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

Summary

SPF flattening involves converting complex SPF records with multiple mechanisms (like 'include', 'a', 'mx') into a simplified record containing only IP addresses. This is primarily done to overcome the 10 DNS lookup limit, which is a common cause of SPF PermErrors that can impact email deliverability. However, implementing SPF flattening can introduce complexities when using email evaluation tools like MxToolbox or Litmus, as these tools may struggle to correctly interpret flattened records or SPF macros.

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What email marketers say

Email marketers frequently encounter challenges with SPF records, particularly when attempting to manage complex sending infrastructures or comply with the 10 DNS lookup limit. Many turn to SPF flattening services or SPF macros as solutions, only to find that common email evaluation tools report issues, leading to confusion and friction with their IT teams.

Marketer view

Marketer from Email Geeks indicates that they are encountering an issue where Litmus and MxToolbox are reporting problems with their SPF record, despite their IT team confirming that the setup is correct. They are questioning if SPF flattening could be the cause of this discrepancy.

22 Sep 2024 - Email Geeks

Marketer view

Marketer from SendLayer Blog notes that SPF flattening simplifies SPF records by directly listing IP addresses, which can make it easier to visually inspect which senders are authorized for a domain. This is useful for quick verification.

24 Jul 2024 - SendLayer Blog

What the experts say

Experts in email deliverability acknowledge that SPF flattening and the use of SPF macros are valid strategies for managing complex SPF records and staying within the 10 DNS lookup limit. However, they also confirm that many existing SPF evaluation tools are not designed to accurately process these advanced configurations, leading to widespread confusion among users and misinterpretations of SPF record health.

Expert view

Expert from Email Geeks (Steve589) clarifies that many SPF evaluation tools indeed have trouble correctly processing SPF macros. This suggests that the issues reported by tools like MxToolbox and Litmus could stem from this incompatibility.

09 Oct 2024 - Email Geeks

Expert view

Expert from Word to the Wise (Steve589) admits that their own SPF checker at tools.wordtothewise.com "fails horribly" on SPF macros. This highlights the widespread nature of the issue across various evaluation platforms.

09 Oct 2024 - Word to the Wise

What the documentation says

Official documentation and technical guides confirm that SPF flattening is a workaround for the 10 DNS lookup limit inherent in SPF. While it addresses this specific technical constraint, the process of flattening itself can introduce complexities that may not be fully supported by all SPF evaluation tools, which are often built to parse the original SPF record syntax.

Technical article

Documentation from AutoSPF Blog explains that SPF flattening reduces the number of records that require updating, offering a simpler management approach compared to frequently changing multiple 'include' mechanisms.

01 Mar 2024 - AutoSPF Blog

Technical article

Documentation from URIports Blog discusses how flattening an SPF record to include only ip4 and ip6 addresses can decrease DNS lookups, but cautions that it may not always be the most reliable long-term solution due to its static nature.

01 Apr 2025 - URIports Blog

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