Email attachments arrive as winmail.dat files
Outlook is sending emails in a Microsoft-only format that other email programs cannot read. Change your compose format from Rich Text to HTML in Outlook settings. This is a one-minute fix.
Outlook has a feature called Rich Text Format that wraps attachments in a way only Microsoft email clients can open. Gmail, Apple Mail, phones, and all non-Microsoft email clients cannot read it. Switch to HTML format and the problem stops.
Risk: Low
⏱ 2-5 minutes
Beginner
Fix-IT-Bot will walk you through each step — just tap, no typing needed.
Skip — I just want a technicianCommon mistakes to avoid
- Asking recipients to download a winmail.dat reader instead of fixing the sending format — the fix is on your end, not theirs
- Changing the format for just one email instead of the global setting — change the default so all future emails use HTML
Signs you need professional help
- Winmail.dat continues even after changing the format to HTML
- The format setting keeps reverting back to Rich Text after you change it
- Multiple contacts have overrides and you need help clearing them all
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