John Dvorak has six ideas on how to spam-proof email. The last three are the biggies:

Spoof-proof authentication. Much of the problem with spam is that it comes from unknown senders who cannot be isolated or shut down. Spoofing is just too easy; we should be able to spoof-proof the system. Along with this idea comes authentication, so you know whom the message is really from. This would also minimize virus outbreaks; today, when you get mail from a friend with an attached virus, you can’t be certain who is really sending it.

Privacy. E-mail systems should be completely encrypted and secure. The U.S. Postal Service guarantees that mail is secure and cannot be opened (once posted) by anyone except the recipient. E-mail should have the same basic safeguards.

Systemic antiviral agents. There is no doubt that e-mail is the major distribution mechanism for viruses. This makes it less useful, because many people will no longer open or examine attachments from anyone. All messages should be signed and encrypted before transmission.

Now, can some of you smart network-type people tell me if any of these ideas are doable without needing an entirely new email system and software?