The correct answer isB, because:

Salesforce Marketing Cloud uses aSender Authentication Package (SAP)to establish proper authentication (including setting up DNS entries for SPF, DKIM, and DMARC) for email sending domains.

When NTO wants tosend emails from a new domain(comms.nto.com.au), they would need anew SAPto configure authentication correctly for that domain — this ensuresdeliverability, maintains sender reputation, and complies with anti-spam regulations.

Salesforce official documentation specifies:

"Sender Authentication Package (SAP)includes branding the sending domain, setting up dedicated IP addresses, and configuring authentication protocols like SPF, DKIM, and DMARC.

If you want to send emails from a different domain, you must purchase an additional SAP to configure and authenticate the new sending domain."

(Source: Salesforce Marketing Cloud Sender Authentication Package Guide)

Important SAP Components:

Custom domain for sending (branded domain).

Authenticated email setup (SPF/DKIM/DMARC).

Private tracking domain.

Dedicated subdomain.

Why the other options are incorrect:

❌A. An additional IP address:

A new IP is not required just because you have a new domain. IPs are more about volume and reputation needs, not domain setup itself.

❌C. An additional private domain:

A private domain refers to atracking domainused for link redirection, not sending domain authentication itself.

❌D. Register the new domain in Setup > From Address Management:

From Address Management is forallowing or restrictingsender addresses butdoes not authenticatethe domain for sending.

Additional Salesforce extract:

"When sending from a new domain that is not covered under an existing SAP, you must purchase and implement a new Sender Authentication Package to maintain deliverability and compliance standards."

(Source: Salesforce Marketing Cloud Deliverability Best Practices)

Thus,Bis the correct and required action.