Rated 5 out of 5 stars
This is one of the most useful Add-ons I use with Thunderbird because I write messages in more than one language.
However, when I replaced the 32 bits Thunderbird for the 64 bits version, my English dictionary was removed. And probably as a result this Add-On stopped checking messages in that language.
I reinstalled the English dictionary and all seems well now! I was previously afraid that this Add-on would not work with the Thunderbird 64 bits version. Apparently I was wrong.