I'm using Outlook 2000 with Exchange 2000 Server. Periodically, Outlook 2000 users report that they can't open the Global Address List (GAL) or check names in the message-composition forms. This problem seems to occur whenever one of the Global Catalog (GC) servers is unavailable. How can I fix this problem?

Exchange 2000 includes a component called DSProxy. Its function is to accept Messaging API (MAPI) directory service requests from Outlook 2000 and refer the caller to a GC server. This mechanism is the same mechanism used when you move a mailbox: The client uses MAPI to talk to an Exchange 2000 server; in return, DSProxy gives the client a MAPI referral that specifies which server has the mailbox.

Outlook 2000 and later clients store the information about the referred server in the currently logged on user's MAPI profile in the HKEY_CURRENT_USER\Software\Microsoft\WindowsNT\CurrentVersion \WindowsMessagingSubsystem\Profiles\profileName\dca740c8c042101ab4b908002b2fe182 registry subkey. If DSProxy isn't running, Outlook 2000 has no way to get answers to its MAPI directory requests. What happens more often, though, is that DSProxy returns a referral for a GC that's unavailable. Outlook 2000 is too dumb to independently find a GC, so it always uses the one listed in the registry subkey. However, Outlook 2000 will request a new referral at startup. You can fix this problem in several ways:

  • Quit and restart Outlook 2000. This restart forces Outlook 2000 to ask for a new referral. However, DSProxy issues referrals in a round-robin manner, so DSProxy might refer the new instance of Outlook to the same GC.
  • Remove the dca740c8c042101ab4b908002b2fe182 subkey, then relaunch Outlook.
  • Set the dca740c8c042101ab4b908002b2fe182 subkey to the name of the GC you want to force Outlook to use. However, resetting the subkey can be counterproductive because if you force Outlook to use a particular GC and that GC fails, you're right back where you started.