My view - as controversial as ever - is that the problem is unfixable, and mail will eventually fade away. That which will take its place is p2p / IM / chat / SMS based.
Which are easier to spam and less secure than smtp.
SMTP is p2p by definition, though you can use servers if you want.
SMS *IS* email , just a different kind of email - and a less secure, more expensive kind, in which the infrastructure is more in the hands of the large companies that run it and less accessible to users installing their own protections.
In that world, it is still reasonable to build ones own IM system for the needs of ones own community, and not to have to worry about standards. Which means one can build in the defences that are needed, when they are needed.
as we can for smtp
Chat is already higher volume (I read somewhere) in raw quantity of messages sent than email.
I suspect you don't get much traffic. The beauty of a non-real-time store-and-forward system like smtp (or SMS, or oldstyle conferencing systems with off-line readers) is precisely that it can be automated. I don't have to see mail I don't want.
A fate for email is that as spam grows to take over more of the share of the shrinking pie, but consumes more of the bandwidth
A higher proportion of the snail-mail I get is junk than the email. In fact almost all of it is (& most of what isn't is bills :-( - usually already paid by the bank) I throw more than half of my incoming paper mail in the bin unopened, and about half of what is left is just put in a cupboard in case I get into some dispute tithe the bank or the electric company or whoever.
A higher proportion of the landline phone calls I get are junk. At least 4 out of 5 calls, maybe 9 out of 10. Email is doing quite well.
> the ISPs will start to charge people for
email, and not for IM.
Why should they charge more for qa service which is not only cheaper for them to run, but has more competition and is harder to subvert? A serious proportion of the rootkits and so on that have been plaguing us for the last few years involves chat & instant messaging & so on. I'd block it at the boundary firewall. People who use it should just learn how to use mail. They'd get through more. Chat is for functional illiterates. Learn to read at adult speed and you'll prefer mail. Why should they put up with being limited to someone else's typing speed?