Blog about design, web technologies, tutorials...

How to open winmail.dat attachments on a Mac OSX

5 Sep 2012

Posted in: Tutorials

I'm sure many of you working on Mac, every once a while receive this strange file from some Windows user. To be precise, Outlook user

Even there are some of the app that claim that they can open this file, some of them are commercial, and don't know if it's worth it.

The problem

Even I'm not very sure what other purposes this winmail.dat has, in my case, it was an Outlook calendar event. Normally, users send standard *.ics format, which is fully recognized in Apple iCal or another calendar app. Even Outlook can, and it's sending *.ics events, but in some cases, you receive winmail.dat.

If you try to open it, I got my VLC player trying to play this event, hm, no music in there :)


Other users on Windows using Outlook doesn't have problems opening it in Outlook Calendar. But wait, Mac users have also Outlook (in Office 2011 for Mac). Lets try to open Outlook file in Outlook for Mac.

If we try to press "Preview", file get preview as VLC file, what means, nothing. It's kinda funny that Outlook cannot open the file he generated. Another Outlook fail.


There are some articles, pointing out How to prevent winmail.dat attachments from being sent in Outlook (link). But even the problem was Windows Outlook, can you really ask your colleagues and friends to modify the settings in their app? Good luck.

The "real" solution

As I sad, there are several apps that claim to open this file on Mac, and convert it to something readable. Even some of them are commercial, I will mention the free one I tried, it's called TNEF's Enough (Says: Extract winmail.dat embedded files). Well, I tried it on Snow Leopard (10.7.4.) and nothing happend, no files for export, so for me it was useless. But you can try it for yourself.

So, if you are using Gmail or have account with it, open that e-mail (or just forward to it) in Gmail, and download it as *.ics file, the Gmail actually converts it for you.

Of course if you are using Google Calendar, you could just "Add it to Calendar", but we need that download button, that way you can add it without problems to iCal. So, download that "invite.ics" and open it in iCal. As the only downside I see, is that "Accept" is not working, I guess the email from is deleted, so iCal doesn't know how to confirm the event, but I think you can do it from Gmail interface.

Davor Peić is a designer & developer with more then ten years of experience.

About the author

Davor Peić is a designer & developer with more then twelve years of experience. Find more about his work on