Maybe it has been many times that you got a WINMAIL.DAT attachement
from another person, using MS Outlook for a mail unfortunately.
That file is in the TNEF (Transport Neutral Encapsulation Format) as a proprietary format of MS. See:
http://support.microsoft.com/default.aspx?scid=KB;en-us;q241538
Apart from asking the sender to turn of TNEF as per above document and ask for re-send we can extract this WINMAIL.DAT.
Initially:
$ file winmail.dat
winmail.dat: Transport Neutral Encapsulation Format
– Go to http://tnef.sourceforge.net/ and download the tnef source package.
– Extract and apply INSTALL document
– Run:
tnef < winmail.dat
The files extracted will be in the local directory.