I have a Windows 2000 domain with a domain controller that I will refer to as 'DC1' that was brought online in Feb of 2000. I have a DC2 running exchange 2000 that was brought online in May of 2002. Exchange on DC2 will only respond to outlook clients when DC1 is up and running. My thought was that all DCs were equal and although they will try to replicate with each other I did not believe that Exchange services would be dependent on another DC. Also when DC1 is down I get an error on DC2's application log 'The Directory Service Referral interface failed to service a client request. RFRI is returning the error code:[0x3f0].' Can anyone shed some light on this?