Thunderbird supports conversational tree-like structure of emails. Here you can know more about them and also how you can turn it on or off. It can be a great feature for those who constantly reply to an email back and forth.
If your links in Thunderbird are not working, read this article to find out what the issue and how to solve it.
Here are three different solutions that has been show to fix this issue. Try them and see which one fits your situation.
What are digital signature and email encryption and how you can use them in your Thunderbird email client to ensure maximum safety and privacy.