Other users are currently experience issues with Verizon e-mail. This appears to be an outage with Verizon.

SOLVED!! Interesting. It does seem to be a Verizon outage. After a mere 2 hours of hold time on the AOL tech support, Sabrina remoted in to my computer and changed the incoming and outgoing servers from the "verizon.net" servers to "aol.com" servers. My email seems to work again.

Another user managed to connect with the Verizon servers by changing the User Name to the full email address:

https://support.mozilla.org/en-US/questions/1272914#answer-1303366

If you switch to the AOL servers, imap.aol.com, pop.aol.com and smtp.aol.com, OAuth2 authentication is available and recommended.

True! Good point! In addition to changing to aol servers vice verizon, she edited my user name to the FULL EMAIL ADDRESS. Based on the above, it sounds like this is a required change.

I changed my email address to the full email address, and I changed the incoming and outgoing servers from Verizon.net to aol.com. Still didn't work. Do I have to change anything else, like the port, the connection security, or the authentication method?

I can't change the servers--I keep getting an error message telling me to provide a valid server name. I can't change my email address from @verizon.net to @aol.com--that was the whole point in keeping the verizon.net. I don't care what servers it goes through, but it doesn't want to accept the change.

I solved my problem--someone else (WKOVI) posted that they were also a former Verizon customer using AOL and they changed the Username on the outgoing server because it uses only the name without the @verizon.net extension when sending messages. If you go up to the AOL website to log in, you always have to enter "username"@verizon.net. SOOO, if you change that setting for the Outgoing server from just "username" to "username"@verizon.net, it works.

When you change a server name or password, or authentication method, delete the old passwords or oauth tokens in Options/Security/Passwords/Saved Passwords, restart TB, and enter the password when prompted.

If you have a @verizon.net address, don't change it to @aol, but put the full address in the User Name field, for both the incoming and outgoing servers.

Other users are currently experience issues with Verizon e-mail. This appears to be an outage with Verizon.

The problem is that Verizon now requires the outgoing server smtp.verizon.net now requires SSL/TLS for its authentication method and Mozilla does not have that choice. It need to be fixed by Mozilla.