You have an Exchange Server 2010 organization. Users on the network use HTTPS to
connect to Outlook Web App (OWA). The Client Access server uses a certificate issued by
an internal certification authority (CA).
You plan to deploy an e-mail encryption solution for all users.
You need to ensure that users can send and receive encrypted e-mail messages by using
S/MIME from OW

A.
What should you do?
Issue a certificate to each user.

A.
What should you do?
Issue a certificate to each user.

B.
Instruct all OWA users to import a root CA certificate.

C.
Modify the authentication settings of the OWA virtual directory.

D.
Configure the Client Access Server to use a certificate issued by a third-party CA.

Explanation:

http://technet.microsoft.com/en-us/library/bb738140.aspx