E-mail messages become stuck in the "Awaiting directory lookup" queue in an Exchange Server 2003 organization

You may experience one or more of the following symptoms in a Microsoft Exchange Server 2003 organization:

• E-mail messages become stuck in the "Awaiting directory lookup" queue.
• The SMTP service stops responding when you try to stop the service. You can successfully stop the service only when you use Kill.exe or when you change the startup type to "manual" and then restart the server.
• The following events may be logged in the System log if diagnostic logging is enabled on the server that is running Exchange Server 2003:

  Event Type: Warning Event Source: MSExchangeTransport Event Category: Connection Manager Event ID: 4006 Message delivery to the host'(IP)failed while delivering to the remote domain (GUID)for the following reason: Unable to open the message for delivery.

  Event Type: Warning Event Source: MSExchangeTransport Event Category: Categorizer Event ID: 6006 Categorizer is temporarily unable to process a message. The function 'CSearchRequestBlock::LDAPCompletion' called 'async' which returned error code '0x800705b4'

Note When you remove messages from Mailroot\VS1\Queues, the issue is temporarily resolved.

This issue may occur when Sybari Antigen Version 7.5.1138 is running on the Exchange Server 2003 server.

To resolve this issue, use one of the following methods.

Method 1: Disassociate Antigen version 7.5.1138 from Exchange Server 2003

Use the Antutil tool to disassociate Antigen from Exchange Server 2003. Then, test to see whether the issue is resolved. For more information about how to do this, click the following article number to view the article in the Microsoft Knowledge Base:

If you verify that Antigen is the cause of this issue, we recommend that you upgrade to the latest version of Antigen.

Method 2: Upgrade Antigen version 7.5.1138 to the latest version of Antigen on the Exchange Server 2003 server

For information about how to upgrade Antigen, visit the following Microsoft Web site:

For more information about issues that resemble the issue that is discussed in this article, click the following article numbers to view the articles in the Microsoft Knowledge Base: