'Messages awaiting directory lookup' Queue is Frozen

[This topic is intended to address a specific issue called out by the Exchange Server Analyzer Tool. You should apply it only to systems that have had the Exchange Server Analyzer Tool run against them and are experiencing that specific issue. The Exchange Server Analyzer Tool, available as a free download, remotely collects configuration data from each server in the topology and automatically analyzes the data. The resulting report details important configuration issues, potential problems, and nondefault product settings. By following these recommendations, you can achieve better performance, scalability, reliability, and uptime. For more information about the tool or to download the latest versions, see "Microsoft Exchange Analyzers" at http://go.microsoft.com/fwlink/?linkid=34707.]  

Topic Last Modified: 2006-05-17

The Microsoft® Exchange Server Analyzer Tool queries the ExchangeLink Windows® Management Instrumentation (WMI) class to determine the value of the StateFrozen key for the Simple Mail Transfer Protocol (SMTP) Messages awaiting directory lookup queue.

If the Exchange Server Analyzer finds that the value of the StateFrozen key for the Messages awaiting directory lookup queue on an Exchange server is set to True, the Exchange Server Analyzer displays an error.

A frozen queue means the transport sessions for that queue are stopped. A frozen queue prevents outgoing messages, although new messages can be added. You can manually change the state of a connection by using the shortcut menu on each link queue. When you use the Force Connection command to change a queue state to Active, you immediately enable a connection that sends the messages from that queue.

The Messages awaiting directory lookup queue contains messages to recipients that have not yet been resolved against the Active Directory® directory service. Messages are also held in the queue while distribution lists are expanded.

Generally, messages accumulate in this queue because the advanced queuing engine is unable to categorize the message. The advanced queuing engine may not be able to access the global catalog servers and access recipient information, or the global catalog servers are unreachable or performing slowly. In addition, messages can accumulate for the following reasons:

  • Active Directory is unavailable.


    The categorizer uses Active Directory to categorize messages.

  • Active Directory may be too heavily loaded if many messages are queuing in the pre-categorization queue.

  • There is a failure in conversion. The categorizer also handles content conversion.

  • The message categorizer cannot find the mailbox stores.

  • If SMTP was reinstalled or removed, this may invalidate the following IIS metabase keys: /smtpsvc/DsUseCat and /smtpsvc/vsi#/DsUseCat.


    Determine whether SMTP was reinstalled or removed.

To resolve this error, increase diagnostic logging for the MSExchangeDSAccess service and for the MSExchangeTransport service to collect information about Categorizer components.

For more information about how to troubleshoot SMTP queues, see the following Exchange resources: