Canonical has announced that Mozilla Thunderbird will be the default mail client for Ubuntu 11.10 Oneric . For this reason, Thunderbird customization add-ons will hold more importance for Ubuntu users than ever before. Unity Unread Count is a Mozilla Thunderbird add-on which displays a mail count on the Unity Launcher. You can also, right click Thunderbird icon and get new quicklist items: Compose New Mail and access Contacts.
Download Unity Unread Count add-on from the download link given at the end of this post. Launch Thunderbird, and select Tools -> Add-ons from the Panel (as shown in the below screenshot).
Click Install button from the Extensions tab and select the downloaded XPI file.
Once the extension is installed,restart Thunderbird for the changes to take effect.
The unread mail count will be displayed for all folders and subfolders of your mail account when thunderbird is active in the Unity Launcher.
Right-clicking on the Thunderbird icon provides additional options such as accessing Compose New Mail And Contacts.
[via OMG Ubuntu]