characteristics of spam filtering methods

Method false Neg. false Pos. 1 false Pos. 2 remarks
conservative DNSBL (against top known spammers) 15% 0.1% 0.01%  
aggressive DNSBL (against potential  spammers) 7% 2%~10% 1%~3%  
Banning Servers from Policy-Based Netblocks (avoid all zombies) 25% 0.1% 0.5%  
content keyword triggers 3%~15% 1%~3% 1%~3%  
content keyword Bayesian pattern filter 2%~10% 0.5%~2% 0.5%~2%  
content type ban policies (scripts, forms, etc.) 99% 15% 0.1% mainly affecting automated email, such as order status notification; and newsletters.
Challenge-Response White-List human test 0.5% 100% 90%  

Points to remember: