1. A method for processing electronic-mail messages, the method comprising: storing information in memory regarding a message previously classified as an unsolicited message, the message including a collection of words, wherein the collection of words is not helpful for the purpose of distinguishing the message, the collection of words including a plurality of words that can be found in a dictionary; executing instructions stored in memory, wherein execution of the instructions by a processor: identifies from the collection of words one or more dictionary words known to be commonly occurring or known to be associated with spam, removes the identified one or more dictionary words from the message, replaces one or more remaining words in the message with an associated canonical equivalent to generate a resulting summary, and generates a signature based on the resulting summary, and storing the generated signature in memory for use in classifying and processing subsequently received messages, wherein a subsequently received message is classified based on the signature and processed based on the classification.