How is the message header generated?

Often people ask how the message header is generated? Why do I have to have headers in each email? We first need to understand the transmission of the message. The transmission of the message is actually sent by the sender and received by the receiving party. The smallest unit is the mailbox. While the user mail is sent from the terminal to its mailbox in the server process, we think it is within the scope of their personal mailbox, not counting the transmission of the mail, only synchronization. Mail submissions are cross-mailbox, and sometimes even cross-server, across-the-organization. This requires the sender and receiver to follow the same rules so that the receiver can read the intent of the sender. SMTP is a common rule for mail submission. Of course, we now have more requirements for mail, including Universal (Spanish mail sent to the Chinese mailbox, the content will not be garbled), security (mail to be scanned to prevent spam), accuracy (the path of the message transmission to be determined and traceable). Therefore, the message is actually divided into two parts: the message header and the message content. Where the message header is scriptable, and the message content is deeply encrypted. In general, we will record in the message header:

A. When the sender submits the message, the message's format and other information are marked in the message header, so that the receiver can receive it using the same protocol. Versatility.

B. During the mail submission process, each hop (the server that the message flows through to process the message) will receive and forward the message, which needs to be recorded in the message header and in the server log for the administrator to query. Certainty.

C. After the e-mail is scanned by antivirus/anti-spam programs, the scan results are also added to the message header so that the message does not have to be scanned repeatedly. Security.

Therefore, we see that the message header is generated when the sender's server communicates with the server on which the receiver resides. The client's communication with the server on which the message resides is not written to the message header. That's why we don't see the headers of the emails we send.

This article is from the "Clumsy birds have" blog, make sure to keep this source http://tingdongwang.blog.51cto.com/1056852/1837922

How is the message header generated?