Docs: expand SRS info

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

diff --git a/doc/doc-docbook/spec.xfpt b/doc/doc-docbook/spec.xfpt
index ae3cc17489d67a00a4d8f0a0d2392fb80d3fbb4d..493c094cde59c939d584bfa8e955ec512d01b3ab 100644 (file)
--- a/doc/doc-docbook/spec.xfpt
+++ b/doc/doc-docbook/spec.xfpt
@@ -39061,7 +39061,7 @@ selection marked by asterisks:
 .irow &`deliver_time`&                   "time taken to attempt delivery"
 .irow &`delivery_size`&                          "add &`S=`&&'nnn'& to => lines"
 .irow &`dkim`&                         *       "DKIM verified domain on <= lines"
-.irow &`dkim_verbose`&                 &nbsp; "separate full DKIM verification result line, per signature"
+.irow &`dkim_verbose`&                 &nbsp; "separate full DKIM verification result line, per signature; DKIM signing"
 .irow &`dnslist_defer`&                        *       "defers of DNS list (aka RBL) lookups"
 .irow &`dnssec`&                       &nbsp; "DNSSEC secured lookups"
 .irow &`etrn`&                         *       "ETRN commands"
@@ -39187,6 +39187,10 @@ verifies successfully a tag of DKIM is added, with one of the verified domains.
 .cindex log "DKIM verification"
 .cindex DKIM "verification logging"
 &%dkim_verbose%&: A log entry is written for each attempted DKIM verification.
+.new
+Also, on message delivery lines signing information (domain and selector)
+is added, tagged with DKIM=.
+.wen
 .next
 .cindex "log" "dnslist defer"
 .cindex "DNS list" "logging defer"
@@ -42243,10 +42247,16 @@ The lookup will return the same result strings as can appear in
 
 .subsection "SRS (Sender Rewriting Scheme)" SECTSRS
 .cindex SRS "sender rewriting scheme"
+.cindex VERP "variable envelope return path"
 
 SRS can be used to modify sender addresses when forwarding so that
 SPF verification does not object to them.
-It operates by encoding the original envelope sender in a new
+It can also be used to identify a received bounce message as
+likely (or not) having been trigged by a message from the
+local system, and for identifying dead addresses in mailing lists.
+It is one implementation of a VERP (Variable Envelope Return Path) method.
+
+SRS operates by encoding the original envelope sender in a new
 sender local part and using a domain run by the forwarding site
 as the new domain for the sender.  Any DSN message should be returned
 to this new sender at the forwarding site, which can extract the