I have Exchange 5.5 on NT4 BDC, and I would like to upgrade/migrate to Exchange 2003 on Windows Server 2003 R2. The domain was originally NT4.0, but I already upgraded to Windows 2003 R2 domain. The new server is already a member server of the upgraded domain. I already ran forestprep and domainprep successfully. I installed and started running ADC tools. The tools ran fine until I started to run the connection Agreement Wizard.
q1) The Connection Agreement Wizard gave me a "warning: the staging area domain is not in native mode. Group membership and security cannot be properly managed unless the staging area is in a native mode domain. I left the domain under mix mode because I have NT4 BDC that's still running. Should I raise the domain/forest functionality before I proceed? How would raising the domain/forest funtionality affect My Exchange 5.5 (also a BD)?
q2) When I'm ready to install Exchange, do I select New Exchagnge 2003 Installation or Coexistence with Exchange 5.5 (since I already have an existing Exchange 5.5 server)? I don't know if I'll have time to move all of the mailboxes over in one shot, so I may not be able to take down my 5.5 that same day.