I am trying to get a handle on spam we receive in our INBOX every day, hour, minute. I guess the only way to curb spam is to charge for e-mail messages sent.
Since e-mail is free (well, you got to pay for your ISP or so), it doesn't really cost a spammer anything to send out millions of messages. If only a minute subset spam recipients respond, and a subset of those buy a product advertised, than it already pays. If nobody bites, no financial harm done for the spammer, since there is no cost involved in sending messages.
So why not charge for e-mail? The amount should be dynamicaly proportional to the relation of e-mails sent vs. e-mails received. So if you receive a lot of e-mail and send a lot, you can keep it the balance, but as soon as your overproportionatly send more than you receive, you're getting dinged for every message sent. And all this should work with a pre-paid plan. Before you can send, you need to pay. Your account is balanced as long as the ratio between send and receive is balanced.
But since that is not going to happen (or is it? See ABM), I helped myself by deploying the following software:
Read all about spam on /., specifically here