DMARC
DMARC is a DNS-published email policy that tells receivers what to do with messages that fail SPF and DKIM alignment for a domain, and reports such failures back to the owner.
How it works
The record at _dmarc.example.com sets a policy (none, quarantine or reject) and reporting addresses. A message passes when SPF or DKIM passes for a domain aligned with the visible From address.
Without an enforcing policy, attackers can send mail that shows your exact domain in the From line.
How to protect yourself
- Publish DMARC, monitor the reports, then move to quarantine or reject.
- Check the policy of any domain before trusting mail from it.