Attachments arrive as winmail.dat files
Outlook is sending emails in a Microsoft-only format that other email programs can't 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 can't read it. Switch to HTML format and the problem stops.
Risk: Low
⏱ 2-5 minutes
Beginner
⚡ Before you start
- ✓Go to File → Options → Mail in Outlook
- ✓Look for the Compose Messages section
- ✓Check what format is selected — it should be HTML, not Rich Text
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, or you have multiple contacts with overrides and need help clearing them all.
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