This event indicates that a performance issue exists on the affected Hub Transport or on the Edge Transport server. This event is generated by an hourly check that determines the Categorizer jobs that are available for message processing on the server.

The Categorizer component runs as a thread in the EdgeTransport.exe Worker Process in Microsoft Exchange Server 2010. Every message in Exchange must pass through the Categorizer. The Categorizer is responsible for processing items from the submission queue. The processing includes the following operations:

• Agent processing
  
  
• Recipient resolution
  
  
• Routing
  
  
• Content conversion
  
  
• Agent processing for external messages
  
  
• Message packaging
  
  

Note:
Although the Categorizer performs many operations, its primary operations are to resolve recipients and to route messages.

After the Categorizer processes the messages, it sends them to the delivery queues for local delivery or for remote delivery.

The transport server has a maximum number of jobs that may be used concurrently for message processing. When the available jobs are consumed, the Categorizer cannot process additional messages.

In this case, you may experience the following symptoms:

• The mail submission queue builds on the transport server
  
  
• Delivery queues do not build up
  
  

When the volume of available Categorizer jobs is less than 100 percent, this indicates that one or more Categorizer jobs are stuck. In this scenario, a component may be preventing the particular job or jobs from finishing in a timely manner.

As a general guideline, if the volume of available Categorizer jobs is less than 99 percent, a problem may exist with the Transport service. A severe problem may exist if the volume of available Categorizer jobs is less than 90 percent.

This event may indicate that a bottleneck exists with regard to the transport server or that there is a problem that affects the transport service.

To resolve this problem, do one or more of the following:

• Review the Application log and System log on your Exchange 2010 servers for related events. For example, events that occur immediately before and after this event may provide more information about the root cause of this error.
  
  
• Review Operations Manager for detailed information about the cause of this problem. For more information, see the "Introduction" section in this article.
  
  
• Check the MSExchangeTransport Categorizer performance counter by using Reliability and Performance monitor.
  
  
• Check the MSExchangeTransport Queues\Messages Completing Categorization performance counter to determine the percentage of messages that completed categorization during the past five minutes. A value that is consistently less than 100 indicates that the categorizer performance is insufficient to handle the rate of message submissions. This value may help you determine the effect that a stuck job has on categorizer throughput.
  
  
• Use the Get-Message cmdlet to check the status of ACTIVE messages in the submission queue. This status can help you determine whether any messages are stuck in the categorizer component. To determine the duration that a message remains stuck in a particular component in the categorizer, use the IncludeComponentLatency parameter.
  
  
• Restart the MSExchangeTransport service to release any messages that are stuck in the categorizer. This action may be useful when a transient error in a component prevents the categorizer job from finishing.
  
  
• Use the Exchange Troubleshooting Assistant (ExTRA) to obtain Event Tracing for the Transport component.
  
  For more information, see Another Method of Obtaining ExTRA Traces. To obtain the Exchange Troubleshooting Assistant, see Microsoft Exchange Troubleshooting Assistant v1.1.
  
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• Resolve your issue by using self-support options, assisted support options, and other resources. You can access these resources from the Exchange Server Solutions Center. From this page, click Self-Support Options in the navigation pane to use self-help options. Self-help options include searching the Microsoft Knowledge Base, posting a question at the Exchange Server forums, and others. Alternatively, in the navigation pane, you can click Assisted Support Options to contact a Microsoft support professional. Because your organization may have a specific procedure for directly contacting Microsoft Technical Support, be sure to review your organization's guidelines first.
  
  

If you are not already doing so, consider running the Exchange tools created to help you analyze and troubleshoot your Exchange environment. These tools can help make sure that your configuration aligns with Microsoft best practices. They can also help you identify and resolve performance issues, improve mail flow, and better manage disaster recovery scenarios. To run these tools, go to the Toolbox node of the Exchange Management Console. To learn more about these tools, see Managing Tools in the Toolbox.