This plugin works as advertised. It creates links to individual emails. It's very useful for keeping track of emails that you need to later re-open. I run a small one man business. When customers write in with a question or request I can't immediately answer, I'll make a note in my TODO list with a ThunderLink to the customers email. Once the request is taken care of I use the ThunderLink to quickly re-open the original email and write back. It's a huge time saver. Without thunderlink I would need to search through my email history to find the relevant email.
I didn't give it five stars because there is no way to open thunderlinks in Thunderbird. There are a couple other ways to open thunderlinks. I use "Find And Run Robot" (which is another awesome time saving application).
This review is for a previous version of the add-on (0.06).