Office 365 apps using the wrong default email app

Hi all.

In Windows 10, I had set Outlook as the default email app. I had previously used Mozilla Thunderbird as the email app on the same computer.

When I am in Word or Excel and choose to share a document as an email attachment, Word/Excel opens up Thunderbird and attaches the document to an email.

What can I do to make Word/Excel use Outlook as the default email?

Thanks in advance.