This slider lets you adjust SpamSieve’s bias. The bias controls how aggressive SpamSieve’s Bayesian classifier is at catching spam. When SpamSieve is more aggressive, it is better at catching spam messages that share some characteristics with your good mail. When SpamSieve is more conservative, it will be better at marking borderline messages such as order confirmations and press releases as good. This setting is very powerful, and most users should stick to the middle range. It is also not a substitute for training SpamSieve or making sure that it’s set up properly. Only change the bias if SpamSieve is consistently making errors in the same direction.