Hi,
Are you talking about the pop-up window as shown below?

If so, please follow the steps below to solve your problem.
- Close Outlook.
- Run Outlook as Administrator and open the attachments
- Removing the check from "Always ask before opening this type of file" box.
- Close Outlook and start it normally.
Hope this can be helpful.
Regards,
Aidan Wang
Please remember to
mark the replies as answers if they helped. If you have feedback for TechNet Subscriber Support, contact
tnsf@microsoft.com.
Click
here to learn more. Visit the dedicated
forum to share, explore and
talk to experts about Microsoft Teams.