Outlook Junk E-Mail filter not working

My Outlook 2003 junk e-mail filter is suddenly not working. All the junk e-mail that would normally go to the Junk E-Mail folder is now just dropping into my Inbox. I mean all the junk e-mail. It’s catching nothing. I have it set on Low and it always let some stuff slip through, but now it is just not working at all. I changed it to High and exited Outlook, re-opened Outlook and set it back to Low, exited Outlook and re-opened it and still I get the same behavior. Never seen this one
before. Any help would be appreciated.