How do feedback loops (FBLs) function for Google and Oath, and what are ESP domain signing practices?
Matthew Whittaker
Co-founder & CTO, Suped
Published 13 May 2025
Updated 19 Aug 2025
8 min read
Feedback loops (FBLs) are crucial for understanding how recipients perceive your emails. They provide a vital communication channel between mailbox providers (like Google and Oath, now part of Yahoo) and email senders, particularly Email Service Providers (ESPs). These systems alert senders when their emails are marked as spam by recipients, offering insights that can help maintain good sender reputation and inbox placement.
However, the way FBLs function varies significantly among different mailbox providers, leading to common questions about what data is actually received. For instance, many senders expect to receive individual complaint reports, but this isn't always the case, especially with major providers like Google. Understanding these nuances is essential for effective email program management and for troubleshooting deliverability issues.
The effectiveness of an FBL (or lack of direct reporting) often depends on how an ESP handles email authentication, specifically domain signing practices like DKIM. Your email's journey to the inbox is heavily influenced by these technical configurations and how they interact with FBL systems.
How Google feedback loops function
Google operates its Feedback Loop (FBL) system differently from many traditional FBLs. Instead of providing individual complaint reports, Google integrates its feedback mechanism into Google Postmaster Tools. This platform offers aggregate data and trends related to your sending reputation, including a "Spam Rate" dashboard.
This aggregate approach means you won't receive real-time notifications for every single spam complaint. Instead, you'll see a consolidated percentage of user complaints over time. This data is invaluable for identifying large-scale campaign issues or sudden spikes in user dissatisfaction, allowing you to react proactively to protect your sender reputation. For more details on this, you can explore the Google Workspace Admin Help page.
While the lack of granular data might seem limiting, it pushes senders to focus on overall list hygiene and engagement rather than individual complaints. A high spam rate in Google Postmaster Tools signals a broader problem with list acquisition, content relevance, or frequency, necessitating a review of your entire email sending strategy. Monitoring your Google Postmaster Tools spam rate dashboard is key.
Google Postmaster Tools insights
Google Postmaster Tools is a free service that provides email senders with data and insights into their email performance with users. It's not just about spam complaints; it also offers data on IP and domain reputation, delivery errors, encryption, and authentication (SPF, DKIM, DMARC) status. For a comprehensive overview, refer to our ultimate guide to Google Postmaster Tools v2.
Oath (which encompasses Yahoo, AOL, and other brands) operates a more traditional, DKIM-based Feedback Loop (FBL). Unlike Google, Oath provides actual spam complaint reports when a recipient clicks the "This is Spam" button. These reports are typically sent to a designated email address that you register with their FBL program.
For these reports to be effective, your email sending domain (the 'd=' tag in your DKIM signature) must be properly registered and enrolled in Oath's FBL program. This is particularly important if you use a custom domain for sending rather than a shared domain provided by your ESP. If your custom domain isn't registered, your ESP might not receive the specific complaint data associated with your sending. More information on how ESPs collect Yahoo FBL data using double DKIM signing is available.
It's common for Email Service Providers to manage these FBL registrations on behalf of their clients, but it's vital to confirm that your specific domain is covered, especially if you're using a dedicated domain. Without proper registration, any spam complaints might not reach your ESP, leaving you blind to potentially damaging recipient feedback. You can find out where to find Yahoo Postmaster data and FBL signup.
ESP shared domain signing
When an ESP signs emails using their own domain (e.g., d=espsending.com), they are responsible for enrolling that domain in FBL programs like Oath's.
FBL data: Complaint reports are sent to the ESP's registered FBL address.
Visibility: Clients may not have direct access to raw complaint data, relying on the ESP's reporting.
Setup: Simpler for the client, as the ESP handles most of the configuration.
Customer custom domain signing
If an ESP allows you to sign emails with your own custom domain (e.g., d=yourdomain.com), your domain needs to be individually enrolled in FBL programs.
FBL data: Complaint reports are tied directly to your domain, potentially offering more direct insights.
Responsibility: You or your ESP must ensure your specific domain is registered.
Control: Offers greater control and visibility over your own domain's reputation.
ESP domain signing practices and FBLs
The way an ESP (Email Service Provider) handles DKIM signing directly impacts how you receive and interpret FBL data. Some ESPs "double sign" emails, meaning they apply both their own DKIM signature (d=espsending.com) and your custom domain's signature (d=yourdomain.com). This practice ensures that the ESP can receive FBL data related to their infrastructure, while your domain also benefits from authentication.
However, some larger organizations or businesses prefer their ESPs not to have any presence in the email headers, meaning the ESP won't double sign. In such cases, only your custom domain's DKIM signature is present. For you to receive FBL data (especially from providers like Oath), your custom domain must be explicitly registered with the respective FBL programs. This places the burden of FBL enrollment directly on you or your ESP for your specific domain, highlighting the importance of clear communication with your provider.
Understanding whether your ESP double signs, or if they only sign with your domain, is critical. If your ESP only signs with your domain, then it is your responsibility to ensure that your domain is enrolled in relevant FBL programs. This distinction is vital for accurate complaint reporting and maintaining a healthy sending reputation, particularly when dealing with providers that rely on DKIM for FBL enrollment. Our article on which ISPs use DKIM domains for Feedback Loops provides more context.
Signing method
Oath (Yahoo/AOL) FBL Impact
Google FBL Impact
ESP shared domain signing
ESP receives FBLs. Client relies on ESP reports.
Client sees aggregate data via Google Postmaster Tools related to IPs/domains used.
Customer custom domain signing (single)
Customer's domain must be enrolled in FBL for reports.
Client sees aggregate data for own domain via Google Postmaster Tools.
Double signing (ESP + customer)
Both ESP and customer's domain can receive FBLs.
Client sees aggregate data for own domain; ESP sees data for shared infrastructure.
Managing FBL data for improved deliverability
Whether you receive detailed FBL reports or aggregate data, the core purpose remains the same: to help you understand and mitigate spam complaints. The absence of FBL reports, particularly from providers like Oath or Google, doesn't necessarily mean zero complaints. It could indicate that your emails are already going to the spam folder (bulk folder), preventing users from marking them as spam and triggering FBLs. If your mail ends up in the spam folder, it won't trigger feedback loops.
To effectively manage your email program, you need to combine FBL data with other deliverability metrics, such as open rates, click-through rates, and bounce rates. A sudden drop in engagement metrics coupled with no FBL data could be a strong indicator of inbox placement issues, even if explicit spam complaints aren't being reported. For more information, consider reading "What you need to know about feedback loops (FBLs)".
Implement a robust suppression list strategy. When you do receive FBL data (especially direct reports from Oath), it's crucial to immediately remove those users from your mailing list. Failing to do so can lead to higher complaint rates, further damaging your sender reputation and increasing the likelihood of future mail being blocked or sent to spam (bulk folder). This proactive approach is essential for maintaining a healthy and engaged subscriber base.
Beyond FBLs, a comprehensive approach to email deliverability involves continuous monitoring of your sender reputation, regular list hygiene, and adherence to email authentication standards like SPF, DKIM, and DMARC. These measures collectively contribute to better inbox placement and reduce the likelihood of your emails being caught by spam filters or being added to a blocklist (or blacklist).
Best practices for FBL management
Monitor Google Postmaster Tools: Regularly check your spam rate and other metrics in Google Postmaster Tools.
Confirm Oath FBL enrollment: Verify with your ESP that your custom domain is properly enrolled in Oath's (Yahoo/AOL) DKIM-based FBL program.
Automate suppression: Ensure that any FBL complaints received lead to immediate removal of the complaining recipient from your lists. ESPs process feedback loop emails for this.
Combine data sources: Don't rely solely on FBLs. Use engagement metrics, bounce rates, and DMARC monitoring reports for a holistic view of deliverability.
Review list acquisition: If complaint rates are high, re-evaluate how you are collecting email addresses.
Views from the trenches
Best practices
Regularly review your domain's DKIM signing practices in conjunction with your ESP.
Utilize Yahoo Postmaster data for direct complaint feedback when using custom domains.
Combine FBL data with other engagement metrics to get a full picture of your deliverability performance.
Common pitfalls
Expecting direct FBL reports from Google for individual spam complaints.
Assuming your ESP automatically enrolls your custom domain for all FBLs.
Ignoring low FBL complaint counts, which might mask emails going to spam (bulk) instead.
Expert tips
Confirm your ESP's FBL enrollment practices, especially if you use a custom sending domain.
Actively monitor Google Postmaster Tools for spam rate trends, as it's their primary FBL insight.
Understand that mail going to the bulk folder won't trigger FBL complaints, indicating a deeper deliverability issue.
Expert view
Expert from Email Geeks says Google doesn't send individual FBL reports; instead, they provide aggregate percentages through Google Postmaster Tools.
August 10, 2019 - Email Geeks
Expert view
Expert from Email Geeks says Oath (Yahoo/AOL) uses a DKIM-based FBL, so if you're signing with a custom domain, you likely need to have participated in a specific signup process for it to function correctly.
August 10, 2019 - Email Geeks
Conclusion
Feedback Loops, while varied in their implementation, remain a foundational element of email deliverability. Understanding the specific mechanisms employed by major mailbox providers like Google and Oath (Yahoo/AOL) is paramount for any sender, especially when factoring in ESP domain signing practices. Google's aggregate approach through Postmaster Tools and Oath's DKIM-based FBLs each require a tailored strategy for monitoring and response.
Effective management of FBL data, whether it's direct reports or aggregate percentages, directly impacts your sender reputation and inbox placement. By actively monitoring these signals and ensuring your domain signing is correctly configured and enrolled, you can proactively address user complaints, maintain list hygiene, and ultimately achieve better email deliverability. Always verify your ESP's FBL enrollment and signing practices to ensure full visibility into your complaint data.
Google and 
Oath, now part of Yahoo) and email senders, particularly Email Service Providers (ESPs). These systems alert senders when their emails are marked as spam by recipients, offering insights that can help maintain good sender reputation and inbox placement.
