winmail from outlook email client

Sometimes I received attachments with a name winmail.dat, which was not able to be read by webmail or some email client. If you use the unix file utility to check it:

$ file winmail.dat
winmail.dat: Transport Neutral Encapsulation Format
The attachment was send by Outlook email client. You can use a tnef program to extract out the content. The tnef program is a open source program which runs on unix operating system, is very easy to compile:-

$ cd tnef-1.4.3
$ ./configure --prefix=/usr
$ make

$ src/tnef -f winmail.dat
( this will extract the winmail file content to current directory )

For OS X users, try tnef's enough.