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Should DMARC checks focus on SPF HELO or Return-Path and should you focus on DKIM or SPF?

Summary

When implementing DMARC, a common point of confusion arises regarding which SPF identity DMARC checks should align with: the HELO domain or the Return-Path (also known as MAILFROM). This issue is compounded by the fact that some email security vendors may implement DMARC validation differently than what is commonly practiced or recommended by the DMARC specification. Simultaneously, there's a broader question of whether email authentication efforts should prioritize DKIM over SPF due to SPF's limitations with email forwarding and intermediary services.

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What email marketers say

Email marketers often face practical challenges when dealing with DMARC implementations, particularly when third-party services or email security gateways deviate from expected authentication behaviors. Their experiences highlight the real-world impact of technical configurations on email deliverability and business-critical communications. The emphasis shifts from theoretical RFC adherence to ensuring emails reliably reach the inbox.

Marketer view

Marketer from Email Geeks explains they are struggling with an issue where Trend Micro is checking SPF alignment on the HELO domain instead of the MAILFROM domain for incoming DMARC checks, despite most webmails and antispam systems using MAILFROM.

03 Jul 2024 - Email Geeks

Marketer view

Marketer from Mxtoolbox Community discusses how misconfigured SPF records can cause emails to be soft-failed or even rejected, significantly impacting deliverability to recipients.

15 Feb 2024 - Mxtoolbox Community

What the experts say

Email deliverability experts consistently advocate for adherence to established RFCs while acknowledging the realities of diverse email system implementations. Their insights provide crucial guidance on prioritizing authentication methods and troubleshooting complex DMARC-related issues. The consensus leans towards a stronger reliance on DKIM for DMARC alignment due to SPF's inherent limitations.

Expert view

Expert from Email Geeks suggests exploring why an aligned DKIM domain might not be signing correctly before focusing solely on SPF issues, as DKIM is often the more reliable indicator.

03 Jul 2024 - Email Geeks

Expert view

Expert from Spam Resource emphasizes that DMARC's primary goal is to enforce alignment, and both SPF and DKIM must align with the From: header domain for successful validation.

01 Jun 2024 - Spam Resource

What the documentation says

Official documentation and RFCs provide the foundational understanding for email authentication protocols. While these documents define the technical specifications, their interpretation and implementation by various systems can sometimes vary. It is essential to refer to these authoritative sources to understand the intended behavior of SPF, DKIM, and DMARC.

Technical article

Documentation from RFC 7489 (DMARC) specifies that the HELO SPF identity is not typically used in the context of DMARC alignment checks, emphasizing the importance of the 'MAIL FROM' identity instead.

01 Jan 2020 - RFC 7489

Technical article

Documentation from RFC 7208 (SPF) outlines that an SPF check can authenticate either the HELO identity or the MAIL FROM identity, offering flexibility in its application before DMARC alignment is considered.

01 Jan 2014 - RFC 7208

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