After months without a problem, I suddenly found that my Outlook 2003 Inbox was full of Spam and that the junk email box was empty. It was as if the junk email filter had been turned off or the rule deleted. I checked the settings but it all looked normal. The last thing I did the day before was install the Microsoft Expression Suite. A quick web search on Google revealed a lot of other people have noticed their Junk Email filter quit unexpectedly also, some after installing Expression Web which probably uses some Microsoft Office 2007 components. Most of the solutions I found suggested removing the email account and re-adding it, or reinstalling Outlook. Keeping those options in mind as my last resort, I frist tried uninstalling the last Junk Email Filter update that was installed via Microsoft Update. Go to Add/Remove Programs > check the 'Show Updates' Box to find it.), Close Outlook, then run Office Update again to re-install the Junk Email Filter update. It worked. I Hope this saves other people the hassle of reinstalling.
Edit: This just happened again, but this time for a different reason - I had added my own email address to the Safe Recipients list. When you do that, all emails sent to that address will then be automatically marked as "not junk".
To remove yourself from the Safe Recipient list;
- Tools-> Options…
- button “Junk E-Mail…”
- tab “Safe Recipients”
- Select your own address and press “Remove”