Summary
When a DMARC (Domain-based Message Authentication, Reporting, and Conformance) policy is added or modified in a domain's DNS records, it typically takes time for these changes to propagate across the internet. This propagation period can range from a few hours to up to 48 hours, or in some cases, even 72 hours, due to DNS caching. This delay means that even if IT confirms the DMARC record is published, its effects might not be immediate. If emails are not being delivered after a DMARC record is implemented, especially with a strict policy like p=reject, it often indicates an underlying authentication issue. Understanding how DMARC works in conjunction with SPF and DKIM is crucial for diagnosing and resolving these failures, ensuring email deliverability.
Key findings
- DNS propagation time: DMARC record changes, like any DNS updates, can take 24 to 48 hours to propagate globally, sometimes longer.
- Policy enforcement: A DMARC policy set to p=reject will cause emails that fail DMARC authentication to be rejected by receiving servers, leading to non-delivery or bounces.
- Authentication issues: Email delivery failures after DMARC implementation often stem from SPF or DKIM alignment issues, meaning emails aren't properly authenticated for the sending domain.
- DMARC reports: DMARC reports provide crucial insights into authentication failures, detailing which emails are failing and why, usually available within 24 hours of emails being sent.
- SPF and DKIM alignment: For DMARC to pass, either SPF or DKIM must align with the From domain. Third-party sending services (like Mailchimp) may require DKIM signing for alignment.
Key considerations
- Initial policy choice: It is generally recommended to start with a DMARC policy of p=none to monitor authentication results without impacting deliverability.
- Monitoring reports: Regularly review DMARC aggregate and forensic reports (if enabled) to identify legitimate sending sources and correct authentication configurations.
- Troubleshooting authentication: If emails fail, verify the SPF record includes all legitimate sending IP addresses or services, and ensure DKIM is correctly configured and signing emails with the domain.
- Gradual policy enforcement: Increase DMARC policy enforcement gradually from p=none to p=quarantine and then p=reject once you are confident that all legitimate emails pass DMARC.
What email marketers say
Email marketers often encounter DMARC propagation delays and authentication failures as they implement or adjust their policies. The general consensus among marketers is that while DNS changes are quick to publish, it's the global propagation that requires patience. When authentication failures occur, especially with a p=rejectpolicy in place, the immediate impact is a halt in email delivery. Marketers emphasize the importance of starting with a lenient policy like p=noneto gather data through DMARC reports before moving to stricter enforcement. This proactive approach helps identify and fix issues with SPF and DKIM alignment from all legitimate sending sources.
Key opinions
- Propagation expectation: Marketers frequently note that DNS changes, including DMARC records, can take up to 48 hours to fully propagateacross the internet.
- Policy impact: Publishing DMARC with a p=reject policy without proper authentication for all sending sources will lead to emails being rejected or bounced.
- Bounced emails: Authentication failures often manifest as bounced emails or messages routed to spam filters, indicating a need for review.
- Mailchimp considerations: When using services like Mailchimp, SPF alignment might not be straightforward, making DKIM alignment the primary method to ensure DMARC passes.
- Monitoring tools: Utilizing DMARC reporting tools is essential to understand which emails are failing authentication and to pinpoint the root cause.
Key considerations
- Start with p=none: To avoid immediate impact on deliverability, marketers should always initially deploy DMARC with a p=none policy.
- Patience for propagation: Allow sufficient time (up to 48 hours or more) for DNS propagation after any DMARC record updates before retesting or expecting full effect.
- Address authentication failures: If emails are bouncing, investigate the bounces to understand the specific authentication failure type (SPF, DKIM, or DMARC alignment).
- Verify SPF and DKIM: Ensure that all sending systems are correctly configured for either SPF or DKIM alignment with the domain in the From header. For third-party ESPs, enabling their domain authentication (often DKIM) is crucial.
Marketer view
Email marketer from Email Geeks inquired about DMARC policy propagation and reported email tests not coming in after IT added a DMARC record to their site. They noted the issue was still present despite being told it was resolved and planned to wait and retest.
Marketer view
Email marketer from Email Geeks explained they lacked access to modify DMARC settings and found the email issues outside their expertise. They observed that the emails were being caught by their spam software and reported as bounces, indicating a delivery problem.
What the experts say
Experts in email deliverability consistently highlight that DMARC policy changes require DNS propagation time, which can vary significantly. They emphasize that strict policies like p=reject should only be implemented after thorough monitoring with p=none or p=quarantineto identify and resolve all authentication issues. A common cause of DMARC failure, even when SPF and DKIM technically pass, is an alignment mismatch between the authenticated domain and the From domain. Experts recommend using DMARC reports to pinpoint the source of failures and ensure all legitimate sending platforms are correctly configured for authentication.
Key opinions
- Initial policy recommendation: Experts advise that when first publishing a DMARC record, it's best to start with p=none to monitor potential authentication issues without blocking emails.
- Rejection impact: A p=reject policy will cause emails with authentication errors to be outright rejected, potentially leading to deliverability issues for legitimate mail.
- DMARC TempErrors: Temporary authentication issues related to SPF and DKIM can lead to DMARC validation failures, often indicated by DMARC TempErrors.
- Authentication requirements: For DMARC to pass, either SPF or DKIM must pass and align with the From domain. This alignment is critical, especially when using third-party email service providers.
Key considerations
- Monitor DMARC reports: Regularly review aggregated DMARC reports to identify email streams that are failing authentication and determine the precise reason for failure, such as IP address or sending service.
- Verify SPF and DKIM configuration: Ensure that SPF records include all authorized sending IPs and that DKIM signatures are correctly applied by all email sending platforms, aligning with the domain.
- Gradual policy transition: Move from p=none to p=quarantine and then p=reject only after all legitimate email traffic consistently passes DMARC authentication.
- Understand alignment modes: Be aware of DMARC's strict versus relaxed alignment modes, as this impacts how closely the authenticated domain must match the From domain for DMARC to pass.
Expert view
Expert from Email Geeks clarified that a bounce indicating an authentication failure means an issue with the sending email's validation. They specifically asked for the sending IP address to further diagnose the problem, highlighting the importance of this detail for troubleshooting.
Expert view
Expert from Email Geeks suggested that if Mailchimp's setup does not allow for SPF alignment, then DKIM signing with the primary domain is crucial for DMARC to pass. This points to the need for understanding ESP-specific authentication mechanisms.
What the documentation says
Official documentation and technical guides consistently state that DNS propagation, including for DMARC records, is not instantaneous. The time it takes for a DMARC policy change to take full effect depends on various factors like TTL (Time to Live) settings and DNS resolver caching. Authentication failures, commonly indicated by DMARC TempErrors or PermErrors, are often a result of misconfigured SPF or DKIM records, or a lack of alignment between the authenticated identity and the From header domain. Documentation advises a cautious approach to DMARC implementation, starting with monitoring policies and gradually increasing enforcement.
Key findings
- Propagation duration: DNS changes, including DMARC record updates, can take up to 48-72 hoursto fully propagate across the internet.
- Authentication standards: DMARC relies on the successful authentication and alignment of either SPF or DKIM records. If both fail or do not align, the DMARC policy will be applied.
- Policy enforcement: A DMARC policy (e.g., p=reject) instructs receiving email servers on how to handle emails that fail DMARC authentication, such as rejecting them outright.
- DMARC record syntax: The DMARC record is a TXT record published in the DNS, starting with v=DMARC1and including policy and reporting tags.
Key considerations
- Monitor reports first: Before enforcing strict DMARC policies, domain owners should analyze DMARC reports to identify all legitimate sending sources and ensure they are properly authenticated.
- Configure SPF and DKIM correctly: Ensure that SPF records are accurate and complete for all sending IPs and that DKIM is signing emails from authorized services with the correct domain.
- Patience with propagation: Do not assume immediate impact after publishing or modifying a DMARC record, as DNS caching mechanisms can delay widespread recognition.
- Best practices for implementation: Follow best practices for DMARC implementation, including careful tag definition and a phased approach to policy enforcement.
Technical article
Documentation from 101domain blog confirms that once a DMARC record is published in DNS, it typically propagates within 24 to 48 hours. This timeframe is standard for DNS updates and should be considered for any new DMARC deployment or modification.
Technical article
Documentation from DuoCircle states that DMARC TempErrors refer to temporary authentication issues related to email standards like DKIM and SPF. These issues can lead to failures in DMARC validation, indicating transient problems that may resolve themselves or require investigation.
Related resources
12 resources
Related pages
How to implement DMARC p=reject policy safely to avoid email deliverability issues?
Why does DMARC authentication fail when SPF and DKIM pass, and how can it be fixed?
When should you use DMARC p=none, p=quarantine, or p=reject policies?
How to troubleshoot intermittent email delivery failures caused by SPF and DNS issues?
What are the best practices for DMARC implementation, including tag definition and tool recommendations?
List of DMARC tags and their meanings
Simple DMARC examples: how to start with a p=none policy
A simple guide to DMARC, SPF, and DKIM
How to safely transition your DMARC policy to quarantine or reject
Understanding and troubleshooting DMARC reports from Google and Yahoo
