POP3 is an abbreviation for "Post Office Protocol 3." Post Office Protocol 3 is a simple internet protocol used in computer networks to allow user terminal machines to read all e-mails from the mail server side. The Post Office Protocol (POP) is utilised in the application layer protocol, and it provides the best capabilities for users to fetch and receive all emails.
POP is currently available in two versions: POP2 and POP3. POP2 requires a Simple Mail Transfer Protocol (SMTP) to transmit emails, whereas POP3 does not. It is built into popular email clients such as Eudora and Outlook Express.
In 1984, the Internet Engineering Task Force published RFC 918, the initial version of POP. However, back-end developers attempted to make the layout simple and effective in order to access all emails from the server machine. Because of the developer team's efforts, the entire email can be viewed even when the server is disconnected. RFC 937 was created in 1985 to develop POP2. Later, POP3 was developed in 1988 as RFC 1081, and it was revised several times over the next ten years until being released with the update in 1996 as RFC 1939.
If users attempt to check all recent emails, a connection needs to be established with the POP3 server. The user sends the credentials to the server machine in order to obtain proper authentication. After connecting, users get all text-based emails, and he/she can save them to their local terminal (computer), delete all server copies and disconnect from the server machine.