I have two Exchange Server 2003 servers

One is the Live Server and the other is the backup server.

currently i am automaticllay backing up the databses onto the backup server nightly. Is there anyway that i can repliacte or synchronise the mailboxes and all items to the backup server. So if the live server fails i can then just rename the backup server and users can continue to use the e-mail service. I have looked at SRS but when i enable the service the service is not available when i expand the tools menu

any help would be really much appreciated!!!