1. At a computer system including at least one processor and a memory, in a computer networking environment including a plurality of computing systems, a computer-implemented method for generating a customized classification rule execution order, the method comprising: identifying one or more specific characteristics of a message received via a computer network; fingerprinting the message based at least in part on the identified one or more specific characteristics of the message; comparing the message's fingerprint to one or more stored message fingerprints generated from previously received messages, the comparison determining that the fingerprint does not match the stored fingerprints; applying a plurality of classification rules to the message to determine a classification for the message, the rules applied sequentially according to a predetermined rule execution order; and generating a customized classification rule execution order, based on the results of the sequential application in the predetermined order of the plurality of classification rules to the message, the customized classification rule execution order defining a new sequential order of the classification rules that optimally identifies the message's class by applying the fewest number of rules of the customized classification rule execution order when applied sequentially to the message.