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\APDU logging required

If the Exchange Server Analyzer finds the value for APDU logging required present and set to anything other than 0, a non-default configuration message is displayed.

Application Protocol Data Unit (APDU) text logs are binary representations of communication among Exchange message transfer agents (MTAs) in different sites and between MTA and client applications within a site. APDU logs can be instrumental in diagnosing problems with the MTA. However, they are valuable only to those familiar with ASCII translations of X.400 protocol.

When the APDU logging required registry parameter is present and configured with a value of 0, all the APDUs sent or received by the MTA are logged as binary data to binary data to MTADATA\BF*.LOG.

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.

To revert to the default MTA APDU logging configuration

  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 APDU logging required value.

  4. In the Value data field, enter 0 and click OK.

  5. Close the registry editor and then 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" (

For more information about APDU logs, see the Knowledge Base article 163324, "XCON: Application Protocol Data Unit (APDU) Logs (BF0.LOG)" (