Hi Theresa J,
There is no such option in Lightroom preferences to change the default settings.
However you may add the additional email account to email the images from Lightroom .
Well if additional account still go to the default Windows setting, then that doesn't help at all. I guess the answer is that this is not a Lightroom problem, but a Windows 10 issue.
I also think so it is an issue with Windows, as it is picking the default email application.
Yes, not a Lightroom problem.
You need to install an email program that does not use that funky OneDrive nonsense.
Then have Lightroom use that email program instead.
Joe, Thank you for confirming.