This is happening due to a configuration problem on the sender’s end with the way their client is configured to Encode attachments. Chances are they are using a version of outlook and you are not using outlook.
This often occurs when they are using stationary, or some cheesy Outlook formatting thing.
Check <a href=”http://www.gpc.edu/~jbenson/resource/winmail.htm”>this </a>link out for more information.
If you happen to be a network administrator of the person actually sending the attachment <a href=”http://support.microsoft.com/kb/138053″>here </a>is a article that may help you from Microsoft.
If all else failes, <a href=”http://www.kopf.com.br/winmail/”>here </a>is a utility that will help you to endure the problem… but it’s generally on the sender’s end that this needs to be resolved.