Office 2010

I need to test an email conversion issue with a downstream host and need to send test messages with TNEF (I know, sounds silly because usually we DON).

How can I generate a sample message in this format? I tried the following procedure:

  1. Open Outlook
  2. Navigate to File -> Options -> Mail -> Message Format (section)
  3. Change "When sending messages in Rich Text format to Internet recipients" to "Send using Outlook Rich Text format".
  4. Save changes. Close Outlook. Reopen Outlook.
  5. Compose a new message. Select the "Format Text" tab and set "Rich Text" for the format.
  6. Add sample stylized text and an attachment for good measure.
  7. Send the message through.

That still doesn't seem to cause it to appear (and I'm checking the MIME source). Is there another way?

2 Answers 2


There are numerous ways to force Outlook to send in TNEF, as detailed here:


It appears you're already following one of these options, but perhaps you could try the others. I suspect, however, that the real problem is at the server level. According to this Microsoft page, it is possible for your Exchange administrator to prevent Winmail.dat files from being sent to Internet users:


If that's the case, you'll need to get the help of your Exchange admin to change these settings for you. If he's unwilling to do so, which would probably be smart, maybe he could setup a test Exchange server for you.


The only way I have found to "force" using TNEF (winmail.dat) format in Outlook 2013 is to add voting buttons! This seems to work every time.

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