Systems and methods for filtering contents of a publication

A method implemented by a computer to filter an electronic publication published by a content publisher, the method comprising:

• registering an electronic publication received from a content publisher, wherein registering includes:
• assigning to the electronic publication a unique address to which the content publisher is to deliver additional content associated with the electronic publication,
• assigning a publication identification (ID) to the electronic publication, and
• registering content of the electronic publication by computing a signature for the content and associating the signature with the electronic publication via the publication ID;
• receiving a request from a client to determine whether additional content is registered, wherein the request includes an additional signature corresponding to the additional content;
• determining that the additional content is registered by using the additional signature as a key to search for a match via the publication ID;
• and
• providing the client with the publication ID in response to a match, wherein the publication ID allows the client to associate the additional content with the electronic publication as an additional electronic publication, wherein the publication ID facilitates automatic movement of the additional electronic publication into a client inbox when the additional electronic publication is on a subscribed list, and the publication ID facilitates automatic diversion of the additional electronic publication into a spam folder when the additional electronic publication is on an unsubscribed list.