How to Fix Recipients Receiving winmail.dat files from Outlook 365
I’ve had an ongoing problem with my email recipients receiving winmail.dat files when I send them emails from Outlook using my Microsoft 365 email account and I’ve tried multiple ways of fixing the problem. I read that the problem is caused by Outlook sending emails in Rich Text Format (RTF). It includes the winmail.dat file invisibly to help preserve the formatting, but non-Outlook email clients can’t interpret the file, so all they see is the winmail.dat file.
Numerous sources said to go to Outlook>File>Options>Mail and change Compose messages in this format: HTML.
It didn’t help. I tried modifying the recipient’s entry in the Personal Address Book, but I couldn’t find that option, I assume because the latest version of Outlook for Microsoft 365 did away with it. I finally gave up and called Microsoft support and got an answer. This finally took care of my problem.
Login to your Office 365 admin account at https://admin.exchange.microsoft.com/ and then click on Mail flow on the left sidebar navigation.
Click on remote domains, then click on Default on the main part of the screen.
Next click on Edit text and character set on the right side sliding panel. Click on the Never radio button, then Save at the bottom.
Please note this post has been updated due to readers who alerted me to changes – Mary Joy M. Chua and Lars, thank you!