Understanding how email service providers (ESPs) like SparkPost gather inbox placement data is crucial for anyone serious about email deliverability. It is not always as straightforward as simply knowing if an email was delivered or bounced. The real challenge lies in discerning whether that email landed in the primary inbox, a promotional tab, or, worse, the spam folder. This distinction directly impacts the effectiveness of email campaigns.
The complexity arises because mailbox providers (ISPs) like Gmail and Yahoo do not openly share detailed inbox placement data for every single email sent. Instead, ESPs employ a combination of sophisticated techniques to provide clients with insights into where their messages land. This includes leveraging various data sources to paint a comprehensive picture of deliverability.
For email marketers and senders, understanding these methods is vital. It allows for more informed decisions regarding campaign strategy, content optimization, and audience segmentation. Knowing how SparkPost, a leading email delivery service, gathers its data helps in interpreting reports and taking actionable steps to improve email performance and ensure messages reach their intended recipients.
How seed lists work
One of the primary methods SparkPost and similar platforms use to assess inbox placement is through seed lists. A seed list is a collection of email addresses controlled by the ESP that are distributed across various mailbox providers, domains, and often, specific geographical locations.
When a client sends an email campaign, a small portion of the messages are also sent to these seed addresses. By monitoring where these seed emails land (inbox, spam, or missing), SparkPost can generate a statistically relevant approximation of overall inbox placement rates for that campaign. This gives senders a real-time snapshot of their deliverability. SparkPost offers options for clients to either include a seed list provided by them in their sends or to use an automatic inline seeding feature, which manages the seed list inclusion automatically.
The power of seed lists comes from their diversity. A robust seed list includes addresses from a wide array of ISPs, including major providers like Google, Microsoft, and Apple, as well as smaller, regional providers. This breadth ensures that the inbox placement data is as representative as possible of actual subscriber engagement and filtering. For more on testing, consider the best inbox placement testing tools.
The role of user panel data
Beyond static seed lists, SparkPost also leverages live user panel data. This approach involves collecting data from a large number of active email accounts, often referred to as a live user panel. These accounts are managed by the ESP and provide real-time insights into where emails are being delivered in actual user inboxes. This method offers a more dynamic and behavioral-based understanding of inbox placement.
The panel data goes beyond just delivery status; it can include how real users interact with emails. This is important because ISPs increasingly use engagement metrics (opens, clicks, replies, deletions, spam complaints) to determine inbox placement. Some panel accounts are non-engaging, behaving like typical dormant accounts, while others are engaging seeds that use machine modeling to simulate realistic user engagement patterns. This mix helps account for the nuanced ways ISPs filter mail.
By combining both traditional seed lists and dynamic panel data, SparkPost aims to offer a more accurate and comprehensive view of inbox placement. This dual-data approach allows them to detect subtle shifts in filtering algorithms and provide more reliable insights for their clients. It’s a sophisticated method for monitoring a constantly evolving landscape.
Traditional seeds
Static accounts: Email addresses created specifically for testing, often with minimal or no real interaction.
Predictive: Provide a snapshot of where emails land at a given moment, good for pre-send testing.
Potential for false negatives: May not fully reflect ISP behavior that relies on long-term user engagement.
Engaging seeds
Dynamic accounts: Real email accounts that simulate human interaction like opening, clicking, and marking as not spam.
Representative: More accurately reflects how ISPs filter based on engagement, providing a truer picture.
Reduced false negatives: Helps mitigate issues where lack of engagement might falsely flag emails as spam.
Direct insights from mailbox providers
Some major mailbox providers offer direct data feeds to trusted ESPs and deliverability platforms. These feeds provide aggregate data on sending reputation, complaint rates, and, importantly, inbox placement. For example, Yahoo's deliverability performance feeds share valuable insights that can help ESPs fine-tune their deliverability predictions.
These direct feeds are invaluable because they come straight from the source. While they may not offer granular, per-email data, they provide a high-level overview of how emails are performing across the entire network of a specific ISP. This partnership with mailbox providers is a key differentiator for platforms that can access such data, offering a level of insight that independent seed testing alone cannot always match.
It is not always exclusive to ESPs; some individual senders or organizations might also be able to access these feeds by reaching out directly to the mailbox provider, though the terms and conditions may vary. This direct access complements the internal data gathered by SparkPost, contributing to a more accurate overall deliverability assessment.
Enhancing data with acquisitions
In 2019, SparkPost acquired eDataSource, a company known for its email intelligence and competitive tracking. This acquisition significantly enhanced SparkPost’s ability to gather comprehensive inbox placement data. eDataSource brought with it an expansive data coverage and proprietary technology, including the IntelliX AI Network™.
The IntelliX AI Network™ is designed to provide extensive, new data that reflects inbox performance across the email ecosystem. This technology goes beyond traditional monitoring, leveraging artificial intelligence to process vast amounts of email data and provide deeper insights into deliverability and competitor performance. This means SparkPost can not only tell you where your emails are landing, but also how your deliverability compares to others in your industry.
This integration allows SparkPost to offer a more robust suite of deliverability analytics. By combining their own sending data with eDataSource’s competitive insights, they provide marketers with a more complete view of their email program's health. This includes understanding the impact of spam filters and blocklists (or blacklists) on email performance. Sometimes it's difficult to troubleshoot these issues, but troubleshooting high soft bounce rates and poor inbox placement is possible.
Data source
Description
Insights provided
Seed lists
Proprietary email addresses at various ISPs included in client sends.
Real user accounts that capture engagement signals and delivery.
Behavioral insights, engagement metrics, and inbox placement based on real user activity.
ISP direct feeds
Aggregate data provided by mailbox providers like Outlook and AOL.
Overall domain/IP reputation, complaint rates, and deliverability performance.
eDataSource acquisition
Integration of competitive intelligence and advanced AI network (IntelliX AI Network™).
Competitive benchmarking, deeper insights into filtering, and expanded data coverage.
A multi-sourced approach
By integrating these diverse data sources, SparkPost creates a holistic view of email deliverability and inbox placement. This multi-sourced approach provides a more accurate and robust understanding than relying on any single method. It allows them to account for various factors that influence inbox placement, from technical configuration to sender reputation and user engagement.
The combination of internal sending data, seed list results, live user panel insights, direct ISP feeds, and competitive intelligence from eDataSource helps SparkPost identify trends, troubleshoot issues, and provide actionable recommendations to their clients. This comprehensive data collection is essential for understanding the nuances of email deliverability in today's complex environment. It allows for a more detailed analysis of key performance indicators (KPIs) related to email marketing health and deliverability.
Ultimately, the goal is to help senders achieve optimal inbox placement and maximize the return on investment for their email programs. This layered approach ensures that the data presented is reliable and actionable, helping businesses navigate the challenges of email deliverability effectively. You can learn more about how to use these indicators in measuring email marketing health.
Views from the trenches
Best practices
Diversify your seed lists to include a wide range of mailbox providers and geographic locations for more accurate placement data.
Monitor both traditional and engaging seed results to understand both instantaneous and engagement-based filtering.
Regularly review your email authentication records like SPF, DKIM, and DMARC, as these significantly impact deliverability.
Segment your audience and tailor content to improve engagement, which in turn positively influences inbox placement.
Pay close attention to user complaints and unsubscribes; high rates signal issues that can harm your sender reputation.
Common pitfalls
Relying solely on your own sending statistics, which don't show where emails land within the inbox (primary, promotions, spam).
Ignoring feedback loops from major ISPs, missing critical data on spam complaints.
Failing to maintain list hygiene, leading to bounces and engagement issues that negatively affect sender reputation.
Not adjusting sending patterns based on inbox placement data, missing opportunities for improvement.
Overlooking the impact of content on deliverability, such as using spammy keywords or broken links.
Expert tips
Use email deliverability monitoring services to gain a holistic view of your inbox placement.
Leverage DMARC reports to identify authentication failures and potential deliverability issues.
Understand that inbox placement is dynamic and requires continuous monitoring and adaptation.
Focus on building a positive sender reputation through consistent sending of valuable content.
Always test new campaign types or significant changes to existing ones with seed lists before a full send.
Marketer view
A marketer from Email Geeks says that many email service providers maintain their own mailboxes at various internet service providers, which they use to monitor where emails are delivered.
2022-08-02 - Email Geeks
Marketer view
A marketer from Email Geeks says that these providers send mail to their own mailboxes and then check for delivery location to inform clients where the mail landed.
2022-08-02 - Email Geeks
Summary of SparkPost's data collection methods
SparkPost's ability to provide comprehensive inbox placement data stems from a multi-faceted approach, combining traditional seed list testing with dynamic user panel data, direct feeds from mailbox providers, and advanced analytics from strategic acquisitions like eDataSource. This layered strategy is essential in deciphering the complex and ever-changing algorithms of ISPs that determine where an email ultimately lands.
For email senders, this means more than just knowing if an email was delivered; it means understanding its true reach within the inbox. By leveraging these diverse data points, SparkPost helps clients optimize their email campaigns for better engagement, improved deliverability, and ultimately, greater success in reaching their audience effectively.
Gmail and 
Yahoo do not openly share detailed inbox placement data for every single email sent. Instead, ESPs employ a combination of sophisticated techniques to provide clients with insights into where their messages land. This includes leveraging various data sources to paint a comprehensive picture of deliverability.
Google, 
Microsoft, and 
Apple, as well as smaller, regional providers. This breadth ensures that the inbox placement data is as representative as possible of actual subscriber engagement and filtering. For more on testing, consider the best inbox placement testing tools.
Outlook and 
AOL.
