DNSai DMARC Lookup

DMARC (Domain-based Message Authentication, Reporting, and Conformance) is an email authentication protocol that builds on SPF and DKIM to protect domains from email spoofing and phishing. It allows domain owners to specify how receiving mail servers should handle messages that fail authentication checks. DMARC is essential because it prevents attackers from sending fraudulent emails that appear to come from your domain, protecting both your brand reputation and your recipients from phishing attacks.

The three DMARC policies control what happens to emails that fail authentication: 'none' (monitoring mode) - emails are delivered normally but you receive reports about authentication failures, useful for initial deployment; 'quarantine' - failing emails are sent to spam/junk folder, providing moderate protection; 'reject' - failing emails are blocked entirely and never delivered, providing maximum protection against spoofing. Most organizations start with 'none' to monitor their email ecosystem, then progressively move to 'quarantine' and finally 'reject'.

DMARC supports two types of reports: Aggregate reports (rua) are daily XML summaries showing authentication results for all emails claiming to be from your domain, including source IPs, pass/fail counts, and policy actions. These help you monitor your email ecosystem and identify unauthorized senders. Forensic reports (ruf) are detailed reports sent immediately when individual messages fail DMARC. Due to privacy concerns, many receivers limit or disable forensic reports. Set up aggregate reports at minimum using the rua= tag.

Alignment determines how strictly DMARC matches the domain in email headers. DKIM alignment (adkim) compares the 'd=' domain in the DKIM signature with the From header domain. SPF alignment (aspf) compares the envelope sender (Return-Path) domain with the From header domain. Both can be set to 'relaxed' (r) allowing subdomains to match, or 'strict' (s) requiring exact domain matches. Strict alignment provides stronger protection but requires careful configuration.

To implement DMARC: 1) First ensure SPF and DKIM are properly configured for all legitimate mail sources; 2) Create a DNS TXT record at _dmarc.yourdomain.com; 3) Start with p=none to monitor: 'v=DMARC1; p=none; rua=mailto:[email protected]'; 4) Analyze aggregate reports for 2-4 weeks; 5) Fix any SPF/DKIM issues found; 6) Gradually increase policy to quarantine, then reject; 7) Set pct= to apply policy to a percentage of mail during transition.