Sometimes our Exchange 2003 server issues NDRs for incoming mail. Unfortunately the NDR doesn't give any information for the failure. Message tracking likewise does not give any useful information. Example below. Any idea why incoming mail like that would fail?
NDR in Outlook:
This is an automatically generated Delivery Status Notification.
Delivery to the following recipients failed.
Exchange Message Tracking:
1/8/2013 2:57 PM SMTP: Message Submitted to Advanced Queuing
1/8/2013 2:57 PM SMTP: Started Message Submission to Advanced Queue
1/8/2013 2:57 PM SMTP: Message Submitted to Categorizer
1/8/2013 2:57 PM SMTP: Message Categorized and Queued for Routing
1/8/2013 2:57 PM SMTP: Non-Delivery Report (NDR) Generated