The issue with this approach is that quite frankly - email by itself should be just like our water supply.
Better water exists, but it's not much better than the usual one. You can use water for many things, but it doesn't matter whose supply you're using.
E-mail must be kept that way: there's nothing to invent in terms of email itself. You can only invent on top of it. It's just like HTTP: HTTP/2 exists, but it doesn't change the idea of HTTP, it only evolves it.
Better water exists, but it's not much better than the usual one. You can use water for many things, but it doesn't matter whose supply you're using.
E-mail must be kept that way: there's nothing to invent in terms of email itself. You can only invent on top of it. It's just like HTTP: HTTP/2 exists, but it doesn't change the idea of HTTP, it only evolves it.