Postal code is essential for improving efficiency of mail sorting. The Korean postal code, which is introduced in 1970 and had been reformed two times, has controversial issues because of changed postal environments such as modification of administrative districts and logistical transformation into a hub-and-spokes structure. In this study, we propose several improvement and evaluation methods in order to prepare an alternative plan of postal code system. After performing status analysis, we define the customers of postal code and analyze the requirements of them. The 6 proposed new postal code systems are based on each customer groups’ requirements. To evaluate the new systems, we develop several quantitative and qualitative indexes and make a survey of postal experts. Besides, we evaluate the influence of them to the postal environments including delivery sequence sorting process.