Email server concept and working principle

First, when you enter email into your computer and start sending it, the computer will "package" your mail ", it is sent to the mail server of your service provider (the mail Post Office is "SMTP mail server", and the mail Post Office is "POP3 mail server, this is equivalent to taking the mail from the mailbox and classifying it by region.

Then, the mail server will find the least crowded path based on the recipient address you specified and the current online transmission situation, and send the mail to the next mail server. Next, the server also worked as a way to send down the mail. This layer-by-layer transmission will eventually reach the user's hands.

Finally, E-mail is sent to the server of the user service provider and stored in the user's E-mail mailbox on the server. The user's personal terminal computer reads his/her e-mail from his/her mailbox through a connection with the server.

The mail server provides the basic structure of the mail system, including mail Transmission, mail distribution, and mail storage, to ensure that mail can be sent to any place on the Internet. Currently, email servers have two different application groups: ISP providers and enterprises and institutions.

Web Mail technology allows Email users to log on to the mail server using a browser anywhere to send and receive emails without configuring the mail client program.

Multi-domain email service is a physical server that provides email services to enterprises or organizations that register Internet domain names independently. Logically, these enterprises and organizations have their own independent mail servers (Enterprise post offices), also known as virtual mail server technology. For ISP providers and enterprise group companies, the support capability of multi-domain mail servers is an important factor in choosing mail servers. It can easily expand its horizontal mail service capabilities.

Using Linux as the mail server can be used together with open-source software such as Sendmail and MySQL, reducing the system price based on user requirements.

Email server security protection, including data identity authentication, transmission encryption, spam filtering, mail virus filtering, security audit, and many other security technologies.

Identity Authentication mainly refers to SMTP mail authentication. This function is an optional function for the mail server, the main purpose is to prevent hackers from using their own servers to attack other mail servers. The improvement of SMTP identity authentication can not only prevent malicious behaviors of hackers, but also ensure that the various resources of your email server can be fully applied to the Daily Mail Processing Process, it will not cause system crashes and waste of resources on the server.

Whether it is POP3 or SMTP, because of its defects at the beginning of design, all use clear code for message transmission, so it is easy to cause information leakage. Two methods can be used to improve system security: link encryption and end-to-end encryption. Link encryption uses encryption tools (software and hardware tools) to encrypt the data of transmission lines, which requires the support of network facilities.

End-to-end encryption is the encryption from the mail client to the mail client. It is a function provided by the mail server. Currently, it is popular to use SSL/TLS for transmission encryption. Most spam are commercial advertisements and other promotional materials. It is estimated that, for commercial spam only, the productivity cost of each spam is about $1. The Internet fee and telephone fee for downloading spam alone cost US $9.4 billion per year for Internet users around the world. In addition, many cases of virus and identity card and credit card theft are also related to spam. Therefore, the mail server must have the spam function to defend against most spam attacks. Hacker attacks and viruses are two relatively independent technical systems. However, with the continuous development of the network, network tools and viruses are becoming increasingly integrated. For example, Nimda virus is both a virus, it is also a method of network attacks, and a wide range of email has become one of the main ways of virus transmission. Currently, most email servers have basic virus protection capabilities.

Currently, the mail server only has several character sets in Chinese, such as GB-2312, Big5, etc. Although we can unify the standard, but in the actual process, we cannot unify all the mail clients, therefore, we can only require the email server to support multi-language environments.

Currently, many email servers are hosted by China Telecom (such as server hosting and server leasing) and cannot perform local operations frequently. Therefore, the mail server currently provides the function of remote email monitoring. You can monitor the working status of the mail server through the Web, including the number of online users, number and speed of mail processing, and storage space usage, in addition, the system can remotely process peak and network attacks at any time.

The email system should have unlimited scalability. One feature of the Internet network is impermanence and needs to cope with application peaks at any time. Therefore, the email system must have unlimited scalability, which is mainly reflected in the mail processing and storage capabilities. To enable unlimited extension of mail processing capabilities, cluster and Server Load balancer technologies need to be introduced so that the application platform can be infinitely expanded as needed to meet long-term or temporary business needs. For more than 20 million of mail users, at least tens of millions of mails are sent each day. To facilitate mail storage, a high-performance mail storage solution is required, the ideal solution is the application of SAN technology in the Mail Server field.