The Client Access Server (CAS) and Edge Transport Server (ETS) roles are deployed in a separate server instance from the mailbox servers.

The CASs are deployed in a 1:1 ratio with mailbox servers. Therefore, because Rainpole.com requires four mailbox servers per DAG for a total of eight mailbox servers, an additional eight servers are installed with the CAS role, distributed evenly across both data centers to provide the required resources to handle the workload generated by 25,000 users with full redundancy. Similarly, to provide the required resources for message hygiene throughput with full site redundancy, three ETSs are deployed on both the on-premises and VMware Cloud Provider Program data center facilities.