Here is a list of things you can do to fix the issue with Outlook not properly formatting or displaying email attachments from specific senders:

1. Check if the attachments are supported by Outlook. If not, consider using an alternative program to view them.
2. Update your version of Outlook to the latest one.
3. Check if you have the most recent version of the program that is used to open the attached file.
4. Open the file in Safe Mode.
5. Verify that the sender has a valid email address.
6. Clear the Outlook cache and reset your user profile.
7. Unblock the sender from the blocked list in Outlook.