Why can't Messaging API (MAPI) clients connect to the server when I install Exchange Server 5.5 on a test Windows 2000 server?

This problem can occur when you're installing Exchange Server 5.5 on a Win2K domain controller (DC) or Global Catalog (GC). Win2K's Active Directory (AD) service is seizing the TCP port that the Name Service Provider Interface (NSPI) service uses; MAPI uses NSPI to perform directory queries. You can run Exchange Server 5.5 on a DC or GC only if the DC or GC is the only computer in the forest—perfect for test labs. To make this setup work, follow these steps:

  1. Build the server with Windows NT 4.0.
  2. Install Exchange Server 5.5.
  3. Change the Exchange Lightweight Directory Access Protocol (LDAP) and LDAP-with-Secure Sockets Layer (SSL) ports to something other than their default values. The Microsoft articles "XADM: How to Change LDAP Port Assignments in Exchange Server" (http://support.microsoft.com/support/kb/articles/q224/4/47.asp) and "XADM: Changing the Port Used by the Exchange Server 5.5 Directory for LDAP over SSL" (http://support.microsoft.com/support/kb/articles/q232/6/06.asp) explain how to change these ports.
  4. Upgrade to Win2K, and run the Dcpromo tool to turn the server into a DC.
  5. Add the Initialize MAPI interface REG_DWORD value to the HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\NTDS\Parameters registry subkey, and assign it a value of 0.
  6. Reboot the machine.
  7. Verify that the Active Directory Connector (ADC) is present and that you can log on to a mailbox with Exchange.

The Microsoft article "XADM: How to Configure Exchange Server 5.5 to Run on a Domain Controller or a Global Catalog" (http://support.microsoft.com/support/kb/articles/q275/1/27.asp) describes this process. This process works only when you have one server in the forest. If you have many computers, you can run Exchange Server 5.5 only on a member server.