Das sollte wirklich in die Prüfungsfragen für Domino-Admins:
Request for Comments 1893 (http://www.ietf.org/rfc/rfc1893.txt): "Enhanced Mail System Status Codes"
2.X.X Success
Success specifies that the DSN is reporting a positive delivery
action. Detail sub-codes may provide notification of
transformations required for delivery.
X.5.X Mail Delivery Protocol Status
The mail delivery protocol status codes report failures
involving the message delivery protocol. These failures
include the full range of problems resulting from
implementation errors or an unreliable connection. Mail
delivery protocol issues may be controlled by many parties
including the originating system, destination system, or
intermediate system administrators.
X.5.0 Other or undefined protocol status
Something was wrong with the protocol necessary to deliver
the message to the next hop and the problem cannot be well
expressed with any of the other provided detail codes.
Problem liegt wenn, dann auf der Empfängerseite.