Principle of Mail Server

Mail Server: Development Protocol: pop3: postofficeprotocol is equivalent to the post office, where emails are stored. Currently, smtp is a commonly used protocol: Simple Mail Transfer Protocol, which is used to deliver mails, which is equivalent to the Postmaster protocol. Smtp port: 25 is used only for mail routing and delivery of pop3 so that users can go to the remote server and use their own accounts

MailServer: Development

Related Protocols:

Pop3: post office protoColEquivalentPost Office, where emails are stored, a common protocol

Smtp:The Simple Mail Transfer Protocol is used to deliver mail, which is equivalent to a postman.

SmtpPort:25Only used for mail routing and delivery

Pop3Allows users to retrieve and retrieve their emails through their accounts and passwords on the remote server.

SmtpPredecessor-----> UUCP (Unix to Unix CopyProtocol)

MainframeComputers can only be used through these mainframe terminals in the early days.

Users are called end users. They cannot feel the existence of each other. Every user has a home directory.

The mail is transmitted from the Home Directory of a user to the Home Directory of another user.

With the development of technical applications,SmtpExtended. If the user is not online, where can the email be placed?

1. SMTPBelongC/SBuild, start a process on the server side------> SmtpdClient---> Smtp

2.When the user needs to send an emailSmtp ------> smtpd

3.When the server receives the mail, this process processes allSmtpdThe process must be handled by a user.---> MailUser

4.Emails are stored in a public location.------->Email Address (email cache pool)#This process is notSMTPButMTA

5.Each email corresponds to a specific user and only belongs to that user. When a user logs in, an email will prompt that the user has an email.

It usesMailCommandYou can accept your emails.

Defects:PCAfter the machine appears, if you want to receive emails, you mustPCEnable on-boardSmptdService

Pop3Protocol generation: accept and retrieve emails (an additional service)

WithPCMachine DevelopmentPCThe mailbox requirements of the machine are different from those of the mainframe:

1.Accept email

2.Verify the user's identity

3.You can obtain your own email.

4.After the email is received, it can be passedPCOn-board

WhilePOP3The agreement was born for these needs.

Verify identity find email

User---------> POP3 -------->User

PCMachine requirements: Mail Delivery

Smtp

User----------->Email server

Summary:POP3The protocol is used to allow users to accept mails. users need to useSmtpMake sure you understand

Mail transmission process: for example

Now: PassWebSend and receive emails--------> Webmail

Webmail:PassWEBServerCGIModule to implement

MTA:MailTransfer AgentEmail Delivery proxy

MRA: Mail RrTrAvel AgentEmail retrieval proxy

MDA: Mail Delivery AgentMail delivery agent

MUA: Mail User AgentEmail user proxy

MSA: Mail Submissiong AgentEmail submission proxy

Conclusion: on the Internet80%All users areWebmail