POP3
POP3 is the abbreviation of Post Office Protocol 3, that is, the third version of the Post Office Protocol, which specifies how to connect a personal computer to an Internet mail server and an electronic protocol for downloading e-mails. It is the first offline protocol standard for Internet e-mail. POP3 allows users to store mail from the server to the local host (ie their own computer), and delete the mail stored on the mail server, while the POP3 server follows POP3 The receiving mail server of the protocol is used to receive emails.
What is the difference with IMAP
The POP3 protocol allows the email client to download the mail on the server, but the operation on the client (such as moving the mail, marking it as read, etc.) will not be fed back to the server. For example, the client receives 3 mails in the mailbox and moves them. To other folders, these messages on the Mailbox server are not moved at the same time.
And IMAP provides two-way communication between webmail and e-mail client, the operation of the client will be fed back to the server, and the operation of the e-mail, the e-mail on the server will also do the corresponding action.
At the same time, IMAP provides a convenient mail download service like POP3, allowing users to read offline. The summary browsing function provided by IMAP allows you to make a decision whether to download or not after reading all the information such as the arrival time, subject, sender, and size of the mail. In addition, IMAP better supports anytime access to new mail from many different devices.
All in all, IMAP brings a more convenient and reliable experience to the user as a whole. POP3 is more prone to losing mail or downloading the same mail multiple times, but IMAP avoids these problems nicely with two-way synchronization between the mail client and webmail.
SMTP
The full name of SMTP is "Simple Mail Transfer Protocol", that is, Simple Mail Transfer Protocol. It is a set of specifications for transferring mail from a source address to a destination address, and it controls how mail is relayed. The SMTP protocol belongs to the TCP/IP protocol family, which helps each computer find the next destination when sending or relaying letters. An SMTP server is an outgoing mail server that follows the SMTP protocol.
SMTP authentication, simply put, requires that you have to provide an account name and password before you can log in to the SMTP server, which makes it impossible for spammers to take advantage.
The purpose of adding SMTP authentication is to protect users from spam.
IMAP
The full name of IMAP is Internet Mail Access Protocol, which is the Interactive Mail Access Protocol, which is one of the standard mail access protocols similar to POP3. The difference is that after IMAP is enabled, the emails you receive on the email client remain on the server, and operations on the client are fed back to the server, such as deleting emails, marking as read, etc. Mail will also do the corresponding action. Therefore, whether you log in to the mailbox from the browser or log in to the mailbox from the client software, the emails and statuses you see are the same.