Here is a few things that you will need to do: 1. Configure postfix properly. Meaning, it is not setup to relay mail, and accepts and delivers mail to the domains and destinations you would like. 2. Install a pop3/imap server so you can retrieve your email (dovecot or courrier should work fine.) 3. Change your DNS MX record to point to you new server. Thats a quick and very high level overview. You also may consider just signing up with google's hosted mail service http://google.com/a/