I see, but to my defence, it was not a high traffic mail-list and the challenge went only out to "suspect" addresses ("hotmail" accounts and similar throw-away addresses)

Of course the challenge was not posted to the list, although the answers of those who were challenged did make it to the list!

Now I have given up on the challenge-response system and use a Bayesian (not sure about the spelling here!) filter which filters better than 98% of all spam.

Strange as it may seem, now that my ISP has installed their own anti-spam protection scheme, the efficiency of my local filtering system dropped.

CountZero

"If you have four groups working on a compiler, you'll get a 4-pass compiler." - Conway's Law