How to open winmail.dat files on Mac?

Recently i always get a complain from my user regarding their email attachment problem. They received an email-message from customer with a file, named winmail.dat, as attachment. They fail to open that attachment file using Thunderbird mail client. But for those Microsoft Outlook user, they able to see and open the attachment file.

It is because Microsoft Outlook e-mail program sometimes sends e-mails in the Transport Neutral Encapsulation Format (TNEF). Most other e-mail programs, including Thunderbird, do not understand TNEF and will the e-mail attachment as “winmail.dat”

To Read, view, open winmail.dat email attachments, you have to convert it. There is a free application on Mac OS X platform called TNEF’s Enough that can open winmail.dat files and extract the attachment

Below are the link to download TNEF’s Enough

  • If you use Mac OS X 10.5 and above, just click HERE to download
  • If you use older Mac OS X version, click HERE to download

To extract winmail.dat, just follow below steps:-

  • Save the attachment on your computer.
  • Launch TNEF’s Enough application
  • Click on the ‘File ->Open’ from the TNEF’s Enough Menu and select the winmail.dat
  • After that, you will see the content of the .dat attachment

  • Just click Save button to save the content of .dat attachment to the location that you prefer.


If you have another tips to solve this problem, please leave your comments here. 🙂


One thought on “How to open winmail.dat files on Mac?

  1. I receive about 3 or 4 windat files annually and I wasn’t going to pay for an app to open them. Thanks Tech Kaki for the lead on this free app.

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