The application provides methods of designing zinc finger binding polypeptides for binding to particular target sequences comprising overlapping nucleotide quadruplets. An embodiment determines whether adding a multicast session to a plurality of multicast bearers will exceed a high bandwidth threshold, requests setup of a new multicast bearer if adding the multicast session will exceed the high bandwidth threshold, and hosts the multicast session on an available one of the plurality of multicast bearers or the new multicast bearer. Both uplink and downlink channels of the different communication protocol may be communicated during the unused timeslots. The receiver has the option of accepting or rejecting email from a sender in this fashion and can change the required setup cost or requirement at any time to ensure that the sender does not try to corrupt the email system once registered.