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  • Outlook is sending winmail.dat attachments

    This article is related to – Support for Windows PC’s

    This article is assuming you are running Outlook 2016, which is currently the latest version


    There is a long standing “problem” between Outlook and Internet email – Outlook uses a proprietary email format that only Outlook and Exchange (and a few other clients, including gmail) can decipher. When the recipient doesn’t use Outlook, they get a plain text message and an attachment named winmail.dat. Additionally, the attachment icon may be hidden by some clients, including OE and Windows Mail, making it look like the attachment was removed.

    The problem? Any attachments included in the message are encased in the winmail.dat attachment.

    A work around for this is to adjust your Registry File adding a new ‘dword’ line as outlined below:


    1. Right click on the ‘Windows Start Button‘ and click on ‘Run
    2. Type in the box ‘Regedit‘ and click the ‘OK‘ button
    3. Navigate to the following section: [HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\Preferences]
    4. In the right side of the screen right click your mouse and choose ‘New‘ then click ‘DWORD (32-bit) Value
    5. Rename the ‘New Value #1‘ to ‘DisableTNEF
    6. Now right click the mouse on the new name and choose ‘Modify
    7. Replace the Value Data with ‘000000001‘ and press ‘OK
    8. Reboot your PC and it should now cure that problem
    9. That’s it – all done!

    In some cases the settings can be stored within the auto-complete cached address list, so you might also need to clear this to resolve the issue fully:

    1. In Outlook click the ‘File’ link
    2. Then go to Options, then Mail, then the ‘Send Message Section’
    3. Click the ‘Empty Auto-Complete List’ which will cleat the entire cache
    4. That’s it – all done!

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