I have an Exchange 2010 CAS server connected to a hardware load balancer and also have an Exchange 2003 front end server providing OWA access for users with mailboxes still on Exchange 2003. Any user who connects to Exchange 2010 OWA is working just fine however any Exchange 2003 mailbox user who comes in through the load balancer and the CAS who gets redirected to the Exchange 2003 front end server gets prompted a second time for their credentials before they are able to access their mailbox through OWA. Anyone have any idea why this happens and how to resolve this issue? Is it an Exchange configuration setting? This works just fine if the hardware load balancer is out of the picture. Any ideas? Thank you.