Link Translation

ISA Server 2006 redirects Outlook Web App requests for internal URLs that are contained in the body of any object in Outlook Web App, such as an e-mail message or calendar entry. Users no longer have to remember the external namespaces for internal corporate information that is mapped to an external namespace. For example, if a user sends a link in an e-mail message to an internal namespace such as http://contoso, and this internal URL is mapped to an external namespace such as http://www.contoso.com, the internal URL is automatically translated into the external URL when the user clicks the internal URL.

Web Publishing Load Balancing

ISA Server 2006 can load balance client requests and send them to an array of Client Access servers. When ISA Server 2006 receives a request for a connection to Outlook Web App, it selects a Client Access server and then sends the name of the Client Access server back to the Web browser in a cookie.

HTTP Compression

In the past, if you used forms-based authentication on the ISA Server computer that had Exchange Server 2003 and ISA Server 2004 or ISA Server 2000 installed, it was not possible to use Gzip compression. This was because ISA Server could not decompress and recompress the information correctly. ISA Server 2006 can decompress, inspect, and then recompress data before it sends the data to your Exchange servers.

Note:
Gzip compression is available in ISA Server 2004, Service Pack 2 (SP2).

Exchange server locations are hidden

When you publish an application through ISA Server, you're protecting the server from direct external access because the name and IP address of the server can't be viewed by the user. The user accesses the ISA Server computer. The ISA Server computer then creates a connection to the Client Access server according to the conditions of the server publishing rule.

SSL bridging and inspection

Secure Sockets Layer (SSL) bridging protects against attacks that are hidden in SSL-encrypted connections. For SSL-enabled Web applications, after ISA Server receives the client's request, ISA Server decrypts the request, inspects it, and acts as the endpoint for the SSL connection with the client computer. The Web publishing rules determine how ISA Server communicates the request for the object to the published Web server. When you use SSL bridging, the secure Web publishing rule is configured to forward the request by using Secure HTTP (HTTPS). ISA Server then initiates a new SSL connection with the published server. Because the ISA Server computer has become an SSL client, it requires the published Web server to respond with a certificate.

An additional advantage of SSL bridging is that an organization has to buy SSL certificates from an external certification authority only for the ISA Server computers. Servers that use ISA Server as a reverse proxy can either not require SSL or use SSL certificates that are generated internally.

You can also terminate the SSL connection at the ISA Server computer and continue to the Client Access server with a connection that isn't encrypted. This is known as SSL offloading. If you do this, the internal URL for Outlook Web App must be set to use HTTP and the external URL must be set to use HTTPS. The internal URL and external URL can be configured through the Exchange Management Console, or by using the Set-OwaVirtualDirectory cmdlet with the InternalURL parameter and ExternalURL parameter in the Exchange Management Shell.

For more information about how to use the Set-OwaVirtualDirectory cmdlet and the EMC to manage Outlook Web App virtual directories, see Set-OwaVirtualDirectory and Managing Outlook Web App Virtual Directories.

Single sign-on

Single sign-on enables users to access a group of published Web sites without being required to authenticate with each Web site. When you use ISA Server 2006 as a reverse proxy server for Outlook Web App, ISA Server 2006 can be configured to obtain the user's credentials and pass them to the Client Access server so that users are prompted for their credentials only one time.