Bug #328988 --> remove dependeny on buildin urls.rdf for the dicionary url.

mail/app/profile/all-thunderbird.js

@@ -340,6 +340,8 @@ pref("news.directory",                  "");
 pref("autoupdate.enabled",              true);
 pref("browser.editor.disabled", false);
 pref("spellchecker.dictionary", "");
+// Dictionary download preference
+pref("spellchecker.dictionaries.download.url", "https://addons.mozilla.org/%LOCALE%/thunderbird/%VERSION%/dictionaries/");
 
 // profile.force.migration can be used to bypass the migration wizard, forcing migration from a particular
 // mail application without any user intervention. Possible values are: