Several Microsoft Windows email applications support the Transport Neutral
Encapsulation Format (TNEF). This is a method for MAPI compliant mail programs
to transfer data to each other across gateways. Generally, a mail agent will
create a MIME multipart message containing the text body of the mail message,
and a single attachment of type application/ms-tnef. This attachment at least
follows the format of MIME messages, if not the intent. Usually, this bitstream
contains no more information than is already contained in the headers and body
of the message, but instead of attaching attachments to the email message as
separate MIME attachments, they are included in the TNEF attachment. To handle
this, I wrote a program tnef2txt which will dump the information in the TNEF
bitstream, and also dump files to disk which are contained in the bitstream.
Just run the program without arguments for usage information. You can call this
program from a mailcap file with the following line:

application/ms-tnef; tnef2txt %s; copiousoutput

or, if you wish to save attachments to disk which are in the bitstream:

application/ms-tnef; tnef2txt -s %s; copiousoutput