It would be monumental to get people to shift en masse, I agree. Perhaps it could start off as a niche service to contact really popular people who could comma

It would be monumental to get people to shift en masse, I agree. Perhaps it could start off as a niche service to contact really popular people who could command high fees to speak to them. For instance, $MOVIE_STAR could have a $500 message fee (that goes to charity) to be able to say something to him/her and maybe get a reply. This could popularize the service, and it could grow over time. Another problem is that the legacy email providers would not like transporting encrypted payloads that they can't mine personal data from. Attachments could also be a headache, do they get stored for free? On the chain or on the recipient server?