MarkedMan writes "The link points to a well researched article on Spam lists and those innocently appended to them. I have seen this myself with MailWasher. A posting will come through as potential spam, with the the bounce already red-flagged, but it is actually from a legitimate source. Only happens once or twice a month but still cause for worry.
I've found that Spam Assassin
has made life easier, but I still have to ban domains like yahoo.com, hotmail.com, mail.com - and *.ru and *.cn. I sort through the spam periodically, but the collateral damage is still there.