POP3
POP3 is the abbreviation of Post Office Protocol 3, which is the third version of the Post Office Protocol. It is a member of the TCP/IP protocol family (the default port is 110). This protocol is primarily used to support remote management of e-mail on the server using the client.
POP与POP3
The POP protocol supports "offline" mail storage and forwarding processing: the client program connects to the server and downloads all unread e-mails; once the mail is sent from the mail server to the client, the mail on the mail server will be deleted. Most of the current POP3 mail servers can "only download mail, the server does not delete", which is an improved POP protocol.
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.
IMAP
The full name of IMAP is Internet Mail Access Protocol, the Interactive Mail Access Protocol, which is an application layer protocol (port 143). Used to access mail on remote servers from local mail clients (Outlook Express, Foxmail, Mozilla Thunderbird, etc.).
Difference between IMAP and POP3
Like POP3, IMAP provides a convenient mail download service, allowing users to read offline. IMAP and POP3 are the most common Internet standard protocols for mail access. the difference is:
1. IMAP provides two-way communication between Webmail and the email client. The emails received by the client are still kept on the server, and the operations on the client will be fed back to the server (such as: delete emails, mark as read, etc., The mail on the server will also act accordingly. So whether you log in to the mailbox from the browser or log in to the mailbox from the client software, the mail and status you see are the same.). The operation of POP3 on the client will not be fed back to the server.
2. IMAP better supports access to new emails from multiple different devices at any time.
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 arrival time, subject, sender, and size of the mail.
IMAP does not need to download all the mails, but directly operates the mails on the server through the client. All data transmitted via IMAP is encrypted to ensure the security of the communication.
IMAP overall brings a more convenient and reliable experience to users. POP3 is more prone to losing mail or downloading the same mail multiple times.
SMTP
The full name of SMTP is "Simple Mail Transfer Protocol", which is the Simple Mail Transfer Protocol (port 25). 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.
SMTP is a "push" protocol, which does not allow messages to be "pulled" from remote servers on demand. The SMTP server is an outgoing mail server that follows the SMTP protocol. SMTP authentication means that you must provide an account name and password before you can log in to the SMTP server, which makes those spammers have no chance.
Deepen the understanding of IMAP, POP3 and SMTP protocols through examples
I use the Foxmail client, and the emails I use include QQ (Foxmail is also the same, because Foxmail has been acquired by Tencent long ago, it can be considered that one person has two names), Gmail, Sina, 163. The picture below is my client's settings. I use IMAP/STMP for Gmail, Foxmail and 163. It can be known from the settings that the IMAP protocol is used to receive mail, and the operation between the client and the server can also be synchronized by using IMAP. SMTP is used for sending emails. As mentioned above, SMTP is a "push" protocol that does not allow "getting" messages from the server.
My sina is using POP3/SMTP protocol. POP3 is used to receive mail. Unlike IMAP, it does not provide synchronous operation between the client and the server, which means that the operation of the client and webmail or other clients is irrelevant. SMTP also provides sending mail services.
My sina account has no unread emails on the Foxmail client, but there are 78 unread emails on the webmail side, which verifies that the POP3 operation is asynchronous. Screenshot below:
After reading the above examples, you should know the role of IMAP, POP3 and SMTP protocols. hope its good for U.S..
Send and receive servers provided by common mailboxes
NetEase mailbox supports POP3/SMTP/IMAP service, which can better send and receive emails through computer client software. NetEase mailbox has enabled POP3/SMTP/IMAP service by default. "POP3/SMTP service" and "IMAP/SMTP service" in QQ mailbox and Gmail mailbox are generally disabled, and you need to manually open them.
The address of Sina Free Mailbox (smtp) server is: smtp.sina.com
The address of the Sina Free Mailbox (pop3) server is: pop.sina.com
SSL (Secure Sockets Layer), and its successor, Transport Layer Security (TLS), is a security protocol that provides security and data integrity for network communications. TLS and SSL encrypt the network connection at the transport layer, so that the communication between the client and the server application cannot be eavesdropped by attackers.
If your email client supports SSL, you can choose to use SSL in the settings. When the SSL protocol is selected, the corresponding server port number needs to be modified. The general configuration of QQ mailbox using SSL is as follows:
Incoming mail server: pop.qq.com, using SSL, port number 995
Outgoing mail server: smtp.qq.com, using SSL, port number 465 or 587
Client settings of POP3/SMTP/IMAP for major mailboxes at home and abroad
POP3 refers to the server that receives mail. Some mail services are POP3, while others are called POP. Different mailboxes have different POP server addresses.
QQ mailbox POP3: pop.qq.com SMTP: smtp.qq.com IMAP: imap.qq.com Port: 143
Foxmail POP3：pop.foxmail.com SMTP：smtp.foxmail.com
Mobile 139 mailbox POP3: pop.139.com SMTP: smtp.139.com
Tianyi 189 mailbox POP3: pop.189.cn SMTP: smtp.189.cn
163邮箱 POP3：pop.163.com SMTP：smtp.163.com
163Vip邮箱 POP3：pop.vip.163.com SMTP：smtp.vip.163.com
126邮箱 POP3：pop3.126.com SMTP：smtp.126.com
Gmail POP3：pop.gmail.com SMTP：smtp.gmail.com IMAP：imap.gmail.com 端口：995 465 993
Yahoo邮箱 POP3：pop.mail.yahoo.com SMTP：smtp.mail.yahoo.com
Hotmail POP3：pop3.live.com SMTP：smtp.live.com 端口：995
Sogou邮箱 POP3：pop3.mail.sogou.com SMTP：smtp.mail.sogou.com