Which of the following is a main feature of the Continuity Monitor?

The main feature of the Continuity Monitor is to ensure service for outgoing messages. This tool is designed to maintain email functionality, particularly during service interruptions or outages. When issues arise with a company's email service, the Continuity Monitor helps to manage and route outgoing email messages effectively, ensuring that communication can continue without significant disruption.

This capability is crucial for maintaining business operations, as uninterrupted email service is vital for organizational communication. By monitoring the status and performance of email services, the Continuity Monitor can provide necessary resilience and reliability, enabling users to send messages even when primary servers are under duress or unavailable.

Other choices do not align with the core function of the Continuity Monitor. For instance, blocking unwanted senders pertains to filtering and spam prevention, which is a different aspect of email security, while managing internal policies and providing user login insights fall under administrative and security management rather than continuity and service reliability.