... it's unstable on my machine running 10.3.4 (unexpected quits after running the filter). Moreover, although the downloaded filters are great, many of the spam-blocking tools are of limited or even negative value. Finally, the help pages simply weren't installed correctly and were no, erm, help whatsoever.

Very few spam mails originate from a bona fide domain, so blocking domains is really pointless and may end up blocking mail you want to receive. Bouncing spam is mostly pointless and just adds to the overall spam traffic (if you've ever had your email addy used by a spammer you'll know how irritating the bounces are -- to you the non-spamnmer).

The whole 'revenge' idea is satisfying but flawed. You really do NOT want to engage in private feuds with spammers. Report them, great. But you are setting yourself up for trouble if you use the WebBugs feature.

Overall it didn't seem to identify any more or less spam than Mail itself, properly configured (and I get THOUSANDS of spam messages a day).

The single best spam trap is simply to quarantine all messages that do not come from a previous recipient or someone in your address book. Junk everything that looks like spam, and anything that isn't classified as spam but comes from an unknown address, put in a 'Possible Spam' folder. Go through this periodically (it won't have much spam in it) and mark the junk as junk to keep your heuristics fed and watered.

That's it.