Hi David, I belive I resolved. But before I post a final of my settings, I hope you can answer a question. My fix: was to change Outgoing SMTP.verizon.net to SMTP.aol.com. This then brought up additional Authentication Methods that now includeds OAuth2, which I selected. The 1st time I sent, I was prompted with a different AOL screen to enter password - the screen looking as though it was direct from AOL & as if I was logging into to my AOL on-line acct. So logged in with on-line acct password (there was no place to request password be saved). My email then sent. I immediately received an eM from AOL "Your AOL account soly4fun@verizon.net was just used to sign in on Thunderbird AOL. If you did this, you’re all set." I closed TB. Reopened a short while later & sent another eM. No password request was received & mail sent. I then shut down, rebooted, opened TB & forwarded an email, again no password request & mail sent. Not knowing a thing about OAuth2, is this method actually sending my mail to/through AOL online site? I do detect a slight delay in the send, but perhaps that is normal when using a 3rd party email?? Thanks once again for all your time & Help. Apologies to all for the wordiness.

It sounds like all is working as desired. That use of AOL for Verizon is unusual, but an agreement between the two several years ago. I think you're good to go. :)