Why is the Google Postmaster Tools feedback loop graph flat or zero?
Michael Ko
Co-founder & CEO, Suped
Published 19 Jul 2025
Updated 19 Aug 2025
7 min read
It can be perplexing to log into your Google Postmaster Tools (GPT) account and find that your Feedback Loop (FBL) graph is consistently flat or showing zero data. This dashboard is meant to provide crucial insights into how Google users perceive your emails, specifically regarding spam complaints. When it's blank or unchanging, it naturally raises concerns about whether your emails are even reaching the inbox or if there's a configuration issue.
Unlike some other Mailbox Providers (MBPs) that send individual complaint reports, Google aggregates the data from users who mark your emails as spam. This aggregate data is then displayed in your Postmaster Tools dashboard, specifically under the Feedback Loop dashboard if you’ve configured your Feedback-ID headers correctly.
A flat or zero FBL graph in GPT typically suggests a few scenarios, ranging from excellent email practices to potential underlying deliverability challenges. Understanding these possibilities is key to diagnosing the situation and ensuring your email program is healthy.
Reasons for a flat feedback loop graph
One of the most common reasons for a flat or zero FBL graph is simply a very low volume of spam complaints. Google's FBL system is designed to provide actionable insights for high-volume senders. If your emails consistently maintain a low complaint rate, below the threshold that Google deems significant, the graph may remain flat. This is often a good sign, indicating that your recipients are not marking your emails as spam.
It's important to remember that GPT doesn't show every single complaint. It only displays data when a certain threshold of complaints is met, which is not publicly disclosed but is widely believed to be around 0.1-0.4% of your total email volume to Gmail users. If your complaint rate is consistently below this internal threshold, you won't see any spikes or changes on the graph, even if a few complaints occur.
Furthermore, if you are sending a relatively low volume of emails to Gmail users, or if your sending volume is inconsistent, you might not generate enough complaints to trigger data reporting in GPT. The tools require a significant baseline of email traffic to collect and display meaningful statistics. If you're experiencing this, it's not necessarily a sign of a problem, but rather a reflection of your mailing habits.
Scenario 1: Low complaint rate
Your emails are well-received and recipients are rarely marking them as spam. Your complaint rate is below Google's internal threshold for displaying data.
Scenario 2: Low email volume
You are not sending enough emails to Gmail addresses to meet the minimum data requirement for Postmaster Tools to populate any graphs, including the FBL.
Verifying your feedback loop configuration
While a flat graph can indicate good sender reputation, it's also worth investigating if a technical misconfiguration is preventing data from being recorded. The Gmail Feedback Loop specifically relies on the presence and correct signing of the Feedback-ID header in your outgoing emails. If this header is missing, malformed, or not properly signed by DKIM, Google will not be able to attribute complaints to your campaigns.
Ensure your Email Service Provider (ESP) or internal sending system is correctly adding the Feedback-ID header. More critically, Google states that this header must be added prior to DKIM signing, and it must be included in the signed headers list (the h= tag in your DKIM signature). If it's not part of the DKIM hash, it could be stripped or modified in transit, invalidating its purpose for FBL reporting.
You can inspect the raw source of an email sent to Gmail to verify the presence and proper signing of the Feedback-ID header. Look for the Feedback-ID: line and then check the Authentication-Results header for the DKIM signature and its h= field to ensure Feedback-ID is included.
A flat or zero FBL graph can sometimes be a symptom of a larger inbox placement problem. If your emails are not reaching the inbox (i.e., they are being filtered to the spam folder or rejected entirely), then recipients won't have the chance to mark them as spam. In such cases, a zero complaint rate isn't a sign of good deliverability but rather a lack of engagement, because the messages are not even seen.
To investigate this, you should cross-reference your FBL data with other metrics. Are your open rates and click-through rates from Gmail recipients significantly lower than for other providers? Are you seeing high bounce rates from Gmail? These could be indicators that your messages are not making it to the inbox, thus preventing users from hitting the 'report spam' button.
Additionally, check your domain and IP reputation scores within Postmaster Tools. If these are low or poor, it's a strong sign of deliverability issues that would also impact FBL reporting. A consistently low or flat FBL graph in combination with poor reputation metrics is a red flag.
Positive indicators
If your FBL graph is flat or zero, but you have consistently high open and click rates for Gmail recipients, it’s likely a sign of healthy sending practices and minimal complaints.
Your other FBLs (e.g., those from Yahoo or Outlook) also show very low or zero complaint rates, confirming consistent user satisfaction across providers.
Negative indicators
If your FBL is flat or zero, but your Gmail open rates are unusually low, it could mean your messages are being filtered to the spam folder, preventing complaints from being registered.
What to do if your graph is consistently flat or zero
First, don't panic. A flat or zero FBL graph is often a sign of healthy email practices, especially if your other deliverability metrics are strong. If your open rates, click-through rates, and overall engagement with Gmail recipients are good, and you're not seeing high bounce rates or blacklisting on other blocklists, then it likely means your complaint rate is simply too low to register in Postmaster Tools.
However, if you have concerns, confirm that your Feedback-ID header is correctly implemented and signed by DKIM. This technical check can rule out a common cause of missing data. Work with your ESP or IT team to review your email headers and ensure everything aligns with Google's guidelines.
Finally, focus on maintaining excellent email list hygiene and sending practices. This includes regularly cleaning your lists, segmenting your audience, sending relevant content, and ensuring easy unsubscribe options. By prioritizing these factors, you naturally minimize spam complaints, and a flat FBL graph becomes a positive indicator of your email program's health rather than a cause for concern.
Views from the trenches
Best practices
Maintain very low spam complaint rates across all Mailbox Providers to ensure healthy sender reputation.
Regularly monitor your email engagement metrics, such as open and click-through rates.
Confirm that your Feedback-ID header is correctly implemented and signed by DKIM.
Common pitfalls
Misinterpreting a flat FBL graph as a deliverability problem when it indicates low complaints.
Failing to include the Feedback-ID header in the DKIM signed headers (the h= tag).
Not having enough email volume to Gmail to generate any FBL data.
Expert tips
A flat FBL graph in Google Postmaster Tools often means your complaint rate is below their reporting threshold. This is usually a good sign, indicating healthy sender practices.
Always check that your Feedback-ID header is properly included in your DKIM signature; otherwise, Google won't be able to process the data.
If other deliverability metrics for Gmail (like open rates and inbox placement via seed lists) are strong, a zero FBL is a positive indicator, not a problem.
Marketer view
Marketer from Email Geeks says that if you have access to the domain on Google Postmaster Tools, you should be able to see the feedback graph for that domain.
2019-08-20 - Email Geeks
Marketer view
Marketer from Email Geeks says a flat FBL data graph in Google Postmaster Tools is not unusual, even for high email volumes, because you might not be generating sufficient complaints from Gmail users to trigger data display.
2019-08-20 - Email Geeks
Understanding your FBL data
A flat or zero FBL graph in Google Postmaster Tools can be confusing, but it's often a positive sign of a healthy sender reputation and low spam complaints. However, it's crucial to rule out technical issues or underlying deliverability problems. By regularly monitoring your broader email metrics and ensuring proper technical configuration, you can accurately interpret this data and maintain optimal email deliverability to Gmail recipients.
Gmail addresses to meet the minimum data requirement for Postmaster Tools to populate any graphs, including the FBL.
Google's guidelines.
