I've been a Thunderbird user for ~12 years without any problems. However, I've been unable to access my email account the past month. I've tried many times and various efforts to re-establish logging in, including resetting my password (numerous times) with my email provider (AT&T) as well as uninstalling and reinstalling Thunderbird (early versions and the latest version). I reboot the computer before each installation. Regardless what version I use, when trying to create an account using my existing email address (kalani1@bellsouth.net), I receive the attached error message. I've tried to switch to an IMAP server setting without success. My computer hardware and software configurations have not changed since I switched from Win 7 to Win 10 in Jan. I'm able to login to my AT&T web mail account each time I reset my password, but unable to login to Thunderbird. Hoping someone can help.