[daurnimator]

A major goal of an email-like system is full decryption of the entire history of messages.

Same as it's a feature of my filing cabinet that items don't incinerate themselves whenever I move house.

[tptacek]

Sure. Because people overwhelmingly aren't relying on the security of their email; it's overwhelmingly stuff no adversary would care to read. Then they retrofit the UX requirements they have for those boring mails onto all emails, and suggest that encrypted email should just accept those as constraints, and then we'll declare victory.