POP3 is fully named "PostOfficeProtocol-Version3", which is "Post Office Protocol Version 3". It is a member of the TCP/IP protocol suite and is defined by RFC1939. This protocol is mainly used to support the use of clients to remotely manage email on the server. The POP3 protocol that provides SSL encryption is called POP3S.
The POP protocol supports "offline" mail processing. The specific process is: the mail is sent to the server, the email client invokes the mail client program to connect to the server, and downloads all unread emails. This offline access mode is a store-and-forward service that sends mail from a mail server to a personal terminal machine, typically a PC or MAC. Once the mail is sent to the PC or MAC, the mail on the mail server will be deleted. However, most of the current POP3 mail servers can “download only mail, and the server does not delete itâ€, which is the improved POP3 protocol.
POP3 protocol features:The default port of the POP3 protocol: 110
POP3 protocol default transmission protocol: TCP
POP3 protocol applicable architecture: C/S
POP3 protocol access mode: offline access
The POP3 protocol is schematically shown in the figure below.
POP The e-mail protocol for the offline model of the C/S structure has now been developed to the third edition, called POP3. The offline model cannot be operated online. POP does not support the expansion of server mail. This process requires a more advanced IMAP4 protocol. The POP protocol is supported to use ASCII code to transmit data messages. These data messages can be commands or responses.
IMAP (Internet Mail Access Protocol, Internet Mail Access Protocol) was formerly known as the Interactive Mail Access Protocol (InteracTIveMailAccessProtocol). IMAP is an email acquisition protocol developed by Stanford University in 1986. Its main role is that e-mail clients (such as MS Outlook Express) can use this protocol to obtain e-mail messages from mail servers, download e-mails, and so on. The current authoritative definition is RFC3501. The IMAP protocol runs above the TCP/IP protocol and uses 143 ports. The main difference between the POP3 protocol and the POP3 protocol is that users can download all the emails without having to download all the emails. The client can directly operate the email on the server.
Imap features:Similar to the POP3 protocol, IMAP (Internet Message Access Protocol) also provides user-oriented mail collection services. The common version is IMAP4.
IMAP4 has improved the deficiencies of POP3, users can browse through the letter header to decide whether to receive, delete and retrieve specific parts of the mail, you can also create or change the folder or mailbox on the server. In addition to the offline operation mode of the POP3 protocol, it also supports online operation and disconnection operation. It provides users with the ability to receive mail from the mail server, server-based information processing, and shared mailbox functions. The offline mode of IMAP4 is different from POP3. It does not automatically delete the mails that have been taken out on the mail server. The online mode and disconnected mode also access the mail server as a “remote file serverâ€, which is more flexible and convenient. IMAP4 supports multiple mailboxes.
These features of IMAP4 are ideal for users who operate emails between different computers or terminals (for example, you can operate the same mailbox on email agents on mobile phones, PADs, and PCs) as well as those who use multiple mailboxes at the same time.
Compared with POP3, IMAP provides a “browse browsing†method that greatly improves the speed of email browsing and effectively saves customers valuable time. This is very useful for users who regularly receive large amounts of mail and want to stop spam. After a user establishes an IMAP account, he can specify which folders are displayed and which folders are hidden. The summary browsing function provided by IMAP enables users to read whether the time, sender, subject, size, and other information of all e-mails are correct. The decision to download, but also can enjoy the decision to selectively download attachments, such as: the user received a letter with 3 attachments, the user can download only one of them according to their needs, thus saving a lot of valuable time, To avoid using the POP3 method to receive mail, all messages must be received locally before being judged passive.
Third, the difference between pop3 and imapThe POP3 protocol allows e-mail clients to download mail on the server, but operations on the client (such as mobile mail, tags, etc.) are not fed back to the server.
IMAP provides two-way communication between webmail and e-mail client. The client's operation will be fed back to the server. The operation of the e-mail and the e-mail on the server will also take corresponding actions.
Compare the following table to see what happens when the client uses IMAP and POP:
At the same time, IMAP provides a convenient email download service like POP, allowing users to read offline. The summary browsing function provided by IMAP allows you to make a decision on whether to download after you have read all the message arrival time, subject, sender, size and other information. In addition, IMAP better supports access to new mail from multiple different devices at any time.
In short, IMAP as a whole brings users a more convenient and reliable experience. POP can easily lose messages or download the same email multiple times, but IMAP avoids these problems by using the two-way synchronization function between the email client and webmail.
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