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 as spam. What should you do？（）
- AImplement Microsoft Forefront Security for Exchange Server.
- BCreate SenderID TXT records for the Edge Transport servers.
- CConfigure the Edge Transport servers to use a real-time block list （RBL）.
- DInstall a server certificate from a trusted third-party certification authority （CA）.