Exchange Server 2003 enabled users to use the Windows RPC over HTTP Proxy component to access their Exchange information from the Internet. This technology wraps remote procedure calls (RPCs) with an HTTP layer. This allows the traffic to traverse network firewalls without requiring RPC ports to be opened. Exchange 2007 builds on this functionality and greatly reduces the difficulty of deploying and managing this feature. To deploy Outlook Anywhere in your Exchange messaging environment, you just have to enable at least one Client Access server by using the Enable Outlook Anywhere Wizard.

There are several benefits to using Outlook Anywhere to enable Outlook 2003 and Outlook 2007 clients to access your Exchange messaging infrastructure. The benefits are as follows:

• Remote access to Exchange servers from the Internet.
  
  
• You can use the same URL and namespace that you use for Microsoft Exchange ActiveSync and Outlook Web Access.
  
  
• You can use the same Secure Sockets Layer (SSL) server certificate that you use for both Outlook Web Access and Exchange ActiveSync.
  
  
• Unauthenticated requests from Outlook cannot access Exchange servers.
  
  
• Clients must trust the certification authority that issues the certificate.
  
  
• You do not have to use a virtual private network (VPN) to access Exchange servers across the Internet.
  
  

You must allow only port 443 through your firewall, because Outlook requests use HTTP over SSL. If you already use Outlook Web Access with SSL or Exchange ActiveSync with SSL, you do not have to open any additional ports from the Internet.

Deploying Outlook Anywhere for your organization is now a straightforward process. The following recommendations should be followed to successfully deploy Outlook Anywhere:

• Use at least one Client Access server per site   In Exchange 2007, a site is a network location with high-bandwidth connectivity between all computers. We recommend that you install at least one Client Access server in each site that is dedicated to providing client access to the Exchange 2007 computer that has the Mailbox server role installed. However, you can have multiple Client Access servers in each site for increased performance and reliability.
  
  
• Enable Outlook Anywhere on at least one Client Access server   We recommend that you have one Client Access server in each site that has Outlook Anywhere enabled. This lets Outlook 2007 clients connect to the Client Access server that is closest to a user's mailbox. Users will connect to the Client Access server that is in the site together with the Mailbox server that contains their mailbox by using HTTPS. This minimizes the risk associated with using remote procedure calls (RPCs) across the Internet. Using RPCs across the Internet can adversely affect performance.
  
  

For more information about how to enable Outlook Anywhere, see How to Enable Outlook Anywhere.

You can Manage Outlook Anywhere by using the Exchange Management Console or the Exchange Management Shell. By default, when you enable Outlook Anywhere on a Client Access server, all users who have mailboxes on Exchange 2007 Mailbox servers are enabled for Outlook Anywhere. For more information about how to manage Outlook Anywhere, see Managing Outlook Anywhere.

Outlook Anywhere can be used in environments where Exchange 2003 is still being used. If you have users who have mailboxes located on Exchange 2003 servers, and these users are using Outlook 2007 or Outlook 2003, you must configure these clients manually. For more information about Outlook Anywhere coexistence, see How to Configure Outlook Anywhere with Exchange 2003.