Can we control spam? Probably not. When every scumbag who can get a used PC and can hook himself up through an ISP; and set up his very own mail server, there is no way to enforce the front-end of the pipeline. As Michael J. Miller’s editorial in the 30 December, 2003 issue of PC Magazine says, "In the long run, the only real solution may be to rearchitect the way the Internet handles e-mail. And that approach has its own problems. One thing’s for sure: There are no silver bullets here."
This reenforces the fact that the only thing that silver bullets are good for are to kill non-existant creatures (Vampires); no wonder they don’t exist for/(work on) real world problems. Spam will only be controlled when the architecture of the mail server changes to prevent the spoofing of valid servers.