HTTPS is one way, which makes it easier for users. The UX for the user is (relatively) easy, even if it still has issues: check the URL bar. On the other hand,

HTTPS is one way, which makes it easier for users. The UX for the user is (relatively) easy, even if it still has issues: check the URL bar. On the other hand, the server administrators have to contract with a CA, get certificates, configure everything correctly, consider browser compatibility, etc. Email must be two way. Suddenly _every user_ has to do what HTTPS server administrators do. And then they have to convey the intent of a signature or the availability of an encryption key to their correspondents. I think this is what inherently makes email cryptography much more complicated from a UX perspective.