-is text/plain if the file contains only ASCII characters or application/octet-stream
-if it contains characters outside of the ASCII range.
-.PP
-Each part contains a name attribute that is the last component of the path name.
-A
-.I x-unix-mode
-attribute containing the file mode accompanies each part.
-Finally, a description attribute is generated by running the
-.I file
-command on the file.
-.PP
-The
-.B -attachformat
-option specifies the MIME header field formats: a value of
-.B 0,
-the default,
-includes the
-.I x-unix-mode
-attribute as noted above. A value of
-.B 1
-suppresses both that and the \*(lqContent-Description\*(rq header, and
-adds a \*(lqContent-Disposition\*(rq header. A value of
-.B 2
-adds the file
-.I modification-date
-parameter to the \*(lqContent-Disposition\*(rq header. You can
-specify one value in your profile, and override it for individual
-messages at the
-.I whatnow
-prompt.