Well, encrypted telepathy might be a bit beyond our tech level this decade, but you do raise an interesting point. If our current email system is essentially useless, we may finally be at the point where we can scrap it and create a replacement that isn't fundamentally vulnerable to spamming. Many of the anti-spam retrofits like SPF are limited by having to retain backwards compatibility. If we're giving that up, we could probably come up with something that works better and is easier to implement

Interesting question: if we don't voluntarily scrap the existing email infrastructure, how long until spam makes it effectively 100% broken anyway?