Dear Support, We have installed Exchange 2007 on a site which was already having exchange 2003 clustered and Exchange 2003 Front End server. Exchange 2007 without SP1 was installed as following. Clustered Mailbox Server (SCC) with active passive roles. CAS and HUB transport server was installed on other server with exchange 2007 Problem mails are not flowing in from old exchange 2003 front end server to old exchange 2003 clustered backend server. prior to installing exchange 2007 mails were flowing in without any problem. After installation they arent flowing in. Could you please let me know what could be the problem. Regards Mohammad Anwaruddin

Hi Mohammad, Would you please provide further information regarding the issue? 1. Whether are the Exchange 2003 Front-End Server and the Exchange 2003 clustered server in the same Routing Group? 2. Whether all the Exchange Servers are in the same AD site 3. Whether the messages hang on the Exchange 2003 Front-End Server when recipient mailbox is on Exchange 2003 clustered server. If the message hangs on the Exchange 2003 Front-End Server, please check which queue the message hangs on and what the Addition queue information is If the message does not hang on the Exchange 2003 Front-End Server, please let me know whether any NDR message is generated or some other symptoms are encountered. For more information regarding the Exchange 2007 coexisting with Exchange Server 2003, you can refer to the following article: http://technet.microsoft.com/en-us/library/aa998604(EXCHG.80).aspx Mike

Hi the problem of Mail flow is sloved as i created a registry entry for MTU value on the backend cluster. Well the other problem i am only facing now is below EventID 2604 Source MSExchange ADAccessProcess MSEXCHANGEADTOPOLOGY (PID=1456). When updating security for a remote procedure call (RPC) access for the Exchange Active Directory Topology service, Exchange could not retrieve the security descriptor for Exchange server object DPQMBXV01 - Error code=8007077f. The Exchange Active Directory Topology service will continue with limited permissions.andEventID 2501 Source MSExchange ADAccessProcess MSEXCHANGEADTOPOLOGY (PID=1456). The site monitor API was unable to verify the site name for this Exchange computer - Call=DsctxGetContext Error code=8007077f. Make sure that Exchange server is correctly registered on the DNS server. Please throw some light on this error.

Hi Mohammad, Please check whether the following update has been installed: http://support.microsoft.com/kb/948496/en-us If the update has not been installed, please install the update and reboot the Server to troubleshoot the issue. Mike