What's your normal routine when you log on in the morning? It's probably something along the lines of: pour cup of coffee, fire up Thunderbird, check your email, check your other email accounts that Thunderbird can't access, pour another cup of coffee. Well, here are a few Thunderbird extensions that may make your mornings go a little more smoothly.
But first, here's an application that is not an extension. With KDocker you can dock any application into your system tray just by clicking on it. With it, you won't have to remember which desktop you left Thunderbird on; the Thunderbird icon will always be visible. And you can use KDocker from the command line with a command like
kdocker thunderbird & to start Thunderbird and dock it at the same time.