Why are legitimate emails blocked when DMARC policy is higher than p=none?

Email marketer from EmailGeeks Community Forum user MailGuru responds to a question about DMARC issues, commenting that misconfiguration of email authentication protocols such as SPF and DKIM is a major cause. Also, use of multiple email sending services/servers is a high risk when you have a higher DMARC policy.

Marketer from Email Geeks shares an edge case where using a free version of Google calendar with a custom email that’s not Google Workspace sometimes results in rejection notices due to DMARC policy, particularly with Microsoft recipients.

Email marketer from SendGrid explains that implementing a strict DMARC policy (p=quarantine or p=reject) can lead to legitimate emails being blocked if the SPF or DKIM records are not correctly set up, or if the emails are altered during forwarding or mailing list processing. This highlights the importance of correct configuration and monitoring.

Email marketer from EasyDMARC suggests that when DMARC policies are set to quarantine or reject, legitimate emails might get blocked due to improper implementation of SPF and DKIM, specifically missing includes in SPF records or issues with DKIM key rotation. Also highlights that third party sending could have issues.

Email marketer from Reddit user u/email_expert explains that a common reason for legitimate emails being blocked with a stricter DMARC policy is misconfigured SPF records or broken DKIM signatures. Forwarding emails also can invalidate SPF as the source IP is no longer the original sending server.

Marketer from Email Geeks suggests considering that the MBP could have a local override of your policy.

Email marketer from Email Marketing Forum user Techguy mentions that DMARC can flag legitimate emails when businesses use multiple email marketing platforms that aren't properly configured with SPF and DKIM. He highlights the importance of aligning all sending sources with the DMARC policy.

Email marketer from Proofpoint notes that a strict DMARC policy, if not properly configured, can block legitimate emails because they fail authentication checks due to SPF limitations or DKIM signing issues. Correct configuration of SPF and DKIM is key to avoiding deliverability problems.

Marketer from Email Geeks explains that Outlook doesn't do anything when forwarding invites, so it uses the original 5322 domain which fails DMARC in some cases.

Email marketer from Mailjet explains that DMARC policies can cause legitimate emails to be blocked if the sender's domain is being spoofed or if the sender's email infrastructure isn't properly authenticated, even if the email itself isn't spam. Mailjet highlights that it can be as simple as a misconfiguration of SPF or DKIM.

Email marketer from Postmark shares that DMARC failures for legitimate emails commonly occur due to forwarding or mailing list practices that break SPF or DKIM. They suggest using SRS (Sender Rewriting Scheme) to mitigate these issues.

Email marketer from SparkPost points out that emails can fail DMARC checks if they are forwarded or processed by mailing lists, particularly if the SPF record doesn't include the forwarding server's IP or if DKIM signatures are invalidated during transit. SparkPost advises senders to monitor DMARC reports to identify and address these issues.

Marketer from Email Geeks shares that authentication allows mailbox providers to anchor reputation to the authenticated identity. A sender with a poor reputation can pass DMARC checks and be confidently blocked based on the sending history of the authenticated identity.

Marketer from Email Geeks explains that a downside risk of DMARC policies of quarantine/reject is that some email will fail authentication due to network problems and thus fail DMARC, but that should be minimal.

Email marketer from Cloudflare explains that common causes of DMARC failures are forwarding, using third-party email services that aren't configured correctly, and failing to keep SPF and DKIM records up to date. This can lead to legitimate emails being blocked or sent to spam.

Marketer from Email Geeks shares to consider rogue sending; for example, if some people at work open a MailChimp account without telling anyone, that's mail that will fail authentication.

Expert from Email Geeks explains that DMARC failures causing rejections at p=reject are due to authentication failures. This can be caused by people spoofing your domain, misconfigured DKIM or SPF, or random issues like email forwarding that breaks DKIM signatures.

Expert from Word to the Wise explains that legitimate emails can be blocked under strict DMARC policies due to common issues such as email forwarding, where the forwarded email fails SPF checks because the sending server doesn't match the original domain's SPF record. Laura suggests implementing SRS (Sender Rewriting Scheme) to address forwarding issues.

Expert from Spam Resource explains that when DMARC policies are set to reject or quarantine, legitimate emails can be blocked if they fail authentication, often because of forwarding issues where the SPF check fails. Also highlights the importance of DKIM and aligning the 'From:' domain with SPF/DKIM.

Expert from Email Geeks responds that if DMARC passes and you get blocked, it's not DMARC that was at fault. DMARC just made it easier for the ISP or MBP to identify you as you.

Documentation from DMARC.org notes that legitimate emails can be affected if they are forwarded in a way that breaks SPF or DKIM. This is often due to changes made by forwarding services that are not DMARC-aware, leading to authentication failures and subsequent blocking or spam filtering.

Documentation from RFC Editor explains that DMARC policy, when set to quarantine or reject, instructs receiving mail servers to handle messages that fail authentication based on the policy. This means legitimate emails lacking proper authentication can be quarantined or rejected, as intended by the domain owner's policy, to prevent spoofing and phishing attacks.

Documentation from Google Workspace Admin Help explains that legitimate emails can be blocked by DMARC if they fail authentication checks (SPF or DKIM) due to forwarding, mailing list modifications, or misconfigured sending servers, even when the sender is not intentionally spoofing the domain.

Documentation from Microsoft Learn discusses that DMARC policies, when strictly enforced, can block legitimate emails if SPF and DKIM records are not properly configured or if the email is altered in transit (e.g., by a forwarding service). This is intended to prevent spoofing but can unintentionally affect normal mail flow.