[bug] implement message bouncing according to RFCs

If we do not adhere to the standads, we may have a lot of problems when
bouncing a message. This commit implements a bounce message according to:

  * RFC 6522 - The Multipart/Report Media Type for the Reporting of Mail
    System Administrative Messages

  * RFC 3834 - Do not bounce for unknown or invalid addresses.

  * RFC 3464 - An Extensible Message Format for Delivery Status Notification.

Closes: #6858.

1 files changed, 2 insertions, 2 deletions

diff --git a/pkg/mx.tac b/pkg/mx.tac
index 48b9ef9..7da59cf 100755
--- a/pkg/mx.tac
+++ b/pkg/mx.tac
@@ -46,8 +46,8 @@ password = config.get("couchdb", "password")
 server = config.get("couchdb", "server")
 port = config.get("couchdb", "port")
 
-bounce_from = "MAILER-DAEMON"
-bounce_subject = "Delivery failure"
+bounce_from = "Mail Delivery Subsystem <MAILER-DAEMON>"
+bounce_subject = "Undelivered Mail Returned to Sender"
 
 try:
     bounce_from = config.get("bounce", "from")