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Lesson 11 Multipurpose Internet Mail Extensions
Objective Explain what MIME is and identify common MIME types.

What exactly is MIME?

Internet email was originally developed to handle ASCII text, which is unformatted text. However, MIME (Multipurpose Internet Mail Extensions) has been developed to send non-text data, such as graphics or programs, in Internet email. The next time you receive an email with an attachment, know that MIME makes it possible for you to open that attachment.

How it works

On the sending side, MIME encodes a file; on the receiving side, MIME decodes the file to its original format. You need to configure both the client and the server for MIME, with the server configuration dependent on the type of server.
The figure below shows the MIME button (the mime face) from the Eudora toolbar that allows you to toggle between the two encoding methods.


Multipurpose Internet mail extension (MIME) is originally a standard for defining the types of files attached to standard Internet mail messages. It is used in situations where one computer program needs to communicate with another program about what kind of file is being sent. Secure multipurpose internet mail extension (S/MIME) describes how encryption information and a digital certificate can be included as part of the message body.

MIME Toggle Button (Eudora)
MIME further manages data using
  1. A MIME header, added to the transferred file, that identifies the kind of data in the file and the encoding method used
  2. RSA encryptions in the S/MIME (Secure) version of MIME for secure transmissions. RSA encryption is industrial-strength public-key encryption technology.

MIME types

A MIME type is a file identifier derived from the encoding method that identifies the contents of a file. MIME types are also embedded in email messages to identify the contents of file attachments. Web servers send the MIME type to the browser so that the browser can launch the appropriate helper or plug-in.
The MIME content identifier is made up of a type and subtype separated by a slash. An example is text/plain. MIME types include:
  1. Application
  2. Audio
  3. Image
  4. Text
  5. Video
In the next lesson, you will learn about MIME examples and file extensions.