You have an Exchange Server 2010 organization named contoso.com that contains a mail-enabled group named Group1. Users from outside the organization report that e-mail messages sent to group1@contoso.com generate a non-delivery report （NDR）.You need to ensure that users outside the organization can successfully send e-mail to group1 @ contoso.com. What should you modify？（）

• A、the authentication settings for the Client Receive connector
• B、the message delivery restrictions for Group1
• C、the moderation settings for Group1
• D、the remote IP address range for the Client Receive connector