Summary
Experts, email marketers, and documentation all suggest that while SNDS and Google Postmaster Tools provide valuable data for monitoring email deliverability and sender reputation, they should not be considered entirely accurate or comprehensive. SNDS is often viewed skeptically, with some experts suggesting it consistently provides misleading information and operates on an outdated system, not reflective of actual Microsoft inbox placement. Google Postmaster Tools data can be delayed. Experts and marketers emphasize these tools reflect trends and aggregate data, not individual user experiences. A comprehensive understanding requires combining data from these tools with internal sending metrics, subscriber feedback, and other reputation data. Maintaining a good sending reputation with all ISPs and employing authentication methods (SPF, DKIM, DMARC) are crucial for optimal deliverability.
Key findings
- SNDS Skepticism: SNDS data is often considered inaccurate, outdated, and not reflective of Microsoft's actual inbox placement algorithms.
- Aggregate Data: Google Postmaster Tools and SNDS primarily provide aggregate data reflecting trends, not individual user experiences.
- Incomplete Picture: These tools offer a limited view of email performance and don't capture the complete picture of sender reputation.
- Data Delays: Google Postmaster Tools data can be delayed, which hinders a quick diagnosis of issues.
- Internal ISP Reputation Systems: Many ISPs use internal reputation systems.
Key considerations
- Combine Data Sources: Combine data from SNDS and Google Postmaster Tools with other monitoring tools, internal metrics, subscriber feedback, and 3rd-party reputation data.
- Monitor Sending Practices: Implement and maintain best practices to prevent your reputation from degrading over time.
- Monitor Blocklists: Actively monitor blocklist status using tools like MXToolbox.
- Authentication: Use SPF, DKIM and DMARC to prove your email's legitimacy.
- Correlate data: The sender should correlate data from SNDS and Google Postmaster tools with other data.
What email marketers say
7 marketer opinions
Email marketers generally agree that SNDS and Google Postmaster Tools offer valuable insights into email deliverability and sender reputation, but they should not be relied upon as definitive sources of truth. The data presented reflects trends and aggregate information, not necessarily the real-time experience of individual recipients. To get a comprehensive understanding of email performance, it is crucial to combine data from these tools with other metrics, such as internal sending data, subscriber feedback, open rates, click-through rates, and unsubscribe rates. Additionally, other factors beyond what SNDS reports influence deliverability. Some sources suggest SNDS data, in particular, can be delayed or inaccurate and may not reflect current inbox placement decisions at Microsoft. Therefore, a degree of skepticism and further investigation are warranted when interpreting the data from these tools.
Key opinions
- Trend Indicators: SNDS and Google Postmaster Tools primarily reflect trends and aggregate data rather than individual user experiences.
- Limited View: These tools offer a limited view of email performance and don't capture the complete picture of sender reputation.
- Potential Inaccuracies: SNDS data may be delayed, inaccurate, or not reflective of current inbox placement decisions.
- Skepticism Advised: A degree of skepticism is warranted when interpreting data from SNDS and Google Postmaster Tools.
Key considerations
- Correlate Data: Correlate data from SNDS and Google Postmaster Tools with other monitoring tools, internal sending metrics, and subscriber feedback.
- Monitor Blocklists: Actively monitor blocklist status using tools like MXToolbox.
- Look for Patterns: Focus on identifying patterns over time rather than fixating on a single day's metrics.
- Investigate Further: Investigate further to confirm if the trends indicated by these tools are affecting actual inbox placement.
- Consider Other Factors: Recognize that other factors beyond what SNDS reports can influence deliverability.
Marketer view
Email marketer from Email Geeks shares that Google reputation definitely trails when you are improving, but it can tank mighty fast!
22 May 2025 - Email Geeks
Marketer view
Email marketer from Stack Overflow explains that SNDS is useful, but it doesn't reflect the complete picture of your sending reputation. Other factors beyond what SNDS reports influence deliverability. They suggest using SNDS as one data point and combining it with other reputation metrics to gain a well-rounded overview.
26 May 2025 - Stack Overflow
What the experts say
6 expert opinions
Experts indicate that both SNDS and Google Postmaster Tools have limitations regarding the accuracy and timeliness of their data. SNDS is often viewed with skepticism, with some suggesting it consistently provides misleading information and operates on an outdated system separate from Microsoft's active inbox placement algorithms. Google Postmaster Tools data can be delayed, hindering quick diagnostics. Gmail reputation is a trailing indicator that can degrade slowly over time if best practices aren't followed. Overall, reputation data should be combined with other signals and metrics for a comprehensive understanding.
Key opinions
- SNDS Inaccuracy: SNDS data is often considered inaccurate and may not reflect current inbox placement factors at Microsoft.
- Outdated SNDS System: SNDS may be based on an outdated reputation engine.
- Gmail Reputation Delay: Gmail reputation is a lagging indicator that can take days or weeks to reflect changes.
- Gradual Degradation: Gmail reputation degrades slowly with continued poor sending practices.
- Postmaster Tools Delay: Google Postmaster Tools data can be delayed, hindering quick diagnostics.
Key considerations
- Combine Signals: Combine reputation data from SNDS and Google Postmaster Tools with other metrics and signals to get a complete picture.
- Monitor Sending Practices: Pay close attention to sending practices to avoid slow degradation of Gmail reputation.
- Account for Delays: Recognize the potential for delays in Google Postmaster Tools data when diagnosing issues.
Expert view
Expert from Email Geeks suspects that SNDS is based on a 15-year-old version of their reputation engine and hasn’t been updated in the same way that their actual spam filters have been updated over the years.
27 Jan 2024 - Email Geeks
Expert view
Expert from Spam Resource notes that data in Google Postmaster Tools can be delayed. Suggesting that this delay can be problematic when you need to quickly diagnose an issue.
9 Dec 2022 - Spam Resource
What the documentation says
6 technical articles
Documentation from various sources, including Microsoft, Google, SparkPost, Validity, AWS and DigitalOcean, agrees that SNDS and Google Postmaster Tools provide valuable data on email sending reputation and deliverability. However, these tools offer an incomplete picture. They present aggregate data, may not reflect individual user experiences, and require careful interpretation. To gain a comprehensive understanding, the data should be combined with internal metrics, subscriber feedback, and other reputation data. Maintaining a good sending reputation across various ISPs is crucial, and employing authentication methods like SPF, DKIM, and DMARC can help improve deliverability.
Key findings
- Valuable Insights: SNDS and Google Postmaster Tools provide valuable data on email sending reputation and deliverability metrics.
- Aggregate Data: The tools present aggregate data and may not reflect the experience of individual users.
- Incomplete Picture: They offer a partial view of sending health and user engagement.
- ISPs Maintain Reputation Systems: ISPs and email providers maintain internal reputation systems that influence message placement.
Key considerations
- Combine Data Sources: Combine data from SNDS and Google Postmaster Tools with internal metrics, subscriber feedback, and 3rd party reputation data.
- Careful Interpretation: Interpret the data carefully, recognizing that deliverability is multifaceted and a single metric shouldn't dictate strategy.
- Maintain Sending Reputation: Maintain a good sending reputation with each ISP.
- Implement Authentication: Implement SPF, DKIM, and DMARC to prove email legitimacy and avoid spam filters.
- Investigate Concerns: Use the data as a guide to identify potential problems and further investigate specific deliverability concerns.
Technical article
Documentation from AWS explains that many ISPs and email providers, such as Gmail, maintain internal reputation systems. These systems track the reputation of IP addresses and domains that send email. These reputation systems often influence the placement of the messages that you send. It is important to maintain a good sending reputation with each ISP, as well as to monitor your reputation and troubleshoot deliverability issues.
11 Feb 2024 - AWS
Technical article
Documentation from Google explains that Google Postmaster Tools provides aggregate data on your email sending reputation, spam rates, and other deliverability metrics for Gmail users. They state the data is intended to help senders diagnose deliverability issues. However, Google notes the data reflects aggregate trends and may not capture the experience of every individual user. They advise using the data as a guide to identify potential problems and further investigate specific deliverability concerns.
4 Nov 2023 - Google
Does Google Postmaster report user-reported spam for Google Workspace users?
Does Google Postmaster Tools domain reputation include subdomains?
Does Google Postmaster Tools (GPT) data include Google Workspace accounts, or only Gmail.com accounts?
How accurate are SNDS colors in reflecting email delivery performance?
How accurate is Microsoft SNDS data for deliverability monitoring?
How accurate is the spam data shown in the new Google Postmaster Tools and how can I get data to appear?
