POP stands for Post Office Protocol. POP was created in 1984. It was used for downloading mail from a remote server.POP usually downloads all the mail from the server and deletes them from the server. Any changes made from a device won’t appear on other devices if you are using this protocol. For example, if you marked a message as read, you will find the same as unread on the other device connected to your account. In 1985 POP2 and in 1988 POP3 was released offering more features.Now let us look in detail what POP and IMAP is.