MTA Submit/deliver 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: 2005-11-18

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

HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\MSExchangeMTA\Parameters\ Submit/deliver threads

If the Exchange Server Analyzer finds the value for Submit/deliver threads present and set to anything other than 2, a non-default configuration message is displayed.

The Submit/deliver threads value is the number of message transfer agent (MTA) Submit/Deliver threads. The MTA uses these threads to pass messages to the information store. On some Exchange Server version 5.5 computers, it is possible that this value was automatically changed by the Exchange Performance Optimizer from its default value of 2 to a value more appropriate for the Exchange server.

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 edit the registry, view the "Restore the Registry" Help topic in Regedit.exe or Regedt32.exe.

  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 double-click the Submit/deliver threads value.

  4. In the Value data field, ensure that a value of 2 is entered, and click OK.

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

On Exchange 2000 Server and Exchange Server 2003 computers, the value for this entry should be set no greater than 3. For Exchange Server 5.5 computers, as an alternative to the preceding procedure, you can run the Exchange Performance Optimizer in verbose mode (perfwiz.exe -v) and set the value using that tool.

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" (

For more information about situations in which the MTA Submit/deliver threads registry value should be changed from its default value, see the following Knowledge Base articles: