You are employed as the enterprise exchange administrator at TestKing.com. TestKing.com makes use of Microsoft Exchange Server messaging solution. You are responsible for managing the Exchange Server2010 organization. TestKing.com makes use of an Edge Transport server to send and receive e-mail messages. You discover that a number of servers on the Internet classify e-mail messages from your organization asspam. You receive an instruction from management to reduce the likelihood of e-mails sent by theorganization to be classified as spam. What should you do？（）

• A、You should consider installing a server certificte from a trusted third-party certification authority （CA）.
• B、You should consider implementing Microsoft Forefront Security for Exchange Server.
• C、You should consider creating SenderID TXT records for the Edge Transport servers.
• D、You should consider configuring the Edge Trasport servers to make use of real-time block list （RBL）.