You have an Exchange Server 2010 organization. You deploy an Edge Transport server. You need to implement a message hygiene solution that meets the following requirements： .Users must be able to receive e-mail from external recipients who have been added to their Safe SendersLists .The Edge Transport server must block all e-mail sent to invalid addresses inside the organization What should you do first？（）
- AEnable sender filtering.
- BCreate Send connectors.
- CConfigure real-time block lists （RBLs）.
- DConfigure EdgeSync synchronization.