> On the other hand, it is also legal and ethical to make a list of which senders are sending spam to people who haven't opted in, and try to filter out all mes

> On the other hand, it is also legal and ethical to make a list of which senders are sending spam to people who haven't opted in, and try to filter out all messages from such spammers. Yes, that's true, and IMHO admirable. The difference is that people who send spam are organized and have substantial resources. Organizations like Spamhaus (which do exactly what you suggest) are under constant threat of extinction by well-heeled adversaries. http://www.spamhaus.org/news/article/698/ http://www.spamhaus.org/news/article/698/ Quote: "The Spamhaus Project offers congratulations and its sincere thanks to the Dutch Public Prosecution Service (OM), the Dutch National High Tech Crime Unit (NHTCU) of the Dutch Police Services Agency (KLPD), the Spanish National Police (Catalonia branch in collaboration with the Central UDEF), and any and all other entities involved in the recent arrest announced in regard to the Distributed Denial of Service (DDoS) attacks on Spamhaus in March 2013." The bottom line is that it's an uphill battle to fight organizations who have both resources and ill-advised laws on their side.