I haven't needed to contact support, but I think they have a manned tech support email address too.
Just get a domain like `Smith.com` and then use the email `John@Smith.com`. Then it doesn't matter if you're using Gmail, Fastmail, Protonmail, etc. You can switch to a different company whenever you want (to get the best rate, avoid abusive terms, bad service, etc) without having to update your business cards, websites, online accounts, etc.
You'll still need to have a way to back up your old messages though.