We have 2 domain controllers - DC01 (win2003) and DC02 (just upgraded to win2008). We are also running Exchange 2003. This past weekend we did maintenance on DC01 and when it was down, all email seemed to fail. The Exchange server also had the following errors in event logs LDAP Bind was unsuccessful on directory server.domain.com for distinguished name ''. Directory returned error:[0x51] Server Down. Windows cannot query for the list of Group Policy objects. Check the event log for possible messages previously logged by the policy engine that describes the reason for this.and a bunch of others similar to these. Why isn't Exchange finding DC02? Both DC's are GCs.It's as if it doesn't recognize it as a DC. If I go to the properties of the Exchange server, the Directory Access tab has "All Domain Controllers" selected. Any help is greatly appreciated.Thanks,Scott

Hai,You may try the following steps toresolve this issue : Open Exchange System Manager. Expand the Recipients container, and then click Recipient Update Services. Double-click each Recipient Update Service, and then change the Windows domain controller setting to the new Windows domain controller in the domain regards from www.windowsadmin.infoManuPhilip

I'd also say make sure that the firewall is open to that 2nd DC. I'm assuming it is since you upgraded it and it was working before. Mark Morowczynski|MCT| MCSE 2003:Messaging, Security|MCITP:ES, SA,EA|MCTS:Windows Mobile Admin|Security+|http://almostdailytech.com

Thanks for the suggestion. I did double check that and Recipient Update Service is pointing to DC02 (the server that was online). But I'm still unclear why Exchange couldn't find the other domain controller when DC01 went down. I checked the Directory Access tab of the server properties and its set to "Automatically Detect servers" and both servers are listed below.As far as the firewall, I did a netstat -aon and the server is connected to both DCs on 3286 and 389. I was also able to telnet to the DCs on these ports. Are there any other ports that need to be opened?

Hi,Please check event 2080 from event log and then check the settings against with the article below:Event ID 2080 from MSExchangeDSAccesshttp://support.microsoft.com/kb/316300Regards,Xiu

Thanks for the great tip.I ran the diagnostics and everything came back fine - as expected. I'm still not sure what's causing this though. I don't know why Exchange couldn't find the other DC.Thanks,Scott

Hi,Please post the event 2080 here.Beside,please try to run policytest.exe to see if it can find the DC.Description of the Policytest.exe Utilityhttp://support.microsoft.com/kb/281537Regards,Xiu

HiIf you have a windows 2008 DC as an additional DC then change all the FSMO roles to the windows 2008 DC.Make all the DNS entries in the new DC and make the windows 2008 DC as a DNS server.Change the DNS server Ip address in the exchange 2003 to the new windows 2008 DC's IP address.Change Recipient Update Services DC to the new Windows 2008 DC in Exchange System Manager.Now you can get rid of the windows 2003 DC and Restart the system attendant service once, so that the new DC will be automatically detected as a configuration DC, DC and GC in the dsaccess tab in the server properties.Now your windows 2008 DC will contact the exchange 2003.ThanksVinod