In Exchange 2010, MAPI traffic to the user’s mailbox goes to the endpoint configured in the database. By default, it is set to the FQDN of the Exchange server. If the database is created after creating the Client Access Array, the new database automatically uses the CAS Array FQDN and will go to the load balancer if DNS is configured correctly.

Public folder traffic is also MAPI but it does not use the CAS Array FQDN and this behaviour cannot be changed. This traffic will always bypass the load balancer in Exchange 2010.