I just tested tutanota. The interface is clean and nice but the encryption to external contacts is the same as in Gmail (link back to tutanota and shared passwords).

Why can't these services use something like OpenPGP's Web Key Discovery [0] fetching key from https://domain.com/.well-known/openpgp/hu/hash-for-localpart and avoid links altogether?

[0]: https://www.gnupg.org/blog/20160830-web-key-service.html