Home Outlook for Mac not deleting emails off Microsoft Exchange Server

I have an exchange server at work and am using Outlook for Mac 2011 at home.  At first I was able to delete emails from my inbox on my Mac at home and not see them when I logged back in from my PC at work.  Now the emails just won't delete.  I get send and receive emails (though if sent from my home Mac they don't show in the sent items on the exchange server.  This is driving me absolutely nuts.  What do I need to change?  I have both iphone and ipad linked to Exchange server and that works just fine so not sure what I'm doing wrong.  Help!