DMARC

DMARC (Domain-based Message Authentication, Reporting & Conformance) is a DNS record that tells Gmail, Outlook, and Yahoo what to do when an email claiming to be from your domain fails SPF or DKIM checks: do nothing (p=none), quarantine to spam (p=quarantine), or reject outright (p=reject). Without DMARC anyone can spoof your domain. The end goal for most orgs is p=reject.