Company.com network consists of a single Active Directory domain named Company.com.Company.com has an Exchange Server 2010 organization.The Company.com employees use Microsoft Office Outlook to connect to their mailboxes.A Company.com employee named Rory Allen complains that he is unable to send encrypted e-mail messages to an external recipient client.Furthermore， both of these users use e-mail encryption certificates.Rory Allen needs to send encrypted e-mail messages to the external recipient client.What should you do？（）

• A、The best option is to inform Rory Allen to change the sensitivity settings of the e-mail message.
• B、The best option is to inform the external recipient client to add a delegate.
• C、The best option is to inform the external recipient client to send a signed e-mail message to Rory Allen.
• D、The best option is to inform Rory Allen to send a signed e-mail message to the external recipient client.