There are a couple useful extensions that will undo the UI changes introduced in Thunderbird 17 as well as the changes to the tabs back with Thunderbird 11. Both of these will work together fine, or you can install on or the other depending on how you would like your Thunderbird UI to be setup. Rise of the Tools – Moves the tabs below the menu bar. Thunderbird still does not have a ‘Tabs on Top’ option that can be changed via the View Menu like that in Firefox. No Restart Needed Title Bar Tabs Cleaner – Restores the Windows Title…