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？（）
- AAdvanced settings
- BGroup scope
- CGroup type
- DThe mail flow setting