XADM: How to Configure Exchange Server 5.5 to Run on a Domain Controller that is a Global Catalog

You cannot run Microsoft Exchange Server 5.5 on a Domain Controller that is also acting as a Global Catalog server. There is one exception to this; and that is if the server is acting as the single server for the entire environment. In other words if this Server is connected in any way to other servers (Windows 2000 DC's or GC's) then Microsoft does not support the work around explained in the More Information section of this article. This behavior occurs because the directory service starts first, and takes the Named Service Provider Interface (NSPI) endpoint. Therefore, when you attempt to connect to Exchange Server 5.5, the endpoint is unavailable.

WARNING: If you use Registry Editor incorrectly, you may cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that you can solve problems that result from using Registry Editor incorrectly. Use Registry Editor at your own risk.

To configure the domain controller for Exchange Server 5.5, follow these steps:

1. Install the latest service packs for Microsoft Windows NT 4.0 and Exchange Server 5.5.
2. Move the Exchange Server LDAP port to an unused port such as 391. For additional information on moving the Exchange Server LDAP port, please see the following knowledge base article:
   224447� XADM How To Change LDAP Port Assignments in Exchange Server
3. Disable Secure Sockets Layer (SSL) for the Exchange Server LDAP component or move it to a new port. For additional information on performing this task, please see the following knowledge base article:
   232606� XADM Changing the Port Used by the Directory for LDAP over SSL
4. Upgrade the computer to Microsoft Windows 2000. After the installation is complete, the Active Directory Installation Wizard (Dcpromo) is forced to quit.
5. Disable the MAPI port of Windows 2000 Active Directory, so that Exchange Server can use it. To do this, add the following registry key:
   HKEY_LOCAL_MACHINE\Systems\CurrentControlSet\Services\NTDS\Parameters\Initialize MAPI interface
   
   Value: REG_DWORD
   Data Value: 0
6. Restart the computer.
7. To ensure that Exchange Server 5.5 is coexisting with Windows 2000 Active Directory, verify that the Active Directory Connector (ADC) has been installed, and that a connection agreement has been created.

To upgrade this computer to Exchange 2000 Server, follow these steps:

1. Verify that the ADC service has started.
2. Install Exchange 2000 Server.
3. Delete the following registry key:
   HKEY_LOCAL_MACHINE\Systems\CurrentControlSet\Services\NTDS\Parameters\Initialize MAPI interface
   
   Value: REG_DWORD
   Data Value: 0
4. Restart the computer.

NOTE: Exchange Server 5.5 is supported on a domain controller which is a global catalog only when there is a single Exchange server in the Site and only one Site exists in the Exchange Organization.

Exchange Server 5.5 is supported on a domain controller which is a global catalog only when there are no other domain controllers in the domain and there is only one domain in the forest. No further Domain controllers can be installed into the environment.

There is no supported migration path to Exchange 2000 while the Exchange 5.5 installation exists on a global catalog server.

If you plan to install another Microsoft Windows 2000-based computer into the domain or forest, then the preceding steps are not supported.