Youneedtodesignamethodtomodifythecurrente-mailorderingsystem.WhichwillbeuseduntilFourthCoffeedeploystheWeb-basedorderingapplication.Yoursolutionmustaddressbusinessconcernsandimprovesecurity.Whatshouldyoudo？（）
A.ConfigurethemailservertodisallowSMTPrelaying
B.Instructcustomerstoobtaindigitalcertificatesfromatrustedcommercialauthority（CA），anddigitallysignallordere-mailmessages.Rejectunsignedordere-mailmessages
C.Providecustomerswithapublicencryptionkey，andinstructthemtoencryptallordere-mailmessages.Rejectunencryptede-mailmessages
D.Implementane-mailfilteringsolution，andaddcustomere-mailaddressestothelistofallowedaddresses.Rejecte-mailmessagesfromotheraddresses
参考答案：B
