The best solution for NTO's campaign is to use a Multi-Step journey with a Data Extension/Automation entry source. This setup allows for the segmentation and targeting of the specific subscribers as per the campaign requirements. Subscribers who have not engaged with previous emails can be identified and targeted. The journey can be configured to monitor open or click activities, and if a subscriber interacts after threemessages, they can be automatically removed from the campaign. This approach provides a dynamic and automated way to manage the campaign's lifecycle based on subscriber behavior.References:Salesforce Journey Builder documentation, Data Extension and Automation Studio in Marketing Cloud