I'm getting this error on my CAS server every 15 minutes. Despite this error, everything has been working just fine so i'm not sure what to make of it. Event Type:ErrorEvent Source:MSExchange Web ServicesEvent Category:Core Event ID:10Date:7/2/2008Time:5:47:53 PMUser:N/AComputer:[server] Description:CAS server[server] running Exchange version 0.1 (8.0.535.0) attempted to find a CAS server in AD Site [Server not in site]. Service Discovery failed in looking up the CAS Server in the target AD Site. For more information, see Help and Support Center at http://go.microsoft.com/fwlink/events.asp. Anyone have any idea how to make this stop?

I got the exact same error. The error itself is a bit strange too. Why would a CAS server look for another CAS server ?

Is there any firewall, Port rules, ACLs on switches/routers between exchange servers and Domain Controllers? Or is the CAS server in perimeter network? This error can also be logged if Exchange 2007 is running in mixed environment with Exchange 2003. Certain web applicatoins issue commands against exchange 2007 CAS where the user running the application have a mailbox on Exchange 2003 server. Since Exchange Web Services fails to contact Exchange 2003 server the event is logged. Do you have any Exchange 2003 server in same AD site? If so, this is normal occurance and can be safely ignored. It happens for the same reason stated above.

Bhargav- I have searched high and low for other responses to this issue. This is the only message I can find on the WWW in response to the CAS Server- EventID10 every 15 minutes or so in the Application Log. I have two CAS servers (different AD sites), only one displays the errors (externally facing). We do have three other Exchange 2003 servers (three other AD sites) If this is truly the issue is there any way to suppress the errors until all of the Exchange 2003 servers have been decommissioned?

Currently there is no way to suppress the errors. Update 5 for Exchange 2007 SP1 will address this. These events are logged when a mailbox is on Exchange 2003 server and Exchange Web Services are used to access the mailbox. EWS cannot access mailboxes on Exchange 2003 servers and the event is logged. Until Update 5 is applied, you can try to find the mailbox causing the events to be raised and move it to Exchange 2007 if possible.