True or False: Directory Groups can be modified in Mimecast.

The statement that Directory Groups can be modified in Mimecast is true. This indicates that users have the capability to make changes to the settings and configurations of these groups within the Mimecast platform. Modifying Directory Groups is essential for administering email security and collaboration effectively, as it allows administrators to manage users and their permissions flexibly according to the organization's evolving needs.

In Mimecast, Directory Groups are used to manage users as a collective, allowing for streamlined policy application and user management. This capability is critical in scenarios where organizational structures change or where new security requirements arise. Being able to modify these groups ensures that organizations can adapt their email management strategy appropriately.

The other options pertain to specific conditions or constraints under which directory groups can be modified, which might not fully reflect the overarching capability to change directory groups in Mimecast. Hence, the clarity of the true statement about the modifiability of these groups is important for a comprehensive understanding of the system's administrative functionalities.