Just open your browser and go to winmaildat.com. It's a straightforward website that lets you upload and open DAT files without needing to sign up or provide an email.

What is the deal with those winmail. dat files? I get them in my email all the time, and nothing seems to be able to open them.

Change Association This Time Sometimes you may want to open a data file with a different program. To open a file by choosing the application, see Win Open With.

Tips on opening a winmail.dat file, keeping seldom-used ink cartridges from drying out, and undoing an Undo.

Every data file on your PC should be associated with an application, so that opening the file will open the right program. But the official "right" program isn't always the right one for you.