Large number of categorizations in progress

[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]  

Topic Last Modified: 2006-08-21

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 Cat: Categorizations in progress performance counter of the SMTP Server performance object to analyze performance data.

The Cat: Categorizations in progress performance counter shows the number of categorizations in progress.

For this query, the Exchange Server Analyzer retrieves a sample every 6 seconds for a two-minute period. The Exchange Server Analyzer reports the average value for the performance counter during the collection interval.

If the Exchange Server Analyzer determines that the average number of categorizations in progress over the sample period exceeds 800, the Exchange Server Analyzer displays an error.

The categorizer performs the following core operations:

  • Resolves and validates all recipients.

  • Determines limits and restrictions for all recipients.

  • Expands distribution lists if that is required.

  • Determines whether the message is for local or remote delivery.

This error may indicate that the server is experiencing an extraordinary load or has a performance related issue.

To resolve this error:

  • Determine whether the stress to the categorizer is expected or from a typical load. If the stress to the categorizer is from an expected load, review the Exchange performance guidance in the following Microsoft TechNet articles.

  • If the stress to the categorizer is not from an expected load, check for virus outbreaks or SPAM that might generate the load.

The message categorizer performance counters are published separately for each Simple Mail Transfer Protocol (SMTP) virtual server instance. For a list of the available performance counters related to the Message Categorizer, see Microsoft Knowledge Base article 231734, "XCON: Performance Monitor Counters for Message Categorizer" (