X-Git-Url: https://git.exim.org/exim.git/blobdiff_plain/d67ad6f989a7df6d20b661b9b5fbddd0acc048b3..ee549a2ed04164407f4f897be3bf545f32579c5c:/doc/doc-docbook/spec.xfpt diff --git a/doc/doc-docbook/spec.xfpt b/doc/doc-docbook/spec.xfpt index 4abe2c9cb..1fec82923 100644 --- a/doc/doc-docbook/spec.xfpt +++ b/doc/doc-docbook/spec.xfpt @@ -446,7 +446,7 @@ website, are hosted at the University of Cambridge. .cindex "FAQ" As well as Exim distribution tar files, the Exim website contains a number of differently formatted versions of the documentation. A recent addition to the -online information is the Exim wiki (&url(https://wiki.exim.org)), +online information is &url(https://wiki.exim.org,the Exim wiki), which contains what used to be a separate FAQ, as well as various other examples, tips, and know-how that have been contributed by Exim users. The wiki site should always redirect to the correct place, which is currently @@ -487,7 +487,7 @@ lists. .cindex "bug reports" .cindex "reporting bugs" Reports of obvious bugs can be emailed to &'bugs@exim.org'& or reported -via the Bugzilla (&url(https://bugs.exim.org)). However, if you are unsure +via &url(https://bugs.exim.org,the Bugzilla). However, if you are unsure whether some behaviour is a bug or not, the best thing to do is to post a message to the &'exim-dev'& mailing list and have it discussed. @@ -577,7 +577,8 @@ distribution, and are also available in &_.bz2_& and &_.xz_& forms. .cindex "limitations of Exim" .cindex "bang paths" "not handled by Exim" Exim is designed for use as an Internet MTA, and therefore handles addresses in -RFC 2822 domain format only. It cannot handle UUCP &"bang paths"&, though +&url(https://www.rfc-editor.org/rfc/rfc2822,RFC 2822) +domain format only. It cannot handle UUCP &"bang paths"&, though simple two-component bang paths can be converted by a straightforward rewriting configuration. This restriction does not prevent Exim from being interfaced to UUCP as a transport mechanism, provided that domain addresses are used. @@ -689,7 +690,8 @@ line. .cindex "local part" "definition of" .cindex "domain" "definition of" -The term &'local part'&, which is taken from RFC 2822, is used to refer to the +The term &'local part'&, which is taken from +&url(https://www.rfc-editor.org/rfc/rfc2822,RFC 2822), is used to refer to the part of an email address that precedes the @ sign. The part that follows the @ sign is called the &'domain'& or &'mail domain'&. @@ -952,7 +954,7 @@ of filtering are available: .ilist Sieve filters are written in the standard filtering language that is defined -by RFC 3028. +by &url(https://www.rfc-editor.org/rfc/rfc3028.html,RFC 3028). .next Exim filters are written in a syntax that is unique to Exim, but which is more powerful than Sieve, which it pre-dates. @@ -1399,7 +1401,8 @@ check an address given in the SMTP EXPN command (see the &%expn%& option). If the &%domains%& option is set, the domain of the address must be in the set of domains that it defines. .cindex "tainted data" "de-tainting" -.cindex "de-tainting" "using router domains option" +.cindex de-tainting "using router domains option" +.cindex de-tainting &$domains$& A match verifies the variable &$domain$& (which carries tainted data) and assigns an untainted value to the &$domain_data$& variable. Such an untainted value is often needed in the transport. @@ -1419,6 +1422,7 @@ rather than the generic &%condition%& option. If the &%local_parts%& option is set, the local part of the address must be in the set of local parts that it defines. A match verifies the variable &$local_part$& (which carries tainted data) +.cindex de-tainting &$local_parts$& and assigns an untainted value to the &$local_part_data$& variable. Such an untainted value is often needed in the transport. For specifics of the matching operation and the resulting untainted value, @@ -1811,7 +1815,7 @@ Yet another DBM library, called &'tdb'&, is available from &url(https://sourceforge.net/projects/tdb/files/). It has its own interface, and also operates on a single file. .next -It is possible to use sqlite3 (&url(https://www.sqlite.org/index.html)) +It is possible to use &url(https://www.sqlite.org/index.html,sqlite3) for the DBM library. .endlist @@ -1931,7 +1935,8 @@ do this. .cindex "&[iconv()]& support" .cindex "RFC 2047" The contents of header lines in messages may be encoded according to the rules -described RFC 2047. This makes it possible to transmit characters that are not +described in &url(https://www.rfc-editor.org/rfc/rfc2047,RFC 2047). +This makes it possible to transmit characters that are not in the ASCII character set, and to label them as being in a particular character set. When Exim is inspecting header lines by means of the &%$h_%& mechanism, it decodes them, and translates them into a specified character set @@ -1956,7 +1961,8 @@ to your &_Local/Makefile_& and rebuild Exim. .cindex "OpenSSL" "building Exim with" .cindex "GnuTLS" "building Exim with" Exim is usually built to support encrypted SMTP connections, using the STARTTLS -command as per RFC 2487. It can also support clients that expect to +command as per &url(https://www.rfc-editor.org/rfc/rfc2487,RFC 2487). +It can also support clients that expect to start a TLS session immediately on connection to a non-standard port (see the &%tls_on_connect_ports%& runtime option and the &%-tls-on-connect%& command line option). @@ -2069,19 +2075,29 @@ withdrawn. -.section "Dynamically loaded lookup module support" "SECTdynamicmodules" +.section "Dynamically loaded module support" "SECTdynamicmodules" .cindex "lookup modules" +.cindex "router modules" +.cindex "transport modules" +.cindex "authenticator modules" .cindex "dynamic modules" .cindex ".so building" On some platforms, Exim supports not compiling all lookup types directly into the main binary, instead putting some into external modules which can be loaded on demand. This permits packagers to build Exim with support for lookups with extensive -library dependencies without requiring all users to install all of those +library dependencies without requiring all systems to install all of those dependencies. -Most, but not all, lookup types can be built this way. +.new +Any combination of lookup types can be built this way. +Lookup types that provide several variants will be loaded as +Exim starts. +Types that provide only one method are not loaded until used by +the runtime configuration. +.wen -Set &`LOOKUP_MODULE_DIR`& to the directory into which the modules will be +For building +set &`LOOKUP_MODULE_DIR`& to the directory into which the modules will be installed; Exim will only load modules from that directory, as a security measure. You will need to set &`CFLAGS_DYNAMIC`& if not already defined for your OS; see &_OS/Makefile-Linux_& for an example. @@ -2091,12 +2107,25 @@ see &_src/EDITME_& for details. Then, for each module to be loaded dynamically, define the relevant &`LOOKUP_`&<&'lookup_type'&> flags to have the value "2" instead of "yes". For example, this will build in lsearch but load sqlite and mysql support -on demand: +only if each is installed: .code LOOKUP_LSEARCH=yes LOOKUP_SQLITE=2 LOOKUP_MYSQL=2 .endd +Set also &`LOOKUP_`&<&'lookup_type'&>&` INCLUDE`& and +&`LOOKUP_`&<&'lookup_type'&>`_LIBS if needed for each lookup type, +ensuring that duplicates are not present in more global values. + +.new +Similarly, authenticator, router and transport drivers can be built +as external modules. +Modules will be searched for as demanded by the runtime configuration, +permitting a smaller Exim binary. + +For building, as above but using +&`AUTH_*`&, &`ROUTER_*`& and &`TRANSPORT_*`& instead of &`LOOKUP_*`&, +.wen .section "The building process" "SECID29" @@ -2810,6 +2839,12 @@ displayed. These options are used by Sendmail for selecting configuration files and are ignored by Exim. +.new +.cmdopt -atrn <&'host'&> <&'domainlist'&> +This option requests an ODMR customer connection. +See &<>& for details. +.wen + .cmdopt -B <&'type'&> .oindex "&%-B%&" .cindex "8-bit characters" @@ -3034,7 +3069,8 @@ test your relay controls using &%-bh%&. &*Warning 1*&: .cindex "RFC 1413" -You can test features of the configuration that rely on ident (RFC 1413) +You can test features of the configuration that rely on ident +(&url(https://www.rfc-editor.org/rfc/rfc2487,RFC 1413)) information by using the &%-oMt%& option. However, Exim cannot actually perform an ident callout when testing using &%-bh%& because there is no incoming SMTP connection. @@ -3057,7 +3093,7 @@ acceptable or not. See section &<>&. Features such as authentication and encryption, where the client input is not plain text, cannot easily be tested with &%-bh%&. Instead, you should use a specialized SMTP test program such as -&url(https://www.jetmore.org/john/code/swaks/,swaks). +&url(https://www.jetmore.org/john/code/swaks/,swaks,swaks). .cmdopt -bhc <&'IP&~address'&> This option operates in the same way as &%-bh%&, except that address @@ -3100,7 +3136,9 @@ recognised DSCP names. .cindex "Sieve filter" "capabilities" This option causes Exim to emit an alphabetically sorted list of all supported Sieve protocol extensions on stdout, one per line. This is anticipated to be -useful for ManageSieve (RFC 5804) implementations, in providing that protocol's +useful for ManageSieve +(&url(https://datatracker.ietf.org/doc/html/rfc5804.html,RFC 5804)) +implementations, in providing that protocol's &`SIEVE`& capability response line. As the precise list may depend upon compile-time build options, which this option will adapt to, this is the only way to guarantee a correct response. @@ -3110,7 +3148,9 @@ way to guarantee a correct response. This option runs an Exim receiving process that accepts an incoming, locally-generated message on the standard input. The recipients are given as the command arguments (except when &%-t%& is also present &-- see below). Each -argument can be a comma-separated list of RFC 2822 addresses. This is the +argument can be a comma-separated list of +&url(https://www.rfc-editor.org/rfc/rfc2822,RFC 2822) addresses. +This is the default option for selecting the overall action of an Exim call; it is assumed if no other conflicting option is present. @@ -3132,7 +3172,9 @@ The format .cindex "&""From""& line" .cindex "UUCP" "&""From""& line" .cindex "Sendmail compatibility" "&""From""& line" -of the message must be as defined in RFC 2822, except that, for +of the message must be as defined in +&url(https://www.rfc-editor.org/rfc/rfc2822,RFC 2822), +except that, for compatibility with Sendmail and Smail, a line in one of the forms .code From sender Fri Jan 5 12:55 GMT 1997 @@ -3401,7 +3443,7 @@ Unqualified addresses are automatically qualified using &%qualify_domain%& and &%qualify_recipient%&, as appropriate, unless the &%-bnq%& option is used. Some other SMTP commands are recognized in the input. HELO and EHLO act -as RSET; VRFY, EXPN, ETRN, and HELP act as NOOP; +as RSET; VRFY, EXPN, ETRN, ATRN, and HELP act as NOOP; QUIT quits, ignoring the rest of the standard input. .cindex "return code" "for &%-bS%&" @@ -4119,8 +4161,9 @@ written to the standard output. This option can be used only by an admin user. .cindex "message" "listing in RFC 2822 format" .cindex "listing" "message in RFC 2822 format" This option causes a copy of the complete message (header lines plus body) to -be written to the standard output in RFC 2822 format. This option can be used -only by an admin user. +be written to the standard output in +&url(https://www.rfc-editor.org/rfc/rfc2822,RFC 2822) +format. This option can be used only by an admin user. .cmdopt -Mvh <&'message&~id'&> .cindex "listing" "message headers" @@ -4785,7 +4828,8 @@ lines instead of from &'To:'&, &'Cc:'&, and &'Bcc:'&. This is for compatibility with Sendmail and other MTAs. (Prior to release 4.20, Exim gave an error if &%-t%& was used in conjunction with &%Resent-%& header lines.) -RFC 2822 talks about different sets of &%Resent-%& header lines (for when a +&url(https://www.rfc-editor.org/rfc/rfc2822,RFC 2822) +talks about different sets of &%Resent-%& header lines (for when a message is resent several times). The RFC also specifies that they should be added at the front of the message, and separated by &'Received:'& lines. It is not at all clear how &%-t%& should operate in the present of multiple sets, @@ -5174,7 +5218,7 @@ This can then be used in a &(redirect)& router setting like this: data = ${lookup mysql{ALIAS_QUERY}} .endd In earlier versions of Exim macros were sometimes used for domain, host, or -address lists. In Exim 4 these are handled better by named lists &-- see +address lists. In Exim version 4 these are handled better by named lists &-- see section &<>&. @@ -5452,7 +5496,7 @@ list items, it is not ignored when parsing the list. The spaces around the first colon in the example above are necessary. If they were not there, the list would be interpreted as the two items 127.0.0.1:: and 1. -.section "Changing list separators" "SECTlistsepchange" +.subsection "Changing list separators" "SECTlistsepchange" .cindex "list separator" "changing" .cindex "IPv6" "addresses in lists" Doubling colons in IPv6 addresses is an unwelcome chore, so a mechanism was @@ -5493,7 +5537,7 @@ enclosing an empty list item. -.section "Empty items in lists" "SECTempitelis" +.subsection "Empty items in lists" "SECTempitelis" .cindex "list" "empty item in" An empty item at the end of a list is always ignored. In other words, trailing separator characters are ignored. Thus, the list in @@ -5752,9 +5796,11 @@ Mail submission from mail clients (MUAs) should be separate from inbound mail to your domain (MX delivery) for various good reasons (eg, ability to impose much saner TLS protocol and ciphersuite requirements without unintended consequences). -RFC 6409 (previously 4409) specifies use of port 587 for SMTP Submission, +&url(https://www.rfc-editor.org/rfc/rfc6409,RFC 6409) (previously 4409) +specifies use of port 587 for SMTP Submission, which uses STARTTLS, so this is the &"submission"& port. -RFC 8314 specifies use of port 465 as the &"submissions"& protocol, +&url(https://www.rfc-editor.org/rfc/rfc8314,RFC 8314) +specifies use of port 465 as the &"submissions"& protocol, which should be used in preference to 587. You should also consider deploying SRV records to help clients find these ports. @@ -5813,8 +5859,9 @@ Note that it is not always possible to find a host name from an IP address, because not all DNS reverse zones are maintained, and sometimes DNS servers are unreachable. -The next two lines are concerned with &'ident'& callbacks, as defined by RFC -1413 (hence their names): +The next two lines are concerned with &'ident'& callbacks, as defined by +&url(https://www.rfc-editor.org/rfc/rfc1413,RFC 1413) +(hence their names): .code rfc1413_hosts = * rfc1413_query_timeout = 0s @@ -5887,7 +5934,8 @@ not often needed). .endd In an ideal world everybody follows the standards. For non-ASCII -messages RFC 2047 is a standard, allowing a maximum line length of 76 +messages &url(https://www.rfc-editor.org/rfc/rfc2048,RFC 2047) +is a standard, allowing a maximum line length of 76 characters. Exim adheres that standard and won't process messages which violate this standard. (Even ${rfc2047:...} expansions will fail.) In particular, the Exim maintainers have had multiple reports of @@ -5989,7 +6037,9 @@ block local parts that begin with a dot or contain &"@"&, &"%"&, &"!"&, &"/"&, or &"|"&. If you have local accounts that include these characters, you will have to modify this rule. -Empty components (two dots in a row) are not valid in RFC 2822, but Exim +Empty components (two dots in a row) are not valid in +&url(https://www.rfc-editor.org/rfc/rfc2822,RFC 2822), +but Exim allows them because they have been encountered in practice. (Consider the common convention of local parts constructed as &"&'first-initial.second-initial.family-name'&"& when applied to someone like @@ -6967,7 +7017,7 @@ For elements of type string, the returned value is de-quoted. The given file is an LMDB database. LMDB is a memory-mapped key-value store, with API modeled loosely on that of BerkeleyDB. -See &url(https://symas.com/products/lightning-memory-mapped-database/) +See &url(https://symas.com/products/lightning-memory-mapped-database/,LMDB) for the feature set and operation modes. Exim provides read-only access via the LMDB C library. @@ -7693,7 +7743,8 @@ First we explain how LDAP queries are coded. .subsection "Format of LDAP queries" SECTforldaque .cindex "LDAP" "query format" -An LDAP query takes the form of a URL as defined in RFC 2255. For example, in +An LDAP query takes the form of a URL as defined in +&url(https://www.rfc-editor.org/rfc/rfc2255,RFC 2255). For example, in the configuration of a &(redirect)& router one might have this setting: .code data = ${lookup ldap \ @@ -7736,7 +7787,9 @@ the string: ) => \29 \ => \5C .endd -in accordance with RFC 2254. The resulting string is then quoted according +in accordance with +&url(https://www.rfc-editor.org/rfc/rfc2254,RFC 2254). +The resulting string is then quoted according to the rules for URLs, that is, all non-alphanumeric characters except .code ! $ ' - . _ ( ) * + @@ -7760,8 +7813,10 @@ by inserting a backslash in front of any of the following characters: , + " \ < > ; .endd It also inserts a backslash before any leading spaces or # characters, and -before any trailing spaces. (These rules are in RFC 2253.) The resulting string -is then quoted according to the rules for URLs. For example: +before any trailing spaces. (These rules are in +&url(https://www.rfc-editor.org/rfc/rfc2255,RFC 2253).) +The resulting string is then quoted according to the rules for URLs. +For example: .code ${quote_ldap_dn: a(bc)*, a; } .endd @@ -7797,7 +7852,8 @@ Errors which cause the next server to be tried are connection failures, bind failures, and timeouts. For each server name in the list, a port number can be given. The standard way -of specifying a host and port is to use a colon separator (RFC 1738). Because +of specifying a host and port is to use a colon separator +(&url(https://www.rfc-editor.org/rfc/rfc1738,RFC 1738)). Because &%ldap_default_servers%& is a colon-separated list, such colons have to be doubled. For example .code @@ -8198,7 +8254,7 @@ ${lookup mysql{servers=master; UPDATE ...} } The new version avoids issues with tainted arguments explicitly expanded as part of the query. The entire string within the braces becomes tainted, -including the server sepcification - which is not permissible. +including the server specification - which is not permissible. If the older sytax is used, a warning message will be logged. This syntax will be removed in a future release. @@ -8213,12 +8269,21 @@ An option group name for MySQL option files can be specified in square brackets; the default value is &"exim"&. The full syntax of each item in &%mysql_servers%& is: .display -<&'hostname'&>::<&'port'&>(<&'socket name'&>)[<&'option group'&>]/&&& - <&'database'&>/<&'user'&>/<&'password'&> +<&'hostspec'&><&'portspec'&>(<&'socket name'&>)[<&'option group'&>]/&&& + <&'database'&>/<&'user'&>/<&'password'&> .endd Any of the four sub-parts of the first field can be omitted. For normal use on the local host it can be left blank or set to just &"localhost"&. +.new +A &'hostspec'& can be a hostname, an IPv4 address or an IPv6 address. +For the latter, a &'portspec'& is a dot followed by a port number; +for the other two a &'portspec'& is a colon followed by a port number. +.wen + +Note that the default list-separator for the list of servers is a colon so +(unless that is changed) all colons in list items must be doubled. + No database need be supplied &-- but if it is absent here, it must be given in the queries. @@ -8234,6 +8299,10 @@ parameters for the connection. .subsection "Special PostgreSQL features" SECID74 +.new +The &'hostspec'& for PostgreSQL follows the same rules as for MySQL above. +.wen + PostgreSQL lookups can also use Unix domain socket connections to the database. This is usually faster and costs less CPU time than a TCP/IP connection. However it can be used only if the mail server runs on the same machine as the @@ -8380,10 +8449,18 @@ type of match and is given below as the &*value*& information. .section "Expansion of lists" "SECTlistexpand" .cindex "expansion" "of lists" -Each list is expanded as a single string before it is used. +.new +Each list, after any leading change-of-separator specification +(see &<>&) is expanded as a single string, .cindex "tainted data" tracking -&*Note*&: As a result, if any componend was tainted then the -entire result string becomes tainted. +&*Note*&: As a result, if any component was tainted then the +entire expansion result string becomes tainted. + +Splitting out a leading explicit change-of-separator permits +one being safely used on a list that has tainted components +while still detecting the use of a tainted setting. +The latter is not permitted. +.wen &'Exception: the router headers_remove option, where list-item splitting is done before string-expansion.'& @@ -8566,6 +8643,11 @@ domainlist dom2 = !a.b : *.b where &'x.y'& does not match. It's best to avoid negation altogether in referenced lists if you can. +.new +The list item which references a named list (&"+"&) +may not be tainted. +.wen + .cindex "hiding named list values" .cindex "named lists" "hiding value of" Some named list definitions may contain sensitive data, for example, passwords for @@ -8670,6 +8752,9 @@ possible to use the same configuration file on several different hosts that differ only in their names. The value for a match will be the primary host name. +.new +The pattern may not be tainted. +.wen .next @@ -8685,6 +8770,9 @@ In today's Internet, the use of domain literals is controversial; see the &%allow_domain_literals%& main option. The value for a match will be the string &`@[]`&. +.new +The pattern may not be tainted. +.wen .next @@ -8701,6 +8789,10 @@ local host, and the second only when no primary MX target is the local host, but a secondary MX target is. &"Primary"& means an MX record with the lowest preference value &-- there may of course be more than one of them. +.new +The pattern may not be tainted. +.wen + The MX lookup that takes place when matching a pattern of this type is performed with the resolver options for widening names turned off. Thus, for example, a single-component domain will &'not'& be expanded by adding the @@ -9169,6 +9261,8 @@ does not match the list. This may not always be what you want to happen. To change Exim's behaviour, the special items &`+include_unknown`& or &`+ignore_unknown`& may appear in the list (at top level &-- they are not recognized in an indirected file). +The effects of these special items do not propagate into referenced +named lists. .ilist If any item that follows &`+include_unknown`& requires information that @@ -9511,7 +9605,8 @@ example it is a named domain list. .cindex "case forcing in address lists" Domains in email addresses are always handled caselessly, but for local parts case may be significant on some systems (see &%caseful_local_part%& for how -Exim deals with this when routing addresses). However, RFC 2505 (&'Anti-Spam +Exim deals with this when routing addresses). However, +&url(https://www.rfc-editor.org/rfc/rfc2505,RFC 2505) (&'Anti-Spam Recommendations for SMTP MTAs'&) suggests that matching of addresses to blocking lists should be done in a case-independent manner. Since most address lists in Exim are used for this kind of control, Exim attempts to do this by @@ -9534,6 +9629,13 @@ longer case-independent. This does not affect the domain, which remains in lower case. However, although independent matches on the domain alone are still performed caselessly, regular expressions that match against an entire address become case-sensitive after &"+caseful"& has been seen. +The effects of &"+caseful"& propagate into any referenced named lists. + +.new +This string may not be tainted. +To do caseful matching on list elements whic are tainted, +place them in a named list. +.wen @@ -9552,6 +9654,12 @@ matching in the local part list, but not elsewhere in the router. If &%caseful_local_part%& is set true in a router, matching in the &%local_parts%& option is case-sensitive from the start. +.new +This string may not be tainted. +To do caseful matching on list elements whic are tainted, +place them in a named list. +.wen + If a local part list is indirected to a file (see section &<>&), comments are handled in the same way as address lists &-- they are recognized only if the # is preceded by white space or the start of the line. @@ -10034,11 +10142,15 @@ leading and trailing quotes are removed from the returned value. .cindex "list" "selecting by condition" .cindex "expansion" "selecting from list by condition" .vindex "&$item$&" -After expansion, <&'string'&> is interpreted as a list, colon-separated by -default, but the separator can be changed in the usual way (&<>&). -For each item -in this list, its value is placed in &$item$&, and then the condition is -evaluated. +.new +<&'string1'&> first has the part after any change-of-list-separator +(see &<>&) expanded, +then the whole is taken as a list. +.wen +The default separator for the list is a colon. + +For each item in this list, +its value is placed in &$item$&, and then the condition is evaluated. Any modification of &$value$& by this evaluation is discarded. If the condition is true, &$item$& is added to the output as an item in a new list; if the condition is false, the item is discarded. The @@ -10154,7 +10266,9 @@ option in the runtime configuration. The value of this option defaults to the value of HEADERS_CHARSET in &_Local/Makefile_&. The ultimate default is ISO-8859-1. -Header names follow the syntax of RFC 2822, which states that they may contain +Header names follow the syntax of +&url(https://www.rfc-editor.org/rfc/rfc2822,RFC 2822), +which states that they may contain any printing characters except space and colon. Consequently, curly brackets &'do not'& terminate header names, and should not be used to enclose them as if they were variables. Attempting to do so causes a syntax error. @@ -10203,7 +10317,8 @@ the result of expanding any of these variables is tainted. .cindex &%hmac%& This function uses cryptographic hashing (either MD5 or SHA-1) to convert a shared secret and some text into a message authentication code, as specified in -RFC 2104. This differs from &`${md5:secret_text...}`& or +&url(https://www.rfc-editor.org/rfc/rfc2104.RFC 2104). +This differs from &`${md5:secret_text...}`& or &`${sha1:secret_text...}`& in that the hmac step adds a signature to the cryptographic hash, allowing for authentication that is not possible with MD5 or SHA-1 alone. The hash name must expand to either &`md5`& or &`sha1`& at @@ -10299,8 +10414,12 @@ The <&'number'&> argument must consist entirely of decimal digits, apart from an optional leading minus, and leading and trailing white space (which is ignored). -After expansion, <&'string1'&> is interpreted as a list, colon-separated by -default, but the separator can be changed in the usual way (&<>&). +.new +The <&'string1'&> argument, after any leading change-of-separator +(see &<>&), +is expanded and the whole forms the list. +.wen +By default, the list separator is a colon. The first field of the list is numbered one. If the number is negative, the fields are @@ -10400,10 +10519,15 @@ ${lookup nisplus {[name=$local_part],passwd.org_dir:gcos} \ .vitem &*${map{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*& .cindex "expansion" "list creation" .vindex "&$item$&" -After expansion, <&'string1'&> is interpreted as a list, colon-separated by -default, but the separator can be changed in the usual way (&<>&). -For each item -in this list, its value is place in &$item$&, and then <&'string2'&> is +.new +<&'string1'&> first has the part after any change-of-list-separator +(see &<>&) expanded, +then the whole is taken as a list. +.wen +The default separator for the list is a colon. + +For each item in this list, +its value is place in &$item$&, and then <&'string2'&> is expanded and added to the output as an item in a new list. The separator used for the output list is the same as the one used for the input, but a separator setting is not included in the output. For example: @@ -10623,9 +10747,15 @@ locks out the use of this expansion item in filter files. .cindex "list" "reducing to a scalar" .vindex "&$value$&" .vindex "&$item$&" -This operation reduces a list to a single, scalar string. After expansion, -<&'string1'&> is interpreted as a list, colon-separated by default, but the -separator can be changed in the usual way (&<>&). +This operation reduces a list to a single, scalar string. + +.new +<&'string1'&> first has the part after any change-of-list-separator +(see &<>&) expanded, +then the whole is taken as a list. +.wen +The default separator for the list is a colon. + Then <&'string2'&> is expanded and assigned to the &$value$& variable. After this, each item in the <&'string1'&> list is assigned to &$item$&, in turn, and <&'string3'&> is expanded for each of @@ -10782,8 +10912,13 @@ rather than any Unicode-aware character handling. .cindex sorting "a list" .cindex list sorting .cindex expansion "list sorting" -After expansion, <&'string'&> is interpreted as a list, colon-separated by -default, but the separator can be changed in the usual way (&<>&). +.new +<&'string'&> first has the part after any change-of-list-separator +(see &<>&) expanded, +then the whole is taken as a list. +.wen +The default separator for the list is a colon. + The <&'comparator'&> argument is interpreted as the operator of a two-argument expansion condition. The numeric operators plus ge, gt, le, lt (and ~i variants) are supported. @@ -10810,7 +10945,7 @@ will sort an MX lookup into priority order. .vitem &*${srs_encode&~{*&<&'secret'&>&*}{*&<&'return&~path'&>&*}{*&<&'original&~domain'&>&*}}*& -SRS encoding. See SECT &<>& for details. +SRS encoding. See section &<>& for details. @@ -10905,7 +11040,9 @@ following operations can be performed: .vitem &*${address:*&<&'string'&>&*}*& .cindex "expansion" "RFC 2822 address handling" .cindex "&%address%& expansion item" -The string is interpreted as an RFC 2822 address, as it might appear in a +The string is interpreted as an +&url(https://www.rfc-editor.org/rfc/rfc2822,RFC 2822) +address, as it might appear in a header line, and the effective address is extracted from it. If the string does not parse successfully, the result is empty. @@ -10915,8 +11052,9 @@ The parsing correctly handles SMTPUTF8 Unicode in the string. .vitem &*${addresses:*&<&'string'&>&*}*& .cindex "expansion" "RFC 2822 address handling" .cindex "&%addresses%& expansion item" -The string (after expansion) is interpreted as a list of addresses in RFC -2822 format, such as can be found in a &'To:'& or &'Cc:'& header line. The +The string (after expansion) is interpreted as a list of addresses in +&url(https://www.rfc-editor.org/rfc/rfc2822,RFC 2822) +format, such as can be found in a &'To:'& or &'Cc:'& header line. The operative address (&'local-part@domain'&) is extracted from each item, and the result of the expansion is a colon-separated list, with appropriate doubling of colons should any happen to be present in the email addresses. @@ -11019,8 +11157,10 @@ This operator converts a base64-encoded string into the un-coded form. .vitem &*${domain:*&<&'string'&>&*}*& .cindex "domain" "extraction" .cindex "expansion" "domain extraction" -The string is interpreted as an RFC 2822 address and the domain is extracted -from it. If the string does not parse successfully, the result is empty. +The string is interpreted as an +&url(https://www.rfc-editor.org/rfc/rfc2822,RFC 2822) +address and the domain is extracted from it. +If the string does not parse successfully, the result is empty. .vitem &*${escape:*&<&'string'&>&*}*& @@ -11234,7 +11374,8 @@ All measurement is done in bytes and is not UTF-8 aware. .cindex "list" "item count" .cindex "list" "count of items" .cindex "&%listcount%& expansion item" -The string is interpreted as a list and the number of items is returned. +The part of the string after any leading change-of-separator is expanded, +then the whole is interpreted as a list and the number of items is returned. .vitem &*${listnamed:*&<&'name'&>&*}*&&~and&~&*${listnamed_*&<&'type'&>&*:*&<&'name'&>&*}*& @@ -11253,9 +11394,10 @@ nor expansion of lookup elements, is done by the &%listnamed%& operator. .vitem &*${local_part:*&<&'string'&>&*}*& .cindex "expansion" "local part extraction" .cindex "&%local_part%& expansion item" -The string is interpreted as an RFC 2822 address and the local part is -extracted from it. If the string does not parse successfully, the result is -empty. +The string is interpreted as an +&url(https://www.rfc-editor.org/rfc/rfc2822,RFC 2822) +address and the local part is extracted from it. +If the string does not parse successfully, the result is empty. The parsing correctly handles SMTPUTF8 Unicode in the string. @@ -11341,8 +11483,10 @@ variable or a message header. .vitem &*${quote_local_part:*&<&'string'&>&*}*& .cindex "&%quote_local_part%& expansion item" This operator is like &%quote%&, except that it quotes the string only if -required to do so by the rules of RFC 2822 for quoting local parts. For -example, a plus sign would not cause quoting (but it would for &%quote%&). +required to do so by the rules of +&url(https://www.rfc-editor.org/rfc/rfc2822,RFC 2822) +for quoting local parts. For example, +a plus sign would not cause quoting (but it would for &%quote%&). If you are creating a new email address from the contents of &$local_part$& (or any other unknown data), you should always use this operator. @@ -11401,7 +11545,8 @@ 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 .cindex "expansion" "RFC 2047" .cindex "RFC 2047" "expansion operator" .cindex "&%rfc2047%& expansion item" -This operator encodes text according to the rules of RFC 2047. This is an +This operator encodes text according to the rules of +&url(https://www.rfc-editor.org/rfc/rfc2047,RFC 2047). This is an encoding that is used in header lines to encode non-ASCII characters. It is assumed that the input string is in the encoding specified by the &%headers_charset%& option, which gets its default at build time. If the string @@ -11419,7 +11564,9 @@ characters. .cindex "expansion" "RFC 2047" .cindex "RFC 2047" "decoding" .cindex "&%rfc2047d%& expansion item" -This operator decodes strings that are encoded as per RFC 2047. Binary zero +This operator decodes strings that are encoded as per +&url(https://www.rfc-editor.org/rfc/rfc2047,RFC 2047). +Binary zero bytes are replaced by question marks. Characters are converted into the character set defined by &%headers_charset%&. Overlong RFC 2047 &"words"& are not recognized unless &%check_rfc2047_length%& is set false. @@ -11605,7 +11752,8 @@ For information on internationalisation support see &<>&. .cindex "string" "xtext decoding" .cindex "xtext" .cindex "&%xtextd%& expansion item" -This performs xtext decoding of the string (per RFC 3461 section 4). +This performs xtext decoding of the string (per +&url(https://www.rfc-editor.org/rfc/rfc3461,RFC 3461) section 4). @@ -11848,9 +11996,14 @@ attempt. It is false during any subsequent delivery attempts. .cindex "expansion" "&*forall*& condition" .cindex "expansion" "&*forany*& condition" .vindex "&$item$&" -These conditions iterate over a list. The first argument is expanded to form -the list. By default, the list separator is a colon, but it can be changed by -the normal method (&<>&). +These conditions iterate over a list. +.new +The first argument, after any leading change-of-separator +(see &<>&), +is expanded and the whole forms the list. +.wen +By default, the list separator is a colon. + The second argument is interpreted as a condition that is to be applied to each item in the list in turn. During the interpretation of the condition, the current list item is placed in a variable called &$item$&. @@ -11927,9 +12080,14 @@ SRS decode. See SECT &<>& for details. &*inlisti&~{*&<&'subject'&>&*}{*&<&'list'&>&*}*& .cindex "string" "comparison" .cindex "list" "iterative conditions" -Both strings are expanded; the second string is treated as a list of simple -strings; if the first string is a member of the second, then the condition -is true. +The <&'subject'&> string is expanded. +.new +The <&'list'&> first has any change-of-list-separator ++(see &<>&) retained verbatim, ++then the remainder is expanded. ++.wen +The whole is treated as a list of simple strings; +if the subject string is a member of that list, then the condition is true. For the case-independent &%inlisti%& condition, case is defined per the system C locale. These are simpler to use versions of the more powerful &*forany*& condition. @@ -12122,6 +12280,10 @@ just as easy to use the fact that a lookup is itself a condition, and write: Note that <&'string2'&> is not itself subject to string expansion, unless Exim was built with the EXPAND_LISTMATCH_RHS option. +.new +For the latter case, only the part after any leading +change-of-separator specification is expanded. +.wen Consult section &<>& for further details of these patterns. @@ -12150,9 +12312,10 @@ ${if match_domain{$domain}{+local_domains}{... .endd .cindex "&`+caseful`&" For address lists, the matching starts off caselessly, but the &`+caseful`& -item can be used, as in all address lists, to cause subsequent items to -have their local parts matched casefully. Domains are always matched -caselessly. +item can be used, as in all address lists, to cause subsequent items +(including those of referenced named lists) +to have their local parts matched casefully. +Domains are always matched caselessly. The variable &$value$& will be set for a successful match and can be used in the success clause of an &%if%& expansion item using the condition. @@ -12167,6 +12330,10 @@ Any previous &$value$& is restored after the if. Note that <&'string2'&> is not itself subject to string expansion, unless Exim was built with the EXPAND_LISTMATCH_RHS option. +.new +For the latter case, only the part after any leading +change-of-separator specification is expanded. +.wen &*Note*&: Host lists are &'not'& supported in this way. This is because hosts have two identities: a name and an IP address, and it is not clear @@ -12257,7 +12424,9 @@ initiated by queue runner processes, and false otherwise. .cindex "Radius" .cindex "expansion" "Radius authentication" .cindex "&%radius%& expansion condition" -Radius authentication (RFC 2865) is supported in a similar way to PAM. You must +Radius authentication +(&url(https://www.rfc-editor.org/rfc/rfc2865,RFC 2865)) +is supported in a similar way to PAM. You must set RADIUS_CONFIG_FILE in &_Local/Makefile_& to specify the location of the Radius client configuration file in order to build Exim with Radius support. @@ -12474,6 +12643,20 @@ to the relevant file. When, as a result of aliasing or forwarding, a message is directed to a pipe, this variable holds the pipe command when the transport is running. +.new +.vitem &$atrn_host$& +.vindex ATRN "data for routing" +When an ATRN command is accepted, this variable is filled in with the client +IP and port, for use in a manualroute router. + +.vitem &$atrn_mode$& +.vindex ATRN mode +.vindex ODMR mode +When in provider mode this variable will contain &"P"&. +When in customer mode it will contain &"C"&. +Otherwise, it will be empty. +.wen + .vitem "&$auth1$& &-- &$auth4$&" .vindex "&$auth1$&, &$auth2$&, etc" These variables are used in SMTP authenticators (see chapters @@ -12611,6 +12794,11 @@ contain the trailing slash. If &$config_file$& does not contain a slash, .vindex "&$config_file$&" The name of the main configuration file Exim is using. +.vitem &$connection_id$& +.vindex "&$connection_id$&" +.cindex connection "identifier logging" +An identifier for the accepted connection, for use in custom logging. + .vitem &$dkim_verify_status$& Results of DKIM verification. For details see section &<>&. @@ -12643,7 +12831,9 @@ When a message has been received this variable contains a colon-separated list of signer domains and identities for the message. For details see section &<>&. -.vitem &$dmarc_domain_policy$& &&& +.vitem &$dmarc_alignment_spf$& &&& + &$dmarc_alignment_dkim$& &&& + &$dmarc_domain_policy$& &&& &$dmarc_status$& &&& &$dmarc_status_text$& &&& &$dmarc_used_domains$& @@ -14503,7 +14693,7 @@ The common use of this option is expected to be .code tls_on_connect_ports = 465 .endd -per RFC 8314. +per &url(https://www.rfc-editor.org/rfc/rfc8314,RFC 8314). There is also a command line option &%-tls-on-connect%&, which forces all ports to behave in this way when a daemon is started. @@ -14843,6 +15033,7 @@ listed in more than one group. .row &%acl_not_smtp%& "ACL for non-SMTP messages" .row &%acl_not_smtp_mime%& "ACL for non-SMTP MIME parts" .row &%acl_not_smtp_start%& "ACL for start of non-SMTP message" +.row &%acl_smtp_atrn%& "ACL for ATRN" .row &%acl_smtp_auth%& "ACL for AUTH" .row &%acl_smtp_connect%& "ACL for connection" .row &%acl_smtp_data%& "ACL for DATA" @@ -15165,6 +15356,20 @@ SMTP messages. This option defines the ACL that is run before Exim starts reading a non-SMTP message. See section &<>& for further details. +.new +.option acl_smtp_atrn main string&!! unset +.cindex ATRN "ACL for" +.cindex ATRN advertisement +.cindex "ESMTP extensions" ATRN +.cindex ODMR provider +This option defines the ACL that is run when an SMTP ATRN command is +received. +If no value is set, or the result after expansion is an empty string, +then the ATRN facility is not advertised. +See chapter &<>& for general information on ACLs, +and section &<>& for description of ATRN. +.wen + .option acl_smtp_auth main string&!! unset .cindex "&ACL;" "setting up for SMTP commands" .cindex "AUTH" "ACL for" @@ -15208,7 +15413,8 @@ See section &<>& for further details. This option defines the ACL that is run when an SMTP ETRN command is received. If no value is set then the ETRN facility is not advertised. -See chapter &<>& for further details. +See chapter &<>& for general information on ACLs, +and section &<>& for description of ETRN. .option acl_smtp_expn main string&!! unset .cindex "EXPN" "ACL for" @@ -15296,7 +15502,9 @@ To permit this, you have to add individuals to the Exim group. .option allow_domain_literals main boolean false .cindex "domain literal" -If this option is set, the RFC 2822 domain literal format is permitted in +If this option is set, the +&url(https://www.rfc-editor.org/rfc/rfc2822,RFC 2822) +domain literal format is permitted in email addresses. The option is not set by default, because the domain literal format is not normally required these days, and few people know about it. It has, however, been exploited by mail abusers. @@ -15542,7 +15750,8 @@ See &%check_spool_space%& below. .oindex "&%check_rfc2047_length%&" .cindex "RFC 2047" "disabling length check" .option check_rfc2047_length main boolean true -RFC 2047 defines a way of encoding non-ASCII characters in headers using a +&url(https://www.rfc-editor.org/rfc/rfc2047,RFC 2047) +defines a way of encoding non-ASCII characters in headers using a system of &"encoded words"&. The RFC specifies a maximum length for an encoded word; strings to be encoded that exceed this length are supposed to use multiple encoded words. By default, Exim does not recognize encoded words that @@ -15607,8 +15816,9 @@ may wish to deliberately disable them. .cindex CHUNKING advertisement .cindex "RFC 3030" "CHUNKING" .cindex "ESMTP extensions" CHUNKING -The CHUNKING extension (RFC3030) will be advertised in the EHLO message to -these hosts. +The CHUNKING extension +(&url(https://www.rfc-editor.org/rfc/rfc3030.html,RFC 3030)) +will be advertised in the EHLO message to these hosts. Hosts may use the BDAT command as an alternate to DATA. .option commandline_checks_require_admin main boolean &`false`& @@ -15754,7 +15964,8 @@ sha256 sha512 .endd -Note that the acceptance of sha1 violates RFC 8301. +Note that the acceptance of sha1 violates +&url(https://www.rfc-editor.org/rfc/rfc8301,RFC 8301). .option dkim_verify_keytypes main "string list" "ed25519 : rsa" This option gives a list of key types which are acceptable in signatures, @@ -15767,7 +15978,9 @@ This option gives a list of key sizes which are acceptable in signatures. The list is keyed by the algorithm type for the key; the values are in bits. Signatures with keys smaller than given by this option will fail verification. -The default enforces the RFC 8301 minimum key size for RSA signatures. +The default enforces the +&url(https://www.rfc-editor.org/rfc/rfc8301,RFC 8301) +minimum key size for RSA signatures. .option dkim_verify_minimal main boolean false If set to true, verification of signatures will terminate after the @@ -15781,9 +15994,9 @@ the ACL once for each signature in the message. See section &<>&. -.option dmarc_forensic_sender main string&!! unset &&& - dmarc_history_file main string unset &&& - dmarc_tld_file main string unset +.options dmarc_forensic_sender main string&!! unset &&& + dmarc_history_file&!! main string unset &&& + dmarc_tld_file main&!! string unset .cindex DMARC "main section options" These options control DMARC processing. See section &<>& for details. @@ -15962,7 +16175,8 @@ described in section &<>&. .cindex "DSN" "success" .cindex "Delivery Status Notification" "success" .cindex "ESMTP extensions" DSN -DSN extensions (RFC3461) will be advertised in the EHLO message to, +DSN extensions (&url(https://www.rfc-editor.org/rfc/rfc3461,RFC 3461)) +will be advertised in the EHLO message to, and accepted from, these hosts. Hosts may use the NOTIFY and ORCPT options on RCPT TO commands, and RET and ENVID options on MAIL FROM commands. @@ -16042,7 +16256,8 @@ and warning messages. For example: .code errors_reply_to = postmaster@my.domain.example .endd -The value of the option is not expanded. It must specify a valid RFC 2822 +The value of the option is not expanded. It must specify a valid +&url(https://www.rfc-editor.org/rfc/rfc2822,RFC 2822) address. However, if a warning message that is generated by the &%quota_warn_message%& option in an &(appendfile)& transport contain its own &'Reply-To:'& header line, the value of the &%errors_reply_to%& option is @@ -16109,9 +16324,11 @@ routing, but which are not used for listening by the daemon. See section . Allow this long option name to split; give it unsplit as a fifth argument . for the automatic .oindex that is generated by .option. +. WAS: +. .option "extract_addresses_remove_ &~&~arguments" +. but apparently this results in searchability problems; bug 1197 -.option "extract_addresses_remove_arguments" main boolean true &&& - extract_addresses_remove_arguments +.option extract_addresses_remove_arguments main boolean true .oindex "&%-t%&" .cindex "command line" "addresses with &%-t%&" .cindex "Sendmail compatibility" "&%-t%& option" @@ -16251,7 +16468,7 @@ set. .cindex "underscore in EHLO/HELO" This option can be set to a string of rogue characters that are permitted in non-ip-literal EHLO and HELO names in addition to the standard letters, digits, -hyphens, and dots. For examplem if you really must allow underscores, +hyphens, and dots. For example if you really must allow underscores, you can set .code helo_allow_chars = _ @@ -16624,8 +16841,9 @@ has been built with LDAP support. .cindex LIMITS "suppressing advertising" .cindex "ESMTP extensions" LIMITS This option can be used to suppress the advertisement of the SMTP -LIMITS extension (RFC 9422) to specific hosts. -If permitted, Exim as a servier will advertise in the EHLO response +LIMITS extension (&url(https://www.ietf.org/rfc/rfc9422.html,RFC 9422)) +to specific hosts. +If permitted, Exim as a server will advertise in the EHLO response the limit for RCPT commands set by the &%recipients_max%& option (if it is set) and the limit for MAIL commands set by the &%smtp_accept_max_per_connection%& option. @@ -16855,8 +17073,9 @@ empty string, the option is ignored. .option message_id_header_text main string&!! unset If this variable is set, the string is expanded and used to augment the text of the &'Message-id:'& header that Exim creates if a locally-originated incoming -message does not have one. The text of this header is required by RFC 2822 to -take the form of an address. By default, Exim uses its internal message id as +message does not have one. The text of this header is required by +&url(https://www.rfc-editor.org/rfc/rfc2822,RFC 2822) +to take the form of an address. By default, Exim uses its internal message id as the local part, and the primary host name as the domain. If this option is set, it is expanded, and provided the expansion is not forced to fail, and does not yield an empty string, the result is inserted into the header immediately @@ -17115,7 +17334,9 @@ common installed configuration. The &"percent hack"& is the convention whereby a local part containing a percent sign is re-interpreted as a new email address, with the percent replaced by @. This is sometimes called &"source routing"&, though that term is -also applied to RFC 2822 addresses that begin with an @ character. If this +also applied to +&url(https://www.rfc-editor.org/rfc/rfc2822,RFC 2822) +addresses that begin with an @ character. If this option is set, Exim implements the percent facility for those domains listed, but no others. This happens before an incoming SMTP address is tested against an ACL. @@ -17189,7 +17410,7 @@ See also the &%hosts_pipe_connect%& smtp transport option. The SMTP service extension keyword advertised is &"PIPECONNECT"&; it permits the client to pipeline -TCP connection and hello command (inclear phase), +TCP connection and hello command (cleatext phase), or TLS-establishment and hello command (encrypted phase), on later connections to the same host. @@ -17243,7 +17464,8 @@ is set, code values of 128 and above are also considered to be printing characters. This option also affects the header syntax checks performed by the -&(autoreply)& transport, and whether Exim uses RFC 2047 encoding of +&(autoreply)& transport, and whether Exim uses +&url(https://www.rfc-editor.org/rfc/rfc2047,RFC 2047) encoding of the user's full name when constructing From: and Sender: addresses (as described in section &<>&). Setting this option can cause Exim to generate eight bit message headers that do not conform to the @@ -17469,8 +17691,9 @@ added to each message, except for the timestamp, which is automatically added on at the end (preceded by a semicolon). The string is expanded each time it is used. If the expansion yields an empty string, no &'Received:'& header line is added to the message. Otherwise, the string should start with the text -&"Received:"& and conform to the RFC 2822 specification for &'Received:'& -header lines. +&"Received:"& and conform to the +&url(https://www.rfc-editor.org/rfc/rfc2822,RFC 2822) +specification for &'Received:'& header lines. The default setting is: .code @@ -17639,7 +17862,8 @@ the default value. .option return_path_remove main boolean true .cindex "&'Return-path:'& header line" "removing" -RFC 2821, section 4.4, states that an SMTP server must insert a +&url(https://www.rfc-editor.org/rfc/rfc2821,RFC 2821), section 4.4, +states that an SMTP server must insert a &'Return-path:'& header line into a message when it makes a &"final delivery"&. The &'Return-path:'& header preserves the sender address as received in the MAIL command. This description implies that this header should not be present @@ -17656,7 +17880,8 @@ This option is an obsolete synonym for &%bounce_return_size_limit%&. .option rfc1413_hosts main "host list&!!" @[] .cindex "RFC 1413" .cindex "host" "for RFC 1413 calls" -RFC 1413 identification calls are made to any client host which matches +&url(https://www.rfc-editor.org/rfc/rfc1413,RFC 1413) +identification calls are made to any client host which matches an item in the list. The default value specifies just this host, being any local interface for the system. @@ -17664,7 +17889,9 @@ for the system. .option rfc1413_query_timeout main time 0s .cindex "RFC 1413" "query timeout" .cindex "timeout" "for RFC 1413 call" -This sets the timeout on RFC 1413 identification calls. If it is set to zero, +This sets the timeout on +&url(https://www.rfc-editor.org/rfc/rfc1413,RFC 1413) +identification calls. If it is set to zero, no RFC 1413 calls are ever made. @@ -17757,8 +17984,7 @@ live with. . searchable. NM changed this occurrence for bug 1197 to no longer allow . the option name to split. -.option "smtp_accept_max_per_connection" main integer&!! 1000 &&& - smtp_accept_max_per_connection +.option smtp_accept_max_per_connection main integer&!! 1000 .cindex "SMTP" "limiting incoming message count" .cindex "limit" "messages per SMTP connection" The value of this option limits the number of MAIL commands that Exim is @@ -17812,8 +18038,7 @@ various &%-od%&&'x'& command line options. . See the comment on smtp_accept_max_per_connection -.option "smtp_accept_queue_per_connection" main integer 10 &&& - smtp_accept_queue_per_connection +.option smtp_accept_queue_per_connection main integer 10 .cindex "queueing incoming messages" .cindex "message" "queueing by message count" This option limits the number of delivery processes that Exim starts @@ -17955,7 +18180,7 @@ hosts), you can do so by an appropriate use of a &%control%& modifier in an ACL .option smtp_etrn_command main string&!! unset -.cindex "ETRN" "command to be run" +.cindex ETRN "command to be run" .cindex "ESMTP extensions" ETRN .vindex "&$domain$&" If this option is set, the given command is run whenever an SMTP ETRN @@ -17982,7 +18207,7 @@ the command. .option smtp_etrn_serialize main boolean true -.cindex "ETRN" "serializing" +.cindex ETRN serializing When this option is set, it prevents the simultaneous execution of more than one identical command as a result of ETRN in an SMTP connection. See section &<>& for details. @@ -18585,11 +18810,16 @@ If Exim is using OpenSSL and this option is empty or unset, then Exim will load a default DH prime; the default is Exim-specific but lacks verifiable provenance. In older versions of Exim the default was the 2048 bit prime described in section -2.2 of RFC 5114, "2048-bit MODP Group with 224-bit Prime Order Subgroup", which +2.2 of &url(https://www.rfc-editor.org/rfc/rfc5114,RFC 5114), +"2048-bit MODP Group with 224-bit Prime Order Subgroup", which in IKE is assigned number 23. Otherwise, the option must expand to the name used by Exim for any of a number -of DH primes specified in RFC 2409, RFC 3526, RFC 5114, RFC 7919, or from other +of DH primes specified in +&url(https://www.rfc-editor.org/rfc/rfc2409,RFC 2409), +&url(https://www.rfc-editor.org/rfc/rfc3526,RFC 3526), +&url(https://www.rfc-editor.org/rfc/rfc5114,RFC 5114), +&url(https://www.rfc-editor.org/rfc/rfc7919,RFC 7919), or from other sources. As names, Exim uses a standard specified name, else "ike" followed by the number used by IKE, or "default" which corresponds to &`exim.dev.20160529.3`&. @@ -18606,13 +18836,15 @@ The available additional primes are: Some of these will be too small to be accepted by clients. Some may be too large to be accepted by clients. The open cryptographic community has suspicions about the integrity of some -of the later IKE values, which led into RFC7919 providing new fixed constants -(the "ffdhe" identifiers). +of the later IKE values, which led into +&url(https://www.rfc-editor.org/rfc/rfc7919,RFC 7919) +providing new fixed constants (the "ffdhe" identifiers). At this point, all of the "ike" values should be considered obsolete; they are still in Exim to avoid breaking unusual configurations, but are candidates for removal the next time we have backwards-incompatible changes. -Two of them in particular (&`ike1`& and &`ike22`&) are called out by RFC 8247 +Two of them in particular (&`ike1`& and &`ike22`&) are called out by +&url(https://www.rfc-editor.org/rfc/rfc8247,RFC 8247) as MUST NOT use for IPSEC, and two more (&`ike23`& and &`ike24`&) as SHOULD NOT. Because of this, Exim regards them as deprecated; if either of the first pair @@ -19251,11 +19483,15 @@ This applies to all of the SRV, MX, AAAA, A lookup sequence. .option domains routers&!? "domain list&!!" unset .cindex "router" "restricting to specific domains" .vindex "&$domain_data$&" -If this option is set, the router is skipped unless the current domain matches -the list. +If this option is set, +the argument is first expanded to give a list. +The router is skipped unless the current domain matches the list. The data returned by the list check is placed in &$domain_data$& for use in string expansions of the driver's private options and in the transport. +If the result of expansion is empty or a forced-fail, +the router is skipped. + See section &<>& for a list of the order in which preconditions are evaluated. @@ -19281,7 +19517,8 @@ to be used. .option dsn_lasthop routers boolean false .cindex "DSN" "success" .cindex "Delivery Status Notification" "success" -If this option is set true, and extended DSN (RFC3461) processing is in effect, +If this option is set true, and extended DSN +(&url(https://www.rfc-editor.org/rfc/rfc3461,RFC 3461)) processing is in effect, Exim will not pass on DSN requests to downstream DSN-aware hosts but will instead send a success DSN as if the next hop does not support DSN. Not effective on redirect routers. @@ -19589,8 +19826,8 @@ real_localuser: For security, it would probably be a good idea to restrict the use of this router to locally-generated messages, using a condition such as this: .code - condition = ${if match {$sender_host_address}\ - {\N^(|127\.0\.0\.1)$\N}} + condition = ${if match_ip {$sender_host_address} \ + {<; ; 127.0.0.1 ; ::1}} .endd If both &%local_part_prefix%& and &%local_part_suffix%& are set for a router, @@ -19624,7 +19861,11 @@ See &%local_part_suffix%& above. .option local_parts routers&!? "local part list&!!" unset .cindex "router" "restricting to specific local parts" .cindex "local part" "checking in router" +If this option is set, the argument is first expanded to give a list. The router is run only if the local part of the address matches the list. +If the result of expansion is empty or a forced-fail, +the router is skipped. + See section &<>& for a list of the order in which preconditions are evaluated, and section &<>& for a discussion of local part lists. Because the @@ -19634,7 +19875,7 @@ example: local_parts = dbm;/usr/local/specials/$domain_data .endd .vindex "&$local_part_data$&" -the data returned by the list check +The data returned by the list check for the local part is placed in the variable &$local_part_data$& for use in expansions of the router's private options or in the transport. You might use this option, for @@ -20324,8 +20565,9 @@ the local host is described in section &<>&. .option check_srv dnslookup string&!! unset .cindex "SRV record" "enabling use of" -The &(dnslookup)& router supports the use of SRV records (see RFC 2782) in -addition to MX and address records. The support is disabled by default. To +The &(dnslookup)& router supports the use of SRV records +(see &url(https://www.rfc-editor.org/rfc/rfc2782,RFC 2782)) +in addition to MX and address records. The support is disabled by default. To enable SRV support, set the &%check_srv%& option to the name of the service required. For example, .code @@ -20553,7 +20795,9 @@ entered. No widening ever takes place for these lookups. This router has no private options. Unless it is being used purely for verification (see &%verify_only%&) a transport is required to be defined by the generic &%transport%& option. The router accepts the address if its domain part -takes the form of an RFC 2822 domain literal. For example, the &(ipliteral)& +takes the form of an +&url(https://www.rfc-editor.org/rfc/rfc2822,RFC 2822) +domain literal. For example, the &(ipliteral)& router handles the address .code root@[192.168.1.1] @@ -21402,8 +21646,9 @@ userforward: If the file does not exist, or causes no action to be taken (for example, it is empty or consists only of comments), the router declines. &*Warning*&: This is not the case when the file contains syntactically valid items that happen to -yield empty addresses, for example, items containing only RFC 2822 address -comments. +yield empty addresses, for example, items containing only +&url(https://www.rfc-editor.org/rfc/rfc2822,RFC 2822) +address comments. .cindex "tainted data" "in filenames" .cindex redirect "tainted data" @@ -21527,8 +21772,9 @@ preceded by &"\"&, but this is not a requirement for loop prevention. However, it does make a difference if more than one domain is being handled synonymously. -If an item begins with &"\"& and the rest of the item parses as a valid RFC -2822 address that does not include a domain, the item is qualified using the +If an item begins with &"\"& and the rest of the item parses as a valid +&url(https://www.rfc-editor.org/rfc/rfc2822,RFC 2822) +address that does not include a domain, the item is qualified using the domain of the incoming address. In the absence of a leading &"\"&, unqualified addresses are qualified using the value in &%qualify_recipient%&, but you can force the incoming domain to be used by setting &%qualify_preserve_domain%&. @@ -21567,7 +21813,9 @@ lists (that is, in non-filter redirection data): .cindex "pipe" "in redirection list" .cindex "address redirection" "to pipe" An item is treated as a pipe command if it begins with &"|"& and does not parse -as a valid RFC 2822 address that includes a domain. A transport for running the +as a valid +&url(https://www.rfc-editor.org/rfc/rfc2822,RFC 2822) +address that includes a domain. A transport for running the command must be specified by the &%pipe_transport%& option. Normally, either the router or the transport specifies a user and a group under which to run the delivery. The default is to use the Exim user and group. @@ -21600,7 +21848,9 @@ an &%accept%& router. .cindex "file" "in redirection list" .cindex "address redirection" "to file" An item is interpreted as a path name if it begins with &"/"& and does not -parse as a valid RFC 2822 address that includes a domain. For example, +parse as a valid +&url(https://www.rfc-editor.org/rfc/rfc2822,RFC 2822) +address that includes a domain. For example, .code /home/world/minbari .endd @@ -22223,6 +22473,12 @@ subject to address rewriting. Otherwise, they are treated like new addresses and are rewritten according to the global rewriting rules. +.option sieve_inbox redirect string&!! inbox +.new +The value of this option is passed to a Sieve filter to specify the +name of the mailbox used for "keep" operations (explicit or implicit). +.wen + .option sieve_subaddress redirect string&!! unset The value of this option is passed to a Sieve filter to specify the :subaddress part of an address. @@ -22271,7 +22527,9 @@ so it is passed to the following routers. .cindex "Sieve filter" "syntax errors in" Syntax errors in a Sieve filter file cause the &"keep"& action to occur. This -action is specified by RFC 3028. The values of &%skip_syntax_errors%&, +action is specified by +&url(https://www.rfc-editor.org/rfc/rfc3028.html,RFC 3028). +The values of &%skip_syntax_errors%&, &%syntax_errors_to%&, and &%syntax_errors_text%& are not used. &%skip_syntax_errors%& can be used to specify that errors in users' forward @@ -22315,8 +22573,8 @@ real_localuser: For security, it would probably be a good idea to restrict the use of this router to locally-generated messages, using a condition such as this: .code - condition = ${if match {$sender_host_address}\ - {\N^(|127\.0\.0\.1)$\N}} + condition = ${if match_ip {$sender_host_address} \ + {<; ; 127.0.0.1 ; ::1}} .endd @@ -22847,7 +23105,8 @@ Although the return path is normally available in the prefix line of BSD mailboxes, this is commonly not displayed by MUAs, and so the user does not have easy access to it. -RFC 2821 states that the &'Return-path:'& header is added to a message &"when +&url(https://www.rfc-editor.org/rfc/rfc2821,RFC 2821) +states that the &'Return-path:'& header is added to a message &"when the delivery SMTP server makes the final delivery"&. This implies that this header should not be present in incoming messages. Exim has a configuration option, &%return_path_remove%&, which requests removal of this header from @@ -22919,7 +23178,9 @@ filter itself, and the original process that reads the result and delivers it are all run in parallel, like a shell pipeline. The filter can perform any transformations it likes, but of course should take -care not to break RFC 2822 syntax. Exim does not check the result, except to +care not to break +&url(https://www.rfc-editor.org/rfc/rfc2822,RFC 2822) +syntax. Exim does not check the result, except to test for a final newline when SMTP is in use. All messages transmitted over SMTP must end with a newline, so Exim supplies one if it is missing. @@ -23259,7 +23520,11 @@ fileinto "folder23"; .endd In this situation, the expansion of &%file%& or &%directory%& in the transport must transform the relative path into an appropriate absolute filename. In the -case of Sieve filters, the name &'inbox'& must be handled. It is the name that +case of Sieve filters, the name &'inbox'& must be handled. It is the +.new +default +.wen +name that is used as a result of a &"keep"& action in the filter. This example shows one way of handling this requirement: .code @@ -23275,6 +23540,12 @@ With this setting of &%file%&, &'inbox'& refers to the standard mailbox location, absolute paths are used without change, and other folders are in the &_mail_& directory within the home directory. +.new +An alternative for the &"keep"& aspect is to use the &%sieve_inbox%& option +on the redirect router that calls the Sieve filter, +to explicitly set the filename used. +.wen + &*Note 1*&: While processing an Exim filter, a relative path such as &_folder23_& is turned into an absolute path if a home directory is known to the router. In particular, this is the case if &%check_local_user%& is set. If @@ -23285,6 +23556,10 @@ path to the transport. &*Note 2*&: An absolute path in &$address_file$& is not treated specially; the &%file%& or &%directory%& option is still used if it is set. +.new +&*Note 3*&: Permitting a user to enable writes to an absolute path +may be a security issue. +.wen @@ -24383,7 +24658,9 @@ The &(autoreply)& transport is not a true transport in that it does not cause the message to be transmitted. Instead, it generates a new mail message as an automatic reply to the incoming message. &'References:'& and &'Auto-Submitted:'& header lines are included. These are constructed according -to the rules in RFCs 2822 and 3834, respectively. +to the rules in RFCs +&url(https://www.rfc-editor.org/rfc/rfc2822,2822) and +&url(https://datatracker.ietf.org/doc/html/rfc3834,3834), respectively. If the router that passes the message to this transport does not have the &%unseen%& option set, the original message (for the current recipient) is not @@ -24479,7 +24756,9 @@ specified by the transport. .option headers autoreply string&!! unset -This specifies additional RFC 2822 headers that are to be added to the message +This specifies additional +&url(https://www.rfc-editor.org/rfc/rfc2822,RFC 2822) +headers that are to be added to the message when the message is specified by the transport. Several can be given by using &"\n"& to separate them. There is no check on the format. @@ -24588,7 +24867,8 @@ when the message is specified by the transport. .cindex "&(lmtp)& transport" .cindex "LMTP" "over a pipe" .cindex "LMTP" "over a unix-domain socket" -The &(lmtp)& transport runs the LMTP protocol (RFC 2033) over a pipe to a +The &(lmtp)& transport runs the LMTP protocol +(&url(https://www.rfc-editor.org/rfc/rfc2033,RFC 2033)) over a pipe to a specified command or by interacting with a Unix domain socket. This transport is something of a cross between the &(pipe)& and &(smtp)& @@ -25432,7 +25712,8 @@ to a remote host. A setting of zero allows the system timeout (typically several minutes) to act. To have any effect, the value of this option must be less than the system timeout. However, it has been observed that on some systems there is no system timeout, which is why the default value for this -option is 5 minutes, a value recommended by RFC 1123. +option is 5 minutes, a value recommended by +&url(https://www.rfc-editor.org/rfc/rfc1123,RFC 1123). .option connection_max_messages smtp integer 500 @@ -25939,7 +26220,7 @@ See section &<>&. .cindex "RFC 7413" "TCP Fast Open" This option provides a list of servers to which, provided the facility is supported by this system, Exim will attempt to -perform a TCP Fast Open. +perform a TCP Fast Open (&url(https://www.rfc-editor.org/rfc/rfc7413,RFC 7413). No data is sent on the SYN segment but, if the remote server also supports the facility, it can send its SMTP banner immediately after the SYN,ACK segment. This can save up to one round-trip time. @@ -26095,7 +26376,9 @@ to put &"smtps"& in its &"/etc/services"& file, resulting is such deferrals. .vindex "&$port$&" If this option is set to &"lmtp"& instead of &"smtp"&, the default value for the &%port%& option changes to &"lmtp"&, and the transport operates the LMTP -protocol (RFC 2033) instead of SMTP. This protocol is sometimes used for local +protocol +(&url(https://www.rfc-editor.org/rfc/rfc2033,RFC 2033)) instead of SMTP. +This protocol is sometimes used for local deliveries into closed message stores. Exim also has support for running LMTP over a pipe to a local process &-- see chapter &<>&. @@ -26106,7 +26389,8 @@ If this option is set to &"smtps"&, the default value for the &%port%& option changes to &"smtps"&, and the transport initiates TLS immediately after connecting, as an outbound SSL-on-connect, instead of using STARTTLS to upgrade. The Internet standards bodies used to strongly discourage use of this mode, -but as of RFC 8314 it is preferred over STARTTLS for message submission +but as of &url(https://www.rfc-editor.org/rfc/rfc8314,RFC 8314) it is preferred +over STARTTLS for message submission (as distinct from MTA-MTA communication). @@ -26590,8 +26874,9 @@ transport time. .cindex "testing" "rewriting" Exim's input rewriting configuration appears in a part of the runtime configuration file headed by &"begin rewrite"&. It can be tested by the -&%-brw%& command line option. This takes an address (which can be a full RFC -2822 address) as its argument. The output is a list of how the address would be +&%-brw%& command line option. This takes an address (which can be a full +&url(https://www.rfc-editor.org/rfc/rfc2822,RFC 2822) +address) as its argument. The output is a list of how the address would be transformed by the rewriting rules for each of the different places it might appear in an incoming message, that is, for each different header and for the envelope sender and recipient fields. For example, @@ -26802,7 +27087,10 @@ data for the command, including any surrounding angle brackets. .vindex "&$domain$&" .vindex "&$local_part$&" This form of rewrite rule allows for the handling of addresses that are not -compliant with RFCs 2821 and 2822 (for example, &"bang paths"& in batched SMTP +compliant with RFCs +&url(https://www.rfc-editor.org/rfc/rfc2821,2821) and +&url(https://www.rfc-editor.org/rfc/rfc2822,2822) +(for example, &"bang paths"& in batched SMTP input). Because the input is not required to be a syntactically valid address, the variables &$local_part$& and &$domain$& are not available during the expansion of the replacement string. The result of rewriting replaces the @@ -26830,8 +27118,9 @@ rewriting once it fails to match (after at least one successful rewrite). .next .cindex "rewriting" "whole addresses" When an address in a header is rewritten, the rewriting normally applies only -to the working part of the address, with any comments and RFC 2822 &"phrase"& -left unchanged. For example, rewriting might change +to the working part of the address, with any comments and +&url(https://www.rfc-editor.org/rfc/rfc2822,RFC 2822) +&"phrase"& left unchanged. For example, rewriting might change .code From: Ford Prefect .endd @@ -26843,10 +27132,12 @@ From: Ford Prefect Sometimes there is a need to replace the whole address item, and this can be done by adding the flag letter &"w"& to a rule. If this is set on a rule that causes an address in a header line to be rewritten, the entire address is -replaced, not just the working part. The replacement must be a complete RFC -2822 address, including the angle brackets if necessary. If text outside angle +replaced, not just the working part. The replacement must be a complete +&url(https://www.rfc-editor.org/rfc/rfc2822,RFC 2822) +address, including the angle brackets if necessary. If text outside angle brackets contains a character whose value is greater than 126 or less than 32 -(except for tab), the text is encoded according to RFC 2047. The character set +(except for tab), the text is encoded according to +&url(https://www.rfc-editor.org/rfc/rfc2047,RFC 2047). The character set is taken from &%headers_charset%&, which gets its default at build time. When the &"w"& flag is set on a rule that causes an envelope address to be @@ -27475,7 +27766,9 @@ considered immediately. .scindex IIDauthconf2 "authentication" The &"authenticators"& section of Exim's runtime configuration is concerned with SMTP authentication. This facility is an extension to the SMTP protocol, -described in RFC 2554, which allows a client SMTP host to authenticate itself +described in +&url(https://www.rfc-editor.org/rfc/rfc2554,RFC 2554), +which allows a client SMTP host to authenticate itself to a server. This is a common way for a server to recognize clients that are permitted to use it as a relay. SMTP authentication is not of relevance to the transfer of mail between servers that have no managerial connection with each @@ -27549,18 +27842,21 @@ AUTH_SPA=yes AUTH_TLS=yes .endd in &_Local/Makefile_&, respectively. The first of these supports the CRAM-MD5 -authentication mechanism (RFC 2195), and the second provides an interface to -the Cyrus SASL authentication library. +authentication mechanism +(&url(https://www.rfc-editor.org/rfc/rfc2195,RFC 2195)), +and the second provides an interface to the Cyrus SASL authentication library. The third is an interface to Dovecot's authentication system, delegating the work via a socket interface. The fourth provides for negotiation of authentication done via non-SMTP means, -as defined by RFC 4422 Appendix A. +as defined by &url(https://www.rfc-editor.org/rfc/rfc4422,RFC 4422) Appendix A. The fifth provides an interface to the GNU SASL authentication library, which provides mechanisms but typically not data sources. The sixth provides direct access to Heimdal GSSAPI, geared for Kerberos, but supporting setting a server keytab. The seventh can be configured to support -the PLAIN authentication mechanism (RFC 2595) or the LOGIN mechanism, which is +the PLAIN authentication mechanism +(&url(https://www.rfc-editor.org/rfc/rfc2595,RFC 2595)) +or the LOGIN mechanism, which is not formally documented, but used by several MUAs. The eighth authenticator supports Microsoft's &'Secure Password Authentication'& mechanism. @@ -27649,7 +27945,8 @@ authenticators is to be used. .option public_name authenticators string unset This option specifies the name of the authentication mechanism that the driver implements, and by which it is known to the outside world. These names should -contain only upper case letters, digits, underscores, and hyphens (RFC 2222), +contain only upper case letters, digits, underscores, and hyphens +(&url(https://www.rfc-editor.org/rfc/rfc2222,RFC 2222)), but Exim in fact matches them caselessly. If &%public_name%& is not set, it defaults to the driver's instance name. @@ -27847,17 +28144,17 @@ Successful authentication sets up information used by the .cindex authentication "failure event, server" If an authenticator is run and does not succeed, -an event (see &<>&) of type "auth:fail" is raised. +an event of type "auth:fail" is raised. While the event is being processed the variables &$sender_host_authenticated$& (with the authenticator name) and &$authenticated_fail_id$& (as set by the authenticator &%server_set_id%& option) will be valid. If the event is serviced and a string is returned then the string will be logged instead of the default log line. -See <> for details on events. +See &<>& for details on events. -.section "Testing server authentication" "SECID169" +.subsection "Testing server authentication" "SECID169" .cindex "authentication" "testing a server" .cindex "AUTH" "testing a server" .cindex "base64 encoding" "creating authentication test data" @@ -27936,12 +28233,12 @@ usual way. .next .cindex authentication "failure event, client" If the response to authentication is a permanent error (5&'xx'& code), -an event (see &<>&) of type "auth:fail" is raised. +an event of type "auth:fail" is raised. While the event is being processed the variable &$sender_host_authenticated$& (with the authenticator name) will be valid. If the event is serviced and a string is returned then the string will be logged. -See <> for details on events. +See &<>& for details on events. .next If the response to authentication is a permanent error (5&'xx'& code), Exim @@ -28066,11 +28363,13 @@ There are good and bad examples at the end of the next section. -.section "The PLAIN authentication mechanism" "SECID172" +.subsection "The PLAIN authentication mechanism" "SECID172" .cindex "PLAIN authentication mechanism" .cindex authentication PLAIN .cindex "binary zero" "in &(plaintext)& authenticator" -The PLAIN authentication mechanism (RFC 2595) specifies that three strings be +The PLAIN authentication mechanism +(&url(https://www.rfc-editor.org/rfc/rfc2595,RFC 2595)) +specifies that three strings be sent as one item of data (that is, one combined string containing two NUL separators). The data is sent either as part of the AUTH command, or subsequently in response to an empty prompt from the server. @@ -28148,7 +28447,7 @@ always fails if its second argument is empty. However, the second way of writing the test makes the logic clearer. -.section "The LOGIN authentication mechanism" "SECID173" +.subsection "The LOGIN authentication mechanism" "SECID173" .cindex "LOGIN authentication mechanism" .cindex authentication LOGIN The LOGIN authentication mechanism is not documented in any RFC, but is in use @@ -28196,7 +28495,7 @@ the password conform to the Exim syntax. At the LDAP level, the password is an uninterpreted string. -.section "Support for different kinds of authentication" "SECID174" +.subsection "Support for different kinds of authentication" "SECID174" A number of string expansion features are provided for the purpose of interfacing to different ways of user authentication. These include checking traditionally encrypted passwords from &_/etc/passwd_& (or equivalent), PAM, @@ -28277,7 +28576,8 @@ prompts. .scindex IIDcramauth2 "authenticators" "&(cram_md5)&" .cindex "CRAM-MD5 authentication mechanism" .cindex authentication CRAM-MD5 -The CRAM-MD5 authentication mechanism is described in RFC 2195. The server +The CRAM-MD5 authentication mechanism is described in +&url(https://www.rfc-editor.org/rfc/rfc2195,RFC 2195). The server sends a challenge string to the client, and the response consists of a user name and the CRAM-MD5 digest of the challenge string combined with a secret string (password) which is known to both server and client. Thus, the secret @@ -28395,7 +28695,9 @@ The code for this authenticator was provided by Matthew Byng-Maddick while at A L Digital Ltd. The &(cyrus_sasl)& authenticator provides server support for the Cyrus SASL -library implementation of the RFC 2222 (&"Simple Authentication and Security +library implementation of the +&url(https://www.rfc-editor.org/rfc/rfc2222,RFC 2222) +(&"Simple Authentication and Security Layer"&). This library supports a number of authentication mechanisms, including PLAIN and LOGIN, but also several others that Exim does not support directly. In particular, there is support for Kerberos authentication. @@ -28885,7 +29187,7 @@ The &(spa)& authenticator provides client support for Microsoft's &'Secure Password Authentication'& mechanism, which is also sometimes known as NTLM (NT LanMan). The code for client side of this authenticator was contributed by Marc Prud'hommeaux, and much of it is -taken from the Samba project (&url(https://www.samba.org/)). The code for the +taken from the &url(https://www.samba.org/,Samba project). The code for the server side was subsequently contributed by Tom Kistner. The mechanism works as follows: @@ -28973,8 +29275,8 @@ msn: .cindex "Certificate-based authentication" The &(external)& authenticator provides support for authentication based on non-SMTP information. -The specification is in RFC 4422 Appendix A -(&url(https://tools.ietf.org/html/rfc4422)). +The specification is in +&url(https://tools.ietf.org/html/rfc4422,RFC 4422) Appendix A. It is only a transport and negotiation mechanism; the process of authentication is entirely controlled by the server configuration. @@ -28985,7 +29287,7 @@ and for clients to only attempt, this authentication method on a secure (eg. under TLS) connection. One possible use, compatible with the -K-9 Mail Android client (&url(https://k9mail.github.io/)), +&url(https://k9mail.github.io/,K-9 Mail Android client) is for using X509 client certificates. It thus overlaps in function with the TLS authenticator @@ -29215,7 +29517,8 @@ You also need to understand the basic concepts of encryption at a managerial level, and in particular, the way that public keys, private keys, and certificates are used. -RFC 3207 defines how SMTP connections can make use of encryption. Once a +&url(https://www.rfc-editor.org/rfc/rfc3207,RFC 3207) +defines how SMTP connections can make use of encryption. Once a connection is established, the client issues a STARTTLS command. If the server accepts this, the client and the server negotiate an encryption mechanism. If the negotiation succeeds, the data that subsequently passes @@ -29242,7 +29545,9 @@ in order to get TLS to work. .cindex "SMTP" "ssmtp protocol" .cindex "SMTP" "smtps protocol" The history of port numbers for TLS in SMTP is a little messy and has been -contentious. As of RFC 8314, the common practice of using the historically +contentious. As of +&url(https://www.rfc-editor.org/rfc/rfc8314,RFC 8314), +the common practice of using the historically allocated port 465 for "email submission but with TLS immediately upon connect instead of using STARTTLS" is officially blessed by the IETF, and recommended by them in preference to STARTTLS. @@ -29312,7 +29617,8 @@ The default value for &%tls_dhparam%& differs for historical reasons. .vindex "&$tls_in_peerdn$&" .vindex "&$tls_out_peerdn$&" Distinguished Name (DN) strings reported by the OpenSSL library use a slash for -separating fields; GnuTLS uses commas, in accordance with RFC 2253. This +separating fields; GnuTLS uses commas, in accordance with +&url(https://www.rfc-editor.org/rfc/rfc2253,RFC 2253). This affects the value of the &$tls_in_peerdn$& and &$tls_out_peerdn$& variables. .next OpenSSL identifies cipher suites using hyphens as separators, for example: @@ -29973,7 +30279,9 @@ initiated by Exim. .oindex "&%tls_in_sni%&" With TLS1.0 or above, there is an extension mechanism by which extra information can be included at various points in the protocol. One of these -extensions, documented in RFC 6066 (and before that RFC 4366) is +extensions, documented in +&url(https://www.rfc-editor.org/rfc/rfc6066,RFC 6066) +(and before that &url(https://www.rfc-editor.org/rfc/rfc4366,RFC 4366)) is &"Server Name Indication"&, commonly &"SNI"&. This extension is sent by the client in the initial handshake, so that the server can examine the servername within and possibly choose to use different certificates and keys (and more) @@ -30308,8 +30616,8 @@ There is no current way to staple a proof for a client certificate. .section "TLS Resumption" "SECTresumption" .cindex TLS resumption TLS Session Resumption for TLS 1.2 and TLS 1.3 connections can be used (defined -in RFC 5077 for 1.2). The support for this requires GnuTLS 3.6.3 or OpenSSL 1.1.1 -(or later). +in &url(https://www.rfc-editor.org/rfc/rfc5077,RFC 5077) for 1.2). +The support for this requires GnuTLS 3.6.3 or OpenSSL 1.1.1 (or later). Session resumption (this is the "stateless" variant) involves the server sending a "session ticket" to the client on one connection, which can be stored by the @@ -30595,12 +30903,14 @@ Section 4.3 of that document. .subsection General Under GnuTLS, DANE is only supported from version 3.0.0 onwards. -DANE is specified in RFC 6698. It decouples certificate authority trust +DANE is specified in &url(https://www.rfc-editor.org/rfc/rfc6698,RFC 6698). +It decouples certificate authority trust selection from a "race to the bottom" of "you must trust everything for mail to get through". It does retain the need to trust the assurances provided by the DNSSEC tree. -There is an alternative technology called MTA-STS (RFC 8461), which +There is an alternative technology called MTA-STS +(&url(https://www.rfc-editor.org/rfc/rfc8461,RFC 8461)), which instead publishes MX trust anchor information on an HTTPS website. The discovery of the address for that website does not (per standard) require DNSSEC, and could be regarded as being less secure than DANE @@ -30664,15 +30974,17 @@ configuration locally by running a fake SMTP session with which you interact. .cindex "&ACL;" "options for specifying" In order to cause an ACL to be used, you have to name it in one of the relevant options in the main part of the configuration. These options are: +.cindex "ATRN" "ACL for" .cindex "AUTH" "ACL for" .cindex "DATA" "ACLs for" +.cindex "DKIM" "ACL for" .cindex "ETRN" "ACL for" .cindex "EXPN" "ACL for" .cindex "HELO" "ACL for" .cindex "EHLO" "ACL for" -.cindex "DKIM" "ACL for" .cindex "MAIL" "ACL for" -.cindex "QUIT, ACL for" +.cindex "QUIT" "ACL for" +.cindex "PRDR" "ACL for" .cindex "RCPT" "ACL for" .cindex "STARTTLS, ACL for" .cindex "VRFY" "ACL for" @@ -30680,12 +30992,12 @@ options in the main part of the configuration. These options are: .cindex "SMTP" "connection, ACL for" .cindex "non-SMTP messages" "ACLs for" .cindex "MIME content scanning" "ACL for" -.cindex "PRDR" "ACL for" .table2 140pt .irow &%acl_not_smtp%& "ACL for non-SMTP messages" .irow &%acl_not_smtp_mime%& "ACL for non-SMTP MIME parts" .irow &%acl_not_smtp_start%& "ACL at start of non-SMTP message" +.irow &%acl_smtp_atrn%& "ACL for ATRN" .irow &%acl_smtp_auth%& "ACL for AUTH" .irow &%acl_smtp_connect%& "ACL for start of SMTP connection" .irow &%acl_smtp_data%& "ACL after DATA is complete" @@ -30928,8 +31240,11 @@ to test/retrieve WELLKNOWN items. Syntax is WELLKNOWN is a ESMTP extension providing access to extended information about the server. It is modelled on the webserver -facilities documented in RFC 8615 and can be used for a security.txt -file and could be used for ACME handshaking (RFC 8555). +facilities documented in +&url(https://www.rfc-editor.org/rfc/rfc8615,RFC 8615) +and can be used for a security.txt file +and could be used for ACME handshaking +(&url(https://www.rfc-editor.org/rfc/rfc8555,RFC 8555)). Exim will advertise WELLKNOWN support in the EHLO response .oindex &%wellknown_advertise_hosts%& @@ -30937,7 +31252,8 @@ Exim will advertise WELLKNOWN support in the EHLO response and service WELLKNOWN smtp verbs having a single parameter giving a key for an item of "site-wide metadata". The verb and key are separated by whitespace, -and the key is xtext-encoded (per RFC 3461 section 4). +and the key is xtext-encoded +(per &url(https://www.rfc-editor.org/rfc/rfc3461,RFC 3461) section 4). .subsection "The QUIT ACL" SECTQUITACL @@ -31013,8 +31329,11 @@ acl_smtp_rcpt = ${if ={25}{$interface_port} \ {acl_check_rcpt} {acl_check_rcpt_submit} } .endd In the default configuration file there are some example settings for -providing an RFC 4409 message &"submission"& service on port 587 and -an RFC 8314 &"submissions"& service on port 465. You can use a string +providing an +&url(https://www.rfc-editor.org/rfc/rfc4409,RFC 4409) +message &"submission"& service on port 587 and an +&url(https://www.rfc-editor.org/rfc/rfc8314,RFC 8314) +&"submissions"& service on port 465. You can use a string expansion like this to choose an ACL for MUAs on these ports which is more appropriate for this purpose than the default ACL on port 25. @@ -31110,9 +31429,11 @@ For &%acl_not_smtp%&, &%acl_smtp_auth%&, &%acl_smtp_connect%&, &%acl_smtp_mime%&, &%acl_smtp_predata%&, and &%acl_smtp_starttls%&, the action when the ACL is not defined is &"accept"&. -For the others (&%acl_smtp_etrn%&, &%acl_smtp_expn%&, &%acl_smtp_rcpt%&, -&%acl_smtp_vrfy%& -and &%acl_smtp_wellknown%&), +.new +For the others (&%acl_smtp_atrn%&, +.wen +&%acl_smtp_etrn%&, &%acl_smtp_expn%&, &%acl_smtp_rcpt%&, +&%acl_smtp_vrfy%& and &%acl_smtp_wellknown%&), the action when the ACL is not defined is &"deny"&. This means that &%acl_smtp_rcpt%& must be defined in order to receive any messages over an SMTP connection. @@ -31163,7 +31484,7 @@ of previously accepted recipients. At DATA time (for both the DATA ACLs), .cindex "&ACL;" "data for non-message ACL" .vindex &$smtp_command_argument$& .vindex &$smtp_command$& -When an ACL is being run for AUTH, EHLO, ETRN, EXPN, HELO, STARTTLS, or VRFY, +When an ACL is being run for ATRN, AUTH, EHLO, ETRN, EXPN, HELO, STARTTLS, or VRFY, the remainder of the SMTP command line is placed in &$smtp_command_argument$&, and the entire SMTP command is available in &$smtp_command$&. These variables can be tested using a &%condition%& condition. For example, @@ -32007,12 +32328,17 @@ This control turns off DKIM verification processing entirely. For details on the operation and configuration of DKIM, see section &<>&. -.vitem &*control&~=&~dmarc_disable_verify*& +.vitem &*control&~=&~dmarc_disable_verify*& &&& + &*control&~=&~dmarc_enable_forensic*& .cindex "disable DMARC verify" -.cindex "DMARC" "disable verify" -This control turns off DMARC verification processing entirely. For details on +.cindex DMARC "disable verify" +.cindex DMARC controls +.cindex DMARC "forensic mails" +These control affect DMARC processing. For details on the operation and configuration of DMARC, see section &<>&. +The &"disable"& turns off DMARC verification processing entirely. + .vitem &*control&~=&~dscp/*&<&'value'&> .cindex "&ACL;" "setting DSCP value" @@ -32121,11 +32447,15 @@ to be useful in production. .cindex "multiline responses, suppressing" This control is permitted for any ACL except the one for non-SMTP messages. It seems that there are broken clients in use that cannot handle multiline -SMTP responses, despite the fact that RFC 821 defined them over 20 years ago. +SMTP responses, despite the fact that +&url(https://www.rfc-editor.org/rfc/rfc821,RFC 821) +defined them over 20 years ago. If this control is set, multiline SMTP responses from ACL rejections are suppressed. One way of doing this would have been to put out these responses as -one long line. However, RFC 2821 specifies a maximum of 512 bytes per response +one long line. However, +&url(https://www.rfc-editor.org/rfc/rfc2821,RFC 2821) +specifies a maximum of 512 bytes per response (&"use multiline responses for more"& it says &-- ha!), and some of the responses might get close to that. So this facility, which is after all only a sop to broken clients, is implemented by doing two very easy things: @@ -32485,6 +32815,18 @@ loops. This condition allows you to use different ACLs in different circumstances. For example, different ACLs can be used to handle RCPT commands for different local users or different local domains. +.new +.vitem &*atrn_domains&~=&~*&<&'domain&~list'&> +.cindex ATRN "checking for queued messages" +This condition is only usable in the ATRN ACL. +It returns true if there are any messages queued for any of the domains given +in the list. +The list supplied must not be tainted +.cindex "tainted data" "de-tainting" +and should contain only domains relevant for the authenticated user +(to avoid leaking information about other users). +.wen + .vitem &*authenticated&~=&~*&<&'string&~list'&> .cindex "&%authenticated%& ACL condition" .cindex "authentication" "ACL checking" @@ -33949,8 +34291,9 @@ updated in this circumstance. .cindex "callout" "full postmaster check" This operates like the &%postmaster%& option (see below), but if the check for &'postmaster@domain'& fails, it tries just &'postmaster'&, without a domain, in -accordance with the specification in RFC 2821. The RFC states that the -unqualified address &'postmaster'& should be accepted. +accordance with the specification in +&url(https://www.rfc-editor.org/rfc/rfc2821,RFC 2821). +The RFC states that the unqualified address &'postmaster'& should be accepted. .vitem &*mailfrom&~=&~*&<&'email&~address'&> @@ -35322,8 +35665,8 @@ containing the decoded data. This is perhaps the most important of the MIME variables. It contains a proposed filename for an attachment, if one was found in either the &'Content-Type:'& or &'Content-Disposition:'& headers. The filename will be -RFC2047 -or RFC2231 +&url(https://www.rfc-editor.org/rfc/rfc2047,RFC 2047) or +&url(https://www.rfc-editor.org/rfc/rfc2231,RFC 2231) decoded, but no additional sanity checks are done. If no filename was found, this variable contains the empty string. @@ -35929,7 +36272,7 @@ The third argument may be NULL, in which case the &%-oMas%& option is omitted. .vitem &*void&~debug_printf(char&~*,&~...)*& -This is Exim's debugging function, with arguments as for &'(printf()'&. The +This is Exim's debugging function, with arguments as for &'printf()'&. The output is written to the standard error stream. If no debugging is selected, calls to &'debug_printf()'& have no effect. Normally, you should make calls conditional on the &`local_scan`& debug selector by coding like this: @@ -36084,7 +36427,8 @@ address. .vlist .vitem "&*uschar&~rfc2047_decode(uschar&~*string,&~BOOL&~lencheck,&&& &~uschar&~*target,&~int&~zeroval,&~int&~*lenptr, &~&~uschar&~**error)*&" -This function decodes strings that are encoded according to RFC 2047. Typically +This function decodes strings that are encoded according to +&url(https://www.rfc-editor.org/rfc/rfc2047,RFC 2047). Typically these are the contents of header lines. First, each &"encoded word"& is decoded from the Q or B encoding into a byte-string. Then, if provided with the name of a charset encoding, and if the &[iconv()]& function is available, an attempt is @@ -36416,7 +36760,8 @@ headers remove .endd The argument for the &%headers add%& is a string that is expanded and then added to the end of the message's headers. It is the responsibility of the -filter maintainer to make sure it conforms to RFC 2822 syntax. Leading white +filter maintainer to make sure it conforms to +&url(https://www.rfc-editor.org/rfc/rfc2822,RFC 2822) syntax. Leading white space is ignored, and if the string is otherwise empty, or if the expansion is forced to fail, the command has no effect. @@ -36636,7 +36981,8 @@ spoof another's address. .cindex "line endings" .cindex "carriage return" .cindex "linefeed" -RFC 2821 specifies that CRLF (two characters: carriage-return, followed by +&url(https://www.rfc-editor.org/rfc/rfc2821,RFC 2821) +specifies that CRLF (two characters: carriage-return, followed by linefeed) is the line ending for messages transmitted over the Internet using SMTP over TCP/IP. However, within individual operating systems, different conventions are used. For example, Unix-like systems use just LF, but others @@ -36720,7 +37066,9 @@ with a line containing the envelope sender and a timestamp, following the word From a.oakley@berlin.mus Fri Jan 5 12:35 GMT 1996 From f.butler@berlin.mus Fri, 7 Jan 97 14:00:00 GMT .endd -This line precedes the RFC 2822 header lines. For compatibility with Sendmail, +This line precedes the +&url(https://www.rfc-editor.org/rfc/rfc2822,RFC 2822) +header lines. For compatibility with Sendmail, Exim recognizes such lines at the start of messages that are submitted to it via the command line (that is, on the standard input). It does not recognize such lines in incoming SMTP messages, unless the sending host matches @@ -36734,7 +37082,9 @@ that follows &"From"& into &$1$&. When the caller of Exim for a non-SMTP message that contains a &"From"& line is a trusted user, the message's sender address is constructed by expanding the contents of &%uucp_sender_address%&, whose default value is &"$1"&. This is -then parsed as an RFC 2822 address. If there is no domain, the local part is +then parsed as an +&url(https://www.rfc-editor.org/rfc/rfc2822,RFC 2822) +address. If there is no domain, the local part is qualified with &%qualify_domain%& unless it is the empty string. However, if the command line &%-f%& option is used, it overrides the &"From"& line. @@ -36752,7 +37102,8 @@ incoming SMTP message from a source that is not permitted to send them. .section "Header lines" .subsection "Resent- header lines" SECID220 .chindex Resent- -RFC 2822 makes provision for sets of header lines starting with the string +&url(https://www.rfc-editor.org/rfc/rfc2822,RFC 2822) +makes provision for sets of header lines starting with the string &`Resent-`& to be added to a message when it is resent by the original recipient to somebody else. These headers are &'Resent-Date:'&, &'Resent-From:'&, &'Resent-Sender:'&, &'Resent-To:'&, &'Resent-Cc:'&, @@ -36815,8 +37166,10 @@ Exim adds one, using the current date and time, unless the .subsection Delivery-date: SECID224 .cindex "&'Delivery-date:'& header line" .oindex "&%delivery_date_remove%&" -&'Delivery-date:'& header lines are not part of the standard RFC 2822 header -set. Exim can be configured to add them to the final delivery of messages. (See +&'Delivery-date:'& header lines are not part of the standard +&url(https://www.rfc-editor.org/rfc/rfc2822,RFC 2822) +header set. +Exim can be configured to add them to the final delivery of messages. (See the generic &%delivery_date_add%& transport option.) They should not be present in messages in transit. If the &%delivery_date_remove%& configuration option is set (the default), Exim removes &'Delivery-date:'& header lines from incoming @@ -36826,7 +37179,8 @@ messages. .subsection Envelope-to: SECID225 .chindex Envelope-to: .oindex "&%envelope_to_remove%&" -&'Envelope-to:'& header lines are not part of the standard RFC 2822 header set. +&'Envelope-to:'& header lines are not part of the standard +&url(https://www.rfc-editor.org/rfc/rfc2822,RFC 2822) header set. Exim can be configured to add them to the final delivery of messages. (See the generic &%envelope_to_add%& transport option.) They should not be present in messages in transit. If the &%envelope_to_remove%& configuration option is set @@ -36912,8 +37266,11 @@ changed to the time of acceptance, which is (apart from a small delay while the .chindex References: Messages created by the &(autoreply)& transport include a &'References:'& header line. This is constructed according to the rules that are described in -section 3.64 of RFC 2822 (which states that replies should contain such a -header line), and section 3.14 of RFC 3834 (which states that automatic +section 3.64 of +&url(https://www.rfc-editor.org/rfc/rfc2822,RFC 2822) +(which states that replies should contain such a header line), +and section 3.14 of &url(https://datatracker.ietf.org/doc/html/rfc3834,RFC 3834) +(which states that automatic responses are not different in this respect). However, because some mail processing software does not cope well with very long header lines, no more than 12 message IDs are copied from the &'References:'& header line in the @@ -37015,8 +37372,9 @@ the transport cannot refer to the modified header lines, because such expansions all occur before the message is actually transported. For both routers and transports, the argument of a &%headers_add%& -option must be in the form of one or more RFC 2822 header lines, separated by -newlines (coded as &"\n"&). For example: +option must be in the form of one or more +&url(https://www.rfc-editor.org/rfc/rfc2822,RFC 2822) +header lines, separated by newlines (coded as &"\n"&). For example: .code headers_add = X-added-header: added by $primary_hostname\n\ X-added-second: another added header line @@ -37127,9 +37485,12 @@ The &%unknown_username%& option can be used to specify user names in cases when there is no password file entry. .cindex "RFC 2047" -In all cases, the user name is made to conform to RFC 2822 by quoting all or +In all cases, the user name is made to conform to +&url(https://www.rfc-editor.org/rfc/rfc2822,RFC 2822) +by quoting all or parts of it if necessary. In addition, if it contains any non-printing -characters, it is encoded as described in RFC 2047, which defines a way of +characters, it is encoded as described in +&url(https://www.rfc-editor.org/rfc/rfc2047,RFC 2047), which defines a way of including non-ASCII characters in header lines. The value of the &%headers_charset%& option specifies the name of the encoding that is used (the characters are assumed to be in this encoding). The setting of @@ -37141,7 +37502,8 @@ is, with codes greater than 127) count as printing characters or not. .section "Case of local parts" "SECID230" .cindex "case of local parts" .cindex "local part" "case of" -RFC 2822 states that the case of letters in the local parts of addresses cannot +&url(https://www.rfc-editor.org/rfc/rfc2822,RFC 2822) +states that the case of letters in the local parts of addresses cannot be assumed to be non-significant. Exim preserves the case of local parts of addresses, but by default it uses a lower-cased form when it is routing, because on most Unix systems, usernames are in lower case and case-insensitive @@ -37173,7 +37535,8 @@ local parts with the correct case in a case-sensitive manner. .section "Dots in local parts" "SECID231" .cindex "dot" "in local part" .cindex "local part" "dots in" -RFC 2822 forbids empty components in local parts. That is, an unquoted local +&url(https://www.rfc-editor.org/rfc/rfc2822,RFC 2822) +forbids empty components in local parts. That is, an unquoted local part may not begin or end with a dot, nor have two consecutive dots in the middle. However, it seems that many MTAs do not enforce this, so Exim permits empty components for compatibility. @@ -37276,8 +37639,9 @@ transport filter. If &%size_addition%& is set negative, the use of SIZE is suppressed. If the remote server advertises support for PIPELINING, Exim uses the -pipelining extension to SMTP (RFC 2197) to reduce the number of TCP/IP packets -required for the transaction. +pipelining extension to SMTP +(&url(https://datatracker.ietf.org/doc/html/rfc2197,RFC 2197)) +to reduce the number of TCP/IP packets required for the transaction. If the remote server advertises support for the STARTTLS command, and Exim was built to support TLS encryption, it tries to start a TLS session unless the @@ -37667,7 +38031,8 @@ destination (eg. one using a dialup connection). The command is only available if permitted by an ACL specfied by the main-section &%acl_smtp_etrn%& option. -RFC 1985 describes an ESMTP command called ETRN that is designed to +&url(https://www.rfc-editor.org/rfc/rfc1985,RFC 1985) +describes an ESMTP command called ETRN that is designed to overcome the security problems of the TURN command (which has fallen into disuse). When Exim receives an ETRN command on a TCP/IP connection, it runs the ACL specified by &%acl_smtp_etrn%& in order to decide whether the command @@ -37720,6 +38085,161 @@ under its own uid and gid when receiving incoming SMTP, so it is not possible for it to change them before running the command. +.new +.subsection "The ATRN command, and ODMR" SECTODMR +.cindex ATRN processing +.cindex "ESMTP extensions" ATRN +.cindex ODMR provider +A second method for handling +On-Demand Message Reception (ODMR) +for intermittently-connecting destinations is specified by +&url(https://www.rfc-editor.org/rfc/rfc2645.html,RFC 2645). + +This describes an ESMTP command called ATRN which requests +a swap in server/client roles of the communicating SMTP endpoints, +and delivery of queued messages. +Note that this supports customers having IP addresses that +change frequently. + +Exim supports both the &"provider"& and &"customer"& sides of ODMR, +to use the terms of that specification. + +. need a sub-subsection here +.subsection "ODMR provider connection" SECTODMRPRDVR + +In the &"provider"& use case Exim is +initially an SMTP server, then transferring to an SMTP client +role if an ATRN command is accepted. + +.oindex "&%acl_smtp_atrn%&" +The command is only available if permitted by an ACL +specfied by the main-section &%acl_smtp_atrn%& option. +Per the standard, this should only be for a specific +provider port number (386, named "odmr"); +Exim should be configured to listen on that port +(in addition to other duties) via &%daemon_smtp_ports%& +or equivalent commandline options, and restrict the +advertising of the facility to the port: +.code +acl_smtp_atrn = ${if = {$received_port}{386} {check_atrn}{}} +.endd + +A recieved ATRN command will be rejected unless +authentication has previously been done on the connection. + +Any arguments supplied with an ATRN command are (per standard) +a comma-separated list of requested domains, +and will be available in the &$smtp_command_argument$& +variable. + +The ACL configured may return &"deny"& for any policy reaons +(for example, the authenticated user is not permitted the facility). +Otherwise it should use the ACL &"atrn_domains"& condition, +which returns true if there are queued messages for any of +the given list of domains. +If that condition fails the ACL should return &"defer"& +with a "453 You have no mail" response; +else it should return &"accept"&. + +For example (with default domain handling, and one possible de-taint method) : +.code +check_atrn: + warn set acl_m0 = clientdom.net + deny condition = ${if def:smtp_command_argument} + set acl_m0 = ${map \ + {<, $smtp_command_argument} \ + {${if inlist{$item}{clientdom.net:cl2dom.net} {$value}}} \ + } + condition = ${if !def:acl_m0} + defer !atrn_domains = <, $acl_m0 + message = 453 You have no mail + accept +.endd + +Acceptance by the ACL will result in a queue-run for messages +having addresses with the given domains. +A suitable router and transport must be configured for the deliveries. + +To access a named queue +.cindex queue named +the ACL should use a "queue =" modifier before the "atrn_domains" +condition. +If the ACL does not accept, re-set the queue to an empty value +so as to not disrupt any later SMTP operations on the connection. + +Use of the &"atrn_domains"& condition additionally sets up +the &$atrn_host$& variable, which can be used by a manualroute +router. Being otherwise empty, this router will decline in +other situations so can be safely placed in a general router chain. + +For example: +.code +begin routers +to_odmr_customer: + driver = manualroute + route_data = <;$atrn_host + transport = call_customer + +begin transports +call_customer: + driver = smtp +.endd + +Although not discssed in the specification document, +Exim supports use of ATRN within a STARTTLS- +or TLS-on-connect- encrypted connection +(which is wise if a plaintext authentication mechanism is used). +In such cases the TLS connection will remain open across the +role-swap, and be used for the sending of queued messages. + +Note that the RFC requires that the CRAM-MD5 authentication +method be supported. +Exim does not enforce this, but leaves it up to the configuration; +see chapter &<>&. + + +.subsection "ODMR customer connection" SECTODMRCUST +.cindex ODMR customer +Exim supports the &"customer"& side of ODMR, +with a command-line option &"-atrn"& that requests a connection +to a given host, issuance of an ATRN command then operation +in SMTP server mode. +The option must be followed by two arguments. + +The first is the name or IP of the provider to be contacted. + +The second, which may be empty, should be a comma-separated list +of domains for which mail is to be requested. +Interpretation of the list is up to the provider; +an empty list is expected to result in some default being returned. + +The provider host is placed in &$domain$& for routing; +router and transport must be configured suitably to make the connection. +For example: +.code +begin routers +to_odmr_provider: + driver = manualroute + condition = ${if eq {$atrn_mode}{C}} + route_data = <;$domain + transport = call_provider + +begin transports +call_provider: + driver = smtp + port = odmr + hosts_try_auth = * + command_timeout = 10m +.endd + +Note that the specification requires a long timeout for the ATRN +command, to allow for scanning of queued messages. + +Configuration should also include client-side authentication +and processing for receiving messages. +.wen + + .section "Incoming local SMTP" "SECID238" .cindex "SMTP" "local incoming" @@ -37739,7 +38259,8 @@ This accepts SMTP messages from local processes without doing any other tests. -.section "Outgoing batched SMTP" "SECTbatchSMTP" +.section "Batched SMTP" "SECTgenbatchSMTP" +.subsection "Outgoing batched SMTP" "SECTbatchSMTP" .cindex "SMTP" "batched outgoing" .cindex "batched SMTP output" Both the &(appendfile)& and &(pipe)& transports can be used for handling @@ -37786,7 +38307,7 @@ message (unless there are more than 1000 recipients). -.section "Incoming batched SMTP" "SECTincomingbatchedSMTP" +.subsection "Incoming batched SMTP" "SECTincomingbatchedSMTP" .cindex "SMTP" "batched incoming" .cindex "batched SMTP input" The &%-bS%& command line option causes Exim to accept one or more messages by @@ -38856,7 +39377,7 @@ calls at each internal newline, and also after a maximum of 870 data characters. (This allows for a total syslog line length of 1024, when additions such as timestamps are added.) If you are running a syslog replacement that can handle lines longer than the 1024 characters allowed by -RFC 3164, you should set +&url(https://www.rfc-editor.org/rfc/rfc3164,RFC 3164), you should set .code SYSLOG_LONG_LINES=yes .endd @@ -39347,17 +39868,19 @@ because the arguments are checked before the configuration file is read. The only way to log such cases is to interpose a script such as &_util/logargs.sh_& between the caller and Exim. .next -.cindex "log" "connection identifier" -&%connection_identifier%&: An identifier for the accepted connection is added to +.cindex log "connection identifier" +.cindex connection "identifier logging" +&%connection_id%&: An identifier for the accepted connection is added to connection start and end lines and to message accept lines. The identifier is tagged by Ci=. The value is PID-based, so will reset on reboot and will wrap. .next -.cindex "log" "connection rejections" +.cindex log "connection rejections" +.cindex connection "rejection logging" &%connection_reject%&: A log entry is written whenever an incoming SMTP connection is rejected, for whatever reason. .next -.cindex "log" "delayed delivery" +.cindex log "delayed delivery" .cindex "delayed delivery, logging" &%delay_delivery%&: A log entry is written whenever a delivery process is not started for an incoming message because the load is too high or too many @@ -39451,7 +39974,8 @@ added to log entries and &'Received:'& header lines, following the IP address in square brackets, and separated from it by a colon. This is implemented by changing the value that is put in the &$sender_fullhost$& and &$sender_rcvhost$& variables. Recording the remote port number has become more -important with the widening use of NAT (see RFC 2505). +important with the widening use of NAT +(see &url(https://www.rfc-editor.org/rfc/rfc2505,RFC 2505)). .next .cindex "log" "dropped connection" &%lost_incoming_connection%&: A log line is written when an incoming SMTP @@ -41012,20 +41536,31 @@ will be used during message reception. .next A queue runner process retains root privilege throughout its execution. Its job is to fork a controlled sequence of delivery processes. + .next -A delivery process retains root privilege throughout most of its execution, -but any actual deliveries (that is, the transports themselves) are run in -subprocesses which always change to a non-root uid and gid. For local -deliveries this is typically the uid and gid of the owner of the mailbox; for -remote deliveries, the Exim uid and gid are used. Once all the delivery +A delivery process retains root privilege throughout most of its execution., +including while the recipient addresses in a message are being routed. + +.ilist +However, if a user's filter file has to be processed, +this is done in a subprocess that runs under the individual user's uid and +gid. A system filter is run as root unless &%system_filter_user%& is set. +.endlist + +Any actual deliveries (that is, the transports themselves) are run in +subprocesses which always change to a non-root uid and gid. +.ilist +For local +deliveries this is typically the uid and gid of the owner of the mailbox. +.next +For remote deliveries, the Exim uid and gid are used. +.endlist + +Once all the delivery subprocesses have been run, a delivery process changes to the Exim uid and gid while doing post-delivery tidying up such as updating the retry database and generating bounce and warning messages. -While the recipient addresses in a message are being routed, the delivery -process runs as root. However, if a user's filter file has to be processed, -this is done in a subprocess that runs under the individual user's uid and -gid. A system filter is run as root unless &%system_filter_user%& is set. .next A process that is testing addresses (the &%-bt%& option) runs as root so that the routing is done in the same environment as a message delivery. @@ -41718,7 +42253,7 @@ There is no dot-stuffing (and no dot-termination). DKIM is a mechanism by which messages sent by some entity can be provably linked to a domain which that entity controls. It permits reputation to be tracked on a per-domain basis, rather than merely upon source IP address. -DKIM is documented in RFC 6376. +DKIM is documented in &url(https://www.rfc-editor.org/rfc/rfc6376,RFC 6376). As DKIM relies on the message being unchanged in transit, messages handled by a mailing-list (which traditionally adds to the message) will not match @@ -41769,7 +42304,8 @@ senders). .cindex DKIM signing For signing to be usable you must have published a DKIM record in DNS. -Note that RFC 8301 (which does not cover EC keys) says: +Note that &url(https://www.rfc-editor.org/rfc/rfc8301,RFC 8301) +(which does not cover EC keys) says: .code rsa-sha1 MUST NOT be used for signing or verifying. @@ -41838,11 +42374,13 @@ To generate keys under OpenSSL: openssl genrsa -out dkim_rsa.private 2048 openssl rsa -in dkim_rsa.private -out /dev/stdout -pubout -outform PEM .endd -The result file from the first command should be retained, and -this option set to use it. +The result file from the first command should be retained, +permissions set so that Exim can read it, +and this option set to use it. Take the base-64 lines from the output of the second command, concatenated, for the DNS TXT record. -See section 3.6 of RFC6376 for the record specification. +See section 3.6 of &url(https://www.rfc-editor.org/rfc/rfc6376,RFC 6376) +for the record specification. Under GnuTLS: .code @@ -41850,13 +42388,14 @@ certtool --generate-privkey --rsa --bits=2048 --password='' -8 --outfile=dkim_rs certtool --load-privkey=dkim_rsa.private --pubkey-info .endd -Note that RFC 8301 says: +Note that &url(https://www.rfc-editor.org/rfc/rfc8301,RFC 8301) says: .code Signers MUST use RSA keys of at least 1024 bits for all keys. Signers SHOULD use RSA keys of at least 2048 bits. .endd -EC keys for DKIM are defined by RFC 8463. +EC keys for DKIM are defined by +&url(https://www.rfc-editor.org/rfc/rfc8463,RFC 8463). They are considerably smaller than RSA keys for equivalent protection. As they are a recent development, users should consider dual-signing (by setting a list of selectors, and an expansion for this option) @@ -41891,7 +42430,7 @@ Can be set to any one of the supported hash methods, which are: &`sha512`& &-- possibly more secure but less well supported .endlist -Note that RFC 8301 says: +Note that &url(https://www.rfc-editor.org/rfc/rfc8301,RFC 8301) says: .code rsa-sha1 MUST NOT be used for signing or verifying. .endd @@ -41921,7 +42460,8 @@ If set, this option must expand to a colon-separated list of header names. Headers with these names, or the absence of such a header, will be included in the message signature. -When unspecified, the header names listed in RFC4871 will be used, +When unspecified, the header names listed in +&url(https://www.rfc-editor.org/rfc/rfc4871,RFC 4871) will be used, whether or not each header is present in the message. The default list is available for the expansion in the macro &"_DKIM_SIGN_HEADERS"& @@ -41945,7 +42485,8 @@ Otherwise, must be an unsigned number giving an offset in seconds from the current time for the expiry tag (e.g. 1209600 for two weeks); both creation (t=) and expiry (x=) tags will be included unless the offset is 0 (no expiry). -RFC 6376 lists these tags as RECOMMENDED. +&url(https://www.rfc-editor.org/rfc/rfc6376,RFC 6376) +lists these tags as RECOMMENDED. .subsection "Verifying DKIM signatures in incoming mail" SECDKIMVFY @@ -42109,7 +42650,7 @@ may also be 'ed25519-sha256'. The "_CRYPTO_SIGN_ED25519" macro will be defined if support is present for EC keys. -Note that RFC 8301 says: +Note that &url(https://www.rfc-editor.org/rfc/rfc8301,RFC 8301) says: .code rsa-sha1 MUST NOT be used for signing or verifying. @@ -42131,7 +42672,8 @@ The header canonicalization method. One of 'relaxed' or 'simple'. .vitem &%$dkim_copiedheaders%& A transcript of headers and their values which are included in the signature (copied from the 'z=' tag of the signature). -Note that RFC6376 requires that verification fail if the From: header is +Note that &url(https://www.rfc-editor.org/rfc/rfc6376,RFC 6376) +requires that verification fail if the From: header is not included in the signature. Exim does not enforce this; sites wishing strict enforcement should code the check explicitly. @@ -42180,7 +42722,7 @@ Number of bits in the key. Valid only once the key is loaded, which is at the time the header signature is verified, which is after the body hash is. -Note that RFC 8301 says: +Note that &url(https://www.rfc-editor.org/rfc/rfc8301,RFC 8301) says: .code Verifiers MUST NOT consider signatures using RSA keys of less than 1024 bits as valid signatures. @@ -42250,7 +42792,8 @@ is any one of the supplied list. .cindex SPF verification SPF is a mechanism whereby a domain may assert which IP addresses may transmit -messages with its domain in the envelope from, documented by RFC 7208. +messages with its domain in the envelope from, documented by +&url(https://www.rfc-editor.org/rfc/rfc7208,RFC 7208). For more information on SPF see &url(http://www.open-spf.org), a static copy of the &url(http://openspf.org). . --- 2019-10-28: still not https, open-spf.org is told to be a @@ -42264,6 +42807,12 @@ This includes retransmissions done by traditional forwarders. SPF verification support is built into Exim if SUPPORT_SPF=yes is set in &_Local/Makefile_&. The support uses the &_libspf2_& library &url(https://www.libspf2.org/). +.new +.cindex "dynamic modules" +The support can be built as a dynamic-load module if desired; +see the comments in that Makefile. +.wen + There is no Exim involvement in the transmission of messages; publishing certain DNS records is all that is required. @@ -42560,14 +43109,14 @@ Example usage: DMARC combines feedback from SPF, DKIM, and header From: in order to attempt to provide better indicators of the authenticity of an email. This document does not explain the fundamentals; you -should read and understand how it works by visiting the website at -&url(http://www.dmarc.org/). +should read and understand how it works by visiting the +&url(http://www.dmarc.org/,DMARC website). If Exim is built with DMARC support, the libopendmarc library is used. For building Exim yourself, obtain the library from -&url(http://sourceforge.net/projects/opendmarc/) +&url(http://sourceforge.net/projects/opendmarc/,sourceforge) to obtain a copy, or find it in your favorite package repository. You will need to attend to the local/Makefile feature SUPPORT_DMARC and the associated LDFLAGS addition. @@ -42590,10 +43139,13 @@ the most current version can be downloaded from a link at &url(https://publicsuffix.org/list/public_suffix_list.dat). See also the util/renew-opendmarc-tlds.sh script. The default for the option is unset. -If not set, DMARC processing is disabled. +.new +It is expanded before use. +If not set (or empty after expansion), DMARC processing is disabled. +.wen -The &%dmarc_history_file%& option, if set +The &%dmarc_history_file%& option .oindex &%dmarc_history_file%& defines the location of a file to log results of dmarc verification on inbound emails. The @@ -42602,7 +43154,11 @@ which will manage the data, send out DMARC reports, and expire the data. Make sure the directory of this file is writable by the user exim runs as. -The default is unset. +The default for the option is unset. +.new +It is expanded before use. +If not set (or empty after expansion), no history is written. +.wen The &%dmarc_forensic_sender%& option .oindex &%dmarc_forensic_sender%& @@ -42717,6 +43273,18 @@ The domain which DMARC used to look up the DMARC policy record. The policy declared in the DMARC record. Valid values are "none", "reject" and "quarantine". It is blank when there is any error, including no DMARC record. + +.new +.vitem &$dmarc_alignment_spf$& +.vindex &$dmarc_alignment_spf$& +The result of the SPF alignment portion of the test status; +"yes" or "no". + +.vitem &$dmarc_alignment_dkim$& +.vindex &$dmarc_alignment_dkim$& +The result of the DKIM alignment portion of the test status; +"yes" or "no". +.wen .endlist .subsection Logging SSECDMARCLOGGING @@ -42881,19 +43449,23 @@ A possible solution is: .cindex proxy SOCKS .cindex SOCKS proxy Exim has support for sending outbound SMTP via a proxy -using a protocol called SOCKS5 (defined by RFC1928). +using a protocol called SOCKS5 (defined by +&url(https://www.rfc-editor.org/rfc/rfc1928,RFC 1928)). The support can be optionally included by defining SUPPORT_SOCKS=yes in Local/Makefile. Use of a proxy is enabled by setting the &%socks_proxy%& option on an smtp transport. -The option value is expanded and should then be a list +.new +If unset (or empty after expansion) then proxying is not done. +.wen +Otherwise, expansion should result in a list (colon-separated by default) of proxy specifiers. Each proxy specifier is a list (space-separated by default) where the initial element is an IP address and any subsequent elements are options. -Options are a string =. +Each option is a string of form =. The list of options is in the following table: .itable none 0 0 2 10* left 90* left .irow &'auth'& "authentication method" @@ -42911,7 +43483,8 @@ More details on each of these options follows: .cindex authentication "to proxy" .cindex proxy authentication &%auth%&: Either &"none"& (default) or &"name"&. -Using &"name"& selects username/password authentication per RFC 1929 +Using &"name"& selects username/password authentication per +&url(https://www.rfc-editor.org/rfc/rfc1929,RFC 1929) for access to the proxy. Default is &"none"&. .next @@ -42958,7 +43531,11 @@ This will add a component tagged with &"PRX="& to the line. Exim has support for Internationalised mail names. To include this it must be built with SUPPORT_I18N and the libidn library. -Standards supported are RFCs 2060, 5890, 6530 and 6533. +Standards supported are RFCs +&url(https://www.rfc-editor.org/rfc/rfc2060.html,2060), +&url(https://www.rfc-editor.org/rfc/rfc5890.html,5890), +&url(https://www.rfc-editor.org/rfc/rfc6530.html,6530) and +&url(https://www.rfc-editor.org/rfc/rfc6533.html,6533). If Exim is built with SUPPORT_I18N_2008 (in addition to SUPPORT_I18N, not instead of it) then IDNA2008 is supported; this adds an extra library @@ -43060,7 +43637,8 @@ The string is converted from the charset specified by the "headers charset" command (in a filter file) or &%headers_charset%& main configuration option (otherwise), to the -modified UTF-7 encoding specified by RFC 2060, +modified UTF-7 encoding specified by +&url(https://www.rfc-editor.org/rfc/rfc2060.html,RFC 2060), with the following exception: All occurrences of (which has to be a single character) are replaced with periods ("."), and all periods and slashes that are not @@ -43123,6 +43701,7 @@ Events have names which correspond to the point in process at which they fire. The name is placed in the variable &$event_name$& and the event action expansion must check this, as it will be called for every possible event type. +.new The current list of events is: .itable all 0 0 4 25* left 10* center 15* center 50* left .row auth:fail after both "per driver per authentication attempt" @@ -43142,7 +43721,10 @@ The current list of events is: .row tls:fail:connect after main "per connection" .row smtp:connect after transport "per connection" .row smtp:ehlo after transport "per connection" +.row smtp:fail:protocol after main "per connection" +.row smtp:fail:syntax after main "per connection" .endtable +.wen New event types may be added in future. The event name is a colon-separated list, defining the type of @@ -43158,6 +43740,7 @@ should define the event action. An additional variable, &$event_data$&, is filled with information varying with the event type: +.new .itable all 0 0 2 20* left 80* left .row auth:fail "smtp response" .row dane:fail "failure reason" @@ -43173,7 +43756,10 @@ with the event type: .row tls:fail:connect "error string" .row smtp:connect "smtp banner" .row smtp:ehlo "smtp ehlo response" +.row smtp:fail:protocol "error string" +.row smtp:fail:syntax "error string" .endtable +.wen The :defer events populate one extra variable: &$event_defer_errno$&.