If you run any scanning test and found that some your ports are not 'Stealthed' but 'Closed' then:
1) check what programs open these ports (see 'Local Port' and 'Application' columns in Open Ports folder of Outpost window)
Imagine that that you found that some xyz.exe application opened local port 9876.
2) go to Options->Applications.
3) If you see xyz.exe in 'Trsuted Applications' then move it to 'Partially Trusted' and set tight rules for it.
4) If you see xyz.exe in 'Partially Trusted' then set the rule for this application:
where the protocol is TCP
and where the local port is 9876
and where direction is Outbound
then Deny it
Also you can try to solve the problem of 'Closed, not Stealthed' by turning Outpost into Block Most mode.