The theory behind closing open relays, blocking port 25, etc., seems to be: (a) That will make it harder on spammers, and that will reduce spam -- some of the spammers will find other other ways to inject spam, but some will just stop, OR (b) Eventually, we'll find technical solutions to *all* the ways spam is injected, and then there will be no more spam.
There's little evidence for either.
the empirical evicence seems to support this theory. spam has continually increased, wich occasional dips when the spammers have to find a new path when an old one is covered. i suspect that, if we opened smtp relays again, unblocked 25 for consumer chokeband, etc., total spam received would likely increase a bit. but my guess, and i mean guess, is that the limiting parameter could well be how many bots the perps can get, not how well those bots are blocked. but, let's look at the upside. with the dying economy, the spam war provides employment for many of our friends. randy