A method of transmitting electronic mail messages using the least possible data capacity. It uses a short message service, an electronic mail message and address and/or identification data for transmission of the electronic mail message in a second communications network is transmitted with a short message in a first communications network. A first header including signaling of at least one data field, including the address and/or identification data, is transmitted with the short message. A second header, indicating the presence of the first header, is transmitted with the short message. The at least one data field is transmitted outside of any header within a data portion of the short message.