Right. I'm saying it's not possible, and that Protonmail should be honest about the limitations with their approach, so that people who have stricter security needs than are met by their threat model don't mistake their system for anything more secure than it is. Their home page has the following text:
>All emails are secured automatically with end-to-end encryption. This means even we cannot decrypt and read your emails. As a result, your encrypted emails cannot be shared with third parties.
>All emails are secured automatically with end-to-end encryption. This means even we cannot decrypt and read your emails. As a result, your encrypted emails cannot be shared with third parties.
This is a lie.