Active Directory Implications of Mergers and Acquisitions


A merger, acquisition, or divestiture of business units may involve merging two or more separate Exchange organizations. During this process, there is likely a period of time during which you must retain coexistence between the Exchange organizations before you can merge them. In this scenario, the concerns are similar to those in a classic multiple forest scenario. In particular, you must ensure that basic messaging, shared global address list, and shared free/busy information are available during coexistence.

When the time comes to merge organizations, the method you follow depends on the versions of Exchange you are running:

  • When merging two forests that are running Exchange 2000 or Exchange 2003, use the Active Directory Migration Tool (ADMT) to migrate accounts and Migration Wizard to migrate mailboxes, as shown in the following figure.

    Merging two forests that are running Exchange 2000 or Exchange 2003


  • When merging a forest that is running Exchange 5.5 with a forest that is running Exchange 2003, follow the guidelines for an external migration from Exchange 5.5 to Exchange 2003, as shown in the following figure.

    Merging an Exchange 5.5 forest with an Exchange 2003 forest


For more information about merging forests, see "Planning to Move from Exchange 5.5 to Exchange 2003" and "Planning to Deploy Exchange in a Multiple Forest Environment."