Upgrading from Exchange 5.0 to Exchange 2003 - is this possible?
I presented at a TechNet evening the other night on upgrading from Exchange 5.5 to 2003, and had a few questions that I thought I'd address here in case anyone else had the same questions. Ian asked if there was a supported path from Exchange 5 to Exchange 2003, or if they will first need to upgrade Exchange 5 to 5.5. Do any of the wizard tools allow them to move mailboxes from Exchange 5 to 2003?
The answer is that you must be running Exchange 5.5 SP3 as a minimum. If you have multiple Exchange 5.0 Servers, you must upgrade at least one server to Exchange 5.5 SP3 to run the Active Directory Connector. KB article.