* Fastmail.com -- good reputation and track record at reasonable prices
* mailbox.org -- long track record, privacy-oriented, German-based. Some people describe the mail UI as aging (it's OX suite), but I like it just fine.
* Protonmail.com -- UX & privacy focused email with fancy in-browser encryption. Protonmail-to-protonmail emails are E2E (OpenPGPjs). No IMAP, and in-browser (read: scary) encryption, albeit open-source. Based in Switzerland, although that means a lot less than they make it out to, re: privacy.
* tutanota.com -- V. similar to Protonmail. Based in Germany and a cheaper than protonmail. Uses a custom-implemented encryption protocol vaguely and unreassuringly described as a "..standardized, hybrid method.." comprised of RSA and AES [0].
[0] https://tutanota.uservoice.com/knowledgebase/articles/470732...
EDIT: Made some corrections re: protonmail & tutanota encryption, pointed out by bartbutler.