You work as the enterprise exchange administrator at Xxx .The Xxx network consists of a domain named xxx .Xxx is using Microsoft Exchange Server 2010.The Xxx network contains a server named XXX-EX10 configured with the following roles. （1）Client Access Role  （2）Hub Transport Role  （3）Mailbox Server Roles  What action must you take to guarantee e-mail availability to Xxx users who are are utilizing regular mail clients like Microsoft Outlook Express or Windows Live Mail？（）

• A、You should use Security/Multipurpose Internet Mail Extensions （S/MIME）.
• B、You should use the Windows Management Instrumentation Command-line （WMIC）.
• C、You should use the Automatic setting of the Microsoft Exchange POP3 service.
• D、You should use the setup /NewProvisionedServer.