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