SMTP Local Queue length beyond threshold

[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: 2006-04-20

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 Local Queue Length performance counter of the SMTP Server performance object to analyze performance data.

If the Exchange Server Analyzer determines that the Local Queue Length counter has exceeded the peak value of 1000 during the sample time slice, the Exchange Server Analyzer displays an error.

The SMTP Server\Local Queue Length counter indicates the number of messages in the Simple Mail Transfer Protocol (SMTP) queue for local delivery to the Microsoft Exchange Information Store service. SMTP local queue data (Mailroot directory) is temporarily held in the storage device while it is being processed by Exchange Server. This design prevents the data from being lost if the server fails. For example, when a destination server is unreachable, the messages that should be routed to that server will be stored on the local server queue directory until they can be delivered.

This error indicates a performance issue or outages on the server, because the server can no longer deliver the incoming mail in a timely manner. The following conditions can cause this delay:

  • The Active Directory® directory service is not being consulted promptly.

  • Messages are not being handed off promptly for local delivery or SMTP.

  • Databases (mailbox stores and public folder stores) have been dismounted.

  • To resolve this issue, take the following steps:

  • Make sure all databases (mailbox stores and public folder stores) are mounted.

  • Identify the source of the performance bottleneck. A performance bottleneck may be CPU, disk, network, or memory related and can be caused by an increase in load to the server or insufficient server resources. Use the Performance Monitor (Perfmon.msc) tool to determine whether the bottleneck is caused by an increased load on the server or whether the server is undersized. If the server load has increased, identify the source of the load and reduce it. If the server has insufficient resources, increase the necessary resources or move users off the server.

  • Monitor external dependencies, such as the Active Directory directory service, for performance issues and troubleshoot and correct as necessary.


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