How do Internet Service Providers track email engagement and its impact on deliverability?

Key findings

• Engagement is paramount: ISPs, particularly webmail providers like Gmail, Microsoft (Outlook.com), and Yahoo (Oath), heavily rely on user engagement metrics to assess sender trustworthiness and filter incoming mail.
• Beyond traditional filters: While traditional spam filters still use signals like spam traps and bounce rates, engagement provides a more dynamic and nuanced picture of how recipients perceive your emails.
• Direct impact on inbox placement: Consistently low engagement can significantly degrade your sender reputation, leading to lower inbox placement rates and increased routing to the spam or junk folder.
• Varying metrics and reporting: Different email platforms may track and report engagement metrics differently, for example, whether a click also generates an open event, or if unsubscribe clicks are counted in general click metrics.
• Enterprise vs. consumer differences: Enterprise inboxes (e.g., Google Workspace, Microsoft 365 for business) tend to prioritize explicit signals such as direct complaints, blocks by executives, and spam traps over subtle engagement patterns.

Key considerations

• Maintain list hygiene: Regularly clean and manage your email lists, removing inactive subscribers to ensure your engagement metrics remain high. This is crucial for improving Gmail deliverability.
• Prioritize relevant content: Send highly targeted and valuable content to encourage positive recipient interactions like opens, clicks, and replies. ISPs evaluate engagement across multiple campaigns.
• Monitor sender reputation: Continuously monitor your sender reputation and various factors that influence email deliverability, including engagement signals.
• Understand ISP algorithms: Be aware that ISPs use their own unique algorithms, meaning engagement metrics may be weighted differently across providers. Understanding how sender score works can be helpful.

Key opinions

• Engagement directly affects deliverability: Marketers frequently observe a direct correlation between high engagement rates and successful inbox placement, advocating for its importance in overall email deliverability strategies.
• Internal validation challenges: Many marketers find it difficult to convey the significance of engagement metrics to internal infrastructure directors or other non-marketing teams who may question ISP's ability to measure such interactions.
• Nuances in metric tracking: Questions often arise regarding how different email service providers (ESPs) handle engagement metrics, such as whether clicks automatically generate open events, or how unsubscribe clicks are categorized.
• Focus on real human interaction: The ultimate goal for marketers is to drive genuine human engagement, as these signals (e.g., replies, forwards, moving to inbox) are the most powerful indicators to ISPs that an email is desired.

Key considerations

• Educate internal stakeholders: Provide clear data and case studies to demonstrate the impact of engagement on deliverability, especially when facing internal resistance to best practices.
• Prioritize audience quality: Focus on acquiring and nurturing highly engaged subscribers rather than simply growing list size, as ISPs look at many factors to assess trustworthiness.
• Optimize for engagement: Design emails and campaigns to maximize positive interactions. Learn how to increase email click-through rate to improve overall engagement.
• Understand ESP reporting: Gain clarity on how your chosen email service provider tracks and reports engagement metrics (unique vs. gross, etc.) to accurately assess performance and avoid common email deliverability issues.

Key opinions

• Webmail providers dominate engagement tracking: Engagement metrics are primarily leveraged by large webmail providers (Gmail, Microsoft, Oath) because they control the user interface, providing direct insight into user interactions.
• Enterprise filters differ: Enterprise email systems rely more on traditional 'spam-like' signals such as spam traps, high bounce rates, and direct user complaints, rather than subtle engagement nuances.
• High-level complaints are critical: A complaint or block from a senior executive (e.g., VP or C-level) within an enterprise can lead to permanent blocking for the entire company, making targeted B2B sending risky if not managed carefully.
• Google Workspace's strict stance: While sharing underlying filters with consumer Gmail, Google Workspace customers generally have a low tolerance for bulk marketing mail, often preferring it to be blocked entirely.
• Complexity of open tracking: Defining what constitutes an 'open' is complex, as various factors can trigger an open event, requiring careful interpretation of metrics.

Key considerations

• Differentiate sending strategies: Tailor your email sending approach based on whether you are targeting consumer webmail users or enterprise recipients, accounting for their distinct filtering priorities.
• Avoid spam traps: Actively manage your lists to avoid hitting email spam traps, as these are significant indicators for enterprise filters.
• Implement strong authentication: Ensure proper SPF, DKIM, and DMARC records are configured to build trust with all ISPs. Consider Gmail's nuanced deliverability factors.
• Strategic IP Warmup: For new sending IPs, implement a gradual IP warmup strategy tailored to individual ISPs to build a positive reputation.

Key findings

• Proprietary algorithms: ISPs employ complex, proprietary algorithms that weigh various factors, with user engagement being a significant determinant for inbox placement.
• User behavior as signals: Positive user behaviors, such as opening emails, clicking links, replying, forwarding, or adding senders to contacts, enhance sender reputation. Conversely, negative actions like deleting without opening or marking as spam severely damage it.
• Reputation contribution: Engagement metrics directly feed into and influence the sender's IP and domain reputation, which then dictates how future emails are routed.
• Authentication as foundation: Proper email authentication protocols (SPF, DKIM, DMARC) are foundational. Without them, even strong engagement signals may be discounted or ignored by ISPs.

Key considerations

• Adhere to ISP guidelines: Strictly follow the sender guidelines and best practices published by major ISPs, such as those found in Google Postmaster Tools and Outlook's Smart Network Data Services (SNDS). For example, deliverability is best measured through real human engagement.
• Leverage feedback loops: Enroll in and actively use ISP feedback loop services (FBLs) to promptly identify and remove subscribers who mark your emails as spam, safeguarding your sender reputation.
• Monitor Postmaster Tools: Regularly check your ISP-provided postmaster tools (e.g., Google Postmaster Tools) for direct insights into your domain reputation, spam rates, and deliverability performance.
• Ensure authentication: Verify that your SPF, DKIM, and DMARC records are correctly implemented and aligned, as these authentication methods are fundamental for ISPs to trust your sending domain. Refer to a simple guide to DMARC, SPF, and DKIM.