What are the best practices for re-engaging inactive email subscribers safely?

Key findings

• Risk assessment: Sending to highly inactive segments can significantly increase spam complaints, bounce rates, and spam trap hits, negatively impacting your sender reputation. It is critical to understand how messaging inactive addresses affects deliverability.
• Segmentation: Effective re-engagement starts with precise segmentation, identifying subscribers based on their last activity (e.g., 6 months, 1 year, 2 years). The older the inactivity, the higher the risk.
• Gradual approach: Instead of a large blast, a staggered or patched send over several days or weeks to small segments is recommended to monitor performance and mitigate deliverability risks.
• List hygiene: Prioritize cleaning your list with an email validation service before sending. This helps remove hard bounces and potential spam traps.
• Content focus: Re-engagement campaigns should feature compelling, value-driven content with a clear call to action, reminding subscribers of the brand's value or offering incentives.

Key considerations

• Define inactivity: Clearly define what constitutes an unengaged subscriber for your specific business model and email frequency. This helps determine the appropriate re-engagement window.
• Automated series: Utilize automated re-engagement series rather than one-off blasts. These can be more forgiving deliverability-wise and allow for a tailored, multi-step approach.
• Sunset policies: Implement a sunset policy to remove subscribers who do not re-engage after a set period. This protects your sender reputation long-term. More on this is available from SiteGround's re-engagement guide.
• Monitor metrics: Closely monitor engagement metrics (opens, clicks), bounce rates, and complaint rates during re-engagement campaigns. Be prepared to pause or adjust sends if negative trends emerge.

Key opinions

• Strategic sending: Many marketers advocate for sending re-engagement emails in smaller patches rather than a single large blast to allow for monitoring and adjustment.
• Automated series preference: There is a strong preference for using automated re-engagement series, often 2-3 emails, tailored specifically for inactive users, rather than adding them back to regular campaigns.
• Permission decay: Some marketers raise concerns about the validity of permission for very old segments, citing legal or best practice guidelines, especially after two years of no contact.
• Personalized content: Customizing content to acknowledge their absence and offer exclusive value is seen as crucial for enticing re-engagement.

Key considerations

• Inactivity timeframe: The length of inactivity is a key determinant for the risk level. Marketers generally agree that the longer a subscriber has been inactive, the more cautiously you should proceed. Understanding when to stop sending emails is important.
• Re-verification: Some marketers suggest re-verifying old segments as a critical first step to remove invalid email addresses.
• Offer clear choices: Provide clear options for subscribers to update preferences, reduce frequency, or unsubscribe. This respects their choice and reduces spam complaints. More tips are available from Customer.io's guide to re-engagement.
• Testing and tagging: Advocates for tagging segments and carefully tracking engagement over short periods (e.g., three days) to identify successful re-engagement patterns before expanding sends.

Key opinions

• Thorough list cleaning: Experts emphasize using a robust email validation service to remove spam traps, hard bounces, and known bad addresses before initiating any re-engagement campaign. This is a crucial step to improve Gmail deliverability.
• Subdomain usage: Sending re-engagement campaigns from a separate, warm subdomain (not your main sending domain) is often recommended. This isolates potential negative impacts on your primary sender reputation.
• Slow sending speed: When sending to inactive lists, experts advise starting with very low sending speeds (e.g., hundreds per hour) and gradually increasing based on positive engagement metrics, mimicking a warm-up process.
• Focus on engagement: The primary goal of re-engagement is to elicit an active response (open or click). If no response is received after a few attempts, these addresses should be suppressed to protect overall deliverability. This relates to understanding how spam traps work.

Key considerations

• Spam trap avoidance: Inactive lists are prone to containing spam traps, which can instantly blacklist your IP or domain. Diligent list cleaning is the best defense.
• Monitoring reputation: Continuously monitor your sender reputation using tools like Google Postmaster Tools, particularly after re-engagement sends. This provides early warnings of negative impacts.
• Strategic opt-out: Offer easy unsubscribe options to quickly remove disengaged users, preventing them from marking your emails as spam. This practice contributes to long-term list health. More expert advice can be found at Kickbox's blog on reviving subscribers.
• Re-engagement timing: Consider the timeframe of inactivity. Very old lists (e.g., dormant for over two years) should be treated with extreme caution, potentially even requiring a warming up process.

Key findings

• Consent validity: Documentation often stresses that explicit consent can expire over time, especially with prolonged inactivity. Re-engaging very old lists without fresh consent can violate regulations (e.g., GDPR) or lead to increased complaints.
• Email validation importance: Technical guides consistently recommend using email validation services to filter out invalid and risky addresses. This proactive measure prevents hard bounces and engagement with spam traps.
• Sender reputation preservation: ISPs (Internet Service Providers) actively monitor engagement rates. Sending to disengaged recipients signals poor list quality, which can lead to higher spam placement and blacklisting, even for subsequent emails to active subscribers.
• Unsubscribe options: Providing clear and easy unsubscribe mechanisms is not just a legal requirement but a deliverability best practice. It allows uninterested users to opt out gracefully, rather than marking emails as spam. This aligns with Gmail's 'manage subscriptions' feature.

Key considerations

• Double opt-in: While not directly for re-engagement, documentation often highlights double opt-in as the gold standard for list quality, reducing the likelihood of inactive subscribers needing re-engagement in the first place.
• Sunset policies: Formal documentation frequently recommends implementing clear sunset policies. This means automatically removing subscribers who remain unengaged after a series of re-engagement attempts to maintain list health and prevent deliverability issues. Mailgun's blog provides more information on this, advising to have a sunset strategy.
• Feedback loops: Utilizing ISP feedback loops (FBLs) is crucial. These alert you to spam complaints, allowing you to immediately suppress those users and prevent further damage to your reputation, especially during re-engagement campaigns.
• Technical compliance: Ensure your email authentication protocols (SPF, DKIM, DMARC) are correctly configured. A strong technical foundation helps maintain trust with ISPs when sending, even to less engaged segments. Review Outlook's new sender requirements.