Summary
Moving to a stricter DMARC policy, like p=quarantine or p=reject, can significantly impact internal email deliverability, especially when using G Suite aliases and email forwarding. These configurations often lead to DMARC failures because the forwarded emails or those sent via aliases do not maintain the necessary SPF or DKIM alignment with your primary domain. While a p=none policy allows these emails to pass due to local overrides, stricter policies instruct recipient mail servers to take action against unaligned messages, potentially leading to internal emails being flagged as spam or rejected entirely.
Key findings
- DMARC failure likelihood: G Suite aliases and email forwarding frequently cause DKIM misalignment, leading to DMARC authentication failures for internal emails.
- Impact of stricter policies: A p=none policy usually allows unaligned emails to pass due to local policies, but p=quarantine or p=reject can result in internal emails being marked as spam or blocked.
- Gmail's role: Gmail's support for ARC (Authenticated Received Chain) might mitigate some issues by preserving authentication results across forwarding hops, but it is not a guaranteed fix for all scenarios.
- Domain alignment limitations: Achieving DMARC alignment (specifically DKIM) with G Suite aliases that rely on a parent company's different sending domain is currently not straightforward and has been a long-standing challenge.
Key considerations
- Prioritize authentication fixes: Before transitioning to a stricter DMARC policy, it is crucial to address the underlying authentication issues causing DMARC failures for internal email flows. For a guide on safe implementation, see how to implement DMARC p=reject safely.
- Gradual policy transition: If proceeding with a stricter policy, start with a low percentage using pct=1 for p=quarantine to monitor the impact on a small fraction of mail. This allows you to observe DMARC reports for any unexpected failures without disrupting all internal communications. You can learn more about how email forwarding impacts DMARC in this article by GoDMARC.
- Monitor DMARC reports diligently: Regularly review your DMARC aggregate and forensic reports (if available) to identify any internal email streams being negatively affected by the new policy. This is key to safely transitioning your DMARC policy.
- Test thoroughly: Before full deployment, consider using a controlled testing environment or a small subset of internal users to gauge the impact. This allows for proactive problem-solving.
What email marketers say
Email marketers often face the dilemma of balancing security with practicality, especially when internal email configurations like G Suite aliases and forwarding interfere with DMARC authentication. Many express concern that a stricter DMARC policy could inadvertently disrupt internal communications. They highlight the challenge of maintaining DMARC alignment when emails are re-routed or sent from domains not directly under their control, leading to potential deliverability issues for legitimate internal mail.
Key opinions
- Risk of internal mail disruption: There's a significant worry that moving to p=quarantine or p=reject might cause internal emails (especially those using aliases or forwarding) to be filtered as spam or blocked.
- Alias challenges: G Suite aliases are a common source of DMARC misalignment issues, as the sending domain might not match the original From: domain when forwarding is involved.
- Dependence on local policy: Many organizations currently rely on recipient mail servers' local_policy to deliver otherwise DMARC-failing internal emails, which becomes precarious with stricter DMARC policies.
Key considerations
- Cautious approach: It is often advised to adopt a very gradual rollout, starting with a low percentage to observe the impact on internal communications without a full-scale disruption. This allows for careful monitoring of DMARC reports, as discussed in this article on GoDMARC.
- Authentication first: The consensus is to resolve underlying authentication problems (SPF and DKIM alignment) before even considering a stricter DMARC policy. You can refer to a simple guide to DMARC, SPF, and DKIM for foundational knowledge.
- Monitoring is critical: Continuous monitoring of DMARC reports is essential to catch any unforeseen internal deliverability issues immediately upon policy changes. This helps in understanding how to test email deliverability with new configurations.
Email marketer from Email Geeks suggests that their internal emails using G Suite aliases are all being forwarded, causing DKIM unalignment and DMARC failures. They currently rely on a local policy override to ensure delivery.
Email marketer from Email Geeks expresses concern that a stricter DMARC policy might disrupt the deliverability of their internal emails due to the current DMARC failures.
What the experts say
Deliverability experts largely agree that while a stricter DMARC policy is beneficial for external security, it presents unique challenges for internal email flows, particularly those involving forwarding or aliases. They emphasize that DMARC failures, when a policy is at p=quarantine or p=reject, will likely result in increased rejection rates unless underlying authentication issues are addressed. They advocate for a cautious, data-driven approach, leveraging DMARC reports and gradual policy implementation to mitigate risks.
Key opinions
- Gmail's handling: Gmail may utilize ARC to correctly handle forwarded mail, potentially preserving DMARC authentication results across hops. However, this isn't a guaranteed solution for all scenarios involving aliases or forwarding.
- Expect increased failures: If internal emails are currently unaligned and DMARC is failing, a stricter policy will likely lead to an increase in actual rejections or quarantines as recipient ISPs follow the DMARC instructions.
- Authentication is paramount: It's strongly recommended to fix all authentication issues for legitimate internal mail flows before making any DMARC policy stricter than p=none. This includes ensuring SPF and DKIM are correctly configured for all sending sources.
Key considerations
- Phased implementation: A cautious approach using p=quarantine with a low pct value (e.g., pct=1) is advised to gain confidence and monitor for issues, treating it like a maintenance window. This aligns with guidance on when to use different DMARC policies.
- Monitor DMARC reports: Continuous and detailed analysis of DMARC aggregate reports is crucial to identify traffic that fails authentication and assess the impact of policy changes on internal email streams. This helps in understanding the effects of email forwarding on DMARC.
- G Suite specific challenges: Be aware that achieving DMARC alignment for G Suite aliases, especially when they involve forwarding through a different parent domain, can be a persistent challenge that Google has yet to fully resolve.
Deliverability expert from Email Geeks indicates that it's very possible internal mail will be rejected once a stricter DMARC policy like p=reject is applied to unaligned DKIM emails, depending on Gmail's internal handling.
Deliverability expert from Email Geeks notes that while Gmail does perform ARC, which helps with forwarded emails, it might not solve all DMARC alignment issues stemming from G Suite aliases.
What the documentation says
Official documentation and technical specifications for DMARC, SPF, and DKIM consistently highlight the importance of domain alignment for successful authentication. When email forwarding or aliases re-write message headers in a way that breaks this alignment, DMARC policies can result in failed authentication. While some receiving mail systems (like Gmail with ARC) attempt to preserve authentication chains, this is not universally guaranteed, making careful configuration essential, especially for internal mail flows that are often taken for granted.
Key findings
- DMARC alignment requirements: For an email to pass DMARC, either the SPF or DKIM domain must align with the From: header domain.
- Forwarding impact: Email forwarding, especially when the forwarding server modifies the message or its path, can invalidate SPF records and sometimes DKIM signatures, leading to DMARC failures.
- ARC as a mitigation: The Authenticated Received Chain (ARC) is designed to allow intermediate mail servers (like forwarders) to attest to the original authentication results, helping DMARC pass even after modifications. However, not all systems support or correctly implement ARC.
- RFC 7489 on DMARC: The DMARC RFC (RFC 7489) outlines the policy's intent for reporting and enforcement, but implicitly assumes that legitimate mail is properly authenticated, which might not be the case with complex internal setups.
Key considerations
- Careful configuration of internal mail flow: Organizations should configure internal mail relays, aliases, and forwarding rules to preserve SPF and DKIM authentication whenever possible to avoid DMARC failures.
- Vendor-specific documentation: Consult G Suite (Google Workspace) documentation for best practices on configuring aliases and internal routing to minimize DMARC impact. Some specific solutions for SPF alignment with Google Workspace alias domains exist.
- Monitor DMARC reports: The documentation for DMARC reporting is critical. It allows administrators to identify sources of DMARC failure, including those originating from internal email flows, before moving to a stricter enforcement policy. This is covered in a list of DMARC tags and their meanings.
Documentation from RFC 7489 (DMARC) states that for an email to pass DMARC, it must pass either SPF or DKIM authentication, and the domain used for that authentication must align with the domain in the From: header.
Documentation from M3AAWG (Messaging Anti-Abuse Working Group) highlights that email forwarding frequently breaks SPF validation because the original sender's IP address is no longer the last hop, leading to SPF fail results.
