We used to run Exchange Server 5.5 on Windows 2000 servers in an Active Directory (AD) environment. We've been preparing to migrate to Exchange 2000 Server. When we upgraded the domain, we used Exchange 2000 ForestPrep to make the necessary schema modifications before we deploy Exchange 2000. Now it looks as though we might skip Exchange 2000 altogether and go directly to Exchange Server 2003. Do we need to rerun ForestPrep?
Yes, you must rerun ForestPrep. Although the ForestPrep operations for Exchange 2003 and Exchange 2000 are largely similar, some important differences do exist. First, and most important, Exchange 2003 ForestPrep adds some attributes and objects to AD that aren't present in a domain prepared using Exchange 2000 ForestPrep. Second, Exchange 2003 ForestPrep will restamp permissions on the Exchange organization object, which can be desirable in certain situations. The bottom line is that you need to rerun ForestPrep, but you can do so at any time before you deploy your first Exchange 2003 server.
