The Active Directory Connector (ADC) has been around since Exchange 2000 Server first hit the streets. You use the ADC to synchronize the Exchange Server 5.5 Directory Service (DS) with Active Directory (AD) so that a mixed Exchange organization containing both Exchange 5.5 and Exchange 2000 or Exchange Server 2003 servers has one consistent Global Address List (GAL) and one consistent set of configuration information.
The ADC has undergone quiet refinement over the years. The version that we use today with Exchange 2003 is much more powerful than earlier versions. Microsoft has silently applied many bug fixes to the ADC and has significantly enhanced behind-the-scenes functionality—most notably in the new support for cross-site mailbox moves, introduced in Exchange 2003 Service Pack 1 (SP1). Let's take a look at a few ill-documented or barely publicized aspects of the ADC that nevertheless have significant importance for Exchange administrators.
ADC Account Creation and Migration
During synchronization of mailbox objects, the Exchange 2000 version of the ADC uses a set of object-matching rules to try to find an object in AD that's related to an in-process Exchange 5.5 object. These rules attempt to match first on globally unique identifiers (GUIDs), then distinguished names (DNs), and finally on SIDs. If the ADC can find no matching object in AD, it creates a new object (typically a user object) in AD. The new user object is created with a samAccountName attribute (also the User logon name) that matches the Exchange 5.5 mailbox alias, as Figure 1 shows. . . .
