I use outlook all the time at work and really got sick of having it hang out on the task bar when I am not using it. Here is a registry edit that will make Outlook run in the system tray when it's minimized.

Remember to back up your registry before you modify it, in case something goes wrong.

Open the run command type “regedit” press enter

Under “My Computer” on the left expand the folder list to the following directory HKEY_CURRENT_USER
Right click on a open area and select NEW DWORD VALUE
Name it “MinToTray”
Right click on your new dword and select MODIFY
Set the value data to 1
Click OK
Go to FILE then EXIT
Start Outlook you should see an Outlook icon in your system tray.