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

• A、Advanced settings
• B、Group scope
• C、Group type
• D、The mail flow settings