Does Google Postmaster Tools' Y-axis represent mail volume or IP percentage?
Matthew Whittaker
Co-founder & CTO, Suped
Published 21 May 2025
Updated 18 Aug 2025
6 min read
I've often heard confusion surrounding the interpretation of Google Postmaster Tools (GPT), especially regarding what the Y-axis on certain dashboards represents. Specifically, when looking at IP reputation, a common question arises: does the Y-axis show the actual volume of mail sent, or the percentage of your sending IPs? This distinction is crucial for accurately assessing your email performance and diagnosing deliverability issues.
It's easy to assume that a graph showing "volume" would directly correlate with the quantity of emails sent. However, Google Postmaster Tools operates with specific methodologies that aren't always immediately intuitive. Understanding these nuances is key to leveraging the tool effectively for your email programs.
Exploring Google Postmaster Tools' dashboards
Google Postmaster Tools provides valuable insights into your email performance with Gmail recipients, helping you monitor key metrics that influence inbox placement. It's a free service designed to help high-volume senders understand their email ecosystem and troubleshoot potential deliverability issues.
The platform offers several dashboards, each focusing on a different aspect of your sending reputation and email authentication. For instance, the Spam Rate dashboard indicates the percent of your emails marked as spam by Gmail users. The IP Reputation and Domain Reputation dashboards show how Gmail views your sending entities, categorized as bad, low, medium, or high.
Other important dashboards include Feedback Loop, Authentication, Encryption, and Delivery Errors. Each provides a unique perspective on your email traffic. To gain data, you typically need to send a sufficient volume of email to Gmail recipients daily. For more details on this, you can review what email volume is required to see data in Google Postmaster Tools.
Decoding the IP reputation chart: percentage of IPs, not mail volume
When examining the "IP Reputation" dashboard in Google Postmaster Tools, the Y-axis on the graph represents the percentage of your sending IP addresses, not the actual mail volume. This means if you have multiple IP addresses sending email to Gmail, the graph will show what proportion of those IPs fall into the "Bad," "Low," "Medium," or "High" reputation categories.
For example, if you send from three distinct IP addresses, and all three maintain a "High" reputation, the graph will display 100% in the "High" category. This holds true regardless of whether one IP sends 1 million emails a day while another sends only a thousand. Each IP is treated as an individual unit contributing to the overall percentage displayed on the Y-axis.
This design choice by Google can be a point of confusion, as many users might intuitively expect to see mail volume correlated with reputation on this graph. However, the intent is to show the health distribution across your sending infrastructure. You can click on the bars in the graph to see a breakdown of individual IP addresses and their respective reputations, as stated in this Google support article.
Why this distinction matters for deliverability
Understanding that the Y-axis reflects IP percentage rather than mail volume is crucial for accurate deliverability analysis. If a small volume IP, or one that sends infrequently, gets a bad reputation, it can significantly skew the "percentage of IPs" metric, even if your main, high-volume IPs are performing well. This could lead to unnecessary alarm if misinterpreted.
Conversely, if a high-volume IP experiences a drop in reputation, but you have many other IPs performing well, the percentage change might appear less severe than the actual impact on your overall mail stream. It's vital to cross-reference this percentage with your actual sending volumes per IP to get a true picture. For more on what to monitor, see what email deliverability metrics to monitor.
Gaining a complete picture beyond IP percentage
While Google Postmaster Tools provides valuable insights into your IP reputation as a percentage of your total IPs, it's essential to integrate this data with other metrics for a holistic view of your deliverability. Relying solely on one dashboard can lead to incomplete or misleading conclusions.
For instance, understanding your overall spam rate and domain reputation is equally important. A low percentage of bad IPs doesn't guarantee inbox placement if your domain reputation is suffering due to other factors like poor engagement or DMARC failures. Consider also supplementing GPT data with insights from other postmaster tools and internal sending logs.
Insights from GPT IP reputation
Google Postmaster Tools shows the percentage breakdown of your registered sending IP addresses by their reputation status (Bad, Low, Medium, High). It gives you a quick overview of the health distribution across your IP infrastructure.
Distribution view: Clearly indicates if a significant portion of your IPs are experiencing reputation issues, regardless of their individual sending volume.
Identification of troubled IPs: Helps to quickly identify which specific IP addresses might be underperforming and require investigation.
High-level overview: Provides a high-level summary of your IP health, which is useful for initial assessment.
Understanding the full context
While the percentage is useful, it needs to be correlated with actual mail volume from each IP. A single low-volume IP with bad reputation can still show up as a significant percentage, but might not impact overall deliverability as much as a high-volume IP with a slightly degraded reputation. This Google Support article provides additional context for Postmaster Tools dashboards.
True impact assessment: Correlating with mail volume helps assess the real impact of reputation changes on your overall email deliverability.
Engagement metrics: Combining with open rates, click-through rates, and complaint rates from your email service provider offers a deeper insight into recipient engagement.
Authentication status:Checking authentication dashboards (SPF, DKIM, DMARC) ensures your emails are properly validated, which is fundamental to reputation.
Best practice for monitoring IP reputation
Always correlate Google Postmaster Tools IP reputation percentages with your actual mail volume data from your Email Service Provider (ESP) or internal sending logs. This ensures you understand the true impact of reputation changes on your overall email deliverability, preventing misinterpretations from low-volume IPs skewing the percentages.
Views from the trenches
When trying to understand how various email services interpret and display data, it often helps to hear from those who are actively managing email programs day-to-day. The nuances of tools like Google Postmaster Tools can sometimes be subtle, and collective experience can shed light on common interpretations and pitfalls.
Many professionals in the email deliverability community frequently discuss these topics, sharing their observations and best practices. These discussions often highlight the practical implications of technical specifications and how different metrics are perceived in real-world scenarios.
Best practices
Always cross-reference Google Postmaster Tools data with internal sending logs for accurate volume correlation.
Monitor all relevant dashboards in GPT, not just IP reputation, for a holistic view of your sender health.
Implement robust DMARC policies to protect your domain and improve deliverability.
Actively manage your sender reputation by maintaining clean lists and engaging content.
Regularly check for any listings on major blocklists that could impact your deliverability.
Common pitfalls
Misinterpreting the IP reputation Y-axis as mail volume instead of IP percentage.
Failing to account for low-volume IPs skewing the percentage-based reputation metrics.
Not integrating GPT data with other deliverability metrics like bounce and open rates.
Overlooking the importance of domain reputation while focusing solely on IP reputation.
Ignoring small fluctuations in reputation, which can escalate into bigger issues.
Expert tips
For a comprehensive view, combine GPT insights with data from other services and your own email sending platform.
Understand that Gmail's reputation system is complex and influenced by many factors beyond just IP health.
Pay close attention to user feedback and complaint rates, as they directly impact your sender score.
Leverage DMARC reports to identify authentication failures and potential abuse of your domain.
Proactive list hygiene and segmentation can significantly improve long-term deliverability.
Expert view
Expert from Email Geeks says: If you click on one of those bars in the IP reputation dashboard, you will see a list of IP addresses below and their individual reputations. Other than the reputation being a function of the number of delivered emails from a said IP address, it does not, in effect, reflect the volume of emails.
May 7, 2019 - Email Geeks
Marketer view
Marketer from Email Geeks says: It's the latter, meaning the Y-axis represents the percentage of your total IPs. If you send from three IPs, and one sends 1 million emails per day, one 10 million per day, and one 1,000 per day, each still shows as 33%.
May 7, 2019 - Email Geeks
Conclusion: mastering your email deliverability data
The Y-axis on the IP Reputation dashboard in Google Postmaster Tools represents the percentage of your IP addresses within each reputation category, not the mail volume. This distinction is vital for accurately interpreting your data and avoiding potential misdiagnoses of deliverability issues.
While this percentage view offers a valuable high-level understanding of your IP infrastructure's health, it should always be considered alongside other critical metrics. Combining insights from your internal sending logs, other GPT dashboards, and external tools provides the most comprehensive picture. A nuanced approach to data interpretation ensures you can effectively manage your sender reputation, maintain high inbox placement rates, and avoid being flagged by ISPs.
Google Postmaster Tools shows the percentage breakdown of your registered sending IP addresses by their reputation status (Bad, Low, Medium, High). It gives you a quick overview of the health distribution across your IP infrastructure.
