DMARC means Domain-based Message Authentication, Reporting, and Conformance, and is used to protect email delivery of senders and recipients from spam, spoofing and phishing attack. It allows domain owner to publish a policy that defines its email authentication practices and provides instructions to receiving mail servers for how to enforce them. Actually DMARC is not itself an email authentication protocol but it helps for authentication standards SPF and DKIM. It is in short a define policy for email authentication on particular SMTP with SPF and DKIM records.
If you are sending transitional or promotional email newsletters then it is required to update your DMARC policy. This means you are send from one to many email receipts.
DKIM will provide the inbound mail server to know and understand that the message received at the end is having an encryption key and digital signature.
DMARC policy is updated in DNS Domain Name System management on web hosting.
DMARC does not work independent form SPF and DKIM standards for email authentication. The DMARC policy will help inbound email server to known and identify proper valid DKIM signature, IP address from sender’s domain SPF record, domain alignment; with this three identifications, inbound email server will decide the incoming email message as spam or to reject or send to inbox.
After using DMARC policy to determine the proper disposition for the message, the receiving mail server will report the outcome to the sending domain owner.
Aggregate reports, which are XML documents showing statistical data about the messages received that claimed to be from a particular domain. Date reported includes authentication results and message disposition.
How DMARC record looks like?
“_dmarc.yourdomain.com” in DNS TXT record
“v=DMARC1\; p=none\; rua=mailto:email@example.com \; ruf=mailto:firstname.lastname@example.org \; pct=100”