Hi, We have Exchange 2007 Mailbox Server in Internal netwrok & CAS server in DMZ. Can any one help me to get the required ports between Mailbox Server & CAS. Thanks in Advance, Regards, Gnanavel

This is not a supported configuration. The only Exchange server that is supported on DMZ is Exchange 2007 Edge role. This link gives you more info http://support.microsoft.com/kb/270836 the standard way of solving this is to use a reverseproxy on DMZ, prefferably an ISA server.