MTA Dispatcher threads parameter is non-default

[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: 2007-11-14

The Microsoft® Exchange Server Analyzer Tool reads the following registry entry to determine its current value:

HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\MSExchangeMTA\Parameters\Dispatcher threads

If the Exchange Server Analyzer finds the value for Dispatcher threads present and larger than zero but set to anything other than 1 or 2, a non-default configuration message is displayed.

The Dispatcher threads value is the number of message transfer agent (MTA) Dispatcher threads. This is multiplied by three for the three subtypes (Router, Fanout, Result) of the Dispatcher thread. One recommended reason for changing this value is when an MTA communicates with more than five Exchange Server version 5.5 computers either within a site, or between sites, or if distribution lists are heavily used. In that event, it is recommended that you change the value to 3. If this MTA does not meet this criterion, you should change the value back to its default setting of 1.


This article contains information about editing the registry. Before you edit the registry, make sure you understand how to restore the registry if a problem occurs. For information about how to restore the registry, view the "Restore the Registry" Help topic in Regedit.exe or Regedt32.exe.

To revert to the default configuration

  1. Open a registry editor, such as Regedit.exe or Regedt32.exe.

  2. Navigate to: HKLM\System\CurrentControlSet\Services\MSExchangeMTA\Parameters

  3. In the right pane, locate and then double-click the Dispatcher threads value.

  4. In the Value data field, enter 1 and then click OK.

  5. Close the registry editor and then restart the Microsoft Exchange MTA Stacks service for the change to take effect.

Before you edit the registry, and for information about how to edit the registry, see the Microsoft Knowledge Base article 256986, "Description of the Microsoft Windows Registry" (