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\Concurrent MDB/delivery queue clients

If the Exchange Server Analyzer finds the value for Concurrent MDB/delivery queue clients present and set to anything other than 3, a non-default configuration message is displayed.

The Concurrent MDB/delivery queue clients value is the maximum number of message database (MDB) and Exchange API message access delivery queue clients that the message transfer agent (MTA) can support. Each client can have more than one session. This value should be set to at least two to support the private and public MDB entities.

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 correct this error

  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 Concurrent MDB/delivery queue clients value.

  4. In the Value data field, enter 3 and click OK.

  5. Exit the registry editor and 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" (