[textile]

(I'm attempting to mark this up in Textile, but the preview doesn't look right. I'm hoping it's just because the Textile isn't processed until it is actually posted and not that I did it wrong...)

bq. If it's by the delivered address, then yes, it is either you or them, because the spam campaign stops when it gets to the number of delivered addresses paid for. If I were a "smart" spammer, this is what I would pay for.

Ah, yes. That's assuming the contractual agreement is of the "send exactly this many emails at $X per email" nature, in which case you are correct. I was assuming is was more of the "for $X I'll send your email to everyone on my list" nature, in which case it is not a me-or-them scenario. But at least for the dictionary attack method of spamming, your assumption seems more plausible.

bq. Alas, once tempfailing becomes very popular, it loses its effectiveness, as the spam software will start dealing with it.

Except, as I noted, spammers will have to send everything twice... at least the first time they send to a particular server.

bq. And it comes at some cost — it does delay your legitimate mail somewhat.

Yes it certaintly does. But today not greylisting has an even greater cost. I run an SMTP sever on a home server which provides email to myself and my family. The less processing and the less bandwidth I deal with the better. I agree with you in principle that the altruistic approach is best... but I'll let the guys with the resources be altruistic O:-)

Anyway, I just read your proposed solution at http://www.templetons.com/brad/spam/endspam.html and it all sounds good to me.