On Mon, Apr 07, 2008 at 02:43:56PM +0200, Johannes Wiedersich wrote: > IIUC, you propose that there is a special way for non-subscribers to > post, that locks out spammers at the same time? How should that work? > > The only thing I could imagine, is one of those silly 'type the letters > that you find in this image' stuff.
I believe the technique you're looking for is "greylisting". Basically, the way it works is that, on receiving mail from an unrecognized address, the server lies and says "I'm too busy to accept that right now. Can you try again in a few minutes?" All full-featured mail software will recognize this, requeue the message, and try again to deliver the message after (usually) 5 to 15 minutes, at which point the mail will be accepted. The vast majority of spam mailers are half-assed pieces of crap thrown together as quick-and-dirty as possible, so they pay no attention to the server's response (if they even hang around to receive it at all) and never come back to try again. No user interaction is required in this process and its only user-perceivable cost is a small delay in receipt of the first message from any given sender address to the greylisting server. Greylisting isn't 100% effective, as it doesn't work on spam that comes through an open relay (or a mailing list...) and some spam mailers actually implement SMTP properly, but it still works very well. When I enabled it on my mail server earlier this year, the volume of spam received immediately dropped by 70-80%. -- News aggregation meets world domination. Can you see the fnews? http://seethefnews.com/ -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of "unsubscribe". Trouble? Contact [EMAIL PROTECTED]
