>Protonmail's method of encryption allows them to encrypt the entire message, including headers/metadata

I would prefer to see them promote standards to extend PGP rather than invest that time in a new, proprietary system with no buy-in from the email-related-software development community. I can follow the logic but I can also see their eyes lighting up when they realize this is a great excuse for having a proprietary, locked-in platform.

>It also encrypts the messages received that weren't encrypted when they weren't first sent

This could be done with PGP