This shows how to open winmail.dat files under Linux. Microsoft mail clients sometimes wrap attachments in Transport Neutral Encapsulaton Format (TNEF). The `tnef` command can decode these winmail.dat attachments.
First you need to install it. This shows how for Ubuntu:
sudo aptitude install tnef
Then use the `tnef` command to open the archive:
tnef -vf winmail.dat