http://www.ietf.org/rfc/rfc1896.txt
MIME [RFC-1521] defines a format and general framework for the representation of a wide variety of data types in Internet mail. This document defines one particular type of MIME data, the text/enriched MIME type. The text/enriched MIME type is intended to facilitate the wider interoperation of simple enriched text across a wide variety of hardware and software platforms. This document is only a minor revision to the text/enriched MIME type that was first described in [RFC-1523] and [RFC-1563], and is only intended to be used in the short term until other MIME types for text formatting in Internet mail are developed and deployed.