Hi I have recently deployed 2 x CAS 2010 servers into an existing 2003/2007 Org. My plan is to move the CAS services across to the 2010 servers early next week. Ever since the installation though users cannot download the OAB (Outlook 2007/2010). The distribution servers on the OAB inlcude 1 x 2007 CAS and 1 x 2010 CAS. The generation server is a 2007 CCR cluster. I tried what is outlined in http://www.confusedamused.com/noteb...07-clients-with-exchange-2007-on-server-2008/ but this has not worked for me. Users dont get an error message - just hangs on " Offline address book Connecting to Microsoft Exchange" during send/receive. Internal and exteranl urls look ok on both 2007 and 2010 CAS servers. Any ideas would be greatly appreciated! Thanks!