zen.spamhaus.org*2,bl.spamcop.net*2,psbl.surriel.com*2,spamrbl.imp.ch*2,noptr.spamrats.com*2,escalations.dnsbl.sorbs.net*2,bl.score.senderscore.com*2,bl.spameatingmonkey.net*2,rbl.realtimeblacklist.com*2,dnsbl.dronebl.org*2,ix.dnsbl.manitu.net,b.barracudacentral.org,truncate.gbudb.net,bl.blocklist.de with threshold of 2 is a good set with really few false positives, zen.spamhaus.org,bl.spamcop.net,psbl.surriel.com,spamrbl.imp.ch,noptr.spamrats.com,escalations.dnsbl.sorbs.net,bl.score.senderscore.com,bl.spameatingmonkey.net,rbl.realtimeblacklist.com,dnsbl.dronebl.org,ix.dnsbl.manitu.net,b.barracudacentral.org,truncate.gbudb.net,bl.blocklist.de is more safe setup with somehow zero false positives, but a few false negatives (undetected spam), also with threshold of 2