See my above SOLVED info int he previous updated post on how I changed my name in Windows 10 Mail.

To change your email name in in Windows 10 mail:
Go to settings (the little gear),
Click on "Manage Accounts",
Click on the account you want to change,
Click on "Change Mailbox Sync...

Windows 10 Email APP
I need to update my last name.

I go to SETTINGS
MANAGE ACCOUNTS
There is no box to update ANY name change.
I could do a work around by deleting and reinstalling the...