The problem with trying to kill email is that you're never going to have everyone migrate off of it. It's going to have to be some type of layer on top of IMAP that then moves to a more sophisticated protocol. Google has done such a great job with NLP/AI/ML that spam from facebook, twitter, etc. are all put into a separate tab that I only see when I want to. When I click on an email about a flight, it gives me updates on the status of the flight. Gmail also makes it seamless to share docs. I could make a clean interface for email groups using the Gmail API and have the same product as slack. What am I missing here?