Open winmail.dat files

Automatically in macOS Mail

See how it works – Replay

Letter Opener for macOS Mail Icon

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Available from our Store for $49.99 per year.

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Requires macOS Ventura, Monterey, Big Sur, or Catalina
Release Notes

Maximize your productivity

Letter Opener converts and displays the content of winmail.dat files automatically inside macOS Mail, so that they appear just like any other email. You will never have to think about winmail.dat attachments again!

What is a winmail.dat file?

Winmail.dat files contain email messages from Microsoft Outlook. Since Macs can’t read them natively, users have to rely on third-party software such as Letter Opener to convert and open them.

Letter Opener speaks your language.

Fully localized in Arabic, Cat, Chinese, Dutch, French, German, Hindi, Italian, Japanese, Korean, Portuguese, Russian, Spanish and Swedish.


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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Meet the family

Letter Opener for macOS
Open Winmail.dat, MSG and XPS files with just a simple double-click!
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Letter Opener for iOS
Get full-featured winmail.dat viewing power for iPhone, iPad and iPod touch!
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