I’ve used iRedMail hosted at home for the last year or so and love it. Even has ActiveSync integration for mobile devices. The key to selfhosting email IMO is to use a SMTP relay service to send outbound mail. I use SMTP2Go and it just works, even free. Everyone’s complaints about blacklists and reputation go away when you use a reliable relay.

Just for future reference, there’s no need to wait until expiration to move to a new registrar. The new registrar is required to honor the time left on your current registration. I’ve moved domains with years left and no issue.