Rated 3 out of 5 stars

Like c9c27f below, I was really hoping that this would replace the old contacts sidebar addon that worked in the "main" view, not just the new message window. Any chance of implementing this?

This review is for a previous version of the add-on (1.3). 

Add-on 'Contacts Sidebar' is not seemed to be maintained for a long time. So I tried to implement this add-on to work in main window.

New version is now being checked by mozilla.org, so please wait. You can see images at add-on page.