> Why hasn't someone built an email system that only accepts signed payloads? Because it requires both parties to play along. Lets say I had such a service a

> Why hasn't someone built an email system that only accepts signed payloads? Because it requires both parties to play along. Lets say I had such a service and I signed up for an account on Github. Github would have to implement this and give me a key. OK, maybe they do; but Stack Overflow don't. Then I end up reverting to Gmail or Fastmail.