What tools or methods can be used to monitor spam rates on a per-user basis within a domain?
Matthew Whittaker
Co-founder & CTO, Suped
Published 12 Aug 2025
Updated 17 Aug 2025
8 min read
Monitoring email performance on a per-user basis within a domain presents unique challenges, especially when the goal is to track specific individuals, like an aggressive sales team, to prevent them from negatively impacting overall domain health. Unlike marketing emails sent through dedicated platforms, direct insight into individual user's outbound spam flags from major mailbox providers is generally not available.
Mailbox providers do not typically share granular data about individual user-reported spam complaints or flags with domain owners. This is primarily due to privacy concerns and the technical complexities of aggregating such specific data across billions of emails. While tools like Google Postmaster Tools and Microsoft SNDS offer domain-level reputation and spam rate data, they do not drill down to individual sender accounts.
However, this doesn't mean you are powerless. By combining available external data with robust internal monitoring and policy enforcement, you can still gain significant insight and mitigate risks. The focus shifts from direct per-user spam flags to identifying patterns of problematic sending behavior and addressing them within your organization.
The limitations of external monitoring for individual users
The primary challenge in monitoring spam rates on a per-user basis is the lack of specific feedback loop (FBL) data for individual senders. While FBLs exist for bulk email senders, they provide aggregate data on complaint rates for entire domains or IP addresses, not for specific users within your organization. This means you won't receive a notification directly tied to a specific sales representative's email being marked as spam.
Most mailbox providers, including major ones, are not designed to provide this level of granular, internal user-specific data to the sending organization. Their tools focus on overall domain and IP reputation. The data they share is intended for high-volume senders managing marketing or transactional email, not for internal oversight of individual employee correspondence.
This limitation means that external tools designed for monitoring email deliverability at a domain or IP level will not provide the precise per-user breakdown you might be hoping for. You will need to think creatively about how to infer problematic behavior from broader metrics and combine that with internal data and policies.
External data sources: Aggregate overview
Domain reputation: Tools provide a general health score for your domain, but not per-user spam rates.
Spam complaint rates: Data is aggregated across all emails from your domain or IP, making it hard to pinpoint individuals.
Leveraging Google Postmaster Tools for domain insights
While direct per-user spam flags are elusive, Google Postmaster Tools (GPT) remains one of the most valuable free resources for understanding your domain's sending reputation with Gmail recipients. It provides aggregated data on spam rates, IP reputation, domain reputation, and DMARC failures. Keep in mind that GPT primarily covers emails sent to Google consumer accounts and not necessarily all business domains or internal Google Workspace accounts. This limitation is critical when trying to monitor an internal sales team that might be emailing other business domains primarily.
To get closer to per-user insights, one advanced tactic with GPT involves using custom headers. If your sending system allows it, you can include a unique identifier for each sales team member in a custom X-header. While GPT doesn't explicitly display per-header spam rates, a spike in your domain's overall spam rate could, in theory, be correlated with activity from a specific X-header ID. This would require careful manual analysis and correlation, and it's not guaranteed to provide definitive per-user data due to data aggregation and sampling by Google.
I often recommend setting up and regularly reviewing your Google Postmaster Tools dashboards regardless of per-user tracking. It is a critical indicator of your domain's health and can alert you to broader issues that might be driven by your sales team's collective sending habits. For more on this, you can read our guide on identifying users generating spam complaints through GPT.
Example of a custom X-headerHTTP
X-Sales-Rep-ID: [unique_sales_rep_id]
Internal monitoring and data analysis
Since direct external per-user spam feedback is limited, focusing on internal monitoring and data is paramount. Your own email sending infrastructure or Email Service Provider (ESP) logs are your best source of granular data. These logs can reveal metrics such as bounce rates, unsubscribe rates, and even DMARC failure reports, which can often be traced back to specific senders or campaigns.
Monitoring bounce rates on a per-user basis can be highly effective. A high bounce rate for a particular user or group might indicate they are sending to old, invalid, or purchased lists, which can quickly degrade your domain's reputation. Similarly, tracking unsubscribe rates from emails sent by specific team members can highlight content or targeting issues that lead recipients to opt-out, indirectly signaling potential spam-like behavior.
Setting up an abuse alias, like abuse@yourdomain.com, and publishing it where it's easily found (e.g., in your DMARC record or website) allows recipients to report unsolicited or problematic emails directly to you. While this requires manual review, it can provide direct evidence of problematic internal senders. You can also analyze DMARC reports (if implemented) for insights into authentication failures, which can point to unauthorized or suspicious sending from your domain.
External monitoring
Scope: Aggregate data for your entire domain or IP addresses.
Limitations: No direct per-user spam rate reporting due to privacy.
Best for: Overall domain reputation and identifying major shifts in deliverability.
Internal monitoring
Scope: Granular data on individual sender activity and campaign performance.
Advantages: Direct access to bounce, unsubscribe, and potentially complaint data from ESPs.
Best for: Pinpointing specific users or teams causing issues.
Proactive measures and internal policies
Given the challenges of per-user spam rate monitoring, the most effective strategy for managing an aggressive sales team's email practices lies in implementing strong internal policies and proactive measures. This preventative approach aims to minimize the likelihood of individuals generating spam complaints or being placed on an email blocklist (or blacklist) in the first place.
Establish clear guidelines for email outreach, including rules for list sourcing, content relevance, and sending frequency. Training your sales team on email deliverability best practices, consent requirements (like GDPR and CAN-SPAM), and the impact of their actions on the company's domain reputation is essential. Ensuring they understand the consequences of poor sending habits can be a strong deterrent.
Another powerful measure is to enforce segmentation of email lists and personalization of content. By sending targeted and relevant emails to engaged recipients, the likelihood of complaints or unsubscribes significantly decreases. This proactive approach not only improves deliverability but also often leads to better engagement rates overall.
Finally, ensure that your email authentication standards are robust. Proper DMARC, SPF, and DKIM configurations are foundational for good deliverability and sender reputation, making it harder for spammers to impersonate your domain and ensuring legitimate mail is recognized as such. For further insight into these measures, consider reviewing our guide on preventing spam complaints from Google Workspace and Microsoft 365.
Maintaining a healthy sending environment
While directly monitoring spam rates on a per-user basis within a domain is challenging due to data privacy limitations from major mailbox providers, a comprehensive strategy can still effectively manage the risk posed by aggressive sending. The key is to blend the insights you can gain from aggregated external tools with robust internal data analysis and proactive policy enforcement. Ultimately, maintaining a healthy domain reputation requires a continuous effort.
By diligently monitoring overall domain health via Google Postmaster Tools, analyzing internal logs for negative engagement metrics like bounces and unsubscribes, and implementing clear email guidelines for all employees, you can identify and address problematic sending behavior before it severely impacts your deliverability. Focusing on education and accountability for your sales team is crucial in preserving your domain's sending reputation.
Views from the trenches
Best practices
Implement strong internal email sending policies and provide mandatory training to all employees, especially sales teams, on email deliverability best practices.
Regularly monitor internal email logs for high bounce rates, low engagement, and unusually high sending volumes from specific user accounts.
Set up an abuse alias for your domain and actively review any complaints received directly from recipients to identify problematic senders.
Utilize Google Postmaster Tools to monitor your domain's overall reputation and spam rate, as these aggregate metrics can indicate underlying per-user issues.
Ensure all outgoing emails have proper authentication records (SPF, DKIM, DMARC) to build trust with mailbox providers and receive DMARC reports for aggregate insights.
Common pitfalls
Assuming external tools can provide granular per-user spam rate data, which is generally not available due to privacy restrictions and data aggregation.
Failing to enforce consequences for sales team members who disregard email sending policies, leading to continued detrimental behavior.
Ignoring high bounce or unsubscribe rates from specific internal users, as these are strong indicators of poor list quality or irrelevant content.
Relying solely on external domain reputation scores without correlating them with internal sending practices and user activity.
Not having a clear feedback mechanism for recipients to report unsolicited or problematic emails sent from your domain.
Expert tips
If sending through Google, track who gets shut down by Google for violating their outbound volume numbers. This indicates problematic users.
Focus on negative metrics like unsubscribe rates and negative replies. This is the closest you can get to per-user spam flags.
Publish an abuse alias and read its contents. It provides pointers to problematic users.
Ensure GDPR data requests are responded to, as legitimate responses demonstrate credibility.
Comply with CAN-SPAM regulations; many unsolicited emails violate these basic rules.
Expert view
Expert from Email Geeks says companies that receive email do not provide per-user data back to senders, making direct individual spam monitoring impossible.
2023-12-08 - Email Geeks
Marketer view
Marketer from Email Geeks says an aggressive sales team is likely to trash domain reputation, and it can take 18-24 months or more to recover if an active opt-in program isn't maintained.
Gmail recipients. It provides aggregated data on spam rates, IP reputation, domain reputation, and DMARC failures. Keep in mind that GPT primarily covers emails sent to 
Google consumer accounts and not necessarily all business domains or internal 
Google Workspace accounts. This limitation is critical when trying to monitor an internal sales team that might be emailing other business domains primarily.
Google Postmaster Tools, analyzing internal logs for negative engagement metrics like bounces and unsubscribes, and implementing clear email guidelines for all employees, you can identify and address problematic sending behavior before it severely impacts your deliverability. Focusing on education and accountability for your sales team is crucial in preserving your domain's sending reputation.
