Microsoft® Exchange Server 2007 Administrator's Companion

Appendix B. Delivery Status Notification Codes

Even in the best-conceived and best-managed Microsoft Exchange environments, you are bound to have messages that just can’t make it through the system. When a message experiences a fatal error and cannot be delivered, Microsoft Exchange Server 2007 (and other mail servers) returns a nondelivery report (NDR) to the sender and optionally to an administrator. Although it’s rare to see NDRs generated by internal transmissions (messages sent between recipients in the same organization), it is possible. It is much more likely to see NDRs generated by non-Exchange mail servers outside the Exchange organization. Understanding the structure and coding of an NDR can help you determine where a mail flow problem ...