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.
+
+
+PRDR support
+--------------------------------------------------------------
+
+Per-Recipient Data Reponse is an SMTP extension proposed by Eric Hall
+in a (now-expired) IETF draft from 2007. It's not hit mainstream
+use, but has apparently been implemented in the META1 MTA.
+
+There is mention at http://mail.aegee.org/intern/sendmail.html
+of a patch to sendmail "to make it PRDR capable".
+
+ ref: http://www.eric-a-hall.com/specs/draft-hall-prdr-00.txt
+
+If Exim is built with EXPERIMENTAL_PRDR there is a new config
+boolean "prdr_enable" which controls whether PRDR is advertised
+as part of an EHLO response, a new "acl_data_smtp_prdr" ACL
+(called for each recipient, after data arrives but before the
+data ACL), and a new smtp transport option "hosts_try_prdr".
+
+PRDR may be used to support per-user content filtering. Without it
+one must defer any recipient after the first that has a different
+content-filter configuration. With PRDR, the RCPT-time check
+for this can be disabled when the MAIL-time $smtp_command included
+"PRDR". Any required difference in behaviour of the main DATA-time
+ACL should however depend on the PRDR-time ACL having run, as Exim
+will avoid doing so in some situations (eg. single-recipient mails).
+
OCSP Stapling support
--------------------------------------------------------------
-X509 PKI certificates expire and can be revoked; to handle this, the
+X.509 PKI certificates expire and can be revoked; to handle this, the
clients need some way to determine if a particular certificate, from a
particular Certificate Authority (CA), is still valid. There are three
main ways to do so.
proof expires. The downside is that it requires server support.
If Exim is built with EXPERIMENTAL_OCSP and it was built with OpenSSL,
-then it gains one new option: "tls_ocsp_file".
+then it gains a new global option: "tls_ocsp_file".
The file specified therein is expected to be in DER format, and contain
an OCSP proof. Exim will serve it as part of the TLS handshake. This
Exim will check for a valid next update timestamp in the OCSP proof;
if not present, or if the proof has expired, it will be ignored.
+Also, given EXPERIMENTAL_OCSP and OpenSSL, the smtp transport gains
+a "hosts_require_ocsp" option; a host-list for which an OCSP Stapling
+is requested and required for the connection to proceed. The host(s)
+should also be in "hosts_require_tls", and "tls_verify_certificates"
+configured for the transport.
+
At this point in time, we're gathering feedback on use, to determine if
it's worth adding complexity to the Exim daemon to periodically re-fetch
-OCSP files and somehow handling multiple files. There is no client support
-for OCSP in Exim, this is feature expected to be used by mail clients.
+OCSP files and somehow handling multiple files.
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
+using it in the RCPT ACL, you can make the checks dependent 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
When the spf_guess condition has run, it sets up the same expansion
variables as when spf condition is run, described above.
-Additionally, since Best-guess is not standarized, you may redefine
+Additionally, since Best-guess is not standardized, you may redefine
what "Best-guess" means to you by redefining spf_guess variable in
global config. For example, the following:
After that "$dcc_header" contains the X-DCC-Header.
-Returnvalues are:
+Return values are:
fail for overall "R", "G" from dccifd
defer for overall "T" from dccifd
accept for overall "A", "S" from dccifd
If you want to pass even more headers in the middle of the
DATA stage you can set
$acl_m_dcc_add_header
-to tell the DCC routines add more information; eg, you might set
+to tell the DCC routines to add more information; eg, you might set
this to some results from ClamAV. Be careful. Header syntax is
not checked and is added "as is".
+In case you've troubles with sites sending the same queue items from several
+hosts and fail to get through greylisting you can use
+$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 acutally uses.
--------------------------------------------------------------
End of file
git://git.exim.org / exim.git / blobdiff