The difference between pop3 and imap

POP3, the full name is "PostOfficeProtocol-Version3", which is "Post Office Protocol Version 3." It is a member of the TCP/IP suite of protocols and is defined by RFC1939. This protocol is primarily intended 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 calls 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, the server does not delete", which is the improved POP3 protocol.

POP3 protocol default port: 110

POP3 protocol default transport protocol: TCP

The structure of the POP3 protocol: C/S

Access mode of POP3 protocol: offline access

The POP3 protocol is shown in the figure below.

POP is an e-mail protocol for the offline model of the C/S structure, which has been developed to the third edition, called POP3. The offline model cannot be operated online, and POP does not support the expansion of server mail. This process requires a more advanced IMAP4 protocol. The POP protocol is supported to transmit data messages using ASCII codes, which can be instructions or replies.

IMAP (Internet Mail Access Protocol, Internet Mail Access Protocol) was formerly known as InteracTIveMail Access Protocol. IMAP is a mail acquisition protocol developed by Stanford University in 1986. Its main role is that mail clients (such as MSOutlookExpress) can obtain mail information, download mail, etc. from the mail server through this protocol. The current authoritative definition is RFC3501. The IMAP protocol runs on top of the TCP/IP protocol and uses a port of 143. The main difference between it and the POP3 protocol is that the user does not have to download all the mails, and can directly operate the mail on the server through the client.

Similar to the POP3 protocol, IMAP (Internet Message Access Protocol) is also a user-oriented mail collection service. The commonly used version is IMAP4.

IMAP4 improves the deficiencies of POP3. Users can browse the letter header to decide whether to collect, delete and retrieve specific parts of the mail. You can also create or change folders or mailboxes on the server. In addition to supporting the offline operation mode of the POP3 protocol, it also supports online operations and disconnect operations. It provides users with the ability to selectively receive mail from a mail server, server-based information processing, and shared mailbox functionality. IMAP4's offline mode is different from POP3. It does not automatically delete the deleted mail on the mail server. Its online mode and disconnected mode also access the mail server as a "remote file server", which is more flexible and convenient. IMAP4 supports multiple mailboxes.

These features of IMAP4 are ideal for users who operate mail between different computers or terminals (for example, you can operate the same mailbox on a mobile phone, PAD, or mail agent on a PC), and those who use multiple mailboxes at the same time.

Compared with POP3, IMAP provides a "summary browsing" method for mail, which greatly improves the speed of mail browsing, and can effectively save customers valuable time. This is very useful for users who regularly receive large amounts of mail and want to block spam. After the user establishes an IMAP account, you can specify which folders are displayed and which folders are hidden. The summary browsing function provided by IMAP allows the user to read all the mail arrival time, sender, subject, size, etc. The decision to download, as well as the option to selectively download attachments, such as: the user received a letter with 3 attachments, users can download only one of them according to their needs, saving a lot of valuable time, It avoids the passive use of the POP3 method to receive the mail when it is received locally.

The POP3 protocol allows email clients to download mail on the server, but operations on the client (such as mobile mail, markup read, etc.) are not fed back to the server.

IMAP provides two-way communication between webmail and the e-mail client. The operation of the client is fed back to the server. The operation of the mail and the mail on the server also perform corresponding actions.

Compare the following table to see what is different when using IMAP and POP on the client side:

At the same time, IMAP provides a convenient email download service like POP, allowing users to read offline. The summary browsing feature provided by IMAP allows you to make a decision on whether to download after reading all the mail 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 provides users with a more convenient and reliable experience. POP is more likely to lose mail or download the same mail multiple times, but IMAP avoids these problems by two-way synchronization between the mail client and webmail.

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