Your network contains two Active Directory sites named Site1 and Site2.
You have an Exchange Server 2013 organization that contains six servers.
The servers are configured as shown in the following table.
All of the mailbox databases replicate to all of the servers.
Users in Site1 connect to site1-mail.contoso.com toaccess their mailbox.
Users in Site2 connect to site2-mail.contoso.com toaccess their mailbox.
All of the users use Microsoft Outlook 2013.
You need to identify which DNS modification must bemade to fail over the email services from Site1 toSite2.
Which DNS modification should you identify?
Answer: 
Explanation: