What is the best way to clean an email list with steadily decreasing open rates?
Matthew Whittaker
Co-founder & CTO, Suped
Published 1 Jul 2025
Updated 18 Aug 2025
8 min read
Seeing a steady decline in your email open rates can be concerning. It often signals that your email list is becoming less engaged or accumulating problematic addresses, which can seriously impact your deliverability and sender reputation. A high volume of unengaged subscribers or invalid email addresses can lead to increased bounce rates, spam complaints, and eventually, blocklisting (or blacklisting).
Cleaning your email list isn't just about removing bad addresses, it's about optimizing your entire email program for better performance. A clean list ensures your messages reach genuinely interested recipients, improving engagement metrics like open rates and click-through rates, and protecting your sending reputation. It's a critical step to ensure the long-term health of your email marketing efforts.
In this guide, I will outline the best strategies for cleaning your email list when open rates are consistently dropping. We will explore how to identify and remove problematic subscribers, re-engage inactive ones, and implement practices to maintain a healthy list going forward.
Understanding the decline in open rates
A steadily decreasing open rate is a clear sign that your email list needs attention. This decline is often a symptom of underlying issues, rather than just a simple lack of interest from your audience. While content relevancy and subject line optimization play a role, list hygiene is fundamental. When open rates drop, it often correlates with an increase in unengaged subscribers who either aren't opening your emails or are actively marking them as spam.
Beyond unengaged users, your list might contain a growing number of invalid or outdated email addresses, known as hard bounces. Sending to these addresses repeatedly signals to internet service providers (ISPs) that your sending practices are poor, harming your sender reputation. It can also lead to hitting spam traps, which are email addresses specifically designed to catch spammers, resulting in your IP address or domain being placed on a blocklist (or blacklist).
Furthermore, a declining open rate can be an early indicator of broader deliverability issues. ISPs monitor how recipients interact with your emails, and low engagement can cause your messages to be routed to the spam folder, or even blocked entirely. This negative feedback loop can be challenging to reverse once established, making proactive list cleaning essential. For more about deliverability issues, read our guide on why your emails are going to spam.
Proactive list hygiene strategies
The most effective way to address steadily decreasing open rates is to implement a robust email list cleaning strategy. This involves several key steps aimed at removing problematic addresses and improving the overall health of your list. Starting with a comprehensive audit is crucial, identifying subscribers who haven't opened or clicked your emails in a significant period, typically 90 days to a year.
One of the first actions to take is to identify and remove hard bounces. These are permanent delivery failures, indicating an invalid or non-existent email address. Continuously sending to hard bounces severely damages your sender reputation. While most email service providers (ESPs) automatically suppress hard bounces, it's wise to review them periodically, especially if you've imported lists or experienced system issues. You can also explore email list cleaning services that specialize in this.
Another critical step is to deal with soft bounces. While these are temporary delivery issues, a consistent pattern for a specific address can indicate a persistent problem. Many ESPs retry soft bounces for a period, but if an email address repeatedly soft bounces over multiple campaigns, it may be best to consider it inactive. Understanding how to clean up soft bounces is important.
Hard bounces
Definition: Permanent delivery failures, meaning the email cannot be delivered to that address now or ever.
Causes: Invalid email address, domain name doesn't exist, recipient server blocked delivery permanently.
Impact: Significantly harms sender reputation, increases spam complaints, and can lead to blacklisting. Prompt removal is crucial for boosted email deliverability.
Action: Immediately remove these addresses from your list. Most ESPs automate this, but regular checks and email verification services are recommended.
Implementing a double opt-in process for new subscribers is one of the most effective long-term strategies for maintaining a healthy list and preventing declining open rates. This ensures that new subscribers genuinely want to receive your emails and that their email addresses are valid, significantly reducing the likelihood of hard bounces and spam complaints from the outset. This proactive measure builds a more engaged audience from day one.
Re-engagement and suppression strategies
Identifying and segmenting inactive subscribers is another crucial step. These are subscribers who haven't engaged with your emails (opened or clicked) for a defined period. While they aren't hard bounces, sending to them continues to dilute your open rates and can negatively impact your sender reputation. Creating segments based on engagement allows you to tailor your approach. Remember, it's about engagement over sheer volume.
Before removing inactive subscribers, consider running a re-engagement campaign. This is a series of emails designed to rekindle their interest or confirm their desire to remain on your list. Offer exclusive content, special discounts, or simply ask if they still want to hear from you. Provide a clear option to opt-out if they're no longer interested, or to update their preferences. This can sometimes revive segments of your list that you thought were lost. For tips on re-engaging inactive subscribers safely, check out our dedicated guide.
For subscribers who do not respond to re-engagement efforts, it's time to sunset them from your active mailing list. This might feel counterintuitive when you're trying to maintain a large audience, but removing disengaged contacts is crucial for improving overall deliverability and open rates. Sending to a smaller, more engaged list will ultimately yield better results and protect your sender reputation from negative signals. This is part of a broader strategy for improving email deliverability.
Re-engagement campaigns
Objective: Give inactive subscribers a chance to reconfirm interest.
Strategy: Send a short series (1-3 emails) with a clear call to action to remain subscribed.
Timing: Target subscribers who haven't opened or clicked in 90-180 days.
Content: Offer exclusive content, a discount, or ask for updated preferences. Example:
Example Re-engagement Email
Subject: Do you still want to hear from us?
Body: It looks like you haven't opened our emails in a while. If you'd like to continue receiving [content type], please click here to confirm!
Suppression (sunsetting)
Objective: Remove unresponsive subscribers to improve list quality.
Strategy: Permanently remove subscribers who did not engage after re-engagement campaigns.
Timing: Quarterly or bi-annually, depending on sending volume and list decay rate.
Benefits: Higher open rates, lower bounce rates, reduced spam complaints, better sender reputation. Read about sunsetting inactive subscribers.
Ongoing maintenance and monitoring
Cleaning your list isn't a one-time event, it's an ongoing process. Regularly scheduled list hygiene, often called list scrubbing, is vital to prevent future declines in open rates and maintain strong deliverability. How often you clean depends on your sending volume, list growth rate, and audience behavior, but a quarterly or bi-annual deep clean is a good starting point.
Monitoring your key email metrics consistently will help you catch issues early. Pay close attention to open rates, click-through rates, bounce rates (both hard and soft), and complaint rates. A sudden spike in bounces or complaints, or a gradual dip in opens, indicates it's time for a more aggressive cleaning. Utilize tools like segmentation features in your ESP to keep an eye on these groups.
Finally, focus on attracting engaged subscribers from the start. Implement clear expectations during the sign-up process, ensure your welcome series is compelling, and consistently deliver valuable content. This reduces the number of disengaged subscribers you'll need to clean later, fostering a healthier, more responsive email list from its inception. You can explore how to maintain a clean list.
Views from the trenches
Best practices
Actively monitor engagement metrics like open rates, click rates, and complaint rates to detect issues early.
Segment your list based on engagement levels to identify and manage inactive subscribers effectively.
Run re-engagement campaigns for dormant segments before considering their removal from your list.
Always use double opt-in for new subscribers to ensure high-quality, genuinely interested contacts from the start.
Regularly clean your list by removing hard bounces and subscribers who repeatedly fail re-engagement efforts.
Common pitfalls
Ignoring consistently decreasing open rates, which can indicate deeper deliverability problems.
Failing to remove hard bounces, leading to damaged sender reputation and higher spam complaints.
Not segmenting inactive subscribers, resulting in diluted engagement metrics and wasted sending efforts.
Over-relying on email list cleaning services without implementing ongoing hygiene practices.
Neglecting to nurture new subscribers, causing them to become inactive quickly.
Expert tips
A comprehensive approach to email list cleaning includes both reactive measures (removing bounces, suppressions) and proactive strategies (double opt-in, continuous monitoring).
Consider the source of your email addresses. Poor acquisition methods often lead to lower engagement and higher decay rates over time.
Beyond open rates, look at conversion rates. An engaged list with lower opens but high conversions is often more valuable than a large list with high opens but low conversions.
Your content strategy plays a significant role in preventing list decay. Consistent, relevant, and valuable content keeps subscribers engaged and reduces churn.
Review your sending frequency. Too many emails can lead to fatigue, while too few can lead to subscribers forgetting they opted in.
Expert view
Expert from Email Geeks says a reconfirmation campaign with confirmed opt-in is necessary to clean the list effectively.
2021-10-21 - Email Geeks
Expert view
Expert from Email Geeks says if open rates are steadily dropping, one must investigate the root cause, which could be statistical due to too many non-engaged recipients, or related to content or general list hygiene methods.
2021-10-21 - Email Geeks
Cleaning for a healthier email ecosystem
Cleaning an email list with steadily decreasing open rates is a multi-faceted process that goes beyond simple removal of addresses. It involves understanding the root causes of disengagement, implementing strategic re-engagement campaigns, and rigorously suppressing (or removing) those who remain unresponsive. The goal is to cultivate a highly engaged list that values your content, leading to improved deliverability, better sender reputation, and ultimately, higher ROI from your email marketing efforts.
By committing to ongoing list hygiene and focusing on attracting genuinely interested subscribers, you can reverse the trend of declining open rates and ensure your emails consistently reach the inbox. Remember, a smaller, highly engaged list is far more valuable than a large list filled with inactive or invalid contacts. For broader strategies to improve your deliverability, review our article on why your emails fail.
