Sending other people’s email in a DMARC compliant manner can be accomplished in a number of different ways. Read all about it in this article.

CNAME-based delegation is when a domain owner creates several CNAMEs that point back to your own domain. In contrast with full sub-domain delegation, individual services are delegated by each CNAME.

This article expands on the "full delegation" approach described in the larger How to send DMARC-compliant email on behalf of others article.