The MIME (Multipurpose Internet Mail Extensions) specification
(RFC 1521 and successors) defines a mechanism for encoding text consisting
primarily of printable ASCII characters, but which may contain characters
(for example, accented letters in the ISO 8859 Latin-1 character set) which
cannot be encoded as 7-bit ASCII or are non-printable characters which may
confuse mail transfer agents.

WWW: http://www.fourmilab.ch/webtools/qprint/