. Update the Copyright year (only) when changing content.
. /////////////////////////////////////////////////////////////////////////////
-.set previousversion "4.92"
+.set previousversion "4.93"
.include ./local_params
.set ACL "access control lists (ACLs)"
.set I " "
.macro copyyear
-2018
+2020
.endmacro
. /////////////////////////////////////////////////////////////////////////////
.section "Exim documentation" "SECID1"
. Keep this example change bar when updating the documentation!
+.new
.cindex "documentation"
This edition of the Exim specification applies to version &version() of Exim.
Substantive changes from the &previousversion; edition are marked in some
renditions of this document; this paragraph is so marked if the rendition is
capable of showing a change indicator.
+.wen
This document is very much a reference manual; it is not a tutorial. The reader
is expected to have some familiarity with the SMTP mail transfer protocol and
of domains that it defines.
.next
.vindex "&$local_part_prefix$&"
+.vindex "&$local_part_prefix_v$&"
.vindex "&$local_part$&"
.vindex "&$local_part_suffix$&"
+.vindex "&$local_part_suffix_v$&"
.cindex affix "router precondition"
If the &%local_parts%& option is set, the local part of the address must be in
the set of local parts that it defines. If &%local_part_prefix%& or
&%local_part_suffix%& is in use, the prefix or suffix is removed from the local
part before this check. If you want to do precondition tests on local parts
that include affixes, you can do so by using a &%condition%& option (see below)
-that uses the variables &$local_part$&, &$local_part_prefix$&, and
-&$local_part_suffix$& as necessary.
+.new
+that uses the variables &$local_part$&, &$local_part_prefix$&,
+&$local_part_prefix_v$&, &$local_part_suffix$&
+and &$local_part_suffix_v$& as necessary.
+.wen
.next
.vindex "&$local_user_uid$&"
.vindex "&$local_user_gid$&"
.section "Including TLS/SSL encryption support" "SECTinctlsssl"
.cindex "TLS" "including support for TLS"
.cindex "encryption" "including support for"
-.cindex "SUPPORT_TLS"
.cindex "OpenSSL" "building Exim with"
.cindex "GnuTLS" "building Exim with"
-Exim can be built to support encrypted SMTP connections, using the STARTTLS
-command as per RFC 2487. It can also support legacy clients that expect to
+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
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).
OpenSSL or GnuTLS library. There is no cryptographic code in Exim itself for
implementing SSL.
+If you do not want TLS support you should set
+.code
+DISABLE_TLS=yes
+.endd
+in &_Local/Makefile_&.
+
If OpenSSL is installed, you should set
.code
-SUPPORT_TLS=yes
+USE_OPENSL=yes
TLS_LIBS=-lssl -lcrypto
.endd
in &_Local/Makefile_&. You may also need to specify the locations of the
OpenSSL library and include files. For example:
.code
-SUPPORT_TLS=yes
+USE_OPENSSL=yes
TLS_LIBS=-L/usr/local/openssl/lib -lssl -lcrypto
TLS_INCLUDE=-I/usr/local/openssl/include/
.endd
.cindex "pkg-config" "OpenSSL"
If you have &'pkg-config'& available, then instead you can just use:
.code
-SUPPORT_TLS=yes
+USE_OPENSSL=yes
USE_OPENSSL_PC=openssl
.endd
.cindex "USE_GNUTLS"
If GnuTLS is installed, you should set
.code
-SUPPORT_TLS=yes
USE_GNUTLS=yes
TLS_LIBS=-lgnutls -ltasn1 -lgcrypt
.endd
in &_Local/Makefile_&, and again you may need to specify the locations of the
library and include files. For example:
.code
-SUPPORT_TLS=yes
USE_GNUTLS=yes
TLS_LIBS=-L/usr/gnu/lib -lgnutls -ltasn1 -lgcrypt
TLS_INCLUDE=-I/usr/gnu/include
.cindex "pkg-config" "GnuTLS"
If you have &'pkg-config'& available, then instead you can just use:
.code
-SUPPORT_TLS=yes
USE_GNUTLS=yes
USE_GNUTLS_PC=gnutls
.endd
by Exim in conjunction with the &%-MC%& option. It signifies that the
remote host supports the ESMTP &_DSN_& extension.
+.new
+.vitem &%-MCd%&
+.oindex "&%-MCd%&"
+This option is not intended for use by external callers. It is used internally
+by Exim in conjunction with the &%-d%& option
+to pass on an information string on the purpose of the process.
+.wen
+
.vitem &%-MCG%&&~<&'queue&~name'&>
.oindex "&%-MCG%&"
This option is not intended for use by external callers. It is used internally
.oindex "&%-MCS%&"
This option is not intended for use by external callers. It is used internally
by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
-SMTP SIZE option should be used on messages delivered down the existing
+ESMTP SIZE option should be used on messages delivered down the existing
connection.
.vitem &%-MCT%&
Bounce messages are just discarded. This option can be used only by an admin
user.
+.vitem &%-MG%&&~<&'queue&~name'&>&~<&'message&~id'&>&~<&'message&~id'&>&~...
+.oindex "&%-MG%&"
+.cindex queue named
+.cindex "named queues" "moving messages"
+.cindex "queue" "moving messages"
+This option requests that each listed message be moved from its current
+queue to the given named queue.
+The destination queue name argument is required, but can be an empty
+string to define the default queue.
+If the messages are not currently located in the default queue,
+a &%-qG<name>%& option will be required to define the source queue.
+
.vitem &%-Mmad%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
.oindex "&%-Mmad%&"
.cindex "delivery" "cancelling all"
.vitem &%-odqs%&
.oindex "&%-odqs%&"
.cindex "SMTP" "delaying delivery"
+.cindex "first pass routing"
This option is a hybrid between &%-odb%&/&%-odi%& and &%-odq%&.
However, like &%-odb%& and &%-odi%&, this option has no effect if
&%queue_only_override%& is false and one of the queueing options in the
without &%-bd%&, this is the only way of causing Exim to write a pid file,
because in those cases, the normal pid file is not used.
+.new
+.vitem &%-oPX%&
+.oindex "&%-oPX%&"
+.cindex "pid (process id)" "of daemon"
+.cindex "daemon" "process id (pid)"
+This option is not intended for general use.
+The daemon uses it when terminating due to a SIGTEM, possibly in
+combination with &%-oP%&&~<&'path'&>.
+It causes the pid file to be removed.
+.wen
+
.vitem &%-or%&&~<&'time'&>
.oindex "&%-or%&"
.cindex "timeout" "for non-SMTP input"
.cindex "queue" "double scanning"
.cindex "queue" "routing"
.cindex "routing" "whole queue before delivery"
+.cindex "first pass routing"
An option starting with &%-qq%& requests a two-stage queue run. In the first
stage, the queue is scanned as if the &%queue_smtp_domains%& option matched
every domain. Addresses are routed, local deliveries happen, but no remote
transports are run.
+.new
+Performance will be best if the &%queue_run_in_order%& option is false.
+.wen
+
.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
.vitem &%-q[q][i][f[f]][l][G<name>[/<time>]]]%&
.oindex "&%-qG%&"
.cindex queue named
-.cindex "named queues"
+.cindex "named queues" "deliver from"
.cindex "queue" "delivering specific messages"
If the &'G'& flag and a name is present, the queue runner operates on the
queue with the given name rather than the default queue.
input and output (that is, not using TCP/IP). A number of MUAs operate in this
manner.
.code
-deny message = Restricted characters in address
- domains = +local_domains
+deny domains = +local_domains
local_parts = ^[.] : ^.*[@%!/|]
+ message = Restricted characters in address
-deny message = Restricted characters in address
- domains = !+local_domains
+deny domains = !+local_domains
local_parts = ^[./|] : ^.*[@%!] : ^.*/\\.\\./
+ message = Restricted characters in address
.endd
These statements are concerned with local parts that contain any of the
characters &"@"&, &"%"&, &"!"&, &"/"&, &"|"&, or dots in unusual places.
This statement requires the recipient address to be verified; if verification
fails, the address is rejected.
.code
-# deny message = rejected because $sender_host_address \
+# deny dnslists = black.list.example
+# message = rejected because $sender_host_address \
# is in a black list at $dnslist_domain\n\
# $dnslist_text
-# dnslists = black.list.example
#
# warn dnslists = black.list.example
# add_header = X-Warning: $sender_host_address is in \
remote_smtp:
driver = smtp
message_size_limit = ${if > {$max_received_linelength}{998} {1}{0}}
-.ifdef _HAVE_DANE
- dnssec_request_domains = *
- hosts_try_dane = *
-.endif
.ifdef _HAVE_PRDR
hosts_try_prdr = *
.endif
This transport is used for delivering messages over SMTP connections.
The list of remote hosts comes from the router.
The &%message_size_limit%& usage is a hack to avoid sending on messages
-with over-long lines. The built-in macro _HAVE_DANE guards configuration
-to try to use DNSSEC for all queries and to use DANE for delivery;
-see section &<<SECDANE>>& for more details.
+with over-long lines.
The &%hosts_try_prdr%& option enables an efficiency SMTP option. It is
negotiated between client and server and not expected to cause problems
.code
local_delivery:
driver = appendfile
- file = /var/mail/$local_part
+ file = /var/mail/$local_part_data
delivery_date_add
envelope_to_add
return_path_add
# mode = 0660
.endd
This &(appendfile)& transport is used for local delivery to user mailboxes in
-traditional BSD mailbox format. By default it runs under the uid and gid of the
+traditional BSD mailbox format.
+
+.new
+We prefer to avoid using &$local_part$& directly to define the mailbox filename,
+as it is provided by a potential bad actor.
+Instead we use &$local_part_data$&,
+the result of looking up &$local_part$& in the user database
+(done by using &%check_local_user%& in the the router).
+.wen
+
+By default &(appendfile)& runs under the uid and gid of the
local user, which requires the sticky bit to be set on the &_/var/mail_&
directory. Some systems use the alternative approach of running mail deliveries
under a particular group instead of using the sticky bit. The commented options
.endd
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"
+The result of the expansion is not tainted.
In the second example, the lookup is a single item in a domain list. It causes
Exim to use a lookup to see if the domain that is being processed can be found
first &%domains%& setting above generates the second setting, which therefore
causes a second lookup to occur.
+.new
+The lookup type may optionally be followed by a comma
+and a comma-separated list of options.
+Each option is a &"name=value"& pair.
+Whether an option is meaningful depands on the lookup type.
+.wen
+
The rest of this chapter describes the different lookup types that are
available. Any of them can be used in any part of the configuration where a
lookup is permitted.
The &'single-key'& type requires the specification of a file in which to look,
and a single key to search for. The key must be a non-empty string for the
lookup to succeed. The lookup type determines how the file is searched.
+.new
+.cindex "tainted data" "single-key lookups"
+The file string may not be tainted
+
+.cindex "tainted data" "de-tainting"
+All single-key lookups support the option &"ret=key"&.
+If this is given and the lookup
+(either underlying implementation or cached value)
+returns data, the result is replaced with a non-tainted
+version of the lookup key.
+.wen
.next
.cindex "query-style lookup" "definition of"
The &'query-style'& type accepts a generalized database query. No particular
tools for building the files can be found in several places:
.display
&url(https://cr.yp.to/cdb.html)
-&url(http://www.corpit.ru/mjt/tinycdb.html)
+&url(https://www.corpit.ru/mjt/tinycdb.html)
&url(https://packages.debian.org/stable/utils/freecdb)
&url(https://github.com/philpennock/cdbtools) (in Go)
.endd
-. --- 2018-09-07: corpit.ru http:-only
A cdb distribution is not needed in order to build Exim with cdb support,
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
.next
.cindex "lookup" "dsearch"
.cindex "dsearch lookup type"
-&(dsearch)&: The given file must be a directory; 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. If &[lstat()]& succeeds, the result of
-the lookup is the name of the entry, which may be a file, directory,
-symbolic link, or any other kind of directory entry. An example of how this
+&(dsearch)&: The given file must be an
+.new
+absolute
+.wen
+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.
+If &[lstat()]& succeeds then so does the lookup.
+.new
+.cindex "tainted data" "dsearch result"
+The result is regarded as untainted.
+
+Options for the lookup can be given by appending them after the word "dsearch",
+separated by a comma. Options, if present, are a comma-separated list having
+each element starting with a tag name and an equals.
+
+Two options are supported, for the return value and for filtering match
+candidates.
+The "ret" option requests an alternate result value of
+the entire path for the entry. Example:
+.code
+${lookup {passwd} dsearch,ret=full {/etc}}
+.endd
+The default result is just the requested entry.
+The "filter" option requests that only directory entries of a given type
+are matched. The match value is one of "file", "dir" or "subdir" (the latter
+not matching "." or ".."). Example:
+.code
+${lookup {passwd} dsearch,filter=file {/etc}}
+.endd
+The default matching is for any entry type, including directories
+and symlinks.
+.wen
+
+An example of how this
lookup can be used to support virtual domains is given in section
&<<SECTvirtualdomains>>&.
.next
the implicit key is the host's IP address rather than its name (see section
&<<SECThoslispatsikey>>&).
-.new
&*Warning 3*&: Do not use an IPv4-mapped IPv6 address for a key; use the
IPv4, in dotted-quad form. (Exim converts IPv4-mapped IPv6 addresses to this
notation before executing the lookup.)
-.wen
.next
-.new
.cindex lookup json
.cindex json "lookup type"
.cindex JSON expansions
nunbered array element is selected.
Otherwise it must apply to a JSON object; the named element is selected.
The final resulting element can be a simple JSON type or a JSON object
-or array; for the latter two a string-representation os the JSON
+or array; for the latter two a string-representation of the JSON
is returned.
For elements of type string, the returned value is de-quoted.
-.wen
.next
.cindex "linear search"
.cindex "lookup" "lsearch"
lookup types support only literal keys.
.next
+.cindex "spf lookup type"
.cindex "lookup" "spf"
-If Exim is built with SPF support, manual lookups can be done
-(as opposed to the standard ACL condition method.
+&(spf)&: 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
.next
.cindex "sqlite lookup type"
.cindex "lookup" "sqlite"
-&(sqlite)&: The format of the query is a filename followed by an SQL statement
+&(sqlite)&: The format of the query is
+new
+an optional filename
+.wen
+followed by an SQL statement
that is passed to an SQLite database. See section &<<SECTsqlite>>&.
.next
With &"strict"& a response from the DNS resolver that
is not labelled as authenticated data
is treated as equivalent to a temporary DNS error.
-The default is &"never"&.
+The default is &"lax"&.
See also the &$lookup_dnssec_authenticated$& variable.
or &%redis_servers%&
option (as appropriate) must be set to a colon-separated list of server
information.
+.oindex &%mysql_servers%&
+.oindex &%pgsql_servers%&
+.oindex &%oracle_servers%&
+.oindex &%ibase_servers%&
+.oindex &%redis_servers%&
(For MySQL and PostgreSQL, the global option need not be set if all
queries contain their own server information &-- see section
&<<SECTspeserque>>&.)
escapes whitespace and backslash characters with a backslash.
.section "Specifying the server in the query" "SECTspeserque"
+.new
For MySQL, PostgreSQL and Redis lookups (but not currently for Oracle and InterBase),
it is possible to specify a list of servers with an individual query. This is
-done by starting the query with
+done by appending a comma-separated option to the query type:
.display
-&`servers=`&&'server1:server2:server3:...'&&`;`&
+&`,servers=`&&'server1:server2:server3:...'&
.endd
+.wen
Each item in the list may take one of two forms:
.olist
If it contains no slashes it is assumed to be just a host name. The appropriate
.endd
In an updating lookup, you could then write:
.code
-${lookup mysql{servers=master; UPDATE ...} }
+${lookup mysql,servers=master {UPDATE ...} }
.endd
That query would then be sent only to the master server. If, on the other hand,
the master is not to be used for reading, and so is not present in the global
option, you can still update it by a query of this form:
.code
-${lookup pgsql{servers=master/db/name/pw; UPDATE ...} }
+${lookup pgsql,servers=master/db/name/pw {UPDATE ...} }
.endd
+.new
+An older syntax places the servers speciification before the qury,
+semicolon separated:
+.code
+${lookup mysql{servers=master; UPDATE ...} }
+.endd
+The new version avoids potential issues with tainted
+arguments in the query, for explicit expansion.
+&*Note*&: server specifications in list-style lookups are still problematic.
+.wen
+
.section "Special MySQL features" "SECID73"
For MySQL, an empty host name or the use of &"localhost"& in &%mysql_servers%&
.cindex "sqlite lookup type"
SQLite is different to the other SQL lookups because a filename is required in
addition to the SQL query. An SQLite database is a single file, and there is no
-daemon as in the other SQL databases. The interface to Exim requires the name
-of the file, as an absolute path, to be given at the start of the query. It is
-separated from the query by white space. This means that the path name cannot
-contain white space. Here is a lookup expansion example:
+daemon as in the other SQL databases.
+
+.new
+.oindex &%sqlite_dbfile%&
+The preferred way of specifying the file is by using the
+&%sqlite_dbfile%& option, set to
+an absolute path.
+.wen
+A deprecated method is available, prefixing the query with the filename
+separated by white space.
+This means that the path name cannot contain white space.
+.cindex "tainted data" "sqlite file"
+It also means that the query cannot use any tainted values, as that taints
+the entire query including the filename - resulting in a refusal to open
+the file.
+
+.new
+Here is a lookup expansion example:
.code
-${lookup sqlite {/some/thing/sqlitedb \
- select name from aliases where id='userx';}}
+sqlite_dbfile = /some/thing/sqlitedb
+...
+${lookup sqlite {select name from aliases where id='userx';}}
.endd
In a list, the syntax is similar. For example:
.code
-domainlist relay_to_domains = sqlite;/some/thing/sqlitedb \
+domainlist relay_to_domains = sqlite;\
select * from relays where ip='$sender_host_address';
.endd
+.wen
The only character affected by the &%quote_sqlite%& operator is a single
quote, which it doubles.
+.new
+.section "Results of list checking" SECTlistresults
+The primary result of doing a list check is a truth value.
+In some contexts additional information is stored
+about the list element that matched:
+.vlist
+.vitem hosts
+A &%hosts%& ACL condition
+will store a result in the &$host_data$& variable.
+.vitem local_parts
+A &%local_parts%& router option or &%local_parts%& ACL condition
+will store a result in the &$local_part_data$& variable.
+.vitem domains
+A &%domains%& router option or &%domains%& ACL condition
+.vitem senders
+A &%senders%& router option or &%senders%& ACL condition
+will store a result in the &$sender_data$& variable.
+.vitem recipients
+A &%recipients%& ACL condition
+will store a result in the &$recipient_data$& variable.
+.endlist
+
+The detail of the additional information depends on the
+type of match and is given below as the &*value*& information.
+.wen
+
+
+
+
.section "Named lists" "SECTnamedlists"
.cindex "named lists"
.cindex "list" "named"
where &'x.y'& does not match. It's best to avoid negation altogether in
referenced lists if you can.
+.new
+.cindex "hiding named list values"
+.cindex "named lists" "hiding value of"
+Some named list definitions may contain sensitive data, for example, passwords for
+accessing databases. To stop non-admin users from using the &%-bP%& command
+line option to read these values, you can precede the definition with the
+word &"hide"&. For example:
+.code
+hide domainlist filter_for_domains = ldap;PASS=secret ldap::/// ...
+.endd
+.wen
+
+
Named lists may have a performance advantage. When Exim is routing an
address or checking an incoming message, it caches the result of tests on named
lists. So, if you have a setting such as
as set by the &%primary_hostname%& option (or defaulted). This makes it
possible to use the same configuration file on several different hosts that
differ only in their names.
+
+.new
+The value for a match will be the primary host name.
+.wen
+
+
.next
.cindex "@[] in a domain list"
.cindex "domain list" "matching local IP interfaces"
only if that IP address is recognized as local for email routing purposes. The
&%local_interfaces%& and &%extra_local_interfaces%& options can be used to
control which of a host's several IP addresses are treated as local.
-In today's Internet, the use of domain literals is controversial.
+In today's Internet, the use of domain literals is controversial;
+see the &%allow_domain_literals%& main option.
+
+.new
+The value for a match will be the string &`@[]`&.
+.wen
+
+
.next
.cindex "@mx_any"
.cindex "@mx_primary"
domains = <? @mx_any/ignore=<;127.0.0.1;::1 ? \
an.other.domain ? ...
.endd
+.new
+The value for a match will be the list element string (starting &`@mx_`&).
+.wen
+
+
.next
.cindex "asterisk" "in domain list"
.cindex "domain list" "asterisk in"
list item such as &`*key.ex`& matches &'donkey.ex'& as well as
&'cipher.key.ex'&.
+.new
+The value for a match will be the list element string (starting with the asterisk).
+Additionally, &$0$& will be set to the matched string
+and &$1$& to the variable portion which the asterisk matched.
+.wen
+
.next
.cindex "regular expressions" "in domain list"
.cindex "domain list" "matching regular expression"
use the special &`\N`& sequence (see chapter &<<CHAPexpand>>&) to specify that
it is not to be expanded (unless you really do want to build a regular
expression by expansion, of course).
+
+.new
+The value for a match will be the list element string (starting with the circumflex).
+Additionally, &$0$& will be set to the string matching the regular expression,
+and &$1$& (onwards) to any submatches identified by parentheses.
+.wen
+
+
+
.next
.cindex "lookup" "in domain list"
.cindex "domain list" "matching by lookup"
domains = cdb;/etc/mail/local_domains.cdb
.endd
The appropriate type of lookup is done on the file using the domain name as the
-key. In most cases, the data that is looked up is not used; Exim is interested
+key. In most cases, the value resulting from the lookup is not used; Exim is interested
only in whether or not the key is present in the file. However, when a lookup
is used for the &%domains%& option on a router
-or a &%domains%& condition in an ACL statement, the data is preserved in the
+or a &%domains%& condition in an ACL statement, the value is preserved in the
&$domain_data$& variable and can be referred to in other router options or
other statements in the same ACL.
+.cindex "tainted data" "de-tainting"
+The value will be untainted.
+
.next
Any of the single-key lookup type names may be preceded by
select particular domains (because any domain would match), but it might have
value if the result of the lookup is being used via the &$domain_data$&
expansion variable.
+
.next
If the pattern starts with the name of a query-style lookup type followed by a
semicolon (for example, &"nisplus;"& or &"ldap;"&), the remainder of the
hold_domains = mysql;select domain from holdlist \
where domain = '${quote_mysql:$domain}';
.endd
-In most cases, the data that is looked up is not used (so for an SQL query, for
+In most cases, the value resulting from the lookup is not used (so for an SQL query, for
example, it doesn't matter what field you select). Exim is interested only in
whether or not the query succeeds. However, when a lookup is used for the
-&%domains%& option on a router, the data is preserved in the &$domain_data$&
+&%domains%& option on a router, the value is preserved in the &$domain_data$&
variable and can be referred to in other options.
+.cindex "tainted data" "de-tainting"
+The value will be untainted.
+
+.next
+.new
+If the pattern starts with the name of a lookup type
+of either kind (single-key or query-style) it may be
+followed by a comma and options,
+The options are lookup-type specific and consist of a comma-separated list.
+Each item starts with a tag and and equals "=".
+.wen
+
.next
.cindex "domain list" "matching literal domain name"
If none of the above cases apply, a caseless textual comparison is made
between the pattern and the domain.
+
+The value for a match will be the list element string.
+.cindex "tainted data" "de-tainting"
+Note that this is commonly untainted
+(depending on the way the list was created).
+This is a useful way of obtaining an untainted equivalent to
+the domain, for later operations.
.endlist
+
Here is an example that uses several different kinds of pattern:
.code
domainlist funny_domains = \
(notated using the quoting facility) so as to distinguish them from IPv4 keys.
For this reason, when the lookup type is &(iplsearch)&, IPv6 addresses are
converted using colons and not dots.
-.new
In all cases except IPv4-mapped IPv6, full, unabbreviated IPv6
addresses are always used.
The latter are converted to IPv4 addresses, in dotted-quad form.
-.wen
Ideally, it would be nice to tidy up this anomalous situation by changing to
colons in all cases, given that quoting is now available for &(lsearch)&.
options for which string expansion is performed are marked with † after
the data type. ACL rules always expand strings. A couple of expansion
conditions do not expand some of the brace-delimited branches, for security
-reasons.
+reasons,
+.cindex "tainted data" expansion
+.cindex expansion "tainted data"
+and expansion of data deriving from the sender (&"tainted data"&)
+is not permitted.
.cindex headers "authentication-results:"
.cindex authentication "expansion item"
This item returns a string suitable for insertion as an
-&'Authentication-Results"'&
+&'Authentication-Results:'&
header line.
The given <&'authserv-id'&> is included in the result; typically this
will be a domain name identifying the system performing the authentications.
object so that it doesn't reload the same object file in the same Exim process
(but of course Exim does start new processes frequently).
-There may be from zero to eight arguments to the function. When compiling
-a local function that is to be called in this way, &_local_scan.h_& should be
-included. The Exim variables and functions that are defined by that API
+There may be from zero to eight arguments to the function.
+
+When compiling
+a local function that is to be called in this way,
+first &_DLFUNC_IMPL_& should be defined,
+and second &_local_scan.h_& should be included.
+The Exim variables and functions that are defined by that API
are also available for dynamically loaded functions. The function itself
must have the following type:
.code
For the &"json"& variant,
if a returned value is a JSON string, it retains its leading and
trailing quotes.
-.new
For the &"jsons"& variant, which is intended for use with JSON strings, the
leading and trailing quotes are removed from the returned value.
-.wen
. XXX should be a UTF-8 compare
The results of matching are handled as above.
For the &"json"& variant,
if a returned value is a JSON string, it retains its leading and
trailing quotes.
-.new
For the &"jsons"& variant, which is intended for use with JSON strings, the
leading and trailing quotes are removed from the returned value.
-.wen
.vitem &*${filter{*&<&'string'&>&*}{*&<&'condition'&>&*}}*&
${filter{a:b:c}{!eq{$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 &*${hash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
"&*$bheader_*&<&'header&~name'&>&*:*&&~or&~&&&
&*$bh_*&<&'header&~name'&>&*:*&" &&&
"&*$lheader_*&<&'header&~name'&>&*:*&&~or&~&&&
- &*$lh_*&<&'header&~name'&>&*:*&"
+ &*$lh_*&<&'header&~name'&>&*:*&" &&&
"&*$rheader_*&<&'header&~name'&>&*:*&&~or&~&&&
&*$rh_*&<&'header&~name'&>&*:*&"
.cindex "expansion" "header insertion"
those headers that contain lists of addresses, a comma is also inserted at the
junctions between headers. This does not happen for the &%rheader%& expansion.
+.new
+.cindex "tainted data"
+When the headers are from an incoming message,
+the result of expanding any of these variables is tainted.
+.wen
+
.vitem &*${hmac{*&<&'hashname'&>&*}{*&<&'secret'&>&*}{*&<&'string'&>&*}}*&
.cindex "expansion" "hmac hashing"
You can use &`fail`& instead of {<&'string3'&>} as in a string extract.
+.new
+.vitem &*${listquote{*&<&'separator'&>&*}{*&<&'string'&>&*}}*"
+.citem quoting "for list"
+.citem list quoting
+This item doubles any occurrence of the separator character
+in the given string.
+An empty string is replaced with a single space.
+This converts the string into a safe form for use as a list element,
+in a list using the given separator.
+.wen
+
+
.vitem "&*${lookup{*&<&'key'&>&*}&~*&<&'search&~type'&>&*&~&&&
{*&<&'file'&>&*}&~{*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&"
This is the first of one of two different types of lookup item, which are both
${map{a:b:c}{[$item]}} ${map{<- x-y-z}{($item)}}
.endd
expands to &`[a]:[b]:[c] (x)-(y)-(z)`&. At the end of the expansion, the
-value of &$item$& is restored to what it was before. See also the &*filter*&
-and &*reduce*& expansion items.
+value of &$item$& is restored to what it was before. See also the &%filter%&
+and &%reduce%& expansion items.
.vitem &*${nhash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
.cindex "expansion" "numeric hash"
.endd
The third argument is a list of options, of which the first element is the timeout
-and must be present if the argument is given.
+and must be present if any options are given.
Further elements are options of form &'name=value'&.
-Two option types is currently recognised: shutdown and tls.
-The first defines whether (the default)
-or not a shutdown is done on the connection after sending the request.
-Example, to not do so (preferred, eg. by some webservers):
+Example:
.code
${readsocket{/socket/name}{request string}{3s:shutdown=no}}
.endd
-The second, tls, controls the use of TLS on the connection. Example:
-.code
-${readsocket{/socket/name}{request string}{3s:tls=yes}}
-.endd
-The default is to not use TLS.
+
+.new
+The following option names are recognised:
+.ilist
+&*cache*&
+Defines if the result data can be cached for use by a later identical
+request in the same process.
+Values are &"yes"& or &"no"& (the default).
+If not, all cached results for this connection specification
+will be invalidated.
+
+.next
+&*shutdown*&
+Defines whether or not a write-shutdown is done on the connection after
+sending the request. Values are &"yes"& (the default) or &"no"&
+(preferred, eg. by some webservers).
+
+.next
+&*tls*&
+Controls the use of TLS on the connection.
+Values are &"yes"& or &"no"& (the default).
If it is enabled, a shutdown as descripbed above is never done.
+.endlist
+.wen
+
A fourth argument allows you to change any newlines that are in the data
that is read, in the same way as for &%readfile%& (see above). This example
list is assigned to &$item$&, in turn, and <&'string3'&> is expanded for each of
them. The result of that expansion is assigned to &$value$& before the next
iteration. When the end of the list is reached, the final value of &$value$& is
-added to the expansion output. The &*reduce*& expansion item can be used in a
+added to the expansion output. The &%reduce%& expansion item can be used in a
number of ways. For example, to add up a list of numbers:
.code
${reduce {<, 1,2,3}{0}{${eval:$value+$item}}}
${reduce {3:0:9:4:6}{0}{${if >{$item}{$value}{$item}{$value}}}}
.endd
At the end of a &*reduce*& expansion, the values of &$item$& and &$value$& are
-restored to what they were before. See also the &*filter*& and &*map*&
+restored to what they were before. See also the &%filter%& and &%map%&
expansion items.
.vitem &*$rheader_*&<&'header&~name'&>&*:*&&~or&~&*$rh_*&<&'header&~name'&>&*:*&
${addresses:>:$h_from:}
.endd
-Compare the &*address*& (singular)
+Compare the &%address%& (singular)
expansion item, which extracts the working address from a single RFC2822
-address. See the &*filter*&, &*map*&, and &*reduce*& items for ways of
+address. See the &%filter%&, &%map%&, and &%reduce%& items for ways of
processing lists.
To clarify "list of addresses in RFC 2822 format" mentioned above, Exim follows
As a more realistic example, in an ACL you might have
.code
-deny message = Too many bad recipients
- condition = \
+deny condition = \
${if and { \
{>{$rcpt_count}{10}} \
{ \
{${eval:$rcpt_count/2}} \
} \
}{yes}{no}}
+ message = Too many bad recipients
.endd
The condition is true if there have been more than 10 RCPT commands and
fewer than half of them have resulted in a valid recipient.
If the string is a single variable of type certificate,
returns the SHA-256 hash fingerprint of the certificate.
-.new
The operator can also be spelled &%sha2%& and does the same as &%sha256%&
(except for certificates, which are not supported).
Finally, if an underbar
and a number is appended it specifies the output length, selecting a
member of the SHA-2 family of hash functions.
Values of 256, 384 and 512 are accepted, with 256 being the default.
-.wen
.vitem &*${sha3:*&<&'string'&>&*}*& &&&
.code
${if forany{<, $recipients}{match{$item}{^user3@}}{yes}{no}}
.endd
-The value of &$item$& is saved and restored while &*forany*& or &*forall*& is
+The value of &$item$& is saved and restored while &%forany%& or &%forall%& is
being processed, to enable these expansion items to be nested.
To scan a named list, expand it with the &*listnamed*& operator.
-.new
.vitem "&*forall_json{*&<&'a JSON array'&>&*}{*&<&'a condition'&>&*}*&" &&&
"&*forany_json{*&<&'a JSON array'&>&*}{*&<&'a condition'&>&*}*&" &&&
"&*forall_jsons{*&<&'a JSON array'&>&*}{*&<&'a condition'&>&*}*&" &&&
The array separator is not changeable.
For the &"jsons"& variants the elements are expected to be JSON strings
and have their quotes removed before the evaluation of the condition.
-.wen
There can be problems if any of the strings are permitted to contain colon
characters. In the usual way, these have to be doubled to avoid being taken as
-separators. If the data is being inserted from a variable, the &%sg%& expansion
-item can be used to double any existing colons. For example, the configuration
+separators.
+The &%listquote%& expansion item can be used for this.
+For example, the configuration
of a LOGIN authenticator might contain this setting:
.code
-server_condition = ${if pam{$auth1:${sg{$auth2}{:}{::}}}}
-.endd
-For a PLAIN authenticator you could use:
-.code
-server_condition = ${if pam{$auth2:${sg{$auth3}{:}{::}}}}
+server_condition = ${if pam{$auth1:${listquote{:}{$auth2}}}}
.endd
In some operating systems, PAM authentication can be done only from a process
running as root. Since Exim is running as the Exim user when receiving
a colon-separated list of signer domains and identities for the message.
For details see section &<<SECDKIMVFY>>&.
+.vitem &$dmarc_domain_policy$& &&&
+ &$dmarc_status$& &&&
+ &$dmarc_status_text$& &&&
+ &$dmarc_used_domains$&
+Results of DMARC verification.
+For details see section &<<SECDMARC>>&.
+
.vitem &$dnslist_domain$& &&&
&$dnslist_matched$& &&&
&$dnslist_text$& &&&
the complete argument of the ETRN command (see section &<<SECTETRN>>&).
.endlist
+.new
+.cindex "tainted data"
+If the origin of the data is an incoming message,
+the result of expanding this variable is tainted.
+When un untainted version is needed, one should be obtained from
+looking up the value in a local (therefore trusted) database.
+Often &$domain_data$& is usable in this role.
+.wen
+
.vitem &$domain_data$&
.vindex "&$domain_data$&"
allows you, for example, to do things like this:
.code
deny hosts = net-lsearch;/some/file
-message = $host_data
+ message = $host_data
.endd
.vitem &$host_lookup_deferred$&
.cindex "host name" "lookup, failure of"
.cindex authentication "expansion item"
Performing these checks sets up information used by the
-&$authresults$& expansion item.
+&%authresults%& expansion item.
.vitem &$host_lookup_failed$&
because a message may have many recipients and the system filter is called just
once.
-.vindex "&$local_part_prefix$&"
-.vindex "&$local_part_suffix$&"
-.cindex affix variables
-If a local part prefix or suffix has been recognized, it is not included in the
-value of &$local_part$& during routing and subsequent delivery. The values of
-any prefix or suffix are in &$local_part_prefix$& and
-&$local_part_suffix$&, respectively.
+.new
+.cindex "tainted data"
+If the origin of the data is an incoming message,
+the result of expanding this variable is tainted.
+
+&*Warning*&: the content of this variable is usually provided by a potential
+attacker.
+Consider carefully the implications of using it unvalidated as a name
+for file access.
+This presents issues for users' &_.forward_& and filter files.
+For traditional full user accounts, use &%check_local_users%& and the
+&$local_part_data$& variable rather than this one.
+For virtual users, store a suitable pathname component in the database
+which is used for account name validation, and use that retrieved value
+rather than this variable.
+Often &$local_part_data$& is usable in this role.
+If needed, use a router &%address_data%& or &%set%& option for
+the retrieved data.
+.wen
When a message is being delivered to a file, pipe, or autoreply transport as a
result of aliasing or forwarding, &$local_part$& is set to the local part of
to a transport, the value is available in that transport. If the transport is
handling multiple addresses, the value from the first address is used.
+.new
+The &%check_local_user%& router option also sets this variable.
+.wen
+
&$local_part_data$& is also set when the &%local_parts%& condition in an ACL
matches a local part by means of a lookup. The data read by the lookup is
available during the rest of the ACL statement. In all other situations, this
variable expands to nothing.
-.vitem &$local_part_prefix$&
-.vindex "&$local_part_prefix$&"
+.vindex &$local_part_prefix$& &&&
+ &$local_part_prefix_v$& &&&
+ &$local_part_suffix$& &&&
+ &$local_part_suffix_v$&
.cindex affix variables
-When an address is being routed or delivered, and a
-specific prefix for the local part was recognized, it is available in this
-variable, having been removed from &$local_part$&.
-
-.vitem &$local_part_suffix$&
-.vindex "&$local_part_suffix$&"
-When an address is being routed or delivered, and a
-specific suffix for the local part was recognized, it is available in this
-variable, having been removed from &$local_part$&.
+If a local part prefix or suffix has been recognized, it is not included in the
+value of &$local_part$& during routing and subsequent delivery. The values of
+any prefix or suffix are in &$local_part_prefix$& and
+&$local_part_suffix$&, respectively.
+.new
+.cindex "tainted data"
+If the specification did not include a wildcard then
+the affix variable value is not tainted.
+
+If the affix specification included a wildcard then the portion of
+the affix matched by the wildcard is in
+&$local_part_prefix_v$& or &$local_part_suffix_v$& as appropriate,
+and both the whole and varying values are tainted.
+.wen
.vitem &$local_scan_data$&
.vindex "&$local_scan_data$&"
Here is an example of the use of this variable in a DATA ACL:
.code
-deny message = Too many lines in message header
- condition = \
+deny condition = \
${if <{250}{${eval:$message_linecount - $body_linecount}}}
+ message = Too many lines in message header
.endd
In the MAIL and RCPT ACLs, the value is zero because at that stage the
message has not yet been received.
.vitem &$queue_name$&
.vindex &$queue_name$&
-.cindex "named queues"
+.cindex "named queues" variable
.cindex queues named
The name of the spool queue in use; empty for the default queue.
-.new
+.vitem &$queue_size$&
+.vindex "&$queue_size$&"
+.cindex "queue" "size of"
+.cindex "spool" "number of messages"
+This variable contains the number of messages queued.
+It is evaluated on demand, but no more often than once every minute.
+
.vitem &$r_...$&
.vindex &$r_...$&
.cindex router variables
They can be given any name that starts with &$r_$&.
The values persist for the address being handled through subsequent routers
and the eventual transport.
-.wen
.vitem &$rcpt_count$&
.vindex "&$rcpt_count$&"
dns_dnssec_ok = 1
.endd
+.new
+In addition, on Linux with glibc 2.31 or newer the resolver library will
+default to stripping out a successful validation status.
+This will break a previously working Exim installation.
+Provided that you do trust the resolver (ie, is on localhost) you can tell
+glibc to pass through any successful validation with a new option in
+&_/etc/resolv.conf_&:
+.code
+options trust-ad
+.endd
+.wen
+
Exim does not perform DNSSEC validation itself, instead leaving that to a
validating resolver (e.g. unbound, or bind with suitable configuration).
&*Note*&: Under versions of OpenSSL preceding 1.1.1,
when a list of more than one
file is used for &%tls_certificate%&, this variable is not reliable.
+The macro "_TLS_BAD_MULTICERT_IN_OURCERT" will be defined for those versions.
.vitem &$tls_in_peercert$&
.vindex "&$tls_in_peercert$&"
but in the context of an outward SMTP delivery taking place via the &(smtp)& transport
becomes the same as &$tls_out_cipher$&.
-.new
.vitem &$tls_in_cipher_std$&
.vindex "&$tls_in_cipher_std$&"
As above, but returning the RFC standard name for the cipher suite.
-.wen
.vitem &$tls_out_cipher$&
.vindex "&$tls_out_cipher$&"
&<<CHAPTLS>>& for details of TLS support and chapter &<<CHAPsmtptrans>>& for
details of the &(smtp)& transport.
-,new
.vitem &$tls_out_cipher_std$&
.vindex "&$tls_out_cipher_std$&"
As above, but returning the RFC standard name for the cipher suite.
-.wen
.vitem &$tls_out_dane$&
.vindex &$tls_out_dane$&
.vindex &$tls_out_tlsa_usage$&
Bitfield of TLSA record types found. See section &<<SECDANE>>&.
+.vitem &$tls_in_ver$&
+.vindex "&$tls_in_ver$&"
+When a message is received from a remote host over an encrypted SMTP connection
+this variable is set to the protocol version, eg &'TLS1.2'&.
+
+.vitem &$tls_out_ver$&
+.vindex "&$tls_out_ver$&"
+When a message is being delivered to a remote host over an encrypted SMTP connection
+this variable is set to the protocol version.
+
+
.vitem &$tod_bsdinbox$&
.vindex "&$tod_bsdinbox$&"
The time of day and the date, in the format required for BSD-style mailbox
.row &%daemon_startup_sleep%& "time to sleep between tries"
.row &%extra_local_interfaces%& "not necessarily listened on"
.row &%local_interfaces%& "on which to listen, with optional ports"
+.row &%notifier_socket%& "override compiled-in value"
.row &%pid_file_path%& "override compiled-in value"
.row &%queue_run_max%& "maximum simultaneous queue runners"
.endtable
.row &%percent_hack_domains%& "recognize %-hack for these domains"
.row &%spamd_address%& "set interface to SpamAssassin"
.row &%strict_acl_vars%& "object to unset ACL variables"
+.row &%spf_smtp_comment_template%& "template for &$spf_smtp_comment$&"
.endtable
See also the &'Policy controls'& section above.
.table2
-.row &%dkim_verify_signers%& "DKIM domain for which DKIM ACL is run"
+.row &%dkim_verify_hashes%& "DKIM hash methods accepted for signatures"
+.row &%dkim_verify_keytypes%& "DKIM key types accepted for signatures"
+.row &%dkim_verify_min_keysizes%& "DKIM key sizes accepted for signatures"
+.row &%dkim_verify_signers%& "DKIM domains for which DKIM ACL is run"
+.row &%dmarc_forensic_sender%& "DMARC sender for report messages"
+.row &%dmarc_history_file%& "DMARC results log"
+.row &%dmarc_tld_file%& "DMARC toplevel domains file"
.row &%host_lookup%& "host name looked up for these hosts"
.row &%host_lookup_order%& "order of DNS and local name lookups"
.row &%recipient_unqualified_hosts%& "may send unqualified recipients"
.cindex "8-bit characters"
.cindex "log" "selectors"
.cindex "log" "8BITMIME"
+.cindex "ESMTP extensions" 8BITMIME
This option causes Exim to send 8BITMIME in its response to an SMTP
EHLO command, and to accept the BODY= parameter on MAIL commands.
However, though Exim is 8-bit clean, it is not a protocol converter, and it
.option add_environment main "string list" empty
.cindex "environment" "set values"
-This option allows to set individual environment variables that the
-currently linked libraries and programs in child processes use.
+This option adds individual environment variables that the
+currently linked libraries and programs in child processes may use.
+Each list element should be of the form &"name=value"&.
+
See &<<SECTpipeenv>>& for the environment of &(pipe)& transports.
.option admin_groups main "string list&!!" unset
.cindex "UTF-8" "in domain name"
Lots of discussion is going on about internationalized domain names. One
camp is strongly in favour of just using UTF-8 characters, and it seems
-that at least two other MTAs permit this. This option allows Exim users to
-experiment if they wish.
+that at least two other MTAs permit this.
+This option allows Exim users to experiment if they wish.
If it is set true, Exim's domain parsing function allows valid
UTF-8 multicharacters to appear in domain name components, in addition to
-letters, digits, and hyphens. However, just setting this option is not
-enough; if you want to look up these domain names in the DNS, you must also
+letters, digits, and hyphens.
+
+If Exim is built with internationalization support
+and the SMTPUTF8 ESMTP option is in use (see chapter &<<CHAPi18n>>&)
+this option can be left as default.
+Without that,
+if you want to look up such domain names in the DNS, you must also
adjust the value of &%dns_check_names_pattern%& to match the extended form. A
suitable setting is:
.code
.option auth_advertise_hosts main "host list&!!" *
.cindex "authentication" "advertising"
.cindex "AUTH" "advertising"
+.cindex "ESMTP extensions" AUTH
If any server authentication mechanisms are configured, Exim advertises them in
response to an EHLO command only if the calling host matches this list.
Otherwise, Exim does not advertise AUTH.
required, it must come from the &%-oA%& command line option.
-.option bounce_message_file main string unset
+.option bounce_message_file main string&!! unset
.cindex "bounce message" "customizing"
.cindex "customizing" "bounce message"
This option defines a template file containing paragraphs of text to be used
for constructing bounce messages. Details of the file's contents are given in
-chapter &<<CHAPemsgcust>>&. See also &%warn_message_file%&.
+chapter &<<CHAPemsgcust>>&.
+.new
+.cindex bounce_message_file "tainted data"
+The option is expanded to give the file path, which must be
+absolute and untainted.
+.wen
+See also &%warn_message_file%&.
.option bounce_message_text main string unset
.option chunking_advertise_hosts main "host list&!!" *
.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.
Hosts may use the BDAT command as an alternate to DATA.
to handle IPv6 literal addresses.
+.new
+.option dkim_verify_hashes main "string list" "sha256 : sha512"
+.cindex DKIM "selecting signature algorithms"
+This option gives a list of hash types which are acceptable in signatures,
+.wen
+and an order of processing.
+Signatures with algorithms not in the list will be ignored.
+
+Acceptable values include:
+.code
+sha1
+sha256
+sha512
+.endd
+
+Note that the acceptance of sha1 violates RFC 8301.
+
+.option dkim_verify_keytypes main "string list" "ed25519 : rsa"
+This option gives a list of key types which are acceptable in signatures,
+and an order of processing.
+Signatures with algorithms not in the list will be ignored.
+
+
+.new
+.option dkim_verify_min_keysizes main "string list" "rsa=1024 ed25519=250"
+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.
+.wen
+
+.option dkim_verify_minimal main boolean false
+If set to true, verification of signatures will terminate after the
+first success.
+
.option dkim_verify_signers main "domain list&!!" $dkim_signers
.cindex DKIM "controlling calls to the ACL"
This option gives a list of DKIM domains for which the DKIM ACL is run.
See section &<<SECDKIMVFY>>&.
+.option dmarc_forensic_sender main string&!! unset
+.option dmarc_history_file main string unset
+.option dmarc_tld_file main string unset
+.cindex DMARC "main section options"
+These options control DMARC processing.
+See section &<<SECDMARC>>& for details.
+
+
.option dns_again_means_nonexist main "domain list&!!" unset
.cindex "DNS" "&""try again""& response; overriding"
DNS lookups give a &"try again"& response for the DNS errors
If the resolver library does not support DNSSEC then this option has no effect.
+.new
+On Linux with glibc 2.31 or newer this is insufficient, the resolver library
+will default to stripping out a successful validation status.
+This will break a previously working Exim installation.
+Provided that you do trust the resolver (ie, is on localhost) you can tell
+glibc to pass through any successful validation with a new option in
+&_/etc/resolv.conf_&:
+.code
+options trust-ad
+.endd
+.wen
+
.option dns_ipv4_lookup main "domain list&!!" unset
.cindex "IPv6" "DNS lookup for AAAA records"
This is a fudge to help with name servers that give big delays or otherwise do
not work for the AAAA record type. In due course, when the world's name
servers have all been upgraded, there should be no need for this option.
-.new
Note that all lookups, including those done for verification, are affected;
this will result in verify failure for IPv6 connections or ones using names
only valid for IPv6 addresses.
-.wen
.option dns_retrans main time 0s
.cindex "bounce messages" "success"
.cindex "DSN" "success"
.cindex "Delivery Status Notification" "success"
+.cindex "ESMTP extensions" DSN
DSN extensions (RFC3461) will be advertised in the EHLO message to,
and accepted from, these hosts.
Hosts may use the NOTIFY and ENVID options on RCPT TO commands,
A NOTIFY=SUCCESS option requests success-DSN messages.
A NOTIFY= option with no argument requests that no delay or failure DSNs
are sent.
+.new
+&*Note*&: Supplying success-DSN messages has been criticised
+on privacy grounds; it can leak details of internal forwarding.
+.wen
.option dsn_from main "string&!!" "see below"
.cindex "&'From:'& header line" "in bounces"
.cindex "Exim version"
.cindex customizing "version number"
.cindex "version number of Exim" override
-This option allows to override the &$version_number$&/&$exim_version$& Exim reports in
-various places. Use with care, this may fool stupid security scanners.
+This option overrides the &$version_number$&/&$exim_version$& that Exim reports in
+various places. Use with care; this may fool stupid security scanners.
.option extra_local_interfaces main "string list" unset
name. If no specific path is set for the log files at compile or runtime,
or if the option is unset at runtime (i.e. &`log_file_path = `&)
they are written in a sub-directory called &_log_& in Exim's spool directory.
+A path must start with a slash.
+To send to syslog, use the word &"syslog"&.
Chapter &<<CHAPlog>>& contains further details about Exim's logging, and
section &<<SECTwhelogwri>>& describes how the contents of &%log_file_path%& are
used. If this string is fixed at your installation (contains no expansion
TCP/IP. After expansion, the value must be a sequence of decimal digits,
optionally followed by K or M.
+.cindex "SIZE" "ESMTP extension, advertising"
+.cindex "ESMTP extensions" SIZE
+If nonzero the value will be advertised as a parameter to the ESMTP SIZE
+service extension keyword.
+
&*Note*&: This limit cannot be made to depend on a message's sender or any
other properties of an individual message, because it has to be advertised in
the server's response to EHLO. String expansion failure causes a temporary
transport driver.
-.option openssl_options main "string list" "+no_sslv2 +no_sslv3 +single_dh_use +no_ticket"
+.new
+.option notifier_socket main string "$spool_directory/exim_daemon_notify"
+This option gives the name for a unix-domain socket on which the daemon
+listens for work and information-requests.
+Only installations running multiple daemons sharing a spool directory
+should need to modify the default.
+
+The option is expanded before use.
+If the platform supports Linux-style abstract socket names, the result
+is used with a nul byte prefixed.
+Otherwise, it should be a full path name and use a directory accessible
+to Exim.
+
+If the Exim command line uses a &%-oX%& option and does not use &%-oP%&
+then a notifier socket is not created.
+.wen
+
+
+.option openssl_options main "string list" "+no_sslv2 +no_sslv3 +single_dh_use +no_ticket +no_renegotiation"
.cindex "OpenSSL "compatibility options"
This option allows an administrator to adjust the SSL options applied
by OpenSSL to connections. It is given as a space-separated list of items,
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 boolean false
+.option perl_taintmode main boolean false
.cindex "Perl"
-This Option enables the taint mode of the embedded Perl interpreter.
+This option enables the taint mode of the embedded Perl interpreter.
.option pgsql_servers main "string list" unset
.option pipelining_advertise_hosts main "host list&!!" *
.cindex "PIPELINING" "suppressing advertising"
+.cindex "ESMTP extensions" PIPELINING
This option can be used to suppress the advertisement of the SMTP
PIPELINING extension to specific hosts. See also the &*no_pipelining*&
control in section &<<SECTcontrols>>&. When PIPELINING is not advertised and
that clients will use it; &"out of order"& commands that are &"expected"& do
not count as protocol errors (see &%smtp_max_synprot_errors%&).
-.new
.option pipelining_connect_advertise_hosts main "host list&!!" *
.cindex "pipelining" "early connection"
.cindex "pipelining" PIPE_CONNECT
+.cindex "ESMTP extensions" X_PIPE_CONNECT
If Exim is built with the SUPPORT_PIPE_CONNECT build option
this option controls which hosts the facility is advertised to
and from which pipeline early-connection (before MAIL) SMTP
commands are acceptable.
When used, the pipelining saves on roundtrip times.
+See also the &%hosts_pipe_connect%& smtp transport option.
+
Currently the option name &"X_PIPE_CONNECT"& is used.
-.wen
.option prdr_enable main boolean false
.cindex "PRDR" "enabling on server"
+.cindex "ESMTP extensions" PRDR
This option can be used to enable the Per-Recipient Data Response extension
to SMTP, defined by Eric Hall.
If the option is set, PRDR is advertised by Exim when operating as a server.
the daemon's command line.
.cindex queues named
-.cindex "named queues"
+.cindex "named queues" "resource limit"
To set limits for different named queues use
an expansion depending on the &$queue_name$& variable.
.option queue_smtp_domains main "domain list&!!" unset
.cindex "queueing incoming messages"
.cindex "message" "queueing remote deliveries"
+.cindex "first pass routing"
When this option is set, a delivery process is started whenever a message is
received, routing is performed, and local deliveries take place.
However, if any SMTP deliveries are required for domains that match
added to the message. Otherwise, the string should start with the text
&"Received:"& and conform to the RFC 2822 specification for &'Received:'&
header lines.
-.new
The default setting is:
.code
${if def:sender_helo_name {(helo=$sender_helo_name)\n\t}}}}\
by $primary_hostname \
${if def:received_protocol {with $received_protocol }}\
+ ${if def:tls_in_ver { ($tls_in_ver)}}\
${if def:tls_in_cipher_std { tls $tls_in_cipher_std\n\t}}\
(Exim $version_number)\n\t\
${if def:sender_address \
id $message_exim_id\
${if def:received_for {\n\tfor $received_for}}
.endd
-.wen
-The reference to the TLS cipher is omitted when Exim is built without TLS
+The references to the TLS version and cipher are
+omitted when Exim is built without TLS
support. The use of conditional expansions ensures that this works for both
locally generated messages and messages received from remote hosts, giving
header lines such as the following:
&%sender_unqualified_hosts%&, or if the message was submitted locally (not
using TCP/IP), and the &%-bnq%& option was not set.
-.option set_environment main "string list" empty
-.cindex "environment"
-This option allows to set individual environment variables that the
-currently linked libraries and programs in child processes use. The
-default list is empty,
-
.option slow_lookup_log main integer 0
.cindex "logging" "slow lookups"
.option smtp_etrn_command main string&!! unset
.cindex "ETRN" "command to be run"
+.cindex "ESMTP extensions" ETRN
.vindex "&$domain$&"
If this option is set, the given command is run whenever an SMTP ETRN
command is received from a host that is permitted to issue such commands (see
smtp_etrn_command = /etc/etrn_command $domain \
$sender_host_address
.endd
+.new
+If the option is not set, the argument for the ETRN command must
+be a &'#'& followed by an address string.
+In this case an &'exim -R <string>'& command is used;
+if the ETRN ACL has set up a named-queue then &'-MCG <queue>'& is appended.
+.wen
+
A new process is created to run the command, but Exim does not wait for it to
complete. Consequently, its status cannot be checked. If the command cannot be
run, a line is written to the panic log, but the ETRN caller still receives
.option smtputf8_advertise_hosts main "host list&!!" *
-.cindex "SMTPUTF8" "advertising"
+.cindex "SMTPUTF8" "ESMTP extension, advertising"
+.cindex "ESMTP extensions" SMTPUTF8
When Exim is built with support for internationalised mail names,
the availability thereof is advertised in
response to EHLO only to those client hosts that match this option. See
This option is available when Exim is compiled with SPF support.
See section &<<SECSPF>>& for more details.
+.new
+.option spf_smtp_comment_template main string&!! "Please%_see%_http://www.open-spf.org/Why"
+This option is available when Exim is compiled with SPF support. It
+allows the customisation of the SMTP comment that the SPF library
+generates. You are strongly encouraged to link to your own explanative
+site. The template must not contain spaces. If you need spaces in the
+output, use the proper placeholder. If libspf2 can not parse the
+template, it uses a built-in default broken link. The following placeholders
+(along with Exim variables (but see below)) are allowed in the template:
+.ilist
+&*%_*&: A space.
+.next
+&*%{L}*&: Envelope sender's local part.
+.next
+&*%{S}*&: Envelope sender.
+.next
+&*%{O}*&: Envelope sender's domain.
+.next
+&*%{D}*&: Current(?) domain.
+.next
+&*%{I}*&: SMTP client Ip.
+.next
+&*%{C}*&: SMTP client pretty IP.
+.next
+&*%{T}*&: Epoch time (UTC).
+.next
+&*%{P}*&: SMTP client domain name.
+.next
+&*%{V}*&: IP version.
+.next
+&*%{H}*&: EHLO/HELO domain.
+.next
+&*%{R}*&: Receiving domain.
+.endlist
+The capitalized placeholders do proper URL encoding, if you use them
+lowercased, no encoding takes place. This list was compiled from the
+libspf2 sources.
+
+A note on using Exim variables: As
+currently the SPF library is initialized before the SMTP EHLO phase,
+the variables useful for expansion are quite limited.
+.wen
.option split_spool_directory main boolean false
.cindex "TLS" "advertising"
.cindex "encryption" "on SMTP connection"
.cindex "SMTP" "encrypted connection"
+.cindex "ESMTP extensions" STARTTLS
When Exim is built with support for TLS encrypted connections, the availability
of the STARTTLS command to set up an encrypted session is advertised in
response to EHLO only to those client hosts that match this option. See
.cindex "TLS" "server certificate; location of"
.cindex "certificate" "server, location of"
The value of this option is expanded, and must then be a list of absolute paths to
-files which contains the server's certificates. Commonly only one file is
-needed.
+files which contain the server's certificates (in PEM format).
+Commonly only one file is needed.
The server's private key is also
assumed to be in this file if &%tls_privatekey%& is unset. See chapter
&<<CHAPTLS>>& for further details.
&*Note*&: Under versions of OpenSSL preceding 1.1.1,
when a list of more than one
file is used, the &$tls_in_ourcert$& variable is unreliable.
-
-&*Note*&: OCSP stapling is not usable under OpenSSL
-when a list of more than one file is used.
+The macro "_TLS_BAD_MULTICERT_IN_OURCERT" will be defined for those versions.
If the option contains &$tls_out_sni$& and Exim is built against OpenSSL, then
if the OpenSSL build supports TLS extensions and the TLS client sends the
The value of this option is expanded and indicates the source of DH parameters
to be used by Exim.
-&*Note: The Exim Maintainers strongly recommend using a filename with site-generated
+This option is ignored for GnuTLS version 3.6.0 and later.
+The library manages parameter negotiation internally.
+
+&*Note: The Exim Maintainers strongly recommend,
+for other TLS library versions,
+using a filename with site-generated
local DH parameters*&, which has been supported across all versions of Exim. The
other specific constants available are a fallback so that even when
"unconfigured", Exim can offer Perfect Forward Secrecy in older ciphersuites in TLS.
Certificate Authority.
Usable for GnuTLS 3.4.4 or 3.3.17 or OpenSSL 1.1.0 (or later).
+The macro "_HAVE_TLS_OCSP" will be defined for those versions.
-For GnuTLS 3.5.6 or later the expanded value of this option can be a list
+For OpenSSL 1.1.0 or later, and
+for GnuTLS 3.5.6 or later the expanded value of this option can be a list
of files, to match a list given for the &%tls_certificate%& option.
The ordering of the two lists must match.
-
+The macro "_HAVE_TLS_OCSP_LIST" will be defined for those versions.
+
+The file(s) should be in DER format,
+except for GnuTLS 3.6.3 or later
+or for OpenSSL,
+when an optional filetype prefix can be used.
+The prefix must be one of "DER" or "PEM", followed by
+a single space. If one is used it sets the format for subsequent
+files in the list; the initial format is DER.
+If multiple proofs are wanted, for multiple chain elements
+(this only works under TLS1.3)
+they must be coded as a combined OCSP response.
+
+Although GnuTLS will accept PEM files with multiple separate
+PEM blobs (ie. separate OCSP responses), it sends them in the
+TLS Certificate record interleaved with the certificates of the chain;
+although a GnuTLS client is happy with that, an OpenSSL client is not.
.option tls_on_connect_ports main "string list" unset
.cindex SSMTP
See &%uucp_from_pattern%& above.
-.option warn_message_file main string unset
+.option warn_message_file main string&!! unset
.cindex "warning of delay" "customizing the message"
.cindex "customizing" "warning message"
This option defines a template file containing paragraphs of text to be used
for constructing the warning message which is sent by Exim when a message has
been in the queue for a specified amount of time, as specified by
&%delay_warning%&. Details of the file's contents are given in chapter
-&<<CHAPemsgcust>>&. See also &%bounce_message_file%&.
+&<<CHAPemsgcust>>&.
+.new
+.cindex warn_message_file "tainted data"
+The option is expanded to give the file path, which must be
+absolute and untainted.
+.wen
+See also &%bounce_message_file%&.
.option write_rejectlog main boolean true
This makes the configuration file less messy, and also reduces the number of
lookups (though Exim does cache lookups).
-.new
See also the &%set%& option below.
-.wen
.vindex "&$sender_address_data$&"
.vindex "&$address_data$&"
unless you really, really know what you are doing. See also the generic
transport option of the same name.
-.option dnssec_request_domains routers "domain list&!!" unset
+.option dnssec_request_domains routers "domain list&!!" *
.cindex "MX record" "security"
.cindex "DNSSEC" "MX lookup"
.cindex "security" "MX lookup"
This option specifies a list of text headers,
colon-separated (by default, changeable in the usual way &<<SECTlistsepchange>>&),
that is associated with any addresses that are accepted by the router.
-Each item is separately expanded, at routing time. However, this
-option has no effect when an address is just being verified. The way in which
+However, the option has no effect when an address is just being verified.
+Each list item is separately expanded, at transport time.
+.new
+If an item ends in *, it will match any header with the given prefix.
+.wen
+The way in which
the text is used to remove header lines at transport time is described in
section &<<SECTheadersaddrem>>&. Header lines are not actually removed until
the message is in the process of being transported. This means that references
to header lines in string expansions in the transport's configuration still
&"see"& the original header lines.
-The &%headers_remove%& option is expanded after &%errors_to%& and
+The &%headers_remove%& option is handled after &%errors_to%& and
&%headers_add%&, but before &%transport%&. If an item expansion is forced to fail,
the item has no effect. Other expansion failures are treated as configuration
errors.
This behaviour can be overridden by setting &%rcpt_include_affixes%& true on
the relevant transport.
+.new
+.vindex &$local_part_prefix_v$&
+If wildcarding (above) was used then the part of the prefix matching the
+wildcard is available in &$local_part_prefix_v$&.
+.wen
+
When an address is being verified, &%local_part_prefix%& affects only the
behaviour of the router. If the callout feature of verification is in use, this
means that the full address, including the prefix, will be used during the
used. For example:
.code
require_files = mail:/some/file
-require_files = $local_part:$home/.procmailrc
+require_files = $local_part_data:$home/.procmailrc
.endd
If a user or group name in a &%require_files%& list does not exist, the
&%require_files%& condition fails.
This option controls whether the local part is used to form the key for retry
hints for addresses that suffer temporary errors while being handled by this
-router. The default value is true for any router that has &%check_local_user%&
+router. The default value is true for any router that has any of
+&%check_local_user%&,
+&%local_parts%&,
+&%condition%&,
+&%local_part_prefix%&,
+&%local_part_suffix%&,
+&%senders%& or
+&%require_files%&
set, and false otherwise. Note that this option does not apply to hints keys
for transport delays; they are controlled by a generic transport option of the
same name.
+Failing to set this option when it is needed
+(because a remote router handles only some of the local-parts for a domain)
+can result in incorrect error messages being generated.
+
The setting of &%retry_use_local_part%& applies only to the router on which it
appears. If the router generates child addresses, they are routed
independently; this setting does not become attached to them.
matters.
-.new
.option set routers "string list" unset
.cindex router variables
This option may be used multiple times on a router;
The list separator is a semicolon but can be changed in the
usual way.
-Each list-element given must be of the form $"name = value"$
+Each list-element given must be of the form &"name = value"&
and the names used must start with the string &"r_"&.
Values containing a list-separator should have them doubled.
When a router runs, the strings are evaluated in order,
(not including any preconditions)
and by the transport.
Later definitions of a given named variable will override former ones.
-Varible use is via the usual &$r_...$& syntax.
+Variable use is via the usual &$r_...$& syntax.
This is similar to the &%address_data%& option, except that
many independent variables can be used, with choice of naming.
-.wen
.option translate_ip_address routers string&!! unset
.section "Format of one host item" "SECTformatonehostitem"
-Each item in the list of hosts is either a host name or an IP address,
-optionally with an attached port number. When no port is given, an IP address
+Each item in the list of hosts can be either a host name or an IP address,
+optionally with an attached port number, or it can be a single "+"
+(see &%hosts_randomize%&).
+When no port is given, an IP address
is not enclosed in brackets. When a port is specified, it overrides the port
specification on the transport. The port is separated from the name or address
by a colon. This leads to some complications:
yield empty addresses, for example, items containing only RFC 2822 address
comments.
+.new
+.cindex "tainted data" "in filenames"
+.cindex redirect "tainted data"
+Tainted data may not be used for a filename.
+
+&*Warning*&: It is unwise to use &$local_part$& or &$domain$&
+directly for redirection,
+as they are provided by a potential attacker.
+In the examples above, &$local_part$& is used for looking up data held locally
+on the system, and not used directly (the second example derives &$home$& via
+the passsword file or database, using &$local_part$&).
+.wen
+
.section "Forward files and address verification" "SECID125"
.code
list1: :include:/opt/lists/list1
.endd
+.new
+.cindex "tainted data" "in filenames"
+.cindex redirect "tainted data"
+Tainted data may not be used for a filename.
+.wen
.next
.cindex "address redirection" "to black hole"
.cindex "delivery" "discard"
# This transport overrides the group
group_delivery:
driver = appendfile
- file = /var/spool/mail/$local_part
+ file = /var/spool/mail/$local_part_data
group = mail
.endd
If &%user%& is set for a transport, its value overrides what is set in the
.option headers_remove transports list&!! unset
.cindex "header lines" "removing"
.cindex "transport" "header lines; removing"
-This option specifies a list of header names,
-colon-separated (by default, changeable in the usual way &<<SECTlistsepchange>>&);
-these headers are omitted from the message as it is transported, as described
-in section &<<SECTheadersaddrem>>&. Header removal can also be specified by
-routers.
+This option specifies a list of text headers,
+colon-separated (by default, changeable in the usual way &<<SECTlistsepchange>>&),
+to be removed from the message.
+However, the option has no effect when an address is just being verified.
Each list item is separately expanded.
If the result of the expansion is an empty string, or if the expansion
is forced to fail, no action is taken. Other expansion failures are treated as
errors and cause the delivery to be deferred.
+.new
+If an item ends in *, it will match any header with the given prefix.
+.wen
+
+Matching headers are omitted from the message as it is transported, as described
+in section &<<SECTheadersaddrem>>&. Header removal can also be specified by
+routers.
Unlike most options, &%headers_remove%& can be specified multiple times
for a transport; all listed headers are removed.
a spam score. This could be interpreted by a filter in the user's MUA. It is
not possible to discard a message at this stage.
-.cindex "SMTP" "SIZE"
+.cindex "SIZE" "ESMTP extension"
A problem might arise if the filter increases the size of a message that is
being sent down an SMTP connection. If the receiving SMTP server has indicated
support for the SIZE parameter, Exim will have sent the size of the message
used to determine the file or directory name for the delivery. Normally, the
contents of &$address_file$& are used in some way in the string expansion.
.endlist
+.new
+.cindex "tainted data" "in filenames"
+.cindex appendfile "tainted data"
+Tainted data may not be used for a file or directory name.
+This means that, for instance, &$local_part$& cannot be used directly
+as a component of a path. It can however be used as the key for a lookup
+which returns a path (or component).
+.wen
.cindex "Sieve filter" "configuring &(appendfile)&"
way of handling this requirement:
.code
file = ${if eq{$address_file}{inbox} \
- {/var/mail/$local_part} \
+ {/var/mail/$local_part_data} \
{${if eq{${substr_0_1:$address_file}}{/} \
{$address_file} \
{$home/mail/$address_file} \
path. The most common settings of this option are variations on one of these
examples:
.code
-file = /var/spool/mail/$local_part
-file = /home/$local_part/inbox
+file = /var/spool/mail/$local_part_data
+file = /home/$local_part_data/inbox
file = $home/inbox
.endd
.cindex "&""sticky""& bit"
Section &<<SECID136>>& contains further information.
+This option should not be used when other message-handling software
+may duplicate messages by making hardlinks to the files. When that is done Exim
+will count the message size once for each filename, in contrast with the actual
+disk usage. When the option is not set, calculating total usage requires
+a system-call per file to get the size; the number of links is then available also
+as is used to adjust the effective size.
+
.option quota_warn_message appendfile string&!! "see below"
See below for the use of this option. If it is not set when
folders. Consider this example:
.code
maildir_format = true
-directory = /var/mail/$local_part\
+directory = /var/mail/$local_part_data\
${if eq{$local_part_suffix}{}{}\
{/.${substr_1:$local_part_suffix}}}
maildirfolder_create_regex = /\.[^/]+$
details of the local delivery environment and chapter &<<CHAPbatching>>&
for a discussion of local delivery batching.
+.new
+.cindex "tainted data" "in pipe command"
+.cindex pipe "tainted data"
+Tainted data may not be used for the command name.
+.wen
+
.section "Concurrent delivery" "SECID140"
If two messages arrive at almost the same time, and both are routed to a pipe
# transport
procmail_pipe:
driver = pipe
- command = /usr/local/bin/procmail -d $local_part
+ command = /usr/local/bin/procmail -d $local_part_data
return_path_add
delivery_date_add
envelope_to_add
check_string = "From "
escape_string = ">From "
umask = 077
- user = $local_part
+ user = $local_part_data
group = mail
# router
.option dkim_canon smtp string&!! unset
+DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
.option dkim_domain smtp string list&!! unset
+DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
.option dkim_hash smtp string&!! sha256
+DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
.option dkim_identity smtp string&!! unset
+DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
.option dkim_private_key smtp string&!! unset
+DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
.option dkim_selector smtp string&!! unset
+DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
.option dkim_strict smtp string&!! unset
+DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
.option dkim_sign_headers smtp string&!! "per RFC"
+DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
.option dkim_timestamps smtp string&!! unset
-DKIM signing options. For details see section &<<SECDKIMSIGN>>&.
+DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
.option delay_after_cutoff smtp boolean true
details.
-.option dnssec_request_domains smtp "domain list&!!" unset
+.option dnssec_request_domains smtp "domain list&!!" *
.cindex "MX record" "security"
.cindex "DNSSEC" "MX lookup"
.cindex "security" "MX lookup"
.cindex "DNS" "DNSSEC"
DNS lookups for domains matching &%dnssec_request_domains%& will be done with
-the dnssec request bit set.
-This applies to all of the SRV, MX, AAAA, A lookup sequence.
+the dnssec request bit set. Setting this transport option is only useful if the
+transport overrides or sets the host names. See the &%dnssec_request_domains%&
+router option.
.cindex "security" "MX lookup"
.cindex "DNS" "DNSSEC"
DNS lookups for domains matching &%dnssec_require_domains%& will be done with
-the dnssec request bit set. Any returns not having the Authenticated Data bit
-(AD bit) set will be ignored and logged as a host-lookup failure.
-This applies to all of the SRV, MX, AAAA, A lookup sequence.
+the dnssec request bit set. Setting this transport option is only
+useful if the transport overrides or sets the host names. See the
+&%dnssec_require_domains%& router option.
.option hosts_avoid_pipelining smtp "host list&!!" unset
.cindex "PIPELINING" "avoiding the use of"
-Exim will not use the SMTP PIPELINING extension when delivering to any host
+.cindex "ESMTP extensions" PIPELINING
+Exim will not use the ESMTP PIPELINING extension when delivering to any host
that matches this list, even if the server host advertises PIPELINING support.
-.new
.option hosts_pipe_connect smtp "host list&!!" unset
.cindex "pipelining" "early connection"
.cindex "pipelining" PIPE_CONNECT
It also turns SMTP into a client-first protocol
so combines well with TCP Fast Open.
+See also the &%pipelining_connect_advertise_hosts%& main option.
+
Note:
When the facility is used, the transport &%helo_data%& option
will be expanded before the &$sending_ip_address$& variable
presence of a &"def:"& test on it, but suitably complex coding
can avoid the check and produce unexpected results.
You have been warned.
-.wen
.option hosts_avoid_tls smtp "host list&!!" unset
message on the same connection. See section &<<SECTmulmessam>>& for an
explanation of when this might be needed.
-.new
.option hosts_noproxy_tls smtp "host list&!!" unset
.cindex "TLS" "passing connection"
.cindex "multiple SMTP deliveries"
For any host that matches this list, a TLS session which has
been started will not be passed to a new delivery process for sending another
message on the same session.
-.wen
The traditional implementation closes down TLS and re-starts it in the new
process, on the same open TCP connection, for each successive message
.cindex DANE "requiring for certain servers"
If built with DANE support, Exim will require that a DNSSEC-validated
TLSA record is present for any host matching the list,
-and that a DANE-verified TLS connection is made.
+and that a DANE-verified TLS connection is made. See
+the &%dnssec_request_domains%& router and transport options.
There will be no fallback to in-clear communication.
See section &<<SECDANE>>&.
.cindex "RFC 3030" "CHUNKING"
This option provides a list of servers to which, provided they announce
CHUNKING support, Exim will attempt to use BDAT commands rather than DATA.
+.new
+Unless DKIM signing is being done,
+.wen
BDAT will not be used in conjunction with a transport filter.
.option hosts_try_dane smtp "host list&!!" *
.cindex DANE "transport options"
.cindex DANE "attempting for certain servers"
-If built with DANE support, Exim will lookup a
-TLSA record for any host matching the list.
-If found and verified by DNSSEC,
-a DANE-verified TLS connection is made to that host;
-there will be no fallback to in-clear communication.
+If built with DANE support, Exim will require that a DNSSEC-validated
+TLSA record is present for any host matching the list,
+and that a DANE-verified TLS connection is made. See
+the &%dnssec_request_domains%& router and transport options.
+There will be no fallback to in-clear communication.
See section &<<SECDANE>>&.
.option hosts_try_fastopen smtp "host list&!!" *
.option hosts_try_prdr smtp "host list&!!" *
.cindex "PRDR" "enabling, optional in client"
+.cindex "ESMTP extensions" PRDR
This option provides a list of servers to which, provided they announce
PRDR support, Exim will attempt to negotiate PRDR
for multi-recipient messages.
.option size_addition smtp integer 1024
-.cindex "SMTP" "SIZE"
+.cindex "SIZE" "ESMTP extension"
.cindex "message" "size issue for transport filter"
.cindex "size" "of message"
.cindex "transport" "filter"
If both this option and &%tls_try_verify_hosts%& are unset
operation is as if this option selected all hosts.
-.option utf8_downconvert smtp integer!! unset
+.option utf8_downconvert smtp integer&!! -1
.cindex utf8 "address downconversion"
.cindex i18n "utf8 address downconversion"
If built with internationalization support,
-this option controls conversion of UTF-8 in message addresses
+this option controls conversion of UTF-8 in message envelope addresses
to a-label form.
-For details see section &<<SECTi18nMTA>>&.
+If, after expansion, the value is 1, 0, or -1 then this value overrides
+any value previously set for the message. Otherwise, any previously
+set value is used. To permit use of a previous value,
+set this option to an empty string.
+For details on the values see section &<<SECTi18nMTA>>&.
other.
.cindex "AUTH" "description of"
+.cindex "ESMTP extensions" AUTH
Very briefly, the way SMTP authentication works is as follows:
.ilist
the Cyrus SASL authentication library.
The third is an interface to Dovecot's authentication system, delegating the
work via a socket interface.
-.new
The fourth provides for negotiation of authentication done via non-SMTP means,
as defined by RFC 4422 Appendix A.
-.wen
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
.cindex authentication "expansion item"
Successful authentication sets up information used by the
-&$authresults$& expansion item.
+&%authresults%& expansion item.
use unencrypted plain text, you should not use the same passwords for SMTP
connections as you do for login accounts.
-.section "Plaintext options" "SECID171"
+.section "Avoiding cleartext use" "SECTplain_TLS"
+The following generic option settings will disable &(plaintext)& authenticators when
+TLS is not being used:
+.code
+ server_advertise_condition = ${if def:tls_in_cipher }
+ client_condition = ${if def:tls_out_cipher}
+.endd
+
+&*Note*&: a plaintext SMTP AUTH done inside TLS is not vulnerable to casual snooping,
+but is still vulnerable to a Man In The Middle attack unless certificates
+(including their names) have been properly verified.
+
+.section "Plaintext server options" "SECID171"
.cindex "options" "&(plaintext)& authenticator (server)"
When configured as a server, &(plaintext)& uses the following options:
This is actually a global authentication option, but it must be set in order to
configure the &(plaintext)& driver as a server. Its use is described below.
-.option server_prompts plaintext string&!! unset
+.option server_prompts plaintext "string list&!!" unset
The contents of this option, after expansion, must be a colon-separated list of
prompt strings. If expansion fails, a temporary authentication rejection is
given.
.section "The PLAIN authentication mechanism" "SECID172"
.cindex "PLAIN authentication mechanism"
-.cindex "authentication" "PLAIN mechanism"
+.cindex authentication PLAIN
.cindex "binary zero" "in &(plaintext)& authenticator"
The PLAIN authentication mechanism (RFC 2595) specifies that three strings be
sent as one item of data (that is, one combined string containing two NUL
.section "The LOGIN authentication mechanism" "SECID173"
.cindex "LOGIN authentication mechanism"
-.cindex "authentication" "LOGIN mechanism"
+.cindex authentication LOGIN
The LOGIN authentication mechanism is not documented in any RFC, but is in use
in a number of programs. No data is sent with the AUTH command. Instead, a
user name and password are supplied separately, in response to prompts. The
.scindex IIDcramauth1 "&(cram_md5)& authenticator"
.scindex IIDcramauth2 "authenticators" "&(cram_md5)&"
.cindex "CRAM-MD5 authentication mechanism"
-.cindex "authentication" "CRAM-MD5 mechanism"
+.cindex authentication CRAM-MD5
The CRAM-MD5 authentication mechanism is described in 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
.scindex IIDdcotauth1 "&(dovecot)& authenticator"
.scindex IIDdcotauth2 "authenticators" "&(dovecot)&"
This authenticator is an interface to the authentication facility of the
-Dovecot POP/IMAP server, which can support a number of authentication methods.
+Dovecot 2 POP/IMAP server, which can support a number of authentication methods.
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
connection, a client certificate has been verified, the &"valid-client-cert"&
option is passed. When authentication succeeds, the identity of the user
who authenticated is placed in &$auth1$&.
+
+.new
+The Dovecot configuration to match the above wil look
+something like:
+.code
+conf.d/10-master.conf :-
+
+service auth {
+...
+#SASL
+ unix_listener auth-client {
+ mode = 0660
+ user = mail
+ }
+...
+}
+
+conf.d/10-auth.conf :-
+
+auth_mechanisms = plain login ntlm
+.endd
+.wen
+
.ecindex IIDdcotauth1
.ecindex IIDdcotauth2
.cindex "authentication" "LOGIN"
.cindex "authentication" "DIGEST-MD5"
.cindex "authentication" "CRAM-MD5"
-.cindex "authentication" "SCRAM-SHA-1"
-The &(gsasl)& authenticator provides server integration for the GNU SASL
+.cindex "authentication" "SCRAM family"
+The &(gsasl)& authenticator provides integration for the GNU SASL
library and the mechanisms it provides. This is new as of the 4.80 release
and there are a few areas where the library does not let Exim smoothly
scale to handle future authentication mechanisms, so no guarantee can be
made that any particular new authentication mechanism will be supported
without code changes in Exim.
-Exim's &(gsasl)& authenticator does not have client-side support at this
-time; only the server-side support is implemented. Patches welcome.
+.new
+The library is expected to add support in an upcoming
+realease for the SCRAM-SHA-256 method.
+The macro _HAVE_AUTH_GSASL_SCRAM_SHA_256 will be defined
+when this happens.
+
+
+.option client_authz gsasl string&!! unset
+This option can be used to supply an &'authorization id'&
+which is different to the &'authentication_id'& provided
+by &%client_username%& option.
+If unset or (after expansion) empty it is not used,
+which is the common case.
+
+.option client_channelbinding gsasl boolean false
+See &%server_channelbinding%& below.
+
+.option client_password gsasl string&!! unset
+This option is exapanded before use, and should result in
+the password to be used, in clear.
+
+.option client_username gsasl string&!! unset
+This option is exapanded before use, and should result in
+the account name to be used.
+.wen
+
+.new
+.option client_spassword gsasl string&!! unset
+If a SCRAM mechanism is being used and this option is set
+it is used in preference to &%client_password%&.
+The value after expansion should be
+a 40 (for SHA-1) or 64 (for SHA-256) character string
+with the PBKDF2-prepared password, hex-encoded.
+Note that this value will depend on the salt and iteration-count
+supplied by the server.
+.wen
+
.option server_channelbinding gsasl boolean false
-Do not set this true without consulting a cryptographic engineer.
+Do not set this true and rely on the properties
+without consulting a cryptographic engineer.
Some authentication mechanisms are able to use external context at both ends
of the session to bind the authentication to that context, and fail the
non-issue, as a man-in-the-middle attack will cause the correct client and
server to see different identifiers and authentication will fail.
-This is currently only supported when using the GnuTLS library. This is
+.new
+This is
only usable by mechanisms which support "channel binding"; at time of
writing, that's the SCRAM family.
+When using this feature the "-PLUS" variants of the method names need to be used.
+.wen
This defaults off to ensure smooth upgrade across Exim releases, in case
this option causes some clients to start failing. Some future release
of Exim might have switched the default to be true.
-However, Channel Binding in TLS has proven to be broken in current versions.
+However, Channel Binding in TLS has proven to be vulnerable in current versions.
Do not plan to rely upon this feature for security, ever, without consulting
with a subject matter expert (a cryptographic engineer).
Some mechanisms will use this data.
-.option server_scram_iter gsasl string&!! unset
+.option server_scram_iter gsasl string&!! 4096
This option provides data for the SCRAM family of mechanisms.
-&$auth1$& is not available at evaluation time.
-(This may change, as we receive feedback on use)
-
+.new
+The &$auth1$&, &$auth2$& and &$auth3$& variables are available
+when this option is expanded.
+
+The result of expansion should be a decimal number,
+and represents both a lower-bound on the security, and
+a compute cost factor imposed on the client
+(if it does not cache results, or the server changes
+either the iteration count or the salt).
+A minimum value of 4096 is required by the standards
+for all current SCRAM mechanism variants.
+.wen
.option server_scram_salt gsasl string&!! unset
This option provides data for the SCRAM family of mechanisms.
-&$auth1$& is not available at evaluation time.
-(This may change, as we receive feedback on use)
+.new
+The &$auth1$&, &$auth2$& and &$auth3$& variables are available
+when this option is expanded.
+The value should be a base64-encoded string,
+of random data typically 4-to-16 bytes long.
+If unset or empty after expansion the library will provides a value for the
+protocol conversation.
+.wen
+
+
+.new
+.option server_key gsasl string&!! unset
+.option server_skey gsasl string&!! unset
+These options can be used for the SCRAM family of mechanisms
+to provide stored information related to a password,
+the storage of which is preferable to plaintext.
+
+&%server_key%& is the value defined in the SCRAM standards as ServerKey;
+&%server_skey%& is StoredKey.
+
+They are only available for version 1.9.0 (or later) of the gsasl library.
+When this is so, the macros
+_OPT_AUTHENTICATOR_GSASL_SERVER_KEY
+and _HAVE_AUTH_GSASL_SCRAM_S_KEY
+will be defined.
+
+The &$authN$& variables are available when these options are expanded.
+
+If set, the results of expansion should for each
+should be a 28 (for SHA-1) or 44 (for SHA-256) character string
+of base64-coded data, and will be used in preference to the
+&%server_password%& option.
+If unset or not of the right length, &%server_password%& will be used.
+
+The libgsasl library release includes a utility &'gsasl'& which can be used
+to generate these values.
+.wen
.option server_service gsasl string &`smtp`&
(which usually means the full set of public CAs)
and which has a mail-SAN matching the claimed identity sent by the client.
-Note that, up to TLS1.2, the client cert is on the wire in-clear, including the SAN,
+&*Note*&: up to TLS1.2, the client cert is on the wire in-clear, including the SAN.
The account name is therefore guessable by an opponent.
TLS 1.3 protects both server and client certificates, and is not vulnerable
in this way.
-Likewise, a traditional plaintext SMTP AUTH done inside TLS is not.
.section "Using external in a client" "SECTexternclient"
.section "OpenSSL vs GnuTLS" "SECTopenvsgnu"
.cindex "TLS" "OpenSSL &'vs'& GnuTLS"
-The first TLS support in Exim was implemented using OpenSSL. Support for GnuTLS
-followed later, when the first versions of GnuTLS were released. To build Exim
-to use GnuTLS, you need to set
+TLS is supported in Exim using either the OpenSSL or GnuTLS library.
+To build Exim to use OpenSSL you need to set
.code
-USE_GNUTLS=yes
+USE_OPENSSL=yes
.endd
-in Local/Makefile, in addition to
+in Local/Makefile.
+
+To build Exim to use GnuTLS, you need to set
.code
-SUPPORT_TLS=yes
+USE_GNUTLS=yes
.endd
+in Local/Makefile.
+
You must also set TLS_LIBS and TLS_INCLUDE appropriately, so that the
include files and libraries for GnuTLS can be found.
.section "Configuring an Exim server to use TLS" "SECID182"
.cindex "TLS" "configuring an Exim server"
+.cindex "ESMTP extensions" STARTTLS
When Exim has been built with TLS support, it advertises the availability of
the STARTTLS command to client hosts that match &%tls_advertise_hosts%&,
but not to any others. The default value of this option is *, which means
server certificate's DN. The remaining client configuration for TLS is all
within the &(smtp)& transport.
+.cindex "ESMTP extensions" STARTTLS
It is not necessary to set any options to have TLS work in the &(smtp)&
transport. If Exim is built with TLS support, and TLS is advertised by a
server, the &(smtp)& transport always tries to start a TLS session. However,
if it requests it. If the server is Exim, it will request a certificate only if
&%tls_verify_hosts%& or &%tls_try_verify_hosts%& matches the client.
-.new
-Do not use a certificate which has the OCSP-must-staple extension,
+&*Note*&: Do not use a certificate which has the OCSP-must-staple extension,
for client use (they are usable for server use).
-As TLS has no means for the client to staple before TLS 1.3 it will result
+As the TLS protocol has no means for the client to staple before TLS 1.3 it will result
in failed connections.
-.wen
If the &%tls_verify_certificates%& option is set on the &(smtp)& transport, it
specifies a collection of expected server certificates.
attacks in the string (&`../`& or SQL), and ensuring that a valid filename
can always be referenced; it is important to remember that &$tls_in_sni$& is
arbitrary unverified data provided prior to authentication.
-Further, the initial certificate is loaded before SNI is arrived, so
+Further, the initial certificate is loaded before SNI has arrived, so
an expansion for &%tls_certificate%& must have a default which is used
when &$tls_in_sni$& is empty.
in &_Local/Makefile_&.
If it has been included, the macro "_HAVE_DANE" will be defined.
-The TLSA record for the server may have "certificate usage" of DANE-TA(2) or DANE-EE(3).
+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
+&url(https://tools.ietf.org/html/rfc7671#page-5,RFC 7671).
+
+The TLSA record for the server may have "Certificate Usage" (1st) field of DANE-TA(2) or DANE-EE(3).
These are the "Trust Anchor" and "End Entity" variants.
The latter specifies the End Entity directly, i.e. the certificate involved is that of the server
(and if only DANE-EE is used then it should be the sole one transmitted during the TLS handshake);
requirements, then we encourage you to avoid all these issues and use a public
CA such as &url(https://letsencrypt.org/,Let's Encrypt) instead.
-The TLSA record should have a Selector field of SPKI(1) and a Matching Type field of SHA2-512(2).
+The TLSA record should have a "Selector" (2nd) field of SPKI(1) and
+a "Matching Type" (3rd) field of SHA2-512(2).
-At the time of writing, &url(https://www.huque.com/bin/gen_tlsa)
-is useful for quickly generating TLSA records; and commands like
+For the "Certificate Authority Data" (4th) field, commands like
.code
- openssl x509 -in -pubkey -noout <certificate.pem \
+ openssl x509 -pubkey -noout <certificate.pem \
| openssl rsa -outform der -pubin 2>/dev/null \
| openssl sha512 \
| awk '{print $2}'
.endd
-are workable for 4th-field hashes.
+are workable to create a hash of the certificate's public key.
+
+An example TLSA record for DANE-EE(3), SPKI(1), and SHA-512 (2) looks like
+
+.code
+ _25._tcp.mail.example.com. TLSA 3 1 2 8BA8A336E...
+.endd
+
+At the time of writing, &url(https://www.huque.com/bin/gen_tlsa)
+is useful for quickly generating TLSA records.
+
For use with the DANE-TA model, server certificates must have a correct name (SubjectName or SubjectAltName).
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 DNSSEC-secured.
+The &"require"& variant will result in failure if the target host is not
+DNSSEC-secured. To get DNSSEC-secured hostname resolution, use
+the &%dnssec_request_domains%& router or transport option.
DANE will only be usable if the target host has DNSSEC-secured MX, A and TLSA records.
If DANE is not usable, whether requested or not, and CA-anchored
verification evaluation is wanted, the above variables should be set appropriately.
-Currently the &%dnssec_request_domains%& must be active and &%dnssec_require_domains%& is ignored.
+The router and transport option &%dnssec_request_domains%& must not be
+set to &"never"&, and &%dnssec_require_domains%& is ignored.
If verification was successful using DANE then the "CV" item in the delivery log line will show as "CV=dane".
&%drop%&: This verb behaves like &%deny%&, except that an SMTP connection is
forcibly closed after the 5&'xx'& error message has been sent. For example:
.code
-drop message = I don't take more than 20 RCPTs
- condition = ${if > {$rcpt_count}{20}}
+drop condition = ${if > {$rcpt_count}{20}}
+ message = I don't take more than 20 RCPTs
.endd
There is no difference between &%deny%& and &%drop%& for the connect-time ACL.
The connection is always dropped after sending a 550 response.
It can be at the end of an &%accept%& statement:
.code
accept ...some conditions
- control = queue_only
+ control = queue
.endd
In this case, the control is applied when this statement yields &"accept"&, in
other words, when the conditions are all true.
It can be in the middle of an &%accept%& statement:
.code
accept ...some conditions...
- control = queue_only
+ control = queue
...some more conditions...
.endd
If the first set of conditions are true, the control is applied, even if the
the operation and configuration of DKIM, see section &<<SECDKIM>>&.
+.vitem &*control&~=&~dmarc_disable_verify*&
+.cindex "disable DMARC verify"
+.cindex "DMARC" "disable verify"
+This control turns off DMARC verification processing entirely. For details on
+the operation and configuration of DMARC, see section &<<SECDMARC>>&.
+
+
.vitem &*control&~=&~dscp/*&<&'value'&>
.cindex "&ACL;" "setting DSCP value"
.cindex "DSCP" "inbound"
.vitem &*control&~=&~no_pipelining*&
.cindex "PIPELINING" "suppressing advertising"
+.cindex "ESMTP extensions" PIPELINING
This control turns off the advertising of the PIPELINING extension to SMTP in
the current session. To be useful, it must be obeyed before Exim sends its
response to an EHLO command. Therefore, it should normally appear in an ACL
controlled by &%acl_smtp_connect%& or &%acl_smtp_helo%&. See also
&%pipelining_advertise_hosts%&.
-.vitem &*control&~=&~queue_only*&
+.new
+.vitem &*control&~=&~queue/*&<&'options'&>* &&&
+ &*control&~=&~queue_only*&
+.oindex "&%queue%&"
.oindex "&%queue_only%&"
.cindex "queueing incoming messages"
+.cindex queueing "forcing in ACL"
+.cindex "first pass routing"
This control is permitted only for the MAIL, RCPT, DATA, and non-SMTP ACLs, in
other words, only when a message is being received. If the message is accepted,
it is placed on Exim's queue and left there for delivery by a subsequent queue
-runner. No immediate delivery process is started. In other words, it has the
-effect as the &%queue_only%& global option. However, the control applies only
-to the current message, not to any subsequent ones that may be received in the
-same SMTP connection.
+runner.
+If used with no options set,
+no immediate delivery process is started. In other words, it has the
+effect as the &%queue_only%& global option or &'-odq'& command-line option.
+
+If the &'first_pass_route'& option is given then
+the behaviour is like the command-line &'-oqds'& option;
+a delivery process is started which stops short of making
+any SMTP delivery. The benefit is that the hints database will be updated for
+the message being waiting for a specific host, and a later queue run will be
+able to send all such messages on a single connection.
+
+The control only applies to the current message, not to any subsequent ones that
+ may be received in the same SMTP connection.
+.wen
.vitem &*control&~=&~submission/*&<&'options'&>
.cindex "message" "submission"
that are being submitted at the same time using &%-bs%& or &%-bS%&.
.vitem &*control&~=&~utf8_downconvert*&
-This control enables conversion of UTF-8 in message addresses
+This control enables conversion of UTF-8 in message envelope addresses
to a-label form.
For details see section &<<SECTi18nMTA>>&.
.endlist vlist
allows you, for example, to set up a statement like this:
.code
deny hosts = net-lsearch;/some/file
-message = $host_data
+ message = $host_data
.endd
which gives a custom error message for each denied host.
.cindex "&ACL;" "virus scanning"
.cindex "&ACL;" "scanning for viruses"
This condition is available only when Exim is compiled with the
-content-scanning extension. It causes the incoming message to be scanned for
+content-scanning extension
+and only after a DATA command.
+It causes the incoming message to be scanned for
viruses. For details, see chapter &<<CHAPexiscan>>&.
.vitem &*mime_regex&~=&~*&<&'list&~of&~regular&~expressions'&>
condition to restrict it to bounce messages only:
.code
deny senders = :
- message = A valid sender header is required for bounces
!verify = header_sender
+ message = A valid sender header is required for bounces
.endd
.vitem &*verify&~=&~header_syntax*&
&'Resent-Cc:'& header lines exist, they are also checked. This condition can be
used only in a DATA or non-SMTP ACL.
-.new
There is one possible option, &`case_insensitive`&. If this is present then
local parts are checked case-insensitively.
-.wen
There are, of course, many legitimate messages that make use of blind (bcc)
recipients. This check should not be used on its own for blocking messages.
warn for one list and block for another, you can use two different statements:
.code
deny dnslists = blackholes.mail-abuse.org
-warn message = X-Warn: sending host is on dialups list
- dnslists = dialups.mail-abuse.org
+warn dnslists = dialups.mail-abuse.org
+ message = X-Warn: sending host is on dialups list
.endd
.cindex caching "of dns lookup"
.cindex DNS TTL
with these lists. You can change the name that is looked up in a DNS list by
listing it after the domain name, introduced by a slash. For example,
.code
-deny message = Sender's domain is listed at $dnslist_domain
- dnslists = dsn.rfc-ignorant.org/$sender_address_domain
+deny dnslists = dsn.rfc-ignorant.org/$sender_address_domain
+ message = Sender's domain is listed at $dnslist_domain
.endd
This particular example is useful only in ACLs that are obeyed after the
RCPT or DATA commands, when a sender address is available. If (for
However, when the data for the list is obtained from a lookup, the second form
is usually much more convenient. Consider this example:
.code
-deny message = The mail servers for the domain \
+deny dnslists = sbl.spamhaus.org/<|${lookup dnsdb {>|a=<|\
+ ${lookup dnsdb {>|mxh=\
+ $sender_address_domain} }} }
+ message = The mail servers for the domain \
$sender_address_domain \
are listed at $dnslist_domain ($dnslist_value); \
see $dnslist_text.
- dnslists = sbl.spamhaus.org/<|${lookup dnsdb {>|a=<|\
- ${lookup dnsdb {>|mxh=\
- $sender_address_domain} }} }
.endd
Note the use of &`>|`& in the dnsdb lookup to specify the separator for
multiple DNS records. The inner dnsdb lookup produces a list of MX hosts
information.
You can use the DNS list variables in &%message%& or &%log_message%& modifiers
-&-- although these appear before the condition in the ACL, they are not
+&-- even if these appear before the condition in the ACL, they are not
expanded until after it has failed. For example:
.code
deny hosts = !+local_networks
a check that the IP being tested is indeed on the first list. The first
domain is the one that is put in &$dnslist_domain$&. For example:
.code
-deny message = \
- rejected because $sender_host_address is blacklisted \
- at $dnslist_domain\n$dnslist_text
- dnslists = \
+deny dnslists = \
sbl.spamhaus.org,sbl-xbl.spamhaus.org=127.0.0.2 : \
dul.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.10
+ message = \
+ rejected because $sender_host_address is blacklisted \
+ at $dnslist_domain\n$dnslist_text
.endd
For the first blacklist item, this starts by doing a lookup in
&'sbl-xbl.spamhaus.org'& and testing for a 127.0.0.2 return. If there is a
.code
acl_check_connect:
deny ratelimit = 100 / 5m / readonly
- log_message = RATE CHECK: $sender_rate/$sender_rate_period \
+ log_message = RATE CHECK: $sender_rate/$sender_rate_period \
(max $sender_rate_limit)
# ...
acl_check_mail:
warn ratelimit = 100 / 5m / strict
- log_message = RATE UPDATE: $sender_rate/$sender_rate_period \
+ log_message = RATE UPDATE: $sender_rate/$sender_rate_period \
(max $sender_rate_limit)
.endd
ratelimit = 100 / 1d / strict / $authenticated_id
# System-wide rate limit
-defer message = Sorry, too busy. Try again later.
- ratelimit = 10 / 1s / $primary_hostname
+defer ratelimit = 10 / 1s / $primary_hostname
+ message = Sorry, too busy. Try again later.
# Restrict incoming rate from each host, with a default
# set using a macro and special cases looked up in a table.
-defer message = Sender rate exceeds $sender_rate_limit \
- messages per $sender_rate_period
- ratelimit = ${lookup {$sender_host_address} \
+defer ratelimit = ${lookup {$sender_host_address} \
cdb {DB/ratelimits.cdb} \
{$value} {RATELIMIT} }
+ message = Sender rate exceeds $sender_rate_limit \
+ messages per $sender_rate_period
.endd
&*Warning*&: If you have a busy server with a lot of &%ratelimit%& tests,
especially with the &%per_rcpt%& option, you may suffer from a performance
use this:
.code
# Bounces: drop unsigned addresses for BATV senders
-deny message = This address does not send an unsigned reverse path
- senders = :
+deny senders = :
recipients = +batv_senders
+ message = This address does not send an unsigned reverse path
# Bounces: In case of prvs-signed address, check signature.
-deny message = Invalid reverse path signature.
- senders = :
+deny senders = :
condition = ${prvscheck {$local_part@$domain}\
{PRVSCHECK_SQL}{1}}
!condition = $prvscheck_result
+ message = Invalid reverse path signature.
.endd
The first statement rejects recipients for bounce messages that are addressed
to plain BATV sender addresses, because it is known that BATV senders do not
specialized interfaces for &"daemon"& type virus scanners, which are resident
in memory and thus are much faster.
+Since message data needs to have arrived,
+the condition may be only called in ACL defined by
+&%acl_smtp_data%&,
+&%acl_smtp_data_prdr%&,
+&%acl_smtp_mime%& or
+&%acl_smtp_dkim%&
+
A timeout of 2 minutes is applied to a scanner call (by default);
if it expires then a defer action is taken.
Here is a very simple scanning example:
.code
-deny message = This message contains malware ($malware_name)
- malware = *
+deny malware = *
+ message = This message contains malware ($malware_name)
.endd
The next example accepts messages when there is a problem with the scanner:
.code
-deny message = This message contains malware ($malware_name)
- malware = */defer_ok
+deny malware = */defer_ok
+ message = This message contains malware ($malware_name)
.endd
The next example shows how to use an ACL variable to scan with both sophie and
aveserver. It assumes you have set:
.endd
in the main Exim configuration.
.code
-deny message = This message contains malware ($malware_name)
- set acl_m0 = sophie
+deny set acl_m0 = sophie
malware = *
+ message = This message contains malware ($malware_name)
-deny message = This message contains malware ($malware_name)
- set acl_m0 = aveserver
+deny set acl_m0 = aveserver
malware = *
+ message = This message contains malware ($malware_name)
.endd
.section "Calling SpamAssassin from an Exim ACL" "SECID206"
Here is a simple example of the use of the &%spam%& condition in a DATA ACL:
.code
-deny message = This message was classified as SPAM
- spam = joe
+deny spam = joe
+ message = This message was classified as SPAM
.endd
The right-hand side of the &%spam%& condition specifies a name. This is
relevant if you have set up multiple SpamAssassin profiles. If you do not want
are quite small, it is recommended that you do not scan the big ones. For
example:
.code
-deny message = This message was classified as SPAM
- condition = ${if < {$message_size}{10K}}
+deny condition = ${if < {$message_size}{10K}}
spam = nobody
+ message = This message was classified as SPAM
.endd
The &%spam%& condition returns true if the threshold specified in the user's
statement block), append &`/defer_ok`& to the right-hand side of the
spam condition, like this:
.code
-deny message = This message was classified as SPAM
- spam = joe/defer_ok
+deny spam = joe/defer_ok
+ message = This message was classified as SPAM
.endd
This causes messages to be accepted even if there is a problem with &%spamd%&.
add_header = Subject: *SPAM* $h_Subject:
# reject spam at high scores (> 12)
-deny message = This message scored $spam_score spam points.
- spam = nobody:true
+deny spam = nobody:true
condition = ${if >{$spam_score_int}{120}{1}{0}}
+ message = This message scored $spam_score spam points.
.endd
available in the MIME ACL:
.vlist
+.vitem &$mime_anomaly_level$& &&&
+ &$mime_anomaly_text$&
+.vindex &$mime_anomaly_level$&
+.vindex &$mime_anomaly_text$&
+If there are problems decoding, these variables contain information on
+the detected issue.
+
.vitem &$mime_boundary$&
-If the current part is a multipart (see &$mime_is_multipart$&) below, it should
+.vindex &$mime_boundary$&
+If the current part is a multipart (see &$mime_is_multipart$& below), it should
have a boundary string, which is stored in this variable. If the current part
has no boundary parameter in the &'Content-Type:'& header, this variable
contains the empty string.
.vitem &$mime_charset$&
+.vindex &$mime_charset$&
This variable contains the character set identifier, if one was found in the
&'Content-Type:'& header. Examples for charset identifiers are:
.code
case-insensitively.
.vitem &$mime_content_description$&
+.vindex &$mime_content_description$&
This variable contains the normalized content of the &'Content-Description:'&
header. It can contain a human-readable description of the parts content. Some
implementations repeat the filename for attachments here, but they are usually
only used for display purposes.
.vitem &$mime_content_disposition$&
+.vindex &$mime_content_disposition$&
This variable contains the normalized content of the &'Content-Disposition:'&
header. You can expect strings like &"attachment"& or &"inline"& here.
.vitem &$mime_content_id$&
+.vindex &$mime_content_id$&
This variable contains the normalized content of the &'Content-ID:'& header.
This is a unique ID that can be used to reference a part from another part.
.vitem &$mime_content_size$&
+.vindex &$mime_content_size$&
This variable is set only after the &%decode%& modifier (see above) has been
successfully run. It contains the size of the decoded part in kilobytes. The
size is always rounded up to full kilobytes, so only a completely empty part
has a &$mime_content_size$& of zero.
.vitem &$mime_content_transfer_encoding$&
+.vindex &$mime_content_transfer_encoding$&
This variable contains the normalized content of the
&'Content-transfer-encoding:'& header. This is a symbolic name for an encoding
type. Typical values are &"base64"& and &"quoted-printable"&.
.vitem &$mime_content_type$&
+.vindex &$mime_content_type$&
If the MIME part has a &'Content-Type:'& header, this variable contains its
value, lowercased, and without any options (like &"name"& or &"charset"&). Here
are some examples of popular MIME types, as they may appear in this variable:
empty string.
.vitem &$mime_decoded_filename$&
+.vindex &$mime_decoded_filename$&
This variable is set only after the &%decode%& modifier (see above) has been
successfully run. It contains the full path and filename of the file
containing the decoded data.
.cindex "RFC 2047"
.vlist
.vitem &$mime_filename$&
+.vindex &$mime_filename$&
This is perhaps the most important of the MIME variables. It contains a
proposed filename for an attachment, if one was found in either the
&'Content-Type:'& or &'Content-Disposition:'& headers. The filename will be
found, this variable contains the empty string.
.vitem &$mime_is_coverletter$&
+.vindex &$mime_is_coverletter$&
This variable attempts to differentiate the &"cover letter"& of an e-mail from
attached data. It can be used to clamp down on flashy or unnecessarily encoded
content in the cover letter, while not restricting attachments at all.
alternative plain text), while allowing HTML files to be attached. HTML
coverletter mail attached to non-HTML coverletter mail will also be allowed:
.code
-deny message = HTML mail is not accepted here
-!condition = $mime_is_rfc822
-condition = $mime_is_coverletter
-condition = ${if eq{$mime_content_type}{text/html}{1}{0}}
+deny !condition = $mime_is_rfc822
+ condition = $mime_is_coverletter
+ condition = ${if eq{$mime_content_type}{text/html}{1}{0}}
+ message = HTML mail is not accepted here
.endd
+
.vitem &$mime_is_multipart$&
+.vindex &$mime_is_multipart$&
This variable has the value 1 (true) when the current part has the main type
&"multipart"&, for example, &"multipart/alternative"& or &"multipart/mixed"&.
Since multipart entities only serve as containers for other parts, you may not
want to carry out specific actions on them.
.vitem &$mime_is_rfc822$&
+.vindex &$mime_is_rfc822$&
This variable has the value 1 (true) if the current part is not a part of the
checked message itself, but part of an attached message. Attached message
decoding is fully recursive.
.vitem &$mime_part_count$&
+.vindex &$mime_part_count$&
This variable is a counter that is raised for each processed MIME part. It
starts at zero for the very first part (which is usually a multipart). The
counter is per-message, so it is reset when processing RFC822 attachments (see
with more backslashes, or use the &`\N`& facility to disable expansion.
Here is a simple example that contains two regular expressions:
.code
-deny message = contains blacklisted regex ($regex_match_string)
- regex = [Mm]ortgage : URGENT BUSINESS PROPOSAL
+deny regex = [Mm]ortgage : URGENT BUSINESS PROPOSAL
+ message = contains blacklisted regex ($regex_match_string)
.endd
The conditions returns true if any one of the regular expressions matches. The
&$regex_match_string$& expansion variable is then set up and contains the
HAVE_LOCAL_SCAN=yes
LOCAL_SCAN_SOURCE=Local/local_scan.c
.endd
-for example. The function must be called &[local_scan()]&. It is called by
+for example. The function must be called &[local_scan()]&;
+.new
+the source file(s) for it should first #define LOCAL_SCAN
+and then #include "local_scan.h".
+.wen
+It is called by
Exim after it has received a message, when the success return code is about to
be sent. This is after all the ACLs have been run. The return code from your
function controls whether the message is actually accepted or not. There is a
.cindex &%dlfunc%& "API description"
You must include this line near the start of your code:
.code
+#define LOCAL_SCAN
#include "local_scan.h"
.endd
This header file defines a number of variables and other values, and the
prototype for the function itself. Exim is coded to use unsigned char values
almost exclusively, and one of the things this header defines is a shorthand
for &`unsigned char`& called &`uschar`&.
-It also contains the following macro definitions, to simplify casting character
+It also makes available the following macro definitions, to simplify casting character
strings and pointers to character strings:
.code
#define CS (char *)
This function is used in conjunction with &'smtp_printf()'&, as described
below.
-.vitem &*void&~smtp_printf(char&~*,&~...)*&
-The arguments of this function are like &[printf()]&; it writes to the SMTP
+.vitem &*void&~smtp_printf(char&~*,BOOL,&~...)*&
+The arguments of this function are almost like &[printf()]&; it writes to the SMTP
output stream. You should use this function only when there is an SMTP output
stream, that is, when the incoming message is being received via interactive
SMTP. This is the case when &%smtp_input%& is TRUE and &%smtp_batched_input%&
If an SMTP TLS connection is established, &'smtp_printf()'& uses the TLS
output function, so it can be used for all forms of SMTP connection.
+The second argument is used to request that the data be buffered
+(when TRUE) or flushed (along with any previously buffered, when FALSE).
+This is advisory only, but likely to save on system-calls and packets
+sent when a sequence of calls to the function are made.
+
+The argument was added in Exim version 4.90 - changing the API/ABI.
+Nobody noticed until 4.93 was imminent, at which point the
+ABI version number was incremented.
+
Strings that are written by &'smtp_printf()'& from within &[local_scan()]&
must start with an appropriate response code: 550 if you are going to return
LOCAL_SCAN_REJECT, 451 if you are going to return
multiple output lines.
The &'smtp_printf()'& function does not return any error indication, because it
-does not automatically flush pending output, and therefore does not test
+does not
+guarantee a flush of
+pending output, and therefore does not test
the state of the stream. (In the main code of Exim, flushing and error
detection is done when Exim is ready for the next SMTP input command.) If
you want to flush the output and check for an error (for example, the
arguments. It flushes the output stream, and returns a non-zero value if there
is an error.
-.vitem &*void&~*store_get(int)*&
+.new
+.vitem &*void&~*store_get(int,BOOL)*&
This function accesses Exim's internal store (memory) manager. It gets a new
-chunk of memory whose size is given by the argument. Exim bombs out if it ever
+chunk of memory whose size is given by the first argument.
+The second argument should be given as TRUE if the memory will be used for
+data possibly coming from an attacker (eg. the message content),
+FALSE if it is locally-sourced.
+Exim bombs out if it ever
runs out of memory. See the next section for a discussion of memory handling.
+.wen
-.vitem &*void&~*store_get_perm(int)*&
+.vitem &*void&~*store_get_perm(int,BOOL)*&
This function is like &'store_get()'&, but it always gets memory from the
permanent pool. See the next section for a discussion of memory handling.
check_local_user
driver = redirect
domains = +local_domains
- file = /central/filters/$local_part
+ file = /central/filters/$local_part_data
no_verify
allow_filter
allow_freeze
.cindex "outgoing LMTP over TCP/IP"
.cindex "EHLO"
.cindex "HELO"
-.cindex "SIZE option on MAIL command"
+.cindex "SIZE" "option on MAIL command"
Outgoing SMTP and LMTP over TCP/IP is implemented by the &(smtp)& transport.
The &%protocol%& option selects which protocol is to be used, but the actual
processing is the same in both cases.
+.cindex "ESMTP extensions" SIZE
If, in response to its EHLO command, Exim is told that the SIZE
-parameter is supported, it adds SIZE=<&'n'&> to each subsequent MAIL
+extension is supported, it adds SIZE=<&'n'&> to each subsequent MAIL
command. The value of <&'n'&> is the message size plus the value of the
&%size_addition%& option (default 1024) to allow for additions to the message
such as per-transport header lines, or changes made in a
.section "The ETRN command" "SECTETRN"
.cindex "ETRN" "processing"
-RFC 1985 describes an SMTP command called ETRN that is designed to
+.cindex "ESMTP extensions" ETRN
+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
lists:
driver = redirect
domains = lists.example
- file = /usr/lists/$local_part
+ file = ${lookup {$local_part} dsearch,ret=full {/usr/lists}}
forbid_pipe
forbid_file
- errors_to = $local_part-request@lists.example
+ errors_to = ${quote_local_part:$local_part-request}@lists.example
no_more
.endd
This router is skipped for domains other than &'lists.example'&. For addresses
driver = redirect
domains = lists.example
local_part_suffix = -request
- file = /usr/lists/$local_part$local_part_suffix
+ local_parts = ${lookup {$local_part} dsearch,filter=file {/usr/lists}}
+ file = /usr/lists/${local_part_data}-request
no_more
lists_post:
domains = lists.example
senders = ${if exists {/usr/lists/$local_part}\
{lsearch;/usr/lists/$local_part}{*}}
- file = /usr/lists/$local_part
+ file = ${lookup {$local_part} dsearch,ret=full {/usr/lists}}
forbid_pipe
forbid_file
- errors_to = $local_part-request@lists.example
+ errors_to = ${quote_local_part:$local_part-request}@lists.example
no_more
lists_closed:
max_rcpt = 1
return_path = \
${if match {$return_path}{^(.+?)-request@your.dom.example\$}\
- {$1-request+$local_part=$domain@your.dom.example}fail}
+ {${quote_local_part:$1-request+$local_part=$domain}@your.dom.example}fail}
.endd
This has the effect of rewriting the return path (envelope sender) on outgoing
SMTP messages, if the local part of the original return path ends in
transport = remote_smtp
errors_to = \
${if match {$return_path}{^(.+?)-request@your.dom.example\$}}
- {$1-request+$local_part=$domain@your.dom.example}fail}
+ {${quote_local_part:$1-request+$local_part=$domain}@your.dom.example}fail}
no_more
.endd
Before you start sending out messages with VERPed return paths, you must also
virtual:
driver = redirect
domains = dsearch;/etc/mail/virtual
- data = ${lookup{$local_part}lsearch{/etc/mail/virtual/$domain}}
+ data = ${lookup{$local_part}lsearch{/etc/mail/virtual/$domain_data}}
no_more
.endd
+.new
The &%domains%& option specifies that the router is to be skipped, unless there
is a file in the &_/etc/mail/virtual_& directory whose name is the same as the
-domain that is being processed. When the router runs, it looks up the local
+domain that is being processed.
+The &(dsearch)& lookup used results in an untainted version of &$domain$&
+being placed into the &$domain_data$& variable.
+.wen
+
+When the router runs, it looks up the local
part in the file to find a new address (or list of addresses). The &%no_more%&
setting ensures that if the lookup fails (leading to &%data%& being an empty
string), Exim gives up on the address without trying any subsequent routers.
.code
my_mailboxes:
driver = appendfile
- file = /var/mail/$domain/$local_part
+ file = /var/mail/$domain/$local_part_data
user = mail
.endd
This uses a directory of mailboxes for each domain. The &%user%& setting is
userforward:
driver = redirect
check_local_user
- file = $home/.forward$local_part_suffix
local_part_suffix = -*
local_part_suffix_optional
+ file = ${lookup {.forward$local_part_suffix} dsearch,ret=full {$home} {$value}fail}
allow_filter
.endd
If there is no suffix, &_.forward_& is used; if the suffix is &'-special'&, for
.cindex "SMTP" "passed connection"
.cindex "SMTP" "multiple deliveries"
.cindex "multiple SMTP deliveries"
+.cindex "first pass routing"
Mail waiting to be sent from an intermittently connected host will probably
not have been routed, because without a connection DNS lookups are not
possible. This means that if a normal queue run is done at connection time,
&`DKIM`& domain verified in incoming message
&`DN `& distinguished name from peer certificate
&`DS `& DNSSEC secured lookups
-&`DT `& on &`=>`& lines: time taken for a delivery
+&`DT `& on &`=>`&, &'=='& and &'**'& lines: time taken for, or to attempt, a delivery
&`F `& sender address (on delivery lines)
&`H `& host name and IP address
&`I `& local interface used
&` arguments `& command line arguments
&`*connection_reject `& connection rejections
&`*delay_delivery `& immediate delivery delayed
-&` deliver_time `& time taken to perform delivery
+&` deliver_time `& time taken to attempt delivery
&` delivery_size `& add &`S=`&&'nnn'& to => lines
&`*dkim `& DKIM verified domain on <= lines
&` dkim_verbose `& separate full DKIM verification result line, per signature
&%millisec%&: Timestamps have a period and three decimal places of finer granularity
appended to the seconds value.
.next
-.new
.cindex "log" "message id"
&%msg_id%&: The value of the Message-ID: header.
.next
This will be either because the message is a bounce, or was submitted locally
(submission mode) without one.
The field identifier will have an asterix appended: &"id*="&.
-.wen
.next
.cindex "log" "outgoing interface"
.cindex "log" "local interface"
On accept lines, where PIPELINING was offered but not used by the client,
the field has a minus appended.
-.new
.cindex "pipelining" "early connection"
If Exim is built with the SUPPORT_PIPE_CONNECT build option
accept "L" fields have a period appended if the feature was
offered but not used, or an asterisk appended if used.
Delivery "L" fields have an asterisk appended if used.
-.wen
.next
.cindex "log" "queue run"
.vitem &*-x*&
Match only non-frozen messages.
-.new
.vitem &*-G*&&~<&'queuename'&>
Match only messages in the given queue. Without this, the default queue is searched.
-.wen
.endlist
The following options control the format of the output:
certificate.
.endlist
+Any of the above may have an extra hyphen prepended, to indicate the the
+corresponding data is untrusted.
+
Following the options there is a list of those addresses to which the message
is not to be delivered. This set of addresses is initialized from the command
line when the &%-t%& option is used and &%extract_addresses_remove_arguments%&
. ////////////////////////////////////////////////////////////////////////////
. ////////////////////////////////////////////////////////////////////////////
-.chapter "DKIM and SPF" "CHAPdkim" &&&
- "DKIM and SPF Support"
-.cindex "DKIM"
+.chapter "DKIM, SPF and DMARC" "CHAPdkim" &&&
+ "DKIM, SPF and DMARC Support"
.section "DKIM (DomainKeys Identified Mail)" SECDKIM
+.cindex "DKIM"
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
The domain(s) you want to sign with.
After expansion, this can be a list.
Each element in turn,
-.new
lowercased,
-.wen
is put into the &%$dkim_domain%& expansion variable
while expanding the remaining signing options.
If it is empty after expansion, DKIM signing is not done,
openssl genrsa -out dkim_rsa.private 2048
openssl rsa -in dkim_rsa.private -out /dev/stdout -pubout -outform PEM
.endd
+The result file from the first command should be retained, and
+this option set to use it.
Take the base-64 lines from the output of the second command, concatenated,
for the DNS TXT record.
See section 3.6 of RFC6376 for the record specification.
Signers SHOULD use RSA keys of at least 2048 bits.
.endd
-.new
EC keys for DKIM are defined by RFC 8463.
-.wen
They are considerably smaller than RSA keys for equivalent protection.
As they are a recent development, users should consider dual-signing
(by setting a list of selectors, and an expansion for this option)
certtool --load_privkey=dkim_ed25519.private --pubkey_info --outder | tail -c +13 | base64
.endd
-.new
Exim also supports an alternate format
of Ed25519 keys in DNS which was a candidate during development
of the standard, but not adopted.
A future release will probably drop that support.
-.wen
.option dkim_hash smtp string&!! sha256
Can be set to any one of the supported hash methods, which are:
.option dkim_strict smtp string&!! unset
This option defines how Exim behaves when signing a message that
should be signed fails for some reason. When the expansion evaluates to
-either "1" or "true", Exim will defer. Otherwise Exim will send the message
+either &"1"& or &"true"&, Exim will defer. Otherwise Exim will send the message
unsigned. You can use the &%$dkim_domain%& and &%$dkim_selector%& expansion
variables here.
When unspecified, the header names listed in RFC4871 will be used,
whether or not each header is present in the message.
The default list is available for the expansion in the macro
-"_DKIM_SIGN_HEADERS".
+&"_DKIM_SIGN_HEADERS"&
+.new
+and an oversigning variant is in &"_DKIM_OVERSIGN_HEADERS"&.
+.wen
If a name is repeated, multiple headers by that name (or the absence thereof)
will be signed. The textually later headers in the headers part of the
message are signed first, if there are multiples.
-A name can be prefixed with either an '=' or a '+' character.
-If an '=' prefix is used, all headers that are present with this name
+A name can be prefixed with either an &"="& or a &"+"& character.
+If an &"="& prefix is used, all headers that are present with this name
will be signed.
-If a '+' prefix if used, all headers that are present with this name
+If a &"+"& prefix if used, all headers that are present with this name
will be signed, and one signature added for a missing header with the
name will be appended.
Verification of DKIM signatures in SMTP incoming email is done for all
messages for which an ACL control &%dkim_disable_verify%& has not been set.
+.cindex DKIM "selecting signature algorithms"
+Individual classes of signature algorithm can be ignored by changing
+the main options &%dkim_verify_hashes%& or &%dkim_verify_keytypes%&.
+The &%dkim_verify_minimal%& option can be set to cease verification
+processing for a message once the first passing signature is found.
+
.cindex authentication "expansion item"
Performing verification sets up information used by the
-&$authresults$& expansion item.
+&%authresults%& expansion item.
+
+For most purposes the default option settings suffice and the remainder
+of this section can be ignored.
-The results of that verification are then made available to the
+The results of verification are made available to the
&%acl_smtp_dkim%& ACL, which can examine and modify them.
-By default, this ACL is called once for each
-syntactically(!) correct signature in the incoming message.
A missing ACL definition defaults to accept.
+By default, the ACL is called once for each
+syntactically(!) correct signature in the incoming message.
If any ACL call does not accept, the message is not accepted.
If a cutthrough delivery was in progress for the message, that is
summarily dropped (having wasted the transmission effort).
runtime of the ACL.
Calling the ACL only for existing signatures is not sufficient to build
-more advanced policies. For that reason, the global option
-&%dkim_verify_signers%&, and a global expansion variable
+more advanced policies. For that reason, the main option
+&%dkim_verify_signers%&, and an expansion variable
&%$dkim_signers%& exist.
-The global option &%dkim_verify_signers%& can be set to a colon-separated
+The main option &%dkim_verify_signers%& can be set to a colon-separated
list of DKIM domains or identities for which the ACL &%acl_smtp_dkim%& is
called. It is expanded when the message has been received. At this point,
the expansion variable &%$dkim_signers%& already contains a colon-separated
If a domain or identity is listed several times in the (expanded) value of
&%dkim_verify_signers%&, the ACL is only called once for that domain or identity.
-.new
Note that if the option is set using untrustworthy data
(such as the From: header)
care should be taken to force lowercase for domains
and for the domain part if identities.
The default setting can be regarded as trustworthy in this respect.
-.wen
If multiple signatures match a domain (or identity), the ACL is called once
for each matching signature.
-Inside the &%acl_smtp_dkim%&, the following expansion variables are
+Inside the DKIM ACL, the following expansion variables are
available (from most to least important):
algorithms (currently, rsa-sha1) have permanently failed evaluation
.endd
-To enforce this you must have a DKIM ACL which checks this variable
-and overwrites the &$dkim_verify_status$& variable as discussed above.
+To enforce this you must either have a DKIM ACL which checks this variable
+and overwrites the &$dkim_verify_status$& variable as discussed above,
+or have set the main option &%dkim_verify_hashes%& to exclude
+processing of such signatures.
.vitem &%$dkim_canon_body%&
The body canonicalization method. One of 'relaxed' or 'simple'.
.vitem &%$dkim_key_length%&
Number of bits in the key.
+.new
+Valid only once the key is loaded, which is at the time the header signature
+is verified, which is after the body hash is.
+.wen
Note that RFC 8301 says:
.code
less than 1024 bits as valid signatures.
.endd
-To enforce this you must have a DKIM ACL which checks this variable
-and overwrites the &$dkim_verify_status$& variable as discussed above.
-As EC keys are much smaller, the check should only do this for RSA keys.
+This is enforced by the default setting for the &%dkim_verify_min_keysizes%&
+option.
.endlist
.code
# Warn when Mail purportedly from GMail has no gmail signature
-warn log_message = GMail sender without gmail.com DKIM signature
- sender_domains = gmail.com
+warn sender_domains = gmail.com
dkim_signers = gmail.com
dkim_status = none
+ log_message = GMail sender without gmail.com DKIM signature
.endd
Note that the above does not check for a total lack of DKIM signing;
to restrict an ACL verb to a list of verification outcomes, for example:
.code
-deny message = Mail from Paypal with invalid/missing signature
- sender_domains = paypal.com:paypal.de
+deny sender_domains = paypal.com:paypal.de
dkim_signers = paypal.com:paypal.de
dkim_status = none:invalid:fail
+ message = Mail from Paypal with invalid/missing signature
.endd
The possible status keywords are: 'none','invalid','fail' and 'pass'. Please
SPF is a mechanism whereby a domain may assert which IP addresses may transmit
messages with its domain in the envelope from, documented by RFC 7208.
-For more information on SPF see &url(http://www.openspf.org).
-. --- 2018-09-07: still not https
+For more information on SPF see &url(http://www.open-spf.org), a static copy of
+the &url(http://openspf.org).
+. --- 2019-10-28: still not https, open-spf.org is told to be a
+. --- web-archive copy of the now dead openspf.org site
+. --- See https://www.mail-archive.com/mailop@mailop.org/msg08019.html for a
+. --- discussion.
Messages sent by a system not authorised will fail checking of such assertions.
This includes retransmissions done by traditional forwarders.
For verification, an ACL condition and an expansion lookup are provided.
.cindex authentication "expansion item"
Performing verification sets up information used by the
-&$authresults$& expansion item.
+&%authresults%& expansion item.
.cindex SPF "ACL condition"
message = $sender_host_address is not allowed to send mail from \
${if def:sender_address_domain \
{$sender_address_domain}{$sender_helo_name}}. \
- Please see http://www.openspf.org/Why?scope=\
- ${if def:sender_address_domain {mfrom}{helo}};\
+ Please see http://www.open-spf.org/Why;\
identity=${if def:sender_address_domain \
{$sender_address}{$sender_helo_name}};\
ip=$sender_host_address
.endd
+Note: The above mentioned URL may not be as helpful as expected. You are
+encouraged to replace the link with a link to a site with more
+explanations.
+
When the spf condition has run, it sets up several expansion
variables:
.vitem &$spf_smtp_comment$&
.vindex &$spf_smtp_comment$&
+.vindex &%spf_smtp_comment_template%&
This contains a string that can be used in a SMTP response
to the calling party. Useful for "fail".
+.new
+ The string is generated by the SPF library from the template configured in the main config
+ option &%spf_smtp_comment_template%&.
+.wen
.endlist
"Best-guess". Strictly speaking, "Best-guess" is not standard
SPF, but it is supported by the same framework that enables SPF
capability.
-Refer to &url(http://www.openspf.org/FAQ/Best_guess_record)
+Refer to &url(http://www.open-spf.org/FAQ/Best_guess_record)
for a description of what it means.
-. --- 2018-09-07: still not https:
+. --- 2019-10-28: still not https:
To access this feature, simply use the spf_guess condition in place
of the spf one. For example:
.cindex SPF "lookup expansion"
.cindex lookup spf
A lookup expansion is also available. It takes an email
-address as the key and an IP address as the database:
+address as the key and an IP address
+(v4 or v6)
+as the database:
.code
${lookup {username@domain} spf {ip.ip.ip.ip}}
The lookup will return the same result strings as can appear in
&$spf_result$& (pass,fail,softfail,neutral,none,err_perm,err_temp).
-Currently, only IPv4 addresses are supported.
+
+
+
+
+
+.section DMARC SECDMARC
+.cindex DMARC verification
+
+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/).
+
+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/)
+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.
+This description assumes
+that headers will be in /usr/local/include, and that the libraries
+are in /usr/local/lib.
+
+. subsection
+
+There are three main-configuration options:
+.cindex DMARC "configuration options"
+
+The &%dmarc_tld_file%& option
+.oindex &%dmarc_tld_file%&
+defines the location of a text file of valid
+top level domains the opendmarc library uses
+during domain parsing. Maintained by Mozilla,
+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.
+.new
+The default for the option is unset.
+If not set, DMARC processing is disabled.
+.wen
+
+
+The &%dmarc_history_file%& option, if set
+.oindex &%dmarc_history_file%&
+defines the location of a file to log results
+of dmarc verification on inbound emails. The
+contents are importable by the opendmarc tools
+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 &%dmarc_forensic_sender%& option
+.oindex &%dmarc_forensic_sender%&
+defines an alternate email address to use when sending a
+forensic report detailing alignment failures
+if a sender domain's dmarc record specifies it
+and you have configured Exim to send them.
+If set, this is expanded and used for the
+From: header line; the address is extracted
+from it and used for the envelope from.
+If not set (the default), the From: header is expanded from
+the dsn_from option, and <> is used for the
+envelope from.
+
+. I wish we had subsections...
+
+.cindex DMARC controls
+By default, the DMARC processing will run for any remote,
+non-authenticated user. It makes sense to only verify DMARC
+status of messages coming from remote, untrusted sources. You can
+use standard conditions such as hosts, senders, etc, to decide that
+DMARC verification should *not* be performed for them and disable
+DMARC with an ACL control modifier:
+.code
+ control = dmarc_disable_verify
+.endd
+A DMARC record can also specify a "forensic address", which gives
+exim an email address to submit reports about failed alignment.
+Exim does not do this by default because in certain conditions it
+results in unintended information leakage (what lists a user might
+be subscribed to, etc). You must configure exim to submit forensic
+reports to the owner of the domain. If the DMARC record contains a
+forensic address and you specify the control statement below, then
+exim will send these forensic emails. It is also advised that you
+configure a &%dmarc_forensic_sender%& because the default sender address
+construction might be inadequate.
+.code
+ control = dmarc_enable_forensic
+.endd
+(AGAIN: You can choose not to send these forensic reports by simply
+not putting the dmarc_enable_forensic control line at any point in
+your exim config. If you don't tell exim to send them, it will not
+send them.)
+
+There are no options to either control. Both must appear before
+the DATA acl.
+
+. subsection
+
+DMARC checks cam 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
+for a DMARC check to actually occur. All of the variables are set
+up before the DATA ACL, but there is no actual DMARC check that
+occurs until a &"dmarc_status"& condition is encountered in the ACLs.
+
+The &"dmarc_status"& condition takes a list of strings on its
+right-hand side. These strings describe recommended action based
+on the DMARC check. To understand what the policy recommendations
+mean, refer to the DMARC website above. Valid strings are:
+.display
+&'accept '& The DMARC check passed and the library recommends accepting the email.
+&'reject '& The DMARC check failed and the library recommends rejecting the email.
+&'quarantine '& The DMARC check failed and the library recommends keeping it for further inspection.
+&'none '& The DMARC check passed and the library recommends no specific action, neutral.
+&'norecord '& No policy section in the DMARC record for this sender domain.
+&'nofrom '& Unable to determine the domain of the sender.
+&'temperror '& Library error or dns error.
+&'off '& The DMARC check was disabled for this email.
+.endd
+You can prefix each string with an exclamation mark to invert its
+meaning, for example "!accept" will match all results but
+"accept". The string list is evaluated left-to-right in a
+short-circuit fashion. When a string matches the outcome of the
+DMARC check, the condition succeeds. If none of the listed
+strings matches the outcome of the DMARC check, the condition
+fails.
+
+Of course, you can also use any other lookup method that Exim
+supports, including LDAP, Postgres, MySQL, etc, as long as the
+result is a list of colon-separated strings.
+
+Performing the check sets up information used by the
+&%authresults%& expansion item.
+
+Several expansion variables are set before the DATA ACL is
+processed, and you can use them in this ACL. The following
+expansion variables are available:
+
+.vlist
+.vitem &$dmarc_status$&
+.vindex &$dmarc_status$&
+.cindex DMARC result
+A one word status indicating what the DMARC library
+thinks of the email. It is a combination of the results of
+DMARC record lookup and the SPF/DKIM/DMARC processing results
+(if a DMARC record was found). The actual policy declared
+in the DMARC record is in a separate expansion variable.
+
+.vitem &$dmarc_status_text$&
+.vindex &$dmarc_status_text$&
+Slightly longer, human readable status.
+
+.vitem &$dmarc_used_domain$&
+.vindex &$dmarc_used_domain$&
+The domain which DMARC used to look up the DMARC policy record.
+
+.vitem &$dmarc_domain_policy$&
+.vindex &$dmarc_domain_policy$&
+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.
+.endlist
+
+. subsection
+
+By default, Exim's DMARC configuration is intended to be
+non-intrusive and conservative. To facilitate this, Exim will not
+create any type of logging files without explicit configuration by
+you, the admin. Nor will Exim send out any emails/reports about
+DMARC issues without explicit configuration by you, the admin (other
+than typical bounce messages that may come about due to ACL
+processing or failure delivery issues).
+
+In order to log statistics suitable to be imported by the opendmarc
+tools, you need to:
+.ilist
+Configure the global option &%dmarc_history_file%&
+.next
+Configure cron jobs to call the appropriate opendmarc history
+import scripts and truncating the dmarc_history_file
+.endlist
+
+In order to send forensic reports, you need to:
+.ilist
+Configure the global option &%dmarc_forensic_sender%&
+.next
+Configure, somewhere before the DATA ACL, the control option to
+enable sending DMARC forensic reports
+.endlist
+
+. subsection
+
+Example usage:
+.code
+(RCPT ACL)
+ warn domains = +local_domains
+ hosts = +local_hosts
+ control = dmarc_disable_verify
+
+ warn !domains = +screwed_up_dmarc_records
+ control = dmarc_enable_forensic
+
+ warn condition = (lookup if destined to mailing list)
+ set acl_m_mailing_list = 1
+
+(DATA ACL)
+ warn dmarc_status = accept : none : off
+ !authenticated = *
+ log_message = DMARC DEBUG: $dmarc_status $dmarc_used_domain
+
+ warn dmarc_status = !accept
+ !authenticated = *
+ log_message = DMARC DEBUG: '$dmarc_status' for $dmarc_used_domain
+
+ warn dmarc_status = quarantine
+ !authenticated = *
+ set $acl_m_quarantine = 1
+ # Do something in a transport with this flag variable
+
+ deny condition = ${if eq{$dmarc_domain_policy}{reject}}
+ condition = ${if eq{$acl_m_mailing_list}{1}}
+ message = Messages from $dmarc_used_domain break mailing lists
+
+ deny dmarc_status = reject
+ !authenticated = *
+ message = Message from $dmarc_used_domain failed sender's DMARC policy, REJECT
+
+ warn add_header = :at_start:${authresults {$primary_hostname}}
+.endd
+
# Or do some kind of IP lookup in a flat file or database
# LIMIT = ${lookup{$sender_host_address}iplsearch{/etc/exim/proxy_limits}}
- defer message = Too many connections from this IP right now
- ratelimit = LIMIT / 5s / per_conn / strict
+ defer ratelimit = LIMIT / 5s / per_conn / strict
+ message = Too many connections from this IP right now
.endd
.section "MTA operations" SECTi18nMTA
.cindex SMTPUTF8 "ESMTP option"
+.cindex "ESMTP extensions" SMTPUTF8
The main configuration option &%smtputf8_advertise_hosts%& specifies
a host list. If this matches the sending host and
accept_8bitmime is true (the default) then the ESMTP option
control = utf8_downconvert
control = utf8_downconvert/<value>
.endd
-This sets a flag requiring that addresses are converted to
-a-label form before smtp delivery, for use in a
-Message Submission Agent context.
+This sets a flag requiring that envelope addresses are converted to
+a-label form before smtp delivery.
+This is usually for use in a Message Submission Agent context,
+but could be used for any message.
+
If a value is appended it may be:
.display
-&`1 `& (default) mandatory downconversion
+&`1 `& mandatory downconversion
&`0 `& no downconversion
&`-1 `& if SMTPUTF8 not supported by destination host
.endd
+If no value is given, 1 is used.
If mua_wrapper is set, the utf8_downconvert control
is initially set to -1.
The smtp transport has an option &%utf8_downconvert%&.
If set it must expand to one of the three values described above,
-and it overrides any previously set value.
+or an empty string.
+If non-empty it overrides value previously set
+(due to mua_wrapper or by an ACL control).
There is no explicit support for VRFY and EXPN.
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:
+.wen
.display
&`dane:fail after transport `& per connection
&`msg:complete after main `& per message
+&`msg:defer after transport `& per message per delivery try
&`msg:delivery after transport `& per recipient
&`msg:rcpt:host:defer after transport `& per recipient per host
&`msg:rcpt:defer after transport `& per recipient
-&`msg:host:defer after transport `& per attempt
+&`msg:host:defer after transport `& per host per delivery try; host errors
&`msg:fail:delivery after transport `& per recipient
&`msg:fail:internal after main `& per recipient
&`tcp:connect before transport `& per connection
&`tcp:close after transport `& per connection
&`tls:cert before both `& per certificate in verification chain
&`smtp:connect after transport `& per connection
+&`smtp:ehlo after transport `& per connection
.endd
New event types may be added in future.
with the event type:
.display
&`dane:fail `& failure reason
+&`msg:defer `& error string
&`msg:delivery `& smtp confirmation message
&`msg:fail:internal `& failure reason
&`msg:fail:delivery `& smtp error message
+&`msg:host:defer `& error string
&`msg:rcpt:host:defer `& error string
&`msg:rcpt:defer `& error string
-&`msg:host:defer `& error string
&`tls:cert `& verification chain depth
&`smtp:connect `& smtp banner
+&`smtp:ehlo `& smtp ehlo response
.endd
The :defer events populate one extra variable: &$event_defer_errno$&.
git://git.exim.org / users / heiko / exim.git / blobdiff