Email is also governed by protocols. Without most users realizing it, whenever they send or receive an email there are specific protocols that go to work to ensure delivery or receipt. This lesson focuses on the four most common email protocols in use today: IMAP, MIME, POP3, and SMTP.
Internet Messaging Access Protocol (IMAP) is a standard mail server that:
Stores messages until users log on and download the messages
Allows messages to be archived in folders, mailboxes to be shared, multiple mail servers to be accessed
Allows users to read only a message header without having to accept the message
Multipurpose Internet Mail Extension (MIME) is a standard email protocol that:
Identifies the type of information in a message or document
Detects and transfers non-text data (such as colors and pictures in email messages) in an email file for email readers, Web servers, and browsers
Post Office Protocol (POP3) is a standard mail server that:
Almost all Internet mail readers use POP; for example, Eudora, Netscape, and Outlook
Holds incoming email until users log on and download it via email clients
Does not encrypt messages
Simple Mail Transport Protocol (SMTP) is the standard TCP/IP email protocol that:
Sends and forwards email to and between email servers over the Internet
Does not encrypt message
As the following image illustrates, these protocols operate at the Application layer of the OSI model.
In the next lesson, you will learn about the protocols used on the Web.