I had this idea a couple years ago, but I think I've found a way to simplify the whole thing.
Email as web pages:
Fundamentally, email is just a message written by one person, intended for another.
Use RSS to see if a friend sent you a message (auth'd RSS access).
Separate channel for requesting a contact: easily eliminate spam.
There is no message sending, just publishing and syndication.
It makes for awesome webby services on top of an incredibly simple API.
Know if someone viewed your message: did they auth into the system and load the page?
Receiving messages is opt in (subscribe to updates from this person), eliminating spam and unknown senders.
Set a message to group-private or world-readable.
Adjust message contents, visibility/recipients later.
Use this, in fully public mode, as a blog.
It's a messaging service built on RSS (or some other pull-notification system).
No passwords: we send you an out-of-band message (email, sms, tweet, FB message...) with a link and/or one-time password.
HTTP caching makes it really simple to build clients. It's just web pages.
No need to subscribe to a company's newsletter: you can convert any RSS feed into a stream of "emails".
This is a totally federated system, since it's built on open RSS tech.
Your messages can be fully-featured web pages; no weird email-safe subset to learn.
This might be a lot of fun to build.
Because it's web tech, you could easily connect RSS updates to emails or text notifications.
To be clear, the new spam is unknown people asking if they can message you.
But that's way way different than email spam: you can start by importing your existing social graph and have a trusted list of senders right off the bat.
How do we connect a person's identity to a given website? How do we prove ownership of a given web address?
How would we address messages? user@domain? Maybe a .well-known file on domain tells you how to convert the user part to an endpoint for viewing and an endpoint for subscribing.
Has this been done before? Would it scale better than existing messaging systems? Could RSS really work?
It would definitely blur the line between email and web pages: content becomes content, whether public or private.
A great reading interface suddenly gives you email and RSS shit in the same bucket. Who would want that?
Would I really wnat that?
Maybe we want an extension to rss/atom that is performant that does the lazy notifications.
Optimizations can come later. The main thing is: would this be an improvement on the insane mindfuck universe of email?
IMAP and POP are silly. They dictate bad UX. Syncing folders? Can't we do better?
Email-as-web-pages lets you build up any kind of interface you want.
Maybe something to play with building.