Summary
A stricter DMARC policy, particularly 'p=reject' or 'p=quarantine', will almost certainly impact internal email deliverability for messages that are forwarded into or within a G Suite environment. While direct G Suite aliases, which map directly to a mailbox, typically do not pose DMARC alignment issues, any active forwarding rules--even those set up internally--can break SPF authentication, leading to rejection or quarantining of legitimate emails from external senders with strict DMARC policies. This issue arises because the forwarding server's IP address does not align with the original sender's SPF record. Close monitoring of DMARC reports and cautious, incremental policy implementation are crucial.
Key findings
- Forwarding Breaks SPF: Email forwarding frequently causes SPF authentication to fail because the forwarding server's IP address will not match the original sender's authorized SPF record.
- Strict DMARC Impact: A strict DMARC policy from the original sender, such as 'p=reject' or 'p=quarantine', will lead to the rejection or quarantining of legitimate forwarded emails due to DMARC alignment failures.
- Aliases vs. Forwarding Rules: G Suite aliases, which are direct mailbox mappings, generally do not cause DMARC alignment issues. However, actual forwarding rules, even those within G Suite, behave like traditional forwarding and are susceptible to DMARC failures.
- DKIM vs. SPF: While DKIM authentication might sometimes survive forwarding if headers are not modified, SPF almost always fails, making it the primary cause of DMARC failure for forwarded messages.
- ARC as Mitigation: Authenticated Received Chain (ARC) is a potential solution, supported by G Suite, that can help preserve email authentication results across forwarding hops, potentially mitigating DMARC failures for forwarded mail.
Key considerations
- Test Policies Cautiously: Implement stricter DMARC policies incrementally, for example, by starting with 'p=quarantine; pct=1' and gradually increasing restrictiveness to observe impact.
- Monitor DMARC Reports: Closely monitor DMARC reports to identify and address any authentication issues or unexpected rejections that arise from stricter policies, especially regarding forwarded internal mail.
- Resolve Auth Issues First: Prioritize resolving any existing email authentication issues, particularly SPF and DKIM alignment, before deploying a strict DMARC policy.
- Plan Like Maintenance: Treat DMARC policy changes as significant updates, planning them carefully like a scheduled maintenance window to minimize disruption to internal email flow.
What email marketers say
11 marketer opinions
A stricter DMARC policy from external senders will indeed impact internal email deliverability, specifically for messages processed via G Suite email forwarding. While direct G Suite aliases typically do not present DMARC challenges, any actual forwarding rules, even those configured internally, can cause SPF authentication to fail. This misalignment leads to legitimate emails being rejected or quarantined when the original sender has a 'reject' or 'quarantine' DMARC policy, necessitating careful implementation and continuous monitoring.
Key opinions
- Forwarding disrupts SPF: Email forwarding commonly breaks SPF authentication, as the forwarding server's IP address will not match the original sender's authorized record.
- Strict DMARC blocks forwarded mail: When the original sender has a DMARC policy of 'p=reject' or 'p=quarantine', legitimate forwarded emails are likely to be blocked or sent to spam due to authentication failures.
- Aliases versus forwarding rules: G Suite's direct mailbox aliases generally avoid DMARC issues. However, true forwarding rules, including those within G Suite for external mail, are prone to DMARC failures and can affect internal deliverability.
- SPF is primary failure point: While DKIM may sometimes survive forwarding, SPF is almost always impacted, making it the dominant cause of DMARC failure for forwarded messages.
- ARC as a solution: Authenticated Received Chain (ARC), supported by G Suite, can help preserve email authentication results across multiple forwarding hops, potentially mitigating DMARC failures.
Key considerations
- Implement DMARC cautiously: Begin with a less restrictive DMARC policy, such as 'p=quarantine; pct=1', and gradually increase its strictness while observing the impact.
- Monitor DMARC reports consistently: Continuously review DMARC reports to identify any unexpected rejections or delivery issues that may arise, especially concerning internal forwarded mail.
- Address authentication issues first: Ensure all existing SPF and DKIM authentication problems are resolved before deploying a stricter DMARC policy to avoid widespread deliverability issues.
- Plan policy changes diligently: Approach DMARC policy adjustments as critical updates, planning them with the same rigor as a maintenance window to minimize disruption to internal email workflows.
Marketer view
Marketer from Email Geeks advises against changing DMARC policy until authentication issues are resolved. If proceeding, he suggests a cautious approach using "p=quarantine; pct=1" to gradually implement DMARC. He emphasizes monitoring DMARC reports closely and planning the change like a maintenance window.
4 Feb 2024 - Email Geeks
Marketer view
Marketer from Email Geeks shares external information indicating that G Suite aliases prevent DMARC alignment and that a short-term fix from Google is not expected. This highlights the inherent problem with DMARC alignment when using aliases.
2 Jun 2025 - Email Geeks
What the experts say
3 expert opinions
Implementing a stricter DMARC policy, particularly a 'p=reject' setting, presents a significant risk to internal email deliverability, especially when G Suite aliases and email forwarding are involved. Experts concur that forwarding servers often break the crucial DMARC alignment for messages by altering the path, causing issues with the original sender's authentication, primarily SPF but sometimes DKIM. If the original domain has a strict DMARC policy, such unaligned forwarded emails are highly likely to be rejected by recipient mail servers, potentially disrupting internal communication flows. While ARC may offer some help in maintaining authentication chains, extensive testing is universally recommended to ascertain the exact impact.
Key opinions
- DMARC and Forwarded Mail: A stricter DMARC policy, especially a reject policy, significantly impacts forwarded emails because the forwarding server's action can break DMARC alignment with the original sender's domain.
- Internal Deliverability Risk: This misalignment can directly affect internal email delivery, particularly when internal forwarding rules or mechanisms are not configured to preserve DMARC alignment.
- Authentication Failures: Messages failing DMARC due to broken SPF or DKIM alignment, common in forwarded scenarios, are prone to rejection by recipient servers adhering to the sending domain's strict DMARC policy.
- ARC's Partial Aid: While technologies like Authenticated Received Chain (ARC) can assist in carrying authentication results across forwarding hops, they do not guarantee complete DMARC alignment for all forwarded messages.
- Necessity of Testing: Experts emphasize the critical need to test the impact of a stricter DMARC policy on internal email flows, especially for those involving forwarding, to anticipate and mitigate potential rejections.
Key considerations
- Thorough Impact Assessment: Carefully assess the potential impact of a stricter DMARC policy on all internal email forwarding rules and G Suite alias configurations within your organization.
- Pre-Implementation Testing: Conduct thorough testing before deploying a stricter DMARC policy to identify and resolve any potential internal email deliverability issues arising from forwarding.
- Internal Forwarding Review: Review current internal email forwarding mechanisms and mailing lists to understand how they interact with DMARC, ensuring they are designed to handle authentication alignment.
- Monitor for Rejections: Closely monitor DMARC reports and internal email delivery logs for increased rejections of legitimate mail after implementing a stricter policy, particularly for messages that have been forwarded.
Expert view
Expert from Email Geeks explains that increasing DMARC policy restrictiveness could lead to rejections for unaligned internal emails, especially those failing DKIM. She notes that while ARC might help Gmail handle it correctly, an increase in failures is likely as DMARC instructs recipient ISPs to reject unaligned mail. She advises to test and see the results.
30 Sep 2024 - Email Geeks
Expert view
Expert from Spam Resource explains that a stricter DMARC policy can significantly impact email deliverability for forwarded messages and mailing lists. When mail is forwarded, the forwarding server acts as the sender, which can break DMARC alignment with the original sender's domain. If the original domain has a reject policy, the forwarded email may be rejected by the recipient's server, potentially affecting internal email delivery if internal forwarding mechanisms are not designed to handle DMARC alignment.
26 Jan 2022 - Spam Resource
What the documentation says
3 technical articles
When a sending domain enforces a stricter DMARC policy, particularly 'p=reject', it significantly increases the likelihood of deliverability issues for emails that are forwarded, even when destined for internal G Suite users. This problem primarily arises because email forwarding often breaks SPF authentication, as the forwarding server's IP address does not align with the original sender's authorized SPF record. While G Suite aliases generally do not cause DMARC issues, any active forwarding rules—whether internal or external—can lead to legitimate emails being rejected or quarantined. This is an inherent challenge within the DMARC standard itself, requiring organizations to be aware of the potential for disrupted internal communication flows.
Key findings
- SPF Fails on Forwarding: Email forwarding commonly causes SPF authentication to fail because the forwarding server's IP address will not match the original sender's authorized SPF records.
- Strict DMARC Rejects Forwarded Mail: When the original sender has a strict DMARC policy, such as 'p=reject', legitimate forwarded emails, including those destined for internal G Suite users, are highly likely to be rejected.
- Internal Delivery Affected: The impact extends to internal email deliverability, as legitimate messages from external sources forwarded into or within your G Suite domain may not reach their intended recipients.
- Standard DMARC Limitation: This issue is a widely recognized limitation of the DMARC standard concerning email forwarding, applicable across various email platforms, not just G Suite.
- Header Modification Risk: Forwarding can sometimes modify email headers or content in transit, further complicating DMARC validation and potentially causing legitimate emails to fail authentication checks.
Key considerations
- Assess Forwarding Workflows: Review all internal email forwarding mechanisms and G Suite alias configurations to understand how a stricter DMARC policy could impact them, identifying any vulnerable flows.
- Understand DMARC Constraints: Recognize that the challenges with DMARC and forwarded mail are inherent limitations of the DMARC standard, not issues specific to G Suite, requiring a proactive approach.
- Monitor Deliverability Logs: In addition to DMARC reports, closely monitor internal email delivery logs for unexpected rejections or quarantines of legitimate messages that have been forwarded.
- Communicate Risks Internally: Inform internal users and stakeholders about the potential for legitimate external emails to be rejected or quarantined when forwarded, especially from domains with strict DMARC policies.
Technical article
Documentation from Google Workspace Admin Help explains that forwarded messages might fail DMARC checks, particularly for SPF authentication, because the original sender's SPF record won't authorize the forwarding server. While this isn't a G Suite issue but a DMARC standard limitation, it means a strict DMARC policy from the original sender can lead to internal deliverability issues for emails forwarded into your G Suite domain.
26 Feb 2025 - Google Workspace Admin Help
Technical article
Documentation from DMARC.org confirms that email forwarding poses a significant challenge for DMARC, particularly due to SPF failure. When an email is forwarded, the SPF check typically fails because the forwarding server's IP address does not match the original sender's authorized SPF records. If the original sender has a strict DMARC policy (e.g., p=reject), legitimate forwarded emails, including those destined for internal G Suite users via forwarding rules, can be rejected.
23 Dec 2022 - DMARC.org
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