I ahve the following on my dnslist entry, which I copied from this list some
month ago and I modified it since.
However, rechecking my configuration make me wonder, wether this is legal,
since there is something about pricing on their homepage.
However, they do not claim, that one needs to pay for it and pricing
information is only available upon form completion.
The list in question is: blackholes.mail-abuse.org