Rename dns_use_dnssec to dns_dnssec_ok.

[exim.git] / doc / doc-txt / experimental-spec.txt

diff --git a/doc/doc-txt/experimental-spec.txt b/doc/doc-txt/experimental-spec.txt
index 7bb17883c77143434880f96872197045d72b3a00..8d1ebef13b227d987dabb449566a93aa75c71383 100644 (file)
--- a/doc/doc-txt/experimental-spec.txt
+++ b/doc/doc-txt/experimental-spec.txt
@@ -6,6 +6,34 @@ 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
 --------------------------------------------------------------
 
@@ -570,10 +598,29 @@ 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 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