Does DMARC require both SPF and DKIM to pass for email authentication?

No, DMARC requires at least one of SPF or DKIM to pass authentication and achieve alignment with the From: header domain. If either SPF or DKIM passes and aligns, the DMARC check will succeed. However, using both provides redundancy and stronger protection.

Can I deploy DMARC if I only have an SPF record and no DKIM?

Yes, you can deploy DMARC with only SPF. As long as your SPF record is correctly configured and achieves alignment , your emails can pass DMARC. It's still recommended to implement DKIM for added resilience against SPF failures, particularly in forwarding scenarios.

What happens if I have a DMARC record but neither SPF nor DKIM are set up?

If you have a DMARC record but no SPF or DKIM is configured, DMARC will always fail for emails sent from your domain. This offers no protection against spoofing and can lead to legitimate emails being marked as spam or rejected, especially if your DMARC policy is set to quarantine or reject.

Is DMARC useful for domains that do not send emails?

Absolutely. For domains that don't send email, you can publish a DMARC record with a p=reject policy and an SPF record of v=spf1 -all . This explicitly tells mail servers that no emails should originate from this domain, providing strong anti-spoofing protection.

How can I monitor DMARC effectiveness without SPF and DKIM?

Even without fully configured SPF and DKIM, deploying DMARC with a p=none policy allows you to receive DMARC reports. These reports will show you all traffic for your domain and the corresponding SPF/DKIM results (likely failures), giving you visibility into who is trying to send email on your behalf. A DMARC monitoring tool like Suped can help you interpret these reports .

Can DMARC policies be applied without an SPF or DKIM record? - DMARC - Email authentication - Knowledge base

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The question of whether DMARC policies can be applied without SPF or DKIM records is a common one in email security. DMARC, or Domain-based Message Authentication, Reporting, and Conformance, is designed to build upon SPF (Sender Policy Framework) and DKIM (DomainKeys Identified Mail) to provide a more robust email authentication framework. While it might seem counterintuitive, DMARC can indeed exist as a DNS record even if SPF or DKIM are not fully configured for a domain.

However, simply having a DMARC record in place without either SPF or DKIM properly configured means that DMARC won't be able to achieve its primary goal: authenticating your emails. DMARC's core function relies on the results of SPF and DKIM checks, along with an additional step called identifier alignment. Without these foundational protocols, DMARC will effectively fail for all outgoing messages, offering no protection against spoofing or phishing.

The recommended approach is always to implement SPF and DKIM first, ensuring they are correctly configured and pass authentication, before advancing your DMARC policy beyond p=none. However, it's possible to start monitoring your email traffic with DMARC even with an incomplete SPF or DKIM setup, which we will explore further.

How DMARC relies on SPF and DKIM for authentication

DMARC works by checking if a message passes either SPF or DKIM authentication, and crucially, if the domain in the From: header (the one users see) aligns with the domain authenticated by SPF or DKIM. This alignment is what gives DMARC its power to prevent direct domain spoofing.

SPF verifies that the sending IP address is authorized to send email on behalf of a domain. The domain checked by SPF is the one in the Return-Path header (also known as the envelope sender). For SPF alignment, this domain must match or be a subdomain of the From: header domain. If there is no SPF record, or if it is configured incorrectly, SPF will fail, making DMARC alignment via SPF impossible.

DKIM, on the other hand, uses a cryptographic signature to verify that the email content hasn't been tampered with in transit and that it originates from an authorized sender. The domain signed by DKIM must also match or be a subdomain of the From: header domain for DKIM alignment to pass. If neither SPF nor DKIM are correctly implemented, DMARC will effectively have no authentication results to evaluate, leading to DMARC failure.

Using DMARC with only SPF or only DKIM

Yes, you can configure a DMARC record and even get reports, even if only SPF or only DKIM is set up. DMARC requires at least one of SPF or DKIM to pass authentication and achieve alignment for a message to be considered DMARC compliant. For example, if you have SPF properly configured and aligning, but no DKIM record, DMARC can still pass based solely on the SPF result.

DMARC with SPF only

Authentication: If SPF passes and aligns, DMARC will pass.
Vulnerability: Susceptible to forwarding issues where SPF can break, leaving you without DKIM as a fallback.
Recommendation: Better than no authentication, but DKIM should be added for resilience.

DMARC with DKIM only

Authentication: If DKIM passes and aligns, DMARC will pass.
Vulnerability: Less susceptible to forwarding issues than SPF, but SPF provides an additional layer of sender verification.
Recommendation: Provides strong authentication, but adding SPF is best practice.

The key takeaway is that DMARC is designed for redundancy. If one method (SPF or DKIM) fails or doesn't align, the other can still ensure DMARC passes. This is why having both is the most robust solution for email authentication and deliverability.

The impact of no SPF or DKIM with DMARC

If a DMARC record exists, but neither SPF nor DKIM are properly configured to pass authentication and achieve alignment with the From: header domain, then DMARC will always fail for emails sent from that domain. This is essentially the same as not having DMARC at all, or even worse, because you might have a policy of p=quarantine or p=reject that would cause legitimate emails to be marked as spam or blocked entirely.

The risks of DMARC without SPF or DKIM

No protection: Your domain remains vulnerable to spoofing and phishing attacks, as there is no mechanism to verify legitimate senders.
Deliverability issues: Legitimate emails will fail DMARC and likely go to spam or be rejected, damaging your sender reputation.
Lack of visibility: While you might receive DMARC reports, they will consistently show DMARC failures, making it difficult to differentiate between legitimate and malicious traffic.

Therefore, if you intend to implement DMARC, it is critical to ensure that at least one of SPF or DKIM is fully configured and operational, with proper alignment, to ensure your legitimate emails are authenticated.

Best practices for DMARC implementation and monitoring

For domains that do not send email, DMARC still plays an important role. You can publish a DMARC record with a policy of p=reject and no SPF or DKIM records (or with SPF set to v=spf1 -all). This immediately tells receiving mail servers that no email should ever come from this domain, and any email purporting to do so should be rejected. This is a powerful anti-spoofing measure for inactive domains.

Example DMARC record for a non-sending domainDNS

_dmarc.yourdomain.com IN TXT "v=DMARC1; p=reject; rua=mailto:reports@yourdomain.com;"

Monitoring DMARC reports is essential, regardless of your SPF and DKIM setup. Even with a p=none policy, you start receiving valuable aggregated reports (RUA) that show you who is sending email on behalf of your domain, and whether those emails pass or fail SPF and DKIM. This visibility is crucial for identifying legitimate sending sources that need to be authenticated and for detecting malicious spoofing attempts.

Magnifying glass over email icons and charts, symbolizing DMARC monitoring.

To effectively implement DMARC and gain insights from your email authentication, a dedicated DMARC monitoring tool is indispensable. Suped offers comprehensive DMARC reporting and monitoring that simplifies the complex data in DMARC reports. Our platform provides AI-powered recommendations, real-time alerts, and a unified view of your DMARC, SPF, and DKIM status, along with blocklist and deliverability insights. This helps you to quickly identify and fix authentication issues, understand your email ecosystem, and confidently move your DMARC policy to enforcement (p=quarantine or p=reject).

The full authentication picture

While a DMARC record can technically exist without SPF or DKIM records, it will not actively authenticate emails without at least one of them being present and correctly configured with alignment. The true power and benefits of DMARC—such as protecting your domain from spoofing and improving deliverability—come from its ability to leverage SPF and DKIM for verification.

Therefore, the recommended path is always to ensure that both SPF and DKIM are properly set up and aligning before deploying DMARC. Start with a DMARC p=none policy to gather reports, analyze the authentication results from these reports, and then gradually move to a more restrictive policy like quarantine or reject once you are confident that all legitimate email sources are authenticated.

Leveraging a DMARC monitoring tool like Suped will significantly streamline this process, providing the actionable insights needed to secure your email channels effectively.