Is Google applying SPF checks to EHLO values for stricter email authentication?
Matthew Whittaker
Co-founder & CTO, Suped
Published 19 Apr 2025
Updated 12 Oct 2025
6 min read
The world of email authentication is constantly evolving, with major mailbox providers like Google frequently updating their requirements to combat spam and enhance security. A question that often comes up among email senders is whether Google has started applying SPF checks to EHLO values, adding another layer to their stricter authentication policies.
This inquiry stems from the observation that Google and Yahoo are indeed tightening their guidelines, emphasizing robust email authentication through SPF, DKIM, and DMARC. Understanding how these protocols interact with different parts of the email transaction, such as the EHLO command and the MAIL FROM address, is crucial for maintaining strong deliverability.
We will dive into the technical specifications, examine Google's stated recommendations, and explore practical insights to clarify Google's approach to SPF verification, particularly concerning the EHLO value versus the more commonly discussed MAIL FROM identity.
SPF, or Sender Policy Framework, is a foundational email authentication protocol that allows domain owners to specify which mail servers are authorized to send email on behalf of their domain. This is done by publishing an SPF record in their DNS. When a receiving mail server gets an email, it checks this record to verify the sender's legitimacy.
There are two main identities involved in an email transaction that SPF can check: the EHLO/HELO identity and the MAIL FROM (or Envelope From) identity. The EHLO/HELO command is sent at the beginning of an SMTP conversation, identifying the sending server. The MAIL FROM address is specified shortly after, indicating the return-path for bounce messages. According to RFC 7208, it is RECOMMENDED that SPF verifiers check both identities, prioritizing the HELO identity first. However, a recommendation is not a strict requirement, and many implementations vary.
The primary goal of checking EHLO first is to improve consistency and potentially reduce DNS resource usage. A HELO identity typically refers to a single host, making it a very reliable source for host authorization status. If a conclusive SPF determination can be made based on HELO, the system might avoid the more complex MAIL FROM SPF record processing.
Google's perspective on SPF verification
While RFCs provide guidelines, mailbox providers often implement their own policies based on their security needs and spam filtering strategies. Google, in its email sender guidelines, strongly recommends setting up SPF, DKIM, and DMARC. Their emphasis is on ensuring that both SPF and DKIM pass and that DMARC is published, with a focus on alignment.
When it comes to SPF, Google primarily performs checks against the MAIL FROM identity. This is the domain specified in the Return-Path header of your email. While Google might observe the EHLO hostname for reputation purposes, direct SPF validation is primarily tied to the MAIL FROM domain for DMARC alignment. This is consistent with how most major ESPs operate.
Google's focus on authentication
Google's current enforcement of email authentication protocols, including SPF, DKIM, and DMARC, primarily scrutinizes the alignment of the MAIL FROM domain with the From header domain. While the EHLO/HELO hostname is part of the SMTP transaction, direct SPF authentication checks by Google are typically performed against the MAIL FROM domain. Misconfigurations or failures in DMARC reports will indicate which identity was checked.
However, it's important not to dismiss the EHLO/HELO entirely. A well-configured EHLO hostname that resolves correctly and has a corresponding PTR record (Forward Confirmed Reverse DNS) is a strong indicator of a legitimate sending server. While not directly an SPF check, these factors contribute to the overall reputation of your sending IP, which Google heavily weighs.
The importance of DMARC and SPF alignment
DMARC plays a pivotal role here, as it relies on both SPF and DKIM to authenticate emails. For DMARC to pass, either SPF or DKIM (or both) must pass and also align with the From header domain. DMARC reports, which you can receive with a platform like Suped, provide invaluable insights. These reports contain an spf_scope field that explicitly states whether the SPF check was performed against the HELO or MAIL FROM identity by the receiving server.
In most DMARC aggregate reports, you will see spf_scope=mfrom, indicating that the MAIL FROM domain was the primary focus for SPF authentication. While the RFC recommends checking HELO first, the practical implementation by major mailbox providers, including Google, generally prioritizes the MAIL FROM for SPF authentication in the context of DMARC.
Therefore, while the EHLO domain itself might not be subject to a direct SPF check for DMARC alignment, maintaining a consistent and valid EHLO hostname that matches your PTR record is a critical aspect of overall server hygiene and helps build a positive sender reputation. Google, like other providers, looks for these cohesive signs of legitimate sending.
Practical implications and best practices
To ensure optimal email deliverability to Google, focusing on all aspects of authentication is key. While the direct SPF check might primarily target the MAIL FROM domain, a holistic approach to email hygiene will always yield better results.
This means ensuring your SPF record is correctly configured for your MAIL FROM domain, your DKIM signatures are valid, and your DMARC policy is in place. Additionally, the EHLO hostname of your sending server should match your PTR record, and both should align with your domain. These are fundamental best practices for any email sender, irrespective of specific EHLO SPF checks.
Best practices for Google deliverability
Robust SPF: Ensure your SPF record is accurate and includes all authorized sending IPs for your MAIL FROM domain.
DKIM implementation: Properly sign all outgoing emails with DKIM, ensuring alignment with the From header.
DMARC adoption: Implement a DMARC policy, starting with p=none and progressing to quarantine or reject as you gain confidence.
Monitor DMARC reports: Regularly analyze your DMARC reports to identify authentication failures and unauthorized sending sources.
Valid FCrDNS: Ensure your sending IP has a valid PTR record that resolves to the EHLO hostname.
Views from the trenches
Best practices
Always fix your PTR records, as they are a low-hanging fruit and prevent issues with multiple providers, including Microsoft.
Address all visible authentication issues, as Google typically requires a comprehensive approach to improve deliverability rates.
Utilize the `spf_scope` field within DMARC aggregate reports to understand which identity (MAIL FROM or HELO) receivers are prioritizing.
Implement SPF, DKIM, and DMARC for your domains to meet evolving sender requirements from major mailbox providers.
Regularly monitor your email authentication status and domain reputation to proactively identify and resolve issues.
Common pitfalls
Assuming that only MAIL FROM SPF checks are relevant and neglecting the importance of a properly configured EHLO hostname and FCrDNS.
Expecting immediate improvements from Google after fixing only one authentication issue, as their system often requires multiple positive signals.
Underestimating the impact of basic server hygiene, such as PTR records, on overall sender reputation and email acceptance.
Not thoroughly analyzing DMARC reports, which can reveal crucial insights into how different receivers are evaluating your email authentication.
Failing to adapt to tightening authentication requirements from providers like Google, leading to increased inbox placement issues.
Expert tips
Prioritize fixing fundamental issues like incorrect PTR records, as they impact deliverability across various receiving systems.
If encountering deliverability challenges with Google, work systematically through all authentication elements until a positive shift is observed.
Remember that EHLO value integrity, though not always directly SPF-checked for DMARC, significantly contributes to sender trust.
Ensure your EHLO hostname resolves and aligns with your sending domain to avoid reputation penalties.
Consider that smaller IP blocks from hosting providers might face more scrutiny from Google, making strong authentication even more vital.
Marketer view
Marketer from Email Geeks says Google is tightening its authentication requirements, and the SPF specification recommends checking the EHLO value first over the MAIL FROM.
March 8, 2022 - Email Geeks
Marketer view
Marketer from Email Geeks says RFC 7208 recommends checking HELO before MAIL FROM, but it doesn't suggest a priority if both have valid SPF records, and many ESPs struggle with aligning 5321.MAIL FROM.
March 8, 2022 - Email Geeks
Final thoughts on Google's SPF checks
While the SPF specification recommends checking the EHLO identity first, practical implementation by Google and other major mailbox providers largely centers on the MAIL FROM identity for SPF validation within the context of DMARC. This is evident from the spf_scope in DMARC reports, which typically shows mfrom.
However, this doesn't mean the EHLO value is irrelevant. A properly configured EHLO hostname, consistent with a valid PTR record, significantly contributes to your sender reputation, which Google vigilantly monitors. Ensuring comprehensive email authentication, including SPF, DKIM, and DMARC, along with strong server hygiene practices like correct FCrDNS, remains paramount for reliable email delivery.
By understanding both the specifications and the real-world practices of mailbox providers, senders can better navigate the complexities of email deliverability and ensure their messages reach the intended inboxes. For effective DMARC reporting and monitoring to help with these issues, consider a tool like Suped.
