Thunderbird is a total redesign of the Mozilla mail component to produce a cross-platform, stand-alone mail application using the XUL user interface language. It has many new features, among them the ability to customize your toolbars the way you want them. a new look and feel with a large number of downloadable themes which alter the appearance of the client, and the ability to add UI extensions.
Arronax is a plugin for Nautilus (the GNOME default file manager) to create and modify application starters (".desktop files"). It adds the menu item "Create starter for this file" to the context menu (the menu you get when you right-click a file in the file manager). If the file is an application starter, you get the item “Modify this starter” instead. If you have icons enabled on your desktop, Arronax adds the menu item “Create starter” to your desktop’s context menu.