+15. New 8bitmime status logging option for received messages. Log field "M8S".
+
+16. New authenticated_sender logging option, adding to log field "A".
+
+17. New expansion variables $router_name and $transport_name. Useful
+ particularly for debug_print as -bt commandline option does not
+ require privilege whereas -d does.
+
+18. If built with EXPERIMENTAL_PRDR, per-recipient data responses per a
+ proposed extension to SMTP from Eric Hall.