Stop Outlook from Sending the Winmail.dat File as an Email Attachment

The cause of the mysterious Winmail.dat file attachment when sending email via Outlook is a mysterious one. We know it’s not harmful, but the problem has existed since Outlook 2007, and Microsoft hasn’t taken any steps to actually get rid of it.

At this point it’s really more of an annoyance than anything, but it’s an annoyance you can get rid of in a few simple steps.

1. Exit Outlook and type regedit in the Search (or Cortana) box. Click the program to continue.

2. Allow the app to make changes by pressing the Yes button.

3. Click HKEY_CURRENT_USER and then navigate to the appropriate folder: Software > Microsoft > Office > (highest version, 16 in this case) > Outlook > Preferences.

4. From the Edit menu, click New and then DWORD Value.

5. Type DisableTNEF and then right click and select Modify.

6. Type 1 for the Value data and then click OK.

7. Exit the registry editor and restart the computer.

Microsoft Outlook Tips

Bryan covers everything you need to know about Windows, social media, and the internet at large for Laptop Mag. Thanks to his extensive knowledge of operating systems and some of the most popular software out there, Bryan has written hundreds of helpful guides, including tips related to Windows 11 drivers, upgrading to a newer version of the OS, editing in Microsoft Photos, or rearranging pages in Google Docs.