You have an Exchange Server 2010 organization.  An Edge Transport server sends and receives all e- mail messages from the Internet.  You notice that some servers on the Internet identify e-mail messages from your organization as spam. You need to minimize the possibility that e-mail messages sent from your organization are identified asspam.  What should you do？（）

• A、Implement Microsoft Forefront Security for Exchange Server.
• B、Create SenderID TXT records for the Edge Transport servers.
• C、Configure the Edge Transport servers to use a real-time block list （RBL）.
• D、Install a server certificate from a trusted third-party certification authority （CA）.