I updated T-bird and it quit working. It starts and the app comes up, but it is dysfunctional. It won't even open the "about" information to see what version it is.
So I downloaded SeaMonkey and it loaded all the configuration info automagically. If I had known it was this easy I would have done it a long time ago.
I'm not as happy with the user interface as I was with T-bird. The fonts are smaller and more crowded when viewing the message and group lists. My vision is not always so good, so this is important to me. More importantly I wasn't able to easily find support of any sort. I'll have to dig further.
At least SeaMonkey works.