STD 11, RFC 822, defines a message representation protocol specifying
considerable detail about US-ASCII message headers, and leaves the
message content, or message body, as flat US-ASCII text. This set of
documents, collectively called the Multipurpose Internet Mail
Extensions, or MIME, redefines the format of messages to allow for
(1) textual message bodies in character sets other than US-ASCII,
(2) an extensible set of different formats for non-textual message
(3) multi-part message bodies, and
(4) textual header information in character sets other than US-ASCII.
These documents are based on earlier work documented in RFC 934, STD
11, and RFC 1049, but extends and revises them. Because RFC 822 said
so little about message bodies, these documents are largely
orthogonal to (rather than a revision of) RFC 822.
This particular document is the third document in the series. It
describes extensions to RFC 822 to allow non-US-ASCII text data in
Internet mail header fields.