Summary
Email forwarding disrupts DMARC authentication because it often causes SPF and DKIM checks to fail, primarily because the forwarding server's IP doesn't align with the original sender's SPF records. The impact on delivery depends on the DMARC policy; 'none' is for reporting only, 'quarantine' sends emails to spam, and 'reject' blocks them. DMARC reports are crucial for identifying these authentication failures, allowing senders to adapt their strategies. SRS (Sender Rewriting Scheme) and SPF flattening are techniques used to mitigate forwarding-related issues. Enforcing strong authentication (SPF, DKIM, DMARC) combined with vigilant monitoring and careful policy adjustments are key to balancing security with legitimate email delivery.
Key findings
- Forwarding Breaks Authentication: Email forwarding commonly results in DMARC authentication failures because the forwarding server's IP and modifications break SPF and DKIM records.
- DMARC Policy Dictates Handling: The DMARC policy (none, quarantine, reject) determines how recipient mail servers treat emails failing authentication. 'None' reports only, 'quarantine' moves to spam, and 'reject' blocks delivery.
- Reports Provide Visibility: DMARC aggregate reports provide visibility into authentication failures, including those caused by forwarding, allowing for analysis and adjustments.
- Mitigation Techniques Exist: SRS (Sender Rewriting Scheme) and SPF flattening are techniques to mitigate forwarding-related authentication issues and improve deliverability.
Key considerations
- Implement Strong Authentication: Implement robust email authentication protocols (SPF, DKIM, DMARC) to protect your domain and enhance email deliverability.
- Monitor DMARC Reports Regularly: Actively monitor DMARC reports to understand authentication failures, including those caused by forwarding, and adapt your approach as needed.
- Strategically Adjust DMARC Policy: Carefully adjust your DMARC policy to balance the need for security with the risk of blocking legitimate forwarded emails; consider a staged approach.
- Consider Implementing SRS: Implement SRS to ensure that forwarded emails still pass authentication, especially when using a stricter DMARC policy.
- Understand Mailing List Impact: Recognize that DMARC can significantly affect mailing list deliverability due to forwarding; consider SRS or other compatible strategies.
What email marketers say
10 marketer opinions
Email forwarding can significantly impact email deliverability when DMARC policies are in place. Forwarding often breaks DMARC authentication, as the forwarding server's IP address or modifications to the message can cause SPF and DKIM checks to fail. This can lead to emails being quarantined or rejected, depending on the DMARC policy (none, quarantine, reject). DMARC reporting provides insights into these failures, helping senders identify and address issues. Techniques like SRS (Sender Rewriting Scheme) and SPF flattening can mitigate these problems. Implementing strong email authentication practices (SPF, DKIM, DMARC) and carefully monitoring DMARC reports are essential for maintaining good deliverability.
Key opinions
- Forwarding Breaks DMARC: Email forwarding frequently causes DMARC authentication failures because the forwarding server's IP address or changes to the message header/body invalidate SPF and DKIM records.
- DMARC Policy Impact: The DMARC policy (none, quarantine, reject) determines how receiving mail servers handle emails that fail authentication. Stricter policies (quarantine, reject) can lead to delivery issues for forwarded emails.
- DMARC Reporting Insights: DMARC reporting provides valuable data on authentication failures, including those caused by forwarding, enabling senders to identify and address these issues.
- SRS and SPF Flattening: Techniques like SRS (Sender Rewriting Scheme) and SPF flattening can help mitigate the impact of forwarding on DMARC authentication by rewriting the sender address or reducing DNS lookups.
Key considerations
- Implement Email Authentication: Implement strong email authentication protocols (SPF, DKIM, DMARC) to protect your domain from spoofing and improve email deliverability.
- Monitor DMARC Reports: Regularly monitor DMARC reports to identify authentication failures and adjust your authentication practices and DMARC policies accordingly.
- Consider SRS: Consider implementing SRS (Sender Rewriting Scheme) to ensure that legitimate forwarded emails are still delivered when DMARC policies are in place.
- Balance Policy and Deliverability: Carefully balance the strictness of your DMARC policy with the need to ensure deliverability of legitimate emails, including those that are forwarded.
- Mailing List Impact: Be aware that DMARC can significantly impact mailing list deliverability, and list owners may need to implement SRS or other workarounds.
Marketer view
Email marketer from SparkPost shares that monitoring DMARC reports is crucial for identifying and addressing email delivery issues caused by forwarding. Regularly reviewing these reports allows senders to adjust their authentication practices and DMARC policies to minimize the impact on legitimate email traffic.
6 Mar 2024 - SparkPost
Marketer view
Email marketer from Validity explains that understanding and managing email forwarding is crucial for maintaining good email deliverability with DMARC. Techniques like SRS (Sender Rewriting Scheme) can help mitigate the impact of forwarding on DMARC authentication and ensure that legitimate forwarded emails are still delivered.
12 Nov 2024 - Validity
What the experts say
6 expert opinions
Email forwarding often breaks DMARC authentication because the forwarding server's IP address doesn't match the original sender's SPF record. DMARC reports highlight these authentication failures, showing unauthenticated emails using your domain. A DMARC policy of 'none' doesn't affect delivery and is used to gather reports. Implementing 'quarantine' or 'reject' prevents delivery of those failing emails. Seeing your IP in reports suggests authentication issues on your end, not just forwarding. Achieving a 'reject' policy is difficult due to forwarding, requiring careful monitoring. DMARC alignment (matching 822.From, 821.From, and DKIM d= domains) is beneficial but not immediately critical.
Key opinions
- Forwarding Breaks SPF: Email forwarding causes SPF checks to fail because the forwarding server's IP differs from the original sender's SPF record.
- DMARC Reports Show Failures: DMARC reports identify authentication failures, including those due to forwarding, highlighting unauthenticated emails using your domain.
- Policy Affects Delivery: DMARC policies of 'quarantine' or 'reject' prevent delivery of emails failing authentication, while 'none' is for reporting only.
- IP in Report = Your Issue: If your IP shows in a DMARC report, it indicates an authentication problem on your end, not just forwarding issues.
- DMARC Alignment Aspirational: DMARC alignment is beneficial but not immediately critical; something to move towards but not immediately required.
Key considerations
- Monitor DMARC Reports: Actively monitor DMARC reports to identify and address authentication issues caused by forwarding and other factors.
- Balance Policy and Impact: Carefully balance the strictness of your DMARC policy (especially 'reject') with the need to avoid blocking legitimate forwarded emails.
- Address Authentication Issues: If your IP address appears in DMARC reports, investigate and correct any underlying authentication problems with your email setup.
- Forwarding Mitigation: Consider implementing Sender Rewriting Scheme (SRS) or other techniques to mitigate forwarding impact if you move to p=quarantine or p=reject.
Expert view
Expert from Email Geeks explains that if your IP address appears in a DMARC report, it likely indicates that you are not authenticating your emails correctly. If the authentication were broken in transit, the report would show the IP address of the forwarder or intermediate mail server.
21 Dec 2024 - Email Geeks
Expert view
Expert from Email Geeks explains that DMARC reports provide information about emails received with your domain in the From: address that weren't authenticated by you, and forwarding is a common cause of broken authentication, leading to forwarded emails appearing in DMARC reports.
28 May 2022 - Email Geeks
What the documentation says
4 technical articles
DMARC policies (quarantine/reject) instruct recipient mail servers on how to handle authentication failures, impacting delivery by potentially sending emails to spam or preventing delivery. A 'none' policy doesn't affect delivery. Email forwarding can cause SPF failures as the forwarder's IP doesn't match the original sender's SPF record, affecting deliverability. DMARC aggregate reports summarize authentication results, highlighting SPF/DKIM failures caused by forwarding. SRS (Sender Rewriting Scheme) rewrites sender addresses in forwarded emails to help them pass SPF, improving deliverability in these scenarios.
Key findings
- DMARC Policy Impact: DMARC policies directly affect delivery, with 'quarantine' potentially sending emails to spam and 'reject' preventing delivery. 'None' has no impact on delivery.
- SPF Failure from Forwarding: Email forwarding often leads to SPF authentication failures because the forwarding server's IP address doesn't match the original sender's SPF record.
- DMARC Reports Provide Data: DMARC aggregate reports summarize authentication results, providing information on SPF and DKIM failures related to forwarding.
- SRS Mitigates SPF Issues: Sender Rewriting Scheme (SRS) rewrites sender addresses in forwarded emails, helping them pass SPF checks and improving deliverability.
Key considerations
- Choose DMARC Policy Wisely: Select a DMARC policy (none, quarantine, reject) that balances security and deliverability, considering the impact on forwarded emails.
- Implement SRS for Forwarding: Implement SRS if you anticipate significant email forwarding to maintain deliverability and avoid SPF failures.
- Analyze DMARC Reports: Regularly analyze DMARC reports to understand authentication failures and adjust your email authentication practices and policies.
- Enforce SPF: Be aware that strict enforcement of SPF can affect deliverability of forwarded emails if proper measures like SRS are not in place.
Technical article
Documentation from RFC 7489 explains that DMARC aggregate reports provide a summary of DMARC authentication results for emails claiming to be from your domain. These reports include information about SPF and DKIM failures, which can be caused by forwarding, and help domain owners understand how their emails are being handled by different mail receivers.
12 Aug 2022 - RFC Editor
Technical article
Documentation from DMARC.org explains that DMARC policies (p=quarantine or p=reject) instruct recipient mail servers on how to handle messages that fail DMARC authentication. These policies can directly impact email delivery, with 'quarantine' potentially sending messages to spam and 'reject' preventing delivery altogether. A policy of 'none' does not affect delivery.
25 May 2022 - DMARC.org
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