In some embodiments, a spam filtering method includes computing the relevance of each of a plurality of anti-spam filters according to a relevance parameter set, and deciding whether an electronic message is spam or non-spam according to the relevancies and individual classification scores generated by the anti-spam filters. The relevance of an anti-spam filter indicates the degree to which a classification score produced by that particular filter determines the final classification of a given message. The relevance parameter set of each anti-spam filter may include, among others, a training maturity indicative of the degree of training of the filter, a filter update age indicative of the time elapsed since the latest update of the filter, a false-positive classification indicator, and a false-negative classification indicator of the anti-spam filter.