Answer
GMS failed to authenticate the user specified in the RCPT clause due to a failure to get a valid response from the user authentication dll. By rejecting the message at the RCPT clause, GMS is saving considerable network bandwidth because the message body has not been sent over the network.
In this case, session Undefined was receiving a message from the server at Undefined apparently from Undefined to Undefined. The internal checking in GMS rejected the email with
Undefined
This points to an issue with the user authentication dll which is often used to connect to external user sources such SQL or LDAP databases. Please check this external source to determine why it is not providing a valid response to user authentication queries.
See Also:
Keywords:Authentication user dll external query queries