Not your server, not your rules. Start self-hosting. With yunohost or freedom it's very easy.
Discussion
I set up a yunohost once, but never switched. Everyone says self hosted email is basically impossible because of spam filters
If you aren’t coming from one of the big companies or haven’t spent money and brokered deals so your messages can get through there’s no way to use email effectively with self hosting.
Totally not true with real experience