I hope this is the proper space to provide the results for problems described in my original post.
Alice, the visit we made to the Xfinity Webmail and back to Classic Outlook seems to have, at least at this point, solved whatever was causing the problem of read or unread emails to remain in the in the Inbox Folder even after they were deleted and also showed up in the Trash Folder. We aren't seeing that problem now.
Stefan, using your Link in the last post, we followed that to a point where we were able to see that none of the items were checked so I checked each one and, which included the one directing sent email to the Sent Folder, clicked to save. Returned to Outlook, shut it down and restarted it and sent emails now are showing up in the Sent Folder.
My thanks for following up on the problems and providing the suggestions to make things work again! I will make a complete copy of this whole situation so I can refer back again should something similar occur once again.