>>106028277Mostly. I don't know much about proton's encryption but I know they, tutamail, and my work exchange all explicitly state that messages are encrypted only if you are sending to someone else on the given service (and they'll usually give like a lock symbol or something to tell you which were encrypted). Which makes it pretty worthless unless you and the person you are communicating with specifically get the same email provided since I don't know anyone IRL that uses an email other than gmail.
>but if they both used IMAP they could use GPG to encrypt it?It's simpler than that. You can always encrypt a plain text file with GPG then send it and have the receiver decrypt it (you encrypt it using the receiver's public key which requires their private key to decrypt). It is not dependent on the use of imap (that is just the method used to sync messages between your client with the mail server). So if you do everything fully manual, you can write the message body in a text file then use the sendmail cli to send that as an email. To encrypt it, you would call the gpg cli on the txt file first, then send the resulting encrypted file. This is independent of the email provider you use. Various email clients have the encryption built in (for example thunderbird). You can add your gpg keys and collect the public keys of people you email with, and it will automatically run gpg before sending a message to someone if it has their public key. And will automatically decrypt a message that has been encrypted.
In short, it has been made reasonably simple. You don't need to be very comfortable with a computer to use this. It is secure and interoperable. It's a solved problem but these email providers found a market in making a worse method to, again, lock consumers in to their environment and allow them to charge for basic features (proton charges for bridge to allow you to use imap so you can access their mail from a regular email client)