Topic Last Modified: 2006-02-13

The Microsoft® Exchange Server Analyzer Tool includes a performance data collection engine that is used to query performance counter objects on computers that are running Exchange 2000 Server or Exchange Server 2003. The performance data collection engine collects data from the Categorizer Queue Length performance counter of the SMTP Server performance object to analyze performance data.

If the Exchange Server Analyzer determines that the Categorizer Queue Length counter has exceeded the peak value of 10 during the sample time slice, the Exchange Server Analyzer displays an error.

The SMTP Server\Categorizer Queue Length counter indicates the number of messages in the Simple Mail Transfer Protocol (SMTP) Categorizer queue waiting for directory service attribute searches using global catalog servers.

The categorizer performs the following core operations:

This error indicates that there may be problems with server or network performance, Directory Service Access (DSAccess), the Active Directory® directory service, or outages with key servers in the Exchange Server organization. An increase in the Categorizer Queue Length counter may indicate a either a slow response or no response in consulting Active Directory or in handing off messages for local delivery or SMTP. This might cause delayed mail delivery.

To address this error:

For More Information

For more information about troubleshooting Exchange Server performance issues, see Troubleshooting Microsoft Exchange Server Performance (