Mac: Received Attachments Appear As Winmail.dat

Steve Krug
Steve Krug Last Updated: May 18, 2022

Software: Office 2011 & 2016 | Last modified on 2018-06-18

All received attachments within emails appear as winmail.dat files. This happens when the sending app uses the Transport Neutral Encapsulation Format (TNEF).

[Solution 1] Send emails as plain text

This step only applies as the sender of the attachments.

  1. Open the Outlook app.
  2. Open File and click Options
  3. Click Mail and change Compose messages in this format to Plain Text.
  4. Restart the Outlook app and resend the attachment.

[Solution 2] Install the Winmail.dat Viewer

This step only applies as the recipient of the attachments.

  1. Open the App Store and install Winmail.dat Viewer.
  2. Open the Outlook app and save the Winmail.dat file in your downloads folder.
  3. Open the Winmail.dat Viewer app and use it to open the saved attachment.

Steve Krug
Written by

Steve Krug

Steve Krug (pronounced "kroog") is best known as the author of Don't Make Me Think: A Common Sense Approach to Web Usability, now in its third edition with over 600,000 copies in print.

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