That will show you how to password protect your .PST files and that's the
closest you'll get to what you're asking for with Outlook. With OE you can
password protect your entire identity but with Outlook that link is the
method.
"A man should keep his little brain attic stocked with all the
furniture that he is likely to use, and the rest he can put away in the
lumber-room of his library where he can get it if he wants it."