Letter Opener

The winmail.dat solution

Some people still use Outlook. And whenever they send you something like an attachment or appointment, it shows up in your Mail with a winmail.dat file attached. (Ugh.)

But Letter Opener seamlessly converts all types of Outlook’s irksome winmail.dat files. (Hooray!)

El Capitan ready version for Letter Opener Pro is available.

Get Letter Opener for macOS Mail — Try it 14-days for free

Letter Opener converts seamlessly winmail.dat file inside macOS Mail. The most popular mail application on macOS.

Letter Opener for macOS Mail

Try it 14-days for free.

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We think you’ll love our apps - and provide email support directly from the people who build our apps to help you whenever you need it.

Available from our Store for $39.99.
Just click to Buy Now.


OS X 10.10 Yosemite or OS X 10.9 Mavericks. . Click here to view the release notes.


OS X Version 8 Version 7 Version 6 Version 5 Version 4 Version 3
10.11 El Capitan Intel
10.10 Yosemite Intel Intel
10.9 Mavericks Intel Intel
10.8 Mountain Lion Intel Intel
10.7 Lion Intel Intel Intel
10.6 Snow Leopard Intel Intel Intel Intel & PPC
10.5 Leopard Intel Intel & PPC
10.4 Tiger Intel & PPC


There’s no fuss with Letter Opener, no need to drag the winmail.dat file onto another application or call upon several programs to help you. Once Letter Opener is installed, you can forget about it.

Outlook compresses all of its attachments together into one winmail.dat file, leaving the rest of us scratching our heads as to what's inside. With Letter Opener the attachments appear like any others!

What a relief! This solves a recurring problem, that was a major irritation! It works flawlessly and seamlessly. You never even know it's there!

Ted O.

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