In this new era, everyone is looking forward for the technology that will reduced the work load. This is because time is the most demanding thing that people hunting for nowadays. As the letter box that we are having now, people need to check the letter box from time to time to make sure they do not miss out ant letter. This is a time consuming habit. If forget to check the letter box, it will result in missing out some important letter. This will lead to in effectiveness. A solution to this problem is to develop a pigeonhole letter detector system. This system can reduce the work of a user. When there are a letter inside the pigeonhole, user will be informed by LED. The user can go to collect the letter when there have the notification. A email will send to the user already collected the letter from the pigeonhole, the LED turns off. This can save a lot of time and avoid extra work. This thesis presents the development and implementation of the pigeonhole letter detector system. The pigeonhole is equipped with sensor circuit. The sensor circuits works to detect the presence of the letter inside the pigeonhole. It is connected to a microcontroller receive and send signal of the sensor status. The system will process the data and send email notification to the user.