-$Cambridge: exim/doc/doc-txt/experimental-spec.txt,v 1.3 2005/06/27 18:32:20 tom Exp $
-
From time to time, experimental features may be added to Exim.
While a feature is experimental, there will be a build-time
option whose name starts "EXPERIMENTAL_" that must be set in
order to include the feature. This file contains information
-about experimenatal features, all of which are unstable and
-liable to incompatibile change.
-
+about experimental features, all of which are unstable and
+liable to incompatible change.
-1. Yahoo DomainKeys support
---------------------------------------------------------------
-
-DomainKeys (DK) support is built into Exim using the
-"libdomainkeys" reference library implementation. It is
-available at
-
-http://domainkeys.sf.net
-
-You must build this library on your system and compile Exim
-against it. To build Exim with DK support, add these lines to
-your Local/Makefile:
-
-EXPERIMENTAL_DOMAINKEYS=yes
-CFLAGS += -I/home/tom/exim-cvs/extra/libdomainkeys
-LDFLAGS += -ldomainkeys -L/home/tom/exim-cvs/extra/libdomainkeys
-
-Remember to tweak the CFLAGS and LDFLAGS lines to match the
-location of the libdomainkeys includes and lib on your system.
-
-The current experimental implementation supports two
-independent functions:
-
-o Validate incoming DK-signed email.
-o Sign outgoing email with DK.
-
-The former is implemented in the ACLs for SMTP, the latter as
-an extension to the SMTP transport. That means both facilities
-are limited to SMTP I/O.
-
-
-
-1) Validate incoming email
-
-Incoming messages are fed to the DK validation process as they
-are received "on the wire". This happens synchronously to
-Exim's buffering of the message in the spool.
-
-You must set "control = dk_verify" in one of the ACLs
-preceding DATA (you will typically use acl_smtp_rcpt), at a
-point where non-local, non-relay, non-submission mail is
-processed. If that control flag is not set, the message will
-NOT be verified.
-
-Example:
-
-warn log_message = Feeding message to DK validator.
- control = dk_verify
-
-You can check for the outcome of the DK check in the ACL after
-data (acl_smtp_data), using a number of ACL conditions and/or
-expansion variables.
-
-
-
-1.1.) DK ACL conditions
-
- dk_sender_domains = <domain list>
-
- This condition takes a domainlist as argument and
- succeeds if the domain that DK has been verifying for is
- found in the list.
-
-
- dk_senders = <address list>
-
- This condition takes an addresslist as argument and
- succeeds if the address that DK has been verifying for
- is found in the list.
-
-
- dk_sender_local_parts = <local part list>
-
- This condition takes a local_part list as argument
- and succeeds if the domain that DK has been
- verifying for is found in the list.
-
-
- dk_status = <colon separated list of keywords>
-
- This condition takes a list of keywords as argument, and
- succeeds if one of the listed keywords matches the outcome
- of the DK check. The available keywords are:
-
- good DK check succeeded, mail is verified.
- bad DK check failed.
- no signature Mail is not signed with DK.
- no key Public key missing in target domain DNS.
- bad format Public key available, but unuseable.
- non-participant Target domain states not to participate in DK.
- revoked The signing key has been revoked by the domain.
-
-
- dk_policy = <colon separated list of keywords>
-
- This condition takes a list of keywords as argument, and
- succeeds if one of the listed keywords matches the policy
- announced by the target domain. The available keywords
- are:
-
- signsall The target domain signs all outgoing email.
- testing The target domain is currently testing DK.
-
-
- dk_domain_source = <colon separated list of keywords>
-
- This condition takes a list of keywords as argument, and
- succeeds if one of the listed keywords matches the
- location where DK found the sender domain it verified for.
- The available keywords are:
-
- from The domain came from the "From:" header.
- sender The domain came from the "Sender:" header.
- none DK was unable to find the responsible domain.
-
-
-
-1.2.) DK verification expansion variables
-
- $dk_sender_domain
-
- Contains the domain that DK has verified for.
-
-
- $dk_sender
-
- Contains the address that DK has verified for.
-
-
- $dk_sender_local_part
-
- Contains the local part that DK has verified for.
-
-
- $dk_sender_source
-
- Contains the "source" of the above three variables, one of
-
- "from" The address came from the "From:" header.
- "sender" The address came from the "Sender:" header.
-
- When DK was unable to find a valid address, this variable
- is "0".
-
-
- $dk_signsall
-
- Is "1" if the target domain signs all outgoing email,
- "0" otherwise.
-
-
- $dk_testing
-
- Is "1" if the target domain is testing DK, "0" otherwise.
-
-
- $dk_is_signed
-
- Is "1" if the message is signed, "0" otherwise.
-
-
- $dk_status
-
- Contains the outcome of the DK check as a string, commonly
- used to add a "DomainKey-Status:" header to messages. Will
- contain one of:
-
- good DK check succeeded, mail is verified.
- bad DK check failed.
- no signature Mail is not signed with DK.
- no key Public key missing in target domain DNS.
- bad format Public key available, but unuseable.
- non-participant Target domain states not to participate in DK.
- revoked The signing key has been revoked by the domain.
-
-
- $dk_result
-
- Contains a human-readable result of the DK check, more
- verbose than $dk_status. Useful for logging purposes.
-
-
-
-2) Sign outgoing email with DK
-
-Outgoing messages are signed just before exim puts them "on
-the wire". The only thing that happens after DK signing is
-eventual TLS encryption.
-
-Signing is implemented by setting private options on the SMTP
-transport. These options take (expandable) strings as
-arguments. The most important variable to use in these
-expansions is $dk_domain. It contains the domain that DK wants
-to sign for.
-
-
- dk_selector = <expanded string> [MANDATORY]
-
- This sets the key selector string. You can use the
- $dk_domain expansion variable to look up a matching
- selector. The result is put in the expansion variable
- $dk_selector which should be used in the dk_private_key
- option along with $dk_domain.
-
-
- dk_private_key = <expanded string> [MANDATORY]
-
- This sets the private key to use. You SHOULD use the
- $dk_domain and $dk_selector expansion variables to
- determine the private key to use. The result can either
-
- o be a valid RSA private key in ASCII armor, including
- line breaks.
- o start with a slash, in which case it is treated as
- a file that contains the private key.
- o be "0", "false" or the empty string, in which case
- the message will not be signed. This case will not
- result in an error, even if dk_strict is set.
-
-
- dk_canon = <expanded string> [OPTIONAL]
-
- This option sets the canonicalization method used when
- signing a message. The DK draft currently supports two
- methods: "simple" and "nofws". The option defaults to
- "simple" when unset.
-
-
- dk_strict = <expanded string> [OPTIONAL]
-
- This option defines how Exim behaves when signing a
- message that should be signed fails for some reason. When
- the expansion evaluates to either "1" or "true", Exim will
- defer. Otherwise Exim will send the message unsigned. You
- can and should use the $dk_domain and $dk_selector
- expansion variables here.
-
-
- dk_domain = <expanded string> [NOT RECOMMENDED]
-
- This option overrides DKs autodetection of the signing
- domain. You should only use this option if you know what
- you are doing. The result of the string expansion is also
- put in $dk_domain.
-
-
-
-
-2. Brighmail AntiSpam (BMI) suppport
+Brightmail AntiSpam (BMI) support
--------------------------------------------------------------
Brightmail AntiSpam is a commercial package. Please see
following steps:
1) Compile Exim with BMI support
- 2) Set up main BMI options (top section of exim config file)
+ 2) Set up main BMI options (top section of Exim config file)
3) Set up ACL control statement (ACL section of the config
file)
4) Set up your routers to use BMI verdicts (routers section
1) Adding support for BMI at compile time
To compile with BMI support, you need to link Exim against
- the Brighmail client SDK, consisting of a library
+ the Brightmail client SDK, consisting of a library
(libbmiclient_single.so) and a header file (bmi_api.h).
You'll also need to explicitly set a flag in the Makefile to
include BMI support in the Exim binary. Both can be achieved
with these lines in Local/Makefile:
EXPERIMENTAL_BRIGHTMAIL=yes
- CFLAGS=-DBRIGHTMAIL -I/path/to/the/dir/with/the/includefile
+ CFLAGS=-I/path/to/the/dir/with/the/includefile
EXTRALIBS_EXIM=-L/path/to/the/dir/with/the/library -lbmiclient_single
If you use other CFLAGS or EXTRALIBS_EXIM settings then
able to find the library file.
-2) Setting up BMI support in the exim main configuration
+2) Setting up BMI support in the Exim main configuration
- To enable BMI support in the main exim configuration, you
+ To enable BMI support in the main Exim configuration, you
should set the path to the main BMI configuration file with
the "bmi_config_file" option, like this:
bmi_config_file = /opt/brightmail/etc/brightmail.cfg
- This must go into section 1 of exims configuration file (You
+ This must go into section 1 of Exim's configuration file (You
can put it right on top). If you omit this option, it
defaults to /opt/brightmail/etc/brightmail.cfg.
an "accept" block in the "acl_check_rcpt" ACL. You should
use the "accept" block(s) that accept messages from remote
servers for your own domain(s). Here is an example that uses
- the "accept" blocks from exims default configuration file:
+ the "accept" blocks from Exim's default configuration file:
accept domains = +local_domains
more "verdicts" are present. Different recipients can have
different verdicts. Each recipient is treated individually
during routing, so you can query the verdicts by recipient
- at that stage. From Exims view, a verdict can have the
+ at that stage. From Exim's view, a verdict can have the
following outcomes:
o deliver the message normally
server and are queried by the BMI server itself. However,
you can also pass opt-in data for each recipient from the
MTA to the BMI server. This is particularly useful if you
- already look up recipient data in exim anyway (which can
+ already look up recipient data in Exim anyway (which can
also be stored in a SQL database or other source). This
implementation enables you to pass opt-in data to the BMI
server in the RCPT ACL. This works by setting the
control = bmi_run
Of course, you can also use any other lookup method that
- exim supports, including LDAP, Postgres, MySQL, Oracle etc.,
+ Exim supports, including LDAP, Postgres, MySQL, Oracle etc.,
as long as the result is a list of colon-separated opt-in
strings.
-3. Sender Policy Framework (SPF) support
+DCC Support
--------------------------------------------------------------
+Distributed Checksum Clearinghouse; http://www.rhyolite.com/dcc/
+
+*) Building exim
+
+In order to build exim with DCC support add
+
+EXPERIMENTAL_DCC=yes
+
+to your Makefile. (Re-)build/install exim. exim -d should show
+EXPERIMENTAL_DCC under "Support for".
+
+
+*) Configuration
+
+In the main section of exim.cf add at least
+ dccifd_address = /usr/local/dcc/var/dccifd
+or
+ dccifd_address = <ip> <port>
+
+In the DATA ACL you can use the new condition
+ dcc = *
+
+After that "$dcc_header" contains the X-DCC-Header.
+
+Return values are:
+ fail for overall "R", "G" from dccifd
+ defer for overall "T" from dccifd
+ accept for overall "A", "S" from dccifd
+
+dcc = */defer_ok works as for spamd.
+
+The "$dcc_result" variable contains the overall result from DCC
+answer. There will an X-DCC: header added to the mail.
+
+Usually you'll use
+ defer !dcc = *
+to greylist with DCC.
+
+If you set, in the main section,
+ dcc_direct_add_header = true
+then the dcc header will be added "in deep" and if the spool
+file was already written it gets removed. This forces Exim to
+write it again if needed. This helps to get the DCC Header
+through to eg. SpamAssassin.
+
+If you want to pass even more headers in the middle of the
+DATA stage you can set
+ $acl_m_dcc_add_header
+to tell the DCC routines to add more information; eg, you might set
+this to some results from ClamAV. Be careful. Header syntax is
+not checked and is added "as is".
+
+In case you've troubles with sites sending the same queue items from several
+hosts and fail to get through greylisting you can use
+$acl_m_dcc_override_client_ip
+
+Setting $acl_m_dcc_override_client_ip to an IP address overrides the default
+of $sender_host_address. eg. use the following ACL in DATA stage:
+
+ warn set acl_m_dcc_override_client_ip = \
+ ${lookup{$sender_helo_name}nwildlsearch{/etc/mail/multipleip_sites}{$value}{}}
+ condition = ${if def:acl_m_dcc_override_client_ip}
+ log_message = dbg: acl_m_dcc_override_client_ip set to \
+ $acl_m_dcc_override_client_ip
+
+Then set something like
+# cat /etc/mail/multipleip_sites
+mout-xforward.gmx.net 82.165.159.12
+mout.gmx.net 212.227.15.16
+
+Use a reasonable IP. eg. one the sending cluster actually uses.
+
+
+
+DSN extra information
+---------------------
+If compiled with EXPERIMENTAL_DSN_INFO extra information will be added
+to DSN fail messages ("bounces"), when available. The intent is to aid
+tracing of specific failing messages, when presented with a "bounce"
+complaint and needing to search logs.
+
+
+The remote MTA IP address, with port number if nonstandard.
+Example:
+ Remote-MTA: X-ip; [127.0.0.1]:587
+Rationale:
+ Several addresses may correspond to the (already available)
+ dns name for the remote MTA.
+
+The remote MTA connect-time greeting.
+Example:
+ X-Remote-MTA-smtp-greeting: X-str; 220 the.local.host.name ESMTP Exim x.yz Tue, 2 Mar 1999 09:44:33 +0000
+Rationale:
+ This string sometimes presents the remote MTA's idea of its
+ own name, and sometimes identifies the MTA software.
+
+The remote MTA response to HELO or EHLO.
+Example:
+ X-Remote-MTA-helo-response: X-str; 250-the.local.host.name Hello localhost [127.0.0.1]
+Limitations:
+ Only the first line of a multiline response is recorded.
+Rationale:
+ This string sometimes presents the remote MTA's view of
+ the peer IP connecting to it.
+
+The reporting MTA detailed diagnostic.
+Example:
+ X-Exim-Diagnostic: X-str; SMTP error from remote mail server after RCPT TO:<d3@myhost.test.ex>: 550 hard error
+Rationale:
+ This string sometimes give extra information over the
+ existing (already available) Diagnostic-Code field.
+
+
+Note that non-RFC-documented field names and data types are used.
+
+
+Queuefile transport
+-------------------
+Queuefile is a pseudo transport which does not perform final delivery.
+It simply copies the exim spool files out of the spool directory into
+an external directory retaining the exim spool format.
+
+The spool files can then be processed by external processes and then
+requeued into exim spool directories for final delivery.
+However, note carefully the warnings in the main documentation on
+qpool file formats.
+
+The motivation/inspiration for the transport is to allow external
+processes to access email queued by exim and have access to all the
+information which would not be available if the messages were delivered
+to the process in the standard email formats.
+
+The mailscanner package is one of the processes that can take advantage
+of this transport to filter email.
+
+The transport can be used in the same way as the other existing transports,
+i.e by configuring a router to route mail to a transport configured with
+the queuefile driver.
+
+The transport only takes one option:
+
+* directory - This is used to specify the directory messages should be
+copied to. Expanded.
+
+The generic transport options (body_only, current_directory, disable_logging,
+debug_print, delivery_date_add, envelope_to_add, event_action, group,
+headers_add, headers_only, headers_remove, headers_rewrite, home_directory,
+initgroups, max_parallel, message_size_limit, rcpt_include_affixes,
+retry_use_local_part, return_path, return_path_add, shadow_condition,
+shadow_transport, transport_filter, transport_filter_timeout, user) are
+ignored.
+
+Sample configuration:
+
+(Router)
+
+scan:
+ driver = accept
+ transport = scan
+
+(Transport)
+
+scan:
+ driver = queuefile
+ directory = /var/spool/baruwa-scanner/input
+
-To learn more about SPF, visit http://spf.pobox.com. This
-document does not explain the SPF fundamentals, you should
-read and understand the implications of deploying SPF on your
-system before doing so.
-
-SPF support is added via the libspf2 library. Visit
-
- http://www.libspf2.org/
-
-to obtain a copy, then compile and install it. By default,
-this will put headers in /usr/local/include and the static
-library in /usr/local/lib.
-
-To compile exim with SPF support, set these additional flags in
-Local/Makefile:
-
-EXPERIMENTAL_SPF=yes
-CFLAGS=-DSPF -I/usr/local/include
-EXTRALIBS_EXIM=-L/usr/local/lib -lspf2
-
-This assumes that the libspf2 files are installed in
-their default locations.
-
-You can now run SPF checks in incoming SMTP by using the "spf"
-ACL condition in either the MAIL, RCPT or DATA ACLs. When
-using it in the RCPT ACL, you can make the checks dependend on
-the RCPT address (or domain), so you can check SPF records
-only for certain target domains. This gives you the
-possibility to opt-out certain customers that do not want
-their mail to be subject to SPF checking.
-
-The spf condition takes a list of strings on its right-hand
-side. These strings describe the outcome of the SPF check for
-which the spf condition should succeed. Valid strings are:
-
- o pass The SPF check passed, the sending host
- is positively verified by SPF.
- o fail The SPF check failed, the sending host
- is NOT allowed to send mail for the domain
- in the envelope-from address.
- o softfail The SPF check failed, but the queried
- domain can't absolutely confirm that this
- is a forgery.
- o none The queried domain does not publish SPF
- records.
- o neutral The SPF check returned a "neutral" state.
- This means the queried domain has published
- a SPF record, but wants to allow outside
- servers to send mail under its domain as well.
- o err_perm This indicates a syntax error in the SPF
- record of the queried domain. This should be
- treated like "none".
- o err_temp This indicates a temporary error during all
- processing, including exim's SPF processing.
- You may defer messages when this occurs.
-
-You can prefix each string with an exclamation mark to invert
-is meaning, for example "!fail" will match all results but
-"fail". The string list is evaluated left-to-right, in a
-short-circuit fashion. When a string matches the outcome of
-the SPF check, the condition succeeds. If none of the listed
-strings matches the outcome of the SPF check, the condition
-fails.
-
-Here is a simple example to fail forgery attempts from domains
-that publish SPF records:
-
-/* -----------------
-deny message = $sender_host_address is not allowed to send mail from $sender_address_domain
- spf = fail
---------------------- */
-
-You can also give special treatment to specific domains:
-
-/* -----------------
-deny message = AOL sender, but not from AOL-approved relay.
- sender_domains = aol.com
- spf = fail:neutral
---------------------- */
-
-Explanation: AOL publishes SPF records, but is liberal and
-still allows non-approved relays to send mail from aol.com.
-This will result in a "neutral" state, while mail from genuine
-AOL servers will result in "pass". The example above takes
-this into account and treats "neutral" like "fail", but only
-for aol.com. Please note that this violates the SPF draft.
-
-When the spf condition has run, it sets up several expansion
-variables.
-
- $spf_header_comment
- This contains a human-readable string describing the outcome
- of the SPF check. You can add it to a custom header or use
- it for logging purposes.
-
- $spf_received
- This contains a complete SPF-Received: header that can be
- added to the message. Please note that according to the SPF
- draft, this header must be added at the top of the header
- list. Please see section 10 on how you can do this.
-
- $spf_result
- This contains the outcome of the SPF check in string form,
- one of pass, fail, softfail, none, neutral, err_perm or
- err_temp.
-
- $spf_smtp_comment
- This contains a string that can be used in a SMTP response
- to the calling party. Useful for "fail".
-
-
-
-4. SRS (Sender Rewriting Scheme) Support
+In order to build exim with Queuefile transport support add or uncomment
+
+EXPERIMENTAL_QUEUEFILE=yes
+
+to your Local/Makefile. (Re-)build/install exim. exim -d should show
+Experimental_QUEUEFILE in the line "Support for:".
+
+
+ARC support
+-----------
+Specification: https://tools.ietf.org/html/draft-ietf-dmarc-arc-protocol-11
+Note that this is not an RFC yet, so may change.
+
+[RFC 8617 was published 2019/06. Draft 11 was 2018/01. A review of the
+changes has not yet been done]
+
+ARC is intended to support the utility of SPF and DKIM in the presence of
+intermediaries in the transmission path - forwarders and mailinglists -
+by establishing a cryptographically-signed chain in headers.
+
+Normally one would only bother doing ARC-signing when functioning as
+an intermediary. One might do verify for local destinations.
+
+ARC uses the notion of a "ADministrative Management Domain" (ADMD).
+Described in RFC 5598 (section 2.3), this is essentially a set of
+mail-handling systems that mail transits that are all under the control
+of one organisation. A label should be chosen to identify the ADMD.
+Messages should be ARC-verified on entry to the ADMD, and ARC-signed on exit
+from it.
+
+
+Building with ARC Support
+--
+Enable using EXPERIMENTAL_ARC=yes in your Local/Makefile.
+You must also have DKIM present (not disabled), and you very likely
+want to have SPF enabled.
+
+It is possible to build as a dynamic-load module: set also SUPPORT_ARC=2.
+
+
+Verification
+--
+An ACL condition is provided to perform the "verifier actions" detailed
+in section 6 of the above specification. It may be called from the DATA ACL
+and succeeds if the result matches any of a given list.
+It also records the highest ARC instance number (the chain size)
+and verification result for later use in creating an Authentication-Results:
+standard header.
+
+ verify = arc/<acceptable_list> none:fail:pass
+
+ add_header = :at_start:${authresults {<admd-identifier>}}
+
+ Note that it would be wise to strip incoming messages of A-R headers
+ that claim to be from our own <admd-identifier>. Eg:
+
+ remove_header = \N^(?i)Authentication-Results\s*::\s*example.org;\N
+
+There are four new variables:
+
+ $arc_state One of pass, fail, none
+ $arc_state_reason (if fail, why)
+ $arc_domains colon-sep list of ARC chain domains, in chain order.
+ problematic elements may have empty list elements
+ $arc_oldest_pass lowest passing instance number of chain
+
+Example:
+ logwrite = oldest-p-ams: <${reduce {$lh_ARC-Authentication-Results:} \
+ {} \
+ {${if = {$arc_oldest_pass} \
+ {${extract {i}{${extract {1}{;}{$item}}}}} \
+ {$item} {$value}}} \
+ }>
+
+Receive log lines for an ARC pass will be tagged "ARC".
+
+
+Signing
+--
+arc_sign = <admd-identifier> : <selector> : <privkey> [ : <options> ]
+An option on the smtp transport, which constructs and prepends to the message
+an ARC set of headers. The textually-first Authentication-Results: header
+is used as a basis (you must have added one on entry to the ADMD).
+Expanded as a whole; if unset, empty or forced-failure then no signing is done.
+If it is set, all of the first three elements must be non-empty.
+
+The fourth element is optional, and if present consists of a comma-separated list
+of options. The options implemented are
+
+ timestamps Add a t= tag to the generated AMS and AS headers, with the
+ current time.
+ expire[=<val>] Add an x= tag to the generated AMS header, with an expiry time.
+ If the value <val> is an plain number it is used unchanged.
+ If it starts with a '+' then the following number is added
+ to the current time, as an offset in seconds.
+ If a value is not given it defaults to a one month offset.
+
+[As of writing, gmail insist that a t= tag on the AS is mandatory]
+
+Caveats:
+ * There must be an Authentication-Results header, presumably added by an ACL
+ while receiving the message, for the same ADMD, for arc_sign to succeed.
+ This requires careful coordination between inbound and outbound logic.
+
+ Only one A-R header is taken account of. This is a limitation versus
+ the ARC spec (which says that all A-R headers from within the ADMD must
+ be used).
+
+ * If passing a message to another system, such as a mailing-list manager
+ (MLM), between receipt and sending, be wary of manipulations to headers made
+ by the MLM.
+ + For instance, Mailman with REMOVE_DKIM_HEADERS==3 might improve
+ deliverability in a pre-ARC world, but that option also renames the
+ Authentication-Results header, which breaks signing.
+
+ * Even if you use multiple DKIM keys for different domains, the ARC concept
+ should try to stick to one ADMD, so pick a primary domain and use that for
+ AR headers and outbound signing.
+
+Signing is not compatible with cutthrough delivery; any (before expansion)
+value set for the option will result in cutthrough delivery not being
+used via the transport in question.
+
+
+
+Dovecot authenticator via inet socket
--------------------------------------------------------------
+If Dovecot is configured similar to :-
+
+service auth {
+...
+#SASL
+ inet_listener {
+ name = exim
+ port = 12345
+ }
+...
+}
+
+then an Exim authenticator can be configured :-
+
+ dovecot-plain:
+ driver = dovecot
+ public_name = PLAIN
+ server_socket = dovecot_server_name 12345
+ server_tls = true
+ server_set_id = $auth1
+
+If the server_socket does not start with a / it is taken as a hostname (or IP);
+and a whitespace-separated port number must be given.
+
+
+
+
+Logging protocol unusual states
+---------------------------------------------------------------
+An extra log_selector, "protocol_detail" has been added in the default build.
+The name may change in future, hence the Experimental status.
+
+Currrently the only effect is to enable logging, under TLS,
+of a TCP RST received directly after a QUIT (in server mode).
+
+Outlook is consistently doing this; not waiting for the SMTP response
+to its QUIT, not properly closing the TLS session and not properly closing
+the TCP connection. Previously this resulted is an error from SSL_write
+being logged.
+
+
+
+XCLIENT proxy support
+---------------------------------------------------------------
+Per https://www.postfix.org/XCLIENT_README.html
+
+XCLIENT is an ESMTP extension supporting an inbound proxy.
+The only client immplementation known is in Nginx
+(https://nginx.org/en/docs/mail/ngx_mail_proxy_module.html)
-Exiscan currently includes SRS support via Miles Wilton's
-libsrs_alt library. The current version of the supported
-library is 0.5.
+If compiled with EXPERIMENTAL_XCLIENT=yes :-
-In order to use SRS, you must get a copy of libsrs_alt from
+As a server, Exim will advertise XCLIENT support (conditional on a new option
+"hosts_xclient") and service XCLIENT commands with parameters
+ ADDR
+ NAME
+ PORT
+ LOGIN
+ DESTADDR
+ DESTPORT
+A fresh HELO/EHLO is required after a succesful XCLIENT, and the usual
+values are derived from that (making the HELO and PROTO paramemters redundant).
-http://srs.mirtol.com/
+An XCLIENT command must give both ADDR and PORT parameters if no previous
+XCLIENT has succeeded in the SMTP session.
-Unpack the tarball, then refer to MTAs/README.EXIM
-to proceed. You need to set
+After a success:
+ $proxy_session variable becomes "yes"
+ $proxy_local_address, $proxy_local_port have the proxy "inside" values
+ $proxy_external_address, $proxy_external_port have the proxy "outside" values
+ $sender_host_address, $sender_host_port have the remot client values
-EXPERIMENTAL_SRS=yes
-in your Local/Makefile.
--------------------------------------------------------------
git://git.exim.org / exim.git / blobdiff