Email Protocols: POP3, IMAP, and SMTP

A protocol is a standard method which is used at communication channels to transmit information. To operate with your mail you have to use an email client in order to access the mail server. The information between mail client and mail server is exchanged by means of various protocols.

IMAP:
IMAP means Internet Message Access Protocol. This is a standard method for accessing email or bulletin board messages from your server. Saying in other words, it allows a "client" email program to access remote messages as if they were stored on a local server. The email is received by your Internet server. IMAP also allows manipulating, creating, and renaming mailboxes or folders or new and saved messages, deleting messages, and so on.

POP3:
The POP3 stands for Post Office Protocol 3. It provides a standardized method of accessing mailboxes and downloading the messages to the computer from the mail server. The data is delivered across the Internet.
The advantage of POP3 is that once you have your messages downloaded, you can read your messages without the Internet connection.

SMTP:
The SMTP stands for Simple Mail Transfer Protocol. It is used by MTA (Mail Transfer Agent) in order to deliver your email. By means of SMTP you can only send emails, but not to receive them.