Compose new mail with Thunderbird 3 in Ubuntu 9.10 via a keyboard shortcut

Compose new mail with Thunderbird 3 in Ubuntu 9.10 via a keyboard shortcut

Is there a way to set up a keyboard shortcut such that, after I hit it, a new mail window for Thunderbird opens up on the current viewport? Under XP I did this by using the OS's built-in mailto: URL handler. I know how to set that in Gnome (using gconf) but I don't know what to set it to....