– Is now a stateless role i.e. it does not do any data rendering it only proxies connections to the mailbox server ( for the UM role it does redirection)

– It no longer supports RPC, therefore no more Outlook MAPI. All Outlook connections are done using Outlook Anywhere ( internal and external )

– Supports the following protocols HTTP, POP and IMAP, and SMTP.

– No more CAS Arrays. Instead using Autodiscover Outlook finds a new connection point made up of the user’s mailbox GUID + @ + the domain portion of the user’s primary SMTP address. Because of this the user will never again see the message “Your administrator has made a change to your mailbox. Please restart.”

– CAS accepts all client connections and authenticates them before it proxy’s the request to the mailbox server with correct active database or in the case of a UM request it redirects it.

– In some cases the CAS will redirect to a more suitable CAS

– Because all processing for the mailbox happens on the Mailbox server, it doesn’t matter which Client Access server in an array of Client Access servers receives each individual client request. Therefore no more need for session affinity when using NLBs. Also possible to use round-robin DNS and NLBs can handle many more connections.

– There is only now an need to install digitally signed CA cert on the CAS, it is now fully supported to only have an self-signed certificate on the mailbox server.