thanks for all + feature request Rated 5 out of 5 stars

All it fine for very minimalistic mode. But lack of buttons for reply and forward is minor inconveninece that could be resolved as buttons in tabbed area on the right (close to calendar and address book)

This review is for a previous version of the add-on (2.0.1). 

Header buttons

You can either use the two line mode (use the context menu "CompactHeader preferences" or change the settings in the addon tab) to see the header toolbar. Or you can change the position of the toolbar either to left or right then it will be a "sidebar". The the requested buttons are always visible.