The connection was refused means server is just not allowing the connection.

Please check your computer to see if there is a VPN which has become enabled. Many servers do not like VPN because it hides your IP address, so server thinks you might be a hacker and decides to block as a precaution. Some Anti-virus products now offer VPN and I've come across some cases where the VPN was auto enabled. Switch it off or create a split tunneling and set up Thunderbird to use it.

Server may want you to set up a new secure key which is done via the webmail account using a browser.

Then you need to update the saved passwords in Thunderbird.

• Settings > Privacy & Security
• scroll to Passwords section
• clickon 'Saved Passwords
• click on 'Show Passwords'

You should have two lines one for incoming and one for outgoing. You need to update password in both lines. Right click on relevant line and selct 'Edit Password' completely clear everything and carefully enter the new secure password you created. When finished, clickon 'Close'

then Exit Thunderbird - wait a few moments for background processes to complete and restart Thunderbird.

Thanks for replying. The problem actually resolved itself after about 24 hours, so apparently some sort of issue between AT&T and Thunderbird.