X-Git-Url: https://git.exim.org/exim.git/blobdiff_plain/328c5688dbe0f4c14418f22350ccd99b3fe8ac71..c5db348c5e29e93e51389fa0079f829967c5da82:/doc/doc-docbook/spec.xfpt diff --git a/doc/doc-docbook/spec.xfpt b/doc/doc-docbook/spec.xfpt index e5c433fbb..a9a048ecb 100644 --- a/doc/doc-docbook/spec.xfpt +++ b/doc/doc-docbook/spec.xfpt @@ -1667,6 +1667,9 @@ Symbolic links to the sources are installed in this directory, which is where the actual building takes place. In most cases, Exim can discover the machine architecture and operating system for itself, but the defaults can be overridden if necessary. +.cindex compiler requirements +.cindex compiler version +A C99-capable compiler will be required for the build. .section "PCRE library" "SECTpcre" @@ -4274,7 +4277,7 @@ or &%-bs%& is used. For &%-bh%&, the protocol is forced to one of the standard SMTP protocol names (see the description of &$received_protocol$& in section &<>&). For &%-bs%&, the protocol is always &"local-"& followed by one of those same names. For &%-bS%& (batched SMTP) however, the protocol can -be set by &%-oMr%&. +be set by &%-oMr%&. Repeated use of this option is not supported. .vitem &%-oMs%&&~<&'host&~name'&> .oindex "&%-oMs%&" @@ -4374,6 +4377,7 @@ host name and its colon can be omitted when only the protocol is to be set. Note the Exim already has two private options, &%-pd%& and &%-ps%&, that refer to embedded Perl. It is therefore impossible to set a protocol value of &`d`& or &`s`& using this option (but that does not seem a real limitation). +Repeated use of this option is not supported. .vitem &%-q%& .oindex "&%-q%&" @@ -9963,7 +9967,7 @@ a regular expression, and a substitution string. For example: ${sg{abcdefabcdef}{abc}{xyz}} .endd yields &"xyzdefxyzdef"&. Because all three arguments are expanded before use, -if any $ or \ characters are required in the regular expression or in the +if any $, } or \ characters are required in the regular expression or in the substitution string, they have to be escaped. For example: .code ${sg{abcdef}{^(...)(...)\$}{\$2\$1}} @@ -10114,7 +10118,15 @@ character. For example: .code ${addresses:>& Chief , sec@base.ment (dogsbody)} .endd -expands to &`ceo@up.stairs&&sec@base.ment`&. Compare the &*address*& (singular) +expands to &`ceo@up.stairs&&sec@base.ment`&. The string is expanded +first, so if the expanded string starts with >, it may change the output +separator unintentionally. This can be avoided by setting the output +separator explicitly: +.code +${addresses:>:$h_from:} +.endd + +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 processing lists. @@ -11195,8 +11207,8 @@ example is: ${if match_domain{a.b.c}{x.y.z:a.b.c:p.q.r}{yes}{no}} .endd In each case, the second argument may contain any of the allowable items for a -list of the appropriate type. Also, because the second argument (after -expansion) is a standard form of list, it is possible to refer to a named list. +list of the appropriate type. Also, because the second argument +is a standard form of list, it is possible to refer to a named list. Thus, you can use conditions like this: .code ${if match_domain{$domain}{+local_domains}{... @@ -12067,6 +12079,9 @@ when the ACL &%malware%& condition is true (see section &<>&). This variable contains the number of bytes in the longest line that was received as part of the message, not counting the line termination character(s). +.new +It is not valid if the &%spool_files_wireformat%& option is used. +.wen .vitem &$message_age$& .cindex "message" "age of" @@ -12109,6 +12124,12 @@ in bytes. The count starts from the character after the blank line that separates the body from the header. Newlines are included in the count. See also &$message_size$&, &$body_linecount$&, and &$body_zerocount$&. +.new +If the spool file is wireformat +(see the &%spool_files_wireformat%& main option) +the CRLF line-terminators are included in the count. +.wen + .vitem &$message_exim_id$& .vindex "&$message_exim_id$&" When a message is being received or delivered, this variable contains the @@ -12159,6 +12180,10 @@ deny message = Too many lines in message header In the MAIL and RCPT ACLs, the value is zero because at that stage the message has not yet been received. +.new +This variable is not valid if the &%spool_files_wireformat%& option is used. +.wen + .vitem &$message_size$& .cindex "size" "of message" .cindex "message" "size" @@ -12779,6 +12804,15 @@ argument, that is, the text that follows the command name, with leading white space removed. Following the introduction of &$smtp_command$&, this variable is somewhat redundant, but is retained for backwards compatibility. +.new +.vitem &$smtp_command_history$& +.cindex SMTP "command history" +.vindex "&$smtp_command_history$&" +A comma-separated list (with no whitespace) of the most-recent SMTP commands +received, in time-order left to right. Only a limited number of commands +are remembered. +.wen + .vitem &$smtp_count_at_connection_start$& .vindex "&$smtp_count_at_connection_start$&" This variable is set greater than zero only in processes spawned by the Exim @@ -13586,6 +13620,7 @@ listed in more than one group. .section "Privilege controls" "SECID98" .table2 .row &%admin_groups%& "groups that are Exim admin users" +.row &%commandline_checks_require_admin%& "require admin for various checks" .row &%deliver_drop_privilege%& "drop root for delivery processes" .row &%local_from_check%& "insert &'Sender:'& if necessary" .row &%local_from_prefix%& "for testing &'From:'& for local sender" @@ -14448,6 +14483,14 @@ 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. +.new +.option commandline_checks_require_admin main boolean &`false`& +.cindex "restricting access to features" +This option restricts various basic checking features to require an +administrative user. +This affects most of the &%-b*%& options, such as &%-be%&. +.wen + .option debug_store main boolean &`false`& .cindex debugging "memory corruption" .cindex memory debugging @@ -15929,12 +15972,13 @@ different spool directories. .option prod_requires_admin main boolean true +.cindex "restricting access to features" .oindex "&%-M%&" .oindex "&%-R%&" .oindex "&%-q%&" The &%-M%&, &%-R%&, and &%-q%& command-line options require the caller to be an admin user unless &%prod_requires_admin%& is set false. See also -&%queue_list_requires_admin%&. +&%queue_list_requires_admin%& and &%commandline_checks_require_admin%&. .option qualify_domain main string "see below" @@ -15973,10 +16017,12 @@ next queue run. See also &%hold_domains%& and &%queue_smtp_domains%&. .option queue_list_requires_admin main boolean true +.cindex "restricting access to features" .oindex "&%-bp%&" The &%-bp%& command-line option, which lists the messages that are on the queue, requires the caller to be an admin user unless -&%queue_list_requires_admin%& is set false. See also &%prod_requires_admin%&. +&%queue_list_requires_admin%& is set false. +See also &%prod_requires_admin%& and &%commandline_checks_require_admin%&. .option queue_only main boolean false @@ -16831,6 +16877,13 @@ Doing this permits more efficient message reception and transmission. Currently it is only done for messages received using the EMSTP CHUNKING option. +The following variables will not have useful values: +.code +$max_received_linelength +$body_linecount +$body_zerocount +.endd + Users of the local_scan() API (see &<>&), and any external programs which are passed a reference to a message data file (except via the &"regex"&, &"malware"& or &"spam"&) ACL conditions) @@ -19436,6 +19489,10 @@ instead of TRY_AGAIN. That is why the default action is to try a DNS lookup first. Only if that gives a definite &"no such host"& is the local function called. +&*Compatibility*&: From Exim 4.85 until fixed for 4.90, there was an +inadvertent constraint that a transport name as an option had to be the last +option specified. + If no IP address for a host can be found, what happens is controlled by the @@ -20313,11 +20370,15 @@ relative path is then passed to the transport unmodified. .option forbid_blackhole redirect boolean false +.cindex "restricting access to features" +.cindex "filter" "locking out certain features" If this option is true, the &':blackhole:'& item may not appear in a redirection list. .option forbid_exim_filter redirect boolean false +.cindex "restricting access to features" +.cindex "filter" "locking out certain features" If this option is set true, only Sieve filters are permitted when &%allow_filter%& is true. @@ -20325,7 +20386,9 @@ If this option is set true, only Sieve filters are permitted when .option forbid_file redirect boolean false +.cindex "restricting access to features" .cindex "delivery" "to file; forbidding" +.cindex "filter" "locking out certain features" .cindex "Sieve filter" "forbidding delivery to a file" .cindex "Sieve filter" "&""keep""& facility; disabling" If this option is true, this router may not generate a new address that @@ -20336,17 +20399,22 @@ locks out the Sieve's &"keep"& facility. .option forbid_filter_dlfunc redirect boolean false +.cindex "restricting access to features" .cindex "filter" "locking out certain features" If this option is true, string expansions in Exim filters are not allowed to make use of the &%dlfunc%& expansion facility to run dynamically loaded functions. .option forbid_filter_existstest redirect boolean false +.cindex "restricting access to features" +.cindex "filter" "locking out certain features" .cindex "expansion" "statting a file" If this option is true, string expansions in Exim filters are not allowed to make use of the &%exists%& condition or the &%stat%& expansion item. .option forbid_filter_logwrite redirect boolean false +.cindex "restricting access to features" +.cindex "filter" "locking out certain features" If this option is true, use of the logging facility in Exim filters is not permitted. Logging is in any case available only if the filter is being run under some unprivileged uid (which is normally the case for ordinary users' @@ -20354,27 +20422,37 @@ under some unprivileged uid (which is normally the case for ordinary users' .option forbid_filter_lookup redirect boolean false +.cindex "restricting access to features" +.cindex "filter" "locking out certain features" If this option is true, string expansions in Exim filter files are not allowed to make use of &%lookup%& items. .option forbid_filter_perl redirect boolean false +.cindex "restricting access to features" +.cindex "filter" "locking out certain features" This option has an effect only if Exim is built with embedded Perl support. If it is true, string expansions in Exim filter files are not allowed to make use of the embedded Perl support. .option forbid_filter_readfile redirect boolean false +.cindex "restricting access to features" +.cindex "filter" "locking out certain features" If this option is true, string expansions in Exim filter files are not allowed to make use of &%readfile%& items. .option forbid_filter_readsocket redirect boolean false +.cindex "restricting access to features" +.cindex "filter" "locking out certain features" If this option is true, string expansions in Exim filter files are not allowed to make use of &%readsocket%& items. .option forbid_filter_reply redirect boolean false +.cindex "restricting access to features" +.cindex "filter" "locking out certain features" If this option is true, this router may not generate an automatic reply message. Automatic replies can be generated only from Exim or Sieve filter files, not from traditional forward files. This option is forced to be true if @@ -20382,11 +20460,15 @@ files, not from traditional forward files. This option is forced to be true if .option forbid_filter_run redirect boolean false +.cindex "restricting access to features" +.cindex "filter" "locking out certain features" If this option is true, string expansions in Exim filter files are not allowed to make use of &%run%& items. .option forbid_include redirect boolean false +.cindex "restricting access to features" +.cindex "filter" "locking out certain features" If this option is true, items of the form .code :include: @@ -20395,6 +20477,8 @@ are not permitted in non-filter redirection lists. .option forbid_pipe redirect boolean false +.cindex "restricting access to features" +.cindex "filter" "locking out certain features" .cindex "delivery" "to pipe; forbidding" If this option is true, this router may not generate a new address which specifies delivery to a pipe, either from an Exim filter or from a conventional @@ -20402,6 +20486,8 @@ forward file. This option is forced to be true if &%one_time%& is set. .option forbid_sieve_filter redirect boolean false +.cindex "restricting access to features" +.cindex "filter" "locking out certain features" If this option is set true, only Exim filters are permitted when &%allow_filter%& is true. @@ -22066,10 +22152,14 @@ the obvious value which users understand most easily. The value of the option is expanded, and must then be a numerical value (decimal point allowed), optionally followed by one of the letters K, M, or G, -for kilobytes, megabytes, or gigabytes. If Exim is running on a system with +for kilobytes, megabytes, or gigabytes, optionally followed by a slash +and further option modifiers. If Exim is running on a system with large file support (Linux and FreeBSD have this), mailboxes larger than 2G can be handled. +The option modifier &%no_check%& can be used to force delivery even if the over +quota condition is met. The quota gets updated as usual. + &*Note*&: A value of zero is interpreted as &"no quota"&. The expansion happens while Exim is running as root, before it changes uid for @@ -22104,6 +22194,8 @@ can only be used if &%quota%& is also set. The value is expanded; an expansion failure causes delivery to be deferred. A value of zero is interpreted as &"no quota"&. +The option modifier &%no_check%& can be used to force delivery even if the over +quota condition is met. The quota gets updated as usual. .option quota_is_inclusive appendfile boolean true See &%quota%& above. @@ -23714,7 +23806,9 @@ of the message. Its value must not be zero. See also &%final_timeout%&. .option dkim_private_key smtp string&!! unset .option dkim_canon smtp string&!! unset .option dkim_strict smtp string&!! unset -.option dkim_sign_headers smtp string&!! unset +.option dkim_sign_headers smtp string&!! "per RFC" +.option dkim_hash smtp string&!! sha256 +.option dkim_identity smtp string&!! unset DKIM signing options. For details see section &<>&. @@ -24053,7 +24147,7 @@ This option provides a list of servers to which, provided they announce CHUNKING support, Exim will attempt to use BDAT commands rather than DATA. BDAT will not be used in conjunction with a transport filter. -.option hosts_try_fastopen smtp "host list!!" unset +.option hosts_try_fastopen smtp "host list&!!" unset .cindex "fast open, TCP" "enabling, in client" .cindex "TCP Fast Open" "enabling, in client" .cindex "RFC 7413" "TCP Fast Open" @@ -24069,6 +24163,9 @@ as the initiator must present a cookie in the SYN segment. On (at least some) current Linux distributions the facility must be enabled in the kernel by the sysadmin before the support is usable. +There is no option for control of the server side; if the system supports +it it is always enebled. Note that legthy operations in the connect ACL, +such as DNSBL lookups, will still delay the emission of the SMTP banner. .option hosts_try_prdr smtp "host list&!!" * .cindex "PRDR" "enabling, optional in client" @@ -27651,13 +27748,22 @@ built, then you have SNI support). "SECTmulmessam" .cindex "multiple SMTP deliveries with TLS" .cindex "TLS" "multiple message deliveries" +.new Exim sends multiple messages down the same TCP/IP connection by starting up an entirely new delivery process for each message, passing the socket from one process to the next. This implementation does not fit well with the use of TLS, because there is quite a lot of state information associated with a TLS connection, not just a socket identification. Passing all the state information -to a new process is not feasible. Consequently, Exim shuts down an existing TLS -session before passing the socket to a new process. The new process may then +to a new process is not feasible. Consequently, for sending using TLS Exim +starts an additional proxy process for handling the encryption, piping the +unencrypted data stream from and to the delivery processes. + +An older mode of operation can be enabled on a per-host basis by the +&%hosts_noproxy_tls%& option on the &(smtp)& transport. If the host matches +this list the proxy process descibed above is not used; instead Exim +.wen +shuts down an existing TLS session being run by the delivery process +before passing the socket to a new process. The new process may then try to start a new TLS session, and if successful, may try to re-authenticate if AUTH is in use, before sending the next message. @@ -28985,6 +29091,11 @@ and cannot depend on content of received headers. Note also that headers cannot be modified by any of the post-data ACLs (DATA, MIME and DKIM). Headers may be modified by routers (subject to the above) and transports. +.new +The Received-By: header is generated as soon as the body reception starts, +rather than the traditional time after the full message is received; +this will affect the timestamp. +.wen All the usual ACLs are called; if one results in the message being rejected, all effort spent in delivery (including the costs on @@ -31627,14 +31738,18 @@ an address (which may be an IP address and port, or the path of a Unix socket), a commandline to send (may include a single %s which will be replaced with the path to the mail file to be scanned), an RE to trigger on from the returned data, -an RE to extract malware_name from the returned data. +and an RE to extract malware_name from the returned data. For example: .code -av_scanner = sock:127.0.0.1 6001:%s:(SPAM|VIRUS):(.*)\$ +av_scanner = sock:127.0.0.1 6001:%s:(SPAM|VIRUS):(.*)$ .endd -Default for the socket specifier is &_/tmp/malware.sock_&. -Default for the commandline is &_%s\n_&. -Both regular-expressions are required. +.new +Note that surrounding whitespace is stripped from each option, meaning +there is no way to specify a trailing newline. +The socket specifier and both regular-expressions are required. +Default for the commandline is &_%s\n_& (note this does have a trailing newline); +specify an empty element to get this. +.wen .vitem &%sophie%& .cindex "virus scanners" "Sophos and Sophie" @@ -32474,9 +32589,15 @@ C variables are as follows: .vlist .vitem &*int&~body_linecount*& This variable contains the number of lines in the message's body. +.new +It is not valid if the &%spool_files_wireformat%& option is used. +.wen .vitem &*int&~body_zerocount*& This variable contains the number of binary zero bytes in the message's body. +.new +It is not valid if the &%spool_files_wireformat%& option is used. +.wen .vitem &*unsigned&~int&~debug_selector*& This variable is set to zero when no debugging is taking place. Otherwise, it @@ -35932,6 +36053,7 @@ the following table: &`SNI `& server name indication from TLS client hello &`ST `& shadow transport name &`T `& on &`<=`& lines: message subject (topic) +&`TFO `& connection took advantage of TCP Fast Open &` `& on &`=>`& &`**`& and &`==`& lines: transport name &`U `& local user or RFC 1413 identity &`X `& TLS cipher suite @@ -36013,6 +36135,7 @@ selection marked by asterisks: &` incoming_interface `& local interface on <= and => lines &` incoming_port `& remote port on <= lines &`*lost_incoming_connection `& as it says (includes timeouts) +&` millisec `& millisecond timestamps and QT,DT,D times &` outgoing_interface `& local interface on => lines &` outgoing_port `& add remote port to => lines &`*queue_run `& start and end queue runs @@ -36102,6 +36225,8 @@ process is started because &%queue_only%& is set or &%-odq%& was used. .cindex "log" "delivery duration" &%deliver_time%&: For each delivery, the amount of real time it has taken to perform the actual delivery is logged as DT=<&'time'&>, for example, &`DT=1s`&. +If millisecond logging is enabled, short times will be shown with greater +precision, eg. &`DT=0.304`&. .next .cindex "log" "message size on delivery" .cindex "size" "of message" @@ -36177,6 +36302,14 @@ important with the widening use of NAT (see RFC 2505). &%lost_incoming_connection%&: A log line is written when an incoming SMTP connection is unexpectedly dropped. .next +.new +.cindex "log" "millisecond timestamps" +.cindex millisecond logging +.cindex timstamps "millisecond, in logs" +&%millisec%&: Timestamps have a period and three decimal places of finer granularity +appended to the seconds value. +.wen +.next .cindex "log" "outgoing interface" .cindex "log" "local interface" .cindex "log" "local address and port" @@ -36215,6 +36348,8 @@ includes reception time as well as the delivery time for the current address. This means that it may be longer than the difference between the arrival and delivery log line times, because the arrival log line is not written until the message has been successfully received. +If millisecond logging is enabled, short times will be shown with greater +precision, eg. &`QT=1.578s`&. .next &%queue_time_overall%&: The amount of time the message has been in the queue on the local host is logged as QT=<&'time'&> on &"Completed"& lines, for @@ -37917,6 +38052,13 @@ the contents of files on the spool via the Exim monitor (which runs unprivileged), Exim must be built to allow group read access to its spool files. +.new +By default, regular users are trusted to perform basic testing and +introspection commands, as themselves. This setting can be tightened by +setting the &%commandline_checks_require_admin%& option. +This affects most of the checking options, +such as &%-be%& and anything else &%-b*%&. +.wen .section "Spool files" "SECID275" @@ -38037,6 +38179,13 @@ file remains in existence. When Exim next processes the message, it notices the -J file and uses it to update the -H file before starting the next delivery attempt. +.new +Files whose names end with -K or .eml may also be seen in the spool. +These are temporaries used for DKIM or malware processing, when that is used. +They should be tidied up by normal operations; any old ones are probably +relics of crashes and can be removed. +.wen + .section "Format of the -H file" "SECID282" .cindex "uid (user id)" "in spool file" .cindex "gid (group id)" "in spool file" @@ -38197,11 +38346,13 @@ to ensure that the caller is displayed in queue listings). If a message was scanned by SpamAssassin, this is present. It records the value of &$spam_score_int$&. +.new .vitem &%-spool_file_wireformat%& The -D file for this message is in wire-format (for ESMTP CHUNKING) rather than Unix-format. The line-ending is CRLF rather than newline. There is still, however, no leading-dot-stuffing. +.wen .vitem &%-tls_certificate_verified%& A TLS certificate was received from the client that sent this message, and the @@ -38310,6 +38461,20 @@ unqualified domain &'foundation'&. .ecindex IIDforspo2 .ecindex IIDforspo3 +.new +.section "Format of the -D file" "SECID282a" +The data file is traditionally in Unix-standard format: lines are ended with +an ASCII newline character. +However, when the &%spool_wireformat%& main option is used some -D files +can have an alternate format. +This is flagged by a &%-spool_file_wireformat%& line in the corresponding -H file. +The -D file lines (not including the first name-component line) are +suitable for direct copying to the wire when transmitting using the +ESMTP CHUNKING option, meaning lower processing overhead. +Lines are terminated with an ASCII CRLF pair. +There is no dot-stuffing (and no dot-termination). +.wen + . //////////////////////////////////////////////////////////////////////////// . //////////////////////////////////////////////////////////////////////////// @@ -38373,13 +38538,15 @@ while expanding the remaining signing options. .wen If it is empty after expansion, DKIM signing is not done. -.option dkim_selector smtp string&!! unset +.option dkim_selector smtp string list&!! unset This sets the key selector string. -You can use the &%$dkim_domain%& expansion variable to look up a matching selector. -The result is put in the expansion +.new +After expansion, which can use &$dkim_domain$&, this can be a list. +Each element in turn is put in the expansion variable &%$dkim_selector%& which may be used in the &%dkim_private_key%& option along with &%$dkim_domain%&. -If the option is empty after expansion, DKIM signing is not done. +If the option is empty after expansion, DKIM signing is not done for this domain. +.wen .option dkim_private_key smtp string&!! unset This sets the private key to use. @@ -38398,6 +38565,19 @@ is set. .endlist If the option is empty after expansion, DKIM signing is not done. +.new +.option dkim_hash smtp string&!! sha256 +Can be set alternatively to &"sha1"& to use an alternate hash +method. Note that sha1 is now condidered insecure, and deprecated. + +.option dkim_identity smtp string&!! unset +If set after expansion, the value is used to set an "i=" tag in +the signing header. The DKIM standards restrict the permissible +syntax of this optional tag to a mail address, with possibly-empty +local part, an @, and a domain identical to or subdomain of the "d=" +tag value. Note that Exim does not check the value. +.wen + .option dkim_canon smtp string&!! unset This option sets the canonicalization method used when signing a message. The DKIM RFC currently supports two methods: "simple" and "relaxed". @@ -38411,11 +38591,17 @@ either "1" or "true", Exim will defer. Otherwise Exim will send the message unsigned. You can use the &%$dkim_domain%& and &%$dkim_selector%& expansion variables here. -.option dkim_sign_headers smtp string&!! unset -If set, this option must expand to (or be specified as) a colon-separated -list of header names. Headers with these names will be included in the message -signature. -When unspecified, the header names recommended in RFC4871 will be used. +.option dkim_sign_headers smtp string&!! "see below" +If set, this option must expand to a colon-separated +list of header names. +.new +Headers with these names, or the absence or such a header, will be included +in the message signature. +When unspecified, the header names listed in RFC4871 will be used, +whether or not each header is present in the message. +The default list is available for the expansion in the macro +"_DKIM_SIGN_HEADERS". +.wen .section "Verifying DKIM signatures in incoming mail" "SECID514" @@ -38426,7 +38612,7 @@ Verification of DKIM signatures in SMTP incoming email is implemented via the syntactically(!) correct signature in the incoming message. A missing ACL definition defaults to accept. If any ACL call does not accept, the message is not accepted. -If a cutthrough delivery was in progress for the message it is +If a cutthrough delivery was in progress for the message, that is summarily dropped (having wasted the transmission effort). To evaluate the signature in the ACL a large number of expansion variables @@ -38529,7 +38715,7 @@ The algorithm used. One of 'rsa-sha1' or 'rsa-sha256'. .vitem &%$dkim_canon_body%& The body canonicalization method. One of 'relaxed' or 'simple'. -.vitem &%dkim_canon_headers%& +.vitem &%$dkim_canon_headers%& The header canonicalization method. One of 'relaxed' or 'simple'. .vitem &%$dkim_copiedheaders%&