End-to-end encrypted messaging does work, and Signal (among others) is proof of that.
With e-mail, either (a) you are backwards compatible and sending unencrypted (even by accident) remains a possibility, or (b) you break compatibility, but then it's no longer e-mail. (Signal is an extreme example of the latter: it just uses its own protocol.)
End-to-end encrypted messaging does work, and Signal (among others) is proof of that.
With e-mail, either (a) you are backwards compatible and sending unencrypted (even by accident) remains a possibility, or (b) you break compatibility, but then it's no longer e-mail. (Signal is an extreme example of the latter: it just uses its own protocol.)