Other people have mentioned Tutanota; as a user myself I can point out a few pros and cons:
Pro:
- Extremely privacy focused - everything is encrypted and even they don't have access to your email content.
- Pretty cheap for a pro subscription (although they recently changed prices and I'm not sure exactly what the new ones are like).
- Pro subscription you can use custom domains and set up a few aliases.
- Generally works fine.
Con:
- Can only use their custom mail clients (in addition to the webmail interface), because they use their own encryption algorithm.
- Tutanota is so extremely hardcore about security that it seems like a detriment to their user experience. I used to follow the Tutanota community on Reddit and there were so many posts from people who tried to sign up or access their email and were blocked, and they had to go through quite a process to get unblocked. I myself went through a period where I kept being unable to access my account on my phone and it turned out to be that they were blocking me because of "too many IPS connecting to my account from the same IP". I have 2 devices connecting - my PC and my phone, so apparently 2 devices is too dangerous for them. That happened 2 or 3 times for a few days to a week each time, but I haven't experienced it for a while now, though.
- The user interface is not for everyone. I don't mind it myself, but I've seen a good number of people complain that it's too sparse and/or ugly.
- Search is annoying - because everything is encrypted, emails can't be searched on the server side so the clients have to do the searching locally which requires building an index. If you happen to clear your storage you have to reindex everything again. It's also pretty slow and annoying to index further back than a few months.
- You don't get much storage (like, only 1gb or something) and you have to pay to get more.
Overall, if privacy and control over your own email is important to you then Tutanota is a great choice. Just be aware that usability can be kind of a hassle.