I don want Outpost running in the system tray, is there anyway to hide the Outpost GUI?
Yes. Open the ‘Options’ menu and select Options -> General… and uncheck Run Automatically at boot-up. This stops the GUI from starting at boot (the engine is still running). Now if on the same tab you have Apply rules without need of interface checked the engine will filter packets according to the rules you have already created. Outpost, in this state, is running in Block Most Mode so any applications without rules will be blocked by default. If you uncheck Apply rules without need of interface then the rules will be ignored, it will be as if you didn’t have any firewall running (the plugins are also disabled in this case).