Update delete_move_next plugin to use standardized preferences. Note: IF YOUR INSTALLATION IS NEW, OR ALL USER PREFS HAVE BEEN CONVERTED FROM "on"/"off" to 0/1 THEN YOU CAN ADD TO FOLLOWING TO THE SQUIRRELMAIL config/config_local.php FILE TO AVOID CONVERTING LEGACY VALUES OVER AND OVER: $do_not_convert_delete_move_next_legacy_preferences = TRUE;