What is Post Office Protocol (POP)?

Post Office Protocol (POP) is an Internet standard that allows downloading email from an email server to a computer. POP has been updated twice since its first launch in 1984 under the name POP1.

Post Office Protocol Version 2 (POP2) was born in 1985, Post Office Protocol Version 3 (POP3) was released in 1988 and includes new mechanisms for authentication, as well as many other actions.

How POP works

Incoming email messages are stored at the POP server until the user logs in (using the email client) and downloads the mail to their computer. The POP standard does not include the means to send messages. Simple Mail Transfer Protocol (SMTP) is used to send email.

Compare POP with IMAP

POP and Internet Message Access Protocol (IMAP) are similar in that both are used to retrieve email. However, POP is older and only defines simple commands for retrieving email; IMAP also allows synchronization between devices and online access.

With POP, messages are stored and managed locally on a computer or device. Therefore, POP is easier to perform, as well as generally more reliable and stable.

Refer to the article: Differentiate POP and IMAP for more details.

Disadvantages of POP

POP is a limited protocol that allows email programs to only download mail to computers or devices, with the option to keep a copy on the server for future download. Although POP allows email programs to track which emails have been fetched, sometimes this process fails and the email cannot be downloaded again. Also, with POP, it is not possible to access the same email account from multiple computers or devices and let the actions be synchronized between them.