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: an act of fingerprinting a message received via a computer network, wherein the fingerprinting identifies one or more specific characteristics of the message; an act of comparing the message's fingerprint to one or more stored message fingerprints generated from previously received messages, wherein the comparison determines that the fingerprint does not match the stored fingerprints; an act of applying one or more classification rules to the message according to a predetermined rule execution order to determine a classification for the message; and an act of generating a customized classification rule execution order to order those classification rules that optimally identified the message's class at the top of the customized classification rule execution order.