XFOR: Queued Message Waiting for ETRN Never Expires

Normally, when a message sent from a client is undelivered after the scheduled time (message time-out value), the Microsoft Exchange Internet Mail Service expires the message on the Internet Mail Service outbound queue and returns a non-delivery report (NDR) to the sender. However, when this problem occurs, the queued message, which is waiting for the ETRN command, remains in the outgoing queue and never expires after the scheduled time. The sender never receives an NDR.

Microsoft Exchange Server supports the use of an SMTP extension called ETRN. An Exchange Server computer can be used as a host SMTP server and will respond to ETRN commands from the remote host. After the remote host submits the ETRN command to the Exchange Server computer, a new connection is established from the Exchange Server computer to the remote host. The Exchange Server computer keeps a message until it receives the ETRN command from the remote host. If the queued message is waiting for the ETRN command, the message never expires even after the scheduled time. Then the sender never receives an NDR. The scheduled time is 48 hours for Normal Message by default.

Microsoft has confirmed this to be a problem in Microsoft Exchange Server version 5.0.

A supported fix is now available, but has not been fully regression-tested and should be applied only to systems experiencing this specific problem. Unless you are severely impacted by this specific problem, Microsoft recommends that you wait for the next Service Pack that contains this fix. Contact Microsoft Technical Support for more information. This fix has been posted to the following Internet location:
Microsoft has confirmed this to be a problem in Microsoft Exchange Server version 5.5. This problem has been corrected in the latest U.S. Service Pack for Microsoft Exchange Server version 5.5. For information about obtaining the Service Pack, query on the following word in the Microsoft Knowledge Base (without the spaces):