MIME++ is a C++ class library for creating, parsing, and
editing messages in MIME format.  The class structure in
MIME++ closely follows the BNF grammar specified in RFC-822
and RFC-2045, making the library intuitive for developers
who are familiar with the MIME standard.  MIME++ supports
quoted-printable and base64 encoding/decoding, and all
header fields specified in RFC-822, RFC-1036, and RFC-2045.
MIME++ is extensible through inheritance and polymorphism.

WWW: http://www.hunnysoft.com/mimepp/