DMARC (Domain-based Message Authentication, Reporting and Conformance)
01 Definition
DMARC (Domain-based Message Authentication, Reporting and Conformance) meaning: A policy that tells receivers what to do when email fails SPF and DKIM checks.
DMARC builds on SPF and DKIM by publishing a DNS policy that tells receiving servers how to handle mail that fails authentication and does not align with the visible From domain. Options are none, quarantine, or reject. It also sends reports to the domain owner about who is sending mail using their domain.
Why it matters
How DMARC (Domain-based Message Authentication, Reporting and Conformance) fits the work
DMARC closes the gap SPF and DKIM leave by protecting the visible From address from spoofing and giving you visibility into abuse, and major inboxes now require it for bulk senders.
In context
After monitoring reports for a month, the company moved its DMARC policy from none to reject, stopping spoofed emails that impersonated its brand.
Practical note
Start at policy none to read reports before enforcing, since jumping straight to reject can block legitimate mail from services you forgot to authenticate.