Have a look at the quick tutorial here: How to install Menu On Top

This is a small extension which makes it possible for Windows users to move the Thunderbird menu above the tabs, like it used to be in Thunderbird 10. The main reason is usability; it is inspired by the excellent Thunderbird themes of Alfred Kayser. Please be sure to try them out!

Table of Contents

Downloads
Where is my menu bar?
Preferences
Style Configuration
Custom Menu
Themes
Avatars / Icons
Contributions
Version History
Feedback / contact me

Preferences

As you may notice on this screen shot, it uses the coloring of your Operating System's theme engine to display the caption + menu area. This means you can use the addon with UI stylers such as Windowblinds - the screenshot shows the UIS2 theme 'Lantana'. It also means I had to add the possibility of making the menus more visible by styling the menu text background. Note that any toolbar buttons do not have backgrounds as it looks much nicer. You can move buttons that you need all the time (e.g. get Mail) to the top which adds some more usability.

Downloads and Source

Menu On Top can be downloaded here. The code is based on the addon Rise of the Tools.

Where is my Menu bar?

Of course to enjoy the "Old school" menus on top, you might have to make the menu toolbar visible; if the menu isn't there at all, simply select from the menu button:
Options... ► Menu Bar

Enabling the Menu

Style Preferences

The addon is restartless and has a quite a few options; either click the toolbar / status bar icon MOT options button, or click on Tools ► Addons ► Extensions and click the Options button of Menu on Top:

Style Configuration

Preferences

To get started, select a Theme from the dropdown. You can then tweak various things in the dialog - all changes are visible immediately. Use the Only Change color Scheme option once you are happy with the way it looks and only want to try different colors.

Custom Menu / Avatar

Advanced Preferences

Enable the Custom Menu in order to add bookmarks and an Avatar if you like. The supplied icons for avatars are 32px * 32px - I highly recommend setting the size to 32 or higher.

The list ion the custom menu is looking at your current tab content, so if you click the Current Page button it may add a web page or the currently viewed email, depending on what you are viewing. Note that you can also add a bookmark to the menu by clicking and chosing Add Current Item at the bottom of the menu.

Tool buttons - these affect the items in the bookmarks list

Bookmark - each menu item has 3 attributes: