Summary
DKIM and DMARC failures in Gmail stem from a combination of technical and configuration issues. Alignment problems, where the 'From' address domain does not match the DKIM signing domain or SPF authorized sending source, are a major cause. This is sometimes due to Gmail's 'you must align' directive. Incorrectly configured or outdated DNS records (SPF, DKIM, and DMARC) are also frequent culprits. Other factors include inadequate DKIM key sizes, email forwarding, and using third-party email services with misconfigured authentication. A review of DNS settings and use of reporting and email testing tools are crucial to address these issues.
Key findings
- Alignment Problems: DMARC failures occur when the 'From' address domain doesn't align with the DKIM signing domain or SPF authorized sending source.
- Gmail Alignment Directive: Gmail's 'you must align' directive from October 2023 affects how DMARC is evaluated.
- DNS Configuration Issues: Incorrectly configured DNS records, including SPF, DKIM, and DMARC, are a common cause.
- DKIM Key Size: DKIM failures can occur if the key size is less than 1024 bits; 2048 bits is recommended.
- Forward/Reverse DNS Mismatch: Mismatched forward and reverse DNS records can lead to authentication failures.
- Third-Party Services: Improper configuration of DKIM and SPF by third-party email service providers can cause failures.
- Email Forwarding: Email forwarding can break DKIM and SPF, leading to DMARC failures.
Key considerations
- Verify Domain Alignment: Ensure that the domain used in the 'From' address matches the domain used for DKIM signing and SPF authentication.
- Check DNS Records: Carefully review SPF, DKIM, and DMARC records in DNS for errors, typos, and correct values.
- Upgrade DKIM Key Size: If using a DKIM key size less than 1024 bits, upgrade to 2048 bits.
- Match Forward/Reverse DNS: Ensure your sending server's IP address has a matching forward and reverse DNS record.
- Configure Third-Party Services: If using a third-party email service, verify their DKIM and SPF settings align with your domain.
- Avoid Email Forwarding: Avoid email forwarding or use methods that preserve authentication.
- Check DMARC Reports: Examine DMARC reports to identify sources of authentication failures.
- Email Testing Tools: Use testing tools to validate the SPF, DKIM and DMARC records. Also check the Authentication-Results: are passing or failing.
What email marketers say
9 marketer opinions
DKIM and DMARC failures in Gmail are often due to alignment issues between the 'From' address domain and the domain used for DKIM signing or SPF authentication. Other common causes include incorrect DNS configuration, outdated DKIM keys, email forwarding, and using third-party email services with misconfigured records. Checking DMARC reports, DNS records, and email headers with testing tools is crucial for identifying and resolving these issues.
Key opinions
- Alignment Issues: DMARC failures often occur when the 'From' address domain doesn't align with the DKIM signing or SPF authentication domain.
- DNS Misconfiguration: Incorrectly configured or outdated DNS records (SPF, DKIM, DMARC) are a frequent cause of authentication failures.
- Third-Party Services: Using third-party email services with improperly configured DKIM or SPF records can lead to DMARC failures.
- Email Forwarding: Email forwarding can break DKIM and SPF, resulting in DMARC failures.
- Importance of Testing: Utilizing testing tools to check DKIM, DMARC records, and email headers is vital for identifying issues.
- DMARC Reports: Analyzing DMARC reports can reveal sources failing authentication, such as misconfigured sending servers or unauthorized sources.
Key considerations
- Check Alignment: Verify that the domain in your 'From' address matches the domain used for DKIM signing and SPF authentication.
- Review DNS Records: Double-check DNS records for typos, incorrect values, and proper propagation. Use online tools to validate your records.
- Third-Party Configuration: If using a third-party email service, ensure their DKIM signature and SPF record are correctly set up to align with your domain.
- Avoid Forwarding: If possible, avoid email forwarding or use alternative solutions that don't break authentication.
- Implement DMARC Policy: Start with a 'p=none' DMARC policy to monitor results before implementing stricter policies (p=quarantine or p=reject).
- Analyze DMARC Reports: Regularly analyze DMARC reports to identify and address authentication failures.
- Key Rotation: Ensure you rotate DKIM keys often for a better security stance.
Marketer view
Email marketer from Email Geeks explains DMARC failures occur when neither DKIM nor SPF are aligned, which is a common cause for emails landing in the spam folder. It is a sender issue where they should be looking at the headers.
14 Jul 2023 - Email Geeks
Marketer view
Email marketer from Reddit shares that a common reason for DKIM/DMARC failure in Gmail is when you're using a third-party email service, and their DKIM signature or SPF record isn't properly set up to align with your domain. Contacting their support to ensure proper configuration is crucial.
22 Apr 2022 - Reddit
What the experts say
4 expert opinions
DKIM and DMARC failures in Gmail can be caused by a variety of factors. Google may report DKIM as failed due to a lack of alignment between the DKIM signature's 'd=' and the 5322.from address, even if the cryptographic validation passes. This issue may be related to Gmail's 'you must align' directive. DMARC failures can also stem from incorrectly configured DNS records or mismatched forward and reverse DNS records, both of which are important for establishing trust with receiving mail servers.
Key opinions
- Alignment Reporting: Google may report DKIM failures due to alignment issues, even if the signature is cryptographically valid.
- Gmail Directive: Gmail's 'you must align' directive may be a contributing factor to DKIM/DMARC failures.
- DNS Configuration: Incorrectly configured DNS records are a common cause of DMARC failures.
- Mismatched DNS Records: Mismatched forward and reverse DNS records can lead to deliverability and authentication failures.
Key considerations
- Check Alignment: Verify the alignment between the DKIM signature's 'd=' and the 5322.from address in your email headers.
- Review Gmail's Directives: Stay informed about Gmail's latest email authentication requirements and directives.
- Verify DNS Configuration: Carefully check your DNS zone file for correct SPF, DKIM, and DMARC record configurations.
- Match DNS Records: Ensure your sending server's IP address resolves to the correct hostname and vice versa.
Expert view
Expert from Email Geeks explains that the DKIM failure might be a reporting choice by Google due to lack of alignment between the 'd=' in the DKIM signature and the 5322.from address, even if the DKIM signature itself passes cryptographic validation.
28 Aug 2022 - Email Geeks
Expert view
Expert from Word to the Wise answers that DMARC failures often stem from not having the DNS records configured correctly. Check your DNS zone file very carefully to make sure that your records are valid and fully propagated. Double check the records with a DNS lookup tool to ensure there are no typos and that it is returning what you expect.
4 Nov 2024 - Word to the Wise
What the documentation says
4 technical articles
DKIM and DMARC failures in Gmail can stem from several technical issues. Google Workspace Admin Help highlights that DKIM failures may occur with key sizes less than 1024 bits, recommending 2048-bit keys for better security. Dmarcian explains that DMARC failures often arise from domain mismatches between the DKIM signature or SPF records and the 'From' address. Microsoft Learn notes that incorrect SPF configuration can also cause DMARC to fail. For AWS SES users, properly adding DKIM DNS records provided by AWS is crucial for successful DKIM authentication.
Key findings
- Inadequate DKIM Key Size: DKIM key sizes less than 1024 bits can cause failures; 2048 bits is recommended.
- Domain Mismatch: Mismatches between the DKIM/SPF domains and the 'From' address domain lead to DMARC failures.
- SPF Configuration Errors: Incorrectly configured SPF records can cause DMARC to fail.
- AWS SES DKIM Setup: Incorrectly added or missing DKIM DNS records in AWS SES result in DKIM failures.
Key considerations
- Upgrade DKIM Key Size: Ensure your DKIM key size is at least 2048 bits for optimal security and compatibility.
- Verify Domain Alignment: Confirm that the domains used for DKIM signing and SPF authentication align with the domain in your 'From' address.
- Correct SPF Configuration: Review your SPF record to ensure it includes all authorized sending sources and is properly formatted.
- Validate AWS SES DKIM Records: If using AWS SES, double-check that the DKIM DNS records provided by AWS are correctly added to your domain's DNS settings.
Technical article
Documentation from Microsoft Learn explains that if SPF is not configured correctly, it can cause DMARC to fail. Ensure that the SPF record includes all authorized sending sources for your domain and that the record is properly formatted to prevent authentication issues.
3 Aug 2023 - Microsoft Learn
Technical article
Documentation from dmarcian explains that DMARC failures typically occur when there is a mismatch between the domain used to sign the email (DKIM) or the sending IP address (SPF) and the domain in the 'From' address of the email. This lack of alignment causes DMARC to fail and can lead to deliverability issues.
11 Feb 2022 - dmarcian
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