Change back to Thunderbird's original icons

wget -c http://frankandjacq.com/ubuntuguide/mozilla-thunderbird.xpm
chmod 644 mozilla-thunderbird.xpm
sudo dpkg-divert --rename /usr/share/pixmaps/mozilla-thunderbird.xpm
sudo dpkg-divert --rename /usr/share/pixmaps/mozilla-thunderbird-menu.xpm
sudo dpkg-divert --rename /usr/share/pixmaps/mozilla-thunderbird-pm-menu.xpm
sudo dpkg-divert --rename /usr/lib/mozilla-thunderbird/chrome/icons/default/mozilla-thunderbird.xpm
sudo dpkg-divert --rename /usr/lib/mozilla-thunderbird/chrome/icons/default/messengerWindow16.xpm
sudo dpkg-divert --rename /usr/lib/mozilla-thunderbird/chrome/icons/default/messengerWindow.xpm
sudo dpkg-divert --rename /usr/lib/mozilla-thunderbird/chrome/icons/default/default.xpm
sudo cp mozilla-thunderbird.xpm /usr/share/pixmaps/mozilla-thunderbird.xpm
sudo cp mozilla-thunderbird.xpm /usr/share/pixmaps/mozilla-thunderbird-menu.xpm
sudo cp mozilla-thunderbird.xpm /usr/share/pixmaps/mozilla-thunderbird-pm-menu.xpm
sudo cp mozilla-thunderbird.xpm /usr/lib/mozilla-thunderbird/chrome/icons/default/mozilla-thunderbird.xpm
sudo cp mozilla-thunderbird.xpm /usr/lib/mozilla-thunderbird/chrome/icons/default/messengerWindow16.xpm
sudo cp mozilla-thunderbird.xpm /usr/lib/mozilla-thunderbird/chrome/icons/default/messengerWindow.xpm
sudo cp mozilla-thunderbird.xpm /usr/lib/mozilla-thunderbird/chrome/icons/default/default.xpm

*from ubuntuguide.org