Research And Implementation Of Secure Email Server Supporting Base91

Electronic mail (E-mail) is one of the most popular apllication services in Internet. Nowadays, more and more people regard it as their main communication method. Transferring for a large amount of information in internet is based on Email system too. By E-mail, we can communicate with any network user in cheap, reapid way wherever the users are , The E-mail can include text, image, audio or other multimedia information, and server system is the key part.This paper analyzes the threat that E-mail server system faces and proposes effective solution to enhance its security. What's more, the paper discusses in detail on the relative security solution,such as the implementation of SASL authentication mechanism in the secure Email server system. Meanwhile the paper analyzes the deficiency of current transmission coding and describes a new data transformation method, base91 coding with high encoding efficiency but low data extension. It can obviously improve the transmission speed when used in E-mail server system.After doing research a series of protocols of E-mail and the international standards concerned, the author proposed a solution of base91 coding secure E-mail server system project which can make user choose client softwares freely to modify the mail transfer agent. The server used many open source softwares and based on the open source mail software Postfix, manage Mysql to administer the user in the system, and provided a Web interface, also include the SMTP, POP3 and IMAP function, support large scale user requests and the SASL authentication mechanismcan.etc.