1) When I send an email to someone, why would I care whether they can forward it and prove I wrote what they forwarded? I want to prove I wrote my emails, not t

1) When I send an email to someone, why would I care whether they can forward it and prove I wrote what they forwarded? I want to prove I wrote my emails, not theirs. If Apple/GMail/Office365 feel this is important, they can include a signature for the decrypted text -- this could even be togglable. Then when you hit "forward" on an email sent with that toggle enabled it includes the signatures of the earlier senders in the chain for provability of those content blocks. But this isn't how DKIM works and I don't think it really matters. If I'm wrong about it mattering, see above for a quick solution. 2-3) What? Not seeing the problem here? Do you also think encrypted emails need to prevent someone taking a photo of their screen with their phone and sending the photo to someone else? If we can't prevent screenshots and copy/paste of decrypted content, we just shouldn't encrypt anything? What is the logic here? 4) It would also be signed by DKIM and/or the sender's private key, so your proposed MITM attack is not trivial at all. Are you aware of DKIM and PGP signing? You're trying to establish authority with "Email wasn’t designed with encrypted headers in mind [so you can't do it]" but that authority is undermined by not demonstrating understanding of modern email. 5) By the magic of controlling 90% of all end-user email in the western world, a consortium of Apple, Gmail and Office365 can do whatever they goddamned well please.