Effects of Email Forwarding on DMARC

In the dynamic digital communication landscape, email remains a cornerstone for professional and personal correspondence. However, with the convenience of email forwarding comes a potential disruption to the security and authenticity of messages. 

Domain-based Message Authentication, Reporting, and Conformance (DMARC) has emerged as a critical tool in the fight against email phishing and fraud. 

In this blog post, we will explore the effects of email forwarding on DMARC and how organizations can navigate this intricate relationship to secure their email security.

Understanding DMARC

DMARC is an email authentication protocol that builds on the existing Sender Policy Framework (SPF) and DomainKeys Identified Mail (DKIM) standards. It allows domain owners to specify how their emails should be authenticated and what actions should be taken if authentication fails. DMARC helps prevent email phishing attacks and domain spoofing by providing a way for email receivers to verify the authenticity of incoming messages.

Email Forwarding and DMARC: The Tug of War

While email forwarding is a convenient feature that enhances communication efficiency, it can introduce complexities to the DMARC ecosystem. When an email is forwarded, the original sender’s DKIM signature may become invalidated, leading to a failed DMARC authentication. This is because the DKIM signature is often tied to the specific mail server the original sender uses.

Moreover, SPF, another component of DMARC, can also be impacted by email forwarding. SPF validates that the IP address sending the email is authorized to send messages on behalf of the domain. In the case of forwarding, the forwarding mail server might not be included in the SPF record of the original sender, leading to SPF failures.

The Effects on DMARC Alignment

DMARC relies on alignment checks to ensure that the DKIM or SPF authentication domains align with the “header from” domain, the visible sender’s domain. Email forwarding can break this alignment, causing a misalignment between the original sender’s domain and the visible sender’s domain. This misalignment triggers DMARC failures, potentially leading to legitimate emails being marked as suspicious or fraudulent.

Mitigating the Impact

Modify Forwarding Servers: Organizations can modify their forwarding servers to ensure that DKIM signatures are preserved during the forwarding process. This involves configuring the forwarding server to re-sign the email with its own DKIM key.

Use DMARC “p=” Tag: The “p=” tag in DMARC allows domain owners to specify the policy for dealing with email that fails authentication. By setting the “p=” tag to “none” or “quarantine,” domain owners can receive reports without affecting the delivery of emails. This enables organizations to monitor the impact of email forwarding on DMARC without immediately enforcing strict policies.

Implement DMARC Subdomains: DMARC policies can be implemented at the subdomain level, allowing organizations to selectively apply DMARC policies to specific subdomains. This can be useful for isolating the impact of email forwarding on DMARC for specific parts of the organization.


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Q1. How does email forwarding impact DMARC authentication?

Email forwarding can break DKIM and SPF authentication, leading to misalignment and potential DMARC failures as the original sender’s signatures may not be preserved.

Q2. Can email forwarding affect the SPF records of the original sender?

Yes, email forwarding may cause SPF failures if the forwarding server is not included in the SPF records of the original sender, potentially leading to authentication issues.

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