Protonmail has the ability to send a password-encrypted message to anyone. They just get a link and you have to give them the password through other means. All

Protonmail has the ability to send a password-encrypted message to anyone. They just get a link and you have to give them the password through other means. All encryption is handled client-side in js (they recently became maintainers of that library as well, iirc). The message can also expire after x days and the recipient can reply. I'm not sure if I like how they're basically inventing their own encryption scheme for emails instead of supporting pgp, but for these use-cases it's quite slick.