It depends, it can be... But tbh just set up a cronjob (auto repeating task) that refreshes your ssl certificate via certbot and you should be good to go. The initial setup might that a few hours of tinkering, but once you've made it you can easily have a mail server for $1-3. If you really don't wanna fully self host you can buy a Plesk workspace for like 99ct-5$ which allows emails, websites and databases