gentoo-overlay/mail-client/thunderbird-bin/files/thunderbird-gentoo-default-prefs-r1.js

// disable auto-update
pref("app.update.enabled", false);
pref("app.update.autoInstallEnabled", false);

// localization
// "intl.locale.matchOS" doesn't exist anymore, see https://mail.mozilla.org/pipermail/firefox-dev/2017-December/005991.html
pref("intl.locale.requested", "");

// misc
pref("browser.display.use_system_colors", true);
pref("mail.folder.views.version", "1");
pref("mail.shell.checkDefaultClient", false);