How to send the Outlook Messenger to system tray of Microsoft Windows 7 when its is minimized ?
Although I am using Outlook 2007 but I think this option was available in 2007 already:
This will hide the Outlook taskband entry when Outlook is minimized.
Edit: Just discovered that indeed Outlook 2007 seems not to have this option. Instead you would have to use a tool called "HideOutlook" or similar. See here for example.
Edit: I just noticed now that the question was rather about Outlook Messenger (Outlook LAN Messenger?) which seems to be some 3rd party software. Of course it does not have to follow the same guidelines as Microsoft Outlook itself.
Although there is a very generic tool called RBTray. Once startet it allows you to simply right-click any minimize button to send the application to tray. There are a couple of other "minimize-to-tray" applications out there but RBTray is very small, simple and I personally like the "right click minimize" feature.