X-Git-Url: https://git.exim.org/users/heiko/exim.git/blobdiff_plain/92562f63be6fae2526d68171d60bf87027551f88..701af1005a6effaac5ce249f1c2086dc6c0c2a7f:/doc/doc-docbook/spec.xfpt diff --git a/doc/doc-docbook/spec.xfpt b/doc/doc-docbook/spec.xfpt index 410a166ab..96d477df3 100644 --- a/doc/doc-docbook/spec.xfpt +++ b/doc/doc-docbook/spec.xfpt @@ -52,7 +52,7 @@ .set I "    " .macro copyyear -2019 +2020 .endmacro . ///////////////////////////////////////////////////////////////////////////// @@ -1399,16 +1399,21 @@ If the &%domains%& option is set, the domain of the address must be in the set of domains that it defines. .next .vindex "&$local_part_prefix$&" +.vindex "&$local_part_prefix_v$&" .vindex "&$local_part$&" .vindex "&$local_part_suffix$&" +.vindex "&$local_part_suffix_v$&" .cindex affix "router precondition" If the &%local_parts%& option is set, the local part of the address must be in the set of local parts that it defines. If &%local_part_prefix%& or &%local_part_suffix%& is in use, the prefix or suffix is removed from the local part before this check. If you want to do precondition tests on local parts that include affixes, you can do so by using a &%condition%& option (see below) -that uses the variables &$local_part$&, &$local_part_prefix$&, and -&$local_part_suffix$& as necessary. +.new +that uses the variables &$local_part$&, &$local_part_prefix$&, +&$local_part_prefix_v$&, &$local_part_suffix$& +and &$local_part_suffix_v$& as necessary. +.wen .next .vindex "&$local_user_uid$&" .vindex "&$local_user_gid$&" @@ -3866,6 +3871,14 @@ This option is not intended for use by external callers. It is used internally by Exim in conjunction with the &%-MC%& option. It signifies that the remote host supports the ESMTP &_DSN_& extension. +.new +.vitem &%-MCd%& +.oindex "&%-MCd%&" +This option is not intended for use by external callers. It is used internally +by Exim in conjunction with the &%-d%& option +to pass on an information string on the purpose of the process. +.wen + .vitem &%-MCG%&&~<&'queue&~name'&> .oindex "&%-MCG%&" This option is not intended for use by external callers. It is used internally @@ -3897,7 +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%& @@ -5892,13 +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. @@ -6002,10 +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: $sender_host_address is in \ @@ -6368,7 +6381,7 @@ All other options are defaulted. .code local_delivery: driver = appendfile - file = /var/mail/$local_part_verified + file = /var/mail/$local_part_data delivery_date_add envelope_to_add return_path_add @@ -6381,7 +6394,7 @@ traditional BSD mailbox format. .new We prefer to avoid using &$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$& in the user database (done by using &%check_local_user%& in the the router). .wen @@ -6628,6 +6641,8 @@ file that is searched could contain lines like this: .endd When the lookup succeeds, the result of the expansion is a list of domains (and possibly other types of item that are allowed in domain lists). +.cindex "tainted data" "de-tainting" +The result of the expansion is not tainted. In the second example, the lookup is a single item in a domain list. It causes Exim to use a lookup to see if the domain that is being processed can be found @@ -6648,6 +6663,13 @@ If the value of &$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. @@ -6662,6 +6684,17 @@ Two different types of data lookup are implemented: The &'single-key'& type requires the specification of a file in which to look, and a single key to search for. The key must be a non-empty string for the lookup to succeed. The lookup type determines how the file is searched. +.new +.cindex "tainted data" "single-key lookups" +The file string may not be tainted + +.cindex "tainted data" "de-tainting" +All single-key lookups support the option &"ret=key"&. +If this is given and the lookup +(either underlying implementation or cached value) +returns data, the result is replaced with a non-tainted +version of the lookup key. +.wen .next .cindex "query-style lookup" "definition of" The &'query-style'& type accepts a generalized database query. No particular @@ -6753,11 +6786,42 @@ by default, but has an option to omit them (see section &<>&). .next .cindex "lookup" "dsearch" .cindex "dsearch lookup type" -&(dsearch)&: The given file must be a directory; this is searched for an entry -whose name is the key by calling the &[lstat()]& function. The key may not -contain any forward slash characters. If &[lstat()]& succeeds, the result of -the lookup is the name of the entry, which may be a file, directory, -symbolic link, or any other kind of directory entry. An example of how this +&(dsearch)&: The given file must be an +.new +absolute +.wen +directory path; this is searched for an entry +whose name is the key by calling the &[lstat()]& function. +The key may not +contain any forward slash characters. +If &[lstat()]& succeeds then so does the lookup. +.new +.cindex "tainted data" "dsearch result" +The result is regarded as untainted. + +Options for the lookup can be given by appending them after the word "dsearch", +separated by a comma. Options, if present, are a comma-separated list having +each element starting with a tag name and an equals. + +Two options are supported, for the return value and for filtering match +candidates. +The "ret" option requests an alternate result value of +the entire path for the entry. Example: +.code +${lookup {passwd} dsearch,ret=full {/etc}} +.endd +The default result is just the requested entry. +The "filter" option requests that only directory entries of a given type +are matched. The match value is one of "file", "dir" or "subdir" (the latter +not matching "." or ".."). Example: +.code +${lookup {passwd} dsearch,filter=file {/etc}} +.endd +The default matching is for any entry type, including directories +and symlinks. +.wen + +An example of how this lookup can be used to support virtual domains is given in section &<>&. .next @@ -6805,7 +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 @@ -6929,9 +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 @@ -7002,7 +7067,11 @@ passed to a Redis database. See section &<>&. .next .cindex "sqlite lookup type" .cindex "lookup" "sqlite" -&(sqlite)&: The format of the query is a filename followed by an SQL statement +&(sqlite)&: The format of the query is +new +an optional filename +.wen +followed by an SQL statement that is passed to an SQLite database. See section &<>&. .next @@ -7909,6 +7978,11 @@ If any MySQL, PostgreSQL, Oracle, InterBase or Redis lookups are used, the or &%redis_servers%& option (as appropriate) must be set to a colon-separated list of server information. +.oindex &%mysql_servers%& +.oindex &%pgsql_servers%& +.oindex &%oracle_servers%& +.oindex &%ibase_servers%& +.oindex &%redis_servers%& (For MySQL and PostgreSQL, the global option need not be set if all queries contain their own server information &-- see section &<>&.) @@ -7959,12 +8033,14 @@ The &%quote_redis%& expansion operator escapes whitespace and backslash characters with a backslash. .section "Specifying the server in the query" "SECTspeserque" +.new For MySQL, PostgreSQL and Redis lookups (but not currently for Oracle and InterBase), it is possible to specify a list of servers with an individual query. This is -done by starting the query with +done by appending a comma-separated option to the query type: .display -&`servers=`&&'server1:server2:server3:...'&&`;`& +&`,servers=`&&'server1:server2:server3:...'& .endd +.wen Each item in the list may take one of two forms: .olist If it contains no slashes it is assumed to be just a host name. The appropriate @@ -7989,15 +8065,26 @@ mysql_servers = slave1/db/name/pw:\ .endd In an updating lookup, you could then write: .code -${lookup mysql{servers=master; UPDATE ...} } +${lookup mysql,servers=master {UPDATE ...} } .endd That query would then be sent only to the master server. If, on the other hand, the master is not to be used for reading, and so is not present in the global option, you can still update it by a query of this form: .code -${lookup pgsql{servers=master/db/name/pw; UPDATE ...} } +${lookup pgsql,servers=master/db/name/pw {UPDATE ...} } .endd +.new +An older syntax places the servers speciification before the qury, +semicolon separated: +.code +${lookup mysql{servers=master; UPDATE ...} } +.endd +The new version avoids potential issues with tainted +arguments in the query, for explicit expansion. +&*Note*&: server specifications in list-style lookups are still problematic. +.wen + .section "Special MySQL features" "SECID73" For MySQL, an empty host name or the use of &"localhost"& in &%mysql_servers%& @@ -8046,19 +8133,35 @@ affected. .cindex "sqlite lookup type" SQLite is different to the other SQL lookups because a filename is required in addition to the SQL query. An SQLite database is a single file, and there is no -daemon as in the other SQL databases. The interface to Exim requires the name -of the file, as an absolute path, to be given at the start of the query. It is -separated from the query by white space. This means that the path name cannot -contain white space. Here is a lookup expansion example: +daemon as in the other SQL databases. + +.new +.oindex &%sqlite_dbfile%& +The preferred way of specifying the file is by using the +&%sqlite_dbfile%& option, set to +an absolute path. +.wen +A deprecated method is available, prefixing the query with the filename +separated by white space. +This means that the path name cannot contain white space. +.cindex "tainted data" "sqlite file" +It also means that the query cannot use any tainted values, as that taints +the entire query including the filename - resulting in a refusal to open +the file. + +.new +Here is a lookup expansion example: .code -${lookup sqlite {/some/thing/sqlitedb \ - select name from aliases where id='userx';}} +sqlite_dbfile = /some/thing/sqlitedb +... +${lookup sqlite {select name from aliases where id='userx';}} .endd In a list, the syntax is similar. For example: .code -domainlist relay_to_domains = sqlite;/some/thing/sqlitedb \ +domainlist relay_to_domains = sqlite;\ select * from relays where ip='$sender_host_address'; .endd +.wen The only character affected by the &%quote_sqlite%& operator is a single quote, which it doubles. @@ -8248,6 +8351,35 @@ in the previous section. You could also use the &(wildlsearch)& or +.new +.section "Results of list checking" SECTlistresults +The primary result of doing a list check is a truth value. +In some contexts additional information is stored +about the list element that matched: +.vlist +.vitem hosts +A &%hosts%& ACL condition +will store a result in the &$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" @@ -8410,6 +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" @@ -8419,7 +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" @@ -8468,6 +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" @@ -8507,12 +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 @@ -8531,6 +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 @@ -8540,17 +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 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 = \ @@ -9981,6 +10170,18 @@ extracted is used. You can use &`fail`& instead of {<&'string3'&>} as in a string extract. +.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{*&<&'key'&>&*}&~*&<&'search&~type'&>&*&~&&& {*&<&'file'&>&*}&~{*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&" This is the first of one of two different types of lookup item, which are both @@ -10191,21 +10392,37 @@ ${readsocket{/socket/name}{request string}{3s}} .endd The third argument is a list of options, of which the first element is the timeout -and must be present if the argument is given. +and must be present if any options are given. Further elements are options of form &'name=value'&. -Two option types is currently recognised: shutdown and tls. -The first defines whether (the default) -or not a shutdown is done on the connection after sending the request. -Example, to not do so (preferred, eg. by some webservers): +Example: .code ${readsocket{/socket/name}{request string}{3s:shutdown=no}} .endd -The second, tls, controls the use of TLS on the connection. Example: -.code -${readsocket{/socket/name}{request string}{3s:tls=yes}} -.endd -The default is to not use TLS. + +.new +The following option names are recognised: +.ilist +&*cache*& +Defines if the result data can be cached for use by a later identical +request in the same process. +Values are &"yes"& or &"no"& (the default). +If not, all cached results for this connection specification +will be invalidated. + +.next +&*shutdown*& +Defines whether or not a write-shutdown is done on the connection after +sending the request. Values are &"yes"& (the default) or &"no"& +(preferred, eg. by some webservers). + +.next +&*tls*& +Controls the use of TLS on the connection. +Values are &"yes"& or &"no"& (the default). If it is enabled, a shutdown as descripbed above is never done. +.endlist +.wen + A fourth argument allows you to change any newlines that are in the data that is read, in the same way as for &%readfile%& (see above). This example @@ -10680,8 +10897,7 @@ 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}} \ { \ @@ -10690,6 +10906,7 @@ 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. @@ -11717,15 +11934,12 @@ request, for a password, so the data consists of just two strings. 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 @@ -12120,13 +12334,6 @@ 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 &<>&. @@ -12159,6 +12366,13 @@ 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 &$dnslist_domain$& &&& &$dnslist_matched$& &&& &$dnslist_text$& &&& @@ -12231,7 +12445,9 @@ 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 @@ -12328,7 +12544,7 @@ 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$& .cindex "host name" "lookup, failure of" @@ -12438,22 +12654,15 @@ Consider carefully the implications of using it unvalidated as a name for file access. This presents issues for users' &_.forward_& and filter files. For traditional full user accounts, use &%check_local_users%& and the -&$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_suffix$&" -.cindex affix variables -If a local part prefix or suffix has been recognized, it is not included in the -value of &$local_part$& during routing and subsequent delivery. The values of -any prefix or suffix are in &$local_part_prefix$& and -&$local_part_suffix$&, respectively. - When a message is being delivered to a file, pipe, or autoreply transport as a result of aliasing or forwarding, &$local_part$& is set to the local part of the parent address, not to the filename or command (see &$address_file$& and @@ -12494,30 +12703,33 @@ router as &$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$&. - -.vitem &$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_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$&. -Such values are not tainted and hence usable for building file names. +.cindex "tainted data" +If the specification did not include a wildcard then +the affix variable value is not tainted. + +If the affix specification included a wildcard then the portion of +the affix matched by the wildcard is in +&$local_part_prefix_v$& or &$local_part_suffix_v$& as appropriate, +and both the whole and varying values are tainted. .wen .vitem &$local_scan_data$& @@ -12684,9 +12896,9 @@ 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 - $body_linecount}}} + message = Too many lines in message header .endd In the MAIL and RCPT ACLs, the value is zero because at that stage the message has not yet been received. @@ -12854,6 +13066,13 @@ or if not set, the value of &$qualify_domain$&. .cindex queues named The name of the spool queue in use; empty for the default queue. +.vitem &$queue_size$& +.vindex "&$queue_size$&" +.cindex "queue" "size of" +.cindex "spool" "number of messages" +This variable contains the number of messages queued. +It is evaluated on demand, but no more often than once every minute. + .vitem &$r_...$& .vindex &$r_...$& .cindex router variables @@ -13168,6 +13387,18 @@ library, by setting: dns_dnssec_ok = 1 .endd +.new +In addition, on Linux with glibc 2.31 or newer the resolver library will +default to stripping out a successful validation status. +This will break a previously working Exim installation. +Provided that you do trust the resolver (ie, is on localhost) you can tell +glibc to pass through any successful validation with a new option in +&_/etc/resolv.conf_&: +.code +options trust-ad +.endd +.wen + Exim does not perform DNSSEC validation itself, instead leaving that to a validating resolver (e.g. unbound, or bind with suitable configuration). @@ -14276,6 +14507,7 @@ listed in more than one group. .row &%daemon_startup_sleep%& "time to sleep between tries" .row &%extra_local_interfaces%& "not necessarily listened on" .row &%local_interfaces%& "on which to listen, with optional ports" +.row &%notifier_socket%& "override compiled-in value" .row &%pid_file_path%& "override compiled-in value" .row &%queue_run_max%& "maximum simultaneous queue runners" .endtable @@ -14355,6 +14587,7 @@ listed in more than one group. .row &%percent_hack_domains%& "recognize %-hack for these domains" .row &%spamd_address%& "set interface to SpamAssassin" .row &%strict_acl_vars%& "object to unset ACL variables" +.row &%spf_smtp_comment_template%& "template for &$spf_smtp_comment$&" .endtable @@ -14439,7 +14672,11 @@ 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" @@ -14587,6 +14824,7 @@ 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 @@ -14800,6 +15038,7 @@ 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. @@ -14861,12 +15100,18 @@ 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 @@ -15055,6 +15300,7 @@ 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. @@ -15213,6 +15459,16 @@ 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. @@ -15225,6 +15481,14 @@ 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 @@ -15295,6 +15559,18 @@ default. A value of 0 coerces DNSSEC off, a value of 1 coerces DNSSEC on. If the resolver library does not support DNSSEC then this option has no effect. +.new +On Linux with glibc 2.31 or newer this is insufficient, the resolver library +will default to stripping out a successful validation status. +This will break a previously working Exim installation. +Provided that you do trust the resolver (ie, is on localhost) you can tell +glibc to pass through any successful validation with a new option in +&_/etc/resolv.conf_&: +.code +options trust-ad +.endd +.wen + .option dns_ipv4_lookup main "domain list&!!" unset .cindex "IPv6" "DNS lookup for AAAA records" @@ -15384,6 +15660,7 @@ 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, @@ -15391,6 +15668,10 @@ 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" @@ -16272,6 +16553,11 @@ 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 @@ -16349,6 +16635,24 @@ harm. This option overrides the &%pipe_as_creator%& option of the &(pipe)& 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. +Only installations running multiple daemons sharing a spool directory +should need to modify the default. + +The option is expanded before use. +If the platform supports Linux-style abstract socket names, the result +is used with a nul byte prefixed. +Otherwise, it should be a full path name and use a directory accessible +to Exim. + +If the Exim command line uses a &%-oX%& option and does not use &%-oP%& +then a notifier socket is not created. +.wen + + .option openssl_options main "string list" "+no_sslv2 +no_sslv3 +single_dh_use +no_ticket +no_renegotiation" .cindex "OpenSSL "compatibility options" This option allows an administrator to adjust the SSL options applied @@ -16521,6 +16825,7 @@ 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 @@ -16532,6 +16837,7 @@ 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 @@ -16545,6 +16851,7 @@ 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. @@ -16814,7 +17121,7 @@ received_header_text = Received: \ ${if def:sender_helo_name {(helo=$sender_helo_name)\n\t}}}}\ by $primary_hostname \ ${if def:received_protocol {with $received_protocol }}\ - ${if def:tls_ver { ($tls_ver)}}\ + ${if def:tls_in_ver { ($tls_in_ver)}}\ ${if def:tls_in_cipher_std { tls $tls_in_cipher_std\n\t}}\ (Exim $version_number)\n\t\ ${if def:sender_address \ @@ -16823,7 +17130,8 @@ received_header_text = Received: \ ${if def:received_for {\n\tfor $received_for}} .endd -The reference to the TLS cipher is omitted when Exim is built without TLS +The references to the TLS version and cipher are +omitted when Exim is built without TLS support. The use of conditional expansions ensures that this works for both locally generated messages and messages received from remote hosts, giving header lines such as the following: @@ -17263,6 +17571,7 @@ hosts), you can do so by an appropriate use of a &%control%& modifier in an ACL .option smtp_etrn_command main string&!! unset .cindex "ETRN" "command to be run" +.cindex "ESMTP extensions" ETRN .vindex "&$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 @@ -17274,6 +17583,13 @@ example: 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 '& command is used; +if the ETRN ACL has set up a named-queue then &'-MCG '& is appended. +.wen + A new process is created to run the command, but Exim does not wait for it to complete. Consequently, its status cannot be checked. If the command cannot be run, a line is written to the panic log, but the ETRN caller still receives @@ -17436,7 +17752,8 @@ 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 @@ -17454,6 +17771,48 @@ 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 template must not contain spaces. If you need spaces in the +output, use the proper placeholder. If libspf2 can not parse the +template, it uses a built-in default broken link. The following placeholders +(along with Exim variables (but see below)) are allowed in the template: +.ilist +&*%_*&: A space. +.next +&*%{L}*&: Envelope sender's local part. +.next +&*%{S}*&: Envelope sender. +.next +&*%{O}*&: Envelope sender's domain. +.next +&*%{D}*&: Current(?) domain. +.next +&*%{I}*&: SMTP client Ip. +.next +&*%{C}*&: SMTP client pretty IP. +.next +&*%{T}*&: Epoch time (UTC). +.next +&*%{P}*&: SMTP client domain name. +.next +&*%{V}*&: IP version. +.next +&*%{H}*&: EHLO/HELO domain. +.next +&*%{R}*&: Receiving domain. +.endlist +The capitalized placeholders do proper URL encoding, if you use them +lowercased, no encoding takes place. This list was compiled from the +libspf2 sources. + +A note on using Exim variables: As +currently the SPF library is initialized before the SMTP EHLO phase, +the variables useful for expansion are quite limited. +.wen .option split_spool_directory main boolean false @@ -17727,6 +18086,7 @@ 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 @@ -18164,14 +18524,20 @@ 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 @@ -18654,15 +19020,19 @@ avoided. The &%repeat_use%& option of the &%redirect%& router may be of help. This option specifies a list of text headers, colon-separated (by default, changeable in the usual way &<>&), that is associated with any addresses that are accepted by the router. -Each item is separately expanded, at routing time. However, this -option has no effect when an address is just being verified. The way in which +However, the option has no effect when an address is just being verified. +Each list item is separately expanded, at transport time. +.new +If an item ends in *, it will match any header with the given prefix. +.wen +The way in which the text is used to remove header lines at transport time is described in section &<>&. Header lines are not actually removed until the message is in the process of being transported. This means that references to header lines in string expansions in the transport's configuration still &"see"& the original header lines. -The &%headers_remove%& option is expanded after &%errors_to%& and +The &%headers_remove%& option is handled after &%errors_to%& and &%headers_add%&, but before &%transport%&. If an item expansion is forced to fail, the item has no effect. Other expansion failures are treated as configuration errors. @@ -18767,6 +19137,12 @@ command for LMTP, SMTP, and BSMTP deliveries has the prefix removed by default. This behaviour can be overridden by setting &%rcpt_include_affixes%& true on the relevant transport. +.new +.vindex &$local_part_prefix_v$& +If wildcarding (above) was used then the part of the prefix matching the +wildcard is available in &$local_part_prefix_v$&. +.wen + When an address is being verified, &%local_part_prefix%& affects only the behaviour of the router. If the callout feature of verification is in use, this means that the full address, including the prefix, will be used during the @@ -18972,7 +19348,7 @@ 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. @@ -20105,8 +20481,10 @@ semicolon is the default route list separator. .section "Format of one host item" "SECTformatonehostitem" -Each item in the list of hosts is either a host name or an IP address, -optionally with an attached port number. When no port is given, an IP address +Each item in the list of hosts can be either a host name or an IP address, +optionally with an attached port number, or it can be a single "+" +(see &%hosts_randomize%&). +When no port is given, an IP address is not enclosed in brackets. When a port is specified, it overrides the port specification on the transport. The port is separated from the name or address by a colon. This leads to some complications: @@ -21601,7 +21979,7 @@ 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 @@ -21841,15 +22219,21 @@ checked, since this option does not automatically suppress them. .option headers_remove transports list&!! unset .cindex "header lines" "removing" .cindex "transport" "header lines; removing" -This option specifies a list of header names, -colon-separated (by default, changeable in the usual way &<>&); -these headers are omitted from the message as it is transported, as described -in section &<>&. Header removal can also be specified by -routers. +This option specifies a list of text headers, +colon-separated (by default, changeable in the usual way &<>&), +to be removed from the message. +However, the option has no effect when an address is just being verified. Each list item is separately expanded. If the result of the expansion is an empty string, or if the expansion is forced to fail, no action is taken. Other expansion failures are treated as errors and cause the delivery to be deferred. +.new +If an item ends in *, it will match any header with the given prefix. +.wen + +Matching headers are omitted from the message as it is transported, as described +in section &<>&. Header removal can also be specified by +routers. Unlike most options, &%headers_remove%& can be specified multiple times for a transport; all listed headers are removed. @@ -22110,7 +22494,7 @@ 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 @@ -22430,7 +22814,7 @@ 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} \ @@ -22611,8 +22995,8 @@ 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 = $home/inbox .endd .cindex "&""sticky""& bit" @@ -23368,7 +23752,7 @@ and directories in a maildir mailbox, including subdirectories for maildir++ folders. Consider this example: .code maildir_format = true -directory = /var/mail/$local_part\ +directory = /var/mail/$local_part_data\ ${if eq{$local_part_suffix}{}{}\ {/.${substr_1:$local_part_suffix}}} maildirfolder_create_regex = /\.[^/]+$ @@ -24358,14 +24742,14 @@ 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 @@ -24823,7 +25207,8 @@ 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 @@ -25027,6 +25412,7 @@ 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. @@ -25184,7 +25570,7 @@ 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" @@ -25369,13 +25755,17 @@ 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 &<>&. @@ -26483,6 +26873,7 @@ 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 @@ -28514,6 +28905,7 @@ 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 @@ -28773,6 +29165,7 @@ 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, @@ -29911,8 +30304,8 @@ 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. @@ -30141,7 +30534,7 @@ in several different ways. For example: It can be at the end of an &%accept%& statement: .code accept ...some conditions - control = queue_only + control = queue .endd In this case, the control is applied when this statement yields &"accept"&, in other words, when the conditions are all true. @@ -30150,7 +30543,7 @@ other words, when the conditions are all true. It can be in the middle of an &%accept%& statement: .code accept ...some conditions... - control = queue_only + control = queue ...some more conditions... .endd If the first set of conditions are true, the control is applied, even if the @@ -30715,6 +31108,7 @@ 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 @@ -30790,7 +31184,7 @@ 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 @@ -31147,7 +31541,7 @@ 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. @@ -31291,8 +31685,8 @@ 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*& @@ -31474,8 +31868,8 @@ 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 @@ -31516,8 +31910,8 @@ 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 $dnslist_domain .endd This particular example is useful only in ACLs that are obeyed after the RCPT or DATA commands, when a sender address is available. If (for @@ -31581,13 +31975,13 @@ dnslists = black.list.tld/a.domain::b.domain However, when the data for the list is obtained from a lookup, the second form is usually much more convenient. Consider this example: .code -deny message = The mail servers for the domain \ +deny dnslists = sbl.spamhaus.org/<|${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=\ - $sender_address_domain} }} } .endd Note the use of &`>|`& in the dnsdb lookup to specify the separator for multiple DNS records. The inner dnsdb lookup produces a list of MX hosts @@ -31660,7 +32054,7 @@ very meaningful. See section &<>& for a way of obtaining more information. You can use the DNS list variables in &%message%& or &%log_message%& modifiers -&-- although these appear before the condition in the ACL, they are not +&-- even if these appear before the condition in the ACL, they are not expanded until after it has failed. For example: .code deny hosts = !+local_networks @@ -31846,12 +32240,12 @@ restrictions, to get the TXT record. As a byproduct of this, there is also a check that the IP being tested is indeed on the first list. The first domain is the one that is put in &$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 @@ -32041,12 +32435,12 @@ 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 @@ -32156,16 +32550,16 @@ 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 @@ -32754,16 +33148,16 @@ 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 = $prvscheck_result + message = Invalid reverse path signature. .endd The first statement rejects recipients for bounce messages that are addressed to plain BATV sender addresses, because it is known that BATV senders do not @@ -33300,13 +33694,13 @@ imposed by your anti-virus scanner. Here is a very simple scanning example: .code -deny message = This message contains malware ($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: @@ -33315,13 +33709,13 @@ 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 @@ -33450,8 +33844,8 @@ 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 @@ -33483,9 +33877,9 @@ 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 @@ -33543,8 +33937,8 @@ 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%&. @@ -33562,9 +33956,9 @@ 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 $spam_score spam points. .endd @@ -33648,13 +34042,22 @@ The following list describes all expansion variables that are available in the MIME ACL: .vlist +.vitem &$mime_anomaly_level$& &&& + &$mime_anomaly_text$& +.vindex &$mime_anomaly_level$& +.vindex &$mime_anomaly_text$& +If there are problems decoding, these variables contain information on +the detected issue. + .vitem &$mime_boundary$& -If the current part is a multipart (see &$mime_is_multipart$&) below, it should +.vindex &$mime_boundary$& +If the current part is a multipart (see &$mime_is_multipart$& below), it should have a boundary string, which is stored in this variable. If the current part has no boundary parameter in the &'Content-Type:'& header, this variable contains the empty string. .vitem &$mime_charset$& +.vindex &$mime_charset$& This variable contains the character set identifier, if one was found in the &'Content-Type:'& header. Examples for charset identifiers are: .code @@ -33666,31 +34069,37 @@ Please note that this value is not normalized, so you should do matches case-insensitively. .vitem &$mime_content_description$& +.vindex &$mime_content_description$& This variable contains the normalized content of the &'Content-Description:'& header. It can contain a human-readable description of the parts content. Some implementations repeat the filename for attachments here, but they are usually only used for display purposes. .vitem &$mime_content_disposition$& +.vindex &$mime_content_disposition$& This variable contains the normalized content of the &'Content-Disposition:'& header. You can expect strings like &"attachment"& or &"inline"& here. .vitem &$mime_content_id$& +.vindex &$mime_content_id$& This variable contains the normalized content of the &'Content-ID:'& header. This is a unique ID that can be used to reference a part from another part. .vitem &$mime_content_size$& +.vindex &$mime_content_size$& This variable is set only after the &%decode%& modifier (see above) has been successfully run. It contains the size of the decoded part in kilobytes. The size is always rounded up to full kilobytes, so only a completely empty part has a &$mime_content_size$& of zero. .vitem &$mime_content_transfer_encoding$& +.vindex &$mime_content_transfer_encoding$& This variable contains the normalized content of the &'Content-transfer-encoding:'& header. This is a symbolic name for an encoding type. Typical values are &"base64"& and &"quoted-printable"&. .vitem &$mime_content_type$& +.vindex &$mime_content_type$& If the MIME part has a &'Content-Type:'& header, this variable contains its value, lowercased, and without any options (like &"name"& or &"charset"&). Here are some examples of popular MIME types, as they may appear in this variable: @@ -33705,6 +34114,7 @@ If the MIME part has no &'Content-Type:'& header, this variable contains the empty string. .vitem &$mime_decoded_filename$& +.vindex &$mime_decoded_filename$& This variable is set only after the &%decode%& modifier (see above) has been successfully run. It contains the full path and filename of the file containing the decoded data. @@ -33713,6 +34123,7 @@ containing the decoded data. .cindex "RFC 2047" .vlist .vitem &$mime_filename$& +.vindex &$mime_filename$& This is perhaps the most important of the MIME variables. It contains a proposed filename for an attachment, if one was found in either the &'Content-Type:'& or &'Content-Disposition:'& headers. The filename will be @@ -33723,6 +34134,7 @@ decoded, but no additional sanity checks are done. found, this variable contains the empty string. .vitem &$mime_is_coverletter$& +.vindex &$mime_is_coverletter$& This variable attempts to differentiate the &"cover letter"& of an e-mail from attached data. It can be used to clamp down on flashy or unnecessarily encoded content in the cover letter, while not restricting attachments at all. @@ -33750,23 +34162,27 @@ 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 &$mime_is_multipart$& +.vindex &$mime_is_multipart$& This variable has the value 1 (true) when the current part has the main type &"multipart"&, for example, &"multipart/alternative"& or &"multipart/mixed"&. Since multipart entities only serve as containers for other parts, you may not want to carry out specific actions on them. .vitem &$mime_is_rfc822$& +.vindex &$mime_is_rfc822$& This variable has the value 1 (true) if the current part is not a part of the checked message itself, but part of an attached message. Attached message decoding is fully recursive. .vitem &$mime_part_count$& +.vindex &$mime_part_count$& This variable is a counter that is raised for each processed MIME part. It starts at zero for the very first part (which is usually a multipart). The counter is per-message, so it is reset when processing RFC822 attachments (see @@ -33802,8 +34218,8 @@ 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 @@ -33897,13 +34313,14 @@ in &_Local/Makefile_& (see section &<>& below). .cindex &%dlfunc%& "API description" You must include this line near the start of your code: .code +#define LOCAL_SCAN #include "local_scan.h" .endd This header file defines a number of variables and other values, and the prototype for the function itself. Exim is coded to use unsigned char values almost exclusively, and one of the things this header defines is a shorthand for &`unsigned char`& called &`uschar`&. -It also contains the following macro definitions, to simplify casting character +It also makes available the following macro definitions, to simplify casting character strings and pointers to character strings: .code #define CS (char *) @@ -34897,7 +35314,7 @@ 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 @@ -35655,13 +36072,14 @@ 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 @@ -36057,7 +36475,8 @@ 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 @@ -36412,10 +36831,10 @@ 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 @@ -36503,7 +36922,8 @@ 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: @@ -36511,10 +36931,10 @@ 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: @@ -36572,7 +36992,7 @@ 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 @@ -36623,7 +37043,7 @@ 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 @@ -36671,12 +37091,18 @@ to a router of this form: virtual: driver = redirect domains = dsearch;/etc/mail/virtual - data = ${lookup{$local_part}lsearch{/etc/mail/virtual/$domain}} + data = ${lookup{$local_part}lsearch{/etc/mail/virtual/$domain_data}} no_more .endd +.new The &%domains%& option specifies that the router is to be skipped, unless there is a file in the &_/etc/mail/virtual_& directory whose name is the same as the -domain that is being processed. When the router runs, it looks up the local +domain that is being processed. +The &(dsearch)& lookup used results in an untainted version of &$domain$& +being placed into the &$domain_data$& variable. +.wen + +When the router runs, it looks up the local part in the file to find a new address (or list of addresses). The &%no_more%& setting ensures that if the lookup fails (leading to &%data%& being an empty string), Exim gives up on the address without trying any subsequent routers. @@ -36705,7 +37131,7 @@ follows: .code my_mailboxes: driver = appendfile - file = /var/mail/$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 @@ -36760,9 +37186,9 @@ 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 @@ -40157,6 +40583,8 @@ To generate keys under OpenSSL: openssl genrsa -out dkim_rsa.private 2048 openssl rsa -in dkim_rsa.private -out /dev/stdout -pubout -outform PEM .endd +The result file from the first command should be retained, and +this option set to use it. Take the base-64 lines from the output of the second command, concatenated, for the DNS TXT record. See section 3.6 of RFC6376 for the record specification. @@ -40229,7 +40657,7 @@ only supports signing with the same canonicalization method for both headers and .option dkim_strict smtp string&!! unset This option defines how Exim behaves when signing a message that should be signed fails for some reason. When the expansion evaluates to -either "1" or "true", Exim will defer. Otherwise Exim will send the message +either &"1"& or &"true"&, Exim will defer. Otherwise Exim will send the message unsigned. You can use the &%$dkim_domain%& and &%$dkim_selector%& expansion variables here. @@ -40241,16 +40669,19 @@ 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". +&"_DKIM_SIGN_HEADERS"& +.new +and an oversigning variant is in &"_DKIM_OVERSIGN_HEADERS"&. +.wen If a name is repeated, multiple headers by that name (or the absence thereof) will be signed. The textually later headers in the headers part of the message are signed first, if there are multiples. -A name can be prefixed with either an '=' or a '+' character. -If an '=' prefix is used, all headers that are present with this name +A name can be prefixed with either an &"="& or a &"+"& character. +If an &"="& prefix is used, all headers that are present with this name will be signed. -If a '+' prefix if used, all headers that are present with this name +If a &"+"& prefix if used, all headers that are present with this name will be signed, and one signature added for a missing header with the name will be appended. @@ -40492,6 +40923,10 @@ Notes from the key record (tag n=). .vitem &%$dkim_key_length%& Number of bits in the key. +.new +Valid only once the key is loaded, which is at the time the header signature +is verified, which is after the body hash is. +.wen Note that RFC 8301 says: .code @@ -40499,9 +40934,8 @@ Verifiers MUST NOT consider signatures using RSA keys of less than 1024 bits as valid signatures. .endd -To enforce this you must have a DKIM ACL which checks this variable -and overwrites the &$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 @@ -40516,10 +40950,10 @@ 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; @@ -40531,10 +40965,10 @@ 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 @@ -40618,13 +41052,16 @@ 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=$sender_host_address .endd +Note: The above mentioned URL may not be as helpful as expected. You are +encouraged to replace the link with a link to a site with more +explanations. + When the spf condition has run, it sets up several expansion variables: @@ -40659,8 +41096,13 @@ variables: .vitem &$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 @@ -41033,8 +41475,8 @@ 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 @@ -41130,6 +41572,7 @@ 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 @@ -41176,22 +41619,27 @@ 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.