BLUNT QUESTIONS: *WHO* pays me to figure out 'which parts' of a provider's network are riddled with problems and 'which parts' are _not_?
I don't know the answer in your case, but in my case the answer is my employer. More specifically, my employer pays me to block junk and let good traffic* through; that mandate does not include "block networks that we have no reason to believe are junk in hopes of inflicting enough collateral damage to force the spammers' upstream to clean up its act." If your customers/employer/whomever understand they may miss data they wanted to receive in order to help you put pressure on lazy/abusive/incompetent ISPs, and they're okay with that, more power to 'em. I think probably more people are in my boat-- I can't afford to launch a crusade, I just have to keep the bits flowing. *On the other hand, in a corporate network "good traffic" can be more strictly defined; for example I block most of APNIC, half of RIPE, most of LACNIC and all of AFRINIC not because I think they're all spammy but because we get no legitimate business traffic from those regions which makes their signal-to-noise ratio effectively 0:infinite. So if you know a provider will never** send you legit messages, go ahead and block. Otherwise, **My sweeping xenoemailphobia has blocked 4 legit messages (3 of which were personal non-work-related messages) in the past 6 years, and since my reject message gives a workaround to reach me all 4 reached their intended recipient. Compared to the 5-15k messages blocked per day over that span, close enough to never for me-- and more importantly, for my boss. -- Dave Pooser, ACSA Manager of Information Services Alford Media http://www.alfordmedia.com