<A target="_blank" href="http://www-01.ibm.com/support/docview.wss?uid=swg21296389">Technote #1296389 explains just how the Out Of Office diagnostic tool</A> works in Notes version 6 through 8.5. Of course, you're still on your own to solve the most likely reason the OOO agent doesn't work, the user's misunderstanding of how it's actually supposed to work.