User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.0; en-US; rv:1.8.1.6) Gecko/20070725 Firefox/2.0.0.6 Build Identifier: version 2.0.0.6 (20070728) spell dictionary (at least both french dictionaries) does not install in Thunderbird... the get install in Firefox!!! Reproducible: Always Steps to Reproduce: 1.- the FireFox tab open with the choice of dictionaries 2.- click on the install link 3.- the software installation window opened, click on install 4.- the dictionaries do get install in FIREFOX !!! and a FireFox window is asking to restard Firefox Actual Results: if I go in Firefox tools\add-on I see both dictionaries but no french dictionaries in thunderbird Expected Results: the dictionaries should be available in thunderbird and they are not it is a major bug for french speaking people !!!

Yes, it's quite annoying, but you have to read the instructions at the top of the page (I assume you mean that you are installing from somewhere like https://addons.mozilla.org/fr/thunderbird/browse/type:3) about clic-droit, choisissez "Enregistrez la cible du lien sous...", and install the saved file in Thunderbird.