X-Git-Url: https://git.exim.org/exim.git/blobdiff_plain/f182293e3a29c4433816803268350f6c2797a3e0..6c9ed72eaa948d340dba0ea0a878f9570852ab35:/doc/doc-docbook/spec.xfpt?ds=inline diff --git a/doc/doc-docbook/spec.xfpt b/doc/doc-docbook/spec.xfpt index 09ce79848..f274db74e 100644 --- a/doc/doc-docbook/spec.xfpt +++ b/doc/doc-docbook/spec.xfpt @@ -45,7 +45,7 @@ . Update the Copyright year (only) when changing content. . ///////////////////////////////////////////////////////////////////////////// -.set previousversion "4.80" +.set previousversion "4.85" .include ./local_params .set ACL "access control lists (ACLs)" @@ -1985,10 +1985,9 @@ Two different types of DNS record for handling IPv6 addresses have been defined. AAAA records (analogous to A records for IPv4) are in use, and are currently seen as the mainstream. Another record type called A6 was proposed as better than AAAA because it had more flexibility. However, it was felt to be -over-complex, and its status was reduced to &"experimental"&. It is not known -if anyone is actually using A6 records. Exim has support for A6 records, but -this is included only if you set &`SUPPORT_A6=YES`& in &_Local/Makefile_&. The -support has not been tested for some time. +over-complex, and its status was reduced to &"experimental"&. Exim used to +have a compile option for including A6 record support but this has now been +withdrawn. @@ -3811,6 +3810,14 @@ 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 connection to the remote host has been authenticated. +.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 &%-MC%& option. It signifies that the +remote host supports the ESMTP &_DSN_& extension. +.wen + .vitem &%-MCP%& .oindex "&%-MCP%&" This option is not intended for use by external callers. It is used internally @@ -4640,6 +4647,13 @@ this option. .oindex "&%-X%&" This option is interpreted by Sendmail to cause debug information to be sent to the named file. It is ignored by Exim. + +.vitem &%-z%&&~<&'log-line'&> +.oindex "&%-z%&" +This option writes its argument to Exim's logfile. +Use is restricted to administrators; the intent is for operational notes. +Quotes should be used to maintain a multi-word item as a single argument, +under most shells. .endlist .ecindex IIDclo1 @@ -5557,7 +5571,7 @@ unreachable. The next two lines are concerned with &'ident'& callbacks, as defined by RFC 1413 (hence their names): .code -rfc1413_query_hosts = * +rfc1413_hosts = * rfc1413_query_timeout = 0s .endd These settings cause Exim to avoid ident callbacks for all incoming SMTP calls. @@ -5567,7 +5581,7 @@ of an incoming SMTP connection. If you have hosts for which you trust RFC1413 and need this information, you can change this. -This line enables an efficiency SMTP option. It is negociated by clients +This line enables an efficiency SMTP option. It is negotiated by clients and not expected to cause problems but can be disabled if needed. .code prdr_enable = true @@ -6865,8 +6879,8 @@ is used on its own as the result. If the lookup does not succeed, the &<>& for an explanation of what this means. The supported DNS record types are A, CNAME, MX, NS, PTR, SPF, SRV, TLSA and TXT, -and, when Exim is compiled with IPv6 support, AAAA (and A6 if that is also -configured). If no type is given, TXT is assumed. When the type is PTR, +and, when Exim is compiled with IPv6 support, AAAA. +If no type is given, TXT is assumed. When the type is PTR, the data can be an IP address, written as normal; inversion and the addition of &%in-addr.arpa%& or &%ip6.arpa%& happens automatically. For example: .code @@ -6875,14 +6889,7 @@ ${lookup dnsdb{ptr=192.168.4.5}{$value}fail} If the data for a PTR record is not a syntactically valid IP address, it is not altered and nothing is added. -.cindex "MX record" "in &(dnsdb)& lookup" -.cindex "SRV record" "in &(dnsdb)& lookup" -For an MX lookup, both the preference value and the host name are returned for -each record, separated by a space. For an SRV lookup, the priority, weight, -port, and host name are returned for each record, separated by spaces. - -For any record type, if multiple records are found (or, for A6 lookups, if a -single record leads to multiple addresses), the data is returned as a +For any record type, if multiple records are found, the data is returned as a concatenation, with newline as the default separator. The order, of course, depends on the DNS resolver. You can specify a different separator character between multiple records by putting a right angle-bracket followed immediately @@ -6893,6 +6900,14 @@ ${lookup dnsdb{>: a=host1.example}} It is permitted to specify a space as the separator character. Further white space is ignored. +.cindex "MX record" "in &(dnsdb)& lookup" +.cindex "SRV record" "in &(dnsdb)& lookup" +For an MX lookup, both the preference value and the host name are returned for +each record, separated by a space. For an SRV lookup, the priority, weight, +port, and host name are returned for each record, separated by spaces. +An alternate field separator can be specified using a comma after the main +separator character, followed immediately by the field separator. + .cindex "TXT record" "in &(dnsdb)& lookup" .cindex "SPF record" "in &(dnsdb)& lookup" For TXT records with multiple items of data, only the first item is returned, @@ -6908,6 +6923,46 @@ ${lookup dnsdb{spf=example.org}} It is permitted to specify a space as the separator character. Further white space is ignored. +.section "Dnsdb lookup modifiers" "SECTdnsdb_mod" +.cindex "dnsdb modifiers" +.cindex "modifiers" "dnsdb" +.cindex "options" "dnsdb" +Modifiers for &(dnsdb)& lookups are givien by optional keywords, +each followed by a comma, +that may appear before the record type. + +The &(dnsdb)& lookup fails only if all the DNS lookups fail. If there is a +temporary DNS error for any of them, the behaviour is controlled by +a defer-option modifier. +The possible keywords are +&"defer_strict"&, &"defer_never"&, and &"defer_lax"&. +With &"strict"& behaviour, any temporary DNS error causes the +whole lookup to defer. With &"never"& behaviour, a temporary DNS error is +ignored, and the behaviour is as if the DNS lookup failed to find anything. +With &"lax"& behaviour, all the queries are attempted, but a temporary DNS +error causes the whole lookup to defer only if none of the other lookups +succeed. The default is &"lax"&, so the following lookups are equivalent: +.code +${lookup dnsdb{defer_lax,a=one.host.com:two.host.com}} +${lookup dnsdb{a=one.host.com:two.host.com}} +.endd +Thus, in the default case, as long as at least one of the DNS lookups +yields some data, the lookup succeeds. + +.cindex "DNSSEC" "dns lookup" +Use of &(DNSSEC)& is controlled by a dnssec modifier. +The possible keywords are +&"dnssec_strict"&, &"dnssec_lax"&, and &"dnssec_never"&. +With &"strict"& or &"lax"& DNSSEC information is requested +with the lookup. +With &"strict"& a response from the DNS resolver that +is not labelled as authenticated data +is treated as equivalent to a temporary DNS error. +The default is &"never"&. + +See also the &$lookup_dnssec_authenticated$& variable. + + .section "Pseudo dnsdb record types" "SECID66" .cindex "MX record" "in &(dnsdb)& lookup" By default, both the preference value and the host name are returned for @@ -6956,7 +7011,7 @@ The authorization code can be &"Y"& for yes, &"N"& for no, &"X"& for explicit authorization required but absent, or &"?"& for unknown. .cindex "A+" "in &(dnsdb)& lookup" -The pseudo-type A+ performs an A6 lookup (if configured) followed by an AAAA +The pseudo-type A+ performs an AAAA and then an A lookup. All results are returned; defer processing (see below) is handled separately for each lookup. Example: .code @@ -6983,43 +7038,6 @@ The data from each lookup is concatenated, with newline separators by default, in the same way that multiple DNS records for a single item are handled. A different separator can be specified, as described above. -Modifiers for &(dnsdb)& lookups are givien by optional keywords, -each followed by a comma, -that may appear before the record type. - -The &(dnsdb)& lookup fails only if all the DNS lookups fail. If there is a -temporary DNS error for any of them, the behaviour is controlled by -a defer-option modifier. -The possible keywords are -&"defer_strict"&, &"defer_never"&, and &"defer_lax"&. -With &"strict"& behaviour, any temporary DNS error causes the -whole lookup to defer. With &"never"& behaviour, a temporary DNS error is -ignored, and the behaviour is as if the DNS lookup failed to find anything. -With &"lax"& behaviour, all the queries are attempted, but a temporary DNS -error causes the whole lookup to defer only if none of the other lookups -succeed. The default is &"lax"&, so the following lookups are equivalent: -.code -${lookup dnsdb{defer_lax,a=one.host.com:two.host.com}} -${lookup dnsdb{a=one.host.com:two.host.com}} -.endd -Thus, in the default case, as long as at least one of the DNS lookups -yields some data, the lookup succeeds. - -.new -.cindex "DNSSEC" "dns lookup" -Use of &(DNSSEC)& is controlled by a dnssec modifier. -The possible keywords are -&"dnssec_strict"&, &"dnssec_lax"&, and &"dnssec_never"&. -With &"strict"& or &"lax"& DNSSEC information is requested -with the lookup. -With &"strict"& a response from the DNS resolver that -is not labelled as authenticated data -is treated as equivalent to a temporary DNS error. -The default is &"never"&. - -See also the &$lookup_dnssec_authenticated$& variable. -.wen - @@ -7084,7 +7102,6 @@ With sufficiently modern LDAP libraries, Exim supports forcing TLS over regular LDAP connections, rather than the SSL-on-connect &`ldaps`&. See the &%ldap_start_tls%& option. -.new Starting with Exim 4.83, the initialization of LDAP with TLS is more tightly controlled. Every part of the TLS configuration can be configured by settings in &_exim.conf_&. Depending on the version of the client libraries installed on @@ -7094,7 +7111,6 @@ certificates. This revealed a nuance where the current UID that exim was running as could affect which config files it read. With Exim 4.83, these methods become optional, only taking effect if not specifically set in &_exim.conf_&. -.wen .section "LDAP quoting" "SECID68" @@ -7242,9 +7258,7 @@ them. The following names are recognized: &`USER `& set the DN, for authenticating the LDAP bind &`PASS `& set the password, likewise &`REFERRALS `& set the referrals parameter -.new &`SERVERS `& set alternate server list for this query only -.wen &`SIZE `& set the limit for the number of entries returned &`TIME `& set the maximum waiting time for a query .endd @@ -7266,15 +7280,13 @@ Netscape SDK; for OpenLDAP no action is taken. The TIME parameter (also a number of seconds) is passed to the server to set a server-side limit on the time taken to complete a search. -.new The SERVERS parameter allows you to specify an alternate list of ldap servers to use for an individual lookup. The global ldap_servers option provides a default list of ldap servers, and a single lookup can specify a single ldap server to use. But when you need to do a lookup with a list of servers that is different than the default list (maybe different order, maybe a completely different set of servers), the SERVERS parameter allows you to specify this -alternate list. -.wen +alternate list (colon-separated). Here is an example of an LDAP query in an Exim lookup that uses some of these values. This is a single line, folded to fit on the page: @@ -7346,30 +7358,38 @@ If you specify multiple attributes, the result contains space-separated, quoted strings, each preceded by the attribute name and an equals sign. Within the quotes, the quote character, backslash, and newline are escaped with backslashes, and commas are used to separate multiple values for the attribute. +Any commas in attribute values are doubled +(permitting treatment of the values as a comma-separated list). Apart from the escaping, the string within quotes takes the same form as the output when a single attribute is requested. Specifying no attributes is the same as specifying all of an entry's attributes. Here are some examples of the output format. The first line of each pair is an LDAP query, and the second is the data that is returned. The attribute called -&%attr1%& has two values, whereas &%attr2%& has only one value: +&%attr1%& has two values, one of them with an embedded comma, whereas +&%attr2%& has only one value: .code ldap:///o=base?attr1?sub?(uid=fred) -value1.1, value1.2 +value1.1,value1,,2 ldap:///o=base?attr2?sub?(uid=fred) value two ldap:///o=base?attr1,attr2?sub?(uid=fred) -attr1="value1.1, value1.2" attr2="value two" +attr1="value1.1,value1,,2" attr2="value two" ldap:///o=base??sub?(uid=fred) -objectClass="top" attr1="value1.1, value1.2" attr2="value two" +objectClass="top" attr1="value1.1,value1,,2" attr2="value two" .endd -The &%extract%& operator in string expansions can be used to pick out -individual fields from data that consists of &'key'&=&'value'& pairs. You can +You can make use of Exim's &%-be%& option to run expansion tests and thereby check the results of LDAP lookups. +The &%extract%& operator in string expansions can be used to pick out +individual fields from data that consists of &'key'&=&'value'& pairs. +The &%listextract%& operator should be used to pick out individual values +of attributes, even when only a single value is expected. +The doubling of embedded commas allows you to use the returned data as a +comma separated list (using the "<," syntax for changing the input list separator). @@ -8354,7 +8374,6 @@ Both &`+include_unknown`& and &`+ignore_unknown`& may appear in the same list. The effect of each one lasts until the next, or until the end of the list. -.new .section "Mixing wildcarded host names and addresses in host lists" &&& "SECTmixwilhos" .cindex "host list" "mixing names and addresses in" @@ -8390,7 +8409,6 @@ If the first &%accept%& fails, Exim goes on to try the second one. See chapter &`+ignore_unknown`&, which was discussed in depth in the first example in this section. .endlist -.wen .section "Temporary DNS errors when looking up host information" &&& @@ -8885,7 +8903,6 @@ the expansion result is an empty string. If the ACL returns defer the result is a forced-fail. Otherwise the expansion fails. -.new .vitem "&*${certextract{*&<&'field'&>&*}{*&<&'certificate'&>&*}&&& {*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&" .cindex "expansion" "extracting cerificate fields" @@ -8932,8 +8949,10 @@ a right angle-bracket followed immediately by the new separator. Recognised RDN type labels include "CN", "O", "OU" and "DC". The field selectors marked as "time" above -may output a number of seconds since epoch -if the modifier "int" is used. +take an optional modifier of "int" +for which the result is the number of seconds since epoch. +Otherwise the result is a human-readable string +in the timezone selected by the main "timezone" option. The field selectors marked as "list" above return a list, newline-separated by default, @@ -8948,7 +8967,6 @@ which is one of "dns", "uri" or "mail"; if so the elenment tags are omitted. If not otherwise noted field values are presented in human-readable form. -.wen .vitem "&*${dlfunc{*&<&'file'&>&*}{*&<&'function'&>&*}{*&<&'arg'&>&*}&&& {*&<&'arg'&>&*}...}*&" @@ -9501,7 +9519,7 @@ locks out the use of this expansion item in filter files. .cindex "expansion" "inserting from a socket" .cindex "socket, use of in expansion" .cindex "&%readsocket%& expansion item" -This item inserts data from a Unix domain or Internet socket into the expanded +This item inserts data from a Unix domain or TCP socket into the expanded string. The minimal way of using it uses just two arguments, as in these examples: .code @@ -9597,7 +9615,6 @@ expansion item above. {*&<&'string2'&>&*}}*&" .cindex "expansion" "running a command" .cindex "&%run%& expansion item" -.new The command and its arguments are first expanded as one string. The string is split apart into individual arguments by spaces, and then the command is run in a separate process, but under the same uid and gid. As in other command @@ -9614,7 +9631,6 @@ in a string containing quotes, because it would interfere with the quotes around the command arguments. A possible guard against this is to wrap the variable in the &%sg%& operator to change any quote marks to some other character. -.wen The standard input for the command exists, but is empty. The standard output and standard error are set to the same file descriptor. @@ -9694,6 +9710,35 @@ the regular expression from string expansion. +.vitem &*${sort{*&<&'string'&>&*}{*&<&'comparator'&>&*}{*&<&'extractor'&>&*}}*& +.cindex sorting a list +.cindex list sorting +After expansion, <&'string'&> is interpreted as a list, colon-separated by +default, but the separator can be changed in the usual way. +The <&'comparator'&> argument is interpreted as the operator +of a two-argument expansion condition. +The numeric operators plus ge, gt, le, lt (and ~i variants) are supported. +The comparison should return true when applied to two values +if the first value should sort before the second value. +The <&'extractor'&> expansion is applied repeatedly to elements of the list, +the element being placed in &$item$&, +to give values for comparison. + +The item result is a sorted list, +with the original list separator, +of the list elements (in full) of the original. + +Examples: +.code +${sort{3:2:1:4}{<}{$item}} +.endd +sorts a list of numbers, and +.code +${sort {${lookup dnsdb{>:,,mx=example.com}}} {<} {${listextract{1}{<,$item}}}} +.endd +will sort an MX lookup into priority order. + + .vitem &*${substr{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*& .cindex "&%substr%& expansion item" .cindex "substring extraction" @@ -11011,6 +11056,11 @@ precedes the expansion of the string. For example, the commands available in Exim filter files include an &%if%& command with its own regular expression matching condition. +.vitem "&$acl_arg1$&, &$acl_arg2$&, etc" +Within an acl condition, expansion condition or expansion item +any arguments are copied to these variables, +any unused variables being made empty. + .vitem "&$acl_c...$&" Values can be placed in these variables by the &%set%& modifier in an ACL. They can be given any name that starts with &$acl_c$& and is at least six characters @@ -11032,6 +11082,10 @@ message is received, the values of these variables are saved with the message, and can be accessed by filters, routers, and transports during subsequent delivery. +.vitem &$acl_narg$& +Within an acl condition, expansion condition or expansion item +this variable has the number of arguments. + .vitem &$acl_verify_message$& .vindex "&$acl_verify_message$&" After an address verification has failed, this variable contains the failure @@ -11213,6 +11267,19 @@ The building process for Exim keeps a count of the number of times it has been compiled. This serves to distinguish different compilations of the same version of the program. +.new +.vitem &$config_dir$& +.vindex "&$config_dir$&" +The directory name of the main configuration file. That is, the content of +&$config_file$& with the last component stripped. The value does not +contain the trailing slash. If &$config_file$& does not contain a slash, +&$config_dir$& is ".". + +.vitem &$config_file$& +.vindex "&$config_file$&" +The name of the main configuration file Exim is using. +.wen + .vitem &$demime_errorlevel$& .vindex "&$demime_errorlevel$&" This variable is available when Exim is compiled with @@ -11320,6 +11387,15 @@ This variable contains the path to the Exim binary. .vindex "&$exim_uid$&" This variable contains the numerical value of the Exim user id. +.new +.vitem &$exim_version$& +.vindex "&$exim_uid$&" +This variable contains the version string of the Exim build. +The first character is a major version number, currently 4. +Then after a dot, the next group of digits is a minor version number. +There may be other characters following the minor version. +.wen + .vitem &$found_extension$& .vindex "&$found_extension$&" This variable is available when Exim is compiled with the @@ -11418,6 +11494,11 @@ the result, the name is not accepted, and &$host_lookup_deferred$& is set to .vindex "&$host_lookup_failed$&" See &$host_lookup_deferred$&. +.vitem &$host_port$& +.vindex "&$host_port$&" +This variable is set to the remote host's TCP port whenever &$host$& is set +for an outbound connection. + .vitem &$inode$& .vindex "&$inode$&" @@ -11570,7 +11651,6 @@ ability to find the amount of free space (only true for experimental systems), the space value is -1. See also the &%check_log_space%& option. -.new .vitem &$lookup_dnssec_authenticated$& .vindex "&$lookup_dnssec_authenticated$&" This variable is set after a DNS lookup done by @@ -11578,7 +11658,6 @@ a dnsdb lookup expansion, dnslookup router or smtp transport. It will be empty if &(DNSSEC)& was not requested, &"no"& if the result was not labelled as authenticated data and &"yes"& if it was. -.wen .vitem &$mailstore_basename$& .vindex "&$mailstore_basename$&" @@ -11666,7 +11745,7 @@ This variable is like &$message_headers$& except that no processing of the contents of header lines is done. .vitem &$message_id$& -This is an old name for &$message_exim_id$&, which is now deprecated. +This is an old name for &$message_exim_id$&. It is now deprecated. .vitem &$message_linecount$& .vindex "&$message_linecount$&" @@ -11883,10 +11962,7 @@ on which interface and/or port is being used for the incoming connection. The values of &$received_ip_address$& and &$received_port$& are saved with any messages that are received, thus making these variables available at delivery time. - -&*Note:*& There are no equivalent variables for outgoing connections, because -the values are unknown (unless they are explicitly set by options of the -&(smtp)& transport). +For outbound connections see &$sending_ip_address$&. .vitem &$received_port$& .vindex "&$received_port$&" @@ -12105,8 +12181,9 @@ the &%-bs%& or &%-bS%& options. .vitem &$sender_host_address$& .vindex "&$sender_host_address$&" -When a message is received from a remote host, this variable contains that -host's IP address. For locally submitted messages, it is empty. +When a message is received from a remote host using SMTP, +this variable contains that +host's IP address. For locally non-SMTP submitted messages, it is empty. .vitem &$sender_host_authenticated$& .vindex "&$sender_host_authenticated$&" @@ -12357,43 +12434,39 @@ on an outbound SMTP connection; the meaning of this depends upon the TLS implementation used. If TLS has not been negotiated, the value will be 0. -.new .vitem &$tls_in_ourcert$& .vindex "&$tls_in_ourcert$&" This variable refers to the certificate presented to the peer of an inbound connection when the message was received. It is only useful as the argument of a -&%certextract%& expansion item, &%md5%& or &%sha1%& operator, +&%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator, or a &%def%& condition. -.wen -.new .vitem &$tls_in_peercert$& .vindex "&$tls_in_peercert$&" This variable refers to the certificate presented by the peer of an inbound connection when the message was received. It is only useful as the argument of a -&%certextract%& expansion item, &%md5%& or &%sha1%& operator, +&%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator, or a &%def%& condition. -.wen +If certificate verification fails it may refer to a failing chain element +which is not the leaf. -.new .vitem &$tls_out_ourcert$& .vindex "&$tls_out_ourcert$&" This variable refers to the certificate presented to the peer of an outbound connection. It is only useful as the argument of a -&%certextract%& expansion item, &%md5%& or &%sha1%& operator, +&%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator, or a &%def%& condition. -.wen -.new .vitem &$tls_out_peercert$& .vindex "&$tls_out_peercert$&" This variable refers to the certificate presented by the peer of an outbound connection. It is only useful as the argument of a -&%certextract%& expansion item, &%md5%& or &%sha1%& operator, +&%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator, or a &%def%& condition. -.wen +If certificate verification fails it may refer to a failing chain element +which is not the leaf. .vitem &$tls_in_certificate_verified$& .vindex "&$tls_in_certificate_verified$&" @@ -12432,6 +12505,24 @@ and then set to the outgoing cipher suite if one is negotiated. See chapter &<>& for details of TLS support and chapter &<>& for details of the &(smtp)& transport. +.vitem &$tls_in_ocsp$& +.vindex "&$tls_in_ocsp$&" +When a message is received from a remote client connection +the result of any OCSP request from the client is encoded in this variable: +.code +0 OCSP proof was not requested (default value) +1 No response to request +2 Response not verified +3 Verification failed +4 Verification succeeded +.endd + +.vitem &$tls_out_ocsp$& +.vindex "&$tls_out_ocsp$&" +When a message is sent to a remote host connection +the result of any OCSP request made is encoded in this variable. +See &$tls_in_ocsp$& for values. + .vitem &$tls_in_peerdn$& .vindex "&$tls_in_peerdn$&" .vindex "&$tls_peerdn$&" @@ -12439,6 +12530,8 @@ When a message is received from a remote host over an encrypted SMTP connection, and Exim is configured to request a certificate from the client, the value of the Distinguished Name of the certificate is made available in the &$tls_in_peerdn$& during subsequent processing. +If certificate verification fails it may refer to a failing chain element +which is not the leaf. The deprecated &$tls_peerdn$& variable refers to the inbound side except when used in the context of an outbound SMTP delivery, when it refers to @@ -12450,6 +12543,8 @@ When a message is being delivered to a remote host over an encrypted SMTP connection, and Exim is configured to request a certificate from the server, the value of the Distinguished Name of the certificate is made available in the &$tls_out_peerdn$& during subsequent processing. +If certificate verification fails it may refer to a failing chain element +which is not the leaf. .vitem &$tls_in_sni$& .vindex "&$tls_in_sni$&" @@ -12527,6 +12622,13 @@ This variable contains the result of an expansion lookup, extraction operation, or external command, as described above. It is also used during a &*reduce*& expansion. +.vitem &$verify_mode$& +.vindex "&$verify_mode$&" +While a router or transport is being run in verify mode +or for cutthrough delivery, +contains "S" for sender-verification or "R" for recipient-verification. +Otherwise, empty. + .vitem &$version_number$& .vindex "&$version_number$&" The version number of Exim. @@ -13186,6 +13288,7 @@ listed in more than one group. .row &%acl_smtp_mail%& "ACL for MAIL" .row &%acl_smtp_mailauth%& "ACL for AUTH on MAIL command" .row &%acl_smtp_mime%& "ACL for MIME parts" +.row &%acl_smtp_notquit%& "ACL for non-QUIT terminations" .row &%acl_smtp_predata%& "ACL for start of data" .row &%acl_smtp_quit%& "ACL for QUIT" .row &%acl_smtp_rcpt%& "ACL for RCPT" @@ -13332,6 +13435,7 @@ See also the &'Policy controls'& section above. .table2 .row &%accept_8bitmime%& "advertise 8BITMIME" .row &%auth_advertise_hosts%& "advertise AUTH to these hosts" +.row &%dsn_advertise_hosts%& "advertise DSN extensions to these hosts" .row &%ignore_fromline_hosts%& "allow &""From ""& from these hosts" .row &%ignore_fromline_local%& "allow &""From ""& from local SMTP" .row &%pipelining_advertise_hosts%& "advertise pipelining to these hosts" @@ -13487,10 +13591,13 @@ This option defines the ACL that is run after an SMTP DATA command has been processed and the message itself has been received, but before the final acknowledgment is sent. See chapter &<>& for further details. -.option acl_smtp_data_prdr main string&!! unset -.cindex "DATA" "ACL for" +.new +.option acl_smtp_data_prdr main string&!! accept +.cindex "PRDR" "ACL for" +.cindex "DATA" "PRDR ACL for" .cindex "&ACL;" "PRDR-related" .cindex "&ACL;" "per-user data processing" +.wen This option defines the ACL that, if the PRDR feature has been negotiated, is run for each recipient after an SMTP DATA command has been @@ -13531,6 +13638,12 @@ This option is available when Exim is built with the content-scanning extension. It defines the ACL that is run for each MIME part in a message. See section &<>& for details. +.option acl_smtp_notquit main string&!! unset +.cindex "not-QUIT, ACL for" +This option defines the ACL that is run when an SMTP session +ends without a QUIT command being received. +See chapter &<>& for further details. + .option acl_smtp_predata main string&!! unset This option defines the ACL that is run when an SMTP DATA command is received, before the message itself is received. See chapter &<>& for @@ -14072,6 +14185,20 @@ This is an obsolete option that is now a no-op. It used to affect the way Exim handled CR and LF characters in incoming messages. What happens now is described in section &<>&. +.new +.option dsn_advertise_hosts main "host list&!!" unset +.cindex "bounce messages" "success" +.cindex "DSN" "success" +.cindex "Delivery Status Notification" "success" +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, +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. +.wen + .option dsn_from main "string&!!" "see below" .cindex "&'From:'& header line" "in bounces" .cindex "bounce messages" "&'From:'& line, specifying" @@ -14989,16 +15116,21 @@ yourself in the foot in various unpleasant ways. This option should not be adjusted lightly. An unrecognised item will be detected at startup, by invoking Exim with the &%-bV%& flag. +The option affects Exim operating both as a server and as a client. + Historical note: prior to release 4.80, Exim defaulted this value to "+dont_insert_empty_fragments", which may still be needed for compatibility with some clients, but which lowers security by increasing exposure to some now infamous attacks. -An example: +Examples: .code # Make both old MS and old Eudora happy: openssl_options = -all +microsoft_big_sslv3_buffer \ +dont_insert_empty_fragments + +# Disable older protocol versions: +openssl_options = +no_sslv2 +no_sslv3 .endd Possible options may include: @@ -15559,13 +15691,19 @@ the time of delivery. They are normally used only for final local deliveries. This option is an obsolete synonym for &%bounce_return_size_limit%&. -.option rfc1413_hosts main "host list&!!" * +.new +.option rfc1413_hosts main "host list&!!" @[] .cindex "RFC 1413" .cindex "host" "for RFC 1413 calls" -RFC 1413 identification calls are made to any client host which matches an item -in the list. +RFC 1413 identification calls are made to any client host which matches +an item in the list. +The default value specifies just this host, being any local interface +for the system. +.wen -.option rfc1413_query_timeout main time 5s +.new +.option rfc1413_query_timeout main time 0s +.wen .cindex "RFC 1413" "query timeout" .cindex "timeout" "for RFC 1413 call" This sets the timeout on RFC 1413 identification calls. If it is set to zero, @@ -15959,7 +16097,7 @@ See &%smtp_ratelimit_hosts%& above. See &%smtp_ratelimit_hosts%& above. -.option smtp_receive_timeout main time 5m +.option smtp_receive_timeout main time&!! 5m .cindex "timeout" "for SMTP input" .cindex "SMTP" "input timeout" This sets a timeout value for SMTP reception. It applies to all forms of SMTP @@ -15974,6 +16112,10 @@ SMTP data timeout on connection from... The former means that Exim was expecting to read an SMTP command; the latter means that it was in the DATA phase, reading the contents of a message. +If the first character of the option is a &"$"& the option is +expanded before use and may depend on +&$sender_host_name$&, &$sender_host_address$& and &$sender_host_port$&. + .oindex "&%-os%&" The value set by this option can be overridden by the @@ -16413,22 +16555,37 @@ preference order of the available ciphers. Details are given in sections See &%tls_verify_hosts%& below. -.option tls_verify_certificates main string&!! unset +.new +.option tls_verify_certificates main string&!! system .cindex "TLS" "client certificate verification" .cindex "certificate" "verification of client" -The value of this option is expanded, and must then be the absolute path to -a file containing permitted certificates for clients that -match &%tls_verify_hosts%& or &%tls_try_verify_hosts%&. Alternatively, if you -are using OpenSSL, you can set &%tls_verify_certificates%& to the name of a -directory containing certificate files. This does not work with GnuTLS; the -option must be set to the name of a single file if you are using GnuTLS. +The value of this option is expanded, and must then be either the +word "system" +or the absolute path to +a file or directory containing permitted certificates for clients that +match &%tls_verify_hosts%& or &%tls_try_verify_hosts%&. + +The "system" value for the option will use a +system default location compiled into the SSL library. +This is not available for GnuTLS versions preceding 3.0.20, +and will be taken as empty; an explicit location +must be specified. + +The use of a directory for the option value is not avilable for GnuTLS versions +preceding 3.3.6 and a single file must be used. + +With OpenSSL the certificates specified +explicitly +either by file or directory +are added to those given by the system default location. +.wen These certificates should be for the certificate authorities trusted, rather than the public cert of individual clients. With both OpenSSL and GnuTLS, if the value is a file then the certificates are sent by Exim as a server to connecting clients, defining the list of accepted certificate authorities. Thus the values defined should be considered public data. To avoid this, -use OpenSSL with a directory. +use the explicit directory version. See &<>& for discussion of when this option might be re-expanded. @@ -16797,6 +16954,46 @@ If the expansion fails (other than forced failure) delivery is deferred. Some of the other precondition options are common special cases that could in fact be specified using &%condition%&. +Historical note: We have &%condition%& on ACLs and on Routers. Routers +are far older, and use one set of semantics. ACLs are newer and when +they were created, the ACL &%condition%& process was given far stricter +parse semantics. The &%bool{}%& expansion condition uses the same rules as +ACLs. The &%bool_lax{}%& expansion condition uses the same rules as +Routers. More pointedly, the &%bool_lax{}%& was written to match the existing +Router rules processing behavior. + +This is best illustrated in an example: +.code +# If used in an ACL condition will fail with a syntax error, but +# in a router condition any extra characters are treated as a string + +$ exim -be '${if eq {${lc:GOOGLE.com}} {google.com}} {yes} {no}}' +true {yes} {no}} + +$ exim -be '${if eq {${lc:WHOIS.com}} {google.com}} {yes} {no}}' + {yes} {no}} +.endd +In each example above, the &%if%& statement actually ends after +&"{google.com}}"&. Since no true or false braces were defined, the +default &%if%& behavior is to return a boolean true or a null answer +(which evaluates to false). The rest of the line is then treated as a +string. So the first example resulted in the boolean answer &"true"& +with the string &" {yes} {no}}"& appended to it. The second example +resulted in the null output (indicating false) with the string +&" {yes} {no}}"& appended to it. + +In fact you can put excess forward braces in too. In the router +&%condition%&, Exim's parser only looks for &"{"& symbols when they +mean something, like after a &"$"& or when required as part of a +conditional. But otherwise &"{"& and &"}"& are treated as ordinary +string characters. + +Thus, in a Router, the above expansion strings will both always evaluate +true, as the result of expansion is a non-empty string which doesn't +match an explicit false value. This can be tricky to debug. By +contrast, in an ACL either of those strings will always result in an +expansion error because the result doesn't look sufficiently boolean. + .option debug_print routers string&!! unset .cindex "testing" "variables in drivers" @@ -16838,6 +17035,17 @@ This option must always be set. It specifies which of the available routers is to be used. +.new +.option dsn_lasthop routers boolean false +.cindex "DSN" "success" +.cindex "Delivery Status Notification" "success" +If this option is set true, and extended DSN (RFC3461) processing is in effect, +Exim will not pass on DSN requests to downstream DSN-aware hosts but will +instead send a success DSN as if the next hop does not support DSN. +Not effective on redirect routers. +.wen + + .option errors_to routers string&!! unset .cindex "envelope sender" @@ -16959,7 +17167,10 @@ and the discussion in chapter &<>&. .option headers_add routers list&!! unset .cindex "header lines" "adding" .cindex "router" "adding header lines" -This option specifies a list of text headers, newline-separated, +This option specifies a list of text headers, +.new +newline-separated (by default, changeable in the usual way), +.wen 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 @@ -16996,7 +17207,10 @@ avoided. The &%repeat_use%& option of the &%redirect%& router may be of help. .option headers_remove routers list&!! unset .cindex "header lines" "removing" .cindex "router" "removing header lines" -This option specifies a list of text headers, colon-separated, +This option specifies a list of text headers, +.new +colon-separated (by default, changeable in the usual way), +.wen 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 @@ -17670,6 +17884,7 @@ delivering in cutthrough mode or testing recipient verification using &%-bv%&. See section &<>& for a list of the order in which preconditions are evaluated. +See also the &$verify_mode$& variable. .option verify_sender routers&!? boolean true @@ -17677,6 +17892,7 @@ If this option is false, the router is skipped when verifying sender addresses or testing sender verification using &%-bvs%&. See section &<>& for a list of the order in which preconditions are evaluated. +See also the &$verify_mode$& variable. .ecindex IIDgenoprou1 .ecindex IIDgenoprou2 @@ -17773,6 +17989,9 @@ There are a few cases where a &(dnslookup)& router will decline to accept an address; if such a router is expected to handle "all remaining non-local domains", then it is important to set &%no_more%&. +The router will defer rather than decline if the domain +is found in the &%fail_defer_domains%& router option. + Reasons for a &(dnslookup)& router to decline currently include: .ilist The domain does not exist in DNS @@ -17851,7 +18070,6 @@ when there is a DNS lookup error. -.new .option dnssec_request_domains dnslookup "domain list&!!" unset .cindex "MX record" "security" .cindex "DNSSEC" "MX lookup" @@ -17859,12 +18077,10 @@ when there is a DNS lookup error. .cindex "DNS" "DNSSEC" DNS lookups for domains matching &%dnssec_request_domains%& will be done with the dnssec request bit set. -This applies to all of the SRV, MX A6, AAAA, A lookup sequence. -.wen +This applies to all of the SRV, MX, AAAA, A lookup sequence. -.new .option dnssec_require_domains dnslookup "domain list&!!" unset .cindex "MX record" "security" .cindex "DNSSEC" "MX lookup" @@ -17873,9 +18089,19 @@ This applies to all of the SRV, MX A6, AAAA, A lookup sequence. DNS lookups for domains matching &%dnssec_request_domains%& will be done with the dnssec request bit set. Any returns not having the Authenticated Data bit (AD bit) set wil be ignored and logged as a host-lookup failure. -This applies to all of the SRV, MX A6, AAAA, A lookup sequence. -.wen +This applies to all of the SRV, MX, AAAA, A lookup sequence. + + +.option fail_defer_domains dnslookup "domain list&!!" unset +.cindex "MX record" "not found" +DNS lookups for domains matching &%fail_defer_domains%& +which find no matching record will cause the router to defer +rather than the default behaviour of decline. +This maybe be useful for queueing messages for a newly created +domain while the DNS configuration is not ready. +However, it will result in any message with mistyped domains +also being queued. .option mx_domains dnslookup "domain list&!!" unset @@ -18846,6 +19072,13 @@ However, there are some private options which define transports for delivery to files and pipes, and for generating autoreplies. See the &%file_transport%&, &%pipe_transport%& and &%reply_transport%& descriptions below. +.new +If success DSNs have been requested +.cindex "DSN" "success" +.cindex "Delivery Status Notification" "success" +redirection triggers one and the DSN options are not passed any further. +.wen + .section "Redirection data" "SECID124" @@ -20038,7 +20271,10 @@ value that the router supplies, and also overriding any value associated with .option headers_add transports list&!! unset .cindex "header lines" "adding in transport" .cindex "transport" "header lines; adding" -This option specifies a list of text headers, newline-separated, +This option specifies a list of text headers, +.new +newline-separated (by default, changeable in the usual way), +.wen which are (separately) expanded and added to the header portion of a message as it is transported, as described in section &<>&. Additional header lines can also be specified by @@ -20063,7 +20299,10 @@ 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; +This option specifies a list of header names, +.new +colon-separated (by default, changeable in the usual way); +.wen these headers are omitted from the message as it is transported, as described in section &<>&. Header removal can also be specified by routers. @@ -22781,7 +23020,6 @@ See the &%search_parents%& option in chapter &<>& for more details. -.new .option dnssec_request_domains smtp "domain list&!!" unset .cindex "MX record" "security" .cindex "DNSSEC" "MX lookup" @@ -22789,12 +23027,10 @@ details. .cindex "DNS" "DNSSEC" DNS lookups for domains matching &%dnssec_request_domains%& will be done with the dnssec request bit set. -This applies to all of the SRV, MX A6, AAAA, A lookup sequence. -.wen +This applies to all of the SRV, MX, AAAA, A lookup sequence. -.new .option dnssec_require_domains smtp "domain list&!!" unset .cindex "MX record" "security" .cindex "DNSSEC" "MX lookup" @@ -22803,8 +23039,7 @@ This applies to all of the SRV, MX A6, AAAA, A lookup sequence. DNS lookups for domains matching &%dnssec_request_domains%& will be done with the dnssec request bit set. Any returns not having the Authenticated Data bit (AD bit) set wil be ignored and logged as a host-lookup failure. -This applies to all of the SRV, MX A6, AAAA, A lookup sequence. -.wen +This applies to all of the SRV, MX, AAAA, A lookup sequence. @@ -22955,12 +23190,13 @@ that matches this list, even if the server host advertises PIPELINING support. Exim will not try to start a TLS session when delivering to any host that matches this list. See chapter &<>& for details of TLS. -.option hosts_verify_avoid_tls smtp "host list&!!" * +.new +.option hosts_verify_avoid_tls smtp "host list&!!" unset .cindex "TLS" "avoiding for certain hosts" Exim will not try to start a TLS session for a verify callout, or when delivering in cutthrough mode, to any host that matches this list. -Note that the default is to not use TLS. +.wen .option hosts_max_try smtp integer 5 @@ -23057,11 +23293,14 @@ connects. If authentication fails, Exim will try to transfer the message unauthenticated. See also &%hosts_require_auth%&, and chapter &<>& for details of authentication. -.option hosts_try_prdr smtp "host list&!!" unset +.new +.option hosts_try_prdr smtp "host list&!!" * .cindex "PRDR" "enabling, optional in client" This option provides a list of servers to which, provided they announce PRDR support, Exim will attempt to negotiate PRDR for multi-recipient messages. +The option can usually be left as default. +.wen .option interface smtp "string list&!!" unset .cindex "bind IP address" @@ -23119,7 +23358,7 @@ so can cause parallel connections to the same host if &%remote_max_parallel%& permits this. -.option multi_domain smtp boolean true +.option multi_domain smtp boolean&!! true .vindex "&$domain$&" When this option is set, the &(smtp)& transport can handle a number of addresses containing a mixture of different domains provided they all resolve @@ -23128,6 +23367,11 @@ handling only one domain at a time. This is useful if you want to use &$domain$& in an expansion for the transport, because it is set only when there is a single domain involved in a remote delivery. +.new +It is expanded per-address and can depend on any of +&$address_data$&, &$domain_data$&, &$local_part_data$&, +&$host$&, &$host_address$& and &$host_port$&. +.wen .option port smtp string&!! "see below" .cindex "port" "sending TCP/IP" @@ -23163,7 +23407,7 @@ connecting, as an outbound SSL-on-connect, instead of using STARTTLS to upgrade. The Internet standards bodies strongly discourage use of this mode. -.option retry_include_ip_address smtp boolean true +.option retry_include_ip_address smtp boolean&!! true Exim normally includes both the host name and the IP address in the key it constructs for indexing retry data after a temporary delivery failure. This means that when one of several IP addresses for a host is failing, it gets @@ -23173,9 +23417,10 @@ addresses is not affected. However, in some dialup environments hosts are assigned a different IP address each time they connect. In this situation the use of the IP address as part of the retry key leads to undesirable behaviour. Setting this option false causes -Exim to use only the host name. This should normally be done on a separate -instance of the &(smtp)& transport, set up specially to handle the dialup -hosts. +Exim to use only the host name. +.new +Since it is expanded it can be made to depend on the host or domain. +.wen .option serialize_hosts smtp "host list&!!" unset @@ -23313,7 +23558,9 @@ unknown state), opens a new one to the same host, and then tries the delivery in clear. -.option tls_try_verify_hosts smtp "host list&!! unset +.new +.option tls_try_verify_hosts smtp "host list&!!" * +.wen .cindex "TLS" "server certificate verification" .cindex "certificate" "verification of server" This option gives a list of hosts for which, on encrypted connections, @@ -23321,31 +23568,63 @@ certificate verification will be tried but need not succeed. The &%tls_verify_certificates%& option must also be set. Note that unless the host is in this list TLS connections will be denied to hosts using self-signed certificates -when &%tls_verify_certificates%& is set. +when &%tls_verify_certificates%& is matched. The &$tls_out_certificate_verified$& variable is set when certificate verification succeeds. -.option tls_verify_certificates smtp string&!! unset +.new +.option tls_verify_cert_hostnames smtp "host list&!!" * +.cindex "TLS" "server certificate hostname verification" +.cindex "certificate" "verification of server" +This option give a list of hosts for which, +while verifying the server certificate, +checks will be included on the host name +(note that this will generally be the result of a DNS MX lookup) +versus Subject and Subject-Alternate-Name fields. Wildcard names are permitted +limited to being the initial component of a 3-or-more component FQDN. + +There is no equivalent checking on client certificates. +.wen + + +.new +.option tls_verify_certificates smtp string&!! system .cindex "TLS" "server certificate verification" .cindex "certificate" "verification of server" .vindex "&$host$&" .vindex "&$host_address$&" -The value of this option must be the absolute path to a file containing -permitted server certificates, for use when setting up an encrypted connection. -Alternatively, if you are using OpenSSL, you can set -&%tls_verify_certificates%& to the name of a directory containing certificate -files. This does not work with GnuTLS; the option must be set to the name of a -single file if you are using GnuTLS. The values of &$host$& and +The value of this option must be either the +word "system" +or the absolute path to +a file or directory containing permitted certificates for servers, +for use when setting up an encrypted connection. + +The "system" value for the option will use a location compiled into the SSL library. +This is not available for GnuTLS versions preceding 3.0.20; a value of "system" +is taken as empty and an explicit location +must be specified. + +The use of a directory for the option value is not avilable for GnuTLS versions +preceding 3.3.6 and a single file must be used. +.wen + +With OpenSSL the certificates specified +explicitly +either by file or directory +are added to those given by the system default location. + +The values of &$host$& and &$host_address$& are set to the name and address of the server during the expansion of this option. See chapter &<>& for details of TLS. For back-compatability, if neither tls_verify_hosts nor tls_try_verify_hosts are set +(a single-colon empty list counts as being set) and certificate verification fails the TLS connection is closed. -.option tls_verify_hosts smtp "host list&!! unset +.option tls_verify_hosts smtp "host list&!!" unset .cindex "TLS" "server certificate verification" .cindex "certificate" "verification of server" This option gives a list of hosts for which. on encrypted connections, @@ -24096,6 +24375,13 @@ A server unexpectedly closed the SMTP connection. There may, of course, legitimate reasons for this (host died, network died), but if it repeats a lot for the same host, it indicates something odd. +.vitem &%lookup%& +A DNS lookup for a host failed. +Note that a &%dnslookup%& router will need to have matched +its &%fail_defer_domains%& option for this retry type to be usable. +Also note that a &%manualroute%& router will probably need +its &%host_find_failed%& option set to &%defer%&. + .vitem &%refused_MX%& A connection to a host obtained from an MX record was refused. @@ -25395,6 +25681,7 @@ but it is present in many binary distributions. .scindex IIDdcotauth2 "authenticators" "&(dovecot)&" This authenticator is an interface to the authentication facility of the Dovecot POP/IMAP server, which can support a number of authentication methods. +Note that Dovecot must be configured to use auth-client not auth-userdb. If you are using Dovecot to authenticate POP/IMAP clients, it might be helpful to use the same mechanisms for SMTP authentication. This is a server authenticator only. There is only one option: @@ -25816,8 +26103,10 @@ include files and libraries for GnuTLS can be found. There are some differences in usage when using GnuTLS instead of OpenSSL: .ilist -The &%tls_verify_certificates%& option must contain the name of a file, not the -name of a directory (for OpenSSL it can be either). +The &%tls_verify_certificates%& option +cannot be the path of a directory +for GnuTLS versions before 3.3.6 +(for later versions, or OpenSSL, it can be either). .next The default value for &%tls_dhparam%& differs for historical reasons. .next @@ -26014,7 +26303,8 @@ The GnuTLS library allows the caller to provide a "priority string", documented as part of the &[gnutls_priority_init]& function. This is very similar to the ciphersuite specification in OpenSSL. -The &%tls_require_ciphers%& option is treated as the GnuTLS priority string. +The &%tls_require_ciphers%& option is treated as the GnuTLS priority string +and controls both protocols and ciphers. The &%tls_require_ciphers%& option is available both as an global option, controlling how Exim behaves as a server, and also as an option of the @@ -26031,6 +26321,12 @@ installed on your system. If you are using GnuTLS 3, &url(http://www.gnutls.org/manual/gnutls.html#Listing-the-ciphersuites-in-a-priority-string, then the example code) on that site can be used to test a given string. +For example: +.code +# Disable older versions of protocols +tls_require_ciphers = NORMAL:%LATEST_RECORD_VERSION:-VERS-SSL3.0 +.endd + Prior to Exim 4.80, an older API of GnuTLS was used, and Exim supported three additional options, "&%gnutls_require_kx%&", "&%gnutls_require_mac%&" and "&%gnutls_require_protocols%&". &%tls_require_ciphers%& was an Exim list. @@ -26081,8 +26377,11 @@ tls_privatekey = /some/file/name These options are, in fact, expanded strings, so you can make them depend on the identity of the client that is connected if you wish. The first file contains the server's X509 certificate, and the second contains the private key -that goes with it. These files need to be readable by the Exim user, and must -always be given as full path names. They can be the same file if both the +that goes with it. These files need to be +PEM format and readable by the Exim user, and must +always be given as full path names. +The key must not be password-protected. +They can be the same file if both the certificate and the key are contained within it. If &%tls_privatekey%& is not set, or if its expansion is forced to fail or results in an empty string, this is assumed to be the case. The certificate file may also contain intermediate @@ -26158,8 +26457,12 @@ session with a client, you must set either &%tls_verify_hosts%& or apply to all TLS connections. For any host that matches one of these options, Exim requests a certificate as part of the setup of the TLS session. The contents of the certificate are verified by comparing it with a list of -expected certificates. These must be available in a file or, -for OpenSSL only (not GnuTLS), a directory, identified by +expected certificates. +.new +These may be the system default set (depending on library version), +.wen +an explicit file or, +depending on library version, a directory, identified by &%tls_verify_certificates%&. A file can contain multiple certificates, concatenated end to end. If a @@ -26209,7 +26512,7 @@ an identically named option for the &(smtp)& transport. In each case, the value of the option is expanded and must then be the name of a file that contains a CRL in PEM format. The downside is that clients have to periodically re-download a potentially huge -file from every certificate authority the know of. +file from every certificate authority they know of. The way with most moving parts at query time is Online Certificate Status Protocol (OCSP), where the client verifies the certificate @@ -26263,6 +26566,8 @@ file named by &%tls_ocsp_file%&. Note that the proof only covers the terminal server certificate, not any of the chain from CA to it. +There is no current way to staple a proof for a client certificate. + .code A helper script "ocsp_fetch.pl" for fetching a proof from a CA OCSP server is supplied. The server URL may be included in the @@ -26317,9 +26622,15 @@ if it requests it. If the server is Exim, it will request a certificate only if &%tls_verify_hosts%& or &%tls_try_verify_hosts%& matches the client. If the &%tls_verify_certificates%& option is set on the &(smtp)& transport, it +specifies a collection of expected server certificates. +.new +These may be the system default set (depending on library version), +.wen +a file or, +depnding on liibrary version, a directory, must name a file or, -for OpenSSL only (not GnuTLS), a directory, that contains a collection of -expected server certificates. The client verifies the server's certificate +for OpenSSL only (not GnuTLS), a directory. +The client verifies the server's certificate against this collection, taking into account any revoked certificates that are in the list defined by &%tls_crl%&. Failure to verify fails the TLS connection unless either of the @@ -26429,7 +26740,7 @@ during TLS session handshake, to permit alternative values to be chosen: &%tls_verify_certificates%& .next .vindex "&%tls_ocsp_file%&" -&%tls_verify_certificates%& +&%tls_ocsp_file%& .endlist Great care should be taken to deal with matters of case, various injection @@ -26788,6 +27099,7 @@ This ACL is evaluated after &%acl_smtp_dkim%& but before &%acl_smtp_data%&. .section "The SMTP PRDR ACL" "SECTPRDRACL" +.cindex "PRDR" "ACL for" .oindex "&%prdr_enable%&" The &%acl_smtp_data_prdr%& ACL is available only when Exim is compiled with PRDR support enabled (which is the default). @@ -26796,8 +27108,9 @@ client and server for a message, and more than one recipient has been accepted. The ACL test specfied by &%acl_smtp_data_prdr%& happens after a message -has been recieved, and is executed for each recipient of the message. -The test may accept or deny for inividual recipients. +has been recieved, and is executed once for each recipient of the message +with &$local_part$& and &$domain$& valid. +The test may accept, defer or deny for inividual recipients. The &%acl_smtp_data%& will still be called after this ACL and can reject the message overall, even if this ACL has accepted it for some or all recipients. @@ -26821,8 +27134,8 @@ the feature was not requested by the client. .cindex "QUIT, ACL for" The ACL for the SMTP QUIT command is anomalous, in that the outcome of the ACL does not affect the response code to QUIT, which is always 221. Thus, the ACL -does not in fact control any access. For this reason, the only verbs that are -permitted are &%accept%& and &%warn%&. +does not in fact control any access. For this reason, it may only accept +or warn as its final result. This ACL can be used for tasks such as custom logging at the end of an SMTP session. For example, you can use ACL variables in other ACLs to count @@ -27626,6 +27939,9 @@ anyway. If the message contains newlines, this gives rise to a multi-line SMTP response. .vindex "&$acl_verify_message$&" +For ACLs that are called by an &%acl =%& ACL condition, the message is +stored in &$acl_verify_message$&, from which the calling ACL may use it. + If &%message%& is used on a statement that verifies an address, the message specified overrides any message that is generated by the verification process. However, the original message is available in the variable @@ -27733,10 +28049,20 @@ is what is wanted for subsequent tests. .cindex "&ACL;" "cutthrough routing" .cindex "cutthrough" "requesting" This option requests delivery be attempted while the item is being received. -It is usable in the RCPT ACL and valid only for single-recipient mails forwarded -from one SMTP connection to another. If a recipient-verify callout connection is -requested in the same ACL it is held open and used for the data, otherwise one is made -after the ACL completes. + +The option is usable in the RCPT ACL. +If enabled for a message recieved via smtp and routed to an smtp transport, +and only one transport, interface, destination host and port combination +is used for all recipients of the message, +then the delivery connection is made while the receiving connection is open +and data is copied from one to the other. + +An attempt to set this option for any recipient but the first +for a mail will be quietly ignored. +If a recipient-verify callout connection is subsequently +requested in the same ACL it is held open and used for +any subsequent receipients and the data, +otherwise one is made after the initial RCPT ACL completes. Note that routers are used in verify mode, and cannot depend on content of received headers. @@ -27747,15 +28073,17 @@ Headers may be modified by routers (subject to the above) and transports. Cutthrough delivery is not supported via transport-filters or when DKIM signing of outgoing messages is done, because it sends data to the ultimate destination before the entire message has been received from the source. +It is not supported for messages recieved with the SMTP PRDR option in use. Should the ultimate destination system positively accept or reject the mail, a corresponding indication is given to the source system and nothing is queued. If there is a temporary error the item is queued for later delivery in the -usual fashion. If the item is successfully delivered in cutthrough mode the log line -is tagged with ">>" rather than "=>" and appears before the acceptance "<=" -line. +usual fashion. If the item is successfully delivered in cutthrough mode +the delivery log lines are tagged with ">>" rather than "=>" and appear +before the acceptance "<=" line. -Delivery in this mode avoids the generation of a bounce mail to a (possibly faked) +Delivery in this mode avoids the generation of a bounce mail to a +(possibly faked) sender when the destination system is doing content-scan based rejection. @@ -28200,6 +28528,8 @@ can be appended; they appear within the called ACL in $acl_arg1 to $acl_arg9, and $acl_narg is set to the count of values. Previous values of these variables are restored after the call returns. The name and values are expanded separately. +Note that spaces in complex expansions which are used as arguments +will act as argument separators. If the nested &%acl%& returns &"drop"& and the outer condition denies access, the connection is dropped. If it returns &"discard"&, the verb must be @@ -28431,7 +28761,6 @@ This condition checks whether the sending host (the client) is authorized to send email. Details of how this works are given in section &<>&. -.new .vitem &*verify&~=&~header_names_ascii*& .cindex "&%verify%& ACL condition" .cindex "&ACL;" "verifying header names only ASCII" @@ -28446,7 +28775,6 @@ allowable characters are decimal ASCII values 33 through 126. Exim itself will handle headers with non-ASCII characters, but it can cause problems for downstream applications, so this option will allow their detection and rejection in the DATA ACL's. -.wen .vitem &*verify&~=&~header_sender/*&<&'options'&> .cindex "&%verify%& ACL condition" @@ -28543,7 +28871,7 @@ verified is redirected to a single address, verification continues with the new address, and in that case, the subsequent value of &$address_data$& is the value for the child address. -.vitem &*verify&~=&~reverse_host_lookup*& +.vitem &*verify&~=&~reverse_host_lookup/*&<&'options'&> .cindex "&%verify%& ACL condition" .cindex "&ACL;" "verifying host reverse lookup" .cindex "host" "verifying reverse lookup" @@ -28554,6 +28882,9 @@ Verification ensures that the host name obtained from a reverse DNS lookup, or one of its aliases, does, when it is itself looked up in the DNS, yield the original IP address. +There is one possible option, &`defer_ok`&. If this is present and a +DNS operation returns a temporary error, the verify condition succeeds. + If this condition is used for a locally generated message (that is, when there is no client host involved), it always succeeds. @@ -30101,10 +30432,14 @@ It supports a &"generic"& interface to scanners called via the shell, and specialized interfaces for &"daemon"& type virus scanners, which are resident in memory and thus are much faster. +.new +A timeout of 2 minutes is applied to a scanner call (by default); +if it expires then a defer action is taken. +.wen .oindex "&%av_scanner%&" -You can set the &%av_scanner%& option in first part of the Exim configuration -file to specify which scanner to use, together with any additional options that +You can set the &%av_scanner%& option in the main part of the configuration +to specify which scanner to use, together with any additional options that are needed. The basic syntax is as follows: .display &`av_scanner = <`&&'scanner-type'&&`>:<`&&'option1'&&`>:<`&&'option2'&&`>:[...]`& @@ -30119,6 +30454,41 @@ The usual list-parsing of the content (see &<>&) applies. The following scanner types are supported in this release: .vlist +.new +.vitem &%avast%& +.cindex "virus scanners" "avast" +This is the scanner daemon of Avast. It has been tested with Avast Core +Security (currenty at version 1.1.7). +You can get a trial version at &url(http://www.avast.com) or for Linux +at &url(http://www.avast.com/linux-server-antivirus). +This scanner type takes one option, +which can be either a full path to a UNIX socket, +or host and port specifiers separated by white space. +The host may be a name or an IP address; the port is either a +single number or a pair of numbers with a dash between. +Any further options are given, on separate lines, +to the daemon as options before the main scan command. +For example: +.code +av_scanner = avast:/var/run/avast/scan.sock:FLAGS -fullfiles:SENSITIVITY -pup +av_scanner = avast:192.168.2.22 5036 +.endd +If you omit the argument, the default path +&_/var/run/avast/scan.sock_& +is used. +If you use a remote host, +you need to make Exim's spool directory available to it, +as the scanner is passed a file path, not file contents. +For information about available commands and their options you may use +.code +$ socat UNIX:/var/run/avast/scan.sock STDIO: + FLAGS + SENSITIVITY + PACK +.endd +.wen + + .vitem &%aveserver%& .cindex "virus scanners" "Kaspersky" This is the scanner daemon of Kaspersky Version 5. You can get a trial version @@ -30135,17 +30505,39 @@ av_scanner = aveserver:/var/run/aveserver This daemon-type scanner is GPL and free. You can get it at &url(http://www.clamav.net/). Some older versions of clamd do not seem to unpack MIME containers, so it used to be recommended to unpack MIME attachments -in the MIME ACL. This no longer believed to be necessary. One option is -required: either the path and name of a UNIX socket file, or a hostname or IP -number, and a port, separated by space, as in the second of these examples: +in the MIME ACL. This is no longer believed to be necessary. + +The options are a list of server specifiers, which may be +a UNIX socket specification, +a TCP socket specification, +or a (global) option. + +A socket specification consists of a space-separated list. +For a Unix socket the first element is a full path for the socket, +for a TCP socket the first element is the IP address +and the second a port number, +Any further elements are per-server (non-global) options. +These per-server options are supported: +.code +retry= Retry on connect fail +.endd + +The &`retry`& option specifies a time after which a single retry for +a failed connect is made. The default is to not retry. + +If a Unix socket file is specified, only one server is supported. + +Examples: .code av_scanner = clamd:/opt/clamd/socket av_scanner = clamd:192.0.2.3 1234 av_scanner = clamd:192.0.2.3 1234:local +av_scanner = clamd:192.0.2.3 1234 retry=10s av_scanner = clamd:192.0.2.3 1234 : 192.0.2.4 1234 .endd -If the value of av_scanner points to a UNIX socket file or contains the local -keyword, then the ClamAV interface will pass a filename containing the data +If the value of av_scanner points to a UNIX socket file or contains the +&`local`& +option, then the ClamAV interface will pass a filename containing the data to be scanned, which will should normally result in less I/O happening and be more efficient. Normally in the TCP case, the data is streamed to ClamAV as Exim does not assume that there is a common filesystem with the remote host. @@ -30207,9 +30599,13 @@ av_scanner = cmdline:\ .endd .vitem &%drweb%& .cindex "virus scanners" "DrWeb" -The DrWeb daemon scanner (&url(http://www.sald.com/)) interface takes one -argument, either a full path to a UNIX socket, or an IP address and port -separated by white space, as in these examples: +The DrWeb daemon scanner (&url(http://www.sald.com/)) interface +takes one option, +either a full path to a UNIX socket, +or host and port specifiers separated by white space. +The host may be a name or an IP address; the port is either a +single number or a pair of numbers with a dash between. +For example: .code av_scanner = drweb:/var/run/drwebd.sock av_scanner = drweb:192.168.2.20 31337 @@ -30217,6 +30613,17 @@ av_scanner = drweb:192.168.2.20 31337 If you omit the argument, the default path &_/usr/local/drweb/run/drwebd.sock_& is used. Thanks to Alex Miller for contributing the code for this scanner. +.vitem &%f-protd%& +.cindex "virus scanners" "f-protd" +The f-protd scanner is accessed via HTTP over TCP. +One argument is taken, being a space-separated hostname and port number +(or port-range). +For example: +.code +av_scanner = f-protd:localhost 10200-10204 +.endd +If you omit the argument, the default values show above are used. + .vitem &%fsecure%& .cindex "virus scanners" "F-Secure" The F-Secure daemon scanner (&url(http://www.f-secure.com)) takes one @@ -30295,7 +30702,10 @@ which case each use of the &%malware%& condition causes a new scan of the message. The &%malware%& condition takes a right-hand argument that is expanded before -use. It can then be one of +.new +use and taken as a list, slash-separated by default. +.wen +The first element can then be one of .ilist &"true"&, &"*"&, or &"1"&, in which case the message is scanned for viruses. @@ -30308,11 +30718,25 @@ the condition fails immediately. A regular expression, in which case the message is scanned for viruses. The condition succeeds if a virus is found and its name matches the regular expression. This allows you to take special actions on certain types of virus. +.new +Note that &"/"& characters in the RE must be doubled due to the list-processing, +unless the separator is changed (in the usual way). +.wen .endlist -You can append &`/defer_ok`& to the &%malware%& condition to accept messages -even if there is a problem with the virus scanner. Otherwise, such a problem -causes the ACL to defer. +You can append a &`defer_ok`& element to the &%malware%& argument list to accept +messages even if there is a problem with the virus scanner. +Otherwise, such a problem causes the ACL to defer. + +.new +You can append a &`tmo=`& element to the &%malware%& argument list to +specify a non-default timeout. The default is two minutes. +For example: +.code +malware = * / defer_ok / tmo=10s +.endd +A timeout causes the ACL to defer. +.wen .vindex "&$malware_name$&" When a virus is found, the condition sets up an expansion variable called @@ -30356,14 +30780,22 @@ deny message = This message contains malware ($malware_name) .endd -.section "Scanning with SpamAssassin" "SECTscanspamass" +.section "Scanning with SpamAssassin and Rspamd" "SECTscanspamass" .cindex "content scanning" "for spam" .cindex "spam scanning" .cindex "SpamAssassin" +.cindex "Rspamd" The &%spam%& ACL condition calls SpamAssassin's &%spamd%& daemon to get a spam -score and a report for the message. You can get SpamAssassin at -&url(http://www.spamassassin.org), or, if you have a working Perl -installation, you can use CPAN by running: +score and a report for the message. +.new +Support is also provided for Rspamd. + +For more information about installation and configuration of SpamAssassin or +Rspamd refer to their respective websites at +&url(http://spamassassin.apache.org) and &url(http://www.rspamd.com) +.wen + +SpamAssassin can be installed with CPAN by running: .code perl -MCPAN -e 'install Mail::SpamAssassin' .endd @@ -30372,36 +30804,90 @@ documentation to see how you can tweak it. The default installation should work nicely, however. .oindex "&%spamd_address%&" -After having installed and configured SpamAssassin, start the &%spamd%& daemon. -By default, it listens on 127.0.0.1, TCP port 783. If you use another host or -port for &%spamd%&, you must set the &%spamd_address%& option in the global -part of the Exim configuration as follows (example): +By default, SpamAssassin listens on 127.0.0.1, TCP port 783 and if you +intend to use an instance running on the local host you do not need to set +&%spamd_address%&. If you intend to use another host or port for SpamAssassin, +you must set the &%spamd_address%& option in the global part of the Exim +configuration as follows (example): .code spamd_address = 192.168.99.45 387 .endd -You do not need to set this option if you use the default. As of version 2.60, -&%spamd%& also supports communication over UNIX sockets. If you want to use -these, supply &%spamd_address%& with an absolute file name instead of a -address/port pair: + +.new +To use Rspamd (which by default listens on all local addresses +on TCP port 11333) +you should add &%variant=rspamd%& after the address/port pair, for example: +.code +spamd_address = 127.0.0.1 11333 variant=rspamd +.endd +.wen + +As of version 2.60, &%SpamAssassin%& also supports communication over UNIX +sockets. If you want to us these, supply &%spamd_address%& with an absolute +file name instead of an address/port pair: .code spamd_address = /var/run/spamd_socket .endd You can have multiple &%spamd%& servers to improve scalability. These can reside on other hardware reachable over the network. To specify multiple &%spamd%& servers, put multiple address/port pairs in the &%spamd_address%& -option, separated with colons: +option, separated with colons (the separator can be changed in the usual way): .code spamd_address = 192.168.2.10 783 : \ 192.168.2.11 783 : \ 192.168.2.12 783 .endd -Up to 32 &%spamd%& servers are supported. The servers are queried in a random -fashion. When a server fails to respond to the connection attempt, all other +Up to 32 &%spamd%& servers are supported. +When a server fails to respond to the connection attempt, all other servers are tried until one succeeds. If no server responds, the &%spam%& condition defers. -&*Warning*&: It is not possible to use the UNIX socket connection method with -multiple &%spamd%& servers. +.new +Unix and TCP socket specifications may be mixed in any order. +Each element of the list is a list itself, space-separated by default +and changeable in the usual way. + +For TCP socket specifications a host name or IP (v4 or v6, but +subject to list-separator quoting rules) address can be used, +and the port can be one or a dash-separated pair. +In the latter case, the range is tried in strict order. + +Elements after the first for Unix sockets, or second for TCP socket, +are options. +The supported option are: +.code +pri= Selection priority +weight= Selection bias +time=- Use only between these times of day +retry= Retry on connect fail +tmo= Connection time limit +variant=rspamd Use Rspamd rather than SpamAssassin protocol +.endd + +The &`pri`& option specifies a priority for the server within the list, +higher values being tried first. +The deafult priority is 1. + +The &`weight`& option specifies a selection bias. +Within a priority set +servers are queried in a random fashion, weighted by this value. +The default value for selection bias is 1. + +Time specifications for the &`time`& option are .. +in the local time zone; each element being one or more digits. +Either the seconds or both minutes and seconds, plus the leading &`.`& +characters, may be omitted and will be taken as zero. + +Timeout specifications for the &`retry`& and &`tmo`& options +are the usual Exim time interval standard, eg. &`20s`& or &`1m`&. + +The &`tmo`& option specifies an overall timeout for communication. +The default value is two minutes. + +The &`retry`& option specifies a time after which a single retry for +a failed connect is made. +The default is to not retry. +.wen The &%spamd_address%& variable is expanded before use if it starts with a dollar sign. In this case, the expansion may return a string that is @@ -30418,7 +30904,10 @@ 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 to scan using a specific profile, but rather use the SpamAssassin system-wide default profile, you can scan for an unknown name, or simply use &"nobody"&. -However, you must put something on the right-hand side. +.new +Rspamd does not use this setting. However, you must put something on the +right-hand side. +.wen The name allows you to use per-domain or per-user antispam profiles in principle, but this is not straightforward in practice, because a message may @@ -30426,6 +30915,12 @@ have multiple recipients, not necessarily all in the same domain. Because the &%spam%& condition has to be called from a DATA ACL in order to be able to read the contents of the message, the variables &$local_part$& and &$domain$& are not set. +Careful enforcement of single-recipient messages +(eg. by responding with defer in the recipient ACL for all recipients +after the first), +or the use of PRDR, +.cindex "PRDR" "use for per-user SpamAssassin profiles" +are needed to use this feature. The right-hand side of the &%spam%& condition is expanded before being used, so you can put lookups or conditions there. When the right-hand side evaluates to @@ -30472,6 +30967,14 @@ headers, since MUAs can match on such strings. .vitem &$spam_report$& A multiline text table, containing the full SpamAssassin report for the message. Useful for inclusion in headers or reject messages. + +.new +.vitem &$spam_action$& +For SpamAssassin either 'reject' or 'no action' depending on the +spam score versus threshold. +For Rspamd, the recommended action. +.wen + .endlist The &%spam%& condition caches its results unless expansion in @@ -32415,6 +32918,9 @@ headers_remove = return-receipt-to:acknowledge-to Multiple &%headers_remove%& options for a single router or transport can be specified; the arguments will append to a single header-names list. Each item is separately expanded. +Note that colons in complex expansions which are used to +form all or part of a &%headers_remove%& list +will act as list separators. When &%headers_add%& or &%headers_remove%& is specified on a router, items are expanded at routing time, @@ -33252,13 +33758,10 @@ failing addresses with their error messages. The third item is used to introduce any text from pipe transports that is to be returned to the sender. It is omitted if there is no such text. .next -The fourth item is used to introduce the copy of the message that is returned -as part of the error report. -.next -The fifth item is added after the fourth one if the returned message is -truncated because it is bigger than &%return_size_limit%&. -.next -The sixth item is added after the copy of the original message. +.new +The fourth, fifth and sixth items will be ignored and may be empty. +The fields exist for back-compatibility +.wen .endlist The default state (&%bounce_message_file%& unset) is equivalent to the @@ -34596,8 +35099,8 @@ selection marked by asterisks: &`*etrn `& ETRN commands &`*host_lookup_failed `& as it says &` ident_timeout `& timeout for ident connection -&` incoming_interface `& incoming interface on <= lines -&` incoming_port `& incoming port on <= lines +&` incoming_interface `& local interface on <= and => lines +&` incoming_port `& remote port on <= lines &`*lost_incoming_connection `& as it says (includes timeouts) &` outgoing_port `& add remote port to => lines &`*queue_run `& start and end queue runs @@ -34621,7 +35124,9 @@ selection marked by asterisks: &` smtp_protocol_error `& SMTP protocol errors &` smtp_syntax_error `& SMTP syntax errors &` subject `& contents of &'Subject:'& on <= lines -&` tls_certificate_verified `& certificate verification status +.new +&`*tls_certificate_verified `& certificate verification status +.wen &`*tls_cipher `& TLS cipher suite on <= and => lines &` tls_peerdn `& TLS peer DN on <= and => lines &` tls_sni `& TLS SNI on <= lines @@ -34714,12 +35219,16 @@ routing email addresses, but it does apply to &"byname"& lookups. client's ident port times out. .next .cindex "log" "incoming interface" +.cindex "log" "local interface" +.cindex "log" "local address and port" +.cindex "TCP/IP" "logging local address and port" .cindex "interface" "logging" &%incoming_interface%&: The interface on which a message was received is added to the &"<="& line as an IP address in square brackets, tagged by I= and followed by a colon and the port number. The local interface and port are also -added to other SMTP log lines, for example &"SMTP connection from"&, and to -rejection lines. +added to other SMTP log lines, for example &"SMTP connection from"& and to +rejection lines +and (despite the name) the local interface is added to &"=>"& lines.. .next .cindex "log" "incoming remote port" .cindex "port" "logging remote" @@ -35060,10 +35569,8 @@ or (in case &*-a*& switch is specified) .code exim -bp .endd -.new The &*-C*& option is used to specify an alternate &_exim.conf_& which might contain alternate exim configuration the queue management might be using. -.wen to obtain a queue listing, and then greps the output to select messages that match given criteria. The following selection options are available: @@ -35171,7 +35678,7 @@ The input files can be in Exim log format or syslog format. If a matching log line is not associated with a specific message, it is included in &'exigrep'&'s output without any additional lines. The usage is: .display -&`exigrep [-t<`&&'n'&&`>] [-I] [-l] [-v] <`&&'pattern'&&`> [<`&&'log file'&&`>] ...`& +&`exigrep [-t<`&&'n'&&`>] [-I] [-l] [-M] [-v] <`&&'pattern'&&`> [<`&&'log file'&&`>] ...`& .endd If no log file names are given on the command line, the standard input is read. @@ -35192,6 +35699,19 @@ regular expression. The &%-v%& option inverts the matching condition. That is, a line is selected if it does &'not'& match the pattern. +The &%-M%& options means &"related messages"&. &'exigrep'& will show messages +that are generated as a result/response to a message that &'exigrep'& matched +normally. + +Example of &%-M%&: +user_a sends a message to user_b, which generates a bounce back to user_b. If +&'exigrep'& is used to search for &"user_a"&, only the first message will be +displayed. But if &'exigrep'& is used to search for &"user_b"&, the first and +the second (bounce) message will be displayed. Using &%-M%& with &'exigrep'& +when searching for &"user_a"& will show both messages since the bounce is +&"related"& to or a &"result"& of the first message that was found by the +search term. + If the location of a &'zcat'& command is known from the definition of ZCAT_COMMAND in &_Local/Makefile_&, &'exigrep'& automatically passes any file whose name ends in COMPRESS_SUFFIX through &'zcat'& as it searches it.