1. A method of reducing a flow of unwanted electronic messages, the method comprising: receiving electronic messages at a relay and determining that at least some of the received electronic messages are unwanted based on contents of a database that codes attributes and derived information characteristic of messages that have been determined to be unwanted; and updating contents of the database for use in the determining for subsequently received ones of the electronic messages, wherein the updating is based, at least in part, on attributes and derived information for electronic messages received by the relay itself.