This section offers a brief discussion of Multipurpose Internet Mail Extensions (MIME) message content. It covers
The MIME specification defines a way to compose, send, receive, read, file, and print mail messages containing multi-media (in other words: audio, video, graphical images, binary files, etc.) data in addition to ASCII text. The specification also includes Enriched Text, which lets you enhance the presentation of ASCII text with attributes such as different fonts and font sizes, bold face, italic, underlined, centered text, indented text, etc.
The MIME specification defines a message format that is backward-compatible with existing Internet mail. In other words, existing mail tools can be used to read, file, and reply to MIME messages. However, the readability of parts of the message depends on the type of data it contains. For example, if you use a non-MIME capable mail tool to read a MIME message containing audio or video data you should not expect that data to be presented in a usable format - but your mail tool will not crash just because you tried to read the MIME-encoded data. However, if you use a non-MIME capable mail tool to read a MIME message which contains only ASCII text, you will likely have no trouble reading the message.
To insure complete compatibility with existing Internet mail systems, all messages (MIME or otherwise) must contain only 7-bit ASCII data. A key part of the MIME specification defines rules for converting arbitrary binary data into 7-bit ASCII, for transmission through the Internet, then converting it back again to its original format, without loss or corruption of data.