File locale.patch of Package MozillaSunbird
--- modules/libpref/src/init/all.js
+++ modules/libpref/src/init/all.js
@@ -783,7 +783,7 @@
pref("intl.charset.detector", "chrome://navigator/locale/navigator.properties");
pref("intl.charset.default", "chrome://navigator-platform/locale/navigator.properties");
pref("intl.content.langcode", "chrome://communicator-region/locale/region.properties");
-pref("intl.locale.matchOS", false);
+pref("intl.locale.matchOS", true);
// fallback charset list for Unicode conversion (converting from Unicode)
// currently used for mail send only to handle symbol characters (e.g Euro, trademark, smartquotes)
// for ISO-8859-1