Improve configuration

README.md

     sender_canonical_maps = tcp:127.0.0.1:10001
     sender_canonical_classes = envelope_sender
     recipient_canonical_maps = tcp:127.0.0.1:10002
-    recipient_canonical_classes= envelope_recipient
+    recipient_canonical_classes= envelope_recipient,header_recipient
+
+This will transparently rewrite incoming and outgoing envelope addresses,
+and additionally undo SRS rewrites in the To: header of bounce notifications
+and vacation autoreplies.
 
-This will transparently rewrite incoming and outgoing envelope addresses.
 Run `service postsrsd start` and `postfix reload` as root, or reboot.
 
 Known Issues

main.cf.ex

 sender_canonical_maps = tcp:127.0.0.1:10001
 sender_canonical_classes = envelope_sender
 recipient_canonical_maps = tcp:127.0.0.1:10002
-recipient_canonical_classes = envelope_recipient
+recipient_canonical_classes = envelope_recipient,header_recipient