I was confused by your answer regarding winmail.dat. The file cannot be opened traditionally, at least to obtain what the receiver believes to be valuable contents. Rather, it's used internally by ...

Many times when receiving mail attachments with the new Exchange-enabled Microsoft Entourage v.X from Windows users, you will get a winmail.dat file that is inaccessible under Mac OS X. Alan Sill ...

So instead of seeing the "rich text" formatting of the original message, you get a plain-text copy, plus a mysterious "winmail.dat" attached file.

We keep getting e-mail attachments in winmail.dat files, and can't open them. What's going on? Is there a utility that can extract the attachments from these?