what do you do to read "winmail.dat" attachments?

[Henry Nelson <netb@xxxxxxxxxx>]

One person keeps sending me attachments called "winmail.dat".  Mutt
shows these as:
  A     2 winmail.dat                           [applica/ms-tnef, quoted, 289K].

What are these attachments, and is there a way to convert them to text to
display them in Mutt?

TIA

-- 
henry nelson
  WWW_HOME=http://yuba(dot)ne(dot)jp/(tilde)home/