X-Git-Url: https://git.exim.org/users/jgh/exim.git/blobdiff_plain/1950cf85b47f7c8407b3318a4f8fc57c0af6d6ba..ef546e788203ac3881abe2ddb17f3e24f6524d15:/doc/doc-docbook/spec.xfpt diff --git a/doc/doc-docbook/spec.xfpt b/doc/doc-docbook/spec.xfpt index 870248570..b1387eb49 100644 --- a/doc/doc-docbook/spec.xfpt +++ b/doc/doc-docbook/spec.xfpt @@ -52,7 +52,7 @@ .set I "    " .macro copyyear -2019 +2020 .endmacro . ///////////////////////////////////////////////////////////////////////////// @@ -3910,7 +3910,7 @@ messages through the same SMTP connection. .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%& @@ -5905,13 +5905,13 @@ messages that are submitted by SMTP from local processes using the standard 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. @@ -6015,10 +6015,10 @@ require verify = recipient 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: $sender_host_address is in \ @@ -6381,7 +6381,7 @@ All other options are defaulted. .code local_delivery: driver = appendfile - file = /var/mail/$local_part_verified + file = /var/mail/$local_part_data delivery_date_add envelope_to_add return_path_add @@ -6394,7 +6394,7 @@ traditional BSD mailbox format. .new We prefer to avoid using &$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$& in the user database (done by using &%check_local_user%& in the the router). .wen @@ -6641,6 +6641,8 @@ file that is searched could contain lines like this: .endd When the lookup succeeds, the result of the expansion is a list of domains (and possibly other types of item that are allowed in domain lists). +.cindex "tainted data" "de-tainting" +The result of the expansion is not tainted. In the second example, the lookup is a single item in a domain list. It causes Exim to use a lookup to see if the domain that is being processed can be found @@ -6661,6 +6663,13 @@ If the value of &$sender_host_address$& is 192.168.5.6, expansion of the first &%domains%& setting above generates the second setting, which therefore causes a second lookup to occur. +.new +The lookup type may optionally be followed by a comma +and a comma-separated list of options. +Each option is a &"name=value"& pair. +Whether an option is meaningful depands on the lookup type. +.wen + The rest of this chapter describes the different lookup types that are available. Any of them can be used in any part of the configuration where a lookup is permitted. @@ -6678,6 +6687,13 @@ lookup to succeed. The lookup type determines how the file is searched. .new .cindex "tainted data" "single-key lookups" The file string may not be tainted + +.cindex "tainted data" "de-tainting" +All single-key lookups support the option &"ret=key"&. +If this is given and the lookup +(either underlying implementation or cached value) +returns data, the result is replaced with a non-tainted +version of the lookup key. .wen .next .cindex "query-style lookup" "definition of" @@ -6853,7 +6869,7 @@ If a selector is numeric, it must apply to a JSON array; the (zero-based) 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. .next @@ -6977,9 +6993,10 @@ be followed by optional colons. 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 &<>&. .endlist ilist @@ -8334,6 +8351,35 @@ in the previous section. You could also use the &(wildlsearch)& or +.new +.section "Results of list checking" SECTlistresults +The primary result of doing a list check is a truth value. +In some contexts additional information is stored +about the list element that matched: +.vlist +.vitem hosts +A &%hosts%& ACL condition +will store a result in the &$host_data$& variable. +.vitem local_parts +A &%local_parts%& router option or &%local_parts%& ACL condition +will store a result in the &$local_part_data$& variable. +.vitem domains +A &%domains%& router option or &%domains%& ACL condition +.vitem senders +A &%senders%& router option or &%senders%& ACL condition +will store a result in the &$sender_data$& variable. +.vitem recipients +A &%recipients%& ACL condition +will store a result in the &$recipient_data$& variable. +.endlist + +The detail of the additional information depends on the +type of match and is given below as the &*value*& information. +.wen + + + + .section "Named lists" "SECTnamedlists" .cindex "named lists" .cindex "list" "named" @@ -8496,6 +8542,12 @@ If a pattern consists of a single @ character, it matches the local host name, as set by the &%primary_hostname%& option (or defaulted). This makes it possible to use the same configuration file on several different hosts that differ only in their names. + +.new +The value for a match will be the primary host name. +.wen + + .next .cindex "@[] in a domain list" .cindex "domain list" "matching local IP interfaces" @@ -8505,7 +8557,14 @@ in square brackets (as in an email address that contains a domain literal), but only if that IP address is recognized as local for email routing purposes. The &%local_interfaces%& and &%extra_local_interfaces%& options can be used to control which of a host's several IP addresses are treated as local. -In today's Internet, the use of domain literals is controversial. +In today's Internet, the use of domain literals is controversial; +see the &%allow_domain_literals%& main option. + +.new +The value for a match will be the string &`@[]`&. +.wen + + .next .cindex "@mx_any" .cindex "@mx_primary" @@ -8554,6 +8613,11 @@ involved, it is easiest to change the delimiter for the main list as well: domains = >&) to specify that it is not to be expanded (unless you really do want to build a regular expression by expansion, of course). + +.new +The value for a match will be the list element string (starting with the circumflex). +Additionally, &$0$& will be set to the string matching the regular expression, +and &$1$& (onwards) to any submatches identified by parentheses. +.wen + + + .next .cindex "lookup" "in domain list" .cindex "domain list" "matching by lookup" @@ -8593,12 +8672,15 @@ must be a filename in a suitable format for the lookup type. For example, for 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 @@ -8617,6 +8699,7 @@ original lookup fails. This is not a useful feature when using a domain list to 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 @@ -8626,25 +8709,37 @@ chapter &<>&. For example: 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 = \ @@ -10790,8 +10885,7 @@ a decimal representation of the answer (without &"K"&, &"M"& or &"G"&). For exam 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}} \ { \ @@ -10800,6 +10894,7 @@ deny message = Too many bad recipients {${eval:$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. @@ -12230,13 +12325,6 @@ contain the trailing slash. If &$config_file$& does not contain a slash, .vindex "&$config_file$&" The name of the main configuration file Exim is using. -.vitem &$dmarc_domain_policy$& &&& - &$dmarc_status$& &&& - &$dmarc_status_text$& &&& - &$dmarc_used_domains$& -Results of DMARC verification. -For details see section &<>&. - .vitem &$dkim_verify_status$& Results of DKIM verification. For details see section &<>&. @@ -12269,6 +12357,13 @@ When a message has been received this variable contains a colon-separated list of signer domains and identities for the message. For details see section &<>&. +.vitem &$dmarc_domain_policy$& &&& + &$dmarc_status$& &&& + &$dmarc_status_text$& &&& + &$dmarc_used_domains$& +Results of DMARC verification. +For details see section &<>&. + .vitem &$dnslist_domain$& &&& &$dnslist_matched$& &&& &$dnslist_text$& &&& @@ -12341,7 +12436,9 @@ the complete argument of the ETRN command (see section &<>&). .cindex "tainted data" If the origin of the data is an incoming message, the result of expanding this variable is tainted. -See also &$domain_verified$&. +When un untainted version is needed, one should be obtained from +looking up the value in a local (therefore trusted) database. +Often &$domain_data$& is usable in this role. .wen @@ -12438,7 +12535,7 @@ result of the lookup is made available in the &$host_data$& variable. This 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$& .cindex "host name" "lookup, failure of" @@ -12548,29 +12645,15 @@ Consider carefully the implications of using it unvalidated as a name for file access. This presents issues for users' &_.forward_& and filter files. For traditional full user accounts, use &%check_local_users%& and the -&$local_part_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$& is set to the local part of the parent address, not to the filename or command (see &$address_file$& and @@ -12611,44 +12694,33 @@ router as &$local_part_data$&. In addition, if the driver routes the address to a transport, the value is available in that transport. If the transport is handling multiple addresses, the value from the first address is used. +.new +The &%check_local_user%& router option also sets this variable. +.wen + &$local_part_data$& is also set when the &%local_parts%& condition in an ACL matches a local part by means of a lookup. The data read by the lookup is available during the rest of the ACL statement. In all other situations, this variable expands to nothing. -.vitem &$local_part_prefix$& -.vindex "&$local_part_prefix$&" +.vindex &$local_part_prefix$& &&& + &$local_part_prefix_v$& &&& + &$local_part_suffix$& &&& + &$local_part_suffix_v$& .cindex affix variables -When an address is being routed or delivered, and a -specific prefix for the local part was recognized, it is available in this -variable, having been removed from &$local_part$&. - -.new -.vitem &$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$&. - +If a local part prefix or suffix has been recognized, it is not included in the +value of &$local_part$& during routing and subsequent delivery. The values of +any prefix or suffix are in &$local_part_prefix$& and +&$local_part_suffix$&, respectively. .new -.vitem &$local_part_suffix_v$& -.vindex "&$local_part_suffix_v$&" -When &$local_part_suffix$& is valid and the suffix match used a wildcard, -the portion matching the wildcard is available in this variable. -.wen +.cindex "tainted data" +If the specification did not include a wildcard then +the affix variable value is not tainted. -.new -.vitem &$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$&. -Such values are not tainted and hence usable for building file names. +If the affix specification included a wildcard then the portion of +the affix matched by the wildcard is in +&$local_part_prefix_v$& or &$local_part_suffix_v$& as appropriate, +and both the whole and varying values are tainted. .wen .vitem &$local_scan_data$& @@ -12815,9 +12887,9 @@ header and the body). 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 - $body_linecount}}} + message = Too many lines in message header .endd In the MAIL and RCPT ACLs, the value is zero because at that stage the message has not yet been received. @@ -14506,6 +14578,7 @@ listed in more than one group. .row &%percent_hack_domains%& "recognize %-hack for these domains" .row &%spamd_address%& "set interface to SpamAssassin" .row &%strict_acl_vars%& "object to unset ACL variables" +.row &%spf_smtp_comment_template%& "template for &$spf_smtp_comment$&" .endtable @@ -14590,7 +14663,11 @@ See also the &'Policy controls'& section above. .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" @@ -14738,6 +14815,7 @@ Those options that undergo string expansion before use are marked with .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 @@ -14951,6 +15029,7 @@ That is, set the option to an empty string so that no check is done. .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. @@ -15012,12 +15091,18 @@ just the command name, it is not a complete command line. If an argument is 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 &<>&. See also &%warn_message_file%&. +chapter &<>&. +.new +.cindex bounce_message_file "tainted data" +The option is expanded to give the file path, which must be +absolute and untainted. +.wen +See also &%warn_message_file%&. .option bounce_message_text main string unset @@ -15206,6 +15291,7 @@ may wish to deliberately disable them. .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. @@ -15364,6 +15450,16 @@ This option gives a list of key types which are acceptable in signatures, and an order of processing. Signatures with algorithms not in the list will be ignored. + +.new +.option dkim_verify_min_keysizes main "string list" "rsa=1024 ed25519=250" +This option gives a list of key sizes which are acceptable in signatures. +The list is keyed by the algorithm type for the key; the values are in bits. +Signatures with keys smaller than given by this option will fail verification. + +The default enforces the RFC 8301 minimum key size for RSA signatures. +.wen + .option dkim_verify_minimal main boolean false If set to true, verification of signatures will terminate after the first success. @@ -15376,6 +15472,14 @@ the ACL once for each signature in the message. See section &<>&. +.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 &<>& 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 @@ -15547,6 +15651,7 @@ described in section &<>&. .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, @@ -15554,6 +15659,10 @@ and RET and ORCPT options on MAIL FROM commands. A NOTIFY=SUCCESS option requests success-DSN messages. A NOTIFY= option with no argument requests that no delay or failure DSNs are sent. +.new +&*Note*&: Supplying success-DSN messages has been criticised +on privacy grounds; it can leak details of internal forwarding. +.wen .option dsn_from main "string&!!" "see below" .cindex "&'From:'& header line" "in bounces" @@ -16435,6 +16544,11 @@ to depend on the IP address of the remote host for messages arriving via 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 @@ -16702,6 +16816,7 @@ of the &%-oX%& option, unless a path is explicitly supplied by &%-oP%&. .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 &<>&. When PIPELINING is not advertised and @@ -16713,6 +16828,7 @@ not count as protocol errors (see &%smtp_max_synprot_errors%&). .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 @@ -16726,6 +16842,7 @@ Currently the option name &"X_PIPE_CONNECT"& is used. .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. @@ -17445,6 +17562,7 @@ hosts), you can do so by an appropriate use of a &%control%& modifier in an ACL .option smtp_etrn_command main string&!! unset .cindex "ETRN" "command to be run" +.cindex "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 @@ -17625,7 +17743,8 @@ example, instead of &"Administrative prohibition"&, it might give: .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 @@ -17643,6 +17762,41 @@ See section &<>& for more details. This option is available when Exim is compiled with SPF support. See section &<>& for more details. +.new +.option spf_smtp_comment_template main string&!! "Please%_see%_http://www.open-spf.org/Why" +This option is available when Exim is compiled with SPF support. It +allows the customisation of the SMTP comment that the SPF library +generates. You are strongly encouraged to link to your own explanative +site. The following placeholders (along with Exim variables) are allowed +in the template (this list is compiled from the libspf2 sources): +.ilist +&*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. A note on using Exim variables: As +currenty the SPF library is initialized already during the EHLO phase, +the amount of variables available for expansion is quite limited. +.wen .option split_spool_directory main boolean false @@ -17916,6 +18070,7 @@ unfortunately not all, operating systems. .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 @@ -18353,14 +18508,20 @@ regular expression by a parenthesized subpattern. The default value for 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 -&<>&. See also &%bounce_message_file%&. +&<>&. +.new +.cindex warn_message_file "tainted data" +The option is expanded to give the file path, which must be +absolute and untainted. +.wen +See also &%bounce_message_file%&. .option write_rejectlog main boolean true @@ -19171,7 +19332,7 @@ but the user is specified symbolically, the gid associated with the uid is 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. @@ -21802,7 +21963,7 @@ local_users: # 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 @@ -22317,7 +22478,7 @@ message. For example, a content scan could insert a new header line containing 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 @@ -22637,7 +22798,7 @@ is used as a result of a &"keep"& action in the filter. This example shows one 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} \ @@ -22818,8 +22979,8 @@ The string value is expanded for each delivery, and must yield an absolute 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 = $home/inbox .endd .cindex "&""sticky""& bit" @@ -23575,7 +23736,7 @@ and directories in a maildir mailbox, including subdirectories for maildir++ folders. Consider this example: .code maildir_format = true -directory = /var/mail/$local_part\ +directory = /var/mail/$local_part_data\ ${if eq{$local_part_suffix}{}{}\ {/.${substr_1:$local_part_suffix}}} maildirfolder_create_regex = /\.[^/]+$ @@ -24565,14 +24726,14 @@ configuration for &%procmail%&: # 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 @@ -25030,7 +25191,8 @@ facilities such as AUTH, PIPELINING, SIZE, and STARTTLS. .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 @@ -25234,6 +25396,7 @@ 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" +.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. @@ -25391,7 +25554,7 @@ See also the &%max_parallel%& generic transport option. .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" @@ -25576,13 +25739,17 @@ The &%tls_verify_certificates%& option must also be set. 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 &<>&. +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 &<>&. @@ -26690,6 +26857,7 @@ transfer of mail between servers that have no managerial connection with each other. .cindex "AUTH" "description of" +.cindex "ESMTP extensions" AUTH Very briefly, the way SMTP authentication works is as follows: .ilist @@ -28721,6 +28889,7 @@ tls_require_ciphers = ${if =={$received_port}{25}\ .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 @@ -28980,6 +29149,7 @@ deliveries as well as to incoming, the latter one causing logging of the 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, @@ -30118,8 +30288,8 @@ The &%message%& modifier operates exactly as it does for &%accept%&. &%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. @@ -30922,6 +31092,7 @@ calling host. Its effect lasts until the end of the SMTP connection. .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 @@ -30997,7 +31168,7 @@ data is read. 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 &<>&. .endlist vlist @@ -31354,7 +31525,7 @@ of the lookup is made available in the &$host_data$& variable. This 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. @@ -31498,8 +31669,8 @@ section &<>& (callouts are described in section 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*& @@ -31681,8 +31852,8 @@ Testing the list of domains stops as soon as a match is found. If you want to 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 @@ -31723,8 +31894,8 @@ addresses (see, e.g., the &'domain based zones'& link at 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 $dnslist_domain .endd This particular example is useful only in ACLs that are obeyed after the RCPT or DATA commands, when a sender address is available. If (for @@ -31788,13 +31959,13 @@ dnslists = black.list.tld/a.domain::b.domain However, when the data for the list is obtained from a lookup, the second form is usually much more convenient. Consider this example: .code -deny message = The mail servers for the domain \ +deny dnslists = sbl.spamhaus.org/<|${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=\ - $sender_address_domain} }} } .endd Note the use of &`>|`& in the dnsdb lookup to specify the separator for multiple DNS records. The inner dnsdb lookup produces a list of MX hosts @@ -31867,7 +32038,7 @@ very meaningful. See section &<>& for a way of obtaining more information. You can use the DNS list variables in &%message%& or &%log_message%& modifiers -&-- although these appear before the condition in the ACL, they are not +&-- even if these appear before the condition in the ACL, they are not expanded until after it has failed. For example: .code deny hosts = !+local_networks @@ -32053,12 +32224,12 @@ restrictions, to get the TXT record. As a byproduct of this, there is also a check that the IP being tested is indeed on the first list. The first domain is the one that is put in &$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 @@ -32248,12 +32419,12 @@ new rate. .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 @@ -32363,16 +32534,16 @@ deny authenticated = * 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 @@ -32961,16 +33132,16 @@ list called &%batv_senders%&. Then, in the ACL for RCPT commands, you could 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 = $prvscheck_result + message = Invalid reverse path signature. .endd The first statement rejects recipients for bounce messages that are addressed to plain BATV sender addresses, because it is known that BATV senders do not @@ -33507,13 +33678,13 @@ imposed by your anti-virus scanner. Here is a very simple scanning example: .code -deny message = This message contains malware ($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: @@ -33522,13 +33693,13 @@ av_scanner = $acl_m0 .endd in the main Exim configuration. .code -deny message = This message contains malware ($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 @@ -33657,8 +33828,8 @@ is set to record the actual address used. .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 @@ -33690,9 +33861,9 @@ large ones may cause significant performance degradation. As most spam messages 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 @@ -33750,8 +33921,8 @@ failed. If you want to treat DEFER as FAIL (to pass on to the next ACL 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%&. @@ -33769,9 +33940,9 @@ warn spam = nobody 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 @@ -33975,10 +34146,10 @@ As an example, the following will ban &"HTML mail"& (including that sent with 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 &$mime_is_multipart$& @@ -34031,8 +34202,8 @@ expanded before being used, you must also escape dollar signs and backslashes 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 @@ -35127,7 +35298,7 @@ central_filter: 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 @@ -35885,13 +36056,14 @@ used to contain the envelope information. .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 @@ -36287,7 +36459,8 @@ RCPT failures. .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 @@ -36642,10 +36815,10 @@ lists in a separate domain from normal mail. For example: 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 @@ -36733,7 +36906,8 @@ lists_request: 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: @@ -36741,10 +36915,10 @@ 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: @@ -36802,7 +36976,7 @@ verp_smtp: 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 @@ -36853,7 +37027,7 @@ verp_dnslookup: 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=$domain}@your.dom.example}fail} no_more .endd Before you start sending out messages with VERPed return paths, you must also @@ -36941,7 +37115,7 @@ follows: .code my_mailboxes: driver = appendfile - file = /var/mail/$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 @@ -36996,9 +37170,9 @@ another MTA: 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 @@ -40733,6 +40907,10 @@ Notes from the key record (tag n=). .vitem &%$dkim_key_length%& Number of bits in the key. +.new +Valid only once the key is loaded, which is at the time the header signature +is verified, which is after the body hash is. +.wen Note that RFC 8301 says: .code @@ -40740,9 +40918,8 @@ Verifiers MUST NOT consider signatures using RSA keys of less than 1024 bits as valid signatures. .endd -To enforce this you must have a DKIM ACL which checks this variable -and overwrites the &$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 @@ -40757,10 +40934,10 @@ verb to a group of domains or identities. For example: .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; @@ -40772,10 +40949,10 @@ results against the actual result of verification. This is typically used 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 @@ -40859,13 +41036,16 @@ deny spf = fail 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=$sender_host_address .endd +Note: The above mentioned URL may not be as helpful as expected. You are +encouraged to replace the link with a link to a site with more +explanations. + When the spf condition has run, it sets up several expansion variables: @@ -40900,8 +41080,13 @@ variables: .vitem &$spf_smtp_comment$& .vindex &$spf_smtp_comment$& +.vindex &%spf_smtp_comment_template%& This contains a string that can be used in a SMTP response to the calling party. Useful for "fail". +.new + The string is generated by the SPF library from the template configured in the main config + option &%spf_smtp_comment_template%&. +.wen .endlist @@ -41274,8 +41459,8 @@ A possible solution is: # 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 @@ -41371,6 +41556,7 @@ requirement, upon libidn2. .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 @@ -41417,22 +41603,27 @@ may use the following modifier: control = utf8_downconvert control = utf8_downconvert/ .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.