You don't even have to forward, gmail can use POP to fetch messages from your email provider and it will also send mail via your providers smtp gateway. If gma

You don't even have to forward, gmail can use POP to fetch messages from your email provider and it will also send mail via your providers smtp gateway. If gmail goes down the mail will just remain on fastmail. I do this for my own domain and it works fine, the only caveat is emails can be delayed by 30 minutes or so as gmail uses some heuristic method to time its POP fetches. Its a good solution as you get gmail features like classification and auto reply hints, but you can ditch gmail at any time if google become too obnoxious.