The original Internet e-mail standards were establised in 1982. They
only allowed for single human readable messages with the following
restrictions :
This list is not definitive. By its nature, MIME is an extensible
system. Consequently it is very likely that the set of
Content-Type/Value pairs will grow over time to include new types. For
example the Text field could have a new value defined if a new formatted text
description language were created.
Introduction
MIME stands for Multipurpose Internet Mail Extensions. It builds
on the original (1982) Internet e-mail standard by adding extra fields
for mail headers which describe new types of message content.
The 1982 Standard
The MIME Standard
MIME standardises new types of content and organisation headers in mail
messages. These allow MIME mail messages to contain:
MIME also permits the user to define their own types for the message part.
MIME Header Fields
MIME defines a number of new types of header field. However most of them
are concerned with different types of Content-Type field.
MIME-Version
This field simply uses a version number to declare that the message
conforms to the MIME standard.
Content-Type
This is the single biggest set of header fields. Each one consists of
Content-Type followed by a textual value which indicates the type
of data in the body of the message. The types are as follows:
Content-Transfer-Encoding
This header field specifies how the data is encoded to allow it to pass
through mail transports which may have data or character set
limitations.
Content-ID / Content-Description
These two header fields are also available to further indentify and
describe the data in the message body.
Links