Once comcast forced a password change Thunderbird required a new password. There should be a field under "Account Settings" for a password. There is a password manager but then you have to enter a password for the password manager. I created another profile and imported my old data but lost my calendar.
This is going to happen again so if anyone knows how to change a password in TB please post a howto or at least post a good reference. Or even recommend a better mail program.