Try this. It took a bit of persistence but I found what works on my system and hope it will help someone.:
After exhausting all other possible solutions I found posted in many forums, I reajlized that my first issue was with allowing my aol verizon.net email account to access the Windows 10 mail app because that was the one highlighted message on top of the mail screen I kept getting.
To allow your email account access to Windows 10 mail app.:
First, sign into your aol verizon.net email account through your browser.
In the very upper right-hand corner of your screen under where you can see your aol username highlighted, there are two options: "sign out" and "options".
Click on the options pull down menu.
Select "account info".
On the left side of your screen, select "account security".
Then toward the bottom, turn on "Allow apps that use less secure sign in"
by clicking on the circle on the right side (gray for off, blue for on}.
Now for the correct server settings (which I think is confusing but this worked):
Incoming mail server (IMAP): imap.aol.com
Outgoing mail server (SMTP): smtp.verizon.net
[Do *not* enter port settings. Only use the server settings listed above.]