What is necessary to complete the Sender Authentication Package (SAP) setup for a new business unit?

To successfully complete the Sender Authentication Package (SAP) setup for a new business unit, it is essential to configure custom Reply Mail Management for that subdomain. This step ensures that replies to messages sent from the business unit are handled appropriately and routed correctly. By setting up Reply Mail Management, you can manage how responses to your email campaigns are organized and processed, which can help in maintaining communication with customers and managing their interactions effectively.

Configuring custom Reply Mail Management allows for better tracking and handling of responses, which is a critical aspect of email marketing efforts, ensuring that the business unit can analyze recipient engagement and respond to inquiries appropriately. This feature ultimately enhances the business unit's ability to connect with its audience and manage its email communications effectively.

The other options may include elements related to domain management or redirection but do not focus directly on the crucial aspect of managing replies associated with outgoing emails. Therefore, configuring the Reply Mail Management is the necessary step to complete the SAP setup effectively.