There are some interesting thoughts here about how to solve email's problems ... but I'd like to put forward some thoughts...
I believe it was Cantor, of Cantor and Siegel, the first big and _well_known_ spammer of Usenet and the Internet (but not the first outright spammer of the internet), who said that the internet we know and love was going to go away, and it was going to be people like him who killed it. What he meant was we had to accept commercialization of the internet and its communities, but I think a more realistic meaning might be "Spam killed Usenet, driving people to web-forums, and Spam will kill email, driving people to the 'embedded email' in social networking sites". Along those lines (and I'm sorry I can't cite this) there was a study a few years ago where late teens (or was it college freshmen, something like that) were asked about communication mechanisms that they use. For them, it was all about social networking sites and texting. How did they characterize email? "that's how you talk to old people". Meaning that the death of email is already on the way, and the cutting edge of this blow is the generation gap between those who used the internet before the rise of social network sites and texting, and those who came into their own during the social networking/texting era. The former group are "old people", and the latter group only use email to talk to those "old people", for everything else they use social networking sites and texting. In a way, social networking sites provide that "end to end authentication" that was proposed in here. Someone definitely authenticates to get on myspace, or facebook, so that they can send their buddy an "email". And all 0 hops are within a protected/authenticated sphere of influence. Now imagine if myspace, facebook, etc. all began to exchange messages with each-other. We'd have definite ability to track a message back to its source and squash misbehaving senders. That's the good news, and it definitely fits the "end to end trusted authentication" model for email. The bad news is threefold. First, there's already spam on myspace. It's not as prevalent, because it's a closed environment, with a single authority that can act unilaterally to squash spammers. Hopefully, in the "social networks talk to each other" model I just presented, they would continue to cooperate on this level (a spam generated on myspace, and delivered to a facebook user, would be honestly/accurately/promptly handled by myspace when the facebook user hits the "this was spam" button). But we can't really know how these competitors will deal with each-other's spam, if this ever happens. Second, it's a completely closed environment. You can't really just register and set up your own domain name, your own mail server, and go at it, like you could with the "old" model of email. This helps to eliminate spammers, but it also eliminates expert-hobbyists, SOHO businesses, etc. It also makes it virtually impossible for the expert end-user to delve into the innards of their email. IMO, one of the great early avenues to learning about how the internet works was ... deciphering the inner workings of email. This version of a closed email environment would, for good and bad, be the end of the "old west" of the internet. No more turbocharged lawnmowers on the information super-highway. Third, without the social networks talking to each other for message exchange ... what we will end up with is islands, or silos, of email. You can't just say "all of my email goes to my home email server" or "all of my email goes to gmail/yahoo/whatever", giving you a single point of contact. Your friends have to somehow let you know "you need to check the message I sent you on myspace" ... not just "you need to check your messages". The good news about myspace and facebook is that they will send your email-of-record a notice that you got a new message, and from whom (facebook will even send you the content of the message). But I've dealt with some social networking sites that can't be made to send you notices -- you have to login to find out whether or not you have messages. And, frankly, I think that creates a huge barrier to communication. As much as I love the historical internet, the "wild west" as it were, and all of its opportunities and capabilities ... I think that's going to die. The younger generation (egad, I turn 40, and immediately start talking about "the younger generation") doesn't care about, nor want to use, the old model of email very much. 95% of email is spam these days. Creating a closed model out of the old model of email is probably not feasible (too many chefs, too many cowboys, too many turbocharged lawnmowers), and a replacement already exists* (social networking sites). And that existing replacement is probably where things will go. Within the social network site model of email, either we will end up with something like the current model (social networking message silos, and perhaps notifications sent back to your dinosaur email address, or notifications sent to your IM/SMS/MMS address(es)), or we'll end up with something that creates a connected version of that, such that the social network sites can send email to each other. Either way, I am willing to bet that email as we knew it 10 years ago is on its death bed (if not already dead or in a coma), and email 10 years from now will be dramatically different than what we thought of it so far. (* and, arguably, that means it's too late to engineer a better replacement; if there's any one truism of the computer age, it's that once the masses get their fingers on it, it's too late to solve it via engineering, you're stuck with whatever model they embrace, whether it's a defacto standard that abuses an existing technology, or a poor standard that got popular before a better one could replace it ... it doesn't matter how stupid the solution they came up with might be; as evidence of that, I'll put forward the success of web forums, the failure of mbone, and the success of email as a file sharing mechanism).
