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Winmail Opener logoWinmail Opener

Winmail Opener is a small and simple utility that allows you to view and extract contents of TNEF-encoded messages (infamous winmail.dat). That means if you receive winmail.dat on your e-mail, with Winmail Opener you can view the rich text message contents and attachments embedded into this file.

You may receive winmail.dat files from the senders who are using Microsoft Outlook (97, 2000). Winmail.dat contains all attachments and rich text message, and not all e-mail clients can recognize its format. Winmail Opener is the solution.

Winmail Opener features


Winmail Opener screenshot

System Requirements

Windows operating system: Windows 95/98/ME, Windows NT, Windows 2000 or Windows XP.


Current version is 1.6 (last update: 25 May 2014).

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

Command line switches

To open specific file in the Winmail Opener use the following syntax:

wmopener.exe c:\path_to_file\winmail.dat

To decode specific file and save its attachments to the dedicated folder without viewing it use the following syntax:

wmopener.exe c:\path_to_file\winmail.dat c:\decoded

If specified directory is not exists, it will be created.

If path to Winmail Opener or 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 widcards in batch operations?


At this time Winmail Opener has been translated into 20 languages (in the order of appearance):

English French Russian Czech Dutch German
Slovak Polish Italian Spanish Chinese traditional Japanese
Hungarian Romanian Swedish Norwegian Danish Turkish
Korean Chinese simplified Greek

Localization instructions are the same as described in the Flash Movie Player translation guide and included in the file /languages/readme.txt located in the Winmail Opener folder. Feel free to translate Winmail Opener into your language and send us the translation!

Every translator name from language files goes to the "Credits" section of About box automatically.

Information for Outlook Express users

Outlook Express does not display any message attachments if TNEF-encoded file (winmail.dat) was received. If you are expecting some attachment, but do not see any, it still can be there.

To decode such a message perform the following steps:

  1. Save the whole e-mail message to an *.EML file via File, Save 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 may change the winmail part as well, if desired.
  5. Save the *.EML file from the text editor.
  6. Double click the *.EML file from 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.


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.

Other information

Winmail Opener version history

Description of Transport Neutral Encapsulation Format (TNEF) in Outlook 2000 (Microsoft)

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


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