@ Morely Dotes

I'm with you on this one. There are certainly overly-aggressive blacklists out there. (Spamcop comes to mind.) Spamhaus, though, is one of the most reliable I've run across; it's one of the few I'll trust to use to outright reject mail on my own server, as opposed to merely tagging it.

When ISPs are mistakenly rejecting legitimate mail, most of the time it seems to be the result of over-zealous and naive keyword blocking.