Personally I prefer Migadu and tend to recommend them to tech savvy people. Their admin panel is excellent and straightforward to use, prices are based on usage limits (amount of emails sent/received) instead of number of mailboxes.

Migadu is just all around good, only downsides I can find are subjective. The fact that they're based in Switzerland and unless you're "good with computers" something like Fastmail will probably be better.