"On July 10th, Microsoft released an update for the Outlook 2007 Junk Email Mail Filter. The new filter is extremely finicky. Although Microsoft doesn't release information about how their Outlook Junk Mail filter works; we are learning more about it's seemingly erratic behavior every day. The only information I can find regarding this update is the description that came with it:
This update provides the Junk E-mail Filter in Microsoft Office Outlook 2007 with a more current definition that defines which e-mail messages should be considered junk e-mail. This update was released in July 2009"...read on
July 23, 2009, Chris Bryan, Email Direct.