You work as the enterprise exchange administrator at Company.com.The Company.com network consists of a single Active Directory domain named Company.com.Company.com has an Exchange Server 2010 organization.Company.com contains a mail-enabled group named TestGr1.You have received complaints from the employees not residing inside the company， that their e-mail messages sent to TestGr1@contoso.com produce a non-delivery report （NDR）.You need to adhere to the problem.What should you do？（）

• A、The best option is to change the authentication settings for the Client Receive connector.
• B、The best option is to change the moderation settings for TestGr1.
• C、The best option is to change the remote IP address range for the Client Receive connector.
• D、The best option is to change the message delivery restrictions for TestGr1.