? Zhong Lei's comparison with traditional mail system ???????????? http://91mail.51.net
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The email system is an indispensable part of the e-government system and office automation system (OA), which can be said to be the support system of the latter two systems. Email System is the infrastructure of my country's information construction, and it must be guaranteed to have the characteristics of safe, stable, efficient and management. The purpose of this topic is to develop a large-scale mail system in safe, stable, efficient and managed concentration. The Internet email system includes two parts: Mail User Agents (MUA) and Mail Transfer Agents (MTA). MUA is a program that users used to read, write and manage mail, such as Outlook, Foxmail; MTA is responsible for sending and receiving emails. The structure of the mail system used by some government agencies and enterprises is shown in Figure 1. Some of this mail system MTA uses Sendmail, although it can meet certain needs, but due to some security vulnerabilities, configuration is complex, and is not module Design, these disadvantages have brought great inconvenience to the use and maintenance of the mail system, so it is being gradually replaced by qmail. This mail system MUA uses Outlook, Foxmail and other software, they are client software, and their mail system is still traditional C / S mode so that users need to install this mail and client if they want to use this mail system. And configure the relevant software, the cost is very high, and the transfer information between MUA and MTA is still transmitted. It can be seen that this mail system is not well adapted to the current demand for modernization in my country. The system structure is shown in Figure 1:
figure 1
The message system structure to be developed in this topic is shown in 2. The qmail is another MTA program facing the Unix environment. It is a modularity of the main difference between Sendmail. It is like a Unix system to divide the mail function between the module. QMAIL extends this practice to the MTA program, QMail uses several different programs to implement the functionality of MTA, so that each module program is much better than a large single program. And another advantage of modularization is security, each module is independent relative to other modules, Qmail requires several different user IDs to be added to the mail server, each module runs under a different ID, if An intruder jezes a module, but he is difficult to have an impact on other modules, so QMAIL's security is often called its largest advantage. QMail has an advantage, that is, reliability, after each message enters the QMAIL system, is placed in a mail queue, qmail uses a system consisting of a mail subdirectory and message status to ensure that each store is in the message queue The message is not lost. There is also a QMAIL configuration very simple, replacing a large profile with a series of small files, each small file contains information about a module in the system, adding elements to these small files to change the entire program. Operation. The MUA modules in the mail system to be developed this topic have three function modules: CGI, Apache, SSL module. Among them, CGI and SSL modules are interactive dependent on Apache servers and users. The CGI module is primarily used to complete the function of MUA, and the SSL module is used to implement secure transmission of information between MUA and users. The centralized management modules in the mail system to be developed in this topic have similar three function modules, where the SSL module, the Apache module, and MUA are identical, and the CGI module is primarily used to achieve centralized management.
figure 2
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Figure 4
The message system structure to be developed in this topic is shown in 2. The qmail is another MTA program facing the Unix environment. It is a modularity of the main difference between Sendmail. It is like a Unix system to divide the mail function between the module. QMAIL extends this practice to the MTA program, QMail uses several different programs to implement the functionality of MTA, so that each module program is much better than a large single program. And another advantage of modularization is security, each module is independent relative to other modules, Qmail requires several different user IDs to be added to the mail server, each module runs under a different ID, if An intruder jezes a module, but he is difficult to have an impact on other modules, so QMAIL's security is often called its largest advantage. QMail has an advantage, that is, reliability, after each message enters the QMAIL system, is placed in a mail queue, qmail uses a system consisting of a mail subdirectory and message status to ensure that each store is in the message queue The message is not lost. There is also a QMAIL configuration very simple, replacing a large profile with a series of small files, each small file contains information about a module in the system, adding elements to these small files to change the entire program. Operation. The MUA modules in the mail system to be developed this topic have three function modules: CGI, Apache, SSL module. Among them, CGI and SSL modules are interactive dependent on Apache servers and users. The CGI module is primarily used to complete the function of MUA, and the SSL module is used to implement secure transmission of information between MUA and users. The centralized management modules in the mail system to be developed in this topic have similar three function modules, where the SSL module, the Apache module, and MUA are identical, and the CGI module is primarily used to achieve centralized management. The mail system structure used in this topic has improved, improved, and innovated traditional system structures, with the following features: 1. It mainly uses B / S mode, and is compatible with C / S mode, which is still guaranteed to ensure normal use of client tools such as Foxmail, Outlook. The greatest advantage of the B / S mode is to be installed and maintained. 2. Differently distinguish between mail system users with UNIX system users, separately in a database, not only facilitating management, but also enhances security of UNIX systems. 3. Added a centralized module, this module is used to implement centralized management of the entire mail system. For example, increase, delete, modify domains, users, mailing lists, alias forwarding, etc. 4. MUA is a CGI program running on UNIX server, which is attached to the Apache server, and users can access the mua program through the HTTP protocol, so the client only needs to have a browser software. 5. Communication between MUA and client browsers is to pass through the SSL protocol. This topic will use the OpenSSL package to achieve this. 6. If you access MTA with Outlook, Foxmail, you have to increase security through the SSL protocol. 7. In the MUA module, it is embedded in anti-virus emails and anti-spam modules. The antivirus anti-spam module currently used by some mail vendors is based on artificial intelligence, such as the application of Bayes network in anti-spam. By comparing the mail system and the mail system shown in Figure 1, it can be seen that the mail system developed by this topic not only improves the security, reliability of the system, but also reduces the cost of system use and maintenance. Very high actual application value. ?
