For this add-on to work you must have MinimizeToTray installed. If you don't this extension will install it for you, and you will see a blinking blue arrow in the status bar, till you click it to restart the application (Firefox, Thunderbird or Sunbird).MinimizeToTray Plus adds a toolbar button to the Customize Toolbar window. Right-click on the toolbar then click Customize then find and drag blue arrow to toolbar.There is also an option to have a status bar item for minimizeing the application.If you want to request another feature please go to http://codefisher.org/emailSeveral other of my extension can be found at http://codefisher. org/How to Install in Thunderbird:1. Right-click the link below and choose "Save Link As..." to download and save the file to your hard disk.2. In Mozilla Thunderbird, open Add-ons from the Tools menu.3. Click the Install button, and locate/select the file you downloaded and click "OK". Requirements: · Mozilla Thunderbird What's New in This Release: · New translations and a max version bump for Sunbird + some problems with the toolbar button fixed.