1. Method for dynamically allocating a cost to an e-mail that a first user of a transmission network who is of a member of a group, wants to forward to a second user of the transmission network who is also a member of said group, comprising the steps of: forwarding by said first user said e-mail to a market engine in charge of allocating a cost to said e-mail; determining by said market engine the cost of said e-mail based upon intrinsic and extrinsic criteria; submitting the cost of said e-mail to said first user for agreement; forwarding by said market engine said e-mail to said second user; and updating a credit account associated with said first user.