A lot of companies that are migrating to Exchange 2000 had Exchange 5.5 deployed previously. To help with the transition process, Microsoft created the Active Directory Connector (ADC), which allows you to migrate at your own pace while maintaining both environments.
The ADC is comprised of a service that does the work and an MMC console to manage the service. While the console can be installed on any client or server, the ADC service has to be installed on a DC for it to work.
To support connection to the ADC, you will need Microsoft Exchange 5.5 Service Pack 1 or above.
When you install the ADC for the first time in a forest, it extends the schema to include new Exchange objects and attributes, as well as modifying existing Active Directory objects to include new Exchange-relevant attributes. The Exchange Schema is also modified if you intend to replicate Active Directory data to Exchange. For example, the User class object in the Active Directory Schema is directly modified to include three Exchange-relevant auxiliary classes in the auxiliary class attribute: msExchMailStorage, msExchCustomAttributes, and msExchCertificateInformation. Auxiliary classes and schema are discussed more fully in Chapter 4.
Once the Active Directory schema is extended, Active Directory then can hold mail attributes for groups, users, and contacts just as the Exchange directory can. This means that the ADC now can replicate data bidirectionally, knowing ...