I am in the process of upgrade our exchange server from 2003 to 2010. Our setup was a single server running Server2003 SBS with Exchange 2003. What I have done is added another 2 servers. Server2 is running Server2003 and is a secondary domain controller and DNS server. Server3 is running Server2008 and is running exchange 2010. I have moved all mailboxes from Server1 (Server2003 SBS) to Server3 and have uninstalled Exchange 2003 from the SBS Server. Exchange is working with no problems. However I want to be able to shutdown Server1 for whatever reason and have users still be able to connect to exchange. However when Server1 is offline outlook will not connect. It says the server is unavailable. Any help would be appreciated.