How does SPF flattening affect email evaluation tools and are there alternatives?

Summary

SPF flattening aims to mitigate DNS lookup limits, but it may not be universally compatible with email evaluation tools due to issues with macro handling and complex records. Experts and marketers recommend DKIM and DMARC as alternatives for robust authentication, as they don't rely on DNS lookups in the same way as SPF. Managing includes, segmenting sending domains, and regularly validating and updating SPF records are crucial. Comprehensive testing with multiple tools and continuous monitoring of deliverability metrics are also essential for maintaining email deliverability.

Key findings

  • Tool Compatibility Issues: Some email evaluation tools struggle with SPF macros, flatteners, and complex records, leading to false positives and inaccurate results.
  • DNS Lookup Limits Impact: SPF records are subject to DNS lookup limits; exceeding these limits causes authentication failures and negatively impacts deliverability.
  • DKIM/DMARC as Alternatives: DKIM and DMARC provide reliable alternatives to SPF, offering authentication methods that don't rely on DNS lookups and enhance overall email security.
  • Importance of Record Management: Careful management of SPF records, including limiting includes and regularly evaluating entries, is essential for avoiding DNS lookup issues.

Key considerations

  • Evaluate Flattening Necessity: Assess whether SPF flattening is truly necessary, as too many unnecessary elements in the SPF record can create problems.
  • Regular Record Validation: Routinely validate SPF records and monitor deliverability metrics to verify their accuracy and effectiveness in preventing deliverability issues.
  • Implement Multi-Tool Testing: Use multiple reputable testing tools and/or manual verification methods to ensure accurate SPF record configuration.
  • Monitor DNS Propagation: Be aware that SPF flattening may cause temporary deliverability issues due to DNS propagation delays, and monitor DMARC reports for insights.
  • Keep Records Updated: If SPF flattening is used, keep the flattened record updated whenever any included IP ranges are changed to avoid authentication failures.

What email marketers say
10Marketer opinions

SPF flattening aims to resolve DNS lookup limitations in SPF records, but it doesn't guarantee universal compatibility with email evaluation tools. Alternatives like DKIM offer authentication without DNS lookups. Regular SPF record validation, deliverability monitoring, and multi-tool testing are essential. Managing SPF includes, segmenting sending domains, and promptly updating records after changes are also key.

Key opinions

  • DNS Lookup Limits: SPF flattening helps address DNS lookup limits, which can cause authentication failures if exceeded.
  • Tool Incompatibilities: Some email evaluation tools struggle with complex SPF records or macros, leading to inaccurate results.
  • DKIM Alternative: DKIM offers a reliable alternative to SPF, providing authentication without relying on DNS lookups.
  • Comprehensive Testing: Using multiple testing tools and manual verification helps ensure SPF records are accurate.

Key considerations

  • Monitor Changes: Monitor SPF records and deliverability metrics after implementing flattening, as DNS propagation delays can cause temporary issues.
  • Record Updates: If flattening is used, keep the flattened record updated whenever any included IP ranges are changed.
  • Managed Includes: Avoid too many includes in the SPF record to minimize DNS lookup limits. Consider segmenting sending domains to distribute the SPF load.
  • Use Alternative Tools: Comprehensive deliverability testing tools provide insight into how different email providers handle the email, which can help mitigate SPF and evaluation issues.
  • Regular Validation: Routinely validate SPF records to ensure accuracy and effectiveness in preventing deliverability problems.
Marketer view

Email marketer from NeilPatel.com shares that SPF records should be optimized to avoid exceeding the DNS lookup limit. While flattening can help, carefully managing included domains and services is crucial to prevent deliverability issues, especially when using evaluation tools that may not handle complex SPF records well.

December 2022 - NeilPatel.com
Marketer view

Email marketer from ZeroBounce points out the need to regularly validate SPF records. They further recommend monitoring deliverability metrics after any changes to SPF, including flattening, to verify effectiveness.

April 2021 - ZeroBounce
Marketer view

Email marketer from Mailgun promotes implementing DKIM to sign all outgoing emails. They indicate this offers superior email authentication and avoids SPF's DNS lookup limitations.

October 2022 - Mailgun
Marketer view

Email marketer from Sendgrid explains that while SPF flattening solves the DNS lookup issue, it is important to monitor the flattened record. If one of the included IP ranges changes, your SPF will need to be updated, which can take time to propagate.

March 2021 - Sendgrid
Marketer view

Email marketer from SparkPost shares that DKIM offers an alternative to SPF flattening, providing authentication without DNS lookups. They also advise segmenting sending domains to distribute the SPF load and using monitoring tools to detect issues before they impact deliverability.

April 2021 - SparkPost
Marketer view

Email marketer from Reddit explains that SPF checkers can sometimes be inaccurate with complex records. They suggest using multiple checkers and manually verifying SPF records using `dig` commands to ensure accuracy before making changes.

August 2022 - Reddit
Marketer view

Email marketer from EasyDMARC shares that SPF flattening may cause temporary deliverability issues due to DNS propagation delays. It is better to implement DKIM and monitor DMARC reports.

December 2024 - EasyDMARC
Marketer view

Email marketer from Mailjet explains that SPF flattening addresses the DNS lookup limit, but it may not resolve all evaluation issues. They suggest monitoring SPF records with tools like Mailjet's SPF record checker and switching to DKIM if problems persist, as DKIM authentication relies on cryptographic signatures rather than DNS lookups.

April 2024 - Mailjet
Marketer view

Email marketer from StackExchange shares that avoiding too many includes in the SPF is key to avoid exceeding DNS lookup limits. If needing multiple ESPs, using subdomains for each one could be better than including them all in the main domain.

September 2021 - StackExchange
Marketer view

Email marketer from GlockApps recommends using comprehensive deliverability testing tools. These can identify problems with SPF records and offer insights into how different email providers handle the email.

February 2022 - GlockApps

What the experts say
6Expert opinions

SPF flattening can negatively impact email evaluation tools because some tools don't handle SPF macros, flatteners, or automation well, leading to inaccurate results. A key finding is that SPF records have limitations, like DNS lookup limits. Alternatives to flattening include using DKIM (which doesn't rely on DNS lookups) and carefully managing includes within the SPF record. Considerations include evaluating whether SPF flattening is truly necessary and managing SPF records carefully to avoid DNS lookup issues. It's recommended to test SPF records using multiple tools or manual verification.

Key opinions

  • Tool Limitations: Some email evaluation tools struggle with SPF macros, flatteners, and automation, resulting in inaccurate assessments.
  • DNS Lookup Limits: SPF records have limitations, including a maximum number of DNS lookups; exceeding these limits causes authentication failures.
  • DKIM Alternative: DKIM offers an alternative authentication method that doesn't rely on DNS lookups.

Key considerations

  • Need for Flattening: Evaluate the actual need for SPF flattening; too many unnecessary elements might be included in the SPF record.
  • Careful Management: Carefully manage SPF records to avoid DNS lookup issues by limiting includes and regularly evaluating and cleaning up entries.
  • Multiple Tests: Test SPF records using multiple evaluation tools and/or manual verification to ensure accuracy.
Expert view

Expert from Email Geeks shares that some checkers have trouble with macros and flatteners and automation in the SPF record. He suggests testing at Gmail and using the Kitterman SPF record checker.

February 2025 - Email Geeks
Expert view

Expert from Email Geeks explains that SPF macros are not handled well by some tools. His checker at tools.wordtothewise.com fails horribly on them.

February 2023 - Email Geeks
Expert view

Expert from Email Geeks suggests evaluating whether SPF flattening is truly necessary, questioning if too many unnecessary elements are included in the SPF record.

January 2023 - Email Geeks
Expert view

Expert from Spam Resource indicates carefully manage your SPF record to avoid DNS lookup issues. Using DKIM could be a good alternative, and to regularly evaluate and clean up your SPF entries.

October 2024 - Spam Resource
Expert view

Expert from Word to the Wise shares that SPF records have limitations, including a maximum number of DNS lookups. When these limits are exceeded, SPF authentication fails. Alternatives include DKIM, which doesn't rely on DNS lookups, and carefully managing includes within the SPF record.

December 2023 - Word to the Wise
Expert view

Expert from Word to the Wise explains that some tools don't handle macros or SPF flattening correctly, which can lead to false negatives when testing. They suggest using multiple test tools or a manual verification.

January 2025 - Word to the Wise

What the documentation says
5Technical articles

SPF implementations have limitations in processing macros and complex SPF records, causing evaluation errors by some tools. While flattening aims to reduce complexity, alternatives like DKIM and DMARC are recommended for robust email authentication, as DKIM isn't subject to the same DNS lookup limitations as SPF. Testing with multiple tools and monitoring deliverability are essential for proper configuration.

Key findings

  • Processing Limitations: SPF implementations struggle with macros and complex SPF records.
  • DKIM/DMARC: DKIM and DMARC offer robust email authentication alternatives, with DKIM not being subject to DNS lookup limits like SPF.
  • Evaluation Errors: Evaluation tools may misinterpret macros and SPF syntax, leading to false positives.

Key considerations

  • Multiple Testing: Test SPF records using multiple reputable tools to mitigate evaluation errors.
  • Deliverability Monitoring: Monitor email deliverability to ensure proper configuration and identify potential issues.
  • SPF Sufficiency: SPF alone may not be sufficient; implement DKIM alongside SPF and align them using DMARC.
  • Best Practices: Adhere to SPF best practices, including limiting the number of DNS lookups and monitoring SPF records for changes.
Technical article

Documentation from Microsoft explains SPF best practices, including limiting the number of DNS lookups. They recommend using alternatives like DKIM and DMARC and monitoring SPF records for changes in included services.

March 2023 - Microsoft Learn
Technical article

Documentation from Google explains that some evaluation tools may not fully support all SPF syntax or macro expansions, which could lead to false positives. It is recommended to test SPF records using multiple reputable tools and to monitor email deliverability to ensure proper configuration.

June 2024 - Google Workspace Admin Help
Technical article

Documentation from RFC Editor explains that SPF implementations have limitations in processing macros and complex SPF records. Flattening aims to reduce complexity, but some tools may still misinterpret expanded macros or have limitations on DNS lookup counts, leading to evaluation errors.

December 2021 - RFC Editor
Technical article

Documentation from IETF emphasizes the importance of adhering to SPF standards but also indicates the challenges associated with DNS lookup limits and macro evaluations. It suggests implementing DKIM and DMARC for robust email authentication.

July 2024 - IETF
Technical article

Documentation from DMARC.org suggests that SPF alone may not be sufficient for robust email authentication. It recommends implementing DKIM alongside SPF and aligning them using DMARC. DKIM offers a different authentication method that isn't subject to the same DNS lookup limitations as SPF, providing a more resilient approach to email deliverability.

October 2021 - DMARC.org