混合电子信函系统是通过PSTN（公用电话交换网）、INTERNET网和邮政综合计算机网将图文信息安全高速传输并保密封装成信函，由邮政营投网实施投递的新型混合电子信函系统。该系统通过装有发信软件的PC机用户发信端或设置了发信机的邮局营业窗口寄发信函，取代了传统实物信函的 Hybrid e-mail system is a new hybrid e-mail system that delivers the secure, high-speed transmission and confidentiality of graphic and text messages through PSTN (public switched telephone network), INTERNET network and postal integrated computer network. The system sends letters by sending letters to the PC user’s letterhead or the post office’s business window where the letterhead is installed, replacing the traditional physical correspondence