Is Google applying SPF checks to EHLO values for stricter email authentication?

The consensus is that while Google's specific implementation isn't explicitly confirmed, applying SPF checks to EHLO values is a potential component of stricter email authentication. This is driven by a combination of factors including reported tightening of authentication requirements, the SPF specification recommending HELO checks, and the increasing importance of DMARC. Though MAIL FROM remains the primary focus for many ESPs, EHLO checks can serve as an early filter and are influenced by domain reputation. The use of proper PTR records, and generally, fully configuring the infrastructure correctly is emphasized. HELO checking's utilization varies from system to system.

The question of whether Google is applying SPF checks to EHLO values for stricter email authentication is complex. While the RFC specification recommends HELO identity checks, implementations vary. Some email providers prioritize HELO checks, particularly for initial connections or when MAIL FROM records are absent. The growing importance of DMARC may indirectly increase the relevance of HELO checks. Some older systems strictly adhere to HELO checks, while many modern ESPs primarily focus on MAIL FROM. Not all ESPs implement HELO SPF checks, but those that do may use it as an early filter to reduce resource usage or improve domain reputation. Fixing PTR records remains a crucial step in improving email deliverability.

The possibility of Google applying SPF checks to EHLO values for stricter email authentication is debated. There are reports of Google tightening authentication requirements, leading to speculation about increased scrutiny of EHLO values and FcrDNS. The SPF specification mandates checking EHLO before MAIL FROM, but implementations vary. An authentication issue to be aware of is the PTR record showing a hostname that results in NXDomain, potentially impacting deliverability. In the age of DMARC, SPF HELO checks are becoming more relevant due to domain alignment requirements. While MAIL FROM remains the primary focus, HELO/EHLO checks can still impact deliverability, and a valid, resolvable hostname in HELO is crucial.

Documentation from various sources outlines the use of SPF records in email authentication. The IETF recommends checking the HELO identity for consistency and resource efficiency. While Google, Microsoft, Dmarcian, and SparkPost emphasize the importance of SPF in preventing unauthorized messages and validating message origin, they do not explicitly confirm Google's use of SPF checks on EHLO values. These resources imply that stricter SPF adherence and comprehensive authentication setups, which *may* include HELO analysis, are increasingly important for deliverability.