Your company has an Office 365 subscription. You need to add the label “External” to the subject line of each email message received by your organization from an external sender. What should you do? organization and take action on them. Transport rules contain a set of conditions, exceptions, and actions, which provides you with the flexibility to implement many types of messaging policies. senders and an action of adding the label “External” to the subject line of the email message.

A.
From the Exchange Control Panel, add a MailTip.

B.
From the Forefront Online Protection Administration Center, set the footer for outbound email.

C.
Run the Enable-InboxRule cmdlet.

D.
From the Exchange Control Panel, run the New Rule wizard.

Explanation:

The New Rule wizard in the Exchange Control Panel is used to configure Transport Rules.
You can use Exchange transport rules to look for specific conditions in messages that pass through your
Transport rules have the following components:
In this question, we would configure a transport rule with a condition configured to specify email from external
References: https://community.office365.com/en-us/f/158/t/5988