Explanation of New Roles in Exchange 2007: Client Access Server (CAS) Role
Microsoft Exchange Server 2007 introduces two new roles-- Client Access server (CAS) and Hub Transport server. Both of these roles are crucial to Exchange 2007 environment and are required in every Active Directory Site.
Client Access Server (CAS) Role
Client Access Server (CAS) Role is a replacement of Front-end server in previous versions of Exchange. It allows end-users to access information without the rich Outlook 2007 client. At least one is required per Active Directory Site. End-users must connect to CAS when using HTTP, RPC over HTTP (Outlook Anywhere), ActiveSync, POP or IMAP4. One exception is that MAPI uses the CAS for the Autodiscover service when connecting via Outlook Anywhere.
Client |
Protocol |
Exchange Role |
Outlook (rich client) |
MAPI |
Mailbox Server |
Outlook Web Access |
HTTP/HTTPS |
Client Access Server |
Exchange ActiveSync |
HTTP/HTTPS |
Client Access Server |
Outlook Anywhere |
PRC over HTTPS |
Client Access Server |
IMAP |
IMAP4/SMTP |
Client Access Server |
POP |
POP/SMTP |
Client Access Server |

Outlook Web Access Features
- Spelling Checker
- Reading Pane
- Compose Message using HTML
- Calendar Options
- Accessibility for Blind and Low Vision Users
- Notification and Reminders
- Voice Mail Options
- Weekly Calendar Views
- Share Point Services Integration
Exchange ActiveSync Features
- HTML messages
- Fast message retrieval
- Enhanced Search
- PIN reset
- Autodiscover for OTA activation
- Tasks synchronization
- Direct Push
- Remote device wipe
- ActiveSync mailbox policies
- Device password polices
How to install Client Access Server (CAS) Role
The installation is simple. When you run the installer, simply check the “Client Access Role” check box. It will also notify you if the prerequisites are not met.

New CAS features
Outlook Anywhere
Outlook Anywhere is a replacement or improved version of the original RPC over HTTP feature in Exchange Server 2003. It allows Outlook clients to encapsulate remote procedure calls RPC over HTTPS protocol to easily travel over firewalls. This requires CAS to have a valid certificate to serve HTTPS clients.
How to install Outlook Anywhere
- Open Control Panel > Add/Remove programs on CAS Server
- Click Add/Remove Windows Components
- Check Networking Services > RPC over HTTP Proxy
- Click OK, click Next, click Finish
- ----------------------------------
- Open Exchange Management Console on CAS Server
- Click on the Client Access folder
- Select the CAS.
- On actions pane, click “Enable Outlook Anywhere”
- Enter the external host name and authentication options
- Click Next, click Finish
Autodiscover Service
The new Exchange 2007 Autodiscover allows end-users to automatically generate an Outlook profile by providing the user’s email address and password. This allows IT administrators and end-users to configure Outlook profiles without knowing the user’s mailbox location. As of today, Autodiscover feature is only compatible with Outlook 2007 and Exchange ActiveSync clients. Note that Autodiscover can be used by Outlook Anywhere clients.
How Auto Discover Service works
When CAS role is installed, it creates Service Connection Point (SCP) objects in Active Directory. CAS also hosts a virtual directory in default website.
- Outlook 2007 uses the DNS Server to look up the SCP record in Active Directory.
- Outlook chooses a CAS server within the same site.
- Outlook communicates with the CAS server and downloads an XML file with profile data.
