Check protonmail.com and tutanota.de as alternatives

It is worth noting that these don't support IMAP and Contacts/Calendar like most email services do. (They say that it has to do with how they handle their encryption)

ProtonMail does have an IMAP bridge you can setup locally.

(Only for Windows and Mac OS, though)

https://protonmail.com/bridge/install

IMAP on Linux does work as well. It's a stable beta. I use it w/o any issues.

Thanks for noting that. Strictly speaking, email doesn't include contacts and calendaring, but it completely slipped my mind and I had already shortlisted Tutanota.