What Is DMARC and Why Is It Important for Your Domain?
Understanding DMARC:
DMARC stands for Domain-based Message Authentication, Reporting & Conformance. It’s an email authentication protocol that builds on SPF (Sender Policy Framework) and DKIM (DomainKeys Identified Mail). DMARC allows domain owners to specify which authentication mechanisms (SPF and/or DKIM) are authorized to send email for their domain, and offers reporting to help identify both authorized and unauthorized use.
Why DMARC Is Now a Requirement:
Major email providers—Google (Gmail), Yahoo, and Microsoft (as of May 2025)—require bulk email senders (5,000+ emails per day) to have DMARC in place. This started with Google and Yahoo in February 2024. The intent is to reduce spam and phishing by enforcing the use of authentication protocols. Bulk email without DMARC is now likely to be delayed, sent to spam, or rejected.
DMARC and SPF Record Examples
DMARC
| Subdomain | Record Data | Suggested to Add Emails for Stat Data |
|---|---|---|
| _dmarc | v=DMARC1; p=none; (Minimum required) | v=DMARC1; p=none; rua=mailto:username@example_1.tld; ruf=mailto:username@example_2.tld;fo=1 |
SPF
| TXT | Root Domain |
| v=spf1 include:_spf.emfwd.name-services.com MX ~all |
Example for use in your DNS:
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Host name: _dmarc
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Address:
textv=DMARC1; p=none; rua=mailto:[email protected]; ruf=mailto:[email protected];fo=1 -
SPF record:
textv=spf1 include:_spf.hostedemail.com ~all
Understanding a DMARC Structure
| Tag | Value | Translation |
| v | DMARC1 | The DMARC version should always be DMARC1. An incorrect tag causes the record to be ignored. |
| p | none | Policy for mail failing DMARC: none (monitor only), quarantine, or reject. |
| rua | mailto:[email protected] | Where aggregated DMARC XML reports should be sent. |
| ruf | mailto:[email protected] | Where forensic (detailed) DMARC reports should be sent. |
Why Domain Owners Must Monitor DMARC Reports:
DMARC isn’t “set and forget.” When you publish a DMARC policy, you’ll receive periodic reports from mail receivers about how messages purporting to come from your domain are being processed—both successful and failed authentication. Monitoring these reports helps you:
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Identify abuse, attempted fraud, or unauthorized sending sources using your domain.
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Determine which legitimate services still need SPF/DKIM aligned, or whose configuration is incomplete.
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Safely transition from monitor-only (p=none) to a protective state (quarantine or reject) once legitimate mail is passing.
What Does DMARC Stop or Allow?
DMARC policies guide receiving servers on what to do when a message fails both SPF AND DKIM (with alignment):
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p=none – monitor/report only; do not affect delivery.
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p=quarantine – send to spam/junk folder.
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p=reject – block outright from delivery.
Policy Example:
| Policy Value | Effect |
| none | Collect data, do not affect mail flow. |
| quarantine | Send failed mail to spam/junk. |
| reject | Block failed mail completely. |
Special Note on Domains Using Forward-Only Email (No Mailbox):
If your domain is configured to forward email but does not host a mailbox:
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SPF Issues: Forwarded mail usually fails SPF because the forwarding server isn’t in your SPF record, so SPF breaks during forwarding.
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DKIM: DKIM signatures typically survive forwarding, as long as the intermediate system doesn’t alter the email.
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Action: For domains with only forwarding, it is critical to configure DKIM signing if your forward provider supports it, and to use a p=none policy and monitor DMARC reports before switching to a stricter (quarantine/reject) policy.
Forwarding & DMARC Impact Table:
| Scenario | SPF Result | DKIM Result | DMARC Impact / Recommendation |
| Forwarding only | Almost always fails | Merely survives if unaltered | Strongly recommend DKIM & monitor policy |
| Outbound with mailbox | SPF + DKIM pass if correctly set | DKIM pass if signed by sender | Strong authentication, move to enforce |
Summary Steps to Set Up DMARC:
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Add SPF includes for all valid sending (and forwarding) servers for your domain.
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Enable DKIM signing—especially important if you use forwarding.
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Publish a DMARC TXT record with p=none for monitoring.
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Regularly check your DMARC reports to see which sources are passing/failing.
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When confident, move gradually to quarantine or reject.
For questions or if you’d like help interpreting DMARC reports or policies, please reach out to KartHost support or your DNS/email provider. DMARC is now an essential step in modern email safety, deliverability, and compliance with the latest requirements by Google, Yahoo, and Microsoft.
