TNEF's Enough allows Macs to read and extract files from Microsoft TNEF stream files. The files are usually received via email from Microsoft Exchange and Microsoft Outlook users. You will usually receive an attachment named "winmail.dat." If someone has even sent you a message or file and all you have received is a "winmail.dat" file then you need TNEF's Enough to open it and extract the embedded file.
Note: Now requires OS X 10.7 or later