An Exchange 2000 organization can operate in two modes: native mode and mixed mode. Native mode offers full Exchange 2000 functionality, while mixed mode offers interoperability between Exchange 2000 and previous versions of Exchange. When you install Exchange 2000, your Exchange organization is in mixed mode by default. This default setting ensures future interoperability with previous versions of Exchange (for example, the installation of an Exchange 5.5 server at a later time), even if no Exchange 5.x servers exist in the organization at the time of installation.
The concept of mixed mode and native mode organizations is
similar to the concept of mixed mode and native mode domains in
For Exchange Server 5.5 and Exchange 2000 to coexist and
replicate directory information, the Exchange 2000 configuration
must remain in a state that can be recognized by Exchange Server
Much of the added functionality of Exchange 2000 is a result of
the Exchange 4.x and 5.x concept of site a being
Note In mixed-mode organizations, Exchange 5.5 sites are represented as administrative groups in Active Directory.
In earlier versions of Exchange, the site concept defined three boundaries: single-hop routing, a collective administration unit, and a namespace hierarchy. To provide a more flexible deployment and administration structure, all three boundaries are separate in Exchange 2000.
The ability to operate an Exchange organization in mixed mode exists for backward compatibility with previous versions of Exchange and other software that relies on previous versions of Exchange. Operating an Exchange organization in native mode is useful when all servers are running the latest version of Exchange and the restrictions imposed by earlier versions no longer apply.
After all previous versions of Exchange are been upgraded or removed from the organization, you can configure Exchange 2000 to no longer support previous versions of Exchange by switching to native mode. This allows you to configure your administrative groups and routing groups independently.
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