Rated 3 out of 5 stars

le peci1 ar Feabh. 17, 2014 · buan-nasc

As the previous review says, only one line needs to be changed to make this addon work in recent TB versions :)

But what he suggests is for making it work in Firefox. To make it work in Thunderbird, change the same line, but in file mail.js (inside dictionary-switcher.jar!/chrome/content).