Cannot connect Yahoo Mail with Thunderbird

Have you read these articles about the migration? You might need to go through some extra steps, especially if you already have some other Yahoo accounts set up in Thunderbird... Upgrade your comcast.net email experience to Yahoo Mail https://www.xfinity.com/support/articles/yahoo-email-migration-overview Information for Xfinity Comcast.net email accounts moving to Yahoo Mail https://help.yahoo.com/kb/new-yahoo-mail/SLN36803.html By the way, despite what Xfinity has been saying for months, they backtracked and now admit that the so-called "upgrade" to Yahoo is voluntary.Had chosen not to do it, your Comcast account would continue to work as always for the near future at least. But at the stage you're at it's too late to change your mind.