How to Set the Dispatcher Threads Registry Value

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The Dispatcher threads value is the number of message transfer agent (MTA) Dispatcher threads. This is multiplied by three for the three types of Dispatcher threads: Fanout, Router and Result. Be aware that a change in this number actually increases the thread count by three, one for each of the Dispatch functions mentioned below.

  • Router   Routes messages.

  • Fanout   Sends message to the right place.

  • Result   Thread handles for notifications, such as non-delivery reports (NDRs).

In smaller organizations, the MTA process typically does not require manual tuning. After you have converted to Native Mode, you should remove these registry settings. Using the MTA tuning described below in a Native Mode Exchange organization decreases the performance of Exchange.

One recommended reason manually configuring the Dispatcher threads registry value is when an MTA communicates with more than five Exchange Server 5.5 computers either within a site, or between sites, or if distribution lists are heavily used. If this applies to your organization, you should set Dispatcher threads to 3. If this does not apply, you should set Dispatcher threads to 1.

Before You Begin

Before you perform the procedure in this topic, be aware that the procedure contains information about editing the registry.

Warning

Incorrectly editing the registry can cause serious problems that may require you to reinstall your operating system. Problems resulting from editing the registry incorrectly may not be able to be resolved. Before editing the registry, back up any valuable data.

Procedure

To set the Dispatcher threads registry value

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

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

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

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

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

For More Information

For information about how to edit the registry, see Microsoft Knowledge Base article 256986, "Description of the Microsoft Windows Registry" (https://go.microsoft.com/fwlink/?linkid=3052&kbid=256986).