XADM: Messages Stuck in Outbox with Antivirus Application Programming Interface in Use

When you send an e-mail message, the message may not be sent and may remain in the Outbox. This behavior only occurs when you use a third-party antivirus scanning program that uses the antivirus application programming interface (API) that is introduced in Exchange Server Service Pack 3.

Typically, a message is sent immediately after you send that message. This issue can occur because when the antivirus API is enabled, the process can take longer than expected and may cause the message to time out while it waits to be sent.

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.