Winmail.dat Opener is a free app to open those annoying 'winmail.dat' attachments.

This app is absolutely free of charge (ad supported) and fully functional giving you access to the files without any need for further in-app purchases.

The app requires only about 4MB space and only the absolute minimum of permissions.

Your files are processed on your phone and not send to some external server. This ensures that your information stays private and the app will still work if you are without internet connection.