With wide-covered businesses and various services

the information system of electric enterprises has to satisfy a special security requirement known as “horizontal isolation and vertical encryption”. For lack of a universal data transmission mechanism

it is hard to efficiently exchange information across secure areas and different levels. The message mail for power system is designed to solve this problem by creating a universal and efficient transmission mechanism based on file transmission. It can be applied to all electric organs(i. e. dispatching and control center

substations and wind power farms etc. )to accomplish cross-regional and inter-agency data transmission. This article describes the structure of the message mail system first. Secondly

it explains some key techniques of this system such as domain management mechanism

route selection strategy and isolated devices ride-through strategy. Last but not least; the system performance test and application are briefly treated. This work is supported by State Grid Corporation of China(No. SGJB0000TKJS1500006).