Sinsing A brief analysis of several concepts in mail service

E-Mail first appeared in 1960, while web-based e-mail first appeared in 1971, while China's first e-Mail appeared in 1987. E-mail is also widely used as an early web-based communication, although many of the features of e-mail are replaced by instant messaging, but in a business environment e-mail remains the primary means of communication.

The first is the concept of MUA, it is the abbreviation of the Mail user agent, that is, the Mail users agent, the user through MUA to send and receive mail, for individuals, generally use the Web page way to view e-mail, these are web-based MUA. Common MUA software is Outlook, Mac Mail, Thunderbird, Foxmail, Mutt, and so on.

and MUA through IMAP or POP3 to receive mail, that is, through the IMAP or POP3 protocol from the mail server to grab a specific user's mail to the local, we can control the crawl, whether or not still on the mail server to save the message has been crawled. The main advantage of IMAP is that all client operations are synchronized with the mail server and the user experience is better. POP3 then downloads the message and all the operations are local, without affecting the messages saved on the server.

Then the concept of MTA, which is the abbreviation of the Mail Transfer agent, MTA is what we call the e-mail Service program, it is responsible for implementing the SMTP protocol, the transmission of mail. The MTA is only responsible for the transmission of the message, and the message is saved on the server by the MDA. SMTP is Simple Mail Transfer Protocol, which is also the standard protocol for sending mail. The main MTA in Linux is SendMail and postfix.

Then there is the concept of MDA, which is shorthand for the mail deliver agent, which is responsible for storing messages received by the MTA on the mail server, usually with the MTA and MDA tightly combined. Its role is to save mail, junk mail processing, virus scanning. The default mail save directory in Linux is the/var/spool/mail/user name, while the most commonly used MDA in Linux is Procmail and Maildrop, while SendMail and postfix use the MDA as the default procmail.

Then the MRA concept, which is the shorthand for the Mail Receive agent, which implements the IMAP and POP3 protocol, which is responsible for interacting with MUA, communicating messages on the server to the client via IMAP or POP3, and the MRA in Linux is usually Dovecot, The protocols supported by MRA typically have IMAP, POP3, IMAPS, pop3s, and for security purposes, the messaging system typically encrypts the transport protocol using digital certificates.

The format of the e-mail address can be in the format of "user name @ Mail Server", such as " [email protected] " format, you can also use the "username @ domain Name" format, such as "[email protected]" format. The second format is typically used, but the mail address in this format does not specify a mail server for the domain, so you must make a DNS query for the domain, that is, query the MX record for the domain, and then locate the domain's mail server before you can send the message.

Sinsing A brief analysis of several concepts in mail service