My domain name, nealhere.com, has been around for a long time. That means spam accumulation. Though I've never responded to a single spam ad in my life, the soul-draining cretins at the other end have been sending me about 1,000 emails per day.
It's a miracle that the internet works at all, considering the signal-to-noise ratio.
Recently I decided to fight back. I'd been using Eudora as my email client for several years, but I switched over to Apple Mail. One of the client features is to fake a bounce of any received email.
The conventional wisdom has been that bouncing spam is useless. Spam usually comes from one-time addresses which are not maintained or even sustained. Yet I decided to try anyway.
I started sending back a "no such address" message to each "From:" address in my 1,000 spam messages.
Some of my bounces got bounced back to me, as expected. But it was a surprisingly low proportion, not more than 20%. My daily spam totals started dropping immediately. After three weeks, I've leveled off at around 500 spam per day. That's a 50% reduction in spam!
The spam filter on my Apple Mail client is very good, I never see more than 2 or 3 spam messages in a day. So this project was just to clean up my corner of the internet a little. If everyone did this, and spam was cut by 50%, the internet would be a much speedier place.
Of course, if more people did this, spammers would just ignore bounced emails, and my strategy wouldn't work anymore.
Update 2008-11-22
I'm down to 150 spam per day. I expected diminishing returns but I haven't reached that threshold yet.