Simple is better...

Winmail Opener

Winmail Opener is a small and simple utility that allows you to view and extract the contents of winmail.dat files sent by Outlook.

If you receive winmail.dat files in your e-mail, this little program will allow you to view the message text and attachments embedded in these files without asking the sender to resend them!

You may receive winmail.dat or AT00001.dat files from the senders who are using Microsoft Outlook (Outlook 2013, Outlook 365, etc.).



Winmail Opener screenshot

System Requirements

Windows operating system: Windows 10, Windows 8, Windows 7, Windows Vista, or even older (including Windows XP, Windows 95/98/ME, Windows NT, Windows 2000).


Winmail Opener has been translated into 21 languages (in the order of appearance):

Localization instructions are the same as described in the Flash Movie Player translation guide and are included in the /languages/readme.txt file located in the Winmail Opener folder.

Feel free to translate Winmail Opener to your language and send us the translation! Each translator name from the language files is automatically added to the "Credits" section of the "About" window.


The current version is 1.7 (last update: 16 March 2021). What's new?

You can download the latest version of Winmail Opener from our download page.

Command Line Switches

To open a specific file in Winmail Opener use the following syntax: wmopener.exe c:\path_to_file\winmail.dat

To decode a specific file and save its attachments to the specified folder without opening it, use the following syntax: wmopener.exe c:\path_to_file\winmail.dat c:\decoded

If a specified directory does not exist, it will be created.

If the path to Winmail Opener or the file to open contains spaces, use double quotes: "c:\Program Files\Winmail Opener\wmopener.exe" "c:\My Mail\winmail.dat"

FAQ: Is it possible to use wildcards in batch operations?

Information for Outlook Express users

Outlook Express does not display attachments when a TNEF-encoded file (winmail.dat) is received. If you are expecting an attachment, but do not see one, it may still be there.

To decode such a message, follow these steps:

  1. Save the entire e-mail message to an *.EML file using FileSave As, or drag-and-drop.
  2. Open the *.EML file in a text editor, such as Wordpad or Notepad.
  3. Locate the line Content-Type: application/ms-tnef; and change the Content subtype to something else, such as Content-Type: application/zzz;
  4. Locate the line name="winmail.dat" and change to name="winmail.tnf". You can also change the winmail part if you wish.
  5. Save the *.EML file from your text editor.
  6. Double-click on the *.EML file in the Windows File Explorer. This will open the message in a mail window and the TNEF attachment should now be available for saving.
  7. Drag the saved attachment into the Winmail Opener program. Decoded attachments will then be there and can be dragged or opened.

Other Information

P.S. No animals were harmed in the making of this software.


If you have a problem, a suggestion, or found a bug, you can post your message at our feedback page.

If you like this program, please recommend it to a friend or link to us.


The software is provided "AS IS" without any warranty, either expressed or implied, including, but not limited to, the implied warranties of merchantability and fitness for a particular purpose. The author will not be liable for any special, incidental, consequential, or indirect damages due to loss of data or any other reason. You are welcome to use this software without paying any kind of fee.