Letter Opener

The winmail.dat solution for Mac, iPhone and iPad

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!)

  • Browser attachment of a winmail.dat file
  • Displays nested messages
  • Adds appointments directly to iCal
  • Converts notes with incredible simplicity
  • Creates contacts in Address Book
  • Reads and delivers receipts

The easiest way to view winmail.dat

What's new in Letter Opener Pro Version 7:

OS X Mavericks
  • Mac OS X 10.10 Yosemite compatible
  • Microsoft Outlook 2011 for Mac support
  • Timezone support in Appointments
  • RTF with images and Device Independent Bitmap support
Features Letter Opener Lite Letter Opener Pro
Convert winmail.dat attachments Check Check
Mac OS X Mail integration Check
Microsoft Outlook 2011 integration Check

Release notes

Our latest release is Mavericks compatible! Click here to view the rest of the release notes.


Mac OS X 10.10 Yosemite, 10.9 Mavericks, 10.8 Mountain Lion, 10.7 Lion or 10.6 Snow Leopard. See support matrix.

Letter Opener Requirements

Mac OS X Version 6 Version 5 Version 4 Version 3
Mavericks 10.9 Check Intel
Mountain Lion 10.8 Check Intel Check Intel
Lion 10.7 Check Intel Check Intel Check Intel
Snow Leopard 10.6 Check Intel Check Intel Check Intel Check Intel & PPC
Leopard 10.5 Check Intel Check Intel & PPC
Tiger 10.4 Check 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 .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 small problem, that was a major irritation! It works flawlessly and seamlessly. You never even know it's there!

Ted O.

Letter Opener Pro also works great with these Mail Plug-ins:

  • Mail Act-On

    Fills in crucial gaps in Mail’s feature set, making it a must-have plug-in for anyone who deals with copious emails. Check out this app

  • MailTags

    MailTags will turn Apple’s Mail into a powerful email organization system. Check out this app

  • Mail Perspectives

    Keep your email a glance away, see only what you want to see, and act quickly without losing focus. Check out this app

  • Attachment Tamer

    Gives you control over viewing and sending attachments in Mail. Check out this app