How does DMARC impact email forwarding and deliverability?
Michael Ko
Co-founder & CEO, Suped
Published 21 Jul 2025
Updated 17 Aug 2025
9 min read
Email forwarding, a seemingly simple act of redirecting a message from one address to another, introduces layers of complexity when DMARC is involved. While DMARC is essential for email security and deliverability, its strict authentication requirements can inadvertently cause legitimate forwarded emails to fail, leading to delivery issues. Understanding how DMARC interacts with forwarding is crucial for maintaining your email sender reputation and ensuring messages reach their intended recipients.
The core challenge lies in how forwarding services often modify email headers, which can break the authentication chain established by SPF (Sender Policy Framework) and DKIM (DomainKeys Identified Mail). When these foundational authentication methods fail, DMARC, designed to enforce policies based on their success, will also fail, potentially leading to the email being rejected or quarantined.
This can be a significant headache for organizations and individuals who rely on email forwarding, whether for internal mail routing, alumni services, or simple redirects. My goal here is to explain the technical details of these interactions and provide actionable insights to navigate the complexities of DMARC and email forwarding.
Email forwarding typically affects SPF and DKIM authentication in different ways, but both can lead to DMARC failures. SPF relies on the sending IP address being authorized by the domain in the "Return-Path" header (also known as the "MAIL FROM" address). When an email is forwarded, the forwarding server often becomes the new sending server, and its IP address might not be included in the original sender's SPF record. This mismatch causes SPF to fail.
DKIM, on the other hand, uses a digital signature to verify that the email content and certain headers haven't been tampered with in transit. This signature is tied to the domain that signed the email. Some forwarding services modify the email's content or headers, such as adding footers or disclaimers, which invalidates the original DKIM signature. When the signature is broken, DKIM authentication fails. Both of these authentication failures can cause DMARC to fail because DMARC requires either SPF or DKIM to pass and align with the "From" domain.
Here's a breakdown of how SPF and DKIM validation typically behave when an email is forwarded:
Authentication type
Impact of forwarding
Result on DMARC
SPF (Sender Policy Framework)
Forwarding servers often change the MAIL FROM (Return-Path) domain to their own. Since the original sending domain's SPF record doesn't authorize the forwarding server's IP, SPF fails.
Direct failure
DKIM (DomainKeys Identified Mail)
Some forwarding servers modify email content (e.g., adding headers, footers), which invalidates the DKIM signature. If the email is unmodified, DKIM may still pass.
Potential failure, depending on modification
DMARC policies and their impact on deliverability
The DMARC policy you set for your domain directly dictates how receiving mail servers handle emails that fail DMARC authentication. This has a profound impact on forwarded emails. There are three primary DMARC policies: p=none, p=quarantine, and p=reject. Each has different implications for deliverability when emails are forwarded. For a detailed overview of these policies, you can refer to this DMARC policy guide.
With a p=none policy, emails that fail DMARC will still be delivered, but DMARC reports (RUA and RUF) will inform you of the failures. This is the safest starting point and ideal for monitoring. For more about this, see simple DMARC examples. Moving to p=quarantine tells receiving servers to place failed emails into the recipient's spam or junk folder. This is a step towards enforcement and helps reduce spoofing, but it can unfortunately divert legitimate forwarded emails away from the inbox.
The most stringent policy, p=reject, instructs receiving servers to outright refuse emails that fail DMARC authentication. While this is the strongest defense against spoofing and phishing attempts, it also carries the highest risk for legitimate forwarded emails. Any forwarded email that breaks SPF or DKIM alignment will simply not be delivered, leading to lost communications. This policy acts more as a security measure rather than a deliverability one, as it directly sacrifices deliverability for strong anti-spoofing protection. For deeper insights, read about DMARC quarantine and reject policies.
The risk of p=reject
While p=reject is excellent for preventing direct domain spoofing, it can also harm the deliverability of legitimate forwarded emails. Many legitimate forwarding services do not support ARC (Authenticated Received Chain) or properly handle DMARC alignment, leading to these emails being dropped.
ARC: The solution for forwarded emails
To address the challenges posed by email forwarding and DMARC, the Authenticated Received Chain (ARC) protocol was developed. ARC allows intermediate mail servers (like forwarding services) to preserve email authentication results, even if the original SPF or DKIM records are broken during transit. It does this by adding a new header, the ARC-Seal, which is signed by each hop in the email's journey. This creates a chain of custody that recipient servers can trust. To learn more, read how to implement ARC.
When a DMARC-enabled receiver receives a forwarded email, it can check the ARC chain. If the ARC chain is valid and indicates that the email passed authentication at an earlier stage, the receiver can choose to override the DMARC failure that occurred due to forwarding. This significantly improves the deliverability of legitimate forwarded emails without compromising security. For additional details, see the article on how DMARC works with ARC.
While ARC is a promising solution, its adoption is not universal. Not all forwarding services or email providers have fully implemented ARC. This means that even with ARC, some forwarded emails might still experience DMARC failures and subsequent deliverability issues. However, major email providers like Google and Yahoo are increasingly relying on ARC to validate forwarded emails, making its implementation crucial for deliverability. Read more about how ARC impacts email deliverability.
Without ARC
Authentication Failure: SPF and DKIM break upon forwarding due to header modifications or IP changes.
DMARC Failure: Email fails DMARC validation, even if originally legitimate.
Deliverability Risk: Emails are subject to DMARC policy (quarantine/reject), risking non-delivery or spam folder placement.
Spoofing Risk: Legitimate forwarded emails might be indistinguishable from spoofed messages.
With ARC
Authentication Preservation: ARC validates and preserves original authentication results.
DMARC Override: Receiving servers can trust the ARC chain and override DMARC failures.
Improved Deliverability: Legitimate forwarded emails are more likely to reach the inbox.
Navigating DMARC with email forwarding requires a strategic approach to ensure both security and deliverability. My first recommendation is to always start with a p=none DMARC policy. This allows you to gather DMARC reports and identify forwarding issues without impacting legitimate email delivery. You can then use these reports to identify which email flows are being affected by forwarding and assess the volume of such emails. This phase is critical for understanding your email ecosystem before moving to stricter policies.
Next, for essential email flows, consider using subdomains. If you have specific services, like transactional emails or marketing campaigns, that are frequently forwarded, sending them from a dedicated subdomain (e.g., marketing.yourdomain.com) can allow you to apply a different DMARC policy to that subdomain. This means you could keep your main domain at p=reject while having a more lenient policy (like p=none) for your marketing subdomain, which might experience higher forwarding rates. This isolates the impact of forwarding-induced failures. For more info, read how to roll out DMARC enforcement.
Another strategy is to encourage your recipients to add your sending IP addresses to their allowlists if they consistently experience issues with forwarded emails. This is a less scalable solution but can be effective for critical communications with specific partners or clients. Finally, always monitor your DMARC reports. These reports are invaluable for understanding how your emails are being authenticated and delivered across the internet. They will show you precisely which emails are failing DMARC due to forwarding and allow you to make informed decisions about adjusting your policies or communication strategies. You can learn how to troubleshoot DMARC failures and their impact.
Remember, the goal is to find a balance between robust security and ensuring your legitimate emails are delivered. Moving to p=reject can be tempting for maximum spoofing protection, but it's crucial to thoroughly assess the impact on legitimate forwarded email before making that jump. A gradual DMARC rollout, starting with p=none, is always the recommended path to prevent unforeseen deliverability issues. Additionally, regularly checking your blocklist checker can provide insights into other deliverability challenges.
Views from the trenches
Best practices
Start with a DMARC policy of p=none to monitor authentication failures without impacting deliverability.
Utilize DMARC reports to identify all legitimate sending sources and any unexpected forwarding paths.
Implement ARC (Authenticated Received Chain) if your email infrastructure or forwarding services support it to preserve authentication.
For distinct email streams like marketing or transactional, use subdomains with their own DMARC policies.
Regularly review and update your SPF and DKIM records to ensure they cover all authorized sending sources.
Common pitfalls
Jumping straight to a p=reject DMARC policy without sufficient monitoring, leading to legitimate email blocking.
Not accounting for third-party senders (ESPs, marketing platforms) that might not properly align with DMARC.
Overlooking legacy forwarding services or mailing lists that break SPF/DKIM and lack ARC support.
Ignoring DMARC reports, thus missing critical insights into authentication failures and potential spoofing attempts.
Assuming all email forwarding scenarios are handled the same way across different providers.
Expert tips
Use DMARC aggregate reports to understand email flow and identify forwarding issues comprehensively.
Consider selective DMARC enforcement using different policies for subdomains based on their traffic patterns.
Be aware that DMARC p=reject is primarily a security measure to combat direct domain spoofing, not a universal deliverability booster.
Continuously validate your DMARC, SPF, and DKIM records to ensure correct configuration.
Work with your email service providers to ensure they support DMARC and ARC for your sending domains.
Marketer view
Marketer from Email Geeks says forwarding often causes issues with email authentication.
2024-05-17 - Email Geeks
Expert view
Expert from Email Geeks notes that some entities, like universities, run forwarding services for their alumni, which can complicate DMARC.
2024-05-17 - Email Geeks
Balancing security and deliverability with DMARC and forwarding
DMARC is a powerful protocol for email authentication and combating spoofing, but its interaction with email forwarding can be a significant hurdle for deliverability. The key takeaway is that forwarding often disrupts SPF and DKIM validation, leading to DMARC failures. My experience has shown that without careful consideration, a strict DMARC policy like p=reject can block legitimate forwarded messages.
Implementing DMARC requires a nuanced approach, particularly when forwarding is part of your email ecosystem. Starting with a monitoring policy (p=none) and gradually transitioning based on DMARC reports is essential. Leveraging technologies like ARC where supported can significantly alleviate deliverability concerns for forwarded emails. While the landscape of email authentication is constantly evolving, a proactive and informed strategy will ensure your emails reach the inbox reliably.
Google and 
Yahoo are increasingly relying on ARC to validate forwarded emails, making its implementation crucial for deliverability. Read more about how ARC impacts email deliverability.
