Enhanced Priority Display Thunderbird / SeaMonkey add-on
AMO home page, from which the add-on can be downloaded and installed: https://addons.mozilla.org/thunderbird/addon/enhanced-priority-display/
Author: Jonathan Kamens <email@example.com>
Copyright (c) 2012,2013,2015 Jonathan Kamens.
Released under the terms of the Mozilla Public License, v. 2.0. The MPL can be found in the file LICENSE.