What do you mean, POP3?

POP3 (Post Office Protocol 3), the 3rd version of the Post Office agreement, provides a way to connect personal computers to the Internet's mail server and electronic protocols for downloading e-mail.

It is the first offline protocol standard for Internet e-mail, POP3 allows users to store messages from a server on a local host (that is, their own computer) while deleting messages that are saved on the mail server, and the POP3 server follows the POP3 protocol's receiving mail server to receive e-mail.

Each e-mail user has at least one e-mail address, which forms a mailbox (account number) on the Internet. We know that this mailbox (account number) must have a password in order to keep others from being trusted. POP3 This is a protocol that is the abbreviation for version 3 of the Post Office PROTOCOL (Post Office Protocol 3), which was founded by Marshall Rose in November 1988. The POP3 protocol allows a client to obtain e-mail (e-mail) from a server (called a POP3 server) via a (temporary or permanent) TCP/IP connection or other network protocol, POP3 not responsible for sending mail, A message can be sent through the SMTP protocol or other protocols that are described later.
The advantage of the Post Office Protocol (POP) is that it supports mobile computing. Since the user's mail is stored in a POP server instead of being automatically stored on the user's computer, the user does not have to establish a permanent connection to the "Post Office" to wait for an email to be sent at any time, This makes it easy for desktop PCs or laptops, which are not easy to connect directly to the local network, to get mail services through dial-up Internet access (a temporary TCP/IP connection), so that it becomes the main form of the current distributed internet user's access to mail services.
Users with POP3 e-mail accounts must provide sufficient information for their mail clients (such as Ms-mail, Netscape Mail, Eudora, etc.) to receive mail services, including account numbers (such as account number rchn0012), Password and the domain name or address of the POP3 server (such as public3.bta.net.cn). We know that the symbol "circle a" (@) in the email address is the meaning of English "at", so the full explanation of the email address rchn0012@public3.bta.net.cn is " RCHN0012 is an account number on the ublic3.bta.net.cn server. The address of the POP3 server can be aliased, making the email address more memorable, such as the name of the network company POP server is mail.netchina.com.cn, and the user's email address can be represented by an alias abcd@ netchina.com.cn, but in some mail programs (Eudora), account information and POP3 address must be provided together, at this time, the user must tell it its mailbox for bcd@netchina.com.cn, in order to let the reply still use abcd@ In the form of netchina.com.cn, the user must explicitly write the following address in the "Return address" option.
Say the letter. When we post regular mail, it is usually possible to send a letter at any post office using any collections, as long as the postage is posted. E-mail is the same, and any user can choose the Post office that they send. If you are a Beijing user to send a letter to Shanghai, and you think it necessary to go to Guangzhou letter, that is no problem. It can even be said that if you are an Internet user with no e-mail address (account number) (which is the same as the two concepts of dial-up Internet access), you can also send e-mail.