In environments that are comprised only of Exchange 2007 servers, Client Access servers that are enabled for Outlook Anywhere will automatically manage which Exchange 2007 servers that have the Mailbox server role installed can be accessed. Additionally, when you add or remove Exchange 2007 Mailbox servers, the Client Access server that is enabled for Outlook Anywhere will automatically provide access to these Mailbox servers for client computers that are running Outlook 2007.

If you are using Exchange 2003 back-end servers with Exchange 2003 SP1, Client Access servers that are enabled for Outlook Anywhere will automatically detect these back-end servers after you enable them for RPC over HTTP access by using the Exchange 2003 System Manager. Designate the servers that you will enable for RPC over HTTP access as back-end servers.

If you are using Exchange 2003 servers that do not have SP1 installed, you must modify the registry on these back-end servers and manage these servers individually to enable them to be accessed by Outlook 2007 or Outlook 2003 clients that are using RPC over HTTP. Therefore, we recommended that you upgrade your Exchange 2003 back-end servers to SP1 or a later version.

If you have multiple sites that are separated by low-bandwidth network connectivity, you can enable a Client Access server in each site. The Autodiscover service will then automatically detect which Client Access server is closest to the user's mailbox that resides on either an Exchange 2007 Mailbox server or on an Exchange 2003 back-end server that is enabled for RPC over HTTP. After the user has connected across the Internet by using RPC over HTTP, the Client Access server will then use RPC requests. This ensures that RPC requests stay within the site's intranet. For more information about how to provide an external host name for Outlook Anywhere, see How to Configure an External Host Name for Outlook Anywhere.

When you enable Outlook Anywhere on a Client Access server, all users who have mailboxes on Exchange 2007 Mailbox servers will be enabled for Outlook Anywhere. Users who have mailboxes on Exchange Server 2003 servers with SP1 or a later version or Exchange 2003 servers that have been enabled for RPC over HTTP will also be able to access their Exchange information from the Internet. You can manage the Outlook Anywhere feature at the server level by using the Exchange Management Shell.

In Exchange Server 2007, you can manage which mailboxes have access to Outlook Anywhere by using the Set-CASMailbox cmdlet in the Exchange Management Shell. To manage mailbox access to Outlook Anywhere, run the following command:

Set-CASMailbox -Identity <UserName> -MAPIBlockOutlookRpcHttp $true

For more information about the Set-CASMailbox cmdlet, see Set- CASMailbox.