. Update the Copyright year (only) when changing content.
. /////////////////////////////////////////////////////////////////////////////
-.set previousversion "4.93"
+.set previousversion "4.94"
.include ./local_params
.set ACL "access control lists (ACLs)"
.set I " "
.macro copyyear
-2019
+2020
.endmacro
. /////////////////////////////////////////////////////////////////////////////
&%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)
-.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 "&$local_user_gid$&"
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%&"
signals the final completion of the sequence of processes that are passing
messages through the same SMTP connection.
+.new
+.vitem &%-MCq%&&~<&'recipient&~address'&>&~<&'size'&>
+.oindex "&%-MCq%&"
+This option is not intended for use by external callers. It is used internally
+by Exim to implement quota checking for local users.
+.wen
+
.vitem &%-MCS%&
.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%&
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"
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 "queue" "routing"
.cindex "routing" "whole queue before delivery"
.cindex "first pass routing"
+.cindex "queue runner" "two phase"
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
+If that is so and the &%queue_fast_ramp%& option is true then
+in the first phase of the run,
+once a threshold number of messages are routed for a given host,
+a delivery process is forked in parallel with the rest of the scan.
.cindex "hints database" "remembering routing"
The hints database that remembers which messages are waiting for specific hosts
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: $sender_host_address is in \
.code
local_delivery:
driver = appendfile
- file = /var/mail/$local_part_verified
+ file = /var/mail/$local_part_data
delivery_date_add
envelope_to_add
return_path_add
This &(appendfile)& transport is used for local delivery to user mailboxes in
traditional BSD mailbox format.
-.new
We prefer to avoid using &$local_part$& directly to define the mailbox filename,
as it is provided by a potential bad actor.
-Instead we use &$local_part_verified$&,
+Instead we use &$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_&
lookup. Lookups of this type are conditional expansion items. Different results
can be defined for the cases of lookup success and failure. See chapter
&<<CHAPexpand>>&, where string expansions are described in detail.
-The key for the lookup is specified as part of the string expansion.
+The key for the lookup is &*specified*& as part of the string expansion.
.next
Lists of domains, hosts, and email addresses can contain lookup requests as a
way of avoiding excessively long linear lists. In this case, the data that is
returned by the lookup is often (but not always) discarded; whether the lookup
succeeds or fails is what really counts. These kinds of list are described in
chapter &<<CHAPdomhosaddlists>>&.
-The key for the lookup is given by the context in which the list is expanded.
+The key for the lookup is &*implicit*&,
+given by the context in which the list is expanded.
.endlist
String expansions, lists, and lookups interact with each other in such a way
.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
-in the file. The file could contains lines like this:
+in the file.
+The file could contains lines like this:
.code
domain1:
domain2:
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.
+
+All lookups support the option &"cache=no_rd"&.
+If this is given then the cache that Exim manages for lookup results
+is not checked before diong the lookup.
+The result of the lookup is still written to the cache.
+.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
-.wen
+
+.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.
+.cindex "tainted data" "de-tainting"
.next
.cindex "query-style lookup" "definition of"
The &'query-style'& type accepts a generalized database query. No particular
.cindex "lookup" "dsearch"
.cindex "dsearch lookup type"
&(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.
.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
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.
+
+
+.new
+.next
+.cindex LMDB
+.cindex lookup lmdb
+.cindex database lmdb
+&(lmdb)&: The given file is an LMDB database.
+LMDB is a memory-mapped key-value store,
+with API modeled loosely on that of BerkeleyDB.
+See &url(https://symas.com/products/lightning-memory-mapped-database/)
+for the feature set and operation modes.
+
+Exim provides read-only access via the LMDB C library.
+The library can be obtained from &url(https://github.com/LMDB/lmdb)
+or your operating system package repository.
+To enable LMDB support in Exim set LOOKUP_LMDB=yes in &_Local/Makefile_&.
+
+You will need to separately create the LMDB database file,
+possibly using the &"mdb_load"& utility.
+.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
.cindex "sqlite lookup type"
.cindex "lookup" "sqlite"
&(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>>&.
+an SQL statement that is passed to an SQLite database. See section &<<SECTsqlite>>&.
.next
&(testdb)&: This is a lookup type that is used for testing Exim. It is
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 appending a comma-separated option to the query type:
.display
-.endd
&`,servers=`&&'server1:server2:server3:...'&
-.wen
+.endd
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
${lookup pgsql,servers=master/db/name/pw {UPDATE ...} }
.endd
-.new
-An older syntax places the servers speciification before the qury,
+An older syntax places the servers specification before the query,
semicolon separated:
.code
${lookup mysql{servers=master; UPDATE ...} }
The new version avoids potential issues with tainted
arguments in the query, for explicit expansion.
&*Note*&: server specifications in list-style lookups are still problematic.
-.wen
.section "Special MySQL features" "SECID73"
.new
.oindex &%sqlite_dbfile%&
-The preferred way of specifying the file is by using the
-&%sqlite_dbfile%& option, set to
-an absolute path.
+There are two ways of
+specifying the file.
+The first is is by using the &%sqlite_dbfile%& main option.
+The second, which allows separate files for each query,
+is to use an option appended, comma-separated, to the &"sqlite"&
+lookup type word. The option is the word &"file"&, then an equals,
+then the filename.
+The filename in this case cannot contain whitespace or open-brace charachters.
.wen
+
A deprecated method is available, prefixing the query with the filename
separated by white space.
-This means that the path name cannot contain white space.
+This means that
.cindex "tainted data" "sqlite file"
-It also means that the query cannot use any tainted values, as that taints
+the query cannot use any tainted values, as that taints
the entire query including the filename - resulting in a refusal to open
the file.
-.new
+In all the above cases the filename must be an absolute path.
+
Here is a lookup expansion example:
.code
sqlite_dbfile = /some/thing/sqlitedb
domainlist relay_to_domains = sqlite;\
select * from relays where ip='$sender_host_address';
.endd
-.wen
The only character affected by the &%quote_sqlite%& operator is a single
quote, which it doubles.
+.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.
+
+
+
+
.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
.code
hide domainlist filter_for_domains = ldap;PASS=secret ldap::/// ...
.endd
-.wen
Named lists may have a performance advantage. When Exim is routing an
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.
+
+The value for a match will be the primary host name.
+
+
.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.
+
+The value for a match will be the string &`@[]`&.
+
+
.next
.cindex "@mx_any"
.cindex "@mx_primary"
domains = <? @mx_any/ignore=<;127.0.0.1;::1 ? \
an.other.domain ? ...
.endd
+The value for a match will be the list element string (starting &`@mx_`&).
+
+
.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'&.
+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.
+
.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).
+
+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.
+
+
+
.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 command and options,
+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 = \
conditions do not expand some of the brace-delimited branches, for security
reasons,
.cindex "tainted data" expansion
+.cindex "tainted data" definition
.cindex expansion "tainted data"
and expansion of data deriving from the sender (&"tainted data"&)
is not permitted.
+.new
+Common ways of obtaining untainted equivalents of variables with
+tainted values
+.cindex "tainted data" "de-tainting"
+come down to using the tainted value as a lookup key in a trusted database.
+This database could be the filesystem structure,
+or the password file,
+or accessed via a DBMS.
+Specific methods are indexed under &"de-tainting"&.
+.wen
+
.section "Literal text in expanded strings" "SECTlittext"
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 &*${hmac{*&<&'hashname'&>&*}{*&<&'secret'&>&*}{*&<&'string'&>&*}}*&
You can use &`fail`& instead of {<&'string3'&>} as in a string extract.
-.vitem "&*${lookup{*&<&'key'&>&*}&~*&<&'search&~type'&>&*&~&&&
- {*&<&'file'&>&*}&~{*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&"
-This is the first of one of two different types of lookup item, which are both
-described in the next item.
+.new
+.vitem &*${listquote{*&<&'separator'&>&*}{*&<&'string'&>&*}}*&
+.cindex quoting "for list"
+.cindex list quoting
+This item doubles any occurrence of the separator character
+in the given string.
+An empty string is replaced with a single space.
+This converts the string into a safe form for use as a list element,
+in a list using the given separator.
+.wen
-.vitem "&*${lookup&~*&<&'search&~type'&>&*&~{*&<&'query'&>&*}&~&&&
+
+.vitem "&*${lookup&~{*&<&'key'&>&*}&~*&<&'search&~type'&>&*&~&&&
+ {*&<&'file'&>&*}&~{*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&" &&&
+ "&*${lookup&~*&<&'search&~type'&>&*&~{*&<&'query'&>&*}&~&&&
{*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&"
.cindex "expansion" "lookup in"
.cindex "file" "lookups"
.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.
+
+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
+
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
will sort an MX lookup into priority order.
+
+.new
+.vitem &*${srs_encode&~{*&<&'secret'&>&*}{*&<&'return&~path'&>&*}{*&<&'original&~domain'&>&*}}*&
+SRS encoding. See SECT &<<SECTSRS>>& for details.
+.wen
+
+
+
.vitem &*${substr{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
.cindex "&%substr%& expansion item"
.cindex "substring extraction"
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.
case-independent.
Case and collation order are defined per the system C locale.
+
+.new
+.vitem &*inbound_srs&~{*&<&'local&~part'&>&*}{*&<&'secret'&>&*}*&
+SRS decode. See SECT &<<SECTSRS>>& for details.
+.wen
+
+
.vitem &*inlist&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
&*inlisti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
.cindex "string" "comparison"
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
.vindex "&$config_file$&"
The name of the main configuration file Exim is using.
-.vitem &$dmarc_domain_policy$& &&&
- &$dmarc_status$& &&&
- &$dmarc_status_text$& &&&
- &$dmarc_used_domains$&
-Results of DMARC verification.
-For details see section &<<SECDMARC>>&.
-
.vitem &$dkim_verify_status$&
Results of DKIM verification.
For details see section &<<SECDKIMVFY>>&.
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.
-See also &$domain_verified$&.
-.wen
+When an 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.
.vitem &$domain_data$&
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$&
.cindex "host name" "lookup, failure of"
because a message may have many recipients and the system filter is called just
once.
-.new
.cindex "tainted data"
If the origin of the data is an incoming message,
the result of expanding this variable is tainted.
for file access.
This presents issues for users' &_.forward_& and filter files.
For traditional full user accounts, use &%check_local_users%& and the
-&$local_part_verified$& variable rather than this one.
+&$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$& is usable in this role.
If needed, use a router &%address_data%& or &%set%& option for
the retrieved data.
-.wen
-
-.vindex "&$local_part_prefix$&"
-.vindex "&$local_part_prefix_v$&"
-.vindex "&$local_part_suffix$&"
-.vindex "&$local_part_suffix_v$&"
-.cindex affix variables
-If a local part prefix or suffix has been recognized, it is not included in the
-value of &$local_part$& during routing and subsequent delivery. The values of
-any prefix or suffix are in &$local_part_prefix$& and
-&$local_part_suffix$&, respectively.
-.new
-If the affix specification included a wildcard then the portion of
-the affix matched by the wildcard is in
-&$local_part_prefix_v$& or &$local_part_suffix_v$& as appropriate.
-.wen
When a message is being delivered to a file, pipe, or autoreply transport as a
result of aliasing or forwarding, &$local_part$& is set to the local part of
to a transport, the value is available in that transport. If the transport is
handling multiple addresses, the value from the first address is used.
+The &%check_local_user%& router option also sets this variable.
+
&$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$&.
-
-.new
-.vitem &$local_part_prefix_v$&
-.vindex "&$local_part_prefix_v$&"
-When &$local_part_prefix$& is valid and the prefix match used a wildcard,
-the portion matching the wildcard is available in this variable.
-.wen
-
-.vitem &$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$&.
-
-.new
-.vitem &$local_part_suffix_v$&
-.vindex "&$local_part_suffix_v$&"
-When &$local_part_suffix$& is valid and the suffix match used a wildcard,
-the portion matching the wildcard is available in this variable.
-.wen
+If a local part prefix or suffix has been recognized, it is not included in the
+value of &$local_part$& during routing and subsequent delivery. The values of
+any prefix or suffix are in &$local_part_prefix$& and
+&$local_part_suffix$&, respectively.
+.cindex "tainted data"
+If the specification did not include a wildcard then
+the affix variable value is not tainted.
-.new
-.vitem &$local_part_verified$&
-.vindex "&$local_part_verified$&"
-If the router generic option &%check_local_part%& has run successfully,
-this variable has the user database version of &$local_part$&.
-Such values are not tainted and hence usable for building file names.
-.wen
+If the affix specification included a wildcard then the portion of
+the affix matched by the wildcard is in
+&$local_part_prefix_v$& or &$local_part_suffix_v$& as appropriate,
+and both the whole and varying values are tainted.
.vitem &$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 - $body_linecount}}}
+ message = Too many lines in message header
.endd
In the MAIL and RCPT ACLs, the value is zero because at that stage the
message has not yet been received.
dns_dnssec_ok = 1
.endd
-.new
In addition, on Linux with glibc 2.31 or newer the resolver library will
default to stripping out a successful validation status.
This will break a previously working Exim installation.
.code
options trust-ad
.endd
-.wen
Exim does not perform DNSSEC validation itself, instead leaving that to a
validating resolver (e.g. unbound, or bind with suitable configuration).
If certificate verification fails it may refer to a failing chain element
which is not the leaf.
+
+.new
+.vitem &$tls_in_resumption$& &&&
+ &$tls_out_resumption$&
+.vindex &$tls_in_resumption$&
+.vindex &$tls_out_resumption$&
+.cindex TLS resumption
+Observability for TLS session resumption. See &<<SECTresumption>>& for details.
+.wen
+
+
.vitem &$tls_in_sni$&
.vindex "&$tls_in_sni$&"
.vindex "&$tls_sni$&"
.row &%percent_hack_domains%& "recognize %-hack for these domains"
.row &%spamd_address%& "set interface to SpamAssassin"
.row &%strict_acl_vars%& "object to unset ACL variables"
+.row &%spf_smtp_comment_template%& "template for &$spf_smtp_comment$&"
.endtable
.table2
.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"
.row &%hold_domains%& "hold delivery for these domains"
.row &%local_interfaces%& "for routing checks"
.row &%queue_domains%& "no immediate delivery for these"
+.row &%queue_fast_ramp%& "parallel delivery with 2-phase queue run"
.row &%queue_only%& "no immediate delivery at all"
.row &%queue_only_file%& "no immediate delivery if file exists"
.row &%queue_only_load%& "no immediate delivery if load is high"
.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 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>>&.
+.cindex bounce_message_file "tainted data"
+The option is expanded to give the file path, which must be
+absolute and untainted.
+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.
and an order of processing.
Signatures with algorithms not in the list will be ignored.
+
+.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.
+
.option dkim_verify_minimal main boolean false
If set to true, verification of signatures will terminate after the
first success.
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.
.code
options trust-ad
.endd
-.wen
.option dns_ipv4_lookup main "domain list&!!" unset
.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.
+&*Note*&: Supplying success-DSN messages has been criticised
+on privacy grounds; it can leak details of internal forwarding.
.option dsn_from main "string&!!" "see below"
.cindex "&'From:'& header line" "in bounces"
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.
-.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.
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"
.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
.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
.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.
next queue run. See also &%hold_domains%& and &%queue_smtp_domains%&.
+.new
+.option queue_fast_ramp main boolean false
+.cindex "queue runner" "two phase"
+.cindex "queue" "double scanning"
+If set to true, two-phase queue runs, initiated using &%-qq%& on the
+command line, may start parallel delivery processes during their first
+phase. This will be done when a threshold number of messages have been
+routed for a single host.
+.wen
+
+
.option queue_list_requires_admin main boolean true
.cindex "restricting access to features"
.oindex "&%-bp%&"
.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
.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.
+.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.
.option split_spool_directory main boolean false
.option syslog_timestamp main boolean true
.cindex "syslog" "timestamps"
+.cindex timestamps syslog
If &%syslog_timestamp%& is set false, the timestamps on Exim's log lines are
omitted when these lines are sent to syslog. See chapter &<<CHAPlog>>& for
details of Exim's logging.
.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
&<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&.
+.new
+.option tls_resumption_hosts main "host list&!!" unset
+.cindex TLS resumption
+This option controls which connections to offer the TLS resumption feature.
+See &<<SECTresumption>>& for details.
+.wen
+
+
.option tls_try_verify_hosts main "host list&!!" unset
.cindex "TLS" "client certificate verification"
.cindex "certificate" "verification of client"
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>>&.
+.cindex warn_message_file "tainted data"
+The option is expanded to give the file path, which must be
+absolute and untainted.
+See also &%bounce_message_file%&.
.option write_rejectlog main boolean true
that is associated with any addresses that are accepted by the router.
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
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
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.
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.
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
.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
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
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 = $home/inbox
.endd
.cindex "&""sticky""& bit"
folders. Consider this example:
.code
maildir_format = true
-directory = /var/mail/$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"
# 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 = $local_part_data
group = mail
# router
.option hosts_avoid_pipelining smtp "host list&!!" unset
.cindex "PIPELINING" "avoiding the use of"
-Exim will not use the SMTP PIPELINING extension when delivering to any host
+.cindex "ESMTP extensions" PIPELINING
+Exim will not use the ESMTP PIPELINING extension when delivering to any host
that matches this list, even if the server host advertises PIPELINING support.
.option hosts_pipe_connect smtp "host list&!!" unset
.cindex "RFC 3030" "CHUNKING"
This option provides a list of servers to which, provided they announce
CHUNKING support, Exim will attempt to use BDAT commands rather than DATA.
-.new
Unless DKIM signing is being done,
-.wen
BDAT will not be used in conjunction with a transport filter.
.option hosts_try_dane smtp "host list&!!" *
.option hosts_try_prdr smtp "host list&!!" *
.cindex "PRDR" "enabling, optional in client"
+.cindex "ESMTP extensions" PRDR
This option provides a list of servers to which, provided they announce
PRDR support, Exim will attempt to negotiate PRDR
for multi-recipient messages.
permits this.
+.new
+.option message_linelength_limit smtp integer 998
+.cindex "line length" limit
+This option sets the maximum line length, in bytes, that the transport
+will send. Any messages with lines exceeding the given value
+will fail and a failure-DSN ("bounce") message will if possible be returned
+to the sender.
+The default value is that defined by the SMTP standards.
+
+It is generally wise to also check in the data ACL so that messages
+received via SMTP can be refused without producing a bounce.
+.wen
+
+
.option multi_domain smtp boolean&!! true
.vindex "&$domain$&"
When this option is set, the &(smtp)& transport can handle a number of
.option size_addition smtp integer 1024
-.cindex "SMTP" "SIZE"
+.cindex "SIZE" "ESMTP extension"
.cindex "message" "size issue for transport filter"
.cindex "size" "of message"
.cindex "transport" "filter"
ciphers is a preference order.
+.new
+.option tls_resumption_hosts smtp "host list&!!" unset
+.cindex TLS resumption
+This option controls which connections to use the TLS resumption feature.
+See &<<SECTresumption>>& for details.
+.wen
+
+
.option tls_sni smtp string&!! unset
.cindex "TLS" "Server Name Indication"
If both this option and &%tls_try_verify_hosts%& are unset
operation is as if this option selected all hosts.
-.option utf8_downconvert smtp integer!! unset
+.option utf8_downconvert smtp integer&!! -1
.cindex utf8 "address downconversion"
.cindex i18n "utf8 address downconversion"
If built with internationalization support,
-this option controls conversion of UTF-8 in message addresses
+this option controls conversion of UTF-8 in message envelope addresses
to a-label form.
-For details see section &<<SECTi18nMTA>>&.
+If, after expansion, the value is 1, 0, or -1 then this value overrides
+any value previously set for the message. Otherwise, any previously
+set value is used. To permit use of a previous value,
+set this option to an empty string.
+For details on the values see section &<<SECTi18nMTA>>&.
other.
.cindex "AUTH" "description of"
+.cindex "ESMTP extensions" AUTH
Very briefly, the way SMTP authentication works is as follows:
.ilist
option is passed. When authentication succeeds, the identity of the user
who authenticated is placed in &$auth1$&.
-.new
The Dovecot configuration to match the above wil look
something like:
.code
auth_mechanisms = plain login ntlm
.endd
-.wen
.ecindex IIDdcotauth1
.ecindex IIDdcotauth2
made that any particular new authentication mechanism will be supported
without code changes in Exim.
-.new
The library is expected to add support in an upcoming
realease for the SCRAM-SHA-256 method.
The macro _HAVE_AUTH_GSASL_SCRAM_SHA_256 will be defined
.option client_username gsasl string&!! unset
This option is exapanded before use, and should result in
the account name to be used.
-.wen
-.new
.option client_spassword gsasl string&!! unset
If a SCRAM mechanism is being used and this option is set
it is used in preference to &%client_password%&.
with the PBKDF2-prepared password, hex-encoded.
Note that this value will depend on the salt and iteration-count
supplied by the server.
-.wen
non-issue, as a man-in-the-middle attack will cause the correct client and
server to see different identifiers and authentication will fail.
-.new
This is
only usable by mechanisms which support "channel binding"; at time of
writing, that's the SCRAM family.
When using this feature the "-PLUS" variants of the method names need to be used.
-.wen
This defaults off to ensure smooth upgrade across Exim releases, in case
this option causes some clients to start failing. Some future release
.option server_scram_iter gsasl string&!! 4096
This option provides data for the SCRAM family of mechanisms.
-.new
The &$auth1$&, &$auth2$& and &$auth3$& variables are available
when this option is expanded.
either the iteration count or the salt).
A minimum value of 4096 is required by the standards
for all current SCRAM mechanism variants.
-.wen
.option server_scram_salt gsasl string&!! unset
This option provides data for the SCRAM family of mechanisms.
-.new
The &$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
The libgsasl library release includes a utility &'gsasl'& which can be used
to generate these values.
-.wen
.option server_service gsasl string &`smtp`&
.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,
or need not succeed respectively.
The &%tls_verify_cert_hostnames%& option lists hosts for which additional
-checks are made: that the host name (the one in the DNS A record)
-is valid for the certificate.
+name checks are made on the server certificate.
+.new
+The match against this list is, as per other Exim usage, the
+IP for the host. That is most closely associated with the
+name on the DNS A (or AAAA) record for the host.
+However, the name that needs to be in the certificate
+is the one at the head of any CNAME chain leading to the A record.
+.wen
The option defaults to always checking.
The &(smtp)& transport has two OCSP-related options:
.ecindex IIDencsmtp2
+.new
+.section "TLS Resumption" "SECTresumption"
+.cindex TLS resumption
+TLS Session Resumption for TLS 1.2 and TLS 1.3 connections can be used (defined
+in RFC 5077 for 1.2). The support for this requires GnuTLS 3.6.3 or OpenSSL 1.1.1
+(or later).
+
+Session resumption (this is the "stateless" variant) involves the server sending
+a "session ticket" to the client on one connection, which can be stored by the
+client and used for a later session. The ticket contains sufficient state for
+the server to reconstruct the TLS session, avoiding some expensive crypto
+calculation and (on TLS1.2) one full packet roundtrip time.
+
+.ilist
+Operational cost/benefit:
+
+ The extra data being transmitted costs a minor amount, and the client has
+ extra costs in storing and retrieving the data.
+
+ In the Exim/Gnutls implementation the extra cost on an initial connection
+ which is TLS1.2 over a loopback path is about 6ms on 2017-laptop class hardware.
+ The saved cost on a subsequent connection is about 4ms; three or more
+ connections become a net win. On longer network paths, two or more
+ connections will have an average lower startup time thanks to the one
+ saved packet roundtrip. TLS1.3 will save the crypto cpu costs but not any
+ packet roundtrips.
+
+.cindex "hints database" tls
+ Since a new hints DB is used on the TLS client,
+ the hints DB maintenance should be updated to additionally handle "tls".
+
+.next
+Security aspects:
+
+ The session ticket is encrypted, but is obviously an additional security
+ vulnarability surface. An attacker able to decrypt it would have access
+ all connections using the resumed session.
+ The session ticket encryption key is not committed to storage by the server
+ and is rotated regularly (OpenSSL: 1hr, and one previous key is used for
+ overlap; GnuTLS 6hr but does not specify any overlap).
+ Tickets have limited lifetime (2hr, and new ones issued after 1hr under
+ OpenSSL. GnuTLS 2hr, appears to not do overlap).
+
+ There is a question-mark over the security of the Diffie-Helman parameters
+ used for session negotiation.
+
+.next
+Observability:
+
+ The &%log_selector%& "tls_resumption" appends an asterisk to the tls_cipher "X="
+ element.
+
+ The variables &$tls_in_resumption$& and &$tls_out_resumption$&
+ have bits 0-4 indicating respectively
+ support built, client requested ticket, client offered session,
+ server issued ticket, resume used. A suitable decode list is provided
+ in the builtin macro _RESUME_DECODE for in &%listextract%& expansions.
+
+.next
+Control:
+
+The &%tls_resumption_hosts%& main option specifies a hostlist for which
+exim, operating as a server, will offer resumption to clients.
+Current best practice is to not offer the feature to MUA connection.
+Commonly this can be done like this:
+.code
+tls_resumption_hosts = ${if inlist {$received_port}{587:465} {:}{*}}
+.endd
+If the peer host matches the list after expansion then resumption
+is offered and/or accepted.
+
+The &%tls_resumption_hosts%& smtp transport option performs the
+equivalent function for operation as a client.
+If the peer host matches the list after expansion then resumption
+is attempted (if a stored session is available) or the information
+stored (if supplied by the peer).
+
+
+.next
+Issues:
+
+ In a resumed session:
+.ilist
+ The variables &$tls_{in,out}_cipher$& will have values different
+ to the original (under GnuTLS).
+.next
+ The variables &$tls_{in,out}_ocsp$& will be "not requested" or "no response",
+ and the &%hosts_require_ocsp%& smtp trasnport option will fail.
+. XXX need to do something with that hosts_require_ocsp
+.endlist
+
+.endlist
+.wen
+
.section DANE "SECDANE"
.cindex 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.
.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%&.
-.new
.vitem &*control&~=&~queue/*&<&'options'&>* &&&
&*control&~=&~queue_only*&
.oindex "&%queue%&"
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 = $host_data
.endd
which gives a custom error message for each denied host.
.cindex "header lines" "verifying header names only ASCII"
.cindex "verifying" "header names only ASCII"
This condition is relevant only in an ACL that is run after a message has been
-received, that is, in an ACL specified by &%acl_smtp_data%& or
-&%acl_not_smtp%&. It checks all header names (not the content) to make sure
+received.
+This usually means an ACL specified by &%acl_smtp_data%& or &%acl_not_smtp%&.
+It checks all header names (not the content) to make sure
there are no non-ASCII characters, also excluding control characters. The
allowable characters are decimal ASCII values 33 through 126.
condition to restrict it to bounce messages only:
.code
deny senders = :
- message = A valid sender header is required for bounces
!verify = header_sender
+ message = A valid sender header is required for bounces
.endd
.vitem &*verify&~=&~header_syntax*&
(eg. is generated from the received message)
they must be protected from the options parsing by doubling:
.code
-verify = sender=${sg{${address:$h_sender:}}{/}{//}}
+verify = sender=${listquote{/}{${address:$h_sender:}}}
.endd
.endlist
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
immediately after a successful redirection. By default, if a redirection
generates just one address, that address is also verified. See further
discussion in section &<<SECTredirwhilveri>>&.
+.new
+.next
+If the &%quota%& option is specified for recipient verify,
+successful routing to an appendfile transport is followed by a call into
+the transport to evaluate the quota status for the recipient.
+No actual delivery is done, but verification will succeed if the quota
+is sufficient for the message (if the sender gave a message size) or
+not already exceeded (otherwise).
+.wen
.endlist
.cindex "verifying address" "differentiating failures"
&%recipient%&: The RCPT command in a callout was rejected.
.next
&%postmaster%&: The postmaster check in a callout was rejected.
+.new
+.next
+&%quota%&: The quota check for a local recipient did non pass.
.endlist
The main use of these variables is expected to be to distinguish between
+.new
+.section "Quota caching" "SECTquotacache"
+.cindex "hints database" "quota cache"
+.cindex "quota" "cache, description of"
+.cindex "caching" "quota"
+Exim caches the results of quota verification
+in order to reduce the amount of resources used.
+The &"callout"& hints database is used.
+
+The default cache periods are five minutes for a positive (good) result
+and one hour for a negative result.
+To change the periods the &%quota%& option can be followed by an equals sign
+and a number of optional paramemters, separated by commas.
+For example:
+.code
+verify = recipient/quota=cachepos=1h,cacheneg=1d
+.endd
+Possible parameters are:
+.vlist
+.vitem &*cachepos&~=&~*&<&'time&~interval'&>
+.cindex "quota cache" "positive entry expiry, specifying"
+Set the lifetime for a positive cache entry.
+A value of zero seconds is legitimate.
+
+.vitem &*cacheneg&~=&~*&<&'time&~interval'&>
+.cindex "quota cache" "negative entry expiry, specifying"
+As above, for a negative entry.
+
+.vitem &*no_cache*&
+Set both positive and negative lifetimes to zero.
+.wen
+
.section "Sender address verification reporting" "SECTsenaddver"
.cindex "verifying" "suppressing error details"
See section &<<SECTaddressverification>>& for a general discussion of
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 = $prvscheck_result
+ message = Invalid reverse path signature.
.endd
The first statement rejects recipients for bounce messages that are addressed
to plain BATV sender addresses, because it is known that BATV senders do not
Here is a very simple scanning example:
.code
-deny message = This message contains malware ($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
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 &$mime_is_multipart$&
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
LOCAL_SCAN_SOURCE=Local/local_scan.c
.endd
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
arguments. It flushes the output stream, and returns a non-zero value if there
is an error.
-.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 first argument.
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,BOOL)*&
This function is like &'store_get()'&, but it always gets memory from the
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
data = ${lookup{$local_part}lsearch{/etc/mail/virtual/$domain_data}}
no_more
.endd
-.new
The &%domains%& option specifies that the router is to be skipped, unless there
is a file in the &_/etc/mail/virtual_& directory whose name is the same as the
domain that is being processed.
The &(dsearch)& lookup used results in an untainted version of &$domain$&
being placed into the &$domain_data$& variable.
-.wen
When the router runs, it looks up the local
part in the file to find a new address (or list of addresses). The &%no_more%&
.code
my_mailboxes:
driver = appendfile
- file = /var/mail/$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
&`*tls_certificate_verified `& certificate verification status
&`*tls_cipher `& TLS cipher suite on <= and => lines
&` tls_peerdn `& TLS peer DN on <= and => lines
+&` tls_resumption `& append * to cipher field
&` tls_sni `& TLS SNI on <= lines
&` unknown_in_list `& DNS lookup failed in list match
connection, and a certificate is supplied by the remote host, the peer DN is
added to the log line, preceded by DN=.
.next
+.cindex "log" "TLS resumption"
+.cindex "TLS" "logging session resumption"
+.new
+&%tls_resumption%&: When a message is sent or received over an encrypted
+connection and the TLS session resumed one used on a previous TCP connection,
+an asterisk is appended to the X= cipher field in the log line.
+.wen
+.next
.cindex "log" "TLS SNI"
.cindex "TLS" "logging SNI"
&%tls_sni%&: When a message is received over an encrypted connection, and
.next
&'ratelimit'&: the data for implementing the ratelimit ACL condition
.next
+.new
+&'tls'&: TLS session resumption data
+.wen
+.next
&'misc'&: other hints data
.endlist
. ////////////////////////////////////////////////////////////////////////////
. ////////////////////////////////////////////////////////////////////////////
-.chapter "DKIM, SPF and DMARC" "CHAPdkim" &&&
- "DKIM, SPF and DMARC Support"
+.chapter "DKIM, SPF, SRS and DMARC" "CHAPdkim" &&&
+ "DKIM, SPF, SRS and DMARC Support"
.section "DKIM (DomainKeys Identified Mail)" SECDKIM
.cindex "DKIM"
whether or not each header is present in the message.
The default list is available for the expansion in the macro
&"_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
.vitem &%$dkim_key_length%&
Number of bits in the key.
+Valid only once the key is loaded, which is at the time the header signature
+is verified, which is after the body hash is.
Note that RFC 8301 says:
.code
less than 1024 bits as valid signatures.
.endd
-To enforce this you must have a DKIM ACL which checks this variable
-and overwrites the &$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
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.open-spf.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$&
+.vindex &%spf_smtp_comment_template%&
This contains a string that can be used in a SMTP response
to the calling party. Useful for "fail".
+ The string is generated by the SPF library from the template configured in the main config
+ option &%spf_smtp_comment_template%&.
.endlist
+.section "SRS (Sender Rewriting Scheme)" SECTSRS
+.cindex SRS "sender rewriting scheme"
+
+.new
+SRS can be used to modify sender addresses when forwarding so that
+SPF verification does not object to them.
+It operates by encoding the original envelope sender in a new
+sender local part and using a domain run by the forwarding site
+as the new domain for the sender. Any DSN message should be returned
+to this new sender at the forwarding site, which can extract the
+original sender from the coded local part and forward the DSN to
+the originator.
+
+This is a way of avoiding the breakage that SPF does to forwarding.
+The constructed local-part will be longer than the original,
+leading to possible problems with very long addresses.
+The changing of the sender address also hinders the tracing of mail
+problems.
+
+Exim can be built to include native SRS support. To do this
+SUPPORT_SRS=yes must be defined in &_Local/Makefile_&.
+If this has been done, the macros _HAVE_SRS and _HAVE_NATIVE_SRS
+will be defined.
+The support is limited to SRS0-encoding; SRS1 is not supported.
+
+.cindex SRS excoding
+To encode an address use this expansion item:
+.vlist
+.vitem &*${srs_encode&~{*&<&'secret'&>&*}{*&<&'return&~path'&>&*}{*&<&'original&~domain'&>&*}}*&
+.cindex "&%srs_encode%& expansion item"
+.cindex SRS "expansion item"
+The first argument should be a secret known and used by all systems
+handling the recipient domain for the original message.
+There is no need to periodically change this key; a timestamp is also
+encoded.
+The second argument should be given as the envelope sender address before this
+encoding operation.
+The third argument should be the recipient domain of the message when
+it arrived at this system.
+.endlist
+
+.cindex SRS decoding
+To decode an address use this expansion condition:
+.vlist
+.vitem &*inbound_srs&~{*&<&'local&~part'&>&*}{*&<&'secret'&>&*}*&
+The first argument should be the recipient local prt as is was received.
+The second argument is the site secret.
+
+If the messages is not for an SRS-encoded recipient the condition will
+return false. If it is, the condition will return true and the variable
+&$srs_recipient$& will be set to the decoded (original) value.
+.endlist
+
+Example usage:
+.code
+ #macro
+ SRS_SECRET = <pick something unique for your site for this. Use on all MXs.>
+
+ #routers
+
+ outbound:
+ driver = dnslookup
+ # if outbound, and forwarding has been done, use an alternate transport
+ domains = ! +my_domains
+ transport = ${if eq {$local_part@$domain} \
+ {$original_local_part@$original_domain} \
+ {remote_smtp} {remote_forwarded_smtp}}
+
+ inbound_srs:
+ driver = redirect
+ senders = :
+ domains = +my_domains
+ # detect inbound bounces which are SRS'd, and decode them
+ condition = ${if inbound_srs {$local_part} {SRS_SECRET}}
+ data = $srs_recipient
+
+ inbound_srs_failure:
+ driver = redirect
+ senders = :
+ domains = +my_domains
+ # detect inbound bounces which look SRS'd but are invalid
+ condition = ${if inbound_srs {$local_part} {}}
+ allow_fail
+ data = :fail: Invalid SRS recipient address
+
+ #... further routers here
+
+
+ # transport; should look like the non-forward outbound
+ # one, plus the max_rcpt and return_path options
+ remote_forwarded_smtp:
+ driver = smtp
+ # modify the envelope from, for mails that we forward
+ max_rcpt = 1
+ return_path = ${srs_encode {SRS_SECRET} {$return_path} {$original_domain}}
+.endd
+
+
+.wen
+
+
+
.section DMARC SECDMARC
.cindex DMARC verification
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
# 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
git://git.exim.org / users / heiko / exim.git / blobdiff