I have 2 CAS/HT and 2 MBX Servers. CAS/HT are using NLB.
RPCClientAccesServer had been properly configured to point to NLB fqdn.
When Outlook starts for the first time, Autodiscover returns Mailbox Server's FQDN instead of CAS or NBL's FQDN, which causes the auto configuration to fail. I have to manually change the server name to the CAS or NBL FQDN in order to get outlook configured.