No it's not death or alive beacuse it's a Mozilla is a browser and thunderbird is his application but , i can understant you feeling because these kind of issue make us to upset because these services become a part of our life and sudunly one day it's stopped working and people get hopeless but dear sir, the problem you're facing it's not that much complicated you can easily findout solution via Mozilla/Thunderbird support forum so you just go there and find the best query you are looking for.
If your problem is spam then the source of the problem is not Thunderbird. I've had spam on Eudora, PMMail, Outlook and Thunderbird. No email program is going to solve the spam problem. The best that can be done is filter it and put it into a Junk folder. I'm currently using Thunderbird and it traps about 99% of all my spam.