IMAP stands for Internet Message Access Protocol, and it is an alternative to the original POP or Post Office Protocol. Its ambition is to allow users to be free to affiliate themselves with more than one email client, as it is the standard email protocol that permits the user to access email accounts on multiple devices. It maintains the messages stored on the user’s local machine all at once. It also allows users to sort through their email messages without having to go to the trouble of downloading first.
POP3 translates to Post Office Protocol version 3. Unlike IMAP, this program is quite simple, and it accepts and holds an email for as long as the person with the email client picks it up. Unlike IMAP, it does not produce copies of the mail it receives and keeps them on the server. It also accesses and downloads as many times as the user wants within the given time frame.