I have a small network that has two domain controllers with DNS running on both and another server hosting exchange 2003. All servers run windows 2003 server but when the Primary domain controller is disconnected/ shut down outlook throws an eppy and won't let me get any mail.Does anyone know what needs to happen to allow exchange to function if only the secondary DC is active?Cheers ears.

The Exchange Server 2000/2003 need Global Catalog server role in the domain, so please make sure your another domain controller is also act global catalog server role. When primary domain controller disconnect exchange server will auto discover(in 15 mins)another online global catalog server and change to use it.