We're currently running Exchange 2003 SP2 and Outlook 2003 in our environment and looking to migrate to Exchange 2010/Outlook 2010. We're looking to go with a 2 node CAS array for one of our offices. For the CAS array, someone suggested using round robin DNS only, (no NLB), and in the event that one of the CAS nodes in the array went down, Outlook 2010 clients would be sophisticated enough to automatically reconnect to the other CAS server. Can someone verify that in a round robin DNS configuration, that Outlook 2010 wouldn't try to connect to a CAS server that is down? My thinking is that it's hit or miss. I always thought one of the shortcomings of round robin DNS is the possibility of connecting to a host that is down.