The XPI package for your language doesnt work?
Here is the solution, Thuderbird use the system’s dictionarie “myspell”, so you have to copy file in /usr/share/myspell/dicts/
Or just copy and paste with the good dictionary file you can find here:
http://wiki.services.openoffice.org/wiki/Dictionaries
wget http://ftp.services.openoffice.org/pub/OpenOffice.org/contrib/dictionaries/fr_FR.zip
sudo unzip fr_FR.zip -d /usr/share/myspell/dicts/
and just restart Thunderbird.
Merci pour ce post !
cela faisait un certain temps que j’essayais de résoudre ce pbm !!!