Handle Proxy Protocol v2 safely as well.

[exim.git] / doc / doc-docbook / spec.xfpt

diff --git a/doc/doc-docbook/spec.xfpt b/doc/doc-docbook/spec.xfpt
index b3f97e1eaea045cc2dd8c34939d0f3d5af5c70db..5cbc126a488a43557b13037421a99c37137ff7ed 100644 (file)
--- a/doc/doc-docbook/spec.xfpt
+++ b/doc/doc-docbook/spec.xfpt
@@ -52,7 +52,7 @@
 .set I   "    "
 
 .macro copyyear
 .set I   "    "
 
 .macro copyyear

-2016
+2017

 .endmacro
 
 . /////////////////////////////////////////////////////////////////////////////
 .endmacro
 
 . /////////////////////////////////////////////////////////////////////////////


@@ -436,6 +436,7 @@ directory are:
 .row &_filter.txt_&          "specification of the filter language"
 .row &_Exim3.upgrade_&       "upgrade notes from release 2 to release 3"
 .row &_Exim4.upgrade_&       "upgrade notes from release 3 to release 4"
 .row &_filter.txt_&          "specification of the filter language"
 .row &_Exim3.upgrade_&       "upgrade notes from release 2 to release 3"
 .row &_Exim4.upgrade_&       "upgrade notes from release 3 to release 4"

+.row &_openssl.txt_&         "installing a current OpenSSL release"

 .endtable
 
 The main specification and the specification of the filtering language are also
 .endtable
 
 The main specification and the specification of the filtering language are also


@@ -4481,12 +4482,12 @@ The name should not contain a &'/'& character.
 For a periodic queue run (see below)
 append to the name a slash and a time value.
 
 For a periodic queue run (see below)
 append to the name a slash and a time value.
 

-If other commandline options speicify an action, a &'-qG<name>'& option
+If other commandline options specify an action, a &'-qG<name>'& option

 will specify a queue to operate on.
 For example:
 .code
 exim -bp -qGquarantine
 will specify a queue to operate on.
 For example:
 .code
 exim -bp -qGquarantine

-mailq -qGquarantime
+mailq -qGquarantine

 exim -qGoffpeak -Rf @special.domain.example
 .endd
 .wen
 exim -qGoffpeak -Rf @special.domain.example
 .endd
 .wen


@@ -4926,8 +4927,12 @@ using this syntax:
 .endd
 on a line by itself. Double quotes round the file name are optional. If you use
 the first form, a configuration error occurs if the file does not exist; the
 .endd
 on a line by itself. Double quotes round the file name are optional. If you use
 the first form, a configuration error occurs if the file does not exist; the

-second form does nothing for non-existent files. In all cases, an absolute file
+second form does nothing for non-existent files.
+.new
+The first form allows a relative name. It is resolved relative to
+the directory of the including file. For the second form an absolute file

 name is required.
 name is required.

+.wen

 
 Includes may be nested to any depth, but remember that Exim reads its
 configuration file often, so it is a good idea to keep them to a minimum.
 
 Includes may be nested to any depth, but remember that Exim reads its
 configuration file often, so it is a good idea to keep them to a minimum.


@@ -5033,6 +5038,33 @@ address lists. In Exim 4 these are handled better by named lists &-- see
 section &<<SECTnamedlists>>&.
 
 
 section &<<SECTnamedlists>>&.
 
 

+.new
+.section "Builtin macros" "SECTbuiltinmacros"
+Exim defines some macros depending on facilities available, which may
+differ due to build-time definitions and from one release to another.
+All of these macros start with an underscore.
+They can be used to conditionally include parts of a configuration
+(see below).
+
+The following classes of macros are defined:
+.display
+&` _HAVE_*                    `&  build-time defines
+&` _DRIVER_ROUTER_*           `&  router drivers
+&` _DRIVER_TRANSPORT_*        `&  transport drivers
+&` _DRIVER_AUTHENTICATOR_*    `&  authenticator drivers
+&` _OPT_MAIN_*                `&  main config options
+&` _OPT_ROUTERS_*             `&  generic router options
+&` _OPT_TRANSPORTS_*          `&  generic transport options
+&` _OPT_AUTHENTICATORS_*      `&  generic authenticator options
+&` _OPT_ROUTER_*_*            `&  private router options
+&` _OPT_TRANSPORT_*_*         `&  private transport options
+&` _OPT_AUTHENTICATOR_*_*     `&  private authenticator options
+.endd
+
+Use an &"exim -bP macros"& command to get the list of macros.
+.wen
+
+

 .section "Conditional skips in the configuration file" "SECID46"
 .cindex "configuration file" "conditional skips"
 .cindex "&`.ifdef`&"
 .section "Conditional skips in the configuration file" "SECID46"
 .cindex "configuration file" "conditional skips"
 .cindex "&`.ifdef`&"


@@ -7092,7 +7124,7 @@ Retries for the dnsdb lookup can be controlled by a retry modifier.
 The form if &"retry_VAL"& where VAL is an integer.
 The default count is set by the main configuration option &%dns_retry%&.
 
 The form if &"retry_VAL"& where VAL is an integer.
 The default count is set by the main configuration option &%dns_retry%&.
 

-.cindex cacheing "of dns lookup"
+.cindex caching "of dns lookup"

 .cindex TTL "of dns lookup"
 .cindex DNS TTL
 Dnsdb lookup results are cached within a single process (and its children).
 .cindex TTL "of dns lookup"
 .cindex DNS TTL
 Dnsdb lookup results are cached within a single process (and its children).


@@ -9089,7 +9121,7 @@ If the ACL returns defer the result is a forced-fail.  Otherwise the expansion f
 
 .vitem "&*${certextract{*&<&'field'&>&*}{*&<&'certificate'&>&*}&&&
        {*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
 
 .vitem "&*${certextract{*&<&'field'&>&*}{*&<&'certificate'&>&*}&&&
        {*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"

-.cindex "expansion" "extracting cerificate fields"
+.cindex "expansion" "extracting certificate fields"

 .cindex "&%certextract%&" "certificate fields"
 .cindex "certificate" "extracting fields"
 The <&'certificate'&> must be a variable of type certificate.
 .cindex "&%certextract%&" "certificate fields"
 .cindex "certificate" "extracting fields"
 The <&'certificate'&> must be a variable of type certificate.


@@ -9406,12 +9438,19 @@ message, and any that are added by an ACL statement or by a system
 filter. Header lines that are added to a particular copy of a message by a
 router or transport are not accessible.
 
 filter. Header lines that are added to a particular copy of a message by a
 router or transport are not accessible.
 

-For incoming SMTP messages, no header lines are visible in ACLs that are obeyed
-before the DATA ACL, because the header structure is not set up until the
-message is received. Header lines that are added in a RCPT ACL (for example)
+For incoming SMTP messages, no header lines are visible in
+.new
+ACLs that are obeyed before the data phase completes,
+.wen
+because the header structure is not set up until the message is received.
+They are visible in DKIM, PRDR and DATA ACLs.
+Header lines that are added in a RCPT ACL (for example)

 are saved until the message's incoming header lines are available, at which
 are saved until the message's incoming header lines are available, at which

-point they are added. When a DATA ACL is running, however, header lines added
-by earlier ACLs are visible.
+point they are added.
+.new
+When any of the above ACLs ar
+.wen
+running, however, header lines added by earlier ACLs are visible.

 
 Upper case and lower case letters are synonymous in header names. If the
 following character is white space, the terminating colon may be omitted, but
 
 Upper case and lower case letters are synonymous in header names. If the
 following character is white space, the terminating colon may be omitted, but


@@ -12195,7 +12234,7 @@ normally the gid of the Exim user.
 .cindex "uid (user id)" "of originating user"
 .cindex "sender" "uid"
 .vindex "&$caller_uid$&"
 .cindex "uid (user id)" "of originating user"
 .cindex "sender" "uid"
 .vindex "&$caller_uid$&"

-.vindex "&$originaltor_uid$&"
+.vindex "&$originator_uid$&"

 The value of &$caller_uid$& that was set when the message was received. For
 messages received via the command line, this is the uid of the sending user.
 For messages received by SMTP over TCP/IP, this is normally the uid of the Exim
 The value of &$caller_uid$& that was set when the message was received. For
 messages received via the command line, this is the uid of the sending user.
 For messages received by SMTP over TCP/IP, this is normally the uid of the Exim


@@ -12596,6 +12635,13 @@ validating resolver (e.g. unbound, or bind with suitable configuration).
 If you have changed &%host_lookup_order%& so that &`bydns`& is not the first
 mechanism in the list, then this variable will be false.
 
 If you have changed &%host_lookup_order%& so that &`bydns`& is not the first
 mechanism in the list, then this variable will be false.
 

+.new
+This requires that your system resolver library support EDNS0 (and that
+DNSSEC flags exist in the system headers).  If the resolver silently drops
+all EDNS0 options, then this will have no effect.  OpenBSD's asr resolver
+is known to currently ignore EDNS0, documented in CAVEATS of asr_run(3).
+.wen
+

 
 .vitem &$sender_host_name$&
 .vindex "&$sender_host_name$&"
 
 .vitem &$sender_host_name$&
 .vindex "&$sender_host_name$&"


@@ -12817,7 +12863,7 @@ If TLS has not been negotiated, the value will be 0.
 
 .vitem &$tls_in_ourcert$&
 .vindex "&$tls_in_ourcert$&"
 
 .vitem &$tls_in_ourcert$&
 .vindex "&$tls_in_ourcert$&"

-.cindex certificate veriables
+.cindex certificate variables

 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
 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


@@ -13088,7 +13134,7 @@ initial startup, even if &%perl_at_start%& is set.
 .oindex "&%perl_taintmode%&"
 .cindex "Perl" "taintmode"
 To provide more security executing Perl code via the embedded Perl
 .oindex "&%perl_taintmode%&"
 .cindex "Perl" "taintmode"
 To provide more security executing Perl code via the embedded Perl

-interpeter, the &%perl_taintmode%& option can be set. This enables the
+interpreter, the &%perl_taintmode%& option can be set. This enables the

 taint mode of the Perl interpreter. You are encouraged to set this
 option to a true value. To avoid breaking existing installations, it
 defaults to false.
 taint mode of the Perl interpreter. You are encouraged to set this
 option to a true value. To avoid breaking existing installations, it
 defaults to false.


@@ -13572,6 +13618,7 @@ listed in more than one group.
 .row &%slow_lookup_log%&             "control logging of slow DNS lookups"
 .row &%syslog_duplication%&          "controls duplicate log lines on syslog"
 .row &%syslog_facility%&             "set syslog &""facility""& field"
 .row &%slow_lookup_log%&             "control logging of slow DNS lookups"
 .row &%syslog_duplication%&          "controls duplicate log lines on syslog"
 .row &%syslog_facility%&             "set syslog &""facility""& field"

+.row &%syslog_pid%&                  "pid in syslog lines"

 .row &%syslog_processname%&          "set syslog &""ident""& field"
 .row &%syslog_timestamp%&            "timestamp syslog lines"
 .row &%write_rejectlog%&             "control use of message log"
 .row &%syslog_processname%&          "set syslog &""ident""& field"
 .row &%syslog_timestamp%&            "timestamp syslog lines"
 .row &%write_rejectlog%&             "control use of message log"


@@ -14008,6 +14055,7 @@ acknowledgment is sent. See chapter &<<CHAPACL>>& for further details.
 .option acl_smtp_dkim main string&!! unset
 .cindex DKIM "ACL for"
 This option defines the ACL that is run for each DKIM signature
 .option acl_smtp_dkim main string&!! unset
 .cindex DKIM "ACL for"
 This option defines the ACL that is run for each DKIM signature

+(by default, or as specified in the dkim_verify_signers option)

 of a received message.
 See chapter &<<CHAPdkim>>& for further details.
 
 of a received message.
 See chapter &<<CHAPdkim>>& for further details.
 


@@ -14404,7 +14452,7 @@ it obviously cannot send an error message of any kind.
 .new
 There is a slight performance penalty for these checks.
 Versions of Exim preceding 4.88 had these disabled by default;
 .new
 There is a slight performance penalty for these checks.
 Versions of Exim preceding 4.88 had these disabled by default;

-high-rate intallations confident they will never run out of resources
+high-rate installations confident they will never run out of resources

 may wish to deliberately disable them.
 .wen
 
 may wish to deliberately disable them.
 .wen
 


@@ -14666,6 +14714,7 @@ record in the authoritative section is used instead.
 .option dns_use_edns0 main integer -1
 .cindex "DNS" "resolver options"
 .cindex "DNS" "EDNS0"
 .option dns_use_edns0 main integer -1
 .cindex "DNS" "resolver options"
 .cindex "DNS" "EDNS0"

+.cindex "DNS" "OpenBSD

 If this option is set to a non-negative number then Exim will initialise the
 DNS resolver library to either use or not use EDNS0 extensions, overriding
 the system default. A value of 0 coerces EDNS0 off, a value of 1 coerces EDNS0
 If this option is set to a non-negative number then Exim will initialise the
 DNS resolver library to either use or not use EDNS0 extensions, overriding
 the system default. A value of 0 coerces EDNS0 off, a value of 1 coerces EDNS0


@@ -14673,6 +14722,12 @@ on.
 
 If the resolver library does not support EDNS0 then this option has no effect.
 
 
 If the resolver library does not support EDNS0 then this option has no effect.
 

+.new
+OpenBSD's asr resolver routines are known to ignore the EDNS0 option; this
+means that DNSSEC will not work with Exim on that platform either, unless Exim
+is linked against an alternative DNS client library.
+.wen
+

 
 .option drop_cr main boolean false
 This is an obsolete option that is now a no-op. It used to affect the way Exim
 
 .option drop_cr main boolean false
 This is an obsolete option that is now a no-op. It used to affect the way Exim


@@ -14771,7 +14826,7 @@ not used.
 .option event_action main string&!! unset
 .cindex events
 This option declares a string to be expanded for Exim's events mechanism.
 .option event_action main string&!! unset
 .cindex events
 This option declares a string to be expanded for Exim's events mechanism.

-For details see &<<CHAPevents>>&.
+For details see chapter &<<CHAPevents>>&.

 
 
 .option exim_group main string "compile-time configured"
 
 
 .option exim_group main string "compile-time configured"


@@ -15122,7 +15177,7 @@ If the &%smtp_connection%& log selector is not set, this option has no effect.
 .option hosts_proxy main "host list&!!" unset
 .cindex proxy "proxy protocol"
 This option enables use of Proxy Protocol proxies for incoming
 .option hosts_proxy main "host list&!!" unset
 .cindex proxy "proxy protocol"
 This option enables use of Proxy Protocol proxies for incoming

-connections.  For details see &<<SECTproxyInbound>>&.
+connections.  For details see section &<<SECTproxyInbound>>&.

 
 
 .option hosts_treat_as_local main "domain list&!!" unset
 
 
 .option hosts_treat_as_local main "domain list&!!" unset


@@ -15296,6 +15351,9 @@ connecting on a regular LDAP port.  This is the LDAP equivalent of SMTP's
 of SSL-on-connect.
 In the event of failure to negotiate TLS, the action taken is controlled
 by &%ldap_require_cert%&.
 of SSL-on-connect.
 In the event of failure to negotiate TLS, the action taken is controlled
 by &%ldap_require_cert%&.

+.new
+This option is ignored for &`ldapi`& connections.
+.wen

 
 
 .option ldap_version main integer unset
 
 
 .option ldap_version main integer unset


@@ -16714,7 +16772,7 @@ example, instead of &"Administrative prohibition"&, it might give:
 .option smtputf8_advertise_hosts main "host list&!!" *
 .cindex "SMTPUTF8" "advertising"
 When Exim is built with support for internationalised mail names,
 .option smtputf8_advertise_hosts main "host list&!!" *
 .cindex "SMTPUTF8" "advertising"
 When Exim is built with support for internationalised mail names,

-the availability therof is advertised in
+the availability thereof is advertised in

 response to EHLO only to those client hosts that match this option. See
 chapter &<<CHAPi18n>>& for details of Exim's support for internationalisation.
 
 response to EHLO only to those client hosts that match this option. See
 chapter &<<CHAPi18n>>& for details of Exim's support for internationalisation.
 


@@ -16835,6 +16893,15 @@ If this option is unset, &"mail"& is used. See chapter &<<CHAPlog>>& for
 details of Exim's logging.
 
 
 details of Exim's logging.
 
 

+.option syslog_pid main boolean true
+.cindex "syslog" "pid"
+If &%syslog_pid%& is set false, the PID on Exim's log lines are
+omitted when these lines are sent to syslog. (Syslog normally prefixes
+the log lines with the PID of the logging process automatically.) You need
+to enable the &`+pid`& log selector item, if you want Exim to write it's PID
+into the logs.) See chapter &<<CHAPlog>>& for details of Exim's logging.
+
+

 
 .option syslog_processname main string &`exim`&
 .cindex "syslog" "process name; setting"
 
 .option syslog_processname main string &`exim`&
 .cindex "syslog" "process name; setting"


@@ -16862,6 +16929,9 @@ generates any deliveries to files or pipes, or any new mail messages, the
 appropriate &%system_filter_..._transport%& option(s) must be set, to define
 which transports are to be used. Details of this facility are given in chapter
 &<<CHAPsystemfilter>>&.
 appropriate &%system_filter_..._transport%& option(s) must be set, to define
 which transports are to be used. Details of this facility are given in chapter
 &<<CHAPsystemfilter>>&.

+.new
+A forced expansion failure results in no filter operation.
+.wen

 
 
 .option system_filter_directory_transport main string&!! unset
 
 
 .option system_filter_directory_transport main string&!! unset


@@ -17034,7 +17104,15 @@ larger prime than requested.
 The value of this option is expanded and indicates the source of DH parameters
 to be used by Exim.
 
 The value of this option is expanded and indicates the source of DH parameters
 to be used by Exim.
 

-If it is a filename starting with a &`/`&, then it names a file from which DH
+.new
+&*Note: The Exim Maintainers strongly recommend using a filename with site-generated
+local DH parameters*&, which has been supported across all versions of Exim.  The
+other specific constants available are a fallback so that even when
+"unconfigured", Exim can offer Perfect Forward Secrecy in older ciphersuites in TLS.
+.wen
+
+If &%tls_dhparam%& is a filename starting with a &`/`&,
+then it names a file from which DH

 parameters should be loaded.  If the file exists, it should hold a PEM-encoded
 PKCS#3 representation of the DH prime.  If the file does not exist, for
 OpenSSL it is an error.  For GnuTLS, Exim will attempt to create the file and
 parameters should be loaded.  If the file exists, it should hold a PEM-encoded
 PKCS#3 representation of the DH prime.  If the file does not exist, for
 OpenSSL it is an error.  For GnuTLS, Exim will attempt to create the file and


@@ -17050,23 +17128,39 @@ Exim will attempt to load a file from inside the spool directory.  If the file
 does not exist, Exim will attempt to create it.
 See section &<<SECTgnutlsparam>>& for further details.
 
 does not exist, Exim will attempt to create it.
 See section &<<SECTgnutlsparam>>& for further details.
 

+.new

 If Exim is using OpenSSL and this option is empty or unset, then Exim will load
 If Exim is using OpenSSL and this option is empty or unset, then Exim will load

-a default DH prime; the default is the 2048 bit prime described in section
+a default DH prime; the default is Exim-specific but lacks verifiable provenance.
+
+In older versions of Exim the default was the 2048 bit prime described in section

 2.2 of RFC 5114, "2048-bit MODP Group with 224-bit Prime Order Subgroup", which
 in IKE is assigned number 23.
 
 Otherwise, the option must expand to the name used by Exim for any of a number
 2.2 of RFC 5114, "2048-bit MODP Group with 224-bit Prime Order Subgroup", which
 in IKE is assigned number 23.
 
 Otherwise, the option must expand to the name used by Exim for any of a number

-of DH primes specified in RFC 2409, RFC 3526 and RFC 5114.  As names, Exim uses
-"ike" followed by the number used by IKE, or "default" which corresponds to
-"ike23".
+of DH primes specified in RFC 2409, RFC 3526, RFC 5114, RFC 7919, or from other
+sources.  As names, Exim uses a standard specified name, else "ike" followed by
+the number used by IKE, or "default" which corresponds to
+&`exim.dev.20160529.3`&.

 
 

-The available primes are:
+The available standard primes are:
+&`ffdhe2048`&, &`ffdhe3072`&, &`ffdhe4096`&, &`ffdhe6144`&, &`ffdhe8192`&,

 &`ike1`&, &`ike2`&, &`ike5`&,
 &`ike14`&, &`ike15`&, &`ike16`&, &`ike17`&, &`ike18`&,
 &`ike1`&, &`ike2`&, &`ike5`&,
 &`ike14`&, &`ike15`&, &`ike16`&, &`ike17`&, &`ike18`&,

-&`ike22`&, &`ike23`& (aka &`default`&) and &`ike24`&.
+&`ike22`&, &`ike23`& and &`ike24`&.
+
+The available additional primes are:
+&`exim.dev.20160529.1`&, &`exim.dev.20160529.2`& and &`exim.dev.20160529.3`&.

 
 Some of these will be too small to be accepted by clients.
 Some may be too large to be accepted by clients.
 
 Some of these will be too small to be accepted by clients.
 Some may be too large to be accepted by clients.

+The open cryptographic community has suspicions about the integrity of some
+of the later IKE values, which led into RFC7919 providing new fixed constants
+(the "ffdhe" identifiers).
+
+At this point, all of the "ike" values should be considered obsolete;
+they're still in Exim to avoid breaking unusual configurations, but are
+candidates for removal the next time we have backwards-incompatible changes.
+.wen

 
 The TLS protocol does not negotiate an acceptable size for this; clients tend
 to hard-drop connections if what is offered by the server is unacceptable,
 
 The TLS protocol does not negotiate an acceptable size for this; clients tend
 to hard-drop connections if what is offered by the server is unacceptable,


@@ -17084,17 +17178,19 @@ prior to the 4.80 release, as Debian used to patch Exim to raise the minimum
 acceptable bound from 1024 to 2048.
 
 
 acceptable bound from 1024 to 2048.
 
 

-.option tls_eccurve main string&!! prime256v1
+.option tls_eccurve main string&!! &`auto`&

 .cindex TLS "EC cryptography"
 .cindex TLS "EC cryptography"

-If built with a recent-enough version of OpenSSL,
-this option selects a EC curve for use by Exim.
+This option selects a EC curve for use by Exim.
+
+After expansion it must contain a valid EC curve parameter, such as
+&`prime256v1`&, &`secp384r1`&, or &`P-512`&. Consult your OpenSSL manual
+for valid selections.

 
 

-Curve names of the form &'prime256v1'& are accepted.
-For even more-recent library versions, names of the form &'P-512'&
-are also accepted, plus the special value &'auto'&
-which tells the library to choose.
+For OpenSSL versions before (and not including) 1.0.2, the string
+&`auto`& selects &`prime256v1`&. For more recent OpenSSL versions
+&`auto`& tells the library to choose.

 
 

-If the option is set to an empty string, no EC curves will be enabled.
+If the option expands to an empty string, no EC curves will be enabled.

 
 
 .option tls_ocsp_file main string&!! unset
 
 
 .option tls_ocsp_file main string&!! unset


@@ -20863,7 +20959,7 @@ resent to other recipients.
 .option event_action transports string&!! unset
 .cindex events
 This option declares a string to be expanded for Exim's events mechanism.
 .option event_action transports string&!! unset
 .cindex events
 This option declares a string to be expanded for Exim's events mechanism.

-For details see &<<CHAPevents>>&.
+For details see chapter &<<CHAPevents>>&.

 
 
 .option group transports string&!! "Exim group"
 
 
 .option group transports string&!! "Exim group"


@@ -20978,7 +21074,7 @@ The control does not apply to shadow transports.
 
 .cindex "hints database" "transport concurrency control"
 Exim implements this control by means of a hints database in which a record is
 
 .cindex "hints database" "transport concurrency control"
 Exim implements this control by means of a hints database in which a record is

-incremented whenever a transport process is beaing created. The record
+incremented whenever a transport process is being created. The record

 is decremented and possibly removed when the process terminates.
 Obviously there is scope for
 records to get left lying around if there is a system or program crash. To
 is decremented and possibly removed when the process terminates.
 Obviously there is scope for
 records to get left lying around if there is a system or program crash. To


@@ -23235,12 +23331,12 @@ message_suffix =
 &`\n`& to &`\r\n`& in &%message_suffix%&.
 
 
 &`\n`& to &`\r\n`& in &%message_suffix%&.
 
 

-.option path pipe string "see below"
-This option specifies the string that is set up in the PATH environment
-variable of the subprocess. The default is:
-.code
-/bin:/usr/bin
-.endd
+.option path pipe string&!! "/bin:/usr/bin"
+.new
+This option is expanded and
+.wen
+specifies the string that is set up in the PATH environment
+variable of the subprocess.

 If the &%command%& option does not yield an absolute path name, the command is
 sought in the PATH directories, in the usual way. &*Warning*&: This does not
 apply to a command specified as a transport filter.
 If the &%command%& option does not yield an absolute path name, the command is
 sought in the PATH directories, in the usual way. &*Warning*&: This does not
 apply to a command specified as a transport filter.


@@ -23625,7 +23721,7 @@ of the message. Its value must not be zero. See also &%final_timeout%&.
 .option dkim_canon smtp string&!! unset
 .option dkim_strict smtp string&!! unset
 .option dkim_sign_headers smtp string&!! unset
 .option dkim_canon smtp string&!! unset
 .option dkim_strict smtp string&!! unset
 .option dkim_sign_headers smtp string&!! unset

-DKIM signing options.  For details see &<<SECDKIMSIGN>>&.
+DKIM signing options.  For details see section &<<SECDKIMSIGN>>&.

 
 
 .option delay_after_cutoff smtp boolean true
 
 
 .option delay_after_cutoff smtp boolean true


@@ -23941,9 +24037,28 @@ unauthenticated. See also &%hosts_require_auth%&, and chapter
 .cindex CHUNKING "enabling, in client"
 .cindex BDAT "SMTP command"
 .cindex "RFC 3030" "CHUNKING"
 .cindex CHUNKING "enabling, in client"
 .cindex BDAT "SMTP command"
 .cindex "RFC 3030" "CHUNKING"

-This option provides a list of server to which, provided they announce
+This option provides a list of servers to which, provided they announce

 CHUNKING support, Exim will attempt to use BDAT commands rather than DATA.
 CHUNKING support, Exim will attempt to use BDAT commands rather than DATA.

-BDAT will not be used in conjuction with a transport filter.
+BDAT will not be used in conjunction with a transport filter.
+.wen
+
+.new
+.option hosts_try_fastopen smtp "host list!!" unset
+.cindex "fast open, TCP" "enabling, in client"
+.cindex "TCP Fast Open" "enabling, in client"
+.cindex "RFC 7413" "TCP Fast Open"
+This option provides a list of servers to which, provided
+the facility is supported by this system, Exim will attempt to
+perform a TCP Fast Open.
+No data is sent on the SYN segment but, if the remote server also
+supports the facility, it can send its SMTP banner immediately after
+the SYN,ACK segment.  This can save up to one round-trip time.
+
+The facility is only active for previously-contacted servers,
+as the initiator must present a cookie in the SYN segment.
+
+On (at least some) current Linux distributions the facility must be enabled
+in the kernel by the sysadmin before the support is usable.

 .wen
 
 .option hosts_try_prdr smtp "host list&!!" *
 .wen
 
 .option hosts_try_prdr smtp "host list&!!" *


@@ -24116,7 +24231,7 @@ the use of the SIZE option altogether.
 .option socks_proxy smtp string&!! unset
 .cindex proxy SOCKS
 This option enables use of SOCKS proxies for connections made by the
 .option socks_proxy smtp string&!! unset
 .cindex proxy SOCKS
 This option enables use of SOCKS proxies for connections made by the

-transport.  For details see &<<SECTproxySOCKS>>&.
+transport.  For details see section &<<SECTproxySOCKS>>&.

 
 
 .option tls_certificate smtp string&!! unset
 
 
 .option tls_certificate smtp string&!! unset


@@ -25821,6 +25936,19 @@ turned into a permanent error if you wish. In the second case, Exim tries to
 deliver the message unauthenticated.
 .endlist
 
 deliver the message unauthenticated.
 .endlist
 

+.new
+Note that the hostlist test for whether to do authentication can be
+confused if name-IP lookups change between the time the peer is decided
+on and the transport running.  For example, with a manualroute
+router given a host name, and DNS "round-robin" use by that name: if
+the local resolver cache times out between the router and the transport
+running, the transport may get an IP for the name for its authentication
+check which does not match the connection peer IP.
+No authentication will then be done, despite the names being identical.
+
+For such cases use a separate transport which always authenticates.
+.wen
+

 .cindex "AUTH" "on MAIL command"
 When Exim has authenticated itself to a remote server, it adds the AUTH
 parameter to the MAIL commands it sends, if it has an authenticated sender for
 .cindex "AUTH" "on MAIL command"
 When Exim has authenticated itself to a remote server, it adds the AUTH
 parameter to the MAIL commands it sends, if it has an authenticated sender for


@@ -26730,7 +26858,7 @@ tls:
 .endd
 This accepts a client certificate that is verifiable against any
 of your configured trust-anchors
 .endd
 This accepts a client certificate that is verifiable against any
 of your configured trust-anchors

-which usually means the full set of public CAs)
+(which usually means the full set of public CAs)

 and which has a SAN with a good account name.
 Note that the client cert is on the wire in-clear, including the SAN,
 whereas a plaintext SMTP AUTH done inside TLS is not.
 and which has a SAN with a good account name.
 Note that the client cert is on the wire in-clear, including the SAN,
 whereas a plaintext SMTP AUTH done inside TLS is not.


@@ -27492,8 +27620,13 @@ during TLS session handshake, to permit alternative values to be chosen:
 
 Great care should be taken to deal with matters of case, various injection
 attacks in the string (&`../`& or SQL), and ensuring that a valid filename
 
 Great care should be taken to deal with matters of case, various injection
 attacks in the string (&`../`& or SQL), and ensuring that a valid filename

-can always be referenced; it is important to remember that &$tls_sni$& is
+can always be referenced; it is important to remember that &$tls_in_sni$& is

 arbitrary unverified data provided prior to authentication.
 arbitrary unverified data provided prior to authentication.

+.new
+Further, the initial certificate is loaded before SNI is arrived, so
+an expansion for &%tls_certificate%& must have a default which is used
+when &$tls_in_sni$& is empty.
+.wen

 
 The Exim developers are proceeding cautiously and so far no other TLS options
 are re-expanded.
 
 The Exim developers are proceeding cautiously and so far no other TLS options
 are re-expanded.


@@ -28037,6 +28170,11 @@ run. A &"discard"& return from the DATA or the non-SMTP ACL discards all the
 remaining recipients. The &"discard"& return is not permitted for the
 &%acl_smtp_predata%& ACL.
 
 remaining recipients. The &"discard"& return is not permitted for the
 &%acl_smtp_predata%& ACL.
 

+.new
+If the ACL for VRFY returns &"accept"&, a recipient verify (without callout)
+is done on the address and the result determines the SMTP response.
+.wen
+

 
 .cindex "&[local_scan()]& function" "when all recipients discarded"
 The &[local_scan()]& function is always run, even if there are no remaining
 
 .cindex "&[local_scan()]& function" "when all recipients discarded"
 The &[local_scan()]& function is always run, even if there are no remaining


@@ -28858,7 +28996,11 @@ message body.
 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.
 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 received with the SMTP PRDR option in use.
+It is not supported for messages received with the SMTP PRDR
+.new
+or CHUNKING
+.wen
+options 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.
 
 Should the ultimate destination system positively accept or reject the mail,
 a corresponding indication is given to the source system and nothing is queued.


@@ -28873,7 +29015,7 @@ This behaviour can be adjusted by appending the option &*defer=*&<&'value'&>
 to the control; the default value is &"spool"& and the alternate value
 &"pass"& copies an SMTP defer response from the target back to the initiator
 and does not queue the message.
 to the control; the default value is &"spool"& and the alternate value
 &"pass"& copies an SMTP defer response from the target back to the initiator
 and does not queue the message.

-Note that this is independent of any receipient verify conditions in the ACL.
+Note that this is independent of any recipient verify conditions in the ACL.

 .wen
 
 Delivery in this mode avoids the generation of a bounce mail to a
 .wen
 
 Delivery in this mode avoids the generation of a bounce mail to a


@@ -29100,7 +29242,7 @@ 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
 to a-label form.
 .vitem &*control&~=&~utf8_downconvert*&
 This control enables conversion of UTF-8 in message addresses
 to a-label form.

-For details see &<<SECTi18nMTA>>&.
+For details see section &<<SECTi18nMTA>>&.

 .endlist vlist
 
 
 .endlist vlist
 
 


@@ -29713,6 +29855,15 @@ to avoid doing it more than once per message.
 .cindex "&%verify%& ACL condition"
 This is a variation of the previous option, in which a modified address is
 verified as a sender.
 .cindex "&%verify%& ACL condition"
 This is a variation of the previous option, in which a modified address is
 verified as a sender.

+
+.new
+Note that '/' is legal in local-parts; if the address may have such
+(eg. is generated from the received message)
+they must be protected from the options parsing by doubling:
+.code
+verify = sender=${sg{${address:$h_sender:}}{/}{//}}
+.endd
+.wen

 .endlist
 
 
 .endlist
 
 


@@ -29772,7 +29923,7 @@ deny  dnslists = blackholes.mail-abuse.org
 warn  message  = X-Warn: sending host is on dialups list
       dnslists = dialups.mail-abuse.org
 .endd
 warn  message  = X-Warn: sending host is on dialups list
       dnslists = dialups.mail-abuse.org
 .endd

-.cindex cacheing "of dns lookup"
+.cindex caching "of dns lookup"

 .cindex DNS TTL
 DNS list lookups are cached by Exim for the duration of the SMTP session
 (but limited by the DNS return TTL value),
 .cindex DNS TTL
 DNS list lookups are cached by Exim for the duration of the SMTP session
 (but limited by the DNS return TTL value),


@@ -29885,7 +30036,7 @@ multiple DNS records. The inner dnsdb lookup produces a list of MX hosts
 and the outer dnsdb lookup finds the IP addresses for these hosts. The result
 of expanding the condition might be something like this:
 .code
 and the outer dnsdb lookup finds the IP addresses for these hosts. The result
 of expanding the condition might be something like this:
 .code

-dnslists = sbl.spahmaus.org/<|192.168.2.3|192.168.5.6|...
+dnslists = sbl.spamhaus.org/<|192.168.2.3|192.168.5.6|...

 .endd
 Thus, this example checks whether or not the IP addresses of the sender
 domain's mail servers are on the Spamhaus black list.
 .endd
 Thus, this example checks whether or not the IP addresses of the sender
 domain's mail servers are on the Spamhaus black list.


@@ -31589,6 +31740,15 @@ configuration as follows (example):
 .code
 spamd_address = 192.168.99.45 387
 .endd
 .code
 spamd_address = 192.168.99.45 387
 .endd

+The SpamAssassin protocol relies on a TCP half-close from the client.
+If your SpamAssassin client side is running a Linux system with an
+iptables firewall, consider setting
+&%net.netfilter.nf_conntrack_tcp_timeout_close_wait%& to at least the
+timeout, Exim uses when waiting for a response from the SpamAssassin
+server (currently defaulting to 120s).  With a lower value the Linux
+connection tracking may consider your half-closed connection as dead too
+soon.
+

 
 To use Rspamd (which by default listens on all local addresses
 on TCP port 11333)
 
 To use Rspamd (which by default listens on all local addresses
 on TCP port 11333)


@@ -36002,7 +36162,7 @@ off the &%outgoing_interface%& option.
 .next
 .cindex "log" "outgoing remote port"
 .cindex "port" "logging outgoint remote"
 .next
 .cindex "log" "outgoing remote port"
 .cindex "port" "logging outgoint remote"

-.cindex "TCP/IP" "logging ougtoing remote port"
+.cindex "TCP/IP" "logging outgoing remote port"

 &%outgoing_port%&: The remote port number is added to delivery log lines (those
 containing => tags) following the IP address.
 The local port is also added if &%incoming_interface%& and
 &%outgoing_port%&: The remote port number is added to delivery log lines (those
 containing => tags) following the IP address.
 The local port is also added if &%incoming_interface%& and


@@ -37831,9 +37991,8 @@ lock will be lost at the instant of rename.
 .next
 .vindex "&$body_linecount$&"
 If you change the number of lines in the file, the value of
 .next
 .vindex "&$body_linecount$&"
 If you change the number of lines in the file, the value of

-&$body_linecount$&, which is stored in the -H file, will be incorrect. At
-present, this value is not used by Exim, but there is no guarantee that this
-will always be the case.
+&$body_linecount$&, which is stored in the -H file, will be incorrect and can
+cause incomplete transmission of messages or undeliverable messages.

 .next
 If the message is in MIME format, you must take care not to break it.
 .next
 .next
 If the message is in MIME format, you must take care not to break it.
 .next


@@ -38177,6 +38336,7 @@ These options take (expandable) strings as arguments.
 MANDATORY:
 The domain you want to sign with. The result of this expanded
 option is put into the &%$dkim_domain%& expansion variable.
 MANDATORY:
 The domain you want to sign with. The result of this expanded
 option is put into the &%$dkim_domain%& expansion variable.

+If it is empty after expansion, DKIM signing is not done.

 
 .option dkim_selector smtp string&!! unset
 MANDATORY:
 
 .option dkim_selector smtp string&!! unset
 MANDATORY:


@@ -38449,9 +38609,9 @@ To include this support, include &"SUPPORT_PROXY=yes"&
 in Local/Makefile.
 
 It was built on specifications from:
 in Local/Makefile.
 
 It was built on specifications from:

-http://haproxy.1wt.eu/download/1.5/doc/proxy-protocol.txt
+(&url(http://haproxy.1wt.eu/download/1.5/doc/proxy-protocol.txt)).

 That URL was revised in May 2014 to version 2 spec:
 That URL was revised in May 2014 to version 2 spec:

-http://git.1wt.eu/web?p=haproxy.git;a=commitdiff;h=afb768340c9d7e50d8e
+(&url(http://git.1wt.eu/web?p=haproxy.git;a=commitdiff;h=afb768340c9d7e50d8e)).

 
 The purpose of this facility is so that an application load balancer,
 such as HAProxy, can sit in front of several Exim servers
 
 The purpose of this facility is so that an application load balancer,
 such as HAProxy, can sit in front of several Exim servers


@@ -38587,6 +38747,12 @@ Exim has support for Internationalised mail names.
 To include this it must be built with SUPPORT_I18N and the libidn library.
 Standards supported are RFCs 2060, 5890, 6530 and 6533.
 
 To include this it must be built with SUPPORT_I18N and the libidn library.
 Standards supported are RFCs 2060, 5890, 6530 and 6533.
 

+.new
+If Exim is built with SUPPORT_I18N_2008 (in addition to SUPPORT_I18N, not
+instead of it) then IDNA2008 is supported; this adds an extra library
+requirement, upon libidn2.
+.wen
+

 .section "MTA operations" SECTi18nMTA
 .cindex SMTPUTF8 "ESMTP option"
 The main configuration option &%smtputf8_advertise_hosts%& specifies
 .section "MTA operations" SECTi18nMTA
 .cindex SMTPUTF8 "ESMTP option"
 The main configuration option &%smtputf8_advertise_hosts%& specifies


@@ -38700,7 +38866,7 @@ must be representable in UTF-16.
 .cindex events
 
 The events mechanism in Exim can be used to intercept processing at a number
 .cindex events
 
 The events mechanism in Exim can be used to intercept processing at a number

-of points.  It was originally invented to giave a way to do customised logging
+of points.  It was originally invented to give a way to do customised logging

 actions (for example, to a database) but can also be used to modify some
 processing actions.
 
 actions (for example, to a database) but can also be used to modify some
 processing actions.
 


@@ -38759,7 +38925,7 @@ can be used to affect that action (more on this below).
 An additional variable, &$event_data$&, is filled with information varying
 with the event type:
 .display
 An additional variable, &$event_data$&, is filled with information varying
 with the event type:
 .display

-&`msg:delivery         `& smtp confirmation mssage
+&`msg:delivery         `& smtp confirmation message

 &`msg:rcpt:host:defer  `& error string
 &`msg:rcpt:defer       `& error string
 &`msg:host:defer       `& error string
 &`msg:rcpt:host:defer  `& error string
 &`msg:rcpt:defer       `& error string
 &`msg:host:defer       `& error string


@@ -38770,7 +38936,7 @@ with the event type:
 The :defer events populate one extra variable: &$event_defer_errno$&.
 
 For complex operations an ACL expansion can be used in &%event_action%&
 The :defer events populate one extra variable: &$event_defer_errno$&.
 
 For complex operations an ACL expansion can be used in &%event_action%&

-however due to the multiple contextx that Exim operates in during
+however due to the multiple contexts that Exim operates in during

 the course of its processing:
 .ilist
 variables set in transport events will not be visible outside that
 the course of its processing:
 .ilist
 variables set in transport events will not be visible outside that