Which three actions should you perform?

You have an Exchange Server 2013 organization.
A new policy requires that all iPhone users access their on-premises mailbox by using the OWA for iPhone app.
You need to ensure that push notifications for the OWA for iPhone app are configured before the users install the app.
Which three actions should you perform? Each correct answer presents part of the solution.
A. Configure Microsoft Azure Active Directory Sync (Azure AD Sync).
B. Modify the EWS virtual directory.
C. Enable push notifications proxy.
D. Enroll in Microsoft Office 365 for business.
E. Modify the OWA virtual directory.
F. Set up on premises Exchange 2013 to Office 365 Authentication.

Correct Answer: CDF
Explanation/Reference:
Configuring push notifications proxying for OWA for Devices
To enable push notifications, the admin must:
1. (D) Enroll your organization in Office 365 for business.
2. Update all on-premises servers to Exchange Server 2013 Cumulative Update 3 (CU3) or later.
3. (F) Set up On-premises Exchange 2013 to Office 365 Authentication
4. (C) Enable push notifications from the on-premises Exchange Server 2013 to Office 365 and verify that push notifications are working.
Illustration below:

Incorrect answers:
Not A: There is no need to configure Microsoft Azure Active Directory Sync.
Not B: You do not have to modify the EWS virtual directory.
Not E: You do not have to modify the OWAvirtual directory.
Reference: https://technet.microsoft.com/en-us/library/dn511017%28v=exchg.150%29.aspx