A method and system of transmitting a message from a transmitting client to a primary receiving client via a proxy server, which is also connected to a secondary receiving client. A message is sent from the transmitting client to the proxy server. The message includes a first header indicative of an address of the primary receiving client and a second header indicative of an address of the secondary receiving client and the primary header being indicative of only a single one of the addresses. The message is then transmitted from the proxy server to the primary receiving client and from the proxy server to the secondary receiving client.