In an organization with Exchange Server 2010 exists Edge Transport Server named Server 1.A partner organization has Exchange Server 2010 Edge Transport Server named Server 2.You need to encrypt SMTP communication between Server 1 and Server 2.The solution must ensure that both servers use a trusted certificate.What should you do？（）

• A、Enable Domain Security Authorization
• B、Enable Exchange Server Authorization
• C、Enable Externally Secured Authorization
• D、Disable anonymous users permission group