DMARC Guide for UserDeck

Setting Up DMARC for Your Domain with UserDeck

This guide explains how to set up DMARC (Domain-based Message Authentication, Reporting & Conformance) for your domain to enhance email security and deliverability when sending emails through UserDeck. DMARC builds on SPF and DKIM by adding an extra layer of protection against spoofing and phishing attacks.

What is DMARC and Why Is It Important?

DMARC lets you instruct receiving mail servers on how to handle emails that fail SPF and/or DKIM authentication checks. This prevents malicious actors from sending forged emails that appear to come from your domain. DMARC also provides reporting features to give you insight into authentication outcomes and potential abuse.

Prerequisites

• SPF and DKIM should already be configured for your domain (see UserDeck’s Outgoing Email setup guide).

• You must have access to your domain’s DNS management (typically via your domain registrar or hosting provider).

Steps to Implement DMARC

1. Create a DMARC DNS Record
   Create a TXT record in your DNS with the name:
   _dmarc.yourdomain.com
   (replace yourdomain.com with your actual domain).

2. Define Your DMARC Policy
   The TXT record value sets your DMARC policy. Key tags include:

   • v=DMARC1
     Specifies the DMARC version.

   • p=
     Policy for emails failing SPF/DKIM checks:

     • none — monitor only (no action taken)

     • quarantine — mark as spam

     • reject — block email completely

   • rua=mailto:
     Email address to receive aggregate reports with authentication statistics.

   • ruf=mailto: (optional)
     Email address for forensic (detailed) reports; use cautiously due to volume.

   • pct= (optional)
     Percentage of emails to apply the policy to (start with 100).

3. Publish the DMARC Record
   Add the TXT record with your chosen policy to your domain’s DNS.

Example DMARC Records

• Monitor Mode (no action, collect data):

  ini

  CopyEdit

  v=DMARC1; p=none; rua=mailto:dmarc-reports@yourdomain.com

• Quarantine Mode (50% of failing emails marked as spam):

  ini

  CopyEdit

  v=DMARC1; p=quarantine; pct=50; rua=mailto:dmarc-reports@yourdomain.com

• Reject Mode (100% of failing emails blocked):

  ini

  CopyEdit

  v=DMARC1; p=reject; rua=mailto:dmarc-reports@yourdomain.com

DMARC Implementation Stages

• Monitor Mode (p=none):
  Collects data without affecting email delivery. Use this to identify legitimate senders that might fail authentication.

• Quarantine Mode (p=quarantine):
  Sends failing emails to the spam/junk folder.

• Reject Mode (p=reject):
  Blocks failing emails outright.

Transition gradually from monitor to reject mode after analyzing reports and ensuring legitimate emails are properly authenticated.

Analyzing DMARC Reports

Regularly review aggregate reports sent to your rua address. These provide valuable insight into your domain’s email authentication status and help you spot configuration issues or abuse. Various third-party tools can simplify report analysis.

Important Considerations

• Gradual Rollout: Start with monitor mode to avoid blocking legitimate email.

• Regular Monitoring: Analyze reports to fine-tune your setup.

• Patience: DMARC implementation requires time and continuous monitoring for best results.

By following these steps, you’ll improve email security and deliverability for emails sent via UserDeck. If you need assistance, please contact our support team.