How to Set the Transfer Threads Registry Value
The Transfer threads registry value is the number of MTA Transfer threads. This is multiplied by two for the two subtypes (Transfer In and Transfer Out) of each Transfer thread. This is the equivalent of the Submit/deliver threads value (which relates to MTA and information store message transfer) but for gateways and MTAs.
If this is an Exchange 2000 Server or Exchange Server 2003 MTA that communicates with a more than one Exchange Server 5.5 computer either within a Site or between Sites, it is recommended that you adjust the value for Transfer threads to 3.
On some Exchange Server 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 computer.
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.
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 Transfer threads registry value
Open a registry editor, such as Regedit.exe or Regedt32.exe.
Navigate to HKLM\System\CurrentControlSet\Services\MSExchangeMTA\Parameters.
In the right pane, locate and double-click Transfer threads.
In the Value data field, enter the appropriate value and click OK.
Close 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. As an alternative to the procedure above for Exchange Server 5.5 computers, you can run the Exchange Performance Optimizer in verbose mode (perfwiz.exe -v) and set the value using that utility.
For More Information
For more information about situations in which the MTA Transfer threads registry value should be altered from its default value, see the following Microsoft Knowledge Base articles:
234280, "XCON: How to Increase the Ability of the MTA to Pass Mail over Slow Network Connections," (https://go.microsoft.com/fwlink/?linkid=3052&kbid=234280)
265186, "XCON: MTA Fanout Slows on Multiprocessor Servers and Messages Back Up in Information Store," (https://go.microsoft.com/fwlink/?linkid=3052&kbid=265186)
327260, "MTA slows down or stalls in Exchange Server 5.5 and messages back up in the private information store," (https://go.microsoft.com/fwlink/?linkid=3052&kbid=327260)
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).