Method to Filter Electronic Messages in A Message Processing System

The present invention proposes a method to filter electronic messages in a message processing system, this message processing system comprising a temporary memory for storing the received messages intended to users, a first database dedicated to a specific recipient, and a second database dedicated to a group of recipients, this method comprising the steps of: a) receiving an electronic message and storing it into the temporary memory, b) generating a plurality of proportional signatures of said message, each signature being generated from predefined length of the message content at random location, c) comparing with a first similarity threshold the generated signatures with the signatures present in the first database related to the message's recipient, and eliminating the generated signatures that are within the first similarity threshold of the first database's signatures, thus forming a set of suspicious signatures, d) comparing with a second predefined similarity threshold the suspicious signatures with activated signatures present in the second database, and flagging the message as spam if at least one of the suspicious signatures is within the second predefined similarity threshold of the second database's activated signatures, e); allowing a user to access the message, and moving said message from the temporary memory into a recipient's memory, f) if the message is accepted by the user, storing the generated signatures related to this message into the first database related to this recipient, g) if the message is declared spam by the user, using the suspicious signatures of said message in the second database for, either, if no similar signature exists, creating a non-activated signature into the second database with said signature or updating a previously stored signature that is within of a third similarity threshold of a suspicious signature by incrementing its first matching counter, and activating said previously stored signature if the matching counter is above a first counter threshold.