Methods and apparatus for identifying unwanted email messages by transmitting metadata with an outbound email message that indicates the total number of email messages sent by that sender in a predetermined time period, or alternatively indicates the total number of email messages which are equivalent to the outgoing message that have been sent. In addition the metadata may include an identification of the sender and a "pledge" made byte sender. A pledge may take the form of a binding commitment from the sender that the information contained in the metadata is accurate, and/or that the sender promises to abide by predetermined good conduct rules designed to limit unwanted email. The outgoing message may be further signed by the sender with a digital signature that provides means for verifying the content of the message and the pledge as well as the identity of the sender.