How to See and Access the Contents of a Winmail.dat File on Your Mac

Wondering ‘What is a Winmail.dat file attachment and how do I open it?” If you have a Mac computer, such as a Macbook, Macbook Pro, or Macbook Air, and if you have any friends or colleagues who still use Windows in general, and Outlook in particular, then you are almost certainly familiar with the issue of your friend or colleague sending you an attachment in email (say, a document), but all you receive in your Mac email is that damned Winmail.dat file. Here’s how to open a Winmail.dat file on a Mac, and get at the contents.