Windows 10 and Outlook font flaw

[Windows Central Question]

I'm having an issue that I'm convinced is a flaw in Windows 10 that is affecting the font for incoming emails to Outlook if the email is sent from an Android or an iPhone. The font for the incoming email automatically changes to the Office default font 'Calibri 11' even though it was not sent in that font from the phone. This issue only happens in Windows 10 with Outlook or Gmail but not in Windows 7 which I have on another computer. I've spent hours and hours on the phone with Microsoft and other IT options and can not find the fix. Ever heard of this issue? Thank you.