Design And Implementation Of POP3 E-mail Client And Server

With the development of Internet technology, E-mail has become an important communication means in daily life. The E-mail system includes email client and server. Email client is often installed on Windows operating system (OS) and email server is often installed on Unix OS. Howerver, it is difficult to enhance these email systems for commercial reasons or for the complex operation methods. Nowadays, many enterprises and universities wish to have their own email system, so that they can manage conveniently and improve the system continuously. So we develop DSPMail which can satisfy these demands.This thesis designs and implements DSPMail system, including POP3 client and POP3 server. The DSPMail system can transport email from POP3 server to POP3 client. The thesis contains the following seven parts:(1) Study the basic theory and method of network application and socket programming, and implement the communication flow between POP3 client and server using Windows Sockets;(2) Analyze the main email protocols thoroughly, and realize POP3 protocol on email client and server;(3) Develop email client program for receiving email on Visual C++ platform on the base of analyzing RFC822 and MIME protocol for email format. The client can communicate with email server in LAN and WAN, and it is also adaptive to different email formats;(4) Research kinds of encoder and decoder methods for email header and body, and reduce the error probability successfully;(5) Ensure many users to receive mails simultaneously using multithread. Mailbox can be operated remotely, such as adding or deleting mailbox;(6) Implement APOP authentication command and analyze the security of MD5 arithmetic;(7) Install background service. The server can be specified to be started automatically during system startup or started by demands after system startup;Testing results show that the POP3 email system achieves the planned function, and it can also cooperate with SMTP email system.