Rated 4 out of 5 stars

A very nice addon indeed.

I support kandilzade's request, to change the background color of the header when the message pane is selected. It would be helpful. I think it would also be nice if a way existed to customize the visibility of the buttons shown in the header (for instance, i hate the "junk" button and would like to remove it).

Thanks for the addon.

This review is for a previous version of the add-on (2.0.6). 

Customization

The customization of the header toolbar is included in this addon (actually in Thunderbird itself):Place the mouse on top of the buttons, then click right mouse button, then "Customize". Then you can add/remove buttons.With the CompactHeader preferences dialog (e.g. also by the right mouse context menu on top of the header) you can choose the location of the header toolbar.

I added an option to the latest beta (2.0.7beta3) to darken the message header if the message pane has focus.