Thanks! I'll check it out, but it looks like there isn't a downloadable list, and inserting an extra DNS lookup as a check in my caching/resolving infrastructure isn't something I have been able to figure out how to do. Looks pretty sweet as part of an anti-spam filter tho!

Edit: I've emailed them asking about the possiblity

That looks interesting, but I would also like to see a read-only rsync endpoint that I could grab the zones (raw) or formatted zone data.