Using Simple Mail Transfer Protocol on the Last Hop

Abstract: Some of the enhancements that hit the mobile phone industry in recent years include checking email, demanded changes in the traditional ways of service delivery. People find it convenient to be able to check for incoming emails without being required to be at a fixed location. High-end mobile phones with high resolution color screens and mail clients (or plug-ins) much like the classic clients that run on desktop and laptop computers, have made mail manipulation on a mobile phone both easy and interesting. However, one key difference is the phone’s battery power source. Where power was not an issue for desktop and even many laptop computers, since they are almost all the time connected to an AC supply or have high capacity battery storage, it is a major issue for mobile phones. While email applications have greatly advanced, there has not been much improvement in mobile battery capacity. In addition the battery lifetime has decreased due to the high power demands of multimedia applications, which may be running almost constantly. Traditionally, a mail client checks for new email messages by polling the mail server. This works well with computers attached to the power mains or with a large capacity battery, but for mobile phones, polling causes significant battery drain. A solution would be to poll the server less frequently by increasing the polling interval, however this would delay email reception hence increasing latency. In this thesis we implement and evaluate a new mail delivery system without changing the underlying mail or communications infrastructure. The new system eliminates the need for polling by using network initiated mail delivery. This means that a mail server will forward mail directly to a particular user. Tests conducted with a prototype are compared to the use of the existing system in terms of power consumption and latency. These tests show that the new mail delivery system reduces both power consumption and delivery delay.