DMARC

DMARC is an email protection against phishing built on top of the already existing SPF and DKIM. The idea behind DMARC is to reject emails that 'pretend' to originate from your organization. Therefore, if an adversary is spoofing an email pretending to be an employee asking for an invoice to be paid, the system will reject the email before it reaches the intended recipient. DMARC is easy and inexpensive to implement, however, I cannot stress enough that thorough testing is mandatory; otherwise (and this is oftentimes the case), you risk blocking legitimate emails with no ability to recover them. - hackthebox