I have a front-end email server in the DMZ and it communicates with a back-end email server in the INSIDE network. Everything is working fine. My question is what tells the FE server what BE Exchange server to use? I don't remember ever telling the FE that here is the BE server...It just found it (probably by saying "this is a back-end" or this is a front-end" in the RPC-HTTP properties of the server). But what happens if I need to fail over to a backup Exchange server? How does the FE know to redirect the email traffic to the failover Exchange server and not he primary Exchang server that is down? Thanks in advance!