8.1. Planning Coexistence with Exchange 2000 Server and Exchange Server 2003 in a Single Organization

This section covers one of the most common coexistence situations: coexistence with a legacy Exchange organization, including 2000, 2003, or a combination of both. If you are still running or working with Exchange Server 5.5, all traces of Exchange Server 5.5 computers must be removed from the organization before Exchange 2007 can be installed and supported. Table 8.1 outlines which versions of Exchange can coexist with Exchange 2007.

Table 8.1. Supported Coexistence Scenarios with Exchange 2007

Legacy Version	Coexistence with Exchange 2007
Exchange Server 5.5	Not supported
Mixed 5.5, 2000, and 2003	Not supported
Exchange 2000 Server	Supported
Exchange Server 2003	Supported
Mixed 2000 and 2003	Supported