Sometimes when you send email from Outlook to someone who isn’t using Outlook you might find they send you an email back saying “I don’t see an attachment… all I have is some sort of winmail.dat file!”
What is a Winmail.dat file?
The “winmail.dat” and a content type “application/ms-tnef” files are Outlook’s way of dealing with the Rich Text Format. when you send emails with BOLD or ITALIC or some sort of fancy font Outlook sends a file along with the email that contains all the format information. Unfortunately sometimes when it try’s to send these files to none Outlook/Exchange systems it sometimes adds your attachments to the newly created “Winmail.dat” file meaning the person at the end (who isn’t using Outlook or Exchange) can’t decode the file and access your attachments.
You can help reduce the chance of it happening again by checking/changing some settings within Outlook.
- Within the “Compose Mail” (Its the first option in Outlook 2016)
- select HTML or Plain Text from the drop down menu “Compose message in this Format”
- Scroll down to the “Message Format” (Right down the bottom in Outlook 2016)
- Select “Convert to HTML format” in the “When sending messages in Rich Text format to Internet recipients”
- Click OK
- Create a new email and try again.