OFF Topic: MS-Exchange bug (winmail.dat)

I need help to disable the long-trailer from MS-Exchange. 
Everytime my friend sends me an e-mail, the "trailer" (winmail.dat)
always there. How to disable it or turn it off? I believe someone
mention about this "feature" in this mailing list long time ago, but
I can't find it in my archive. 
Thank you.
Sent.

ps. can Winmail.Dat be considered as cryto-useless? <grin>