Multipurpose Internet Mail Extensions - MIME
MIME - the Multipurpose Internet Mail Extensions -
[RFC-2045] defines a format that allows Internet email [RFC-822] to
carry multipart textual and non-textual messages without loss of data.
Each message part is assigned a 'Content-Type' header that allows MIME
processing software to determine the format of data that is contained in
that part. A Content-Type is made up of two parts; a general 'type', for
example 'text', and a more specific 'sub-type', for example 'html'. Such
a Content-Type is represented in the form 'text/html'. To allow for
multipart messages there is a special type of 'multipart'. Associated
with the 'multipart' type are several sub-types including 'alternative'
and 'mixed'. Where binary data is being transfered, the body part is
assigned a 'Content-Transfer-Encoding' header which allows the data to be
encoded as plain text for transmission using email. Finally, MIME
supports the use of multiple character sets for the 'text' Content-Types
using the 'charset' parameter.
MIME Content-Types are registered with IANA.
Although MIME was originally developed to enhance mail functionality it is also used by other transport mechanisms including HTTP [RFC-1945]. The most important difference between MIME as used in mail [RFC-1521] and MIME as used in HTTP is that no use needs to be made of the Content-Transfer-Encoding header because binary data can be carried directly without encoding.
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