BREAKING NEWS: 1500 SATS now lets you route mails from your own domain (you@yourdomain.com) to relays of your choosing.
All e2ee encrypted to your npub ofcourse.
Check it out at: 

Mail by Formstr
Mail by Formstr — Email only your key can open. you@mailstr.app
Mail to you@mailstr.app is encrypted to your key and stored on relays you choose. Pay once with Lightning.