Do external domains need to be managed in Mimecast?

The correct understanding of external domain management in Mimecast is that they are managed automatically. This means that Mimecast has built-in processes to handle external domains without requiring manual intervention from users or administrators. This automation helps streamline the management of email traffic, ensuring that policies and security measures are applied consistently across all domains, whether they are internal or external to an organization.

Automatic management of external domains also contributes to security by ensuring that threats from external sources are mitigated effectively, without relying on users to configure or monitor external domains manually. This feature allows organizations to focus on their core operations while maintaining robust email security processes.

In contrast, the other options imply varying levels of manual oversight or restrictions that do not reflect the actual functionality of Mimecast in terms of external domain management.