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DMARC Configuration

Domain-based Message Authentication, Reporting, and Conformance (DMARC) protects your domain from email spoofing.

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What is DMARC?

DMARC tells receiving email servers what to do when emails claiming to be from your domain fail SPF or DKIM checks.

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DMARC Policies

PolicyActionUse Case
noneMonitor onlyInitial setup, gathering data
quarantineSend to spamTransitioning to enforcement
rejectBlock the emailFull protection

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Setting Up DMARC

Add a TXT record to your domain: 
Type: TXT
Host: _dmarc
Value: v=DMARC1; p=none; rua=mailto:dmarc@example.com

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DMARC Record Explained

v=DMARC1;           # DMARC version (required)
p=none;             # Policy: none, quarantine, or reject
rua=mailto:...;     # Aggregate report email
ruf=mailto:...;     # Forensic report email (optional)
pct=100;            # Percentage of messages to apply policy
adkim=r;            # DKIM alignment: r (relaxed) or s (strict)
aspf=r;             # SPF alignment: r (relaxed) or s (strict)
1

Monitor (2-4 weeks)

Start with p=none to receive reports without affecting delivery.
v=DMARC1; p=none; rua=mailto:dmarc@example.com
2

Quarantine (2-4 weeks)

Move to p=quarantine with a low percentage.
v=DMARC1; p=quarantine; pct=10; rua=mailto:dmarc@example.com
3

Enforce

Gradually increase to p=reject at 100%.
v=DMARC1; p=reject; rua=mailto:dmarc@example.com

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Lettr DMARC Alignment

Lettr automatically aligns SPF and DKIM for DMARC compliance:
  • DKIM: Signs emails with your domain’s DKIM key
  • SPF: Return-path domain aligns with your sending domain

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Check DMARC Status

const domain = await lettr.domains.get('dom_123');

console.log({
  dmarcStatus: domain.dmarcStatus,
  dmarcPolicy: domain.dmarcPolicy
});

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DMARC Reports

Configure report recipients in your DMARC record: 
v=DMARC1; p=none; rua=mailto:dmarc-reports@example.com
Reports include:
  • Source IPs sending email for your domain
  • SPF/DKIM pass/fail rates
  • Emails that failed authentication
Use a DMARC report analyzer service to parse and visualize the XML reports you receive.

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Troubleshooting

IssueSolution
DMARC failingEnsure SPF and DKIM are properly configured
Reports not receivedVerify the email address in rua
Legitimate emails rejectedStart with p=none and monitor first