Using classic Outlook for Windows in business environments
Thanks, Alessandro R and Andy Dobbs.
As you suggested, I tried setting up my outlook.com emails in the New Outlook app. Now I have folders from another account (used in the New Outlook app) showing in the MS outlook.com email account that I added! Very Weird. There are now two Inboxes, two Sent, etc. in the MS outlook account navigation sidebar. When I highlight one of the folders from the other account, I see the emails from that other account, AND the highlight on the folder in the navigation sidebar is shown in both accounts. It's like creepy! It makes it look like both accounts' data has been merged together somehow! I've tried change View setting from Focused to Non-focused, and back again, but that didn't do anything. What a debacle!
Nonetheless, I'll leave this outlook.com account in the New Outlook app for a few days to see if it solves the continuous asking for a password issue in my Outlook desktop software - the only reason to put this account in the New app.