A Winmail DAT file is a computer file containing data relating to the installation of Windows Mail on your computer. The program itself uses these files to keep track of various information, the specifics of which will change the more you use the program. If you want to open a Winmail DAT file on your computer, all you need to do is use the native Windows word processing utility, "Notepad."
Right-click on the Winmail DAT file.
Click "Open With."
Click "Notepad" to open your Winmail DAT file on your computer.