Mac App Store Link: https://itunes.apple.com/us/app/winmail-reader-pro/id979129525?ls=1&mt=12
iOS App Store Link: https://itunes.apple.com/us/app/winmail.dat-viewer-letter/id994423211?ls=1&mt=8
You may receive winmail.dat files from the senders who are using Microsoft Outlook (1997, 2000, 2003, 2007, 2010). Winmail.dat contains all attachments and rich text message, and not all e-mail clients can recognize its format.Winmail Reader Pro is the solution.
Winmail Reader Pro is the easiest, fastest, most reliable way to extract, view, and save the contents of winmail.dat files.
It's completely frustration-free: just double-click the win mail.dat file and you're instantly presented with a list of its contents. Double-click the attached files to open them, or drag and drop them on the desktop. In most circumstances, you won't even need to leave your Mail program.