''<p>s.geer [[#question-1514303|said]]</p>'' <blockquote> The Email and password have not changed. No other settings have changed. Anyone else having this issue? </blockquote> Probably a lot of folks with Third party antivirus solutions. The Norton product is historically particularly good at messing up mail post an update. My normal recommendation is to remove any non windows defender security package and see if that helps. <blockquote> If this cannot be corrected, I cannot continue using Thunderbird. Help! </blockquote> The issue is rarely one with Thunderbird. It does happen, be it is extremely rare. Post update interruptions are almost always related to antivurs products and their associated software firewalls. This is exacerbated for ATT customers by the fact that the user password is NOT used in the email client, but a mailkey. Unfortunately the prompt that comes up asks for a password, as that is what the mailkey is, so often folks replace a previously working mailkey with the user password they use on the ATT web site. That is designed to fail by the way ATT have implemented their email.