Outlook Rule for All but Exchange Server Mail

I get junk email at work from a few places every day. The in place junk filter does not seem to catch them.  I was thinking of trying SpamBayes again, then I thought that all of my junk mail comes from outside my company.  And I rarely have email from outside my company that is not junk mail.

I just created a rule in Outlook that applies to all emails that are not from my company.  It moves all email to a folder "except with /ou in the sender's address".  This site says that "/ou" will filter for internal Exchange server mail.