Thunderbird-Version: 52.8.0 (64-Bit) on Archlinux (up-to-date) Hello, we'd like to use thunderbird as the mail and calendar client in our non-profit organisation. The whole network consists only of linux servers and workstations running archlinux. To prevent our users from changing some of the settings in the mail client (especially a mail BCC to our mail archive) I read about locking preferences here: http://kb.mozillazine.org/Locking_preferences I then created a file local-settings.js with the content: pref("general.config.filename", "mozilla.cfg"); pref("general.config.obscure_value", 0); and copied it to /usr/lib/thunderbird/default/pref after that i created file mozilla.cfg with the content: // Don't allow to edit bcc to mail archive lockPref("mail.identity.id7.doBccList", [email protected]); lockPref("mail.identity.id9.doBccList", [email protected]); (These are the values I became from about:config) and copied it to /usr/lib/thunderbird/ I start thunderbird and only get this message: Failed to read the configuration file. Please contact your system administrator. Well - thats me :( I then tried to encode the file mozilla.cfg to ROT13 as suggested in another post and removed the line pref("general.config.obscure_value", 0); from the file local-settings.js. Now thunderbird starts again, but the pereferences are still clickable and the user can edit or delete the BCC which is not what was intended... I am stuck here. Can somebody shed some light on the problem or at least push me in the right direction? Greetings Harvey