Summary
Even when SPF and DMARC pass, DKIM failures with Yahoo emails can stem from a multitude of interconnected issues. These include alignment problems between SPF, the 5322.from address, and DKIM; Yahoo's stricter DMARC implementation combined with inconsistent domain policies; DNS instability; message content modification during transit; incorrect DKIM configuration (such as selector mismatches, key size limitations, and syntax errors in DKIM records); problems with DKIM signing consistency; and negative domain reputation. Comprehensive troubleshooting involves examining email headers, DNS records, and mail server logs; using DKIM record lookup tools; registering for Yahoo's feedback loop; and monitoring DMARC aggregate reports.
Key findings
- Alignment: Mismatched SPF, 5322.from, and DKIM domains can trigger DMARC failures.
- Yahoo Policies: Yahoo's DMARC policies and enforcement can cause DKIM failures even with technically valid configurations.
- Infrastructure: DNS issues and MTA misconfigurations can lead to DKIM PermFail errors.
- Message Integrity: Modifications to email content during transit invalidate DKIM signatures.
- DKIM Configuration: Incorrect selectors, key sizes, or record syntax cause DKIM failures.
- DKIM signing: Inconsistent application of DKIM signing to all outgoing emails.
- Domain Reputation: Poor domain reputation results in stricter enforcement by Yahoo.
Key considerations
- DMARC Monitoring: Set up and actively monitor DMARC aggregate reports.
- Record validation: Use DKIM record lookup tools to validate and diagnose DKIM issues.
- Feedback Loops: Subscribe to Yahoo's feedback loop for deliverability information.
- Key Size & Encryption: Use a sufficient (e.g., 2048-bit) DKIM key for enhanced security.
- DNS Stability: Ensure your DNS records propagate and are globally available.
- Policy Testing: Temporarily change DMARC settings to understand interaction
What email marketers say
11 marketer opinions
Even when SPF and DMARC pass, DKIM failures with Yahoo can stem from various issues, including Yahoo's stricter DMARC policies, DKIM alignment problems (where the signing domain doesn't match the 'From' domain), intermittent DNS issues, message modification in transit, DKIM selector misconfiguration, insufficient DKIM key sizes, or sporadic DKIM signing. Domain reputation, DNS stability, and syntax errors in DKIM records can also contribute to these failures. Registering for Yahoo's feedback loop and using DKIM record lookup tools can aid in diagnosis and resolution.
Key opinions
- Alignment: DKIM alignment is crucial. Ensure the domain used for signing matches the 'From' domain.
- Yahoo Policy: Yahoo's DMARC policies are strict and can cause issues even if DKIM passes technically.
- DNS: Intermittent DNS issues can cause DKIM failures. Check DNS propagation and stability.
- Message Tampering: Message modification during transit can invalidate the DKIM signature.
- DKIM Configuration: Incorrect DKIM selector, syntax errors in DKIM record, or small key sizes (less than 1024) can cause failures.
- Signing Consistency: Sporadic DKIM signing can lead to deliverability issues.
- Domain Reputation: Low domain reputation may trigger stricter scrutiny from Yahoo.
Key considerations
- DMARC Reports: Set up DMARC aggregate reports to identify failing emails and diagnose issues.
- Key Size: Upgrade to a 2048-bit DKIM key for improved security and compliance.
- Yahoo Feedback Loop: Register for Yahoo's feedback loop to receive detailed deliverability reports.
- Record Validation: Use DKIM record lookup tools to ensure the DKIM record is valid and reachable.
- Signing Consistency: Ensure that you are DKIM signing all outgoing emails
- Domain Reputation: Ensure to check and improve domain reputation as Yahoo will scrutinize senders with low reputation
Marketer view
Email marketer from StackOverflow user explains that intermittent DNS issues can cause temporary DKIM failures. They recommend checking DNS propagation and stability.
11 Jan 2024 - StackOverflow
Marketer view
Email marketer from SparkPost explains ensuring the DKIM signing process is consistently applied to outgoing emails. SparkPost mentions issues with sporadic DKIM signing which means not every email is signed, it can cause deliverability problems.
6 Aug 2021 - SparkPost
What the experts say
7 expert opinions
Even with passing SPF and DMARC, DKIM failures in Yahoo emails can be caused by a variety of factors. These include alignment issues between SPF, the 5322.from address, and DKIM; problems with the DKIM signature itself (due to message alterations or encoding issues); misconfigured DKIM settings (such as deleted keys or MTA misconfiguration); transient issues like DNS server downtime; potential policy issues beyond DMARC, such as duplicate headers; and invalid DKIM signatures detected by Yahoo. It's crucial to monitor DMARC aggregate reports and troubleshoot DKIM at a granular level to identify and rectify these issues.
Key opinions
- Alignment Issues: Mismatch between SPF, the 5322.from address, and DKIM can lead to DMARC rejections.
- DKIM Perm Fail: DKIM failures (Perm Fail) can be caused by key deletion, MTA misconfiguration, or DNS problems.
- Signature Validation: Online DKIM checkers may not fully validate signatures; encoding issues can cause DKIM to fail.
- Message Alteration: Alterations to the email content during transit can invalidate the DKIM signature.
- Yahoo Specific Rejection: Yahoo may reject messages with invalid DKIM signatures even when SPF and DMARC pass.
Key considerations
- DMARC Policy Testing: Temporarily change DMARC policy (p=reject to p=none) to determine if DMARC is the primary cause.
- Header Review: Check for duplicate headers that might be causing policy rejections.
- DMARC Reports: Set up DMARC aggregate reports to identify which specific emails are failing DKIM.
- Detailed Troubleshooting: Investigate DKIM failures at a granular level to identify root causes (encoding, configuration, etc.).
Expert view
Expert from Email Geeks suggests temporarily changing the DMARC policy from p=reject to p=none to determine if the issue is DMARC-related.
28 Oct 2023 - Email Geeks
Expert view
Expert from Email Geeks explains that DKIM Perm fail can be caused by deleting the public DKIM key from DNS, misconfiguring the MTA, or a DNS server being down.
27 Nov 2022 - Email Geeks
What the documentation says
5 technical articles
DKIM failures with Yahoo, despite passing SPF and DMARC, can arise from various technical issues. These include invalid DKIM signatures due to email content modifications during transit, domain mismatches between the signing domain and the 'From' header, syntactically incorrect signatures, unavailable public keys, failed signature verification, incorrect key deployment, DNS propagation issues, and mismatches between the DKIM selector and the configured DNS settings. Proper troubleshooting involves examining email headers, DNS records, and mail server logs to identify the specific cause.
Key findings
- Signature Validity: DKIM signatures can be invalidated by modifications during transit.
- Domain Mismatch: The signing domain must align with the 'From' header domain.
- Technical Errors: Syntax errors, unavailable keys, and failed verification can cause DKIM failures.
- Deployment Issues: Incorrect key deployment and DNS propagation problems can disrupt DKIM.
- Selector Mismatch: DKIM selector must match the configured DNS settings.
Key considerations
- Header Examination: Thoroughly examine email headers for modifications and domain discrepancies.
- DNS Record Review: Carefully review DNS records to ensure correct key deployment and selector configuration.
- Log Analysis: Analyze mail server logs for detailed information on DKIM verification failures.
- DNS Propagation: Ensure DNS records have propagated and are available.
Technical article
Documentation from ietf.org (RFC 6376) states that DKIM verification can fail (return PERMFAIL) if the signature is syntactically incorrect, the public key is unavailable, the signature does not verify, or the message has been altered since signing.
23 May 2022 - ietf.org
Technical article
Documentation from Yahoo Help explains that a DKIM failure, even with passing SPF and DMARC, can occur if the DKIM signature is invalid due to modifications to the email content during transit or if the signing domain doesn't match the domain in the 'From' header.
30 Nov 2021 - Yahoo Help
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