Tutanota went with a different tradeoff so they have E2E encryption of subject lines etc. Downside is that they can't support other clients, which is why I woul

Tutanota went with a different tradeoff so they have E2E encryption of subject lines etc. Downside is that they can't support other clients, which is why I wouldn't have even considered them if the apps hadn't been open source. https://tutanota.com/secure-email/ https://tutanota.com/secure-email/ They also have a pseudo-workaround for using E2E with external users - if I send a secure message to foo@bar.com, I can encrypt it with a pre-shared password and their mail will get a link to a web "mailbox" where they can enter that password to decrypt the message. Clunky, but I wouldn't know how to do better.