As per Microsoft’s update that rolled out on March 21, 2023,  reports on authentication and deliverability with DMARC can be received by all domain owners having their MX pointed to Office 365. This major update will allow domain owners…

Mail domain authentication ensures that the sender of the email is who they claim to be, and the recipient can trust the email.

In order to delegate a subdomain to another nameserver you need to identify the subdomain, create new zone file and NS record.