How to fix missing dmarc on Magento Open Source

Steps for Magento Open Source

1. Same DNS and mail-authentication process as Adobe Commerce above — DMARC is purely a DNS TXT record managed at your registrar or DNS host.
2. Add TXT record at _dmarc.yourdomain.com with value: v=DMARC1; p=none; rua=mailto:dmarc@yourdomain.com
3. Configure SMTP authentication in Magento Open Source via Stores → Configuration → Advanced → System → Mail Sending Settings, pointing to an SPF/DKIM-enabled relay.
4. Use a community SMTP extension from the Magento Marketplace to enable authenticated outbound mail if the default server configuration does not support it.

; DNS TXT record — hostname: _dmarc.yourdomain.com
; Phase 1 – monitoring only (safe starting point)
v=DMARC1; p=none; rua=mailto:dmarc@yourdomain.com

; Phase 2 – enforcement (after confirming all legitimate mail passes)
v=DMARC1; p=quarantine; rua=mailto:dmarc@yourdomain.com; pct=100

; Phase 3 – strictest (recommended long-term goal)
v=DMARC1; p=reject; rua=mailto:dmarc@yourdomain.com; pct=100

What is missing dmarc?

DMARC (Domain-based Message Authentication, Reporting & Conformance) is a free email authentication standard you publish as a DNS record. It tells the world's email providers — Gmail, Outlook, Yahoo, and others — what to do when someone sends an email that pretends to be from your domain but fails authentication checks. Without a DMARC record, anyone can forge your store's "From" address and send convincing phishing or spam emails that appear to come from you. The record lives at a specific DNS address (_dmarc.yourdomain.com) and takes effect within 24–48 hours of being added.

Without DMARC, criminals can send emails that look exactly like they came from your store — order confirmations, password resets, or fake promotions — tricking your customers into handing over payment details or passwords. This directly damages customer trust, can result in your domain being blacklisted by mail providers (destroying your legitimate email deliverability), and exposes you to legal and reputational liability under consumer-protection and data-privacy laws. OWASP classifies this as a Security Misconfiguration (A05:2021) — one of the most common and impactful categories of web security failures. Fixing it is free and takes under 30 minutes yet closes a major attack vector immediately.

See the complete Missing dmarc guide for every platform and the full background.