How to Set the Max RPC Calls Outstanding Registry Value
The Max RPC Calls Outstanding registry value is the maximum number of remote procedure call (RPC) threads. This limits the maximum number of RPC procedure calls that are guaranteed to be processed at one time.
The default value for Max RPC Calls Outstanding is 50 (decimal). In mixed-vintage scenarios where Exchange 2000 Server and/or Exchange Server 2003 co-exists with Exchange Server 5.5 computers and you have increased the number of Gateway In/Out threads in the Store.exe process, it is recommended that you increase the value data to 0x80 (hex) or 128 (decimal).
The Max RPC Calls Outstanding registry value is typically set concurrently with the Gateway In Threads and Gateway Out Threads and registry values.
For detailed instructions on setting the Gateway In Threads registry value, see How to Set the Gateway In Threads Registry Value.
For detailed instructions on setting the Gateway Out Threads registry value, see How to Set the Gateway Out Threads Registry Value.
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 Max RPC Calls Outstanding 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 Max RPC Calls Outstanding.
In the Value data field, enter the appropriate value for your organization and click OK.
Exit the registry editor and restart the Microsoft Exchange MTA Stacks service for the change to take effect.
For More Information
For information about MTA tuning in Exchange Server 5.5 organizations that coexist with Exchange 2000 Server or Exchange Server 2003, see Microsoft Knowledge Base article 264075, "Description of MTA tuning when Exchange 5.5 coexists with Exchange 2000 Server or with Exchange Server 2003," (https://go.microsoft.com/fwlink/?LinkId=3052&kbid=264075).
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).