How to Open Winmail.dat Files

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.

Winmail.dat is a proprietary email file format generated by Outlook or a Microsoft Exchange Server that provides rich-text formatting (like bold, italics, color, and more). The problem is that the files can only be read by certain email clients.

There are two ways to solve this problem. If you know the sender well, you can ask the sender to stop sending them. To disable this file format in Outlook on Windows, navigate to Options > Tools > Mail Format. From the Send In This Message Format list, select either Plain Text or HTML, then click OK to save the new setting.

With the $0.99 Winmail File Viewer app for the iPhone, you can view your Winmail.dat files while on the go.

If you can’t convince the sender to use standard email formats, you also have a few options for reading these Winmail.dat-formatted messages. On the Mac, TNEF’s Enough, can open winmail.dat files. If you are on an iOS device, try Winmail File Viewer.


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