How do I add the messaging menu to the xfce-panel?

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http://askubuntu.com – I am running a pretty peculiar setup right now with LXDE, plank and the XFCE4-panel. This works fine, but I can't seem to find the messaging menu under the system tray options: Is there any service I have to add to my autostart apps for the messaging menu to show? (HowTos)