Learn · Guide · 5 min read

What is DMARC, and how to set it up safely

DMARC helps protect the domain people see in your email. Here is how to roll it out without overlooking a legitimate sender.

The problem it solves

Attackers can impersonate a visible From address to make a phishing email look familiar. DMARC combines an aligned SPF or DKIM result with a domain policy that receiving mail systems can use. It reduces some forms of direct domain spoofing, but it cannot stop lookalike domains, compromised accounts or every phishing message.

The three records

• SPF lists which servers may send mail for your domain.
• DKIM adds a cryptographic signature that proves a message really came from you and wasn't altered.
• DMARC ties them together and tells receivers what to do with mail that fails, plus sends you reports.

Turn it on without breaking your email

The safe path is to start in monitoring mode, watch, then tighten. First make sure SPF and DKIM are set up (your email provider has guides). Then add a DMARC record:

Host:  _dmarc
Value: v=DMARC1; p=none; rua=mailto:dmarc@example.com

With p=none, nothing is blocked yet, but you start receiving reports showing who's sending as you. Review reports and actual message delivery until all legitimate senders are accounted for and alignment works. Then consider p=quarantine and later p=reject under a change plan. Receiving systems decide how to handle messages, so monitor delivery after each step.

Common mistakes

• Jumping straight to p=reject and silently losing real mail. Always start at none.
• Forgetting a legitimate sender like a newsletter tool or your CRM. The reports catch these.
• Setting up DMARC but never reading the reports. A report-viewing service makes them readable.

Torva checks the published SPF and DMARC signals for the relevant domain in supported scans. Confirm sender alignment and real message delivery in your mail provider; a DNS record alone does not prove the policy protects every message. For related work, see how to group several observations into one fix plan.

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