I have Exchange 2003 servers and two Windows 2003 domain controllers. None of the Exchange servers are domain controllers. Both domain controllers are in the same 'site' and have global catalog checked in the NTDS settings. When I disconnected the main domain controller Exchange email stopped flowing.
Right now I don't have any event log errors, but might add them after I try this again. Is anyone aware of something else that might need to be done for this to work?