Update for Outlook 2003 Junk Email Filter (KB894384)
Microsoft has just released the latest update for Outlook 2003 Junk E-Mail filter. You can get it here.
"This optional update provides the Junk E-mail Filter in Microsoft Office Outlook 2003 with a more current definition of the e-mail messages that should be considered junk e-mail messages. This update was released in May 2005."
You can also read the correspondent KB article:
Description of the Outlook 2003 Junk E-mail Filter update: May, 2005