Does pruning your email lists help with deliverability?

Key findings

• Improved metrics: Removing inactive subscribers generally leads to higher open rates, click-through rates, and lower bounce rates, which are positive signals to mailbox providers.
• Enhanced sender reputation: A clean list signals to ISPs (Internet Service Providers) that your emails are valued and relevant, leading to better domain and IP reputation.
• Reduced costs: Many email service providers (ESPs) charge based on subscriber count, so pruning can lead to significant cost savings.
• Spam trap avoidance: Inactive email addresses can turn into spam traps. Sending to them can severely damage your deliverability and lead to blocklisting.
• Context matters: The impact and necessity of pruning vary significantly between different types of emails, such as marketing campaigns versus content newsletters.

Key considerations

• Defining engagement: Mailbox providers assess engagement differently than senders. Factors beyond opens and clicks, such as replies, forwards, and moving emails to the primary inbox, are crucial. Apple Mail Privacy Protection (MPP) also complicates open tracking.
• Win-back campaigns: Before outright removal, consider implementing re-engagement campaigns to give inactive subscribers a chance to confirm their interest, as suggested by Klaviyo.
• Subscriber intent: Subscribers who actively opted in may still want your emails even if they don't appear to engage. Removing them without sufficient negative signals (like spam complaints or hard bounces) could lead to lost readership.
• Data-driven decisions: Rely on your own historic data and specific business goals rather than arbitrary cut-off points or generalized best practices that may not apply to your unique sending patterns.

Key opinions

• Essential hygiene: Pruning is considered a basic and crucial element of email list hygiene to prevent negative impacts on deliverability metrics.
• Performance improvement: It helps uncover risky data, boosts sender reputation, and can lead to higher ROI by ensuring emails reach interested recipients.
• Cost efficiency: Mailing lists with many unengaged subscribers can be costly due to ESP pricing models, making pruning a financially sensible move.
• Contextual application: The aggressiveness of pruning should depend on the type of email sent. It is more critical for marketing emails aiming for clicks and conversions than for content newsletters focused on readership.
• Re-engagement first: Many advocate for attempting re-engagement campaigns before removing subscribers outright.

Key considerations

• Engagement measurement: Marketers must understand that their perception of engagement (e.g., opens, clicks) might differ from how mailbox providers assess it. This can lead to inadvertently removing active, albeit passively engaged, readers.
• Avoiding over-pruning: Blindly applying generic best practices without considering specific audience behavior can be counterproductive.
• List segmentation: For larger lists, segmenting non-engagers can help monitor potential issues and facilitate targeted win-back efforts without immediately impacting the primary sending list.
• Long-term vs. short-term: While pruning can offer quick wins in improving metrics, a sustainable strategy involves balancing engagement with subscriber retention, as discussed by Benchmark Email.

Key opinions

• Gmail's emphasis on engagement: Pruning is particularly relevant for Gmail's filtering algorithms, where sustained disengagement can lead to poor inbox placement.
• Beyond opens and clicks: Mailbox providers' assessment of engagement is more complex than what ESPs typically track. Relying solely on these metrics can be misleading and may result in the removal of genuinely interested subscribers.
• Subscriber lifecycle management: Instead of immediate pruning, a phased approach involving re-engagement campaigns is often recommended to confirm subscriber interest.
• Nuance is key: Simplistic best practices often lack the necessary nuance required for diverse sending scenarios (e.g., newsletters vs. marketing emails).
• Negative signals are paramount: Focusing on negative signals, such as bounces and spam complaints, is more reliable for list hygiene than perceived low engagement.

Key considerations

• Understanding proxies and pre-fetching: Features like Apple Mail Privacy Protection and other mailbox provider proxying can artificially inflate open rates, making them unreliable indicators of true engagement.
• Risk of removing active readers: Over-pruning based on incomplete engagement data can lead to the removal of subscribers who are genuinely reading emails through methods not tracked by sender metrics (e.g., RSS readers, text-only clients).
• Adaptability: Deliverability rules and metrics constantly evolve, requiring senders to stay informed and adapt their list management strategies accordingly.
• Win-back strategies: Implementing thoughtful win-back campaigns is critical for addressing edge cases and re-confirming interest from seemingly inactive subscribers.

Key findings

• Impact on sender reputation: A clean list with high engagement metrics is a strong indicator of a reputable sender to ISPs.
• Reduced bounces: Pruning helps minimize both soft and hard bounces, which negatively affect deliverability and sender scores.
• Better inbox placement: A healthy list ensures that emails are more likely to land in the primary inbox rather than spam folders.
• Improved ROI: By focusing efforts on engaged subscribers, email marketing campaigns yield better returns.

Key considerations

• Segmenting unengaged contacts: A common recommendation involves creating segments of unengaged contacts to manage them separately or exclude them from regular sends.
• Win-back campaigns: Before removal, documentation often suggests attempting re-engagement campaigns to revive interest from inactive subscribers, as highlighted by Mailgun.
• Continuous process: List cleaning is not a one-time event but an ongoing process vital for maintaining long-term deliverability.
• User experience: Beyond metrics, a clean list contributes to a better customer experience by ensuring that only relevant emails are sent to willing recipients.