Spam Control, why is it so hard ?
It seems easy to me if you assume that spammers take down their email server. Require that every email provider sign the message with their IP or name. Also reqire it is send in an incripted form and requires a password ( or key) to decript it.
When the user goes to his client software ( Mozilla, Outlook etc) and clicks on "check for spam", the software goes back to the original provider of the email that was proviced in the email and requests the password ( or key) to decript it. Now just have the new versions of email servers out there refuse to forward mail that is in the encripted anti spam format.
They could use a form of PKI if they wanted, There are likely one hundred ways to do this.
There are things out there for Linux that will fire back an email to the sender saying "did you send this" That is another way to control spam. Can it be that hard to control ? I think I must be very nieve about spam. If a user does not have a ID ( IP or name) just do not forward his emails from email server to the next and do not have the client software accept the message. Spam too much, loose you ID.