Microsoft posted an update for Outlook 2003 at its Download Center. The company said the update provides a "more current definition of which e-mail messages should be considered junk e-mail." So if you use Outlook 2003 consider loading the new update as it might lessen the load on your inbox.
You can learn more about the update in Microsoft's article 870765. But note that the article was not yet available on their support site at the time I posted this blog entry.