XFOR: Internet Mail Service Does Not Generate the Non-Delivery Report to the Sender

If you send an e-mail message to an invalid domain name that contains a trailing space (for example, SMTP:joeuser@invaliddomain.com ), a non-delivery report (NDR) that indicates an invalid host is generated as expected. But if you click Send Again, you do not receive an additional NDR message. Instead, the Internet Mail Service logs the following event 4120 error message, and moves the message into the Archive folder:

To resolve this problem, obtain the latest service pack for Exchange Server 5.5. For additional information, click the following article number to view the article in the Microsoft Knowledge Base: The following files are available for download from the Microsoft Download Center:
For additional information about how to download Microsoft Support files, click the following article number to view the article in the Microsoft Knowledge Base: Microsoft scanned this file for viruses. Microsoft used the most current virus-detection software that was available on the date that the file was posted. The file is stored on security-enhanced servers that help to prevent any unauthorized changes to the file.

Microsoft has confirmed that this is a problem in Microsoft Exchange Server version 5.5 Service Pack 3. This problem was first corrected in Exchange Server 5.5 Service Pack 4.