I don't think they're using a bayesian filter. If so, it would improve itself automatically and Outlook would probably have a "Mark as junk" option to help the bayesian filter in classification junk and not junk. And if it's a bayesian filter there would be no need to update it regularly via office update.

I really would like to have a bayesian filter in Outlook. I'm using Mozilla Thunderbird at home and it's much better in filtering Spam than Outlook 2003.

Martin