Spam Filter for Outlook - Version 2.0 Outlook Spam Filter uses built-in algorithm of message filtration, which is based on Bayesian approach of defining whether a message is spam or not. This filtering technology is one of the most exact and reliable approaches of differentiating spam and not spam messages nowadays. The algorithm applies to the results of statistical analysis of more than 30 000 spam letters that enables to determine spam with the accuracy no less than 99%.