Your network contains three Active Directory sites named Site1， Site2， and Site3. Users can only access Site1 from the Internet. 
In each site， you plan to deploy a Mailbox server and a Hub Transport server. 
You need to plan the deployment of Exchange servers to meet the following requirements：
.Ensure that Exchange ActiveSync and Outlook Anywhere clients can connect to their Mailboxes from theInternet
.Minimize hardware costs
What should you include in your plan？（）

You have a Microsoft Internet Security and Accelerator （ISA） 2006 server that provides all Internet accessfor your company. 
You have two Mailbox servers configured in a database availability group （DAG）， two Client Accessservers， and two Hub Transport servers. 
You need to recommend changes to the environment to ensure that users can access Outlook Web App（OWA） from the Internet if any single server fails. 
What should you recommend？（）