+
. /////////////////////////////////////////////////////////////////////////////
. This is the primary source of the Exim Manual. It is an xfpt document that is
. converted into DocBook XML for subsequent conversion into printable and online
. --- table with four columns. For cases when the option name is given with
. --- a space, so that it can be split, a fifth argument is used for the
. --- index entry.
+. --- Also one for multiple option def headings be grouped in a single
+. --- table (but without the split capability).
+
+.macro otable
+.itable all 0 0 4 8* left 6* center 6* center 6* right
+.endmacro
+
+.macro orow
+.row "&%$1%&" "Use: &'$2'&" "Type: &'$3'&" "Default: &'$4'&"
+.endmacro
.macro option
.arg 5
.arg -5
.oindex "&%$1%&"
.endarg
-.itable all 0 0 4 8* left 6* center 6* center 6* right
-.row "&%$1%&" "Use: &'$2'&" "Type: &'$3'&" "Default: &'$4'&"
+.otable
+.orow "$1" "$2" "$3" "$4"
+.endtable
+.endmacro
+
+.macro options
+.eacharg
+.oindex "&%$+1%&"
+.endeach 4
+.otable
+.eacharg
+.orow "$+1" "$+2" "$+3" "$+4"
+.endeach 4
.endtable
.endmacro
The following Exim mailing lists exist:
.table2 140pt
-.row &'exim-announce@exim.org'& "Moderated, low volume announcements list"
-.row &'exim-users@exim.org'& "General discussion list"
-.row &'exim-dev@exim.org'& "Discussion of bugs, enhancements, etc."
-.row &'exim-cvs@exim.org'& "Automated commit messages from the VCS"
+.row &'exim-announce@lists.exim.org'& "Moderated, low volume announcements list"
+.row &'exim-users@lists.exim.org'& "General discussion list"
+.row &'exim-users-de@lists.exim.org'& "General discussion list in German language"
+.row &'exim-dev@lists.exim.org'& "Discussion of bugs, enhancements, etc."
+.row &'exim-cvs@lists.exim.org'& "Automated commit messages from the VCS"
.endtable
You can subscribe to these lists, change your existing subscriptions, and view
.cindex "base36"
.cindex "Darwin"
.cindex "Cygwin"
-Every message handled by Exim is given a &'message id'& which is sixteen
+.cindex "exim_msgdate"
+Every message handled by Exim is given a &'message id'& which is 23
characters long. It is divided into three parts, separated by hyphens, for
-example &`16VDhn-0001bo-D3`&. Each part is a sequence of letters and digits,
+example &`16VDhn-000000001bo-D342`&. Each part is a sequence of letters and digits,
normally encoding numbers in base 62. However, in the Darwin operating
system (Mac OS X) and when Exim is compiled to run under Cygwin, base 36
(avoiding the use of lower case letters) is used instead, because the message
contains the number of seconds since the start of the epoch (the normal Unix
way of representing the date and time of day).
.next
-After the first hyphen, the next six characters are the id of the process that
-received the message.
+After the first hyphen, the next
+.new
+eleven
+.wen
+characters are the id of the process that received the message.
.next
-There are two different possibilities for the final two characters:
+.new
+There are two different possibilities for the final four characters:
.olist
.oindex "&%localhost_number%&"
If &%localhost_number%& is not set, this value is the fractional part of the
-time of reception, normally in units of 1/2000 of a second, but for systems
+time of reception, normally in units of
+microseconds.
+but for systems
that must use base 36 instead of base 62 (because of case-insensitive file
-systems), the units are 1/1000 of a second.
+systems), the units are
+2 us.
.next
-If &%localhost_number%& is set, it is multiplied by 200 (100) and added to
-the fractional part of the time, which in this case is in units of 1/200
-(1/100) of a second.
+If &%localhost_number%& is set, it is multiplied by
+500000 (250000) and added to
+the fractional part of the time, which in this case is in units of 2 us (4 us).
.endlist
+.wen
.endlist
After a message has been received, Exim waits for the clock to tick at the
pid, it is guaranteed that the time will be different. In most cases, the clock
will already have ticked while the message was being received.
+The exim_msgdate utility (see section &<<SECTexim_msgdate>>&) can be
+used to display the date, and optionally the process id, of an Exim
+Message ID.
+
.section "Receiving mail" "SECID13"
.cindex "receiving mail"
referenced from the configuration (for example, alias files) are changed,
because these are reread each time they are used.
+.new
+Either a SIGTERM or a SIGINT signal should be used to cause the daemon
+to cleanly shut down.
+Subprocesses handling recceiving or delivering messages,
+or for scanning the queue,
+will not be affected by the termination of the daemon process.
+.wen
+
.cmdopt -bdf
This option has the same effect as &%-bd%& except that it never disconnects
from the controlling terminal, even when no debugging is specified.
&%queue_list_requires_admin%& is set false.
+.cmdopt -bpi
+.cindex queue "list of message IDs"
+This option operates like &%-bp%&, but only outputs message ids
+(one per line).
+
+
.cmdopt -bpr
This option operates like &%-bp%&, but the output is not sorted into
chronological order of message arrival. This can speed it up when there are
.cmdopt -bpra
This option is a combination of &%-bpr%& and &%-bpa%&.
+.cmdopt -bpri
+This option is a combination of &%-bpr%& and &%-bpi%&.
+
.cmdopt -bpru
This option is a combination of &%-bpr%& and &%-bpu%&.
given.
Normally the daemon creates this socket, unless a &%-oX%& and &*no*& &%-oP%&
option is also present.
-If this option is given then the socket will not be created. This could be
-required if the system is running multiple daemons.
+.new
+If this option is given then the socket will not be created. This is required
+if the system is running multiple daemons, in which case it should
+be used on all.
+The features supported by the socket will not be available in such cases.
The socket is currently used for
.ilist
fast ramp-up of queue runner processes
.next
+caching compiled regexes
+.next
obtaining a current queue size
.endlist
+.wen
.cmdopt -pd
.cindex "Perl" "starting the interpreter"
transports are run.
Performance will be best if the &%queue_run_in_order%& option is false.
-If that is so and the &%queue_fast_ramp%& option is true then
-in the first phase of the run,
+If that is so and
+the &%queue_fast_ramp%& option is true
+and a daemon-notifier socket is available
+then in the first phase of the run,
once a threshold number of messages are routed for a given host,
a delivery process is forked in parallel with the rest of the scan.
.cindex "hints database" "remembering routing"
The hints database that remembers which messages are waiting for specific hosts
-is updated, as if delivery to those hosts had been deferred. After this is
-complete, a second, normal queue scan happens, with routing and delivery taking
-place as normal. Messages that are routed to the same host should mostly be
+is updated, as if delivery to those hosts had been deferred.
+
+After the first queue scan complete,
+a second, normal queue scan is done, with routing and delivery taking
+place as normal.
+Messages that are routed to the same host should mostly be
delivered down a single SMTP
.cindex "SMTP" "passed connection"
.cindex "SMTP" "multiple deliveries"
.cindex "multiple SMTP deliveries"
connection because of the hints that were set up during the first queue scan.
-This option may be useful for hosts that are connected to the Internet
+
+.new
+Two-phase queue runs should be used on systems which, even intermittently,
+have a large queue (such as mailing-list operators).
+They may also be useful for hosts that are connected to the Internet
intermittently.
+.wen
.vitem &%-q[q]i...%&
.oindex "&%-qi%&"
Such a daemon listens for incoming SMTP calls, and also starts a queue runner
process every 30 minutes.
+.new
+.cindex "named queues" "queue runners"
+It is possible to set up runners for multiple named queues within one daemon,
+For example:
+.code
+exim -qGhipri/2m -q10m -qqGmailinglist/1h
+.endd
+.wen
+
When a daemon is started by &%-q%& with a time value, but without &%-bd%&, no
pid file is written unless one is explicitly requested by the &%-oP%& option.
&` _DRIVER_ROUTER_* `& router drivers
&` _DRIVER_TRANSPORT_* `& transport drivers
&` _DRIVER_AUTHENTICATOR_* `& authenticator drivers
+&` _EXP_COND_* `& expansion conditions
+&` _EXP_ITEM_* `& expansion items
+&` _EXP_OP_* `& expansion operators
+&` _EXP_VAR_* `& expansion variables
&` _LOG_* `& log_selector values
&` _OPT_MAIN_* `& main config options
&` _OPT_ROUTERS_* `& generic router options
When the lookup succeeds, the result of the expansion is a list of domains (and
possibly other types of item that are allowed in domain lists).
.cindex "tainted data" "de-tainting"
-.cindex "de-tainting" "using a lookup expansion""
+.cindex "de-tainting" "using a lookup expansion"
The result of the expansion is not tainted.
.next
The &'query-style'& type accepts a generalized database query. No particular
key value is assumed by Exim for query-style lookups. You can use whichever
Exim variables you need to construct the database query.
+
+For the string-expansion kind of lookups, the query is given in the first
+bracketed argument of the &${lookup ...}$& expansion.
+For the list-argument kind of lookup the quury is given by the remainder of the
+list item after the first semicolon.
+
.cindex "tainted data" "quoting for lookups"
If tainted data is used in the query then it should be quuted by
using the &*${quote_*&<&'lookup-type'&>&*:*&<&'string'&>&*}*& expansion operator
.cindex "single-key lookup" "list of types"
The following single-key lookup types are implemented:
-.ilist
+.subsection cdb
.cindex "cdb" "description of"
.cindex "lookup" "cdb"
.cindex "binary zero" "in lookup key"
-&(cdb)&: The given file is searched as a Constant DataBase file, using the key
+The given file is searched as a Constant DataBase file, using the key
string without a terminating binary zero. The cdb format is designed for
indexed files that are read frequently and never updated, except by total
re-creation. As such, it is particularly suitable for large files containing
because the code for reading cdb files is included directly in Exim itself.
However, no means of building or testing cdb files is provided with Exim, so
you need to obtain a cdb distribution in order to do this.
-.next
+
+.subsection dbm
.cindex "DBM" "lookup type"
.cindex "lookup" "dbm"
.cindex "binary zero" "in lookup key"
-&(dbm)&: Calls to DBM library functions are used to extract data from the given
+Calls to DBM library functions are used to extract data from the given
DBM file by looking up the record with the given key. A terminating binary
zero is included in the key that is passed to the DBM library. See section
&<<SECTdb>>& for a discussion of DBM libraries.
the DB_UNKNOWN option. This enables it to handle any of the types of database
that the library supports, and can be useful for accessing DBM files created by
other applications. (For earlier DB versions, DB_HASH is always used.)
-.next
+
+.subsection dbmjz
.cindex "lookup" "dbmjz"
.cindex "lookup" "dbm &-- embedded NULs"
.cindex "sasldb2"
.cindex "dbmjz lookup type"
-&(dbmjz)&: This is the same as &(dbm)&, except that the lookup key is
+This is the same as &(dbm)&, except that the lookup key is
interpreted as an Exim list; the elements of the list are joined together with
ASCII NUL characters to form the lookup key. An example usage would be to
authenticate incoming SMTP calls using the passwords from Cyrus SASL's
&_/etc/sasldb2_& file with the &(gsasl)& authenticator or Exim's own
&(cram_md5)& authenticator.
-.next
+
+.subsection dbmnz
.cindex "lookup" "dbmnz"
.cindex "lookup" "dbm &-- terminating zero"
.cindex "binary zero" "in lookup key"
.cindex "Courier"
.cindex "&_/etc/userdbshadow.dat_&"
.cindex "dbmnz lookup type"
-&(dbmnz)&: This is the same as &(dbm)&, except that a terminating binary zero
+This is the same as &(dbm)&, except that a terminating binary zero
is not included in the key that is passed to the DBM library. You may need this
if you want to look up data in files that are created by or shared with some
other application that does not use terminating zeros. For example, you need to
calls using the passwords from Courier's &_/etc/userdbshadow.dat_& file. Exim's
utility program for creating DBM files (&'exim_dbmbuild'&) includes the zeros
by default, but has an option to omit them (see section &<<SECTdbmbuild>>&).
-.next
+
+.subsection dsearch
.cindex "lookup" "dsearch"
.cindex "dsearch lookup type"
-&(dsearch)&: The given file must be an
-absolute
-directory path; this is searched for an entry
+The given file must be an absolute directory path; this is searched for an entry
whose name is the key by calling the &[lstat()]& function.
-The key may not
-contain any forward slash characters.
+The key may not contain any forward slash characters.
If &[lstat()]& succeeds then so does the lookup.
.cindex "tainted data" "dsearch result"
The result is regarded as untainted.
An example of how this
lookup can be used to support virtual domains is given in section
&<<SECTvirtualdomains>>&.
-.next
+
+.subsection iplsearch
.cindex "lookup" "iplsearch"
.cindex "iplsearch lookup type"
-&(iplsearch)&: The given file is a text file containing keys and data. A key is
+The given file is a text file containing keys and data. A key is
terminated by a colon or white space or the end of the line. The keys in the
file must be IP addresses, or IP addresses with CIDR masks. Keys that involve
IPv6 addresses must be enclosed in quotes to prevent the first internal colon
rather than omitting the key portion.
Note however that the key portion will have been de-quoted.
-.next
+.subsection json
.cindex lookup json
.cindex json "lookup type"
.cindex JSON expansions
-&(json)&: The given file is a text file with a JSON structure.
+The given file is a text file with a JSON structure.
An element of the structure is extracted, defined by the search key.
The key is a list of subelement selectors
(colon-separated by default but changeable in the usual way)
For elements of type string, the returned value is de-quoted.
-.next
+.subsection lmdb
.cindex LMDB
.cindex lookup lmdb
.cindex database lmdb
-&(lmdb)&: The given file is an LMDB database.
+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/)
possibly using the &"mdb_load"& utility.
-.next
+.subsection lsearch
.cindex "linear search"
.cindex "lookup" "lsearch"
.cindex "lsearch lookup type"
.cindex "case sensitivity" "in lsearch lookup"
-&(lsearch)&: The given file is a text file that is searched linearly for a
+The given file is a text file that is searched linearly for a
line beginning with the search key, terminated by a colon or white space or the
end of the line. The search is case-insensitive; that is, upper and lower case
letters are treated as the same. The first occurrence of the key that is found
quoted keys (exactly as for unquoted keys). There is no special handling of
quotes for the data part of an &(lsearch)& line.
-.next
+.subsection nis
.cindex "NIS lookup type"
.cindex "lookup" "NIS"
.cindex "binary zero" "in lookup key"
-&(nis)&: The given file is the name of a NIS map, and a NIS lookup is done with
+The given file is the name of a NIS map, and a NIS lookup is done with
the given key, without a terminating binary zero. There is a variant called
&(nis0)& which does include the terminating binary zero in the key. This is
reportedly needed for Sun-style alias files. Exim does not recognize NIS
aliases; the full map names must be used.
-.next
+.subsection (n)wildlsearch
.cindex "wildlsearch lookup type"
.cindex "lookup" "wildlsearch"
.cindex "nwildlsearch lookup type"
file that are regular expressions can be made case-sensitive by the use of
&`(-i)`& within the pattern. The following forms of wildcard are recognized:
-. ==== As this is a nested list, any displays it contains must be indented
-. ==== as otherwise they are too far to the left.
-
.olist
The string may begin with an asterisk to mean &"ends with"&. For example:
.code
- *.a.b.c data for anything.a.b.c
- *fish data for anythingfish
+*.a.b.c data for anything.a.b.c
+*fish data for anythingfish
.endd
.next
The string may begin with a circumflex to indicate a regular expression. For
example, for &(wildlsearch)&:
.code
- ^\N\d+\.a\.b\N data for <digits>.a.b
+^\N\d+\.a\.b\N data for <digits>.a.b
.endd
Note the use of &`\N`& to disable expansion of the contents of the regular
expression. If you are using &(nwildlsearch)&, where the keys are not
string-expanded, the equivalent entry is:
.code
- ^\d+\.a\.b data for <digits>.a.b
+^\d+\.a\.b data for <digits>.a.b
.endd
The case-insensitive flag is set at the start of compiling the regular
expression, but it can be turned off by using &`(-i)`& at an appropriate point.
For example, to make the entire pattern case-sensitive:
.code
- ^(?-i)\d+\.a\.b data for <digits>.a.b
+^(?-i)\d+\.a\.b data for <digits>.a.b
.endd
If the regular expression contains white space or colon characters, you must
lookup name terminated by a semicolon, and followed by lookup data. For
example:
.code
- cdb;/some/file data for keys that match the file
+cdb;/some/file data for keys that match the file
.endd
The data that is obtained from the nested lookup is discarded.
.endlist olist
&((n)wildlsearch)& can &'not'& be turned into a DBM or cdb file, because those
lookup types support only literal keys.
-.next
+.subsection spf
.cindex "spf lookup type"
.cindex "lookup" "spf"
-&(spf)&: If Exim is built with SPF support, manual lookups can be done
+If Exim is built with SPF support, manual lookups can be done
(as opposed to the standard ACL condition method).
For details see section &<<SECSPF>>&.
-.endlist ilist
.section "Query-style lookup types" "SECTquerystylelookups"
The supported query-style lookup types are listed below. Further details about
many of them are given in later sections.
-.ilist
+.subsection dnsdb
.cindex "DNS" "as a lookup type"
.cindex "lookup" "DNS"
-&(dnsdb)&: This does a DNS search for one or more records whose domain names
+This does a DNS search for one or more records whose domain names
are given in the supplied query. The resulting data is the contents of the
records. See section &<<SECTdnsdb>>&.
-.next
+
+.subsection ibase
.cindex "InterBase lookup type"
.cindex "lookup" "InterBase"
-&(ibase)&: This does a lookup in an InterBase database.
-.next
+This does a lookup in an InterBase database.
+
+.subsection ldap
.cindex "LDAP" "lookup type"
.cindex "lookup" "LDAP"
-&(ldap)&: This does an LDAP lookup using a query in the form of a URL, and
+This does an LDAP lookup using a query in the form of a URL, and
returns attributes from a single entry. There is a variant called &(ldapm)&
that permits values from multiple entries to be returned. A third variant
called &(ldapdn)& returns the Distinguished Name of a single entry instead of
any attribute values. See section &<<SECTldap>>&.
-.next
+
+.subsection mysql
.cindex "MySQL" "lookup type"
.cindex "lookup" "MySQL"
-&(mysql)&: The format of the query is an SQL statement that is passed to a
+The format of the query is an SQL statement that is passed to a
MySQL database. See section &<<SECTsql>>&.
-.next
+
+.subsection nisplus
.cindex "NIS+ lookup type"
.cindex "lookup" "NIS+"
-&(nisplus)&: This does a NIS+ lookup using a query that can specify the name of
+This does a NIS+ lookup using a query that can specify the name of
the field to be returned. See section &<<SECTnisplus>>&.
-.next
+
+.subsection oracle
.cindex "Oracle" "lookup type"
.cindex "lookup" "Oracle"
-&(oracle)&: The format of the query is an SQL statement that is passed to an
+The format of the query is an SQL statement that is passed to an
Oracle database. See section &<<SECTsql>>&.
-.next
+
+.subsection passwd
.cindex "lookup" "passwd"
.cindex "passwd lookup type"
.cindex "&_/etc/passwd_&"
-&(passwd)& is a query-style lookup with queries that are just user names. The
+This is a query-style lookup with queries that are just user names. The
lookup calls &[getpwnam()]& to interrogate the system password data, and on
success, the result string is the same as you would get from an &(lsearch)&
lookup on a traditional &_/etc/passwd file_&, though with &`*`& for the
.code
*:42:42:King Rat:/home/kr:/bin/bash
.endd
-.next
+
+.subsection pgsql
.cindex "PostgreSQL lookup type"
.cindex "lookup" "PostgreSQL"
-&(pgsql)&: The format of the query is an SQL statement that is passed to a
+The format of the query is an SQL statement that is passed to a
PostgreSQL database. See section &<<SECTsql>>&.
-.next
+.subsection redis
.cindex "Redis lookup type"
.cindex lookup Redis
-&(redis)&: The format of the query is either a simple get or simple set,
+The format of the query is either a simple get or simple set,
passed to a Redis database. See section &<<SECTsql>>&.
-.next
+.subsection sqlite
.cindex "sqlite lookup type"
.cindex "lookup" "sqlite"
-&(sqlite)&: The format of the query is
+The format of the query is
an SQL statement that is passed to an SQLite database. See section &<<SECTsqlite>>&.
-.next
-&(testdb)&: This is a lookup type that is used for testing Exim. It is
+.subsection testdb
+This is a lookup type that is used for testing Exim. It is
not likely to be useful in normal operation.
-.next
+
+.subsection whoson
.cindex "whoson lookup type"
.cindex "lookup" "whoson"
-. --- still http:-only, 2018-09-07
-&(whoson)&: &'Whoson'& (&url(http://whoson.sourceforge.net)) is a protocol that
+&'Whoson'& (&url(http://whoson.sourceforge.net)) is a protocol that
allows a server to check whether a particular (dynamically allocated) IP
address is currently allocated to a known (trusted) user and, optionally, to
obtain the identity of the said user. For SMTP servers, &'Whoson'& was popular
the authenticated user, which is stored in the variable &$value$&. However, in
this example, the data in &$value$& is not used; the result of the lookup is
one of the fixed strings &"yes"& or &"no"&.
-.endlist
in a database file is useless, because the asterisk in a partial matching
subject key is always followed by a dot.
+When the lookup is done from a string-expansion,
+the variables &$1$& and &$2$& contain the wild and non-wild parts of the key
+during the expansion of the replacement text.
+They return to their previous values at the end of the lookup item.
+
.code
${quote_<lookup-type>:<string>}
.endd
-For example, the safest way to write the NIS+ query is
+For example, the way to write the NIS+ query is
.code
[name="${quote_nisplus:$local_part}"]
.endd
+.cindex "tainted data" "in lookups"
+.new
+&*All*& tainted data used in a query-style lookup must be quoted
+using a mechanism appropriate for the lookup type.
+.wen
See chapter &<<CHAPexpand>>& for full coverage of string expansions. The quote
operator can be used for all lookup types, but has no effect for single-key
lookups, since no quoting is ever needed in their key strings.
on the number of entries returned, and no time limit on queries.
When a DN is quoted in the USER= setting for LDAP authentication, Exim
-removes any URL quoting that it may contain before passing it LDAP. Apparently
+removes any URL quoting that it may contain before passing it to the LDAP library.
+Apparently
some libraries do this for themselves, but some do not. Removing the URL
quoting has two advantages:
.code
add_header = :at_start:${authresults {$primary_hostname}}
.endd
-This is safe even if no authentication results are available.
+This is safe even if no authentication results are available
+.new
+and would generally be placed in the DATA ACL.
+.wen
.vitem "&*${certextract{*&<&'field'&>&*}{*&<&'certificate'&>&*}&&&
After expansion, <&'string'&> is interpreted as a list, colon-separated by
default, but the separator can be changed in the usual way (&<<SECTlistsepchange>>&).
For each item
-in this list, its value is place in &$item$&, and then the condition is
-evaluated. If the condition is true, &$item$& is added to the output as an
+in this list, its value is placed in &$item$&, and then the condition is
+evaluated.
+.new
+Any modification of &$value$& by this evaluation is discarded.
+.wen
+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
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:
${filter{a:b:c}{!eq{$item}{b}}}
.endd
yields &`a:c`&. At the end of the expansion, the value of &$item$& is restored
-to what it was before. See also the &%map%& and &%reduce%& expansion items.
+to what it was before.
+See also the &%map%& and &%reduce%& expansion items.
.vitem &*${hash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
sending the request. Values are &"yes"& (the default) or &"no"&
(preferred, eg. by some webservers).
+.next
+&*sni*&
+Controls the use of Server Name Identification on the connection.
+Any nonempty value will be the SNI sent; TLS will be forced.
+
.next
&*tls*&
Controls the use of TLS on the connection.
restored to what they were before. See also the &%filter%& and &%map%&
expansion items.
+. A bit of a special-case logic error in writing an expansion;
+. probably not worth including in the mainline of documentation.
+. If only we had footnotes (the html output variant is the problem).
+.
+. .new
+. &*Note*&: if an &'expansion condition'& is used in <&'string3'&>
+. and that condition modifies &$value$&,
+. then the string expansions dependent on the condition cannot use
+. the &$value$& of the reduce iteration.
+. .wen
+
.vitem &*$rheader_*&<&'header&~name'&>&*:*&&~or&~&*$rh_*&<&'header&~name'&>&*:*&
This item inserts &"raw"& header lines. It is described with the &%header%&
expansion item in section &<<SECTexpansionitems>>& above.
-.vitem "&*${run <&'options'&> {*&<&'command&~arg&~list'&>&*}{*&<&'string1'&>&*}&&&
+.vitem "&*${run<&'options'&> {*&<&'command&~arg&~list'&>&*}{*&<&'string1'&>&*}&&&
{*&<&'string2'&>&*}}*&"
.cindex "expansion" "running a command"
.cindex "&%run%& expansion item"
This item runs an external command, as a subprocess.
-One option is supported after the word &'run'&, comma-separated.
+One option is supported after the word &'run'&, comma-separated
+and without whitespace.
If the option &'preexpand'& is not used,
the command string is split into individual arguments by spaces
.code
${run{/bin/bash -c "/usr/bin/id >/tmp/id"}{yes}{yes}}
.endd
+Note that &$value$& will not persist beyond the reception of a single message.
.vindex "&$runrc$&"
The return code from the command is put in the variable &$runrc$&, and this
+.new
+.vitem &*${headerwrap_*&<&'cols'&>&*_*&<&'limit'&>&*:*&<&'string'&>&*}*&
+.cindex header "wrapping operator"
+.cindex expansion "header wrapping"
+This operator line-wraps its argument in a way useful for headers.
+The &'cols'& value gives the column number to wrap after,
+the &'limit'& gives a limit number of result characters to truncate at.
+Either just the &'limit'& and the preceding underbar, or both, can be omitted;
+the defaults are 80 and 998.
+Wrapping will be inserted at a space if possible before the
+column number is reached.
+Whitespace at a chosen wrap point is removed.
+A line-wrap consists of a newline followed by a tab,
+and the tab is counted as 8 columns.
+.wen
+
+
+
.vitem &*${hex2b64:*&<&'hexstring'&>&*}*&
.cindex "base64 encoding" "conversion from hex"
.cindex "expansion" "hex to base64"
.cindex "first delivery"
.cindex "expansion" "first delivery test"
.cindex "&%first_delivery%& expansion condition"
+.cindex retry condition
This condition, which has no data, is true during a message's first delivery
attempt. It is false during any subsequent delivery attempts.
.endlist
Note that negation of &*forany*& means that the condition must be false for all
items for the overall condition to succeed, and negation of &*forall*& means
-that the condition must be false for at least one item. In this example, the
-list separator is changed to a comma:
+that the condition must be false for at least one item.
+
+Example:
.code
-${if forany{<, $recipients}{match{$item}{^user3@}}{yes}{no}}
+${if forany{$recipients_list}{match{$item}{^user3@}}{yes}{no}}
.endd
The value of &$item$& is saved and restored while &%forany%& or &%forall%& is
being processed, to enable these expansion items to be nested.
SRS decode. See SECT &<<SECTSRS>>& for details.
-.vitem &*inlist&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
- &*inlisti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
+.vitem &*inlist&~{*&<&'subject'&>&*}{*&<&'list'&>&*}*& &&&
+ &*inlisti&~{*&<&'subject'&>&*}{*&<&'list'&>&*}*&
.cindex "string" "comparison"
.cindex "list" "iterative conditions"
Both strings are expanded; the second string is treated as a list of simple
rejections of MAIL and rejections of RCPT.
.tvar &$recipients$&
-This variable contains a list of envelope recipients for a message. A comma and
-a space separate the addresses in the replacement text. However, the variable
-is not generally available, to prevent exposure of Bcc recipients in
-unprivileged users' filter files. You can use &$recipients$& only in these
+.new
+.tvar &$recipients_list$&
+These variables both contain the envelope recipients for a message.
+
+The first uses a comma and a space separate the addresses in the replacement text.
+&*Note*&: an address can legitimately contain a comma;
+this variable is not intended for further processing.
+
+The second is a proper Exim list; colon-separated.
+.wen
+
+However, the variables
+are not generally available, to prevent exposure of Bcc recipients in
+unprivileged users' filter files. You can use either of them only in these
cases:
.olist
.cindex "router" "name"
.cindex "name" "of router"
.vindex "&$router_name$&"
-During the running of a router this variable contains its name.
+During the running of a router, or a transport called,
+this variable contains the router name.
.vitem &$runrc$&
.cindex "return code" "from &%run%& expansion"
single connection is being processed. When a child process terminates, the
daemon decrements its copy of the variable.
+.vitem &$smtp_notquit_reason$&
+.vindex "&$smtp_notquit_reason$&"
+When the not-QUIT ACL is running, this variable is set to a string
+that indicates the reason for the termination of the SMTP connection.
+
.vitem "&$sn0$& &-- &$sn9$&"
These variables are copies of the values of the &$n0$& &-- &$n9$& accumulators
that were current at the end of the system filter file. This allows a system
See section &<<CALLaddparcall>>& for details of how this value is used.
-.option check_log_inodes main integer 100
-See &%check_spool_space%& below.
-
-
-.option check_log_space main integer 10M
+.options check_log_inodes main integer 100 &&&
+ check_log_space main integer 10M
See &%check_spool_space%& below.
.oindex "&%check_rfc2047_length%&"
set false, Exim recognizes encoded words of any length.
-.option check_spool_inodes main integer 100
-See &%check_spool_space%& below.
-
-
-.option check_spool_space main integer 10M
+.options check_spool_inodes main integer 100 &&&
+ check_spool_space main integer 10M
.cindex "checking disk space"
.cindex "disk space, checking"
.cindex "spool directory" "checking space"
listens. See chapter &<<CHAPinterfaces>>& for details of how it is used. For
backward compatibility, &%daemon_smtp_port%& (singular) is a synonym.
-.option daemon_startup_retries main integer 9
+.options daemon_startup_retries main integer 9 &&&
+ daemon_startup_sleep main time 30s
.cindex "daemon startup, retrying"
-This option, along with &%daemon_startup_sleep%&, controls the retrying done by
+These options control the retrying done by
the daemon at startup when it cannot immediately bind a listening socket
(typically because the socket is already in use): &%daemon_startup_retries%&
defines the number of retries after the first failure, and
&%daemon_startup_sleep%& defines the length of time to wait between retries.
-.option daemon_startup_sleep main time 30s
-See &%daemon_startup_retries%&.
-
.option delay_warning main "time list" 24h
.cindex "warning of delay"
.cindex "delay warning, specifying"
.code
dns_again_means_nonexist = *.in-addr.arpa
.endd
-This option applies to all DNS lookups that Exim does. It also applies when the
+This option applies to all DNS lookups that Exim does,
+.new
+except for TLSA lookups (where knowing about such failures
+is security-relevant).
+.wen
+It also applies when the
&[gethostbyname()]& or &[getipnodebyname()]& functions give temporary errors,
since these are most likely to be caused by DNS lookup problems. The
&(dnslookup)& router has some options of its own for controlling what happens
.option freeze_tell main "string list, comma separated" unset
.cindex "freezing messages" "sending a message when freezing"
+.cindex "frozen messages" "sending a message when freezing"
On encountering certain errors, or when configured to do so in a system filter,
ACL, or special router, Exim freezes a message. This means that no further
delivery attempts take place until an administrator thaws the message, or the
logging that you require.
-.option gecos_name main string&!! unset
+.options gecos_name main string&!! unset &&&
+ gecos_pattern main string unset
.cindex "HP-UX"
.cindex "&""gecos""& field, parsing"
Some operating systems, notably HP-UX, use the &"gecos"& field in the system
gecos_name = $1
.endd
-.option gecos_pattern main string unset
-See &%gecos_name%& above.
-
.option gnutls_compat_mode main boolean unset
This option controls whether GnuTLS is used in compatibility mode in an Exim
nowadays the ACL specified by &%acl_smtp_connect%& can also reject incoming
connections immediately.
+.new
+If the connection is on a TLS-on-connect port then the TCP connection is
+just dropped. Otherwise, an SMTP error is sent first.
+.wen
+
The ability to give an immediate rejection (either by this option or using an
ACL) is provided for use in unusual cases. Many hosts will just try again,
sometimes without much delay. Normally, it is better to use an ACL to reject
&%timeout_frozen_after%&.
-.option ignore_fromline_hosts main "host list&!!" unset
+.options ignore_fromline_hosts main "host list&!!" unset &&&
+ ignore_fromline_local main boolean false
.cindex "&""From""& line"
.cindex "UUCP" "&""From""& line"
Some broken SMTP clients insist on sending a UUCP-like &"From&~"& line before
&%ignore_fromline_local%& must be set to achieve this effect.
-.option ignore_fromline_local main boolean false
-See &%ignore_fromline_hosts%& above.
.option keep_environment main "string list" unset
.cindex "environment" "values from"
-.option local_from_prefix main string unset
+.options local_from_prefix main string unset &&&
+ local_from_suffix main string unset
When Exim checks the &'From:'& header line of locally submitted messages for
matching the login id (see &%local_from_check%& above), it can be configured to
ignore certain prefixes and suffixes in the local part of the address. This is
qualify domain.
-.option local_from_suffix main string unset
-See &%local_from_prefix%& above.
-
-
.option local_interfaces main "string list" "see below"
This option controls which network interfaces are used by the daemon for
listening; they are also used to identify the local host when routing. Chapter
local parts. Exim's default configuration does this.
-.option perl_at_start main boolean false
-.cindex "Perl"
-This option is available only when Exim is built with an embedded Perl
-interpreter. See chapter &<<CHAPperl>>& for details of its use.
-
-
-.option perl_startup main string unset
+.options perl_at_start main boolean false &&&
+ perl_startup main string unset
.cindex "Perl"
-This option is available only when Exim is built with an embedded Perl
-interpreter. See chapter &<<CHAPperl>>& for details of its use.
+These options are available only when Exim is built with an embedded Perl
+interpreter. See chapter &<<CHAPperl>>& for details of their use.
.option perl_taintmode main boolean false
.cindex "Perl"
&%queue_only_load%&, and &%smtp_accept_queue%&.
-.option queue_only_file main string unset
+.option queue_only_file main "string list" unset
.cindex "queueing incoming messages"
.cindex "message" "queueing by file existence"
This option can be set to a colon-separated list of absolute path names, each
.cindex "banner for SMTP"
.cindex "welcome banner for SMTP"
.cindex "customizing" "SMTP banner"
-This string, which is expanded every time it is used, is output as the initial
+If a connect ACL does not supply a message,
+this string (which is expanded every time it is used) is output as the initial
positive response to an SMTP connection. The default setting is:
.code
smtp_banner = $smtp_active_hostname ESMTP Exim \
$version_number $tod_full
.endd
-Failure to expand the string causes a panic error. If you want to create a
+.new
+Failure to expand the string causes a panic error;
+a forced fail just closes the connection.
+.wen
+If you want to create a
multiline response to the initial SMTP connection, use &"\n"& in the string at
appropriate points, but not at the end. Note that the 220 code is not included
in this string. Exim adds it automatically (several times in the case of a
-.option smtp_ratelimit_hosts main "host list&!!" unset
+.options smtp_ratelimit_hosts main "host list&!!" unset &&&
+ smtp_ratelimit_mail main string unset &&&
+ smtp_ratelimit_rcpt main string unset
.cindex "SMTP" "rate limiting"
.cindex "limit" "rate of message arrival"
.cindex "RCPT" "rate limiting"
delays to RCPT commands when more than four occur in a single message.
-.option smtp_ratelimit_mail main string unset
-See &%smtp_ratelimit_hosts%& above.
-
-
-.option smtp_ratelimit_rcpt main string unset
-See &%smtp_ratelimit_hosts%& above.
-
.option smtp_receive_timeout main time&!! 5m
.cindex "timeout" "for SMTP input"
.cindex ALPN "set acceptable names for server"
If this option is set,
the TLS library supports ALPN,
-and the client offers either more than
+and the client offers either more than one
ALPN name or a name which does not match the list,
the TLS connection is declined.
acceptable bound from 1024 to 2048.
-.option tls_eccurve main string&!! &`auto`&
+.option tls_eccurve main string list&!! &`auto`&
.cindex TLS "EC cryptography"
-This option selects a EC curve for use by Exim when used with OpenSSL.
-It has no effect when Exim is used with GnuTLS.
+This option selects EC curves for use by Exim when used with OpenSSL.
+It has no effect when Exim is used with GnuTLS
+(the equivalent can be done using a priority string for the
+&%tls_require_ciphers%& option).
-After expansion it must contain a valid EC curve parameter, such as
-&`prime256v1`&, &`secp384r1`&, or &`P-512`&. Consult your OpenSSL manual
-for valid selections.
+After expansion it must contain
+.new
+one or (only for OpenSSL versiona 1.1.1 onwards) more
+.wen
+EC curve names, such as &`prime256v1`&, &`secp384r1`&, or &`P-521`&.
+Consult your OpenSSL manual for valid curve names.
For OpenSSL versions before (and not including) 1.0.2, the string
&`auto`& selects &`prime256v1`&. For more recent OpenSSL versions
&`auto`& tells the library to choose.
-If the option expands to an empty string, no EC curves will be enabled.
+.new
+If the option expands to an empty string, the effect is undefined.
+.wen
.option tls_ocsp_file main string&!! unset
.cindex "router" "restricting to specific domains"
.vindex "&$domain_data$&"
If this option is set, the router is skipped unless the current domain matches
-the list. If the match is achieved by means of a file lookup, the data that the
-lookup returned for the domain is placed in &$domain_data$& for use in string
+the list.
+The data returned by the list check
+is placed in &$domain_data$& for use in string
expansions of the driver's private options and in the transport.
See section &<<SECTrouprecon>>& for
a list of the order in which preconditions are evaluated.
+A complex example, using a file like:
+.code
+alice@dom1
+bill@dom1
+maggie@dom1
+.endd
+and checking both domain and local_part
+.code
+domains = ${domain:${lookup {$local_part@$domain} lseach,ret=key {/path/to/accountsfile}}}
+local_parts = ${local_part:${lookup {$local_part@$domain} lseach,ret=key {/path/to/accountsfile}}}
+.endd
+
.option driver routers string unset
local_parts = dbm;/usr/local/specials/$domain_data
.endd
.vindex "&$local_part_data$&"
-If the match is achieved by a lookup, the data that the lookup returned
+the data returned by the list check
for the local part is placed in the variable &$local_part_data$& for use in
expansions of the router's private options or in the transport.
You might use this option, for
resent to other recipients.
&*Note:*& If used on a transport handling multiple recipients
-(the smtp transport unless &%rcpt_max%& is 1, the appendfile, pipe or lmtp
+(the smtp transport unless &%max_rcpt%& is 1, the appendfile, pipe or lmtp
transport if &%batch_max%& is greater than 1)
then information about Bcc recipients will be leaked.
Doing so is generally not advised.
transport_filter = '/bin/cmd${if eq{$host}{a.b.c}{1}{2}}'
.endd
This runs the command &(/bin/cmd1)& if the host name is &'a.b.c'&, and
-&(/bin/cmd2)& otherwise. If double quotes had been used, they would have been
+&(/bin/cmd2)& otherwise.
+
+Option strings in general have any fully-surrounding double quote wrapping
+removed early in parsing (see &<<SECTstrings>>&).
+Then, for this option, quotes protect against whitespace being
+regarded as a separator while splitting into the command argument vector.
+Either double or single quotes can be used here;
+the former interprets backlash-quoted charachters
+and the latter does not.
+
+If double quotes had been used in this example, they would have been
stripped by Exim when it read the option's value. When the value is used, if
the single quotes were missing, the line would be split into two items,
&`/bin/cmd${if`& and &`eq{$host}{a.b.c}{1}{2}`&, and an error would occur when
&<<CHAPSMTPAUTH>>& for details of authentication.
-.option hosts_request_ocsp smtp "host list&!!" *
+.option hosts_request_ocsp smtp "host list&!!" "see below"
.cindex "TLS" "requiring for certain servers"
Exim will request a Certificate Status on a
TLS session for any host that matches this list.
&%tls_verify_certificates%& should also be set for the transport.
+.new
+The default is &"**"& if DANE is not in use for the connection,
+or if DANE-TA us used.
+It is empty if DANE-EE is used.
+.wen
+
.option hosts_require_alpn smtp "host list&!!" unset
.cindex ALPN "require negotiation in client"
.cindex TLS ALPN
string &`IGNOREQUOTA`& is added to RCPT commands, provided that the LMTP server
has advertised support for IGNOREQUOTA in its response to the LHLO command.
-.option max_rcpt smtp integer 100
+.option max_rcpt smtp integer&!! 100
.cindex "RCPT" "maximum number of outgoing"
-This option limits the number of RCPT commands that are sent in a single
-SMTP message transaction. Each set of addresses is treated independently, and
+This option,
+.new
+after expansion,
+.wen
+limits the number of RCPT commands that are sent in a single
+SMTP message transaction.
+A value setting of zero disables the limit.
+
+.new
+If a constant is given,
+.wen
+each set of addresses is treated independently, and
so can cause parallel connections to the same host if &%remote_max_parallel%&
-permits this. A value setting of zero disables the limit.
+permits this.
.option message_linelength_limit smtp integer 998
while verifying the server certificate,
checks will be included on the host name
(note that this will generally be the result of a DNS MX lookup)
-versus Subject and Subject-Alternate-Name fields. Wildcard names are permitted
+versus the Subject-Alternate-Name (or, if none, Subject-Name) fields.
+Wildcard names are permitted,
limited to being the initial component of a 3-or-more component FQDN.
There is no equivalent checking on client certificates.
operation is as if this option selected all hosts.
&*Warning*&: Including a host in &%tls_verify_hosts%& does not require
that connections use TLS.
-Fallback to in-clear communication will be done unless restricted by
+Fallback to in-clear communication will be done unless restricted by
the &%hosts_require_tls%& option.
.option utf8_downconvert smtp integer&!! -1
Note that Dovecot must be configured to use auth-client not auth-userdb.
If you are using Dovecot to authenticate POP/IMAP clients, it might be helpful
to use the same mechanisms for SMTP authentication. This is a server
-authenticator only. There is only one option:
+authenticator only. There is only one non-generic option:
.option server_socket dovecot string unset
dovecot_plain:
driver = dovecot
public_name = PLAIN
+ server_advertise_condition = ${if def:tls_in_cipher}
server_socket = /var/run/dovecot/auth-client
server_set_id = $auth1
server_socket = /var/run/dovecot/auth-client
server_set_id = $auth1
.endd
+
+.new
+&*Note*&: plaintext authentication methods such as PLAIN and LOGIN
+should not be advertised on cleartext SMTP connections.
+See the discussion in section &<<SECTplain_TLS>>&.
+.wen
+
If the SMTP connection is encrypted, or if &$sender_host_address$& is equal to
&$received_ip_address$& (that is, the connection is local), the &"secured"&
option is passed in the Dovecot authentication command. If, for a TLS
(see &<<CHAPTLS>>&).
If an authenticator of this type is configured it is
-run before any SMTP-level communication is done,
+run immediately after a TLS connection being negotiated
+(due to either STARTTLS or TLS-on-connect)
and can authenticate the connection.
-If it does, SMTP authentication is not offered.
+If it does, SMTP authentication is not subsequently offered.
A maximum of one authenticator of this type may be present.
(again depending on the &%tls_cipher%& log selector).
-.subsection "Requesting and verifying client certificates" SECID183
+.subsection "Requesting and verifying client certificates"
.cindex "certificate" "verification of client"
.cindex "TLS" "client certificate verification"
If you want an Exim server to request a certificate when negotiating a TLS
certificate is supplied, &$tls_in_peerdn$& is empty.
-.section "Revoked certificates" "SECID184"
-.cindex "TLS" "revoked certificates"
-.cindex "revocation list"
-.cindex "certificate" "revocation list"
-.cindex "OCSP" "stapling"
-Certificate issuing authorities issue Certificate Revocation Lists (CRLs) when
-certificates are revoked. If you have such a list, you can pass it to an Exim
-server using the global option called &%tls_crl%& and to an Exim client using
-an identically named option for the &(smtp)& transport. In each case, the value
-of the option is expanded and must then be the name of a file that contains a
-CRL in PEM format.
-The downside is that clients have to periodically re-download a potentially huge
-file from every certificate authority they know of.
-
-The way with most moving parts at query time is Online Certificate
-Status Protocol (OCSP), where the client verifies the certificate
-against an OCSP server run by the CA. This lets the CA track all
-usage of the certs. It requires running software with access to the
-private key of the CA, to sign the responses to the OCSP queries. OCSP
-is based on HTTP and can be proxied accordingly.
-
-The only widespread OCSP server implementation (known to this writer)
-comes as part of OpenSSL and aborts on an invalid request, such as
-connecting to the port and then disconnecting. This requires
-re-entering the passphrase each time some random client does this.
-
-The third way is OCSP Stapling; in this, the server using a certificate
-issued by the CA periodically requests an OCSP proof of validity from
-the OCSP server, then serves it up inline as part of the TLS
-negotiation. This approach adds no extra round trips, does not let the
-CA track users, scales well with number of certs issued by the CA and is
-resilient to temporary OCSP server failures, as long as the server
-starts retrying to fetch an OCSP proof some time before its current
-proof expires. The downside is that it requires server support.
-
-Unless Exim is built with the support disabled,
-or with GnuTLS earlier than version 3.3.16 / 3.4.8
-support for OCSP stapling is included.
-
-There is a global option called &%tls_ocsp_file%&.
-The file specified therein is expected to be in DER format, and contain
-an OCSP proof. Exim will serve it as part of the TLS handshake. This
-option will be re-expanded for SNI, if the &%tls_certificate%& option
-contains &`tls_in_sni`&, as per other TLS options.
-
-Exim does not at this time implement any support for fetching a new OCSP
-proof. The burden is on the administrator to handle this, outside of
-Exim. The file specified should be replaced atomically, so that the
-contents are always valid. Exim will expand the &%tls_ocsp_file%& option
-on each connection, so a new file will be handled transparently on the
-next connection.
-
-When built with OpenSSL Exim will check for a valid next update timestamp
-in the OCSP proof; if not present, or if the proof has expired, it will be
-ignored.
-
-For the client to be able to verify the stapled OCSP the server must
-also supply, in its stapled information, any intermediate
-certificates for the chain leading to the OCSP proof from the signer
-of the server certificate. There may be zero or one such. These
-intermediate certificates should be added to the server OCSP stapling
-file named by &%tls_ocsp_file%&.
-
-Note that the proof only covers the terminal server certificate,
-not any of the chain from CA to it.
-
-There is no current way to staple a proof for a client certificate.
-
-.code
- A helper script "ocsp_fetch.pl" for fetching a proof from a CA
- OCSP server is supplied. The server URL may be included in the
- server certificate, if the CA is helpful.
-
- One failure mode seen was the OCSP Signer cert expiring before the end
- of validity of the OCSP proof. The checking done by Exim/OpenSSL
- noted this as invalid overall, but the re-fetch script did not.
-.endd
-
-
-.section "Caching of static server configuration items" "SECTserverTLScache"
+.subsection "Caching of static server configuration items" "SSECTserverTLScache"
.cindex certificate caching
.cindex privatekey caching
.cindex crl caching
The value &"system"& results in no caching under GnuTLS.
The macro _HAVE_TLS_CA_CACHE will be defined if the suffix for "system"
-is acceptable in configurations for the Exim executavble.
+is acceptable in configurations for the Exim executable.
Caching of the system Certificate Authorities bundle can
-save siginificant time and processing on every TLS connection
+save significant time and processing on every TLS connection
accepted by Exim.
The value &"system"& results in no caching under GnuTLS.
The macro _HAVE_TLS_CA_CACHE will be defined if the suffix for "system"
-is acceptable in configurations for the Exim executavble.
+is acceptable in configurations for the Exim executable.
Caching of the system Certificate Authorities bundle can
-save siginificant time and processing on every TLS connection
+save significant time and processing on every TLS connection
initiated by Exim.
0.5.10. (Its presence predates the current API which Exim uses, so if Exim
built, then you have SNI support).
+.subsection ALPN
.cindex TLS ALPN
.cindex ALPN "general information"
.cindex TLS "Application Layer Protocol Names"
The client for the connection proposes a set of protocol names, and
the server responds with a selected one.
It is not, as of 2021, commonly used for SMTP connections.
-However, to guard against misirected or malicious use of web clients
+However, to guard against misdirected or malicious use of web clients
(which often do use ALPN) against MTA ports, Exim by default check that
there is no incompatible ALPN specified by a client for a TLS connection.
If there is, the connection is rejected.
&%tls_alpn%& and &%hosts_require_alpn%&.
There are no variables providing observability.
Some feature-specific logging may appear on denied connections, but this
-depends on the behavious of the peer
+depends on the behaviour of the peer
(not all peers can send a feature-specific TLS Alert).
This feature is available when Exim is built with
user certificates, see the &'General implementation overview'& chapter of the
Open-source PKI book, available online at
&url(https://sourceforge.net/projects/ospkibook/).
+
+
+.subsection "Revoked certificates"
+.cindex "TLS" "revoked certificates"
+.cindex "revocation list"
+.cindex "certificate" "revocation list"
+.cindex "OCSP" "stapling"
+There are three ways for a certificate to be made unusable
+before its expiry.
+
+.ilist
+Certificate issuing authorities issue Certificate Revocation Lists (CRLs) when
+certificates are revoked. If you have such a list, you can pass it to an Exim
+server using the global option called &%tls_crl%& and to an Exim client using
+an identically named option for the &(smtp)& transport. In each case, the value
+of the option is expanded and must then be the name of a file that contains a
+CRL in PEM format.
+The downside is that clients have to periodically re-download a potentially huge
+file from every certificate authority they know of.
+
+.next
+The way with most moving parts at query time is Online Certificate
+Status Protocol (OCSP), where the client verifies the certificate
+against an OCSP server run by the CA. This lets the CA track all
+usage of the certs. It requires running software with access to the
+private key of the CA, to sign the responses to the OCSP queries. OCSP
+is based on HTTP and can be proxied accordingly.
+
+The only widespread OCSP server implementation (known to this writer)
+comes as part of OpenSSL and aborts on an invalid request, such as
+connecting to the port and then disconnecting. This requires
+re-entering the passphrase each time some random client does this.
+
+.next
+The third way is OCSP Stapling; in this, the server using a certificate
+issued by the CA periodically requests an OCSP proof of validity from
+the OCSP server, then serves it up inline as part of the TLS
+negotiation. This approach adds no extra round trips, does not let the
+CA track users, scales well with number of certs issued by the CA and is
+resilient to temporary OCSP server failures, as long as the server
+starts retrying to fetch an OCSP proof some time before its current
+proof expires. The downside is that it requires server support.
+
+Unless Exim is built with the support disabled,
+or with GnuTLS earlier than version 3.3.16 / 3.4.8
+support for OCSP stapling is included.
+
+There is a global option called &%tls_ocsp_file%&.
+The file specified therein is expected to be in DER format, and contain
+an OCSP proof. Exim will serve it as part of the TLS handshake. This
+option will be re-expanded for SNI, if the &%tls_certificate%& option
+contains &`tls_in_sni`&, as per other TLS options.
+
+Exim does not at this time implement any support for fetching a new OCSP
+proof. The burden is on the administrator to handle this, outside of
+Exim. The file specified should be replaced atomically, so that the
+contents are always valid. Exim will expand the &%tls_ocsp_file%& option
+on each connection, so a new file will be handled transparently on the
+next connection.
+
+When built with OpenSSL Exim will check for a valid next update timestamp
+in the OCSP proof; if not present, or if the proof has expired, it will be
+ignored.
+
+For the client to be able to verify the stapled OCSP the server must
+also supply, in its stapled information, any intermediate
+certificates for the chain leading to the OCSP proof from the signer
+of the server certificate. There may be zero or one such. These
+intermediate certificates should be added to the server OCSP stapling
+file named by &%tls_ocsp_file%&.
+
+Note that the proof only covers the terminal server certificate,
+not any of the chain from CA to it.
+
+There is no current way to staple a proof for a client certificate.
+
+.code
+ A helper script "ocsp_fetch.pl" for fetching a proof from a CA
+ OCSP server is supplied. The server URL may be included in the
+ server certificate, if the CA is helpful.
+
+ One failure mode seen was the OCSP Signer cert expiring before the end
+ of validity of the OCSP proof. The checking done by Exim/OpenSSL
+ noted this as invalid overall, but the re-fetch script did not.
+.endd
+.endlist
+
+
.ecindex IIDencsmtp1
.ecindex IIDencsmtp2
for every possible target server. It also scales (slightly) better than having to maintain on an SMTP
client a copy of the standard CAs bundle. It also means not having to pay a CA for certificates.
-DANE requires a server operator to do three things: 1) run DNSSEC. This provides assurance to clients
+DANE requires a server operator to do three things:
+.olist
+Run DNSSEC. This provides assurance to clients
that DNS lookups they do for the server have not been tampered with. The domain MX record applying
to this server, its A record, its TLSA record and any associated CNAME records must all be covered by
DNSSEC.
-2) add TLSA DNS records. These say what the server certificate for a TLS connection should be.
-3) offer a server certificate, or certificate chain, in TLS connections which is is anchored by one of the TLSA records.
+.next
+Add TLSA DNS records. These say what the server certificate for a TLS connection should be.
+.next
+Offer a server certificate, or certificate chain, in TLS connections which is is anchored by one of the TLSA records.
+.endlist
There are no changes to Exim specific to server-side operation of DANE.
Support for client-side operation of DANE can be included at compile time by defining SUPPORT_DANE=yes
in &_Local/Makefile_&.
If it has been included, the macro "_HAVE_DANE" will be defined.
+.subsection "DNS records"
A TLSA record consist of 4 fields, the "Certificate Usage", the
"Selector", the "Matching type", and the "Certificate Association Data".
For a detailed description of the TLSA record see
This means no MD5 and no SHA-1. SHA2-256 is the minimum for reliable
interoperability (and probably the maximum too, in 2018).
+.subsection "Interaction with OCSP"
The use of OCSP-stapling should be considered, allowing for fast revocation of certificates (which would otherwise
be limited by the DNS TTL on the TLSA records). However, this is likely to only be usable with DANE-TA. NOTE: the
default of requesting OCSP for all hosts is modified iff DANE is in use, to:
those who use &%hosts_require_ocsp%&, should consider the interaction with DANE in their OCSP settings.
+.subsection "Client configuration"
For client-side DANE there are three new smtp transport options, &%hosts_try_dane%&, &%hosts_require_dane%&
and &%dane_require_tls_ciphers%&.
The &"require"& variant will result in failure if the target host is not
The router and transport option &%dnssec_request_domains%& must not be
set to &"never"&, and &%dnssec_require_domains%& is ignored.
+.subsection Observability
If verification was successful using DANE then the "CV" item in the delivery log line will show as "CV=dane".
There is a new variable &$tls_out_dane$& which will have "yes" if
The &$event_data$& will be one of the Result Types defined in
Section 4.3 of that document.
+.subsection General
Under GnuTLS, DANE is only supported from version 3.0.0 onwards.
DANE is specified in published RFCs and decouples certificate authority trust
selection from a "race to the bottom" of "you must trust everything for mail
-to get through". There is an alternative technology called MTA-STS, which
+to get through".
+There is an alternative technology called MTA-STS, which
instead publishes MX trust anchor information on an HTTPS website. At the
time this text was last updated, MTA-STS was still a draft, not yet an RFC.
Exim has no support for MTA-STS as a client, but Exim mail server operators
the message override the banner message that is otherwise specified by the
&%smtp_banner%& option.
-For tls-on-connect connections, the ACL is run after the TLS connection
-is accepted (however, &%host_reject_connection%& is tested before).
+.new
+For tls-on-connect connections, the ACL is run before the TLS connection
+is accepted; if the ACL does not accept then the TCP connection is dropped without
+any TLS startup attempt and without any SMTP response being transmitted.
+.wen
.subsection "The EHLO/HELO ACL" SECID192
The text in a &%message%& modifier is literal; any quotes are taken as
literals, but because the string is expanded, backslash escapes are processed
-anyway. If the message contains newlines, this gives rise to a multi-line SMTP
+anyway.
+If the message contains newlines, this gives rise to a multi-line SMTP
response.
+A long message line will also be split into multi-line SMTP responses,
+on word boundaries if possible.
.vindex "&$acl_verify_message$&"
While the text is being expanded, the &$acl_verify_message$& variable
immediate writes to file are done as normal.
trigger=<&'reason'&> This option selects cause for the pretrigger buffer
- see above) to be copied to file. A reason of $*now*
+ see above) to be copied to file. A reason of &*now*&
take effect immediately; one of &*paniclog*& triggers
on a write to the panic log.
.endd
.vitem &*control&~=&~fakedefer/*&<&'message'&>
.cindex "fake defer"
.cindex "defer, fake"
+.cindex fakedefer
This control works in exactly the same way as &%fakereject%& (described below)
except that it causes an SMTP 450 response after the message data instead of a
550 response. You must take care when using &%fakedefer%& because it causes the
.vitem &*control&~=&~fakereject/*&<&'message'&>
.cindex "fake rejection"
.cindex "rejection, fake"
+.cindex fakereject
This control is permitted only for the MAIL, RCPT, and DATA ACLs, in other
words, only when an SMTP message is being received. If Exim accepts the
message, instead the final 250 response, a 550 rejection message is sent.
DATA, MIME or DKIM ACLs for a message delivered by cutthrough routing.
More than one header can be removed at the same time by using a colon separated
-list of header names. The header matching is case insensitive. Wildcards are
-not permitted, nor is list expansion performed, so you cannot use hostlists to
+list of header specifiers.
+.new
+If a specifier does not start with a circumflex (^)
+then it is treated as a header name.
+The header name matching is case insensitive.
+If it does, then it is treated as a (front-anchored)
+regular expression applied to the whole header.
+
+&*Note*&: The colon terminating a header name will need to be doubled
+if used in an RE, and there can legitimately be whitepace before it.
+
+Example:
+.code
+remove_header = \N^(?i)Authentication-Results\s*::\s*example.org;\N
+.endd
+.wen
+
+List expansion is not performed, so you cannot use hostlists to
create a list of headers, however both connection and message variable expansion
are performed (&%$acl_c_*%& and &%$acl_m_*%&), illustrated in this example:
.code
warn message = Remove internal headers
remove_header = $acl_c_ihdrs
.endd
-Header names for removal are accumulated during the MAIL, RCPT, and predata ACLs.
+Header specifiers for removal are accumulated during the MAIL, RCPT, and predata ACLs.
Matching header lines are removed from the message before processing the DATA and MIME ACLs.
If multiple header lines match, all are removed.
There is no harm in attempting to remove the same header twice nor in removing
-a non-existent header. Further header lines to be removed may be accumulated
-during the DATA and MIME ACLs, after which they are removed from the message,
-if present. In the case of non-SMTP messages, headers to be removed are
-accumulated during the non-SMTP ACLs, and are removed from the message after
+a non-existent header. Further header specifiers for removal may be accumulated
+during the DATA and MIME ACLs, after which matching headers are removed
+if present. In the case of non-SMTP messages, remove specifiers are
+accumulated during the non-SMTP ACLs, and are acted on after
all the ACLs have run. If a message is rejected after DATA or by the non-SMTP
ACL, there really is no effect because there is no logging of what headers
would have been removed.
The &%seen%& ACL condition can be used to test whether a
situation has been previously met.
It uses a hints database to record a timestamp against a key.
-host. The syntax of the condition is:
+The syntax of the condition is:
.display
&`seen =`& <&'optional flag'&><&'time interval'&> &`/`& <&'options'&>
.endd
.subsection "Ratelimit options for what is being measured" ratoptmea
.cindex "rate limiting" "per_* options"
-The &%per_conn%& option limits the client's connection rate. It is not
+.vlist
+.vitem per_conn
+.cindex "rate limiting" per_conn
+This option limits the client's connection rate. It is not
normally used in the &%acl_not_smtp%&, &%acl_not_smtp_mime%&, or
&%acl_not_smtp_start%& ACLs.
-The &%per_mail%& option limits the client's rate of sending messages. This is
+.vitem per_mail
+.cindex "rate limiting" per_conn
+This option limits the client's rate of sending messages. This is
the default if none of the &%per_*%& options is specified. It can be used in
&%acl_smtp_mail%&, &%acl_smtp_rcpt%&, &%acl_smtp_predata%&, &%acl_smtp_mime%&,
&%acl_smtp_data%&, or &%acl_not_smtp%&.
-The &%per_byte%& option limits the sender's email bandwidth. It can be used in
+.vitem per_byte
+.cindex "rate limiting" per_conn
+This option limits the sender's email bandwidth. It can be used in
the same ACLs as the &%per_mail%& option, though it is best to use this option
in the &%acl_smtp_mime%&, &%acl_smtp_data%& or &%acl_not_smtp%& ACLs; if it is
used in an earlier ACL, Exim relies on the SIZE parameter given by the client
follow the limit &'m'& in the configuration with K, M, or G to specify limits
in kilobytes, megabytes, or gigabytes, respectively.
-The &%per_rcpt%& option causes Exim to limit the rate at which recipients are
+.vitem per_rcpt
+.cindex "rate limiting" per_rcpt
+This option causes Exim to limit the rate at which recipients are
accepted. It can be used in the &%acl_smtp_rcpt%&, &%acl_smtp_predata%&,
&%acl_smtp_mime%&, or &%acl_smtp_data%& ACLs. In
&%acl_smtp_rcpt%& the rate is updated one recipient at a time; in the other
in either case the rate limiting engine will see a message with many
recipients as a large high-speed burst.
-The &%per_addr%& option is like the &%per_rcpt%& option, except it counts the
+.vitem per_addr
+.cindex "rate limiting" per_addr
+This option is like the &%per_rcpt%& option, except it counts the
number of different recipients that the client has sent messages to in the
last time period. That is, if the client repeatedly sends messages to the same
recipient, its measured rate is not increased. This option can only be used in
&%acl_smtp_rcpt%&.
-The &%per_cmd%& option causes Exim to recompute the rate every time the
+.vitem per_cmd
+.cindex "rate limiting" per_cmd
+This option causes Exim to recompute the rate every time the
condition is processed. This can be used to limit the rate of any SMTP
command. If it is used in multiple ACLs it can limit the aggregate rate of
multiple different commands.
-The &%count=%& option can be used to alter how much Exim adds to the client's
-measured rate. For example, the &%per_byte%& option is equivalent to
-&`per_mail/count=$message_size`&. If there is no &%count=%& option, Exim
+.vitem count
+.cindex "rate limiting" count
+This option can be used to alter how much Exim adds to the client's
+measured rate.
+A value is required, after an equals sign.
+For example, the &%per_byte%& option is equivalent to
+&`per_mail/count=$message_size`&.
+If there is no &%count=%& option, Exim
increases the measured rate by one (except for the &%per_rcpt%& option in ACLs
-other than &%acl_smtp_rcpt%&). The count does not have to be an integer.
+other than &%acl_smtp_rcpt%&).
+The count does not have to be an integer.
-The &%unique=%& option is described in section &<<ratoptuniq>>& below.
+.vitem unique
+.cindex "rate limiting" unique
+This option is described in section &<<ratoptuniq>>& below.
+.endlist
.subsection "Ratelimit update modes" ratoptupd
is done. If a message fails to be completely delivered at the first attempt,
the system filter is run again at the start of every retry.
If you want your filter to do something only once per message, you can make use
+.cindex retry condition
of the &%first_delivery%& condition in an &%if%& command in the filter to
prevent it happening on retries.
.display
&`A `& authenticator name (and optional id and sender)
&`C `& SMTP confirmation on delivery
+&`Ci `& connection identifier
&` `& command list for &"no mail in SMTP session"&
&`CV `& certificate verification status
&`D `& duration of &"no mail in SMTP session"&
.section "Reducing or increasing what is logged" "SECTlogselector"
.cindex "log" "selectors"
By setting the &%log_selector%& global option, you can disable some of Exim's
-default logging, or you can request additional logging. The value of
+default logging to the main log, or you can request additional logging. The value of
&%log_selector%& is made up of names preceded by plus or minus characters. For
example:
.code
.irow &`address_rewrite`& "address rewriting"
.irow &`all_parents`& "all parents in => lines"
.irow &`arguments`& "command line arguments"
+.irow &`connection_id`& "connection identifier"
.irow &`connection_reject`& * "connection rejections"
.irow &`delay_delivery`& * "immediate delivery delayed"
.irow &`deliver_time`& "time taken to attempt delivery"
.irow &`etrn`& * "ETRN commands"
.irow &`host_lookup_failed`& * "as it says"
.irow &`ident_timeout`& "timeout for ident connection"
-.irow &`incoming_interface`& "local interface on <= and => lines"
+.irow &`incoming_interface`& "local interface & port on <= and => lines"
.irow &`incoming_port`& "remote port on <= lines"
.irow &`lost_incoming_connection`& * "as it says (includes timeouts)"
.irow &`millisec`& "millisecond timestamps and RT,QT,DT,D times"
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"
+.new
+&%connection_identifier%&: 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.
+.wen
+.next
.cindex "log" "connection rejections"
&%connection_reject%&: A log entry is written whenever an incoming SMTP
connection is rejected, for whatever reason.
.irow &<<SECTtidydb>>& &'exim_tidydb'& "clean up a hints database"
.irow &<<SECTfixdb>>& &'exim_fixdb'& "patch a hints database"
.irow &<<SECTmailboxmaint>>& &'exim_lock'& "lock a mailbox file"
+.irow &<<SECTexim_msgdate>>& &'exim_msgdate'& "Message Ids for humans (exim_msgdate)"
.endtable
Another utility that might be of use to sites with many MTAs is Tom Kistner's
.next
Limiting the concurrency of specific transports (when &%max_parallel%& is set
in a transport)
+.next
+Recording EHLO-time facilities advertised by hosts
.endlist
.endd
Note that if a command is supplied, it must be entirely contained within the
second argument &-- hence the quotes.
-.ecindex IIDutils
+.section "Message Ids for humans (exim_msgdate)" "SECTexim_msgdate"
+.cindex "exim_msgdate"
+The &'exim_msgdate'& utility is written by Andrew Aitchison and included in the Exim distribution.
+This Perl script converts an Exim Mesage ID back into a human readable form.
+For details of &'exim_msgdate'&'s options, run &'exim_msgdate'& with the &%--help%& option.
+
+Section &<<SECTmessiden>>& (Message identification) describes Exim Mesage IDs.
+.ecindex IIDutils
. ////////////////////////////////////////////////////////////////////////////
. ////////////////////////////////////////////////////////////////////////////
# one, plus the max_rcpt and return_path options
remote_forwarded_smtp:
driver = smtp
- # modify the envelope from, for mails that we forward
+ # single-recipient so that $original_domain is valid
max_rcpt = 1
+ # modify the envelope from, for mails that we forward
return_path = ${srs_encode {SRS_SECRET} {$return_path} {$original_domain}}
.endd
.subsection ACL SSECDMARCACL
.cindex DMARC "ACL condition"
-DMARC checks cam be run on incoming SMTP messages by using the
+DMARC checks can be run on incoming SMTP messages by using the
&"dmarc_status"& ACL condition in the DATA ACL. You are required to
call the &"spf"& condition first in the ACLs, then the &"dmarc_status"&
condition. Putting this condition in the ACLs is required in order
git://git.exim.org / exim.git / blobdiff