What is the use of SMTP protocol in computer network
This article mainly introduces what is the use of SMTP protocol in computer network. It is very detailed and has certain reference value. Friends who are interested must finish it.
The SMTP protocol is used to deliver e-mail to a mail server on Internet. SMTP is a protocol that provides reliable and efficient e-mail transmission, mainly for the delivery of mail messages between systems, and provides notifications about letters.
The SMTP protocol is used to deliver e-mail to a mail server on Internet.
SMTP is a protocol that provides reliable and efficient e-mail delivery. SMTP is a mail service based on FTP file transfer service, which is mainly used for the transmission of mail information between systems and provides notification about letters.
SMTP is a relatively simple text-based protocol. One or more recipients of a message are specified on top of it (which is confirmed to exist in most cases), and then the message text is transmitted. You can easily test a SMTP server through the telnet program. SMTP uses TCP port 25. To determine a SMTP server for a given domain name, you need to use MX (Mail eXchange) DNS.
SMTP is independent of a specific transmission subsystem and only needs reliable and orderly data flow channel support. One of the important features of SMTP is that it can transmit mail across the network, that is, "SMTP mail relay".
Using SMTP, mail transmission between the same network processing process can be realized, and mail transmission between a processing process and other networks can also be realized through a repeater or gateway.
Working process
The working process of SMTP protocol can be divided into the following three processes:
(1) establish a connection: at this stage, the SMTP client requests to establish an TCP connection to port 25 of the server. Once the connection is established, the SMTP server and the customer begin to advertise each other's domain names and confirm each other's domain names.
(2) Mail transmission: using the command, the SMTP client transmits the source address, destination address and specific content of the mail to the SMTP server, and the SMTP server responds and receives the mail accordingly.
(3) connection release: the SMTP client issues an exit command, the server responds after processing the command, and then closes the TCP connection.
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