I've been using Outlook 2003 for a long time. A couple of days ago, Outlook no longer filtered junk mail into the special Junk Mail folder. All the spam just accumulated in my Inbox. Since I have public email addresses, I get literally hundreds of spam messages an hour. I rely on the Junk Filter working properly.

I am suspicious that this behavior began right after I installed the trial version of Microsoft Publisher 2007 (so I could view a .pub document someone sent me). I'm my search for a solution to the problem, I did see some other reports of people suspecting Office 2007 (and other Microsoft updates) affecting Outlook.

I stumbled on the solution that worked for me in a forum article titled "Junk mail filter stopped working". This solution is very simple:

1. In Outlook 2003, select Help > Detect and Repair from the menu.
2. Follow the on-screen instructions.

After this, I restarted Outlook and the Junk Mail filter started working again!