Your company subscribes to the Office 365 Enterprise E1 plan. You are the Microsoft Exchange Online administrator. In th

[answerhappygod]

Your company subscribes to the Office 365 Enterprise E1 plan. You are the Microsoft Exchange Online administrator.
In the last week, employees have reported that they are receiving non-delivery report messages from other companies. The employees have not sent messages to recipients within those companies.
You need to prevent non-delivery report messages from reaching employees.
Which content filter option should you turn on in the Exchange admin center?

A. NDR backscatter
B. Conditional Sender ID filtering: hard fail
C. SPF record: hard fail
D. Block all bulk email messages