attachments

I am using mhonarc 2.4.1 and trying to translate a single message to
html.

When there are attachments that it does not understand, instead of
trying to write the attachment to a file and adding a hyperlink to that
file, it just ignores it.

I have tried making the attachment application/unknown and
Application/octet-stream, but both just seem to get ignored. There is a
setting that specifies that application/* should be handled by
mhexternal.pl??? Should this not be writing a file to disk??