US Patent 7853660 Method for discouraging unsolicited bulk email

A protocol-based method for email forwarding by an email server is performed as follows. An initial email is received from a sender, and checked to ensure that the initial email includes a reusable electronic paying means. If the initial email carries a reusable electronic paying means, the initial email is forwarded to the recipient. An acceptance email containing a reusable electronic paying means is later received from the recipient of the initial email, and forwarded to the sender. Email not carrying an electronic paying means is rejected.