Hi, We had our original domain controller Server 2003 with Exchange Server 2003 running on a separate server We then Installed 2008 R2 domain controller on another server And also Installed Exchange 2010 on additional server Migrated all mailboxes from Exchange 2003 to 2010 Everything is working OK, mail received, OWA working, everything is fine. However when we shutdown (before we attempt to dcpromo and remove) the 2003 domain controller, everything stops working (people cannot log on, OWA stops working, Outlook stops working for users). I am sure the 2008 R2 domain controller is a GC server, could anyone please advise on the above. Thanks, ShutMo

Hello, please check that you don't have replication problems using Dcdiag.exe. Make sure that: Each DC is a GC Each DC is a DNS server Each DC points to the other as primary DNS server Each DC points to its private IP address as secondary DNS server Each DC points to 127.0.0.1 as third DNS server Each public DNS server is set as a forwarder and not as a secondary DNS server Once done, run ipconfig /registerdns and restart netlogon on each DC. Also, make sure that DNS ports needed for AD replication are opened: http://technet.microsoft.com/en-us/library/bb727063.aspx Another thing is to make sure that client computers points to both DCs as DNS servers (One as primary and the other as secondary). Once done, use nslookup to check DNS resolution. If DNS resolution can not be made then check connectivity and firewalls on your network. This posting is provided "AS IS" with no warranties or guarantees , and confers no rights. Microsoft Student Partner 2010 / 2011 Microsoft Certified Professional Microsoft Certified Systems Administrator: Security Microsoft Certified Systems Engineer: Security Microsoft Certified Technology Specialist: Windows Server 2008 Active Directory, Configuration Microsoft Certified Technology Specialist: Windows Server 2008 Network Infrastructure, Configuration Microsoft Certified Technology Specialist: Windows Server 2008 Applications Infrastructure, Configuration Microsoft Certified Technology Specialist: Windows 7, Configuring Microsoft Certified IT Professional: Enterprise Administrator Microsoft Certified IT Professional: Server Administrator