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Why are emails sent via an HR system connected to Gmail landing in spam despite authentication passing?

Summary

Even when email authentication mechanisms like SPF, DKIM, and DMARC pass, emails from HR systems connected via OAuth to Gmail SMTP can still land in the spam folder, particularly when sending to Microsoft domains. This often indicates underlying sender reputation issues not directly caught by authentication protocols.

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What email marketers say

Email marketers often face complex deliverability challenges, especially when integrating third-party systems like HR platforms with their main email providers. Their insights typically center on practical troubleshooting steps and identifying subtle factors beyond basic authentication that can impact inbox placement.

Marketer view

Email marketer from Email Geeks suggests checking email headers rigorously. They state that confirming authentication, like SPF, DKIM, and DMARC, is always the first step. If these protocols pass, then the problem lies elsewhere, leading to a deeper investigation of other factors impacting deliverability. This foundational check helps rule out common misconfigurations.

21 Nov 2019 - Email Geeks

Marketer view

An email marketer from Quora observes that if your sending domain has a poor reputation with Gmail, or if your email content triggers spam filters, your emails will likely go to spam. They explain that even for genuine emails, these factors can override positive authentication results. Addressing both domain reputation and content quality is crucial for better inbox placement.

01 Jan 2025 - Quora

What the experts say

Deliverability experts often delve into the technical intricacies of email routing and server configuration when addressing spam placement issues, especially when standard authentication protocols are already passing. Their focus is typically on identifying subtle misconfigurations or underlying reputation factors that sophisticated spam filters, like Gmail's or Microsoft's, can detect.

Expert view

Deliverability expert from Email Geeks suggests that the problem is likely related to the AWS instance connecting to Gmail, specifically its generic reverse DNS (rDNS). They point out that a generic rDNS like ec2-*-compute.amazonaws.com signals poor reputation. Such IPs are frequently associated with spam, and sending through Gmail further amplifies the likelihood of being flagged.

22 Nov 2019 - Email Geeks

Expert view

A deliverability expert from Word to the Wise explains that even if SPF, DKIM, and DMARC are correctly configured, email deliverability issues can persist due to underlying IP and domain reputation. They clarify that passing authentication merely verifies the sender's identity, but it does not guarantee inbox placement if the sender's history or current sending practices are deemed suspicious by recipient filters. Maintaining a clean reputation is vital.

10 Mar 2024 - Word to the Wise

What the documentation says

Official documentation from major mailbox providers and industry standards bodies provides critical guidelines for email deliverability. While often technical, these documents emphasize that passing authentication (SPF, DKIM, DMARC) is a baseline, not a guarantee, and that broader sender reputation, content quality, and proper server configuration play equally significant roles in inbox placement.

Technical article

Microsoft's official documentation on email filtering explains that their systems utilize a multi-layered approach to spam detection, where successful SPF, DKIM, and DMARC authentication are necessary but not sufficient conditions for inbox delivery. They emphasize that sender reputation, volume, content analysis, and recipient engagement all contribute to a message's final spam confidence level (SCL) score. Even minor deviations from best practices can significantly increase the likelihood of filtering.

01 Oct 2024 - Microsoft Docs

Technical article

Google's postmaster tools documentation outlines how sender reputation is built and maintained, primarily through consistent sending of wanted mail, low spam complaint rates, and strong engagement metrics. It highlights that the IP address and domain reputation are continuously evaluated based on historical performance. A sudden change in sending patterns or unexpected content can negatively impact this established trust, even for authenticated senders.

15 Nov 2024 - Google Postmaster Tools

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