I read this

  Of course, we’re a hosted “cloud” service. If we turned bad, we could start silently changing your email. The best defence against any cloud service doing that is keeping your own copies, or at least digests of them.

Does this remind anyone else of that old Gmail Paper April Fool's prank? Last bastion of immutability. http://content.time.com/time/specials/packages/article/0,288...

Wait why do they have a legit link to it still? https://www.gmail.com/mail/help/paper/