Which Mimecast service is specifically mentioned as enforcing Continuity Mode?

The correct answer is Mimecast for Outlook, as it is specifically designed to provide users with access to their email even when their primary mail system is down. Continuity Mode allows users to send and receive emails seamlessly during an outage, thereby ensuring business continuity. This service integrates with the user's email client, enabling a smooth transition between the normal email environment and the continuity service without significant disruptions to daily operations.

This focus on providing uninterrupted access to emails highlights the importance of continuity in email services, especially in a corporate setting where downtime can significantly impact productivity and communication. The other services listed do not specifically relate to the enforcement of Continuity Mode; they serve different purposes within the Mimecast ecosystem, focusing on security, synchronization, and recovery, respectively.