I suggest you contact AOL for help. The site I think is useful would be https://help.aol.com/articles/Create-and-manage-app-password If you used an app password, it will be different from that used on AOL website.

yahoo/aol servers have been making changes when it comes to people using third party programs and passwords. You need to set up 2 step verification and generate an app specific password. Switch on 2 step: * https://help.aol.com/articles/2-step-verification-stronger-than-your-password-alone Generate app password: * https://help.aol.com/articles/Create-and-manage-app-password quote: 1. Sign in to your AOL Account Security page. 2. Click Generate app password or Generate and manage app passwords. 3. Enter your app's name in the text field. 4. Click Generate password. 5. Follow the instructions below the password. - Be sure to enter the password into your app without any spaces. 6. Click Done. Use this app password and your email address to sign in to your email app. In Thunderbird * Menu app icon > Preferences > Privacy & Security * Passwords section * Click on 'Saved Passwords' * click on 'Show Passwords' There will be two lines for the mail account - incoming and smtp outgoing, both lines need the password updating. * Right click on line and select edit password. * Make sure it is completely cleared and then copy in the app generated password. Alternately : * select each line and click on 'Remove' * then click on 'Close' * Exit and restart Thunderbird * At the password prompt - enter the app generated password, select checkbox for Password Manager to remember it. Send an email as well, as it may also ask for password and it will need same app gnerated password.