作者 Access Firefox Project (开发者) 日期 April 28, 2012 · 永久链接

Will you please tell me what operating system that you're using and what version of Thunderbird?

This add-on has been available on this site since February 28, 2012 and this is the first time that I've heard that it doesn't work. I use it myself.
It accesses and triggers Thunderbird's default zoom feature and that's about all there is to it.