Proton's full encryption is only if you email to another Proton user. Other email providers would not be able to decrypt the message for the user to read. While

Proton's full encryption is only if you email to another Proton user. Other email providers would not be able to decrypt the message for the user to read. While readers of this board might not need the distinction to be made, the vast majority of the population definitely does though. I have had multiple conversations with people that did not consider their Proton mail sent to a Gmail user wasn't fully encrypted. Encryption is hard to get right on multiple levels. The biggest hurdle however will always be end users.