Rated 1 out of 5 stars

This is already built-in to Thunderbird, you just have to use the advanced config editor.
You can add string property with the name:
network.protocol-handler.app.http
and give it the path to your browser. Add a second one called network.protocol-handler.app.https and it will work with secure sites too.

This review is for a previous version of the add-on (0.7). 

Unfortunately, that doesn't always work. If it works for you, that's great. But it does not work for a majority of people that use Thunderbird (especially on Linux). Despite that, it also lets you choose if you want links to load in a portable browser, which you cannot do just by rewriting config strings as drives change and that's annoying.

You probably didn't even try this extension, so why don't you go flame somewhere else.