
17711 except that IPv6 addresses are always sorted before IPv4 addresses. If all the
17712 IP addresses found are discarded by a setting of the &%ignore_target_hosts%&
17713 generic option, the router declines.
17715 Unless they have the highest priority (lowest MX value), MX records that point
17716 to the local host, or to any host name that matches &%hosts_treat_as_local%&,
17717 are discarded, together with any other MX records of equal or lower priority.
17719 .cindex "MX record" "pointing to local host"
17720 .cindex "local host" "MX pointing to"
17721 .oindex "&%self%&" "in &(dnslookup)& router"
17722 If the host pointed to by the highest priority MX record, or looked up as an
17723 address record, is the local host, or matches &%hosts_treat_as_local%&, what
17724 happens is controlled by the generic &%self%& option.
17727 .section "Problems with DNS lookups" "SECTprowitdnsloo"
17728 There have been problems with DNS servers when SRV records are looked up.
17729 Some mis-behaving servers return a DNS error or timeout when a non-existent
17730 SRV record is sought. Similar problems have in the past been reported for
17731 MX records. The global &%dns_again_means_nonexist%& option can help with this
17732 problem, but it is heavy-handed because it is a global option.
17734 For this reason, there are two options, &%srv_fail_domains%& and
17735 &%mx_fail_domains%&, that control what happens when a DNS lookup in a
17736 &(dnslookup)& router results in a DNS failure or a &"try again"& response. If
17737 an attempt to look up an SRV or MX record causes one of these results, and the
17738 domain matches the relevant list, Exim behaves as if the DNS had responded &"no
17739 such record"&. In the case of an SRV lookup, this means that the router
17740 proceeds to look for MX records; in the case of an MX lookup, it proceeds to
17741 look for A or AAAA records, unless the domain matches &%mx_domains%&, in which
17742 case routing fails.
17745 .section "Declining addresses by dnslookup" "SECTdnslookupdecline"
17746 .cindex "&(dnslookup)& router" "declines"
17747 There are a few cases where a &(dnslookup)& router will decline to accept
17748 an address; if such a router is expected to handle "all remaining non-local
17749 domains", then it is important to set &%no_more%&.
17751 Reasons for a &(dnslookup)& router to decline currently include:
17753 The domain does not exist in DNS
17755 The domain exists but the MX record's host part is just "."; this is a common
17756 convention (borrowed from SRV) used to indicate that there is no such service
17757 for this domain and to not fall back to trying A/AAAA records.
17759 Ditto, but for SRV records, when &%check_srv%& is set on this router.
17761 MX record points to a non-existent host.
17763 MX record points to an IP address and the main section option
17764 &%allow_mx_to_ip%& is not set.
17766 MX records exist and point to valid hosts, but all hosts resolve only to
17767 addresses blocked by the &%ignore_target_hosts%& generic option on this router.
17769 The domain is not syntactically valid (see also &%allow_utf8_domains%& and
17770 &%dns_check_names_pattern%& for handling one variant of this)
17772 &%check_secondary_mx%& is set on this router but the local host can
17773 not be found in the MX records (see below)
17779 .section "Private options for dnslookup" "SECID118"
17780 .cindex "options" "&(dnslookup)& router"
17781 The private options for the &(dnslookup)& router are as follows:
17783 .option check_secondary_mx dnslookup boolean false
17784 .cindex "MX record" "checking for secondary"
17785 If this option is set, the router declines unless the local host is found in
17786 (and removed from) the list of hosts obtained by MX lookup. This can be used to
17787 process domains for which the local host is a secondary mail exchanger
17788 differently to other domains. The way in which Exim decides whether a host is
17789 the local host is described in section &<<SECTreclocipadd>>&.
17792 .option check_srv dnslookup string&!! unset
17793 .cindex "SRV record" "enabling use of"
17794 The &(dnslookup)& router supports the use of SRV records (see RFC 2782) in
17795 addition to MX and address records. The support is disabled by default. To
17796 enable SRV support, set the &%check_srv%& option to the name of the service
17797 required. For example,
17801 looks for SRV records that refer to the normal smtp service. The option is
17802 expanded, so the service name can vary from message to message or address
17803 to address. This might be helpful if SRV records are being used for a
17804 submission service. If the expansion is forced to fail, the &%check_srv%&
17805 option is ignored, and the router proceeds to look for MX records in the
17808 When the expansion succeeds, the router searches first for SRV records for
17809 the given service (it assumes TCP protocol). A single SRV record with a
17810 host name that consists of just a single dot indicates &"no such service for
17811 this domain"&; if this is encountered, the router declines. If other kinds of
17812 SRV record are found, they are used to construct a host list for delivery
17813 according to the rules of RFC 2782. MX records are not sought in this case.
17815 When no SRV records are found, MX records (and address records) are sought in
17816 the traditional way. In other words, SRV records take precedence over MX
17817 records, just as MX records take precedence over address records. Note that
17818 this behaviour is not sanctioned by RFC 2782, though a previous draft RFC
17819 defined it. It is apparently believed that MX records are sufficient for email
17820 and that SRV records should not be used for this purpose. However, SRV records
17821 have an additional &"weight"& feature which some people might find useful when
17822 trying to split an SMTP load between hosts of different power.
17824 See section &<<SECTprowitdnsloo>>& above for a discussion of Exim's behaviour
17825 when there is a DNS lookup error.
17830 .option dnssec_request_domains dnslookup "domain list&!!" unset
17831 .cindex "MX record" "security"
17832 .cindex "DNSSEC" "MX lookup"
17833 .cindex "security" "MX lookup"
17834 .cindex "DNS" "DNSSEC"
17835 DNS lookups for domains matching &%dnssec_request_domains%& will be done with
17836 the dnssec request bit set.
17837 This applies to all of the SRV, MX A6, AAAA, A lookup sequence.
17843 .option dnssec_require_domains dnslookup "domain list&!!" unset
17844 .cindex "MX record" "security"
17845 .cindex "DNSSEC" "MX lookup"
17846 .cindex "security" "MX lookup"
17847 .cindex "DNS" "DNSSEC"
17848 DNS lookups for domains matching &%dnssec_request_domains%& will be done with
17849 the dnssec request bit set. Any returns not having the Authenticated Data bit
17850 (AD bit) set wil be ignored and logged as a host-lookup failure.
17851 This applies to all of the SRV, MX A6, AAAA, A lookup sequence.
17856 .option mx_domains dnslookup "domain list&!!" unset
17857 .cindex "MX record" "required to exist"
17858 .cindex "SRV record" "required to exist"
17859 A domain that matches &%mx_domains%& is required to have either an MX or an SRV
17860 record in order to be recognized. (The name of this option could be improved.)
17861 For example, if all the mail hosts in &'fict.example'& are known to have MX
17862 records, except for those in &'discworld.fict.example'&, you could use this
17865 mx_domains = ! *.discworld.fict.example : *.fict.example
17867 This specifies that messages addressed to a domain that matches the list but
17868 has no MX record should be bounced immediately instead of being routed using
17869 the address record.
17872 .option mx_fail_domains dnslookup "domain list&!!" unset
17873 If the DNS lookup for MX records for one of the domains in this list causes a
17874 DNS lookup error, Exim behaves as if no MX records were found. See section
17875 &<<SECTprowitdnsloo>>& for more discussion.
17880 .option qualify_single dnslookup boolean true
17881 .cindex "DNS" "resolver options"
17882 .cindex "DNS" "qualifying single-component names"
17883 When this option is true, the resolver option RES_DEFNAMES is set for DNS
17884 lookups. Typically, but not standardly, this causes the resolver to qualify
17885 single-component names with the default domain. For example, on a machine
17886 called &'dictionary.ref.example'&, the domain &'thesaurus'& would be changed to
17887 &'thesaurus.ref.example'& inside the resolver. For details of what your
17888 resolver actually does, consult your man pages for &'resolver'& and
17893 .option rewrite_headers dnslookup boolean true
17894 .cindex "rewriting" "header lines"
17895 .cindex "header lines" "rewriting"
17896 If the domain name in the address that is being processed is not fully
17897 qualified, it may be expanded to its full form by a DNS lookup. For example, if
17898 an address is specified as &'dormouse@teaparty'&, the domain might be
17899 expanded to &'teaparty.wonderland.fict.example'&. Domain expansion can also
17900 occur as a result of setting the &%widen_domains%& option. If
17901 &%rewrite_headers%& is true, all occurrences of the abbreviated domain name in
17902 any &'Bcc:'&, &'Cc:'&, &'From:'&, &'Reply-to:'&, &'Sender:'&, and &'To:'&
17903 header lines of the message are rewritten with the full domain name.
17905 This option should be turned off only when it is known that no message is
17906 ever going to be sent outside an environment where the abbreviation makes
17909 When an MX record is looked up in the DNS and matches a wildcard record, name
17910 servers normally return a record containing the name that has been looked up,
17911 making it impossible to detect whether a wildcard was present or not. However,
17912 some name servers have recently been seen to return the wildcard entry. If the
17913 name returned by a DNS lookup begins with an asterisk, it is not used for
17917 .option same_domain_copy_routing dnslookup boolean false
17918 .cindex "address" "copying routing"
17919 Addresses with the same domain are normally routed by the &(dnslookup)& router
17920 to the same list of hosts. However, this cannot be presumed, because the router
17921 options and preconditions may refer to the local part of the address. By
17922 default, therefore, Exim routes each address in a message independently. DNS
17923 servers run caches, so repeated DNS lookups are not normally expensive, and in
17924 any case, personal messages rarely have more than a few recipients.
17926 If you are running mailing lists with large numbers of subscribers at the same
17927 domain, and you are using a &(dnslookup)& router which is independent of the
17928 local part, you can set &%same_domain_copy_routing%& to bypass repeated DNS
17929 lookups for identical domains in one message. In this case, when &(dnslookup)&
17930 routes an address to a remote transport, any other unrouted addresses in the
17931 message that have the same domain are automatically given the same routing
17932 without processing them independently,
17933 provided the following conditions are met:
17936 No router that processed the address specified &%headers_add%& or
17937 &%headers_remove%&.
17939 The router did not change the address in any way, for example, by &"widening"&
17946 .option search_parents dnslookup boolean false
17947 .cindex "DNS" "resolver options"
17948 When this option is true, the resolver option RES_DNSRCH is set for DNS
17949 lookups. This is different from the &%qualify_single%& option in that it
17950 applies to domains containing dots. Typically, but not standardly, it causes
17951 the resolver to search for the name in the current domain and in parent
17952 domains. For example, on a machine in the &'fict.example'& domain, if looking
17953 up &'teaparty.wonderland'& failed, the resolver would try
17954 &'teaparty.wonderland.fict.example'&. For details of what your resolver
17955 actually does, consult your man pages for &'resolver'& and &'resolv.conf'&.
17957 Setting this option true can cause problems in domains that have a wildcard MX
17958 record, because any domain that does not have its own MX record matches the
17963 .option srv_fail_domains dnslookup "domain list&!!" unset
17964 If the DNS lookup for SRV records for one of the domains in this list causes a
17965 DNS lookup error, Exim behaves as if no SRV records were found. See section
17966 &<<SECTprowitdnsloo>>& for more discussion.
17971 .option widen_domains dnslookup "string list" unset
17972 .cindex "domain" "partial; widening"
17973 If a DNS lookup fails and this option is set, each of its strings in turn is
17974 added onto the end of the domain, and the lookup is tried again. For example,
17977 widen_domains = fict.example:ref.example
17979 is set and a lookup of &'klingon.dictionary'& fails,
17980 &'klingon.dictionary.fict.example'& is looked up, and if this fails,
17981 &'klingon.dictionary.ref.example'& is tried. Note that the &%qualify_single%&
17982 and &%search_parents%& options can cause some widening to be undertaken inside
17983 the DNS resolver. &%widen_domains%& is not applied to sender addresses
17984 when verifying, unless &%rewrite_headers%& is false (not the default).
17987 .section "Effect of qualify_single and search_parents" "SECID119"
17988 When a domain from an envelope recipient is changed by the resolver as a result
17989 of the &%qualify_single%& or &%search_parents%& options, Exim rewrites the
17990 corresponding address in the message's header lines unless &%rewrite_headers%&
17991 is set false. Exim then re-routes the address, using the full domain.
17993 These two options affect only the DNS lookup that takes place inside the router
17994 for the domain of the address that is being routed. They do not affect lookups
17995 such as that implied by
17999 that may happen while processing a router precondition before the router is
18000 entered. No widening ever takes place for these lookups.
18001 .ecindex IIDdnsrou1
18002 .ecindex IIDdnsrou2
18012 . ////////////////////////////////////////////////////////////////////////////
18013 . ////////////////////////////////////////////////////////////////////////////
18015 .chapter "The ipliteral router" "CHID5"
18016 .cindex "&(ipliteral)& router"
18017 .cindex "domain literal" "routing"
18018 .cindex "routers" "&(ipliteral)&"
18019 This router has no private options. Unless it is being used purely for
18020 verification (see &%verify_only%&) a transport is required to be defined by the
18021 generic &%transport%& option. The router accepts the address if its domain part
18022 takes the form of an RFC 2822 domain literal. For example, the &(ipliteral)&
18023 router handles the address
18027 by setting up delivery to the host with that IP address. IPv4 domain literals
18028 consist of an IPv4 address enclosed in square brackets. IPv6 domain literals
18029 are similar, but the address is preceded by &`ipv6:`&. For example:
18031 postmaster@[ipv6:fe80::a00:20ff:fe86:a061.5678]
18033 Exim allows &`ipv4:`& before IPv4 addresses, for consistency, and on the
18034 grounds that sooner or later somebody will try it.
18036 .oindex "&%self%&" "in &(ipliteral)& router"
18037 If the IP address matches something in &%ignore_target_hosts%&, the router
18038 declines. If an IP literal turns out to refer to the local host, the generic
18039 &%self%& option determines what happens.
18041 The RFCs require support for domain literals; however, their use is
18042 controversial in today's Internet. If you want to use this router, you must
18043 also set the main configuration option &%allow_domain_literals%&. Otherwise,
18044 Exim will not recognize the domain literal syntax in addresses.
18048 . ////////////////////////////////////////////////////////////////////////////
18049 . ////////////////////////////////////////////////////////////////////////////
18051 .chapter "The iplookup router" "CHID6"
18052 .cindex "&(iplookup)& router"
18053 .cindex "routers" "&(iplookup)&"
18054 The &(iplookup)& router was written to fulfil a specific requirement in
18055 Cambridge University (which in fact no longer exists). For this reason, it is
18056 not included in the binary of Exim by default. If you want to include it, you
18059 ROUTER_IPLOOKUP=yes
18061 in your &_Local/Makefile_& configuration file.
18063 The &(iplookup)& router routes an address by sending it over a TCP or UDP
18064 connection to one or more specific hosts. The host can then return the same or
18065 a different address &-- in effect rewriting the recipient address in the
18066 message's envelope. The new address is then passed on to subsequent routers. If
18067 this process fails, the address can be passed on to other routers, or delivery
18068 can be deferred. Since &(iplookup)& is just a rewriting router, a transport
18069 must not be specified for it.
18071 .cindex "options" "&(iplookup)& router"
18072 .option hosts iplookup string unset
18073 This option must be supplied. Its value is a colon-separated list of host
18074 names. The hosts are looked up using &[gethostbyname()]&
18075 (or &[getipnodebyname()]& when available)
18076 and are tried in order until one responds to the query. If none respond, what
18077 happens is controlled by &%optional%&.
18080 .option optional iplookup boolean false
18081 If &%optional%& is true, if no response is obtained from any host, the address
18082 is passed to the next router, overriding &%no_more%&. If &%optional%& is false,
18083 delivery to the address is deferred.
18086 .option port iplookup integer 0
18087 .cindex "port" "&(iplookup)& router"
18088 This option must be supplied. It specifies the port number for the TCP or UDP
18092 .option protocol iplookup string udp
18093 This option can be set to &"udp"& or &"tcp"& to specify which of the two
18094 protocols is to be used.
18097 .option query iplookup string&!! "see below"
18098 This defines the content of the query that is sent to the remote hosts. The
18101 $local_part@$domain $local_part@$domain
18103 The repetition serves as a way of checking that a response is to the correct
18104 query in the default case (see &%response_pattern%& below).
18107 .option reroute iplookup string&!! unset
18108 If this option is not set, the rerouted address is precisely the byte string
18109 returned by the remote host, up to the first white space, if any. If set, the
18110 string is expanded to form the rerouted address. It can include parts matched
18111 in the response by &%response_pattern%& by means of numeric variables such as
18112 &$1$&, &$2$&, etc. The variable &$0$& refers to the entire input string,
18113 whether or not a pattern is in use. In all cases, the rerouted address must end
18114 up in the form &'local_part@domain'&.
18117 .option response_pattern iplookup string unset
18118 This option can be set to a regular expression that is applied to the string
18119 returned from the remote host. If the pattern does not match the response, the
18120 router declines. If &%response_pattern%& is not set, no checking of the
18121 response is done, unless the query was defaulted, in which case there is a
18122 check that the text returned after the first white space is the original
18123 address. This checks that the answer that has been received is in response to
18124 the correct question. For example, if the response is just a new domain, the
18125 following could be used:
18127 response_pattern = ^([^@]+)$
18128 reroute = $local_part@$1
18131 .option timeout iplookup time 5s
18132 This specifies the amount of time to wait for a response from the remote
18133 machine. The same timeout is used for the &[connect()]& function for a TCP
18134 call. It does not apply to UDP.
18139 . ////////////////////////////////////////////////////////////////////////////
18140 . ////////////////////////////////////////////////////////////////////////////
18142 .chapter "The manualroute router" "CHID7"
18143 .scindex IIDmanrou1 "&(manualroute)& router"
18144 .scindex IIDmanrou2 "routers" "&(manualroute)&"
18145 .cindex "domain" "manually routing"
18146 The &(manualroute)& router is so-called because it provides a way of manually
18147 routing an address according to its domain. It is mainly used when you want to
18148 route addresses to remote hosts according to your own rules, bypassing the
18149 normal DNS routing that looks up MX records. However, &(manualroute)& can also
18150 route to local transports, a facility that may be useful if you want to save
18151 messages for dial-in hosts in local files.
18153 The &(manualroute)& router compares a list of domain patterns with the domain
18154 it is trying to route. If there is no match, the router declines. Each pattern
18155 has associated with it a list of hosts and some other optional data, which may
18156 include a transport. The combination of a pattern and its data is called a
18157 &"routing rule"&. For patterns that do not have an associated transport, the
18158 generic &%transport%& option must specify a transport, unless the router is
18159 being used purely for verification (see &%verify_only%&).
18162 In the case of verification, matching the domain pattern is sufficient for the
18163 router to accept the address. When actually routing an address for delivery,
18164 an address that matches a domain pattern is queued for the associated
18165 transport. If the transport is not a local one, a host list must be associated
18166 with the pattern; IP addresses are looked up for the hosts, and these are
18167 passed to the transport along with the mail address. For local transports, a
18168 host list is optional. If it is present, it is passed in &$host$& as a single
18171 The list of routing rules can be provided as an inline string in
18172 &%route_list%&, or the data can be obtained by looking up the domain in a file
18173 or database by setting &%route_data%&. Only one of these settings may appear in
18174 any one instance of &(manualroute)&. The format of routing rules is described
18175 below, following the list of private options.
18178 .section "Private options for manualroute" "SECTprioptman"
18180 .cindex "options" "&(manualroute)& router"
18181 The private options for the &(manualroute)& router are as follows:
18183 .option host_all_ignored manualroute string defer
18184 See &%host_find_failed%&.
18186 .option host_find_failed manualroute string freeze
18187 This option controls what happens when &(manualroute)& tries to find an IP
18188 address for a host, and the host does not exist. The option can be set to one
18189 of the following values:
18198 The default (&"freeze"&) assumes that this state is a serious configuration
18199 error. The difference between &"pass"& and &"decline"& is that the former
18200 forces the address to be passed to the next router (or the router defined by
18203 overriding &%no_more%&, whereas the latter passes the address to the next
18204 router only if &%more%& is true.
18206 The value &"ignore"& causes Exim to completely ignore a host whose IP address
18207 cannot be found. If all the hosts in the list are ignored, the behaviour is
18208 controlled by the &%host_all_ignored%& option. This takes the same values
18209 as &%host_find_failed%&, except that it cannot be set to &"ignore"&.
18211 The &%host_find_failed%& option applies only to a definite &"does not exist"&
18212 state; if a host lookup gets a temporary error, delivery is deferred unless the
18213 generic &%pass_on_timeout%& option is set.
18216 .option hosts_randomize manualroute boolean false
18217 .cindex "randomized host list"
18218 .cindex "host" "list of; randomized"
18219 If this option is set, the order of the items in a host list in a routing rule
18220 is randomized each time the list is used, unless an option in the routing rule
18221 overrides (see below). Randomizing the order of a host list can be used to do
18222 crude load sharing. However, if more than one mail address is routed by the
18223 same router to the same host list, the host lists are considered to be the same
18224 (even though they may be randomized into different orders) for the purpose of
18225 deciding whether to batch the deliveries into a single SMTP transaction.
18227 When &%hosts_randomize%& is true, a host list may be split
18228 into groups whose order is separately randomized. This makes it possible to
18229 set up MX-like behaviour. The boundaries between groups are indicated by an
18230 item that is just &`+`& in the host list. For example:
18232 route_list = * host1:host2:host3:+:host4:host5
18234 The order of the first three hosts and the order of the last two hosts is
18235 randomized for each use, but the first three always end up before the last two.
18236 If &%hosts_randomize%& is not set, a &`+`& item in the list is ignored. If a
18237 randomized host list is passed to an &(smtp)& transport that also has
18238 &%hosts_randomize set%&, the list is not re-randomized.
18241 .option route_data manualroute string&!! unset
18242 If this option is set, it must expand to yield the data part of a routing rule.
18243 Typically, the expansion string includes a lookup based on the domain. For
18246 route_data = ${lookup{$domain}dbm{/etc/routes}}
18248 If the expansion is forced to fail, or the result is an empty string, the
18249 router declines. Other kinds of expansion failure cause delivery to be
18253 .option route_list manualroute "string list" unset
18254 This string is a list of routing rules, in the form defined below. Note that,
18255 unlike most string lists, the items are separated by semicolons. This is so
18256 that they may contain colon-separated host lists.
18259 .option same_domain_copy_routing manualroute boolean false
18260 .cindex "address" "copying routing"
18261 Addresses with the same domain are normally routed by the &(manualroute)&
18262 router to the same list of hosts. However, this cannot be presumed, because the
18263 router options and preconditions may refer to the local part of the address. By
18264 default, therefore, Exim routes each address in a message independently. DNS
18265 servers run caches, so repeated DNS lookups are not normally expensive, and in
18266 any case, personal messages rarely have more than a few recipients.
18268 If you are running mailing lists with large numbers of subscribers at the same
18269 domain, and you are using a &(manualroute)& router which is independent of the
18270 local part, you can set &%same_domain_copy_routing%& to bypass repeated DNS
18271 lookups for identical domains in one message. In this case, when
18272 &(manualroute)& routes an address to a remote transport, any other unrouted
18273 addresses in the message that have the same domain are automatically given the
18274 same routing without processing them independently. However, this is only done
18275 if &%headers_add%& and &%headers_remove%& are unset.
18280 .section "Routing rules in route_list" "SECID120"
18281 The value of &%route_list%& is a string consisting of a sequence of routing
18282 rules, separated by semicolons. If a semicolon is needed in a rule, it can be
18283 entered as two semicolons. Alternatively, the list separator can be changed as
18284 described (for colon-separated lists) in section &<<SECTlistconstruct>>&.
18285 Empty rules are ignored. The format of each rule is
18287 <&'domain pattern'&> <&'list of hosts'&> <&'options'&>
18289 The following example contains two rules, each with a simple domain pattern and
18293 dict.ref.example mail-1.ref.example:mail-2.ref.example ; \
18294 thes.ref.example mail-3.ref.example:mail-4.ref.example
18296 The three parts of a rule are separated by white space. The pattern and the
18297 list of hosts can be enclosed in quotes if necessary, and if they are, the
18298 usual quoting rules apply. Each rule in a &%route_list%& must start with a
18299 single domain pattern, which is the only mandatory item in the rule. The
18300 pattern is in the same format as one item in a domain list (see section
18301 &<<SECTdomainlist>>&),
18302 except that it may not be the name of an interpolated file.
18303 That is, it may be wildcarded, or a regular expression, or a file or database
18304 lookup (with semicolons doubled, because of the use of semicolon as a separator
18305 in a &%route_list%&).
18307 The rules in &%route_list%& are searched in order until one of the patterns
18308 matches the domain that is being routed. The list of hosts and then options are
18309 then used as described below. If there is no match, the router declines. When
18310 &%route_list%& is set, &%route_data%& must not be set.
18314 .section "Routing rules in route_data" "SECID121"
18315 The use of &%route_list%& is convenient when there are only a small number of
18316 routing rules. For larger numbers, it is easier to use a file or database to
18317 hold the routing information, and use the &%route_data%& option instead.
18318 The value of &%route_data%& is a list of hosts, followed by (optional) options.
18319 Most commonly, &%route_data%& is set as a string that contains an
18320 expansion lookup. For example, suppose we place two routing rules in a file
18323 dict.ref.example: mail-1.ref.example:mail-2.ref.example
18324 thes.ref.example: mail-3.ref.example:mail-4.ref.example
18326 This data can be accessed by setting
18328 route_data = ${lookup{$domain}lsearch{/the/file/name}}
18330 Failure of the lookup results in an empty string, causing the router to
18331 decline. However, you do not have to use a lookup in &%route_data%&. The only
18332 requirement is that the result of expanding the string is a list of hosts,
18333 possibly followed by options, separated by white space. The list of hosts must
18334 be enclosed in quotes if it contains white space.
18339 .section "Format of the list of hosts" "SECID122"
18340 A list of hosts, whether obtained via &%route_data%& or &%route_list%&, is
18341 always separately expanded before use. If the expansion fails, the router
18342 declines. The result of the expansion must be a colon-separated list of names
18343 and/or IP addresses, optionally also including ports. The format of each item
18344 in the list is described in the next section. The list separator can be changed
18345 as described in section &<<SECTlistconstruct>>&.
18347 If the list of hosts was obtained from a &%route_list%& item, the following
18348 variables are set during its expansion:
18351 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(manualroute)& router"
18352 If the domain was matched against a regular expression, the numeric variables
18353 &$1$&, &$2$&, etc. may be set. For example:
18355 route_list = ^domain(\d+) host-$1.text.example
18358 &$0$& is always set to the entire domain.
18360 &$1$& is also set when partial matching is done in a file lookup.
18363 .vindex "&$value$&"
18364 If the pattern that matched the domain was a lookup item, the data that was
18365 looked up is available in the expansion variable &$value$&. For example:
18367 route_list = lsearch;;/some/file.routes $value
18371 Note the doubling of the semicolon in the pattern that is necessary because
18372 semicolon is the default route list separator.
18376 .section "Format of one host item" "SECTformatonehostitem"
18377 Each item in the list of hosts is either a host name or an IP address,
18378 optionally with an attached port number. When no port is given, an IP address
18379 is not enclosed in brackets. When a port is specified, it overrides the port
18380 specification on the transport. The port is separated from the name or address
18381 by a colon. This leads to some complications:
18384 Because colon is the default separator for the list of hosts, either
18385 the colon that specifies a port must be doubled, or the list separator must
18386 be changed. The following two examples have the same effect:
18388 route_list = * "host1.tld::1225 : host2.tld::1226"
18389 route_list = * "<+ host1.tld:1225 + host2.tld:1226"
18392 When IPv6 addresses are involved, it gets worse, because they contain
18393 colons of their own. To make this case easier, it is permitted to
18394 enclose an IP address (either v4 or v6) in square brackets if a port
18395 number follows. For example:
18397 route_list = * "</ [10.1.1.1]:1225 / [::1]:1226"
18401 .section "How the list of hosts is used" "SECThostshowused"
18402 When an address is routed to an &(smtp)& transport by &(manualroute)&, each of
18403 the hosts is tried, in the order specified, when carrying out the SMTP
18404 delivery. However, the order can be changed by setting the &%hosts_randomize%&
18405 option, either on the router (see section &<<SECTprioptman>>& above), or on the
18408 Hosts may be listed by name or by IP address. An unadorned name in the list of
18409 hosts is interpreted as a host name. A name that is followed by &`/MX`& is
18410 interpreted as an indirection to a sublist of hosts obtained by looking up MX
18411 records in the DNS. For example:
18413 route_list = * x.y.z:p.q.r/MX:e.f.g
18415 If this feature is used with a port specifier, the port must come last. For
18418 route_list = * dom1.tld/mx::1225
18420 If the &%hosts_randomize%& option is set, the order of the items in the list is
18421 randomized before any lookups are done. Exim then scans the list; for any name
18422 that is not followed by &`/MX`& it looks up an IP address. If this turns out to
18423 be an interface on the local host and the item is not the first in the list,
18424 Exim discards it and any subsequent items. If it is the first item, what
18425 happens is controlled by the
18426 .oindex "&%self%&" "in &(manualroute)& router"
18427 &%self%& option of the router.
18429 A name on the list that is followed by &`/MX`& is replaced with the list of
18430 hosts obtained by looking up MX records for the name. This is always a DNS
18431 lookup; the &%bydns%& and &%byname%& options (see section &<<SECThowoptused>>&
18432 below) are not relevant here. The order of these hosts is determined by the
18433 preference values in the MX records, according to the usual rules. Because
18434 randomizing happens before the MX lookup, it does not affect the order that is
18435 defined by MX preferences.
18437 If the local host is present in the sublist obtained from MX records, but is
18438 not the most preferred host in that list, it and any equally or less
18439 preferred hosts are removed before the sublist is inserted into the main list.
18441 If the local host is the most preferred host in the MX list, what happens
18442 depends on where in the original list of hosts the &`/MX`& item appears. If it
18443 is not the first item (that is, there are previous hosts in the main list),
18444 Exim discards this name and any subsequent items in the main list.
18446 If the MX item is first in the list of hosts, and the local host is the
18447 most preferred host, what happens is controlled by the &%self%& option of the
18450 DNS failures when lookup up the MX records are treated in the same way as DNS
18451 failures when looking up IP addresses: &%pass_on_timeout%& and
18452 &%host_find_failed%& are used when relevant.
18454 The generic &%ignore_target_hosts%& option applies to all hosts in the list,
18455 whether obtained from an MX lookup or not.
18459 .section "How the options are used" "SECThowoptused"
18460 The options are a sequence of words; in practice no more than three are ever
18461 present. One of the words can be the name of a transport; this overrides the
18462 &%transport%& option on the router for this particular routing rule only. The
18463 other words (if present) control randomization of the list of hosts on a
18464 per-rule basis, and how the IP addresses of the hosts are to be found when
18465 routing to a remote transport. These options are as follows:
18468 &%randomize%&: randomize the order of the hosts in this list, overriding the
18469 setting of &%hosts_randomize%& for this routing rule only.
18471 &%no_randomize%&: do not randomize the order of the hosts in this list,
18472 overriding the setting of &%hosts_randomize%& for this routing rule only.
18474 &%byname%&: use &[getipnodebyname()]& (&[gethostbyname()]& on older systems) to
18475 find IP addresses. This function may ultimately cause a DNS lookup, but it may
18476 also look in &_/etc/hosts_& or other sources of information.
18478 &%bydns%&: look up address records for the hosts directly in the DNS; fail if
18479 no address records are found. If there is a temporary DNS error (such as a
18480 timeout), delivery is deferred.
18485 route_list = domain1 host1:host2:host3 randomize bydns;\
18486 domain2 host4:host5
18488 If neither &%byname%& nor &%bydns%& is given, Exim behaves as follows: First, a
18489 DNS lookup is done. If this yields anything other than HOST_NOT_FOUND, that
18490 result is used. Otherwise, Exim goes on to try a call to &[getipnodebyname()]&
18491 or &[gethostbyname()]&, and the result of the lookup is the result of that
18494 &*Warning*&: It has been discovered that on some systems, if a DNS lookup
18495 called via &[getipnodebyname()]& times out, HOST_NOT_FOUND is returned
18496 instead of TRY_AGAIN. That is why the default action is to try a DNS
18497 lookup first. Only if that gives a definite &"no such host"& is the local
18502 If no IP address for a host can be found, what happens is controlled by the
18503 &%host_find_failed%& option.
18506 When an address is routed to a local transport, IP addresses are not looked up.
18507 The host list is passed to the transport in the &$host$& variable.
18511 .section "Manualroute examples" "SECID123"
18512 In some of the examples that follow, the presence of the &%remote_smtp%&
18513 transport, as defined in the default configuration file, is assumed:
18516 .cindex "smart host" "example router"
18517 The &(manualroute)& router can be used to forward all external mail to a
18518 &'smart host'&. If you have set up, in the main part of the configuration, a
18519 named domain list that contains your local domains, for example:
18521 domainlist local_domains = my.domain.example
18523 You can arrange for all other domains to be routed to a smart host by making
18524 your first router something like this:
18527 driver = manualroute
18528 domains = !+local_domains
18529 transport = remote_smtp
18530 route_list = * smarthost.ref.example
18532 This causes all non-local addresses to be sent to the single host
18533 &'smarthost.ref.example'&. If a colon-separated list of smart hosts is given,
18534 they are tried in order
18535 (but you can use &%hosts_randomize%& to vary the order each time).
18536 Another way of configuring the same thing is this:
18539 driver = manualroute
18540 transport = remote_smtp
18541 route_list = !+local_domains smarthost.ref.example
18543 There is no difference in behaviour between these two routers as they stand.
18544 However, they behave differently if &%no_more%& is added to them. In the first
18545 example, the router is skipped if the domain does not match the &%domains%&
18546 precondition; the following router is always tried. If the router runs, it
18547 always matches the domain and so can never decline. Therefore, &%no_more%&
18548 would have no effect. In the second case, the router is never skipped; it
18549 always runs. However, if it doesn't match the domain, it declines. In this case
18550 &%no_more%& would prevent subsequent routers from running.
18553 .cindex "mail hub example"
18554 A &'mail hub'& is a host which receives mail for a number of domains via MX
18555 records in the DNS and delivers it via its own private routing mechanism. Often
18556 the final destinations are behind a firewall, with the mail hub being the one
18557 machine that can connect to machines both inside and outside the firewall. The
18558 &(manualroute)& router is usually used on a mail hub to route incoming messages
18559 to the correct hosts. For a small number of domains, the routing can be inline,
18560 using the &%route_list%& option, but for a larger number a file or database
18561 lookup is easier to manage.
18563 If the domain names are in fact the names of the machines to which the mail is
18564 to be sent by the mail hub, the configuration can be quite simple. For
18568 driver = manualroute
18569 transport = remote_smtp
18570 route_list = *.rhodes.tvs.example $domain
18572 This configuration routes domains that match &`*.rhodes.tvs.example`& to hosts
18573 whose names are the same as the mail domains. A similar approach can be taken
18574 if the host name can be obtained from the domain name by a string manipulation
18575 that the expansion facilities can handle. Otherwise, a lookup based on the
18576 domain can be used to find the host:
18579 driver = manualroute
18580 transport = remote_smtp
18581 route_data = ${lookup {$domain} cdb {/internal/host/routes}}
18583 The result of the lookup must be the name or IP address of the host (or
18584 hosts) to which the address is to be routed. If the lookup fails, the route
18585 data is empty, causing the router to decline. The address then passes to the
18589 .cindex "batched SMTP output example"
18590 .cindex "SMTP" "batched outgoing; example"
18591 You can use &(manualroute)& to deliver messages to pipes or files in batched
18592 SMTP format for onward transportation by some other means. This is one way of
18593 storing mail for a dial-up host when it is not connected. The route list entry
18594 can be as simple as a single domain name in a configuration like this:
18597 driver = manualroute
18598 transport = batchsmtp_appendfile
18599 route_list = saved.domain.example
18601 though often a pattern is used to pick up more than one domain. If there are
18602 several domains or groups of domains with different transport requirements,
18603 different transports can be listed in the routing information:
18606 driver = manualroute
18608 *.saved.domain1.example $domain batch_appendfile; \
18609 *.saved.domain2.example \
18610 ${lookup{$domain}dbm{/domain2/hosts}{$value}fail} \
18613 .vindex "&$domain$&"
18615 The first of these just passes the domain in the &$host$& variable, which
18616 doesn't achieve much (since it is also in &$domain$&), but the second does a
18617 file lookup to find a value to pass, causing the router to decline to handle
18618 the address if the lookup fails.
18621 .cindex "UUCP" "example of router for"
18622 Routing mail directly to UUCP software is a specific case of the use of
18623 &(manualroute)& in a gateway to another mail environment. This is an example of
18624 one way it can be done:
18630 command = /usr/local/bin/uux -r - \
18631 ${substr_-5:$host}!rmail ${local_part}
18632 return_fail_output = true
18637 driver = manualroute
18639 ${lookup{$domain}lsearch{/usr/local/exim/uucphosts}}
18641 The file &_/usr/local/exim/uucphosts_& contains entries like
18643 darksite.ethereal.example: darksite.UUCP
18645 It can be set up more simply without adding and removing &".UUCP"& but this way
18646 makes clear the distinction between the domain name
18647 &'darksite.ethereal.example'& and the UUCP host name &'darksite'&.
18649 .ecindex IIDmanrou1
18650 .ecindex IIDmanrou2
18659 . ////////////////////////////////////////////////////////////////////////////
18660 . ////////////////////////////////////////////////////////////////////////////
18662 .chapter "The queryprogram router" "CHAPdriverlast"
18663 .scindex IIDquerou1 "&(queryprogram)& router"
18664 .scindex IIDquerou2 "routers" "&(queryprogram)&"
18665 .cindex "routing" "by external program"
18666 The &(queryprogram)& router routes an address by running an external command
18667 and acting on its output. This is an expensive way to route, and is intended
18668 mainly for use in lightly-loaded systems, or for performing experiments.
18669 However, if it is possible to use the precondition options (&%domains%&,
18670 &%local_parts%&, etc) to skip this router for most addresses, it could sensibly
18671 be used in special cases, even on a busy host. There are the following private
18673 .cindex "options" "&(queryprogram)& router"
18675 .option command queryprogram string&!! unset
18676 This option must be set. It specifies the command that is to be run. The
18677 command is split up into a command name and arguments, and then each is
18678 expanded separately (exactly as for a &(pipe)& transport, described in chapter
18679 &<<CHAPpipetransport>>&).
18682 .option command_group queryprogram string unset
18683 .cindex "gid (group id)" "in &(queryprogram)& router"
18684 This option specifies a gid to be set when running the command while routing an
18685 address for deliver. It must be set if &%command_user%& specifies a numerical
18686 uid. If it begins with a digit, it is interpreted as the numerical value of the
18687 gid. Otherwise it is looked up using &[getgrnam()]&.
18690 .option command_user queryprogram string unset
18691 .cindex "uid (user id)" "for &(queryprogram)&"
18692 This option must be set. It specifies the uid which is set when running the
18693 command while routing an address for delivery. If the value begins with a digit,
18694 it is interpreted as the numerical value of the uid. Otherwise, it is looked up
18695 using &[getpwnam()]& to obtain a value for the uid and, if &%command_group%& is
18696 not set, a value for the gid also.
18698 &*Warning:*& Changing uid and gid is possible only when Exim is running as
18699 root, which it does during a normal delivery in a conventional configuration.
18700 However, when an address is being verified during message reception, Exim is
18701 usually running as the Exim user, not as root. If the &(queryprogram)& router
18702 is called from a non-root process, Exim cannot change uid or gid before running
18703 the command. In this circumstance the command runs under the current uid and
18707 .option current_directory queryprogram string /
18708 This option specifies an absolute path which is made the current directory
18709 before running the command.
18712 .option timeout queryprogram time 1h
18713 If the command does not complete within the timeout period, its process group
18714 is killed and the message is frozen. A value of zero time specifies no
18718 The standard output of the command is connected to a pipe, which is read when
18719 the command terminates. It should consist of a single line of output,
18720 containing up to five fields, separated by white space. The maximum length of
18721 the line is 1023 characters. Longer lines are silently truncated. The first
18722 field is one of the following words (case-insensitive):
18725 &'Accept'&: routing succeeded; the remaining fields specify what to do (see
18728 &'Decline'&: the router declines; pass the address to the next router, unless
18729 &%no_more%& is set.
18731 &'Fail'&: routing failed; do not pass the address to any more routers. Any
18732 subsequent text on the line is an error message. If the router is run as part
18733 of address verification during an incoming SMTP message, the message is
18734 included in the SMTP response.
18736 &'Defer'&: routing could not be completed at this time; try again later. Any
18737 subsequent text on the line is an error message which is logged. It is not
18738 included in any SMTP response.
18740 &'Freeze'&: the same as &'defer'&, except that the message is frozen.
18742 &'Pass'&: pass the address to the next router (or the router specified by
18743 &%pass_router%&), overriding &%no_more%&.
18745 &'Redirect'&: the message is redirected. The remainder of the line is a list of
18746 new addresses, which are routed independently, starting with the first router,
18747 or the router specified by &%redirect_router%&, if set.
18750 When the first word is &'accept'&, the remainder of the line consists of a
18751 number of keyed data values, as follows (split into two lines here, to fit on
18754 ACCEPT TRANSPORT=<transport> HOSTS=<list of hosts>
18755 LOOKUP=byname|bydns DATA=<text>
18757 The data items can be given in any order, and all are optional. If no transport
18758 is included, the transport specified by the generic &%transport%& option is
18759 used. The list of hosts and the lookup type are needed only if the transport is
18760 an &(smtp)& transport that does not itself supply a list of hosts.
18762 The format of the list of hosts is the same as for the &(manualroute)& router.
18763 As well as host names and IP addresses with optional port numbers, as described
18764 in section &<<SECTformatonehostitem>>&, it may contain names followed by
18765 &`/MX`& to specify sublists of hosts that are obtained by looking up MX records
18766 (see section &<<SECThostshowused>>&).
18768 If the lookup type is not specified, Exim behaves as follows when trying to
18769 find an IP address for each host: First, a DNS lookup is done. If this yields
18770 anything other than HOST_NOT_FOUND, that result is used. Otherwise, Exim
18771 goes on to try a call to &[getipnodebyname()]& or &[gethostbyname()]&, and the
18772 result of the lookup is the result of that call.
18774 .vindex "&$address_data$&"
18775 If the DATA field is set, its value is placed in the &$address_data$&
18776 variable. For example, this return line
18778 accept hosts=x1.y.example:x2.y.example data="rule1"
18780 routes the address to the default transport, passing a list of two hosts. When
18781 the transport runs, the string &"rule1"& is in &$address_data$&.
18782 .ecindex IIDquerou1
18783 .ecindex IIDquerou2
18788 . ////////////////////////////////////////////////////////////////////////////
18789 . ////////////////////////////////////////////////////////////////////////////
18791 .chapter "The redirect router" "CHAPredirect"
18792 .scindex IIDredrou1 "&(redirect)& router"
18793 .scindex IIDredrou2 "routers" "&(redirect)&"
18794 .cindex "alias file" "in a &(redirect)& router"
18795 .cindex "address redirection" "&(redirect)& router"
18796 The &(redirect)& router handles several kinds of address redirection. Its most
18797 common uses are for resolving local part aliases from a central alias file
18798 (usually called &_/etc/aliases_&) and for handling users' personal &_.forward_&
18799 files, but it has many other potential uses. The incoming address can be
18800 redirected in several different ways:
18803 It can be replaced by one or more new addresses which are themselves routed
18806 It can be routed to be delivered to a given file or directory.
18808 It can be routed to be delivered to a specified pipe command.
18810 It can cause an automatic reply to be generated.
18812 It can be forced to fail, optionally with a custom error message.
18814 It can be temporarily deferred, optionally with a custom message.
18816 It can be discarded.
18819 The generic &%transport%& option must not be set for &(redirect)& routers.
18820 However, there are some private options which define transports for delivery to
18821 files and pipes, and for generating autoreplies. See the &%file_transport%&,
18822 &%pipe_transport%& and &%reply_transport%& descriptions below.
18826 .section "Redirection data" "SECID124"
18827 The router operates by interpreting a text string which it obtains either by
18828 expanding the contents of the &%data%& option, or by reading the entire
18829 contents of a file whose name is given in the &%file%& option. These two
18830 options are mutually exclusive. The first is commonly used for handling system
18831 aliases, in a configuration like this:
18835 data = ${lookup{$local_part}lsearch{/etc/aliases}}
18837 If the lookup fails, the expanded string in this example is empty. When the
18838 expansion of &%data%& results in an empty string, the router declines. A forced
18839 expansion failure also causes the router to decline; other expansion failures
18840 cause delivery to be deferred.
18842 A configuration using &%file%& is commonly used for handling users'
18843 &_.forward_& files, like this:
18848 file = $home/.forward
18851 If the file does not exist, or causes no action to be taken (for example, it is
18852 empty or consists only of comments), the router declines. &*Warning*&: This
18853 is not the case when the file contains syntactically valid items that happen to
18854 yield empty addresses, for example, items containing only RFC 2822 address
18859 .section "Forward files and address verification" "SECID125"
18860 .cindex "address redirection" "while verifying"
18861 It is usual to set &%no_verify%& on &(redirect)& routers which handle users'
18862 &_.forward_& files, as in the example above. There are two reasons for this:
18865 When Exim is receiving an incoming SMTP message from a remote host, it is
18866 running under the Exim uid, not as root. Exim is unable to change uid to read
18867 the file as the user, and it may not be able to read it as the Exim user. So in
18868 practice the router may not be able to operate.
18870 However, even when the router can operate, the existence of a &_.forward_& file
18871 is unimportant when verifying an address. What should be checked is whether the
18872 local part is a valid user name or not. Cutting out the redirection processing
18873 saves some resources.
18881 .section "Interpreting redirection data" "SECID126"
18882 .cindex "Sieve filter" "specifying in redirection data"
18883 .cindex "filter" "specifying in redirection data"
18884 The contents of the data string, whether obtained from &%data%& or &%file%&,
18885 can be interpreted in two different ways:
18888 If the &%allow_filter%& option is set true, and the data begins with the text
18889 &"#Exim filter"& or &"#Sieve filter"&, it is interpreted as a list of
18890 &'filtering'& instructions in the form of an Exim or Sieve filter file,
18891 respectively. Details of the syntax and semantics of filter files are described
18892 in a separate document entitled &'Exim's interfaces to mail filtering'&; this
18893 document is intended for use by end users.
18895 Otherwise, the data must be a comma-separated list of redirection items, as
18896 described in the next section.
18899 When a message is redirected to a file (a &"mail folder"&), the file name given
18900 in a non-filter redirection list must always be an absolute path. A filter may
18901 generate a relative path &-- how this is handled depends on the transport's
18902 configuration. See section &<<SECTfildiropt>>& for a discussion of this issue
18903 for the &(appendfile)& transport.
18907 .section "Items in a non-filter redirection list" "SECTitenonfilred"
18908 .cindex "address redirection" "non-filter list items"
18909 When the redirection data is not an Exim or Sieve filter, for example, if it
18910 comes from a conventional alias or forward file, it consists of a list of
18911 addresses, file names, pipe commands, or certain special items (see section
18912 &<<SECTspecitredli>>& below). The special items can be individually enabled or
18913 disabled by means of options whose names begin with &%allow_%& or &%forbid_%&,
18914 depending on their default values. The items in the list are separated by
18915 commas or newlines.
18916 If a comma is required in an item, the entire item must be enclosed in double
18919 Lines starting with a # character are comments, and are ignored, and # may
18920 also appear following a comma, in which case everything between the # and the
18921 next newline character is ignored.
18923 If an item is entirely enclosed in double quotes, these are removed. Otherwise
18924 double quotes are retained because some forms of mail address require their use
18925 (but never to enclose the entire address). In the following description,
18926 &"item"& refers to what remains after any surrounding double quotes have been
18929 .vindex "&$local_part$&"
18930 &*Warning*&: If you use an Exim expansion to construct a redirection address,
18931 and the expansion contains a reference to &$local_part$&, you should make use
18932 of the &%quote_local_part%& expansion operator, in case the local part contains
18933 special characters. For example, to redirect all mail for the domain
18934 &'obsolete.example'&, retaining the existing local part, you could use this
18937 data = ${quote_local_part:$local_part}@newdomain.example
18941 .section "Redirecting to a local mailbox" "SECTredlocmai"
18942 .cindex "routing" "loops in"
18943 .cindex "loop" "while routing, avoidance of"
18944 .cindex "address redirection" "to local mailbox"
18945 A redirection item may safely be the same as the address currently under
18946 consideration. This does not cause a routing loop, because a router is
18947 automatically skipped if any ancestor of the address that is being processed
18948 is the same as the current address and was processed by the current router.
18949 Such an address is therefore passed to the following routers, so it is handled
18950 as if there were no redirection. When making this loop-avoidance test, the
18951 complete local part, including any prefix or suffix, is used.
18953 .cindex "address redirection" "local part without domain"
18954 Specifying the same local part without a domain is a common usage in personal
18955 filter files when the user wants to have messages delivered to the local
18956 mailbox and also forwarded elsewhere. For example, the user whose login is
18957 &'cleo'& might have a &_.forward_& file containing this:
18959 cleo, cleopatra@egypt.example
18961 .cindex "backslash in alias file"
18962 .cindex "alias file" "backslash in"
18963 For compatibility with other MTAs, such unqualified local parts may be
18964 preceded by &"\"&, but this is not a requirement for loop prevention. However,
18965 it does make a difference if more than one domain is being handled
18968 If an item begins with &"\"& and the rest of the item parses as a valid RFC
18969 2822 address that does not include a domain, the item is qualified using the
18970 domain of the incoming address. In the absence of a leading &"\"&, unqualified
18971 addresses are qualified using the value in &%qualify_recipient%&, but you can
18972 force the incoming domain to be used by setting &%qualify_preserve_domain%&.
18974 Care must be taken if there are alias names for local users.
18975 Consider an MTA handling a single local domain where the system alias file
18980 Now suppose that Sam (whose login id is &'spqr'&) wants to save copies of
18981 messages in the local mailbox, and also forward copies elsewhere. He creates
18984 Sam.Reman, spqr@reme.elsewhere.example
18986 With these settings, an incoming message addressed to &'Sam.Reman'& fails. The
18987 &(redirect)& router for system aliases does not process &'Sam.Reman'& the
18988 second time round, because it has previously routed it,
18989 and the following routers presumably cannot handle the alias. The forward file
18990 should really contain
18992 spqr, spqr@reme.elsewhere.example
18994 but because this is such a common error, the &%check_ancestor%& option (see
18995 below) exists to provide a way to get round it. This is normally set on a
18996 &(redirect)& router that is handling users' &_.forward_& files.
19000 .section "Special items in redirection lists" "SECTspecitredli"
19001 In addition to addresses, the following types of item may appear in redirection
19002 lists (that is, in non-filter redirection data):
19005 .cindex "pipe" "in redirection list"
19006 .cindex "address redirection" "to pipe"
19007 An item is treated as a pipe command if it begins with &"|"& and does not parse
19008 as a valid RFC 2822 address that includes a domain. A transport for running the
19009 command must be specified by the &%pipe_transport%& option.
19010 Normally, either the router or the transport specifies a user and a group under
19011 which to run the delivery. The default is to use the Exim user and group.
19013 Single or double quotes can be used for enclosing the individual arguments of
19014 the pipe command; no interpretation of escapes is done for single quotes. If
19015 the command contains a comma character, it is necessary to put the whole item
19016 in double quotes, for example:
19018 "|/some/command ready,steady,go"
19020 since items in redirection lists are terminated by commas. Do not, however,
19021 quote just the command. An item such as
19023 |"/some/command ready,steady,go"
19025 is interpreted as a pipe with a rather strange command name, and no arguments.
19027 Note that the above example assumes that the text comes from a lookup source
19028 of some sort, so that the quotes are part of the data. If composing a
19029 redirect router with a &%data%& option directly specifying this command, the
19030 quotes will be used by the configuration parser to define the extent of one
19031 string, but will not be passed down into the redirect router itself. There
19032 are two main approaches to get around this: escape quotes to be part of the
19033 data itself, or avoid using this mechanism and instead create a custom
19034 transport with the &%command%& option set and reference that transport from
19035 an &%accept%& router.
19038 .cindex "file" "in redirection list"
19039 .cindex "address redirection" "to file"
19040 An item is interpreted as a path name if it begins with &"/"& and does not
19041 parse as a valid RFC 2822 address that includes a domain. For example,
19043 /home/world/minbari
19045 is treated as a file name, but
19047 /s=molari/o=babylon/@x400gate.way
19049 is treated as an address. For a file name, a transport must be specified using
19050 the &%file_transport%& option. However, if the generated path name ends with a
19051 forward slash character, it is interpreted as a directory name rather than a
19052 file name, and &%directory_transport%& is used instead.
19054 Normally, either the router or the transport specifies a user and a group under
19055 which to run the delivery. The default is to use the Exim user and group.
19057 .cindex "&_/dev/null_&"
19058 However, if a redirection item is the path &_/dev/null_&, delivery to it is
19059 bypassed at a high level, and the log entry shows &"**bypassed**"&
19060 instead of a transport name. In this case the user and group are not used.
19063 .cindex "included address list"
19064 .cindex "address redirection" "included external list"
19065 If an item is of the form
19067 :include:<path name>
19069 a list of further items is taken from the given file and included at that
19070 point. &*Note*&: Such a file can not be a filter file; it is just an
19071 out-of-line addition to the list. The items in the included list are separated
19072 by commas or newlines and are not subject to expansion. If this is the first
19073 item in an alias list in an &(lsearch)& file, a colon must be used to terminate
19074 the alias name. This example is incorrect:
19076 list1 :include:/opt/lists/list1
19078 It must be given as
19080 list1: :include:/opt/lists/list1
19083 .cindex "address redirection" "to black hole"
19084 Sometimes you want to throw away mail to a particular local part. Making the
19085 &%data%& option expand to an empty string does not work, because that causes
19086 the router to decline. Instead, the alias item
19087 .cindex "black hole"
19088 .cindex "abandoning mail"
19089 &':blackhole:'& can be used. It does what its name implies. No delivery is
19090 done, and no error message is generated. This has the same effect as specifing
19091 &_/dev/null_& as a destination, but it can be independently disabled.
19093 &*Warning*&: If &':blackhole:'& appears anywhere in a redirection list, no
19094 delivery is done for the original local part, even if other redirection items
19095 are present. If you are generating a multi-item list (for example, by reading a
19096 database) and need the ability to provide a no-op item, you must use
19100 .cindex "delivery" "forcing failure"
19101 .cindex "delivery" "forcing deferral"
19102 .cindex "failing delivery" "forcing"
19103 .cindex "deferred delivery, forcing"
19104 .cindex "customizing" "failure message"
19105 An attempt to deliver a particular address can be deferred or forced to fail by
19106 redirection items of the form
19111 respectively. When a redirection list contains such an item, it applies
19112 to the entire redirection; any other items in the list are ignored. Any
19113 text following &':fail:'& or &':defer:'& is placed in the error text
19114 associated with the failure. For example, an alias file might contain:
19116 X.Employee: :fail: Gone away, no forwarding address
19118 In the case of an address that is being verified from an ACL or as the subject
19120 .cindex "VRFY" "error text, display of"
19121 VRFY command, the text is included in the SMTP error response by
19123 .cindex "EXPN" "error text, display of"
19124 The text is not included in the response to an EXPN command. In non-SMTP cases
19125 the text is included in the error message that Exim generates.
19127 .cindex "SMTP" "error codes"
19128 By default, Exim sends a 451 SMTP code for a &':defer:'&, and 550 for
19129 &':fail:'&. However, if the message starts with three digits followed by a
19130 space, optionally followed by an extended code of the form &'n.n.n'&, also
19131 followed by a space, and the very first digit is the same as the default error
19132 code, the code from the message is used instead. If the very first digit is
19133 incorrect, a panic error is logged, and the default code is used. You can
19134 suppress the use of the supplied code in a redirect router by setting the
19135 &%forbid_smtp_code%& option true. In this case, any SMTP code is quietly
19138 .vindex "&$acl_verify_message$&"
19139 In an ACL, an explicitly provided message overrides the default, but the
19140 default message is available in the variable &$acl_verify_message$& and can
19141 therefore be included in a custom message if this is desired.
19143 Normally the error text is the rest of the redirection list &-- a comma does
19144 not terminate it &-- but a newline does act as a terminator. Newlines are not
19145 normally present in alias expansions. In &(lsearch)& lookups they are removed
19146 as part of the continuation process, but they may exist in other kinds of
19147 lookup and in &':include:'& files.
19149 During routing for message delivery (as opposed to verification), a redirection
19150 containing &':fail:'& causes an immediate failure of the incoming address,
19151 whereas &':defer:'& causes the message to remain on the queue so that a
19152 subsequent delivery attempt can happen at a later time. If an address is
19153 deferred for too long, it will ultimately fail, because the normal retry
19157 .cindex "alias file" "exception to default"
19158 Sometimes it is useful to use a single-key search type with a default (see
19159 chapter &<<CHAPfdlookup>>&) to look up aliases. However, there may be a need
19160 for exceptions to the default. These can be handled by aliasing them to
19161 &':unknown:'&. This differs from &':fail:'& in that it causes the &(redirect)&
19162 router to decline, whereas &':fail:'& forces routing to fail. A lookup which
19163 results in an empty redirection list has the same effect.
19167 .section "Duplicate addresses" "SECTdupaddr"
19168 .cindex "duplicate addresses"
19169 .cindex "address duplicate, discarding"
19170 .cindex "pipe" "duplicated"
19171 Exim removes duplicate addresses from the list to which it is delivering, so as
19172 to deliver just one copy to each address. This does not apply to deliveries
19173 routed to pipes by different immediate parent addresses, but an indirect
19174 aliasing scheme of the type
19176 pipe: |/some/command $local_part
19180 does not work with a message that is addressed to both local parts, because
19181 when the second is aliased to the intermediate local part &"pipe"& it gets
19182 discarded as being the same as a previously handled address. However, a scheme
19185 localpart1: |/some/command $local_part
19186 localpart2: |/some/command $local_part
19188 does result in two different pipe deliveries, because the immediate parents of
19189 the pipes are distinct.
19193 .section "Repeated redirection expansion" "SECID128"
19194 .cindex "repeated redirection expansion"
19195 .cindex "address redirection" "repeated for each delivery attempt"
19196 When a message cannot be delivered to all of its recipients immediately,
19197 leading to two or more delivery attempts, redirection expansion is carried out
19198 afresh each time for those addresses whose children were not all previously
19199 delivered. If redirection is being used as a mailing list, this can lead to new
19200 members of the list receiving copies of old messages. The &%one_time%& option
19201 can be used to avoid this.
19204 .section "Errors in redirection lists" "SECID129"
19205 .cindex "address redirection" "errors"
19206 If &%skip_syntax_errors%& is set, a malformed address that causes a parsing
19207 error is skipped, and an entry is written to the main log. This may be useful
19208 for mailing lists that are automatically managed. Otherwise, if an error is
19209 detected while generating the list of new addresses, the original address is
19210 deferred. See also &%syntax_errors_to%&.
19214 .section "Private options for the redirect router" "SECID130"
19216 .cindex "options" "&(redirect)& router"
19217 The private options for the &(redirect)& router are as follows:
19220 .option allow_defer redirect boolean false
19221 Setting this option allows the use of &':defer:'& in non-filter redirection
19222 data, or the &%defer%& command in an Exim filter file.
19225 .option allow_fail redirect boolean false
19226 .cindex "failing delivery" "from filter"
19227 If this option is true, the &':fail:'& item can be used in a redirection list,
19228 and the &%fail%& command may be used in an Exim filter file.
19231 .option allow_filter redirect boolean false
19232 .cindex "filter" "enabling use of"
19233 .cindex "Sieve filter" "enabling use of"
19234 Setting this option allows Exim to interpret redirection data that starts with
19235 &"#Exim filter"& or &"#Sieve filter"& as a set of filtering instructions. There
19236 are some features of Exim filter files that some administrators may wish to
19237 lock out; see the &%forbid_filter_%&&'xxx'& options below.
19239 It is also possible to lock out Exim filters or Sieve filters while allowing
19240 the other type; see &%forbid_exim_filter%& and &%forbid_sieve_filter%&.
19243 The filter is run using the uid and gid set by the generic &%user%& and
19244 &%group%& options. These take their defaults from the password data if
19245 &%check_local_user%& is set, so in the normal case of users' personal filter
19246 files, the filter is run as the relevant user. When &%allow_filter%& is set
19247 true, Exim insists that either &%check_local_user%& or &%user%& is set.
19251 .option allow_freeze redirect boolean false
19252 .cindex "freezing messages" "allowing in filter"
19253 Setting this option allows the use of the &%freeze%& command in an Exim filter.
19254 This command is more normally encountered in system filters, and is disabled by
19255 default for redirection filters because it isn't something you usually want to
19256 let ordinary users do.
19260 .option check_ancestor redirect boolean false
19261 This option is concerned with handling generated addresses that are the same
19262 as some address in the list of redirection ancestors of the current address.
19263 Although it is turned off by default in the code, it is set in the default
19264 configuration file for handling users' &_.forward_& files. It is recommended
19265 for this use of the &(redirect)& router.
19267 When &%check_ancestor%& is set, if a generated address (including the domain)
19268 is the same as any ancestor of the current address, it is replaced by a copy of
19269 the current address. This helps in the case where local part A is aliased to B,
19270 and B has a &_.forward_& file pointing back to A. For example, within a single
19271 domain, the local part &"Joe.Bloggs"& is aliased to &"jb"& and
19272 &_&~jb/.forward_& contains:
19274 \Joe.Bloggs, <other item(s)>
19276 Without the &%check_ancestor%& setting, either local part (&"jb"& or
19277 &"joe.bloggs"&) gets processed once by each router and so ends up as it was
19278 originally. If &"jb"& is the real mailbox name, mail to &"jb"& gets delivered
19279 (having been turned into &"joe.bloggs"& by the &_.forward_& file and back to
19280 &"jb"& by the alias), but mail to &"joe.bloggs"& fails. Setting
19281 &%check_ancestor%& on the &(redirect)& router that handles the &_.forward_&
19282 file prevents it from turning &"jb"& back into &"joe.bloggs"& when that was the
19283 original address. See also the &%repeat_use%& option below.
19286 .option check_group redirect boolean "see below"
19287 When the &%file%& option is used, the group owner of the file is checked only
19288 when this option is set. The permitted groups are those listed in the
19289 &%owngroups%& option, together with the user's default group if
19290 &%check_local_user%& is set. If the file has the wrong group, routing is
19291 deferred. The default setting for this option is true if &%check_local_user%&
19292 is set and the &%modemask%& option permits the group write bit, or if the
19293 &%owngroups%& option is set. Otherwise it is false, and no group check occurs.
19297 .option check_owner redirect boolean "see below"
19298 When the &%file%& option is used, the owner of the file is checked only when
19299 this option is set. If &%check_local_user%& is set, the local user is
19300 permitted; otherwise the owner must be one of those listed in the &%owners%&
19301 option. The default value for this option is true if &%check_local_user%& or
19302 &%owners%& is set. Otherwise the default is false, and no owner check occurs.
19305 .option data redirect string&!! unset
19306 This option is mutually exclusive with &%file%&. One or other of them must be
19307 set, but not both. The contents of &%data%& are expanded, and then used as the
19308 list of forwarding items, or as a set of filtering instructions. If the
19309 expansion is forced to fail, or the result is an empty string or a string that
19310 has no effect (consists entirely of comments), the router declines.
19312 When filtering instructions are used, the string must begin with &"#Exim
19313 filter"&, and all comments in the string, including this initial one, must be
19314 terminated with newline characters. For example:
19316 data = #Exim filter\n\
19317 if $h_to: contains Exim then save $home/mail/exim endif
19319 If you are reading the data from a database where newlines cannot be included,
19320 you can use the &${sg}$& expansion item to turn the escape string of your
19321 choice into a newline.
19324 .option directory_transport redirect string&!! unset
19325 A &(redirect)& router sets up a direct delivery to a directory when a path name
19326 ending with a slash is specified as a new &"address"&. The transport used is
19327 specified by this option, which, after expansion, must be the name of a
19328 configured transport. This should normally be an &(appendfile)& transport.
19331 .option file redirect string&!! unset
19332 This option specifies the name of a file that contains the redirection data. It
19333 is mutually exclusive with the &%data%& option. The string is expanded before
19334 use; if the expansion is forced to fail, the router declines. Other expansion
19335 failures cause delivery to be deferred. The result of a successful expansion
19336 must be an absolute path. The entire file is read and used as the redirection
19337 data. If the data is an empty string or a string that has no effect (consists
19338 entirely of comments), the router declines.
19340 .cindex "NFS" "checking for file existence"
19341 If the attempt to open the file fails with a &"does not exist"& error, Exim
19342 runs a check on the containing directory,
19343 unless &%ignore_enotdir%& is true (see below).
19344 If the directory does not appear to exist, delivery is deferred. This can
19345 happen when users' &_.forward_& files are in NFS-mounted directories, and there
19346 is a mount problem. If the containing directory does exist, but the file does
19347 not, the router declines.
19350 .option file_transport redirect string&!! unset
19351 .vindex "&$address_file$&"
19352 A &(redirect)& router sets up a direct delivery to a file when a path name not
19353 ending in a slash is specified as a new &"address"&. The transport used is
19354 specified by this option, which, after expansion, must be the name of a
19355 configured transport. This should normally be an &(appendfile)& transport. When
19356 it is running, the file name is in &$address_file$&.
19359 .option filter_prepend_home redirect boolean true
19360 When this option is true, if a &(save)& command in an Exim filter specifies a
19361 relative path, and &$home$& is defined, it is automatically prepended to the
19362 relative path. If this option is set false, this action does not happen. The
19363 relative path is then passed to the transport unmodified.
19366 .option forbid_blackhole redirect boolean false
19367 If this option is true, the &':blackhole:'& item may not appear in a
19371 .option forbid_exim_filter redirect boolean false
19372 If this option is set true, only Sieve filters are permitted when
19373 &%allow_filter%& is true.
19378 .option forbid_file redirect boolean false
19379 .cindex "delivery" "to file; forbidding"
19380 .cindex "Sieve filter" "forbidding delivery to a file"
19381 .cindex "Sieve filter" "&""keep""& facility; disabling"
19382 If this option is true, this router may not generate a new address that
19383 specifies delivery to a local file or directory, either from a filter or from a
19384 conventional forward file. This option is forced to be true if &%one_time%& is
19385 set. It applies to Sieve filters as well as to Exim filters, but if true, it
19386 locks out the Sieve's &"keep"& facility.
19389 .option forbid_filter_dlfunc redirect boolean false
19390 .cindex "filter" "locking out certain features"
19391 If this option is true, string expansions in Exim filters are not allowed to
19392 make use of the &%dlfunc%& expansion facility to run dynamically loaded
19395 .option forbid_filter_existstest redirect boolean false
19396 .cindex "expansion" "statting a file"
19397 If this option is true, string expansions in Exim filters are not allowed to
19398 make use of the &%exists%& condition or the &%stat%& expansion item.
19400 .option forbid_filter_logwrite redirect boolean false
19401 If this option is true, use of the logging facility in Exim filters is not
19402 permitted. Logging is in any case available only if the filter is being run
19403 under some unprivileged uid (which is normally the case for ordinary users'
19404 &_.forward_& files).
19407 .option forbid_filter_lookup redirect boolean false
19408 If this option is true, string expansions in Exim filter files are not allowed
19409 to make use of &%lookup%& items.
19412 .option forbid_filter_perl redirect boolean false
19413 This option has an effect only if Exim is built with embedded Perl support. If
19414 it is true, string expansions in Exim filter files are not allowed to make use
19415 of the embedded Perl support.
19418 .option forbid_filter_readfile redirect boolean false
19419 If this option is true, string expansions in Exim filter files are not allowed
19420 to make use of &%readfile%& items.
19423 .option forbid_filter_readsocket redirect boolean false
19424 If this option is true, string expansions in Exim filter files are not allowed
19425 to make use of &%readsocket%& items.
19428 .option forbid_filter_reply redirect boolean false
19429 If this option is true, this router may not generate an automatic reply
19430 message. Automatic replies can be generated only from Exim or Sieve filter
19431 files, not from traditional forward files. This option is forced to be true if
19432 &%one_time%& is set.
19435 .option forbid_filter_run redirect boolean false
19436 If this option is true, string expansions in Exim filter files are not allowed
19437 to make use of &%run%& items.
19440 .option forbid_include redirect boolean false
19441 If this option is true, items of the form
19443 :include:<path name>
19445 are not permitted in non-filter redirection lists.
19448 .option forbid_pipe redirect boolean false
19449 .cindex "delivery" "to pipe; forbidding"
19450 If this option is true, this router may not generate a new address which
19451 specifies delivery to a pipe, either from an Exim filter or from a conventional
19452 forward file. This option is forced to be true if &%one_time%& is set.
19455 .option forbid_sieve_filter redirect boolean false
19456 If this option is set true, only Exim filters are permitted when
19457 &%allow_filter%& is true.
19460 .cindex "SMTP" "error codes"
19461 .option forbid_smtp_code redirect boolean false
19462 If this option is set true, any SMTP error codes that are present at the start
19463 of messages specified for &`:defer:`& or &`:fail:`& are quietly ignored, and
19464 the default codes (451 and 550, respectively) are always used.
19469 .option hide_child_in_errmsg redirect boolean false
19470 .cindex "bounce message" "redirection details; suppressing"
19471 If this option is true, it prevents Exim from quoting a child address if it
19472 generates a bounce or delay message for it. Instead it says &"an address
19473 generated from <&'the top level address'&>"&. Of course, this applies only to
19474 bounces generated locally. If a message is forwarded to another host, &'its'&
19475 bounce may well quote the generated address.
19478 .option ignore_eacces redirect boolean false
19480 If this option is set and an attempt to open a redirection file yields the
19481 EACCES error (permission denied), the &(redirect)& router behaves as if the
19482 file did not exist.
19485 .option ignore_enotdir redirect boolean false
19487 If this option is set and an attempt to open a redirection file yields the
19488 ENOTDIR error (something on the path is not a directory), the &(redirect)&
19489 router behaves as if the file did not exist.
19491 Setting &%ignore_enotdir%& has another effect as well: When a &(redirect)&
19492 router that has the &%file%& option set discovers that the file does not exist
19493 (the ENOENT error), it tries to &[stat()]& the parent directory, as a check
19494 against unmounted NFS directories. If the parent can not be statted, delivery
19495 is deferred. However, it seems wrong to do this check when &%ignore_enotdir%&
19496 is set, because that option tells Exim to ignore &"something on the path is not
19497 a directory"& (the ENOTDIR error). This is a confusing area, because it seems
19498 that some operating systems give ENOENT where others give ENOTDIR.
19502 .option include_directory redirect string unset
19503 If this option is set, the path names of any &':include:'& items in a
19504 redirection list must start with this directory.
19507 .option modemask redirect "octal integer" 022
19508 This specifies mode bits which must not be set for a file specified by the
19509 &%file%& option. If any of the forbidden bits are set, delivery is deferred.
19512 .option one_time redirect boolean false
19513 .cindex "one-time aliasing/forwarding expansion"
19514 .cindex "alias file" "one-time expansion"
19515 .cindex "forward file" "one-time expansion"
19516 .cindex "mailing lists" "one-time expansion"
19517 .cindex "address redirection" "one-time expansion"
19518 Sometimes the fact that Exim re-evaluates aliases and reprocesses redirection
19519 files each time it tries to deliver a message causes a problem when one or more
19520 of the generated addresses fails be delivered at the first attempt. The problem
19521 is not one of duplicate delivery &-- Exim is clever enough to handle that &--
19522 but of what happens when the redirection list changes during the time that the
19523 message is on Exim's queue. This is particularly true in the case of mailing
19524 lists, where new subscribers might receive copies of messages that were posted
19525 before they subscribed.
19527 If &%one_time%& is set and any addresses generated by the router fail to
19528 deliver at the first attempt, the failing addresses are added to the message as
19529 &"top level"& addresses, and the parent address that generated them is marked
19530 &"delivered"&. Thus, redirection does not happen again at the next delivery
19533 &*Warning 1*&: Any header line addition or removal that is specified by this
19534 router would be lost if delivery did not succeed at the first attempt. For this
19535 reason, the &%headers_add%& and &%headers_remove%& generic options are not
19536 permitted when &%one_time%& is set.
19538 &*Warning 2*&: To ensure that the router generates only addresses (as opposed
19539 to pipe or file deliveries or auto-replies) &%forbid_file%&, &%forbid_pipe%&,
19540 and &%forbid_filter_reply%& are forced to be true when &%one_time%& is set.
19542 &*Warning 3*&: The &%unseen%& generic router option may not be set with
19545 The original top-level address is remembered with each of the generated
19546 addresses, and is output in any log messages. However, any intermediate parent
19547 addresses are not recorded. This makes a difference to the log only if
19548 &%all_parents%& log selector is set. It is expected that &%one_time%& will
19549 typically be used for mailing lists, where there is normally just one level of
19553 .option owners redirect "string list" unset
19554 .cindex "ownership" "alias file"
19555 .cindex "ownership" "forward file"
19556 .cindex "alias file" "ownership"
19557 .cindex "forward file" "ownership"
19558 This specifies a list of permitted owners for the file specified by &%file%&.
19559 This list is in addition to the local user when &%check_local_user%& is set.
19560 See &%check_owner%& above.
19563 .option owngroups redirect "string list" unset
19564 This specifies a list of permitted groups for the file specified by &%file%&.
19565 The list is in addition to the local user's primary group when
19566 &%check_local_user%& is set. See &%check_group%& above.
19569 .option pipe_transport redirect string&!! unset
19570 .vindex "&$address_pipe$&"
19571 A &(redirect)& router sets up a direct delivery to a pipe when a string
19572 starting with a vertical bar character is specified as a new &"address"&. The
19573 transport used is specified by this option, which, after expansion, must be the
19574 name of a configured transport. This should normally be a &(pipe)& transport.
19575 When the transport is run, the pipe command is in &$address_pipe$&.
19578 .option qualify_domain redirect string&!! unset
19579 .vindex "&$qualify_recipient$&"
19580 If this option is set, and an unqualified address (one without a domain) is
19581 generated, and that address would normally be qualified by the global setting
19582 in &%qualify_recipient%&, it is instead qualified with the domain specified by
19583 expanding this string. If the expansion fails, the router declines. If you want
19584 to revert to the default, you can have the expansion generate
19585 &$qualify_recipient$&.
19587 This option applies to all unqualified addresses generated by Exim filters,
19588 but for traditional &_.forward_& files, it applies only to addresses that are
19589 not preceded by a backslash. Sieve filters cannot generate unqualified
19592 .option qualify_preserve_domain redirect boolean false
19593 .cindex "domain" "in redirection; preserving"
19594 .cindex "preserving domain in redirection"
19595 .cindex "address redirection" "domain; preserving"
19596 If this option is set, the router's local &%qualify_domain%& option must not be
19597 set (a configuration error occurs if it is). If an unqualified address (one
19598 without a domain) is generated, it is qualified with the domain of the parent
19599 address (the immediately preceding ancestor) instead of the global
19600 &%qualify_recipient%& value. In the case of a traditional &_.forward_& file,
19601 this applies whether or not the address is preceded by a backslash.
19604 .option repeat_use redirect boolean true
19605 If this option is set false, the router is skipped for a child address that has
19606 any ancestor that was routed by this router. This test happens before any of
19607 the other preconditions are tested. Exim's default anti-looping rules skip
19608 only when the ancestor is the same as the current address. See also
19609 &%check_ancestor%& above and the generic &%redirect_router%& option.
19612 .option reply_transport redirect string&!! unset
19613 A &(redirect)& router sets up an automatic reply when a &%mail%& or
19614 &%vacation%& command is used in a filter file. The transport used is specified
19615 by this option, which, after expansion, must be the name of a configured
19616 transport. This should normally be an &(autoreply)& transport. Other transports
19617 are unlikely to do anything sensible or useful.
19620 .option rewrite redirect boolean true
19621 .cindex "address redirection" "disabling rewriting"
19622 If this option is set false, addresses generated by the router are not
19623 subject to address rewriting. Otherwise, they are treated like new addresses
19624 and are rewritten according to the global rewriting rules.
19627 .option sieve_subaddress redirect string&!! unset
19628 The value of this option is passed to a Sieve filter to specify the
19629 :subaddress part of an address.
19631 .option sieve_useraddress redirect string&!! unset
19632 The value of this option is passed to a Sieve filter to specify the :user part
19633 of an address. However, if it is unset, the entire original local part
19634 (including any prefix or suffix) is used for :user.
19637 .option sieve_vacation_directory redirect string&!! unset
19638 .cindex "Sieve filter" "vacation directory"
19639 To enable the &"vacation"& extension for Sieve filters, you must set
19640 &%sieve_vacation_directory%& to the directory where vacation databases are held
19641 (do not put anything else in that directory), and ensure that the
19642 &%reply_transport%& option refers to an &(autoreply)& transport. Each user
19643 needs their own directory; Exim will create it if necessary.
19647 .option skip_syntax_errors redirect boolean false
19648 .cindex "forward file" "broken"
19649 .cindex "address redirection" "broken files"
19650 .cindex "alias file" "broken"
19651 .cindex "broken alias or forward files"
19652 .cindex "ignoring faulty addresses"
19653 .cindex "skipping faulty addresses"
19654 .cindex "error" "skipping bad syntax"
19655 If &%skip_syntax_errors%& is set, syntactically malformed addresses in
19656 non-filter redirection data are skipped, and each failing address is logged. If
19657 &%syntax_errors_to%& is set, a message is sent to the address it defines,
19658 giving details of the failures. If &%syntax_errors_text%& is set, its contents
19659 are expanded and placed at the head of the error message generated by
19660 &%syntax_errors_to%&. Usually it is appropriate to set &%syntax_errors_to%& to
19661 be the same address as the generic &%errors_to%& option. The
19662 &%skip_syntax_errors%& option is often used when handling mailing lists.
19664 If all the addresses in a redirection list are skipped because of syntax
19665 errors, the router declines to handle the original address, and it is passed to
19666 the following routers.
19668 If &%skip_syntax_errors%& is set when an Exim filter is interpreted, any syntax
19669 error in the filter causes filtering to be abandoned without any action being
19670 taken. The incident is logged, and the router declines to handle the address,
19671 so it is passed to the following routers.
19673 .cindex "Sieve filter" "syntax errors in"
19674 Syntax errors in a Sieve filter file cause the &"keep"& action to occur. This
19675 action is specified by RFC 3028. The values of &%skip_syntax_errors%&,
19676 &%syntax_errors_to%&, and &%syntax_errors_text%& are not used.
19678 &%skip_syntax_errors%& can be used to specify that errors in users' forward
19679 lists or filter files should not prevent delivery. The &%syntax_errors_to%&
19680 option, used with an address that does not get redirected, can be used to
19681 notify users of these errors, by means of a router like this:
19687 file = $home/.forward
19688 file_transport = address_file
19689 pipe_transport = address_pipe
19690 reply_transport = address_reply
19693 syntax_errors_to = real-$local_part@$domain
19694 syntax_errors_text = \
19695 This is an automatically generated message. An error has\n\
19696 been found in your .forward file. Details of the error are\n\
19697 reported below. While this error persists, you will receive\n\
19698 a copy of this message for every message that is addressed\n\
19699 to you. If your .forward file is a filter file, or if it is\n\
19700 a non-filter file containing no valid forwarding addresses,\n\
19701 a copy of each incoming message will be put in your normal\n\
19702 mailbox. If a non-filter file contains at least one valid\n\
19703 forwarding address, forwarding to the valid addresses will\n\
19704 happen, and those will be the only deliveries that occur.
19706 You also need a router to ensure that local addresses that are prefixed by
19707 &`real-`& are recognized, but not forwarded or filtered. For example, you could
19708 put this immediately before the &(userforward)& router:
19713 local_part_prefix = real-
19714 transport = local_delivery
19716 For security, it would probably be a good idea to restrict the use of this
19717 router to locally-generated messages, using a condition such as this:
19719 condition = ${if match {$sender_host_address}\
19720 {\N^(|127\.0\.0\.1)$\N}}
19724 .option syntax_errors_text redirect string&!! unset
19725 See &%skip_syntax_errors%& above.
19728 .option syntax_errors_to redirect string unset
19729 See &%skip_syntax_errors%& above.
19730 .ecindex IIDredrou1
19731 .ecindex IIDredrou2
19738 . ////////////////////////////////////////////////////////////////////////////
19739 . ////////////////////////////////////////////////////////////////////////////
19741 .chapter "Environment for running local transports" "CHAPenvironment" &&&
19742 "Environment for local transports"
19743 .scindex IIDenvlotra1 "local transports" "environment for"
19744 .scindex IIDenvlotra2 "environment for local transports"
19745 .scindex IIDenvlotra3 "transport" "local; environment for"
19746 Local transports handle deliveries to files and pipes. (The &(autoreply)&
19747 transport can be thought of as similar to a pipe.) Exim always runs transports
19748 in subprocesses, under specified uids and gids. Typical deliveries to local
19749 mailboxes run under the uid and gid of the local user.
19751 Exim also sets a specific current directory while running the transport; for
19752 some transports a home directory setting is also relevant. The &(pipe)&
19753 transport is the only one that sets up environment variables; see section
19754 &<<SECTpipeenv>>& for details.
19756 The values used for the uid, gid, and the directories may come from several
19757 different places. In many cases, the router that handles the address associates
19758 settings with that address as a result of its &%check_local_user%&, &%group%&,
19759 or &%user%& options. However, values may also be given in the transport's own
19760 configuration, and these override anything that comes from the router.
19764 .section "Concurrent deliveries" "SECID131"
19765 .cindex "concurrent deliveries"
19766 .cindex "simultaneous deliveries"
19767 If two different messages for the same local recipient arrive more or less
19768 simultaneously, the two delivery processes are likely to run concurrently. When
19769 the &(appendfile)& transport is used to write to a file, Exim applies locking
19770 rules to stop concurrent processes from writing to the same file at the same
19773 However, when you use a &(pipe)& transport, it is up to you to arrange any
19774 locking that is needed. Here is a silly example:
19778 command = /bin/sh -c 'cat >>/some/file'
19780 This is supposed to write the message at the end of the file. However, if two
19781 messages arrive at the same time, the file will be scrambled. You can use the
19782 &%exim_lock%& utility program (see section &<<SECTmailboxmaint>>&) to lock a
19783 file using the same algorithm that Exim itself uses.
19788 .section "Uids and gids" "SECTenvuidgid"
19789 .cindex "local transports" "uid and gid"
19790 .cindex "transport" "local; uid and gid"
19791 All transports have the options &%group%& and &%user%&. If &%group%& is set, it
19792 overrides any group that the router set in the address, even if &%user%& is not
19793 set for the transport. This makes it possible, for example, to run local mail
19794 delivery under the uid of the recipient (set by the router), but in a special
19795 group (set by the transport). For example:
19798 # User/group are set by check_local_user in this router
19802 transport = group_delivery
19805 # This transport overrides the group
19807 driver = appendfile
19808 file = /var/spool/mail/$local_part
19811 If &%user%& is set for a transport, its value overrides what is set in the
19812 address by the router. If &%user%& is non-numeric and &%group%& is not set, the
19813 gid associated with the user is used. If &%user%& is numeric, &%group%& must be
19816 .oindex "&%initgroups%&"
19817 When the uid is taken from the transport's configuration, the &[initgroups()]&
19818 function is called for the groups associated with that uid if the
19819 &%initgroups%& option is set for the transport. When the uid is not specified
19820 by the transport, but is associated with the address by a router, the option
19821 for calling &[initgroups()]& is taken from the router configuration.
19823 .cindex "&(pipe)& transport" "uid for"
19824 The &(pipe)& transport contains the special option &%pipe_as_creator%&. If this
19825 is set and &%user%& is not set, the uid of the process that called Exim to
19826 receive the message is used, and if &%group%& is not set, the corresponding
19827 original gid is also used.
19829 This is the detailed preference order for obtaining a gid; the first of the
19830 following that is set is used:
19833 A &%group%& setting of the transport;
19835 A &%group%& setting of the router;
19837 A gid associated with a user setting of the router, either as a result of
19838 &%check_local_user%& or an explicit non-numeric &%user%& setting;
19840 The group associated with a non-numeric &%user%& setting of the transport;
19842 In a &(pipe)& transport, the creator's gid if &%deliver_as_creator%& is set and
19843 the uid is the creator's uid;
19845 The Exim gid if the Exim uid is being used as a default.
19848 If, for example, the user is specified numerically on the router and there are
19849 no group settings, no gid is available. In this situation, an error occurs.
19850 This is different for the uid, for which there always is an ultimate default.
19851 The first of the following that is set is used:
19854 A &%user%& setting of the transport;
19856 In a &(pipe)& transport, the creator's uid if &%deliver_as_creator%& is set;
19858 A &%user%& setting of the router;
19860 A &%check_local_user%& setting of the router;
19865 Of course, an error will still occur if the uid that is chosen is on the
19866 &%never_users%& list.
19872 .section "Current and home directories" "SECID132"
19873 .cindex "current directory for local transport"
19874 .cindex "home directory" "for local transport"
19875 .cindex "transport" "local; home directory for"
19876 .cindex "transport" "local; current directory for"
19877 Routers may set current and home directories for local transports by means of
19878 the &%transport_current_directory%& and &%transport_home_directory%& options.
19879 However, if the transport's &%current_directory%& or &%home_directory%& options
19880 are set, they override the router's values. In detail, the home directory
19881 for a local transport is taken from the first of these values that is set:
19884 The &%home_directory%& option on the transport;
19886 The &%transport_home_directory%& option on the router;
19888 The password data if &%check_local_user%& is set on the router;
19890 The &%router_home_directory%& option on the router.
19893 The current directory is taken from the first of these values that is set:
19896 The &%current_directory%& option on the transport;
19898 The &%transport_current_directory%& option on the router.
19902 If neither the router nor the transport sets a current directory, Exim uses the
19903 value of the home directory, if it is set. Otherwise it sets the current
19904 directory to &_/_& before running a local transport.
19908 .section "Expansion variables derived from the address" "SECID133"
19909 .vindex "&$domain$&"
19910 .vindex "&$local_part$&"
19911 .vindex "&$original_domain$&"
19912 Normally a local delivery is handling a single address, and in that case the
19913 variables such as &$domain$& and &$local_part$& are set during local
19914 deliveries. However, in some circumstances more than one address may be handled
19915 at once (for example, while writing batch SMTP for onward transmission by some
19916 other means). In this case, the variables associated with the local part are
19917 never set, &$domain$& is set only if all the addresses have the same domain,
19918 and &$original_domain$& is never set.
19919 .ecindex IIDenvlotra1
19920 .ecindex IIDenvlotra2
19921 .ecindex IIDenvlotra3
19929 . ////////////////////////////////////////////////////////////////////////////
19930 . ////////////////////////////////////////////////////////////////////////////
19932 .chapter "Generic options for transports" "CHAPtransportgeneric"
19933 .scindex IIDgenoptra1 "generic options" "transport"
19934 .scindex IIDgenoptra2 "options" "generic; for transports"
19935 .scindex IIDgenoptra3 "transport" "generic options for"
19936 The following generic options apply to all transports:
19939 .option body_only transports boolean false
19940 .cindex "transport" "body only"
19941 .cindex "message" "transporting body only"
19942 .cindex "body of message" "transporting"
19943 If this option is set, the message's headers are not transported. It is
19944 mutually exclusive with &%headers_only%&. If it is used with the &(appendfile)&
19945 or &(pipe)& transports, the settings of &%message_prefix%& and
19946 &%message_suffix%& should be checked, because this option does not
19947 automatically suppress them.
19950 .option current_directory transports string&!! unset
19951 .cindex "transport" "current directory for"
19952 This specifies the current directory that is to be set while running the
19953 transport, overriding any value that may have been set by the router.
19954 If the expansion fails for any reason, including forced failure, an error is
19955 logged, and delivery is deferred.
19958 .option disable_logging transports boolean false
19959 If this option is set true, nothing is logged for any
19960 deliveries by the transport or for any
19961 transport errors. You should not set this option unless you really, really know
19962 what you are doing.
19965 .option debug_print transports string&!! unset
19966 .cindex "testing" "variables in drivers"
19967 If this option is set and debugging is enabled (see the &%-d%& command line
19968 option), the string is expanded and included in the debugging output when the
19970 If expansion of the string fails, the error message is written to the debugging
19971 output, and Exim carries on processing.
19972 This facility is provided to help with checking out the values of variables and
19973 so on when debugging driver configurations. For example, if a &%headers_add%&
19974 option is not working properly, &%debug_print%& could be used to output the
19975 variables it references. A newline is added to the text if it does not end with
19977 The variables &$transport_name$& and &$router_name$& contain the name of the
19978 transport and the router that called it.
19980 .option delivery_date_add transports boolean false
19981 .cindex "&'Delivery-date:'& header line"
19982 If this option is true, a &'Delivery-date:'& header is added to the message.
19983 This gives the actual time the delivery was made. As this is not a standard
19984 header, Exim has a configuration option (&%delivery_date_remove%&) which
19985 requests its removal from incoming messages, so that delivered messages can
19986 safely be resent to other recipients.
19989 .option driver transports string unset
19990 This specifies which of the available transport drivers is to be used.
19991 There is no default, and this option must be set for every transport.
19994 .option envelope_to_add transports boolean false
19995 .cindex "&'Envelope-to:'& header line"
19996 If this option is true, an &'Envelope-to:'& header is added to the message.
19997 This gives the original address(es) in the incoming envelope that caused this
19998 delivery to happen. More than one address may be present if the transport is
19999 configured to handle several addresses at once, or if more than one original
20000 address was redirected to the same final address. As this is not a standard
20001 header, Exim has a configuration option (&%envelope_to_remove%&) which requests
20002 its removal from incoming messages, so that delivered messages can safely be
20003 resent to other recipients.
20006 .option group transports string&!! "Exim group"
20007 .cindex "transport" "group; specifying"
20008 This option specifies a gid for running the transport process, overriding any
20009 value that the router supplies, and also overriding any value associated with
20010 &%user%& (see below).
20013 .option headers_add transports list&!! unset
20014 .cindex "header lines" "adding in transport"
20015 .cindex "transport" "header lines; adding"
20016 This option specifies a list of text headers, newline-separated,
20017 which are (separately) expanded and added to the header
20018 portion of a message as it is transported, as described in section
20019 &<<SECTheadersaddrem>>&. Additional header lines can also be specified by
20020 routers. If the result of the expansion is an empty string, or if the expansion
20021 is forced to fail, no action is taken. Other expansion failures are treated as
20022 errors and cause the delivery to be deferred.
20024 Unlike most options, &%headers_add%& can be specified multiple times
20025 for a transport; all listed headers are added.
20028 .option headers_only transports boolean false
20029 .cindex "transport" "header lines only"
20030 .cindex "message" "transporting headers only"
20031 .cindex "header lines" "transporting"
20032 If this option is set, the message's body is not transported. It is mutually
20033 exclusive with &%body_only%&. If it is used with the &(appendfile)& or &(pipe)&
20034 transports, the settings of &%message_prefix%& and &%message_suffix%& should be
20035 checked, since this option does not automatically suppress them.
20038 .option headers_remove transports list&!! unset
20039 .cindex "header lines" "removing"
20040 .cindex "transport" "header lines; removing"
20041 This option specifies a list of header names, colon-separated;
20042 these headers are omitted from the message as it is transported, as described
20043 in section &<<SECTheadersaddrem>>&. Header removal can also be specified by
20045 Each list item is separately expanded.
20046 If the result of the expansion is an empty string, or if the expansion
20047 is forced to fail, no action is taken. Other expansion failures are treated as
20048 errors and cause the delivery to be deferred.
20050 Unlike most options, &%headers_remove%& can be specified multiple times
20051 for a router; all listed headers are removed.
20055 .option headers_rewrite transports string unset
20056 .cindex "transport" "header lines; rewriting"
20057 .cindex "rewriting" "at transport time"
20058 This option allows addresses in header lines to be rewritten at transport time,
20059 that is, as the message is being copied to its destination. The contents of the
20060 option are a colon-separated list of rewriting rules. Each rule is in exactly
20061 the same form as one of the general rewriting rules that are applied when a
20062 message is received. These are described in chapter &<<CHAPrewrite>>&. For
20065 headers_rewrite = a@b c@d f : \
20068 changes &'a@b'& into &'c@d'& in &'From:'& header lines, and &'x@y'& into
20069 &'w@z'& in all address-bearing header lines. The rules are applied to the
20070 header lines just before they are written out at transport time, so they affect
20071 only those copies of the message that pass through the transport. However, only
20072 the message's original header lines, and any that were added by a system
20073 filter, are rewritten. If a router or transport adds header lines, they are not
20074 affected by this option. These rewriting rules are &'not'& applied to the
20075 envelope. You can change the return path using &%return_path%&, but you cannot
20076 change envelope recipients at this time.
20079 .option home_directory transports string&!! unset
20080 .cindex "transport" "home directory for"
20082 This option specifies a home directory setting for a local transport,
20083 overriding any value that may be set by the router. The home directory is
20084 placed in &$home$& while expanding the transport's private options. It is also
20085 used as the current directory if no current directory is set by the
20086 &%current_directory%& option on the transport or the
20087 &%transport_current_directory%& option on the router. If the expansion fails
20088 for any reason, including forced failure, an error is logged, and delivery is
20092 .option initgroups transports boolean false
20093 .cindex "additional groups"
20094 .cindex "groups" "additional"
20095 .cindex "transport" "group; additional"
20096 If this option is true and the uid for the delivery process is provided by the
20097 transport, the &[initgroups()]& function is called when running the transport
20098 to ensure that any additional groups associated with the uid are set up.
20101 .option message_size_limit transports string&!! 0
20102 .cindex "limit" "message size per transport"
20103 .cindex "size" "of message, limit"
20104 .cindex "transport" "message size; limiting"
20105 This option controls the size of messages passed through the transport. It is
20106 expanded before use; the result of the expansion must be a sequence of decimal
20107 digits, optionally followed by K or M. If the expansion fails for any reason,
20108 including forced failure, or if the result is not of the required form,
20109 delivery is deferred. If the value is greater than zero and the size of a
20110 message exceeds this limit, the address is failed. If there is any chance that
20111 the resulting bounce message could be routed to the same transport, you should
20112 ensure that &%return_size_limit%& is less than the transport's
20113 &%message_size_limit%&, as otherwise the bounce message will fail to get
20118 .option rcpt_include_affixes transports boolean false
20119 .cindex "prefix" "for local part, including in envelope"
20120 .cindex "suffix for local part" "including in envelope"
20121 .cindex "local part" "prefix"
20122 .cindex "local part" "suffix"
20123 When this option is false (the default), and an address that has had any
20124 affixes (prefixes or suffixes) removed from the local part is delivered by any
20125 form of SMTP or LMTP, the affixes are not included. For example, if a router
20128 local_part_prefix = *-
20130 routes the address &'abc-xyz@some.domain'& to an SMTP transport, the envelope
20133 RCPT TO:<xyz@some.domain>
20135 This is also the case when an ACL-time callout is being used to verify a
20136 recipient address. However, if &%rcpt_include_affixes%& is set true, the
20137 whole local part is included in the RCPT command. This option applies to BSMTP
20138 deliveries by the &(appendfile)& and &(pipe)& transports as well as to the
20139 &(lmtp)& and &(smtp)& transports.
20142 .option retry_use_local_part transports boolean "see below"
20143 .cindex "hints database" "retry keys"
20144 When a delivery suffers a temporary failure, a retry record is created
20145 in Exim's hints database. For remote deliveries, the key for the retry record
20146 is based on the name and/or IP address of the failing remote host. For local
20147 deliveries, the key is normally the entire address, including both the local
20148 part and the domain. This is suitable for most common cases of local delivery
20149 temporary failure &-- for example, exceeding a mailbox quota should delay only
20150 deliveries to that mailbox, not to the whole domain.
20152 However, in some special cases you may want to treat a temporary local delivery
20153 as a failure associated with the domain, and not with a particular local part.
20154 (For example, if you are storing all mail for some domain in files.) You can do
20155 this by setting &%retry_use_local_part%& false.
20157 For all the local transports, its default value is true. For remote transports,
20158 the default value is false for tidiness, but changing the value has no effect
20159 on a remote transport in the current implementation.
20162 .option return_path transports string&!! unset
20163 .cindex "envelope sender"
20164 .cindex "transport" "return path; changing"
20165 .cindex "return path" "changing in transport"
20166 If this option is set, the string is expanded at transport time and replaces
20167 the existing return path (envelope sender) value in the copy of the message
20168 that is being delivered. An empty return path is permitted. This feature is
20169 designed for remote deliveries, where the value of this option is used in the
20170 SMTP MAIL command. If you set &%return_path%& for a local transport, the
20171 only effect is to change the address that is placed in the &'Return-path:'&
20172 header line, if one is added to the message (see the next option).
20174 &*Note:*& A changed return path is not logged unless you add
20175 &%return_path_on_delivery%& to the log selector.
20177 .vindex "&$return_path$&"
20178 The expansion can refer to the existing value via &$return_path$&. This is
20179 either the message's envelope sender, or an address set by the
20180 &%errors_to%& option on a router. If the expansion is forced to fail, no
20181 replacement occurs; if it fails for another reason, delivery is deferred. This
20182 option can be used to support VERP (Variable Envelope Return Paths) &-- see
20183 section &<<SECTverp>>&.
20185 &*Note*&: If a delivery error is detected locally, including the case when a
20186 remote server rejects a message at SMTP time, the bounce message is not sent to
20187 the value of this option. It is sent to the previously set errors address.
20188 This defaults to the incoming sender address, but can be changed by setting
20189 &%errors_to%& in a router.
20193 .option return_path_add transports boolean false
20194 .cindex "&'Return-path:'& header line"
20195 If this option is true, a &'Return-path:'& header is added to the message.
20196 Although the return path is normally available in the prefix line of BSD
20197 mailboxes, this is commonly not displayed by MUAs, and so the user does not
20198 have easy access to it.
20200 RFC 2821 states that the &'Return-path:'& header is added to a message &"when
20201 the delivery SMTP server makes the final delivery"&. This implies that this
20202 header should not be present in incoming messages. Exim has a configuration
20203 option, &%return_path_remove%&, which requests removal of this header from
20204 incoming messages, so that delivered messages can safely be resent to other
20208 .option shadow_condition transports string&!! unset
20209 See &%shadow_transport%& below.
20212 .option shadow_transport transports string unset
20213 .cindex "shadow transport"
20214 .cindex "transport" "shadow"
20215 A local transport may set the &%shadow_transport%& option to the name of
20216 another local transport. Shadow remote transports are not supported.
20218 Whenever a delivery to the main transport succeeds, and either
20219 &%shadow_condition%& is unset, or its expansion does not result in the empty
20220 string or one of the strings &"0"& or &"no"& or &"false"&, the message is also
20221 passed to the shadow transport, with the same delivery address or addresses. If
20222 expansion fails, no action is taken except that non-forced expansion failures
20223 cause a log line to be written.
20225 The result of the shadow transport is discarded and does not affect the
20226 subsequent processing of the message. Only a single level of shadowing is
20227 provided; the &%shadow_transport%& option is ignored on any transport when it
20228 is running as a shadow. Options concerned with output from pipes are also
20229 ignored. The log line for the successful delivery has an item added on the end,
20232 ST=<shadow transport name>
20234 If the shadow transport did not succeed, the error message is put in
20235 parentheses afterwards. Shadow transports can be used for a number of different
20236 purposes, including keeping more detailed log information than Exim normally
20237 provides, and implementing automatic acknowledgment policies based on message
20238 headers that some sites insist on.
20241 .option transport_filter transports string&!! unset
20242 .cindex "transport" "filter"
20243 .cindex "filter" "transport filter"
20244 This option sets up a filtering (in the Unix shell sense) process for messages
20245 at transport time. It should not be confused with mail filtering as set up by
20246 individual users or via a system filter.
20248 When the message is about to be written out, the command specified by
20249 &%transport_filter%& is started up in a separate, parallel process, and
20250 the entire message, including the header lines, is passed to it on its standard
20251 input (this in fact is done from a third process, to avoid deadlock). The
20252 command must be specified as an absolute path.
20254 The lines of the message that are written to the transport filter are
20255 terminated by newline (&"\n"&). The message is passed to the filter before any
20256 SMTP-specific processing, such as turning &"\n"& into &"\r\n"& and escaping
20257 lines beginning with a dot, and also before any processing implied by the
20258 settings of &%check_string%& and &%escape_string%& in the &(appendfile)& or
20259 &(pipe)& transports.
20261 The standard error for the filter process is set to the same destination as its
20262 standard output; this is read and written to the message's ultimate
20263 destination. The process that writes the message to the filter, the
20264 filter itself, and the original process that reads the result and delivers it
20265 are all run in parallel, like a shell pipeline.
20267 The filter can perform any transformations it likes, but of course should take
20268 care not to break RFC 2822 syntax. Exim does not check the result, except to
20269 test for a final newline when SMTP is in use. All messages transmitted over
20270 SMTP must end with a newline, so Exim supplies one if it is missing.
20272 .cindex "content scanning" "per user"
20273 A transport filter can be used to provide content-scanning on a per-user basis
20274 at delivery time if the only required effect of the scan is to modify the
20275 message. For example, a content scan could insert a new header line containing
20276 a spam score. This could be interpreted by a filter in the user's MUA. It is
20277 not possible to discard a message at this stage.
20279 .cindex "SMTP" "SIZE"
20280 A problem might arise if the filter increases the size of a message that is
20281 being sent down an SMTP connection. If the receiving SMTP server has indicated
20282 support for the SIZE parameter, Exim will have sent the size of the message
20283 at the start of the SMTP session. If what is actually sent is substantially
20284 more, the server might reject the message. This can be worked round by setting
20285 the &%size_addition%& option on the &(smtp)& transport, either to allow for
20286 additions to the message, or to disable the use of SIZE altogether.
20288 .vindex "&$pipe_addresses$&"
20289 The value of the &%transport_filter%& option is the command string for starting
20290 the filter, which is run directly from Exim, not under a shell. The string is
20291 parsed by Exim in the same way as a command string for the &(pipe)& transport:
20292 Exim breaks it up into arguments and then expands each argument separately (see
20293 section &<<SECThowcommandrun>>&). Any kind of expansion failure causes delivery
20294 to be deferred. The special argument &$pipe_addresses$& is replaced by a number
20295 of arguments, one for each address that applies to this delivery. (This isn't
20296 an ideal name for this feature here, but as it was already implemented for the
20297 &(pipe)& transport, it seemed sensible not to change it.)
20300 .vindex "&$host_address$&"
20301 The expansion variables &$host$& and &$host_address$& are available when the
20302 transport is a remote one. They contain the name and IP address of the host to
20303 which the message is being sent. For example:
20305 transport_filter = /some/directory/transport-filter.pl \
20306 $host $host_address $sender_address $pipe_addresses
20309 Two problems arise if you want to use more complicated expansion items to
20310 generate transport filter commands, both of which due to the fact that the
20311 command is split up &'before'& expansion.
20313 If an expansion item contains white space, you must quote it, so that it is all
20314 part of the same command item. If the entire option setting is one such
20315 expansion item, you have to take care what kind of quoting you use. For
20318 transport_filter = '/bin/cmd${if eq{$host}{a.b.c}{1}{2}}'
20320 This runs the command &(/bin/cmd1)& if the host name is &'a.b.c'&, and
20321 &(/bin/cmd2)& otherwise. If double quotes had been used, they would have been
20322 stripped by Exim when it read the option's value. When the value is used, if
20323 the single quotes were missing, the line would be split into two items,
20324 &`/bin/cmd${if`& and &`eq{$host}{a.b.c}{1}{2}`&, and an error would occur when
20325 Exim tried to expand the first one.
20327 Except for the special case of &$pipe_addresses$& that is mentioned above, an
20328 expansion cannot generate multiple arguments, or a command name followed by
20329 arguments. Consider this example:
20331 transport_filter = ${lookup{$host}lsearch{/a/file}\
20332 {$value}{/bin/cat}}
20334 The result of the lookup is interpreted as the name of the command, even
20335 if it contains white space. The simplest way round this is to use a shell:
20337 transport_filter = /bin/sh -c ${lookup{$host}lsearch{/a/file}\
20338 {$value}{/bin/cat}}
20342 The filter process is run under the same uid and gid as the normal delivery.
20343 For remote deliveries this is the Exim uid/gid by default. The command should
20344 normally yield a zero return code. Transport filters are not supposed to fail.
20345 A non-zero code is taken to mean that the transport filter encountered some
20346 serious problem. Delivery of the message is deferred; the message remains on
20347 the queue and is tried again later. It is not possible to cause a message to be
20348 bounced from a transport filter.
20350 If a transport filter is set on an autoreply transport, the original message is
20351 passed through the filter as it is being copied into the newly generated
20352 message, which happens if the &%return_message%& option is set.
20355 .option transport_filter_timeout transports time 5m
20356 .cindex "transport" "filter, timeout"
20357 When Exim is reading the output of a transport filter, it applies a timeout
20358 that can be set by this option. Exceeding the timeout is normally treated as a
20359 temporary delivery failure. However, if a transport filter is used with a
20360 &(pipe)& transport, a timeout in the transport filter is treated in the same
20361 way as a timeout in the pipe command itself. By default, a timeout is a hard
20362 error, but if the &(pipe)& transport's &%timeout_defer%& option is set true, it
20363 becomes a temporary error.
20366 .option user transports string&!! "Exim user"
20367 .cindex "uid (user id)" "local delivery"
20368 .cindex "transport" "user, specifying"
20369 This option specifies the user under whose uid the delivery process is to be
20370 run, overriding any uid that may have been set by the router. If the user is
20371 given as a name, the uid is looked up from the password data, and the
20372 associated group is taken as the value of the gid to be used if the &%group%&
20375 For deliveries that use local transports, a user and group are normally
20376 specified explicitly or implicitly (for example, as a result of
20377 &%check_local_user%&) by the router or transport.
20379 .cindex "hints database" "access by remote transport"
20380 For remote transports, you should leave this option unset unless you really are
20381 sure you know what you are doing. When a remote transport is running, it needs
20382 to be able to access Exim's hints databases, because each host may have its own
20384 .ecindex IIDgenoptra1
20385 .ecindex IIDgenoptra2
20386 .ecindex IIDgenoptra3
20393 . ////////////////////////////////////////////////////////////////////////////
20394 . ////////////////////////////////////////////////////////////////////////////
20396 .chapter "Address batching in local transports" "CHAPbatching" &&&
20398 .cindex "transport" "local; address batching in"
20399 The only remote transport (&(smtp)&) is normally configured to handle more than
20400 one address at a time, so that when several addresses are routed to the same
20401 remote host, just one copy of the message is sent. Local transports, however,
20402 normally handle one address at a time. That is, a separate instance of the
20403 transport is run for each address that is routed to the transport. A separate
20404 copy of the message is delivered each time.
20406 .cindex "batched local delivery"
20407 .oindex "&%batch_max%&"
20408 .oindex "&%batch_id%&"
20409 In special cases, it may be desirable to handle several addresses at once in a
20410 local transport, for example:
20413 In an &(appendfile)& transport, when storing messages in files for later
20414 delivery by some other means, a single copy of the message with multiple
20415 recipients saves space.
20417 In an &(lmtp)& transport, when delivering over &"local SMTP"& to some process,
20418 a single copy saves time, and is the normal way LMTP is expected to work.
20420 In a &(pipe)& transport, when passing the message
20421 to a scanner program or
20422 to some other delivery mechanism such as UUCP, multiple recipients may be
20426 These three local transports all have the same options for controlling multiple
20427 (&"batched"&) deliveries, namely &%batch_max%& and &%batch_id%&. To save
20428 repeating the information for each transport, these options are described here.
20430 The &%batch_max%& option specifies the maximum number of addresses that can be
20431 delivered together in a single run of the transport. Its default value is one
20432 (no batching). When more than one address is routed to a transport that has a
20433 &%batch_max%& value greater than one, the addresses are delivered in a batch
20434 (that is, in a single run of the transport with multiple recipients), subject
20435 to certain conditions:
20438 .vindex "&$local_part$&"
20439 If any of the transport's options contain a reference to &$local_part$&, no
20440 batching is possible.
20442 .vindex "&$domain$&"
20443 If any of the transport's options contain a reference to &$domain$&, only
20444 addresses with the same domain are batched.
20446 .cindex "customizing" "batching condition"
20447 If &%batch_id%& is set, it is expanded for each address, and only those
20448 addresses with the same expanded value are batched. This allows you to specify
20449 customized batching conditions. Failure of the expansion for any reason,
20450 including forced failure, disables batching, but it does not stop the delivery
20453 Batched addresses must also have the same errors address (where to send
20454 delivery errors), the same header additions and removals, the same user and
20455 group for the transport, and if a host list is present, the first host must
20459 In the case of the &(appendfile)& and &(pipe)& transports, batching applies
20460 both when the file or pipe command is specified in the transport, and when it
20461 is specified by a &(redirect)& router, but all the batched addresses must of
20462 course be routed to the same file or pipe command. These two transports have an
20463 option called &%use_bsmtp%&, which causes them to deliver the message in
20464 &"batched SMTP"& format, with the envelope represented as SMTP commands. The
20465 &%check_string%& and &%escape_string%& options are forced to the values
20468 escape_string = ".."
20470 when batched SMTP is in use. A full description of the batch SMTP mechanism is
20471 given in section &<<SECTbatchSMTP>>&. The &(lmtp)& transport does not have a
20472 &%use_bsmtp%& option, because it always delivers using the SMTP protocol.
20474 .cindex "&'Envelope-to:'& header line"
20475 If the generic &%envelope_to_add%& option is set for a batching transport, the
20476 &'Envelope-to:'& header that is added to the message contains all the addresses
20477 that are being processed together. If you are using a batching &(appendfile)&
20478 transport without &%use_bsmtp%&, the only way to preserve the recipient
20479 addresses is to set the &%envelope_to_add%& option.
20481 .cindex "&(pipe)& transport" "with multiple addresses"
20482 .vindex "&$pipe_addresses$&"
20483 If you are using a &(pipe)& transport without BSMTP, and setting the
20484 transport's &%command%& option, you can include &$pipe_addresses$& as part of
20485 the command. This is not a true variable; it is a bit of magic that causes each
20486 of the recipient addresses to be inserted into the command as a separate
20487 argument. This provides a way of accessing all the addresses that are being
20488 delivered in the batch. &*Note:*& This is not possible for pipe commands that
20489 are specified by a &(redirect)& router.
20494 . ////////////////////////////////////////////////////////////////////////////
20495 . ////////////////////////////////////////////////////////////////////////////
20497 .chapter "The appendfile transport" "CHAPappendfile"
20498 .scindex IIDapptra1 "&(appendfile)& transport"
20499 .scindex IIDapptra2 "transports" "&(appendfile)&"
20500 .cindex "directory creation"
20501 .cindex "creating directories"
20502 The &(appendfile)& transport delivers a message by appending it to an existing
20503 file, or by creating an entirely new file in a specified directory. Single
20504 files to which messages are appended can be in the traditional Unix mailbox
20505 format, or optionally in the MBX format supported by the Pine MUA and
20506 University of Washington IMAP daemon, &'inter alia'&. When each message is
20507 being delivered as a separate file, &"maildir"& format can optionally be used
20508 to give added protection against failures that happen part-way through the
20509 delivery. A third form of separate-file delivery known as &"mailstore"& is also
20510 supported. For all file formats, Exim attempts to create as many levels of
20511 directory as necessary, provided that &%create_directory%& is set.
20513 The code for the optional formats is not included in the Exim binary by
20514 default. It is necessary to set SUPPORT_MBX, SUPPORT_MAILDIR and/or
20515 SUPPORT_MAILSTORE in &_Local/Makefile_& to have the appropriate code
20518 .cindex "quota" "system"
20519 Exim recognizes system quota errors, and generates an appropriate message. Exim
20520 also supports its own quota control within the transport, for use when the
20521 system facility is unavailable or cannot be used for some reason.
20523 If there is an error while appending to a file (for example, quota exceeded or
20524 partition filled), Exim attempts to reset the file's length and last
20525 modification time back to what they were before. If there is an error while
20526 creating an entirely new file, the new file is removed.
20528 Before appending to a file, a number of security checks are made, and the
20529 file is locked. A detailed description is given below, after the list of
20532 The &(appendfile)& transport is most commonly used for local deliveries to
20533 users' mailboxes. However, it can also be used as a pseudo-remote transport for
20534 putting messages into files for remote delivery by some means other than Exim.
20535 &"Batch SMTP"& format is often used in this case (see the &%use_bsmtp%&
20540 .section "The file and directory options" "SECTfildiropt"
20541 The &%file%& option specifies a single file, to which the message is appended;
20542 the &%directory%& option specifies a directory, in which a new file containing
20543 the message is created. Only one of these two options can be set, and for
20544 normal deliveries to mailboxes, one of them &'must'& be set.
20546 .vindex "&$address_file$&"
20547 .vindex "&$local_part$&"
20548 However, &(appendfile)& is also used for delivering messages to files or
20549 directories whose names (or parts of names) are obtained from alias,
20550 forwarding, or filtering operations (for example, a &%save%& command in a
20551 user's Exim filter). When such a transport is running, &$local_part$& contains
20552 the local part that was aliased or forwarded, and &$address_file$& contains the
20553 name (or partial name) of the file or directory generated by the redirection
20554 operation. There are two cases:
20557 If neither &%file%& nor &%directory%& is set, the redirection operation
20558 must specify an absolute path (one that begins with &`/`&). This is the most
20559 common case when users with local accounts use filtering to sort mail into
20560 different folders. See for example, the &(address_file)& transport in the
20561 default configuration. If the path ends with a slash, it is assumed to be the
20562 name of a directory. A delivery to a directory can also be forced by setting
20563 &%maildir_format%& or &%mailstore_format%&.
20565 If &%file%& or &%directory%& is set for a delivery from a redirection, it is
20566 used to determine the file or directory name for the delivery. Normally, the
20567 contents of &$address_file$& are used in some way in the string expansion.
20571 .cindex "Sieve filter" "configuring &(appendfile)&"
20572 .cindex "Sieve filter" "relative mailbox path handling"
20573 As an example of the second case, consider an environment where users do not
20574 have home directories. They may be permitted to use Exim filter commands of the
20579 or Sieve filter commands of the form:
20581 require "fileinto";
20582 fileinto "folder23";
20584 In this situation, the expansion of &%file%& or &%directory%& in the transport
20585 must transform the relative path into an appropriate absolute file name. In the
20586 case of Sieve filters, the name &'inbox'& must be handled. It is the name that
20587 is used as a result of a &"keep"& action in the filter. This example shows one
20588 way of handling this requirement:
20590 file = ${if eq{$address_file}{inbox} \
20591 {/var/mail/$local_part} \
20592 {${if eq{${substr_0_1:$address_file}}{/} \
20594 {$home/mail/$address_file} \
20598 With this setting of &%file%&, &'inbox'& refers to the standard mailbox
20599 location, absolute paths are used without change, and other folders are in the
20600 &_mail_& directory within the home directory.
20602 &*Note 1*&: While processing an Exim filter, a relative path such as
20603 &_folder23_& is turned into an absolute path if a home directory is known to
20604 the router. In particular, this is the case if &%check_local_user%& is set. If
20605 you want to prevent this happening at routing time, you can set
20606 &%router_home_directory%& empty. This forces the router to pass the relative
20607 path to the transport.
20609 &*Note 2*&: An absolute path in &$address_file$& is not treated specially;
20610 the &%file%& or &%directory%& option is still used if it is set.
20615 .section "Private options for appendfile" "SECID134"
20616 .cindex "options" "&(appendfile)& transport"
20620 .option allow_fifo appendfile boolean false
20621 .cindex "fifo (named pipe)"
20622 .cindex "named pipe (fifo)"
20623 .cindex "pipe" "named (fifo)"
20624 Setting this option permits delivery to named pipes (FIFOs) as well as to
20625 regular files. If no process is reading the named pipe at delivery time, the
20626 delivery is deferred.
20629 .option allow_symlink appendfile boolean false
20630 .cindex "symbolic link" "to mailbox"
20631 .cindex "mailbox" "symbolic link"
20632 By default, &(appendfile)& will not deliver if the path name for the file is
20633 that of a symbolic link. Setting this option relaxes that constraint, but there
20634 are security issues involved in the use of symbolic links. Be sure you know
20635 what you are doing if you set this. Details of exactly what this option affects
20636 are included in the discussion which follows this list of options.
20639 .option batch_id appendfile string&!! unset
20640 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
20641 However, batching is automatically disabled for &(appendfile)& deliveries that
20642 happen as a result of forwarding or aliasing or other redirection directly to a
20646 .option batch_max appendfile integer 1
20647 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
20650 .option check_group appendfile boolean false
20651 When this option is set, the group owner of the file defined by the &%file%&
20652 option is checked to see that it is the same as the group under which the
20653 delivery process is running. The default setting is false because the default
20654 file mode is 0600, which means that the group is irrelevant.
20657 .option check_owner appendfile boolean true
20658 When this option is set, the owner of the file defined by the &%file%& option
20659 is checked to ensure that it is the same as the user under which the delivery
20660 process is running.
20663 .option check_string appendfile string "see below"
20664 .cindex "&""From""& line"
20665 As &(appendfile)& writes the message, the start of each line is tested for
20666 matching &%check_string%&, and if it does, the initial matching characters are
20667 replaced by the contents of &%escape_string%&. The value of &%check_string%& is
20668 a literal string, not a regular expression, and the case of any letters it
20669 contains is significant.
20671 If &%use_bsmtp%& is set the values of &%check_string%& and &%escape_string%&
20672 are forced to &"."& and &".."& respectively, and any settings in the
20673 configuration are ignored. Otherwise, they default to &"From&~"& and
20674 &">From&~"& when the &%file%& option is set, and unset when any of the
20675 &%directory%&, &%maildir%&, or &%mailstore%& options are set.
20677 The default settings, along with &%message_prefix%& and &%message_suffix%&, are
20678 suitable for traditional &"BSD"& mailboxes, where a line beginning with
20679 &"From&~"& indicates the start of a new message. All four options need changing
20680 if another format is used. For example, to deliver to mailboxes in MMDF format:
20681 .cindex "MMDF format mailbox"
20682 .cindex "mailbox" "MMDF format"
20684 check_string = "\1\1\1\1\n"
20685 escape_string = "\1\1\1\1 \n"
20686 message_prefix = "\1\1\1\1\n"
20687 message_suffix = "\1\1\1\1\n"
20689 .option create_directory appendfile boolean true
20690 .cindex "directory creation"
20691 When this option is true, Exim attempts to create any missing superior
20692 directories for the file that it is about to write. A created directory's mode
20693 is given by the &%directory_mode%& option.
20695 The group ownership of a newly created directory is highly dependent on the
20696 operating system (and possibly the file system) that is being used. For
20697 example, in Solaris, if the parent directory has the setgid bit set, its group
20698 is propagated to the child; if not, the currently set group is used. However,
20699 in FreeBSD, the parent's group is always used.
20703 .option create_file appendfile string anywhere
20704 This option constrains the location of files and directories that are created
20705 by this transport. It applies to files defined by the &%file%& option and
20706 directories defined by the &%directory%& option. In the case of maildir
20707 delivery, it applies to the top level directory, not the maildir directories
20710 The option must be set to one of the words &"anywhere"&, &"inhome"&, or
20711 &"belowhome"&. In the second and third cases, a home directory must have been
20712 set for the transport. This option is not useful when an explicit file name is
20713 given for normal mailbox deliveries. It is intended for the case when file
20714 names are generated from users' &_.forward_& files. These are usually handled
20715 by an &(appendfile)& transport called &%address_file%&. See also
20716 &%file_must_exist%&.
20719 .option directory appendfile string&!! unset
20720 This option is mutually exclusive with the &%file%& option, but one of &%file%&
20721 or &%directory%& must be set, unless the delivery is the direct result of a
20722 redirection (see section &<<SECTfildiropt>>&).
20724 When &%directory%& is set, the string is expanded, and the message is delivered
20725 into a new file or files in or below the given directory, instead of being
20726 appended to a single mailbox file. A number of different formats are provided
20727 (see &%maildir_format%& and &%mailstore_format%&), and see section
20728 &<<SECTopdir>>& for further details of this form of delivery.
20731 .option directory_file appendfile string&!! "see below"
20733 .vindex "&$inode$&"
20734 When &%directory%& is set, but neither &%maildir_format%& nor
20735 &%mailstore_format%& is set, &(appendfile)& delivers each message into a file
20736 whose name is obtained by expanding this string. The default value is:
20738 q${base62:$tod_epoch}-$inode
20740 This generates a unique name from the current time, in base 62 form, and the
20741 inode of the file. The variable &$inode$& is available only when expanding this
20745 .option directory_mode appendfile "octal integer" 0700
20746 If &(appendfile)& creates any directories as a result of the
20747 &%create_directory%& option, their mode is specified by this option.
20750 .option escape_string appendfile string "see description"
20751 See &%check_string%& above.
20754 .option file appendfile string&!! unset
20755 This option is mutually exclusive with the &%directory%& option, but one of
20756 &%file%& or &%directory%& must be set, unless the delivery is the direct result
20757 of a redirection (see section &<<SECTfildiropt>>&). The &%file%& option
20758 specifies a single file, to which the message is appended. One or more of
20759 &%use_fcntl_lock%&, &%use_flock_lock%&, or &%use_lockfile%& must be set with
20762 .cindex "NFS" "lock file"
20763 .cindex "locking files"
20764 .cindex "lock files"
20765 If you are using more than one host to deliver over NFS into the same
20766 mailboxes, you should always use lock files.
20768 The string value is expanded for each delivery, and must yield an absolute
20769 path. The most common settings of this option are variations on one of these
20772 file = /var/spool/mail/$local_part
20773 file = /home/$local_part/inbox
20776 .cindex "&""sticky""& bit"
20777 In the first example, all deliveries are done into the same directory. If Exim
20778 is configured to use lock files (see &%use_lockfile%& below) it must be able to
20779 create a file in the directory, so the &"sticky"& bit must be turned on for
20780 deliveries to be possible, or alternatively the &%group%& option can be used to
20781 run the delivery under a group id which has write access to the directory.
20785 .option file_format appendfile string unset
20786 .cindex "file" "mailbox; checking existing format"
20787 This option requests the transport to check the format of an existing file
20788 before adding to it. The check consists of matching a specific string at the
20789 start of the file. The value of the option consists of an even number of
20790 colon-separated strings. The first of each pair is the test string, and the
20791 second is the name of a transport. If the transport associated with a matched
20792 string is not the current transport, control is passed over to the other
20793 transport. For example, suppose the standard &(local_delivery)& transport has
20796 file_format = "From : local_delivery :\
20797 \1\1\1\1\n : local_mmdf_delivery"
20799 Mailboxes that begin with &"From"& are still handled by this transport, but if
20800 a mailbox begins with four binary ones followed by a newline, control is passed
20801 to a transport called &%local_mmdf_delivery%&, which presumably is configured
20802 to do the delivery in MMDF format. If a mailbox does not exist or is empty, it
20803 is assumed to match the current transport. If the start of a mailbox doesn't
20804 match any string, or if the transport named for a given string is not defined,
20805 delivery is deferred.
20808 .option file_must_exist appendfile boolean false
20809 If this option is true, the file specified by the &%file%& option must exist.
20810 A temporary error occurs if it does not, causing delivery to be deferred.
20811 If this option is false, the file is created if it does not exist.
20814 .option lock_fcntl_timeout appendfile time 0s
20815 .cindex "timeout" "mailbox locking"
20816 .cindex "mailbox" "locking, blocking and non-blocking"
20817 .cindex "locking files"
20818 By default, the &(appendfile)& transport uses non-blocking calls to &[fcntl()]&
20819 when locking an open mailbox file. If the call fails, the delivery process
20820 sleeps for &%lock_interval%& and tries again, up to &%lock_retries%& times.
20821 Non-blocking calls are used so that the file is not kept open during the wait
20822 for the lock; the reason for this is to make it as safe as possible for
20823 deliveries over NFS in the case when processes might be accessing an NFS
20824 mailbox without using a lock file. This should not be done, but
20825 misunderstandings and hence misconfigurations are not unknown.
20827 On a busy system, however, the performance of a non-blocking lock approach is
20828 not as good as using a blocking lock with a timeout. In this case, the waiting
20829 is done inside the system call, and Exim's delivery process acquires the lock
20830 and can proceed as soon as the previous lock holder releases it.
20832 If &%lock_fcntl_timeout%& is set to a non-zero time, blocking locks, with that
20833 timeout, are used. There may still be some retrying: the maximum number of
20836 (lock_retries * lock_interval) / lock_fcntl_timeout
20838 rounded up to the next whole number. In other words, the total time during
20839 which &(appendfile)& is trying to get a lock is roughly the same, unless
20840 &%lock_fcntl_timeout%& is set very large.
20842 You should consider setting this option if you are getting a lot of delayed
20843 local deliveries because of errors of the form
20845 failed to lock mailbox /some/file (fcntl)
20848 .option lock_flock_timeout appendfile time 0s
20849 This timeout applies to file locking when using &[flock()]& (see
20850 &%use_flock%&); the timeout operates in a similar manner to
20851 &%lock_fcntl_timeout%&.
20854 .option lock_interval appendfile time 3s
20855 This specifies the time to wait between attempts to lock the file. See below
20856 for details of locking.
20859 .option lock_retries appendfile integer 10
20860 This specifies the maximum number of attempts to lock the file. A value of zero
20861 is treated as 1. See below for details of locking.
20864 .option lockfile_mode appendfile "octal integer" 0600
20865 This specifies the mode of the created lock file, when a lock file is being
20866 used (see &%use_lockfile%& and &%use_mbx_lock%&).
20869 .option lockfile_timeout appendfile time 30m
20870 .cindex "timeout" "mailbox locking"
20871 When a lock file is being used (see &%use_lockfile%&), if a lock file already
20872 exists and is older than this value, it is assumed to have been left behind by
20873 accident, and Exim attempts to remove it.
20876 .option mailbox_filecount appendfile string&!! unset
20877 .cindex "mailbox" "specifying size of"
20878 .cindex "size" "of mailbox"
20879 If this option is set, it is expanded, and the result is taken as the current
20880 number of files in the mailbox. It must be a decimal number, optionally
20881 followed by K or M. This provides a way of obtaining this information from an
20882 external source that maintains the data.
20885 .option mailbox_size appendfile string&!! unset
20886 .cindex "mailbox" "specifying size of"
20887 .cindex "size" "of mailbox"
20888 If this option is set, it is expanded, and the result is taken as the current
20889 size the mailbox. It must be a decimal number, optionally followed by K or M.
20890 This provides a way of obtaining this information from an external source that
20891 maintains the data. This is likely to be helpful for maildir deliveries where
20892 it is computationally expensive to compute the size of a mailbox.
20896 .option maildir_format appendfile boolean false
20897 .cindex "maildir format" "specifying"
20898 If this option is set with the &%directory%& option, the delivery is into a new
20899 file, in the &"maildir"& format that is used by other mail software. When the
20900 transport is activated directly from a &(redirect)& router (for example, the
20901 &(address_file)& transport in the default configuration), setting
20902 &%maildir_format%& causes the path received from the router to be treated as a
20903 directory, whether or not it ends with &`/`&. This option is available only if
20904 SUPPORT_MAILDIR is present in &_Local/Makefile_&. See section
20905 &<<SECTmaildirdelivery>>& below for further details.
20908 .option maildir_quota_directory_regex appendfile string "See below"
20909 .cindex "maildir format" "quota; directories included in"
20910 .cindex "quota" "maildir; directories included in"
20911 This option is relevant only when &%maildir_use_size_file%& is set. It defines
20912 a regular expression for specifying directories, relative to the quota
20913 directory (see &%quota_directory%&), that should be included in the quota
20914 calculation. The default value is:
20916 maildir_quota_directory_regex = ^(?:cur|new|\..*)$
20918 This includes the &_cur_& and &_new_& directories, and any maildir++ folders
20919 (directories whose names begin with a dot). If you want to exclude the
20921 folder from the count (as some sites do), you need to change this setting to
20923 maildir_quota_directory_regex = ^(?:cur|new|\.(?!Trash).*)$
20925 This uses a negative lookahead in the regular expression to exclude the
20926 directory whose name is &_.Trash_&. When a directory is excluded from quota
20927 calculations, quota processing is bypassed for any messages that are delivered
20928 directly into that directory.
20931 .option maildir_retries appendfile integer 10
20932 This option specifies the number of times to retry when writing a file in
20933 &"maildir"& format. See section &<<SECTmaildirdelivery>>& below.
20936 .option maildir_tag appendfile string&!! unset
20937 This option applies only to deliveries in maildir format, and is described in
20938 section &<<SECTmaildirdelivery>>& below.
20941 .option maildir_use_size_file appendfile&!! boolean false
20942 .cindex "maildir format" "&_maildirsize_& file"
20943 The result of string expansion for this option must be a valid boolean value.
20944 If it is true, it enables support for &_maildirsize_& files. Exim
20945 creates a &_maildirsize_& file in a maildir if one does not exist, taking the
20946 quota from the &%quota%& option of the transport. If &%quota%& is unset, the
20947 value is zero. See &%maildir_quota_directory_regex%& above and section
20948 &<<SECTmaildirdelivery>>& below for further details.
20950 .option maildirfolder_create_regex appendfile string unset
20951 .cindex "maildir format" "&_maildirfolder_& file"
20952 .cindex "&_maildirfolder_&, creating"
20953 The value of this option is a regular expression. If it is unset, it has no
20954 effect. Otherwise, before a maildir delivery takes place, the pattern is
20955 matched against the name of the maildir directory, that is, the directory
20956 containing the &_new_& and &_tmp_& subdirectories that will be used for the
20957 delivery. If there is a match, Exim checks for the existence of a file called
20958 &_maildirfolder_& in the directory, and creates it if it does not exist.
20959 See section &<<SECTmaildirdelivery>>& for more details.
20962 .option mailstore_format appendfile boolean false
20963 .cindex "mailstore format" "specifying"
20964 If this option is set with the &%directory%& option, the delivery is into two
20965 new files in &"mailstore"& format. The option is available only if
20966 SUPPORT_MAILSTORE is present in &_Local/Makefile_&. See section &<<SECTopdir>>&
20967 below for further details.
20970 .option mailstore_prefix appendfile string&!! unset
20971 This option applies only to deliveries in mailstore format, and is described in
20972 section &<<SECTopdir>>& below.
20975 .option mailstore_suffix appendfile string&!! unset
20976 This option applies only to deliveries in mailstore format, and is described in
20977 section &<<SECTopdir>>& below.
20980 .option mbx_format appendfile boolean false
20981 .cindex "locking files"
20982 .cindex "file" "locking"
20983 .cindex "file" "MBX format"
20984 .cindex "MBX format, specifying"
20985 This option is available only if Exim has been compiled with SUPPORT_MBX
20986 set in &_Local/Makefile_&. If &%mbx_format%& is set with the &%file%& option,
20987 the message is appended to the mailbox file in MBX format instead of
20988 traditional Unix format. This format is supported by Pine4 and its associated
20989 IMAP and POP daemons, by means of the &'c-client'& library that they all use.
20991 &*Note*&: The &%message_prefix%& and &%message_suffix%& options are not
20992 automatically changed by the use of &%mbx_format%&. They should normally be set
20993 empty when using MBX format, so this option almost always appears in this
21000 If none of the locking options are mentioned in the configuration,
21001 &%use_mbx_lock%& is assumed and the other locking options default to false. It
21002 is possible to specify the other kinds of locking with &%mbx_format%&, but
21003 &%use_fcntl_lock%& and &%use_mbx_lock%& are mutually exclusive. MBX locking
21004 interworks with &'c-client'&, providing for shared access to the mailbox. It
21005 should not be used if any program that does not use this form of locking is
21006 going to access the mailbox, nor should it be used if the mailbox file is NFS
21007 mounted, because it works only when the mailbox is accessed from a single host.
21009 If you set &%use_fcntl_lock%& with an MBX-format mailbox, you cannot use
21010 the standard version of &'c-client'&, because as long as it has a mailbox open
21011 (this means for the whole of a Pine or IMAP session), Exim will not be able to
21012 append messages to it.
21015 .option message_prefix appendfile string&!! "see below"
21016 .cindex "&""From""& line"
21017 The string specified here is expanded and output at the start of every message.
21018 The default is unset unless &%file%& is specified and &%use_bsmtp%& is not set,
21019 in which case it is:
21021 message_prefix = "From ${if def:return_path{$return_path}\
21022 {MAILER-DAEMON}} $tod_bsdinbox\n"
21024 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
21025 &`\n`& to &`\r\n`& in &%message_prefix%&.
21027 .option message_suffix appendfile string&!! "see below"
21028 The string specified here is expanded and output at the end of every message.
21029 The default is unset unless &%file%& is specified and &%use_bsmtp%& is not set,
21030 in which case it is a single newline character. The suffix can be suppressed by
21035 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
21036 &`\n`& to &`\r\n`& in &%message_suffix%&.
21038 .option mode appendfile "octal integer" 0600
21039 If the output file is created, it is given this mode. If it already exists and
21040 has wider permissions, they are reduced to this mode. If it has narrower
21041 permissions, an error occurs unless &%mode_fail_narrower%& is false. However,
21042 if the delivery is the result of a &%save%& command in a filter file specifying
21043 a particular mode, the mode of the output file is always forced to take that
21044 value, and this option is ignored.
21047 .option mode_fail_narrower appendfile boolean true
21048 This option applies in the case when an existing mailbox file has a narrower
21049 mode than that specified by the &%mode%& option. If &%mode_fail_narrower%& is
21050 true, the delivery is deferred (&"mailbox has the wrong mode"&); otherwise Exim
21051 continues with the delivery attempt, using the existing mode of the file.
21054 .option notify_comsat appendfile boolean false
21055 If this option is true, the &'comsat'& daemon is notified after every
21056 successful delivery to a user mailbox. This is the daemon that notifies logged
21057 on users about incoming mail.
21060 .option quota appendfile string&!! unset
21061 .cindex "quota" "imposed by Exim"
21062 This option imposes a limit on the size of the file to which Exim is appending,
21063 or to the total space used in the directory tree when the &%directory%& option
21064 is set. In the latter case, computation of the space used is expensive, because
21065 all the files in the directory (and any sub-directories) have to be
21066 individually inspected and their sizes summed. (See &%quota_size_regex%& and
21067 &%maildir_use_size_file%& for ways to avoid this in environments where users
21068 have no shell access to their mailboxes).
21070 As there is no interlock against two simultaneous deliveries into a
21071 multi-file mailbox, it is possible for the quota to be overrun in this case.
21072 For single-file mailboxes, of course, an interlock is a necessity.
21074 A file's size is taken as its &'used'& value. Because of blocking effects, this
21075 may be a lot less than the actual amount of disk space allocated to the file.
21076 If the sizes of a number of files are being added up, the rounding effect can
21077 become quite noticeable, especially on systems that have large block sizes.
21078 Nevertheless, it seems best to stick to the &'used'& figure, because this is
21079 the obvious value which users understand most easily.
21081 The value of the option is expanded, and must then be a numerical value
21082 (decimal point allowed), optionally followed by one of the letters K, M, or G,
21083 for kilobytes, megabytes, or gigabytes. If Exim is running on a system with
21084 large file support (Linux and FreeBSD have this), mailboxes larger than 2G can
21087 &*Note*&: A value of zero is interpreted as &"no quota"&.
21089 The expansion happens while Exim is running as root, before it changes uid for
21090 the delivery. This means that files that are inaccessible to the end user can
21091 be used to hold quota values that are looked up in the expansion. When delivery
21092 fails because this quota is exceeded, the handling of the error is as for
21093 system quota failures.
21095 By default, Exim's quota checking mimics system quotas, and restricts the
21096 mailbox to the specified maximum size, though the value is not accurate to the
21097 last byte, owing to separator lines and additional headers that may get added
21098 during message delivery. When a mailbox is nearly full, large messages may get
21099 refused even though small ones are accepted, because the size of the current
21100 message is added to the quota when the check is made. This behaviour can be
21101 changed by setting &%quota_is_inclusive%& false. When this is done, the check
21102 for exceeding the quota does not include the current message. Thus, deliveries
21103 continue until the quota has been exceeded; thereafter, no further messages are
21104 delivered. See also &%quota_warn_threshold%&.
21107 .option quota_directory appendfile string&!! unset
21108 This option defines the directory to check for quota purposes when delivering
21109 into individual files. The default is the delivery directory, or, if a file
21110 called &_maildirfolder_& exists in a maildir directory, the parent of the
21111 delivery directory.
21114 .option quota_filecount appendfile string&!! 0
21115 This option applies when the &%directory%& option is set. It limits the total
21116 number of files in the directory (compare the inode limit in system quotas). It
21117 can only be used if &%quota%& is also set. The value is expanded; an expansion
21118 failure causes delivery to be deferred. A value of zero is interpreted as
21122 .option quota_is_inclusive appendfile boolean true
21123 See &%quota%& above.
21126 .option quota_size_regex appendfile string unset
21127 This option applies when one of the delivery modes that writes a separate file
21128 for each message is being used. When Exim wants to find the size of one of
21129 these files in order to test the quota, it first checks &%quota_size_regex%&.
21130 If this is set to a regular expression that matches the file name, and it
21131 captures one string, that string is interpreted as a representation of the
21132 file's size. The value of &%quota_size_regex%& is not expanded.
21134 This feature is useful only when users have no shell access to their mailboxes
21135 &-- otherwise they could defeat the quota simply by renaming the files. This
21136 facility can be used with maildir deliveries, by setting &%maildir_tag%& to add
21137 the file length to the file name. For example:
21139 maildir_tag = ,S=$message_size
21140 quota_size_regex = ,S=(\d+)
21142 An alternative to &$message_size$& is &$message_linecount$&, which contains the
21143 number of lines in the message.
21145 The regular expression should not assume that the length is at the end of the
21146 file name (even though &%maildir_tag%& puts it there) because maildir MUAs
21147 sometimes add other information onto the ends of message file names.
21149 Section &<<SECID136>>& contains further information.
21152 .option quota_warn_message appendfile string&!! "see below"
21153 See below for the use of this option. If it is not set when
21154 &%quota_warn_threshold%& is set, it defaults to
21156 quota_warn_message = "\
21157 To: $local_part@$domain\n\
21158 Subject: Your mailbox\n\n\
21159 This message is automatically created \
21160 by mail delivery software.\n\n\
21161 The size of your mailbox has exceeded \
21162 a warning threshold that is\n\
21163 set by the system administrator.\n"
21167 .option quota_warn_threshold appendfile string&!! 0
21168 .cindex "quota" "warning threshold"
21169 .cindex "mailbox" "size warning"
21170 .cindex "size" "of mailbox"
21171 This option is expanded in the same way as &%quota%& (see above). If the
21172 resulting value is greater than zero, and delivery of the message causes the
21173 size of the file or total space in the directory tree to cross the given
21174 threshold, a warning message is sent. If &%quota%& is also set, the threshold
21175 may be specified as a percentage of it by following the value with a percent
21179 quota_warn_threshold = 75%
21181 If &%quota%& is not set, a setting of &%quota_warn_threshold%& that ends with a
21182 percent sign is ignored.
21184 The warning message itself is specified by the &%quota_warn_message%& option,
21185 and it must start with a &'To:'& header line containing the recipient(s) of the
21186 warning message. These do not necessarily have to include the recipient(s) of
21187 the original message. A &'Subject:'& line should also normally be supplied. You
21188 can include any other header lines that you want. If you do not include a
21189 &'From:'& line, the default is:
21191 From: Mail Delivery System <mailer-daemon@$qualify_domain_sender>
21193 .oindex &%errors_reply_to%&
21194 If you supply a &'Reply-To:'& line, it overrides the global &%errors_reply_to%&
21197 The &%quota%& option does not have to be set in order to use this option; they
21198 are independent of one another except when the threshold is specified as a
21202 .option use_bsmtp appendfile boolean false
21203 .cindex "envelope sender"
21204 If this option is set true, &(appendfile)& writes messages in &"batch SMTP"&
21205 format, with the envelope sender and recipient(s) included as SMTP commands. If
21206 you want to include a leading HELO command with such messages, you can do
21207 so by setting the &%message_prefix%& option. See section &<<SECTbatchSMTP>>&
21208 for details of batch SMTP.
21211 .option use_crlf appendfile boolean false
21212 .cindex "carriage return"
21214 This option causes lines to be terminated with the two-character CRLF sequence
21215 (carriage return, linefeed) instead of just a linefeed character. In the case
21216 of batched SMTP, the byte sequence written to the file is then an exact image
21217 of what would be sent down a real SMTP connection.
21219 &*Note:*& The contents of the &%message_prefix%& and &%message_suffix%& options
21220 (which are used to supply the traditional &"From&~"& and blank line separators
21221 in Berkeley-style mailboxes) are written verbatim, so must contain their own
21222 carriage return characters if these are needed. In cases where these options
21223 have non-empty defaults, the values end with a single linefeed, so they must be
21224 changed to end with &`\r\n`& if &%use_crlf%& is set.
21227 .option use_fcntl_lock appendfile boolean "see below"
21228 This option controls the use of the &[fcntl()]& function to lock a file for
21229 exclusive use when a message is being appended. It is set by default unless
21230 &%use_flock_lock%& is set. Otherwise, it should be turned off only if you know
21231 that all your MUAs use lock file locking. When both &%use_fcntl_lock%& and
21232 &%use_flock_lock%& are unset, &%use_lockfile%& must be set.
21235 .option use_flock_lock appendfile boolean false
21236 This option is provided to support the use of &[flock()]& for file locking, for
21237 the few situations where it is needed. Most modern operating systems support
21238 &[fcntl()]& and &[lockf()]& locking, and these two functions interwork with
21239 each other. Exim uses &[fcntl()]& locking by default.
21241 This option is required only if you are using an operating system where
21242 &[flock()]& is used by programs that access mailboxes (typically MUAs), and
21243 where &[flock()]& does not correctly interwork with &[fcntl()]&. You can use
21244 both &[fcntl()]& and &[flock()]& locking simultaneously if you want.
21246 .cindex "Solaris" "&[flock()]& support"
21247 Not all operating systems provide &[flock()]&. Some versions of Solaris do not
21248 have it (and some, I think, provide a not quite right version built on top of
21249 &[lockf()]&). If the OS does not have &[flock()]&, Exim will be built without
21250 the ability to use it, and any attempt to do so will cause a configuration
21253 &*Warning*&: &[flock()]& locks do not work on NFS files (unless &[flock()]&
21254 is just being mapped onto &[fcntl()]& by the OS).
21257 .option use_lockfile appendfile boolean "see below"
21258 If this option is turned off, Exim does not attempt to create a lock file when
21259 appending to a mailbox file. In this situation, the only locking is by
21260 &[fcntl()]&. You should only turn &%use_lockfile%& off if you are absolutely
21261 sure that every MUA that is ever going to look at your users' mailboxes uses
21262 &[fcntl()]& rather than a lock file, and even then only when you are not
21263 delivering over NFS from more than one host.
21265 .cindex "NFS" "lock file"
21266 In order to append to an NFS file safely from more than one host, it is
21267 necessary to take out a lock &'before'& opening the file, and the lock file
21268 achieves this. Otherwise, even with &[fcntl()]& locking, there is a risk of
21271 The &%use_lockfile%& option is set by default unless &%use_mbx_lock%& is set.
21272 It is not possible to turn both &%use_lockfile%& and &%use_fcntl_lock%& off,
21273 except when &%mbx_format%& is set.
21276 .option use_mbx_lock appendfile boolean "see below"
21277 This option is available only if Exim has been compiled with SUPPORT_MBX
21278 set in &_Local/Makefile_&. Setting the option specifies that special MBX
21279 locking rules be used. It is set by default if &%mbx_format%& is set and none
21280 of the locking options are mentioned in the configuration. The locking rules
21281 are the same as are used by the &'c-client'& library that underlies Pine and
21282 the IMAP4 and POP daemons that come with it (see the discussion below). The
21283 rules allow for shared access to the mailbox. However, this kind of locking
21284 does not work when the mailbox is NFS mounted.
21286 You can set &%use_mbx_lock%& with either (or both) of &%use_fcntl_lock%& and
21287 &%use_flock_lock%& to control what kind of locking is used in implementing the
21288 MBX locking rules. The default is to use &[fcntl()]& if &%use_mbx_lock%& is set
21289 without &%use_fcntl_lock%& or &%use_flock_lock%&.
21294 .section "Operational details for appending" "SECTopappend"
21295 .cindex "appending to a file"
21296 .cindex "file" "appending"
21297 Before appending to a file, the following preparations are made:
21300 If the name of the file is &_/dev/null_&, no action is taken, and a success
21304 .cindex "directory creation"
21305 If any directories on the file's path are missing, Exim creates them if the
21306 &%create_directory%& option is set. A created directory's mode is given by the
21307 &%directory_mode%& option.
21310 If &%file_format%& is set, the format of an existing file is checked. If this
21311 indicates that a different transport should be used, control is passed to that
21315 .cindex "file" "locking"
21316 .cindex "locking files"
21317 .cindex "NFS" "lock file"
21318 If &%use_lockfile%& is set, a lock file is built in a way that will work
21319 reliably over NFS, as follows:
21322 Create a &"hitching post"& file whose name is that of the lock file with the
21323 current time, primary host name, and process id added, by opening for writing
21324 as a new file. If this fails with an access error, delivery is deferred.
21326 Close the hitching post file, and hard link it to the lock file name.
21328 If the call to &[link()]& succeeds, creation of the lock file has succeeded.
21329 Unlink the hitching post name.
21331 Otherwise, use &[stat()]& to get information about the hitching post file, and
21332 then unlink hitching post name. If the number of links is exactly two, creation
21333 of the lock file succeeded but something (for example, an NFS server crash and
21334 restart) caused this fact not to be communicated to the &[link()]& call.
21336 If creation of the lock file failed, wait for &%lock_interval%& and try again,
21337 up to &%lock_retries%& times. However, since any program that writes to a
21338 mailbox should complete its task very quickly, it is reasonable to time out old
21339 lock files that are normally the result of user agent and system crashes. If an
21340 existing lock file is older than &%lockfile_timeout%& Exim attempts to unlink
21341 it before trying again.
21345 A call is made to &[lstat()]& to discover whether the main file exists, and if
21346 so, what its characteristics are. If &[lstat()]& fails for any reason other
21347 than non-existence, delivery is deferred.
21350 .cindex "symbolic link" "to mailbox"
21351 .cindex "mailbox" "symbolic link"
21352 If the file does exist and is a symbolic link, delivery is deferred, unless the
21353 &%allow_symlink%& option is set, in which case the ownership of the link is
21354 checked, and then &[stat()]& is called to find out about the real file, which
21355 is then subjected to the checks below. The check on the top-level link
21356 ownership prevents one user creating a link for another's mailbox in a sticky
21357 directory, though allowing symbolic links in this case is definitely not a good
21358 idea. If there is a chain of symbolic links, the intermediate ones are not
21362 If the file already exists but is not a regular file, or if the file's owner
21363 and group (if the group is being checked &-- see &%check_group%& above) are
21364 different from the user and group under which the delivery is running,
21365 delivery is deferred.
21368 If the file's permissions are more generous than specified, they are reduced.
21369 If they are insufficient, delivery is deferred, unless &%mode_fail_narrower%&
21370 is set false, in which case the delivery is tried using the existing
21374 The file's inode number is saved, and the file is then opened for appending.
21375 If this fails because the file has vanished, &(appendfile)& behaves as if it
21376 hadn't existed (see below). For any other failures, delivery is deferred.
21379 If the file is opened successfully, check that the inode number hasn't
21380 changed, that it is still a regular file, and that the owner and permissions
21381 have not changed. If anything is wrong, defer delivery and freeze the message.
21384 If the file did not exist originally, defer delivery if the &%file_must_exist%&
21385 option is set. Otherwise, check that the file is being created in a permitted
21386 directory if the &%create_file%& option is set (deferring on failure), and then
21387 open for writing as a new file, with the O_EXCL and O_CREAT options,
21388 except when dealing with a symbolic link (the &%allow_symlink%& option must be
21389 set). In this case, which can happen if the link points to a non-existent file,
21390 the file is opened for writing using O_CREAT but not O_EXCL, because
21391 that prevents link following.
21394 .cindex "loop" "while file testing"
21395 If opening fails because the file exists, obey the tests given above for
21396 existing files. However, to avoid looping in a situation where the file is
21397 being continuously created and destroyed, the exists/not-exists loop is broken
21398 after 10 repetitions, and the message is then frozen.
21401 If opening fails with any other error, defer delivery.
21404 .cindex "file" "locking"
21405 .cindex "locking files"
21406 Once the file is open, unless both &%use_fcntl_lock%& and &%use_flock_lock%&
21407 are false, it is locked using &[fcntl()]& or &[flock()]& or both. If
21408 &%use_mbx_lock%& is false, an exclusive lock is requested in each case.
21409 However, if &%use_mbx_lock%& is true, Exim takes out a shared lock on the open
21410 file, and an exclusive lock on the file whose name is
21412 /tmp/.<device-number>.<inode-number>
21414 using the device and inode numbers of the open mailbox file, in accordance with
21415 the MBX locking rules. This file is created with a mode that is specified by
21416 the &%lockfile_mode%& option.
21418 If Exim fails to lock the file, there are two possible courses of action,
21419 depending on the value of the locking timeout. This is obtained from
21420 &%lock_fcntl_timeout%& or &%lock_flock_timeout%&, as appropriate.
21422 If the timeout value is zero, the file is closed, Exim waits for
21423 &%lock_interval%&, and then goes back and re-opens the file as above and tries
21424 to lock it again. This happens up to &%lock_retries%& times, after which the
21425 delivery is deferred.
21427 If the timeout has a value greater than zero, blocking calls to &[fcntl()]& or
21428 &[flock()]& are used (with the given timeout), so there has already been some
21429 waiting involved by the time locking fails. Nevertheless, Exim does not give up
21430 immediately. It retries up to
21432 (lock_retries * lock_interval) / <timeout>
21434 times (rounded up).
21437 At the end of delivery, Exim closes the file (which releases the &[fcntl()]&
21438 and/or &[flock()]& locks) and then deletes the lock file if one was created.
21441 .section "Operational details for delivery to a new file" "SECTopdir"
21442 .cindex "delivery" "to single file"
21443 .cindex "&""From""& line"
21444 When the &%directory%& option is set instead of &%file%&, each message is
21445 delivered into a newly-created file or set of files. When &(appendfile)& is
21446 activated directly from a &(redirect)& router, neither &%file%& nor
21447 &%directory%& is normally set, because the path for delivery is supplied by the
21448 router. (See for example, the &(address_file)& transport in the default
21449 configuration.) In this case, delivery is to a new file if either the path name
21450 ends in &`/`&, or the &%maildir_format%& or &%mailstore_format%& option is set.
21452 No locking is required while writing the message to a new file, so the various
21453 locking options of the transport are ignored. The &"From"& line that by default
21454 separates messages in a single file is not normally needed, nor is the escaping
21455 of message lines that start with &"From"&, and there is no need to ensure a
21456 newline at the end of each message. Consequently, the default values for
21457 &%check_string%&, &%message_prefix%&, and &%message_suffix%& are all unset when
21458 any of &%directory%&, &%maildir_format%&, or &%mailstore_format%& is set.
21460 If Exim is required to check a &%quota%& setting, it adds up the sizes of all
21461 the files in the delivery directory by default. However, you can specify a
21462 different directory by setting &%quota_directory%&. Also, for maildir
21463 deliveries (see below) the &_maildirfolder_& convention is honoured.
21466 .cindex "maildir format"
21467 .cindex "mailstore format"
21468 There are three different ways in which delivery to individual files can be
21469 done, controlled by the settings of the &%maildir_format%& and
21470 &%mailstore_format%& options. Note that code to support maildir or mailstore
21471 formats is not included in the binary unless SUPPORT_MAILDIR or
21472 SUPPORT_MAILSTORE, respectively, is set in &_Local/Makefile_&.
21474 .cindex "directory creation"
21475 In all three cases an attempt is made to create the directory and any necessary
21476 sub-directories if they do not exist, provided that the &%create_directory%&
21477 option is set (the default). The location of a created directory can be
21478 constrained by setting &%create_file%&. A created directory's mode is given by
21479 the &%directory_mode%& option. If creation fails, or if the
21480 &%create_directory%& option is not set when creation is required, delivery is
21485 .section "Maildir delivery" "SECTmaildirdelivery"
21486 .cindex "maildir format" "description of"
21487 If the &%maildir_format%& option is true, Exim delivers each message by writing
21488 it to a file whose name is &_tmp/<stime>.H<mtime>P<pid>.<host>_& in the
21489 directory that is defined by the &%directory%& option (the &"delivery
21490 directory"&). If the delivery is successful, the file is renamed into the
21491 &_new_& subdirectory.
21493 In the file name, <&'stime'&> is the current time of day in seconds, and
21494 <&'mtime'&> is the microsecond fraction of the time. After a maildir delivery,
21495 Exim checks that the time-of-day clock has moved on by at least one microsecond
21496 before terminating the delivery process. This guarantees uniqueness for the
21497 file name. However, as a precaution, Exim calls &[stat()]& for the file before
21498 opening it. If any response other than ENOENT (does not exist) is given,
21499 Exim waits 2 seconds and tries again, up to &%maildir_retries%& times.
21501 Before Exim carries out a maildir delivery, it ensures that subdirectories
21502 called &_new_&, &_cur_&, and &_tmp_& exist in the delivery directory. If they
21503 do not exist, Exim tries to create them and any superior directories in their
21504 path, subject to the &%create_directory%& and &%create_file%& options. If the
21505 &%maildirfolder_create_regex%& option is set, and the regular expression it
21506 contains matches the delivery directory, Exim also ensures that a file called
21507 &_maildirfolder_& exists in the delivery directory. If a missing directory or
21508 &_maildirfolder_& file cannot be created, delivery is deferred.
21510 These features make it possible to use Exim to create all the necessary files
21511 and directories in a maildir mailbox, including subdirectories for maildir++
21512 folders. Consider this example:
21514 maildir_format = true
21515 directory = /var/mail/$local_part\
21516 ${if eq{$local_part_suffix}{}{}\
21517 {/.${substr_1:$local_part_suffix}}}
21518 maildirfolder_create_regex = /\.[^/]+$
21520 If &$local_part_suffix$& is empty (there was no suffix for the local part),
21521 delivery is into a toplevel maildir with a name like &_/var/mail/pimbo_& (for
21522 the user called &'pimbo'&). The pattern in &%maildirfolder_create_regex%& does
21523 not match this name, so Exim will not look for or create the file
21524 &_/var/mail/pimbo/maildirfolder_&, though it will create
21525 &_/var/mail/pimbo/{cur,new,tmp}_& if necessary.
21527 However, if &$local_part_suffix$& contains &`-eximusers`& (for example),
21528 delivery is into the maildir++ folder &_/var/mail/pimbo/.eximusers_&, which
21529 does match &%maildirfolder_create_regex%&. In this case, Exim will create
21530 &_/var/mail/pimbo/.eximusers/maildirfolder_& as well as the three maildir
21531 directories &_/var/mail/pimbo/.eximusers/{cur,new,tmp}_&.
21533 &*Warning:*& Take care when setting &%maildirfolder_create_regex%& that it does
21534 not inadvertently match the toplevel maildir directory, because a
21535 &_maildirfolder_& file at top level would completely break quota calculations.
21537 .cindex "quota" "in maildir delivery"
21538 .cindex "maildir++"
21539 If Exim is required to check a &%quota%& setting before a maildir delivery, and
21540 &%quota_directory%& is not set, it looks for a file called &_maildirfolder_& in
21541 the maildir directory (alongside &_new_&, &_cur_&, &_tmp_&). If this exists,
21542 Exim assumes the directory is a maildir++ folder directory, which is one level
21543 down from the user's top level mailbox directory. This causes it to start at
21544 the parent directory instead of the current directory when calculating the
21545 amount of space used.
21547 One problem with delivering into a multi-file mailbox is that it is
21548 computationally expensive to compute the size of the mailbox for quota
21549 checking. Various approaches have been taken to reduce the amount of work
21550 needed. The next two sections describe two of them. A third alternative is to
21551 use some external process for maintaining the size data, and use the expansion
21552 of the &%mailbox_size%& option as a way of importing it into Exim.
21557 .section "Using tags to record message sizes" "SECID135"
21558 If &%maildir_tag%& is set, the string is expanded for each delivery.
21559 When the maildir file is renamed into the &_new_& sub-directory, the
21560 tag is added to its name. However, if adding the tag takes the length of the
21561 name to the point where the test &[stat()]& call fails with ENAMETOOLONG,
21562 the tag is dropped and the maildir file is created with no tag.
21565 .vindex "&$message_size$&"
21566 Tags can be used to encode the size of files in their names; see
21567 &%quota_size_regex%& above for an example. The expansion of &%maildir_tag%&
21568 happens after the message has been written. The value of the &$message_size$&
21569 variable is set to the number of bytes actually written. If the expansion is
21570 forced to fail, the tag is ignored, but a non-forced failure causes delivery to
21571 be deferred. The expanded tag may contain any printing characters except &"/"&.
21572 Non-printing characters in the string are ignored; if the resulting string is
21573 empty, it is ignored. If it starts with an alphanumeric character, a leading
21574 colon is inserted; this default has not proven to be the path that popular
21575 maildir implementations have chosen (but changing it in Exim would break
21576 backwards compatibility).
21578 For one common implementation, you might set:
21580 maildir_tag = ,S=${message_size}
21582 but you should check the documentation of the other software to be sure.
21584 It is advisable to also set &%quota_size_regex%& when setting &%maildir_tag%&
21585 as this allows Exim to extract the size from your tag, instead of having to
21586 &[stat()]& each message file.
21589 .section "Using a maildirsize file" "SECID136"
21590 .cindex "quota" "in maildir delivery"
21591 .cindex "maildir format" "&_maildirsize_& file"
21592 If &%maildir_use_size_file%& is true, Exim implements the maildir++ rules for
21593 storing quota and message size information in a file called &_maildirsize_&
21594 within the toplevel maildir directory. If this file does not exist, Exim
21595 creates it, setting the quota from the &%quota%& option of the transport. If
21596 the maildir directory itself does not exist, it is created before any attempt
21597 to write a &_maildirsize_& file.
21599 The &_maildirsize_& file is used to hold information about the sizes of
21600 messages in the maildir, thus speeding up quota calculations. The quota value
21601 in the file is just a cache; if the quota is changed in the transport, the new
21602 value overrides the cached value when the next message is delivered. The cache
21603 is maintained for the benefit of other programs that access the maildir and
21604 need to know the quota.
21606 If the &%quota%& option in the transport is unset or zero, the &_maildirsize_&
21607 file is maintained (with a zero quota setting), but no quota is imposed.
21609 A regular expression is available for controlling which directories in the
21610 maildir participate in quota calculations when a &_maildirsizefile_& is in use.
21611 See the description of the &%maildir_quota_directory_regex%& option above for
21615 .section "Mailstore delivery" "SECID137"
21616 .cindex "mailstore format" "description of"
21617 If the &%mailstore_format%& option is true, each message is written as two
21618 files in the given directory. A unique base name is constructed from the
21619 message id and the current delivery process, and the files that are written use
21620 this base name plus the suffixes &_.env_& and &_.msg_&. The &_.env_& file
21621 contains the message's envelope, and the &_.msg_& file contains the message
21622 itself. The base name is placed in the variable &$mailstore_basename$&.
21624 During delivery, the envelope is first written to a file with the suffix
21625 &_.tmp_&. The &_.msg_& file is then written, and when it is complete, the
21626 &_.tmp_& file is renamed as the &_.env_& file. Programs that access messages in
21627 mailstore format should wait for the presence of both a &_.msg_& and a &_.env_&
21628 file before accessing either of them. An alternative approach is to wait for
21629 the absence of a &_.tmp_& file.
21631 The envelope file starts with any text defined by the &%mailstore_prefix%&
21632 option, expanded and terminated by a newline if there isn't one. Then follows
21633 the sender address on one line, then all the recipient addresses, one per line.
21634 There can be more than one recipient only if the &%batch_max%& option is set
21635 greater than one. Finally, &%mailstore_suffix%& is expanded and the result
21636 appended to the file, followed by a newline if it does not end with one.
21638 If expansion of &%mailstore_prefix%& or &%mailstore_suffix%& ends with a forced
21639 failure, it is ignored. Other expansion errors are treated as serious
21640 configuration errors, and delivery is deferred. The variable
21641 &$mailstore_basename$& is available for use during these expansions.
21644 .section "Non-special new file delivery" "SECID138"
21645 If neither &%maildir_format%& nor &%mailstore_format%& is set, a single new
21646 file is created directly in the named directory. For example, when delivering
21647 messages into files in batched SMTP format for later delivery to some host (see
21648 section &<<SECTbatchSMTP>>&), a setting such as
21650 directory = /var/bsmtp/$host
21652 might be used. A message is written to a file with a temporary name, which is
21653 then renamed when the delivery is complete. The final name is obtained by
21654 expanding the contents of the &%directory_file%& option.
21655 .ecindex IIDapptra1
21656 .ecindex IIDapptra2
21663 . ////////////////////////////////////////////////////////////////////////////
21664 . ////////////////////////////////////////////////////////////////////////////
21666 .chapter "The autoreply transport" "CHID8"
21667 .scindex IIDauttra1 "transports" "&(autoreply)&"
21668 .scindex IIDauttra2 "&(autoreply)& transport"
21669 The &(autoreply)& transport is not a true transport in that it does not cause
21670 the message to be transmitted. Instead, it generates a new mail message as an
21671 automatic reply to the incoming message. &'References:'& and
21672 &'Auto-Submitted:'& header lines are included. These are constructed according
21673 to the rules in RFCs 2822 and 3834, respectively.
21675 If the router that passes the message to this transport does not have the
21676 &%unseen%& option set, the original message (for the current recipient) is not
21677 delivered anywhere. However, when the &%unseen%& option is set on the router
21678 that passes the message to this transport, routing of the address continues, so
21679 another router can set up a normal message delivery.
21682 The &(autoreply)& transport is usually run as the result of mail filtering, a
21683 &"vacation"& message being the standard example. However, it can also be run
21684 directly from a router like any other transport. To reduce the possibility of
21685 message cascades, messages created by the &(autoreply)& transport always have
21686 empty envelope sender addresses, like bounce messages.
21688 The parameters of the message to be sent can be specified in the configuration
21689 by options described below. However, these are used only when the address
21690 passed to the transport does not contain its own reply information. When the
21691 transport is run as a consequence of a
21693 or &%vacation%& command in a filter file, the parameters of the message are
21694 supplied by the filter, and passed with the address. The transport's options
21695 that define the message are then ignored (so they are not usually set in this
21696 case). The message is specified entirely by the filter or by the transport; it
21697 is never built from a mixture of options. However, the &%file_optional%&,
21698 &%mode%&, and &%return_message%& options apply in all cases.
21700 &(Autoreply)& is implemented as a local transport. When used as a result of a
21701 command in a user's filter file, &(autoreply)& normally runs under the uid and
21702 gid of the user, and with appropriate current and home directories (see chapter
21703 &<<CHAPenvironment>>&).
21705 There is a subtle difference between routing a message to a &(pipe)& transport
21706 that generates some text to be returned to the sender, and routing it to an
21707 &(autoreply)& transport. This difference is noticeable only if more than one
21708 address from the same message is so handled. In the case of a pipe, the
21709 separate outputs from the different addresses are gathered up and returned to
21710 the sender in a single message, whereas if &(autoreply)& is used, a separate
21711 message is generated for each address that is passed to it.
21713 Non-printing characters are not permitted in the header lines generated for the
21714 message that &(autoreply)& creates, with the exception of newlines that are
21715 immediately followed by white space. If any non-printing characters are found,
21716 the transport defers.
21717 Whether characters with the top bit set count as printing characters or not is
21718 controlled by the &%print_topbitchars%& global option.
21720 If any of the generic options for manipulating headers (for example,
21721 &%headers_add%&) are set on an &(autoreply)& transport, they apply to the copy
21722 of the original message that is included in the generated message when
21723 &%return_message%& is set. They do not apply to the generated message itself.
21725 .vindex "&$sender_address$&"
21726 If the &(autoreply)& transport receives return code 2 from Exim when it submits
21727 the message, indicating that there were no recipients, it does not treat this
21728 as an error. This means that autoreplies sent to &$sender_address$& when this
21729 is empty (because the incoming message is a bounce message) do not cause
21730 problems. They are just discarded.
21734 .section "Private options for autoreply" "SECID139"
21735 .cindex "options" "&(autoreply)& transport"
21737 .option bcc autoreply string&!! unset
21738 This specifies the addresses that are to receive &"blind carbon copies"& of the
21739 message when the message is specified by the transport.
21742 .option cc autoreply string&!! unset
21743 This specifies recipients of the message and the contents of the &'Cc:'& header
21744 when the message is specified by the transport.
21747 .option file autoreply string&!! unset
21748 The contents of the file are sent as the body of the message when the message
21749 is specified by the transport. If both &%file%& and &%text%& are set, the text
21750 string comes first.
21753 .option file_expand autoreply boolean false
21754 If this is set, the contents of the file named by the &%file%& option are
21755 subjected to string expansion as they are added to the message.
21758 .option file_optional autoreply boolean false
21759 If this option is true, no error is generated if the file named by the &%file%&
21760 option or passed with the address does not exist or cannot be read.
21763 .option from autoreply string&!! unset
21764 This specifies the contents of the &'From:'& header when the message is
21765 specified by the transport.
21768 .option headers autoreply string&!! unset
21769 This specifies additional RFC 2822 headers that are to be added to the message
21770 when the message is specified by the transport. Several can be given by using
21771 &"\n"& to separate them. There is no check on the format.
21774 .option log autoreply string&!! unset
21775 This option names a file in which a record of every message sent is logged when
21776 the message is specified by the transport.
21779 .option mode autoreply "octal integer" 0600
21780 If either the log file or the &"once"& file has to be created, this mode is
21784 .option never_mail autoreply "address list&!!" unset
21785 If any run of the transport creates a message with a recipient that matches any
21786 item in the list, that recipient is quietly discarded. If all recipients are
21787 discarded, no message is created. This applies both when the recipients are
21788 generated by a filter and when they are specified in the transport.
21792 .option once autoreply string&!! unset
21793 This option names a file or DBM database in which a record of each &'To:'&
21794 recipient is kept when the message is specified by the transport. &*Note*&:
21795 This does not apply to &'Cc:'& or &'Bcc:'& recipients.
21797 If &%once%& is unset, or is set to an empty string, the message is always sent.
21798 By default, if &%once%& is set to a non-empty file name, the message
21799 is not sent if a potential recipient is already listed in the database.
21800 However, if the &%once_repeat%& option specifies a time greater than zero, the
21801 message is sent if that much time has elapsed since a message was last sent to
21802 this recipient. A setting of zero time for &%once_repeat%& (the default)
21803 prevents a message from being sent a second time &-- in this case, zero means
21806 If &%once_file_size%& is zero, a DBM database is used to remember recipients,
21807 and it is allowed to grow as large as necessary. If &%once_file_size%& is set
21808 greater than zero, it changes the way Exim implements the &%once%& option.
21809 Instead of using a DBM file to record every recipient it sends to, it uses a
21810 regular file, whose size will never get larger than the given value.
21812 In the file, Exim keeps a linear list of recipient addresses and the times at
21813 which they were sent messages. If the file is full when a new address needs to
21814 be added, the oldest address is dropped. If &%once_repeat%& is not set, this
21815 means that a given recipient may receive multiple messages, but at
21816 unpredictable intervals that depend on the rate of turnover of addresses in the
21817 file. If &%once_repeat%& is set, it specifies a maximum time between repeats.
21820 .option once_file_size autoreply integer 0
21821 See &%once%& above.
21824 .option once_repeat autoreply time&!! 0s
21825 See &%once%& above.
21826 After expansion, the value of this option must be a valid time value.
21829 .option reply_to autoreply string&!! unset
21830 This specifies the contents of the &'Reply-To:'& header when the message is
21831 specified by the transport.
21834 .option return_message autoreply boolean false
21835 If this is set, a copy of the original message is returned with the new
21836 message, subject to the maximum size set in the &%return_size_limit%& global
21837 configuration option.
21840 .option subject autoreply string&!! unset
21841 This specifies the contents of the &'Subject:'& header when the message is
21842 specified by the transport. It is tempting to quote the original subject in
21843 automatic responses. For example:
21845 subject = Re: $h_subject:
21847 There is a danger in doing this, however. It may allow a third party to
21848 subscribe your users to an opt-in mailing list, provided that the list accepts
21849 bounce messages as subscription confirmations. Well-managed lists require a
21850 non-bounce message to confirm a subscription, so the danger is relatively
21855 .option text autoreply string&!! unset
21856 This specifies a single string to be used as the body of the message when the
21857 message is specified by the transport. If both &%text%& and &%file%& are set,
21858 the text comes first.
21861 .option to autoreply string&!! unset
21862 This specifies recipients of the message and the contents of the &'To:'& header
21863 when the message is specified by the transport.
21864 .ecindex IIDauttra1
21865 .ecindex IIDauttra2
21870 . ////////////////////////////////////////////////////////////////////////////
21871 . ////////////////////////////////////////////////////////////////////////////
21873 .chapter "The lmtp transport" "CHAPLMTP"
21874 .cindex "transports" "&(lmtp)&"
21875 .cindex "&(lmtp)& transport"
21876 .cindex "LMTP" "over a pipe"
21877 .cindex "LMTP" "over a socket"
21878 The &(lmtp)& transport runs the LMTP protocol (RFC 2033) over a pipe to a
21880 or by interacting with a Unix domain socket.
21881 This transport is something of a cross between the &(pipe)& and &(smtp)&
21882 transports. Exim also has support for using LMTP over TCP/IP; this is
21883 implemented as an option for the &(smtp)& transport. Because LMTP is expected
21884 to be of minority interest, the default build-time configure in &_src/EDITME_&
21885 has it commented out. You need to ensure that
21889 .cindex "options" "&(lmtp)& transport"
21890 is present in your &_Local/Makefile_& in order to have the &(lmtp)& transport
21891 included in the Exim binary. The private options of the &(lmtp)& transport are
21894 .option batch_id lmtp string&!! unset
21895 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
21898 .option batch_max lmtp integer 1
21899 This limits the number of addresses that can be handled in a single delivery.
21900 Most LMTP servers can handle several addresses at once, so it is normally a
21901 good idea to increase this value. See the description of local delivery
21902 batching in chapter &<<CHAPbatching>>&.
21905 .option command lmtp string&!! unset
21906 This option must be set if &%socket%& is not set. The string is a command which
21907 is run in a separate process. It is split up into a command name and list of
21908 arguments, each of which is separately expanded (so expansion cannot change the
21909 number of arguments). The command is run directly, not via a shell. The message
21910 is passed to the new process using the standard input and output to operate the
21913 .option ignore_quota lmtp boolean false
21914 .cindex "LMTP" "ignoring quota errors"
21915 If this option is set true, the string &`IGNOREQUOTA`& is added to RCPT
21916 commands, provided that the LMTP server has advertised support for IGNOREQUOTA
21917 in its response to the LHLO command.
21919 .option socket lmtp string&!! unset
21920 This option must be set if &%command%& is not set. The result of expansion must
21921 be the name of a Unix domain socket. The transport connects to the socket and
21922 delivers the message to it using the LMTP protocol.
21925 .option timeout lmtp time 5m
21926 The transport is aborted if the created process or Unix domain socket does not
21927 respond to LMTP commands or message input within this timeout. Delivery
21928 is deferred, and will be tried again later. Here is an example of a typical
21933 command = /some/local/lmtp/delivery/program
21937 This delivers up to 20 addresses at a time, in a mixture of domains if
21938 necessary, running as the user &'exim'&.
21942 . ////////////////////////////////////////////////////////////////////////////
21943 . ////////////////////////////////////////////////////////////////////////////
21945 .chapter "The pipe transport" "CHAPpipetransport"
21946 .scindex IIDpiptra1 "transports" "&(pipe)&"
21947 .scindex IIDpiptra2 "&(pipe)& transport"
21948 The &(pipe)& transport is used to deliver messages via a pipe to a command
21949 running in another process. One example is the use of &(pipe)& as a
21950 pseudo-remote transport for passing messages to some other delivery mechanism
21951 (such as UUCP). Another is the use by individual users to automatically process
21952 their incoming messages. The &(pipe)& transport can be used in one of the
21956 .vindex "&$local_part$&"
21957 A router routes one address to a transport in the normal way, and the
21958 transport is configured as a &(pipe)& transport. In this case, &$local_part$&
21959 contains the local part of the address (as usual), and the command that is run
21960 is specified by the &%command%& option on the transport.
21962 .vindex "&$pipe_addresses$&"
21963 If the &%batch_max%& option is set greater than 1 (the default is 1), the
21964 transport can handle more than one address in a single run. In this case, when
21965 more than one address is routed to the transport, &$local_part$& is not set
21966 (because it is not unique). However, the pseudo-variable &$pipe_addresses$&
21967 (described in section &<<SECThowcommandrun>>& below) contains all the addresses
21968 that are routed to the transport.
21970 .vindex "&$address_pipe$&"
21971 A router redirects an address directly to a pipe command (for example, from an
21972 alias or forward file). In this case, &$address_pipe$& contains the text of the
21973 pipe command, and the &%command%& option on the transport is ignored unless
21974 &%force_command%& is set. If only one address is being transported
21975 (&%batch_max%& is not greater than one, or only one address was redirected to
21976 this pipe command), &$local_part$& contains the local part that was redirected.
21980 The &(pipe)& transport is a non-interactive delivery method. Exim can also
21981 deliver messages over pipes using the LMTP interactive protocol. This is
21982 implemented by the &(lmtp)& transport.
21984 In the case when &(pipe)& is run as a consequence of an entry in a local user's
21985 &_.forward_& file, the command runs under the uid and gid of that user. In
21986 other cases, the uid and gid have to be specified explicitly, either on the
21987 transport or on the router that handles the address. Current and &"home"&
21988 directories are also controllable. See chapter &<<CHAPenvironment>>& for
21989 details of the local delivery environment and chapter &<<CHAPbatching>>&
21990 for a discussion of local delivery batching.
21993 .section "Concurrent delivery" "SECID140"
21994 If two messages arrive at almost the same time, and both are routed to a pipe
21995 delivery, the two pipe transports may be run concurrently. You must ensure that
21996 any pipe commands you set up are robust against this happening. If the commands
21997 write to a file, the &%exim_lock%& utility might be of use.
22002 .section "Returned status and data" "SECID141"
22003 .cindex "&(pipe)& transport" "returned data"
22004 If the command exits with a non-zero return code, the delivery is deemed to
22005 have failed, unless either the &%ignore_status%& option is set (in which case
22006 the return code is treated as zero), or the return code is one of those listed
22007 in the &%temp_errors%& option, which are interpreted as meaning &"try again
22008 later"&. In this case, delivery is deferred. Details of a permanent failure are
22009 logged, but are not included in the bounce message, which merely contains
22010 &"local delivery failed"&.
22012 If the command exits on a signal and the &%freeze_signal%& option is set then
22013 the message will be frozen in the queue. If that option is not set, a bounce
22014 will be sent as normal.
22016 If the return code is greater than 128 and the command being run is a shell
22017 script, it normally means that the script was terminated by a signal whose
22018 value is the return code minus 128. The &%freeze_signal%& option does not
22019 apply in this case.
22021 If Exim is unable to run the command (that is, if &[execve()]& fails), the
22022 return code is set to 127. This is the value that a shell returns if it is
22023 asked to run a non-existent command. The wording for the log line suggests that
22024 a non-existent command may be the problem.
22026 The &%return_output%& option can affect the result of a pipe delivery. If it is
22027 set and the command produces any output on its standard output or standard
22028 error streams, the command is considered to have failed, even if it gave a zero
22029 return code or if &%ignore_status%& is set. The output from the command is
22030 included as part of the bounce message. The &%return_fail_output%& option is
22031 similar, except that output is returned only when the command exits with a
22032 failure return code, that is, a value other than zero or a code that matches
22037 .section "How the command is run" "SECThowcommandrun"
22038 .cindex "&(pipe)& transport" "path for command"
22039 The command line is (by default) broken down into a command name and arguments
22040 by the &(pipe)& transport itself. The &%allow_commands%& and
22041 &%restrict_to_path%& options can be used to restrict the commands that may be
22044 .cindex "quoting" "in pipe command"
22045 Unquoted arguments are delimited by white space. If an argument appears in
22046 double quotes, backslash is interpreted as an escape character in the usual
22047 way. If an argument appears in single quotes, no escaping is done.
22049 String expansion is applied to the command line except when it comes from a
22050 traditional &_.forward_& file (commands from a filter file are expanded). The
22051 expansion is applied to each argument in turn rather than to the whole line.
22052 For this reason, any string expansion item that contains white space must be
22053 quoted so as to be contained within a single argument. A setting such as
22055 command = /some/path ${if eq{$local_part}{postmaster}{xx}{yy}}
22057 will not work, because the expansion item gets split between several
22058 arguments. You have to write
22060 command = /some/path "${if eq{$local_part}{postmaster}{xx}{yy}}"
22062 to ensure that it is all in one argument. The expansion is done in this way,
22063 argument by argument, so that the number of arguments cannot be changed as a
22064 result of expansion, and quotes or backslashes in inserted variables do not
22065 interact with external quoting. However, this leads to problems if you want to
22066 generate multiple arguments (or the command name plus arguments) from a single
22067 expansion. In this situation, the simplest solution is to use a shell. For
22070 command = /bin/sh -c ${lookup{$local_part}lsearch{/some/file}}
22073 .cindex "transport" "filter"
22074 .cindex "filter" "transport filter"
22075 .vindex "&$pipe_addresses$&"
22076 Special handling takes place when an argument consists of precisely the text
22077 &`$pipe_addresses`&. This is not a general expansion variable; the only
22078 place this string is recognized is when it appears as an argument for a pipe or
22079 transport filter command. It causes each address that is being handled to be
22080 inserted in the argument list at that point &'as a separate argument'&. This
22081 avoids any problems with spaces or shell metacharacters, and is of use when a
22082 &(pipe)& transport is handling groups of addresses in a batch.
22084 If &%force_command%& is enabled on the transport, Special handling takes place
22085 for an argument that consists of precisely the text &`$address_pipe`&. It
22086 is handled similarly to &$pipe_addresses$& above. It is expanded and each
22087 argument is inserted in the argument list at that point
22088 &'as a separate argument'&. The &`$address_pipe`& item does not need to be
22089 the only item in the argument; in fact, if it were then &%force_command%&
22090 should behave as a no-op. Rather, it should be used to adjust the command
22091 run while preserving the argument vector separation.
22093 After splitting up into arguments and expansion, the resulting command is run
22094 in a subprocess directly from the transport, &'not'& under a shell. The
22095 message that is being delivered is supplied on the standard input, and the
22096 standard output and standard error are both connected to a single pipe that is
22097 read by Exim. The &%max_output%& option controls how much output the command
22098 may produce, and the &%return_output%& and &%return_fail_output%& options
22099 control what is done with it.
22101 Not running the command under a shell (by default) lessens the security risks
22102 in cases when a command from a user's filter file is built out of data that was
22103 taken from an incoming message. If a shell is required, it can of course be
22104 explicitly specified as the command to be run. However, there are circumstances
22105 where existing commands (for example, in &_.forward_& files) expect to be run
22106 under a shell and cannot easily be modified. To allow for these cases, there is
22107 an option called &%use_shell%&, which changes the way the &(pipe)& transport
22108 works. Instead of breaking up the command line as just described, it expands it
22109 as a single string and passes the result to &_/bin/sh_&. The
22110 &%restrict_to_path%& option and the &$pipe_addresses$& facility cannot be used
22111 with &%use_shell%&, and the whole mechanism is inherently less secure.
22115 .section "Environment variables" "SECTpipeenv"
22116 .cindex "&(pipe)& transport" "environment for command"
22117 .cindex "environment for pipe transport"
22118 The environment variables listed below are set up when the command is invoked.
22119 This list is a compromise for maximum compatibility with other MTAs. Note that
22120 the &%environment%& option can be used to add additional variables to this
22123 &`DOMAIN `& the domain of the address
22124 &`HOME `& the home directory, if set
22125 &`HOST `& the host name when called from a router (see below)
22126 &`LOCAL_PART `& see below
22127 &`LOCAL_PART_PREFIX `& see below
22128 &`LOCAL_PART_SUFFIX `& see below
22129 &`LOGNAME `& see below
22130 &`MESSAGE_ID `& Exim's local ID for the message
22131 &`PATH `& as specified by the &%path%& option below
22132 &`QUALIFY_DOMAIN `& the sender qualification domain
22133 &`RECIPIENT `& the complete recipient address
22134 &`SENDER `& the sender of the message (empty if a bounce)
22135 &`SHELL `& &`/bin/sh`&
22136 &`TZ `& the value of the &%timezone%& option, if set
22137 &`USER `& see below
22139 When a &(pipe)& transport is called directly from (for example) an &(accept)&
22140 router, LOCAL_PART is set to the local part of the address. When it is
22141 called as a result of a forward or alias expansion, LOCAL_PART is set to
22142 the local part of the address that was expanded. In both cases, any affixes are
22143 removed from the local part, and made available in LOCAL_PART_PREFIX and
22144 LOCAL_PART_SUFFIX, respectively. LOGNAME and USER are set to the
22145 same value as LOCAL_PART for compatibility with other MTAs.
22148 HOST is set only when a &(pipe)& transport is called from a router that
22149 associates hosts with an address, typically when using &(pipe)& as a
22150 pseudo-remote transport. HOST is set to the first host name specified by
22154 If the transport's generic &%home_directory%& option is set, its value is used
22155 for the HOME environment variable. Otherwise, a home directory may be set
22156 by the router's &%transport_home_directory%& option, which defaults to the
22157 user's home directory if &%check_local_user%& is set.
22160 .section "Private options for pipe" "SECID142"
22161 .cindex "options" "&(pipe)& transport"
22165 .option allow_commands pipe "string list&!!" unset
22166 .cindex "&(pipe)& transport" "permitted commands"
22167 The string is expanded, and is then interpreted as a colon-separated list of
22168 permitted commands. If &%restrict_to_path%& is not set, the only commands
22169 permitted are those in the &%allow_commands%& list. They need not be absolute
22170 paths; the &%path%& option is still used for relative paths. If
22171 &%restrict_to_path%& is set with &%allow_commands%&, the command must either be
22172 in the &%allow_commands%& list, or a name without any slashes that is found on
22173 the path. In other words, if neither &%allow_commands%& nor
22174 &%restrict_to_path%& is set, there is no restriction on the command, but
22175 otherwise only commands that are permitted by one or the other are allowed. For
22178 allow_commands = /usr/bin/vacation
22180 and &%restrict_to_path%& is not set, the only permitted command is
22181 &_/usr/bin/vacation_&. The &%allow_commands%& option may not be set if
22182 &%use_shell%& is set.
22185 .option batch_id pipe string&!! unset
22186 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
22189 .option batch_max pipe integer 1
22190 This limits the number of addresses that can be handled in a single delivery.
22191 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
22194 .option check_string pipe string unset
22195 As &(pipe)& writes the message, the start of each line is tested for matching
22196 &%check_string%&, and if it does, the initial matching characters are replaced
22197 by the contents of &%escape_string%&, provided both are set. The value of
22198 &%check_string%& is a literal string, not a regular expression, and the case of
22199 any letters it contains is significant. When &%use_bsmtp%& is set, the contents
22200 of &%check_string%& and &%escape_string%& are forced to values that implement
22201 the SMTP escaping protocol. Any settings made in the configuration file are
22205 .option command pipe string&!! unset
22206 This option need not be set when &(pipe)& is being used to deliver to pipes
22207 obtained directly from address redirections. In other cases, the option must be
22208 set, to provide a command to be run. It need not yield an absolute path (see
22209 the &%path%& option below). The command is split up into separate arguments by
22210 Exim, and each argument is separately expanded, as described in section
22211 &<<SECThowcommandrun>>& above.
22214 .option environment pipe string&!! unset
22215 .cindex "&(pipe)& transport" "environment for command"
22216 .cindex "environment for &(pipe)& transport"
22217 This option is used to add additional variables to the environment in which the
22218 command runs (see section &<<SECTpipeenv>>& for the default list). Its value is
22219 a string which is expanded, and then interpreted as a colon-separated list of
22220 environment settings of the form <&'name'&>=<&'value'&>.
22223 .option escape_string pipe string unset
22224 See &%check_string%& above.
22227 .option freeze_exec_fail pipe boolean false
22228 .cindex "exec failure"
22229 .cindex "failure of exec"
22230 .cindex "&(pipe)& transport" "failure of exec"
22231 Failure to exec the command in a pipe transport is by default treated like
22232 any other failure while running the command. However, if &%freeze_exec_fail%&
22233 is set, failure to exec is treated specially, and causes the message to be
22234 frozen, whatever the setting of &%ignore_status%&.
22237 .option freeze_signal pipe boolean false
22238 .cindex "signal exit"
22239 .cindex "&(pipe)& transport", "signal exit"
22240 Normally if the process run by a command in a pipe transport exits on a signal,
22241 a bounce message is sent. If &%freeze_signal%& is set, the message will be
22242 frozen in Exim's queue instead.
22245 .option force_command pipe boolean false
22246 .cindex "force command"
22247 .cindex "&(pipe)& transport", "force command"
22248 Normally when a router redirects an address directly to a pipe command
22249 the &%command%& option on the transport is ignored. If &%force_command%&
22250 is set, the &%command%& option will used. This is especially
22251 useful for forcing a wrapper or additional argument to be added to the
22252 command. For example:
22254 command = /usr/bin/remote_exec myhost -- $address_pipe
22258 Note that &$address_pipe$& is handled specially in &%command%& when
22259 &%force_command%& is set, expanding out to the original argument vector as
22260 separate items, similarly to a Unix shell &`"$@"`& construct.
22262 .option ignore_status pipe boolean false
22263 If this option is true, the status returned by the subprocess that is set up to
22264 run the command is ignored, and Exim behaves as if zero had been returned.
22265 Otherwise, a non-zero status or termination by signal causes an error return
22266 from the transport unless the status value is one of those listed in
22267 &%temp_errors%&; these cause the delivery to be deferred and tried again later.
22269 &*Note*&: This option does not apply to timeouts, which do not return a status.
22270 See the &%timeout_defer%& option for how timeouts are handled.
22272 .option log_defer_output pipe boolean false
22273 .cindex "&(pipe)& transport" "logging output"
22274 If this option is set, and the status returned by the command is
22275 one of the codes listed in &%temp_errors%& (that is, delivery was deferred),
22276 and any output was produced, the first line of it is written to the main log.
22279 .option log_fail_output pipe boolean false
22280 If this option is set, and the command returns any output, and also ends with a
22281 return code that is neither zero nor one of the return codes listed in
22282 &%temp_errors%& (that is, the delivery failed), the first line of output is
22283 written to the main log. This option and &%log_output%& are mutually exclusive.
22284 Only one of them may be set.
22288 .option log_output pipe boolean false
22289 If this option is set and the command returns any output, the first line of
22290 output is written to the main log, whatever the return code. This option and
22291 &%log_fail_output%& are mutually exclusive. Only one of them may be set.
22295 .option max_output pipe integer 20K
22296 This specifies the maximum amount of output that the command may produce on its
22297 standard output and standard error file combined. If the limit is exceeded, the
22298 process running the command is killed. This is intended as a safety measure to
22299 catch runaway processes. The limit is applied independently of the settings of
22300 the options that control what is done with such output (for example,
22301 &%return_output%&). Because of buffering effects, the amount of output may
22302 exceed the limit by a small amount before Exim notices.
22305 .option message_prefix pipe string&!! "see below"
22306 The string specified here is expanded and output at the start of every message.
22307 The default is unset if &%use_bsmtp%& is set. Otherwise it is
22310 From ${if def:return_path{$return_path}{MAILER-DAEMON}}\
22314 .cindex "&%tmail%&"
22315 .cindex "&""From""& line"
22316 This is required by the commonly used &_/usr/bin/vacation_& program.
22317 However, it must &'not'& be present if delivery is to the Cyrus IMAP server,
22318 or to the &%tmail%& local delivery agent. The prefix can be suppressed by
22323 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
22324 &`\n`& to &`\r\n`& in &%message_prefix%&.
22327 .option message_suffix pipe string&!! "see below"
22328 The string specified here is expanded and output at the end of every message.
22329 The default is unset if &%use_bsmtp%& is set. Otherwise it is a single newline.
22330 The suffix can be suppressed by setting
22334 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
22335 &`\n`& to &`\r\n`& in &%message_suffix%&.
22338 .option path pipe string "see below"
22339 This option specifies the string that is set up in the PATH environment
22340 variable of the subprocess. The default is:
22344 If the &%command%& option does not yield an absolute path name, the command is
22345 sought in the PATH directories, in the usual way. &*Warning*&: This does not
22346 apply to a command specified as a transport filter.
22349 .option permit_coredump pipe boolean false
22350 Normally Exim inhibits core-dumps during delivery. If you have a need to get
22351 a core-dump of a pipe command, enable this command. This enables core-dumps
22352 during delivery and affects both the Exim binary and the pipe command run.
22353 It is recommended that this option remain off unless and until you have a need
22354 for it and that this only be enabled when needed, as the risk of excessive
22355 resource consumption can be quite high. Note also that Exim is typically
22356 installed as a setuid binary and most operating systems will inhibit coredumps
22357 of these by default, so further OS-specific action may be required.
22360 .option pipe_as_creator pipe boolean false
22361 .cindex "uid (user id)" "local delivery"
22362 If the generic &%user%& option is not set and this option is true, the delivery
22363 process is run under the uid that was in force when Exim was originally called
22364 to accept the message. If the group id is not otherwise set (via the generic
22365 &%group%& option), the gid that was in force when Exim was originally called to
22366 accept the message is used.
22369 .option restrict_to_path pipe boolean false
22370 When this option is set, any command name not listed in &%allow_commands%& must
22371 contain no slashes. The command is searched for only in the directories listed
22372 in the &%path%& option. This option is intended for use in the case when a pipe
22373 command has been generated from a user's &_.forward_& file. This is usually
22374 handled by a &(pipe)& transport called &%address_pipe%&.
22377 .option return_fail_output pipe boolean false
22378 If this option is true, and the command produced any output and ended with a
22379 return code other than zero or one of the codes listed in &%temp_errors%& (that
22380 is, the delivery failed), the output is returned in the bounce message.
22381 However, if the message has a null sender (that is, it is itself a bounce
22382 message), output from the command is discarded. This option and
22383 &%return_output%& are mutually exclusive. Only one of them may be set.
22387 .option return_output pipe boolean false
22388 If this option is true, and the command produced any output, the delivery is
22389 deemed to have failed whatever the return code from the command, and the output
22390 is returned in the bounce message. Otherwise, the output is just discarded.
22391 However, if the message has a null sender (that is, it is a bounce message),
22392 output from the command is always discarded, whatever the setting of this
22393 option. This option and &%return_fail_output%& are mutually exclusive. Only one
22394 of them may be set.
22398 .option temp_errors pipe "string list" "see below"
22399 .cindex "&(pipe)& transport" "temporary failure"
22400 This option contains either a colon-separated list of numbers, or a single
22401 asterisk. If &%ignore_status%& is false
22402 and &%return_output%& is not set,
22403 and the command exits with a non-zero return code, the failure is treated as
22404 temporary and the delivery is deferred if the return code matches one of the
22405 numbers, or if the setting is a single asterisk. Otherwise, non-zero return
22406 codes are treated as permanent errors. The default setting contains the codes
22407 defined by EX_TEMPFAIL and EX_CANTCREAT in &_sysexits.h_&. If Exim is
22408 compiled on a system that does not define these macros, it assumes values of 75
22409 and 73, respectively.
22412 .option timeout pipe time 1h
22413 If the command fails to complete within this time, it is killed. This normally
22414 causes the delivery to fail (but see &%timeout_defer%&). A zero time interval
22415 specifies no timeout. In order to ensure that any subprocesses created by the
22416 command are also killed, Exim makes the initial process a process group leader,
22417 and kills the whole process group on a timeout. However, this can be defeated
22418 if one of the processes starts a new process group.
22420 .option timeout_defer pipe boolean false
22421 A timeout in a &(pipe)& transport, either in the command that the transport
22422 runs, or in a transport filter that is associated with it, is by default
22423 treated as a hard error, and the delivery fails. However, if &%timeout_defer%&
22424 is set true, both kinds of timeout become temporary errors, causing the
22425 delivery to be deferred.
22427 .option umask pipe "octal integer" 022
22428 This specifies the umask setting for the subprocess that runs the command.
22431 .option use_bsmtp pipe boolean false
22432 .cindex "envelope sender"
22433 If this option is set true, the &(pipe)& transport writes messages in &"batch
22434 SMTP"& format, with the envelope sender and recipient(s) included as SMTP
22435 commands. If you want to include a leading HELO command with such messages,
22436 you can do so by setting the &%message_prefix%& option. See section
22437 &<<SECTbatchSMTP>>& for details of batch SMTP.
22439 .option use_classresources pipe boolean false
22440 .cindex "class resources (BSD)"
22441 This option is available only when Exim is running on FreeBSD, NetBSD, or
22442 BSD/OS. If it is set true, the &[setclassresources()]& function is used to set
22443 resource limits when a &(pipe)& transport is run to perform a delivery. The
22444 limits for the uid under which the pipe is to run are obtained from the login
22448 .option use_crlf pipe boolean false
22449 .cindex "carriage return"
22451 This option causes lines to be terminated with the two-character CRLF sequence
22452 (carriage return, linefeed) instead of just a linefeed character. In the case
22453 of batched SMTP, the byte sequence written to the pipe is then an exact image
22454 of what would be sent down a real SMTP connection.
22456 The contents of the &%message_prefix%& and &%message_suffix%& options are
22457 written verbatim, so must contain their own carriage return characters if these
22458 are needed. When &%use_bsmtp%& is not set, the default values for both
22459 &%message_prefix%& and &%message_suffix%& end with a single linefeed, so their
22460 values must be changed to end with &`\r\n`& if &%use_crlf%& is set.
22463 .option use_shell pipe boolean false
22464 .vindex "&$pipe_addresses$&"
22465 If this option is set, it causes the command to be passed to &_/bin/sh_&
22466 instead of being run directly from the transport, as described in section
22467 &<<SECThowcommandrun>>&. This is less secure, but is needed in some situations
22468 where the command is expected to be run under a shell and cannot easily be
22469 modified. The &%allow_commands%& and &%restrict_to_path%& options, and the
22470 &`$pipe_addresses`& facility are incompatible with &%use_shell%&. The
22471 command is expanded as a single string, and handed to &_/bin/sh_& as data for
22476 .section "Using an external local delivery agent" "SECID143"
22477 .cindex "local delivery" "using an external agent"
22478 .cindex "&'procmail'&"
22479 .cindex "external local delivery"
22480 .cindex "delivery" "&'procmail'&"
22481 .cindex "delivery" "by external agent"
22482 The &(pipe)& transport can be used to pass all messages that require local
22483 delivery to a separate local delivery agent such as &%procmail%&. When doing
22484 this, care must be taken to ensure that the pipe is run under an appropriate
22485 uid and gid. In some configurations one wants this to be a uid that is trusted
22486 by the delivery agent to supply the correct sender of the message. It may be
22487 necessary to recompile or reconfigure the delivery agent so that it trusts an
22488 appropriate user. The following is an example transport and router
22489 configuration for &%procmail%&:
22494 command = /usr/local/bin/procmail -d $local_part
22498 check_string = "From "
22499 escape_string = ">From "
22508 transport = procmail_pipe
22510 In this example, the pipe is run as the local user, but with the group set to
22511 &'mail'&. An alternative is to run the pipe as a specific user such as &'mail'&
22512 or &'exim'&, but in this case you must arrange for &%procmail%& to trust that
22513 user to supply a correct sender address. If you do not specify either a
22514 &%group%& or a &%user%& option, the pipe command is run as the local user. The
22515 home directory is the user's home directory by default.
22517 &*Note*&: The command that the pipe transport runs does &'not'& begin with
22521 as shown in some &%procmail%& documentation, because Exim does not by default
22522 use a shell to run pipe commands.
22525 The next example shows a transport and a router for a system where local
22526 deliveries are handled by the Cyrus IMAP server.
22529 local_delivery_cyrus:
22531 command = /usr/cyrus/bin/deliver \
22532 -m ${substr_1:$local_part_suffix} -- $local_part
22544 local_part_suffix = .*
22545 transport = local_delivery_cyrus
22547 Note the unsetting of &%message_prefix%& and &%message_suffix%&, and the use of
22548 &%return_output%& to cause any text written by Cyrus to be returned to the
22550 .ecindex IIDpiptra1
22551 .ecindex IIDpiptra2
22554 . ////////////////////////////////////////////////////////////////////////////
22555 . ////////////////////////////////////////////////////////////////////////////
22557 .chapter "The smtp transport" "CHAPsmtptrans"
22558 .scindex IIDsmttra1 "transports" "&(smtp)&"
22559 .scindex IIDsmttra2 "&(smtp)& transport"
22560 The &(smtp)& transport delivers messages over TCP/IP connections using the SMTP
22561 or LMTP protocol. The list of hosts to try can either be taken from the address
22562 that is being processed (having been set up by the router), or specified
22563 explicitly for the transport. Timeout and retry processing (see chapter
22564 &<<CHAPretry>>&) is applied to each IP address independently.
22567 .section "Multiple messages on a single connection" "SECID144"
22568 The sending of multiple messages over a single TCP/IP connection can arise in
22572 If a message contains more than &%max_rcpt%& (see below) addresses that are
22573 routed to the same host, more than one copy of the message has to be sent to
22574 that host. In this situation, multiple copies may be sent in a single run of
22575 the &(smtp)& transport over a single TCP/IP connection. (What Exim actually
22576 does when it has too many addresses to send in one message also depends on the
22577 value of the global &%remote_max_parallel%& option. Details are given in
22578 section &<<SECToutSMTPTCP>>&.)
22580 .cindex "hints database" "remembering routing"
22581 When a message has been successfully delivered over a TCP/IP connection, Exim
22582 looks in its hints database to see if there are any other messages awaiting a
22583 connection to the same host. If there are, a new delivery process is started
22584 for one of them, and the current TCP/IP connection is passed on to it. The new
22585 process may in turn send multiple copies and possibly create yet another
22590 For each copy sent over the same TCP/IP connection, a sequence counter is
22591 incremented, and if it ever gets to the value of &%connection_max_messages%&,
22592 no further messages are sent over that connection.
22596 .section "Use of the $host and $host_address variables" "SECID145"
22598 .vindex "&$host_address$&"
22599 At the start of a run of the &(smtp)& transport, the values of &$host$& and
22600 &$host_address$& are the name and IP address of the first host on the host list
22601 passed by the router. However, when the transport is about to connect to a
22602 specific host, and while it is connected to that host, &$host$& and
22603 &$host_address$& are set to the values for that host. These are the values
22604 that are in force when the &%helo_data%&, &%hosts_try_auth%&, &%interface%&,
22605 &%serialize_hosts%&, and the various TLS options are expanded.
22608 .section "Use of $tls_cipher and $tls_peerdn" "usecippeer"
22609 .vindex &$tls_bits$&
22610 .vindex &$tls_cipher$&
22611 .vindex &$tls_peerdn$&
22612 .vindex &$tls_sni$&
22613 At the start of a run of the &(smtp)& transport, the values of &$tls_bits$&,
22614 &$tls_cipher$&, &$tls_peerdn$& and &$tls_sni$&
22615 are the values that were set when the message was received.
22616 These are the values that are used for options that are expanded before any
22617 SMTP connections are made. Just before each connection is made, these four
22618 variables are emptied. If TLS is subsequently started, they are set to the
22619 appropriate values for the outgoing connection, and these are the values that
22620 are in force when any authenticators are run and when the
22621 &%authenticated_sender%& option is expanded.
22623 These variables are deprecated in favour of &$tls_in_cipher$& et. al.
22624 and will be removed in a future release.
22627 .section "Private options for smtp" "SECID146"
22628 .cindex "options" "&(smtp)& transport"
22629 The private options of the &(smtp)& transport are as follows:
22632 .option address_retry_include_sender smtp boolean true
22633 .cindex "4&'xx'& responses" "retrying after"
22634 When an address is delayed because of a 4&'xx'& response to a RCPT command, it
22635 is the combination of sender and recipient that is delayed in subsequent queue
22636 runs until the retry time is reached. You can delay the recipient without
22637 reference to the sender (which is what earlier versions of Exim did), by
22638 setting &%address_retry_include_sender%& false. However, this can lead to
22639 problems with servers that regularly issue 4&'xx'& responses to RCPT commands.
22641 .option allow_localhost smtp boolean false
22642 .cindex "local host" "sending to"
22643 .cindex "fallback" "hosts specified on transport"
22644 When a host specified in &%hosts%& or &%fallback_hosts%& (see below) turns out
22645 to be the local host, or is listed in &%hosts_treat_as_local%&, delivery is
22646 deferred by default. However, if &%allow_localhost%& is set, Exim goes on to do
22647 the delivery anyway. This should be used only in special cases when the
22648 configuration ensures that no looping will result (for example, a differently
22649 configured Exim is listening on the port to which the message is sent).
22652 .option authenticated_sender smtp string&!! unset
22654 When Exim has authenticated as a client, or if &%authenticated_sender_force%&
22655 is true, this option sets a value for the AUTH= item on outgoing MAIL commands,
22656 overriding any existing authenticated sender value. If the string expansion is
22657 forced to fail, the option is ignored. Other expansion failures cause delivery
22658 to be deferred. If the result of expansion is an empty string, that is also
22661 The expansion happens after the outgoing connection has been made and TLS
22662 started, if required. This means that the &$host$&, &$host_address$&,
22663 &$tls_out_cipher$&, and &$tls_out_peerdn$& variables are set according to the
22664 particular connection.
22666 If the SMTP session is not authenticated, the expansion of
22667 &%authenticated_sender%& still happens (and can cause the delivery to be
22668 deferred if it fails), but no AUTH= item is added to MAIL commands
22669 unless &%authenticated_sender_force%& is true.
22671 This option allows you to use the &(smtp)& transport in LMTP mode to
22672 deliver mail to Cyrus IMAP and provide the proper local part as the
22673 &"authenticated sender"&, via a setting such as:
22675 authenticated_sender = $local_part
22677 This removes the need for IMAP subfolders to be assigned special ACLs to
22678 allow direct delivery to those subfolders.
22680 Because of expected uses such as that just described for Cyrus (when no
22681 domain is involved), there is no checking on the syntax of the provided
22685 .option authenticated_sender_force smtp boolean false
22686 If this option is set true, the &%authenticated_sender%& option's value
22687 is used for the AUTH= item on outgoing MAIL commands, even if Exim has not
22688 authenticated as a client.
22691 .option command_timeout smtp time 5m
22692 This sets a timeout for receiving a response to an SMTP command that has been
22693 sent out. It is also used when waiting for the initial banner line from the
22694 remote host. Its value must not be zero.
22697 .option connect_timeout smtp time 5m
22698 This sets a timeout for the &[connect()]& function, which sets up a TCP/IP call
22699 to a remote host. A setting of zero allows the system timeout (typically
22700 several minutes) to act. To have any effect, the value of this option must be
22701 less than the system timeout. However, it has been observed that on some
22702 systems there is no system timeout, which is why the default value for this
22703 option is 5 minutes, a value recommended by RFC 1123.
22706 .option connection_max_messages smtp integer 500
22707 .cindex "SMTP" "passed connection"
22708 .cindex "SMTP" "multiple deliveries"
22709 .cindex "multiple SMTP deliveries"
22710 This controls the maximum number of separate message deliveries that are sent
22711 over a single TCP/IP connection. If the value is zero, there is no limit.
22712 For testing purposes, this value can be overridden by the &%-oB%& command line
22716 .option data_timeout smtp time 5m
22717 This sets a timeout for the transmission of each block in the data portion of
22718 the message. As a result, the overall timeout for a message depends on the size
22719 of the message. Its value must not be zero. See also &%final_timeout%&.
22722 .option delay_after_cutoff smtp boolean true
22723 This option controls what happens when all remote IP addresses for a given
22724 domain have been inaccessible for so long that they have passed their retry
22727 In the default state, if the next retry time has not been reached for any of
22728 them, the address is bounced without trying any deliveries. In other words,
22729 Exim delays retrying an IP address after the final cutoff time until a new
22730 retry time is reached, and can therefore bounce an address without ever trying
22731 a delivery, when machines have been down for a long time. Some people are
22732 unhappy at this prospect, so...
22734 If &%delay_after_cutoff%& is set false, Exim behaves differently. If all IP
22735 addresses are past their final cutoff time, Exim tries to deliver to those
22736 IP addresses that have not been tried since the message arrived. If there are
22737 none, of if they all fail, the address is bounced. In other words, it does not
22738 delay when a new message arrives, but immediately tries those expired IP
22739 addresses that haven't been tried since the message arrived. If there is a
22740 continuous stream of messages for the dead hosts, unsetting
22741 &%delay_after_cutoff%& means that there will be many more attempts to deliver
22745 .option dns_qualify_single smtp boolean true
22746 If the &%hosts%& or &%fallback_hosts%& option is being used,
22747 and the &%gethostbyname%& option is false,
22748 the RES_DEFNAMES resolver option is set. See the &%qualify_single%& option
22749 in chapter &<<CHAPdnslookup>>& for more details.
22752 .option dns_search_parents smtp boolean false
22753 If the &%hosts%& or &%fallback_hosts%& option is being used, and the
22754 &%gethostbyname%& option is false, the RES_DNSRCH resolver option is set.
22755 See the &%search_parents%& option in chapter &<<CHAPdnslookup>>& for more
22760 .option dnssec_request_domains smtp "domain list&!!" unset
22761 .cindex "MX record" "security"
22762 .cindex "DNSSEC" "MX lookup"
22763 .cindex "security" "MX lookup"
22764 .cindex "DNS" "DNSSEC"
22765 DNS lookups for domains matching &%dnssec_request_domains%& will be done with
22766 the dnssec request bit set.
22767 This applies to all of the SRV, MX A6, AAAA, A lookup sequence.
22773 .option dnssec_require_domains smtp "domain list&!!" unset
22774 .cindex "MX record" "security"
22775 .cindex "DNSSEC" "MX lookup"
22776 .cindex "security" "MX lookup"
22777 .cindex "DNS" "DNSSEC"
22778 DNS lookups for domains matching &%dnssec_request_domains%& will be done with
22779 the dnssec request bit set. Any returns not having the Authenticated Data bit
22780 (AD bit) set wil be ignored and logged as a host-lookup failure.
22781 This applies to all of the SRV, MX A6, AAAA, A lookup sequence.
22786 .option dscp smtp string&!! unset
22787 .cindex "DCSP" "outbound"
22788 This option causes the DSCP value associated with a socket to be set to one
22789 of a number of fixed strings or to numeric value.
22790 The &%-bI:dscp%& option may be used to ask Exim which names it knows of.
22791 Common values include &`throughput`&, &`mincost`&, and on newer systems
22792 &`ef`&, &`af41`&, etc. Numeric values may be in the range 0 to 0x3F.
22794 The outbound packets from Exim will be marked with this value in the header
22795 (for IPv4, the TOS field; for IPv6, the TCLASS field); there is no guarantee
22796 that these values will have any effect, not be stripped by networking
22797 equipment, or do much of anything without cooperation with your Network
22798 Engineer and those of all network operators between the source and destination.
22801 .option fallback_hosts smtp "string list" unset
22802 .cindex "fallback" "hosts specified on transport"
22803 String expansion is not applied to this option. The argument must be a
22804 colon-separated list of host names or IP addresses, optionally also including
22805 port numbers, though the separator can be changed, as described in section
22806 &<<SECTlistconstruct>>&. Each individual item in the list is the same as an
22807 item in a &%route_list%& setting for the &(manualroute)& router, as described
22808 in section &<<SECTformatonehostitem>>&.
22810 Fallback hosts can also be specified on routers, which associate them with the
22811 addresses they process. As for the &%hosts%& option without &%hosts_override%&,
22812 &%fallback_hosts%& specified on the transport is used only if the address does
22813 not have its own associated fallback host list. Unlike &%hosts%&, a setting of
22814 &%fallback_hosts%& on an address is not overridden by &%hosts_override%&.
22815 However, &%hosts_randomize%& does apply to fallback host lists.
22817 If Exim is unable to deliver to any of the hosts for a particular address, and
22818 the errors are not permanent rejections, the address is put on a separate
22819 transport queue with its host list replaced by the fallback hosts, unless the
22820 address was routed via MX records and the current host was in the original MX
22821 list. In that situation, the fallback host list is not used.
22823 Once normal deliveries are complete, the fallback queue is delivered by
22824 re-running the same transports with the new host lists. If several failing
22825 addresses have the same fallback hosts (and &%max_rcpt%& permits it), a single
22826 copy of the message is sent.
22828 The resolution of the host names on the fallback list is controlled by the
22829 &%gethostbyname%& option, as for the &%hosts%& option. Fallback hosts apply
22830 both to cases when the host list comes with the address and when it is taken
22831 from &%hosts%&. This option provides a &"use a smart host only if delivery
22835 .option final_timeout smtp time 10m
22836 This is the timeout that applies while waiting for the response to the final
22837 line containing just &"."& that terminates a message. Its value must not be
22840 .option gethostbyname smtp boolean false
22841 If this option is true when the &%hosts%& and/or &%fallback_hosts%& options are
22842 being used, names are looked up using &[gethostbyname()]&
22843 (or &[getipnodebyname()]& when available)
22844 instead of using the DNS. Of course, that function may in fact use the DNS, but
22845 it may also consult other sources of information such as &_/etc/hosts_&.
22847 .option gnutls_compat_mode smtp boolean unset
22848 This option controls whether GnuTLS is used in compatibility mode in an Exim
22849 server. This reduces security slightly, but improves interworking with older
22850 implementations of TLS.
22852 .option helo_data smtp string&!! "see below"
22853 .cindex "HELO" "argument, setting"
22854 .cindex "EHLO" "argument, setting"
22855 .cindex "LHLO argument setting"
22856 The value of this option is expanded after a connection to a another host has
22857 been set up. The result is used as the argument for the EHLO, HELO, or LHLO
22858 command that starts the outgoing SMTP or LMTP session. The default value of the
22863 During the expansion, the variables &$host$& and &$host_address$& are set to
22864 the identity of the remote host, and the variables &$sending_ip_address$& and
22865 &$sending_port$& are set to the local IP address and port number that are being
22866 used. These variables can be used to generate different values for different
22867 servers or different local IP addresses. For example, if you want the string
22868 that is used for &%helo_data%& to be obtained by a DNS lookup of the outgoing
22869 interface address, you could use this:
22871 helo_data = ${lookup dnsdb{ptr=$sending_ip_address}{$value}\
22872 {$primary_hostname}}
22874 The use of &%helo_data%& applies both to sending messages and when doing
22877 .option hosts smtp "string list&!!" unset
22878 Hosts are associated with an address by a router such as &(dnslookup)&, which
22879 finds the hosts by looking up the address domain in the DNS, or by
22880 &(manualroute)&, which has lists of hosts in its configuration. However,
22881 email addresses can be passed to the &(smtp)& transport by any router, and not
22882 all of them can provide an associated list of hosts.
22884 The &%hosts%& option specifies a list of hosts to be used if the address being
22885 processed does not have any hosts associated with it. The hosts specified by
22886 &%hosts%& are also used, whether or not the address has its own hosts, if
22887 &%hosts_override%& is set.
22889 The string is first expanded, before being interpreted as a colon-separated
22890 list of host names or IP addresses, possibly including port numbers. The
22891 separator may be changed to something other than colon, as described in section
22892 &<<SECTlistconstruct>>&. Each individual item in the list is the same as an
22893 item in a &%route_list%& setting for the &(manualroute)& router, as described
22894 in section &<<SECTformatonehostitem>>&. However, note that the &`/MX`& facility
22895 of the &(manualroute)& router is not available here.
22897 If the expansion fails, delivery is deferred. Unless the failure was caused by
22898 the inability to complete a lookup, the error is logged to the panic log as
22899 well as the main log. Host names are looked up either by searching directly for
22900 address records in the DNS or by calling &[gethostbyname()]& (or
22901 &[getipnodebyname()]& when available), depending on the setting of the
22902 &%gethostbyname%& option. When Exim is compiled with IPv6 support, if a host
22903 that is looked up in the DNS has both IPv4 and IPv6 addresses, both types of
22906 During delivery, the hosts are tried in order, subject to their retry status,
22907 unless &%hosts_randomize%& is set.
22910 .option hosts_avoid_esmtp smtp "host list&!!" unset
22911 .cindex "ESMTP, avoiding use of"
22912 .cindex "HELO" "forcing use of"
22913 .cindex "EHLO" "avoiding use of"
22914 .cindex "PIPELINING" "avoiding the use of"
22915 This option is for use with broken hosts that announce ESMTP facilities (for
22916 example, PIPELINING) and then fail to implement them properly. When a host
22917 matches &%hosts_avoid_esmtp%&, Exim sends HELO rather than EHLO at the
22918 start of the SMTP session. This means that it cannot use any of the ESMTP
22919 facilities such as AUTH, PIPELINING, SIZE, and STARTTLS.
22922 .option hosts_avoid_pipelining smtp "host list&!!" unset
22923 .cindex "PIPELINING" "avoiding the use of"
22924 Exim will not use the SMTP PIPELINING extension when delivering to any host
22925 that matches this list, even if the server host advertises PIPELINING support.
22928 .option hosts_avoid_tls smtp "host list&!!" unset
22929 .cindex "TLS" "avoiding for certain hosts"
22930 Exim will not try to start a TLS session when delivering to any host that
22931 matches this list. See chapter &<<CHAPTLS>>& for details of TLS.
22933 .option hosts_verify_avoid_tls smtp "host list&!!" *
22934 .cindex "TLS" "avoiding for certain hosts"
22935 Exim will not try to start a TLS session for a verify callout,
22936 or when delivering in cutthrough mode,
22937 to any host that matches this list.
22938 Note that the default is to not use TLS.
22941 .option hosts_max_try smtp integer 5
22942 .cindex "host" "maximum number to try"
22943 .cindex "limit" "number of hosts tried"
22944 .cindex "limit" "number of MX tried"
22945 .cindex "MX record" "maximum tried"
22946 This option limits the number of IP addresses that are tried for any one
22947 delivery in cases where there are temporary delivery errors. Section
22948 &<<SECTvalhosmax>>& describes in detail how the value of this option is used.
22951 .option hosts_max_try_hardlimit smtp integer 50
22952 This is an additional check on the maximum number of IP addresses that Exim
22953 tries for any one delivery. Section &<<SECTvalhosmax>>& describes its use and
22958 .option hosts_nopass_tls smtp "host list&!!" unset
22959 .cindex "TLS" "passing connection"
22960 .cindex "multiple SMTP deliveries"
22961 .cindex "TLS" "multiple message deliveries"
22962 For any host that matches this list, a connection on which a TLS session has
22963 been started will not be passed to a new delivery process for sending another
22964 message on the same connection. See section &<<SECTmulmessam>>& for an
22965 explanation of when this might be needed.
22968 .option hosts_override smtp boolean false
22969 If this option is set and the &%hosts%& option is also set, any hosts that are
22970 attached to the address are ignored, and instead the hosts specified by the
22971 &%hosts%& option are always used. This option does not apply to
22972 &%fallback_hosts%&.
22975 .option hosts_randomize smtp boolean false
22976 .cindex "randomized host list"
22977 .cindex "host" "list of; randomized"
22978 .cindex "fallback" "randomized hosts"
22979 If this option is set, and either the list of hosts is taken from the
22980 &%hosts%& or the &%fallback_hosts%& option, or the hosts supplied by the router
22981 were not obtained from MX records (this includes fallback hosts from the
22982 router), and were not randomized by the router, the order of trying the hosts
22983 is randomized each time the transport runs. Randomizing the order of a host
22984 list can be used to do crude load sharing.
22986 When &%hosts_randomize%& is true, a host list may be split into groups whose
22987 order is separately randomized. This makes it possible to set up MX-like
22988 behaviour. The boundaries between groups are indicated by an item that is just
22989 &`+`& in the host list. For example:
22991 hosts = host1:host2:host3:+:host4:host5
22993 The order of the first three hosts and the order of the last two hosts is
22994 randomized for each use, but the first three always end up before the last two.
22995 If &%hosts_randomize%& is not set, a &`+`& item in the list is ignored.
22997 .option hosts_require_auth smtp "host list&!!" unset
22998 .cindex "authentication" "required by client"
22999 This option provides a list of servers for which authentication must succeed
23000 before Exim will try to transfer a message. If authentication fails for
23001 servers which are not in this list, Exim tries to send unauthenticated. If
23002 authentication fails for one of these servers, delivery is deferred. This
23003 temporary error is detectable in the retry rules, so it can be turned into a
23004 hard failure if required. See also &%hosts_try_auth%&, and chapter
23005 &<<CHAPSMTPAUTH>>& for details of authentication.
23008 .option hosts_require_tls smtp "host list&!!" unset
23009 .cindex "TLS" "requiring for certain servers"
23010 Exim will insist on using a TLS session when delivering to any host that
23011 matches this list. See chapter &<<CHAPTLS>>& for details of TLS.
23012 &*Note*&: This option affects outgoing mail only. To insist on TLS for
23013 incoming messages, use an appropriate ACL.
23015 .option hosts_try_auth smtp "host list&!!" unset
23016 .cindex "authentication" "optional in client"
23017 This option provides a list of servers to which, provided they announce
23018 authentication support, Exim will attempt to authenticate as a client when it
23019 connects. If authentication fails, Exim will try to transfer the message
23020 unauthenticated. See also &%hosts_require_auth%&, and chapter
23021 &<<CHAPSMTPAUTH>>& for details of authentication.
23023 .option hosts_try_prdr smtp "host list&!!" unset
23024 .cindex "PRDR" "enabling, optional in client"
23025 This option provides a list of servers to which, provided they announce
23026 PRDR support, Exim will attempt to negotiate PRDR
23027 for multi-recipient messages.
23029 .option interface smtp "string list&!!" unset
23030 .cindex "bind IP address"
23031 .cindex "IP address" "binding"
23033 .vindex "&$host_address$&"
23034 This option specifies which interface to bind to when making an outgoing SMTP
23035 call. The value is an IP address, not an interface name such as
23036 &`eth0`&. Do not confuse this with the interface address that was used when a
23037 message was received, which is in &$received_ip_address$&, formerly known as
23038 &$interface_address$&. The name was changed to minimize confusion with the
23039 outgoing interface address. There is no variable that contains an outgoing
23040 interface address because, unless it is set by this option, its value is
23043 During the expansion of the &%interface%& option the variables &$host$& and
23044 &$host_address$& refer to the host to which a connection is about to be made
23045 during the expansion of the string. Forced expansion failure, or an empty
23046 string result causes the option to be ignored. Otherwise, after expansion, the
23047 string must be a list of IP addresses, colon-separated by default, but the
23048 separator can be changed in the usual way. For example:
23050 interface = <; 192.168.123.123 ; 3ffe:ffff:836f::fe86:a061
23052 The first interface of the correct type (IPv4 or IPv6) is used for the outgoing
23053 connection. If none of them are the correct type, the option is ignored. If
23054 &%interface%& is not set, or is ignored, the system's IP functions choose which
23055 interface to use if the host has more than one.
23058 .option keepalive smtp boolean true
23059 .cindex "keepalive" "on outgoing connection"
23060 This option controls the setting of SO_KEEPALIVE on outgoing TCP/IP socket
23061 connections. When set, it causes the kernel to probe idle connections
23062 periodically, by sending packets with &"old"& sequence numbers. The other end
23063 of the connection should send a acknowledgment if the connection is still okay
23064 or a reset if the connection has been aborted. The reason for doing this is
23065 that it has the beneficial effect of freeing up certain types of connection
23066 that can get stuck when the remote host is disconnected without tidying up the
23067 TCP/IP call properly. The keepalive mechanism takes several hours to detect
23071 .option lmtp_ignore_quota smtp boolean false
23072 .cindex "LMTP" "ignoring quota errors"
23073 If this option is set true when the &%protocol%& option is set to &"lmtp"&, the
23074 string &`IGNOREQUOTA`& is added to RCPT commands, provided that the LMTP server
23075 has advertised support for IGNOREQUOTA in its response to the LHLO command.
23077 .option max_rcpt smtp integer 100
23078 .cindex "RCPT" "maximum number of outgoing"
23079 This option limits the number of RCPT commands that are sent in a single
23080 SMTP message transaction. Each set of addresses is treated independently, and
23081 so can cause parallel connections to the same host if &%remote_max_parallel%&
23085 .option multi_domain smtp boolean true
23086 .vindex "&$domain$&"
23087 When this option is set, the &(smtp)& transport can handle a number of
23088 addresses containing a mixture of different domains provided they all resolve
23089 to the same list of hosts. Turning the option off restricts the transport to
23090 handling only one domain at a time. This is useful if you want to use
23091 &$domain$& in an expansion for the transport, because it is set only when there
23092 is a single domain involved in a remote delivery.
23095 .option port smtp string&!! "see below"
23096 .cindex "port" "sending TCP/IP"
23097 .cindex "TCP/IP" "setting outgoing port"
23098 This option specifies the TCP/IP port on the server to which Exim connects.
23099 &*Note:*& Do not confuse this with the port that was used when a message was
23100 received, which is in &$received_port$&, formerly known as &$interface_port$&.
23101 The name was changed to minimize confusion with the outgoing port. There is no
23102 variable that contains an outgoing port.
23104 If the value of this option begins with a digit it is taken as a port number;
23105 otherwise it is looked up using &[getservbyname()]&. The default value is
23106 normally &"smtp"&, but if &%protocol%& is set to &"lmtp"&, the default is
23107 &"lmtp"&. If the expansion fails, or if a port number cannot be found, delivery
23112 .option protocol smtp string smtp
23113 .cindex "LMTP" "over TCP/IP"
23114 .cindex "ssmtp protocol" "outbound"
23115 .cindex "TLS" "SSL-on-connect outbound"
23117 If this option is set to &"lmtp"& instead of &"smtp"&, the default value for
23118 the &%port%& option changes to &"lmtp"&, and the transport operates the LMTP
23119 protocol (RFC 2033) instead of SMTP. This protocol is sometimes used for local
23120 deliveries into closed message stores. Exim also has support for running LMTP
23121 over a pipe to a local process &-- see chapter &<<CHAPLMTP>>&.
23123 If this option is set to &"smtps"&, the default vaule for the &%port%& option
23124 changes to &"smtps"&, and the transport initiates TLS immediately after
23125 connecting, as an outbound SSL-on-connect, instead of using STARTTLS to upgrade.
23126 The Internet standards bodies strongly discourage use of this mode.
23129 .option retry_include_ip_address smtp boolean true
23130 Exim normally includes both the host name and the IP address in the key it
23131 constructs for indexing retry data after a temporary delivery failure. This
23132 means that when one of several IP addresses for a host is failing, it gets
23133 tried periodically (controlled by the retry rules), but use of the other IP
23134 addresses is not affected.
23136 However, in some dialup environments hosts are assigned a different IP address
23137 each time they connect. In this situation the use of the IP address as part of
23138 the retry key leads to undesirable behaviour. Setting this option false causes
23139 Exim to use only the host name. This should normally be done on a separate
23140 instance of the &(smtp)& transport, set up specially to handle the dialup
23144 .option serialize_hosts smtp "host list&!!" unset
23145 .cindex "serializing connections"
23146 .cindex "host" "serializing connections"
23147 Because Exim operates in a distributed manner, if several messages for the same
23148 host arrive at around the same time, more than one simultaneous connection to
23149 the remote host can occur. This is not usually a problem except when there is a
23150 slow link between the hosts. In that situation it may be helpful to restrict
23151 Exim to one connection at a time. This can be done by setting
23152 &%serialize_hosts%& to match the relevant hosts.
23154 .cindex "hints database" "serializing deliveries to a host"
23155 Exim implements serialization by means of a hints database in which a record is
23156 written whenever a process connects to one of the restricted hosts. The record
23157 is deleted when the connection is completed. Obviously there is scope for
23158 records to get left lying around if there is a system or program crash. To
23159 guard against this, Exim ignores any records that are more than six hours old.
23161 If you set up this kind of serialization, you should also arrange to delete the
23162 relevant hints database whenever your system reboots. The names of the files
23163 start with &_misc_& and they are kept in the &_spool/db_& directory. There
23164 may be one or two files, depending on the type of DBM in use. The same files
23165 are used for ETRN serialization.
23168 .option size_addition smtp integer 1024
23169 .cindex "SMTP" "SIZE"
23170 .cindex "message" "size issue for transport filter"
23171 .cindex "size" "of message"
23172 .cindex "transport" "filter"
23173 .cindex "filter" "transport filter"
23174 If a remote SMTP server indicates that it supports the SIZE option of the
23175 MAIL command, Exim uses this to pass over the message size at the start of
23176 an SMTP transaction. It adds the value of &%size_addition%& to the value it
23177 sends, to allow for headers and other text that may be added during delivery by
23178 configuration options or in a transport filter. It may be necessary to increase
23179 this if a lot of text is added to messages.
23181 Alternatively, if the value of &%size_addition%& is set negative, it disables
23182 the use of the SIZE option altogether.
23185 .option tls_certificate smtp string&!! unset
23186 .cindex "TLS" "client certificate, location of"
23187 .cindex "certificate" "client, location of"
23189 .vindex "&$host_address$&"
23190 The value of this option must be the absolute path to a file which contains the
23191 client's certificate, for possible use when sending a message over an encrypted
23192 connection. The values of &$host$& and &$host_address$& are set to the name and
23193 address of the server during the expansion. See chapter &<<CHAPTLS>>& for
23196 &*Note*&: This option must be set if you want Exim to be able to use a TLS
23197 certificate when sending messages as a client. The global option of the same
23198 name specifies the certificate for Exim as a server; it is not automatically
23199 assumed that the same certificate should be used when Exim is operating as a
23203 .option tls_crl smtp string&!! unset
23204 .cindex "TLS" "client certificate revocation list"
23205 .cindex "certificate" "revocation list for client"
23206 This option specifies a certificate revocation list. The expanded value must
23207 be the name of a file that contains a CRL in PEM format.
23210 .option tls_dh_min_bits smtp integer 1024
23211 .cindex "TLS" "Diffie-Hellman minimum acceptable size"
23212 When establishing a TLS session, if a ciphersuite which uses Diffie-Hellman
23213 key agreement is negotiated, the server will provide a large prime number
23214 for use. This option establishes the minimum acceptable size of that number.
23215 If the parameter offered by the server is too small, then the TLS handshake
23218 Only supported when using GnuTLS.
23221 .option tls_privatekey smtp string&!! unset
23222 .cindex "TLS" "client private key, location of"
23224 .vindex "&$host_address$&"
23225 The value of this option must be the absolute path to a file which contains the
23226 client's private key. This is used when sending a message over an encrypted
23227 connection using a client certificate. The values of &$host$& and
23228 &$host_address$& are set to the name and address of the server during the
23229 expansion. If this option is unset, or the expansion is forced to fail, or the
23230 result is an empty string, the private key is assumed to be in the same file as
23231 the certificate. See chapter &<<CHAPTLS>>& for details of TLS.
23234 .option tls_require_ciphers smtp string&!! unset
23235 .cindex "TLS" "requiring specific ciphers"
23236 .cindex "cipher" "requiring specific"
23238 .vindex "&$host_address$&"
23239 The value of this option must be a list of permitted cipher suites, for use
23240 when setting up an outgoing encrypted connection. (There is a global option of
23241 the same name for controlling incoming connections.) The values of &$host$& and
23242 &$host_address$& are set to the name and address of the server during the
23243 expansion. See chapter &<<CHAPTLS>>& for details of TLS; note that this option
23244 is used in different ways by OpenSSL and GnuTLS (see sections
23245 &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&). For GnuTLS, the order of the
23246 ciphers is a preference order.
23250 .option tls_sni smtp string&!! unset
23251 .cindex "TLS" "Server Name Indication"
23252 .vindex "&$tls_sni$&"
23253 If this option is set then it sets the $tls_out_sni variable and causes any
23254 TLS session to pass this value as the Server Name Indication extension to
23255 the remote side, which can be used by the remote side to select an appropriate
23256 certificate and private key for the session.
23258 See &<<SECTtlssni>>& for more information.
23260 Note that for OpenSSL, this feature requires a build of OpenSSL that supports
23266 .option tls_tempfail_tryclear smtp boolean true
23267 .cindex "4&'xx'& responses" "to STARTTLS"
23268 When the server host is not in &%hosts_require_tls%&, and there is a problem in
23269 setting up a TLS session, this option determines whether or not Exim should try
23270 to deliver the message unencrypted. If it is set false, delivery to the
23271 current host is deferred; if there are other hosts, they are tried. If this
23272 option is set true, Exim attempts to deliver unencrypted after a 4&'xx'&
23273 response to STARTTLS. Also, if STARTTLS is accepted, but the subsequent
23274 TLS negotiation fails, Exim closes the current connection (because it is in an
23275 unknown state), opens a new one to the same host, and then tries the delivery
23279 .option tls_try_verify_hosts smtp "host list&!! unset
23280 .cindex "TLS" "server certificate verification"
23281 .cindex "certificate" "verification of server"
23282 This option gives a list of hosts for which, on encrypted connections,
23283 certificate verification will be tried but need not succeed.
23284 The &%tls_verify_certificates%& option must also be set.
23285 Note that unless the host is in this list
23286 TLS connections will be denied to hosts using self-signed certificates
23287 when &%tls_verify_certificates%& is set.
23288 The &$tls_out_certificate_verified$& variable is set when
23289 certificate verification succeeds.
23292 .option tls_verify_certificates smtp string&!! unset
23293 .cindex "TLS" "server certificate verification"
23294 .cindex "certificate" "verification of server"
23296 .vindex "&$host_address$&"
23297 The value of this option must be the absolute path to a file containing
23298 permitted server certificates, for use when setting up an encrypted connection.
23299 Alternatively, if you are using OpenSSL, you can set
23300 &%tls_verify_certificates%& to the name of a directory containing certificate
23301 files. This does not work with GnuTLS; the option must be set to the name of a
23302 single file if you are using GnuTLS. The values of &$host$& and
23303 &$host_address$& are set to the name and address of the server during the
23304 expansion of this option. See chapter &<<CHAPTLS>>& for details of TLS.
23306 For back-compatability,
23307 if neither tls_verify_hosts nor tls_try_verify_hosts are set
23308 and certificate verification fails the TLS connection is closed.
23311 .option tls_verify_hosts smtp "host list&!! unset
23312 .cindex "TLS" "server certificate verification"
23313 .cindex "certificate" "verification of server"
23314 This option gives a list of hosts for which. on encrypted connections,
23315 certificate verification must succeed.
23316 The &%tls_verify_certificates%& option must also be set.
23317 If both this option and &%tls_try_verify_hosts%& are unset
23318 operation is as if this option selected all hosts.
23323 .section "How the limits for the number of hosts to try are used" &&&
23325 .cindex "host" "maximum number to try"
23326 .cindex "limit" "hosts; maximum number tried"
23327 There are two options that are concerned with the number of hosts that are
23328 tried when an SMTP delivery takes place. They are &%hosts_max_try%& and
23329 &%hosts_max_try_hardlimit%&.
23332 The &%hosts_max_try%& option limits the number of hosts that are tried
23333 for a single delivery. However, despite the term &"host"& in its name, the
23334 option actually applies to each IP address independently. In other words, a
23335 multihomed host is treated as several independent hosts, just as it is for
23338 Many of the larger ISPs have multiple MX records which often point to
23339 multihomed hosts. As a result, a list of a dozen or more IP addresses may be
23340 created as a result of routing one of these domains.
23342 Trying every single IP address on such a long list does not seem sensible; if
23343 several at the top of the list fail, it is reasonable to assume there is some
23344 problem that is likely to affect all of them. Roughly speaking, the value of
23345 &%hosts_max_try%& is the maximum number that are tried before deferring the
23346 delivery. However, the logic cannot be quite that simple.
23348 Firstly, IP addresses that are skipped because their retry times have not
23349 arrived do not count, and in addition, addresses that are past their retry
23350 limits are also not counted, even when they are tried. This means that when
23351 some IP addresses are past their retry limits, more than the value of
23352 &%hosts_max_retry%& may be tried. The reason for this behaviour is to ensure
23353 that all IP addresses are considered before timing out an email address (but
23354 see below for an exception).
23356 Secondly, when the &%hosts_max_try%& limit is reached, Exim looks down the host
23357 list to see if there is a subsequent host with a different (higher valued) MX.
23358 If there is, that host is considered next, and the current IP address is used
23359 but not counted. This behaviour helps in the case of a domain with a retry rule
23360 that hardly ever delays any hosts, as is now explained:
23362 Consider the case of a long list of hosts with one MX value, and a few with a
23363 higher MX value. If &%hosts_max_try%& is small (the default is 5) only a few
23364 hosts at the top of the list are tried at first. With the default retry rule,
23365 which specifies increasing retry times, the higher MX hosts are eventually
23366 tried when those at the top of the list are skipped because they have not
23367 reached their retry times.
23369 However, it is common practice to put a fixed short retry time on domains for
23370 large ISPs, on the grounds that their servers are rarely down for very long.
23371 Unfortunately, these are exactly the domains that tend to resolve to long lists
23372 of hosts. The short retry time means that the lowest MX hosts are tried every
23373 time. The attempts may be in a different order because of random sorting, but
23374 without the special MX check, the higher MX hosts would never be tried until
23375 all the lower MX hosts had timed out (which might be several days), because
23376 there are always some lower MX hosts that have reached their retry times. With
23377 the special check, Exim considers at least one IP address from each MX value at
23378 every delivery attempt, even if the &%hosts_max_try%& limit has already been
23381 The above logic means that &%hosts_max_try%& is not a hard limit, and in
23382 particular, Exim normally eventually tries all the IP addresses before timing
23383 out an email address. When &%hosts_max_try%& was implemented, this seemed a
23384 reasonable thing to do. Recently, however, some lunatic DNS configurations have
23385 been set up with hundreds of IP addresses for some domains. It can
23386 take a very long time indeed for an address to time out in these cases.
23388 The &%hosts_max_try_hardlimit%& option was added to help with this problem.
23389 Exim never tries more than this number of IP addresses; if it hits this limit
23390 and they are all timed out, the email address is bounced, even though not all
23391 possible IP addresses have been tried.
23392 .ecindex IIDsmttra1
23393 .ecindex IIDsmttra2
23399 . ////////////////////////////////////////////////////////////////////////////
23400 . ////////////////////////////////////////////////////////////////////////////
23402 .chapter "Address rewriting" "CHAPrewrite"
23403 .scindex IIDaddrew "rewriting" "addresses"
23404 There are some circumstances in which Exim automatically rewrites domains in
23405 addresses. The two most common are when an address is given without a domain
23406 (referred to as an &"unqualified address"&) or when an address contains an
23407 abbreviated domain that is expanded by DNS lookup.
23409 Unqualified envelope addresses are accepted only for locally submitted
23410 messages, or for messages that are received from hosts matching
23411 &%sender_unqualified_hosts%& or &%recipient_unqualified_hosts%&, as
23412 appropriate. Unqualified addresses in header lines are qualified if they are in
23413 locally submitted messages, or messages from hosts that are permitted to send
23414 unqualified envelope addresses. Otherwise, unqualified addresses in header
23415 lines are neither qualified nor rewritten.
23417 One situation in which Exim does &'not'& automatically rewrite a domain is
23418 when it is the name of a CNAME record in the DNS. The older RFCs suggest that
23419 such a domain should be rewritten using the &"canonical"& name, and some MTAs
23420 do this. The new RFCs do not contain this suggestion.
23423 .section "Explicitly configured address rewriting" "SECID147"
23424 This chapter describes the rewriting rules that can be used in the
23425 main rewrite section of the configuration file, and also in the generic
23426 &%headers_rewrite%& option that can be set on any transport.
23428 Some people believe that configured address rewriting is a Mortal Sin.
23429 Others believe that life is not possible without it. Exim provides the
23430 facility; you do not have to use it.
23432 The main rewriting rules that appear in the &"rewrite"& section of the
23433 configuration file are applied to addresses in incoming messages, both envelope
23434 addresses and addresses in header lines. Each rule specifies the types of
23435 address to which it applies.
23437 Whether or not addresses in header lines are rewritten depends on the origin of
23438 the headers and the type of rewriting. Global rewriting, that is, rewriting
23439 rules from the rewrite section of the configuration file, is applied only to
23440 those headers that were received with the message. Header lines that are added
23441 by ACLs or by a system filter or by individual routers or transports (which
23442 are specific to individual recipient addresses) are not rewritten by the global
23445 Rewriting at transport time, by means of the &%headers_rewrite%& option,
23446 applies all headers except those added by routers and transports. That is, as
23447 well as the headers that were received with the message, it also applies to
23448 headers that were added by an ACL or a system filter.
23451 In general, rewriting addresses from your own system or domain has some
23452 legitimacy. Rewriting other addresses should be done only with great care and
23453 in special circumstances. The author of Exim believes that rewriting should be
23454 used sparingly, and mainly for &"regularizing"& addresses in your own domains.
23455 Although it can sometimes be used as a routing tool, this is very strongly
23458 There are two commonly encountered circumstances where rewriting is used, as
23459 illustrated by these examples:
23462 The company whose domain is &'hitch.fict.example'& has a number of hosts that
23463 exchange mail with each other behind a firewall, but there is only a single
23464 gateway to the outer world. The gateway rewrites &'*.hitch.fict.example'& as
23465 &'hitch.fict.example'& when sending mail off-site.
23467 A host rewrites the local parts of its own users so that, for example,
23468 &'fp42@hitch.fict.example'& becomes &'Ford.Prefect@hitch.fict.example'&.
23473 .section "When does rewriting happen?" "SECID148"
23474 .cindex "rewriting" "timing of"
23475 .cindex "&ACL;" "rewriting addresses in"
23476 Configured address rewriting can take place at several different stages of a
23477 message's processing.
23479 .vindex "&$sender_address$&"
23480 At the start of an ACL for MAIL, the sender address may have been rewritten
23481 by a special SMTP-time rewrite rule (see section &<<SECTrewriteS>>&), but no
23482 ordinary rewrite rules have yet been applied. If, however, the sender address
23483 is verified in the ACL, it is rewritten before verification, and remains
23484 rewritten thereafter. The subsequent value of &$sender_address$& is the
23485 rewritten address. This also applies if sender verification happens in a
23486 RCPT ACL. Otherwise, when the sender address is not verified, it is
23487 rewritten as soon as a message's header lines have been received.
23489 .vindex "&$domain$&"
23490 .vindex "&$local_part$&"
23491 Similarly, at the start of an ACL for RCPT, the current recipient's address
23492 may have been rewritten by a special SMTP-time rewrite rule, but no ordinary
23493 rewrite rules have yet been applied to it. However, the behaviour is different
23494 from the sender address when a recipient is verified. The address is rewritten
23495 for the verification, but the rewriting is not remembered at this stage. The
23496 value of &$local_part$& and &$domain$& after verification are always the same
23497 as they were before (that is, they contain the unrewritten &-- except for
23498 SMTP-time rewriting &-- address).
23500 As soon as a message's header lines have been received, all the envelope
23501 recipient addresses are permanently rewritten, and rewriting is also applied to
23502 the addresses in the header lines (if configured). This happens before adding
23503 any header lines that were specified in MAIL or RCPT ACLs, and
23504 .cindex "&[local_scan()]& function" "address rewriting; timing of"
23505 before the DATA ACL and &[local_scan()]& functions are run.
23507 When an address is being routed, either for delivery or for verification,
23508 rewriting is applied immediately to child addresses that are generated by
23509 redirection, unless &%no_rewrite%& is set on the router.
23511 .cindex "envelope sender" "rewriting at transport time"
23512 .cindex "rewriting" "at transport time"
23513 .cindex "header lines" "rewriting at transport time"
23514 At transport time, additional rewriting of addresses in header lines can be
23515 specified by setting the generic &%headers_rewrite%& option on a transport.
23516 This option contains rules that are identical in form to those in the rewrite
23517 section of the configuration file. They are applied to the original message
23518 header lines and any that were added by ACLs or a system filter. They are not
23519 applied to header lines that are added by routers or the transport.
23521 The outgoing envelope sender can be rewritten by means of the &%return_path%&
23522 transport option. However, it is not possible to rewrite envelope recipients at
23528 .section "Testing the rewriting rules that apply on input" "SECID149"
23529 .cindex "rewriting" "testing"
23530 .cindex "testing" "rewriting"
23531 Exim's input rewriting configuration appears in a part of the run time
23532 configuration file headed by &"begin rewrite"&. It can be tested by the
23533 &%-brw%& command line option. This takes an address (which can be a full RFC
23534 2822 address) as its argument. The output is a list of how the address would be
23535 transformed by the rewriting rules for each of the different places it might
23536 appear in an incoming message, that is, for each different header and for the
23537 envelope sender and recipient fields. For example,
23539 exim -brw ph10@exim.workshop.example
23541 might produce the output
23543 sender: Philip.Hazel@exim.workshop.example
23544 from: Philip.Hazel@exim.workshop.example
23545 to: ph10@exim.workshop.example
23546 cc: ph10@exim.workshop.example
23547 bcc: ph10@exim.workshop.example
23548 reply-to: Philip.Hazel@exim.workshop.example
23549 env-from: Philip.Hazel@exim.workshop.example
23550 env-to: ph10@exim.workshop.example
23552 which shows that rewriting has been set up for that address when used in any of
23553 the source fields, but not when it appears as a recipient address. At the
23554 present time, there is no equivalent way of testing rewriting rules that are
23555 set for a particular transport.
23558 .section "Rewriting rules" "SECID150"
23559 .cindex "rewriting" "rules"
23560 The rewrite section of the configuration file consists of lines of rewriting
23563 <&'source pattern'&> <&'replacement'&> <&'flags'&>
23565 Rewriting rules that are specified for the &%headers_rewrite%& generic
23566 transport option are given as a colon-separated list. Each item in the list
23567 takes the same form as a line in the main rewriting configuration (except that
23568 any colons must be doubled, of course).
23570 The formats of source patterns and replacement strings are described below.
23571 Each is terminated by white space, unless enclosed in double quotes, in which
23572 case normal quoting conventions apply inside the quotes. The flags are single
23573 characters which may appear in any order. Spaces and tabs between them are
23576 For each address that could potentially be rewritten, the rules are scanned in
23577 order, and replacements for the address from earlier rules can themselves be
23578 replaced by later rules (but see the &"q"& and &"R"& flags).
23580 The order in which addresses are rewritten is undefined, may change between
23581 releases, and must not be relied on, with one exception: when a message is
23582 received, the envelope sender is always rewritten first, before any header
23583 lines are rewritten. For example, the replacement string for a rewrite of an
23584 address in &'To:'& must not assume that the message's address in &'From:'& has
23585 (or has not) already been rewritten. However, a rewrite of &'From:'& may assume
23586 that the envelope sender has already been rewritten.
23588 .vindex "&$domain$&"
23589 .vindex "&$local_part$&"
23590 The variables &$local_part$& and &$domain$& can be used in the replacement
23591 string to refer to the address that is being rewritten. Note that lookup-driven
23592 rewriting can be done by a rule of the form
23596 where the lookup key uses &$1$& and &$2$& or &$local_part$& and &$domain$& to
23597 refer to the address that is being rewritten.
23600 .section "Rewriting patterns" "SECID151"
23601 .cindex "rewriting" "patterns"
23602 .cindex "address list" "in a rewriting pattern"
23603 The source pattern in a rewriting rule is any item which may appear in an
23604 address list (see section &<<SECTaddresslist>>&). It is in fact processed as a
23605 single-item address list, which means that it is expanded before being tested
23606 against the address. As always, if you use a regular expression as a pattern,
23607 you must take care to escape dollar and backslash characters, or use the &`\N`&
23608 facility to suppress string expansion within the regular expression.
23610 Domains in patterns should be given in lower case. Local parts in patterns are
23611 case-sensitive. If you want to do case-insensitive matching of local parts, you
23612 can use a regular expression that starts with &`^(?i)`&.
23614 .cindex "numerical variables (&$1$& &$2$& etc)" "in rewriting rules"
23615 After matching, the numerical variables &$1$&, &$2$&, etc. may be set,
23616 depending on the type of match which occurred. These can be used in the
23617 replacement string to insert portions of the incoming address. &$0$& always
23618 refers to the complete incoming address. When a regular expression is used, the
23619 numerical variables are set from its capturing subexpressions. For other types
23620 of pattern they are set as follows:
23623 If a local part or domain starts with an asterisk, the numerical variables
23624 refer to the character strings matched by asterisks, with &$1$& associated with
23625 the first asterisk, and &$2$& with the second, if present. For example, if the
23628 *queen@*.fict.example
23630 is matched against the address &'hearts-queen@wonderland.fict.example'& then
23632 $0 = hearts-queen@wonderland.fict.example
23636 Note that if the local part does not start with an asterisk, but the domain
23637 does, it is &$1$& that contains the wild part of the domain.
23640 If the domain part of the pattern is a partial lookup, the wild and fixed parts
23641 of the domain are placed in the next available numerical variables. Suppose,
23642 for example, that the address &'foo@bar.baz.example'& is processed by a
23643 rewriting rule of the form
23645 &`*@partial-dbm;/some/dbm/file`& <&'replacement string'&>
23647 and the key in the file that matches the domain is &`*.baz.example`&. Then
23653 If the address &'foo@baz.example'& is looked up, this matches the same
23654 wildcard file entry, and in this case &$2$& is set to the empty string, but
23655 &$3$& is still set to &'baz.example'&. If a non-wild key is matched in a
23656 partial lookup, &$2$& is again set to the empty string and &$3$& is set to the
23657 whole domain. For non-partial domain lookups, no numerical variables are set.
23661 .section "Rewriting replacements" "SECID152"
23662 .cindex "rewriting" "replacements"
23663 If the replacement string for a rule is a single asterisk, addresses that
23664 match the pattern and the flags are &'not'& rewritten, and no subsequent
23665 rewriting rules are scanned. For example,
23667 hatta@lookingglass.fict.example * f
23669 specifies that &'hatta@lookingglass.fict.example'& is never to be rewritten in
23672 .vindex "&$domain$&"
23673 .vindex "&$local_part$&"
23674 If the replacement string is not a single asterisk, it is expanded, and must
23675 yield a fully qualified address. Within the expansion, the variables
23676 &$local_part$& and &$domain$& refer to the address that is being rewritten.
23677 Any letters they contain retain their original case &-- they are not lower
23678 cased. The numerical variables are set up according to the type of pattern that
23679 matched the address, as described above. If the expansion is forced to fail by
23680 the presence of &"fail"& in a conditional or lookup item, rewriting by the
23681 current rule is abandoned, but subsequent rules may take effect. Any other
23682 expansion failure causes the entire rewriting operation to be abandoned, and an
23683 entry written to the panic log.
23687 .section "Rewriting flags" "SECID153"
23688 There are three different kinds of flag that may appear on rewriting rules:
23691 Flags that specify which headers and envelope addresses to rewrite: E, F, T, b,
23694 A flag that specifies rewriting at SMTP time: S.
23696 Flags that control the rewriting process: Q, q, R, w.
23699 For rules that are part of the &%headers_rewrite%& generic transport option,
23700 E, F, T, and S are not permitted.
23704 .section "Flags specifying which headers and envelope addresses to rewrite" &&&
23706 .cindex "rewriting" "flags"
23707 If none of the following flag letters, nor the &"S"& flag (see section
23708 &<<SECTrewriteS>>&) are present, a main rewriting rule applies to all headers
23709 and to both the sender and recipient fields of the envelope, whereas a
23710 transport-time rewriting rule just applies to all headers. Otherwise, the
23711 rewriting rule is skipped unless the relevant addresses are being processed.
23713 &`E`& rewrite all envelope fields
23714 &`F`& rewrite the envelope From field
23715 &`T`& rewrite the envelope To field
23716 &`b`& rewrite the &'Bcc:'& header
23717 &`c`& rewrite the &'Cc:'& header
23718 &`f`& rewrite the &'From:'& header
23719 &`h`& rewrite all headers
23720 &`r`& rewrite the &'Reply-To:'& header
23721 &`s`& rewrite the &'Sender:'& header
23722 &`t`& rewrite the &'To:'& header
23724 "All headers" means all of the headers listed above that can be selected
23725 individually, plus their &'Resent-'& versions. It does not include
23726 other headers such as &'Subject:'& etc.
23728 You should be particularly careful about rewriting &'Sender:'& headers, and
23729 restrict this to special known cases in your own domains.
23732 .section "The SMTP-time rewriting flag" "SECTrewriteS"
23733 .cindex "SMTP" "rewriting malformed addresses"
23734 .cindex "RCPT" "rewriting argument of"
23735 .cindex "MAIL" "rewriting argument of"
23736 The rewrite flag &"S"& specifies a rewrite of incoming envelope addresses at
23737 SMTP time, as soon as an address is received in a MAIL or RCPT command, and
23738 before any other processing; even before syntax checking. The pattern is
23739 required to be a regular expression, and it is matched against the whole of the
23740 data for the command, including any surrounding angle brackets.
23742 .vindex "&$domain$&"
23743 .vindex "&$local_part$&"
23744 This form of rewrite rule allows for the handling of addresses that are not
23745 compliant with RFCs 2821 and 2822 (for example, &"bang paths"& in batched SMTP
23746 input). Because the input is not required to be a syntactically valid address,
23747 the variables &$local_part$& and &$domain$& are not available during the
23748 expansion of the replacement string. The result of rewriting replaces the
23749 original address in the MAIL or RCPT command.
23752 .section "Flags controlling the rewriting process" "SECID155"
23753 There are four flags which control the way the rewriting process works. These
23754 take effect only when a rule is invoked, that is, when the address is of the
23755 correct type (matches the flags) and matches the pattern:
23758 If the &"Q"& flag is set on a rule, the rewritten address is permitted to be an
23759 unqualified local part. It is qualified with &%qualify_recipient%&. In the
23760 absence of &"Q"& the rewritten address must always include a domain.
23762 If the &"q"& flag is set on a rule, no further rewriting rules are considered,
23763 even if no rewriting actually takes place because of a &"fail"& in the
23764 expansion. The &"q"& flag is not effective if the address is of the wrong type
23765 (does not match the flags) or does not match the pattern.
23767 The &"R"& flag causes a successful rewriting rule to be re-applied to the new
23768 address, up to ten times. It can be combined with the &"q"& flag, to stop
23769 rewriting once it fails to match (after at least one successful rewrite).
23771 .cindex "rewriting" "whole addresses"
23772 When an address in a header is rewritten, the rewriting normally applies only
23773 to the working part of the address, with any comments and RFC 2822 &"phrase"&
23774 left unchanged. For example, rewriting might change
23776 From: Ford Prefect <fp42@restaurant.hitch.fict.example>
23780 From: Ford Prefect <prefectf@hitch.fict.example>
23783 Sometimes there is a need to replace the whole address item, and this can be
23784 done by adding the flag letter &"w"& to a rule. If this is set on a rule that
23785 causes an address in a header line to be rewritten, the entire address is
23786 replaced, not just the working part. The replacement must be a complete RFC
23787 2822 address, including the angle brackets if necessary. If text outside angle
23788 brackets contains a character whose value is greater than 126 or less than 32
23789 (except for tab), the text is encoded according to RFC 2047. The character set
23790 is taken from &%headers_charset%&, which defaults to ISO-8859-1.
23792 When the &"w"& flag is set on a rule that causes an envelope address to be
23793 rewritten, all but the working part of the replacement address is discarded.
23797 .section "Rewriting examples" "SECID156"
23798 Here is an example of the two common rewriting paradigms:
23800 *@*.hitch.fict.example $1@hitch.fict.example
23801 *@hitch.fict.example ${lookup{$1}dbm{/etc/realnames}\
23802 {$value}fail}@hitch.fict.example bctfrF
23804 Note the use of &"fail"& in the lookup expansion in the second rule, forcing
23805 the string expansion to fail if the lookup does not succeed. In this context it
23806 has the effect of leaving the original address unchanged, but Exim goes on to
23807 consider subsequent rewriting rules, if any, because the &"q"& flag is not
23808 present in that rule. An alternative to &"fail"& would be to supply &$1$&
23809 explicitly, which would cause the rewritten address to be the same as before,
23810 at the cost of a small bit of processing. Not supplying either of these is an
23811 error, since the rewritten address would then contain no local part.
23813 The first example above replaces the domain with a superior, more general
23814 domain. This may not be desirable for certain local parts. If the rule
23816 root@*.hitch.fict.example *
23818 were inserted before the first rule, rewriting would be suppressed for the
23819 local part &'root'& at any domain ending in &'hitch.fict.example'&.
23821 Rewriting can be made conditional on a number of tests, by making use of
23822 &${if$& in the expansion item. For example, to apply a rewriting rule only to
23823 messages that originate outside the local host:
23825 *@*.hitch.fict.example "${if !eq {$sender_host_address}{}\
23826 {$1@hitch.fict.example}fail}"
23828 The replacement string is quoted in this example because it contains white
23831 .cindex "rewriting" "bang paths"
23832 .cindex "bang paths" "rewriting"
23833 Exim does not handle addresses in the form of &"bang paths"&. If it sees such
23834 an address it treats it as an unqualified local part which it qualifies with
23835 the local qualification domain (if the source of the message is local or if the
23836 remote host is permitted to send unqualified addresses). Rewriting can
23837 sometimes be used to handle simple bang paths with a fixed number of
23838 components. For example, the rule
23840 \N^([^!]+)!(.*)@your.domain.example$\N $2@$1
23842 rewrites a two-component bang path &'host.name!user'& as the domain address
23843 &'user@host.name'&. However, there is a security implication in using this as
23844 a global rewriting rule for envelope addresses. It can provide a backdoor
23845 method for using your system as a relay, because the incoming addresses appear
23846 to be local. If the bang path addresses are received via SMTP, it is safer to
23847 use the &"S"& flag to rewrite them as they are received, so that relay checking
23848 can be done on the rewritten addresses.
23855 . ////////////////////////////////////////////////////////////////////////////
23856 . ////////////////////////////////////////////////////////////////////////////
23858 .chapter "Retry configuration" "CHAPretry"
23859 .scindex IIDretconf1 "retry" "configuration, description of"
23860 .scindex IIDregconf2 "configuration file" "retry section"
23861 The &"retry"& section of the runtime configuration file contains a list of
23862 retry rules that control how often Exim tries to deliver messages that cannot
23863 be delivered at the first attempt. If there are no retry rules (the section is
23864 empty or not present), there are no retries. In this situation, temporary
23865 errors are treated as permanent. The default configuration contains a single,
23866 general-purpose retry rule (see section &<<SECID57>>&). The &%-brt%& command
23867 line option can be used to test which retry rule will be used for a given
23868 address, domain and error.
23870 The most common cause of retries is temporary failure to deliver to a remote
23871 host because the host is down, or inaccessible because of a network problem.
23872 Exim's retry processing in this case is applied on a per-host (strictly, per IP
23873 address) basis, not on a per-message basis. Thus, if one message has recently
23874 been delayed, delivery of a new message to the same host is not immediately
23875 tried, but waits for the host's retry time to arrive. If the &%retry_defer%&
23876 log selector is set, the message
23877 .cindex "retry" "time not reached"
23878 &"retry time not reached"& is written to the main log whenever a delivery is
23879 skipped for this reason. Section &<<SECToutSMTPerr>>& contains more details of
23880 the handling of errors during remote deliveries.
23882 Retry processing applies to routing as well as to delivering, except as covered
23883 in the next paragraph. The retry rules do not distinguish between these
23884 actions. It is not possible, for example, to specify different behaviour for
23885 failures to route the domain &'snark.fict.example'& and failures to deliver to
23886 the host &'snark.fict.example'&. I didn't think anyone would ever need this
23887 added complication, so did not implement it. However, although they share the
23888 same retry rule, the actual retry times for routing and transporting a given
23889 domain are maintained independently.
23891 When a delivery is not part of a queue run (typically an immediate delivery on
23892 receipt of a message), the routers are always run, and local deliveries are
23893 always attempted, even if retry times are set for them. This makes for better
23894 behaviour if one particular message is causing problems (for example, causing
23895 quota overflow, or provoking an error in a filter file). If such a delivery
23896 suffers a temporary failure, the retry data is updated as normal, and
23897 subsequent delivery attempts from queue runs occur only when the retry time for
23898 the local address is reached.
23900 .section "Changing retry rules" "SECID157"
23901 If you change the retry rules in your configuration, you should consider
23902 whether or not to delete the retry data that is stored in Exim's spool area in
23903 files with names like &_db/retry_&. Deleting any of Exim's hints files is
23904 always safe; that is why they are called &"hints"&.
23906 The hints retry data contains suggested retry times based on the previous
23907 rules. In the case of a long-running problem with a remote host, it might
23908 record the fact that the host has timed out. If your new rules increase the
23909 timeout time for such a host, you should definitely remove the old retry data
23910 and let Exim recreate it, based on the new rules. Otherwise Exim might bounce
23911 messages that it should now be retaining.
23915 .section "Format of retry rules" "SECID158"
23916 .cindex "retry" "rules"
23917 Each retry rule occupies one line and consists of three or four parts,
23918 separated by white space: a pattern, an error name, an optional list of sender
23919 addresses, and a list of retry parameters. The pattern and sender lists must be
23920 enclosed in double quotes if they contain white space. The rules are searched
23921 in order until one is found where the pattern, error name, and sender list (if
23922 present) match the failing host or address, the error that occurred, and the
23923 message's sender, respectively.
23926 The pattern is any single item that may appear in an address list (see section
23927 &<<SECTaddresslist>>&). It is in fact processed as a one-item address list,
23928 which means that it is expanded before being tested against the address that
23929 has been delayed. A negated address list item is permitted. Address
23930 list processing treats a plain domain name as if it were preceded by &"*@"&,
23931 which makes it possible for many retry rules to start with just a domain. For
23934 lookingglass.fict.example * F,24h,30m;
23936 provides a rule for any address in the &'lookingglass.fict.example'& domain,
23939 alice@lookingglass.fict.example * F,24h,30m;
23941 applies only to temporary failures involving the local part &%alice%&.
23942 In practice, almost all rules start with a domain name pattern without a local
23945 .cindex "regular expressions" "in retry rules"
23946 &*Warning*&: If you use a regular expression in a retry rule pattern, it
23947 must match a complete address, not just a domain, because that is how regular
23948 expressions work in address lists.
23950 &`^\Nxyz\d+\.abc\.example$\N * G,1h,10m,2`& &%Wrong%&
23951 &`^\N[^@]+@xyz\d+\.abc\.example$\N * G,1h,10m,2`& &%Right%&
23955 .section "Choosing which retry rule to use for address errors" "SECID159"
23956 When Exim is looking for a retry rule after a routing attempt has failed (for
23957 example, after a DNS timeout), each line in the retry configuration is tested
23958 against the complete address only if &%retry_use_local_part%& is set for the
23959 router. Otherwise, only the domain is used, except when matching against a
23960 regular expression, when the local part of the address is replaced with &"*"&.
23961 A domain on its own can match a domain pattern, or a pattern that starts with
23962 &"*@"&. By default, &%retry_use_local_part%& is true for routers where
23963 &%check_local_user%& is true, and false for other routers.
23965 Similarly, when Exim is looking for a retry rule after a local delivery has
23966 failed (for example, after a mailbox full error), each line in the retry
23967 configuration is tested against the complete address only if
23968 &%retry_use_local_part%& is set for the transport (it defaults true for all
23971 .cindex "4&'xx'& responses" "retry rules for"
23972 However, when Exim is looking for a retry rule after a remote delivery attempt
23973 suffers an address error (a 4&'xx'& SMTP response for a recipient address), the
23974 whole address is always used as the key when searching the retry rules. The
23975 rule that is found is used to create a retry time for the combination of the
23976 failing address and the message's sender. It is the combination of sender and
23977 recipient that is delayed in subsequent queue runs until its retry time is
23978 reached. You can delay the recipient without regard to the sender by setting
23979 &%address_retry_include_sender%& false in the &(smtp)& transport but this can
23980 lead to problems with servers that regularly issue 4&'xx'& responses to RCPT
23985 .section "Choosing which retry rule to use for host and message errors" &&&
23987 For a temporary error that is not related to an individual address (for
23988 example, a connection timeout), each line in the retry configuration is checked
23989 twice. First, the name of the remote host is used as a domain name (preceded by
23990 &"*@"& when matching a regular expression). If this does not match the line,
23991 the domain from the email address is tried in a similar fashion. For example,
23992 suppose the MX records for &'a.b.c.example'& are
23994 a.b.c.example MX 5 x.y.z.example
23998 and the retry rules are
24000 p.q.r.example * F,24h,30m;
24001 a.b.c.example * F,4d,45m;
24003 and a delivery to the host &'x.y.z.example'& suffers a connection failure. The
24004 first rule matches neither the host nor the domain, so Exim looks at the second
24005 rule. This does not match the host, but it does match the domain, so it is used
24006 to calculate the retry time for the host &'x.y.z.example'&. Meanwhile, Exim
24007 tries to deliver to &'p.q.r.example'&. If this also suffers a host error, the
24008 first retry rule is used, because it matches the host.
24010 In other words, temporary failures to deliver to host &'p.q.r.example'& use the
24011 first rule to determine retry times, but for all the other hosts for the domain
24012 &'a.b.c.example'&, the second rule is used. The second rule is also used if
24013 routing to &'a.b.c.example'& suffers a temporary failure.
24015 &*Note*&: The host name is used when matching the patterns, not its IP address.
24016 However, if a message is routed directly to an IP address without the use of a
24017 host name, for example, if a &(manualroute)& router contains a setting such as:
24019 route_list = *.a.example 192.168.34.23
24021 then the &"host name"& that is used when searching for a retry rule is the
24022 textual form of the IP address.
24024 .section "Retry rules for specific errors" "SECID161"
24025 .cindex "retry" "specific errors; specifying"
24026 The second field in a retry rule is the name of a particular error, or an
24027 asterisk, which matches any error. The errors that can be tested for are:
24030 .vitem &%auth_failed%&
24031 Authentication failed when trying to send to a host in the
24032 &%hosts_require_auth%& list in an &(smtp)& transport.
24034 .vitem &%data_4xx%&
24035 A 4&'xx'& error was received for an outgoing DATA command, either immediately
24036 after the command, or after sending the message's data.
24038 .vitem &%mail_4xx%&
24039 A 4&'xx'& error was received for an outgoing MAIL command.
24041 .vitem &%rcpt_4xx%&
24042 A 4&'xx'& error was received for an outgoing RCPT command.
24045 For the three 4&'xx'& errors, either the first or both of the x's can be given
24046 as specific digits, for example: &`mail_45x`& or &`rcpt_436`&. For example, to
24047 recognize 452 errors given to RCPT commands for addresses in a certain domain,
24048 and have retries every ten minutes with a one-hour timeout, you could set up a
24049 retry rule of this form:
24051 the.domain.name rcpt_452 F,1h,10m
24053 These errors apply to both outgoing SMTP (the &(smtp)& transport) and outgoing
24054 LMTP (either the &(lmtp)& transport, or the &(smtp)& transport in LMTP mode).
24057 .vitem &%lost_connection%&
24058 A server unexpectedly closed the SMTP connection. There may, of course,
24059 legitimate reasons for this (host died, network died), but if it repeats a lot
24060 for the same host, it indicates something odd.
24062 .vitem &%refused_MX%&
24063 A connection to a host obtained from an MX record was refused.
24065 .vitem &%refused_A%&
24066 A connection to a host not obtained from an MX record was refused.
24069 A connection was refused.
24071 .vitem &%timeout_connect_MX%&
24072 A connection attempt to a host obtained from an MX record timed out.
24074 .vitem &%timeout_connect_A%&
24075 A connection attempt to a host not obtained from an MX record timed out.
24077 .vitem &%timeout_connect%&
24078 A connection attempt timed out.
24080 .vitem &%timeout_MX%&
24081 There was a timeout while connecting or during an SMTP session with a host
24082 obtained from an MX record.
24084 .vitem &%timeout_A%&
24085 There was a timeout while connecting or during an SMTP session with a host not
24086 obtained from an MX record.
24089 There was a timeout while connecting or during an SMTP session.
24091 .vitem &%tls_required%&
24092 The server was required to use TLS (it matched &%hosts_require_tls%& in the
24093 &(smtp)& transport), but either did not offer TLS, or it responded with 4&'xx'&
24094 to STARTTLS, or there was a problem setting up the TLS connection.
24097 A mailbox quota was exceeded in a local delivery by the &(appendfile)&
24100 .vitem &%quota_%&<&'time'&>
24101 .cindex "quota" "error testing in retry rule"
24102 .cindex "retry" "quota error testing"
24103 A mailbox quota was exceeded in a local delivery by the &(appendfile)&
24104 transport, and the mailbox has not been accessed for <&'time'&>. For example,
24105 &'quota_4d'& applies to a quota error when the mailbox has not been accessed
24109 .cindex "mailbox" "time of last read"
24110 The idea of &%quota_%&<&'time'&> is to make it possible to have shorter
24111 timeouts when the mailbox is full and is not being read by its owner. Ideally,
24112 it should be based on the last time that the user accessed the mailbox.
24113 However, it is not always possible to determine this. Exim uses the following
24117 If the mailbox is a single file, the time of last access (the &"atime"&) is
24118 used. As no new messages are being delivered (because the mailbox is over
24119 quota), Exim does not access the file, so this is the time of last user access.
24121 .cindex "maildir format" "time of last read"
24122 For a maildir delivery, the time of last modification of the &_new_&
24123 subdirectory is used. As the mailbox is over quota, no new files are created in
24124 the &_new_& subdirectory, because no new messages are being delivered. Any
24125 change to the &_new_& subdirectory is therefore assumed to be the result of an
24126 MUA moving a new message to the &_cur_& directory when it is first read. The
24127 time that is used is therefore the last time that the user read a new message.
24129 For other kinds of multi-file mailbox, the time of last access cannot be
24130 obtained, so a retry rule that uses this type of error field is never matched.
24133 The quota errors apply both to system-enforced quotas and to Exim's own quota
24134 mechanism in the &(appendfile)& transport. The &'quota'& error also applies
24135 when a local delivery is deferred because a partition is full (the ENOSPC
24140 .section "Retry rules for specified senders" "SECID162"
24141 .cindex "retry" "rules; sender-specific"
24142 You can specify retry rules that apply only when the failing message has a
24143 specific sender. In particular, this can be used to define retry rules that
24144 apply only to bounce messages. The third item in a retry rule can be of this
24147 &`senders=`&<&'address list'&>
24149 The retry timings themselves are then the fourth item. For example:
24151 * rcpt_4xx senders=: F,1h,30m
24153 matches recipient 4&'xx'& errors for bounce messages sent to any address at any
24154 host. If the address list contains white space, it must be enclosed in quotes.
24157 a.domain rcpt_452 senders="xb.dom : yc.dom" G,8h,10m,1.5
24159 &*Warning*&: This facility can be unhelpful if it is used for host errors
24160 (which do not depend on the recipient). The reason is that the sender is used
24161 only to match the retry rule. Once the rule has been found for a host error,
24162 its contents are used to set a retry time for the host, and this will apply to
24163 all messages, not just those with specific senders.
24165 When testing retry rules using &%-brt%&, you can supply a sender using the
24166 &%-f%& command line option, like this:
24168 exim -f "" -brt user@dom.ain
24170 If you do not set &%-f%& with &%-brt%&, a retry rule that contains a senders
24171 list is never matched.
24177 .section "Retry parameters" "SECID163"
24178 .cindex "retry" "parameters in rules"
24179 The third (or fourth, if a senders list is present) field in a retry rule is a
24180 sequence of retry parameter sets, separated by semicolons. Each set consists of
24182 <&'letter'&>,<&'cutoff time'&>,<&'arguments'&>
24184 The letter identifies the algorithm for computing a new retry time; the cutoff
24185 time is the time beyond which this algorithm no longer applies, and the
24186 arguments vary the algorithm's action. The cutoff time is measured from the
24187 time that the first failure for the domain (combined with the local part if
24188 relevant) was detected, not from the time the message was received.
24190 .cindex "retry" "algorithms"
24191 .cindex "retry" "fixed intervals"
24192 .cindex "retry" "increasing intervals"
24193 .cindex "retry" "random intervals"
24194 The available algorithms are:
24197 &'F'&: retry at fixed intervals. There is a single time parameter specifying
24200 &'G'&: retry at geometrically increasing intervals. The first argument
24201 specifies a starting value for the interval, and the second a multiplier, which
24202 is used to increase the size of the interval at each retry.
24204 &'H'&: retry at randomized intervals. The arguments are as for &'G'&. For each
24205 retry, the previous interval is multiplied by the factor in order to get a
24206 maximum for the next interval. The minimum interval is the first argument of
24207 the parameter, and an actual interval is chosen randomly between them. Such a
24208 rule has been found to be helpful in cluster configurations when all the
24209 members of the cluster restart at once, and may therefore synchronize their
24210 queue processing times.
24213 When computing the next retry time, the algorithm definitions are scanned in
24214 order until one whose cutoff time has not yet passed is reached. This is then
24215 used to compute a new retry time that is later than the current time. In the
24216 case of fixed interval retries, this simply means adding the interval to the
24217 current time. For geometrically increasing intervals, retry intervals are
24218 computed from the rule's parameters until one that is greater than the previous
24219 interval is found. The main configuration variable
24220 .cindex "limit" "retry interval"
24221 .cindex "retry" "interval, maximum"
24222 .oindex "&%retry_interval_max%&"
24223 &%retry_interval_max%& limits the maximum interval between retries. It
24224 cannot be set greater than &`24h`&, which is its default value.
24226 A single remote domain may have a number of hosts associated with it, and each
24227 host may have more than one IP address. Retry algorithms are selected on the
24228 basis of the domain name, but are applied to each IP address independently. If,
24229 for example, a host has two IP addresses and one is unusable, Exim will
24230 generate retry times for it and will not try to use it until its next retry
24231 time comes. Thus the good IP address is likely to be tried first most of the
24234 .cindex "hints database" "use for retrying"
24235 Retry times are hints rather than promises. Exim does not make any attempt to
24236 run deliveries exactly at the computed times. Instead, a queue runner process
24237 starts delivery processes for delayed messages periodically, and these attempt
24238 new deliveries only for those addresses that have passed their next retry time.
24239 If a new message arrives for a deferred address, an immediate delivery attempt
24240 occurs only if the address has passed its retry time. In the absence of new
24241 messages, the minimum time between retries is the interval between queue runner
24242 processes. There is not much point in setting retry times of five minutes if
24243 your queue runners happen only once an hour, unless there are a significant
24244 number of incoming messages (which might be the case on a system that is
24245 sending everything to a smart host, for example).
24247 The data in the retry hints database can be inspected by using the
24248 &'exim_dumpdb'& or &'exim_fixdb'& utility programs (see chapter
24249 &<<CHAPutils>>&). The latter utility can also be used to change the data. The
24250 &'exinext'& utility script can be used to find out what the next retry times
24251 are for the hosts associated with a particular mail domain, and also for local
24252 deliveries that have been deferred.
24255 .section "Retry rule examples" "SECID164"
24256 Here are some example retry rules:
24258 alice@wonderland.fict.example quota_5d F,7d,3h
24259 wonderland.fict.example quota_5d
24260 wonderland.fict.example * F,1h,15m; G,2d,1h,2;
24261 lookingglass.fict.example * F,24h,30m;
24262 * refused_A F,2h,20m;
24263 * * F,2h,15m; G,16h,1h,1.5; F,5d,8h
24265 The first rule sets up special handling for mail to
24266 &'alice@wonderland.fict.example'& when there is an over-quota error and the
24267 mailbox has not been read for at least 5 days. Retries continue every three
24268 hours for 7 days. The second rule handles over-quota errors for all other local
24269 parts at &'wonderland.fict.example'&; the absence of a local part has the same
24270 effect as supplying &"*@"&. As no retry algorithms are supplied, messages that
24271 fail are bounced immediately if the mailbox has not been read for at least 5
24274 The third rule handles all other errors at &'wonderland.fict.example'&; retries
24275 happen every 15 minutes for an hour, then with geometrically increasing
24276 intervals until two days have passed since a delivery first failed. After the
24277 first hour there is a delay of one hour, then two hours, then four hours, and
24278 so on (this is a rather extreme example).
24280 The fourth rule controls retries for the domain &'lookingglass.fict.example'&.
24281 They happen every 30 minutes for 24 hours only. The remaining two rules handle
24282 all other domains, with special action for connection refusal from hosts that
24283 were not obtained from an MX record.
24285 The final rule in a retry configuration should always have asterisks in the
24286 first two fields so as to provide a general catch-all for any addresses that do
24287 not have their own special handling. This example tries every 15 minutes for 2
24288 hours, then with intervals starting at one hour and increasing by a factor of
24289 1.5 up to 16 hours, then every 8 hours up to 5 days.
24293 .section "Timeout of retry data" "SECID165"
24294 .cindex "timeout" "of retry data"
24295 .oindex "&%retry_data_expire%&"
24296 .cindex "hints database" "data expiry"
24297 .cindex "retry" "timeout of data"
24298 Exim timestamps the data that it writes to its retry hints database. When it
24299 consults the data during a delivery it ignores any that is older than the value
24300 set in &%retry_data_expire%& (default 7 days). If, for example, a host hasn't
24301 been tried for 7 days, Exim will try to deliver to it immediately a message
24302 arrives, and if that fails, it will calculate a retry time as if it were
24303 failing for the first time.
24305 This improves the behaviour for messages routed to rarely-used hosts such as MX
24306 backups. If such a host was down at one time, and happens to be down again when
24307 Exim tries a month later, using the old retry data would imply that it had been
24308 down all the time, which is not a justified assumption.
24310 If a host really is permanently dead, this behaviour causes a burst of retries
24311 every now and again, but only if messages routed to it are rare. If there is a
24312 message at least once every 7 days the retry data never expires.
24317 .section "Long-term failures" "SECID166"
24318 .cindex "delivery failure, long-term"
24319 .cindex "retry" "after long-term failure"
24320 Special processing happens when an email address has been failing for so long
24321 that the cutoff time for the last algorithm is reached. For example, using the
24322 default retry rule:
24324 * * F,2h,15m; G,16h,1h,1.5; F,4d,6h
24326 the cutoff time is four days. Reaching the retry cutoff is independent of how
24327 long any specific message has been failing; it is the length of continuous
24328 failure for the recipient address that counts.
24330 When the cutoff time is reached for a local delivery, or for all the IP
24331 addresses associated with a remote delivery, a subsequent delivery failure
24332 causes Exim to give up on the address, and a bounce message is generated.
24333 In order to cater for new messages that use the failing address, a next retry
24334 time is still computed from the final algorithm, and is used as follows:
24336 For local deliveries, one delivery attempt is always made for any subsequent
24337 messages. If this delivery fails, the address fails immediately. The
24338 post-cutoff retry time is not used.
24340 If the delivery is remote, there are two possibilities, controlled by the
24341 .oindex "&%delay_after_cutoff%&"
24342 &%delay_after_cutoff%& option of the &(smtp)& transport. The option is true by
24343 default. Until the post-cutoff retry time for one of the IP addresses is
24344 reached, the failing email address is bounced immediately, without a delivery
24345 attempt taking place. After that time, one new delivery attempt is made to
24346 those IP addresses that are past their retry times, and if that still fails,
24347 the address is bounced and new retry times are computed.
24349 In other words, when all the hosts for a given email address have been failing
24350 for a long time, Exim bounces rather then defers until one of the hosts' retry
24351 times is reached. Then it tries once, and bounces if that attempt fails. This
24352 behaviour ensures that few resources are wasted in repeatedly trying to deliver
24353 to a broken destination, but if the host does recover, Exim will eventually
24356 If &%delay_after_cutoff%& is set false, Exim behaves differently. If all IP
24357 addresses are past their final cutoff time, Exim tries to deliver to those IP
24358 addresses that have not been tried since the message arrived. If there are
24359 no suitable IP addresses, or if they all fail, the address is bounced. In other
24360 words, it does not delay when a new message arrives, but tries the expired
24361 addresses immediately, unless they have been tried since the message arrived.
24362 If there is a continuous stream of messages for the failing domains, setting
24363 &%delay_after_cutoff%& false means that there will be many more attempts to
24364 deliver to permanently failing IP addresses than when &%delay_after_cutoff%& is
24367 .section "Deliveries that work intermittently" "SECID167"
24368 .cindex "retry" "intermittently working deliveries"
24369 Some additional logic is needed to cope with cases where a host is
24370 intermittently available, or when a message has some attribute that prevents
24371 its delivery when others to the same address get through. In this situation,
24372 because some messages are successfully delivered, the &"retry clock"& for the
24373 host or address keeps getting reset by the successful deliveries, and so
24374 failing messages remain on the queue for ever because the cutoff time is never
24377 Two exceptional actions are applied to prevent this happening. The first
24378 applies to errors that are related to a message rather than a remote host.
24379 Section &<<SECToutSMTPerr>>& has a discussion of the different kinds of error;
24380 examples of message-related errors are 4&'xx'& responses to MAIL or DATA
24381 commands, and quota failures. For this type of error, if a message's arrival
24382 time is earlier than the &"first failed"& time for the error, the earlier time
24383 is used when scanning the retry rules to decide when to try next and when to
24384 time out the address.
24386 The exceptional second action applies in all cases. If a message has been on
24387 the queue for longer than the cutoff time of any applicable retry rule for a
24388 given address, a delivery is attempted for that address, even if it is not yet
24389 time, and if this delivery fails, the address is timed out. A new retry time is
24390 not computed in this case, so that other messages for the same address are
24391 considered immediately.
24392 .ecindex IIDretconf1
24393 .ecindex IIDregconf2
24400 . ////////////////////////////////////////////////////////////////////////////
24401 . ////////////////////////////////////////////////////////////////////////////
24403 .chapter "SMTP authentication" "CHAPSMTPAUTH"
24404 .scindex IIDauthconf1 "SMTP" "authentication configuration"
24405 .scindex IIDauthconf2 "authentication"
24406 The &"authenticators"& section of Exim's run time configuration is concerned
24407 with SMTP authentication. This facility is an extension to the SMTP protocol,
24408 described in RFC 2554, which allows a client SMTP host to authenticate itself
24409 to a server. This is a common way for a server to recognize clients that are
24410 permitted to use it as a relay. SMTP authentication is not of relevance to the
24411 transfer of mail between servers that have no managerial connection with each
24414 .cindex "AUTH" "description of"
24415 Very briefly, the way SMTP authentication works is as follows:
24418 The server advertises a number of authentication &'mechanisms'& in response to
24419 the client's EHLO command.
24421 The client issues an AUTH command, naming a specific mechanism. The command
24422 may, optionally, contain some authentication data.
24424 The server may issue one or more &'challenges'&, to which the client must send
24425 appropriate responses. In simple authentication mechanisms, the challenges are
24426 just prompts for user names and passwords. The server does not have to issue
24427 any challenges &-- in some mechanisms the relevant data may all be transmitted
24428 with the AUTH command.
24430 The server either accepts or denies authentication.
24432 If authentication succeeds, the client may optionally make use of the AUTH
24433 option on the MAIL command to pass an authenticated sender in subsequent
24434 mail transactions. Authentication lasts for the remainder of the SMTP
24437 If authentication fails, the client may give up, or it may try a different
24438 authentication mechanism, or it may try transferring mail over the
24439 unauthenticated connection.
24442 If you are setting up a client, and want to know which authentication
24443 mechanisms the server supports, you can use Telnet to connect to port 25 (the
24444 SMTP port) on the server, and issue an EHLO command. The response to this
24445 includes the list of supported mechanisms. For example:
24447 &`$ `&&*&`telnet server.example 25`&*&
24448 &`Trying 192.168.34.25...`&
24449 &`Connected to server.example.`&
24450 &`Escape character is '^]'.`&
24451 &`220 server.example ESMTP Exim 4.20 ...`&
24452 &*&`ehlo client.example`&*&
24453 &`250-server.example Hello client.example [10.8.4.5]`&
24454 &`250-SIZE 52428800`&
24459 The second-last line of this example output shows that the server supports
24460 authentication using the PLAIN mechanism. In Exim, the different authentication
24461 mechanisms are configured by specifying &'authenticator'& drivers. Like the
24462 routers and transports, which authenticators are included in the binary is
24463 controlled by build-time definitions. The following are currently available,
24464 included by setting
24467 AUTH_CYRUS_SASL=yes
24470 AUTH_HEIMDAL_GSSAPI=yes
24474 in &_Local/Makefile_&, respectively. The first of these supports the CRAM-MD5
24475 authentication mechanism (RFC 2195), and the second provides an interface to
24476 the Cyrus SASL authentication library.
24477 The third is an interface to Dovecot's authentication system, delegating the
24478 work via a socket interface.
24479 The fourth provides an interface to the GNU SASL authentication library, which
24480 provides mechanisms but typically not data sources.
24481 The fifth provides direct access to Heimdal GSSAPI, geared for Kerberos, but
24482 supporting setting a server keytab.
24483 The sixth can be configured to support
24484 the PLAIN authentication mechanism (RFC 2595) or the LOGIN mechanism, which is
24485 not formally documented, but used by several MUAs. The seventh authenticator
24486 supports Microsoft's &'Secure Password Authentication'& mechanism.
24488 The authenticators are configured using the same syntax as other drivers (see
24489 section &<<SECTfordricon>>&). If no authenticators are required, no
24490 authentication section need be present in the configuration file. Each
24491 authenticator can in principle have both server and client functions. When Exim
24492 is receiving SMTP mail, it is acting as a server; when it is sending out
24493 messages over SMTP, it is acting as a client. Authenticator configuration
24494 options are provided for use in both these circumstances.
24496 To make it clear which options apply to which situation, the prefixes
24497 &%server_%& and &%client_%& are used on option names that are specific to
24498 either the server or the client function, respectively. Server and client
24499 functions are disabled if none of their options are set. If an authenticator is
24500 to be used for both server and client functions, a single definition, using
24501 both sets of options, is required. For example:
24505 public_name = CRAM-MD5
24506 server_secret = ${if eq{$auth1}{ph10}{secret1}fail}
24508 client_secret = secret2
24510 The &%server_%& option is used when Exim is acting as a server, and the
24511 &%client_%& options when it is acting as a client.
24513 Descriptions of the individual authenticators are given in subsequent chapters.
24514 The remainder of this chapter covers the generic options for the
24515 authenticators, followed by general discussion of the way authentication works
24518 &*Beware:*& the meaning of &$auth1$&, &$auth2$&, ... varies on a per-driver and
24519 per-mechanism basis. Please read carefully to determine which variables hold
24520 account labels such as usercodes and which hold passwords or other
24521 authenticating data.
24523 Note that some mechanisms support two different identifiers for accounts: the
24524 &'authentication id'& and the &'authorization id'&. The contractions &'authn'&
24525 and &'authz'& are commonly encountered. The American spelling is standard here.
24526 Conceptually, authentication data such as passwords are tied to the identifier
24527 used to authenticate; servers may have rules to permit one user to act as a
24528 second user, so that after login the session is treated as though that second
24529 user had logged in. That second user is the &'authorization id'&. A robust
24530 configuration might confirm that the &'authz'& field is empty or matches the
24531 &'authn'& field. Often this is just ignored. The &'authn'& can be considered
24532 as verified data, the &'authz'& as an unverified request which the server might
24535 A &'realm'& is a text string, typically a domain name, presented by a server
24536 to a client to help it select an account and credentials to use. In some
24537 mechanisms, the client and server provably agree on the realm, but clients
24538 typically can not treat the realm as secure data to be blindly trusted.
24542 .section "Generic options for authenticators" "SECID168"
24543 .cindex "authentication" "generic options"
24544 .cindex "options" "generic; for authenticators"
24546 .option client_condition authenticators string&!! unset
24547 When Exim is authenticating as a client, it skips any authenticator whose
24548 &%client_condition%& expansion yields &"0"&, &"no"&, or &"false"&. This can be
24549 used, for example, to skip plain text authenticators when the connection is not
24550 encrypted by a setting such as:
24552 client_condition = ${if !eq{$tls_out_cipher}{}}
24556 .option client_set_id authenticators string&!! unset
24557 When client authentication succeeds, this condition is expanded; the
24558 result is used in the log lines for outbound messasges.
24559 Typically it will be the user name used for authentication.
24562 .option driver authenticators string unset
24563 This option must always be set. It specifies which of the available
24564 authenticators is to be used.
24567 .option public_name authenticators string unset
24568 This option specifies the name of the authentication mechanism that the driver
24569 implements, and by which it is known to the outside world. These names should
24570 contain only upper case letters, digits, underscores, and hyphens (RFC 2222),
24571 but Exim in fact matches them caselessly. If &%public_name%& is not set, it
24572 defaults to the driver's instance name.
24575 .option server_advertise_condition authenticators string&!! unset
24576 When a server is about to advertise an authentication mechanism, the condition
24577 is expanded. If it yields the empty string, &"0"&, &"no"&, or &"false"&, the
24578 mechanism is not advertised.
24579 If the expansion fails, the mechanism is not advertised. If the failure was not
24580 forced, and was not caused by a lookup defer, the incident is logged.
24581 See section &<<SECTauthexiser>>& below for further discussion.
24584 .option server_condition authenticators string&!! unset
24585 This option must be set for a &%plaintext%& server authenticator, where it
24586 is used directly to control authentication. See section &<<SECTplainserver>>&
24589 For the &(gsasl)& authenticator, this option is required for various
24590 mechanisms; see chapter &<<CHAPgsasl>>& for details.
24592 For the other authenticators, &%server_condition%& can be used as an additional
24593 authentication or authorization mechanism that is applied after the other
24594 authenticator conditions succeed. If it is set, it is expanded when the
24595 authenticator would otherwise return a success code. If the expansion is forced
24596 to fail, authentication fails. Any other expansion failure causes a temporary
24597 error code to be returned. If the result of a successful expansion is an empty
24598 string, &"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
24599 expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds. For any
24600 other result, a temporary error code is returned, with the expanded string as
24604 .option server_debug_print authenticators string&!! unset
24605 If this option is set and authentication debugging is enabled (see the &%-d%&
24606 command line option), the string is expanded and included in the debugging
24607 output when the authenticator is run as a server. This can help with checking
24608 out the values of variables.
24609 If expansion of the string fails, the error message is written to the debugging
24610 output, and Exim carries on processing.
24613 .option server_set_id authenticators string&!! unset
24614 .vindex "&$authenticated_id$&"
24615 When an Exim server successfully authenticates a client, this string is
24616 expanded using data from the authentication, and preserved for any incoming
24617 messages in the variable &$authenticated_id$&. It is also included in the log
24618 lines for incoming messages. For example, a user/password authenticator
24619 configuration might preserve the user name that was used to authenticate, and
24620 refer to it subsequently during delivery of the message.
24621 If expansion fails, the option is ignored.
24624 .option server_mail_auth_condition authenticators string&!! unset
24625 This option allows a server to discard authenticated sender addresses supplied
24626 as part of MAIL commands in SMTP connections that are authenticated by the
24627 driver on which &%server_mail_auth_condition%& is set. The option is not used
24628 as part of the authentication process; instead its (unexpanded) value is
24629 remembered for later use.
24630 How it is used is described in the following section.
24636 .section "The AUTH parameter on MAIL commands" "SECTauthparamail"
24637 .cindex "authentication" "sender; authenticated"
24638 .cindex "AUTH" "on MAIL command"
24639 When a client supplied an AUTH= item on a MAIL command, Exim applies
24640 the following checks before accepting it as the authenticated sender of the
24644 If the connection is not using extended SMTP (that is, HELO was used rather
24645 than EHLO), the use of AUTH= is a syntax error.
24647 If the value of the AUTH= parameter is &"<>"&, it is ignored.
24649 .vindex "&$authenticated_sender$&"
24650 If &%acl_smtp_mailauth%& is defined, the ACL it specifies is run. While it is
24651 running, the value of &$authenticated_sender$& is set to the value obtained
24652 from the AUTH= parameter. If the ACL does not yield &"accept"&, the value of
24653 &$authenticated_sender$& is deleted. The &%acl_smtp_mailauth%& ACL may not
24654 return &"drop"& or &"discard"&. If it defers, a temporary error code (451) is
24655 given for the MAIL command.
24657 If &%acl_smtp_mailauth%& is not defined, the value of the AUTH= parameter
24658 is accepted and placed in &$authenticated_sender$& only if the client has
24661 If the AUTH= value was accepted by either of the two previous rules, and
24662 the client has authenticated, and the authenticator has a setting for the
24663 &%server_mail_auth_condition%&, the condition is checked at this point. The
24664 valued that was saved from the authenticator is expanded. If the expansion
24665 fails, or yields an empty string, &"0"&, &"no"&, or &"false"&, the value of
24666 &$authenticated_sender$& is deleted. If the expansion yields any other value,
24667 the value of &$authenticated_sender$& is retained and passed on with the
24672 When &$authenticated_sender$& is set for a message, it is passed on to other
24673 hosts to which Exim authenticates as a client. Do not confuse this value with
24674 &$authenticated_id$&, which is a string obtained from the authentication
24675 process, and which is not usually a complete email address.
24677 .vindex "&$sender_address$&"
24678 Whenever an AUTH= value is ignored, the incident is logged. The ACL for
24679 MAIL, if defined, is run after AUTH= is accepted or ignored. It can
24680 therefore make use of &$authenticated_sender$&. The converse is not true: the
24681 value of &$sender_address$& is not yet set up when the &%acl_smtp_mailauth%&
24686 .section "Authentication on an Exim server" "SECTauthexiser"
24687 .cindex "authentication" "on an Exim server"
24688 When Exim receives an EHLO command, it advertises the public names of those
24689 authenticators that are configured as servers, subject to the following
24693 The client host must match &%auth_advertise_hosts%& (default *).
24695 It the &%server_advertise_condition%& option is set, its expansion must not
24696 yield the empty string, &"0"&, &"no"&, or &"false"&.
24699 The order in which the authenticators are defined controls the order in which
24700 the mechanisms are advertised.
24702 Some mail clients (for example, some versions of Netscape) require the user to
24703 provide a name and password for authentication whenever AUTH is advertised,
24704 even though authentication may not in fact be needed (for example, Exim may be
24705 set up to allow unconditional relaying from the client by an IP address check).
24706 You can make such clients more friendly by not advertising AUTH to them.
24707 For example, if clients on the 10.9.8.0/24 network are permitted (by the ACL
24708 that runs for RCPT) to relay without authentication, you should set
24710 auth_advertise_hosts = ! 10.9.8.0/24
24712 so that no authentication mechanisms are advertised to them.
24714 The &%server_advertise_condition%& controls the advertisement of individual
24715 authentication mechanisms. For example, it can be used to restrict the
24716 advertisement of a particular mechanism to encrypted connections, by a setting
24719 server_advertise_condition = ${if eq{$tls_in_cipher}{}{no}{yes}}
24721 .vindex "&$tls_in_cipher$&"
24722 If the session is encrypted, &$tls_in_cipher$& is not empty, and so the expansion
24723 yields &"yes"&, which allows the advertisement to happen.
24725 When an Exim server receives an AUTH command from a client, it rejects it
24726 immediately if AUTH was not advertised in response to an earlier EHLO
24727 command. This is the case if
24730 The client host does not match &%auth_advertise_hosts%&; or
24732 No authenticators are configured with server options; or
24734 Expansion of &%server_advertise_condition%& blocked the advertising of all the
24735 server authenticators.
24739 Otherwise, Exim runs the ACL specified by &%acl_smtp_auth%& in order
24740 to decide whether to accept the command. If &%acl_smtp_auth%& is not set,
24741 AUTH is accepted from any client host.
24743 If AUTH is not rejected by the ACL, Exim searches its configuration for a
24744 server authentication mechanism that was advertised in response to EHLO and
24745 that matches the one named in the AUTH command. If it finds one, it runs
24746 the appropriate authentication protocol, and authentication either succeeds or
24747 fails. If there is no matching advertised mechanism, the AUTH command is
24748 rejected with a 504 error.
24750 .vindex "&$received_protocol$&"
24751 .vindex "&$sender_host_authenticated$&"
24752 When a message is received from an authenticated host, the value of
24753 &$received_protocol$& is set to &"esmtpa"& or &"esmtpsa"& instead of &"esmtp"&
24754 or &"esmtps"&, and &$sender_host_authenticated$& contains the name (not the
24755 public name) of the authenticator driver that successfully authenticated the
24756 client from which the message was received. This variable is empty if there was
24757 no successful authentication.
24762 .section "Testing server authentication" "SECID169"
24763 .cindex "authentication" "testing a server"
24764 .cindex "AUTH" "testing a server"
24765 .cindex "base64 encoding" "creating authentication test data"
24766 Exim's &%-bh%& option can be useful for testing server authentication
24767 configurations. The data for the AUTH command has to be sent using base64
24768 encoding. A quick way to produce such data for testing is the following Perl
24772 printf ("%s", encode_base64(eval "\"$ARGV[0]\""));
24774 .cindex "binary zero" "in authentication data"
24775 This interprets its argument as a Perl string, and then encodes it. The
24776 interpretation as a Perl string allows binary zeros, which are required for
24777 some kinds of authentication, to be included in the data. For example, a
24778 command line to run this script on such data might be
24780 encode '\0user\0password'
24782 Note the use of single quotes to prevent the shell interpreting the
24783 backslashes, so that they can be interpreted by Perl to specify characters
24784 whose code value is zero.
24786 &*Warning 1*&: If either of the user or password strings starts with an octal
24787 digit, you must use three zeros instead of one after the leading backslash. If
24788 you do not, the octal digit that starts your string will be incorrectly
24789 interpreted as part of the code for the first character.
24791 &*Warning 2*&: If there are characters in the strings that Perl interprets
24792 specially, you must use a Perl escape to prevent them being misinterpreted. For
24793 example, a command such as
24795 encode '\0user@domain.com\0pas$$word'
24797 gives an incorrect answer because of the unescaped &"@"& and &"$"& characters.
24799 If you have the &%mimencode%& command installed, another way to do produce
24800 base64-encoded strings is to run the command
24802 echo -e -n `\0user\0password' | mimencode
24804 The &%-e%& option of &%echo%& enables the interpretation of backslash escapes
24805 in the argument, and the &%-n%& option specifies no newline at the end of its
24806 output. However, not all versions of &%echo%& recognize these options, so you
24807 should check your version before relying on this suggestion.
24811 .section "Authentication by an Exim client" "SECID170"
24812 .cindex "authentication" "on an Exim client"
24813 The &(smtp)& transport has two options called &%hosts_require_auth%& and
24814 &%hosts_try_auth%&. When the &(smtp)& transport connects to a server that
24815 announces support for authentication, and the host matches an entry in either
24816 of these options, Exim (as a client) tries to authenticate as follows:
24819 For each authenticator that is configured as a client, in the order in which
24820 they are defined in the configuration, it searches the authentication
24821 mechanisms announced by the server for one whose name matches the public name
24822 of the authenticator.
24825 .vindex "&$host_address$&"
24826 When it finds one that matches, it runs the authenticator's client code. The
24827 variables &$host$& and &$host_address$& are available for any string expansions
24828 that the client might do. They are set to the server's name and IP address. If
24829 any expansion is forced to fail, the authentication attempt is abandoned, and
24830 Exim moves on to the next authenticator. Otherwise an expansion failure causes
24831 delivery to be deferred.
24833 If the result of the authentication attempt is a temporary error or a timeout,
24834 Exim abandons trying to send the message to the host for the moment. It will
24835 try again later. If there are any backup hosts available, they are tried in the
24838 If the response to authentication is a permanent error (5&'xx'& code), Exim
24839 carries on searching the list of authenticators and tries another one if
24840 possible. If all authentication attempts give permanent errors, or if there are
24841 no attempts because no mechanisms match (or option expansions force failure),
24842 what happens depends on whether the host matches &%hosts_require_auth%& or
24843 &%hosts_try_auth%&. In the first case, a temporary error is generated, and
24844 delivery is deferred. The error can be detected in the retry rules, and thereby
24845 turned into a permanent error if you wish. In the second case, Exim tries to
24846 deliver the message unauthenticated.
24849 .cindex "AUTH" "on MAIL command"
24850 When Exim has authenticated itself to a remote server, it adds the AUTH
24851 parameter to the MAIL commands it sends, if it has an authenticated sender for
24852 the message. If the message came from a remote host, the authenticated sender
24853 is the one that was receiving on an incoming MAIL command, provided that the
24854 incoming connection was authenticated and the &%server_mail_auth%& condition
24855 allowed the authenticated sender to be retained. If a local process calls Exim
24856 to send a message, the sender address that is built from the login name and
24857 &%qualify_domain%& is treated as authenticated. However, if the
24858 &%authenticated_sender%& option is set on the &(smtp)& transport, it overrides
24859 the authenticated sender that was received with the message.
24860 .ecindex IIDauthconf1
24861 .ecindex IIDauthconf2
24868 . ////////////////////////////////////////////////////////////////////////////
24869 . ////////////////////////////////////////////////////////////////////////////
24871 .chapter "The plaintext authenticator" "CHAPplaintext"
24872 .scindex IIDplaiauth1 "&(plaintext)& authenticator"
24873 .scindex IIDplaiauth2 "authenticators" "&(plaintext)&"
24874 The &(plaintext)& authenticator can be configured to support the PLAIN and
24875 LOGIN authentication mechanisms, both of which transfer authentication data as
24876 plain (unencrypted) text (though base64 encoded). The use of plain text is a
24877 security risk; you are strongly advised to insist on the use of SMTP encryption
24878 (see chapter &<<CHAPTLS>>&) if you use the PLAIN or LOGIN mechanisms. If you do
24879 use unencrypted plain text, you should not use the same passwords for SMTP
24880 connections as you do for login accounts.
24882 .section "Plaintext options" "SECID171"
24883 .cindex "options" "&(plaintext)& authenticator (server)"
24884 When configured as a server, &(plaintext)& uses the following options:
24886 .option server_condition authenticators string&!! unset
24887 This is actually a global authentication option, but it must be set in order to
24888 configure the &(plaintext)& driver as a server. Its use is described below.
24890 .option server_prompts plaintext string&!! unset
24891 The contents of this option, after expansion, must be a colon-separated list of
24892 prompt strings. If expansion fails, a temporary authentication rejection is
24895 .section "Using plaintext in a server" "SECTplainserver"
24896 .cindex "AUTH" "in &(plaintext)& authenticator"
24897 .cindex "binary zero" "in &(plaintext)& authenticator"
24898 .cindex "numerical variables (&$1$& &$2$& etc)" &&&
24899 "in &(plaintext)& authenticator"
24900 .vindex "&$auth1$&, &$auth2$&, etc"
24901 .cindex "base64 encoding" "in &(plaintext)& authenticator"
24903 When running as a server, &(plaintext)& performs the authentication test by
24904 expanding a string. The data sent by the client with the AUTH command, or in
24905 response to subsequent prompts, is base64 encoded, and so may contain any byte
24906 values when decoded. If any data is supplied with the command, it is treated as
24907 a list of strings, separated by NULs (binary zeros), the first three of which
24908 are placed in the expansion variables &$auth1$&, &$auth2$&, and &$auth3$&
24909 (neither LOGIN nor PLAIN uses more than three strings).
24911 For compatibility with previous releases of Exim, the values are also placed in
24912 the expansion variables &$1$&, &$2$&, and &$3$&. However, the use of these
24913 variables for this purpose is now deprecated, as it can lead to confusion in
24914 string expansions that also use them for other things.
24916 If there are more strings in &%server_prompts%& than the number of strings
24917 supplied with the AUTH command, the remaining prompts are used to obtain more
24918 data. Each response from the client may be a list of NUL-separated strings.
24920 .vindex "&$authenticated_id$&"
24921 Once a sufficient number of data strings have been received,
24922 &%server_condition%& is expanded. If the expansion is forced to fail,
24923 authentication fails. Any other expansion failure causes a temporary error code
24924 to be returned. If the result of a successful expansion is an empty string,
24925 &"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
24926 expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds and the
24927 generic &%server_set_id%& option is expanded and saved in &$authenticated_id$&.
24928 For any other result, a temporary error code is returned, with the expanded
24929 string as the error text
24931 &*Warning*&: If you use a lookup in the expansion to find the user's
24932 password, be sure to make the authentication fail if the user is unknown.
24933 There are good and bad examples at the end of the next section.
24937 .section "The PLAIN authentication mechanism" "SECID172"
24938 .cindex "PLAIN authentication mechanism"
24939 .cindex "authentication" "PLAIN mechanism"
24940 .cindex "binary zero" "in &(plaintext)& authenticator"
24941 The PLAIN authentication mechanism (RFC 2595) specifies that three strings be
24942 sent as one item of data (that is, one combined string containing two NUL
24943 separators). The data is sent either as part of the AUTH command, or
24944 subsequently in response to an empty prompt from the server.
24946 The second and third strings are a user name and a corresponding password.
24947 Using a single fixed user name and password as an example, this could be
24948 configured as follows:
24952 public_name = PLAIN
24954 server_condition = \
24955 ${if and {{eq{$auth2}{username}}{eq{$auth3}{mysecret}}}}
24956 server_set_id = $auth2
24958 Note that the default result strings from &%if%& (&"true"& or an empty string)
24959 are exactly what we want here, so they need not be specified. Obviously, if the
24960 password contains expansion-significant characters such as dollar, backslash,
24961 or closing brace, they have to be escaped.
24963 The &%server_prompts%& setting specifies a single, empty prompt (empty items at
24964 the end of a string list are ignored). If all the data comes as part of the
24965 AUTH command, as is commonly the case, the prompt is not used. This
24966 authenticator is advertised in the response to EHLO as
24970 and a client host can authenticate itself by sending the command
24972 AUTH PLAIN AHVzZXJuYW1lAG15c2VjcmV0
24974 As this contains three strings (more than the number of prompts), no further
24975 data is required from the client. Alternatively, the client may just send
24979 to initiate authentication, in which case the server replies with an empty
24980 prompt. The client must respond with the combined data string.
24982 The data string is base64 encoded, as required by the RFC. This example,
24983 when decoded, is <&'NUL'&>&`username`&<&'NUL'&>&`mysecret`&, where <&'NUL'&>
24984 represents a zero byte. This is split up into three strings, the first of which
24985 is empty. The &%server_condition%& option in the authenticator checks that the
24986 second two are &`username`& and &`mysecret`& respectively.
24988 Having just one fixed user name and password, as in this example, is not very
24989 realistic, though for a small organization with only a handful of
24990 authenticating clients it could make sense.
24992 A more sophisticated instance of this authenticator could use the user name in
24993 &$auth2$& to look up a password in a file or database, and maybe do an encrypted
24994 comparison (see &%crypteq%& in chapter &<<CHAPexpand>>&). Here is a example of
24995 this approach, where the passwords are looked up in a DBM file. &*Warning*&:
24996 This is an incorrect example:
24998 server_condition = \
24999 ${if eq{$auth3}{${lookup{$auth2}dbm{/etc/authpwd}}}}
25001 The expansion uses the user name (&$auth2$&) as the key to look up a password,
25002 which it then compares to the supplied password (&$auth3$&). Why is this example
25003 incorrect? It works fine for existing users, but consider what happens if a
25004 non-existent user name is given. The lookup fails, but as no success/failure
25005 strings are given for the lookup, it yields an empty string. Thus, to defeat
25006 the authentication, all a client has to do is to supply a non-existent user
25007 name and an empty password. The correct way of writing this test is:
25009 server_condition = ${lookup{$auth2}dbm{/etc/authpwd}\
25010 {${if eq{$value}{$auth3}}} {false}}
25012 In this case, if the lookup succeeds, the result is checked; if the lookup
25013 fails, &"false"& is returned and authentication fails. If &%crypteq%& is being
25014 used instead of &%eq%&, the first example is in fact safe, because &%crypteq%&
25015 always fails if its second argument is empty. However, the second way of
25016 writing the test makes the logic clearer.
25019 .section "The LOGIN authentication mechanism" "SECID173"
25020 .cindex "LOGIN authentication mechanism"
25021 .cindex "authentication" "LOGIN mechanism"
25022 The LOGIN authentication mechanism is not documented in any RFC, but is in use
25023 in a number of programs. No data is sent with the AUTH command. Instead, a
25024 user name and password are supplied separately, in response to prompts. The
25025 plaintext authenticator can be configured to support this as in this example:
25029 public_name = LOGIN
25030 server_prompts = User Name : Password
25031 server_condition = \
25032 ${if and {{eq{$auth1}{username}}{eq{$auth2}{mysecret}}}}
25033 server_set_id = $auth1
25035 Because of the way plaintext operates, this authenticator accepts data supplied
25036 with the AUTH command (in contravention of the specification of LOGIN), but
25037 if the client does not supply it (as is the case for LOGIN clients), the prompt
25038 strings are used to obtain two data items.
25040 Some clients are very particular about the precise text of the prompts. For
25041 example, Outlook Express is reported to recognize only &"Username:"& and
25042 &"Password:"&. Here is an example of a LOGIN authenticator that uses those
25043 strings. It uses the &%ldapauth%& expansion condition to check the user
25044 name and password by binding to an LDAP server:
25048 public_name = LOGIN
25049 server_prompts = Username:: : Password::
25050 server_condition = ${if and{{ \
25053 user="uid=${quote_ldap_dn:$auth1},ou=people,o=example.org" \
25054 pass=${quote:$auth2} \
25055 ldap://ldap.example.org/} }} }
25056 server_set_id = uid=$auth1,ou=people,o=example.org
25058 We have to check that the username is not empty before using it, because LDAP
25059 does not permit empty DN components. We must also use the &%quote_ldap_dn%&
25060 operator to correctly quote the DN for authentication. However, the basic
25061 &%quote%& operator, rather than any of the LDAP quoting operators, is the
25062 correct one to use for the password, because quoting is needed only to make
25063 the password conform to the Exim syntax. At the LDAP level, the password is an
25064 uninterpreted string.
25067 .section "Support for different kinds of authentication" "SECID174"
25068 A number of string expansion features are provided for the purpose of
25069 interfacing to different ways of user authentication. These include checking
25070 traditionally encrypted passwords from &_/etc/passwd_& (or equivalent), PAM,
25071 Radius, &%ldapauth%&, &'pwcheck'&, and &'saslauthd'&. For details see section
25077 .section "Using plaintext in a client" "SECID175"
25078 .cindex "options" "&(plaintext)& authenticator (client)"
25079 The &(plaintext)& authenticator has two client options:
25081 .option client_ignore_invalid_base64 plaintext boolean false
25082 If the client receives a server prompt that is not a valid base64 string,
25083 authentication is abandoned by default. However, if this option is set true,
25084 the error in the challenge is ignored and the client sends the response as
25087 .option client_send plaintext string&!! unset
25088 The string is a colon-separated list of authentication data strings. Each
25089 string is independently expanded before being sent to the server. The first
25090 string is sent with the AUTH command; any more strings are sent in response
25091 to prompts from the server. Before each string is expanded, the value of the
25092 most recent prompt is placed in the next &$auth$&<&'n'&> variable, starting
25093 with &$auth1$& for the first prompt. Up to three prompts are stored in this
25094 way. Thus, the prompt that is received in response to sending the first string
25095 (with the AUTH command) can be used in the expansion of the second string, and
25096 so on. If an invalid base64 string is received when
25097 &%client_ignore_invalid_base64%& is set, an empty string is put in the
25098 &$auth$&<&'n'&> variable.
25100 &*Note*&: You cannot use expansion to create multiple strings, because
25101 splitting takes priority and happens first.
25103 Because the PLAIN authentication mechanism requires NUL (binary zero) bytes in
25104 the data, further processing is applied to each string before it is sent. If
25105 there are any single circumflex characters in the string, they are converted to
25106 NULs. Should an actual circumflex be required as data, it must be doubled in
25109 This is an example of a client configuration that implements the PLAIN
25110 authentication mechanism with a fixed user name and password:
25114 public_name = PLAIN
25115 client_send = ^username^mysecret
25117 The lack of colons means that the entire text is sent with the AUTH
25118 command, with the circumflex characters converted to NULs. A similar example
25119 that uses the LOGIN mechanism is:
25123 public_name = LOGIN
25124 client_send = : username : mysecret
25126 The initial colon means that the first string is empty, so no data is sent with
25127 the AUTH command itself. The remaining strings are sent in response to
25129 .ecindex IIDplaiauth1
25130 .ecindex IIDplaiauth2
25135 . ////////////////////////////////////////////////////////////////////////////
25136 . ////////////////////////////////////////////////////////////////////////////
25138 .chapter "The cram_md5 authenticator" "CHID9"
25139 .scindex IIDcramauth1 "&(cram_md5)& authenticator"
25140 .scindex IIDcramauth2 "authenticators" "&(cram_md5)&"
25141 .cindex "CRAM-MD5 authentication mechanism"
25142 .cindex "authentication" "CRAM-MD5 mechanism"
25143 The CRAM-MD5 authentication mechanism is described in RFC 2195. The server
25144 sends a challenge string to the client, and the response consists of a user
25145 name and the CRAM-MD5 digest of the challenge string combined with a secret
25146 string (password) which is known to both server and client. Thus, the secret
25147 is not sent over the network as plain text, which makes this authenticator more
25148 secure than &(plaintext)&. However, the downside is that the secret has to be
25149 available in plain text at either end.
25152 .section "Using cram_md5 as a server" "SECID176"
25153 .cindex "options" "&(cram_md5)& authenticator (server)"
25154 This authenticator has one server option, which must be set to configure the
25155 authenticator as a server:
25157 .option server_secret cram_md5 string&!! unset
25158 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(cram_md5)& authenticator"
25159 When the server receives the client's response, the user name is placed in
25160 the expansion variable &$auth1$&, and &%server_secret%& is expanded to
25161 obtain the password for that user. The server then computes the CRAM-MD5 digest
25162 that the client should have sent, and checks that it received the correct
25163 string. If the expansion of &%server_secret%& is forced to fail, authentication
25164 fails. If the expansion fails for some other reason, a temporary error code is
25165 returned to the client.
25167 For compatibility with previous releases of Exim, the user name is also placed
25168 in &$1$&. However, the use of this variables for this purpose is now
25169 deprecated, as it can lead to confusion in string expansions that also use
25170 numeric variables for other things.
25172 For example, the following authenticator checks that the user name given by the
25173 client is &"ph10"&, and if so, uses &"secret"& as the password. For any other
25174 user name, authentication fails.
25178 public_name = CRAM-MD5
25179 server_secret = ${if eq{$auth1}{ph10}{secret}fail}
25180 server_set_id = $auth1
25182 .vindex "&$authenticated_id$&"
25183 If authentication succeeds, the setting of &%server_set_id%& preserves the user
25184 name in &$authenticated_id$&. A more typical configuration might look up the
25185 secret string in a file, using the user name as the key. For example:
25189 public_name = CRAM-MD5
25190 server_secret = ${lookup{$auth1}lsearch{/etc/authpwd}\
25192 server_set_id = $auth1
25194 Note that this expansion explicitly forces failure if the lookup fails
25195 because &$auth1$& contains an unknown user name.
25197 As another example, if you wish to re-use a Cyrus SASL sasldb2 file without
25198 using the relevant libraries, you need to know the realm to specify in the
25199 lookup and then ask for the &"userPassword"& attribute for that user in that
25204 public_name = CRAM-MD5
25205 server_secret = ${lookup{$auth1:mail.example.org:userPassword}\
25206 dbmjz{/etc/sasldb2}}
25207 server_set_id = $auth1
25210 .section "Using cram_md5 as a client" "SECID177"
25211 .cindex "options" "&(cram_md5)& authenticator (client)"
25212 When used as a client, the &(cram_md5)& authenticator has two options:
25216 .option client_name cram_md5 string&!! "the primary host name"
25217 This string is expanded, and the result used as the user name data when
25218 computing the response to the server's challenge.
25221 .option client_secret cram_md5 string&!! unset
25222 This option must be set for the authenticator to work as a client. Its value is
25223 expanded and the result used as the secret string when computing the response.
25227 .vindex "&$host_address$&"
25228 Different user names and secrets can be used for different servers by referring
25229 to &$host$& or &$host_address$& in the options. Forced failure of either
25230 expansion string is treated as an indication that this authenticator is not
25231 prepared to handle this case. Exim moves on to the next configured client
25232 authenticator. Any other expansion failure causes Exim to give up trying to
25233 send the message to the current server.
25235 A simple example configuration of a &(cram_md5)& authenticator, using fixed
25240 public_name = CRAM-MD5
25242 client_secret = secret
25244 .ecindex IIDcramauth1
25245 .ecindex IIDcramauth2
25249 . ////////////////////////////////////////////////////////////////////////////
25250 . ////////////////////////////////////////////////////////////////////////////
25252 .chapter "The cyrus_sasl authenticator" "CHID10"
25253 .scindex IIDcyrauth1 "&(cyrus_sasl)& authenticator"
25254 .scindex IIDcyrauth2 "authenticators" "&(cyrus_sasl)&"
25255 .cindex "Cyrus" "SASL library"
25257 The code for this authenticator was provided by Matthew Byng-Maddick of A L
25258 Digital Ltd (&url(http://www.aldigital.co.uk)).
25260 The &(cyrus_sasl)& authenticator provides server support for the Cyrus SASL
25261 library implementation of the RFC 2222 (&"Simple Authentication and Security
25262 Layer"&). This library supports a number of authentication mechanisms,
25263 including PLAIN and LOGIN, but also several others that Exim does not support
25264 directly. In particular, there is support for Kerberos authentication.
25266 The &(cyrus_sasl)& authenticator provides a gatewaying mechanism directly to
25267 the Cyrus interface, so if your Cyrus library can do, for example, CRAM-MD5,
25268 then so can the &(cyrus_sasl)& authenticator. By default it uses the public
25269 name of the driver to determine which mechanism to support.
25271 Where access to some kind of secret file is required, for example in GSSAPI
25272 or CRAM-MD5, it is worth noting that the authenticator runs as the Exim
25273 user, and that the Cyrus SASL library has no way of escalating privileges
25274 by default. You may also find you need to set environment variables,
25275 depending on the driver you are using.
25277 The application name provided by Exim is &"exim"&, so various SASL options may
25278 be set in &_exim.conf_& in your SASL directory. If you are using GSSAPI for
25279 Kerberos, note that because of limitations in the GSSAPI interface,
25280 changing the server keytab might need to be communicated down to the Kerberos
25281 layer independently. The mechanism for doing so is dependent upon the Kerberos
25284 For example, for older releases of Heimdal, the environment variable KRB5_KTNAME
25285 may be set to point to an alternative keytab file. Exim will pass this
25286 variable through from its own inherited environment when started as root or the
25287 Exim user. The keytab file needs to be readable by the Exim user.
25288 With newer releases of Heimdal, a setuid Exim may cause Heimdal to discard the
25289 environment variable. In practice, for those releases, the Cyrus authenticator
25290 is not a suitable interface for GSSAPI (Kerberos) support. Instead, consider
25291 the &(heimdal_gssapi)& authenticator, described in chapter &<<CHAPheimdalgss>>&
25294 .section "Using cyrus_sasl as a server" "SECID178"
25295 The &(cyrus_sasl)& authenticator has four private options. It puts the username
25296 (on a successful authentication) into &$auth1$&. For compatibility with
25297 previous releases of Exim, the username is also placed in &$1$&. However, the
25298 use of this variable for this purpose is now deprecated, as it can lead to
25299 confusion in string expansions that also use numeric variables for other
25303 .option server_hostname cyrus_sasl string&!! "see below"
25304 This option selects the hostname that is used when communicating with the
25305 library. The default value is &`$primary_hostname`&. It is up to the underlying
25306 SASL plug-in what it does with this data.
25309 .option server_mech cyrus_sasl string "see below"
25310 This option selects the authentication mechanism this driver should use. The
25311 default is the value of the generic &%public_name%& option. This option allows
25312 you to use a different underlying mechanism from the advertised name. For
25316 driver = cyrus_sasl
25317 public_name = X-ANYTHING
25318 server_mech = CRAM-MD5
25319 server_set_id = $auth1
25322 .option server_realm cyrus_sasl string&!! unset
25323 This specifies the SASL realm that the server claims to be in.
25326 .option server_service cyrus_sasl string &`smtp`&
25327 This is the SASL service that the server claims to implement.
25330 For straightforward cases, you do not need to set any of the authenticator's
25331 private options. All you need to do is to specify an appropriate mechanism as
25332 the public name. Thus, if you have a SASL library that supports CRAM-MD5 and
25333 PLAIN, you could have two authenticators as follows:
25336 driver = cyrus_sasl
25337 public_name = CRAM-MD5
25338 server_set_id = $auth1
25341 driver = cyrus_sasl
25342 public_name = PLAIN
25343 server_set_id = $auth2
25345 Cyrus SASL does implement the LOGIN authentication method, even though it is
25346 not a standard method. It is disabled by default in the source distribution,
25347 but it is present in many binary distributions.
25348 .ecindex IIDcyrauth1
25349 .ecindex IIDcyrauth2
25354 . ////////////////////////////////////////////////////////////////////////////
25355 . ////////////////////////////////////////////////////////////////////////////
25356 .chapter "The dovecot authenticator" "CHAPdovecot"
25357 .scindex IIDdcotauth1 "&(dovecot)& authenticator"
25358 .scindex IIDdcotauth2 "authenticators" "&(dovecot)&"
25359 This authenticator is an interface to the authentication facility of the
25360 Dovecot POP/IMAP server, which can support a number of authentication methods.
25361 If you are using Dovecot to authenticate POP/IMAP clients, it might be helpful
25362 to use the same mechanisms for SMTP authentication. This is a server
25363 authenticator only. There is only one option:
25365 .option server_socket dovecot string unset
25367 This option must specify the socket that is the interface to Dovecot
25368 authentication. The &%public_name%& option must specify an authentication
25369 mechanism that Dovecot is configured to support. You can have several
25370 authenticators for different mechanisms. For example:
25374 public_name = PLAIN
25375 server_socket = /var/run/dovecot/auth-client
25376 server_set_id = $auth1
25381 server_socket = /var/run/dovecot/auth-client
25382 server_set_id = $auth1
25384 If the SMTP connection is encrypted, or if &$sender_host_address$& is equal to
25385 &$received_ip_address$& (that is, the connection is local), the &"secured"&
25386 option is passed in the Dovecot authentication command. If, for a TLS
25387 connection, a client certificate has been verified, the &"valid-client-cert"&
25388 option is passed. When authentication succeeds, the identity of the user
25389 who authenticated is placed in &$auth1$&.
25390 .ecindex IIDdcotauth1
25391 .ecindex IIDdcotauth2
25394 . ////////////////////////////////////////////////////////////////////////////
25395 . ////////////////////////////////////////////////////////////////////////////
25396 .chapter "The gsasl authenticator" "CHAPgsasl"
25397 .scindex IIDgsaslauth1 "&(gsasl)& authenticator"
25398 .scindex IIDgsaslauth2 "authenticators" "&(gsasl)&"
25399 .cindex "authentication" "GNU SASL"
25400 .cindex "authentication" "SASL"
25401 .cindex "authentication" "EXTERNAL"
25402 .cindex "authentication" "ANONYMOUS"
25403 .cindex "authentication" "PLAIN"
25404 .cindex "authentication" "LOGIN"
25405 .cindex "authentication" "DIGEST-MD5"
25406 .cindex "authentication" "CRAM-MD5"
25407 .cindex "authentication" "SCRAM-SHA-1"
25408 The &(gsasl)& authenticator provides server integration for the GNU SASL
25409 library and the mechanisms it provides. This is new as of the 4.80 release
25410 and there are a few areas where the library does not let Exim smoothly
25411 scale to handle future authentication mechanisms, so no guarantee can be
25412 made that any particular new authentication mechanism will be supported
25413 without code changes in Exim.
25416 .option server_channelbinding gsasl boolean false
25417 Some authentication mechanisms are able to use external context at both ends
25418 of the session to bind the authentication to that context, and fail the
25419 authentication process if that context differs. Specifically, some TLS
25420 ciphersuites can provide identifying information about the cryptographic
25423 This means that certificate identity and verification becomes a non-issue,
25424 as a man-in-the-middle attack will cause the correct client and server to
25425 see different identifiers and authentication will fail.
25427 This is currently only supported when using the GnuTLS library. This is
25428 only usable by mechanisms which support "channel binding"; at time of
25429 writing, that's the SCRAM family.
25431 This defaults off to ensure smooth upgrade across Exim releases, in case
25432 this option causes some clients to start failing. Some future release
25433 of Exim may switch the default to be true.
25436 .option server_hostname gsasl string&!! "see below"
25437 This option selects the hostname that is used when communicating with the
25438 library. The default value is &`$primary_hostname`&.
25439 Some mechanisms will use this data.
25442 .option server_mech gsasl string "see below"
25443 This option selects the authentication mechanism this driver should use. The
25444 default is the value of the generic &%public_name%& option. This option allows
25445 you to use a different underlying mechanism from the advertised name. For
25450 public_name = X-ANYTHING
25451 server_mech = CRAM-MD5
25452 server_set_id = $auth1
25456 .option server_password gsasl string&!! unset
25457 Various mechanisms need access to the cleartext password on the server, so
25458 that proof-of-possession can be demonstrated on the wire, without sending
25459 the password itself.
25461 The data available for lookup varies per mechanism.
25462 In all cases, &$auth1$& is set to the &'authentication id'&.
25463 The &$auth2$& variable will always be the &'authorization id'& (&'authz'&)
25464 if available, else the empty string.
25465 The &$auth3$& variable will always be the &'realm'& if available,
25466 else the empty string.
25468 A forced failure will cause authentication to defer.
25470 If using this option, it may make sense to set the &%server_condition%&
25471 option to be simply "true".
25474 .option server_realm gsasl string&!! unset
25475 This specifies the SASL realm that the server claims to be in.
25476 Some mechanisms will use this data.
25479 .option server_scram_iter gsasl string&!! unset
25480 This option provides data for the SCRAM family of mechanisms.
25481 &$auth1$& is not available at evaluation time.
25482 (This may change, as we receive feedback on use)
25485 .option server_scram_salt gsasl string&!! unset
25486 This option provides data for the SCRAM family of mechanisms.
25487 &$auth1$& is not available at evaluation time.
25488 (This may change, as we receive feedback on use)
25491 .option server_service gsasl string &`smtp`&
25492 This is the SASL service that the server claims to implement.
25493 Some mechanisms will use this data.
25496 .section "&(gsasl)& auth variables" "SECTgsaslauthvar"
25497 .vindex "&$auth1$&, &$auth2$&, etc"
25498 These may be set when evaluating specific options, as detailed above.
25499 They will also be set when evaluating &%server_condition%&.
25501 Unless otherwise stated below, the &(gsasl)& integration will use the following
25502 meanings for these variables:
25505 .vindex "&$auth1$&"
25506 &$auth1$&: the &'authentication id'&
25508 .vindex "&$auth2$&"
25509 &$auth2$&: the &'authorization id'&
25511 .vindex "&$auth3$&"
25512 &$auth3$&: the &'realm'&
25515 On a per-mechanism basis:
25518 .cindex "authentication" "EXTERNAL"
25519 EXTERNAL: only &$auth1$& is set, to the possibly empty &'authorization id'&;
25520 the &%server_condition%& option must be present.
25522 .cindex "authentication" "ANONYMOUS"
25523 ANONYMOUS: only &$auth1$& is set, to the possibly empty &'anonymous token'&;
25524 the &%server_condition%& option must be present.
25526 .cindex "authentication" "GSSAPI"
25527 GSSAPI: &$auth1$& will be set to the &'GSSAPI Display Name'&;
25528 &$auth2$& will be set to the &'authorization id'&,
25529 the &%server_condition%& option must be present.
25532 An &'anonymous token'& is something passed along as an unauthenticated
25533 identifier; this is analogous to FTP anonymous authentication passing an
25534 email address, or software-identifier@, as the "password".
25537 An example showing the password having the realm specified in the callback
25538 and demonstrating a Cyrus SASL to GSASL migration approach is:
25540 gsasl_cyrusless_crammd5:
25542 public_name = CRAM-MD5
25543 server_realm = imap.example.org
25544 server_password = ${lookup{$auth1:$auth3:userPassword}\
25545 dbmjz{/etc/sasldb2}{$value}fail}
25546 server_set_id = ${quote:$auth1}
25547 server_condition = yes
25551 . ////////////////////////////////////////////////////////////////////////////
25552 . ////////////////////////////////////////////////////////////////////////////
25554 .chapter "The heimdal_gssapi authenticator" "CHAPheimdalgss"
25555 .scindex IIDheimdalgssauth1 "&(heimdal_gssapi)& authenticator"
25556 .scindex IIDheimdalgssauth2 "authenticators" "&(heimdal_gssapi)&"
25557 .cindex "authentication" "GSSAPI"
25558 .cindex "authentication" "Kerberos"
25559 The &(heimdal_gssapi)& authenticator provides server integration for the
25560 Heimdal GSSAPI/Kerberos library, permitting Exim to set a keytab pathname
25563 .option server_hostname heimdal_gssapi string&!! "see below"
25564 This option selects the hostname that is used, with &%server_service%&,
25565 for constructing the GSS server name, as a &'GSS_C_NT_HOSTBASED_SERVICE'&
25566 identifier. The default value is &`$primary_hostname`&.
25568 .option server_keytab heimdal_gssapi string&!! unset
25569 If set, then Heimdal will not use the system default keytab (typically
25570 &_/etc/krb5.keytab_&) but instead the pathname given in this option.
25571 The value should be a pathname, with no &"file:"& prefix.
25573 .option server_service heimdal_gssapi string&!! "smtp"
25574 This option specifies the service identifier used, in conjunction with
25575 &%server_hostname%&, for building the identifer for finding credentials
25579 .section "&(heimdal_gssapi)& auth variables" "SECTheimdalgssauthvar"
25580 Beware that these variables will typically include a realm, thus will appear
25581 to be roughly like an email address already. The &'authzid'& in &$auth2$& is
25582 not verified, so a malicious client can set it to anything.
25584 The &$auth1$& field should be safely trustable as a value from the Key
25585 Distribution Center. Note that these are not quite email addresses.
25586 Each identifier is for a role, and so the left-hand-side may include a
25587 role suffix. For instance, &"joe/admin@EXAMPLE.ORG"&.
25589 .vindex "&$auth1$&, &$auth2$&, etc"
25591 .vindex "&$auth1$&"
25592 &$auth1$&: the &'authentication id'&, set to the GSS Display Name.
25594 .vindex "&$auth2$&"
25595 &$auth2$&: the &'authorization id'&, sent within SASL encapsulation after
25596 authentication. If that was empty, this will also be set to the
25601 . ////////////////////////////////////////////////////////////////////////////
25602 . ////////////////////////////////////////////////////////////////////////////
25604 .chapter "The spa authenticator" "CHAPspa"
25605 .scindex IIDspaauth1 "&(spa)& authenticator"
25606 .scindex IIDspaauth2 "authenticators" "&(spa)&"
25607 .cindex "authentication" "Microsoft Secure Password"
25608 .cindex "authentication" "NTLM"
25609 .cindex "Microsoft Secure Password Authentication"
25610 .cindex "NTLM authentication"
25611 The &(spa)& authenticator provides client support for Microsoft's &'Secure
25612 Password Authentication'& mechanism,
25613 which is also sometimes known as NTLM (NT LanMan). The code for client side of
25614 this authenticator was contributed by Marc Prud'hommeaux, and much of it is
25615 taken from the Samba project (&url(http://www.samba.org)). The code for the
25616 server side was subsequently contributed by Tom Kistner. The mechanism works as
25620 After the AUTH command has been accepted, the client sends an SPA
25621 authentication request based on the user name and optional domain.
25623 The server sends back a challenge.
25625 The client builds a challenge response which makes use of the user's password
25626 and sends it to the server, which then accepts or rejects it.
25629 Encryption is used to protect the password in transit.
25633 .section "Using spa as a server" "SECID179"
25634 .cindex "options" "&(spa)& authenticator (server)"
25635 The &(spa)& authenticator has just one server option:
25637 .option server_password spa string&!! unset
25638 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(spa)& authenticator"
25639 This option is expanded, and the result must be the cleartext password for the
25640 authenticating user, whose name is at this point in &$auth1$&. For
25641 compatibility with previous releases of Exim, the user name is also placed in
25642 &$1$&. However, the use of this variable for this purpose is now deprecated, as
25643 it can lead to confusion in string expansions that also use numeric variables
25644 for other things. For example:
25649 server_password = \
25650 ${lookup{$auth1}lsearch{/etc/exim/spa_clearpass}{$value}fail}
25652 If the expansion is forced to fail, authentication fails. Any other expansion
25653 failure causes a temporary error code to be returned.
25659 .section "Using spa as a client" "SECID180"
25660 .cindex "options" "&(spa)& authenticator (client)"
25661 The &(spa)& authenticator has the following client options:
25665 .option client_domain spa string&!! unset
25666 This option specifies an optional domain for the authentication.
25669 .option client_password spa string&!! unset
25670 This option specifies the user's password, and must be set.
25673 .option client_username spa string&!! unset
25674 This option specifies the user name, and must be set. Here is an example of a
25675 configuration of this authenticator for use with the mail servers at
25681 client_username = msn/msn_username
25682 client_password = msn_plaintext_password
25683 client_domain = DOMAIN_OR_UNSET
25685 .ecindex IIDspaauth1
25686 .ecindex IIDspaauth2
25692 . ////////////////////////////////////////////////////////////////////////////
25693 . ////////////////////////////////////////////////////////////////////////////
25695 .chapter "Encrypted SMTP connections using TLS/SSL" "CHAPTLS" &&&
25696 "Encrypted SMTP connections"
25697 .scindex IIDencsmtp1 "encryption" "on SMTP connection"
25698 .scindex IIDencsmtp2 "SMTP" "encryption"
25699 .cindex "TLS" "on SMTP connection"
25702 Support for TLS (Transport Layer Security), formerly known as SSL (Secure
25703 Sockets Layer), is implemented by making use of the OpenSSL library or the
25704 GnuTLS library (Exim requires GnuTLS release 1.0 or later). There is no
25705 cryptographic code in the Exim distribution itself for implementing TLS. In
25706 order to use this feature you must install OpenSSL or GnuTLS, and then build a
25707 version of Exim that includes TLS support (see section &<<SECTinctlsssl>>&).
25708 You also need to understand the basic concepts of encryption at a managerial
25709 level, and in particular, the way that public keys, private keys, and
25710 certificates are used.
25712 RFC 3207 defines how SMTP connections can make use of encryption. Once a
25713 connection is established, the client issues a STARTTLS command. If the
25714 server accepts this, the client and the server negotiate an encryption
25715 mechanism. If the negotiation succeeds, the data that subsequently passes
25716 between them is encrypted.
25718 Exim's ACLs can detect whether the current SMTP session is encrypted or not,
25719 and if so, what cipher suite is in use, whether the client supplied a
25720 certificate, and whether or not that certificate was verified. This makes it
25721 possible for an Exim server to deny or accept certain commands based on the
25724 &*Warning*&: Certain types of firewall and certain anti-virus products can
25725 disrupt TLS connections. You need to turn off SMTP scanning for these products
25726 in order to get TLS to work.
25730 .section "Support for the legacy &""ssmtp""& (aka &""smtps""&) protocol" &&&
25732 .cindex "ssmtp protocol"
25733 .cindex "smtps protocol"
25734 .cindex "SMTP" "ssmtp protocol"
25735 .cindex "SMTP" "smtps protocol"
25736 Early implementations of encrypted SMTP used a different TCP port from normal
25737 SMTP, and expected an encryption negotiation to start immediately, instead of
25738 waiting for a STARTTLS command from the client using the standard SMTP
25739 port. The protocol was called &"ssmtp"& or &"smtps"&, and port 465 was
25740 allocated for this purpose.
25742 This approach was abandoned when encrypted SMTP was standardized, but there are
25743 still some legacy clients that use it. Exim supports these clients by means of
25744 the &%tls_on_connect_ports%& global option. Its value must be a list of port
25745 numbers; the most common use is expected to be:
25747 tls_on_connect_ports = 465
25749 The port numbers specified by this option apply to all SMTP connections, both
25750 via the daemon and via &'inetd'&. You still need to specify all the ports that
25751 the daemon uses (by setting &%daemon_smtp_ports%& or &%local_interfaces%& or
25752 the &%-oX%& command line option) because &%tls_on_connect_ports%& does not add
25753 an extra port &-- rather, it specifies different behaviour on a port that is
25756 There is also a &%-tls-on-connect%& command line option. This overrides
25757 &%tls_on_connect_ports%&; it forces the legacy behaviour for all ports.
25764 .section "OpenSSL vs GnuTLS" "SECTopenvsgnu"
25765 .cindex "TLS" "OpenSSL &'vs'& GnuTLS"
25766 The first TLS support in Exim was implemented using OpenSSL. Support for GnuTLS
25767 followed later, when the first versions of GnuTLS were released. To build Exim
25768 to use GnuTLS, you need to set
25772 in Local/Makefile, in addition to
25776 You must also set TLS_LIBS and TLS_INCLUDE appropriately, so that the
25777 include files and libraries for GnuTLS can be found.
25779 There are some differences in usage when using GnuTLS instead of OpenSSL:
25782 The &%tls_verify_certificates%& option must contain the name of a file, not the
25783 name of a directory (for OpenSSL it can be either).
25785 The default value for &%tls_dhparam%& differs for historical reasons.
25787 .vindex "&$tls_in_peerdn$&"
25788 .vindex "&$tls_out_peerdn$&"
25789 Distinguished Name (DN) strings reported by the OpenSSL library use a slash for
25790 separating fields; GnuTLS uses commas, in accordance with RFC 2253. This
25791 affects the value of the &$tls_in_peerdn$& and &$tls_out_peerdn$& variables.
25793 OpenSSL identifies cipher suites using hyphens as separators, for example:
25794 DES-CBC3-SHA. GnuTLS historically used underscores, for example:
25795 RSA_ARCFOUR_SHA. What is more, OpenSSL complains if underscores are present
25796 in a cipher list. To make life simpler, Exim changes underscores to hyphens
25797 for OpenSSL and passes the string unchanged to GnuTLS (expecting the library
25798 to handle its own older variants) when processing lists of cipher suites in the
25799 &%tls_require_ciphers%& options (the global option and the &(smtp)& transport
25802 The &%tls_require_ciphers%& options operate differently, as described in the
25803 sections &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&.
25805 The &%tls_dh_min_bits%& SMTP transport option is only honoured by GnuTLS.
25806 When using OpenSSL, this option is ignored.
25807 (If an API is found to let OpenSSL be configured in this way,
25808 let the Exim Maintainers know and we'll likely use it).
25810 Some other recently added features may only be available in one or the other.
25811 This should be documented with the feature. If the documentation does not
25812 explicitly state that the feature is infeasible in the other TLS
25813 implementation, then patches are welcome.
25817 .section "GnuTLS parameter computation" "SECTgnutlsparam"
25818 This section only applies if &%tls_dhparam%& is set to &`historic`& or to
25819 an explicit path; if the latter, then the text about generation still applies,
25820 but not the chosen filename.
25821 By default, as of Exim 4.80 a hard-coded D-H prime is used.
25822 See the documentation of &%tls_dhparam%& for more information.
25824 GnuTLS uses D-H parameters that may take a substantial amount of time
25825 to compute. It is unreasonable to re-compute them for every TLS session.
25826 Therefore, Exim keeps this data in a file in its spool directory, called
25827 &_gnutls-params-NNNN_& for some value of NNNN, corresponding to the number
25829 The file is owned by the Exim user and is readable only by
25830 its owner. Every Exim process that start up GnuTLS reads the D-H
25831 parameters from this file. If the file does not exist, the first Exim process
25832 that needs it computes the data and writes it to a temporary file which is
25833 renamed once it is complete. It does not matter if several Exim processes do
25834 this simultaneously (apart from wasting a few resources). Once a file is in
25835 place, new Exim processes immediately start using it.
25837 For maximum security, the parameters that are stored in this file should be
25838 recalculated periodically, the frequency depending on your paranoia level.
25839 If you are avoiding using the fixed D-H primes published in RFCs, then you
25840 are concerned about some advanced attacks and will wish to do this; if you do
25841 not regenerate then you might as well stick to the standard primes.
25843 Arranging this is easy in principle; just delete the file when you want new
25844 values to be computed. However, there may be a problem. The calculation of new
25845 parameters needs random numbers, and these are obtained from &_/dev/random_&.
25846 If the system is not very active, &_/dev/random_& may delay returning data
25847 until enough randomness (entropy) is available. This may cause Exim to hang for
25848 a substantial amount of time, causing timeouts on incoming connections.
25850 The solution is to generate the parameters externally to Exim. They are stored
25851 in &_gnutls-params-N_& in PEM format, which means that they can be
25852 generated externally using the &(certtool)& command that is part of GnuTLS.
25854 To replace the parameters with new ones, instead of deleting the file
25855 and letting Exim re-create it, you can generate new parameters using
25856 &(certtool)& and, when this has been done, replace Exim's cache file by
25857 renaming. The relevant commands are something like this:
25860 [ look for file; assume gnutls-params-2236 is the most recent ]
25863 # chown exim:exim new-params
25864 # chmod 0600 new-params
25865 # certtool --generate-dh-params --bits 2236 >>new-params
25866 # openssl dhparam -noout -text -in new-params | head
25867 [ check the first line, make sure it's not more than 2236;
25868 if it is, then go back to the start ("rm") and repeat
25869 until the size generated is at most the size requested ]
25870 # chmod 0400 new-params
25871 # mv new-params gnutls-params-2236
25873 If Exim never has to generate the parameters itself, the possibility of
25874 stalling is removed.
25876 The filename changed in Exim 4.80, to gain the -bits suffix. The value which
25877 Exim will choose depends upon the version of GnuTLS in use. For older GnuTLS,
25878 the value remains hard-coded in Exim as 1024. As of GnuTLS 2.12.x, there is
25879 a way for Exim to ask for the "normal" number of bits for D-H public-key usage,
25880 and Exim does so. This attempt to remove Exim from TLS policy decisions
25881 failed, as GnuTLS 2.12 returns a value higher than the current hard-coded limit
25882 of the NSS library. Thus Exim gains the &%tls_dh_max_bits%& global option,
25883 which applies to all D-H usage, client or server. If the value returned by
25884 GnuTLS is greater than &%tls_dh_max_bits%& then the value will be clamped down
25885 to &%tls_dh_max_bits%&. The default value has been set at the current NSS
25886 limit, which is still much higher than Exim historically used.
25888 The filename and bits used will change as the GnuTLS maintainers change the
25889 value for their parameter &`GNUTLS_SEC_PARAM_NORMAL`&, as clamped by
25890 &%tls_dh_max_bits%&. At the time of writing (mid 2012), GnuTLS 2.12 recommends
25891 2432 bits, while NSS is limited to 2236 bits.
25893 In fact, the requested value will be *lower* than &%tls_dh_max_bits%&, to
25894 increase the chance of the generated prime actually being within acceptable
25895 bounds, as GnuTLS has been observed to overshoot. Note the check step in the
25896 procedure above. There is no sane procedure available to Exim to double-check
25897 the size of the generated prime, so it might still be too large.
25900 .section "Requiring specific ciphers in OpenSSL" "SECTreqciphssl"
25901 .cindex "TLS" "requiring specific ciphers (OpenSSL)"
25902 .oindex "&%tls_require_ciphers%&" "OpenSSL"
25903 There is a function in the OpenSSL library that can be passed a list of cipher
25904 suites before the cipher negotiation takes place. This specifies which ciphers
25905 are acceptable. The list is colon separated and may contain names like
25906 DES-CBC3-SHA. Exim passes the expanded value of &%tls_require_ciphers%&
25907 directly to this function call.
25908 Many systems will install the OpenSSL manual-pages, so you may have
25909 &'ciphers(1)'& available to you.
25910 The following quotation from the OpenSSL
25911 documentation specifies what forms of item are allowed in the cipher string:
25914 It can consist of a single cipher suite such as RC4-SHA.
25916 It can represent a list of cipher suites containing a certain algorithm,
25917 or cipher suites of a certain type. For example SHA1 represents all
25918 ciphers suites using the digest algorithm SHA1 and SSLv3 represents all
25921 Lists of cipher suites can be combined in a single cipher string using
25922 the + character. This is used as a logical and operation. For example
25923 SHA1+DES represents all cipher suites containing the SHA1 and the DES
25927 Each cipher string can be optionally preceded by one of the characters &`!`&,
25930 If &`!`& is used, the ciphers are permanently deleted from the list. The
25931 ciphers deleted can never reappear in the list even if they are explicitly
25934 If &`-`& is used, the ciphers are deleted from the list, but some or all
25935 of the ciphers can be added again by later options.
25937 If &`+`& is used, the ciphers are moved to the end of the list. This
25938 option does not add any new ciphers; it just moves matching existing ones.
25941 If none of these characters is present, the string is interpreted as
25942 a list of ciphers to be appended to the current preference list. If the list
25943 includes any ciphers already present they will be ignored: that is, they will
25944 not be moved to the end of the list.
25947 The OpenSSL &'ciphers(1)'& command may be used to test the results of a given
25950 # note single-quotes to get ! past any shell history expansion
25951 $ openssl ciphers 'HIGH:!MD5:!SHA1'
25954 This example will let the library defaults be permitted on the MX port, where
25955 there's probably no identity verification anyway, but ups the ante on the
25956 submission ports where the administrator might have some influence on the
25957 choice of clients used:
25959 # OpenSSL variant; see man ciphers(1)
25960 tls_require_ciphers = ${if =={$received_port}{25}\
25967 .section "Requiring specific ciphers or other parameters in GnuTLS" &&&
25969 .cindex "GnuTLS" "specifying parameters for"
25970 .cindex "TLS" "specifying ciphers (GnuTLS)"
25971 .cindex "TLS" "specifying key exchange methods (GnuTLS)"
25972 .cindex "TLS" "specifying MAC algorithms (GnuTLS)"
25973 .cindex "TLS" "specifying protocols (GnuTLS)"
25974 .cindex "TLS" "specifying priority string (GnuTLS)"
25975 .oindex "&%tls_require_ciphers%&" "GnuTLS"
25976 The GnuTLS library allows the caller to provide a "priority string", documented
25977 as part of the &[gnutls_priority_init]& function. This is very similar to the
25978 ciphersuite specification in OpenSSL.
25980 The &%tls_require_ciphers%& option is treated as the GnuTLS priority string.
25982 The &%tls_require_ciphers%& option is available both as an global option,
25983 controlling how Exim behaves as a server, and also as an option of the
25984 &(smtp)& transport, controlling how Exim behaves as a client. In both cases
25985 the value is string expanded. The resulting string is not an Exim list and
25986 the string is given to the GnuTLS library, so that Exim does not need to be
25987 aware of future feature enhancements of GnuTLS.
25989 Documentation of the strings accepted may be found in the GnuTLS manual, under
25990 "Priority strings". This is online as
25991 &url(http://www.gnutls.org/manual/html_node/Priority-Strings.html),
25992 but beware that this relates to GnuTLS 3, which may be newer than the version
25993 installed on your system. If you are using GnuTLS 3,
25994 &url(http://www.gnutls.org/manual/gnutls.html#Listing-the-ciphersuites-in-a-priority-string, then the example code)
25995 on that site can be used to test a given string.
25997 Prior to Exim 4.80, an older API of GnuTLS was used, and Exim supported three
25998 additional options, "&%gnutls_require_kx%&", "&%gnutls_require_mac%&" and
25999 "&%gnutls_require_protocols%&". &%tls_require_ciphers%& was an Exim list.
26001 This example will let the library defaults be permitted on the MX port, where
26002 there's probably no identity verification anyway, and lowers security further
26003 by increasing compatibility; but this ups the ante on the submission ports
26004 where the administrator might have some influence on the choice of clients
26008 tls_require_ciphers = ${if =={$received_port}{25}\
26014 .section "Configuring an Exim server to use TLS" "SECID182"
26015 .cindex "TLS" "configuring an Exim server"
26016 When Exim has been built with TLS support, it advertises the availability of
26017 the STARTTLS command to client hosts that match &%tls_advertise_hosts%&,
26018 but not to any others. The default value of this option is unset, which means
26019 that STARTTLS is not advertised at all. This default is chosen because you
26020 need to set some other options in order to make TLS available, and also it is
26021 sensible for systems that want to use TLS only as a client.
26023 If a client issues a STARTTLS command and there is some configuration
26024 problem in the server, the command is rejected with a 454 error. If the client
26025 persists in trying to issue SMTP commands, all except QUIT are rejected
26028 554 Security failure
26030 If a STARTTLS command is issued within an existing TLS session, it is
26031 rejected with a 554 error code.
26033 To enable TLS operations on a server, you must set &%tls_advertise_hosts%& to
26034 match some hosts. You can, of course, set it to * to match all hosts.
26035 However, this is not all you need to do. TLS sessions to a server won't work
26036 without some further configuration at the server end.
26038 It is rumoured that all existing clients that support TLS/SSL use RSA
26039 encryption. To make this work you need to set, in the server,
26041 tls_certificate = /some/file/name
26042 tls_privatekey = /some/file/name
26044 These options are, in fact, expanded strings, so you can make them depend on
26045 the identity of the client that is connected if you wish. The first file
26046 contains the server's X509 certificate, and the second contains the private key
26047 that goes with it. These files need to be readable by the Exim user, and must
26048 always be given as full path names. They can be the same file if both the
26049 certificate and the key are contained within it. If &%tls_privatekey%& is not
26050 set, or if its expansion is forced to fail or results in an empty string, this
26051 is assumed to be the case. The certificate file may also contain intermediate
26052 certificates that need to be sent to the client to enable it to authenticate
26053 the server's certificate.
26055 If you do not understand about certificates and keys, please try to find a
26056 source of this background information, which is not Exim-specific. (There are a
26057 few comments below in section &<<SECTcerandall>>&.)
26059 &*Note*&: These options do not apply when Exim is operating as a client &--
26060 they apply only in the case of a server. If you need to use a certificate in an
26061 Exim client, you must set the options of the same names in an &(smtp)&
26064 With just these options, an Exim server will be able to use TLS. It does not
26065 require the client to have a certificate (but see below for how to insist on
26066 this). There is one other option that may be needed in other situations. If
26068 tls_dhparam = /some/file/name
26070 is set, the SSL library is initialized for the use of Diffie-Hellman ciphers
26071 with the parameters contained in the file.
26072 Set this to &`none`& to disable use of DH entirely, by making no prime
26077 This may also be set to a string identifying a standard prime to be used for
26078 DH; if it is set to &`default`& or, for OpenSSL, is unset, then the prime
26079 used is &`ike23`&. There are a few standard primes available, see the
26080 documentation for &%tls_dhparam%& for the complete list.
26086 for a way of generating file data.
26088 The strings supplied for these three options are expanded every time a client
26089 host connects. It is therefore possible to use different certificates and keys
26090 for different hosts, if you so wish, by making use of the client's IP address
26091 in &$sender_host_address$& to control the expansion. If a string expansion is
26092 forced to fail, Exim behaves as if the option is not set.
26094 .cindex "cipher" "logging"
26095 .cindex "log" "TLS cipher"
26096 .vindex "&$tls_in_cipher$&"
26097 The variable &$tls_in_cipher$& is set to the cipher suite that was negotiated for
26098 an incoming TLS connection. It is included in the &'Received:'& header of an
26099 incoming message (by default &-- you can, of course, change this), and it is
26100 also included in the log line that records a message's arrival, keyed by
26101 &"X="&, unless the &%tls_cipher%& log selector is turned off. The &%encrypted%&
26102 condition can be used to test for specific cipher suites in ACLs.
26104 Once TLS has been established, the ACLs that run for subsequent SMTP commands
26105 can check the name of the cipher suite and vary their actions accordingly. The
26106 cipher suite names vary, depending on which TLS library is being used. For
26107 example, OpenSSL uses the name DES-CBC3-SHA for the cipher suite which in other
26108 contexts is known as TLS_RSA_WITH_3DES_EDE_CBC_SHA. Check the OpenSSL or GnuTLS
26109 documentation for more details.
26111 For outgoing SMTP deliveries, &$tls_out_cipher$& is used and logged
26112 (again depending on the &%tls_cipher%& log selector).
26115 .section "Requesting and verifying client certificates" "SECID183"
26116 .cindex "certificate" "verification of client"
26117 .cindex "TLS" "client certificate verification"
26118 If you want an Exim server to request a certificate when negotiating a TLS
26119 session with a client, you must set either &%tls_verify_hosts%& or
26120 &%tls_try_verify_hosts%&. You can, of course, set either of them to * to
26121 apply to all TLS connections. For any host that matches one of these options,
26122 Exim requests a certificate as part of the setup of the TLS session. The
26123 contents of the certificate are verified by comparing it with a list of
26124 expected certificates. These must be available in a file or,
26125 for OpenSSL only (not GnuTLS), a directory, identified by
26126 &%tls_verify_certificates%&.
26128 A file can contain multiple certificates, concatenated end to end. If a
26131 each certificate must be in a separate file, with a name (or a symbolic link)
26132 of the form <&'hash'&>.0, where <&'hash'&> is a hash value constructed from the
26133 certificate. You can compute the relevant hash by running the command
26135 openssl x509 -hash -noout -in /cert/file
26137 where &_/cert/file_& contains a single certificate.
26139 The difference between &%tls_verify_hosts%& and &%tls_try_verify_hosts%& is
26140 what happens if the client does not supply a certificate, or if the certificate
26141 does not match any of the certificates in the collection named by
26142 &%tls_verify_certificates%&. If the client matches &%tls_verify_hosts%&, the
26143 attempt to set up a TLS session is aborted, and the incoming connection is
26144 dropped. If the client matches &%tls_try_verify_hosts%&, the (encrypted) SMTP
26145 session continues. ACLs that run for subsequent SMTP commands can detect the
26146 fact that no certificate was verified, and vary their actions accordingly. For
26147 example, you can insist on a certificate before accepting a message for
26148 relaying, but not when the message is destined for local delivery.
26150 .vindex "&$tls_in_peerdn$&"
26151 When a client supplies a certificate (whether it verifies or not), the value of
26152 the Distinguished Name of the certificate is made available in the variable
26153 &$tls_in_peerdn$& during subsequent processing of the message.
26155 .cindex "log" "distinguished name"
26156 Because it is often a long text string, it is not included in the log line or
26157 &'Received:'& header by default. You can arrange for it to be logged, keyed by
26158 &"DN="&, by setting the &%tls_peerdn%& log selector, and you can use
26159 &%received_header_text%& to change the &'Received:'& header. When no
26160 certificate is supplied, &$tls_in_peerdn$& is empty.
26163 .section "Revoked certificates" "SECID184"
26164 .cindex "TLS" "revoked certificates"
26165 .cindex "revocation list"
26166 .cindex "certificate" "revocation list"
26167 Certificate issuing authorities issue Certificate Revocation Lists (CRLs) when
26168 certificates are revoked. If you have such a list, you can pass it to an Exim
26169 server using the global option called &%tls_crl%& and to an Exim client using
26170 an identically named option for the &(smtp)& transport. In each case, the value
26171 of the option is expanded and must then be the name of a file that contains a
26175 .section "Configuring an Exim client to use TLS" "SECID185"
26176 .cindex "cipher" "logging"
26177 .cindex "log" "TLS cipher"
26178 .cindex "log" "distinguished name"
26179 .cindex "TLS" "configuring an Exim client"
26180 The &%tls_cipher%& and &%tls_peerdn%& log selectors apply to outgoing SMTP
26181 deliveries as well as to incoming, the latter one causing logging of the
26182 server certificate's DN. The remaining client configuration for TLS is all
26183 within the &(smtp)& transport.
26185 It is not necessary to set any options to have TLS work in the &(smtp)&
26186 transport. If Exim is built with TLS support, and TLS is advertised by a
26187 server, the &(smtp)& transport always tries to start a TLS session. However,
26188 this can be prevented by setting &%hosts_avoid_tls%& (an option of the
26189 transport) to a list of server hosts for which TLS should not be used.
26191 If you do not want Exim to attempt to send messages unencrypted when an attempt
26192 to set up an encrypted connection fails in any way, you can set
26193 &%hosts_require_tls%& to a list of hosts for which encryption is mandatory. For
26194 those hosts, delivery is always deferred if an encrypted connection cannot be
26195 set up. If there are any other hosts for the address, they are tried in the
26198 When the server host is not in &%hosts_require_tls%&, Exim may try to deliver
26199 the message unencrypted. It always does this if the response to STARTTLS is
26200 a 5&'xx'& code. For a temporary error code, or for a failure to negotiate a TLS
26201 session after a success response code, what happens is controlled by the
26202 &%tls_tempfail_tryclear%& option of the &(smtp)& transport. If it is false,
26203 delivery to this host is deferred, and other hosts (if available) are tried. If
26204 it is true, Exim attempts to deliver unencrypted after a 4&'xx'& response to
26205 STARTTLS, and if STARTTLS is accepted, but the subsequent TLS
26206 negotiation fails, Exim closes the current connection (because it is in an
26207 unknown state), opens a new one to the same host, and then tries the delivery
26210 The &%tls_certificate%& and &%tls_privatekey%& options of the &(smtp)&
26211 transport provide the client with a certificate, which is passed to the server
26212 if it requests it. If the server is Exim, it will request a certificate only if
26213 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& matches the client.
26215 If the &%tls_verify_certificates%& option is set on the &(smtp)& transport, it
26216 must name a file or,
26217 for OpenSSL only (not GnuTLS), a directory, that contains a collection of
26218 expected server certificates. The client verifies the server's certificate
26219 against this collection, taking into account any revoked certificates that are
26220 in the list defined by &%tls_crl%&.
26221 Failure to verify fails the TLS connection unless either of the
26222 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& options are set.
26224 The &%tls_verify_hosts%& and &%tls_try_verify_hosts%& options restrict
26225 certificate verification to the listed servers. Verification either must
26226 or need not succeed respectively.
26229 &%tls_require_ciphers%& is set on the &(smtp)& transport, it must contain a
26230 list of permitted cipher suites. If either of these checks fails, delivery to
26231 the current host is abandoned, and the &(smtp)& transport tries to deliver to
26232 alternative hosts, if any.
26235 These options must be set in the &(smtp)& transport for Exim to use TLS when it
26236 is operating as a client. Exim does not assume that a server certificate (set
26237 by the global options of the same name) should also be used when operating as a
26241 .vindex "&$host_address$&"
26242 All the TLS options in the &(smtp)& transport are expanded before use, with
26243 &$host$& and &$host_address$& containing the name and address of the server to
26244 which the client is connected. Forced failure of an expansion causes Exim to
26245 behave as if the relevant option were unset.
26247 .vindex &$tls_out_bits$&
26248 .vindex &$tls_out_cipher$&
26249 .vindex &$tls_out_peerdn$&
26250 .vindex &$tls_out_sni$&
26251 Before an SMTP connection is established, the
26252 &$tls_out_bits$&, &$tls_out_cipher$&, &$tls_out_peerdn$& and &$tls_out_sni$&
26253 variables are emptied. (Until the first connection, they contain the values
26254 that were set when the message was received.) If STARTTLS is subsequently
26255 successfully obeyed, these variables are set to the relevant values for the
26256 outgoing connection.
26260 .section "Use of TLS Server Name Indication" "SECTtlssni"
26261 .cindex "TLS" "Server Name Indication"
26262 .vindex "&$tls_in_sni$&"
26263 .oindex "&%tls_in_sni%&"
26264 With TLS1.0 or above, there is an extension mechanism by which extra
26265 information can be included at various points in the protocol. One of these
26266 extensions, documented in RFC 6066 (and before that RFC 4366) is
26267 &"Server Name Indication"&, commonly &"SNI"&. This extension is sent by the
26268 client in the initial handshake, so that the server can examine the servername
26269 within and possibly choose to use different certificates and keys (and more)
26272 This is analagous to HTTP's &"Host:"& header, and is the main mechanism by
26273 which HTTPS-enabled web-sites can be virtual-hosted, many sites to one IP
26276 With SMTP to MX, there are the same problems here as in choosing the identity
26277 against which to validate a certificate: you can't rely on insecure DNS to
26278 provide the identity which you then cryptographically verify. So this will
26279 be of limited use in that environment.
26281 With SMTP to Submission, there is a well-defined hostname which clients are
26282 connecting to and can validate certificates against. Thus clients &*can*&
26283 choose to include this information in the TLS negotiation. If this becomes
26284 wide-spread, then hosters can choose to present different certificates to
26285 different clients. Or even negotiate different cipher suites.
26287 The &%tls_sni%& option on an SMTP transport is an expanded string; the result,
26288 if not empty, will be sent on a TLS session as part of the handshake. There's
26289 nothing more to it. Choosing a sensible value not derived insecurely is the
26290 only point of caution. The &$tls_out_sni$& variable will be set to this string
26291 for the lifetime of the client connection (including during authentication).
26293 Except during SMTP client sessions, if &$tls_in_sni$& is set then it is a string
26294 received from a client.
26295 It can be logged with the &%log_selector%& item &`+tls_sni`&.
26297 If the string &`tls_in_sni`& appears in the main section's &%tls_certificate%&
26298 option (prior to expansion) then the following options will be re-expanded
26299 during TLS session handshake, to permit alternative values to be chosen:
26302 .vindex "&%tls_certificate%&"
26303 &%tls_certificate%&
26305 .vindex "&%tls_crl%&"
26308 .vindex "&%tls_privatekey%&"
26311 .vindex "&%tls_verify_certificates%&"
26312 &%tls_verify_certificates%&
26315 Great care should be taken to deal with matters of case, various injection
26316 attacks in the string (&`../`& or SQL), and ensuring that a valid filename
26317 can always be referenced; it is important to remember that &$tls_sni$& is
26318 arbitrary unverified data provided prior to authentication.
26320 The Exim developers are proceeding cautiously and so far no other TLS options
26323 When Exim is built againt OpenSSL, OpenSSL must have been built with support
26324 for TLS Extensions. This holds true for OpenSSL 1.0.0+ and 0.9.8+ with
26325 enable-tlsext in EXTRACONFIGURE. If you invoke &(openssl s_client -h)& and
26326 see &`-servername`& in the output, then OpenSSL has support.
26328 When Exim is built against GnuTLS, SNI support is available as of GnuTLS
26329 0.5.10. (Its presence predates the current API which Exim uses, so if Exim
26330 built, then you have SNI support).
26334 .section "Multiple messages on the same encrypted TCP/IP connection" &&&
26336 .cindex "multiple SMTP deliveries with TLS"
26337 .cindex "TLS" "multiple message deliveries"
26338 Exim sends multiple messages down the same TCP/IP connection by starting up
26339 an entirely new delivery process for each message, passing the socket from
26340 one process to the next. This implementation does not fit well with the use
26341 of TLS, because there is quite a lot of state information associated with a TLS
26342 connection, not just a socket identification. Passing all the state information
26343 to a new process is not feasible. Consequently, Exim shuts down an existing TLS
26344 session before passing the socket to a new process. The new process may then
26345 try to start a new TLS session, and if successful, may try to re-authenticate
26346 if AUTH is in use, before sending the next message.
26348 The RFC is not clear as to whether or not an SMTP session continues in clear
26349 after TLS has been shut down, or whether TLS may be restarted again later, as
26350 just described. However, if the server is Exim, this shutdown and
26351 reinitialization works. It is not known which (if any) other servers operate
26352 successfully if the client closes a TLS session and continues with unencrypted
26353 SMTP, but there are certainly some that do not work. For such servers, Exim
26354 should not pass the socket to another process, because the failure of the
26355 subsequent attempt to use it would cause Exim to record a temporary host error,
26356 and delay other deliveries to that host.
26358 To test for this case, Exim sends an EHLO command to the server after
26359 closing down the TLS session. If this fails in any way, the connection is
26360 closed instead of being passed to a new delivery process, but no retry
26361 information is recorded.
26363 There is also a manual override; you can set &%hosts_nopass_tls%& on the
26364 &(smtp)& transport to match those hosts for which Exim should not pass
26365 connections to new processes if TLS has been used.
26370 .section "Certificates and all that" "SECTcerandall"
26371 .cindex "certificate" "references to discussion"
26372 In order to understand fully how TLS works, you need to know about
26373 certificates, certificate signing, and certificate authorities. This is not the
26374 place to give a tutorial, especially as I do not know very much about it
26375 myself. Some helpful introduction can be found in the FAQ for the SSL addition
26376 to Apache, currently at
26378 &url(http://www.modssl.org/docs/2.7/ssl_faq.html#ToC24)
26380 Other parts of the &'modssl'& documentation are also helpful, and have
26381 links to further files.
26382 Eric Rescorla's book, &'SSL and TLS'&, published by Addison-Wesley (ISBN
26383 0-201-61598-3), contains both introductory and more in-depth descriptions.
26384 Some sample programs taken from the book are available from
26386 &url(http://www.rtfm.com/openssl-examples/)
26390 .section "Certificate chains" "SECID186"
26391 The file named by &%tls_certificate%& may contain more than one
26392 certificate. This is useful in the case where the certificate that is being
26393 sent is validated by an intermediate certificate which the other end does
26394 not have. Multiple certificates must be in the correct order in the file.
26395 First the host's certificate itself, then the first intermediate
26396 certificate to validate the issuer of the host certificate, then the next
26397 intermediate certificate to validate the issuer of the first intermediate
26398 certificate, and so on, until finally (optionally) the root certificate.
26399 The root certificate must already be trusted by the recipient for
26400 validation to succeed, of course, but if it's not preinstalled, sending the
26401 root certificate along with the rest makes it available for the user to
26402 install if the receiving end is a client MUA that can interact with a user.
26404 Note that certificates using MD5 are unlikely to work on today's Internet;
26405 even if your libraries allow loading them for use in Exim when acting as a
26406 server, increasingly clients will not accept such certificates. The error
26407 diagnostics in such a case can be frustratingly vague.
26411 .section "Self-signed certificates" "SECID187"
26412 .cindex "certificate" "self-signed"
26413 You can create a self-signed certificate using the &'req'& command provided
26414 with OpenSSL, like this:
26415 . ==== Do not shorten the duration here without reading and considering
26416 . ==== the text below. Please leave it at 9999 days.
26418 openssl req -x509 -newkey rsa:1024 -keyout file1 -out file2 \
26421 &_file1_& and &_file2_& can be the same file; the key and the certificate are
26422 delimited and so can be identified independently. The &%-days%& option
26423 specifies a period for which the certificate is valid. The &%-nodes%& option is
26424 important: if you do not set it, the key is encrypted with a passphrase
26425 that you are prompted for, and any use that is made of the key causes more
26426 prompting for the passphrase. This is not helpful if you are going to use
26427 this certificate and key in an MTA, where prompting is not possible.
26429 . ==== I expect to still be working 26 years from now. The less technical
26430 . ==== debt I create, in terms of storing up trouble for my later years, the
26431 . ==== happier I will be then. We really have reached the point where we
26432 . ==== should start, at the very least, provoking thought and making folks
26433 . ==== pause before proceeding, instead of leaving all the fixes until two
26434 . ==== years before 2^31 seconds after the 1970 Unix epoch.
26436 NB: we are now past the point where 9999 days takes us past the 32-bit Unix
26437 epoch. If your system uses unsigned time_t (most do) and is 32-bit, then
26438 the above command might produce a date in the past. Think carefully about
26439 the lifetime of the systems you're deploying, and either reduce the duration
26440 of the certificate or reconsider your platform deployment. (At time of
26441 writing, reducing the duration is the most likely choice, but the inexorable
26442 progression of time takes us steadily towards an era where this will not
26443 be a sensible resolution).
26445 A self-signed certificate made in this way is sufficient for testing, and
26446 may be adequate for all your requirements if you are mainly interested in
26447 encrypting transfers, and not in secure identification.
26449 However, many clients require that the certificate presented by the server be a
26450 user (also called &"leaf"& or &"site"&) certificate, and not a self-signed
26451 certificate. In this situation, the self-signed certificate described above
26452 must be installed on the client host as a trusted root &'certification
26453 authority'& (CA), and the certificate used by Exim must be a user certificate
26454 signed with that self-signed certificate.
26456 For information on creating self-signed CA certificates and using them to sign
26457 user certificates, see the &'General implementation overview'& chapter of the
26458 Open-source PKI book, available online at
26459 &url(http://ospkibook.sourceforge.net/).
26460 .ecindex IIDencsmtp1
26461 .ecindex IIDencsmtp2
26465 . ////////////////////////////////////////////////////////////////////////////
26466 . ////////////////////////////////////////////////////////////////////////////
26468 .chapter "Access control lists" "CHAPACL"
26469 .scindex IIDacl "&ACL;" "description"
26470 .cindex "control of incoming mail"
26471 .cindex "message" "controlling incoming"
26472 .cindex "policy control" "access control lists"
26473 Access Control Lists (ACLs) are defined in a separate section of the run time
26474 configuration file, headed by &"begin acl"&. Each ACL definition starts with a
26475 name, terminated by a colon. Here is a complete ACL section that contains just
26476 one very small ACL:
26480 accept hosts = one.host.only
26482 You can have as many lists as you like in the ACL section, and the order in
26483 which they appear does not matter. The lists are self-terminating.
26485 The majority of ACLs are used to control Exim's behaviour when it receives
26486 certain SMTP commands. This applies both to incoming TCP/IP connections, and
26487 when a local process submits a message using SMTP by specifying the &%-bs%&
26488 option. The most common use is for controlling which recipients are accepted
26489 in incoming messages. In addition, you can define an ACL that is used to check
26490 local non-SMTP messages. The default configuration file contains an example of
26491 a realistic ACL for checking RCPT commands. This is discussed in chapter
26492 &<<CHAPdefconfil>>&.
26495 .section "Testing ACLs" "SECID188"
26496 The &%-bh%& command line option provides a way of testing your ACL
26497 configuration locally by running a fake SMTP session with which you interact.
26498 The host &'relay-test.mail-abuse.org'& provides a service for checking your
26499 relaying configuration (see section &<<SECTcheralcon>>& for more details).
26503 .section "Specifying when ACLs are used" "SECID189"
26504 .cindex "&ACL;" "options for specifying"
26505 In order to cause an ACL to be used, you have to name it in one of the relevant
26506 options in the main part of the configuration. These options are:
26507 .cindex "AUTH" "ACL for"
26508 .cindex "DATA" "ACLs for"
26509 .cindex "ETRN" "ACL for"
26510 .cindex "EXPN" "ACL for"
26511 .cindex "HELO" "ACL for"
26512 .cindex "EHLO" "ACL for"
26513 .cindex "MAIL" "ACL for"
26514 .cindex "QUIT, ACL for"
26515 .cindex "RCPT" "ACL for"
26516 .cindex "STARTTLS, ACL for"
26517 .cindex "VRFY" "ACL for"
26518 .cindex "SMTP" "connection, ACL for"
26519 .cindex "non-SMTP messages" "ACLs for"
26520 .cindex "MIME content scanning" "ACL for"
26521 .cindex "PRDR" "ACL for"
26524 .irow &%acl_not_smtp%& "ACL for non-SMTP messages"
26525 .irow &%acl_not_smtp_mime%& "ACL for non-SMTP MIME parts"
26526 .irow &%acl_not_smtp_start%& "ACL at start of non-SMTP message"
26527 .irow &%acl_smtp_auth%& "ACL for AUTH"
26528 .irow &%acl_smtp_connect%& "ACL for start of SMTP connection"
26529 .irow &%acl_smtp_data%& "ACL after DATA is complete"
26530 .irow &%acl_smtp_data_prdr%& "ACL for each recipient, after DATA is complete"
26531 .irow &%acl_smtp_etrn%& "ACL for ETRN"
26532 .irow &%acl_smtp_expn%& "ACL for EXPN"
26533 .irow &%acl_smtp_helo%& "ACL for HELO or EHLO"
26534 .irow &%acl_smtp_mail%& "ACL for MAIL"
26535 .irow &%acl_smtp_mailauth%& "ACL for the AUTH parameter of MAIL"
26536 .irow &%acl_smtp_mime%& "ACL for content-scanning MIME parts"
26537 .irow &%acl_smtp_notquit%& "ACL for non-QUIT terminations"
26538 .irow &%acl_smtp_predata%& "ACL at start of DATA command"
26539 .irow &%acl_smtp_quit%& "ACL for QUIT"
26540 .irow &%acl_smtp_rcpt%& "ACL for RCPT"
26541 .irow &%acl_smtp_starttls%& "ACL for STARTTLS"
26542 .irow &%acl_smtp_vrfy%& "ACL for VRFY"
26545 For example, if you set
26547 acl_smtp_rcpt = small_acl
26549 the little ACL defined above is used whenever Exim receives a RCPT command
26550 in an SMTP dialogue. The majority of policy tests on incoming messages can be
26551 done when RCPT commands arrive. A rejection of RCPT should cause the
26552 sending MTA to give up on the recipient address contained in the RCPT
26553 command, whereas rejection at other times may cause the client MTA to keep on
26554 trying to deliver the message. It is therefore recommended that you do as much
26555 testing as possible at RCPT time.
26558 .section "The non-SMTP ACLs" "SECID190"
26559 .cindex "non-SMTP messages" "ACLs for"
26560 The non-SMTP ACLs apply to all non-interactive incoming messages, that is, they
26561 apply to batched SMTP as well as to non-SMTP messages. (Batched SMTP is not
26562 really SMTP.) Many of the ACL conditions (for example, host tests, and tests on
26563 the state of the SMTP connection such as encryption and authentication) are not
26564 relevant and are forbidden in these ACLs. However, the sender and recipients
26565 are known, so the &%senders%& and &%sender_domains%& conditions and the
26566 &$sender_address$& and &$recipients$& variables can be used. Variables such as
26567 &$authenticated_sender$& are also available. You can specify added header lines
26568 in any of these ACLs.
26570 The &%acl_not_smtp_start%& ACL is run right at the start of receiving a
26571 non-SMTP message, before any of the message has been read. (This is the
26572 analogue of the &%acl_smtp_predata%& ACL for SMTP input.) In the case of
26573 batched SMTP input, it runs after the DATA command has been reached. The
26574 result of this ACL is ignored; it cannot be used to reject a message. If you
26575 really need to, you could set a value in an ACL variable here and reject based
26576 on that in the &%acl_not_smtp%& ACL. However, this ACL can be used to set
26577 controls, and in particular, it can be used to set
26579 control = suppress_local_fixups
26581 This cannot be used in the other non-SMTP ACLs because by the time they are
26582 run, it is too late.
26584 The &%acl_not_smtp_mime%& ACL is available only when Exim is compiled with the
26585 content-scanning extension. For details, see chapter &<<CHAPexiscan>>&.
26587 The &%acl_not_smtp%& ACL is run just before the &[local_scan()]& function. Any
26588 kind of rejection is treated as permanent, because there is no way of sending a
26589 temporary error for these kinds of message.
26592 .section "The SMTP connect ACL" "SECID191"
26593 .cindex "SMTP" "connection, ACL for"
26594 .oindex &%smtp_banner%&
26595 The ACL test specified by &%acl_smtp_connect%& happens at the start of an SMTP
26596 session, after the test specified by &%host_reject_connection%& (which is now
26597 an anomaly) and any TCP Wrappers testing (if configured). If the connection is
26598 accepted by an &%accept%& verb that has a &%message%& modifier, the contents of
26599 the message override the banner message that is otherwise specified by the
26600 &%smtp_banner%& option.
26603 .section "The EHLO/HELO ACL" "SECID192"
26604 .cindex "EHLO" "ACL for"
26605 .cindex "HELO" "ACL for"
26606 The ACL test specified by &%acl_smtp_helo%& happens when the client issues an
26607 EHLO or HELO command, after the tests specified by &%helo_accept_junk_hosts%&,
26608 &%helo_allow_chars%&, &%helo_verify_hosts%&, and &%helo_try_verify_hosts%&.
26609 Note that a client may issue more than one EHLO or HELO command in an SMTP
26610 session, and indeed is required to issue a new EHLO or HELO after successfully
26611 setting up encryption following a STARTTLS command.
26613 If the command is accepted by an &%accept%& verb that has a &%message%&
26614 modifier, the message may not contain more than one line (it will be truncated
26615 at the first newline and a panic logged if it does). Such a message cannot
26616 affect the EHLO options that are listed on the second and subsequent lines of
26620 .section "The DATA ACLs" "SECID193"
26621 .cindex "DATA" "ACLs for"
26622 Two ACLs are associated with the DATA command, because it is two-stage
26623 command, with two responses being sent to the client.
26624 When the DATA command is received, the ACL defined by &%acl_smtp_predata%&
26625 is obeyed. This gives you control after all the RCPT commands, but before
26626 the message itself is received. It offers the opportunity to give a negative
26627 response to the DATA command before the data is transmitted. Header lines
26628 added by MAIL or RCPT ACLs are not visible at this time, but any that
26629 are defined here are visible when the &%acl_smtp_data%& ACL is run.
26631 You cannot test the contents of the message, for example, to verify addresses
26632 in the headers, at RCPT time or when the DATA command is received. Such
26633 tests have to appear in the ACL that is run after the message itself has been
26634 received, before the final response to the DATA command is sent. This is
26635 the ACL specified by &%acl_smtp_data%&, which is the second ACL that is
26636 associated with the DATA command.
26638 For both of these ACLs, it is not possible to reject individual recipients. An
26639 error response rejects the entire message. Unfortunately, it is known that some
26640 MTAs do not treat hard (5&'xx'&) responses to the DATA command (either
26641 before or after the data) correctly &-- they keep the message on their queues
26642 and try again later, but that is their problem, though it does waste some of
26645 The &%acl_smtp_data%& ACL is run after
26646 the &%acl_smtp_data_prdr%&,
26647 the &%acl_smtp_dkim%&
26648 and the &%acl_smtp_mime%& ACLs.
26650 .section "The SMTP DKIM ACL" "SECTDKIMACL"
26651 The &%acl_smtp_dkim%& ACL is available only when Exim is compiled with DKIM support
26652 enabled (which is the default).
26654 The ACL test specified by &%acl_smtp_dkim%& happens after a message has been
26655 received, and is executed for each DKIM signature found in a message. If not
26656 otherwise specified, the default action is to accept.
26658 This ACL is evaluated before &%acl_smtp_mime%& and &%acl_smtp_data%&.
26660 For details on the operation of DKIM, see chapter &<<CHAPdkim>>&.
26663 .section "The SMTP MIME ACL" "SECID194"
26664 The &%acl_smtp_mime%& option is available only when Exim is compiled with the
26665 content-scanning extension. For details, see chapter &<<CHAPexiscan>>&.
26667 This ACL is evaluated after &%acl_smtp_dkim%& but before &%acl_smtp_data%&.
26670 .section "The SMTP PRDR ACL" "SECTPRDRACL"
26671 .oindex "&%prdr_enable%&"
26672 The &%acl_smtp_data_prdr%& ACL is available only when Exim is compiled
26673 with PRDR support enabled (which is the default).
26674 It becomes active only when the PRDR feature is negotiated between
26675 client and server for a message, and more than one recipient
26678 The ACL test specfied by &%acl_smtp_data_prdr%& happens after a message
26679 has been recieved, and is executed for each recipient of the message.
26680 The test may accept or deny for inividual recipients.
26681 The &%acl_smtp_data%& will still be called after this ACL and
26682 can reject the message overall, even if this ACL has accepted it
26683 for some or all recipients.
26685 PRDR may be used to support per-user content filtering. Without it
26686 one must defer any recipient after the first that has a different
26687 content-filter configuration. With PRDR, the RCPT-time check
26688 for this can be disabled when the MAIL-time $smtp_command included
26689 "PRDR". Any required difference in behaviour of the main DATA-time
26690 ACL should however depend on the PRDR-time ACL having run, as Exim
26691 will avoid doing so in some situations (eg. single-recipient mails).
26693 See also the &%prdr_enable%& global option
26694 and the &%hosts_try_prdr%& smtp transport option.
26696 This ACL is evaluated after &%acl_smtp_dkim%& but before &%acl_smtp_data%&.
26697 If the ACL is not defined, processing completes as if
26698 the feature was not requested by the client.
26700 .section "The QUIT ACL" "SECTQUITACL"
26701 .cindex "QUIT, ACL for"
26702 The ACL for the SMTP QUIT command is anomalous, in that the outcome of the ACL
26703 does not affect the response code to QUIT, which is always 221. Thus, the ACL
26704 does not in fact control any access. For this reason, the only verbs that are
26705 permitted are &%accept%& and &%warn%&.
26707 This ACL can be used for tasks such as custom logging at the end of an SMTP
26708 session. For example, you can use ACL variables in other ACLs to count
26709 messages, recipients, etc., and log the totals at QUIT time using one or
26710 more &%logwrite%& modifiers on a &%warn%& verb.
26712 &*Warning*&: Only the &$acl_c$&&'x'& variables can be used for this, because
26713 the &$acl_m$&&'x'& variables are reset at the end of each incoming message.
26715 You do not need to have a final &%accept%&, but if you do, you can use a
26716 &%message%& modifier to specify custom text that is sent as part of the 221
26719 This ACL is run only for a &"normal"& QUIT. For certain kinds of disastrous
26720 failure (for example, failure to open a log file, or when Exim is bombing out
26721 because it has detected an unrecoverable error), all SMTP commands from the
26722 client are given temporary error responses until QUIT is received or the
26723 connection is closed. In these special cases, the QUIT ACL does not run.
26726 .section "The not-QUIT ACL" "SECTNOTQUITACL"
26727 .vindex &$acl_smtp_notquit$&
26728 The not-QUIT ACL, specified by &%acl_smtp_notquit%&, is run in most cases when
26729 an SMTP session ends without sending QUIT. However, when Exim itself is in bad
26730 trouble, such as being unable to write to its log files, this ACL is not run,
26731 because it might try to do things (such as write to log files) that make the
26732 situation even worse.
26734 Like the QUIT ACL, this ACL is provided to make it possible to do customized
26735 logging or to gather statistics, and its outcome is ignored. The &%delay%&
26736 modifier is forbidden in this ACL, and the only permitted verbs are &%accept%&
26739 .vindex &$smtp_notquit_reason$&
26740 When the not-QUIT ACL is running, the variable &$smtp_notquit_reason$& is set
26741 to a string that indicates the reason for the termination of the SMTP
26742 connection. The possible values are:
26744 .irow &`acl-drop`& "Another ACL issued a &%drop%& command"
26745 .irow &`bad-commands`& "Too many unknown or non-mail commands"
26746 .irow &`command-timeout`& "Timeout while reading SMTP commands"
26747 .irow &`connection-lost`& "The SMTP connection has been lost"
26748 .irow &`data-timeout`& "Timeout while reading message data"
26749 .irow &`local-scan-error`& "The &[local_scan()]& function crashed"
26750 .irow &`local-scan-timeout`& "The &[local_scan()]& function timed out"
26751 .irow &`signal-exit`& "SIGTERM or SIGINT"
26752 .irow &`synchronization-error`& "SMTP synchronization error"
26753 .irow &`tls-failed`& "TLS failed to start"
26755 In most cases when an SMTP connection is closed without having received QUIT,
26756 Exim sends an SMTP response message before actually closing the connection.
26757 With the exception of the &`acl-drop`& case, the default message can be
26758 overridden by the &%message%& modifier in the not-QUIT ACL. In the case of a
26759 &%drop%& verb in another ACL, it is the message from the other ACL that is
26763 .section "Finding an ACL to use" "SECID195"
26764 .cindex "&ACL;" "finding which to use"
26765 The value of an &%acl_smtp_%&&'xxx'& option is expanded before use, so
26766 you can use different ACLs in different circumstances. For example,
26768 acl_smtp_rcpt = ${if ={25}{$interface_port} \
26769 {acl_check_rcpt} {acl_check_rcpt_submit} }
26771 In the default configuration file there are some example settings for
26772 providing an RFC 4409 message submission service on port 587 and a
26773 non-standard &"smtps"& service on port 465. You can use a string
26774 expansion like this to choose an ACL for MUAs on these ports which is
26775 more appropriate for this purpose than the default ACL on port 25.
26777 The expanded string does not have to be the name of an ACL in the
26778 configuration file; there are other possibilities. Having expanded the
26779 string, Exim searches for an ACL as follows:
26782 If the string begins with a slash, Exim uses it as a file name, and reads its
26783 contents as an ACL. The lines are processed in the same way as lines in the
26784 Exim configuration file. In particular, continuation lines are supported, blank
26785 lines are ignored, as are lines whose first non-whitespace character is &"#"&.
26786 If the file does not exist or cannot be read, an error occurs (typically
26787 causing a temporary failure of whatever caused the ACL to be run). For example:
26789 acl_smtp_data = /etc/acls/\
26790 ${lookup{$sender_host_address}lsearch\
26791 {/etc/acllist}{$value}{default}}
26793 This looks up an ACL file to use on the basis of the host's IP address, falling
26794 back to a default if the lookup fails. If an ACL is successfully read from a
26795 file, it is retained in memory for the duration of the Exim process, so that it
26796 can be re-used without having to re-read the file.
26798 If the string does not start with a slash, and does not contain any spaces,
26799 Exim searches the ACL section of the configuration for an ACL whose name
26800 matches the string.
26802 If no named ACL is found, or if the string contains spaces, Exim parses
26803 the string as an inline ACL. This can save typing in cases where you just
26804 want to have something like
26806 acl_smtp_vrfy = accept
26808 in order to allow free use of the VRFY command. Such a string may contain
26809 newlines; it is processed in the same way as an ACL that is read from a file.
26815 .section "ACL return codes" "SECID196"
26816 .cindex "&ACL;" "return codes"
26817 Except for the QUIT ACL, which does not affect the SMTP return code (see
26818 section &<<SECTQUITACL>>& above), the result of running an ACL is either
26819 &"accept"& or &"deny"&, or, if some test cannot be completed (for example, if a
26820 database is down), &"defer"&. These results cause 2&'xx'&, 5&'xx'&, and 4&'xx'&
26821 return codes, respectively, to be used in the SMTP dialogue. A fourth return,
26822 &"error"&, occurs when there is an error such as invalid syntax in the ACL.
26823 This also causes a 4&'xx'& return code.
26825 For the non-SMTP ACL, &"defer"& and &"error"& are treated in the same way as
26826 &"deny"&, because there is no mechanism for passing temporary errors to the
26827 submitters of non-SMTP messages.
26830 ACLs that are relevant to message reception may also return &"discard"&. This
26831 has the effect of &"accept"&, but causes either the entire message or an
26832 individual recipient address to be discarded. In other words, it is a
26833 blackholing facility. Use it with care.
26835 If the ACL for MAIL returns &"discard"&, all recipients are discarded, and no
26836 ACL is run for subsequent RCPT commands. The effect of &"discard"& in a
26837 RCPT ACL is to discard just the one recipient address. If there are no
26838 recipients left when the message's data is received, the DATA ACL is not
26839 run. A &"discard"& return from the DATA or the non-SMTP ACL discards all the
26840 remaining recipients. The &"discard"& return is not permitted for the
26841 &%acl_smtp_predata%& ACL.
26844 .cindex "&[local_scan()]& function" "when all recipients discarded"
26845 The &[local_scan()]& function is always run, even if there are no remaining
26846 recipients; it may create new recipients.
26850 .section "Unset ACL options" "SECID197"
26851 .cindex "&ACL;" "unset options"
26852 The default actions when any of the &%acl_%&&'xxx'& options are unset are not
26853 all the same. &*Note*&: These defaults apply only when the relevant ACL is
26854 not defined at all. For any defined ACL, the default action when control
26855 reaches the end of the ACL statements is &"deny"&.
26857 For &%acl_smtp_quit%& and &%acl_not_smtp_start%& there is no default because
26858 these two are ACLs that are used only for their side effects. They cannot be
26859 used to accept or reject anything.
26861 For &%acl_not_smtp%&, &%acl_smtp_auth%&, &%acl_smtp_connect%&,
26862 &%acl_smtp_data%&, &%acl_smtp_helo%&, &%acl_smtp_mail%&, &%acl_smtp_mailauth%&,
26863 &%acl_smtp_mime%&, &%acl_smtp_predata%&, and &%acl_smtp_starttls%&, the action
26864 when the ACL is not defined is &"accept"&.
26866 For the others (&%acl_smtp_etrn%&, &%acl_smtp_expn%&, &%acl_smtp_rcpt%&, and
26867 &%acl_smtp_vrfy%&), the action when the ACL is not defined is &"deny"&.
26868 This means that &%acl_smtp_rcpt%& must be defined in order to receive any
26869 messages over an SMTP connection. For an example, see the ACL in the default
26870 configuration file.
26875 .section "Data for message ACLs" "SECID198"
26876 .cindex "&ACL;" "data for message ACL"
26878 .vindex &$local_part$&
26879 .vindex &$sender_address$&
26880 .vindex &$sender_host_address$&
26881 .vindex &$smtp_command$&
26882 When a MAIL or RCPT ACL, or either of the DATA ACLs, is running, the variables
26883 that contain information about the host and the message's sender (for example,
26884 &$sender_host_address$& and &$sender_address$&) are set, and can be used in ACL
26885 statements. In the case of RCPT (but not MAIL or DATA), &$domain$& and
26886 &$local_part$& are set from the argument address. The entire SMTP command
26887 is available in &$smtp_command$&.
26889 When an ACL for the AUTH parameter of MAIL is running, the variables that
26890 contain information about the host are set, but &$sender_address$& is not yet
26891 set. Section &<<SECTauthparamail>>& contains a discussion of this parameter and
26894 .vindex "&$message_size$&"
26895 The &$message_size$& variable is set to the value of the SIZE parameter on
26896 the MAIL command at MAIL, RCPT and pre-data time, or to -1 if
26897 that parameter is not given. The value is updated to the true message size by
26898 the time the final DATA ACL is run (after the message data has been
26901 .vindex "&$rcpt_count$&"
26902 .vindex "&$recipients_count$&"
26903 The &$rcpt_count$& variable increases by one for each RCPT command received.
26904 The &$recipients_count$& variable increases by one each time a RCPT command is
26905 accepted, so while an ACL for RCPT is being processed, it contains the number
26906 of previously accepted recipients. At DATA time (for both the DATA ACLs),
26907 &$rcpt_count$& contains the total number of RCPT commands, and
26908 &$recipients_count$& contains the total number of accepted recipients.
26914 .section "Data for non-message ACLs" "SECTdatfornon"
26915 .cindex "&ACL;" "data for non-message ACL"
26916 .vindex &$smtp_command_argument$&
26917 .vindex &$smtp_command$&
26918 When an ACL is being run for AUTH, EHLO, ETRN, EXPN, HELO, STARTTLS, or VRFY,
26919 the remainder of the SMTP command line is placed in &$smtp_command_argument$&,
26920 and the entire SMTP command is available in &$smtp_command$&.
26921 These variables can be tested using a &%condition%& condition. For example,
26922 here is an ACL for use with AUTH, which insists that either the session is
26923 encrypted, or the CRAM-MD5 authentication method is used. In other words, it
26924 does not permit authentication methods that use cleartext passwords on
26925 unencrypted connections.
26928 accept encrypted = *
26929 accept condition = ${if eq{${uc:$smtp_command_argument}}\
26931 deny message = TLS encryption or CRAM-MD5 required
26933 (Another way of applying this restriction is to arrange for the authenticators
26934 that use cleartext passwords not to be advertised when the connection is not
26935 encrypted. You can use the generic &%server_advertise_condition%& authenticator
26936 option to do this.)
26940 .section "Format of an ACL" "SECID199"
26941 .cindex "&ACL;" "format of"
26942 .cindex "&ACL;" "verbs, definition of"
26943 An individual ACL consists of a number of statements. Each statement starts
26944 with a verb, optionally followed by a number of conditions and &"modifiers"&.
26945 Modifiers can change the way the verb operates, define error and log messages,
26946 set variables, insert delays, and vary the processing of accepted messages.
26948 If all the conditions are met, the verb is obeyed. The same condition may be
26949 used (with different arguments) more than once in the same statement. This
26950 provides a means of specifying an &"and"& conjunction between conditions. For
26953 deny dnslists = list1.example
26954 dnslists = list2.example
26956 If there are no conditions, the verb is always obeyed. Exim stops evaluating
26957 the conditions and modifiers when it reaches a condition that fails. What
26958 happens then depends on the verb (and in one case, on a special modifier). Not
26959 all the conditions make sense at every testing point. For example, you cannot
26960 test a sender address in the ACL that is run for a VRFY command.
26963 .section "ACL verbs" "SECID200"
26964 The ACL verbs are as follows:
26967 .cindex "&%accept%& ACL verb"
26968 &%accept%&: If all the conditions are met, the ACL returns &"accept"&. If any
26969 of the conditions are not met, what happens depends on whether &%endpass%&
26970 appears among the conditions (for syntax see below). If the failing condition
26971 is before &%endpass%&, control is passed to the next ACL statement; if it is
26972 after &%endpass%&, the ACL returns &"deny"&. Consider this statement, used to
26973 check a RCPT command:
26975 accept domains = +local_domains
26979 If the recipient domain does not match the &%domains%& condition, control
26980 passes to the next statement. If it does match, the recipient is verified, and
26981 the command is accepted if verification succeeds. However, if verification
26982 fails, the ACL yields &"deny"&, because the failing condition is after
26985 The &%endpass%& feature has turned out to be confusing to many people, so its
26986 use is not recommended nowadays. It is always possible to rewrite an ACL so
26987 that &%endpass%& is not needed, and it is no longer used in the default
26990 .cindex "&%message%& ACL modifier" "with &%accept%&"
26991 If a &%message%& modifier appears on an &%accept%& statement, its action
26992 depends on whether or not &%endpass%& is present. In the absence of &%endpass%&
26993 (when an &%accept%& verb either accepts or passes control to the next
26994 statement), &%message%& can be used to vary the message that is sent when an
26995 SMTP command is accepted. For example, in a RCPT ACL you could have:
26997 &`accept `&<&'some conditions'&>
26998 &` message = OK, I will allow you through today`&
27000 You can specify an SMTP response code, optionally followed by an &"extended
27001 response code"& at the start of the message, but the first digit must be the
27002 same as would be sent by default, which is 2 for an &%accept%& verb.
27004 If &%endpass%& is present in an &%accept%& statement, &%message%& specifies
27005 an error message that is used when access is denied. This behaviour is retained
27006 for backward compatibility, but current &"best practice"& is to avoid the use
27011 .cindex "&%defer%& ACL verb"
27012 &%defer%&: If all the conditions are true, the ACL returns &"defer"& which, in
27013 an SMTP session, causes a 4&'xx'& response to be given. For a non-SMTP ACL,
27014 &%defer%& is the same as &%deny%&, because there is no way of sending a
27015 temporary error. For a RCPT command, &%defer%& is much the same as using a
27016 &(redirect)& router and &`:defer:`& while verifying, but the &%defer%& verb can
27017 be used in any ACL, and even for a recipient it might be a simpler approach.
27021 .cindex "&%deny%& ACL verb"
27022 &%deny%&: If all the conditions are met, the ACL returns &"deny"&. If any of
27023 the conditions are not met, control is passed to the next ACL statement. For
27026 deny dnslists = blackholes.mail-abuse.org
27028 rejects commands from hosts that are on a DNS black list.
27032 .cindex "&%discard%& ACL verb"
27033 &%discard%&: This verb behaves like &%accept%&, except that it returns
27034 &"discard"& from the ACL instead of &"accept"&. It is permitted only on ACLs
27035 that are concerned with receiving messages. When all the conditions are true,
27036 the sending entity receives a &"success"& response. However, &%discard%& causes
27037 recipients to be discarded. If it is used in an ACL for RCPT, just the one
27038 recipient is discarded; if used for MAIL, DATA or in the non-SMTP ACL, all the
27039 message's recipients are discarded. Recipients that are discarded before DATA
27040 do not appear in the log line when the &%received_recipients%& log selector is set.
27042 If the &%log_message%& modifier is set when &%discard%& operates,
27043 its contents are added to the line that is automatically written to the log.
27044 The &%message%& modifier operates exactly as it does for &%accept%&.
27048 .cindex "&%drop%& ACL verb"
27049 &%drop%&: This verb behaves like &%deny%&, except that an SMTP connection is
27050 forcibly closed after the 5&'xx'& error message has been sent. For example:
27052 drop message = I don't take more than 20 RCPTs
27053 condition = ${if > {$rcpt_count}{20}}
27055 There is no difference between &%deny%& and &%drop%& for the connect-time ACL.
27056 The connection is always dropped after sending a 550 response.
27059 .cindex "&%require%& ACL verb"
27060 &%require%&: If all the conditions are met, control is passed to the next ACL
27061 statement. If any of the conditions are not met, the ACL returns &"deny"&. For
27062 example, when checking a RCPT command,
27064 require message = Sender did not verify
27067 passes control to subsequent statements only if the message's sender can be
27068 verified. Otherwise, it rejects the command. Note the positioning of the
27069 &%message%& modifier, before the &%verify%& condition. The reason for this is
27070 discussed in section &<<SECTcondmodproc>>&.
27073 .cindex "&%warn%& ACL verb"
27074 &%warn%&: If all the conditions are true, a line specified by the
27075 &%log_message%& modifier is written to Exim's main log. Control always passes
27076 to the next ACL statement. If any condition is false, the log line is not
27077 written. If an identical log line is requested several times in the same
27078 message, only one copy is actually written to the log. If you want to force
27079 duplicates to be written, use the &%logwrite%& modifier instead.
27081 If &%log_message%& is not present, a &%warn%& verb just checks its conditions
27082 and obeys any &"immediate"& modifiers (such as &%control%&, &%set%&,
27083 &%logwrite%&, &%add_header%&, and &%remove_header%&) that appear before the
27084 first failing condition. There is more about adding header lines in section
27085 &<<SECTaddheadacl>>&.
27087 If any condition on a &%warn%& statement cannot be completed (that is, there is
27088 some sort of defer), the log line specified by &%log_message%& is not written.
27089 This does not include the case of a forced failure from a lookup, which
27090 is considered to be a successful completion. After a defer, no further
27091 conditions or modifiers in the &%warn%& statement are processed. The incident
27092 is logged, and the ACL continues to be processed, from the next statement
27096 .vindex "&$acl_verify_message$&"
27097 When one of the &%warn%& conditions is an address verification that fails, the
27098 text of the verification failure message is in &$acl_verify_message$&. If you
27099 want this logged, you must set it up explicitly. For example:
27101 warn !verify = sender
27102 log_message = sender verify failed: $acl_verify_message
27106 At the end of each ACL there is an implicit unconditional &%deny%&.
27108 As you can see from the examples above, the conditions and modifiers are
27109 written one to a line, with the first one on the same line as the verb, and
27110 subsequent ones on following lines. If you have a very long condition, you can
27111 continue it onto several physical lines by the usual backslash continuation
27112 mechanism. It is conventional to align the conditions vertically.
27116 .section "ACL variables" "SECTaclvariables"
27117 .cindex "&ACL;" "variables"
27118 There are some special variables that can be set during ACL processing. They
27119 can be used to pass information between different ACLs, different invocations
27120 of the same ACL in the same SMTP connection, and between ACLs and the routers,
27121 transports, and filters that are used to deliver a message. The names of these
27122 variables must begin with &$acl_c$& or &$acl_m$&, followed either by a digit or
27123 an underscore, but the remainder of the name can be any sequence of
27124 alphanumeric characters and underscores that you choose. There is no limit on
27125 the number of ACL variables. The two sets act as follows:
27127 The values of those variables whose names begin with &$acl_c$& persist
27128 throughout an SMTP connection. They are never reset. Thus, a value that is set
27129 while receiving one message is still available when receiving the next message
27130 on the same SMTP connection.
27132 The values of those variables whose names begin with &$acl_m$& persist only
27133 while a message is being received. They are reset afterwards. They are also
27134 reset by MAIL, RSET, EHLO, HELO, and after starting up a TLS session.
27137 When a message is accepted, the current values of all the ACL variables are
27138 preserved with the message and are subsequently made available at delivery
27139 time. The ACL variables are set by a modifier called &%set%&. For example:
27141 accept hosts = whatever
27142 set acl_m4 = some value
27143 accept authenticated = *
27144 set acl_c_auth = yes
27146 &*Note*&: A leading dollar sign is not used when naming a variable that is to
27147 be set. If you want to set a variable without taking any action, you can use a
27148 &%warn%& verb without any other modifiers or conditions.
27150 .oindex &%strict_acl_vars%&
27151 What happens if a syntactically valid but undefined ACL variable is
27152 referenced depends on the setting of the &%strict_acl_vars%& option. If it is
27153 false (the default), an empty string is substituted; if it is true, an
27154 error is generated.
27156 Versions of Exim before 4.64 have a limited set of numbered variables, but
27157 their names are compatible, so there is no problem with upgrading.
27160 .section "Condition and modifier processing" "SECTcondmodproc"
27161 .cindex "&ACL;" "conditions; processing"
27162 .cindex "&ACL;" "modifiers; processing"
27163 An exclamation mark preceding a condition negates its result. For example:
27165 deny domains = *.dom.example
27166 !verify = recipient
27168 causes the ACL to return &"deny"& if the recipient domain ends in
27169 &'dom.example'& and the recipient address cannot be verified. Sometimes
27170 negation can be used on the right-hand side of a condition. For example, these
27171 two statements are equivalent:
27173 deny hosts = !192.168.3.4
27174 deny !hosts = 192.168.3.4
27176 However, for many conditions (&%verify%& being a good example), only left-hand
27177 side negation of the whole condition is possible.
27179 The arguments of conditions and modifiers are expanded. A forced failure
27180 of an expansion causes a condition to be ignored, that is, it behaves as if the
27181 condition is true. Consider these two statements:
27183 accept senders = ${lookup{$host_name}lsearch\
27184 {/some/file}{$value}fail}
27185 accept senders = ${lookup{$host_name}lsearch\
27186 {/some/file}{$value}{}}
27188 Each attempts to look up a list of acceptable senders. If the lookup succeeds,
27189 the returned list is searched, but if the lookup fails the behaviour is
27190 different in the two cases. The &%fail%& in the first statement causes the
27191 condition to be ignored, leaving no further conditions. The &%accept%& verb
27192 therefore succeeds. The second statement, however, generates an empty list when
27193 the lookup fails. No sender can match an empty list, so the condition fails,
27194 and therefore the &%accept%& also fails.
27196 ACL modifiers appear mixed in with conditions in ACL statements. Some of them
27197 specify actions that are taken as the conditions for a statement are checked;
27198 others specify text for messages that are used when access is denied or a
27199 warning is generated. The &%control%& modifier affects the way an incoming
27200 message is handled.
27202 The positioning of the modifiers in an ACL statement is important, because the
27203 processing of a verb ceases as soon as its outcome is known. Only those
27204 modifiers that have already been encountered will take effect. For example,
27205 consider this use of the &%message%& modifier:
27207 require message = Can't verify sender
27209 message = Can't verify recipient
27211 message = This message cannot be used
27213 If sender verification fails, Exim knows that the result of the statement is
27214 &"deny"&, so it goes no further. The first &%message%& modifier has been seen,
27215 so its text is used as the error message. If sender verification succeeds, but
27216 recipient verification fails, the second message is used. If recipient
27217 verification succeeds, the third message becomes &"current"&, but is never used
27218 because there are no more conditions to cause failure.
27220 For the &%deny%& verb, on the other hand, it is always the last &%message%&
27221 modifier that is used, because all the conditions must be true for rejection to
27222 happen. Specifying more than one &%message%& modifier does not make sense, and
27223 the message can even be specified after all the conditions. For example:
27226 !senders = *@my.domain.example
27227 message = Invalid sender from client host
27229 The &"deny"& result does not happen until the end of the statement is reached,
27230 by which time Exim has set up the message.
27234 .section "ACL modifiers" "SECTACLmodi"
27235 .cindex "&ACL;" "modifiers; list of"
27236 The ACL modifiers are as follows:
27239 .vitem &*add_header*&&~=&~<&'text'&>
27240 This modifier specifies one or more header lines that are to be added to an
27241 incoming message, assuming, of course, that the message is ultimately
27242 accepted. For details, see section &<<SECTaddheadacl>>&.
27244 .vitem &*continue*&&~=&~<&'text'&>
27245 .cindex "&%continue%& ACL modifier"
27246 .cindex "database" "updating in ACL"
27247 This modifier does nothing of itself, and processing of the ACL always
27248 continues with the next condition or modifier. The value of &%continue%& is in
27249 the side effects of expanding its argument. Typically this could be used to
27250 update a database. It is really just a syntactic tidiness, to avoid having to
27251 write rather ugly lines like this:
27253 &`condition = ${if eq{0}{`&<&'some expansion'&>&`}{true}{true}}`&
27255 Instead, all you need is
27257 &`continue = `&<&'some expansion'&>
27260 .vitem &*control*&&~=&~<&'text'&>
27261 .cindex "&%control%& ACL modifier"
27262 This modifier affects the subsequent processing of the SMTP connection or of an
27263 incoming message that is accepted. The effect of the first type of control
27264 lasts for the duration of the connection, whereas the effect of the second type
27265 lasts only until the current message has been received. The message-specific
27266 controls always apply to the whole message, not to individual recipients,
27267 even if the &%control%& modifier appears in a RCPT ACL.
27269 As there are now quite a few controls that can be applied, they are described
27270 separately in section &<<SECTcontrols>>&. The &%control%& modifier can be used
27271 in several different ways. For example:
27273 . ==== As this is a nested list, any displays it contains must be indented
27274 . ==== as otherwise they are too far to the left. That comment applies only
27275 . ==== when xmlto and fop are used; formatting with sdop gets it right either
27279 It can be at the end of an &%accept%& statement:
27281 accept ...some conditions
27282 control = queue_only
27284 In this case, the control is applied when this statement yields &"accept"&, in
27285 other words, when the conditions are all true.
27288 It can be in the middle of an &%accept%& statement:
27290 accept ...some conditions...
27291 control = queue_only
27292 ...some more conditions...
27294 If the first set of conditions are true, the control is applied, even if the
27295 statement does not accept because one of the second set of conditions is false.
27296 In this case, some subsequent statement must yield &"accept"& for the control
27300 It can be used with &%warn%& to apply the control, leaving the
27301 decision about accepting or denying to a subsequent verb. For
27304 warn ...some conditions...
27308 This example of &%warn%& does not contain &%message%&, &%log_message%&, or
27309 &%logwrite%&, so it does not add anything to the message and does not write a
27313 If you want to apply a control unconditionally, you can use it with a
27314 &%require%& verb. For example:
27316 require control = no_multiline_responses
27320 .vitem &*delay*&&~=&~<&'time'&>
27321 .cindex "&%delay%& ACL modifier"
27323 This modifier may appear in any ACL except notquit. It causes Exim to wait for
27324 the time interval before proceeding. However, when testing Exim using the
27325 &%-bh%& option, the delay is not actually imposed (an appropriate message is
27326 output instead). The time is given in the usual Exim notation, and the delay
27327 happens as soon as the modifier is processed. In an SMTP session, pending
27328 output is flushed before the delay is imposed.
27330 Like &%control%&, &%delay%& can be used with &%accept%& or &%deny%&, for
27333 deny ...some conditions...
27336 The delay happens if all the conditions are true, before the statement returns
27337 &"deny"&. Compare this with:
27340 ...some conditions...
27342 which waits for 30s before processing the conditions. The &%delay%& modifier
27343 can also be used with &%warn%& and together with &%control%&:
27345 warn ...some conditions...
27351 If &%delay%& is encountered when the SMTP PIPELINING extension is in use,
27352 responses to several commands are no longer buffered and sent in one packet (as
27353 they would normally be) because all output is flushed before imposing the
27354 delay. This optimization is disabled so that a number of small delays do not
27355 appear to the client as one large aggregated delay that might provoke an
27356 unwanted timeout. You can, however, disable output flushing for &%delay%& by
27357 using a &%control%& modifier to set &%no_delay_flush%&.
27361 .cindex "&%endpass%& ACL modifier"
27362 This modifier, which has no argument, is recognized only in &%accept%& and
27363 &%discard%& statements. It marks the boundary between the conditions whose
27364 failure causes control to pass to the next statement, and the conditions whose
27365 failure causes the ACL to return &"deny"&. This concept has proved to be
27366 confusing to some people, so the use of &%endpass%& is no longer recommended as
27367 &"best practice"&. See the description of &%accept%& above for more details.
27370 .vitem &*log_message*&&~=&~<&'text'&>
27371 .cindex "&%log_message%& ACL modifier"
27372 This modifier sets up a message that is used as part of the log message if the
27373 ACL denies access or a &%warn%& statement's conditions are true. For example:
27375 require log_message = wrong cipher suite $tls_in_cipher
27376 encrypted = DES-CBC3-SHA
27378 &%log_message%& is also used when recipients are discarded by &%discard%&. For
27381 &`discard `&<&'some conditions'&>
27382 &` log_message = Discarded $local_part@$domain because...`&
27384 When access is denied, &%log_message%& adds to any underlying error message
27385 that may exist because of a condition failure. For example, while verifying a
27386 recipient address, a &':fail:'& redirection might have already set up a
27389 The message may be defined before the conditions to which it applies, because
27390 the string expansion does not happen until Exim decides that access is to be
27391 denied. This means that any variables that are set by the condition are
27392 available for inclusion in the message. For example, the &$dnslist_$&<&'xxx'&>
27393 variables are set after a DNS black list lookup succeeds. If the expansion of
27394 &%log_message%& fails, or if the result is an empty string, the modifier is
27397 .vindex "&$acl_verify_message$&"
27398 If you want to use a &%warn%& statement to log the result of an address
27399 verification, you can use &$acl_verify_message$& to include the verification
27402 If &%log_message%& is used with a &%warn%& statement, &"Warning:"& is added to
27403 the start of the logged message. If the same warning log message is requested
27404 more than once while receiving a single email message, only one copy is
27405 actually logged. If you want to log multiple copies, use &%logwrite%& instead
27406 of &%log_message%&. In the absence of &%log_message%& and &%logwrite%&, nothing
27407 is logged for a successful &%warn%& statement.
27409 If &%log_message%& is not present and there is no underlying error message (for
27410 example, from the failure of address verification), but &%message%& is present,
27411 the &%message%& text is used for logging rejections. However, if any text for
27412 logging contains newlines, only the first line is logged. In the absence of
27413 both &%log_message%& and &%message%&, a default built-in message is used for
27414 logging rejections.
27417 .vitem "&*log_reject_target*&&~=&~<&'log name list'&>"
27418 .cindex "&%log_reject_target%& ACL modifier"
27419 .cindex "logging in ACL" "specifying which log"
27420 This modifier makes it possible to specify which logs are used for messages
27421 about ACL rejections. Its argument is a colon-separated list of words that can
27422 be &"main"&, &"reject"&, or &"panic"&. The default is &`main:reject`&. The list
27423 may be empty, in which case a rejection is not logged at all. For example, this
27424 ACL fragment writes no logging information when access is denied:
27426 &`deny `&<&'some conditions'&>
27427 &` log_reject_target =`&
27429 This modifier can be used in SMTP and non-SMTP ACLs. It applies to both
27430 permanent and temporary rejections. Its effect lasts for the rest of the
27434 .vitem &*logwrite*&&~=&~<&'text'&>
27435 .cindex "&%logwrite%& ACL modifier"
27436 .cindex "logging in ACL" "immediate"
27437 This modifier writes a message to a log file as soon as it is encountered when
27438 processing an ACL. (Compare &%log_message%&, which, except in the case of
27439 &%warn%& and &%discard%&, is used only if the ACL statement denies
27440 access.) The &%logwrite%& modifier can be used to log special incidents in
27443 &`accept `&<&'some special conditions'&>
27444 &` control = freeze`&
27445 &` logwrite = froze message because ...`&
27447 By default, the message is written to the main log. However, it may begin
27448 with a colon, followed by a comma-separated list of log names, and then
27449 another colon, to specify exactly which logs are to be written. For
27452 logwrite = :main,reject: text for main and reject logs
27453 logwrite = :panic: text for panic log only
27457 .vitem &*message*&&~=&~<&'text'&>
27458 .cindex "&%message%& ACL modifier"
27459 This modifier sets up a text string that is expanded and used as a response
27460 message when an ACL statement terminates the ACL with an &"accept"&, &"deny"&,
27461 or &"defer"& response. (In the case of the &%accept%& and &%discard%& verbs,
27462 there is some complication if &%endpass%& is involved; see the description of
27463 &%accept%& for details.)
27465 The expansion of the message happens at the time Exim decides that the ACL is
27466 to end, not at the time it processes &%message%&. If the expansion fails, or
27467 generates an empty string, the modifier is ignored. Here is an example where
27468 &%message%& must be specified first, because the ACL ends with a rejection if
27469 the &%hosts%& condition fails:
27471 require message = Host not recognized
27474 (Once a condition has failed, no further conditions or modifiers are
27477 .cindex "SMTP" "error codes"
27478 .oindex "&%smtp_banner%&
27479 For ACLs that are triggered by SMTP commands, the message is returned as part
27480 of the SMTP response. The use of &%message%& with &%accept%& (or &%discard%&)
27481 is meaningful only for SMTP, as no message is returned when a non-SMTP message
27482 is accepted. In the case of the connect ACL, accepting with a message modifier
27483 overrides the value of &%smtp_banner%&. For the EHLO/HELO ACL, a customized
27484 accept message may not contain more than one line (otherwise it will be
27485 truncated at the first newline and a panic logged), and it cannot affect the
27488 When SMTP is involved, the message may begin with an overriding response code,
27489 consisting of three digits optionally followed by an &"extended response code"&
27490 of the form &'n.n.n'&, each code being followed by a space. For example:
27492 deny message = 599 1.2.3 Host not welcome
27493 hosts = 192.168.34.0/24
27495 The first digit of the supplied response code must be the same as would be sent
27496 by default. A panic occurs if it is not. Exim uses a 550 code when it denies
27497 access, but for the predata ACL, note that the default success code is 354, not
27500 Notwithstanding the previous paragraph, for the QUIT ACL, unlike the others,
27501 the message modifier cannot override the 221 response code.
27503 The text in a &%message%& modifier is literal; any quotes are taken as
27504 literals, but because the string is expanded, backslash escapes are processed
27505 anyway. If the message contains newlines, this gives rise to a multi-line SMTP
27508 .vindex "&$acl_verify_message$&"
27509 If &%message%& is used on a statement that verifies an address, the message
27510 specified overrides any message that is generated by the verification process.
27511 However, the original message is available in the variable
27512 &$acl_verify_message$&, so you can incorporate it into your message if you
27513 wish. In particular, if you want the text from &%:fail:%& items in &(redirect)&
27514 routers to be passed back as part of the SMTP response, you should either not
27515 use a &%message%& modifier, or make use of &$acl_verify_message$&.
27517 For compatibility with previous releases of Exim, a &%message%& modifier that
27518 is used with a &%warn%& verb behaves in a similar way to the &%add_header%&
27519 modifier, but this usage is now deprecated. However, &%message%& acts only when
27520 all the conditions are true, wherever it appears in an ACL command, whereas
27521 &%add_header%& acts as soon as it is encountered. If &%message%& is used with
27522 &%warn%& in an ACL that is not concerned with receiving a message, it has no
27526 .vitem &*remove_header*&&~=&~<&'text'&>
27527 This modifier specifies one or more header names in a colon-separated list
27528 that are to be removed from an incoming message, assuming, of course, that
27529 the message is ultimately accepted. For details, see section &<<SECTremoveheadacl>>&.
27532 .vitem &*set*&&~<&'acl_name'&>&~=&~<&'value'&>
27533 .cindex "&%set%& ACL modifier"
27534 This modifier puts a value into one of the ACL variables (see section
27535 &<<SECTaclvariables>>&).
27538 .vitem &*udpsend*&&~=&~<&'parameters'&>
27539 This modifier sends a UDP packet, for purposes such as statistics
27540 collection or behaviour monitoring. The parameters are expanded, and
27541 the result of the expansion must be a colon-separated list consisting
27542 of a destination server, port number, and the packet contents. The
27543 server can be specified as a host name or IPv4 or IPv6 address. The
27544 separator can be changed with the usual angle bracket syntax. For
27545 example, you might want to collect information on which hosts connect
27548 udpsend = <; 2001:dB8::dead:beef ; 1234 ;\
27549 $tod_zulu $sender_host_address
27556 .section "Use of the control modifier" "SECTcontrols"
27557 .cindex "&%control%& ACL modifier"
27558 The &%control%& modifier supports the following settings:
27561 .vitem &*control&~=&~allow_auth_unadvertised*&
27562 This modifier allows a client host to use the SMTP AUTH command even when it
27563 has not been advertised in response to EHLO. Furthermore, because there are
27564 apparently some really broken clients that do this, Exim will accept AUTH after
27565 HELO (rather than EHLO) when this control is set. It should be used only if you
27566 really need it, and you should limit its use to those broken clients that do
27567 not work without it. For example:
27569 warn hosts = 192.168.34.25
27570 control = allow_auth_unadvertised
27572 Normally, when an Exim server receives an AUTH command, it checks the name of
27573 the authentication mechanism that is given in the command to ensure that it
27574 matches an advertised mechanism. When this control is set, the check that a
27575 mechanism has been advertised is bypassed. Any configured mechanism can be used
27576 by the client. This control is permitted only in the connection and HELO ACLs.
27579 .vitem &*control&~=&~caseful_local_part*& &&&
27580 &*control&~=&~caselower_local_part*&
27581 .cindex "&ACL;" "case of local part in"
27582 .cindex "case of local parts"
27583 .vindex "&$local_part$&"
27584 These two controls are permitted only in the ACL specified by &%acl_smtp_rcpt%&
27585 (that is, during RCPT processing). By default, the contents of &$local_part$&
27586 are lower cased before ACL processing. If &"caseful_local_part"& is specified,
27587 any uppercase letters in the original local part are restored in &$local_part$&
27588 for the rest of the ACL, or until a control that sets &"caselower_local_part"&
27591 These controls affect only the current recipient. Moreover, they apply only to
27592 local part handling that takes place directly in the ACL (for example, as a key
27593 in lookups). If a test to verify the recipient is obeyed, the case-related
27594 handling of the local part during the verification is controlled by the router
27595 configuration (see the &%caseful_local_part%& generic router option).
27597 This facility could be used, for example, to add a spam score to local parts
27598 containing upper case letters. For example, using &$acl_m4$& to accumulate the
27601 warn control = caseful_local_part
27602 set acl_m4 = ${eval:\
27604 ${if match{$local_part}{[A-Z]}{1}{0}}\
27606 control = caselower_local_part
27608 Notice that we put back the lower cased version afterwards, assuming that
27609 is what is wanted for subsequent tests.
27612 .vitem &*control&~=&~cutthrough_delivery*&
27613 .cindex "&ACL;" "cutthrough routing"
27614 .cindex "cutthrough" "requesting"
27615 This option requests delivery be attempted while the item is being received.
27616 It is usable in the RCPT ACL and valid only for single-recipient mails forwarded
27617 from one SMTP connection to another. If a recipient-verify callout connection is
27618 requested in the same ACL it is held open and used for the data, otherwise one is made
27619 after the ACL completes.
27621 Note that routers are used in verify mode,
27622 and cannot depend on content of received headers.
27623 Note also that headers cannot be
27624 modified by any of the post-data ACLs (DATA, MIME and DKIM).
27625 Headers may be modified by routers (subject to the above) and transports.
27627 Cutthrough delivery is not supported via transport-filters or when DKIM signing
27628 of outgoing messages is done, because it sends data to the ultimate destination
27629 before the entire message has been received from the source.
27631 Should the ultimate destination system positively accept or reject the mail,
27632 a corresponding indication is given to the source system and nothing is queued.
27633 If there is a temporary error the item is queued for later delivery in the
27634 usual fashion. If the item is successfully delivered in cutthrough mode the log line
27635 is tagged with ">>" rather than "=>" and appears before the acceptance "<="
27638 Delivery in this mode avoids the generation of a bounce mail to a (possibly faked)
27639 sender when the destination system is doing content-scan based rejection.
27642 .vitem &*control&~=&~debug/*&<&'options'&>
27643 .cindex "&ACL;" "enabling debug logging"
27644 .cindex "debugging" "enabling from an ACL"
27645 This control turns on debug logging, almost as though Exim had been invoked
27646 with &`-d`&, with the output going to a new logfile, by default called
27647 &'debuglog'&. The filename can be adjusted with the &'tag'& option, which
27648 may access any variables already defined. The logging may be adjusted with
27649 the &'opts'& option, which takes the same values as the &`-d`& command-line
27650 option. Some examples (which depend on variables that don't exist in all
27654 control = debug/tag=.$sender_host_address
27655 control = debug/opts=+expand+acl
27656 control = debug/tag=.$message_exim_id/opts=+expand
27660 .vitem &*control&~=&~dkim_disable_verify*&
27661 .cindex "disable DKIM verify"
27662 .cindex "DKIM" "disable verify"
27663 This control turns off DKIM verification processing entirely. For details on
27664 the operation and configuration of DKIM, see chapter &<<CHAPdkim>>&.
27667 .vitem &*control&~=&~dscp/*&<&'value'&>
27668 .cindex "&ACL;" "setting DSCP value"
27669 .cindex "DSCP" "inbound"
27670 This option causes the DSCP value associated with the socket for the inbound
27671 connection to be adjusted to a given value, given as one of a number of fixed
27672 strings or to numeric value.
27673 The &%-bI:dscp%& option may be used to ask Exim which names it knows of.
27674 Common values include &`throughput`&, &`mincost`&, and on newer systems
27675 &`ef`&, &`af41`&, etc. Numeric values may be in the range 0 to 0x3F.
27677 The outbound packets from Exim will be marked with this value in the header
27678 (for IPv4, the TOS field; for IPv6, the TCLASS field); there is no guarantee
27679 that these values will have any effect, not be stripped by networking
27680 equipment, or do much of anything without cooperation with your Network
27681 Engineer and those of all network operators between the source and destination.
27684 .vitem &*control&~=&~enforce_sync*& &&&
27685 &*control&~=&~no_enforce_sync*&
27686 .cindex "SMTP" "synchronization checking"
27687 .cindex "synchronization checking in SMTP"
27688 These controls make it possible to be selective about when SMTP synchronization
27689 is enforced. The global option &%smtp_enforce_sync%& specifies the initial
27690 state of the switch (it is true by default). See the description of this option
27691 in chapter &<<CHAPmainconfig>>& for details of SMTP synchronization checking.
27693 The effect of these two controls lasts for the remainder of the SMTP
27694 connection. They can appear in any ACL except the one for the non-SMTP
27695 messages. The most straightforward place to put them is in the ACL defined by
27696 &%acl_smtp_connect%&, which is run at the start of an incoming SMTP connection,
27697 before the first synchronization check. The expected use is to turn off the
27698 synchronization checks for badly-behaved hosts that you nevertheless need to
27702 .vitem &*control&~=&~fakedefer/*&<&'message'&>
27703 .cindex "fake defer"
27704 .cindex "defer, fake"
27705 This control works in exactly the same way as &%fakereject%& (described below)
27706 except that it causes an SMTP 450 response after the message data instead of a
27707 550 response. You must take care when using &%fakedefer%& because it causes the
27708 messages to be duplicated when the sender retries. Therefore, you should not
27709 use &%fakedefer%& if the message is to be delivered normally.
27711 .vitem &*control&~=&~fakereject/*&<&'message'&>
27712 .cindex "fake rejection"
27713 .cindex "rejection, fake"
27714 This control is permitted only for the MAIL, RCPT, and DATA ACLs, in other
27715 words, only when an SMTP message is being received. If Exim accepts the
27716 message, instead the final 250 response, a 550 rejection message is sent.
27717 However, Exim proceeds to deliver the message as normal. The control applies
27718 only to the current message, not to any subsequent ones that may be received in
27719 the same SMTP connection.
27721 The text for the 550 response is taken from the &%control%& modifier. If no
27722 message is supplied, the following is used:
27724 550-Your message has been rejected but is being
27725 550-kept for evaluation.
27726 550-If it was a legitimate message, it may still be
27727 550 delivered to the target recipient(s).
27729 This facility should be used with extreme caution.
27731 .vitem &*control&~=&~freeze*&
27732 .cindex "frozen messages" "forcing in ACL"
27733 This control is permitted only for the MAIL, RCPT, DATA, and non-SMTP ACLs, in
27734 other words, only when a message is being received. If the message is accepted,
27735 it is placed on Exim's queue and frozen. The control applies only to the
27736 current message, not to any subsequent ones that may be received in the same
27739 This modifier can optionally be followed by &`/no_tell`&. If the global option
27740 &%freeze_tell%& is set, it is ignored for the current message (that is, nobody
27741 is told about the freezing), provided all the &*control=freeze*& modifiers that
27742 are obeyed for the current message have the &`/no_tell`& option.
27744 .vitem &*control&~=&~no_delay_flush*&
27745 .cindex "SMTP" "output flushing, disabling for delay"
27746 Exim normally flushes SMTP output before implementing a delay in an ACL, to
27747 avoid unexpected timeouts in clients when the SMTP PIPELINING extension is in
27748 use. This control, as long as it is encountered before the &%delay%& modifier,
27749 disables such output flushing.
27751 .vitem &*control&~=&~no_callout_flush*&
27752 .cindex "SMTP" "output flushing, disabling for callout"
27753 Exim normally flushes SMTP output before performing a callout in an ACL, to
27754 avoid unexpected timeouts in clients when the SMTP PIPELINING extension is in
27755 use. This control, as long as it is encountered before the &%verify%& condition
27756 that causes the callout, disables such output flushing.
27758 .vitem &*control&~=&~no_mbox_unspool*&
27759 This control is available when Exim is compiled with the content scanning
27760 extension. Content scanning may require a copy of the current message, or parts
27761 of it, to be written in &"mbox format"& to a spool file, for passing to a virus
27762 or spam scanner. Normally, such copies are deleted when they are no longer
27763 needed. If this control is set, the copies are not deleted. The control applies
27764 only to the current message, not to any subsequent ones that may be received in
27765 the same SMTP connection. It is provided for debugging purposes and is unlikely
27766 to be useful in production.
27768 .vitem &*control&~=&~no_multiline_responses*&
27769 .cindex "multiline responses, suppressing"
27770 This control is permitted for any ACL except the one for non-SMTP messages.
27771 It seems that there are broken clients in use that cannot handle multiline
27772 SMTP responses, despite the fact that RFC 821 defined them over 20 years ago.
27774 If this control is set, multiline SMTP responses from ACL rejections are
27775 suppressed. One way of doing this would have been to put out these responses as
27776 one long line. However, RFC 2821 specifies a maximum of 512 bytes per response
27777 (&"use multiline responses for more"& it says &-- ha!), and some of the
27778 responses might get close to that. So this facility, which is after all only a
27779 sop to broken clients, is implemented by doing two very easy things:
27782 Extra information that is normally output as part of a rejection caused by
27783 sender verification failure is omitted. Only the final line (typically &"sender
27784 verification failed"&) is sent.
27786 If a &%message%& modifier supplies a multiline response, only the first
27790 The setting of the switch can, of course, be made conditional on the
27791 calling host. Its effect lasts until the end of the SMTP connection.
27793 .vitem &*control&~=&~no_pipelining*&
27794 .cindex "PIPELINING" "suppressing advertising"
27795 This control turns off the advertising of the PIPELINING extension to SMTP in
27796 the current session. To be useful, it must be obeyed before Exim sends its
27797 response to an EHLO command. Therefore, it should normally appear in an ACL
27798 controlled by &%acl_smtp_connect%& or &%acl_smtp_helo%&. See also
27799 &%pipelining_advertise_hosts%&.
27801 .vitem &*control&~=&~queue_only*&
27802 .oindex "&%queue_only%&"
27803 .cindex "queueing incoming messages"
27804 This control is permitted only for the MAIL, RCPT, DATA, and non-SMTP ACLs, in
27805 other words, only when a message is being received. If the message is accepted,
27806 it is placed on Exim's queue and left there for delivery by a subsequent queue
27807 runner. No immediate delivery process is started. In other words, it has the
27808 effect as the &%queue_only%& global option. However, the control applies only
27809 to the current message, not to any subsequent ones that may be received in the
27810 same SMTP connection.
27812 .vitem &*control&~=&~submission/*&<&'options'&>
27813 .cindex "message" "submission"
27814 .cindex "submission mode"
27815 This control is permitted only for the MAIL, RCPT, and start of data ACLs (the
27816 latter is the one defined by &%acl_smtp_predata%&). Setting it tells Exim that
27817 the current message is a submission from a local MUA. In this case, Exim
27818 operates in &"submission mode"&, and applies certain fixups to the message if
27819 necessary. For example, it adds a &'Date:'& header line if one is not present.
27820 This control is not permitted in the &%acl_smtp_data%& ACL, because that is too
27821 late (the message has already been created).
27823 Chapter &<<CHAPmsgproc>>& describes the processing that Exim applies to
27824 messages. Section &<<SECTsubmodnon>>& covers the processing that happens in
27825 submission mode; the available options for this control are described there.
27826 The control applies only to the current message, not to any subsequent ones
27827 that may be received in the same SMTP connection.
27829 .vitem &*control&~=&~suppress_local_fixups*&
27830 .cindex "submission fixups, suppressing"
27831 This control applies to locally submitted (non TCP/IP) messages, and is the
27832 complement of &`control = submission`&. It disables the fixups that are
27833 normally applied to locally-submitted messages. Specifically:
27836 Any &'Sender:'& header line is left alone (in this respect, it is a
27837 dynamic version of &%local_sender_retain%&).
27839 No &'Message-ID:'&, &'From:'&, or &'Date:'& header lines are added.
27841 There is no check that &'From:'& corresponds to the actual sender.
27844 This control may be useful when a remotely-originated message is accepted,
27845 passed to some scanning program, and then re-submitted for delivery. It can be
27846 used only in the &%acl_smtp_mail%&, &%acl_smtp_rcpt%&, &%acl_smtp_predata%&,
27847 and &%acl_not_smtp_start%& ACLs, because it has to be set before the message's
27850 &*Note:*& This control applies only to the current message, not to any others
27851 that are being submitted at the same time using &%-bs%& or &%-bS%&.
27855 .section "Summary of message fixup control" "SECTsummesfix"
27856 All four possibilities for message fixups can be specified:
27859 Locally submitted, fixups applied: the default.
27861 Locally submitted, no fixups applied: use
27862 &`control = suppress_local_fixups`&.
27864 Remotely submitted, no fixups applied: the default.
27866 Remotely submitted, fixups applied: use &`control = submission`&.
27871 .section "Adding header lines in ACLs" "SECTaddheadacl"
27872 .cindex "header lines" "adding in an ACL"
27873 .cindex "header lines" "position of added lines"
27874 .cindex "&%add_header%& ACL modifier"
27875 The &%add_header%& modifier can be used to add one or more extra header lines
27876 to an incoming message, as in this example:
27878 warn dnslists = sbl.spamhaus.org : \
27879 dialup.mail-abuse.org
27880 add_header = X-blacklisted-at: $dnslist_domain
27882 The &%add_header%& modifier is permitted in the MAIL, RCPT, PREDATA, DATA,
27883 MIME, DKIM, and non-SMTP ACLs (in other words, those that are concerned with
27884 receiving a message). The message must ultimately be accepted for
27885 &%add_header%& to have any significant effect. You can use &%add_header%& with
27886 any ACL verb, including &%deny%& (though this is potentially useful only in a
27889 Headers will not be added to the message if the modifier is used in
27890 DATA, MIME or DKIM ACLs for messages delivered by cutthrough routing.
27892 Leading and trailing newlines are removed from
27893 the data for the &%add_header%& modifier; if it then
27894 contains one or more newlines that
27895 are not followed by a space or a tab, it is assumed to contain multiple header
27896 lines. Each one is checked for valid syntax; &`X-ACL-Warn:`& is added to the
27897 front of any line that is not a valid header line.
27899 Added header lines are accumulated during the MAIL, RCPT, and predata ACLs.
27900 They are added to the message before processing the DATA and MIME ACLs.
27901 However, if an identical header line is requested more than once, only one copy
27902 is actually added to the message. Further header lines may be accumulated
27903 during the DATA and MIME ACLs, after which they are added to the message, again
27904 with duplicates suppressed. Thus, it is possible to add two identical header
27905 lines to an SMTP message, but only if one is added before DATA and one after.
27906 In the case of non-SMTP messages, new headers are accumulated during the
27907 non-SMTP ACLs, and are added to the message after all the ACLs have run. If a
27908 message is rejected after DATA or by the non-SMTP ACL, all added header lines
27909 are included in the entry that is written to the reject log.
27911 .cindex "header lines" "added; visibility of"
27912 Header lines are not visible in string expansions
27914 until they are added to the
27915 message. It follows that header lines defined in the MAIL, RCPT, and predata
27916 ACLs are not visible until the DATA ACL and MIME ACLs are run. Similarly,
27917 header lines that are added by the DATA or MIME ACLs are not visible in those
27918 ACLs. Because of this restriction, you cannot use header lines as a way of
27919 passing data between (for example) the MAIL and RCPT ACLs. If you want to do
27920 this, you can use ACL variables, as described in section
27921 &<<SECTaclvariables>>&.
27923 The list of headers yet to be added is given by the &%$headers_added%& variable.
27925 The &%add_header%& modifier acts immediately as it is encountered during the
27926 processing of an ACL. Notice the difference between these two cases:
27928 &`accept add_header = ADDED: some text`&
27929 &` `&<&'some condition'&>
27931 &`accept `&<&'some condition'&>
27932 &` add_header = ADDED: some text`&
27934 In the first case, the header line is always added, whether or not the
27935 condition is true. In the second case, the header line is added only if the
27936 condition is true. Multiple occurrences of &%add_header%& may occur in the same
27937 ACL statement. All those that are encountered before a condition fails are
27940 .cindex "&%warn%& ACL verb"
27941 For compatibility with previous versions of Exim, a &%message%& modifier for a
27942 &%warn%& verb acts in the same way as &%add_header%&, except that it takes
27943 effect only if all the conditions are true, even if it appears before some of
27944 them. Furthermore, only the last occurrence of &%message%& is honoured. This
27945 usage of &%message%& is now deprecated. If both &%add_header%& and &%message%&
27946 are present on a &%warn%& verb, both are processed according to their
27949 By default, new header lines are added to a message at the end of the existing
27950 header lines. However, you can specify that any particular header line should
27951 be added right at the start (before all the &'Received:'& lines), immediately
27952 after the first block of &'Received:'& lines, or immediately before any line
27953 that is not a &'Received:'& or &'Resent-something:'& header.
27955 This is done by specifying &":at_start:"&, &":after_received:"&, or
27956 &":at_start_rfc:"& (or, for completeness, &":at_end:"&) before the text of the
27957 header line, respectively. (Header text cannot start with a colon, as there has
27958 to be a header name first.) For example:
27960 warn add_header = \
27961 :after_received:X-My-Header: something or other...
27963 If more than one header line is supplied in a single &%add_header%& modifier,
27964 each one is treated independently and can therefore be placed differently. If
27965 you add more than one line at the start, or after the Received: block, they end
27966 up in reverse order.
27968 &*Warning*&: This facility currently applies only to header lines that are
27969 added in an ACL. It does NOT work for header lines that are added in a
27970 system filter or in a router or transport.
27974 .section "Removing header lines in ACLs" "SECTremoveheadacl"
27975 .cindex "header lines" "removing in an ACL"
27976 .cindex "header lines" "position of removed lines"
27977 .cindex "&%remove_header%& ACL modifier"
27978 The &%remove_header%& modifier can be used to remove one or more header lines
27979 from an incoming message, as in this example:
27981 warn message = Remove internal headers
27982 remove_header = x-route-mail1 : x-route-mail2
27984 The &%remove_header%& modifier is permitted in the MAIL, RCPT, PREDATA, DATA,
27985 MIME, DKIM, and non-SMTP ACLs (in other words, those that are concerned with
27986 receiving a message). The message must ultimately be accepted for
27987 &%remove_header%& to have any significant effect. You can use &%remove_header%&
27988 with any ACL verb, including &%deny%&, though this is really not useful for
27989 any verb that doesn't result in a delivered message.
27991 Headers will not be removed to the message if the modifier is used in
27992 DATA, MIME or DKIM ACLs for messages delivered by cutthrough routing.
27994 More than one header can be removed at the same time by using a colon separated
27995 list of header names. The header matching is case insensitive. Wildcards are
27996 not permitted, nor is list expansion performed, so you cannot use hostlists to
27997 create a list of headers, however both connection and message variable expansion
27998 are performed (&%$acl_c_*%& and &%$acl_m_*%&), illustrated in this example:
28000 warn hosts = +internal_hosts
28001 set acl_c_ihdrs = x-route-mail1 : x-route-mail2
28002 warn message = Remove internal headers
28003 remove_header = $acl_c_ihdrs
28005 Removed header lines are accumulated during the MAIL, RCPT, and predata ACLs.
28006 They are removed from the message before processing the DATA and MIME ACLs.
28007 There is no harm in attempting to remove the same header twice nor is removing
28008 a non-existent header. Further header lines to be removed may be accumulated
28009 during the DATA and MIME ACLs, after which they are removed from the message,
28010 if present. In the case of non-SMTP messages, headers to be removed are
28011 accumulated during the non-SMTP ACLs, and are removed from the message after
28012 all the ACLs have run. If a message is rejected after DATA or by the non-SMTP
28013 ACL, there really is no effect because there is no logging of what headers
28014 would have been removed.
28016 .cindex "header lines" "removed; visibility of"
28017 Header lines are not visible in string expansions until the DATA phase when it
28018 is received. Any header lines removed in the MAIL, RCPT, and predata ACLs are
28019 not visible in the DATA ACL and MIME ACLs. Similarly, header lines that are
28020 removed by the DATA or MIME ACLs are still visible in those ACLs. Because of
28021 this restriction, you cannot use header lines as a way of controlling data
28022 passed between (for example) the MAIL and RCPT ACLs. If you want to do this,
28023 you should instead use ACL variables, as described in section
28024 &<<SECTaclvariables>>&.
28026 The &%remove_header%& modifier acts immediately as it is encountered during the
28027 processing of an ACL. Notice the difference between these two cases:
28029 &`accept remove_header = X-Internal`&
28030 &` `&<&'some condition'&>
28032 &`accept `&<&'some condition'&>
28033 &` remove_header = X-Internal`&
28035 In the first case, the header line is always removed, whether or not the
28036 condition is true. In the second case, the header line is removed only if the
28037 condition is true. Multiple occurrences of &%remove_header%& may occur in the
28038 same ACL statement. All those that are encountered before a condition fails
28041 &*Warning*&: This facility currently applies only to header lines that are
28042 present during ACL processing. It does NOT remove header lines that are added
28043 in a system filter or in a router or transport.
28048 .section "ACL conditions" "SECTaclconditions"
28049 .cindex "&ACL;" "conditions; list of"
28050 Some of the conditions listed in this section are available only when Exim is
28051 compiled with the content-scanning extension. They are included here briefly
28052 for completeness. More detailed descriptions can be found in the discussion on
28053 content scanning in chapter &<<CHAPexiscan>>&.
28055 Not all conditions are relevant in all circumstances. For example, testing
28056 senders and recipients does not make sense in an ACL that is being run as the
28057 result of the arrival of an ETRN command, and checks on message headers can be
28058 done only in the ACLs specified by &%acl_smtp_data%& and &%acl_not_smtp%&. You
28059 can use the same condition (with different parameters) more than once in the
28060 same ACL statement. This provides a way of specifying an &"and"& conjunction.
28061 The conditions are as follows:
28065 .vitem &*acl&~=&~*&<&'name&~of&~acl&~or&~ACL&~string&~or&~file&~name&~'&>
28066 .cindex "&ACL;" "nested"
28067 .cindex "&ACL;" "indirect"
28068 .cindex "&ACL;" "arguments"
28069 .cindex "&%acl%& ACL condition"
28070 The possible values of the argument are the same as for the
28071 &%acl_smtp_%&&'xxx'& options. The named or inline ACL is run. If it returns
28072 &"accept"& the condition is true; if it returns &"deny"& the condition is
28073 false. If it returns &"defer"&, the current ACL returns &"defer"& unless the
28074 condition is on a &%warn%& verb. In that case, a &"defer"& return makes the
28075 condition false. This means that further processing of the &%warn%& verb
28076 ceases, but processing of the ACL continues.
28078 If the argument is a named ACL, up to nine space-separated optional values
28079 can be appended; they appear within the called ACL in $acl_arg1 to $acl_arg9,
28080 and $acl_narg is set to the count of values.
28081 Previous values of these variables are restored after the call returns.
28082 The name and values are expanded separately.
28084 If the nested &%acl%& returns &"drop"& and the outer condition denies access,
28085 the connection is dropped. If it returns &"discard"&, the verb must be
28086 &%accept%& or &%discard%&, and the action is taken immediately &-- no further
28087 conditions are tested.
28089 ACLs may be nested up to 20 deep; the limit exists purely to catch runaway
28090 loops. This condition allows you to use different ACLs in different
28091 circumstances. For example, different ACLs can be used to handle RCPT commands
28092 for different local users or different local domains.
28094 .vitem &*authenticated&~=&~*&<&'string&~list'&>
28095 .cindex "&%authenticated%& ACL condition"
28096 .cindex "authentication" "ACL checking"
28097 .cindex "&ACL;" "testing for authentication"
28098 If the SMTP connection is not authenticated, the condition is false. Otherwise,
28099 the name of the authenticator is tested against the list. To test for
28100 authentication by any authenticator, you can set
28105 .vitem &*condition&~=&~*&<&'string'&>
28106 .cindex "&%condition%& ACL condition"
28107 .cindex "customizing" "ACL condition"
28108 .cindex "&ACL;" "customized test"
28109 .cindex "&ACL;" "testing, customized"
28110 This feature allows you to make up custom conditions. If the result of
28111 expanding the string is an empty string, the number zero, or one of the strings
28112 &"no"& or &"false"&, the condition is false. If the result is any non-zero
28113 number, or one of the strings &"yes"& or &"true"&, the condition is true. For
28114 any other value, some error is assumed to have occurred, and the ACL returns
28115 &"defer"&. However, if the expansion is forced to fail, the condition is
28116 ignored. The effect is to treat it as true, whether it is positive or
28119 .vitem &*decode&~=&~*&<&'location'&>
28120 .cindex "&%decode%& ACL condition"
28121 This condition is available only when Exim is compiled with the
28122 content-scanning extension, and it is allowed only in the ACL defined by
28123 &%acl_smtp_mime%&. It causes the current MIME part to be decoded into a file.
28124 If all goes well, the condition is true. It is false only if there are
28125 problems such as a syntax error or a memory shortage. For more details, see
28126 chapter &<<CHAPexiscan>>&.
28128 .vitem &*demime&~=&~*&<&'extension&~list'&>
28129 .cindex "&%demime%& ACL condition"
28130 This condition is available only when Exim is compiled with the
28131 content-scanning extension. Its use is described in section
28132 &<<SECTdemimecond>>&.
28134 .vitem &*dnslists&~=&~*&<&'list&~of&~domain&~names&~and&~other&~data'&>
28135 .cindex "&%dnslists%& ACL condition"
28136 .cindex "DNS list" "in ACL"
28137 .cindex "black list (DNS)"
28138 .cindex "&ACL;" "testing a DNS list"
28139 This condition checks for entries in DNS black lists. These are also known as
28140 &"RBL lists"&, after the original Realtime Blackhole List, but note that the
28141 use of the lists at &'mail-abuse.org'& now carries a charge. There are too many
28142 different variants of this condition to describe briefly here. See sections
28143 &<<SECTmorednslists>>&&--&<<SECTmorednslistslast>>& for details.
28145 .vitem &*domains&~=&~*&<&'domain&~list'&>
28146 .cindex "&%domains%& ACL condition"
28147 .cindex "domain" "ACL checking"
28148 .cindex "&ACL;" "testing a recipient domain"
28149 .vindex "&$domain_data$&"
28150 This condition is relevant only after a RCPT command. It checks that the domain
28151 of the recipient address is in the domain list. If percent-hack processing is
28152 enabled, it is done before this test is done. If the check succeeds with a
28153 lookup, the result of the lookup is placed in &$domain_data$& until the next
28156 &*Note carefully*& (because many people seem to fall foul of this): you cannot
28157 use &%domains%& in a DATA ACL.
28160 .vitem &*encrypted&~=&~*&<&'string&~list'&>
28161 .cindex "&%encrypted%& ACL condition"
28162 .cindex "encryption" "checking in an ACL"
28163 .cindex "&ACL;" "testing for encryption"
28164 If the SMTP connection is not encrypted, the condition is false. Otherwise, the
28165 name of the cipher suite in use is tested against the list. To test for
28166 encryption without testing for any specific cipher suite(s), set
28172 .vitem &*hosts&~=&~*&<&'host&~list'&>
28173 .cindex "&%hosts%& ACL condition"
28174 .cindex "host" "ACL checking"
28175 .cindex "&ACL;" "testing the client host"
28176 This condition tests that the calling host matches the host list. If you have
28177 name lookups or wildcarded host names and IP addresses in the same host list,
28178 you should normally put the IP addresses first. For example, you could have:
28180 accept hosts = 10.9.8.7 : dbm;/etc/friendly/hosts
28182 The lookup in this example uses the host name for its key. This is implied by
28183 the lookup type &"dbm"&. (For a host address lookup you would use &"net-dbm"&
28184 and it wouldn't matter which way round you had these two items.)
28186 The reason for the problem with host names lies in the left-to-right way that
28187 Exim processes lists. It can test IP addresses without doing any DNS lookups,
28188 but when it reaches an item that requires a host name, it fails if it cannot
28189 find a host name to compare with the pattern. If the above list is given in the
28190 opposite order, the &%accept%& statement fails for a host whose name cannot be
28191 found, even if its IP address is 10.9.8.7.
28193 If you really do want to do the name check first, and still recognize the IP
28194 address even if the name lookup fails, you can rewrite the ACL like this:
28196 accept hosts = dbm;/etc/friendly/hosts
28197 accept hosts = 10.9.8.7
28199 The default action on failing to find the host name is to assume that the host
28200 is not in the list, so the first &%accept%& statement fails. The second
28201 statement can then check the IP address.
28203 .vindex "&$host_data$&"
28204 If a &%hosts%& condition is satisfied by means of a lookup, the result
28205 of the lookup is made available in the &$host_data$& variable. This
28206 allows you, for example, to set up a statement like this:
28208 deny hosts = net-lsearch;/some/file
28209 message = $host_data
28211 which gives a custom error message for each denied host.
28213 .vitem &*local_parts&~=&~*&<&'local&~part&~list'&>
28214 .cindex "&%local_parts%& ACL condition"
28215 .cindex "local part" "ACL checking"
28216 .cindex "&ACL;" "testing a local part"
28217 .vindex "&$local_part_data$&"
28218 This condition is relevant only after a RCPT command. It checks that the local
28219 part of the recipient address is in the list. If percent-hack processing is
28220 enabled, it is done before this test. If the check succeeds with a lookup, the
28221 result of the lookup is placed in &$local_part_data$&, which remains set until
28222 the next &%local_parts%& test.
28224 .vitem &*malware&~=&~*&<&'option'&>
28225 .cindex "&%malware%& ACL condition"
28226 .cindex "&ACL;" "virus scanning"
28227 .cindex "&ACL;" "scanning for viruses"
28228 This condition is available only when Exim is compiled with the
28229 content-scanning extension. It causes the incoming message to be scanned for
28230 viruses. For details, see chapter &<<CHAPexiscan>>&.
28232 .vitem &*mime_regex&~=&~*&<&'list&~of&~regular&~expressions'&>
28233 .cindex "&%mime_regex%& ACL condition"
28234 .cindex "&ACL;" "testing by regex matching"
28235 This condition is available only when Exim is compiled with the
28236 content-scanning extension, and it is allowed only in the ACL defined by
28237 &%acl_smtp_mime%&. It causes the current MIME part to be scanned for a match
28238 with any of the regular expressions. For details, see chapter
28241 .vitem &*ratelimit&~=&~*&<&'parameters'&>
28242 .cindex "rate limiting"
28243 This condition can be used to limit the rate at which a user or host submits
28244 messages. Details are given in section &<<SECTratelimiting>>&.
28246 .vitem &*recipients&~=&~*&<&'address&~list'&>
28247 .cindex "&%recipients%& ACL condition"
28248 .cindex "recipient" "ACL checking"
28249 .cindex "&ACL;" "testing a recipient"
28250 This condition is relevant only after a RCPT command. It checks the entire
28251 recipient address against a list of recipients.
28253 .vitem &*regex&~=&~*&<&'list&~of&~regular&~expressions'&>
28254 .cindex "&%regex%& ACL condition"
28255 .cindex "&ACL;" "testing by regex matching"
28256 This condition is available only when Exim is compiled with the
28257 content-scanning extension, and is available only in the DATA, MIME, and
28258 non-SMTP ACLs. It causes the incoming message to be scanned for a match with
28259 any of the regular expressions. For details, see chapter &<<CHAPexiscan>>&.
28261 .vitem &*sender_domains&~=&~*&<&'domain&~list'&>
28262 .cindex "&%sender_domains%& ACL condition"
28263 .cindex "sender" "ACL checking"
28264 .cindex "&ACL;" "testing a sender domain"
28265 .vindex "&$domain$&"
28266 .vindex "&$sender_address_domain$&"
28267 This condition tests the domain of the sender of the message against the given
28268 domain list. &*Note*&: The domain of the sender address is in
28269 &$sender_address_domain$&. It is &'not'& put in &$domain$& during the testing
28270 of this condition. This is an exception to the general rule for testing domain
28271 lists. It is done this way so that, if this condition is used in an ACL for a
28272 RCPT command, the recipient's domain (which is in &$domain$&) can be used to
28273 influence the sender checking.
28275 &*Warning*&: It is a bad idea to use this condition on its own as a control on
28276 relaying, because sender addresses are easily, and commonly, forged.
28278 .vitem &*senders&~=&~*&<&'address&~list'&>
28279 .cindex "&%senders%& ACL condition"
28280 .cindex "sender" "ACL checking"
28281 .cindex "&ACL;" "testing a sender"
28282 This condition tests the sender of the message against the given list. To test
28283 for a bounce message, which has an empty sender, set
28287 &*Warning*&: It is a bad idea to use this condition on its own as a control on
28288 relaying, because sender addresses are easily, and commonly, forged.
28290 .vitem &*spam&~=&~*&<&'username'&>
28291 .cindex "&%spam%& ACL condition"
28292 .cindex "&ACL;" "scanning for spam"
28293 This condition is available only when Exim is compiled with the
28294 content-scanning extension. It causes the incoming message to be scanned by
28295 SpamAssassin. For details, see chapter &<<CHAPexiscan>>&.
28297 .vitem &*verify&~=&~certificate*&
28298 .cindex "&%verify%& ACL condition"
28299 .cindex "TLS" "client certificate verification"
28300 .cindex "certificate" "verification of client"
28301 .cindex "&ACL;" "certificate verification"
28302 .cindex "&ACL;" "testing a TLS certificate"
28303 This condition is true in an SMTP session if the session is encrypted, and a
28304 certificate was received from the client, and the certificate was verified. The
28305 server requests a certificate only if the client matches &%tls_verify_hosts%&
28306 or &%tls_try_verify_hosts%& (see chapter &<<CHAPTLS>>&).
28308 .vitem &*verify&~=&~csa*&
28309 .cindex "CSA verification"
28310 This condition checks whether the sending host (the client) is authorized to
28311 send email. Details of how this works are given in section
28312 &<<SECTverifyCSA>>&.
28315 .vitem &*verify&~=&~header_names_ascii*&
28316 .cindex "&%verify%& ACL condition"
28317 .cindex "&ACL;" "verifying header names only ASCII"
28318 .cindex "header lines" "verifying header names only ASCII"
28319 .cindex "verifying" "header names only ASCII"
28320 This condition is relevant only in an ACL that is run after a message has been
28321 received, that is, in an ACL specified by &%acl_smtp_data%& or
28322 &%acl_not_smtp%&. It checks all header names (not the content) to make sure
28323 there are no non-ASCII characters, also excluding control characters. The
28324 allowable characters are decimal ASCII values 33 through 126.
28326 Exim itself will handle headers with non-ASCII characters, but it can cause
28327 problems for downstream applications, so this option will allow their
28328 detection and rejection in the DATA ACL's.
28331 .vitem &*verify&~=&~header_sender/*&<&'options'&>
28332 .cindex "&%verify%& ACL condition"
28333 .cindex "&ACL;" "verifying sender in the header"
28334 .cindex "header lines" "verifying the sender in"
28335 .cindex "sender" "verifying in header"
28336 .cindex "verifying" "sender in header"
28337 This condition is relevant only in an ACL that is run after a message has been
28338 received, that is, in an ACL specified by &%acl_smtp_data%& or
28339 &%acl_not_smtp%&. It checks that there is a verifiable address in at least one
28340 of the &'Sender:'&, &'Reply-To:'&, or &'From:'& header lines. Such an address
28341 is loosely thought of as a &"sender"& address (hence the name of the test).
28342 However, an address that appears in one of these headers need not be an address
28343 that accepts bounce messages; only sender addresses in envelopes are required
28344 to accept bounces. Therefore, if you use the callout option on this check, you
28345 might want to arrange for a non-empty address in the MAIL command.
28347 Details of address verification and the options are given later, starting at
28348 section &<<SECTaddressverification>>& (callouts are described in section
28349 &<<SECTcallver>>&). You can combine this condition with the &%senders%&
28350 condition to restrict it to bounce messages only:
28353 message = A valid sender header is required for bounces
28354 !verify = header_sender
28357 .vitem &*verify&~=&~header_syntax*&
28358 .cindex "&%verify%& ACL condition"
28359 .cindex "&ACL;" "verifying header syntax"
28360 .cindex "header lines" "verifying syntax"
28361 .cindex "verifying" "header syntax"
28362 This condition is relevant only in an ACL that is run after a message has been
28363 received, that is, in an ACL specified by &%acl_smtp_data%& or
28364 &%acl_not_smtp%&. It checks the syntax of all header lines that can contain
28365 lists of addresses (&'Sender:'&, &'From:'&, &'Reply-To:'&, &'To:'&, &'Cc:'&,
28366 and &'Bcc:'&). Unqualified addresses (local parts without domains) are
28367 permitted only in locally generated messages and from hosts that match
28368 &%sender_unqualified_hosts%& or &%recipient_unqualified_hosts%&, as
28371 Note that this condition is a syntax check only. However, a common spamming
28372 ploy used to be to send syntactically invalid headers such as
28376 and this condition can be used to reject such messages, though they are not as
28377 common as they used to be.
28379 .vitem &*verify&~=&~helo*&
28380 .cindex "&%verify%& ACL condition"
28381 .cindex "&ACL;" "verifying HELO/EHLO"
28382 .cindex "HELO" "verifying"
28383 .cindex "EHLO" "verifying"
28384 .cindex "verifying" "EHLO"
28385 .cindex "verifying" "HELO"
28386 This condition is true if a HELO or EHLO command has been received from the
28387 client host, and its contents have been verified. If there has been no previous
28388 attempt to verify the HELO/EHLO contents, it is carried out when this
28389 condition is encountered. See the description of the &%helo_verify_hosts%& and
28390 &%helo_try_verify_hosts%& options for details of how to request verification
28391 independently of this condition.
28393 For SMTP input that does not come over TCP/IP (the &%-bs%& command line
28394 option), this condition is always true.
28397 .vitem &*verify&~=&~not_blind*&
28398 .cindex "verifying" "not blind"
28399 .cindex "bcc recipients, verifying none"
28400 This condition checks that there are no blind (bcc) recipients in the message.
28401 Every envelope recipient must appear either in a &'To:'& header line or in a
28402 &'Cc:'& header line for this condition to be true. Local parts are checked
28403 case-sensitively; domains are checked case-insensitively. If &'Resent-To:'& or
28404 &'Resent-Cc:'& header lines exist, they are also checked. This condition can be
28405 used only in a DATA or non-SMTP ACL.
28407 There are, of course, many legitimate messages that make use of blind (bcc)
28408 recipients. This check should not be used on its own for blocking messages.
28411 .vitem &*verify&~=&~recipient/*&<&'options'&>
28412 .cindex "&%verify%& ACL condition"
28413 .cindex "&ACL;" "verifying recipient"
28414 .cindex "recipient" "verifying"
28415 .cindex "verifying" "recipient"
28416 .vindex "&$address_data$&"
28417 This condition is relevant only after a RCPT command. It verifies the current
28418 recipient. Details of address verification are given later, starting at section
28419 &<<SECTaddressverification>>&. After a recipient has been verified, the value
28420 of &$address_data$& is the last value that was set while routing the address.
28421 This applies even if the verification fails. When an address that is being
28422 verified is redirected to a single address, verification continues with the new
28423 address, and in that case, the subsequent value of &$address_data$& is the
28424 value for the child address.
28426 .vitem &*verify&~=&~reverse_host_lookup*&
28427 .cindex "&%verify%& ACL condition"
28428 .cindex "&ACL;" "verifying host reverse lookup"
28429 .cindex "host" "verifying reverse lookup"
28430 This condition ensures that a verified host name has been looked up from the IP
28431 address of the client host. (This may have happened already if the host name
28432 was needed for checking a host list, or if the host matched &%host_lookup%&.)
28433 Verification ensures that the host name obtained from a reverse DNS lookup, or
28434 one of its aliases, does, when it is itself looked up in the DNS, yield the
28435 original IP address.
28437 If this condition is used for a locally generated message (that is, when there
28438 is no client host involved), it always succeeds.
28440 .vitem &*verify&~=&~sender/*&<&'options'&>
28441 .cindex "&%verify%& ACL condition"
28442 .cindex "&ACL;" "verifying sender"
28443 .cindex "sender" "verifying"
28444 .cindex "verifying" "sender"
28445 This condition is relevant only after a MAIL or RCPT command, or after a
28446 message has been received (the &%acl_smtp_data%& or &%acl_not_smtp%& ACLs). If
28447 the message's sender is empty (that is, this is a bounce message), the
28448 condition is true. Otherwise, the sender address is verified.
28450 .vindex "&$address_data$&"
28451 .vindex "&$sender_address_data$&"
28452 If there is data in the &$address_data$& variable at the end of routing, its
28453 value is placed in &$sender_address_data$& at the end of verification. This
28454 value can be used in subsequent conditions and modifiers in the same ACL
28455 statement. It does not persist after the end of the current statement. If you
28456 want to preserve the value for longer, you can save it in an ACL variable.
28458 Details of verification are given later, starting at section
28459 &<<SECTaddressverification>>&. Exim caches the result of sender verification,
28460 to avoid doing it more than once per message.
28462 .vitem &*verify&~=&~sender=*&<&'address'&>&*/*&<&'options'&>
28463 .cindex "&%verify%& ACL condition"
28464 This is a variation of the previous option, in which a modified address is
28465 verified as a sender.
28470 .section "Using DNS lists" "SECTmorednslists"
28471 .cindex "DNS list" "in ACL"
28472 .cindex "black list (DNS)"
28473 .cindex "&ACL;" "testing a DNS list"
28474 In its simplest form, the &%dnslists%& condition tests whether the calling host
28475 is on at least one of a number of DNS lists by looking up the inverted IP
28476 address in one or more DNS domains. (Note that DNS list domains are not mail
28477 domains, so the &`+`& syntax for named lists doesn't work - it is used for
28478 special options instead.) For example, if the calling host's IP
28479 address is 192.168.62.43, and the ACL statement is
28481 deny dnslists = blackholes.mail-abuse.org : \
28482 dialups.mail-abuse.org
28484 the following records are looked up:
28486 43.62.168.192.blackholes.mail-abuse.org
28487 43.62.168.192.dialups.mail-abuse.org
28489 As soon as Exim finds an existing DNS record, processing of the list stops.
28490 Thus, multiple entries on the list provide an &"or"& conjunction. If you want
28491 to test that a host is on more than one list (an &"and"& conjunction), you can
28492 use two separate conditions:
28494 deny dnslists = blackholes.mail-abuse.org
28495 dnslists = dialups.mail-abuse.org
28497 If a DNS lookup times out or otherwise fails to give a decisive answer, Exim
28498 behaves as if the host does not match the list item, that is, as if the DNS
28499 record does not exist. If there are further items in the DNS list, they are
28502 This is usually the required action when &%dnslists%& is used with &%deny%&
28503 (which is the most common usage), because it prevents a DNS failure from
28504 blocking mail. However, you can change this behaviour by putting one of the
28505 following special items in the list:
28507 &`+include_unknown `& behave as if the item is on the list
28508 &`+exclude_unknown `& behave as if the item is not on the list (default)
28509 &`+defer_unknown `& give a temporary error
28511 .cindex "&`+include_unknown`&"
28512 .cindex "&`+exclude_unknown`&"
28513 .cindex "&`+defer_unknown`&"
28514 Each of these applies to any subsequent items on the list. For example:
28516 deny dnslists = +defer_unknown : foo.bar.example
28518 Testing the list of domains stops as soon as a match is found. If you want to
28519 warn for one list and block for another, you can use two different statements:
28521 deny dnslists = blackholes.mail-abuse.org
28522 warn message = X-Warn: sending host is on dialups list
28523 dnslists = dialups.mail-abuse.org
28525 DNS list lookups are cached by Exim for the duration of the SMTP session,
28526 so a lookup based on the IP address is done at most once for any incoming
28527 connection. Exim does not share information between multiple incoming
28528 connections (but your local name server cache should be active).
28532 .section "Specifying the IP address for a DNS list lookup" "SECID201"
28533 .cindex "DNS list" "keyed by explicit IP address"
28534 By default, the IP address that is used in a DNS list lookup is the IP address
28535 of the calling host. However, you can specify another IP address by listing it
28536 after the domain name, introduced by a slash. For example:
28538 deny dnslists = black.list.tld/192.168.1.2
28540 This feature is not very helpful with explicit IP addresses; it is intended for
28541 use with IP addresses that are looked up, for example, the IP addresses of the
28542 MX hosts or nameservers of an email sender address. For an example, see section
28543 &<<SECTmulkeyfor>>& below.
28548 .section "DNS lists keyed on domain names" "SECID202"
28549 .cindex "DNS list" "keyed by domain name"
28550 There are some lists that are keyed on domain names rather than inverted IP
28551 addresses (see for example the &'domain based zones'& link at
28552 &url(http://www.rfc-ignorant.org/)). No reversing of components is used
28553 with these lists. You can change the name that is looked up in a DNS list by
28554 listing it after the domain name, introduced by a slash. For example,
28556 deny message = Sender's domain is listed at $dnslist_domain
28557 dnslists = dsn.rfc-ignorant.org/$sender_address_domain
28559 This particular example is useful only in ACLs that are obeyed after the
28560 RCPT or DATA commands, when a sender address is available. If (for
28561 example) the message's sender is &'user@tld.example'& the name that is looked
28562 up by this example is
28564 tld.example.dsn.rfc-ignorant.org
28566 A single &%dnslists%& condition can contain entries for both names and IP
28567 addresses. For example:
28569 deny dnslists = sbl.spamhaus.org : \
28570 dsn.rfc-ignorant.org/$sender_address_domain
28572 The first item checks the sending host's IP address; the second checks a domain
28573 name. The whole condition is true if either of the DNS lookups succeeds.
28578 .section "Multiple explicit keys for a DNS list" "SECTmulkeyfor"
28579 .cindex "DNS list" "multiple keys for"
28580 The syntax described above for looking up explicitly-defined values (either
28581 names or IP addresses) in a DNS blacklist is a simplification. After the domain
28582 name for the DNS list, what follows the slash can in fact be a list of items.
28583 As with all lists in Exim, the default separator is a colon. However, because
28584 this is a sublist within the list of DNS blacklist domains, it is necessary
28585 either to double the separators like this:
28587 dnslists = black.list.tld/name.1::name.2
28589 or to change the separator character, like this:
28591 dnslists = black.list.tld/<;name.1;name.2
28593 If an item in the list is an IP address, it is inverted before the DNS
28594 blacklist domain is appended. If it is not an IP address, no inversion
28595 occurs. Consider this condition:
28597 dnslists = black.list.tld/<;192.168.1.2;a.domain
28599 The DNS lookups that occur are:
28601 2.1.168.192.black.list.tld
28602 a.domain.black.list.tld
28604 Once a DNS record has been found (that matches a specific IP return
28605 address, if specified &-- see section &<<SECTaddmatcon>>&), no further lookups
28606 are done. If there is a temporary DNS error, the rest of the sublist of domains
28607 or IP addresses is tried. A temporary error for the whole dnslists item occurs
28608 only if no other DNS lookup in this sublist succeeds. In other words, a
28609 successful lookup for any of the items in the sublist overrides a temporary
28610 error for a previous item.
28612 The ability to supply a list of items after the slash is in some sense just a
28613 syntactic convenience. These two examples have the same effect:
28615 dnslists = black.list.tld/a.domain : black.list.tld/b.domain
28616 dnslists = black.list.tld/a.domain::b.domain
28618 However, when the data for the list is obtained from a lookup, the second form
28619 is usually much more convenient. Consider this example:
28621 deny message = The mail servers for the domain \
28622 $sender_address_domain \
28623 are listed at $dnslist_domain ($dnslist_value); \
28625 dnslists = sbl.spamhaus.org/<|${lookup dnsdb {>|a=<|\
28626 ${lookup dnsdb {>|mxh=\
28627 $sender_address_domain} }} }
28629 Note the use of &`>|`& in the dnsdb lookup to specify the separator for
28630 multiple DNS records. The inner dnsdb lookup produces a list of MX hosts
28631 and the outer dnsdb lookup finds the IP addresses for these hosts. The result
28632 of expanding the condition might be something like this:
28634 dnslists = sbl.spahmaus.org/<|192.168.2.3|192.168.5.6|...
28636 Thus, this example checks whether or not the IP addresses of the sender
28637 domain's mail servers are on the Spamhaus black list.
28639 The key that was used for a successful DNS list lookup is put into the variable
28640 &$dnslist_matched$& (see section &<<SECID204>>&).
28645 .section "Data returned by DNS lists" "SECID203"
28646 .cindex "DNS list" "data returned from"
28647 DNS lists are constructed using address records in the DNS. The original RBL
28648 just used the address 127.0.0.1 on the right hand side of each record, but the
28649 RBL+ list and some other lists use a number of values with different meanings.
28650 The values used on the RBL+ list are:
28654 127.1.0.3 DUL and RBL
28656 127.1.0.5 RSS and RBL
28657 127.1.0.6 RSS and DUL
28658 127.1.0.7 RSS and DUL and RBL
28660 Section &<<SECTaddmatcon>>& below describes how you can distinguish between
28661 different values. Some DNS lists may return more than one address record;
28662 see section &<<SECThanmuldnsrec>>& for details of how they are checked.
28665 .section "Variables set from DNS lists" "SECID204"
28666 .cindex "expansion" "variables, set from DNS list"
28667 .cindex "DNS list" "variables set from"
28668 .vindex "&$dnslist_domain$&"
28669 .vindex "&$dnslist_matched$&"
28670 .vindex "&$dnslist_text$&"
28671 .vindex "&$dnslist_value$&"
28672 When an entry is found in a DNS list, the variable &$dnslist_domain$& contains
28673 the name of the overall domain that matched (for example,
28674 &`spamhaus.example`&), &$dnslist_matched$& contains the key within that domain
28675 (for example, &`192.168.5.3`&), and &$dnslist_value$& contains the data from
28676 the DNS record. When the key is an IP address, it is not reversed in
28677 &$dnslist_matched$& (though it is, of course, in the actual lookup). In simple
28678 cases, for example:
28680 deny dnslists = spamhaus.example
28682 the key is also available in another variable (in this case,
28683 &$sender_host_address$&). In more complicated cases, however, this is not true.
28684 For example, using a data lookup (as described in section &<<SECTmulkeyfor>>&)
28685 might generate a dnslists lookup like this:
28687 deny dnslists = spamhaus.example/<|192.168.1.2|192.168.6.7|...
28689 If this condition succeeds, the value in &$dnslist_matched$& might be
28690 &`192.168.6.7`& (for example).
28692 If more than one address record is returned by the DNS lookup, all the IP
28693 addresses are included in &$dnslist_value$&, separated by commas and spaces.
28694 The variable &$dnslist_text$& contains the contents of any associated TXT
28695 record. For lists such as RBL+ the TXT record for a merged entry is often not
28696 very meaningful. See section &<<SECTmordetinf>>& for a way of obtaining more
28699 You can use the DNS list variables in &%message%& or &%log_message%& modifiers
28700 &-- although these appear before the condition in the ACL, they are not
28701 expanded until after it has failed. For example:
28703 deny hosts = !+local_networks
28704 message = $sender_host_address is listed \
28706 dnslists = rbl-plus.mail-abuse.example
28711 .section "Additional matching conditions for DNS lists" "SECTaddmatcon"
28712 .cindex "DNS list" "matching specific returned data"
28713 You can add an equals sign and an IP address after a &%dnslists%& domain name
28714 in order to restrict its action to DNS records with a matching right hand side.
28717 deny dnslists = rblplus.mail-abuse.org=127.0.0.2
28719 rejects only those hosts that yield 127.0.0.2. Without this additional data,
28720 any address record is considered to be a match. For the moment, we assume
28721 that the DNS lookup returns just one record. Section &<<SECThanmuldnsrec>>&
28722 describes how multiple records are handled.
28724 More than one IP address may be given for checking, using a comma as a
28725 separator. These are alternatives &-- if any one of them matches, the
28726 &%dnslists%& condition is true. For example:
28728 deny dnslists = a.b.c=127.0.0.2,127.0.0.3
28730 If you want to specify a constraining address list and also specify names or IP
28731 addresses to be looked up, the constraining address list must be specified
28732 first. For example:
28734 deny dnslists = dsn.rfc-ignorant.org\
28735 =127.0.0.2/$sender_address_domain
28738 If the character &`&&`& is used instead of &`=`&, the comparison for each
28739 listed IP address is done by a bitwise &"and"& instead of by an equality test.
28740 In other words, the listed addresses are used as bit masks. The comparison is
28741 true if all the bits in the mask are present in the address that is being
28742 tested. For example:
28744 dnslists = a.b.c&0.0.0.3
28746 matches if the address is &'x.x.x.'&3, &'x.x.x.'&7, &'x.x.x.'&11, etc. If you
28747 want to test whether one bit or another bit is present (as opposed to both
28748 being present), you must use multiple values. For example:
28750 dnslists = a.b.c&0.0.0.1,0.0.0.2
28752 matches if the final component of the address is an odd number or two times
28757 .section "Negated DNS matching conditions" "SECID205"
28758 You can supply a negative list of IP addresses as part of a &%dnslists%&
28761 deny dnslists = a.b.c=127.0.0.2,127.0.0.3
28763 means &"deny if the host is in the black list at the domain &'a.b.c'& and the
28764 IP address yielded by the list is either 127.0.0.2 or 127.0.0.3"&,
28766 deny dnslists = a.b.c!=127.0.0.2,127.0.0.3
28768 means &"deny if the host is in the black list at the domain &'a.b.c'& and the
28769 IP address yielded by the list is not 127.0.0.2 and not 127.0.0.3"&. In other
28770 words, the result of the test is inverted if an exclamation mark appears before
28771 the &`=`& (or the &`&&`&) sign.
28773 &*Note*&: This kind of negation is not the same as negation in a domain,
28774 host, or address list (which is why the syntax is different).
28776 If you are using just one list, the negation syntax does not gain you much. The
28777 previous example is precisely equivalent to
28779 deny dnslists = a.b.c
28780 !dnslists = a.b.c=127.0.0.2,127.0.0.3
28782 However, if you are using multiple lists, the negation syntax is clearer.
28783 Consider this example:
28785 deny dnslists = sbl.spamhaus.org : \
28787 dnsbl.njabl.org!=127.0.0.3 : \
28790 Using only positive lists, this would have to be:
28792 deny dnslists = sbl.spamhaus.org : \
28794 deny dnslists = dnsbl.njabl.org
28795 !dnslists = dnsbl.njabl.org=127.0.0.3
28796 deny dnslists = relays.ordb.org
28798 which is less clear, and harder to maintain.
28803 .section "Handling multiple DNS records from a DNS list" "SECThanmuldnsrec"
28804 A DNS lookup for a &%dnslists%& condition may return more than one DNS record,
28805 thereby providing more than one IP address. When an item in a &%dnslists%& list
28806 is followed by &`=`& or &`&&`& and a list of IP addresses, in order to restrict
28807 the match to specific results from the DNS lookup, there are two ways in which
28808 the checking can be handled. For example, consider the condition:
28810 dnslists = a.b.c=127.0.0.1
28812 What happens if the DNS lookup for the incoming IP address yields both
28813 127.0.0.1 and 127.0.0.2 by means of two separate DNS records? Is the
28814 condition true because at least one given value was found, or is it false
28815 because at least one of the found values was not listed? And how does this
28816 affect negated conditions? Both possibilities are provided for with the help of
28817 additional separators &`==`& and &`=&&`&.
28820 If &`=`& or &`&&`& is used, the condition is true if any one of the looked up
28821 IP addresses matches one of the listed addresses. For the example above, the
28822 condition is true because 127.0.0.1 matches.
28824 If &`==`& or &`=&&`& is used, the condition is true only if every one of the
28825 looked up IP addresses matches one of the listed addresses. If the condition is
28828 dnslists = a.b.c==127.0.0.1
28830 and the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
28831 false because 127.0.0.2 is not listed. You would need to have:
28833 dnslists = a.b.c==127.0.0.1,127.0.0.2
28835 for the condition to be true.
28838 When &`!`& is used to negate IP address matching, it inverts the result, giving
28839 the precise opposite of the behaviour above. Thus:
28841 If &`!=`& or &`!&&`& is used, the condition is true if none of the looked up IP
28842 addresses matches one of the listed addresses. Consider:
28844 dnslists = a.b.c!&0.0.0.1
28846 If the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
28847 false because 127.0.0.1 matches.
28849 If &`!==`& or &`!=&&`& is used, the condition is true if there is at least one
28850 looked up IP address that does not match. Consider:
28852 dnslists = a.b.c!=&0.0.0.1
28854 If the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
28855 true, because 127.0.0.2 does not match. You would need to have:
28857 dnslists = a.b.c!=&0.0.0.1,0.0.0.2
28859 for the condition to be false.
28861 When the DNS lookup yields only a single IP address, there is no difference
28862 between &`=`& and &`==`& and between &`&&`& and &`=&&`&.
28867 .section "Detailed information from merged DNS lists" "SECTmordetinf"
28868 .cindex "DNS list" "information from merged"
28869 When the facility for restricting the matching IP values in a DNS list is used,
28870 the text from the TXT record that is set in &$dnslist_text$& may not reflect
28871 the true reason for rejection. This happens when lists are merged and the IP
28872 address in the A record is used to distinguish them; unfortunately there is
28873 only one TXT record. One way round this is not to use merged lists, but that
28874 can be inefficient because it requires multiple DNS lookups where one would do
28875 in the vast majority of cases when the host of interest is not on any of the
28878 A less inefficient way of solving this problem is available. If
28879 two domain names, comma-separated, are given, the second is used first to
28880 do an initial check, making use of any IP value restrictions that are set.
28881 If there is a match, the first domain is used, without any IP value
28882 restrictions, to get the TXT record. As a byproduct of this, there is also
28883 a check that the IP being tested is indeed on the first list. The first
28884 domain is the one that is put in &$dnslist_domain$&. For example:
28887 rejected because $sender_host_address is blacklisted \
28888 at $dnslist_domain\n$dnslist_text
28890 sbl.spamhaus.org,sbl-xbl.spamhaus.org=127.0.0.2 : \
28891 dul.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.10
28893 For the first blacklist item, this starts by doing a lookup in
28894 &'sbl-xbl.spamhaus.org'& and testing for a 127.0.0.2 return. If there is a
28895 match, it then looks in &'sbl.spamhaus.org'&, without checking the return
28896 value, and as long as something is found, it looks for the corresponding TXT
28897 record. If there is no match in &'sbl-xbl.spamhaus.org'&, nothing more is done.
28898 The second blacklist item is processed similarly.
28900 If you are interested in more than one merged list, the same list must be
28901 given several times, but because the results of the DNS lookups are cached,
28902 the DNS calls themselves are not repeated. For example:
28904 reject dnslists = \
28905 http.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.2 : \
28906 socks.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.3 : \
28907 misc.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.4 : \
28908 dul.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.10
28910 In this case there is one lookup in &'dnsbl.sorbs.net'&, and if none of the IP
28911 values matches (or if no record is found), this is the only lookup that is
28912 done. Only if there is a match is one of the more specific lists consulted.
28916 .section "DNS lists and IPv6" "SECTmorednslistslast"
28917 .cindex "IPv6" "DNS black lists"
28918 .cindex "DNS list" "IPv6 usage"
28919 If Exim is asked to do a dnslist lookup for an IPv6 address, it inverts it
28920 nibble by nibble. For example, if the calling host's IP address is
28921 3ffe:ffff:836f:0a00:000a:0800:200a:c031, Exim might look up
28923 1.3.0.c.a.0.0.2.0.0.8.0.a.0.0.0.0.0.a.0.f.6.3.8.
28924 f.f.f.f.e.f.f.3.blackholes.mail-abuse.org
28926 (split over two lines here to fit on the page). Unfortunately, some of the DNS
28927 lists contain wildcard records, intended for IPv4, that interact badly with
28928 IPv6. For example, the DNS entry
28930 *.3.some.list.example. A 127.0.0.1
28932 is probably intended to put the entire 3.0.0.0/8 IPv4 network on the list.
28933 Unfortunately, it also matches the entire 3::/4 IPv6 network.
28935 You can exclude IPv6 addresses from DNS lookups by making use of a suitable
28936 &%condition%& condition, as in this example:
28938 deny condition = ${if isip4{$sender_host_address}}
28939 dnslists = some.list.example
28942 If an explicit key is being used for a DNS lookup and it may be an IPv6
28943 address you should specify alternate list separators for both the outer
28944 (DNS list name) list and inner (lookup keys) list:
28946 dnslists = <; dnsbl.example.com/<|$acl_m_addrslist
28949 .section "Rate limiting incoming messages" "SECTratelimiting"
28950 .cindex "rate limiting" "client sending"
28951 .cindex "limiting client sending rates"
28952 .oindex "&%smtp_ratelimit_*%&"
28953 The &%ratelimit%& ACL condition can be used to measure and control the rate at
28954 which clients can send email. This is more powerful than the
28955 &%smtp_ratelimit_*%& options, because those options control the rate of
28956 commands in a single SMTP session only, whereas the &%ratelimit%& condition
28957 works across all connections (concurrent and sequential) from the same client
28958 host. The syntax of the &%ratelimit%& condition is:
28960 &`ratelimit =`& <&'m'&> &`/`& <&'p'&> &`/`& <&'options'&> &`/`& <&'key'&>
28962 If the average client sending rate is less than &'m'& messages per time
28963 period &'p'& then the condition is false; otherwise it is true.
28965 As a side-effect, the &%ratelimit%& condition sets the expansion variable
28966 &$sender_rate$& to the client's computed rate, &$sender_rate_limit$& to the
28967 configured value of &'m'&, and &$sender_rate_period$& to the configured value
28970 The parameter &'p'& is the smoothing time constant, in the form of an Exim
28971 time interval, for example, &`8h`& for eight hours. A larger time constant
28972 means that it takes Exim longer to forget a client's past behaviour. The
28973 parameter &'m'& is the maximum number of messages that a client is permitted to
28974 send in each time interval. It also specifies the number of messages permitted
28975 in a fast burst. By increasing both &'m'& and &'p'& but keeping &'m/p'&
28976 constant, you can allow a client to send more messages in a burst without
28977 changing its long-term sending rate limit. Conversely, if &'m'& and &'p'& are
28978 both small, messages must be sent at an even rate.
28980 There is a script in &_util/ratelimit.pl_& which extracts sending rates from
28981 log files, to assist with choosing appropriate settings for &'m'& and &'p'&
28982 when deploying the &%ratelimit%& ACL condition. The script prints usage
28983 instructions when it is run with no arguments.
28985 The key is used to look up the data for calculating the client's average
28986 sending rate. This data is stored in Exim's spool directory, alongside the
28987 retry and other hints databases. The default key is &$sender_host_address$&,
28988 which means Exim computes the sending rate of each client host IP address.
28989 By changing the key you can change how Exim identifies clients for the purpose
28990 of ratelimiting. For example, to limit the sending rate of each authenticated
28991 user, independent of the computer they are sending from, set the key to
28992 &$authenticated_id$&. You must ensure that the lookup key is meaningful; for
28993 example, &$authenticated_id$& is only meaningful if the client has
28994 authenticated (which you can check with the &%authenticated%& ACL condition).
28996 The lookup key does not have to identify clients: If you want to limit the
28997 rate at which a recipient receives messages, you can use the key
28998 &`$local_part@$domain`& with the &%per_rcpt%& option (see below) in a RCPT
29001 Each &%ratelimit%& condition can have up to four options. A &%per_*%& option
29002 specifies what Exim measures the rate of, for example messages or recipients
29003 or bytes. You can adjust the measurement using the &%unique=%& and/or
29004 &%count=%& options. You can also control when Exim updates the recorded rate
29005 using a &%strict%&, &%leaky%&, or &%readonly%& option. The options are
29006 separated by a slash, like the other parameters. They may appear in any order.
29008 Internally, Exim appends the smoothing constant &'p'& onto the lookup key with
29009 any options that alter the meaning of the stored data. The limit &'m'& is not
29010 stored, so you can alter the configured maximum rate and Exim will still
29011 remember clients' past behaviour. If you change the &%per_*%& mode or add or
29012 remove the &%unique=%& option, the lookup key changes so Exim will forget past
29013 behaviour. The lookup key is not affected by changes to the update mode and
29014 the &%count=%& option.
29017 .section "Ratelimit options for what is being measured" "ratoptmea"
29018 .cindex "rate limiting" "per_* options"
29019 The &%per_conn%& option limits the client's connection rate. It is not
29020 normally used in the &%acl_not_smtp%&, &%acl_not_smtp_mime%&, or
29021 &%acl_not_smtp_start%& ACLs.
29023 The &%per_mail%& option limits the client's rate of sending messages. This is
29024 the default if none of the &%per_*%& options is specified. It can be used in
29025 &%acl_smtp_mail%&, &%acl_smtp_rcpt%&, &%acl_smtp_predata%&, &%acl_smtp_mime%&,
29026 &%acl_smtp_data%&, or &%acl_not_smtp%&.
29028 The &%per_byte%& option limits the sender's email bandwidth. It can be used in
29029 the same ACLs as the &%per_mail%& option, though it is best to use this option
29030 in the &%acl_smtp_mime%&, &%acl_smtp_data%& or &%acl_not_smtp%& ACLs; if it is
29031 used in an earlier ACL, Exim relies on the SIZE parameter given by the client
29032 in its MAIL command, which may be inaccurate or completely missing. You can
29033 follow the limit &'m'& in the configuration with K, M, or G to specify limits
29034 in kilobytes, megabytes, or gigabytes, respectively.
29036 The &%per_rcpt%& option causes Exim to limit the rate at which recipients are
29037 accepted. It can be used in the &%acl_smtp_rcpt%&, &%acl_smtp_predata%&,
29038 &%acl_smtp_mime%&, &%acl_smtp_data%&, or &%acl_smtp_rcpt%& ACLs. In
29039 &%acl_smtp_rcpt%& the rate is updated one recipient at a time; in the other
29040 ACLs the rate is updated with the total recipient count in one go. Note that
29041 in either case the rate limiting engine will see a message with many
29042 recipients as a large high-speed burst.
29044 The &%per_addr%& option is like the &%per_rcpt%& option, except it counts the
29045 number of different recipients that the client has sent messages to in the
29046 last time period. That is, if the client repeatedly sends messages to the same
29047 recipient, its measured rate is not increased. This option can only be used in
29050 The &%per_cmd%& option causes Exim to recompute the rate every time the
29051 condition is processed. This can be used to limit the rate of any SMTP
29052 command. If it is used in multiple ACLs it can limit the aggregate rate of
29053 multiple different commands.
29055 The &%count=%& option can be used to alter how much Exim adds to the client's
29056 measured rate. For example, the &%per_byte%& option is equivalent to
29057 &`per_mail/count=$message_size`&. If there is no &%count=%& option, Exim
29058 increases the measured rate by one (except for the &%per_rcpt%& option in ACLs
29059 other than &%acl_smtp_rcpt%&). The count does not have to be an integer.
29061 The &%unique=%& option is described in section &<<ratoptuniq>>& below.
29064 .section "Ratelimit update modes" "ratoptupd"
29065 .cindex "rate limiting" "reading data without updating"
29066 You can specify one of three options with the &%ratelimit%& condition to
29067 control when its database is updated. This section describes the &%readonly%&
29068 mode, and the next section describes the &%strict%& and &%leaky%& modes.
29070 If the &%ratelimit%& condition is used in &%readonly%& mode, Exim looks up a
29071 previously-computed rate to check against the limit.
29073 For example, you can test the client's sending rate and deny it access (when
29074 it is too fast) in the connect ACL. If the client passes this check then it
29075 can go on to send a message, in which case its recorded rate will be updated
29076 in the MAIL ACL. Subsequent connections from the same client will check this
29080 deny ratelimit = 100 / 5m / readonly
29081 log_message = RATE CHECK: $sender_rate/$sender_rate_period \
29082 (max $sender_rate_limit)
29085 warn ratelimit = 100 / 5m / strict
29086 log_message = RATE UPDATE: $sender_rate/$sender_rate_period \
29087 (max $sender_rate_limit)
29090 If Exim encounters multiple &%ratelimit%& conditions with the same key when
29091 processing a message then it may increase the client's measured rate more than
29092 it should. For example, this will happen if you check the &%per_rcpt%& option
29093 in both &%acl_smtp_rcpt%& and &%acl_smtp_data%&. However it's OK to check the
29094 same &%ratelimit%& condition multiple times in the same ACL. You can avoid any
29095 multiple update problems by using the &%readonly%& option on later ratelimit
29098 The &%per_*%& options described above do not make sense in some ACLs. If you
29099 use a &%per_*%& option in an ACL where it is not normally permitted then the
29100 update mode defaults to &%readonly%& and you cannot specify the &%strict%& or
29101 &%leaky%& modes. In other ACLs the default update mode is &%leaky%& (see the
29102 next section) so you must specify the &%readonly%& option explicitly.
29105 .section "Ratelimit options for handling fast clients" "ratoptfast"
29106 .cindex "rate limiting" "strict and leaky modes"
29107 If a client's average rate is greater than the maximum, the rate limiting
29108 engine can react in two possible ways, depending on the presence of the
29109 &%strict%& or &%leaky%& update modes. This is independent of the other
29110 counter-measures (such as rejecting the message) that may be specified by the
29113 The &%leaky%& (default) option means that the client's recorded rate is not
29114 updated if it is above the limit. The effect of this is that Exim measures the
29115 client's average rate of successfully sent email, which cannot be greater than
29116 the maximum allowed. If the client is over the limit it may suffer some
29117 counter-measures (as specified in the ACL), but it will still be able to send
29118 email at the configured maximum rate, whatever the rate of its attempts. This
29119 is generally the better choice if you have clients that retry automatically.
29120 For example, it does not prevent a sender with an over-aggressive retry rate
29121 from getting any email through.
29123 The &%strict%& option means that the client's recorded rate is always
29124 updated. The effect of this is that Exim measures the client's average rate
29125 of attempts to send email, which can be much higher than the maximum it is
29126 actually allowed. If the client is over the limit it may be subjected to
29127 counter-measures by the ACL. It must slow down and allow sufficient time to
29128 pass that its computed rate falls below the maximum before it can send email
29129 again. The time (the number of smoothing periods) it must wait and not
29130 attempt to send mail can be calculated with this formula:
29132 ln(peakrate/maxrate)
29136 .section "Limiting the rate of different events" "ratoptuniq"
29137 .cindex "rate limiting" "counting unique events"
29138 The &%ratelimit%& &%unique=%& option controls a mechanism for counting the
29139 rate of different events. For example, the &%per_addr%& option uses this
29140 mechanism to count the number of different recipients that the client has
29141 sent messages to in the last time period; it is equivalent to
29142 &`per_rcpt/unique=$local_part@$domain`&. You could use this feature to
29143 measure the rate that a client uses different sender addresses with the
29144 options &`per_mail/unique=$sender_address`&.
29146 For each &%ratelimit%& key Exim stores the set of &%unique=%& values that it
29147 has seen for that key. The whole set is thrown away when it is older than the
29148 rate smoothing period &'p'&, so each different event is counted at most once
29149 per period. In the &%leaky%& update mode, an event that causes the client to
29150 go over the limit is not added to the set, in the same way that the client's
29151 recorded rate is not updated in the same situation.
29153 When you combine the &%unique=%& and &%readonly%& options, the specific
29154 &%unique=%& value is ignored, and Exim just retrieves the client's stored
29157 The &%unique=%& mechanism needs more space in the ratelimit database than the
29158 other &%ratelimit%& options in order to store the event set. The number of
29159 unique values is potentially as large as the rate limit, so the extra space
29160 required increases with larger limits.
29162 The uniqueification is not perfect: there is a small probability that Exim
29163 will think a new event has happened before. If the sender's rate is less than
29164 the limit, Exim should be more than 99.9% correct. However in &%strict%& mode
29165 the measured rate can go above the limit, in which case Exim may under-count
29166 events by a significant margin. Fortunately, if the rate is high enough (2.7
29167 times the limit) that the false positive rate goes above 9%, then Exim will
29168 throw away the over-full event set before the measured rate falls below the
29169 limit. Therefore the only harm should be that exceptionally high sending rates
29170 are logged incorrectly; any countermeasures you configure will be as effective
29174 .section "Using rate limiting" "useratlim"
29175 Exim's other ACL facilities are used to define what counter-measures are taken
29176 when the rate limit is exceeded. This might be anything from logging a warning
29177 (for example, while measuring existing sending rates in order to define
29178 policy), through time delays to slow down fast senders, up to rejecting the
29179 message. For example:
29181 # Log all senders' rates
29182 warn ratelimit = 0 / 1h / strict
29183 log_message = Sender rate $sender_rate / $sender_rate_period
29185 # Slow down fast senders; note the need to truncate $sender_rate
29186 # at the decimal point.
29187 warn ratelimit = 100 / 1h / per_rcpt / strict
29188 delay = ${eval: ${sg{$sender_rate}{[.].*}{}} - \
29189 $sender_rate_limit }s
29191 # Keep authenticated users under control
29192 deny authenticated = *
29193 ratelimit = 100 / 1d / strict / $authenticated_id
29195 # System-wide rate limit
29196 defer message = Sorry, too busy. Try again later.
29197 ratelimit = 10 / 1s / $primary_hostname
29199 # Restrict incoming rate from each host, with a default
29200 # set using a macro and special cases looked up in a table.
29201 defer message = Sender rate exceeds $sender_rate_limit \
29202 messages per $sender_rate_period
29203 ratelimit = ${lookup {$sender_host_address} \
29204 cdb {DB/ratelimits.cdb} \
29205 {$value} {RATELIMIT} }
29207 &*Warning*&: If you have a busy server with a lot of &%ratelimit%& tests,
29208 especially with the &%per_rcpt%& option, you may suffer from a performance
29209 bottleneck caused by locking on the ratelimit hints database. Apart from
29210 making your ACLs less complicated, you can reduce the problem by using a
29211 RAM disk for Exim's hints directory (usually &_/var/spool/exim/db/_&). However
29212 this means that Exim will lose its hints data after a reboot (including retry
29213 hints, the callout cache, and ratelimit data).
29217 .section "Address verification" "SECTaddressverification"
29218 .cindex "verifying address" "options for"
29219 .cindex "policy control" "address verification"
29220 Several of the &%verify%& conditions described in section
29221 &<<SECTaclconditions>>& cause addresses to be verified. Section
29222 &<<SECTsenaddver>>& discusses the reporting of sender verification failures.
29223 The verification conditions can be followed by options that modify the
29224 verification process. The options are separated from the keyword and from each
29225 other by slashes, and some of them contain parameters. For example:
29227 verify = sender/callout
29228 verify = recipient/defer_ok/callout=10s,defer_ok
29230 The first stage of address verification, which always happens, is to run the
29231 address through the routers, in &"verify mode"&. Routers can detect the
29232 difference between verification and routing for delivery, and their actions can
29233 be varied by a number of generic options such as &%verify%& and &%verify_only%&
29234 (see chapter &<<CHAProutergeneric>>&). If routing fails, verification fails.
29235 The available options are as follows:
29238 If the &%callout%& option is specified, successful routing to one or more
29239 remote hosts is followed by a &"callout"& to those hosts as an additional
29240 check. Callouts and their sub-options are discussed in the next section.
29242 If there is a defer error while doing verification routing, the ACL
29243 normally returns &"defer"&. However, if you include &%defer_ok%& in the
29244 options, the condition is forced to be true instead. Note that this is a main
29245 verification option as well as a suboption for callouts.
29247 The &%no_details%& option is covered in section &<<SECTsenaddver>>&, which
29248 discusses the reporting of sender address verification failures.
29250 The &%success_on_redirect%& option causes verification always to succeed
29251 immediately after a successful redirection. By default, if a redirection
29252 generates just one address, that address is also verified. See further
29253 discussion in section &<<SECTredirwhilveri>>&.
29256 .cindex "verifying address" "differentiating failures"
29257 .vindex "&$recipient_verify_failure$&"
29258 .vindex "&$sender_verify_failure$&"
29259 .vindex "&$acl_verify_message$&"
29260 After an address verification failure, &$acl_verify_message$& contains the
29261 error message that is associated with the failure. It can be preserved by
29264 warn !verify = sender
29265 set acl_m0 = $acl_verify_message
29267 If you are writing your own custom rejection message or log message when
29268 denying access, you can use this variable to include information about the
29269 verification failure.
29271 In addition, &$sender_verify_failure$& or &$recipient_verify_failure$& (as
29272 appropriate) contains one of the following words:
29275 &%qualify%&: The address was unqualified (no domain), and the message
29276 was neither local nor came from an exempted host.
29278 &%route%&: Routing failed.
29280 &%mail%&: Routing succeeded, and a callout was attempted; rejection
29281 occurred at or before the MAIL command (that is, on initial
29282 connection, HELO, or MAIL).
29284 &%recipient%&: The RCPT command in a callout was rejected.
29286 &%postmaster%&: The postmaster check in a callout was rejected.
29289 The main use of these variables is expected to be to distinguish between
29290 rejections of MAIL and rejections of RCPT in callouts.
29295 .section "Callout verification" "SECTcallver"
29296 .cindex "verifying address" "by callout"
29297 .cindex "callout" "verification"
29298 .cindex "SMTP" "callout verification"
29299 For non-local addresses, routing verifies the domain, but is unable to do any
29300 checking of the local part. There are situations where some means of verifying
29301 the local part is desirable. One way this can be done is to make an SMTP
29302 &'callback'& to a delivery host for the sender address or a &'callforward'& to
29303 a subsequent host for a recipient address, to see if the host accepts the
29304 address. We use the term &'callout'& to cover both cases. Note that for a
29305 sender address, the callback is not to the client host that is trying to
29306 deliver the message, but to one of the hosts that accepts incoming mail for the
29309 Exim does not do callouts by default. If you want them to happen, you must
29310 request them by setting appropriate options on the &%verify%& condition, as
29311 described below. This facility should be used with care, because it can add a
29312 lot of resource usage to the cost of verifying an address. However, Exim does
29313 cache the results of callouts, which helps to reduce the cost. Details of
29314 caching are in section &<<SECTcallvercache>>&.
29316 Recipient callouts are usually used only between hosts that are controlled by
29317 the same administration. For example, a corporate gateway host could use
29318 callouts to check for valid recipients on an internal mailserver. A successful
29319 callout does not guarantee that a real delivery to the address would succeed;
29320 on the other hand, a failing callout does guarantee that a delivery would fail.
29322 If the &%callout%& option is present on a condition that verifies an address, a
29323 second stage of verification occurs if the address is successfully routed to
29324 one or more remote hosts. The usual case is routing by a &(dnslookup)& or a
29325 &(manualroute)& router, where the router specifies the hosts. However, if a
29326 router that does not set up hosts routes to an &(smtp)& transport with a
29327 &%hosts%& setting, the transport's hosts are used. If an &(smtp)& transport has
29328 &%hosts_override%& set, its hosts are always used, whether or not the router
29329 supplies a host list.
29330 Callouts are only supported on &(smtp)& transports.
29332 The port that is used is taken from the transport, if it is specified and is a
29333 remote transport. (For routers that do verification only, no transport need be
29334 specified.) Otherwise, the default SMTP port is used. If a remote transport
29335 specifies an outgoing interface, this is used; otherwise the interface is not
29336 specified. Likewise, the text that is used for the HELO command is taken from
29337 the transport's &%helo_data%& option; if there is no transport, the value of
29338 &$smtp_active_hostname$& is used.
29340 For a sender callout check, Exim makes SMTP connections to the remote hosts, to
29341 test whether a bounce message could be delivered to the sender address. The
29342 following SMTP commands are sent:
29344 &`HELO `&<&'local host name'&>
29346 &`RCPT TO:`&<&'the address to be tested'&>
29349 LHLO is used instead of HELO if the transport's &%protocol%& option is
29352 The callout may use EHLO, AUTH and/or STARTTLS given appropriate option
29355 A recipient callout check is similar. By default, it also uses an empty address
29356 for the sender. This default is chosen because most hosts do not make use of
29357 the sender address when verifying a recipient. Using the same address means
29358 that a single cache entry can be used for each recipient. Some sites, however,
29359 do make use of the sender address when verifying. These are catered for by the
29360 &%use_sender%& and &%use_postmaster%& options, described in the next section.
29362 If the response to the RCPT command is a 2&'xx'& code, the verification
29363 succeeds. If it is 5&'xx'&, the verification fails. For any other condition,
29364 Exim tries the next host, if any. If there is a problem with all the remote
29365 hosts, the ACL yields &"defer"&, unless the &%defer_ok%& parameter of the
29366 &%callout%& option is given, in which case the condition is forced to succeed.
29368 .cindex "SMTP" "output flushing, disabling for callout"
29369 A callout may take a little time. For this reason, Exim normally flushes SMTP
29370 output before performing a callout in an ACL, to avoid unexpected timeouts in
29371 clients when the SMTP PIPELINING extension is in use. The flushing can be
29372 disabled by using a &%control%& modifier to set &%no_callout_flush%&.
29377 .section "Additional parameters for callouts" "CALLaddparcall"
29378 .cindex "callout" "additional parameters for"
29379 The &%callout%& option can be followed by an equals sign and a number of
29380 optional parameters, separated by commas. For example:
29382 verify = recipient/callout=10s,defer_ok
29384 The old syntax, which had &%callout_defer_ok%& and &%check_postmaster%& as
29385 separate verify options, is retained for backwards compatibility, but is now
29386 deprecated. The additional parameters for &%callout%& are as follows:
29390 .vitem <&'a&~time&~interval'&>
29391 .cindex "callout" "timeout, specifying"
29392 This specifies the timeout that applies for the callout attempt to each host.
29395 verify = sender/callout=5s
29397 The default is 30 seconds. The timeout is used for each response from the
29398 remote host. It is also used for the initial connection, unless overridden by
29399 the &%connect%& parameter.
29402 .vitem &*connect&~=&~*&<&'time&~interval'&>
29403 .cindex "callout" "connection timeout, specifying"
29404 This parameter makes it possible to set a different (usually smaller) timeout
29405 for making the SMTP connection. For example:
29407 verify = sender/callout=5s,connect=1s
29409 If not specified, this timeout defaults to the general timeout value.
29411 .vitem &*defer_ok*&
29412 .cindex "callout" "defer, action on"
29413 When this parameter is present, failure to contact any host, or any other kind
29414 of temporary error, is treated as success by the ACL. However, the cache is not
29415 updated in this circumstance.
29417 .vitem &*fullpostmaster*&
29418 .cindex "callout" "full postmaster check"
29419 This operates like the &%postmaster%& option (see below), but if the check for
29420 &'postmaster@domain'& fails, it tries just &'postmaster'&, without a domain, in
29421 accordance with the specification in RFC 2821. The RFC states that the
29422 unqualified address &'postmaster'& should be accepted.
29425 .vitem &*mailfrom&~=&~*&<&'email&~address'&>
29426 .cindex "callout" "sender when verifying header"
29427 When verifying addresses in header lines using the &%header_sender%&
29428 verification option, Exim behaves by default as if the addresses are envelope
29429 sender addresses from a message. Callout verification therefore tests to see
29430 whether a bounce message could be delivered, by using an empty address in the
29431 MAIL command. However, it is arguable that these addresses might never be used
29432 as envelope senders, and could therefore justifiably reject bounce messages
29433 (empty senders). The &%mailfrom%& callout parameter allows you to specify what
29434 address to use in the MAIL command. For example:
29436 require verify = header_sender/callout=mailfrom=abcd@x.y.z
29438 This parameter is available only for the &%header_sender%& verification option.
29441 .vitem &*maxwait&~=&~*&<&'time&~interval'&>
29442 .cindex "callout" "overall timeout, specifying"
29443 This parameter sets an overall timeout for performing a callout verification.
29446 verify = sender/callout=5s,maxwait=30s
29448 This timeout defaults to four times the callout timeout for individual SMTP
29449 commands. The overall timeout applies when there is more than one host that can
29450 be tried. The timeout is checked before trying the next host. This prevents
29451 very long delays if there are a large number of hosts and all are timing out
29452 (for example, when network connections are timing out).
29455 .vitem &*no_cache*&
29456 .cindex "callout" "cache, suppressing"
29457 .cindex "caching callout, suppressing"
29458 When this parameter is given, the callout cache is neither read nor updated.
29460 .vitem &*postmaster*&
29461 .cindex "callout" "postmaster; checking"
29462 When this parameter is set, a successful callout check is followed by a similar
29463 check for the local part &'postmaster'& at the same domain. If this address is
29464 rejected, the callout fails (but see &%fullpostmaster%& above). The result of
29465 the postmaster check is recorded in a cache record; if it is a failure, this is
29466 used to fail subsequent callouts for the domain without a connection being
29467 made, until the cache record expires.
29469 .vitem &*postmaster_mailfrom&~=&~*&<&'email&~address'&>
29470 The postmaster check uses an empty sender in the MAIL command by default.
29471 You can use this parameter to do a postmaster check using a different address.
29474 require verify = sender/callout=postmaster_mailfrom=abc@x.y.z
29476 If both &%postmaster%& and &%postmaster_mailfrom%& are present, the rightmost
29477 one overrides. The &%postmaster%& parameter is equivalent to this example:
29479 require verify = sender/callout=postmaster_mailfrom=
29481 &*Warning*&: The caching arrangements for postmaster checking do not take
29482 account of the sender address. It is assumed that either the empty address or
29483 a fixed non-empty address will be used. All that Exim remembers is that the
29484 postmaster check for the domain succeeded or failed.
29488 .cindex "callout" "&""random""& check"
29489 When this parameter is set, before doing the normal callout check, Exim does a
29490 check for a &"random"& local part at the same domain. The local part is not
29491 really random &-- it is defined by the expansion of the option
29492 &%callout_random_local_part%&, which defaults to
29494 $primary_hostname-$tod_epoch-testing
29496 The idea here is to try to determine whether the remote host accepts all local
29497 parts without checking. If it does, there is no point in doing callouts for
29498 specific local parts. If the &"random"& check succeeds, the result is saved in
29499 a cache record, and used to force the current and subsequent callout checks to
29500 succeed without a connection being made, until the cache record expires.
29502 .vitem &*use_postmaster*&
29503 .cindex "callout" "sender for recipient check"
29504 This parameter applies to recipient callouts only. For example:
29506 deny !verify = recipient/callout=use_postmaster
29508 .vindex "&$qualify_domain$&"
29509 It causes a non-empty postmaster address to be used in the MAIL command when
29510 performing the callout for the recipient, and also for a &"random"& check if
29511 that is configured. The local part of the address is &`postmaster`& and the
29512 domain is the contents of &$qualify_domain$&.
29514 .vitem &*use_sender*&
29515 This option applies to recipient callouts only. For example:
29517 require verify = recipient/callout=use_sender
29519 It causes the message's actual sender address to be used in the MAIL
29520 command when performing the callout, instead of an empty address. There is no
29521 need to use this option unless you know that the called hosts make use of the
29522 sender when checking recipients. If used indiscriminately, it reduces the
29523 usefulness of callout caching.
29526 If you use any of the parameters that set a non-empty sender for the MAIL
29527 command (&%mailfrom%&, &%postmaster_mailfrom%&, &%use_postmaster%&, or
29528 &%use_sender%&), you should think about possible loops. Recipient checking is
29529 usually done between two hosts that are under the same management, and the host
29530 that receives the callouts is not normally configured to do callouts itself.
29531 Therefore, it is normally safe to use &%use_postmaster%& or &%use_sender%& in
29532 these circumstances.
29534 However, if you use a non-empty sender address for a callout to an arbitrary
29535 host, there is the likelihood that the remote host will itself initiate a
29536 callout check back to your host. As it is checking what appears to be a message
29537 sender, it is likely to use an empty address in MAIL, thus avoiding a
29538 callout loop. However, to be on the safe side it would be best to set up your
29539 own ACLs so that they do not do sender verification checks when the recipient
29540 is the address you use for header sender or postmaster callout checking.
29542 Another issue to think about when using non-empty senders for callouts is
29543 caching. When you set &%mailfrom%& or &%use_sender%&, the cache record is keyed
29544 by the sender/recipient combination; thus, for any given recipient, many more
29545 actual callouts are performed than when an empty sender or postmaster is used.
29550 .section "Callout caching" "SECTcallvercache"
29551 .cindex "hints database" "callout cache"
29552 .cindex "callout" "cache, description of"
29553 .cindex "caching" "callout"
29554 Exim caches the results of callouts in order to reduce the amount of resources
29555 used, unless you specify the &%no_cache%& parameter with the &%callout%&
29556 option. A hints database called &"callout"& is used for the cache. Two
29557 different record types are used: one records the result of a callout check for
29558 a specific address, and the other records information that applies to the
29559 entire domain (for example, that it accepts the local part &'postmaster'&).
29561 When an original callout fails, a detailed SMTP error message is given about
29562 the failure. However, for subsequent failures use the cache data, this message
29565 The expiry times for negative and positive address cache records are
29566 independent, and can be set by the global options &%callout_negative_expire%&
29567 (default 2h) and &%callout_positive_expire%& (default 24h), respectively.
29569 If a host gives a negative response to an SMTP connection, or rejects any
29570 commands up to and including
29574 (but not including the MAIL command with a non-empty address),
29575 any callout attempt is bound to fail. Exim remembers such failures in a
29576 domain cache record, which it uses to fail callouts for the domain without
29577 making new connections, until the domain record times out. There are two
29578 separate expiry times for domain cache records:
29579 &%callout_domain_negative_expire%& (default 3h) and
29580 &%callout_domain_positive_expire%& (default 7d).
29582 Domain records expire when the negative expiry time is reached if callouts
29583 cannot be made for the domain, or if the postmaster check failed.
29584 Otherwise, they expire when the positive expiry time is reached. This
29585 ensures that, for example, a host that stops accepting &"random"& local parts
29586 will eventually be noticed.
29588 The callout caching mechanism is based on the domain of the address that is
29589 being tested. If the domain routes to several hosts, it is assumed that their
29590 behaviour will be the same.
29594 .section "Sender address verification reporting" "SECTsenaddver"
29595 .cindex "verifying" "suppressing error details"
29596 See section &<<SECTaddressverification>>& for a general discussion of
29597 verification. When sender verification fails in an ACL, the details of the
29598 failure are given as additional output lines before the 550 response to the
29599 relevant SMTP command (RCPT or DATA). For example, if sender callout is in use,
29602 MAIL FROM:<xyz@abc.example>
29604 RCPT TO:<pqr@def.example>
29605 550-Verification failed for <xyz@abc.example>
29606 550-Called: 192.168.34.43
29607 550-Sent: RCPT TO:<xyz@abc.example>
29608 550-Response: 550 Unknown local part xyz in <xyz@abc.example>
29609 550 Sender verification failed
29611 If more than one RCPT command fails in the same way, the details are given
29612 only for the first of them. However, some administrators do not want to send
29613 out this much information. You can suppress the details by adding
29614 &`/no_details`& to the ACL statement that requests sender verification. For
29617 verify = sender/no_details
29620 .section "Redirection while verifying" "SECTredirwhilveri"
29621 .cindex "verifying" "redirection while"
29622 .cindex "address redirection" "while verifying"
29623 A dilemma arises when a local address is redirected by aliasing or forwarding
29624 during verification: should the generated addresses themselves be verified,
29625 or should the successful expansion of the original address be enough to verify
29626 it? By default, Exim takes the following pragmatic approach:
29629 When an incoming address is redirected to just one child address, verification
29630 continues with the child address, and if that fails to verify, the original
29631 verification also fails.
29633 When an incoming address is redirected to more than one child address,
29634 verification does not continue. A success result is returned.
29637 This seems the most reasonable behaviour for the common use of aliasing as a
29638 way of redirecting different local parts to the same mailbox. It means, for
29639 example, that a pair of alias entries of the form
29642 aw123: :fail: Gone away, no forwarding address
29644 work as expected, with both local parts causing verification failure. When a
29645 redirection generates more than one address, the behaviour is more like a
29646 mailing list, where the existence of the alias itself is sufficient for
29647 verification to succeed.
29649 It is possible, however, to change the default behaviour so that all successful
29650 redirections count as successful verifications, however many new addresses are
29651 generated. This is specified by the &%success_on_redirect%& verification
29652 option. For example:
29654 require verify = recipient/success_on_redirect/callout=10s
29656 In this example, verification succeeds if a router generates a new address, and
29657 the callout does not occur, because no address was routed to a remote host.
29659 When verification is being tested via the &%-bv%& option, the treatment of
29660 redirections is as just described, unless the &%-v%& or any debugging option is
29661 also specified. In that case, full verification is done for every generated
29662 address and a report is output for each of them.
29666 .section "Client SMTP authorization (CSA)" "SECTverifyCSA"
29667 .cindex "CSA" "verifying"
29668 Client SMTP Authorization is a system that allows a site to advertise
29669 which machines are and are not permitted to send email. This is done by placing
29670 special SRV records in the DNS; these are looked up using the client's HELO
29671 domain. At the time of writing, CSA is still an Internet Draft. Client SMTP
29672 Authorization checks in Exim are performed by the ACL condition:
29676 This fails if the client is not authorized. If there is a DNS problem, or if no
29677 valid CSA SRV record is found, or if the client is authorized, the condition
29678 succeeds. These three cases can be distinguished using the expansion variable
29679 &$csa_status$&, which can take one of the values &"fail"&, &"defer"&,
29680 &"unknown"&, or &"ok"&. The condition does not itself defer because that would
29681 be likely to cause problems for legitimate email.
29683 The error messages produced by the CSA code include slightly more
29684 detail. If &$csa_status$& is &"defer"&, this may be because of problems
29685 looking up the CSA SRV record, or problems looking up the CSA target
29686 address record. There are four reasons for &$csa_status$& being &"fail"&:
29689 The client's host name is explicitly not authorized.
29691 The client's IP address does not match any of the CSA target IP addresses.
29693 The client's host name is authorized but it has no valid target IP addresses
29694 (for example, the target's addresses are IPv6 and the client is using IPv4).
29696 The client's host name has no CSA SRV record but a parent domain has asserted
29697 that all subdomains must be explicitly authorized.
29700 The &%csa%& verification condition can take an argument which is the domain to
29701 use for the DNS query. The default is:
29703 verify = csa/$sender_helo_name
29705 This implementation includes an extension to CSA. If the query domain
29706 is an address literal such as [192.0.2.95], or if it is a bare IP
29707 address, Exim searches for CSA SRV records in the reverse DNS as if
29708 the HELO domain was (for example) &'95.2.0.192.in-addr.arpa'&. Therefore it is
29711 verify = csa/$sender_host_address
29713 In fact, this is the check that Exim performs if the client does not say HELO.
29714 This extension can be turned off by setting the main configuration option
29715 &%dns_csa_use_reverse%& to be false.
29717 If a CSA SRV record is not found for the domain itself, a search
29718 is performed through its parent domains for a record which might be
29719 making assertions about subdomains. The maximum depth of this search is limited
29720 using the main configuration option &%dns_csa_search_limit%&, which is 5 by
29721 default. Exim does not look for CSA SRV records in a top level domain, so the
29722 default settings handle HELO domains as long as seven
29723 (&'hostname.five.four.three.two.one.com'&). This encompasses the vast majority
29724 of legitimate HELO domains.
29726 The &'dnsdb'& lookup also has support for CSA. Although &'dnsdb'& also supports
29727 direct SRV lookups, this is not sufficient because of the extra parent domain
29728 search behaviour of CSA, and (as with PTR lookups) &'dnsdb'& also turns IP
29729 addresses into lookups in the reverse DNS space. The result of a successful
29732 ${lookup dnsdb {csa=$sender_helo_name}}
29734 has two space-separated fields: an authorization code and a target host name.
29735 The authorization code can be &"Y"& for yes, &"N"& for no, &"X"& for explicit
29736 authorization required but absent, or &"?"& for unknown.
29741 .section "Bounce address tag validation" "SECTverifyPRVS"
29742 .cindex "BATV, verifying"
29743 Bounce address tag validation (BATV) is a scheme whereby the envelope senders
29744 of outgoing messages have a cryptographic, timestamped &"tag"& added to them.
29745 Genuine incoming bounce messages should therefore always be addressed to
29746 recipients that have a valid tag. This scheme is a way of detecting unwanted
29747 bounce messages caused by sender address forgeries (often called &"collateral
29748 spam"&), because the recipients of such messages do not include valid tags.
29750 There are two expansion items to help with the implementation of the BATV
29751 &"prvs"& (private signature) scheme in an Exim configuration. This scheme signs
29752 the original envelope sender address by using a simple key to add a hash of the
29753 address and some time-based randomizing information. The &%prvs%& expansion
29754 item creates a signed address, and the &%prvscheck%& expansion item checks one.
29755 The syntax of these expansion items is described in section
29756 &<<SECTexpansionitems>>&.
29758 As an example, suppose the secret per-address keys are stored in an MySQL
29759 database. A query to look up the key for an address could be defined as a macro
29762 PRVSCHECK_SQL = ${lookup mysql{SELECT secret FROM batv_prvs \
29763 WHERE sender='${quote_mysql:$prvscheck_address}'\
29766 Suppose also that the senders who make use of BATV are defined by an address
29767 list called &%batv_senders%&. Then, in the ACL for RCPT commands, you could
29770 # Bounces: drop unsigned addresses for BATV senders
29771 deny message = This address does not send an unsigned reverse path
29773 recipients = +batv_senders
29775 # Bounces: In case of prvs-signed address, check signature.
29776 deny message = Invalid reverse path signature.
29778 condition = ${prvscheck {$local_part@$domain}\
29779 {PRVSCHECK_SQL}{1}}
29780 !condition = $prvscheck_result
29782 The first statement rejects recipients for bounce messages that are addressed
29783 to plain BATV sender addresses, because it is known that BATV senders do not
29784 send out messages with plain sender addresses. The second statement rejects
29785 recipients that are prvs-signed, but with invalid signatures (either because
29786 the key is wrong, or the signature has timed out).
29788 A non-prvs-signed address is not rejected by the second statement, because the
29789 &%prvscheck%& expansion yields an empty string if its first argument is not a
29790 prvs-signed address, thus causing the &%condition%& condition to be false. If
29791 the first argument is a syntactically valid prvs-signed address, the yield is
29792 the third string (in this case &"1"&), whether or not the cryptographic and
29793 timeout checks succeed. The &$prvscheck_result$& variable contains the result
29794 of the checks (empty for failure, &"1"& for success).
29796 There is one more issue you must consider when implementing prvs-signing:
29797 you have to ensure that the routers accept prvs-signed addresses and
29798 deliver them correctly. The easiest way to handle this is to use a &(redirect)&
29799 router to remove the signature with a configuration along these lines:
29803 data = ${prvscheck {$local_part@$domain}{PRVSCHECK_SQL}}
29805 This works because, if the third argument of &%prvscheck%& is empty, the result
29806 of the expansion of a prvs-signed address is the decoded value of the original
29807 address. This router should probably be the first of your routers that handles
29810 To create BATV-signed addresses in the first place, a transport of this form
29813 external_smtp_batv:
29815 return_path = ${prvs {$return_path} \
29816 {${lookup mysql{SELECT \
29817 secret FROM batv_prvs WHERE \
29818 sender='${quote_mysql:$sender_address}'} \
29821 If no key can be found for the existing return path, no signing takes place.
29825 .section "Using an ACL to control relaying" "SECTrelaycontrol"
29826 .cindex "&ACL;" "relay control"
29827 .cindex "relaying" "control by ACL"
29828 .cindex "policy control" "relay control"
29829 An MTA is said to &'relay'& a message if it receives it from some host and
29830 delivers it directly to another host as a result of a remote address contained
29831 within it. Redirecting a local address via an alias or forward file and then
29832 passing the message on to another host is not relaying,
29833 .cindex "&""percent hack""&"
29834 but a redirection as a result of the &"percent hack"& is.
29836 Two kinds of relaying exist, which are termed &"incoming"& and &"outgoing"&.
29837 A host which is acting as a gateway or an MX backup is concerned with incoming
29838 relaying from arbitrary hosts to a specific set of domains. On the other hand,
29839 a host which is acting as a smart host for a number of clients is concerned
29840 with outgoing relaying from those clients to the Internet at large. Often the
29841 same host is fulfilling both functions,
29843 . as illustrated in the diagram below,
29845 but in principle these two kinds of relaying are entirely independent. What is
29846 not wanted is the transmission of mail from arbitrary remote hosts through your
29847 system to arbitrary domains.
29850 You can implement relay control by means of suitable statements in the ACL that
29851 runs for each RCPT command. For convenience, it is often easiest to use
29852 Exim's named list facility to define the domains and hosts involved. For
29853 example, suppose you want to do the following:
29856 Deliver a number of domains to mailboxes on the local host (or process them
29857 locally in some other way). Let's say these are &'my.dom1.example'& and
29858 &'my.dom2.example'&.
29860 Relay mail for a number of other domains for which you are the secondary MX.
29861 These might be &'friend1.example'& and &'friend2.example'&.
29863 Relay mail from the hosts on your local LAN, to whatever domains are involved.
29864 Suppose your LAN is 192.168.45.0/24.
29868 In the main part of the configuration, you put the following definitions:
29870 domainlist local_domains = my.dom1.example : my.dom2.example
29871 domainlist relay_to_domains = friend1.example : friend2.example
29872 hostlist relay_from_hosts = 192.168.45.0/24
29874 Now you can use these definitions in the ACL that is run for every RCPT
29878 accept domains = +local_domains : +relay_to_domains
29879 accept hosts = +relay_from_hosts
29881 The first statement accepts any RCPT command that contains an address in
29882 the local or relay domains. For any other domain, control passes to the second
29883 statement, which accepts the command only if it comes from one of the relay
29884 hosts. In practice, you will probably want to make your ACL more sophisticated
29885 than this, for example, by including sender and recipient verification. The
29886 default configuration includes a more comprehensive example, which is described
29887 in chapter &<<CHAPdefconfil>>&.
29891 .section "Checking a relay configuration" "SECTcheralcon"
29892 .cindex "relaying" "checking control of"
29893 You can check the relay characteristics of your configuration in the same way
29894 that you can test any ACL behaviour for an incoming SMTP connection, by using
29895 the &%-bh%& option to run a fake SMTP session with which you interact.
29897 For specifically testing for unwanted relaying, the host
29898 &'relay-test.mail-abuse.org'& provides a useful service. If you telnet to this
29899 host from the host on which Exim is running, using the normal telnet port, you
29900 will see a normal telnet connection message and then quite a long delay. Be
29901 patient. The remote host is making an SMTP connection back to your host, and
29902 trying a number of common probes to test for open relay vulnerability. The
29903 results of the tests will eventually appear on your terminal.
29908 . ////////////////////////////////////////////////////////////////////////////
29909 . ////////////////////////////////////////////////////////////////////////////
29911 .chapter "Content scanning at ACL time" "CHAPexiscan"
29912 .scindex IIDcosca "content scanning" "at ACL time"
29913 The extension of Exim to include content scanning at ACL time, formerly known
29914 as &"exiscan"&, was originally implemented as a patch by Tom Kistner. The code
29915 was integrated into the main source for Exim release 4.50, and Tom continues to
29916 maintain it. Most of the wording of this chapter is taken from Tom's
29919 It is also possible to scan the content of messages at other times. The
29920 &[local_scan()]& function (see chapter &<<CHAPlocalscan>>&) allows for content
29921 scanning after all the ACLs have run. A transport filter can be used to scan
29922 messages at delivery time (see the &%transport_filter%& option, described in
29923 chapter &<<CHAPtransportgeneric>>&).
29925 If you want to include the ACL-time content-scanning features when you compile
29926 Exim, you need to arrange for WITH_CONTENT_SCAN to be defined in your
29927 &_Local/Makefile_&. When you do that, the Exim binary is built with:
29930 Two additional ACLs (&%acl_smtp_mime%& and &%acl_not_smtp_mime%&) that are run
29931 for all MIME parts for SMTP and non-SMTP messages, respectively.
29933 Additional ACL conditions and modifiers: &%decode%&, &%malware%&,
29934 &%mime_regex%&, &%regex%&, and &%spam%&. These can be used in the ACL that is
29935 run at the end of message reception (the &%acl_smtp_data%& ACL).
29937 An additional control feature (&"no_mbox_unspool"&) that saves spooled copies
29938 of messages, or parts of messages, for debugging purposes.
29940 Additional expansion variables that are set in the new ACL and by the new
29943 Two new main configuration options: &%av_scanner%& and &%spamd_address%&.
29946 There is another content-scanning configuration option for &_Local/Makefile_&,
29947 called WITH_OLD_DEMIME. If this is set, the old, deprecated &%demime%& ACL
29948 condition is compiled, in addition to all the other content-scanning features.
29950 Content-scanning is continually evolving, and new features are still being
29951 added. While such features are still unstable and liable to incompatible
29952 changes, they are made available in Exim by setting options whose names begin
29953 EXPERIMENTAL_ in &_Local/Makefile_&. Such features are not documented in
29954 this manual. You can find out about them by reading the file called
29955 &_doc/experimental.txt_&.
29957 All the content-scanning facilities work on a MBOX copy of the message that is
29958 temporarily created in a file called:
29960 <&'spool_directory'&>&`/scan/`&<&'message_id'&>/<&'message_id'&>&`.eml`&
29962 The &_.eml_& extension is a friendly hint to virus scanners that they can
29963 expect an MBOX-like structure inside that file. The file is created when the
29964 first content scanning facility is called. Subsequent calls to content
29965 scanning conditions open the same file again. The directory is recursively
29966 removed when the &%acl_smtp_data%& ACL has finished running, unless
29968 control = no_mbox_unspool
29970 has been encountered. When the MIME ACL decodes files, they are put into the
29971 same directory by default.
29975 .section "Scanning for viruses" "SECTscanvirus"
29976 .cindex "virus scanning"
29977 .cindex "content scanning" "for viruses"
29978 .cindex "content scanning" "the &%malware%& condition"
29979 The &%malware%& ACL condition lets you connect virus scanner software to Exim.
29980 It supports a &"generic"& interface to scanners called via the shell, and
29981 specialized interfaces for &"daemon"& type virus scanners, which are resident
29982 in memory and thus are much faster.
29985 .oindex "&%av_scanner%&"
29986 You can set the &%av_scanner%& option in first part of the Exim configuration
29987 file to specify which scanner to use, together with any additional options that
29988 are needed. The basic syntax is as follows:
29990 &`av_scanner = <`&&'scanner-type'&&`>:<`&&'option1'&&`>:<`&&'option2'&&`>:[...]`&
29992 If you do not set &%av_scanner%&, it defaults to
29994 av_scanner = sophie:/var/run/sophie
29996 If the value of &%av_scanner%& starts with a dollar character, it is expanded
29998 The usual list-parsing of the content (see &<<SECTlistconstruct>>&) applies.
29999 The following scanner types are supported in this release:
30002 .vitem &%aveserver%&
30003 .cindex "virus scanners" "Kaspersky"
30004 This is the scanner daemon of Kaspersky Version 5. You can get a trial version
30005 at &url(http://www.kaspersky.com). This scanner type takes one option,
30006 which is the path to the daemon's UNIX socket. The default is shown in this
30009 av_scanner = aveserver:/var/run/aveserver
30014 .cindex "virus scanners" "clamd"
30015 This daemon-type scanner is GPL and free. You can get it at
30016 &url(http://www.clamav.net/). Some older versions of clamd do not seem to
30017 unpack MIME containers, so it used to be recommended to unpack MIME attachments
30018 in the MIME ACL. This no longer believed to be necessary. One option is
30019 required: either the path and name of a UNIX socket file, or a hostname or IP
30020 number, and a port, separated by space, as in the second of these examples:
30022 av_scanner = clamd:/opt/clamd/socket
30023 av_scanner = clamd:192.0.2.3 1234
30024 av_scanner = clamd:192.0.2.3 1234:local
30025 av_scanner = clamd:192.0.2.3 1234 : 192.0.2.4 1234
30027 If the value of av_scanner points to a UNIX socket file or contains the local
30028 keyword, then the ClamAV interface will pass a filename containing the data
30029 to be scanned, which will should normally result in less I/O happening and be
30030 more efficient. Normally in the TCP case, the data is streamed to ClamAV as
30031 Exim does not assume that there is a common filesystem with the remote host.
30032 There is an option WITH_OLD_CLAMAV_STREAM in &_src/EDITME_& available, should
30033 you be running a version of ClamAV prior to 0.95.
30035 The final example shows that multiple TCP targets can be specified. Exim will
30036 randomly use one for each incoming email (i.e. it load balances them). Note
30037 that only TCP targets may be used if specifying a list of scanners; a UNIX
30038 socket cannot be mixed in with TCP targets. If one of the servers becomes
30039 unavailable, Exim will try the remaining one(s) until it finds one that works.
30040 When a clamd server becomes unreachable, Exim will log a message. Exim does
30041 not keep track of scanner state between multiple messages, and the scanner
30042 selection is random, so the message will get logged in the mainlog for each
30043 email that the down scanner gets chosen first (message wrapped to be readable):
30045 2013-10-09 14:30:39 1VTumd-0000Y8-BQ malware acl condition:
30046 clamd: connection to localhost, port 3310 failed
30047 (Connection refused)
30050 If the option is unset, the default is &_/tmp/clamd_&. Thanks to David Saez for
30051 contributing the code for this scanner.
30054 .cindex "virus scanners" "command line interface"
30055 This is the keyword for the generic command line scanner interface. It can be
30056 used to attach virus scanners that are invoked from the shell. This scanner
30057 type takes 3 mandatory options:
30060 The full path and name of the scanner binary, with all command line options,
30061 and a placeholder (&`%s`&) for the directory to scan.
30064 A regular expression to match against the STDOUT and STDERR output of the
30065 virus scanner. If the expression matches, a virus was found. You must make
30066 absolutely sure that this expression matches on &"virus found"&. This is called
30067 the &"trigger"& expression.
30070 Another regular expression, containing exactly one pair of parentheses, to
30071 match the name of the virus found in the scanners output. This is called the
30072 &"name"& expression.
30075 For example, Sophos Sweep reports a virus on a line like this:
30077 Virus 'W32/Magistr-B' found in file ./those.bat
30079 For the trigger expression, we can match the phrase &"found in file"&. For the
30080 name expression, we want to extract the W32/Magistr-B string, so we can match
30081 for the single quotes left and right of it. Altogether, this makes the
30082 configuration setting:
30084 av_scanner = cmdline:\
30085 /path/to/sweep -ss -all -rec -archive %s:\
30086 found in file:'(.+)'
30089 .cindex "virus scanners" "DrWeb"
30090 The DrWeb daemon scanner (&url(http://www.sald.com/)) interface takes one
30091 argument, either a full path to a UNIX socket, or an IP address and port
30092 separated by white space, as in these examples:
30094 av_scanner = drweb:/var/run/drwebd.sock
30095 av_scanner = drweb:192.168.2.20 31337
30097 If you omit the argument, the default path &_/usr/local/drweb/run/drwebd.sock_&
30098 is used. Thanks to Alex Miller for contributing the code for this scanner.
30101 .cindex "virus scanners" "F-Secure"
30102 The F-Secure daemon scanner (&url(http://www.f-secure.com)) takes one
30103 argument which is the path to a UNIX socket. For example:
30105 av_scanner = fsecure:/path/to/.fsav
30107 If no argument is given, the default is &_/var/run/.fsav_&. Thanks to Johan
30108 Thelmen for contributing the code for this scanner.
30110 .vitem &%kavdaemon%&
30111 .cindex "virus scanners" "Kaspersky"
30112 This is the scanner daemon of Kaspersky Version 4. This version of the
30113 Kaspersky scanner is outdated. Please upgrade (see &%aveserver%& above). This
30114 scanner type takes one option, which is the path to the daemon's UNIX socket.
30117 av_scanner = kavdaemon:/opt/AVP/AvpCtl
30119 The default path is &_/var/run/AvpCtl_&.
30122 .cindex "virus scanners" "mksd"
30123 This is a daemon type scanner that is aimed mainly at Polish users, though some
30124 parts of documentation are now available in English. You can get it at
30125 &url(http://linux.mks.com.pl/). The only option for this scanner type is
30126 the maximum number of processes used simultaneously to scan the attachments,
30127 provided that the demime facility is employed and also provided that mksd has
30128 been run with at least the same number of child processes. For example:
30130 av_scanner = mksd:2
30132 You can safely omit this option (the default value is 1).
30135 .cindex "virus scanners" "simple socket-connected"
30136 This is a general-purpose way of talking to simple scanner daemons
30137 running on the local machine.
30138 There are four options:
30139 an address (which may be an IP addres and port, or the path of a Unix socket),
30140 a commandline to send (may include a single %s which will be replaced with
30141 the path to the mail file to be scanned),
30142 an RE to trigger on from the returned data,
30143 an RE to extract malware_name from the returned data.
30146 av_scanner = sock:127.0.0.1 6001:%s:(SPAM|VIRUS):(.*)\$
30148 Default for the socket specifier is &_/tmp/malware.sock_&.
30149 Default for the commandline is &_%s\n_&.
30150 Both regular-expressions are required.
30153 .cindex "virus scanners" "Sophos and Sophie"
30154 Sophie is a daemon that uses Sophos' &%libsavi%& library to scan for viruses.
30155 You can get Sophie at &url(http://www.clanfield.info/sophie/). The only option
30156 for this scanner type is the path to the UNIX socket that Sophie uses for
30157 client communication. For example:
30159 av_scanner = sophie:/tmp/sophie
30161 The default path is &_/var/run/sophie_&, so if you are using this, you can omit
30165 When &%av_scanner%& is correctly set, you can use the &%malware%& condition in
30166 the DATA ACL. &*Note*&: You cannot use the &%malware%& condition in the MIME
30169 The &%av_scanner%& option is expanded each time &%malware%& is called. This
30170 makes it possible to use different scanners. See further below for an example.
30171 The &%malware%& condition caches its results, so when you use it multiple times
30172 for the same message, the actual scanning process is only carried out once.
30173 However, using expandable items in &%av_scanner%& disables this caching, in
30174 which case each use of the &%malware%& condition causes a new scan of the
30177 The &%malware%& condition takes a right-hand argument that is expanded before
30178 use. It can then be one of
30181 &"true"&, &"*"&, or &"1"&, in which case the message is scanned for viruses.
30182 The condition succeeds if a virus was found, and fail otherwise. This is the
30185 &"false"& or &"0"& or an empty string, in which case no scanning is done and
30186 the condition fails immediately.
30188 A regular expression, in which case the message is scanned for viruses. The
30189 condition succeeds if a virus is found and its name matches the regular
30190 expression. This allows you to take special actions on certain types of virus.
30193 You can append &`/defer_ok`& to the &%malware%& condition to accept messages
30194 even if there is a problem with the virus scanner. Otherwise, such a problem
30195 causes the ACL to defer.
30197 .vindex "&$malware_name$&"
30198 When a virus is found, the condition sets up an expansion variable called
30199 &$malware_name$& that contains the name of the virus. You can use it in a
30200 &%message%& modifier that specifies the error returned to the sender, and/or in
30203 If your virus scanner cannot unpack MIME and TNEF containers itself, you should
30204 use the &%demime%& condition (see section &<<SECTdemimecond>>&) before the
30205 &%malware%& condition.
30207 Beware the interaction of Exim's &%message_size_limit%& with any size limits
30208 imposed by your anti-virus scanner.
30210 Here is a very simple scanning example:
30212 deny message = This message contains malware ($malware_name)
30216 The next example accepts messages when there is a problem with the scanner:
30218 deny message = This message contains malware ($malware_name)
30220 malware = */defer_ok
30222 The next example shows how to use an ACL variable to scan with both sophie and
30223 aveserver. It assumes you have set:
30225 av_scanner = $acl_m0
30227 in the main Exim configuration.
30229 deny message = This message contains malware ($malware_name)
30230 set acl_m0 = sophie
30233 deny message = This message contains malware ($malware_name)
30234 set acl_m0 = aveserver
30239 .section "Scanning with SpamAssassin" "SECTscanspamass"
30240 .cindex "content scanning" "for spam"
30241 .cindex "spam scanning"
30242 .cindex "SpamAssassin"
30243 The &%spam%& ACL condition calls SpamAssassin's &%spamd%& daemon to get a spam
30244 score and a report for the message. You can get SpamAssassin at
30245 &url(http://www.spamassassin.org), or, if you have a working Perl
30246 installation, you can use CPAN by running:
30248 perl -MCPAN -e 'install Mail::SpamAssassin'
30250 SpamAssassin has its own set of configuration files. Please review its
30251 documentation to see how you can tweak it. The default installation should work
30254 .oindex "&%spamd_address%&"
30255 After having installed and configured SpamAssassin, start the &%spamd%& daemon.
30256 By default, it listens on 127.0.0.1, TCP port 783. If you use another host or
30257 port for &%spamd%&, you must set the &%spamd_address%& option in the global
30258 part of the Exim configuration as follows (example):
30260 spamd_address = 192.168.99.45 387
30262 You do not need to set this option if you use the default. As of version 2.60,
30263 &%spamd%& also supports communication over UNIX sockets. If you want to use
30264 these, supply &%spamd_address%& with an absolute file name instead of a
30267 spamd_address = /var/run/spamd_socket
30269 You can have multiple &%spamd%& servers to improve scalability. These can
30270 reside on other hardware reachable over the network. To specify multiple
30271 &%spamd%& servers, put multiple address/port pairs in the &%spamd_address%&
30272 option, separated with colons:
30274 spamd_address = 192.168.2.10 783 : \
30275 192.168.2.11 783 : \
30278 Up to 32 &%spamd%& servers are supported. The servers are queried in a random
30279 fashion. When a server fails to respond to the connection attempt, all other
30280 servers are tried until one succeeds. If no server responds, the &%spam%&
30283 &*Warning*&: It is not possible to use the UNIX socket connection method with
30284 multiple &%spamd%& servers.
30286 The &%spamd_address%& variable is expanded before use if it starts with
30287 a dollar sign. In this case, the expansion may return a string that is
30288 used as the list so that multiple spamd servers can be the result of an
30291 .section "Calling SpamAssassin from an Exim ACL" "SECID206"
30292 Here is a simple example of the use of the &%spam%& condition in a DATA ACL:
30294 deny message = This message was classified as SPAM
30297 The right-hand side of the &%spam%& condition specifies a name. This is
30298 relevant if you have set up multiple SpamAssassin profiles. If you do not want
30299 to scan using a specific profile, but rather use the SpamAssassin system-wide
30300 default profile, you can scan for an unknown name, or simply use &"nobody"&.
30301 However, you must put something on the right-hand side.
30303 The name allows you to use per-domain or per-user antispam profiles in
30304 principle, but this is not straightforward in practice, because a message may
30305 have multiple recipients, not necessarily all in the same domain. Because the
30306 &%spam%& condition has to be called from a DATA ACL in order to be able to
30307 read the contents of the message, the variables &$local_part$& and &$domain$&
30310 The right-hand side of the &%spam%& condition is expanded before being used, so
30311 you can put lookups or conditions there. When the right-hand side evaluates to
30312 &"0"& or &"false"&, no scanning is done and the condition fails immediately.
30315 Scanning with SpamAssassin uses a lot of resources. If you scan every message,
30316 large ones may cause significant performance degradation. As most spam messages
30317 are quite small, it is recommended that you do not scan the big ones. For
30320 deny message = This message was classified as SPAM
30321 condition = ${if < {$message_size}{10K}}
30325 The &%spam%& condition returns true if the threshold specified in the user's
30326 SpamAssassin profile has been matched or exceeded. If you want to use the
30327 &%spam%& condition for its side effects (see the variables below), you can make
30328 it always return &"true"& by appending &`:true`& to the username.
30330 .cindex "spam scanning" "returned variables"
30331 When the &%spam%& condition is run, it sets up a number of expansion
30332 variables. These variables are saved with the received message, thus they are
30333 available for use at delivery time.
30336 .vitem &$spam_score$&
30337 The spam score of the message, for example &"3.4"& or &"30.5"&. This is useful
30338 for inclusion in log or reject messages.
30340 .vitem &$spam_score_int$&
30341 The spam score of the message, multiplied by ten, as an integer value. For
30342 example &"34"& or &"305"&. It may appear to disagree with &$spam_score$&
30343 because &$spam_score$& is rounded and &$spam_score_int$& is truncated.
30344 The integer value is useful for numeric comparisons in conditions.
30346 .vitem &$spam_bar$&
30347 A string consisting of a number of &"+"& or &"-"& characters, representing the
30348 integer part of the spam score value. A spam score of 4.4 would have a
30349 &$spam_bar$& value of &"++++"&. This is useful for inclusion in warning
30350 headers, since MUAs can match on such strings.
30352 .vitem &$spam_report$&
30353 A multiline text table, containing the full SpamAssassin report for the
30354 message. Useful for inclusion in headers or reject messages.
30357 The &%spam%& condition caches its results unless expansion in
30358 spamd_address was used. If you call it again with the same user name, it
30359 does not scan again, but rather returns the same values as before.
30361 The &%spam%& condition returns DEFER if there is any error while running
30362 the message through SpamAssassin or if the expansion of spamd_address
30363 failed. If you want to treat DEFER as FAIL (to pass on to the next ACL
30364 statement block), append &`/defer_ok`& to the right-hand side of the
30365 spam condition, like this:
30367 deny message = This message was classified as SPAM
30368 spam = joe/defer_ok
30370 This causes messages to be accepted even if there is a problem with &%spamd%&.
30372 Here is a longer, commented example of the use of the &%spam%&
30375 # put headers in all messages (no matter if spam or not)
30376 warn spam = nobody:true
30377 add_header = X-Spam-Score: $spam_score ($spam_bar)
30378 add_header = X-Spam-Report: $spam_report
30380 # add second subject line with *SPAM* marker when message
30381 # is over threshold
30383 add_header = Subject: *SPAM* $h_Subject:
30385 # reject spam at high scores (> 12)
30386 deny message = This message scored $spam_score spam points.
30388 condition = ${if >{$spam_score_int}{120}{1}{0}}
30393 .section "Scanning MIME parts" "SECTscanmimepart"
30394 .cindex "content scanning" "MIME parts"
30395 .cindex "MIME content scanning"
30396 .oindex "&%acl_smtp_mime%&"
30397 .oindex "&%acl_not_smtp_mime%&"
30398 The &%acl_smtp_mime%& global option specifies an ACL that is called once for
30399 each MIME part of an SMTP message, including multipart types, in the sequence
30400 of their position in the message. Similarly, the &%acl_not_smtp_mime%& option
30401 specifies an ACL that is used for the MIME parts of non-SMTP messages. These
30402 options may both refer to the same ACL if you want the same processing in both
30405 These ACLs are called (possibly many times) just before the &%acl_smtp_data%&
30406 ACL in the case of an SMTP message, or just before the &%acl_not_smtp%& ACL in
30407 the case of a non-SMTP message. However, a MIME ACL is called only if the
30408 message contains a &'Content-Type:'& header line. When a call to a MIME
30409 ACL does not yield &"accept"&, ACL processing is aborted and the appropriate
30410 result code is sent to the client. In the case of an SMTP message, the
30411 &%acl_smtp_data%& ACL is not called when this happens.
30413 You cannot use the &%malware%& or &%spam%& conditions in a MIME ACL; these can
30414 only be used in the DATA or non-SMTP ACLs. However, you can use the &%regex%&
30415 condition to match against the raw MIME part. You can also use the
30416 &%mime_regex%& condition to match against the decoded MIME part (see section
30417 &<<SECTscanregex>>&).
30419 At the start of a MIME ACL, a number of variables are set from the header
30420 information for the relevant MIME part. These are described below. The contents
30421 of the MIME part are not by default decoded into a disk file except for MIME
30422 parts whose content-type is &"message/rfc822"&. If you want to decode a MIME
30423 part into a disk file, you can use the &%decode%& condition. The general
30426 &`decode = [/`&<&'path'&>&`/]`&<&'filename'&>
30428 The right hand side is expanded before use. After expansion,
30432 &"0"& or &"false"&, in which case no decoding is done.
30434 The string &"default"&. In that case, the file is put in the temporary
30435 &"default"& directory <&'spool_directory'&>&_/scan/_&<&'message_id'&>&_/_& with
30436 a sequential file name consisting of the message id and a sequence number. The
30437 full path and name is available in &$mime_decoded_filename$& after decoding.
30439 A full path name starting with a slash. If the full name is an existing
30440 directory, it is used as a replacement for the default directory. The filename
30441 is then sequentially assigned. If the path does not exist, it is used as
30442 the full path and file name.
30444 If the string does not start with a slash, it is used as the
30445 filename, and the default path is then used.
30447 The &%decode%& condition normally succeeds. It is only false for syntax
30448 errors or unusual circumstances such as memory shortages. You can easily decode
30449 a file with its original, proposed filename using
30451 decode = $mime_filename
30453 However, you should keep in mind that &$mime_filename$& might contain
30454 anything. If you place files outside of the default path, they are not
30455 automatically unlinked.
30457 For RFC822 attachments (these are messages attached to messages, with a
30458 content-type of &"message/rfc822"&), the ACL is called again in the same manner
30459 as for the primary message, only that the &$mime_is_rfc822$& expansion
30460 variable is set (see below). Attached messages are always decoded to disk
30461 before being checked, and the files are unlinked once the check is done.
30463 The MIME ACL supports the &%regex%& and &%mime_regex%& conditions. These can be
30464 used to match regular expressions against raw and decoded MIME parts,
30465 respectively. They are described in section &<<SECTscanregex>>&.
30467 .cindex "MIME content scanning" "returned variables"
30468 The following list describes all expansion variables that are
30469 available in the MIME ACL:
30472 .vitem &$mime_boundary$&
30473 If the current part is a multipart (see &$mime_is_multipart$&) below, it should
30474 have a boundary string, which is stored in this variable. If the current part
30475 has no boundary parameter in the &'Content-Type:'& header, this variable
30476 contains the empty string.
30478 .vitem &$mime_charset$&
30479 This variable contains the character set identifier, if one was found in the
30480 &'Content-Type:'& header. Examples for charset identifiers are:
30486 Please note that this value is not normalized, so you should do matches
30487 case-insensitively.
30489 .vitem &$mime_content_description$&
30490 This variable contains the normalized content of the &'Content-Description:'&
30491 header. It can contain a human-readable description of the parts content. Some
30492 implementations repeat the filename for attachments here, but they are usually
30493 only used for display purposes.
30495 .vitem &$mime_content_disposition$&
30496 This variable contains the normalized content of the &'Content-Disposition:'&
30497 header. You can expect strings like &"attachment"& or &"inline"& here.
30499 .vitem &$mime_content_id$&
30500 This variable contains the normalized content of the &'Content-ID:'& header.
30501 This is a unique ID that can be used to reference a part from another part.
30503 .vitem &$mime_content_size$&
30504 This variable is set only after the &%decode%& modifier (see above) has been
30505 successfully run. It contains the size of the decoded part in kilobytes. The
30506 size is always rounded up to full kilobytes, so only a completely empty part
30507 has a &$mime_content_size$& of zero.
30509 .vitem &$mime_content_transfer_encoding$&
30510 This variable contains the normalized content of the
30511 &'Content-transfer-encoding:'& header. This is a symbolic name for an encoding
30512 type. Typical values are &"base64"& and &"quoted-printable"&.
30514 .vitem &$mime_content_type$&
30515 If the MIME part has a &'Content-Type:'& header, this variable contains its
30516 value, lowercased, and without any options (like &"name"& or &"charset"&). Here
30517 are some examples of popular MIME types, as they may appear in this variable:
30521 application/octet-stream
30525 If the MIME part has no &'Content-Type:'& header, this variable contains the
30528 .vitem &$mime_decoded_filename$&
30529 This variable is set only after the &%decode%& modifier (see above) has been
30530 successfully run. It contains the full path and file name of the file
30531 containing the decoded data.
30536 .vitem &$mime_filename$&
30537 This is perhaps the most important of the MIME variables. It contains a
30538 proposed filename for an attachment, if one was found in either the
30539 &'Content-Type:'& or &'Content-Disposition:'& headers. The filename will be
30540 RFC2047 decoded, but no additional sanity checks are done. If no filename was
30541 found, this variable contains the empty string.
30543 .vitem &$mime_is_coverletter$&
30544 This variable attempts to differentiate the &"cover letter"& of an e-mail from
30545 attached data. It can be used to clamp down on flashy or unnecessarily encoded
30546 content in the cover letter, while not restricting attachments at all.
30548 The variable contains 1 (true) for a MIME part believed to be part of the
30549 cover letter, and 0 (false) for an attachment. At present, the algorithm is as
30553 The outermost MIME part of a message is always a cover letter.
30556 If a multipart/alternative or multipart/related MIME part is a cover letter,
30557 so are all MIME subparts within that multipart.
30560 If any other multipart is a cover letter, the first subpart is a cover letter,
30561 and the rest are attachments.
30564 All parts contained within an attachment multipart are attachments.
30567 As an example, the following will ban &"HTML mail"& (including that sent with
30568 alternative plain text), while allowing HTML files to be attached. HTML
30569 coverletter mail attached to non-HMTL coverletter mail will also be allowed:
30571 deny message = HTML mail is not accepted here
30572 !condition = $mime_is_rfc822
30573 condition = $mime_is_coverletter
30574 condition = ${if eq{$mime_content_type}{text/html}{1}{0}}
30576 .vitem &$mime_is_multipart$&
30577 This variable has the value 1 (true) when the current part has the main type
30578 &"multipart"&, for example &"multipart/alternative"& or &"multipart/mixed"&.
30579 Since multipart entities only serve as containers for other parts, you may not
30580 want to carry out specific actions on them.
30582 .vitem &$mime_is_rfc822$&
30583 This variable has the value 1 (true) if the current part is not a part of the
30584 checked message itself, but part of an attached message. Attached message
30585 decoding is fully recursive.
30587 .vitem &$mime_part_count$&
30588 This variable is a counter that is raised for each processed MIME part. It
30589 starts at zero for the very first part (which is usually a multipart). The
30590 counter is per-message, so it is reset when processing RFC822 attachments (see
30591 &$mime_is_rfc822$&). The counter stays set after &%acl_smtp_mime%& is
30592 complete, so you can use it in the DATA ACL to determine the number of MIME
30593 parts of a message. For non-MIME messages, this variable contains the value -1.
30598 .section "Scanning with regular expressions" "SECTscanregex"
30599 .cindex "content scanning" "with regular expressions"
30600 .cindex "regular expressions" "content scanning with"
30601 You can specify your own custom regular expression matches on the full body of
30602 the message, or on individual MIME parts.
30604 The &%regex%& condition takes one or more regular expressions as arguments and
30605 matches them against the full message (when called in the DATA ACL) or a raw
30606 MIME part (when called in the MIME ACL). The &%regex%& condition matches
30607 linewise, with a maximum line length of 32K characters. That means you cannot
30608 have multiline matches with the &%regex%& condition.
30610 The &%mime_regex%& condition can be called only in the MIME ACL. It matches up
30611 to 32K of decoded content (the whole content at once, not linewise). If the
30612 part has not been decoded with the &%decode%& modifier earlier in the ACL, it
30613 is decoded automatically when &%mime_regex%& is executed (using default path
30614 and filename values). If the decoded data is larger than 32K, only the first
30615 32K characters are checked.
30617 The regular expressions are passed as a colon-separated list. To include a
30618 literal colon, you must double it. Since the whole right-hand side string is
30619 expanded before being used, you must also escape dollar signs and backslashes
30620 with more backslashes, or use the &`\N`& facility to disable expansion.
30621 Here is a simple example that contains two regular expressions:
30623 deny message = contains blacklisted regex ($regex_match_string)
30624 regex = [Mm]ortgage : URGENT BUSINESS PROPOSAL
30626 The conditions returns true if any one of the regular expressions matches. The
30627 &$regex_match_string$& expansion variable is then set up and contains the
30628 matching regular expression.
30630 &*Warning*&: With large messages, these conditions can be fairly
30636 .section "The demime condition" "SECTdemimecond"
30637 .cindex "content scanning" "MIME checking"
30638 .cindex "MIME content scanning"
30639 The &%demime%& ACL condition provides MIME unpacking, sanity checking and file
30640 extension blocking. It is usable only in the DATA and non-SMTP ACLs. The
30641 &%demime%& condition uses a simpler interface to MIME decoding than the MIME
30642 ACL functionality, but provides no additional facilities. Please note that this
30643 condition is deprecated and kept only for backward compatibility. You must set
30644 the WITH_OLD_DEMIME option in &_Local/Makefile_& at build time to be able to
30645 use the &%demime%& condition.
30647 The &%demime%& condition unpacks MIME containers in the message. It detects
30648 errors in MIME containers and can match file extensions found in the message
30649 against a list. Using this facility produces files containing the unpacked MIME
30650 parts of the message in the temporary scan directory. If you do antivirus
30651 scanning, it is recommended that you use the &%demime%& condition before the
30652 antivirus (&%malware%&) condition.
30654 On the right-hand side of the &%demime%& condition you can pass a
30655 colon-separated list of file extensions that it should match against. For
30658 deny message = Found blacklisted file attachment
30659 demime = vbs:com:bat:pif:prf:lnk
30661 If one of the file extensions is found, the condition is true, otherwise it is
30662 false. If there is a temporary error while demimeing (for example, &"disk
30663 full"&), the condition defers, and the message is temporarily rejected (unless
30664 the condition is on a &%warn%& verb).
30666 The right-hand side is expanded before being treated as a list, so you can have
30667 conditions and lookups there. If it expands to an empty string, &"false"&, or
30668 zero (&"0"&), no demimeing is done and the condition is false.
30670 The &%demime%& condition set the following variables:
30673 .vitem &$demime_errorlevel$&
30674 .vindex "&$demime_errorlevel$&"
30675 When an error is detected in a MIME container, this variable contains the
30676 severity of the error, as an integer number. The higher the value, the more
30677 severe the error (the current maximum value is 3). If this variable is unset or
30678 zero, no error occurred.
30680 .vitem &$demime_reason$&
30681 .vindex "&$demime_reason$&"
30682 When &$demime_errorlevel$& is greater than zero, this variable contains a
30683 human-readable text string describing the MIME error that occurred.
30687 .vitem &$found_extension$&
30688 .vindex "&$found_extension$&"
30689 When the &%demime%& condition is true, this variable contains the file
30690 extension it found.
30693 Both &$demime_errorlevel$& and &$demime_reason$& are set by the first call of
30694 the &%demime%& condition, and are not changed on subsequent calls.
30696 If you do not want to check for file extensions, but rather use the &%demime%&
30697 condition for unpacking or error checking purposes, pass &"*"& as the
30698 right-hand side value. Here is a more elaborate example of how to use this
30701 # Reject messages with serious MIME container errors
30702 deny message = Found MIME error ($demime_reason).
30704 condition = ${if >{$demime_errorlevel}{2}{1}{0}}
30706 # Reject known virus spreading file extensions.
30707 # Accepting these is pretty much braindead.
30708 deny message = contains $found_extension file (blacklisted).
30709 demime = com:vbs:bat:pif:scr
30711 # Freeze .exe and .doc files. Postmaster can
30712 # examine them and eventually thaw them.
30713 deny log_message = Another $found_extension file.
30722 . ////////////////////////////////////////////////////////////////////////////
30723 . ////////////////////////////////////////////////////////////////////////////
30725 .chapter "Adding a local scan function to Exim" "CHAPlocalscan" &&&
30726 "Local scan function"
30727 .scindex IIDlosca "&[local_scan()]& function" "description of"
30728 .cindex "customizing" "input scan using C function"
30729 .cindex "policy control" "by local scan function"
30730 In these days of email worms, viruses, and ever-increasing spam, some sites
30731 want to apply a lot of checking to messages before accepting them.
30733 The content scanning extension (chapter &<<CHAPexiscan>>&) has facilities for
30734 passing messages to external virus and spam scanning software. You can also do
30735 a certain amount in Exim itself through string expansions and the &%condition%&
30736 condition in the ACL that runs after the SMTP DATA command or the ACL for
30737 non-SMTP messages (see chapter &<<CHAPACL>>&), but this has its limitations.
30739 To allow for further customization to a site's own requirements, there is the
30740 possibility of linking Exim with a private message scanning function, written
30741 in C. If you want to run code that is written in something other than C, you
30742 can of course use a little C stub to call it.
30744 The local scan function is run once for every incoming message, at the point
30745 when Exim is just about to accept the message.
30746 It can therefore be used to control non-SMTP messages from local processes as
30747 well as messages arriving via SMTP.
30749 Exim applies a timeout to calls of the local scan function, and there is an
30750 option called &%local_scan_timeout%& for setting it. The default is 5 minutes.
30751 Zero means &"no timeout"&.
30752 Exim also sets up signal handlers for SIGSEGV, SIGILL, SIGFPE, and SIGBUS
30753 before calling the local scan function, so that the most common types of crash
30754 are caught. If the timeout is exceeded or one of those signals is caught, the
30755 incoming message is rejected with a temporary error if it is an SMTP message.
30756 For a non-SMTP message, the message is dropped and Exim ends with a non-zero
30757 code. The incident is logged on the main and reject logs.
30761 .section "Building Exim to use a local scan function" "SECID207"
30762 .cindex "&[local_scan()]& function" "building Exim to use"
30763 To make use of the local scan function feature, you must tell Exim where your
30764 function is before building Exim, by setting LOCAL_SCAN_SOURCE in your
30765 &_Local/Makefile_&. A recommended place to put it is in the &_Local_&
30766 directory, so you might set
30768 LOCAL_SCAN_SOURCE=Local/local_scan.c
30770 for example. The function must be called &[local_scan()]&. It is called by
30771 Exim after it has received a message, when the success return code is about to
30772 be sent. This is after all the ACLs have been run. The return code from your
30773 function controls whether the message is actually accepted or not. There is a
30774 commented template function (that just accepts the message) in the file
30775 _src/local_scan.c_.
30777 If you want to make use of Exim's run time configuration file to set options
30778 for your &[local_scan()]& function, you must also set
30780 LOCAL_SCAN_HAS_OPTIONS=yes
30782 in &_Local/Makefile_& (see section &<<SECTconoptloc>>& below).
30787 .section "API for local_scan()" "SECTapiforloc"
30788 .cindex "&[local_scan()]& function" "API description"
30789 You must include this line near the start of your code:
30791 #include "local_scan.h"
30793 This header file defines a number of variables and other values, and the
30794 prototype for the function itself. Exim is coded to use unsigned char values
30795 almost exclusively, and one of the things this header defines is a shorthand
30796 for &`unsigned char`& called &`uschar`&.
30797 It also contains the following macro definitions, to simplify casting character
30798 strings and pointers to character strings:
30800 #define CS (char *)
30801 #define CCS (const char *)
30802 #define CSS (char **)
30803 #define US (unsigned char *)
30804 #define CUS (const unsigned char *)
30805 #define USS (unsigned char **)
30807 The function prototype for &[local_scan()]& is:
30809 extern int local_scan(int fd, uschar **return_text);
30811 The arguments are as follows:
30814 &%fd%& is a file descriptor for the file that contains the body of the message
30815 (the -D file). The file is open for reading and writing, but updating it is not
30816 recommended. &*Warning*&: You must &'not'& close this file descriptor.
30818 The descriptor is positioned at character 19 of the file, which is the first
30819 character of the body itself, because the first 19 characters are the message
30820 id followed by &`-D`& and a newline. If you rewind the file, you should use the
30821 macro SPOOL_DATA_START_OFFSET to reset to the start of the data, just in
30822 case this changes in some future version.
30824 &%return_text%& is an address which you can use to return a pointer to a text
30825 string at the end of the function. The value it points to on entry is NULL.
30828 The function must return an &%int%& value which is one of the following macros:
30831 .vitem &`LOCAL_SCAN_ACCEPT`&
30832 .vindex "&$local_scan_data$&"
30833 The message is accepted. If you pass back a string of text, it is saved with
30834 the message, and made available in the variable &$local_scan_data$&. No
30835 newlines are permitted (if there are any, they are turned into spaces) and the
30836 maximum length of text is 1000 characters.
30838 .vitem &`LOCAL_SCAN_ACCEPT_FREEZE`&
30839 This behaves as LOCAL_SCAN_ACCEPT, except that the accepted message is
30840 queued without immediate delivery, and is frozen.
30842 .vitem &`LOCAL_SCAN_ACCEPT_QUEUE`&
30843 This behaves as LOCAL_SCAN_ACCEPT, except that the accepted message is
30844 queued without immediate delivery.
30846 .vitem &`LOCAL_SCAN_REJECT`&
30847 The message is rejected; the returned text is used as an error message which is
30848 passed back to the sender and which is also logged. Newlines are permitted &--
30849 they cause a multiline response for SMTP rejections, but are converted to
30850 &`\n`& in log lines. If no message is given, &"Administrative prohibition"& is
30853 .vitem &`LOCAL_SCAN_TEMPREJECT`&
30854 The message is temporarily rejected; the returned text is used as an error
30855 message as for LOCAL_SCAN_REJECT. If no message is given, &"Temporary local
30858 .vitem &`LOCAL_SCAN_REJECT_NOLOGHDR`&
30859 This behaves as LOCAL_SCAN_REJECT, except that the header of the rejected
30860 message is not written to the reject log. It has the effect of unsetting the
30861 &%rejected_header%& log selector for just this rejection. If
30862 &%rejected_header%& is already unset (see the discussion of the
30863 &%log_selection%& option in section &<<SECTlogselector>>&), this code is the
30864 same as LOCAL_SCAN_REJECT.
30866 .vitem &`LOCAL_SCAN_TEMPREJECT_NOLOGHDR`&
30867 This code is a variation of LOCAL_SCAN_TEMPREJECT in the same way that
30868 LOCAL_SCAN_REJECT_NOLOGHDR is a variation of LOCAL_SCAN_REJECT.
30871 If the message is not being received by interactive SMTP, rejections are
30872 reported by writing to &%stderr%& or by sending an email, as configured by the
30873 &%-oe%& command line options.
30877 .section "Configuration options for local_scan()" "SECTconoptloc"
30878 .cindex "&[local_scan()]& function" "configuration options"
30879 It is possible to have option settings in the main configuration file
30880 that set values in static variables in the &[local_scan()]& module. If you
30881 want to do this, you must have the line
30883 LOCAL_SCAN_HAS_OPTIONS=yes
30885 in your &_Local/Makefile_& when you build Exim. (This line is in
30886 &_OS/Makefile-Default_&, commented out). Then, in the &[local_scan()]& source
30887 file, you must define static variables to hold the option values, and a table
30890 The table must be a vector called &%local_scan_options%&, of type
30891 &`optionlist`&. Each entry is a triplet, consisting of a name, an option type,
30892 and a pointer to the variable that holds the value. The entries must appear in
30893 alphabetical order. Following &%local_scan_options%& you must also define a
30894 variable called &%local_scan_options_count%& that contains the number of
30895 entries in the table. Here is a short example, showing two kinds of option:
30897 static int my_integer_option = 42;
30898 static uschar *my_string_option = US"a default string";
30900 optionlist local_scan_options[] = {
30901 { "my_integer", opt_int, &my_integer_option },
30902 { "my_string", opt_stringptr, &my_string_option }
30905 int local_scan_options_count =
30906 sizeof(local_scan_options)/sizeof(optionlist);
30908 The values of the variables can now be changed from Exim's runtime
30909 configuration file by including a local scan section as in this example:
30913 my_string = some string of text...
30915 The available types of option data are as follows:
30918 .vitem &*opt_bool*&
30919 This specifies a boolean (true/false) option. The address should point to a
30920 variable of type &`BOOL`&, which will be set to TRUE or FALSE, which are macros
30921 that are defined as &"1"& and &"0"&, respectively. If you want to detect
30922 whether such a variable has been set at all, you can initialize it to
30923 TRUE_UNSET. (BOOL variables are integers underneath, so can hold more than two
30926 .vitem &*opt_fixed*&
30927 This specifies a fixed point number, such as is used for load averages.
30928 The address should point to a variable of type &`int`&. The value is stored
30929 multiplied by 1000, so, for example, 1.4142 is truncated and stored as 1414.
30932 This specifies an integer; the address should point to a variable of type
30933 &`int`&. The value may be specified in any of the integer formats accepted by
30936 .vitem &*opt_mkint*&
30937 This is the same as &%opt_int%&, except that when such a value is output in a
30938 &%-bP%& listing, if it is an exact number of kilobytes or megabytes, it is
30939 printed with the suffix K or M.
30941 .vitem &*opt_octint*&
30942 This also specifies an integer, but the value is always interpreted as an
30943 octal integer, whether or not it starts with the digit zero, and it is
30944 always output in octal.
30946 .vitem &*opt_stringptr*&
30947 This specifies a string value; the address must be a pointer to a
30948 variable that points to a string (for example, of type &`uschar *`&).
30950 .vitem &*opt_time*&
30951 This specifies a time interval value. The address must point to a variable of
30952 type &`int`&. The value that is placed there is a number of seconds.
30955 If the &%-bP%& command line option is followed by &`local_scan`&, Exim prints
30956 out the values of all the &[local_scan()]& options.
30960 .section "Available Exim variables" "SECID208"
30961 .cindex "&[local_scan()]& function" "available Exim variables"
30962 The header &_local_scan.h_& gives you access to a number of C variables. These
30963 are the only ones that are guaranteed to be maintained from release to release.
30964 Note, however, that you can obtain the value of any Exim expansion variable,
30965 including &$recipients$&, by calling &'expand_string()'&. The exported
30966 C variables are as follows:
30969 .vitem &*int&~body_linecount*&
30970 This variable contains the number of lines in the message's body.
30972 .vitem &*int&~body_zerocount*&
30973 This variable contains the number of binary zero bytes in the message's body.
30975 .vitem &*unsigned&~int&~debug_selector*&
30976 This variable is set to zero when no debugging is taking place. Otherwise, it
30977 is a bitmap of debugging selectors. Two bits are identified for use in
30978 &[local_scan()]&; they are defined as macros:
30981 The &`D_v`& bit is set when &%-v%& was present on the command line. This is a
30982 testing option that is not privileged &-- any caller may set it. All the
30983 other selector bits can be set only by admin users.
30986 The &`D_local_scan`& bit is provided for use by &[local_scan()]&; it is set
30987 by the &`+local_scan`& debug selector. It is not included in the default set
30991 Thus, to write to the debugging output only when &`+local_scan`& has been
30992 selected, you should use code like this:
30994 if ((debug_selector & D_local_scan) != 0)
30995 debug_printf("xxx", ...);
30997 .vitem &*uschar&~*expand_string_message*&
30998 After a failing call to &'expand_string()'& (returned value NULL), the
30999 variable &%expand_string_message%& contains the error message, zero-terminated.
31001 .vitem &*header_line&~*header_list*&
31002 A pointer to a chain of header lines. The &%header_line%& structure is
31005 .vitem &*header_line&~*header_last*&
31006 A pointer to the last of the header lines.
31008 .vitem &*uschar&~*headers_charset*&
31009 The value of the &%headers_charset%& configuration option.
31011 .vitem &*BOOL&~host_checking*&
31012 This variable is TRUE during a host checking session that is initiated by the
31013 &%-bh%& command line option.
31015 .vitem &*uschar&~*interface_address*&
31016 The IP address of the interface that received the message, as a string. This
31017 is NULL for locally submitted messages.
31019 .vitem &*int&~interface_port*&
31020 The port on which this message was received. When testing with the &%-bh%&
31021 command line option, the value of this variable is -1 unless a port has been
31022 specified via the &%-oMi%& option.
31024 .vitem &*uschar&~*message_id*&
31025 This variable contains Exim's message id for the incoming message (the value of
31026 &$message_exim_id$&) as a zero-terminated string.
31028 .vitem &*uschar&~*received_protocol*&
31029 The name of the protocol by which the message was received.
31031 .vitem &*int&~recipients_count*&
31032 The number of accepted recipients.
31034 .vitem &*recipient_item&~*recipients_list*&
31035 .cindex "recipient" "adding in local scan"
31036 .cindex "recipient" "removing in local scan"
31037 The list of accepted recipients, held in a vector of length
31038 &%recipients_count%&. The &%recipient_item%& structure is discussed below. You
31039 can add additional recipients by calling &'receive_add_recipient()'& (see
31040 below). You can delete recipients by removing them from the vector and
31041 adjusting the value in &%recipients_count%&. In particular, by setting
31042 &%recipients_count%& to zero you remove all recipients. If you then return the
31043 value &`LOCAL_SCAN_ACCEPT`&, the message is accepted, but immediately
31044 blackholed. To replace the recipients, you can set &%recipients_count%& to zero
31045 and then call &'receive_add_recipient()'& as often as needed.
31047 .vitem &*uschar&~*sender_address*&
31048 The envelope sender address. For bounce messages this is the empty string.
31050 .vitem &*uschar&~*sender_host_address*&
31051 The IP address of the sending host, as a string. This is NULL for
31052 locally-submitted messages.
31054 .vitem &*uschar&~*sender_host_authenticated*&
31055 The name of the authentication mechanism that was used, or NULL if the message
31056 was not received over an authenticated SMTP connection.
31058 .vitem &*uschar&~*sender_host_name*&
31059 The name of the sending host, if known.
31061 .vitem &*int&~sender_host_port*&
31062 The port on the sending host.
31064 .vitem &*BOOL&~smtp_input*&
31065 This variable is TRUE for all SMTP input, including BSMTP.
31067 .vitem &*BOOL&~smtp_batched_input*&
31068 This variable is TRUE for BSMTP input.
31070 .vitem &*int&~store_pool*&
31071 The contents of this variable control which pool of memory is used for new
31072 requests. See section &<<SECTmemhanloc>>& for details.
31076 .section "Structure of header lines" "SECID209"
31077 The &%header_line%& structure contains the members listed below.
31078 You can add additional header lines by calling the &'header_add()'& function
31079 (see below). You can cause header lines to be ignored (deleted) by setting
31084 .vitem &*struct&~header_line&~*next*&
31085 A pointer to the next header line, or NULL for the last line.
31087 .vitem &*int&~type*&
31088 A code identifying certain headers that Exim recognizes. The codes are printing
31089 characters, and are documented in chapter &<<CHAPspool>>& of this manual.
31090 Notice in particular that any header line whose type is * is not transmitted
31091 with the message. This flagging is used for header lines that have been
31092 rewritten, or are to be removed (for example, &'Envelope-sender:'& header
31093 lines.) Effectively, * means &"deleted"&.
31095 .vitem &*int&~slen*&
31096 The number of characters in the header line, including the terminating and any
31099 .vitem &*uschar&~*text*&
31100 A pointer to the text of the header. It always ends with a newline, followed by
31101 a zero byte. Internal newlines are preserved.
31106 .section "Structure of recipient items" "SECID210"
31107 The &%recipient_item%& structure contains these members:
31110 .vitem &*uschar&~*address*&
31111 This is a pointer to the recipient address as it was received.
31113 .vitem &*int&~pno*&
31114 This is used in later Exim processing when top level addresses are created by
31115 the &%one_time%& option. It is not relevant at the time &[local_scan()]& is run
31116 and must always contain -1 at this stage.
31118 .vitem &*uschar&~*errors_to*&
31119 If this value is not NULL, bounce messages caused by failing to deliver to the
31120 recipient are sent to the address it contains. In other words, it overrides the
31121 envelope sender for this one recipient. (Compare the &%errors_to%& generic
31122 router option.) If a &[local_scan()]& function sets an &%errors_to%& field to
31123 an unqualified address, Exim qualifies it using the domain from
31124 &%qualify_recipient%&. When &[local_scan()]& is called, the &%errors_to%& field
31125 is NULL for all recipients.
31130 .section "Available Exim functions" "SECID211"
31131 .cindex "&[local_scan()]& function" "available Exim functions"
31132 The header &_local_scan.h_& gives you access to a number of Exim functions.
31133 These are the only ones that are guaranteed to be maintained from release to
31137 .vitem "&*pid_t&~child_open(uschar&~**argv,&~uschar&~**envp,&~int&~newumask,&&&
31138 &~int&~*infdptr,&~int&~*outfdptr, &~&~BOOL&~make_leader)*&"
31140 This function creates a child process that runs the command specified by
31141 &%argv%&. The environment for the process is specified by &%envp%&, which can
31142 be NULL if no environment variables are to be passed. A new umask is supplied
31143 for the process in &%newumask%&.
31145 Pipes to the standard input and output of the new process are set up
31146 and returned to the caller via the &%infdptr%& and &%outfdptr%& arguments. The
31147 standard error is cloned to the standard output. If there are any file
31148 descriptors &"in the way"& in the new process, they are closed. If the final
31149 argument is TRUE, the new process is made into a process group leader.
31151 The function returns the pid of the new process, or -1 if things go wrong.
31153 .vitem &*int&~child_close(pid_t&~pid,&~int&~timeout)*&
31154 This function waits for a child process to terminate, or for a timeout (in
31155 seconds) to expire. A timeout value of zero means wait as long as it takes. The
31156 return value is as follows:
31161 The process terminated by a normal exit and the value is the process
31167 The process was terminated by a signal and the value is the negation of the
31173 The process timed out.
31177 The was some other error in wait(); &%errno%& is still set.
31180 .vitem &*pid_t&~child_open_exim(int&~*fd)*&
31181 This function provide you with a means of submitting a new message to
31182 Exim. (Of course, you can also call &_/usr/sbin/sendmail_& yourself if you
31183 want, but this packages it all up for you.) The function creates a pipe,
31184 forks a subprocess that is running
31186 exim -t -oem -oi -f <>
31188 and returns to you (via the &`int *`& argument) a file descriptor for the pipe
31189 that is connected to the standard input. The yield of the function is the PID
31190 of the subprocess. You can then write a message to the file descriptor, with
31191 recipients in &'To:'&, &'Cc:'&, and/or &'Bcc:'& header lines.
31193 When you have finished, call &'child_close()'& to wait for the process to
31194 finish and to collect its ending status. A timeout value of zero is usually
31195 fine in this circumstance. Unless you have made a mistake with the recipient
31196 addresses, you should get a return code of zero.
31199 .vitem &*pid_t&~child_open_exim2(int&~*fd,&~uschar&~*sender,&~uschar&~&&&
31200 *sender_authentication)*&
31201 This function is a more sophisticated version of &'child_open()'&. The command
31204 &`exim -t -oem -oi -f `&&'sender'&&` -oMas `&&'sender_authentication'&
31206 The third argument may be NULL, in which case the &%-oMas%& option is omitted.
31209 .vitem &*void&~debug_printf(char&~*,&~...)*&
31210 This is Exim's debugging function, with arguments as for &'(printf()'&. The
31211 output is written to the standard error stream. If no debugging is selected,
31212 calls to &'debug_printf()'& have no effect. Normally, you should make calls
31213 conditional on the &`local_scan`& debug selector by coding like this:
31215 if ((debug_selector & D_local_scan) != 0)
31216 debug_printf("xxx", ...);
31219 .vitem &*uschar&~*expand_string(uschar&~*string)*&
31220 This is an interface to Exim's string expansion code. The return value is the
31221 expanded string, or NULL if there was an expansion failure.
31222 The C variable &%expand_string_message%& contains an error message after an
31223 expansion failure. If expansion does not change the string, the return value is
31224 the pointer to the input string. Otherwise, the return value points to a new
31225 block of memory that was obtained by a call to &'store_get()'&. See section
31226 &<<SECTmemhanloc>>& below for a discussion of memory handling.
31228 .vitem &*void&~header_add(int&~type,&~char&~*format,&~...)*&
31229 This function allows you to an add additional header line at the end of the
31230 existing ones. The first argument is the type, and should normally be a space
31231 character. The second argument is a format string and any number of
31232 substitution arguments as for &[sprintf()]&. You may include internal newlines
31233 if you want, and you must ensure that the string ends with a newline.
31235 .vitem "&*void&~header_add_at_position(BOOL&~after,&~uschar&~*name,&~&&&
31236 BOOL&~topnot,&~int&~type,&~char&~*format, &~&~...)*&"
31237 This function adds a new header line at a specified point in the header
31238 chain. The header itself is specified as for &'header_add()'&.
31240 If &%name%& is NULL, the new header is added at the end of the chain if
31241 &%after%& is true, or at the start if &%after%& is false. If &%name%& is not
31242 NULL, the header lines are searched for the first non-deleted header that
31243 matches the name. If one is found, the new header is added before it if
31244 &%after%& is false. If &%after%& is true, the new header is added after the
31245 found header and any adjacent subsequent ones with the same name (even if
31246 marked &"deleted"&). If no matching non-deleted header is found, the &%topnot%&
31247 option controls where the header is added. If it is true, addition is at the
31248 top; otherwise at the bottom. Thus, to add a header after all the &'Received:'&
31249 headers, or at the top if there are no &'Received:'& headers, you could use
31251 header_add_at_position(TRUE, US"Received", TRUE,
31252 ' ', "X-xxx: ...");
31254 Normally, there is always at least one non-deleted &'Received:'& header, but
31255 there may not be if &%received_header_text%& expands to an empty string.
31258 .vitem &*void&~header_remove(int&~occurrence,&~uschar&~*name)*&
31259 This function removes header lines. If &%occurrence%& is zero or negative, all
31260 occurrences of the header are removed. If occurrence is greater than zero, that
31261 particular instance of the header is removed. If no header(s) can be found that
31262 match the specification, the function does nothing.
31265 .vitem "&*BOOL&~header_testname(header_line&~*hdr,&~uschar&~*name,&~&&&
31266 int&~length,&~BOOL&~notdel)*&"
31267 This function tests whether the given header has the given name. It is not just
31268 a string comparison, because white space is permitted between the name and the
31269 colon. If the &%notdel%& argument is true, a false return is forced for all
31270 &"deleted"& headers; otherwise they are not treated specially. For example:
31272 if (header_testname(h, US"X-Spam", 6, TRUE)) ...
31274 .vitem &*uschar&~*lss_b64encode(uschar&~*cleartext,&~int&~length)*&
31275 .cindex "base64 encoding" "functions for &[local_scan()]& use"
31276 This function base64-encodes a string, which is passed by address and length.
31277 The text may contain bytes of any value, including zero. The result is passed
31278 back in dynamic memory that is obtained by calling &'store_get()'&. It is
31281 .vitem &*int&~lss_b64decode(uschar&~*codetext,&~uschar&~**cleartext)*&
31282 This function decodes a base64-encoded string. Its arguments are a
31283 zero-terminated base64-encoded string and the address of a variable that is set
31284 to point to the result, which is in dynamic memory. The length of the decoded
31285 string is the yield of the function. If the input is invalid base64 data, the
31286 yield is -1. A zero byte is added to the end of the output string to make it
31287 easy to interpret as a C string (assuming it contains no zeros of its own). The
31288 added zero byte is not included in the returned count.
31290 .vitem &*int&~lss_match_domain(uschar&~*domain,&~uschar&~*list)*&
31291 This function checks for a match in a domain list. Domains are always
31292 matched caselessly. The return value is one of the following:
31294 &`OK `& match succeeded
31295 &`FAIL `& match failed
31296 &`DEFER `& match deferred
31298 DEFER is usually caused by some kind of lookup defer, such as the
31299 inability to contact a database.
31301 .vitem "&*int&~lss_match_local_part(uschar&~*localpart,&~uschar&~*list,&~&&&
31303 This function checks for a match in a local part list. The third argument
31304 controls case-sensitivity. The return values are as for
31305 &'lss_match_domain()'&.
31307 .vitem "&*int&~lss_match_address(uschar&~*address,&~uschar&~*list,&~&&&
31309 This function checks for a match in an address list. The third argument
31310 controls the case-sensitivity of the local part match. The domain is always
31311 matched caselessly. The return values are as for &'lss_match_domain()'&.
31313 .vitem "&*int&~lss_match_host(uschar&~*host_name,&~uschar&~*host_address,&~&&&
31315 This function checks for a match in a host list. The most common usage is
31318 lss_match_host(sender_host_name, sender_host_address, ...)
31320 .vindex "&$sender_host_address$&"
31321 An empty address field matches an empty item in the host list. If the host name
31322 is NULL, the name corresponding to &$sender_host_address$& is automatically
31323 looked up if a host name is required to match an item in the list. The return
31324 values are as for &'lss_match_domain()'&, but in addition, &'lss_match_host()'&
31325 returns ERROR in the case when it had to look up a host name, but the lookup
31328 .vitem "&*void&~log_write(unsigned&~int&~selector,&~int&~which,&~char&~&&&
31330 This function writes to Exim's log files. The first argument should be zero (it
31331 is concerned with &%log_selector%&). The second argument can be &`LOG_MAIN`& or
31332 &`LOG_REJECT`& or &`LOG_PANIC`& or the inclusive &"or"& of any combination of
31333 them. It specifies to which log or logs the message is written. The remaining
31334 arguments are a format and relevant insertion arguments. The string should not
31335 contain any newlines, not even at the end.
31338 .vitem &*void&~receive_add_recipient(uschar&~*address,&~int&~pno)*&
31339 This function adds an additional recipient to the message. The first argument
31340 is the recipient address. If it is unqualified (has no domain), it is qualified
31341 with the &%qualify_recipient%& domain. The second argument must always be -1.
31343 This function does not allow you to specify a private &%errors_to%& address (as
31344 described with the structure of &%recipient_item%& above), because it pre-dates
31345 the addition of that field to the structure. However, it is easy to add such a
31346 value afterwards. For example:
31348 receive_add_recipient(US"monitor@mydom.example", -1);
31349 recipients_list[recipients_count-1].errors_to =
31350 US"postmaster@mydom.example";
31353 .vitem &*BOOL&~receive_remove_recipient(uschar&~*recipient)*&
31354 This is a convenience function to remove a named recipient from the list of
31355 recipients. It returns true if a recipient was removed, and false if no
31356 matching recipient could be found. The argument must be a complete email
31363 .vitem "&*uschar&~rfc2047_decode(uschar&~*string,&~BOOL&~lencheck,&&&
31364 &~uschar&~*target,&~int&~zeroval,&~int&~*lenptr, &~&~uschar&~**error)*&"
31365 This function decodes strings that are encoded according to RFC 2047. Typically
31366 these are the contents of header lines. First, each &"encoded word"& is decoded
31367 from the Q or B encoding into a byte-string. Then, if provided with the name of
31368 a charset encoding, and if the &[iconv()]& function is available, an attempt is
31369 made to translate the result to the named character set. If this fails, the
31370 binary string is returned with an error message.
31372 The first argument is the string to be decoded. If &%lencheck%& is TRUE, the
31373 maximum MIME word length is enforced. The third argument is the target
31374 encoding, or NULL if no translation is wanted.
31376 .cindex "binary zero" "in RFC 2047 decoding"
31377 .cindex "RFC 2047" "binary zero in"
31378 If a binary zero is encountered in the decoded string, it is replaced by the
31379 contents of the &%zeroval%& argument. For use with Exim headers, the value must
31380 not be 0 because header lines are handled as zero-terminated strings.
31382 The function returns the result of processing the string, zero-terminated; if
31383 &%lenptr%& is not NULL, the length of the result is set in the variable to
31384 which it points. When &%zeroval%& is 0, &%lenptr%& should not be NULL.
31386 If an error is encountered, the function returns NULL and uses the &%error%&
31387 argument to return an error message. The variable pointed to by &%error%& is
31388 set to NULL if there is no error; it may be set non-NULL even when the function
31389 returns a non-NULL value if decoding was successful, but there was a problem
31393 .vitem &*int&~smtp_fflush(void)*&
31394 This function is used in conjunction with &'smtp_printf()'&, as described
31397 .vitem &*void&~smtp_printf(char&~*,&~...)*&
31398 The arguments of this function are like &[printf()]&; it writes to the SMTP
31399 output stream. You should use this function only when there is an SMTP output
31400 stream, that is, when the incoming message is being received via interactive
31401 SMTP. This is the case when &%smtp_input%& is TRUE and &%smtp_batched_input%&
31402 is FALSE. If you want to test for an incoming message from another host (as
31403 opposed to a local process that used the &%-bs%& command line option), you can
31404 test the value of &%sender_host_address%&, which is non-NULL when a remote host
31407 If an SMTP TLS connection is established, &'smtp_printf()'& uses the TLS
31408 output function, so it can be used for all forms of SMTP connection.
31410 Strings that are written by &'smtp_printf()'& from within &[local_scan()]&
31411 must start with an appropriate response code: 550 if you are going to return
31412 LOCAL_SCAN_REJECT, 451 if you are going to return
31413 LOCAL_SCAN_TEMPREJECT, and 250 otherwise. Because you are writing the
31414 initial lines of a multi-line response, the code must be followed by a hyphen
31415 to indicate that the line is not the final response line. You must also ensure
31416 that the lines you write terminate with CRLF. For example:
31418 smtp_printf("550-this is some extra info\r\n");
31419 return LOCAL_SCAN_REJECT;
31421 Note that you can also create multi-line responses by including newlines in
31422 the data returned via the &%return_text%& argument. The added value of using
31423 &'smtp_printf()'& is that, for instance, you could introduce delays between
31424 multiple output lines.
31426 The &'smtp_printf()'& function does not return any error indication, because it
31427 does not automatically flush pending output, and therefore does not test
31428 the state of the stream. (In the main code of Exim, flushing and error
31429 detection is done when Exim is ready for the next SMTP input command.) If
31430 you want to flush the output and check for an error (for example, the
31431 dropping of a TCP/IP connection), you can call &'smtp_fflush()'&, which has no
31432 arguments. It flushes the output stream, and returns a non-zero value if there
31435 .vitem &*void&~*store_get(int)*&
31436 This function accesses Exim's internal store (memory) manager. It gets a new
31437 chunk of memory whose size is given by the argument. Exim bombs out if it ever
31438 runs out of memory. See the next section for a discussion of memory handling.
31440 .vitem &*void&~*store_get_perm(int)*&
31441 This function is like &'store_get()'&, but it always gets memory from the
31442 permanent pool. See the next section for a discussion of memory handling.
31444 .vitem &*uschar&~*string_copy(uschar&~*string)*&
31447 .vitem &*uschar&~*string_copyn(uschar&~*string,&~int&~length)*&
31450 .vitem &*uschar&~*string_sprintf(char&~*format,&~...)*&
31451 These three functions create strings using Exim's dynamic memory facilities.
31452 The first makes a copy of an entire string. The second copies up to a maximum
31453 number of characters, indicated by the second argument. The third uses a format
31454 and insertion arguments to create a new string. In each case, the result is a
31455 pointer to a new string in the current memory pool. See the next section for
31461 .section "More about Exim's memory handling" "SECTmemhanloc"
31462 .cindex "&[local_scan()]& function" "memory handling"
31463 No function is provided for freeing memory, because that is never needed.
31464 The dynamic memory that Exim uses when receiving a message is automatically
31465 recycled if another message is received by the same process (this applies only
31466 to incoming SMTP connections &-- other input methods can supply only one
31467 message at a time). After receiving the last message, a reception process
31470 Because it is recycled, the normal dynamic memory cannot be used for holding
31471 data that must be preserved over a number of incoming messages on the same SMTP
31472 connection. However, Exim in fact uses two pools of dynamic memory; the second
31473 one is not recycled, and can be used for this purpose.
31475 If you want to allocate memory that remains available for subsequent messages
31476 in the same SMTP connection, you should set
31478 store_pool = POOL_PERM
31480 before calling the function that does the allocation. There is no need to
31481 restore the value if you do not need to; however, if you do want to revert to
31482 the normal pool, you can either restore the previous value of &%store_pool%& or
31483 set it explicitly to POOL_MAIN.
31485 The pool setting applies to all functions that get dynamic memory, including
31486 &'expand_string()'&, &'store_get()'&, and the &'string_xxx()'& functions.
31487 There is also a convenience function called &'store_get_perm()'& that gets a
31488 block of memory from the permanent pool while preserving the value of
31495 . ////////////////////////////////////////////////////////////////////////////
31496 . ////////////////////////////////////////////////////////////////////////////
31498 .chapter "System-wide message filtering" "CHAPsystemfilter"
31499 .scindex IIDsysfil1 "filter" "system filter"
31500 .scindex IIDsysfil2 "filtering all mail"
31501 .scindex IIDsysfil3 "system filter"
31502 The previous chapters (on ACLs and the local scan function) describe checks
31503 that can be applied to messages before they are accepted by a host. There is
31504 also a mechanism for checking messages once they have been received, but before
31505 they are delivered. This is called the &'system filter'&.
31507 The system filter operates in a similar manner to users' filter files, but it
31508 is run just once per message (however many recipients the message has).
31509 It should not normally be used as a substitute for routing, because &%deliver%&
31510 commands in a system router provide new envelope recipient addresses.
31511 The system filter must be an Exim filter. It cannot be a Sieve filter.
31513 The system filter is run at the start of a delivery attempt, before any routing
31514 is done. If a message fails to be completely delivered at the first attempt,
31515 the system filter is run again at the start of every retry.
31516 If you want your filter to do something only once per message, you can make use
31517 of the &%first_delivery%& condition in an &%if%& command in the filter to
31518 prevent it happening on retries.
31520 .vindex "&$domain$&"
31521 .vindex "&$local_part$&"
31522 &*Warning*&: Because the system filter runs just once, variables that are
31523 specific to individual recipient addresses, such as &$local_part$& and
31524 &$domain$&, are not set, and the &"personal"& condition is not meaningful. If
31525 you want to run a centrally-specified filter for each recipient address
31526 independently, you can do so by setting up a suitable &(redirect)& router, as
31527 described in section &<<SECTperaddfil>>& below.
31530 .section "Specifying a system filter" "SECID212"
31531 .cindex "uid (user id)" "system filter"
31532 .cindex "gid (group id)" "system filter"
31533 The name of the file that contains the system filter must be specified by
31534 setting &%system_filter%&. If you want the filter to run under a uid and gid
31535 other than root, you must also set &%system_filter_user%& and
31536 &%system_filter_group%& as appropriate. For example:
31538 system_filter = /etc/mail/exim.filter
31539 system_filter_user = exim
31541 If a system filter generates any deliveries directly to files or pipes (via the
31542 &%save%& or &%pipe%& commands), transports to handle these deliveries must be
31543 specified by setting &%system_filter_file_transport%& and
31544 &%system_filter_pipe_transport%&, respectively. Similarly,
31545 &%system_filter_reply_transport%& must be set to handle any messages generated
31546 by the &%reply%& command.
31549 .section "Testing a system filter" "SECID213"
31550 You can run simple tests of a system filter in the same way as for a user
31551 filter, but you should use &%-bF%& rather than &%-bf%&, so that features that
31552 are permitted only in system filters are recognized.
31554 If you want to test the combined effect of a system filter and a user filter,
31555 you can use both &%-bF%& and &%-bf%& on the same command line.
31559 .section "Contents of a system filter" "SECID214"
31560 The language used to specify system filters is the same as for users' filter
31561 files. It is described in the separate end-user document &'Exim's interface to
31562 mail filtering'&. However, there are some additional features that are
31563 available only in system filters; these are described in subsequent sections.
31564 If they are encountered in a user's filter file or when testing with &%-bf%&,
31567 .cindex "frozen messages" "manual thaw; testing in filter"
31568 There are two special conditions which, though available in users' filter
31569 files, are designed for use in system filters. The condition &%first_delivery%&
31570 is true only for the first attempt at delivering a message, and
31571 &%manually_thawed%& is true only if the message has been frozen, and
31572 subsequently thawed by an admin user. An explicit forced delivery counts as a
31573 manual thaw, but thawing as a result of the &%auto_thaw%& setting does not.
31575 &*Warning*&: If a system filter uses the &%first_delivery%& condition to
31576 specify an &"unseen"& (non-significant) delivery, and that delivery does not
31577 succeed, it will not be tried again.
31578 If you want Exim to retry an unseen delivery until it succeeds, you should
31579 arrange to set it up every time the filter runs.
31581 When a system filter finishes running, the values of the variables &$n0$& &--
31582 &$n9$& are copied into &$sn0$& &-- &$sn9$& and are thereby made available to
31583 users' filter files. Thus a system filter can, for example, set up &"scores"&
31584 to which users' filter files can refer.
31588 .section "Additional variable for system filters" "SECID215"
31589 .vindex "&$recipients$&"
31590 The expansion variable &$recipients$&, containing a list of all the recipients
31591 of the message (separated by commas and white space), is available in system
31592 filters. It is not available in users' filters for privacy reasons.
31596 .section "Defer, freeze, and fail commands for system filters" "SECID216"
31597 .cindex "freezing messages"
31598 .cindex "message" "freezing"
31599 .cindex "message" "forced failure"
31600 .cindex "&%fail%&" "in system filter"
31601 .cindex "&%freeze%& in system filter"
31602 .cindex "&%defer%& in system filter"
31603 There are three extra commands (&%defer%&, &%freeze%& and &%fail%&) which are
31604 always available in system filters, but are not normally enabled in users'
31605 filters. (See the &%allow_defer%&, &%allow_freeze%& and &%allow_fail%& options
31606 for the &(redirect)& router.) These commands can optionally be followed by the
31607 word &%text%& and a string containing an error message, for example:
31609 fail text "this message looks like spam to me"
31611 The keyword &%text%& is optional if the next character is a double quote.
31613 The &%defer%& command defers delivery of the original recipients of the
31614 message. The &%fail%& command causes all the original recipients to be failed,
31615 and a bounce message to be created. The &%freeze%& command suspends all
31616 delivery attempts for the original recipients. In all cases, any new deliveries
31617 that are specified by the filter are attempted as normal after the filter has
31620 The &%freeze%& command is ignored if the message has been manually unfrozen and
31621 not manually frozen since. This means that automatic freezing by a system
31622 filter can be used as a way of checking out suspicious messages. If a message
31623 is found to be all right, manually unfreezing it allows it to be delivered.
31625 .cindex "log" "&%fail%& command log line"
31626 .cindex "&%fail%&" "log line; reducing"
31627 The text given with a fail command is used as part of the bounce message as
31628 well as being written to the log. If the message is quite long, this can fill
31629 up a lot of log space when such failures are common. To reduce the size of the
31630 log message, Exim interprets the text in a special way if it starts with the
31631 two characters &`<<`& and contains &`>>`& later. The text between these two
31632 strings is written to the log, and the rest of the text is used in the bounce
31633 message. For example:
31635 fail "<<filter test 1>>Your message is rejected \
31636 because it contains attachments that we are \
31637 not prepared to receive."
31640 .cindex "loop" "caused by &%fail%&"
31641 Take great care with the &%fail%& command when basing the decision to fail on
31642 the contents of the message, because the bounce message will of course include
31643 the contents of the original message and will therefore trigger the &%fail%&
31644 command again (causing a mail loop) unless steps are taken to prevent this.
31645 Testing the &%error_message%& condition is one way to prevent this. You could
31648 if $message_body contains "this is spam" and not error_message
31649 then fail text "spam is not wanted here" endif
31651 though of course that might let through unwanted bounce messages. The
31652 alternative is clever checking of the body and/or headers to detect bounces
31653 generated by the filter.
31655 The interpretation of a system filter file ceases after a
31657 &%freeze%&, or &%fail%& command is obeyed. However, any deliveries that were
31658 set up earlier in the filter file are honoured, so you can use a sequence such
31664 to send a specified message when the system filter is freezing (or deferring or
31665 failing) a message. The normal deliveries for the message do not, of course,
31670 .section "Adding and removing headers in a system filter" "SECTaddremheasys"
31671 .cindex "header lines" "adding; in system filter"
31672 .cindex "header lines" "removing; in system filter"
31673 .cindex "filter" "header lines; adding/removing"
31674 Two filter commands that are available only in system filters are:
31676 headers add <string>
31677 headers remove <string>
31679 The argument for the &%headers add%& is a string that is expanded and then
31680 added to the end of the message's headers. It is the responsibility of the
31681 filter maintainer to make sure it conforms to RFC 2822 syntax. Leading white
31682 space is ignored, and if the string is otherwise empty, or if the expansion is
31683 forced to fail, the command has no effect.
31685 You can use &"\n"& within the string, followed by white space, to specify
31686 continued header lines. More than one header may be added in one command by
31687 including &"\n"& within the string without any following white space. For
31690 headers add "X-header-1: ....\n \
31691 continuation of X-header-1 ...\n\
31694 Note that the header line continuation white space after the first newline must
31695 be placed before the backslash that continues the input string, because white
31696 space after input continuations is ignored.
31698 The argument for &%headers remove%& is a colon-separated list of header names.
31699 This command applies only to those headers that are stored with the message;
31700 those that are added at delivery time (such as &'Envelope-To:'& and
31701 &'Return-Path:'&) cannot be removed by this means. If there is more than one
31702 header with the same name, they are all removed.
31704 The &%headers%& command in a system filter makes an immediate change to the set
31705 of header lines that was received with the message (with possible additions
31706 from ACL processing). Subsequent commands in the system filter operate on the
31707 modified set, which also forms the basis for subsequent message delivery.
31708 Unless further modified during routing or transporting, this set of headers is
31709 used for all recipients of the message.
31711 During routing and transporting, the variables that refer to the contents of
31712 header lines refer only to those lines that are in this set. Thus, header lines
31713 that are added by a system filter are visible to users' filter files and to all
31714 routers and transports. This contrasts with the manipulation of header lines by
31715 routers and transports, which is not immediate, but which instead is saved up
31716 until the message is actually being written (see section
31717 &<<SECTheadersaddrem>>&).
31719 If the message is not delivered at the first attempt, header lines that were
31720 added by the system filter are stored with the message, and so are still
31721 present at the next delivery attempt. Header lines that were removed are still
31722 present, but marked &"deleted"& so that they are not transported with the
31723 message. For this reason, it is usual to make the &%headers%& command
31724 conditional on &%first_delivery%& so that the set of header lines is not
31725 modified more than once.
31727 Because header modification in a system filter acts immediately, you have to
31728 use an indirect approach if you want to modify the contents of a header line.
31731 headers add "Old-Subject: $h_subject:"
31732 headers remove "Subject"
31733 headers add "Subject: new subject (was: $h_old-subject:)"
31734 headers remove "Old-Subject"
31739 .section "Setting an errors address in a system filter" "SECID217"
31740 .cindex "envelope sender"
31741 In a system filter, if a &%deliver%& command is followed by
31743 errors_to <some address>
31745 in order to change the envelope sender (and hence the error reporting) for that
31746 delivery, any address may be specified. (In a user filter, only the current
31747 user's address can be set.) For example, if some mail is being monitored, you
31750 unseen deliver monitor@spying.example errors_to root@local.example
31752 to take a copy which would not be sent back to the normal error reporting
31753 address if its delivery failed.
31757 .section "Per-address filtering" "SECTperaddfil"
31758 .vindex "&$domain$&"
31759 .vindex "&$local_part$&"
31760 In contrast to the system filter, which is run just once per message for each
31761 delivery attempt, it is also possible to set up a system-wide filtering
31762 operation that runs once for each recipient address. In this case, variables
31763 such as &$local_part$& and &$domain$& can be used, and indeed, the choice of
31764 filter file could be made dependent on them. This is an example of a router
31765 which implements such a filter:
31770 domains = +local_domains
31771 file = /central/filters/$local_part
31776 The filter is run in a separate process under its own uid. Therefore, either
31777 &%check_local_user%& must be set (as above), in which case the filter is run as
31778 the local user, or the &%user%& option must be used to specify which user to
31779 use. If both are set, &%user%& overrides.
31781 Care should be taken to ensure that none of the commands in the filter file
31782 specify a significant delivery if the message is to go on to be delivered to
31783 its intended recipient. The router will not then claim to have dealt with the
31784 address, so it will be passed on to subsequent routers to be delivered in the
31786 .ecindex IIDsysfil1
31787 .ecindex IIDsysfil2
31788 .ecindex IIDsysfil3
31795 . ////////////////////////////////////////////////////////////////////////////
31796 . ////////////////////////////////////////////////////////////////////////////
31798 .chapter "Message processing" "CHAPmsgproc"
31799 .scindex IIDmesproc "message" "general processing"
31800 Exim performs various transformations on the sender and recipient addresses of
31801 all messages that it handles, and also on the messages' header lines. Some of
31802 these are optional and configurable, while others always take place. All of
31803 this processing, except rewriting as a result of routing, and the addition or
31804 removal of header lines while delivering, happens when a message is received,
31805 before it is placed on Exim's queue.
31807 Some of the automatic processing takes place by default only for
31808 &"locally-originated"& messages. This adjective is used to describe messages
31809 that are not received over TCP/IP, but instead are passed to an Exim process on
31810 its standard input. This includes the interactive &"local SMTP"& case that is
31811 set up by the &%-bs%& command line option.
31813 &*Note*&: Messages received over TCP/IP on the loopback interface (127.0.0.1
31814 or ::1) are not considered to be locally-originated. Exim does not treat the
31815 loopback interface specially in any way.
31817 If you want the loopback interface to be treated specially, you must ensure
31818 that there are appropriate entries in your ACLs.
31823 .section "Submission mode for non-local messages" "SECTsubmodnon"
31824 .cindex "message" "submission"
31825 .cindex "submission mode"
31826 Processing that happens automatically for locally-originated messages (unless
31827 &%suppress_local_fixups%& is set) can also be requested for messages that are
31828 received over TCP/IP. The term &"submission mode"& is used to describe this
31829 state. Submission mode is set by the modifier
31831 control = submission
31833 in a MAIL, RCPT, or pre-data ACL for an incoming message (see sections
31834 &<<SECTACLmodi>>& and &<<SECTcontrols>>&). This makes Exim treat the message as
31835 a local submission, and is normally used when the source of the message is
31836 known to be an MUA running on a client host (as opposed to an MTA). For
31837 example, to set submission mode for messages originating on the IPv4 loopback
31838 interface, you could include the following in the MAIL ACL:
31840 warn hosts = 127.0.0.1
31841 control = submission
31843 .cindex "&%sender_retain%& submission option"
31844 There are some options that can be used when setting submission mode. A slash
31845 is used to separate options. For example:
31847 control = submission/sender_retain
31849 Specifying &%sender_retain%& has the effect of setting &%local_sender_retain%&
31850 true and &%local_from_check%& false for the current incoming message. The first
31851 of these allows an existing &'Sender:'& header in the message to remain, and
31852 the second suppresses the check to ensure that &'From:'& matches the
31853 authenticated sender. With this setting, Exim still fixes up messages by adding
31854 &'Date:'& and &'Message-ID:'& header lines if they are missing, but makes no
31855 attempt to check sender authenticity in header lines.
31857 When &%sender_retain%& is not set, a submission mode setting may specify a
31858 domain to be used when generating a &'From:'& or &'Sender:'& header line. For
31861 control = submission/domain=some.domain
31863 The domain may be empty. How this value is used is described in sections
31864 &<<SECTthefrohea>>& and &<<SECTthesenhea>>&. There is also a &%name%& option
31865 that allows you to specify the user's full name for inclusion in a created
31866 &'Sender:'& or &'From:'& header line. For example:
31868 accept authenticated = *
31869 control = submission/domain=wonderland.example/\
31870 name=${lookup {$authenticated_id} \
31871 lsearch {/etc/exim/namelist}}
31873 Because the name may contain any characters, including slashes, the &%name%&
31874 option must be given last. The remainder of the string is used as the name. For
31875 the example above, if &_/etc/exim/namelist_& contains:
31877 bigegg: Humpty Dumpty
31879 then when the sender has authenticated as &'bigegg'&, the generated &'Sender:'&
31882 Sender: Humpty Dumpty <bigegg@wonderland.example>
31884 .cindex "return path" "in submission mode"
31885 By default, submission mode forces the return path to the same address as is
31886 used to create the &'Sender:'& header. However, if &%sender_retain%& is
31887 specified, the return path is also left unchanged.
31889 &*Note*&: The changes caused by submission mode take effect after the predata
31890 ACL. This means that any sender checks performed before the fix-ups use the
31891 untrusted sender address specified by the user, not the trusted sender address
31892 specified by submission mode. Although this might be slightly unexpected, it
31893 does mean that you can configure ACL checks to spot that a user is trying to
31894 spoof another's address.
31896 .section "Line endings" "SECTlineendings"
31897 .cindex "line endings"
31898 .cindex "carriage return"
31900 RFC 2821 specifies that CRLF (two characters: carriage-return, followed by
31901 linefeed) is the line ending for messages transmitted over the Internet using
31902 SMTP over TCP/IP. However, within individual operating systems, different
31903 conventions are used. For example, Unix-like systems use just LF, but others
31904 use CRLF or just CR.
31906 Exim was designed for Unix-like systems, and internally, it stores messages
31907 using the system's convention of a single LF as a line terminator. When
31908 receiving a message, all line endings are translated to this standard format.
31909 Originally, it was thought that programs that passed messages directly to an
31910 MTA within an operating system would use that system's convention. Experience
31911 has shown that this is not the case; for example, there are Unix applications
31912 that use CRLF in this circumstance. For this reason, and for compatibility with
31913 other MTAs, the way Exim handles line endings for all messages is now as
31917 LF not preceded by CR is treated as a line ending.
31919 CR is treated as a line ending; if it is immediately followed by LF, the LF
31922 The sequence &"CR, dot, CR"& does not terminate an incoming SMTP message,
31923 nor a local message in the state where a line containing only a dot is a
31926 If a bare CR is encountered within a header line, an extra space is added after
31927 the line terminator so as not to end the header line. The reasoning behind this
31928 is that bare CRs in header lines are most likely either to be mistakes, or
31929 people trying to play silly games.
31931 If the first header line received in a message ends with CRLF, a subsequent
31932 bare LF in a header line is treated in the same way as a bare CR in a header
31940 .section "Unqualified addresses" "SECID218"
31941 .cindex "unqualified addresses"
31942 .cindex "address" "qualification"
31943 By default, Exim expects every envelope address it receives from an external
31944 host to be fully qualified. Unqualified addresses cause negative responses to
31945 SMTP commands. However, because SMTP is used as a means of transporting
31946 messages from MUAs running on personal workstations, there is sometimes a
31947 requirement to accept unqualified addresses from specific hosts or IP networks.
31949 Exim has two options that separately control which hosts may send unqualified
31950 sender or recipient addresses in SMTP commands, namely
31951 &%sender_unqualified_hosts%& and &%recipient_unqualified_hosts%&. In both
31952 cases, if an unqualified address is accepted, it is qualified by adding the
31953 value of &%qualify_domain%& or &%qualify_recipient%&, as appropriate.
31955 .oindex "&%qualify_domain%&"
31956 .oindex "&%qualify_recipient%&"
31957 Unqualified addresses in header lines are automatically qualified for messages
31958 that are locally originated, unless the &%-bnq%& option is given on the command
31959 line. For messages received over SMTP, unqualified addresses in header lines
31960 are qualified only if unqualified addresses are permitted in SMTP commands. In
31961 other words, such qualification is also controlled by
31962 &%sender_unqualified_hosts%& and &%recipient_unqualified_hosts%&,
31967 .section "The UUCP From line" "SECID219"
31968 .cindex "&""From""& line"
31969 .cindex "UUCP" "&""From""& line"
31970 .cindex "sender" "address"
31971 .oindex "&%uucp_from_pattern%&"
31972 .oindex "&%uucp_from_sender%&"
31973 .cindex "envelope sender"
31974 .cindex "Sendmail compatibility" "&""From""& line"
31975 Messages that have come from UUCP (and some other applications) often begin
31976 with a line containing the envelope sender and a timestamp, following the word
31977 &"From"&. Examples of two common formats are:
31979 From a.oakley@berlin.mus Fri Jan 5 12:35 GMT 1996
31980 From f.butler@berlin.mus Fri, 7 Jan 97 14:00:00 GMT
31982 This line precedes the RFC 2822 header lines. For compatibility with Sendmail,
31983 Exim recognizes such lines at the start of messages that are submitted to it
31984 via the command line (that is, on the standard input). It does not recognize
31985 such lines in incoming SMTP messages, unless the sending host matches
31986 &%ignore_fromline_hosts%& or the &%-bs%& option was used for a local message
31987 and &%ignore_fromline_local%& is set. The recognition is controlled by a
31988 regular expression that is defined by the &%uucp_from_pattern%& option, whose
31989 default value matches the two common cases shown above and puts the address
31990 that follows &"From"& into &$1$&.
31992 .cindex "numerical variables (&$1$& &$2$& etc)" "in &""From ""& line handling"
31993 When the caller of Exim for a non-SMTP message that contains a &"From"& line is
31994 a trusted user, the message's sender address is constructed by expanding the
31995 contents of &%uucp_sender_address%&, whose default value is &"$1"&. This is
31996 then parsed as an RFC 2822 address. If there is no domain, the local part is
31997 qualified with &%qualify_domain%& unless it is the empty string. However, if
31998 the command line &%-f%& option is used, it overrides the &"From"& line.
32000 If the caller of Exim is not trusted, the &"From"& line is recognized, but the
32001 sender address is not changed. This is also the case for incoming SMTP messages
32002 that are permitted to contain &"From"& lines.
32004 Only one &"From"& line is recognized. If there is more than one, the second is
32005 treated as a data line that starts the body of the message, as it is not valid
32006 as a header line. This also happens if a &"From"& line is present in an
32007 incoming SMTP message from a source that is not permitted to send them.
32011 .section "Resent- header lines" "SECID220"
32012 .cindex "&%Resent-%& header lines"
32013 RFC 2822 makes provision for sets of header lines starting with the string
32014 &`Resent-`& to be added to a message when it is resent by the original
32015 recipient to somebody else. These headers are &'Resent-Date:'&,
32016 &'Resent-From:'&, &'Resent-Sender:'&, &'Resent-To:'&, &'Resent-Cc:'&,
32017 &'Resent-Bcc:'& and &'Resent-Message-ID:'&. The RFC says:
32020 &'Resent fields are strictly informational. They MUST NOT be used in the normal
32021 processing of replies or other such automatic actions on messages.'&
32024 This leaves things a bit vague as far as other processing actions such as
32025 address rewriting are concerned. Exim treats &%Resent-%& header lines as
32029 A &'Resent-From:'& line that just contains the login id of the submitting user
32030 is automatically rewritten in the same way as &'From:'& (see below).
32032 If there's a rewriting rule for a particular header line, it is also applied to
32033 &%Resent-%& header lines of the same type. For example, a rule that rewrites
32034 &'From:'& also rewrites &'Resent-From:'&.
32036 For local messages, if &'Sender:'& is removed on input, &'Resent-Sender:'& is
32039 For a locally-submitted message,
32040 if there are any &%Resent-%& header lines but no &'Resent-Date:'&,
32041 &'Resent-From:'&, or &'Resent-Message-Id:'&, they are added as necessary. It is
32042 the contents of &'Resent-Message-Id:'& (rather than &'Message-Id:'&) which are
32043 included in log lines in this case.
32045 The logic for adding &'Sender:'& is duplicated for &'Resent-Sender:'& when any
32046 &%Resent-%& header lines are present.
32052 .section "The Auto-Submitted: header line" "SECID221"
32053 Whenever Exim generates an autoreply, a bounce, or a delay warning message, it
32054 includes the header line:
32056 Auto-Submitted: auto-replied
32059 .section "The Bcc: header line" "SECID222"
32060 .cindex "&'Bcc:'& header line"
32061 If Exim is called with the &%-t%& option, to take recipient addresses from a
32062 message's header, it removes any &'Bcc:'& header line that may exist (after
32063 extracting its addresses). If &%-t%& is not present on the command line, any
32064 existing &'Bcc:'& is not removed.
32067 .section "The Date: header line" "SECID223"
32068 .cindex "&'Date:'& header line"
32069 If a locally-generated or submission-mode message has no &'Date:'& header line,
32070 Exim adds one, using the current date and time, unless the
32071 &%suppress_local_fixups%& control has been specified.
32073 .section "The Delivery-date: header line" "SECID224"
32074 .cindex "&'Delivery-date:'& header line"
32075 .oindex "&%delivery_date_remove%&"
32076 &'Delivery-date:'& header lines are not part of the standard RFC 2822 header
32077 set. Exim can be configured to add them to the final delivery of messages. (See
32078 the generic &%delivery_date_add%& transport option.) They should not be present
32079 in messages in transit. If the &%delivery_date_remove%& configuration option is
32080 set (the default), Exim removes &'Delivery-date:'& header lines from incoming
32084 .section "The Envelope-to: header line" "SECID225"
32085 .cindex "&'Envelope-to:'& header line"
32086 .oindex "&%envelope_to_remove%&"
32087 &'Envelope-to:'& header lines are not part of the standard RFC 2822 header set.
32088 Exim can be configured to add them to the final delivery of messages. (See the
32089 generic &%envelope_to_add%& transport option.) They should not be present in
32090 messages in transit. If the &%envelope_to_remove%& configuration option is set
32091 (the default), Exim removes &'Envelope-to:'& header lines from incoming
32095 .section "The From: header line" "SECTthefrohea"
32096 .cindex "&'From:'& header line"
32097 .cindex "Sendmail compatibility" "&""From""& line"
32098 .cindex "message" "submission"
32099 .cindex "submission mode"
32100 If a submission-mode message does not contain a &'From:'& header line, Exim
32101 adds one if either of the following conditions is true:
32104 The envelope sender address is not empty (that is, this is not a bounce
32105 message). The added header line copies the envelope sender address.
32107 .vindex "&$authenticated_id$&"
32108 The SMTP session is authenticated and &$authenticated_id$& is not empty.
32110 .vindex "&$qualify_domain$&"
32111 If no domain is specified by the submission control, the local part is
32112 &$authenticated_id$& and the domain is &$qualify_domain$&.
32114 If a non-empty domain is specified by the submission control, the local
32115 part is &$authenticated_id$&, and the domain is the specified domain.
32117 If an empty domain is specified by the submission control,
32118 &$authenticated_id$& is assumed to be the complete address.
32122 A non-empty envelope sender takes precedence.
32124 If a locally-generated incoming message does not contain a &'From:'& header
32125 line, and the &%suppress_local_fixups%& control is not set, Exim adds one
32126 containing the sender's address. The calling user's login name and full name
32127 are used to construct the address, as described in section &<<SECTconstr>>&.
32128 They are obtained from the password data by calling &[getpwuid()]& (but see the
32129 &%unknown_login%& configuration option). The address is qualified with
32130 &%qualify_domain%&.
32132 For compatibility with Sendmail, if an incoming, non-SMTP message has a
32133 &'From:'& header line containing just the unqualified login name of the calling
32134 user, this is replaced by an address containing the user's login name and full
32135 name as described in section &<<SECTconstr>>&.
32138 .section "The Message-ID: header line" "SECID226"
32139 .cindex "&'Message-ID:'& header line"
32140 .cindex "message" "submission"
32141 .oindex "&%message_id_header_text%&"
32142 If a locally-generated or submission-mode incoming message does not contain a
32143 &'Message-ID:'& or &'Resent-Message-ID:'& header line, and the
32144 &%suppress_local_fixups%& control is not set, Exim adds a suitable header line
32145 to the message. If there are any &'Resent-:'& headers in the message, it
32146 creates &'Resent-Message-ID:'&. The id is constructed from Exim's internal
32147 message id, preceded by the letter E to ensure it starts with a letter, and
32148 followed by @ and the primary host name. Additional information can be included
32149 in this header line by setting the &%message_id_header_text%& and/or
32150 &%message_id_header_domain%& options.
32153 .section "The Received: header line" "SECID227"
32154 .cindex "&'Received:'& header line"
32155 A &'Received:'& header line is added at the start of every message. The
32156 contents are defined by the &%received_header_text%& configuration option, and
32157 Exim automatically adds a semicolon and a timestamp to the configured string.
32159 The &'Received:'& header is generated as soon as the message's header lines
32160 have been received. At this stage, the timestamp in the &'Received:'& header
32161 line is the time that the message started to be received. This is the value
32162 that is seen by the DATA ACL and by the &[local_scan()]& function.
32164 Once a message is accepted, the timestamp in the &'Received:'& header line is
32165 changed to the time of acceptance, which is (apart from a small delay while the
32166 -H spool file is written) the earliest time at which delivery could start.
32169 .section "The References: header line" "SECID228"
32170 .cindex "&'References:'& header line"
32171 Messages created by the &(autoreply)& transport include a &'References:'&
32172 header line. This is constructed according to the rules that are described in
32173 section 3.64 of RFC 2822 (which states that replies should contain such a
32174 header line), and section 3.14 of RFC 3834 (which states that automatic
32175 responses are not different in this respect). However, because some mail
32176 processing software does not cope well with very long header lines, no more
32177 than 12 message IDs are copied from the &'References:'& header line in the
32178 incoming message. If there are more than 12, the first one and then the final
32179 11 are copied, before adding the message ID of the incoming message.
32183 .section "The Return-path: header line" "SECID229"
32184 .cindex "&'Return-path:'& header line"
32185 .oindex "&%return_path_remove%&"
32186 &'Return-path:'& header lines are defined as something an MTA may insert when
32187 it does the final delivery of messages. (See the generic &%return_path_add%&
32188 transport option.) Therefore, they should not be present in messages in
32189 transit. If the &%return_path_remove%& configuration option is set (the
32190 default), Exim removes &'Return-path:'& header lines from incoming messages.
32194 .section "The Sender: header line" "SECTthesenhea"
32195 .cindex "&'Sender:'& header line"
32196 .cindex "message" "submission"
32197 For a locally-originated message from an untrusted user, Exim may remove an
32198 existing &'Sender:'& header line, and it may add a new one. You can modify
32199 these actions by setting the &%local_sender_retain%& option true, the
32200 &%local_from_check%& option false, or by using the &%suppress_local_fixups%&
32203 When a local message is received from an untrusted user and
32204 &%local_from_check%& is true (the default), and the &%suppress_local_fixups%&
32205 control has not been set, a check is made to see if the address given in the
32206 &'From:'& header line is the correct (local) sender of the message. The address
32207 that is expected has the login name as the local part and the value of
32208 &%qualify_domain%& as the domain. Prefixes and suffixes for the local part can
32209 be permitted by setting &%local_from_prefix%& and &%local_from_suffix%&
32210 appropriately. If &'From:'& does not contain the correct sender, a &'Sender:'&
32211 line is added to the message.
32213 If you set &%local_from_check%& false, this checking does not occur. However,
32214 the removal of an existing &'Sender:'& line still happens, unless you also set
32215 &%local_sender_retain%& to be true. It is not possible to set both of these
32216 options true at the same time.
32218 .cindex "submission mode"
32219 By default, no processing of &'Sender:'& header lines is done for messages
32220 received over TCP/IP or for messages submitted by trusted users. However, when
32221 a message is received over TCP/IP in submission mode, and &%sender_retain%& is
32222 not specified on the submission control, the following processing takes place:
32224 .vindex "&$authenticated_id$&"
32225 First, any existing &'Sender:'& lines are removed. Then, if the SMTP session is
32226 authenticated, and &$authenticated_id$& is not empty, a sender address is
32227 created as follows:
32230 .vindex "&$qualify_domain$&"
32231 If no domain is specified by the submission control, the local part is
32232 &$authenticated_id$& and the domain is &$qualify_domain$&.
32234 If a non-empty domain is specified by the submission control, the local part
32235 is &$authenticated_id$&, and the domain is the specified domain.
32237 If an empty domain is specified by the submission control,
32238 &$authenticated_id$& is assumed to be the complete address.
32241 This address is compared with the address in the &'From:'& header line. If they
32242 are different, a &'Sender:'& header line containing the created address is
32243 added. Prefixes and suffixes for the local part in &'From:'& can be permitted
32244 by setting &%local_from_prefix%& and &%local_from_suffix%& appropriately.
32246 .cindex "return path" "created from &'Sender:'&"
32247 &*Note*&: Whenever a &'Sender:'& header line is created, the return path for
32248 the message (the envelope sender address) is changed to be the same address,
32249 except in the case of submission mode when &%sender_retain%& is specified.
32253 .section "Adding and removing header lines in routers and transports" &&&
32254 "SECTheadersaddrem"
32255 .cindex "header lines" "adding; in router or transport"
32256 .cindex "header lines" "removing; in router or transport"
32257 When a message is delivered, the addition and removal of header lines can be
32258 specified in a system filter, or on any of the routers and transports that
32259 process the message. Section &<<SECTaddremheasys>>& contains details about
32260 modifying headers in a system filter. Header lines can also be added in an ACL
32261 as a message is received (see section &<<SECTaddheadacl>>&).
32263 In contrast to what happens in a system filter, header modifications that are
32264 specified on routers and transports apply only to the particular recipient
32265 addresses that are being processed by those routers and transports. These
32266 changes do not actually take place until a copy of the message is being
32267 transported. Therefore, they do not affect the basic set of header lines, and
32268 they do not affect the values of the variables that refer to header lines.
32270 &*Note*&: In particular, this means that any expansions in the configuration of
32271 the transport cannot refer to the modified header lines, because such
32272 expansions all occur before the message is actually transported.
32274 For both routers and transports, the argument of a &%headers_add%&
32275 option must be in the form of one or more RFC 2822 header lines, separated by
32276 newlines (coded as &"\n"&). For example:
32278 headers_add = X-added-header: added by $primary_hostname\n\
32279 X-added-second: another added header line
32281 Exim does not check the syntax of these added header lines.
32283 Multiple &%headers_add%& options for a single router or transport can be
32284 specified; the values will append to a single list of header lines.
32285 Each header-line is separately expanded.
32287 The argument of a &%headers_remove%& option must consist of a colon-separated
32288 list of header names. This is confusing, because header names themselves are
32289 often terminated by colons. In this case, the colons are the list separators,
32290 not part of the names. For example:
32292 headers_remove = return-receipt-to:acknowledge-to
32295 Multiple &%headers_remove%& options for a single router or transport can be
32296 specified; the arguments will append to a single header-names list.
32297 Each item is separately expanded.
32299 When &%headers_add%& or &%headers_remove%& is specified on a router,
32300 items are expanded at routing time,
32301 and then associated with all addresses that are
32302 accepted by that router, and also with any new addresses that it generates. If
32303 an address passes through several routers as a result of aliasing or
32304 forwarding, the changes are cumulative.
32306 .oindex "&%unseen%&"
32307 However, this does not apply to multiple routers that result from the use of
32308 the &%unseen%& option. Any header modifications that were specified by the
32309 &"unseen"& router or its predecessors apply only to the &"unseen"& delivery.
32311 Addresses that end up with different &%headers_add%& or &%headers_remove%&
32312 settings cannot be delivered together in a batch, so a transport is always
32313 dealing with a set of addresses that have the same header-processing
32316 The transport starts by writing the original set of header lines that arrived
32317 with the message, possibly modified by the system filter. As it writes out
32318 these lines, it consults the list of header names that were attached to the
32319 recipient address(es) by &%headers_remove%& options in routers, and it also
32320 consults the transport's own &%headers_remove%& option. Header lines whose
32321 names are on either of these lists are not written out. If there are multiple
32322 instances of any listed header, they are all skipped.
32324 After the remaining original header lines have been written, new header
32325 lines that were specified by routers' &%headers_add%& options are written, in
32326 the order in which they were attached to the address. These are followed by any
32327 header lines specified by the transport's &%headers_add%& option.
32329 This way of handling header line modifications in routers and transports has
32330 the following consequences:
32333 The original set of header lines, possibly modified by the system filter,
32334 remains &"visible"&, in the sense that the &$header_$&&'xxx'& variables refer
32335 to it, at all times.
32337 Header lines that are added by a router's
32338 &%headers_add%& option are not accessible by means of the &$header_$&&'xxx'&
32339 expansion syntax in subsequent routers or the transport.
32341 Conversely, header lines that are specified for removal by &%headers_remove%&
32342 in a router remain visible to subsequent routers and the transport.
32344 Headers added to an address by &%headers_add%& in a router cannot be removed by
32345 a later router or by a transport.
32347 An added header can refer to the contents of an original header that is to be
32348 removed, even it has the same name as the added header. For example:
32350 headers_remove = subject
32351 headers_add = Subject: new subject (was: $h_subject:)
32355 &*Warning*&: The &%headers_add%& and &%headers_remove%& options cannot be used
32356 for a &(redirect)& router that has the &%one_time%& option set.
32362 .section "Constructed addresses" "SECTconstr"
32363 .cindex "address" "constructed"
32364 .cindex "constructed address"
32365 When Exim constructs a sender address for a locally-generated message, it uses
32368 <&'user name'&>&~&~<&'login'&&`@`&&'qualify_domain'&>
32372 Zaphod Beeblebrox <zaphod@end.univ.example>
32374 The user name is obtained from the &%-F%& command line option if set, or
32375 otherwise by looking up the calling user by &[getpwuid()]& and extracting the
32376 &"gecos"& field from the password entry. If the &"gecos"& field contains an
32377 ampersand character, this is replaced by the login name with the first letter
32378 upper cased, as is conventional in a number of operating systems. See the
32379 &%gecos_name%& option for a way to tailor the handling of the &"gecos"& field.
32380 The &%unknown_username%& option can be used to specify user names in cases when
32381 there is no password file entry.
32384 In all cases, the user name is made to conform to RFC 2822 by quoting all or
32385 parts of it if necessary. In addition, if it contains any non-printing
32386 characters, it is encoded as described in RFC 2047, which defines a way of
32387 including non-ASCII characters in header lines. The value of the
32388 &%headers_charset%& option specifies the name of the encoding that is used (the
32389 characters are assumed to be in this encoding). The setting of
32390 &%print_topbitchars%& controls whether characters with the top bit set (that
32391 is, with codes greater than 127) count as printing characters or not.
32395 .section "Case of local parts" "SECID230"
32396 .cindex "case of local parts"
32397 .cindex "local part" "case of"
32398 RFC 2822 states that the case of letters in the local parts of addresses cannot
32399 be assumed to be non-significant. Exim preserves the case of local parts of
32400 addresses, but by default it uses a lower-cased form when it is routing,
32401 because on most Unix systems, usernames are in lower case and case-insensitive
32402 routing is required. However, any particular router can be made to use the
32403 original case for local parts by setting the &%caseful_local_part%& generic
32406 .cindex "mixed-case login names"
32407 If you must have mixed-case user names on your system, the best way to proceed,
32408 assuming you want case-independent handling of incoming email, is to set up
32409 your first router to convert incoming local parts in your domains to the
32410 correct case by means of a file lookup. For example:
32414 domains = +local_domains
32415 data = ${lookup{$local_part}cdb\
32416 {/etc/usercased.cdb}{$value}fail}\
32419 For this router, the local part is forced to lower case by the default action
32420 (&%caseful_local_part%& is not set). The lower-cased local part is used to look
32421 up a new local part in the correct case. If you then set &%caseful_local_part%&
32422 on any subsequent routers which process your domains, they will operate on
32423 local parts with the correct case in a case-sensitive manner.
32427 .section "Dots in local parts" "SECID231"
32428 .cindex "dot" "in local part"
32429 .cindex "local part" "dots in"
32430 RFC 2822 forbids empty components in local parts. That is, an unquoted local
32431 part may not begin or end with a dot, nor have two consecutive dots in the
32432 middle. However, it seems that many MTAs do not enforce this, so Exim permits
32433 empty components for compatibility.
32437 .section "Rewriting addresses" "SECID232"
32438 .cindex "rewriting" "addresses"
32439 Rewriting of sender and recipient addresses, and addresses in headers, can
32440 happen automatically, or as the result of configuration options, as described
32441 in chapter &<<CHAPrewrite>>&. The headers that may be affected by this are
32442 &'Bcc:'&, &'Cc:'&, &'From:'&, &'Reply-To:'&, &'Sender:'&, and &'To:'&.
32444 Automatic rewriting includes qualification, as mentioned above. The other case
32445 in which it can happen is when an incomplete non-local domain is given. The
32446 routing process may cause this to be expanded into the full domain name. For
32447 example, a header such as
32451 might get rewritten as
32453 To: hare@teaparty.wonderland.fict.example
32455 Rewriting as a result of routing is the one kind of message processing that
32456 does not happen at input time, as it cannot be done until the address has
32459 Strictly, one should not do &'any'& deliveries of a message until all its
32460 addresses have been routed, in case any of the headers get changed as a
32461 result of routing. However, doing this in practice would hold up many
32462 deliveries for unreasonable amounts of time, just because one address could not
32463 immediately be routed. Exim therefore does not delay other deliveries when
32464 routing of one or more addresses is deferred.
32465 .ecindex IIDmesproc
32469 . ////////////////////////////////////////////////////////////////////////////
32470 . ////////////////////////////////////////////////////////////////////////////
32472 .chapter "SMTP processing" "CHAPSMTP"
32473 .scindex IIDsmtpproc1 "SMTP" "processing details"
32474 .scindex IIDsmtpproc2 "LMTP" "processing details"
32475 Exim supports a number of different ways of using the SMTP protocol, and its
32476 LMTP variant, which is an interactive protocol for transferring messages into a
32477 closed mail store application. This chapter contains details of how SMTP is
32478 processed. For incoming mail, the following are available:
32481 SMTP over TCP/IP (Exim daemon or &'inetd'&);
32483 SMTP over the standard input and output (the &%-bs%& option);
32485 Batched SMTP on the standard input (the &%-bS%& option).
32488 For mail delivery, the following are available:
32491 SMTP over TCP/IP (the &(smtp)& transport);
32493 LMTP over TCP/IP (the &(smtp)& transport with the &%protocol%& option set to
32496 LMTP over a pipe to a process running in the local host (the &(lmtp)&
32499 Batched SMTP to a file or pipe (the &(appendfile)& and &(pipe)& transports with
32500 the &%use_bsmtp%& option set).
32503 &'Batched SMTP'& is the name for a process in which batches of messages are
32504 stored in or read from files (or pipes), in a format in which SMTP commands are
32505 used to contain the envelope information.
32509 .section "Outgoing SMTP and LMTP over TCP/IP" "SECToutSMTPTCP"
32510 .cindex "SMTP" "outgoing over TCP/IP"
32511 .cindex "outgoing SMTP over TCP/IP"
32512 .cindex "LMTP" "over TCP/IP"
32513 .cindex "outgoing LMTP over TCP/IP"
32516 .cindex "SIZE option on MAIL command"
32517 Outgoing SMTP and LMTP over TCP/IP is implemented by the &(smtp)& transport.
32518 The &%protocol%& option selects which protocol is to be used, but the actual
32519 processing is the same in both cases.
32521 If, in response to its EHLO command, Exim is told that the SIZE
32522 parameter is supported, it adds SIZE=<&'n'&> to each subsequent MAIL
32523 command. The value of <&'n'&> is the message size plus the value of the
32524 &%size_addition%& option (default 1024) to allow for additions to the message
32525 such as per-transport header lines, or changes made in a
32526 .cindex "transport" "filter"
32527 .cindex "filter" "transport filter"
32528 transport filter. If &%size_addition%& is set negative, the use of SIZE is
32531 If the remote server advertises support for PIPELINING, Exim uses the
32532 pipelining extension to SMTP (RFC 2197) to reduce the number of TCP/IP packets
32533 required for the transaction.
32535 If the remote server advertises support for the STARTTLS command, and Exim
32536 was built to support TLS encryption, it tries to start a TLS session unless the
32537 server matches &%hosts_avoid_tls%&. See chapter &<<CHAPTLS>>& for more details.
32538 Either a match in that or &%hosts_verify_avoid_tls%& apply when the transport
32539 is called for verification.
32541 If the remote server advertises support for the AUTH command, Exim scans
32542 the authenticators configuration for any suitable client settings, as described
32543 in chapter &<<CHAPSMTPAUTH>>&.
32545 .cindex "carriage return"
32547 Responses from the remote host are supposed to be terminated by CR followed by
32548 LF. However, there are known to be hosts that do not send CR characters, so in
32549 order to be able to interwork with such hosts, Exim treats LF on its own as a
32552 If a message contains a number of different addresses, all those with the same
32553 characteristics (for example, the same envelope sender) that resolve to the
32554 same set of hosts, in the same order, are sent in a single SMTP transaction,
32555 even if they are for different domains, unless there are more than the setting
32556 of the &%max_rcpt%&s option in the &(smtp)& transport allows, in which case
32557 they are split into groups containing no more than &%max_rcpt%&s addresses
32558 each. If &%remote_max_parallel%& is greater than one, such groups may be sent
32559 in parallel sessions. The order of hosts with identical MX values is not
32560 significant when checking whether addresses can be batched in this way.
32562 When the &(smtp)& transport suffers a temporary failure that is not
32563 message-related, Exim updates its transport-specific database, which contains
32564 records indexed by host name that remember which messages are waiting for each
32565 particular host. It also updates the retry database with new retry times.
32567 .cindex "hints database" "retry keys"
32568 Exim's retry hints are based on host name plus IP address, so if one address of
32569 a multi-homed host is broken, it will soon be skipped most of the time.
32570 See the next section for more detail about error handling.
32572 .cindex "SMTP" "passed connection"
32573 .cindex "SMTP" "batching over TCP/IP"
32574 When a message is successfully delivered over a TCP/IP SMTP connection, Exim
32575 looks in the hints database for the transport to see if there are any queued
32576 messages waiting for the host to which it is connected. If it finds one, it
32577 creates a new Exim process using the &%-MC%& option (which can only be used by
32578 a process running as root or the Exim user) and passes the TCP/IP socket to it
32579 so that it can deliver another message using the same socket. The new process
32580 does only those deliveries that are routed to the connected host, and may in
32581 turn pass the socket on to a third process, and so on.
32583 The &%connection_max_messages%& option of the &(smtp)& transport can be used to
32584 limit the number of messages sent down a single TCP/IP connection.
32586 .cindex "asterisk" "after IP address"
32587 The second and subsequent messages delivered down an existing connection are
32588 identified in the main log by the addition of an asterisk after the closing
32589 square bracket of the IP address.
32594 .section "Errors in outgoing SMTP" "SECToutSMTPerr"
32595 .cindex "error" "in outgoing SMTP"
32596 .cindex "SMTP" "errors in outgoing"
32597 .cindex "host" "error"
32598 Three different kinds of error are recognized for outgoing SMTP: host errors,
32599 message errors, and recipient errors.
32602 .vitem "&*Host errors*&"
32603 A host error is not associated with a particular message or with a
32604 particular recipient of a message. The host errors are:
32607 Connection refused or timed out,
32609 Any error response code on connection,
32611 Any error response code to EHLO or HELO,
32613 Loss of connection at any time, except after &"."&,
32615 I/O errors at any time,
32617 Timeouts during the session, other than in response to MAIL, RCPT or
32618 the &"."& at the end of the data.
32621 For a host error, a permanent error response on connection, or in response to
32622 EHLO, causes all addresses routed to the host to be failed. Any other host
32623 error causes all addresses to be deferred, and retry data to be created for the
32624 host. It is not tried again, for any message, until its retry time arrives. If
32625 the current set of addresses are not all delivered in this run (to some
32626 alternative host), the message is added to the list of those waiting for this
32627 host, so if it is still undelivered when a subsequent successful delivery is
32628 made to the host, it will be sent down the same SMTP connection.
32630 .vitem "&*Message errors*&"
32631 .cindex "message" "error"
32632 A message error is associated with a particular message when sent to a
32633 particular host, but not with a particular recipient of the message. The
32634 message errors are:
32637 Any error response code to MAIL, DATA, or the &"."& that terminates
32640 Timeout after MAIL,
32642 Timeout or loss of connection after the &"."& that terminates the data. A
32643 timeout after the DATA command itself is treated as a host error, as is loss of
32644 connection at any other time.
32647 For a message error, a permanent error response (5&'xx'&) causes all addresses
32648 to be failed, and a delivery error report to be returned to the sender. A
32649 temporary error response (4&'xx'&), or one of the timeouts, causes all
32650 addresses to be deferred. Retry data is not created for the host, but instead,
32651 a retry record for the combination of host plus message id is created. The
32652 message is not added to the list of those waiting for this host. This ensures
32653 that the failing message will not be sent to this host again until the retry
32654 time arrives. However, other messages that are routed to the host are not
32655 affected, so if it is some property of the message that is causing the error,
32656 it will not stop the delivery of other mail.
32658 If the remote host specified support for the SIZE parameter in its response
32659 to EHLO, Exim adds SIZE=&'nnn'& to the MAIL command, so an
32660 over-large message will cause a message error because the error arrives as a
32663 .vitem "&*Recipient errors*&"
32664 .cindex "recipient" "error"
32665 A recipient error is associated with a particular recipient of a message. The
32666 recipient errors are:
32669 Any error response to RCPT,
32671 Timeout after RCPT.
32674 For a recipient error, a permanent error response (5&'xx'&) causes the
32675 recipient address to be failed, and a bounce message to be returned to the
32676 sender. A temporary error response (4&'xx'&) or a timeout causes the failing
32677 address to be deferred, and routing retry data to be created for it. This is
32678 used to delay processing of the address in subsequent queue runs, until its
32679 routing retry time arrives. This applies to all messages, but because it
32680 operates only in queue runs, one attempt will be made to deliver a new message
32681 to the failing address before the delay starts to operate. This ensures that,
32682 if the failure is really related to the message rather than the recipient
32683 (&"message too big for this recipient"& is a possible example), other messages
32684 have a chance of getting delivered. If a delivery to the address does succeed,
32685 the retry information gets cleared, so all stuck messages get tried again, and
32686 the retry clock is reset.
32688 The message is not added to the list of those waiting for this host. Use of the
32689 host for other messages is unaffected, and except in the case of a timeout,
32690 other recipients are processed independently, and may be successfully delivered
32691 in the current SMTP session. After a timeout it is of course impossible to
32692 proceed with the session, so all addresses get deferred. However, those other
32693 than the one that failed do not suffer any subsequent retry delays. Therefore,
32694 if one recipient is causing trouble, the others have a chance of getting
32695 through when a subsequent delivery attempt occurs before the failing
32696 recipient's retry time.
32699 In all cases, if there are other hosts (or IP addresses) available for the
32700 current set of addresses (for example, from multiple MX records), they are
32701 tried in this run for any undelivered addresses, subject of course to their
32702 own retry data. In other words, recipient error retry data does not take effect
32703 until the next delivery attempt.
32705 Some hosts have been observed to give temporary error responses to every
32706 MAIL command at certain times (&"insufficient space"& has been seen). It
32707 would be nice if such circumstances could be recognized, and defer data for the
32708 host itself created, but this is not possible within the current Exim design.
32709 What actually happens is that retry data for every (host, message) combination
32712 The reason that timeouts after MAIL and RCPT are treated specially is that
32713 these can sometimes arise as a result of the remote host's verification
32714 procedures. Exim makes this assumption, and treats them as if a temporary error
32715 response had been received. A timeout after &"."& is treated specially because
32716 it is known that some broken implementations fail to recognize the end of the
32717 message if the last character of the last line is a binary zero. Thus, it is
32718 helpful to treat this case as a message error.
32720 Timeouts at other times are treated as host errors, assuming a problem with the
32721 host, or the connection to it. If a timeout after MAIL, RCPT,
32722 or &"."& is really a connection problem, the assumption is that at the next try
32723 the timeout is likely to occur at some other point in the dialogue, causing it
32724 then to be treated as a host error.
32726 There is experimental evidence that some MTAs drop the connection after the
32727 terminating &"."& if they do not like the contents of the message for some
32728 reason, in contravention of the RFC, which indicates that a 5&'xx'& response
32729 should be given. That is why Exim treats this case as a message rather than a
32730 host error, in order not to delay other messages to the same host.
32735 .section "Incoming SMTP messages over TCP/IP" "SECID233"
32736 .cindex "SMTP" "incoming over TCP/IP"
32737 .cindex "incoming SMTP over TCP/IP"
32740 Incoming SMTP messages can be accepted in one of two ways: by running a
32741 listening daemon, or by using &'inetd'&. In the latter case, the entry in
32742 &_/etc/inetd.conf_& should be like this:
32744 smtp stream tcp nowait exim /opt/exim/bin/exim in.exim -bs
32746 Exim distinguishes between this case and the case of a locally running user
32747 agent using the &%-bs%& option by checking whether or not the standard input is
32748 a socket. When it is, either the port must be privileged (less than 1024), or
32749 the caller must be root or the Exim user. If any other user passes a socket
32750 with an unprivileged port number, Exim prints a message on the standard error
32751 stream and exits with an error code.
32753 By default, Exim does not make a log entry when a remote host connects or
32754 disconnects (either via the daemon or &'inetd'&), unless the disconnection is
32755 unexpected. It can be made to write such log entries by setting the
32756 &%smtp_connection%& log selector.
32758 .cindex "carriage return"
32760 Commands from the remote host are supposed to be terminated by CR followed by
32761 LF. However, there are known to be hosts that do not send CR characters. In
32762 order to be able to interwork with such hosts, Exim treats LF on its own as a
32764 Furthermore, because common code is used for receiving messages from all
32765 sources, a CR on its own is also interpreted as a line terminator. However, the
32766 sequence &"CR, dot, CR"& does not terminate incoming SMTP data.
32768 .cindex "EHLO" "invalid data"
32769 .cindex "HELO" "invalid data"
32770 One area that sometimes gives rise to problems concerns the EHLO or
32771 HELO commands. Some clients send syntactically invalid versions of these
32772 commands, which Exim rejects by default. (This is nothing to do with verifying
32773 the data that is sent, so &%helo_verify_hosts%& is not relevant.) You can tell
32774 Exim not to apply a syntax check by setting &%helo_accept_junk_hosts%& to
32775 match the broken hosts that send invalid commands.
32777 .cindex "SIZE option on MAIL command"
32778 .cindex "MAIL" "SIZE option"
32779 The amount of disk space available is checked whenever SIZE is received on
32780 a MAIL command, independently of whether &%message_size_limit%& or
32781 &%check_spool_space%& is configured, unless &%smtp_check_spool_space%& is set
32782 false. A temporary error is given if there is not enough space. If
32783 &%check_spool_space%& is set, the check is for that amount of space plus the
32784 value given with SIZE, that is, it checks that the addition of the incoming
32785 message will not reduce the space below the threshold.
32787 When a message is successfully received, Exim includes the local message id in
32788 its response to the final &"."& that terminates the data. If the remote host
32789 logs this text it can help with tracing what has happened to a message.
32791 The Exim daemon can limit the number of simultaneous incoming connections it is
32792 prepared to handle (see the &%smtp_accept_max%& option). It can also limit the
32793 number of simultaneous incoming connections from a single remote host (see the
32794 &%smtp_accept_max_per_host%& option). Additional connection attempts are
32795 rejected using the SMTP temporary error code 421.
32797 The Exim daemon does not rely on the SIGCHLD signal to detect when a
32798 subprocess has finished, as this can get lost at busy times. Instead, it looks
32799 for completed subprocesses every time it wakes up. Provided there are other
32800 things happening (new incoming calls, starts of queue runs), completed
32801 processes will be noticed and tidied away. On very quiet systems you may
32802 sometimes see a &"defunct"& Exim process hanging about. This is not a problem;
32803 it will be noticed when the daemon next wakes up.
32805 When running as a daemon, Exim can reserve some SMTP slots for specific hosts,
32806 and can also be set up to reject SMTP calls from non-reserved hosts at times of
32807 high system load &-- for details see the &%smtp_accept_reserve%&,
32808 &%smtp_load_reserve%&, and &%smtp_reserve_hosts%& options. The load check
32809 applies in both the daemon and &'inetd'& cases.
32811 Exim normally starts a delivery process for each message received, though this
32812 can be varied by means of the &%-odq%& command line option and the
32813 &%queue_only%&, &%queue_only_file%&, and &%queue_only_load%& options. The
32814 number of simultaneously running delivery processes started in this way from
32815 SMTP input can be limited by the &%smtp_accept_queue%& and
32816 &%smtp_accept_queue_per_connection%& options. When either limit is reached,
32817 subsequently received messages are just put on the input queue without starting
32818 a delivery process.
32820 The controls that involve counts of incoming SMTP calls (&%smtp_accept_max%&,
32821 &%smtp_accept_queue%&, &%smtp_accept_reserve%&) are not available when Exim is
32822 started up from the &'inetd'& daemon, because in that case each connection is
32823 handled by an entirely independent Exim process. Control by load average is,
32824 however, available with &'inetd'&.
32826 Exim can be configured to verify addresses in incoming SMTP commands as they
32827 are received. See chapter &<<CHAPACL>>& for details. It can also be configured
32828 to rewrite addresses at this time &-- before any syntax checking is done. See
32829 section &<<SECTrewriteS>>&.
32831 Exim can also be configured to limit the rate at which a client host submits
32832 MAIL and RCPT commands in a single SMTP session. See the
32833 &%smtp_ratelimit_hosts%& option.
32837 .section "Unrecognized SMTP commands" "SECID234"
32838 .cindex "SMTP" "unrecognized commands"
32839 If Exim receives more than &%smtp_max_unknown_commands%& unrecognized SMTP
32840 commands during a single SMTP connection, it drops the connection after sending
32841 the error response to the last command. The default value for
32842 &%smtp_max_unknown_commands%& is 3. This is a defence against some kinds of
32843 abuse that subvert web servers into making connections to SMTP ports; in these
32844 circumstances, a number of non-SMTP lines are sent first.
32847 .section "Syntax and protocol errors in SMTP commands" "SECID235"
32848 .cindex "SMTP" "syntax errors"
32849 .cindex "SMTP" "protocol errors"
32850 A syntax error is detected if an SMTP command is recognized, but there is
32851 something syntactically wrong with its data, for example, a malformed email
32852 address in a RCPT command. Protocol errors include invalid command
32853 sequencing such as RCPT before MAIL. If Exim receives more than
32854 &%smtp_max_synprot_errors%& such commands during a single SMTP connection, it
32855 drops the connection after sending the error response to the last command. The
32856 default value for &%smtp_max_synprot_errors%& is 3. This is a defence against
32857 broken clients that loop sending bad commands (yes, it has been seen).
32861 .section "Use of non-mail SMTP commands" "SECID236"
32862 .cindex "SMTP" "non-mail commands"
32863 The &"non-mail"& SMTP commands are those other than MAIL, RCPT, and
32864 DATA. Exim counts such commands, and drops the connection if there are too
32865 many of them in a single SMTP session. This action catches some
32866 denial-of-service attempts and things like repeated failing AUTHs, or a mad
32867 client looping sending EHLO. The global option &%smtp_accept_max_nonmail%&
32868 defines what &"too many"& means. Its default value is 10.
32870 When a new message is expected, one occurrence of RSET is not counted. This
32871 allows a client to send one RSET between messages (this is not necessary,
32872 but some clients do it). Exim also allows one uncounted occurrence of HELO
32873 or EHLO, and one occurrence of STARTTLS between messages. After
32874 starting up a TLS session, another EHLO is expected, and so it too is not
32877 The first occurrence of AUTH in a connection, or immediately following
32878 STARTTLS is also not counted. Otherwise, all commands other than MAIL,
32879 RCPT, DATA, and QUIT are counted.
32881 You can control which hosts are subject to the limit set by
32882 &%smtp_accept_max_nonmail%& by setting
32883 &%smtp_accept_max_nonmail_hosts%&. The default value is &`*`&, which makes
32884 the limit apply to all hosts. This option means that you can exclude any
32885 specific badly-behaved hosts that you have to live with.
32890 .section "The VRFY and EXPN commands" "SECID237"
32891 When Exim receives a VRFY or EXPN command on a TCP/IP connection, it
32892 runs the ACL specified by &%acl_smtp_vrfy%& or &%acl_smtp_expn%& (as
32893 appropriate) in order to decide whether the command should be accepted or not.
32894 If no ACL is defined, the command is rejected.
32896 .cindex "VRFY" "processing"
32897 When VRFY is accepted, it runs exactly the same code as when Exim is
32898 called with the &%-bv%& option.
32900 .cindex "EXPN" "processing"
32901 When EXPN is accepted, a single-level expansion of the address is done.
32902 EXPN is treated as an &"address test"& (similar to the &%-bt%& option) rather
32903 than a verification (the &%-bv%& option). If an unqualified local part is given
32904 as the argument to EXPN, it is qualified with &%qualify_domain%&. Rejections
32905 of VRFY and EXPN commands are logged on the main and reject logs, and
32906 VRFY verification failures are logged on the main log for consistency with
32911 .section "The ETRN command" "SECTETRN"
32912 .cindex "ETRN" "processing"
32913 RFC 1985 describes an SMTP command called ETRN that is designed to
32914 overcome the security problems of the TURN command (which has fallen into
32915 disuse). When Exim receives an ETRN command on a TCP/IP connection, it runs
32916 the ACL specified by &%acl_smtp_etrn%& in order to decide whether the command
32917 should be accepted or not. If no ACL is defined, the command is rejected.
32919 The ETRN command is concerned with &"releasing"& messages that are awaiting
32920 delivery to certain hosts. As Exim does not organize its message queue by host,
32921 the only form of ETRN that is supported by default is the one where the
32922 text starts with the &"#"& prefix, in which case the remainder of the text is
32923 specific to the SMTP server. A valid ETRN command causes a run of Exim with
32924 the &%-R%& option to happen, with the remainder of the ETRN text as its
32925 argument. For example,
32933 which causes a delivery attempt on all messages with undelivered addresses
32934 containing the text &"brigadoon"&. When &%smtp_etrn_serialize%& is set (the
32935 default), Exim prevents the simultaneous execution of more than one queue run
32936 for the same argument string as a result of an ETRN command. This stops
32937 a misbehaving client from starting more than one queue runner at once.
32939 .cindex "hints database" "ETRN serialization"
32940 Exim implements the serialization by means of a hints database in which a
32941 record is written whenever a process is started by ETRN, and deleted when
32942 the process completes. However, Exim does not keep the SMTP session waiting for
32943 the ETRN process to complete. Once ETRN is accepted, the client is sent
32944 a &"success"& return code. Obviously there is scope for hints records to get
32945 left lying around if there is a system or program crash. To guard against this,
32946 Exim ignores any records that are more than six hours old.
32948 .oindex "&%smtp_etrn_command%&"
32949 For more control over what ETRN does, the &%smtp_etrn_command%& option can
32950 used. This specifies a command that is run whenever ETRN is received,
32951 whatever the form of its argument. For
32954 smtp_etrn_command = /etc/etrn_command $domain \
32955 $sender_host_address
32957 .vindex "&$domain$&"
32958 The string is split up into arguments which are independently expanded. The
32959 expansion variable &$domain$& is set to the argument of the ETRN command,
32960 and no syntax checking is done on the contents of this argument. Exim does not
32961 wait for the command to complete, so its status code is not checked. Exim runs
32962 under its own uid and gid when receiving incoming SMTP, so it is not possible
32963 for it to change them before running the command.
32967 .section "Incoming local SMTP" "SECID238"
32968 .cindex "SMTP" "local incoming"
32969 Some user agents use SMTP to pass messages to their local MTA using the
32970 standard input and output, as opposed to passing the envelope on the command
32971 line and writing the message to the standard input. This is supported by the
32972 &%-bs%& option. This form of SMTP is handled in the same way as incoming
32973 messages over TCP/IP (including the use of ACLs), except that the envelope
32974 sender given in a MAIL command is ignored unless the caller is trusted. In
32975 an ACL you can detect this form of SMTP input by testing for an empty host
32976 identification. It is common to have this as the first line in the ACL that
32977 runs for RCPT commands:
32981 This accepts SMTP messages from local processes without doing any other tests.
32985 .section "Outgoing batched SMTP" "SECTbatchSMTP"
32986 .cindex "SMTP" "batched outgoing"
32987 .cindex "batched SMTP output"
32988 Both the &(appendfile)& and &(pipe)& transports can be used for handling
32989 batched SMTP. Each has an option called &%use_bsmtp%& which causes messages to
32990 be output in BSMTP format. No SMTP responses are possible for this form of
32991 delivery. All it is doing is using SMTP commands as a way of transmitting the
32992 envelope along with the message.
32994 The message is written to the file or pipe preceded by the SMTP commands
32995 MAIL and RCPT, and followed by a line containing a single dot. Lines in
32996 the message that start with a dot have an extra dot added. The SMTP command
32997 HELO is not normally used. If it is required, the &%message_prefix%& option
32998 can be used to specify it.
33000 Because &(appendfile)& and &(pipe)& are both local transports, they accept only
33001 one recipient address at a time by default. However, you can arrange for them
33002 to handle several addresses at once by setting the &%batch_max%& option. When
33003 this is done for BSMTP, messages may contain multiple RCPT commands. See
33004 chapter &<<CHAPbatching>>& for more details.
33007 When one or more addresses are routed to a BSMTP transport by a router that
33008 sets up a host list, the name of the first host on the list is available to the
33009 transport in the variable &$host$&. Here is an example of such a transport and
33014 driver = manualroute
33015 transport = smtp_appendfile
33016 route_list = domain.example batch.host.example
33020 driver = appendfile
33021 directory = /var/bsmtp/$host
33026 This causes messages addressed to &'domain.example'& to be written in BSMTP
33027 format to &_/var/bsmtp/batch.host.example_&, with only a single copy of each
33028 message (unless there are more than 1000 recipients).
33032 .section "Incoming batched SMTP" "SECTincomingbatchedSMTP"
33033 .cindex "SMTP" "batched incoming"
33034 .cindex "batched SMTP input"
33035 The &%-bS%& command line option causes Exim to accept one or more messages by
33036 reading SMTP on the standard input, but to generate no responses. If the caller
33037 is trusted, the senders in the MAIL commands are believed; otherwise the
33038 sender is always the caller of Exim. Unqualified senders and receivers are not
33039 rejected (there seems little point) but instead just get qualified. HELO
33040 and EHLO act as RSET; VRFY, EXPN, ETRN and HELP, act
33041 as NOOP; QUIT quits.
33043 Minimal policy checking is done for BSMTP input. Only the non-SMTP
33044 ACL is run in the same way as for non-SMTP local input.
33046 If an error is detected while reading a message, including a missing &"."& at
33047 the end, Exim gives up immediately. It writes details of the error to the
33048 standard output in a stylized way that the calling program should be able to
33049 make some use of automatically, for example:
33051 554 Unexpected end of file
33052 Transaction started in line 10
33053 Error detected in line 14
33055 It writes a more verbose version, for human consumption, to the standard error
33058 An error was detected while processing a file of BSMTP input.
33059 The error message was:
33061 501 '>' missing at end of address
33063 The SMTP transaction started in line 10.
33064 The error was detected in line 12.
33065 The SMTP command at fault was:
33067 rcpt to:<malformed@in.com.plete
33069 1 previous message was successfully processed.
33070 The rest of the batch was abandoned.
33072 The return code from Exim is zero only if there were no errors. It is 1 if some
33073 messages were accepted before an error was detected, and 2 if no messages were
33075 .ecindex IIDsmtpproc1
33076 .ecindex IIDsmtpproc2
33080 . ////////////////////////////////////////////////////////////////////////////
33081 . ////////////////////////////////////////////////////////////////////////////
33083 .chapter "Customizing bounce and warning messages" "CHAPemsgcust" &&&
33084 "Customizing messages"
33085 When a message fails to be delivered, or remains on the queue for more than a
33086 configured amount of time, Exim sends a message to the original sender, or
33087 to an alternative configured address. The text of these messages is built into
33088 the code of Exim, but it is possible to change it, either by adding a single
33089 string, or by replacing each of the paragraphs by text supplied in a file.
33091 The &'From:'& and &'To:'& header lines are automatically generated; you can
33092 cause a &'Reply-To:'& line to be added by setting the &%errors_reply_to%&
33093 option. Exim also adds the line
33095 Auto-Submitted: auto-generated
33097 to all warning and bounce messages,
33100 .section "Customizing bounce messages" "SECID239"
33101 .cindex "customizing" "bounce message"
33102 .cindex "bounce message" "customizing"
33103 If &%bounce_message_text%& is set, its contents are included in the default
33104 message immediately after &"This message was created automatically by mail
33105 delivery software."& The string is not expanded. It is not used if
33106 &%bounce_message_file%& is set.
33108 When &%bounce_message_file%& is set, it must point to a template file for
33109 constructing error messages. The file consists of a series of text items,
33110 separated by lines consisting of exactly four asterisks. If the file cannot be
33111 opened, default text is used and a message is written to the main and panic
33112 logs. If any text item in the file is empty, default text is used for that
33115 .vindex "&$bounce_recipient$&"
33116 .vindex "&$bounce_return_size_limit$&"
33117 Each item of text that is read from the file is expanded, and there are two
33118 expansion variables which can be of use here: &$bounce_recipient$& is set to
33119 the recipient of an error message while it is being created, and
33120 &$bounce_return_size_limit$& contains the value of the &%return_size_limit%&
33121 option, rounded to a whole number.
33123 The items must appear in the file in the following order:
33126 The first item is included in the headers, and should include at least a
33127 &'Subject:'& header. Exim does not check the syntax of these headers.
33129 The second item forms the start of the error message. After it, Exim lists the
33130 failing addresses with their error messages.
33132 The third item is used to introduce any text from pipe transports that is to be
33133 returned to the sender. It is omitted if there is no such text.
33135 The fourth item is used to introduce the copy of the message that is returned
33136 as part of the error report.
33138 The fifth item is added after the fourth one if the returned message is
33139 truncated because it is bigger than &%return_size_limit%&.
33141 The sixth item is added after the copy of the original message.
33144 The default state (&%bounce_message_file%& unset) is equivalent to the
33145 following file, in which the sixth item is empty. The &'Subject:'& and some
33146 other lines have been split in order to fit them on the page:
33148 Subject: Mail delivery failed
33149 ${if eq{$sender_address}{$bounce_recipient}
33150 {: returning message to sender}}
33152 This message was created automatically by mail delivery software.
33154 A message ${if eq{$sender_address}{$bounce_recipient}
33155 {that you sent }{sent by
33159 }}could not be delivered to all of its recipients.
33160 This is a permanent error. The following address(es) failed:
33162 The following text was generated during the delivery attempt(s):
33164 ------ This is a copy of the message, including all the headers.
33167 ------ The body of the message is $message_size characters long;
33169 ------ $bounce_return_size_limit or so are included here.
33172 .section "Customizing warning messages" "SECTcustwarn"
33173 .cindex "customizing" "warning message"
33174 .cindex "warning of delay" "customizing the message"
33175 The option &%warn_message_file%& can be pointed at a template file for use when
33176 warnings about message delays are created. In this case there are only three
33180 The first item is included in the headers, and should include at least a
33181 &'Subject:'& header. Exim does not check the syntax of these headers.
33183 The second item forms the start of the warning message. After it, Exim lists
33184 the delayed addresses.
33186 The third item then ends the message.
33189 The default state is equivalent to the following file, except that some lines
33190 have been split here, in order to fit them on the page:
33192 Subject: Warning: message $message_exim_id delayed
33193 $warn_message_delay
33195 This message was created automatically by mail delivery software.
33197 A message ${if eq{$sender_address}{$warn_message_recipients}
33198 {that you sent }{sent by
33202 }}has not been delivered to all of its recipients after
33203 more than $warn_message_delay on the queue on $primary_hostname.
33205 The message identifier is: $message_exim_id
33206 The subject of the message is: $h_subject
33207 The date of the message is: $h_date
33209 The following address(es) have not yet been delivered:
33211 No action is required on your part. Delivery attempts will
33212 continue for some time, and this warning may be repeated at
33213 intervals if the message remains undelivered. Eventually the
33214 mail delivery software will give up, and when that happens,
33215 the message will be returned to you.
33217 .vindex "&$warn_message_delay$&"
33218 .vindex "&$warn_message_recipients$&"
33219 However, in the default state the subject and date lines are omitted if no
33220 appropriate headers exist. During the expansion of this file,
33221 &$warn_message_delay$& is set to the delay time in one of the forms &"<&'n'&>
33222 minutes"& or &"<&'n'&> hours"&, and &$warn_message_recipients$& contains a list
33223 of recipients for the warning message. There may be more than one if there are
33224 multiple addresses with different &%errors_to%& settings on the routers that
33230 . ////////////////////////////////////////////////////////////////////////////
33231 . ////////////////////////////////////////////////////////////////////////////
33233 .chapter "Some common configuration settings" "CHAPcomconreq"
33234 This chapter discusses some configuration settings that seem to be fairly
33235 common. More examples and discussion can be found in the Exim book.
33239 .section "Sending mail to a smart host" "SECID240"
33240 .cindex "smart host" "example router"
33241 If you want to send all mail for non-local domains to a &"smart host"&, you
33242 should replace the default &(dnslookup)& router with a router which does the
33243 routing explicitly:
33245 send_to_smart_host:
33246 driver = manualroute
33247 route_list = !+local_domains smart.host.name
33248 transport = remote_smtp
33250 You can use the smart host's IP address instead of the name if you wish.
33251 If you are using Exim only to submit messages to a smart host, and not for
33252 receiving incoming messages, you can arrange for it to do the submission
33253 synchronously by setting the &%mua_wrapper%& option (see chapter
33254 &<<CHAPnonqueueing>>&).
33259 .section "Using Exim to handle mailing lists" "SECTmailinglists"
33260 .cindex "mailing lists"
33261 Exim can be used to run simple mailing lists, but for large and/or complicated
33262 requirements, the use of additional specialized mailing list software such as
33263 Majordomo or Mailman is recommended.
33265 The &(redirect)& router can be used to handle mailing lists where each list
33266 is maintained in a separate file, which can therefore be managed by an
33267 independent manager. The &%domains%& router option can be used to run these
33268 lists in a separate domain from normal mail. For example:
33272 domains = lists.example
33273 file = /usr/lists/$local_part
33276 errors_to = $local_part-request@lists.example
33279 This router is skipped for domains other than &'lists.example'&. For addresses
33280 in that domain, it looks for a file that matches the local part. If there is no
33281 such file, the router declines, but because &%no_more%& is set, no subsequent
33282 routers are tried, and so the whole delivery fails.
33284 The &%forbid_pipe%& and &%forbid_file%& options prevent a local part from being
33285 expanded into a file name or a pipe delivery, which is usually inappropriate in
33288 .oindex "&%errors_to%&"
33289 The &%errors_to%& option specifies that any delivery errors caused by addresses
33290 taken from a mailing list are to be sent to the given address rather than the
33291 original sender of the message. However, before acting on this, Exim verifies
33292 the error address, and ignores it if verification fails.
33294 For example, using the configuration above, mail sent to
33295 &'dicts@lists.example'& is passed on to those addresses contained in
33296 &_/usr/lists/dicts_&, with error reports directed to
33297 &'dicts-request@lists.example'&, provided that this address can be verified.
33298 There could be a file called &_/usr/lists/dicts-request_& containing
33299 the address(es) of this particular list's manager(s), but other approaches,
33300 such as setting up an earlier router (possibly using the &%local_part_prefix%&
33301 or &%local_part_suffix%& options) to handle addresses of the form
33302 &%owner-%&&'xxx'& or &%xxx-%&&'request'&, are also possible.
33306 .section "Syntax errors in mailing lists" "SECID241"
33307 .cindex "mailing lists" "syntax errors in"
33308 If an entry in redirection data contains a syntax error, Exim normally defers
33309 delivery of the original address. That means that a syntax error in a mailing
33310 list holds up all deliveries to the list. This may not be appropriate when a
33311 list is being maintained automatically from data supplied by users, and the
33312 addresses are not rigorously checked.
33314 If the &%skip_syntax_errors%& option is set, the &(redirect)& router just skips
33315 entries that fail to parse, noting the incident in the log. If in addition
33316 &%syntax_errors_to%& is set to a verifiable address, a message is sent to it
33317 whenever a broken address is skipped. It is usually appropriate to set
33318 &%syntax_errors_to%& to the same address as &%errors_to%&.
33322 .section "Re-expansion of mailing lists" "SECID242"
33323 .cindex "mailing lists" "re-expansion of"
33324 Exim remembers every individual address to which a message has been delivered,
33325 in order to avoid duplication, but it normally stores only the original
33326 recipient addresses with a message. If all the deliveries to a mailing list
33327 cannot be done at the first attempt, the mailing list is re-expanded when the
33328 delivery is next tried. This means that alterations to the list are taken into
33329 account at each delivery attempt, so addresses that have been added to
33330 the list since the message arrived will therefore receive a copy of the
33331 message, even though it pre-dates their subscription.
33333 If this behaviour is felt to be undesirable, the &%one_time%& option can be set
33334 on the &(redirect)& router. If this is done, any addresses generated by the
33335 router that fail to deliver at the first attempt are added to the message as
33336 &"top level"& addresses, and the parent address that generated them is marked
33337 &"delivered"&. Thus, expansion of the mailing list does not happen again at the
33338 subsequent delivery attempts. The disadvantage of this is that if any of the
33339 failing addresses are incorrect, correcting them in the file has no effect on
33340 pre-existing messages.
33342 The original top-level address is remembered with each of the generated
33343 addresses, and is output in any log messages. However, any intermediate parent
33344 addresses are not recorded. This makes a difference to the log only if the
33345 &%all_parents%& selector is set, but for mailing lists there is normally only
33346 one level of expansion anyway.
33350 .section "Closed mailing lists" "SECID243"
33351 .cindex "mailing lists" "closed"
33352 The examples so far have assumed open mailing lists, to which anybody may
33353 send mail. It is also possible to set up closed lists, where mail is accepted
33354 from specified senders only. This is done by making use of the generic
33355 &%senders%& option to restrict the router that handles the list.
33357 The following example uses the same file as a list of recipients and as a list
33358 of permitted senders. It requires three routers:
33362 domains = lists.example
33363 local_part_suffix = -request
33364 file = /usr/lists/$local_part$local_part_suffix
33369 domains = lists.example
33370 senders = ${if exists {/usr/lists/$local_part}\
33371 {lsearch;/usr/lists/$local_part}{*}}
33372 file = /usr/lists/$local_part
33375 errors_to = $local_part-request@lists.example
33380 domains = lists.example
33382 data = :fail: $local_part@lists.example is a closed mailing list
33384 All three routers have the same &%domains%& setting, so for any other domains,
33385 they are all skipped. The first router runs only if the local part ends in
33386 &%-request%&. It handles messages to the list manager(s) by means of an open
33389 The second router runs only if the &%senders%& precondition is satisfied. It
33390 checks for the existence of a list that corresponds to the local part, and then
33391 checks that the sender is on the list by means of a linear search. It is
33392 necessary to check for the existence of the file before trying to search it,
33393 because otherwise Exim thinks there is a configuration error. If the file does
33394 not exist, the expansion of &%senders%& is *, which matches all senders. This
33395 means that the router runs, but because there is no list, declines, and
33396 &%no_more%& ensures that no further routers are run. The address fails with an
33397 &"unrouteable address"& error.
33399 The third router runs only if the second router is skipped, which happens when
33400 a mailing list exists, but the sender is not on it. This router forcibly fails
33401 the address, giving a suitable error message.
33406 .section "Variable Envelope Return Paths (VERP)" "SECTverp"
33408 .cindex "Variable Envelope Return Paths"
33409 .cindex "envelope sender"
33410 Variable Envelope Return Paths &-- see &url(http://cr.yp.to/proto/verp.txt) &--
33411 are a way of helping mailing list administrators discover which subscription
33412 address is the cause of a particular delivery failure. The idea is to encode
33413 the original recipient address in the outgoing envelope sender address, so that
33414 if the message is forwarded by another host and then subsequently bounces, the
33415 original recipient can be extracted from the recipient address of the bounce.
33417 .oindex &%errors_to%&
33418 .oindex &%return_path%&
33419 Envelope sender addresses can be modified by Exim using two different
33420 facilities: the &%errors_to%& option on a router (as shown in previous mailing
33421 list examples), or the &%return_path%& option on a transport. The second of
33422 these is effective only if the message is successfully delivered to another
33423 host; it is not used for errors detected on the local host (see the description
33424 of &%return_path%& in chapter &<<CHAPtransportgeneric>>&). Here is an example
33425 of the use of &%return_path%& to implement VERP on an &(smtp)& transport:
33431 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}\
33432 {$1-request+$local_part=$domain@your.dom.example}fail}
33434 This has the effect of rewriting the return path (envelope sender) on outgoing
33435 SMTP messages, if the local part of the original return path ends in
33436 &"-request"&, and the domain is &'your.dom.example'&. The rewriting inserts the
33437 local part and domain of the recipient into the return path. Suppose, for
33438 example, that a message whose return path has been set to
33439 &'somelist-request@your.dom.example'& is sent to
33440 &'subscriber@other.dom.example'&. In the transport, the return path is
33443 somelist-request+subscriber=other.dom.example@your.dom.example
33445 .vindex "&$local_part$&"
33446 For this to work, you must tell Exim to send multiple copies of messages that
33447 have more than one recipient, so that each copy has just one recipient. This is
33448 achieved by setting &%max_rcpt%& to 1. Without this, a single copy of a message
33449 might be sent to several different recipients in the same domain, in which case
33450 &$local_part$& is not available in the transport, because it is not unique.
33452 Unless your host is doing nothing but mailing list deliveries, you should
33453 probably use a separate transport for the VERP deliveries, so as not to use
33454 extra resources in making one-per-recipient copies for other deliveries. This
33455 can easily be done by expanding the &%transport%& option in the router:
33459 domains = ! +local_domains
33461 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}\
33462 {verp_smtp}{remote_smtp}}
33465 If you want to change the return path using &%errors_to%& in a router instead
33466 of using &%return_path%& in the transport, you need to set &%errors_to%& on all
33467 routers that handle mailing list addresses. This will ensure that all delivery
33468 errors, including those detected on the local host, are sent to the VERP
33471 On a host that does no local deliveries and has no manual routing, only the
33472 &(dnslookup)& router needs to be changed. A special transport is not needed for
33473 SMTP deliveries. Every mailing list recipient has its own return path value,
33474 and so Exim must hand them to the transport one at a time. Here is an example
33475 of a &(dnslookup)& router that implements VERP:
33479 domains = ! +local_domains
33480 transport = remote_smtp
33482 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}}
33483 {$1-request+$local_part=$domain@your.dom.example}fail}
33486 Before you start sending out messages with VERPed return paths, you must also
33487 configure Exim to accept the bounce messages that come back to those paths.
33488 Typically this is done by setting a &%local_part_suffix%& option for a
33489 router, and using this to route the messages to wherever you want to handle
33492 The overhead incurred in using VERP depends very much on the size of the
33493 message, the number of recipient addresses that resolve to the same remote
33494 host, and the speed of the connection over which the message is being sent. If
33495 a lot of addresses resolve to the same host and the connection is slow, sending
33496 a separate copy of the message for each address may take substantially longer
33497 than sending a single copy with many recipients (for which VERP cannot be
33505 .section "Virtual domains" "SECTvirtualdomains"
33506 .cindex "virtual domains"
33507 .cindex "domain" "virtual"
33508 The phrase &'virtual domain'& is unfortunately used with two rather different
33512 A domain for which there are no real mailboxes; all valid local parts are
33513 aliases for other email addresses. Common examples are organizational
33514 top-level domains and &"vanity"& domains.
33516 One of a number of independent domains that are all handled by the same host,
33517 with mailboxes on that host, but where the mailbox owners do not necessarily
33518 have login accounts on that host.
33521 The first usage is probably more common, and does seem more &"virtual"& than
33522 the second. This kind of domain can be handled in Exim with a straightforward
33523 aliasing router. One approach is to create a separate alias file for each
33524 virtual domain. Exim can test for the existence of the alias file to determine
33525 whether the domain exists. The &(dsearch)& lookup type is useful here, leading
33526 to a router of this form:
33530 domains = dsearch;/etc/mail/virtual
33531 data = ${lookup{$local_part}lsearch{/etc/mail/virtual/$domain}}
33534 The &%domains%& option specifies that the router is to be skipped, unless there
33535 is a file in the &_/etc/mail/virtual_& directory whose name is the same as the
33536 domain that is being processed. When the router runs, it looks up the local
33537 part in the file to find a new address (or list of addresses). The &%no_more%&
33538 setting ensures that if the lookup fails (leading to &%data%& being an empty
33539 string), Exim gives up on the address without trying any subsequent routers.
33541 This one router can handle all the virtual domains because the alias file names
33542 follow a fixed pattern. Permissions can be arranged so that appropriate people
33543 can edit the different alias files. A successful aliasing operation results in
33544 a new envelope recipient address, which is then routed from scratch.
33546 The other kind of &"virtual"& domain can also be handled in a straightforward
33547 way. One approach is to create a file for each domain containing a list of
33548 valid local parts, and use it in a router like this:
33552 domains = dsearch;/etc/mail/domains
33553 local_parts = lsearch;/etc/mail/domains/$domain
33554 transport = my_mailboxes
33556 The address is accepted if there is a file for the domain, and the local part
33557 can be found in the file. The &%domains%& option is used to check for the
33558 file's existence because &%domains%& is tested before the &%local_parts%&
33559 option (see section &<<SECTrouprecon>>&). You cannot use &%require_files%&,
33560 because that option is tested after &%local_parts%&. The transport is as
33564 driver = appendfile
33565 file = /var/mail/$domain/$local_part
33568 This uses a directory of mailboxes for each domain. The &%user%& setting is
33569 required, to specify which uid is to be used for writing to the mailboxes.
33571 The configuration shown here is just one example of how you might support this
33572 requirement. There are many other ways this kind of configuration can be set
33573 up, for example, by using a database instead of separate files to hold all the
33574 information about the domains.
33578 .section "Multiple user mailboxes" "SECTmulbox"
33579 .cindex "multiple mailboxes"
33580 .cindex "mailbox" "multiple"
33581 .cindex "local part" "prefix"
33582 .cindex "local part" "suffix"
33583 Heavy email users often want to operate with multiple mailboxes, into which
33584 incoming mail is automatically sorted. A popular way of handling this is to
33585 allow users to use multiple sender addresses, so that replies can easily be
33586 identified. Users are permitted to add prefixes or suffixes to their local
33587 parts for this purpose. The wildcard facility of the generic router options
33588 &%local_part_prefix%& and &%local_part_suffix%& can be used for this. For
33589 example, consider this router:
33594 file = $home/.forward
33595 local_part_suffix = -*
33596 local_part_suffix_optional
33599 .vindex "&$local_part_suffix$&"
33600 It runs a user's &_.forward_& file for all local parts of the form
33601 &'username-*'&. Within the filter file the user can distinguish different
33602 cases by testing the variable &$local_part_suffix$&. For example:
33604 if $local_part_suffix contains -special then
33605 save /home/$local_part/Mail/special
33608 If the filter file does not exist, or does not deal with such addresses, they
33609 fall through to subsequent routers, and, assuming no subsequent use of the
33610 &%local_part_suffix%& option is made, they presumably fail. Thus, users have
33611 control over which suffixes are valid.
33613 Alternatively, a suffix can be used to trigger the use of a different
33614 &_.forward_& file &-- which is the way a similar facility is implemented in
33620 file = $home/.forward$local_part_suffix
33621 local_part_suffix = -*
33622 local_part_suffix_optional
33625 If there is no suffix, &_.forward_& is used; if the suffix is &'-special'&, for
33626 example, &_.forward-special_& is used. Once again, if the appropriate file
33627 does not exist, or does not deal with the address, it is passed on to
33628 subsequent routers, which could, if required, look for an unqualified
33629 &_.forward_& file to use as a default.
33633 .section "Simplified vacation processing" "SECID244"
33634 .cindex "vacation processing"
33635 The traditional way of running the &'vacation'& program is for a user to set up
33636 a pipe command in a &_.forward_& file
33637 (see section &<<SECTspecitredli>>& for syntax details).
33638 This is prone to error by inexperienced users. There are two features of Exim
33639 that can be used to make this process simpler for users:
33642 A local part prefix such as &"vacation-"& can be specified on a router which
33643 can cause the message to be delivered directly to the &'vacation'& program, or
33644 alternatively can use Exim's &(autoreply)& transport. The contents of a user's
33645 &_.forward_& file are then much simpler. For example:
33647 spqr, vacation-spqr
33650 The &%require_files%& generic router option can be used to trigger a
33651 vacation delivery by checking for the existence of a certain file in the
33652 user's home directory. The &%unseen%& generic option should also be used, to
33653 ensure that the original delivery also proceeds. In this case, all the user has
33654 to do is to create a file called, say, &_.vacation_&, containing a vacation
33658 Another advantage of both these methods is that they both work even when the
33659 use of arbitrary pipes by users is locked out.
33663 .section "Taking copies of mail" "SECID245"
33664 .cindex "message" "copying every"
33665 Some installations have policies that require archive copies of all messages to
33666 be made. A single copy of each message can easily be taken by an appropriate
33667 command in a system filter, which could, for example, use a different file for
33668 each day's messages.
33670 There is also a shadow transport mechanism that can be used to take copies of
33671 messages that are successfully delivered by local transports, one copy per
33672 delivery. This could be used, &'inter alia'&, to implement automatic
33673 notification of delivery by sites that insist on doing such things.
33677 .section "Intermittently connected hosts" "SECID246"
33678 .cindex "intermittently connected hosts"
33679 It has become quite common (because it is cheaper) for hosts to connect to the
33680 Internet periodically rather than remain connected all the time. The normal
33681 arrangement is that mail for such hosts accumulates on a system that is
33682 permanently connected.
33684 Exim was designed for use on permanently connected hosts, and so it is not
33685 particularly well-suited to use in an intermittently connected environment.
33686 Nevertheless there are some features that can be used.
33689 .section "Exim on the upstream server host" "SECID247"
33690 It is tempting to arrange for incoming mail for the intermittently connected
33691 host to remain on Exim's queue until the client connects. However, this
33692 approach does not scale very well. Two different kinds of waiting message are
33693 being mixed up in the same queue &-- those that cannot be delivered because of
33694 some temporary problem, and those that are waiting for their destination host
33695 to connect. This makes it hard to manage the queue, as well as wasting
33696 resources, because each queue runner scans the entire queue.
33698 A better approach is to separate off those messages that are waiting for an
33699 intermittently connected host. This can be done by delivering these messages
33700 into local files in batch SMTP, &"mailstore"&, or other envelope-preserving
33701 format, from where they are transmitted by other software when their
33702 destination connects. This makes it easy to collect all the mail for one host
33703 in a single directory, and to apply local timeout rules on a per-message basis
33706 On a very small scale, leaving the mail on Exim's queue can be made to work. If
33707 you are doing this, you should configure Exim with a long retry period for the
33708 intermittent host. For example:
33710 cheshire.wonderland.fict.example * F,5d,24h
33712 This stops a lot of failed delivery attempts from occurring, but Exim remembers
33713 which messages it has queued up for that host. Once the intermittent host comes
33714 online, forcing delivery of one message (either by using the &%-M%& or &%-R%&
33715 options, or by using the ETRN SMTP command (see section &<<SECTETRN>>&)
33716 causes all the queued up messages to be delivered, often down a single SMTP
33717 connection. While the host remains connected, any new messages get delivered
33720 If the connecting hosts do not have fixed IP addresses, that is, if a host is
33721 issued with a different IP address each time it connects, Exim's retry
33722 mechanisms on the holding host get confused, because the IP address is normally
33723 used as part of the key string for holding retry information. This can be
33724 avoided by unsetting &%retry_include_ip_address%& on the &(smtp)& transport.
33725 Since this has disadvantages for permanently connected hosts, it is best to
33726 arrange a separate transport for the intermittently connected ones.
33730 .section "Exim on the intermittently connected client host" "SECID248"
33731 The value of &%smtp_accept_queue_per_connection%& should probably be
33732 increased, or even set to zero (that is, disabled) on the intermittently
33733 connected host, so that all incoming messages down a single connection get
33734 delivered immediately.
33736 .cindex "SMTP" "passed connection"
33737 .cindex "SMTP" "multiple deliveries"
33738 .cindex "multiple SMTP deliveries"
33739 Mail waiting to be sent from an intermittently connected host will probably
33740 not have been routed, because without a connection DNS lookups are not
33741 possible. This means that if a normal queue run is done at connection time,
33742 each message is likely to be sent in a separate SMTP session. This can be
33743 avoided by starting the queue run with a command line option beginning with
33744 &%-qq%& instead of &%-q%&. In this case, the queue is scanned twice. In the
33745 first pass, routing is done but no deliveries take place. The second pass is a
33746 normal queue run; since all the messages have been previously routed, those
33747 destined for the same host are likely to get sent as multiple deliveries in a
33748 single SMTP connection.
33752 . ////////////////////////////////////////////////////////////////////////////
33753 . ////////////////////////////////////////////////////////////////////////////
33755 .chapter "Using Exim as a non-queueing client" "CHAPnonqueueing" &&&
33756 "Exim as a non-queueing client"
33757 .cindex "client, non-queueing"
33758 .cindex "smart host" "suppressing queueing"
33759 On a personal computer, it is a common requirement for all
33760 email to be sent to a &"smart host"&. There are plenty of MUAs that can be
33761 configured to operate that way, for all the popular operating systems.
33762 However, there are some MUAs for Unix-like systems that cannot be so
33763 configured: they submit messages using the command line interface of
33764 &_/usr/sbin/sendmail_&. Furthermore, utility programs such as &'cron'& submit
33767 If the personal computer runs continuously, there is no problem, because it can
33768 run a conventional MTA that handles delivery to the smart host, and deal with
33769 any delays via its queueing mechanism. However, if the computer does not run
33770 continuously or runs different operating systems at different times, queueing
33771 email is not desirable.
33773 There is therefore a requirement for something that can provide the
33774 &_/usr/sbin/sendmail_& interface but deliver messages to a smart host without
33775 any queueing or retrying facilities. Furthermore, the delivery to the smart
33776 host should be synchronous, so that if it fails, the sending MUA is immediately
33777 informed. In other words, we want something that extends an MUA that submits
33778 to a local MTA via the command line so that it behaves like one that submits
33779 to a remote smart host using TCP/SMTP.
33781 There are a number of applications (for example, there is one called &'ssmtp'&)
33782 that do this job. However, people have found them to be lacking in various
33783 ways. For instance, you might want to allow aliasing and forwarding to be done
33784 before sending a message to the smart host.
33786 Exim already had the necessary infrastructure for doing this job. Just a few
33787 tweaks were needed to make it behave as required, though it is somewhat of an
33788 overkill to use a fully-featured MTA for this purpose.
33790 .oindex "&%mua_wrapper%&"
33791 There is a Boolean global option called &%mua_wrapper%&, defaulting false.
33792 Setting &%mua_wrapper%& true causes Exim to run in a special mode where it
33793 assumes that it is being used to &"wrap"& a command-line MUA in the manner
33794 just described. As well as setting &%mua_wrapper%&, you also need to provide a
33795 compatible router and transport configuration. Typically there will be just one
33796 router and one transport, sending everything to a smart host.
33798 When run in MUA wrapping mode, the behaviour of Exim changes in the
33802 A daemon cannot be run, nor will Exim accept incoming messages from &'inetd'&.
33803 In other words, the only way to submit messages is via the command line.
33805 Each message is synchronously delivered as soon as it is received (&%-odi%& is
33806 assumed). All queueing options (&%queue_only%&, &%queue_smtp_domains%&,
33807 &%control%& in an ACL, etc.) are quietly ignored. The Exim reception process
33808 does not finish until the delivery attempt is complete. If the delivery is
33809 successful, a zero return code is given.
33811 Address redirection is permitted, but the final routing for all addresses must
33812 be to the same remote transport, and to the same list of hosts. Furthermore,
33813 the return address (envelope sender) must be the same for all recipients, as
33814 must any added or deleted header lines. In other words, it must be possible to
33815 deliver the message in a single SMTP transaction, however many recipients there
33818 If these conditions are not met, or if routing any address results in a
33819 failure or defer status, or if Exim is unable to deliver all the recipients
33820 successfully to one of the smart hosts, delivery of the entire message fails.
33822 Because no queueing is allowed, all failures are treated as permanent; there
33823 is no distinction between 4&'xx'& and 5&'xx'& SMTP response codes from the
33824 smart host. Furthermore, because only a single yes/no response can be given to
33825 the caller, it is not possible to deliver to some recipients and not others. If
33826 there is an error (temporary or permanent) for any recipient, all are failed.
33828 If more than one smart host is listed, Exim will try another host after a
33829 connection failure or a timeout, in the normal way. However, if this kind of
33830 failure happens for all the hosts, the delivery fails.
33832 When delivery fails, an error message is written to the standard error stream
33833 (as well as to Exim's log), and Exim exits to the caller with a return code
33834 value 1. The message is expunged from Exim's spool files. No bounce messages
33835 are ever generated.
33837 No retry data is maintained, and any retry rules are ignored.
33839 A number of Exim options are overridden: &%deliver_drop_privilege%& is forced
33840 true, &%max_rcpt%& in the &(smtp)& transport is forced to &"unlimited"&,
33841 &%remote_max_parallel%& is forced to one, and fallback hosts are ignored.
33844 The overall effect is that Exim makes a single synchronous attempt to deliver
33845 the message, failing if there is any kind of problem. Because no local
33846 deliveries are done and no daemon can be run, Exim does not need root
33847 privilege. It should be possible to run it setuid to &'exim'& instead of setuid
33848 to &'root'&. See section &<<SECTrunexiwitpri>>& for a general discussion about
33849 the advantages and disadvantages of running without root privilege.
33854 . ////////////////////////////////////////////////////////////////////////////
33855 . ////////////////////////////////////////////////////////////////////////////
33857 .chapter "Log files" "CHAPlog"
33858 .scindex IIDloggen "log" "general description"
33859 .cindex "log" "types of"
33860 Exim writes three different logs, referred to as the main log, the reject log,
33865 The main log records the arrival of each message and each delivery in a single
33866 line in each case. The format is as compact as possible, in an attempt to keep
33867 down the size of log files. Two-character flag sequences make it easy to pick
33868 out these lines. A number of other events are recorded in the main log. Some of
33869 them are optional, in which case the &%log_selector%& option controls whether
33870 they are included or not. A Perl script called &'eximstats'&, which does simple
33871 analysis of main log files, is provided in the Exim distribution (see section
33872 &<<SECTmailstat>>&).
33874 .cindex "reject log"
33875 The reject log records information from messages that are rejected as a result
33876 of a configuration option (that is, for policy reasons).
33877 The first line of each rejection is a copy of the line that is also written to
33878 the main log. Then, if the message's header has been read at the time the log
33879 is written, its contents are written to this log. Only the original header
33880 lines are available; header lines added by ACLs are not logged. You can use the
33881 reject log to check that your policy controls are working correctly; on a busy
33882 host this may be easier than scanning the main log for rejection messages. You
33883 can suppress the writing of the reject log by setting &%write_rejectlog%&
33886 .cindex "panic log"
33887 .cindex "system log"
33888 When certain serious errors occur, Exim writes entries to its panic log. If the
33889 error is sufficiently disastrous, Exim bombs out afterwards. Panic log entries
33890 are usually written to the main log as well, but can get lost amid the mass of
33891 other entries. The panic log should be empty under normal circumstances. It is
33892 therefore a good idea to check it (or to have a &'cron'& script check it)
33893 regularly, in order to become aware of any problems. When Exim cannot open its
33894 panic log, it tries as a last resort to write to the system log (syslog). This
33895 is opened with LOG_PID+LOG_CONS and the facility code of LOG_MAIL. The
33896 message itself is written at priority LOG_CRIT.
33899 Every log line starts with a timestamp, in the format shown in the following
33900 example. Note that many of the examples shown in this chapter are line-wrapped.
33901 In the log file, this would be all on one line:
33903 2001-09-16 16:09:47 SMTP connection from [127.0.0.1] closed
33906 By default, the timestamps are in the local timezone. There are two
33907 ways of changing this:
33910 You can set the &%timezone%& option to a different time zone; in particular, if
33915 the timestamps will be in UTC (aka GMT).
33917 If you set &%log_timezone%& true, the time zone is added to the timestamp, for
33920 2003-04-25 11:17:07 +0100 Start queue run: pid=12762
33924 .cindex "log" "process ids in"
33925 .cindex "pid (process id)" "in log lines"
33926 Exim does not include its process id in log lines by default, but you can
33927 request that it does so by specifying the &`pid`& log selector (see section
33928 &<<SECTlogselector>>&). When this is set, the process id is output, in square
33929 brackets, immediately after the time and date.
33934 .section "Where the logs are written" "SECTwhelogwri"
33935 .cindex "log" "destination"
33936 .cindex "log" "to file"
33937 .cindex "log" "to syslog"
33939 The logs may be written to local files, or to syslog, or both. However, it
33940 should be noted that many syslog implementations use UDP as a transport, and
33941 are therefore unreliable in the sense that messages are not guaranteed to
33942 arrive at the loghost, nor is the ordering of messages necessarily maintained.
33943 It has also been reported that on large log files (tens of megabytes) you may
33944 need to tweak syslog to prevent it syncing the file with each write &-- on
33945 Linux this has been seen to make syslog take 90% plus of CPU time.
33947 The destination for Exim's logs is configured by setting LOG_FILE_PATH in
33948 &_Local/Makefile_& or by setting &%log_file_path%& in the run time
33949 configuration. This latter string is expanded, so it can contain, for example,
33950 references to the host name:
33952 log_file_path = /var/log/$primary_hostname/exim_%slog
33954 It is generally advisable, however, to set the string in &_Local/Makefile_&
33955 rather than at run time, because then the setting is available right from the
33956 start of Exim's execution. Otherwise, if there's something it wants to log
33957 before it has read the configuration file (for example, an error in the
33958 configuration file) it will not use the path you want, and may not be able to
33961 The value of LOG_FILE_PATH or &%log_file_path%& is a colon-separated
33962 list, currently limited to at most two items. This is one option where the
33963 facility for changing a list separator may not be used. The list must always be
33964 colon-separated. If an item in the list is &"syslog"& then syslog is used;
33965 otherwise the item must either be an absolute path, containing &`%s`& at the
33966 point where &"main"&, &"reject"&, or &"panic"& is to be inserted, or be empty,
33967 implying the use of a default path.
33969 When Exim encounters an empty item in the list, it searches the list defined by
33970 LOG_FILE_PATH, and uses the first item it finds that is neither empty nor
33971 &"syslog"&. This means that an empty item in &%log_file_path%& can be used to
33972 mean &"use the path specified at build time"&. It no such item exists, log
33973 files are written in the &_log_& subdirectory of the spool directory. This is
33974 equivalent to the setting:
33976 log_file_path = $spool_directory/log/%slog
33978 If you do not specify anything at build time or run time, that is where the
33981 A log file path may also contain &`%D`& or &`%M`& if datestamped log file names
33982 are in use &-- see section &<<SECTdatlogfil>>& below.
33984 Here are some examples of possible settings:
33986 &`LOG_FILE_PATH=syslog `& syslog only
33987 &`LOG_FILE_PATH=:syslog `& syslog and default path
33988 &`LOG_FILE_PATH=syslog : /usr/log/exim_%s `& syslog and specified path
33989 &`LOG_FILE_PATH=/usr/log/exim_%s `& specified path only
33991 If there are more than two paths in the list, the first is used and a panic
33996 .section "Logging to local files that are periodically &""cycled""&" "SECID285"
33997 .cindex "log" "cycling local files"
33998 .cindex "cycling logs"
33999 .cindex "&'exicyclog'&"
34000 .cindex "log" "local files; writing to"
34001 Some operating systems provide centralized and standardized methods for cycling
34002 log files. For those that do not, a utility script called &'exicyclog'& is
34003 provided (see section &<<SECTcyclogfil>>&). This renames and compresses the
34004 main and reject logs each time it is called. The maximum number of old logs to
34005 keep can be set. It is suggested this script is run as a daily &'cron'& job.
34007 An Exim delivery process opens the main log when it first needs to write to it,
34008 and it keeps the file open in case subsequent entries are required &-- for
34009 example, if a number of different deliveries are being done for the same
34010 message. However, remote SMTP deliveries can take a long time, and this means
34011 that the file may be kept open long after it is renamed if &'exicyclog'& or
34012 something similar is being used to rename log files on a regular basis. To
34013 ensure that a switch of log files is noticed as soon as possible, Exim calls
34014 &[stat()]& on the main log's name before reusing an open file, and if the file
34015 does not exist, or its inode has changed, the old file is closed and Exim
34016 tries to open the main log from scratch. Thus, an old log file may remain open
34017 for quite some time, but no Exim processes should write to it once it has been
34022 .section "Datestamped log files" "SECTdatlogfil"
34023 .cindex "log" "datestamped files"
34024 Instead of cycling the main and reject log files by renaming them
34025 periodically, some sites like to use files whose names contain a datestamp,
34026 for example, &_mainlog-20031225_&. The datestamp is in the form &_yyyymmdd_& or
34027 &_yyyymm_&. Exim has support for this way of working. It is enabled by setting
34028 the &%log_file_path%& option to a path that includes &`%D`& or &`%M`& at the
34029 point where the datestamp is required. For example:
34031 log_file_path = /var/spool/exim/log/%slog-%D
34032 log_file_path = /var/log/exim-%s-%D.log
34033 log_file_path = /var/spool/exim/log/%D-%slog
34034 log_file_path = /var/log/exim/%s.%M
34036 As before, &`%s`& is replaced by &"main"& or &"reject"&; the following are
34037 examples of names generated by the above examples:
34039 /var/spool/exim/log/mainlog-20021225
34040 /var/log/exim-reject-20021225.log
34041 /var/spool/exim/log/20021225-mainlog
34042 /var/log/exim/main.200212
34044 When this form of log file is specified, Exim automatically switches to new
34045 files at midnight. It does not make any attempt to compress old logs; you
34046 will need to write your own script if you require this. You should not
34047 run &'exicyclog'& with this form of logging.
34049 The location of the panic log is also determined by &%log_file_path%&, but it
34050 is not datestamped, because rotation of the panic log does not make sense.
34051 When generating the name of the panic log, &`%D`& or &`%M`& are removed from
34052 the string. In addition, if it immediately follows a slash, a following
34053 non-alphanumeric character is removed; otherwise a preceding non-alphanumeric
34054 character is removed. Thus, the four examples above would give these panic
34057 /var/spool/exim/log/paniclog
34058 /var/log/exim-panic.log
34059 /var/spool/exim/log/paniclog
34060 /var/log/exim/panic
34064 .section "Logging to syslog" "SECID249"
34065 .cindex "log" "syslog; writing to"
34066 The use of syslog does not change what Exim logs or the format of its messages,
34067 except in one respect. If &%syslog_timestamp%& is set false, the timestamps on
34068 Exim's log lines are omitted when these lines are sent to syslog. Apart from
34069 that, the same strings are written to syslog as to log files. The syslog
34070 &"facility"& is set to LOG_MAIL, and the program name to &"exim"&
34071 by default, but you can change these by setting the &%syslog_facility%& and
34072 &%syslog_processname%& options, respectively. If Exim was compiled with
34073 SYSLOG_LOG_PID set in &_Local/Makefile_& (this is the default in
34074 &_src/EDITME_&), then, on systems that permit it (all except ULTRIX), the
34075 LOG_PID flag is set so that the &[syslog()]& call adds the pid as well as
34076 the time and host name to each line.
34077 The three log streams are mapped onto syslog priorities as follows:
34080 &'mainlog'& is mapped to LOG_INFO
34082 &'rejectlog'& is mapped to LOG_NOTICE
34084 &'paniclog'& is mapped to LOG_ALERT
34087 Many log lines are written to both &'mainlog'& and &'rejectlog'&, and some are
34088 written to both &'mainlog'& and &'paniclog'&, so there will be duplicates if
34089 these are routed by syslog to the same place. You can suppress this duplication
34090 by setting &%syslog_duplication%& false.
34092 Exim's log lines can sometimes be very long, and some of its &'rejectlog'&
34093 entries contain multiple lines when headers are included. To cope with both
34094 these cases, entries written to syslog are split into separate &[syslog()]&
34095 calls at each internal newline, and also after a maximum of
34096 870 data characters. (This allows for a total syslog line length of 1024, when
34097 additions such as timestamps are added.) If you are running a syslog
34098 replacement that can handle lines longer than the 1024 characters allowed by
34099 RFC 3164, you should set
34101 SYSLOG_LONG_LINES=yes
34103 in &_Local/Makefile_& before building Exim. That stops Exim from splitting long
34104 lines, but it still splits at internal newlines in &'reject'& log entries.
34106 To make it easy to re-assemble split lines later, each component of a split
34107 entry starts with a string of the form [<&'n'&>/<&'m'&>] or [<&'n'&>\<&'m'&>]
34108 where <&'n'&> is the component number and <&'m'&> is the total number of
34109 components in the entry. The / delimiter is used when the line was split
34110 because it was too long; if it was split because of an internal newline, the \
34111 delimiter is used. For example, supposing the length limit to be 50 instead of
34112 870, the following would be the result of a typical rejection message to
34113 &'mainlog'& (LOG_INFO), each line in addition being preceded by the time, host
34114 name, and pid as added by syslog:
34116 [1/5] 2002-09-16 16:09:43 16RdAL-0006pc-00 rejected from
34117 [2/5] [127.0.0.1] (ph10): syntax error in 'From' header
34118 [3/5] when scanning for sender: missing or malformed lo
34119 [4/5] cal part in "<>" (envelope sender is <ph10@cam.exa
34122 The same error might cause the following lines to be written to &"rejectlog"&
34125 [1/18] 2002-09-16 16:09:43 16RdAL-0006pc-00 rejected fro
34126 [2/18] m [127.0.0.1] (ph10): syntax error in 'From' head
34127 [3/18] er when scanning for sender: missing or malformed
34128 [4/18] local part in "<>" (envelope sender is <ph10@cam
34130 [6\18] Recipients: ph10@some.domain.cam.example
34131 [7\18] P Received: from [127.0.0.1] (ident=ph10)
34132 [8\18] by xxxxx.cam.example with smtp (Exim 4.00)
34133 [9\18] id 16RdAL-0006pc-00
34134 [10/18] for ph10@cam.example; Mon, 16 Sep 2002 16:
34135 [11\18] 09:43 +0100
34137 [13\18] Subject: this is a test header
34138 [18\18] X-something: this is another header
34139 [15/18] I Message-Id: <E16RdAL-0006pc-00@xxxxx.cam.examp
34142 [18/18] Date: Mon, 16 Sep 2002 16:09:43 +0100
34144 Log lines that are neither too long nor contain newlines are written to syslog
34145 without modification.
34147 If only syslog is being used, the Exim monitor is unable to provide a log tail
34148 display, unless syslog is routing &'mainlog'& to a file on the local host and
34149 the environment variable EXIMON_LOG_FILE_PATH is set to tell the monitor
34154 .section "Log line flags" "SECID250"
34155 One line is written to the main log for each message received, and for each
34156 successful, unsuccessful, and delayed delivery. These lines can readily be
34157 picked out by the distinctive two-character flags that immediately follow the
34158 timestamp. The flags are:
34160 &`<=`& message arrival
34161 &`=>`& normal message delivery
34162 &`->`& additional address in same delivery
34163 &`>>`& cutthrough message delivery
34164 &`*>`& delivery suppressed by &%-N%&
34165 &`**`& delivery failed; address bounced
34166 &`==`& delivery deferred; temporary problem
34170 .section "Logging message reception" "SECID251"
34171 .cindex "log" "reception line"
34172 The format of the single-line entry in the main log that is written for every
34173 message received is shown in the basic example below, which is split over
34174 several lines in order to fit it on the page:
34176 2002-10-31 08:57:53 16ZCW1-0005MB-00 <= kryten@dwarf.fict.example
34177 H=mailer.fict.example [192.168.123.123] U=exim
34178 P=smtp S=5678 id=<incoming message id>
34180 The address immediately following &"<="& is the envelope sender address. A
34181 bounce message is shown with the sender address &"<>"&, and if it is locally
34182 generated, this is followed by an item of the form
34186 which is a reference to the message that caused the bounce to be sent.
34190 For messages from other hosts, the H and U fields identify the remote host and
34191 record the RFC 1413 identity of the user that sent the message, if one was
34192 received. The number given in square brackets is the IP address of the sending
34193 host. If there is a single, unparenthesized host name in the H field, as
34194 above, it has been verified to correspond to the IP address (see the
34195 &%host_lookup%& option). If the name is in parentheses, it was the name quoted
34196 by the remote host in the SMTP HELO or EHLO command, and has not been
34197 verified. If verification yields a different name to that given for HELO or
34198 EHLO, the verified name appears first, followed by the HELO or EHLO
34199 name in parentheses.
34201 Misconfigured hosts (and mail forgers) sometimes put an IP address, with or
34202 without brackets, in the HELO or EHLO command, leading to entries in
34203 the log containing text like these examples:
34205 H=(10.21.32.43) [192.168.8.34]
34206 H=([10.21.32.43]) [192.168.8.34]
34208 This can be confusing. Only the final address in square brackets can be relied
34211 For locally generated messages (that is, messages not received over TCP/IP),
34212 the H field is omitted, and the U field contains the login name of the caller
34215 .cindex "authentication" "logging"
34216 .cindex "AUTH" "logging"
34217 For all messages, the P field specifies the protocol used to receive the
34218 message. This is the value that is stored in &$received_protocol$&. In the case
34219 of incoming SMTP messages, the value indicates whether or not any SMTP
34220 extensions (ESMTP), encryption, or authentication were used. If the SMTP
34221 session was encrypted, there is an additional X field that records the cipher
34222 suite that was used.
34224 The protocol is set to &"esmtpsa"& or &"esmtpa"& for messages received from
34225 hosts that have authenticated themselves using the SMTP AUTH command. The first
34226 value is used when the SMTP connection was encrypted (&"secure"&). In this case
34227 there is an additional item A= followed by the name of the authenticator that
34228 was used. If an authenticated identification was set up by the authenticator's
34229 &%server_set_id%& option, this is logged too, separated by a colon from the
34230 authenticator name.
34232 .cindex "size" "of message"
34233 The id field records the existing message id, if present. The size of the
34234 received message is given by the S field. When the message is delivered,
34235 headers may be removed or added, so that the size of delivered copies of the
34236 message may not correspond with this value (and indeed may be different to each
34239 The &%log_selector%& option can be used to request the logging of additional
34240 data when a message is received. See section &<<SECTlogselector>>& below.
34244 .section "Logging deliveries" "SECID252"
34245 .cindex "log" "delivery line"
34246 The format of the single-line entry in the main log that is written for every
34247 delivery is shown in one of the examples below, for local and remote
34248 deliveries, respectively. Each example has been split into two lines in order
34249 to fit it on the page:
34251 2002-10-31 08:59:13 16ZCW1-0005MB-00 => marv
34252 <marv@hitch.fict.example> R=localuser T=local_delivery
34253 2002-10-31 09:00:10 16ZCW1-0005MB-00 =>
34254 monk@holistic.fict.example R=dnslookup T=remote_smtp
34255 H=holistic.fict.example [192.168.234.234]
34257 For ordinary local deliveries, the original address is given in angle brackets
34258 after the final delivery address, which might be a pipe or a file. If
34259 intermediate address(es) exist between the original and the final address, the
34260 last of these is given in parentheses after the final address. The R and T
34261 fields record the router and transport that were used to process the address.
34263 If SMTP AUTH was used for the delivery there is an additional item A=
34264 followed by the name of the authenticator that was used.
34265 If an authenticated identification was set up by the authenticator's &%client_set_id%&
34266 option, this is logged too, separated by a colon from the authenticator name.
34268 If a shadow transport was run after a successful local delivery, the log line
34269 for the successful delivery has an item added on the end, of the form
34271 &`ST=<`&&'shadow transport name'&&`>`&
34273 If the shadow transport did not succeed, the error message is put in
34274 parentheses afterwards.
34276 .cindex "asterisk" "after IP address"
34277 When more than one address is included in a single delivery (for example, two
34278 SMTP RCPT commands in one transaction) the second and subsequent addresses are
34279 flagged with &`->`& instead of &`=>`&. When two or more messages are delivered
34280 down a single SMTP connection, an asterisk follows the IP address in the log
34281 lines for the second and subsequent messages.
34283 .cindex "delivery" "cutthrough; logging"
34284 .cindex "cutthrough" "logging"
34285 When delivery is done in cutthrough mode it is flagged with &`>>`& and the log
34286 line precedes the reception line, since cutthrough waits for a possible
34287 rejection from the destination in case it can reject the sourced item.
34289 The generation of a reply message by a filter file gets logged as a
34290 &"delivery"& to the addressee, preceded by &">"&.
34292 The &%log_selector%& option can be used to request the logging of additional
34293 data when a message is delivered. See section &<<SECTlogselector>>& below.
34296 .section "Discarded deliveries" "SECID253"
34297 .cindex "discarded messages"
34298 .cindex "message" "discarded"
34299 .cindex "delivery" "discarded; logging"
34300 When a message is discarded as a result of the command &"seen finish"& being
34301 obeyed in a filter file which generates no deliveries, a log entry of the form
34303 2002-12-10 00:50:49 16auJc-0001UB-00 => discarded
34304 <low.club@bridge.example> R=userforward
34306 is written, to record why no deliveries are logged. When a message is discarded
34307 because it is aliased to &":blackhole:"& the log line is like this:
34309 1999-03-02 09:44:33 10HmaX-0005vi-00 => :blackhole:
34310 <hole@nowhere.example> R=blackhole_router
34314 .section "Deferred deliveries" "SECID254"
34315 When a delivery is deferred, a line of the following form is logged:
34317 2002-12-19 16:20:23 16aiQz-0002Q5-00 == marvin@endrest.example
34318 R=dnslookup T=smtp defer (146): Connection refused
34320 In the case of remote deliveries, the error is the one that was given for the
34321 last IP address that was tried. Details of individual SMTP failures are also
34322 written to the log, so the above line would be preceded by something like
34324 2002-12-19 16:20:23 16aiQz-0002Q5-00 Failed to connect to
34325 mail1.endrest.example [192.168.239.239]: Connection refused
34327 When a deferred address is skipped because its retry time has not been reached,
34328 a message is written to the log, but this can be suppressed by setting an
34329 appropriate value in &%log_selector%&.
34333 .section "Delivery failures" "SECID255"
34334 .cindex "delivery" "failure; logging"
34335 If a delivery fails because an address cannot be routed, a line of the
34336 following form is logged:
34338 1995-12-19 16:20:23 0tRiQz-0002Q5-00 ** jim@trek99.example
34339 <jim@trek99.example>: unknown mail domain
34341 If a delivery fails at transport time, the router and transport are shown, and
34342 the response from the remote host is included, as in this example:
34344 2002-07-11 07:14:17 17SXDU-000189-00 ** ace400@pb.example
34345 R=dnslookup T=remote_smtp: SMTP error from remote mailer
34346 after pipelined RCPT TO:<ace400@pb.example>: host
34347 pbmail3.py.example [192.168.63.111]: 553 5.3.0
34348 <ace400@pb.example>...Addressee unknown
34350 The word &"pipelined"& indicates that the SMTP PIPELINING extension was being
34351 used. See &%hosts_avoid_esmtp%& in the &(smtp)& transport for a way of
34352 disabling PIPELINING. The log lines for all forms of delivery failure are
34353 flagged with &`**`&.
34357 .section "Fake deliveries" "SECID256"
34358 .cindex "delivery" "fake; logging"
34359 If a delivery does not actually take place because the &%-N%& option has been
34360 used to suppress it, a normal delivery line is written to the log, except that
34361 &"=>"& is replaced by &"*>"&.
34365 .section "Completion" "SECID257"
34368 2002-10-31 09:00:11 16ZCW1-0005MB-00 Completed
34370 is written to the main log when a message is about to be removed from the spool
34371 at the end of its processing.
34376 .section "Summary of Fields in Log Lines" "SECID258"
34377 .cindex "log" "summary of fields"
34378 A summary of the field identifiers that are used in log lines is shown in
34379 the following table:
34381 &`A `& authenticator name (and optional id and sender)
34382 &`C `& SMTP confirmation on delivery
34383 &` `& command list for &"no mail in SMTP session"&
34384 &`CV `& certificate verification status
34385 &`D `& duration of &"no mail in SMTP session"&
34386 &`DN `& distinguished name from peer certificate
34387 &`DT `& on &`=>`& lines: time taken for a delivery
34388 &`F `& sender address (on delivery lines)
34389 &`H `& host name and IP address
34390 &`I `& local interface used
34391 &`id `& message id for incoming message
34392 &`P `& on &`<=`& lines: protocol used
34393 &` `& on &`=>`& and &`**`& lines: return path
34394 &`QT `& on &`=>`& lines: time spent on queue so far
34395 &` `& on &"Completed"& lines: time spent on queue
34396 &`R `& on &`<=`& lines: reference for local bounce
34397 &` `& on &`=>`& &`**`& and &`==`& lines: router name
34398 &`S `& size of message
34399 &`SNI `& server name indication from TLS client hello
34400 &`ST `& shadow transport name
34401 &`T `& on &`<=`& lines: message subject (topic)
34402 &` `& on &`=>`& &`**`& and &`==`& lines: transport name
34403 &`U `& local user or RFC 1413 identity
34404 &`X `& TLS cipher suite
34408 .section "Other log entries" "SECID259"
34409 Various other types of log entry are written from time to time. Most should be
34410 self-explanatory. Among the more common are:
34413 .cindex "retry" "time not reached"
34414 &'retry time not reached'&&~&~An address previously suffered a temporary error
34415 during routing or local delivery, and the time to retry has not yet arrived.
34416 This message is not written to an individual message log file unless it happens
34417 during the first delivery attempt.
34419 &'retry time not reached for any host'&&~&~An address previously suffered
34420 temporary errors during remote delivery, and the retry time has not yet arrived
34421 for any of the hosts to which it is routed.
34423 .cindex "spool directory" "file locked"
34424 &'spool file locked'&&~&~An attempt to deliver a message cannot proceed because
34425 some other Exim process is already working on the message. This can be quite
34426 common if queue running processes are started at frequent intervals. The
34427 &'exiwhat'& utility script can be used to find out what Exim processes are
34430 .cindex "error" "ignored"
34431 &'error ignored'&&~&~There are several circumstances that give rise to this
34434 Exim failed to deliver a bounce message whose age was greater than
34435 &%ignore_bounce_errors_after%&. The bounce was discarded.
34437 A filter file set up a delivery using the &"noerror"& option, and the delivery
34438 failed. The delivery was discarded.
34440 A delivery set up by a router configured with
34441 . ==== As this is a nested list, any displays it contains must be indented
34442 . ==== as otherwise they are too far to the left.
34446 failed. The delivery was discarded.
34454 .section "Reducing or increasing what is logged" "SECTlogselector"
34455 .cindex "log" "selectors"
34456 By setting the &%log_selector%& global option, you can disable some of Exim's
34457 default logging, or you can request additional logging. The value of
34458 &%log_selector%& is made up of names preceded by plus or minus characters. For
34461 log_selector = +arguments -retry_defer
34463 The list of optional log items is in the following table, with the default
34464 selection marked by asterisks:
34466 &` 8bitmime `& received 8BITMIME status
34467 &`*acl_warn_skipped `& skipped &%warn%& statement in ACL
34468 &` address_rewrite `& address rewriting
34469 &` all_parents `& all parents in => lines
34470 &` arguments `& command line arguments
34471 &`*connection_reject `& connection rejections
34472 &`*delay_delivery `& immediate delivery delayed
34473 &` deliver_time `& time taken to perform delivery
34474 &` delivery_size `& add &`S=`&&'nnn'& to => lines
34475 &`*dnslist_defer `& defers of DNS list (aka RBL) lookups
34476 &`*etrn `& ETRN commands
34477 &`*host_lookup_failed `& as it says
34478 &` ident_timeout `& timeout for ident connection
34479 &` incoming_interface `& incoming interface on <= lines
34480 &` incoming_port `& incoming port on <= lines
34481 &`*lost_incoming_connection `& as it says (includes timeouts)
34482 &` outgoing_port `& add remote port to => lines
34483 &`*queue_run `& start and end queue runs
34484 &` queue_time `& time on queue for one recipient
34485 &` queue_time_overall `& time on queue for whole message
34486 &` pid `& Exim process id
34487 &` received_recipients `& recipients on <= lines
34488 &` received_sender `& sender on <= lines
34489 &`*rejected_header `& header contents on reject log
34490 &`*retry_defer `& &"retry time not reached"&
34491 &` return_path_on_delivery `& put return path on => and ** lines
34492 &` sender_on_delivery `& add sender to => lines
34493 &`*sender_verify_fail `& sender verification failures
34494 &`*size_reject `& rejection because too big
34495 &`*skip_delivery `& delivery skipped in a queue run
34496 &`*smtp_confirmation `& SMTP confirmation on => lines
34497 &` smtp_connection `& SMTP connections
34498 &` smtp_incomplete_transaction`& incomplete SMTP transactions
34499 &` smtp_mailauth `& AUTH argument to MAIL commands
34500 &` smtp_no_mail `& session with no MAIL commands
34501 &` smtp_protocol_error `& SMTP protocol errors
34502 &` smtp_syntax_error `& SMTP syntax errors
34503 &` subject `& contents of &'Subject:'& on <= lines
34504 &` tls_certificate_verified `& certificate verification status
34505 &`*tls_cipher `& TLS cipher suite on <= and => lines
34506 &` tls_peerdn `& TLS peer DN on <= and => lines
34507 &` tls_sni `& TLS SNI on <= lines
34508 &` unknown_in_list `& DNS lookup failed in list match
34510 &` all `& all of the above
34512 More details on each of these items follows:
34516 .cindex "log" "8BITMIME"
34517 &%8bitmime%&: This causes Exim to log any 8BITMIME status of received messages,
34518 which may help in tracking down interoperability issues with ancient MTAs
34519 that are not 8bit clean. This is added to the &"<="& line, tagged with
34520 &`M8S=`& and a value of &`0`&, &`7`& or &`8`&, corresponding to "not given",
34521 &`7BIT`& and &`8BITMIME`& respectively.
34523 .cindex "&%warn%& ACL verb" "log when skipping"
34524 &%acl_warn_skipped%&: When an ACL &%warn%& statement is skipped because one of
34525 its conditions cannot be evaluated, a log line to this effect is written if
34526 this log selector is set.
34528 .cindex "log" "rewriting"
34529 .cindex "rewriting" "logging"
34530 &%address_rewrite%&: This applies both to global rewrites and per-transport
34531 rewrites, but not to rewrites in filters run as an unprivileged user (because
34532 such users cannot access the log).
34534 .cindex "log" "full parentage"
34535 &%all_parents%&: Normally only the original and final addresses are logged on
34536 delivery lines; with this selector, intermediate parents are given in
34537 parentheses between them.
34539 .cindex "log" "Exim arguments"
34540 .cindex "Exim arguments, logging"
34541 &%arguments%&: This causes Exim to write the arguments with which it was called
34542 to the main log, preceded by the current working directory. This is a debugging
34543 feature, added to make it easier to find out how certain MUAs call
34544 &_/usr/sbin/sendmail_&. The logging does not happen if Exim has given up root
34545 privilege because it was called with the &%-C%& or &%-D%& options. Arguments
34546 that are empty or that contain white space are quoted. Non-printing characters
34547 are shown as escape sequences. This facility cannot log unrecognized arguments,
34548 because the arguments are checked before the configuration file is read. The
34549 only way to log such cases is to interpose a script such as &_util/logargs.sh_&
34550 between the caller and Exim.
34552 .cindex "log" "connection rejections"
34553 &%connection_reject%&: A log entry is written whenever an incoming SMTP
34554 connection is rejected, for whatever reason.
34556 .cindex "log" "delayed delivery"
34557 .cindex "delayed delivery, logging"
34558 &%delay_delivery%&: A log entry is written whenever a delivery process is not
34559 started for an incoming message because the load is too high or too many
34560 messages were received on one connection. Logging does not occur if no delivery
34561 process is started because &%queue_only%& is set or &%-odq%& was used.
34563 .cindex "log" "delivery duration"
34564 &%deliver_time%&: For each delivery, the amount of real time it has taken to
34565 perform the actual delivery is logged as DT=<&'time'&>, for example, &`DT=1s`&.
34567 .cindex "log" "message size on delivery"
34568 .cindex "size" "of message"
34569 &%delivery_size%&: For each delivery, the size of message delivered is added to
34570 the &"=>"& line, tagged with S=.
34572 .cindex "log" "dnslist defer"
34573 .cindex "DNS list" "logging defer"
34574 .cindex "black list (DNS)"
34575 &%dnslist_defer%&: A log entry is written if an attempt to look up a host in a
34576 DNS black list suffers a temporary error.
34578 .cindex "log" "ETRN commands"
34579 .cindex "ETRN" "logging"
34580 &%etrn%&: Every valid ETRN command that is received is logged, before the ACL
34581 is run to determine whether or not it is actually accepted. An invalid ETRN
34582 command, or one received within a message transaction is not logged by this
34583 selector (see &%smtp_syntax_error%& and &%smtp_protocol_error%&).
34585 .cindex "log" "host lookup failure"
34586 &%host_lookup_failed%&: When a lookup of a host's IP addresses fails to find
34587 any addresses, or when a lookup of an IP address fails to find a host name, a
34588 log line is written. This logging does not apply to direct DNS lookups when
34589 routing email addresses, but it does apply to &"byname"& lookups.
34591 .cindex "log" "ident timeout"
34592 .cindex "RFC 1413" "logging timeout"
34593 &%ident_timeout%&: A log line is written whenever an attempt to connect to a
34594 client's ident port times out.
34596 .cindex "log" "incoming interface"
34597 .cindex "interface" "logging"
34598 &%incoming_interface%&: The interface on which a message was received is added
34599 to the &"<="& line as an IP address in square brackets, tagged by I= and
34600 followed by a colon and the port number. The local interface and port are also
34601 added to other SMTP log lines, for example &"SMTP connection from"&, and to
34604 .cindex "log" "incoming remote port"
34605 .cindex "port" "logging remote"
34606 .cindex "TCP/IP" "logging incoming remote port"
34607 .vindex "&$sender_fullhost$&"
34608 .vindex "&$sender_rcvhost$&"
34609 &%incoming_port%&: The remote port number from which a message was received is
34610 added to log entries and &'Received:'& header lines, following the IP address
34611 in square brackets, and separated from it by a colon. This is implemented by
34612 changing the value that is put in the &$sender_fullhost$& and
34613 &$sender_rcvhost$& variables. Recording the remote port number has become more
34614 important with the widening use of NAT (see RFC 2505).
34616 .cindex "log" "dropped connection"
34617 &%lost_incoming_connection%&: A log line is written when an incoming SMTP
34618 connection is unexpectedly dropped.
34620 .cindex "log" "outgoing remote port"
34621 .cindex "port" "logging outgoint remote"
34622 .cindex "TCP/IP" "logging ougtoing remote port"
34623 &%outgoing_port%&: The remote port number is added to delivery log lines (those
34624 containing => tags) following the IP address. This option is not included in
34625 the default setting, because for most ordinary configurations, the remote port
34626 number is always 25 (the SMTP port).
34628 .cindex "log" "process ids in"
34629 .cindex "pid (process id)" "in log lines"
34630 &%pid%&: The current process id is added to every log line, in square brackets,
34631 immediately after the time and date.
34633 .cindex "log" "queue run"
34634 .cindex "queue runner" "logging"
34635 &%queue_run%&: The start and end of every queue run are logged.
34637 .cindex "log" "queue time"
34638 &%queue_time%&: The amount of time the message has been in the queue on the
34639 local host is logged as QT=<&'time'&> on delivery (&`=>`&) lines, for example,
34640 &`QT=3m45s`&. The clock starts when Exim starts to receive the message, so it
34641 includes reception time as well as the delivery time for the current address.
34642 This means that it may be longer than the difference between the arrival and
34643 delivery log line times, because the arrival log line is not written until the
34644 message has been successfully received.
34646 &%queue_time_overall%&: The amount of time the message has been in the queue on
34647 the local host is logged as QT=<&'time'&> on &"Completed"& lines, for
34648 example, &`QT=3m45s`&. The clock starts when Exim starts to receive the
34649 message, so it includes reception time as well as the total delivery time.
34651 .cindex "log" "recipients"
34652 &%received_recipients%&: The recipients of a message are listed in the main log
34653 as soon as the message is received. The list appears at the end of the log line
34654 that is written when a message is received, preceded by the word &"for"&. The
34655 addresses are listed after they have been qualified, but before any rewriting
34657 Recipients that were discarded by an ACL for MAIL or RCPT do not appear
34660 .cindex "log" "sender reception"
34661 &%received_sender%&: The unrewritten original sender of a message is added to
34662 the end of the log line that records the message's arrival, after the word
34663 &"from"& (before the recipients if &%received_recipients%& is also set).
34665 .cindex "log" "header lines for rejection"
34666 &%rejected_header%&: If a message's header has been received at the time a
34667 rejection is written to the reject log, the complete header is added to the
34668 log. Header logging can be turned off individually for messages that are
34669 rejected by the &[local_scan()]& function (see section &<<SECTapiforloc>>&).
34671 .cindex "log" "retry defer"
34672 &%retry_defer%&: A log line is written if a delivery is deferred because a
34673 retry time has not yet been reached. However, this &"retry time not reached"&
34674 message is always omitted from individual message logs after the first delivery
34677 .cindex "log" "return path"
34678 &%return_path_on_delivery%&: The return path that is being transmitted with
34679 the message is included in delivery and bounce lines, using the tag P=.
34680 This is omitted if no delivery actually happens, for example, if routing fails,
34681 or if delivery is to &_/dev/null_& or to &`:blackhole:`&.
34683 .cindex "log" "sender on delivery"
34684 &%sender_on_delivery%&: The message's sender address is added to every delivery
34685 and bounce line, tagged by F= (for &"from"&).
34686 This is the original sender that was received with the message; it is not
34687 necessarily the same as the outgoing return path.
34689 .cindex "log" "sender verify failure"
34690 &%sender_verify_fail%&: If this selector is unset, the separate log line that
34691 gives details of a sender verification failure is not written. Log lines for
34692 the rejection of SMTP commands contain just &"sender verify failed"&, so some
34695 .cindex "log" "size rejection"
34696 &%size_reject%&: A log line is written whenever a message is rejected because
34699 .cindex "log" "frozen messages; skipped"
34700 .cindex "frozen messages" "logging skipping"
34701 &%skip_delivery%&: A log line is written whenever a message is skipped during a
34702 queue run because it is frozen or because another process is already delivering
34704 .cindex "&""spool file is locked""&"
34705 The message that is written is &"spool file is locked"&.
34707 .cindex "log" "smtp confirmation"
34708 .cindex "SMTP" "logging confirmation"
34709 .cindex "LMTP" "logging confirmation"
34710 &%smtp_confirmation%&: The response to the final &"."& in the SMTP or LMTP dialogue for
34711 outgoing messages is added to delivery log lines in the form &`C=`&<&'text'&>.
34712 A number of MTAs (including Exim) return an identifying string in this
34715 .cindex "log" "SMTP connections"
34716 .cindex "SMTP" "logging connections"
34717 &%smtp_connection%&: A log line is written whenever an SMTP connection is
34718 established or closed, unless the connection is from a host that matches
34719 &%hosts_connection_nolog%&. (In contrast, &%lost_incoming_connection%& applies
34720 only when the closure is unexpected.) This applies to connections from local
34721 processes that use &%-bs%& as well as to TCP/IP connections. If a connection is
34722 dropped in the middle of a message, a log line is always written, whether or
34723 not this selector is set, but otherwise nothing is written at the start and end
34724 of connections unless this selector is enabled.
34726 For TCP/IP connections to an Exim daemon, the current number of connections is
34727 included in the log message for each new connection, but note that the count is
34728 reset if the daemon is restarted.
34729 Also, because connections are closed (and the closure is logged) in
34730 subprocesses, the count may not include connections that have been closed but
34731 whose termination the daemon has not yet noticed. Thus, while it is possible to
34732 match up the opening and closing of connections in the log, the value of the
34733 logged counts may not be entirely accurate.
34735 .cindex "log" "SMTP transaction; incomplete"
34736 .cindex "SMTP" "logging incomplete transactions"
34737 &%smtp_incomplete_transaction%&: When a mail transaction is aborted by
34738 RSET, QUIT, loss of connection, or otherwise, the incident is logged,
34739 and the message sender plus any accepted recipients are included in the log
34740 line. This can provide evidence of dictionary attacks.
34742 .cindex "log" "non-MAIL SMTP sessions"
34743 .cindex "MAIL" "logging session without"
34744 &%smtp_no_mail%&: A line is written to the main log whenever an accepted SMTP
34745 connection terminates without having issued a MAIL command. This includes both
34746 the case when the connection is dropped, and the case when QUIT is used. It
34747 does not include cases where the connection is rejected right at the start (by
34748 an ACL, or because there are too many connections, or whatever). These cases
34749 already have their own log lines.
34751 The log line that is written contains the identity of the client in the usual
34752 way, followed by D= and a time, which records the duration of the connection.
34753 If the connection was authenticated, this fact is logged exactly as it is for
34754 an incoming message, with an A= item. If the connection was encrypted, CV=,
34755 DN=, and X= items may appear as they do for an incoming message, controlled by
34756 the same logging options.
34758 Finally, if any SMTP commands were issued during the connection, a C= item
34759 is added to the line, listing the commands that were used. For example,
34763 shows that the client issued QUIT straight after EHLO. If there were fewer
34764 than 20 commands, they are all listed. If there were more than 20 commands,
34765 the last 20 are listed, preceded by &"..."&. However, with the default
34766 setting of 10 for &%smtp_accep_max_nonmail%&, the connection will in any case
34767 have been aborted before 20 non-mail commands are processed.
34769 &%smtp_mailauth%&: A third subfield with the authenticated sender,
34770 colon-separated, is appended to the A= item for a message arrival or delivery
34771 log line, if an AUTH argument to the SMTP MAIL command (see &<<SECTauthparamail>>&)
34772 was accepted or used.
34774 .cindex "log" "SMTP protocol error"
34775 .cindex "SMTP" "logging protocol error"
34776 &%smtp_protocol_error%&: A log line is written for every SMTP protocol error
34777 encountered. Exim does not have perfect detection of all protocol errors
34778 because of transmission delays and the use of pipelining. If PIPELINING has
34779 been advertised to a client, an Exim server assumes that the client will use
34780 it, and therefore it does not count &"expected"& errors (for example, RCPT
34781 received after rejecting MAIL) as protocol errors.
34783 .cindex "SMTP" "logging syntax errors"
34784 .cindex "SMTP" "syntax errors; logging"
34785 .cindex "SMTP" "unknown command; logging"
34786 .cindex "log" "unknown SMTP command"
34787 .cindex "log" "SMTP syntax error"
34788 &%smtp_syntax_error%&: A log line is written for every SMTP syntax error
34789 encountered. An unrecognized command is treated as a syntax error. For an
34790 external connection, the host identity is given; for an internal connection
34791 using &%-bs%& the sender identification (normally the calling user) is given.
34793 .cindex "log" "subject"
34794 .cindex "subject, logging"
34795 &%subject%&: The subject of the message is added to the arrival log line,
34796 preceded by &"T="& (T for &"topic"&, since S is already used for &"size"&).
34797 Any MIME &"words"& in the subject are decoded. The &%print_topbitchars%& option
34798 specifies whether characters with values greater than 127 should be logged
34799 unchanged, or whether they should be rendered as escape sequences.
34801 .cindex "log" "certificate verification"
34802 &%tls_certificate_verified%&: An extra item is added to <= and => log lines
34803 when TLS is in use. The item is &`CV=yes`& if the peer's certificate was
34804 verified, and &`CV=no`& if not.
34806 .cindex "log" "TLS cipher"
34807 .cindex "TLS" "logging cipher"
34808 &%tls_cipher%&: When a message is sent or received over an encrypted
34809 connection, the cipher suite used is added to the log line, preceded by X=.
34811 .cindex "log" "TLS peer DN"
34812 .cindex "TLS" "logging peer DN"
34813 &%tls_peerdn%&: When a message is sent or received over an encrypted
34814 connection, and a certificate is supplied by the remote host, the peer DN is
34815 added to the log line, preceded by DN=.
34817 .cindex "log" "TLS SNI"
34818 .cindex "TLS" "logging SNI"
34819 &%tls_sni%&: When a message is received over an encrypted connection, and
34820 the remote host provided the Server Name Indication extension, the SNI is
34821 added to the log line, preceded by SNI=.
34823 .cindex "log" "DNS failure in list"
34824 &%unknown_in_list%&: This setting causes a log entry to be written when the
34825 result of a list match is failure because a DNS lookup failed.
34829 .section "Message log" "SECID260"
34830 .cindex "message" "log file for"
34831 .cindex "log" "message log; description of"
34832 .cindex "&_msglog_& directory"
34833 .oindex "&%preserve_message_logs%&"
34834 In addition to the general log files, Exim writes a log file for each message
34835 that it handles. The names of these per-message logs are the message ids, and
34836 they are kept in the &_msglog_& sub-directory of the spool directory. Each
34837 message log contains copies of the log lines that apply to the message. This
34838 makes it easier to inspect the status of an individual message without having
34839 to search the main log. A message log is deleted when processing of the message
34840 is complete, unless &%preserve_message_logs%& is set, but this should be used
34841 only with great care because they can fill up your disk very quickly.
34843 On a heavily loaded system, it may be desirable to disable the use of
34844 per-message logs, in order to reduce disk I/O. This can be done by setting the
34845 &%message_logs%& option false.
34851 . ////////////////////////////////////////////////////////////////////////////
34852 . ////////////////////////////////////////////////////////////////////////////
34854 .chapter "Exim utilities" "CHAPutils"
34855 .scindex IIDutils "utilities"
34856 A number of utility scripts and programs are supplied with Exim and are
34857 described in this chapter. There is also the Exim Monitor, which is covered in
34858 the next chapter. The utilities described here are:
34860 .itable none 0 0 3 7* left 15* left 40* left
34861 .irow &<<SECTfinoutwha>>& &'exiwhat'& &&&
34862 "list what Exim processes are doing"
34863 .irow &<<SECTgreptheque>>& &'exiqgrep'& "grep the queue"
34864 .irow &<<SECTsumtheque>>& &'exiqsumm'& "summarize the queue"
34865 .irow &<<SECTextspeinf>>& &'exigrep'& "search the main log"
34866 .irow &<<SECTexipick>>& &'exipick'& "select messages on &&&
34868 .irow &<<SECTcyclogfil>>& &'exicyclog'& "cycle (rotate) log files"
34869 .irow &<<SECTmailstat>>& &'eximstats'& &&&
34870 "extract statistics from the log"
34871 .irow &<<SECTcheckaccess>>& &'exim_checkaccess'& &&&
34872 "check address acceptance from given IP"
34873 .irow &<<SECTdbmbuild>>& &'exim_dbmbuild'& "build a DBM file"
34874 .irow &<<SECTfinindret>>& &'exinext'& "extract retry information"
34875 .irow &<<SECThindatmai>>& &'exim_dumpdb'& "dump a hints database"
34876 .irow &<<SECThindatmai>>& &'exim_tidydb'& "clean up a hints database"
34877 .irow &<<SECThindatmai>>& &'exim_fixdb'& "patch a hints database"
34878 .irow &<<SECTmailboxmaint>>& &'exim_lock'& "lock a mailbox file"
34881 Another utility that might be of use to sites with many MTAs is Tom Kistner's
34882 &'exilog'&. It provides log visualizations across multiple Exim servers. See
34883 &url(http://duncanthrax.net/exilog/) for details.
34888 .section "Finding out what Exim processes are doing (exiwhat)" "SECTfinoutwha"
34889 .cindex "&'exiwhat'&"
34890 .cindex "process, querying"
34892 On operating systems that can restart a system call after receiving a signal
34893 (most modern OS), an Exim process responds to the SIGUSR1 signal by writing
34894 a line describing what it is doing to the file &_exim-process.info_& in the
34895 Exim spool directory. The &'exiwhat'& script sends the signal to all Exim
34896 processes it can find, having first emptied the file. It then waits for one
34897 second to allow the Exim processes to react before displaying the results. In
34898 order to run &'exiwhat'& successfully you have to have sufficient privilege to
34899 send the signal to the Exim processes, so it is normally run as root.
34901 &*Warning*&: This is not an efficient process. It is intended for occasional
34902 use by system administrators. It is not sensible, for example, to set up a
34903 script that sends SIGUSR1 signals to Exim processes at short intervals.
34906 Unfortunately, the &'ps'& command that &'exiwhat'& uses to find Exim processes
34907 varies in different operating systems. Not only are different options used,
34908 but the format of the output is different. For this reason, there are some
34909 system configuration options that configure exactly how &'exiwhat'& works. If
34910 it doesn't seem to be working for you, check the following compile-time
34913 &`EXIWHAT_PS_CMD `& the command for running &'ps'&
34914 &`EXIWHAT_PS_ARG `& the argument for &'ps'&
34915 &`EXIWHAT_EGREP_ARG `& the argument for &'egrep'& to select from &'ps'& output
34916 &`EXIWHAT_KILL_ARG `& the argument for the &'kill'& command
34918 An example of typical output from &'exiwhat'& is
34920 164 daemon: -q1h, listening on port 25
34921 10483 running queue: waiting for 0tAycK-0002ij-00 (10492)
34922 10492 delivering 0tAycK-0002ij-00 to mail.ref.example
34923 [10.19.42.42] (editor@ref.example)
34924 10592 handling incoming call from [192.168.243.242]
34925 10628 accepting a local non-SMTP message
34927 The first number in the output line is the process number. The third line has
34928 been split here, in order to fit it on the page.
34932 .section "Selective queue listing (exiqgrep)" "SECTgreptheque"
34933 .cindex "&'exiqgrep'&"
34934 .cindex "queue" "grepping"
34935 This utility is a Perl script contributed by Matt Hubbard. It runs
34939 or (in case &*-a*& switch is specified)
34944 The &*-C*& option is used to specify an alternate &_exim.conf_& which might
34945 contain alternate exim configuration the queue management might be using.
34948 to obtain a queue listing, and then greps the output to select messages
34949 that match given criteria. The following selection options are available:
34952 .vitem &*-f*&&~<&'regex'&>
34953 Match the sender address using a case-insensitive search. The field that is
34954 tested is enclosed in angle brackets, so you can test for bounce messages with
34958 .vitem &*-r*&&~<&'regex'&>
34959 Match a recipient address using a case-insensitve search. The field that is
34960 tested is not enclosed in angle brackets.
34962 .vitem &*-s*&&~<&'regex'&>
34963 Match against the size field.
34965 .vitem &*-y*&&~<&'seconds'&>
34966 Match messages that are younger than the given time.
34968 .vitem &*-o*&&~<&'seconds'&>
34969 Match messages that are older than the given time.
34972 Match only frozen messages.
34975 Match only non-frozen messages.
34978 The following options control the format of the output:
34982 Display only the count of matching messages.
34985 Long format &-- display the full message information as output by Exim. This is
34989 Display message ids only.
34992 Brief format &-- one line per message.
34995 Display messages in reverse order.
34998 Include delivered recipients in queue listing.
35001 There is one more option, &%-h%&, which outputs a list of options.
35005 .section "Summarizing the queue (exiqsumm)" "SECTsumtheque"
35006 .cindex "&'exiqsumm'&"
35007 .cindex "queue" "summary"
35008 The &'exiqsumm'& utility is a Perl script which reads the output of &`exim
35009 -bp`& and produces a summary of the messages on the queue. Thus, you use it by
35010 running a command such as
35012 exim -bp | exiqsumm
35014 The output consists of one line for each domain that has messages waiting for
35015 it, as in the following example:
35017 3 2322 74m 66m msn.com.example
35019 Each line lists the number of pending deliveries for a domain, their total
35020 volume, and the length of time that the oldest and the newest messages have
35021 been waiting. Note that the number of pending deliveries is greater than the
35022 number of messages when messages have more than one recipient.
35024 A summary line is output at the end. By default the output is sorted on the
35025 domain name, but &'exiqsumm'& has the options &%-a%& and &%-c%&, which cause
35026 the output to be sorted by oldest message and by count of messages,
35027 respectively. There are also three options that split the messages for each
35028 domain into two or more subcounts: &%-b%& separates bounce messages, &%-f%&
35029 separates frozen messages, and &%-s%& separates messages according to their
35032 The output of &'exim -bp'& contains the original addresses in the message, so
35033 this also applies to the output from &'exiqsumm'&. No domains from addresses
35034 generated by aliasing or forwarding are included (unless the &%one_time%&
35035 option of the &(redirect)& router has been used to convert them into &"top
35036 level"& addresses).
35041 .section "Extracting specific information from the log (exigrep)" &&&
35043 .cindex "&'exigrep'&"
35044 .cindex "log" "extracts; grepping for"
35045 The &'exigrep'& utility is a Perl script that searches one or more main log
35046 files for entries that match a given pattern. When it finds a match, it
35047 extracts all the log entries for the relevant message, not just those that
35048 match the pattern. Thus, &'exigrep'& can extract complete log entries for a
35049 given message, or all mail for a given user, or for a given host, for example.
35050 The input files can be in Exim log format or syslog format.
35051 If a matching log line is not associated with a specific message, it is
35052 included in &'exigrep'&'s output without any additional lines. The usage is:
35054 &`exigrep [-t<`&&'n'&&`>] [-I] [-l] [-v] <`&&'pattern'&&`> [<`&&'log file'&&`>] ...`&
35056 If no log file names are given on the command line, the standard input is read.
35058 The &%-t%& argument specifies a number of seconds. It adds an additional
35059 condition for message selection. Messages that are complete are shown only if
35060 they spent more than <&'n'&> seconds on the queue.
35062 By default, &'exigrep'& does case-insensitive matching. The &%-I%& option
35063 makes it case-sensitive. This may give a performance improvement when searching
35064 large log files. Without &%-I%&, the Perl pattern matches use Perl's &`/i`&
35065 option; with &%-I%& they do not. In both cases it is possible to change the
35066 case sensitivity within the pattern by using &`(?i)`& or &`(?-i)`&.
35068 The &%-l%& option means &"literal"&, that is, treat all characters in the
35069 pattern as standing for themselves. Otherwise the pattern must be a Perl
35070 regular expression.
35072 The &%-v%& option inverts the matching condition. That is, a line is selected
35073 if it does &'not'& match the pattern.
35075 If the location of a &'zcat'& command is known from the definition of
35076 ZCAT_COMMAND in &_Local/Makefile_&, &'exigrep'& automatically passes any file
35077 whose name ends in COMPRESS_SUFFIX through &'zcat'& as it searches it.
35080 .section "Selecting messages by various criteria (exipick)" "SECTexipick"
35081 .cindex "&'exipick'&"
35082 John Jetmore's &'exipick'& utility is included in the Exim distribution. It
35083 lists messages from the queue according to a variety of criteria. For details
35084 of &'exipick'&'s facilities, visit the web page at
35085 &url(http://www.exim.org/eximwiki/ToolExipickManPage) or run &'exipick'& with
35086 the &%--help%& option.
35089 .section "Cycling log files (exicyclog)" "SECTcyclogfil"
35090 .cindex "log" "cycling local files"
35091 .cindex "cycling logs"
35092 .cindex "&'exicyclog'&"
35093 The &'exicyclog'& script can be used to cycle (rotate) &'mainlog'& and
35094 &'rejectlog'& files. This is not necessary if only syslog is being used, or if
35095 you are using log files with datestamps in their names (see section
35096 &<<SECTdatlogfil>>&). Some operating systems have their own standard mechanisms
35097 for log cycling, and these can be used instead of &'exicyclog'& if preferred.
35098 There are two command line options for &'exicyclog'&:
35100 &%-k%& <&'count'&> specifies the number of log files to keep, overriding the
35101 default that is set when Exim is built. The default default is 10.
35103 &%-l%& <&'path'&> specifies the log file path, in the same format as Exim's
35104 &%log_file_path%& option (for example, &`/var/log/exim_%slog`&), again
35105 overriding the script's default, which is to find the setting from Exim's
35109 Each time &'exicyclog'& is run the file names get &"shuffled down"& by one. If
35110 the main log file name is &_mainlog_& (the default) then when &'exicyclog'& is
35111 run &_mainlog_& becomes &_mainlog.01_&, the previous &_mainlog.01_& becomes
35112 &_mainlog.02_& and so on, up to the limit that is set in the script or by the
35113 &%-k%& option. Log files whose numbers exceed the limit are discarded. Reject
35114 logs are handled similarly.
35116 If the limit is greater than 99, the script uses 3-digit numbers such as
35117 &_mainlog.001_&, &_mainlog.002_&, etc. If you change from a number less than 99
35118 to one that is greater, or &'vice versa'&, you will have to fix the names of
35119 any existing log files.
35121 If no &_mainlog_& file exists, the script does nothing. Files that &"drop off"&
35122 the end are deleted. All files with numbers greater than 01 are compressed,
35123 using a compression command which is configured by the COMPRESS_COMMAND
35124 setting in &_Local/Makefile_&. It is usual to run &'exicyclog'& daily from a
35125 root &%crontab%& entry of the form
35127 1 0 * * * su exim -c /usr/exim/bin/exicyclog
35129 assuming you have used the name &"exim"& for the Exim user. You can run
35130 &'exicyclog'& as root if you wish, but there is no need.
35134 .section "Mail statistics (eximstats)" "SECTmailstat"
35135 .cindex "statistics"
35136 .cindex "&'eximstats'&"
35137 A Perl script called &'eximstats'& is provided for extracting statistical
35138 information from log files. The output is either plain text, or HTML.
35139 Exim log files are also supported by the &'Lire'& system produced by the
35140 LogReport Foundation &url(http://www.logreport.org).
35142 The &'eximstats'& script has been hacked about quite a bit over time. The
35143 latest version is the result of some extensive revision by Steve Campbell. A
35144 lot of information is given by default, but there are options for suppressing
35145 various parts of it. Following any options, the arguments to the script are a
35146 list of files, which should be main log files. For example:
35148 eximstats -nr /var/spool/exim/log/mainlog.01
35150 By default, &'eximstats'& extracts information about the number and volume of
35151 messages received from or delivered to various hosts. The information is sorted
35152 both by message count and by volume, and the top fifty hosts in each category
35153 are listed on the standard output. Similar information, based on email
35154 addresses or domains instead of hosts can be requested by means of various
35155 options. For messages delivered and received locally, similar statistics are
35156 also produced per user.
35158 The output also includes total counts and statistics about delivery errors, and
35159 histograms showing the number of messages received and deliveries made in each
35160 hour of the day. A delivery with more than one address in its envelope (for
35161 example, an SMTP transaction with more than one RCPT command) is counted
35162 as a single delivery by &'eximstats'&.
35164 Though normally more deliveries than receipts are reported (as messages may
35165 have multiple recipients), it is possible for &'eximstats'& to report more
35166 messages received than delivered, even though the queue is empty at the start
35167 and end of the period in question. If an incoming message contains no valid
35168 recipients, no deliveries are recorded for it. A bounce message is handled as
35169 an entirely separate message.
35171 &'eximstats'& always outputs a grand total summary giving the volume and number
35172 of messages received and deliveries made, and the number of hosts involved in
35173 each case. It also outputs the number of messages that were delayed (that is,
35174 not completely delivered at the first attempt), and the number that had at
35175 least one address that failed.
35177 The remainder of the output is in sections that can be independently disabled
35178 or modified by various options. It consists of a summary of deliveries by
35179 transport, histograms of messages received and delivered per time interval
35180 (default per hour), information about the time messages spent on the queue,
35181 a list of relayed messages, lists of the top fifty sending hosts, local
35182 senders, destination hosts, and destination local users by count and by volume,
35183 and a list of delivery errors that occurred.
35185 The relay information lists messages that were actually relayed, that is, they
35186 came from a remote host and were directly delivered to some other remote host,
35187 without being processed (for example, for aliasing or forwarding) locally.
35189 There are quite a few options for &'eximstats'& to control exactly what it
35190 outputs. These are documented in the Perl script itself, and can be extracted
35191 by running the command &(perldoc)& on the script. For example:
35193 perldoc /usr/exim/bin/eximstats
35196 .section "Checking access policy (exim_checkaccess)" "SECTcheckaccess"
35197 .cindex "&'exim_checkaccess'&"
35198 .cindex "policy control" "checking access"
35199 .cindex "checking access"
35200 The &%-bh%& command line argument allows you to run a fake SMTP session with
35201 debugging output, in order to check what Exim is doing when it is applying
35202 policy controls to incoming SMTP mail. However, not everybody is sufficiently
35203 familiar with the SMTP protocol to be able to make full use of &%-bh%&, and
35204 sometimes you just want to answer the question &"Does this address have
35205 access?"& without bothering with any further details.
35207 The &'exim_checkaccess'& utility is a &"packaged"& version of &%-bh%&. It takes
35208 two arguments, an IP address and an email address:
35210 exim_checkaccess 10.9.8.7 A.User@a.domain.example
35212 The utility runs a call to Exim with the &%-bh%& option, to test whether the
35213 given email address would be accepted in a RCPT command in a TCP/IP
35214 connection from the host with the given IP address. The output of the utility
35215 is either the word &"accepted"&, or the SMTP error response, for example:
35218 550 Relay not permitted
35220 When running this test, the utility uses &`<>`& as the envelope sender address
35221 for the MAIL command, but you can change this by providing additional
35222 options. These are passed directly to the Exim command. For example, to specify
35223 that the test is to be run with the sender address &'himself@there.example'&
35226 exim_checkaccess 10.9.8.7 A.User@a.domain.example \
35227 -f himself@there.example
35229 Note that these additional Exim command line items must be given after the two
35230 mandatory arguments.
35232 Because the &%exim_checkaccess%& uses &%-bh%&, it does not perform callouts
35233 while running its checks. You can run checks that include callouts by using
35234 &%-bhc%&, but this is not yet available in a &"packaged"& form.
35238 .section "Making DBM files (exim_dbmbuild)" "SECTdbmbuild"
35239 .cindex "DBM" "building dbm files"
35240 .cindex "building DBM files"
35241 .cindex "&'exim_dbmbuild'&"
35242 .cindex "lower casing"
35243 .cindex "binary zero" "in lookup key"
35244 The &'exim_dbmbuild'& program reads an input file containing keys and data in
35245 the format used by the &(lsearch)& lookup (see section
35246 &<<SECTsinglekeylookups>>&). It writes a DBM file using the lower-cased alias
35247 names as keys and the remainder of the information as data. The lower-casing
35248 can be prevented by calling the program with the &%-nolc%& option.
35250 A terminating zero is included as part of the key string. This is expected by
35251 the &(dbm)& lookup type. However, if the option &%-nozero%& is given,
35252 &'exim_dbmbuild'& creates files without terminating zeroes in either the key
35253 strings or the data strings. The &(dbmnz)& lookup type can be used with such
35256 The program requires two arguments: the name of the input file (which can be a
35257 single hyphen to indicate the standard input), and the name of the output file.
35258 It creates the output under a temporary name, and then renames it if all went
35262 If the native DB interface is in use (USE_DB is set in a compile-time
35263 configuration file &-- this is common in free versions of Unix) the two file
35264 names must be different, because in this mode the Berkeley DB functions create
35265 a single output file using exactly the name given. For example,
35267 exim_dbmbuild /etc/aliases /etc/aliases.db
35269 reads the system alias file and creates a DBM version of it in
35270 &_/etc/aliases.db_&.
35272 In systems that use the &'ndbm'& routines (mostly proprietary versions of
35273 Unix), two files are used, with the suffixes &_.dir_& and &_.pag_&. In this
35274 environment, the suffixes are added to the second argument of
35275 &'exim_dbmbuild'&, so it can be the same as the first. This is also the case
35276 when the Berkeley functions are used in compatibility mode (though this is not
35277 recommended), because in that case it adds a &_.db_& suffix to the file name.
35279 If a duplicate key is encountered, the program outputs a warning, and when it
35280 finishes, its return code is 1 rather than zero, unless the &%-noduperr%&
35281 option is used. By default, only the first of a set of duplicates is used &--
35282 this makes it compatible with &(lsearch)& lookups. There is an option
35283 &%-lastdup%& which causes it to use the data for the last duplicate instead.
35284 There is also an option &%-nowarn%&, which stops it listing duplicate keys to
35285 &%stderr%&. For other errors, where it doesn't actually make a new file, the
35291 .section "Finding individual retry times (exinext)" "SECTfinindret"
35292 .cindex "retry" "times"
35293 .cindex "&'exinext'&"
35294 A utility called &'exinext'& (mostly a Perl script) provides the ability to
35295 fish specific information out of the retry database. Given a mail domain (or a
35296 complete address), it looks up the hosts for that domain, and outputs any retry
35297 information for the hosts or for the domain. At present, the retry information
35298 is obtained by running &'exim_dumpdb'& (see below) and post-processing the
35299 output. For example:
35301 $ exinext piglet@milne.fict.example
35302 kanga.milne.example:192.168.8.1 error 146: Connection refused
35303 first failed: 21-Feb-1996 14:57:34
35304 last tried: 21-Feb-1996 14:57:34
35305 next try at: 21-Feb-1996 15:02:34
35306 roo.milne.example:192.168.8.3 error 146: Connection refused
35307 first failed: 20-Jan-1996 13:12:08
35308 last tried: 21-Feb-1996 11:42:03
35309 next try at: 21-Feb-1996 19:42:03
35310 past final cutoff time
35312 You can also give &'exinext'& a local part, without a domain, and it
35313 will give any retry information for that local part in your default domain.
35314 A message id can be used to obtain retry information pertaining to a specific
35315 message. This exists only when an attempt to deliver a message to a remote host
35316 suffers a message-specific error (see section &<<SECToutSMTPerr>>&).
35317 &'exinext'& is not particularly efficient, but then it is not expected to be
35320 The &'exinext'& utility calls Exim to find out information such as the location
35321 of the spool directory. The utility has &%-C%& and &%-D%& options, which are
35322 passed on to the &'exim'& commands. The first specifies an alternate Exim
35323 configuration file, and the second sets macros for use within the configuration
35324 file. These features are mainly to help in testing, but might also be useful in
35325 environments where more than one configuration file is in use.
35329 .section "Hints database maintenance" "SECThindatmai"
35330 .cindex "hints database" "maintenance"
35331 .cindex "maintaining Exim's hints database"
35332 Three utility programs are provided for maintaining the DBM files that Exim
35333 uses to contain its delivery hint information. Each program requires two
35334 arguments. The first specifies the name of Exim's spool directory, and the
35335 second is the name of the database it is to operate on. These are as follows:
35338 &'retry'&: the database of retry information
35340 &'wait-'&<&'transport name'&>: databases of information about messages waiting
35343 &'callout'&: the callout cache
35345 &'ratelimit'&: the data for implementing the ratelimit ACL condition
35347 &'misc'&: other hints data
35350 The &'misc'& database is used for
35353 Serializing ETRN runs (when &%smtp_etrn_serialize%& is set)
35355 Serializing delivery to a specific host (when &%serialize_hosts%& is set in an
35356 &(smtp)& transport)
35361 .section "exim_dumpdb" "SECID261"
35362 .cindex "&'exim_dumpdb'&"
35363 The entire contents of a database are written to the standard output by the
35364 &'exim_dumpdb'& program, which has no options or arguments other than the
35365 spool and database names. For example, to dump the retry database:
35367 exim_dumpdb /var/spool/exim retry
35369 Two lines of output are produced for each entry:
35371 T:mail.ref.example:192.168.242.242 146 77 Connection refused
35372 31-Oct-1995 12:00:12 02-Nov-1995 12:21:39 02-Nov-1995 20:21:39 *
35374 The first item on the first line is the key of the record. It starts with one
35375 of the letters R, or T, depending on whether it refers to a routing or
35376 transport retry. For a local delivery, the next part is the local address; for
35377 a remote delivery it is the name of the remote host, followed by its failing IP
35378 address (unless &%retry_include_ip_address%& is set false on the &(smtp)&
35379 transport). If the remote port is not the standard one (port 25), it is added
35380 to the IP address. Then there follows an error code, an additional error code,
35381 and a textual description of the error.
35383 The three times on the second line are the time of first failure, the time of
35384 the last delivery attempt, and the computed time for the next attempt. The line
35385 ends with an asterisk if the cutoff time for the last retry rule has been
35388 Each output line from &'exim_dumpdb'& for the &'wait-xxx'& databases
35389 consists of a host name followed by a list of ids for messages that are or were
35390 waiting to be delivered to that host. If there are a very large number for any
35391 one host, continuation records, with a sequence number added to the host name,
35392 may be seen. The data in these records is often out of date, because a message
35393 may be routed to several alternative hosts, and Exim makes no effort to keep
35398 .section "exim_tidydb" "SECID262"
35399 .cindex "&'exim_tidydb'&"
35400 The &'exim_tidydb'& utility program is used to tidy up the contents of a hints
35401 database. If run with no options, it removes all records that are more than 30
35402 days old. The age is calculated from the date and time that the record was last
35403 updated. Note that, in the case of the retry database, it is &'not'& the time
35404 since the first delivery failure. Information about a host that has been down
35405 for more than 30 days will remain in the database, provided that the record is
35406 updated sufficiently often.
35408 The cutoff date can be altered by means of the &%-t%& option, which must be
35409 followed by a time. For example, to remove all records older than a week from
35410 the retry database:
35412 exim_tidydb -t 7d /var/spool/exim retry
35414 Both the &'wait-xxx'& and &'retry'& databases contain items that involve
35415 message ids. In the former these appear as data in records keyed by host &--
35416 they were messages that were waiting for that host &-- and in the latter they
35417 are the keys for retry information for messages that have suffered certain
35418 types of error. When &'exim_tidydb'& is run, a check is made to ensure that
35419 message ids in database records are those of messages that are still on the
35420 queue. Message ids for messages that no longer exist are removed from
35421 &'wait-xxx'& records, and if this leaves any records empty, they are deleted.
35422 For the &'retry'& database, records whose keys are non-existent message ids are
35423 removed. The &'exim_tidydb'& utility outputs comments on the standard output
35424 whenever it removes information from the database.
35426 Certain records are automatically removed by Exim when they are no longer
35427 needed, but others are not. For example, if all the MX hosts for a domain are
35428 down, a retry record is created for each one. If the primary MX host comes back
35429 first, its record is removed when Exim successfully delivers to it, but the
35430 records for the others remain because Exim has not tried to use those hosts.
35432 It is important, therefore, to run &'exim_tidydb'& periodically on all the
35433 hints databases. You should do this at a quiet time of day, because it requires
35434 a database to be locked (and therefore inaccessible to Exim) while it does its
35435 work. Removing records from a DBM file does not normally make the file smaller,
35436 but all the common DBM libraries are able to re-use the space that is released.
35437 After an initial phase of increasing in size, the databases normally reach a
35438 point at which they no longer get any bigger, as long as they are regularly
35441 &*Warning*&: If you never run &'exim_tidydb'&, the space used by the hints
35442 databases is likely to keep on increasing.
35447 .section "exim_fixdb" "SECID263"
35448 .cindex "&'exim_fixdb'&"
35449 The &'exim_fixdb'& program is a utility for interactively modifying databases.
35450 Its main use is for testing Exim, but it might also be occasionally useful for
35451 getting round problems in a live system. It has no options, and its interface
35452 is somewhat crude. On entry, it prompts for input with a right angle-bracket. A
35453 key of a database record can then be entered, and the data for that record is
35456 If &"d"& is typed at the next prompt, the entire record is deleted. For all
35457 except the &'retry'& database, that is the only operation that can be carried
35458 out. For the &'retry'& database, each field is output preceded by a number, and
35459 data for individual fields can be changed by typing the field number followed
35460 by new data, for example:
35464 resets the time of the next delivery attempt. Time values are given as a
35465 sequence of digit pairs for year, month, day, hour, and minute. Colons can be
35466 used as optional separators.
35471 .section "Mailbox maintenance (exim_lock)" "SECTmailboxmaint"
35472 .cindex "mailbox" "maintenance"
35473 .cindex "&'exim_lock'&"
35474 .cindex "locking mailboxes"
35475 The &'exim_lock'& utility locks a mailbox file using the same algorithm as
35476 Exim. For a discussion of locking issues, see section &<<SECTopappend>>&.
35477 &'Exim_lock'& can be used to prevent any modification of a mailbox by Exim or
35478 a user agent while investigating a problem. The utility requires the name of
35479 the file as its first argument. If the locking is successful, the second
35480 argument is run as a command (using C's &[system()]& function); if there is no
35481 second argument, the value of the SHELL environment variable is used; if this
35482 is unset or empty, &_/bin/sh_& is run. When the command finishes, the mailbox
35483 is unlocked and the utility ends. The following options are available:
35487 Use &[fcntl()]& locking on the open mailbox.
35490 Use &[flock()]& locking on the open mailbox, provided the operating system
35493 .vitem &%-interval%&
35494 This must be followed by a number, which is a number of seconds; it sets the
35495 interval to sleep between retries (default 3).
35497 .vitem &%-lockfile%&
35498 Create a lock file before opening the mailbox.
35501 Lock the mailbox using MBX rules.
35504 Suppress verification output.
35506 .vitem &%-retries%&
35507 This must be followed by a number; it sets the number of times to try to get
35508 the lock (default 10).
35510 .vitem &%-restore_time%&
35511 This option causes &%exim_lock%& to restore the modified and read times to the
35512 locked file before exiting. This allows you to access a locked mailbox (for
35513 example, to take a backup copy) without disturbing the times that the user
35516 .vitem &%-timeout%&
35517 This must be followed by a number, which is a number of seconds; it sets a
35518 timeout to be used with a blocking &[fcntl()]& lock. If it is not set (the
35519 default), a non-blocking call is used.
35522 Generate verbose output.
35525 If none of &%-fcntl%&, &%-flock%&, &%-lockfile%& or &%-mbx%& are given, the
35526 default is to create a lock file and also to use &[fcntl()]& locking on the
35527 mailbox, which is the same as Exim's default. The use of &%-flock%& or
35528 &%-fcntl%& requires that the file be writeable; the use of &%-lockfile%&
35529 requires that the directory containing the file be writeable. Locking by lock
35530 file does not last for ever; Exim assumes that a lock file is expired if it is
35531 more than 30 minutes old.
35533 The &%-mbx%& option can be used with either or both of &%-fcntl%& or
35534 &%-flock%&. It assumes &%-fcntl%& by default. MBX locking causes a shared lock
35535 to be taken out on the open mailbox, and an exclusive lock on the file
35536 &_/tmp/.n.m_& where &'n'& and &'m'& are the device number and inode
35537 number of the mailbox file. When the locking is released, if an exclusive lock
35538 can be obtained for the mailbox, the file in &_/tmp_& is deleted.
35540 The default output contains verification of the locking that takes place. The
35541 &%-v%& option causes some additional information to be given. The &%-q%& option
35542 suppresses all output except error messages.
35546 exim_lock /var/spool/mail/spqr
35548 runs an interactive shell while the file is locked, whereas
35550 &`exim_lock -q /var/spool/mail/spqr <<End`&
35551 <&'some commands'&>
35554 runs a specific non-interactive sequence of commands while the file is locked,
35555 suppressing all verification output. A single command can be run by a command
35558 exim_lock -q /var/spool/mail/spqr \
35559 "cp /var/spool/mail/spqr /some/where"
35561 Note that if a command is supplied, it must be entirely contained within the
35562 second argument &-- hence the quotes.
35566 . ////////////////////////////////////////////////////////////////////////////
35567 . ////////////////////////////////////////////////////////////////////////////
35569 .chapter "The Exim monitor" "CHAPeximon"
35570 .scindex IIDeximon "Exim monitor" "description"
35571 .cindex "X-windows"
35572 .cindex "&'eximon'&"
35573 .cindex "Local/eximon.conf"
35574 .cindex "&_exim_monitor/EDITME_&"
35575 The Exim monitor is an application which displays in an X window information
35576 about the state of Exim's queue and what Exim is doing. An admin user can
35577 perform certain operations on messages from this GUI interface; however all
35578 such facilities are also available from the command line, and indeed, the
35579 monitor itself makes use of the command line to perform any actions requested.
35583 .section "Running the monitor" "SECID264"
35584 The monitor is started by running the script called &'eximon'&. This is a shell
35585 script that sets up a number of environment variables, and then runs the
35586 binary called &_eximon.bin_&. The default appearance of the monitor window can
35587 be changed by editing the &_Local/eximon.conf_& file created by editing
35588 &_exim_monitor/EDITME_&. Comments in that file describe what the various
35589 parameters are for.
35591 The parameters that get built into the &'eximon'& script can be overridden for
35592 a particular invocation by setting up environment variables of the same names,
35593 preceded by &`EXIMON_`&. For example, a shell command such as
35595 EXIMON_LOG_DEPTH=400 eximon
35597 (in a Bourne-compatible shell) runs &'eximon'& with an overriding setting of
35598 the LOG_DEPTH parameter. If EXIMON_LOG_FILE_PATH is set in the environment, it
35599 overrides the Exim log file configuration. This makes it possible to have
35600 &'eximon'& tailing log data that is written to syslog, provided that MAIL.INFO
35601 syslog messages are routed to a file on the local host.
35603 X resources can be used to change the appearance of the window in the normal
35604 way. For example, a resource setting of the form
35606 Eximon*background: gray94
35608 changes the colour of the background to light grey rather than white. The
35609 stripcharts are drawn with both the data lines and the reference lines in
35610 black. This means that the reference lines are not visible when on top of the
35611 data. However, their colour can be changed by setting a resource called
35612 &"highlight"& (an odd name, but that's what the Athena stripchart widget uses).
35613 For example, if your X server is running Unix, you could set up lighter
35614 reference lines in the stripcharts by obeying
35617 Eximon*highlight: gray
35620 .cindex "admin user"
35621 In order to see the contents of messages on the queue, and to operate on them,
35622 &'eximon'& must either be run as root or by an admin user.
35624 The command-line parameters of &'eximon'& are passed to &_eximon.bin_& and may
35625 contain X11 resource parameters interpreted by the X11 library. In addition,
35626 if the first parameter starts with the string "gdb" then it is removed and the
35627 binary is invoked under gdb (the parameter is used as the gdb command-name, so
35628 versioned variants of gdb can be invoked).
35630 The monitor's window is divided into three parts. The first contains one or
35631 more stripcharts and two action buttons, the second contains a &"tail"& of the
35632 main log file, and the third is a display of the queue of messages awaiting
35633 delivery, with two more action buttons. The following sections describe these
35634 different parts of the display.
35639 .section "The stripcharts" "SECID265"
35640 .cindex "stripchart"
35641 The first stripchart is always a count of messages on the queue. Its name can
35642 be configured by setting QUEUE_STRIPCHART_NAME in the
35643 &_Local/eximon.conf_& file. The remaining stripcharts are defined in the
35644 configuration script by regular expression matches on log file entries, making
35645 it possible to display, for example, counts of messages delivered to certain
35646 hosts or using certain transports. The supplied defaults display counts of
35647 received and delivered messages, and of local and SMTP deliveries. The default
35648 period between stripchart updates is one minute; this can be adjusted by a
35649 parameter in the &_Local/eximon.conf_& file.
35651 The stripchart displays rescale themselves automatically as the value they are
35652 displaying changes. There are always 10 horizontal lines in each chart; the
35653 title string indicates the value of each division when it is greater than one.
35654 For example, &"x2"& means that each division represents a value of 2.
35656 It is also possible to have a stripchart which shows the percentage fullness of
35657 a particular disk partition, which is useful when local deliveries are confined
35658 to a single partition.
35660 .cindex "&%statvfs%& function"
35661 This relies on the availability of the &[statvfs()]& function or equivalent in
35662 the operating system. Most, but not all versions of Unix that support Exim have
35663 this. For this particular stripchart, the top of the chart always represents
35664 100%, and the scale is given as &"x10%"&. This chart is configured by setting
35665 SIZE_STRIPCHART and (optionally) SIZE_STRIPCHART_NAME in the
35666 &_Local/eximon.conf_& file.
35671 .section "Main action buttons" "SECID266"
35672 .cindex "size" "of monitor window"
35673 .cindex "Exim monitor" "window size"
35674 .cindex "window size"
35675 Below the stripcharts there is an action button for quitting the monitor. Next
35676 to this is another button marked &"Size"&. They are placed here so that
35677 shrinking the window to its default minimum size leaves just the queue count
35678 stripchart and these two buttons visible. Pressing the &"Size"& button causes
35679 the window to expand to its maximum size, unless it is already at the maximum,
35680 in which case it is reduced to its minimum.
35682 When expanding to the maximum, if the window cannot be fully seen where it
35683 currently is, it is moved back to where it was the last time it was at full
35684 size. When it is expanding from its minimum size, the old position is
35685 remembered, and next time it is reduced to the minimum it is moved back there.
35687 The idea is that you can keep a reduced window just showing one or two
35688 stripcharts at a convenient place on your screen, easily expand it to show
35689 the full window when required, and just as easily put it back to what it was.
35690 The idea is copied from what the &'twm'& window manager does for its
35691 &'f.fullzoom'& action. The minimum size of the window can be changed by setting
35692 the MIN_HEIGHT and MIN_WIDTH values in &_Local/eximon.conf_&.
35694 Normally, the monitor starts up with the window at its full size, but it can be
35695 built so that it starts up with the window at its smallest size, by setting
35696 START_SMALL=yes in &_Local/eximon.conf_&.
35700 .section "The log display" "SECID267"
35701 .cindex "log" "tail of; in monitor"
35702 The second section of the window is an area in which a display of the tail of
35703 the main log is maintained.
35704 To save space on the screen, the timestamp on each log line is shortened by
35705 removing the date and, if &%log_timezone%& is set, the timezone.
35706 The log tail is not available when the only destination for logging data is
35707 syslog, unless the syslog lines are routed to a local file whose name is passed
35708 to &'eximon'& via the EXIMON_LOG_FILE_PATH environment variable.
35710 The log sub-window has a scroll bar at its lefthand side which can be used to
35711 move back to look at earlier text, and the up and down arrow keys also have a
35712 scrolling effect. The amount of log that is kept depends on the setting of
35713 LOG_BUFFER in &_Local/eximon.conf_&, which specifies the amount of memory
35714 to use. When this is full, the earlier 50% of data is discarded &-- this is
35715 much more efficient than throwing it away line by line. The sub-window also has
35716 a horizontal scroll bar for accessing the ends of long log lines. This is the
35717 only means of horizontal scrolling; the right and left arrow keys are not
35718 available. Text can be cut from this part of the window using the mouse in the
35719 normal way. The size of this subwindow is controlled by parameters in the
35720 configuration file &_Local/eximon.conf_&.
35722 Searches of the text in the log window can be carried out by means of the ^R
35723 and ^S keystrokes, which default to a reverse and a forward search,
35724 respectively. The search covers only the text that is displayed in the window.
35725 It cannot go further back up the log.
35727 The point from which the search starts is indicated by a caret marker. This is
35728 normally at the end of the text in the window, but can be positioned explicitly
35729 by pointing and clicking with the left mouse button, and is moved automatically
35730 by a successful search. If new text arrives in the window when it is scrolled
35731 back, the caret remains where it is, but if the window is not scrolled back,
35732 the caret is moved to the end of the new text.
35734 Pressing ^R or ^S pops up a window into which the search text can be typed.
35735 There are buttons for selecting forward or reverse searching, for carrying out
35736 the search, and for cancelling. If the &"Search"& button is pressed, the search
35737 happens and the window remains so that further searches can be done. If the
35738 &"Return"& key is pressed, a single search is done and the window is closed. If
35739 ^C is typed the search is cancelled.
35741 The searching facility is implemented using the facilities of the Athena text
35742 widget. By default this pops up a window containing both &"search"& and
35743 &"replace"& options. In order to suppress the unwanted &"replace"& portion for
35744 eximon, a modified version of the &%TextPop%& widget is distributed with Exim.
35745 However, the linkers in BSDI and HP-UX seem unable to handle an externally
35746 provided version of &%TextPop%& when the remaining parts of the text widget
35747 come from the standard libraries. The compile-time option EXIMON_TEXTPOP can be
35748 unset to cut out the modified &%TextPop%&, making it possible to build Eximon
35749 on these systems, at the expense of having unwanted items in the search popup
35754 .section "The queue display" "SECID268"
35755 .cindex "queue" "display in monitor"
35756 The bottom section of the monitor window contains a list of all messages that
35757 are on the queue, which includes those currently being received or delivered,
35758 as well as those awaiting delivery. The size of this subwindow is controlled by
35759 parameters in the configuration file &_Local/eximon.conf_&, and the frequency
35760 at which it is updated is controlled by another parameter in the same file &--
35761 the default is 5 minutes, since queue scans can be quite expensive. However,
35762 there is an &"Update"& action button just above the display which can be used
35763 to force an update of the queue display at any time.
35765 When a host is down for some time, a lot of pending mail can build up for it,
35766 and this can make it hard to deal with other messages on the queue. To help
35767 with this situation there is a button next to &"Update"& called &"Hide"&. If
35768 pressed, a dialogue box called &"Hide addresses ending with"& is put up. If you
35769 type anything in here and press &"Return"&, the text is added to a chain of
35770 such texts, and if every undelivered address in a message matches at least one
35771 of the texts, the message is not displayed.
35773 If there is an address that does not match any of the texts, all the addresses
35774 are displayed as normal. The matching happens on the ends of addresses so, for
35775 example, &'cam.ac.uk'& specifies all addresses in Cambridge, while
35776 &'xxx@foo.com.example'& specifies just one specific address. When any hiding
35777 has been set up, a button called &"Unhide"& is displayed. If pressed, it
35778 cancels all hiding. Also, to ensure that hidden messages do not get forgotten,
35779 a hide request is automatically cancelled after one hour.
35781 While the dialogue box is displayed, you can't press any buttons or do anything
35782 else to the monitor window. For this reason, if you want to cut text from the
35783 queue display to use in the dialogue box, you have to do the cutting before
35784 pressing the &"Hide"& button.
35786 The queue display contains, for each unhidden queued message, the length of
35787 time it has been on the queue, the size of the message, the message id, the
35788 message sender, and the first undelivered recipient, all on one line. If it is
35789 a bounce message, the sender is shown as &"<>"&. If there is more than one
35790 recipient to which the message has not yet been delivered, subsequent ones are
35791 listed on additional lines, up to a maximum configured number, following which
35792 an ellipsis is displayed. Recipients that have already received the message are
35795 .cindex "frozen messages" "display"
35796 If a message is frozen, an asterisk is displayed at the left-hand side.
35798 The queue display has a vertical scroll bar, and can also be scrolled by means
35799 of the arrow keys. Text can be cut from it using the mouse in the normal way.
35800 The text searching facilities, as described above for the log window, are also
35801 available, but the caret is always moved to the end of the text when the queue
35802 display is updated.
35806 .section "The queue menu" "SECID269"
35807 .cindex "queue" "menu in monitor"
35808 If the &%shift%& key is held down and the left button is clicked when the mouse
35809 pointer is over the text for any message, an action menu pops up, and the first
35810 line of the queue display for the message is highlighted. This does not affect
35813 If you want to use some other event for popping up the menu, you can set the
35814 MENU_EVENT parameter in &_Local/eximon.conf_& to change the default, or
35815 set EXIMON_MENU_EVENT in the environment before starting the monitor. The
35816 value set in this parameter is a standard X event description. For example, to
35817 run eximon using &%ctrl%& rather than &%shift%& you could use
35819 EXIMON_MENU_EVENT='Ctrl<Btn1Down>' eximon
35821 The title of the menu is the message id, and it contains entries which act as
35825 &'message log'&: The contents of the message log for the message are displayed
35826 in a new text window.
35828 &'headers'&: Information from the spool file that contains the envelope
35829 information and headers is displayed in a new text window. See chapter
35830 &<<CHAPspool>>& for a description of the format of spool files.
35832 &'body'&: The contents of the spool file containing the body of the message are
35833 displayed in a new text window. There is a default limit of 20,000 bytes to the
35834 amount of data displayed. This can be changed by setting the BODY_MAX
35835 option at compile time, or the EXIMON_BODY_MAX option at run time.
35837 &'deliver message'&: A call to Exim is made using the &%-M%& option to request
35838 delivery of the message. This causes an automatic thaw if the message is
35839 frozen. The &%-v%& option is also set, and the output from Exim is displayed in
35840 a new text window. The delivery is run in a separate process, to avoid holding
35841 up the monitor while the delivery proceeds.
35843 &'freeze message'&: A call to Exim is made using the &%-Mf%& option to request
35844 that the message be frozen.
35846 .cindex "thawing messages"
35847 .cindex "unfreezing messages"
35848 .cindex "frozen messages" "thawing"
35849 &'thaw message'&: A call to Exim is made using the &%-Mt%& option to request
35850 that the message be thawed.
35852 .cindex "delivery" "forcing failure"
35853 &'give up on msg'&: A call to Exim is made using the &%-Mg%& option to request
35854 that Exim gives up trying to deliver the message. A bounce message is generated
35855 for any remaining undelivered addresses.
35857 &'remove message'&: A call to Exim is made using the &%-Mrm%& option to request
35858 that the message be deleted from the system without generating a bounce
35861 &'add recipient'&: A dialog box is displayed into which a recipient address can
35862 be typed. If the address is not qualified and the QUALIFY_DOMAIN parameter
35863 is set in &_Local/eximon.conf_&, the address is qualified with that domain.
35864 Otherwise it must be entered as a fully qualified address. Pressing RETURN
35865 causes a call to Exim to be made using the &%-Mar%& option to request that an
35866 additional recipient be added to the message, unless the entry box is empty, in
35867 which case no action is taken.
35869 &'mark delivered'&: A dialog box is displayed into which a recipient address
35870 can be typed. If the address is not qualified and the QUALIFY_DOMAIN parameter
35871 is set in &_Local/eximon.conf_&, the address is qualified with that domain.
35872 Otherwise it must be entered as a fully qualified address. Pressing RETURN
35873 causes a call to Exim to be made using the &%-Mmd%& option to mark the given
35874 recipient address as already delivered, unless the entry box is empty, in which
35875 case no action is taken.
35877 &'mark all delivered'&: A call to Exim is made using the &%-Mmad%& option to
35878 mark all recipient addresses as already delivered.
35880 &'edit sender'&: A dialog box is displayed initialized with the current
35881 sender's address. Pressing RETURN causes a call to Exim to be made using the
35882 &%-Mes%& option to replace the sender address, unless the entry box is empty,
35883 in which case no action is taken. If you want to set an empty sender (as in
35884 bounce messages), you must specify it as &"<>"&. Otherwise, if the address is
35885 not qualified and the QUALIFY_DOMAIN parameter is set in &_Local/eximon.conf_&,
35886 the address is qualified with that domain.
35889 When a delivery is forced, a window showing the &%-v%& output is displayed. In
35890 other cases when a call to Exim is made, if there is any output from Exim (in
35891 particular, if the command fails) a window containing the command and the
35892 output is displayed. Otherwise, the results of the action are normally apparent
35893 from the log and queue displays. However, if you set ACTION_OUTPUT=yes in
35894 &_Local/eximon.conf_&, a window showing the Exim command is always opened, even
35895 if no output is generated.
35897 The queue display is automatically updated for actions such as freezing and
35898 thawing, unless ACTION_QUEUE_UPDATE=no has been set in
35899 &_Local/eximon.conf_&. In this case the &"Update"& button has to be used to
35900 force an update of the display after one of these actions.
35902 In any text window that is displayed as result of a menu action, the normal
35903 cut-and-paste facility is available, and searching can be carried out using ^R
35904 and ^S, as described above for the log tail window.
35911 . ////////////////////////////////////////////////////////////////////////////
35912 . ////////////////////////////////////////////////////////////////////////////
35914 .chapter "Security considerations" "CHAPsecurity"
35915 .scindex IIDsecurcon "security" "discussion of"
35916 This chapter discusses a number of issues concerned with security, some of
35917 which are also covered in other parts of this manual.
35919 For reasons that this author does not understand, some people have promoted
35920 Exim as a &"particularly secure"& mailer. Perhaps it is because of the
35921 existence of this chapter in the documentation. However, the intent of the
35922 chapter is simply to describe the way Exim works in relation to certain
35923 security concerns, not to make any specific claims about the effectiveness of
35924 its security as compared with other MTAs.
35926 What follows is a description of the way Exim is supposed to be. Best efforts
35927 have been made to try to ensure that the code agrees with the theory, but an
35928 absence of bugs can never be guaranteed. Any that are reported will get fixed
35929 as soon as possible.
35932 .section "Building a more &""hardened""& Exim" "SECID286"
35933 .cindex "security" "build-time features"
35934 There are a number of build-time options that can be set in &_Local/Makefile_&
35935 to create Exim binaries that are &"harder"& to attack, in particular by a rogue
35936 Exim administrator who does not have the root password, or by someone who has
35937 penetrated the Exim (but not the root) account. These options are as follows:
35940 ALT_CONFIG_PREFIX can be set to a string that is required to match the
35941 start of any file names used with the &%-C%& option. When it is set, these file
35942 names are also not allowed to contain the sequence &"/../"&. (However, if the
35943 value of the &%-C%& option is identical to the value of CONFIGURE_FILE in
35944 &_Local/Makefile_&, Exim ignores &%-C%& and proceeds as usual.) There is no
35945 default setting for &%ALT_CONFIG_PREFIX%&.
35947 If the permitted configuration files are confined to a directory to
35948 which only root has access, this guards against someone who has broken
35949 into the Exim account from running a privileged Exim with an arbitrary
35950 configuration file, and using it to break into other accounts.
35953 If a non-trusted configuration file (i.e. not the default configuration file
35954 or one which is trusted by virtue of being listed in the TRUSTED_CONFIG_LIST
35955 file) is specified with &%-C%&, or if macros are given with &%-D%& (but see
35956 the next item), then root privilege is retained only if the caller of Exim is
35957 root. This locks out the possibility of testing a configuration using &%-C%&
35958 right through message reception and delivery, even if the caller is root. The
35959 reception works, but by that time, Exim is running as the Exim user, so when
35960 it re-execs to regain privilege for the delivery, the use of &%-C%& causes
35961 privilege to be lost. However, root can test reception and delivery using two
35965 The WHITELIST_D_MACROS build option declares some macros to be safe to override
35966 with &%-D%& if the real uid is one of root, the Exim run-time user or the
35967 CONFIGURE_OWNER, if defined. The potential impact of this option is limited by
35968 requiring the run-time value supplied to &%-D%& to match a regex that errs on
35969 the restrictive side. Requiring build-time selection of safe macros is onerous
35970 but this option is intended solely as a transition mechanism to permit
35971 previously-working configurations to continue to work after release 4.73.
35973 If DISABLE_D_OPTION is defined, the use of the &%-D%& command line option
35976 FIXED_NEVER_USERS can be set to a colon-separated list of users that are
35977 never to be used for any deliveries. This is like the &%never_users%& runtime
35978 option, but it cannot be overridden; the runtime option adds additional users
35979 to the list. The default setting is &"root"&; this prevents a non-root user who
35980 is permitted to modify the runtime file from using Exim as a way to get root.
35985 .section "Root privilege" "SECID270"
35987 .cindex "root privilege"
35988 The Exim binary is normally setuid to root, which means that it gains root
35989 privilege (runs as root) when it starts execution. In some special cases (for
35990 example, when the daemon is not in use and there are no local deliveries), it
35991 may be possible to run Exim setuid to some user other than root. This is
35992 discussed in the next section. However, in most installations, root privilege
35993 is required for two things:
35996 To set up a socket connected to the standard SMTP port (25) when initialising
35997 the listening daemon. If Exim is run from &'inetd'&, this privileged action is
36000 To be able to change uid and gid in order to read users' &_.forward_& files and
36001 perform local deliveries as the receiving user or as specified in the
36005 It is not necessary to be root to do any of the other things Exim does, such as
36006 receiving messages and delivering them externally over SMTP, and it is
36007 obviously more secure if Exim does not run as root except when necessary.
36008 For this reason, a user and group for Exim to use must be defined in
36009 &_Local/Makefile_&. These are known as &"the Exim user"& and &"the Exim
36010 group"&. Their values can be changed by the run time configuration, though this
36011 is not recommended. Often a user called &'exim'& is used, but some sites use
36012 &'mail'& or another user name altogether.
36014 Exim uses &[setuid()]& whenever it gives up root privilege. This is a permanent
36015 abdication; the process cannot regain root afterwards. Prior to release 4.00,
36016 &[seteuid()]& was used in some circumstances, but this is no longer the case.
36018 After a new Exim process has interpreted its command line options, it changes
36019 uid and gid in the following cases:
36024 If the &%-C%& option is used to specify an alternate configuration file, or if
36025 the &%-D%& option is used to define macro values for the configuration, and the
36026 calling process is not running as root, the uid and gid are changed to those of
36027 the calling process.
36028 However, if DISABLE_D_OPTION is defined in &_Local/Makefile_&, the &%-D%&
36029 option may not be used at all.
36030 If WHITELIST_D_MACROS is defined in &_Local/Makefile_&, then some macro values
36031 can be supplied if the calling process is running as root, the Exim run-time
36032 user or CONFIGURE_OWNER, if defined.
36037 If the expansion test option (&%-be%&) or one of the filter testing options
36038 (&%-bf%& or &%-bF%&) are used, the uid and gid are changed to those of the
36041 If the process is not a daemon process or a queue runner process or a delivery
36042 process or a process for testing address routing (started with &%-bt%&), the
36043 uid and gid are changed to the Exim user and group. This means that Exim always
36044 runs under its own uid and gid when receiving messages. This also applies when
36045 testing address verification
36048 (the &%-bv%& option) and testing incoming message policy controls (the &%-bh%&
36051 For a daemon, queue runner, delivery, or address testing process, the uid
36052 remains as root at this stage, but the gid is changed to the Exim group.
36055 The processes that initially retain root privilege behave as follows:
36058 A daemon process changes the gid to the Exim group and the uid to the Exim
36059 user after setting up one or more listening sockets. The &[initgroups()]&
36060 function is called, so that if the Exim user is in any additional groups, they
36061 will be used during message reception.
36063 A queue runner process retains root privilege throughout its execution. Its
36064 job is to fork a controlled sequence of delivery processes.
36066 A delivery process retains root privilege throughout most of its execution,
36067 but any actual deliveries (that is, the transports themselves) are run in
36068 subprocesses which always change to a non-root uid and gid. For local
36069 deliveries this is typically the uid and gid of the owner of the mailbox; for
36070 remote deliveries, the Exim uid and gid are used. Once all the delivery
36071 subprocesses have been run, a delivery process changes to the Exim uid and gid
36072 while doing post-delivery tidying up such as updating the retry database and
36073 generating bounce and warning messages.
36075 While the recipient addresses in a message are being routed, the delivery
36076 process runs as root. However, if a user's filter file has to be processed,
36077 this is done in a subprocess that runs under the individual user's uid and
36078 gid. A system filter is run as root unless &%system_filter_user%& is set.
36080 A process that is testing addresses (the &%-bt%& option) runs as root so that
36081 the routing is done in the same environment as a message delivery.
36087 .section "Running Exim without privilege" "SECTrunexiwitpri"
36088 .cindex "privilege, running without"
36089 .cindex "unprivileged running"
36090 .cindex "root privilege" "running without"
36091 Some installations like to run Exim in an unprivileged state for more of its
36092 operation, for added security. Support for this mode of operation is provided
36093 by the global option &%deliver_drop_privilege%&. When this is set, the uid and
36094 gid are changed to the Exim user and group at the start of a delivery process
36095 (and also queue runner and address testing processes). This means that address
36096 routing is no longer run as root, and the deliveries themselves cannot change
36100 .cindex "daemon" "restarting"
36101 Leaving the binary setuid to root, but setting &%deliver_drop_privilege%& means
36102 that the daemon can still be started in the usual way, and it can respond
36103 correctly to SIGHUP because the re-invocation regains root privilege.
36105 An alternative approach is to make Exim setuid to the Exim user and also setgid
36106 to the Exim group. If you do this, the daemon must be started from a root
36107 process. (Calling Exim from a root process makes it behave in the way it does
36108 when it is setuid root.) However, the daemon cannot restart itself after a
36109 SIGHUP signal because it cannot regain privilege.
36111 It is still useful to set &%deliver_drop_privilege%& in this case, because it
36112 stops Exim from trying to re-invoke itself to do a delivery after a message has
36113 been received. Such a re-invocation is a waste of resources because it has no
36116 If restarting the daemon is not an issue (for example, if &%mua_wrapper%& is
36117 set, or &'inetd'& is being used instead of a daemon), having the binary setuid
36118 to the Exim user seems a clean approach, but there is one complication:
36120 In this style of operation, Exim is running with the real uid and gid set to
36121 those of the calling process, and the effective uid/gid set to Exim's values.
36122 Ideally, any association with the calling process' uid/gid should be dropped,
36123 that is, the real uid/gid should be reset to the effective values so as to
36124 discard any privileges that the caller may have. While some operating systems
36125 have a function that permits this action for a non-root effective uid, quite a
36126 number of them do not. Because of this lack of standardization, Exim does not
36127 address this problem at this time.
36129 For this reason, the recommended approach for &"mostly unprivileged"& running
36130 is to keep the Exim binary setuid to root, and to set
36131 &%deliver_drop_privilege%&. This also has the advantage of allowing a daemon to
36132 be used in the most straightforward way.
36134 If you configure Exim not to run delivery processes as root, there are a
36135 number of restrictions on what you can do:
36138 You can deliver only as the Exim user/group. You should explicitly use the
36139 &%user%& and &%group%& options to override routers or local transports that
36140 normally deliver as the recipient. This makes sure that configurations that
36141 work in this mode function the same way in normal mode. Any implicit or
36142 explicit specification of another user causes an error.
36144 Use of &_.forward_& files is severely restricted, such that it is usually
36145 not worthwhile to include them in the configuration.
36147 Users who wish to use &_.forward_& would have to make their home directory and
36148 the file itself accessible to the Exim user. Pipe and append-to-file entries,
36149 and their equivalents in Exim filters, cannot be used. While they could be
36150 enabled in the Exim user's name, that would be insecure and not very useful.
36152 Unless the local user mailboxes are all owned by the Exim user (possible in
36153 some POP3 or IMAP-only environments):
36156 They must be owned by the Exim group and be writeable by that group. This
36157 implies you must set &%mode%& in the appendfile configuration, as well as the
36158 mode of the mailbox files themselves.
36160 You must set &%no_check_owner%&, since most or all of the files will not be
36161 owned by the Exim user.
36163 You must set &%file_must_exist%&, because Exim cannot set the owner correctly
36164 on a newly created mailbox when unprivileged. This also implies that new
36165 mailboxes need to be created manually.
36170 These restrictions severely restrict what can be done in local deliveries.
36171 However, there are no restrictions on remote deliveries. If you are running a
36172 gateway host that does no local deliveries, setting &%deliver_drop_privilege%&
36173 gives more security at essentially no cost.
36175 If you are using the &%mua_wrapper%& facility (see chapter
36176 &<<CHAPnonqueueing>>&), &%deliver_drop_privilege%& is forced to be true.
36181 .section "Delivering to local files" "SECID271"
36182 Full details of the checks applied by &(appendfile)& before it writes to a file
36183 are given in chapter &<<CHAPappendfile>>&.
36187 .section "Running local commands" "SECTsecconslocalcmds"
36188 .cindex "security" "local commands"
36189 .cindex "security" "command injection attacks"
36190 There are a number of ways in which an administrator can configure Exim to run
36191 commands based upon received, untrustworthy, data. Further, in some
36192 configurations a user who can control a &_.forward_& file can also arrange to
36193 run commands. Configuration to check includes, but is not limited to:
36196 Use of &%use_shell%& in the pipe transport: various forms of shell command
36197 injection may be possible with this option present. It is dangerous and should
36198 be used only with considerable caution. Consider constraints which whitelist
36199 allowed characters in a variable which is to be used in a pipe transport that
36200 has &%use_shell%& enabled.
36202 A number of options such as &%forbid_filter_run%&, &%forbid_filter_perl%&,
36203 &%forbid_filter_dlfunc%& and so forth which restrict facilities available to
36204 &_.forward_& files in a redirect router. If Exim is running on a central mail
36205 hub to which ordinary users do not have shell access, but home directories are
36206 NFS mounted (for instance) then administrators should review the list of these
36207 forbid options available, and should bear in mind that the options that may
36208 need forbidding can change as new features are added between releases.
36210 The &%${run...}%& expansion item does not use a shell by default, but
36211 administrators can configure use of &_/bin/sh_& as part of the command.
36212 Such invocations should be viewed with prejudicial suspicion.
36214 Administrators who use embedded Perl are advised to explore how Perl's
36215 taint checking might apply to their usage.
36217 Use of &%${expand...}%& is somewhat analagous to shell's eval builtin and
36218 administrators are well advised to view its use with suspicion, in case (for
36219 instance) it allows a local-part to contain embedded Exim directives.
36221 Use of &%${match_local_part...}%& and friends becomes more dangerous if
36222 Exim was built with EXPAND_LISTMATCH_RHS defined: the second string in
36223 each can reference arbitrary lists and files, rather than just being a list
36225 The EXPAND_LISTMATCH_RHS option was added and set false by default because of
36226 real-world security vulnerabilities caused by its use with untrustworthy data
36227 injected in, for SQL injection attacks.
36228 Consider the use of the &%inlisti%& expansion condition instead.
36234 .section "Trust in configuration data" "SECTsecconfdata"
36235 .cindex "security" "data sources"
36236 .cindex "security" "regular expressions"
36237 .cindex "regular expressions" "security"
36238 .cindex "PCRE" "security"
36239 If configuration data for Exim can come from untrustworthy sources, there
36240 are some issues to be aware of:
36243 Use of &%${expand...}%& may provide a path for shell injection attacks.
36245 Letting untrusted data provide a regular expression is unwise.
36247 Using &%${match...}%& to apply a fixed regular expression against untrusted
36248 data may result in pathological behaviour within PCRE. Be aware of what
36249 "backtracking" means and consider options for being more strict with a regular
36250 expression. Avenues to explore include limiting what can match (avoiding &`.`&
36251 when &`[a-z0-9]`& or other character class will do), use of atomic grouping and
36252 possessive quantifiers or just not using regular expressions against untrusted
36255 It can be important to correctly use &%${quote:...}%&,
36256 &%${quote_local_part:...}%& and &%${quote_%&<&'lookup-type'&>&%:...}%& expansion
36257 items to ensure that data is correctly constructed.
36259 Some lookups might return multiple results, even though normal usage is only
36260 expected to yield one result.
36266 .section "IPv4 source routing" "SECID272"
36267 .cindex "source routing" "in IP packets"
36268 .cindex "IP source routing"
36269 Many operating systems suppress IP source-routed packets in the kernel, but
36270 some cannot be made to do this, so Exim does its own check. It logs incoming
36271 IPv4 source-routed TCP calls, and then drops them. Things are all different in
36272 IPv6. No special checking is currently done.
36276 .section "The VRFY, EXPN, and ETRN commands in SMTP" "SECID273"
36277 Support for these SMTP commands is disabled by default. If required, they can
36278 be enabled by defining suitable ACLs.
36283 .section "Privileged users" "SECID274"
36284 .cindex "trusted users"
36285 .cindex "admin user"
36286 .cindex "privileged user"
36287 .cindex "user" "trusted"
36288 .cindex "user" "admin"
36289 Exim recognizes two sets of users with special privileges. Trusted users are
36290 able to submit new messages to Exim locally, but supply their own sender
36291 addresses and information about a sending host. For other users submitting
36292 local messages, Exim sets up the sender address from the uid, and doesn't
36293 permit a remote host to be specified.
36296 However, an untrusted user is permitted to use the &%-f%& command line option
36297 in the special form &%-f <>%& to indicate that a delivery failure for the
36298 message should not cause an error report. This affects the message's envelope,
36299 but it does not affect the &'Sender:'& header. Untrusted users may also be
36300 permitted to use specific forms of address with the &%-f%& option by setting
36301 the &%untrusted_set_sender%& option.
36303 Trusted users are used to run processes that receive mail messages from some
36304 other mail domain and pass them on to Exim for delivery either locally, or over
36305 the Internet. Exim trusts a caller that is running as root, as the Exim user,
36306 as any user listed in the &%trusted_users%& configuration option, or under any
36307 group listed in the &%trusted_groups%& option.
36309 Admin users are permitted to do things to the messages on Exim's queue. They
36310 can freeze or thaw messages, cause them to be returned to their senders, remove
36311 them entirely, or modify them in various ways. In addition, admin users can run
36312 the Exim monitor and see all the information it is capable of providing, which
36313 includes the contents of files on the spool.
36317 By default, the use of the &%-M%& and &%-q%& options to cause Exim to attempt
36318 delivery of messages on its queue is restricted to admin users. This
36319 restriction can be relaxed by setting the &%no_prod_requires_admin%& option.
36320 Similarly, the use of &%-bp%& (and its variants) to list the contents of the
36321 queue is also restricted to admin users. This restriction can be relaxed by
36322 setting &%no_queue_list_requires_admin%&.
36324 Exim recognizes an admin user if the calling process is running as root or as
36325 the Exim user or if any of the groups associated with the calling process is
36326 the Exim group. It is not necessary actually to be running under the Exim
36327 group. However, if admin users who are not root or the Exim user are to access
36328 the contents of files on the spool via the Exim monitor (which runs
36329 unprivileged), Exim must be built to allow group read access to its spool
36334 .section "Spool files" "SECID275"
36335 .cindex "spool directory" "files"
36336 Exim's spool directory and everything it contains is owned by the Exim user and
36337 set to the Exim group. The mode for spool files is defined in the
36338 &_Local/Makefile_& configuration file, and defaults to 0640. This means that
36339 any user who is a member of the Exim group can access these files.
36343 .section "Use of argv[0]" "SECID276"
36344 Exim examines the last component of &%argv[0]%&, and if it matches one of a set
36345 of specific strings, Exim assumes certain options. For example, calling Exim
36346 with the last component of &%argv[0]%& set to &"rsmtp"& is exactly equivalent
36347 to calling it with the option &%-bS%&. There are no security implications in
36352 .section "Use of %f formatting" "SECID277"
36353 The only use made of &"%f"& by Exim is in formatting load average values. These
36354 are actually stored in integer variables as 1000 times the load average.
36355 Consequently, their range is limited and so therefore is the length of the
36360 .section "Embedded Exim path" "SECID278"
36361 Exim uses its own path name, which is embedded in the code, only when it needs
36362 to re-exec in order to regain root privilege. Therefore, it is not root when it
36363 does so. If some bug allowed the path to get overwritten, it would lead to an
36364 arbitrary program's being run as exim, not as root.
36368 .section "Dynamic module directory" "SECTdynmoddir"
36369 Any dynamically loadable modules must be installed into the directory
36370 defined in &`LOOKUP_MODULE_DIR`& in &_Local/Makefile_& for Exim to permit
36374 .section "Use of sprintf()" "SECID279"
36375 .cindex "&[sprintf()]&"
36376 A large number of occurrences of &"sprintf"& in the code are actually calls to
36377 &'string_sprintf()'&, a function that returns the result in malloc'd store.
36378 The intermediate formatting is done into a large fixed buffer by a function
36379 that runs through the format string itself, and checks the length of each
36380 conversion before performing it, thus preventing buffer overruns.
36382 The remaining uses of &[sprintf()]& happen in controlled circumstances where
36383 the output buffer is known to be sufficiently long to contain the converted
36388 .section "Use of debug_printf() and log_write()" "SECID280"
36389 Arbitrary strings are passed to both these functions, but they do their
36390 formatting by calling the function &'string_vformat()'&, which runs through
36391 the format string itself, and checks the length of each conversion.
36395 .section "Use of strcat() and strcpy()" "SECID281"
36396 These are used only in cases where the output buffer is known to be large
36397 enough to hold the result.
36398 .ecindex IIDsecurcon
36403 . ////////////////////////////////////////////////////////////////////////////
36404 . ////////////////////////////////////////////////////////////////////////////
36406 .chapter "Format of spool files" "CHAPspool"
36407 .scindex IIDforspo1 "format" "spool files"
36408 .scindex IIDforspo2 "spool directory" "format of files"
36409 .scindex IIDforspo3 "spool files" "format of"
36410 .cindex "spool files" "editing"
36411 A message on Exim's queue consists of two files, whose names are the message id
36412 followed by -D and -H, respectively. The data portion of the message is kept in
36413 the -D file on its own. The message's envelope, status, and headers are all
36414 kept in the -H file, whose format is described in this chapter. Each of these
36415 two files contains the final component of its own name as its first line. This
36416 is insurance against disk crashes where the directory is lost but the files
36417 themselves are recoverable.
36419 Some people are tempted into editing -D files in order to modify messages. You
36420 need to be extremely careful if you do this; it is not recommended and you are
36421 on your own if you do it. Here are some of the pitfalls:
36424 You must ensure that Exim does not try to deliver the message while you are
36425 fiddling with it. The safest way is to take out a write lock on the -D file,
36426 which is what Exim itself does, using &[fcntl()]&. If you update the file in
36427 place, the lock will be retained. If you write a new file and rename it, the
36428 lock will be lost at the instant of rename.
36430 .vindex "&$body_linecount$&"
36431 If you change the number of lines in the file, the value of
36432 &$body_linecount$&, which is stored in the -H file, will be incorrect. At
36433 present, this value is not used by Exim, but there is no guarantee that this
36434 will always be the case.
36436 If the message is in MIME format, you must take care not to break it.
36438 If the message is cryptographically signed, any change will invalidate the
36441 All in all, modifying -D files is fraught with danger.
36443 Files whose names end with -J may also be seen in the &_input_& directory (or
36444 its subdirectories when &%split_spool_directory%& is set). These are journal
36445 files, used to record addresses to which the message has been delivered during
36446 the course of a delivery attempt. If there are still undelivered recipients at
36447 the end, the -H file is updated, and the -J file is deleted. If, however, there
36448 is some kind of crash (for example, a power outage) before this happens, the -J
36449 file remains in existence. When Exim next processes the message, it notices the
36450 -J file and uses it to update the -H file before starting the next delivery
36453 .section "Format of the -H file" "SECID282"
36454 .cindex "uid (user id)" "in spool file"
36455 .cindex "gid (group id)" "in spool file"
36456 The second line of the -H file contains the login name for the uid of the
36457 process that called Exim to read the message, followed by the numerical uid and
36458 gid. For a locally generated message, this is normally the user who sent the
36459 message. For a message received over TCP/IP via the daemon, it is
36460 normally the Exim user.
36462 The third line of the file contains the address of the message's sender as
36463 transmitted in the envelope, contained in angle brackets. The sender address is
36464 empty for bounce messages. For incoming SMTP mail, the sender address is given
36465 in the MAIL command. For locally generated mail, the sender address is
36466 created by Exim from the login name of the current user and the configured
36467 &%qualify_domain%&. However, this can be overridden by the &%-f%& option or a
36468 leading &"From&~"& line if the caller is trusted, or if the supplied address is
36469 &"<>"& or an address that matches &%untrusted_set_senders%&.
36471 The fourth line contains two numbers. The first is the time that the message
36472 was received, in the conventional Unix form &-- the number of seconds since the
36473 start of the epoch. The second number is a count of the number of messages
36474 warning of delayed delivery that have been sent to the sender.
36476 There follow a number of lines starting with a hyphen. These can appear in any
36477 order, and are omitted when not relevant:
36480 .vitem "&%-acl%&&~<&'number'&>&~<&'length'&>"
36481 This item is obsolete, and is not generated from Exim release 4.61 onwards;
36482 &%-aclc%& and &%-aclm%& are used instead. However, &%-acl%& is still
36483 recognized, to provide backward compatibility. In the old format, a line of
36484 this form is present for every ACL variable that is not empty. The number
36485 identifies the variable; the &%acl_c%&&*x*& variables are numbered 0&--9 and
36486 the &%acl_m%&&*x*& variables are numbered 10&--19. The length is the length of
36487 the data string for the variable. The string itself starts at the beginning of
36488 the next line, and is followed by a newline character. It may contain internal
36491 .vitem "&%-aclc%&&~<&'rest-of-name'&>&~<&'length'&>"
36492 A line of this form is present for every ACL connection variable that is
36493 defined. Note that there is a space between &%-aclc%& and the rest of the name.
36494 The length is the length of the data string for the variable. The string itself
36495 starts at the beginning of the next line, and is followed by a newline
36496 character. It may contain internal newlines.
36498 .vitem "&%-aclm%&&~<&'rest-of-name'&>&~<&'length'&>"
36499 A line of this form is present for every ACL message variable that is defined.
36500 Note that there is a space between &%-aclm%& and the rest of the name. The
36501 length is the length of the data string for the variable. The string itself
36502 starts at the beginning of the next line, and is followed by a newline
36503 character. It may contain internal newlines.
36505 .vitem "&%-active_hostname%&&~<&'hostname'&>"
36506 This is present if, when the message was received over SMTP, the value of
36507 &$smtp_active_hostname$& was different to the value of &$primary_hostname$&.
36509 .vitem &%-allow_unqualified_recipient%&
36510 This is present if unqualified recipient addresses are permitted in header
36511 lines (to stop such addresses from being qualified if rewriting occurs at
36512 transport time). Local messages that were input using &%-bnq%& and remote
36513 messages from hosts that match &%recipient_unqualified_hosts%& set this flag.
36515 .vitem &%-allow_unqualified_sender%&
36516 This is present if unqualified sender addresses are permitted in header lines
36517 (to stop such addresses from being qualified if rewriting occurs at transport
36518 time). Local messages that were input using &%-bnq%& and remote messages from
36519 hosts that match &%sender_unqualified_hosts%& set this flag.
36521 .vitem "&%-auth_id%&&~<&'text'&>"
36522 The id information for a message received on an authenticated SMTP connection
36523 &-- the value of the &$authenticated_id$& variable.
36525 .vitem "&%-auth_sender%&&~<&'address'&>"
36526 The address of an authenticated sender &-- the value of the
36527 &$authenticated_sender$& variable.
36529 .vitem "&%-body_linecount%&&~<&'number'&>"
36530 This records the number of lines in the body of the message, and is always
36533 .vitem "&%-body_zerocount%&&~<&'number'&>"
36534 This records the number of binary zero bytes in the body of the message, and is
36535 present if the number is greater than zero.
36537 .vitem &%-deliver_firsttime%&
36538 This is written when a new message is first added to the spool. When the spool
36539 file is updated after a deferral, it is omitted.
36541 .vitem "&%-frozen%&&~<&'time'&>"
36542 .cindex "frozen messages" "spool data"
36543 The message is frozen, and the freezing happened at <&'time'&>.
36545 .vitem "&%-helo_name%&&~<&'text'&>"
36546 This records the host name as specified by a remote host in a HELO or EHLO
36549 .vitem "&%-host_address%&&~<&'address'&>.<&'port'&>"
36550 This records the IP address of the host from which the message was received and
36551 the remote port number that was used. It is omitted for locally generated
36554 .vitem "&%-host_auth%&&~<&'text'&>"
36555 If the message was received on an authenticated SMTP connection, this records
36556 the name of the authenticator &-- the value of the
36557 &$sender_host_authenticated$& variable.
36559 .vitem &%-host_lookup_failed%&
36560 This is present if an attempt to look up the sending host's name from its IP
36561 address failed. It corresponds to the &$host_lookup_failed$& variable.
36563 .vitem "&%-host_name%&&~<&'text'&>"
36564 .cindex "reverse DNS lookup"
36565 .cindex "DNS" "reverse lookup"
36566 This records the name of the remote host from which the message was received,
36567 if the host name was looked up from the IP address when the message was being
36568 received. It is not present if no reverse lookup was done.
36570 .vitem "&%-ident%&&~<&'text'&>"
36571 For locally submitted messages, this records the login of the originating user,
36572 unless it was a trusted user and the &%-oMt%& option was used to specify an
36573 ident value. For messages received over TCP/IP, this records the ident string
36574 supplied by the remote host, if any.
36576 .vitem "&%-interface_address%&&~<&'address'&>.<&'port'&>"
36577 This records the IP address of the local interface and the port number through
36578 which a message was received from a remote host. It is omitted for locally
36579 generated messages.
36582 The message is from a local sender.
36584 .vitem &%-localerror%&
36585 The message is a locally-generated bounce message.
36587 .vitem "&%-local_scan%&&~<&'string'&>"
36588 This records the data string that was returned by the &[local_scan()]& function
36589 when the message was received &-- the value of the &$local_scan_data$&
36590 variable. It is omitted if no data was returned.
36592 .vitem &%-manual_thaw%&
36593 The message was frozen but has been thawed manually, that is, by an explicit
36594 Exim command rather than via the auto-thaw process.
36597 A testing delivery process was started using the &%-N%& option to suppress any
36598 actual deliveries, but delivery was deferred. At any further delivery attempts,
36601 .vitem &%-received_protocol%&
36602 This records the value of the &$received_protocol$& variable, which contains
36603 the name of the protocol by which the message was received.
36605 .vitem &%-sender_set_untrusted%&
36606 The envelope sender of this message was set by an untrusted local caller (used
36607 to ensure that the caller is displayed in queue listings).
36609 .vitem "&%-spam_score_int%&&~<&'number'&>"
36610 If a message was scanned by SpamAssassin, this is present. It records the value
36611 of &$spam_score_int$&.
36613 .vitem &%-tls_certificate_verified%&
36614 A TLS certificate was received from the client that sent this message, and the
36615 certificate was verified by the server.
36617 .vitem "&%-tls_cipher%&&~<&'cipher name'&>"
36618 When the message was received over an encrypted connection, this records the
36619 name of the cipher suite that was used.
36621 .vitem "&%-tls_peerdn%&&~<&'peer DN'&>"
36622 When the message was received over an encrypted connection, and a certificate
36623 was received from the client, this records the Distinguished Name from that
36627 Following the options there is a list of those addresses to which the message
36628 is not to be delivered. This set of addresses is initialized from the command
36629 line when the &%-t%& option is used and &%extract_addresses_remove_arguments%&
36630 is set; otherwise it starts out empty. Whenever a successful delivery is made,
36631 the address is added to this set. The addresses are kept internally as a
36632 balanced binary tree, and it is a representation of that tree which is written
36633 to the spool file. If an address is expanded via an alias or forward file, the
36634 original address is added to the tree when deliveries to all its child
36635 addresses are complete.
36637 If the tree is empty, there is a single line in the spool file containing just
36638 the text &"XX"&. Otherwise, each line consists of two letters, which are either
36639 Y or N, followed by an address. The address is the value for the node of the
36640 tree, and the letters indicate whether the node has a left branch and/or a
36641 right branch attached to it, respectively. If branches exist, they immediately
36642 follow. Here is an example of a three-node tree:
36644 YY darcy@austen.fict.example
36645 NN alice@wonderland.fict.example
36646 NN editor@thesaurus.ref.example
36648 After the non-recipients tree, there is a list of the message's recipients.
36649 This is a simple list, preceded by a count. It includes all the original
36650 recipients of the message, including those to whom the message has already been
36651 delivered. In the simplest case, the list contains one address per line. For
36655 editor@thesaurus.ref.example
36656 darcy@austen.fict.example
36658 alice@wonderland.fict.example
36660 However, when a child address has been added to the top-level addresses as a
36661 result of the use of the &%one_time%& option on a &(redirect)& router, each
36662 line is of the following form:
36664 <&'top-level address'&> <&'errors_to address'&> &&&
36665 <&'length'&>,<&'parent number'&>#<&'flag bits'&>
36667 The 01 flag bit indicates the presence of the three other fields that follow
36668 the top-level address. Other bits may be used in future to support additional
36669 fields. The <&'parent number'&> is the offset in the recipients list of the
36670 original parent of the &"one time"& address. The first two fields are the
36671 envelope sender that is associated with this address and its length. If the
36672 length is zero, there is no special envelope sender (there are then two space
36673 characters in the line). A non-empty field can arise from a &(redirect)& router
36674 that has an &%errors_to%& setting.
36677 A blank line separates the envelope and status information from the headers
36678 which follow. A header may occupy several lines of the file, and to save effort
36679 when reading it in, each header is preceded by a number and an identifying
36680 character. The number is the number of characters in the header, including any
36681 embedded newlines and the terminating newline. The character is one of the
36685 .row <&'blank'&> "header in which Exim has no special interest"
36686 .row &`B`& "&'Bcc:'& header"
36687 .row &`C`& "&'Cc:'& header"
36688 .row &`F`& "&'From:'& header"
36689 .row &`I`& "&'Message-id:'& header"
36690 .row &`P`& "&'Received:'& header &-- P for &""postmark""&"
36691 .row &`R`& "&'Reply-To:'& header"
36692 .row &`S`& "&'Sender:'& header"
36693 .row &`T`& "&'To:'& header"
36694 .row &`*`& "replaced or deleted header"
36697 Deleted or replaced (rewritten) headers remain in the spool file for debugging
36698 purposes. They are not transmitted when the message is delivered. Here is a
36699 typical set of headers:
36701 111P Received: by hobbit.fict.example with local (Exim 4.00)
36702 id 14y9EI-00026G-00; Fri, 11 May 2001 10:28:59 +0100
36703 049 Message-Id: <E14y9EI-00026G-00@hobbit.fict.example>
36704 038* X-rewrote-sender: bb@hobbit.fict.example
36705 042* From: Bilbo Baggins <bb@hobbit.fict.example>
36706 049F From: Bilbo Baggins <B.Baggins@hobbit.fict.example>
36707 099* To: alice@wonderland.fict.example, rdo@foundation,
36708 darcy@austen.fict.example, editor@thesaurus.ref.example
36709 104T To: alice@wonderland.fict.example, rdo@foundation.example,
36710 darcy@austen.fict.example, editor@thesaurus.ref.example
36711 038 Date: Fri, 11 May 2001 10:28:59 +0100
36713 The asterisked headers indicate that the envelope sender, &'From:'& header, and
36714 &'To:'& header have been rewritten, the last one because routing expanded the
36715 unqualified domain &'foundation'&.
36716 .ecindex IIDforspo1
36717 .ecindex IIDforspo2
36718 .ecindex IIDforspo3
36720 . ////////////////////////////////////////////////////////////////////////////
36721 . ////////////////////////////////////////////////////////////////////////////
36723 .chapter "Support for DKIM (DomainKeys Identified Mail)" "CHAPdkim" &&&
36727 DKIM is a mechanism by which messages sent by some entity can be provably
36728 linked to a domain which that entity controls. It permits reputation to
36729 be tracked on a per-domain basis, rather than merely upon source IP address.
36730 DKIM is documented in RFC 4871.
36732 Since version 4.70, DKIM support is compiled into Exim by default. It can be
36733 disabled by setting DISABLE_DKIM=yes in Local/Makefile.
36735 Exim's DKIM implementation allows to
36737 Sign outgoing messages: This function is implemented in the SMTP transport.
36738 It can co-exist with all other Exim features
36739 (including transport filters)
36740 except cutthrough delivery.
36742 Verify signatures in incoming messages: This is implemented by an additional
36743 ACL (acl_smtp_dkim), which can be called several times per message, with
36744 different signature contexts.
36747 In typical Exim style, the verification implementation does not include any
36748 default "policy". Instead it enables you to build your own policy using
36749 Exim's standard controls.
36751 Please note that verification of DKIM signatures in incoming mail is turned
36752 on by default for logging purposes. For each signature in incoming email,
36753 exim will log a line displaying the most important signature details, and the
36754 signature status. Here is an example (with line-breaks added for clarity):
36756 2009-09-09 10:22:28 1MlIRf-0003LU-U3 DKIM:
36757 d=facebookmail.com s=q1-2009b
36758 c=relaxed/relaxed a=rsa-sha1
36759 i=@facebookmail.com t=1252484542 [verification succeeded]
36761 You might want to turn off DKIM verification processing entirely for internal
36762 or relay mail sources. To do that, set the &%dkim_disable_verify%& ACL
36763 control modifier. This should typically be done in the RCPT ACL, at points
36764 where you accept mail from relay sources (internal hosts or authenticated
36768 .section "Signing outgoing messages" "SECID513"
36769 .cindex "DKIM" "signing"
36771 Signing is implemented by setting private options on the SMTP transport.
36772 These options take (expandable) strings as arguments.
36774 .option dkim_domain smtp string&!! unset
36776 The domain you want to sign with. The result of this expanded
36777 option is put into the &%$dkim_domain%& expansion variable.
36779 .option dkim_selector smtp string&!! unset
36781 This sets the key selector string. You can use the &%$dkim_domain%& expansion
36782 variable to look up a matching selector. The result is put in the expansion
36783 variable &%$dkim_selector%& which should be used in the &%dkim_private_key%&
36784 option along with &%$dkim_domain%&.
36786 .option dkim_private_key smtp string&!! unset
36788 This sets the private key to use. You can use the &%$dkim_domain%& and
36789 &%$dkim_selector%& expansion variables to determine the private key to use.
36790 The result can either
36792 be a valid RSA private key in ASCII armor, including line breaks.
36794 start with a slash, in which case it is treated as a file that contains
36797 be "0", "false" or the empty string, in which case the message will not
36798 be signed. This case will not result in an error, even if &%dkim_strict%&
36802 .option dkim_canon smtp string&!! unset
36804 This option sets the canonicalization method used when signing a message.
36805 The DKIM RFC currently supports two methods: "simple" and "relaxed".
36806 The option defaults to "relaxed" when unset. Note: the current implementation
36807 only supports using the same canonicalization method for both headers and body.
36809 .option dkim_strict smtp string&!! unset
36811 This option defines how Exim behaves when signing a message that
36812 should be signed fails for some reason. When the expansion evaluates to
36813 either "1" or "true", Exim will defer. Otherwise Exim will send the message
36814 unsigned. You can use the &%$dkim_domain%& and &%$dkim_selector%& expansion
36817 .option dkim_sign_headers smtp string&!! unset
36819 When set, this option must expand to (or be specified as) a colon-separated
36820 list of header names. Headers with these names will be included in the message
36821 signature. When unspecified, the header names recommended in RFC4871 will be
36825 .section "Verifying DKIM signatures in incoming mail" "SECID514"
36826 .cindex "DKIM" "verification"
36828 Verification of DKIM signatures in incoming email is implemented via the
36829 &%acl_smtp_dkim%& ACL. By default, this ACL is called once for each
36830 syntactically(!) correct signature in the incoming message.
36831 A missing ACL definition defaults to accept.
36832 If any ACL call does not acccept, the message is not accepted.
36833 If a cutthrough delivery was in progress for the message it is
36834 summarily dropped (having wasted the transmission effort).
36836 To evaluate the signature in the ACL a large number of expansion variables
36837 containing the signature status and its details are set up during the
36838 runtime of the ACL.
36840 Calling the ACL only for existing signatures is not sufficient to build
36841 more advanced policies. For that reason, the global option
36842 &%dkim_verify_signers%&, and a global expansion variable
36843 &%$dkim_signers%& exist.
36845 The global option &%dkim_verify_signers%& can be set to a colon-separated
36846 list of DKIM domains or identities for which the ACL &%acl_smtp_dkim%& is
36847 called. It is expanded when the message has been received. At this point,
36848 the expansion variable &%$dkim_signers%& already contains a colon-separated
36849 list of signer domains and identities for the message. When
36850 &%dkim_verify_signers%& is not specified in the main configuration,
36853 dkim_verify_signers = $dkim_signers
36855 This leads to the default behaviour of calling &%acl_smtp_dkim%& for each
36856 DKIM signature in the message. Current DKIM verifiers may want to explicitly
36857 call the ACL for known domains or identities. This would be achieved as follows:
36859 dkim_verify_signers = paypal.com:ebay.com:$dkim_signers
36861 This would result in &%acl_smtp_dkim%& always being called for "paypal.com"
36862 and "ebay.com", plus all domains and identities that have signatures in the message.
36863 You can also be more creative in constructing your policy. For example:
36865 dkim_verify_signers = $sender_address_domain:$dkim_signers
36868 If a domain or identity is listed several times in the (expanded) value of
36869 &%dkim_verify_signers%&, the ACL is only called once for that domain or identity.
36872 Inside the &%acl_smtp_dkim%&, the following expansion variables are
36873 available (from most to least important):
36877 .vitem &%$dkim_cur_signer%&
36878 The signer that is being evaluated in this ACL run. This can be a domain or
36879 an identity. This is one of the list items from the expanded main option
36880 &%dkim_verify_signers%& (see above).
36881 .vitem &%$dkim_verify_status%&
36882 A string describing the general status of the signature. One of
36884 &%none%&: There is no signature in the message for the current domain or
36885 identity (as reflected by &%$dkim_cur_signer%&).
36887 &%invalid%&: The signature could not be verified due to a processing error.
36888 More detail is available in &%$dkim_verify_reason%&.
36890 &%fail%&: Verification of the signature failed. More detail is
36891 available in &%$dkim_verify_reason%&.
36893 &%pass%&: The signature passed verification. It is valid.
36895 .vitem &%$dkim_verify_reason%&
36896 A string giving a litte bit more detail when &%$dkim_verify_status%& is either
36897 "fail" or "invalid". One of
36899 &%pubkey_unavailable%& (when &%$dkim_verify_status%&="invalid"): The public
36900 key for the domain could not be retrieved. This may be a temporary problem.
36902 &%pubkey_syntax%& (when &%$dkim_verify_status%&="invalid"): The public key
36903 record for the domain is syntactically invalid.
36905 &%bodyhash_mismatch%& (when &%$dkim_verify_status%&="fail"): The calculated
36906 body hash does not match the one specified in the signature header. This
36907 means that the message body was modified in transit.
36909 &%signature_incorrect%& (when &%$dkim_verify_status%&="fail"): The signature
36910 could not be verified. This may mean that headers were modified,
36911 re-written or otherwise changed in a way which is incompatible with
36912 DKIM verification. It may of course also mean that the signature is forged.
36914 .vitem &%$dkim_domain%&
36915 The signing domain. IMPORTANT: This variable is only populated if there is
36916 an actual signature in the message for the current domain or identity (as
36917 reflected by &%$dkim_cur_signer%&).
36918 .vitem &%$dkim_identity%&
36919 The signing identity, if present. IMPORTANT: This variable is only populated
36920 if there is an actual signature in the message for the current domain or
36921 identity (as reflected by &%$dkim_cur_signer%&).
36922 .vitem &%$dkim_selector%&
36923 The key record selector string.
36924 .vitem &%$dkim_algo%&
36925 The algorithm used. One of 'rsa-sha1' or 'rsa-sha256'.
36926 .vitem &%$dkim_canon_body%&
36927 The body canonicalization method. One of 'relaxed' or 'simple'.
36928 .vitem &%dkim_canon_headers%&
36929 The header canonicalization method. One of 'relaxed' or 'simple'.
36930 .vitem &%$dkim_copiedheaders%&
36931 A transcript of headers and their values which are included in the signature
36932 (copied from the 'z=' tag of the signature).
36933 .vitem &%$dkim_bodylength%&
36934 The number of signed body bytes. If zero ("0"), the body is unsigned. If no
36935 limit was set by the signer, "9999999999999" is returned. This makes sure
36936 that this variable always expands to an integer value.
36937 .vitem &%$dkim_created%&
36938 UNIX timestamp reflecting the date and time when the signature was created.
36939 When this was not specified by the signer, "0" is returned.
36940 .vitem &%$dkim_expires%&
36941 UNIX timestamp reflecting the date and time when the signer wants the
36942 signature to be treated as "expired". When this was not specified by the
36943 signer, "9999999999999" is returned. This makes it possible to do useful
36944 integer size comparisons against this value.
36945 .vitem &%$dkim_headernames%&
36946 A colon-separated list of names of headers included in the signature.
36947 .vitem &%$dkim_key_testing%&
36948 "1" if the key record has the "testing" flag set, "0" if not.
36949 .vitem &%$dkim_key_nosubdomains%&
36950 "1" if the key record forbids subdomaining, "0" otherwise.
36951 .vitem &%$dkim_key_srvtype%&
36952 Service type (tag s=) from the key record. Defaults to "*" if not specified
36954 .vitem &%$dkim_key_granularity%&
36955 Key granularity (tag g=) from the key record. Defaults to "*" if not specified
36957 .vitem &%$dkim_key_notes%&
36958 Notes from the key record (tag n=).
36961 In addition, two ACL conditions are provided:
36964 .vitem &%dkim_signers%&
36965 ACL condition that checks a colon-separated list of domains or identities
36966 for a match against the domain or identity that the ACL is currently verifying
36967 (reflected by &%$dkim_cur_signer%&). This is typically used to restrict an ACL
36968 verb to a group of domains or identities. For example:
36971 # Warn when Mail purportedly from GMail has no signature at all
36972 warn log_message = GMail sender without DKIM signature
36973 sender_domains = gmail.com
36974 dkim_signers = gmail.com
36978 .vitem &%dkim_status%&
36979 ACL condition that checks a colon-separated list of possible DKIM verification
36980 results against the actual result of verification. This is typically used
36981 to restrict an ACL verb to a list of verification outcomes, for example:
36984 deny message = Mail from Paypal with invalid/missing signature
36985 sender_domains = paypal.com:paypal.de
36986 dkim_signers = paypal.com:paypal.de
36987 dkim_status = none:invalid:fail
36990 The possible status keywords are: 'none','invalid','fail' and 'pass'. Please
36991 see the documentation of the &%$dkim_verify_status%& expansion variable above
36992 for more information of what they mean.
36995 . ////////////////////////////////////////////////////////////////////////////
36996 . ////////////////////////////////////////////////////////////////////////////
36998 .chapter "Adding new drivers or lookup types" "CHID13" &&&
36999 "Adding drivers or lookups"
37000 .cindex "adding drivers"
37001 .cindex "new drivers, adding"
37002 .cindex "drivers" "adding new"
37003 The following actions have to be taken in order to add a new router, transport,
37004 authenticator, or lookup type to Exim:
37007 Choose a name for the driver or lookup type that does not conflict with any
37008 existing name; I will use &"newdriver"& in what follows.
37010 Add to &_src/EDITME_& the line:
37012 <&'type'&>&`_NEWDRIVER=yes`&
37014 where <&'type'&> is ROUTER, TRANSPORT, AUTH, or LOOKUP. If the
37015 code is not to be included in the binary by default, comment this line out. You
37016 should also add any relevant comments about the driver or lookup type.
37018 Add to &_src/config.h.defaults_& the line:
37020 #define <type>_NEWDRIVER
37023 Edit &_src/drtables.c_&, adding conditional code to pull in the private header
37024 and create a table entry as is done for all the other drivers and lookup types.
37026 Edit &_scripts/lookups-Makefile_& if this is a new lookup; there is a for-loop
37027 near the bottom, ranging the &`name_mod`& variable over a list of all lookups.
37028 Add your &`NEWDRIVER`& to that list.
37029 As long as the dynamic module would be named &_newdriver.so_&, you can use the
37030 simple form that most lookups have.
37032 Edit &_Makefile_& in the appropriate sub-directory (&_src/routers_&,
37033 &_src/transports_&, &_src/auths_&, or &_src/lookups_&); add a line for the new
37034 driver or lookup type and add it to the definition of OBJ.
37036 Create &_newdriver.h_& and &_newdriver.c_& in the appropriate sub-directory of
37039 Edit &_scripts/MakeLinks_& and add commands to link the &_.h_& and &_.c_& files
37040 as for other drivers and lookups.
37043 Then all you need to do is write the code! A good way to start is to make a
37044 proforma by copying an existing module of the same type, globally changing all
37045 occurrences of the name, and cutting out most of the code. Note that any
37046 options you create must be listed in alphabetical order, because the tables are
37047 searched using a binary chop procedure.
37049 There is a &_README_& file in each of the sub-directories of &_src_& describing
37050 the interface that is expected.
37055 . ////////////////////////////////////////////////////////////////////////////
37056 . ////////////////////////////////////////////////////////////////////////////
37058 . /////////////////////////////////////////////////////////////////////////////
37059 . These lines are processing instructions for the Simple DocBook Processor that
37060 . Philip Hazel has developed as a less cumbersome way of making PostScript and
37061 . PDFs than using xmlto and fop. They will be ignored by all other XML
37063 . /////////////////////////////////////////////////////////////////////////////
37068 foot_right_recto="&chaptertitle;"
37069 foot_right_verso="&chaptertitle;"
37073 .makeindex "Options index" "option"
37074 .makeindex "Variables index" "variable"
37075 .makeindex "Concept index" "concept"
37078 . /////////////////////////////////////////////////////////////////////////////
37079 . /////////////////////////////////////////////////////////////////////////////