doc/example-config: Added description for a few generic settings that were...

doc/example-config: Added description for a few generic settings that were only mentioned in the INSTALL file.

doc/example-config/conf.d/90-sieve.conf

@@ -135,4 +135,25 @@ plugin {
   # set to 0, no limit on the used amount of disk storage is enforced.
   # (Currently only relevant for ManageSieve)
   #sieve_quota_max_storage = 0
+
+  # The path to the file where the user log is written. If not configured, a
+  # default location is used. If the main user's personal Sieve (as configured
+  # with sieve=) is a file, the logfile is set to <filename>.log by default. If
+  # it is not a file, the default user log file is ~/.dovecot.sieve.log.
+  #sieve_user_log =
+
+  # Specifies what envelope sender address is used for redirected messages.
+  # The following values are supported for this setting:
+  #
+  #   "sender"         - The sender address is used (default).
+  #   "recipient"      - The final recipient address is used.
+  #   "orig_recipient" - The original recipient is used.
+  #   "postmaster"     - The postmaster_address configured for the LDA.
+  #   "<user@domain>"  - Redirected messages are always sent from user@domain.
+  #                      The angle brackets are mandatory. The null "<>" address
+  #                      is also supported.
+  #
+  # This setting is ignored when the envelope sender is "<>". In that case the
+  # sender of the redirected message is also always "<>".
+  #sieve_redirect_envelope_from = sender
 }