[MinimizeToTray] Help!

[Above Suspicion 56]

I use both Firefox and Thunderbird, and I'm trying to install this 
extension into Thunderbird.

I install the xpi file ok, but you have to click Tools>Minimize to Tray 
to get it to work!
I would've thought there would just be a setting where you say you want 
it to minimize to tray...
Which makes it go to the tray when you hit the minimize button.

Am I missing something here?

By the way: Keep up the good work.