Extract, view, share, and save the contents of Winmail.dat files sent from Windows Outlook or Exchange.
Winmail Reader for Outlook allows you to open .dat files and to preview, extract, share and save all contents.
What is Winmail.dat files?
Winmail.dat files are in fact TNEF format (Transport Neutral Encapsulation Format) sent by Microsoft Windows Outlook or Microsoft Exchange. Winmail.dat contains all attachments and rich text messages, but not all mail clients can recognize its format. Now, Winmail Viewer Letter Opener is the tool.
How to Set Winmail Viewer as default application for open Winmail.dat files?
On your Mac, click Finder in the Dock to open a Finder window.
Select a file, then choose File > Get Info.
You can also Control-click the file, then choose Get Info.
In the Info window, click next to “Open with.”
Click the pop-up menu, choose Winmail Viewer app, then click Change All.
Note: Don’t click Change All if you only want the specific file you selected to open with that app.
If it fails to set, please refer to the link.