Will a stricter DMARC policy impact internal email deliverability when using G Suite aliases and email forwarding?
Matthew Whittaker
Co-founder & CTO, Suped
Published 3 May 2025
Updated 19 Aug 2025
7 min read
Moving to a stricter DMARC policy is a significant step towards improving your domain's email security. It tells recipient mail servers how to handle emails that fail DMARC authentication, protecting your brand from impersonation and phishing attacks. However, when you rely on services like G Suite (now Google Workspace) for internal communications, especially with aliases and email forwarding in play, there can be complexities.
I've seen many organizations use a DMARC policy of p=none during the initial monitoring phase. This policy allows you to gather DMARC reports without impacting email delivery, giving you visibility into authentication failures. It's an important first step, but it doesn't provide enforcement against fraudulent emails.
The concern arises when you decide to move to a more restrictive policy, such as p=quarantine or p=reject. This is where internal email deliverability, especially for emails sent via G Suite aliases and those that are forwarded, can be affected. The core issue often stems from DMARC alignment and how forwarding changes the authentication results of an email.
DMARC relies on either SPF or DKIM aligning with the "From" domain of the email. When an email is forwarded, its authentication results can be altered, particularly SPF. SPF (Sender Policy Framework) checks the sender's IP address against a list of authorized sending IPs published in the domain's SPF record. If an email is forwarded, it often passes through an intermediary server, which can change the sending IP address. This break in the chain means the original SPF authentication often fails upon re-evaluation by the final recipient server. This is a common challenge for email administrators and can lead to significant deliverability issues if not managed correctly.
DKIM (DomainKeys Identified Mail) is more resilient to forwarding because it relies on a cryptographic signature in the email header. As long as the email content and headers aren't significantly modified by the forwarding server, the DKIM signature should remain valid. However, some forwarding services might modify the email in ways that break the DKIM signature, leading to DKIM authentication failures. If both SPF and DKIM fail to align, an email will fail DMARC.
The critical point is that when an email fails DMARC, a stricter policy like p=quarantine (send to spam) or p=reject (block entirely) will instruct recipient servers to act upon that failure. This is why understanding how email forwarding impacts DMARC policies is crucial.
Before forwarding (direct send)
SPF: Passes and aligns if the sending IP is authorized.
DKIM: Passes and aligns if the domain's DKIM key signed the email.
DMARC: Passes if either SPF or DKIM passes alignment.
A good understanding of how forwarding interacts with authentication is key. You can find more details on troubleshooting DMARC issues and general email sender guidelines for Google Workspace to deepen your knowledge in this area.
G Suite aliases and DMARC alignment challenges
G Suite (now Google Workspace) uses aliases extensively, especially in corporate setups where a parent company domain might differ from its subsidiaries' domains. When employees use aliases that point to a different sending domain, the email often gets forwarded internally. This forwarding process, combined with DMARC, creates a unique challenge. The issue typically arises because the DKIM signature or SPF record for the alias domain doesn't align with the actual sending domain of the parent company.
For instance, if your internal emails are being forwarded through a G Suite alias from your parent company's domain, the original DKIM signature might not align with your domain's DMARC policy. This means that even though the email is legitimate and internal, it could fail DMARC checks. Historically, G Suite had a "local policy" override that would ensure these internal, DMARC-failing emails were still delivered. This override helped maintain internal deliverability despite the technical DMARC failures. However, with stricter policies becoming the norm, this override might not always prevent issues.
Google Workspace is aware of these complexities, and there have been discussions about improving DMARC alignment for aliases. Until these improvements are widely implemented, a manual approach to managing these configurations is often necessary. You can refer to our guides on how email forwarding and DMARC policies affect delivery for more insights.
This record instructs recipient servers to take no action on DMARC failures, but to send aggregate reports to the specified email address. This is helpful for initial monitoring, but doesn't prevent email spoofing.
Migrating to stricter DMARC policies
When you transition your DMARC policy from p=none to p=quarantine or p=reject, any email that fails DMARC authentication and does not have an ARC (Authenticated Received Chain) seal or other override mechanism will be subject to that policy. For internal emails using G Suite aliases, where DKIM is unaligned due to forwarding or alias configuration, this could mean legitimate internal emails might start landing in spam folders (quarantine) or being rejected outright.
This is a significant risk, as it can disrupt internal communications and lead to confusion and lost productivity. It is essential to monitor your DMARC reports diligently after making any policy changes. These reports will show you which emails are failing DMARC and why, allowing you to identify if internal forwarded emails or alias-based emails are being impacted.
The key is to resolve any underlying authentication issues before moving to an enforcement policy. For scenarios involving G Suite aliases, this might involve re-evaluating your email routing, ensuring proper DKIM signing for all relevant domains, or investigating if ARC is sufficiently mitigating the DMARC failures. Understanding how email forwarding errors can occur with DMARC is a good starting point.
P=none (monitoring)
Impact: Emails that fail DMARC still reach the inbox. No direct deliverability impact on legitimate email, even if authentication is broken.
Visibility: Provides DMARC aggregate and forensic reports to identify authentication issues without blocking emails.
Security: Offers no protection against spoofing or phishing attempts using your domain.
P=quarantine or p=reject (enforcement)
Impact: Emails failing DMARC are sent to spam (quarantine) or blocked entirely (reject). Significant impact on legitimate emails that fail authentication.
Visibility: Provides reports, but misconfigured legitimate emails will be affected.
Security: Strong protection against domain spoofing and phishing.
Moving to a stricter policy is a crucial step for email security, but it requires careful planning and continuous monitoring. Before making the switch, ensure your DMARC reports show minimal legitimate failures, especially for internal and forwarded emails.
Views from the trenches
Best practices
Ensure SPF and DKIM are properly configured and aligned for all sending domains and services.
Monitor DMARC reports constantly to identify any legitimate emails failing authentication.
Gradually increase DMARC policy enforcement using the `pct` tag, starting with a low percentage.
Common pitfalls
Moving directly to `p=quarantine` or `p=reject` without thorough testing and monitoring.
Not accounting for email forwarding and aliases in DMARC deployment plans.
Failing to address underlying DKIM alignment issues, especially with G Suite aliases.
Expert tips
A gradual rollout using `pct=1` on quarantine is a safe way to test the waters.
Always prioritize fixing authentication issues before moving to a stricter DMARC policy.
Consider how Google (and other major mailbox providers) handles ARC when planning your DMARC enforcement.
Expert view
Expert from Email Geeks says that strict DMARC policies can cause rejections for unaligned emails, as recipient ISPs are instructed to do so.
2023-09-10 - Email Geeks
Expert view
Expert from Email Geeks notes that Google Workspace (formerly Gmail) supports ARC, which might help handle forwarded emails correctly.
2023-09-12 - Email Geeks
Ensuring smooth internal email flow
Implementing a stricter DMARC policy is essential for safeguarding your domain against phishing and spoofing. However, it requires a thorough understanding of how email authentication, forwarding, and services like Google Workspace aliases interact. The key takeaway is to proceed with caution and a data-driven approach.
Before you move from a p=none policy, ensure that all legitimate email streams, including those from G Suite aliases and forwarded emails, consistently pass DMARC alignment. This might involve adjusting SPF records, ensuring correct DKIM signing, or leveraging ARC. Continuous monitoring of your DMARC reports will provide the insights needed to make informed decisions and prevent unexpected deliverability issues for your internal communications.
Prioritizing the health of your authentication protocols ensures that your move towards a more secure DMARC policy doesn't inadvertently block essential internal emails, keeping your organization's communication flowing smoothly and securely. For more on this, check out our guide on how to handle DMARC failures when email is forwarded.
