Spamhaus and some other antispam lists can be extremely aggressive with their filtering, sometimes blocking whole networks because of a couple reported incidents of spam. They are also, in my experience, completely unresponsive when contacted for information on why the blocks are in place. So it's not like they're making it easy for abuse departments to comply.<p>In some cases (don't remember if this was spamhaus though) the list owners will suggest that if you pay them a consulting fee, they might assist you (where assist means forwarding the message that got flagged so you actually know what spam they're talking about). The lists that do this are running an extortion racket, but unfortunately the people using them don't really see that side so they think they're just following best practices by using them.<p>I hate spam. But having had to deal with the people running these blocking lists, I hate them too.