Use the contents of the file in the body of the part
(@code{Content-Disposition}).
+@item recipient-filename
+Use this as the file name in the generated @acronym{MIME} message for
+the recipient. That is, even if the file is called @file{foo.txt}
+locally, use this name instead in the @code{Content-Disposition} in
+the sent message.
+
@item charset
The contents of the body of the part are to be encoded in the character
set specified (@code{Content-Type}). @xref{Charset Translation}.