Topic Last Modified: 2007-12-17

The Microsoft® Exchange Server Analyzer Tool reads the following registry entries to determine whether the Directory Services Proxy referral (DSProxy RFR) service has been disabled:

HKEY_LOCAL_MACHINE\ System\CurrentControlSet\Services\MSExchangeSA\Parameters\ No RFR Service

If the Exchange Server Analyzer finds No RFR Service to be present and set to 1, a non-default configuration message is displayed.

The DSProxy component in Exchange 2000 Server and Exchange Server 2003 provides directory access to a domain controller or global catalog for Microsoft Outlook® 98 and Outlook 97 clients. Outlook 2000 Service Release 2 (SR-2) and later versions can query a global catalog server directly.

The first time an Outlook 2000 SR-2 or a later version client connects to an Exchange 2000 server or later version computer, it looks for the directory service on the home Exchange server. Outlook at first goes through the DSProxy process for the very first session. After the client contacts the DSProxy service (it tries all available transport protocols), a referral is passed back to the client informing it that all future directory requests should go to the global catalog server. Outlook sets the referral in the MAPI profile in the registry. The DSProxy referral mechanism reduces load on the Exchange server and reduces the latency for address book searches. If an explicit server name is entered into the profile, Outlook must restart if that Active Directory® directory service server fails. If this occurs, the Exchange server sends Outlook a new referral.

In some scenarios you might want to force Outlook clients, even the latest versions, to always go through the DSProxy process without being referred. For example, you may need to do this if a firewall exists between Outlook and the Exchange server.

By adding the No RFR Service registry entry and setting it to 1, the Exchange server will behaves like a proxy for Outlook clients instead of referring the clients to the appropriate global catalog server for direct communication. Setting the No RFR Service registry parameter to 1 will decrease Exchange server performance because the Exchange server will be acting as a proxy for all Outlook clients, including Outlook 2000 SR-2 and newer clients that can communicate directly with Active Directory.

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 enable the DSProxy RFR service

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

  2. Navigate to: HKLM\System\CurrentControlSet\Services\MSExchangeSA\Parameters

  3. In the right pane, right-click and Delete the No RFR Service registry value.

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 how Outlook 2000 SR-2 and newer clients interact with Active Directory, see the Knowledge Base article 256976, "XCCC: How Outlook 2000 Accesses Active Directory" (

For information about how MAPI clients access Active Directory, see the Knowledge Base article 256976, "XCLN: How MAPI Clients Access Active Directory" (