...have not been able to get "Thunder B1rd" to get verified with my email server at my ISP, that is being handled by YAHOO!
Since Yahoo! was recently taken over by Verizon, it is possible that could introduce problems configuring email (but I doubt that is it). This is another good topic for a new thread, if you want to start one. A possible Subject title might be, "Configure Thunderbird settings" or something like that. I agree with Wizard that it is helpful for the Subject to describe the problem, or desired solution.