How to improve email deliverability and newsletter open rates through list cleaning?
Matthew Whittaker
Co-founder & CTO, Suped
Published 24 May 2025
Updated 18 Aug 2025
8 min read
Email newsletters are a powerful tool for engaging with your audience, but declining open rates can be a sign of deeper issues. Many marketers notice their open rates steadily decreasing over time, and while it's easy to assume it's just a deliverability problem, the reality is often more nuanced. A significant factor contributing to this decline, and to overall email deliverability, is the health of your email list.
Poor list hygiene can lead to emails landing in spam folders, impacting your sender reputation, and ultimately diminishing the effectiveness of your campaigns. Understanding why and how to clean your email list is crucial for ensuring your messages reach the inbox and get noticed. It’s about more than just numbers, it’s about reaching the right people.
This guide will walk you through the importance of email list cleaning, how it impacts deliverability and open rates, and practical strategies to maintain a healthy subscriber base. We’ll explore how proactive list management can transform your email marketing performance.
Why list cleaning boosts deliverability and open rates
A clean email list is fundamental to good email deliverability. When you send emails to a list filled with inactive, invalid, or spam trap addresses, it sends negative signals to internet service providers (ISPs). These signals can severely damage your sender reputation, leading to lower inbox placement rates and higher bounce rates.
For example, sending to non-existent email addresses results in hard bounces, which tell ISPs that you might not be managing your list effectively. Too many hard bounces can quickly flag your sending IP and domain as suspicious, potentially leading to your emails being directed to the spam folder or even being blocked entirely. Similarly, hitting spam traps can instantly land you on a blacklist (or blocklist).
While open rates are often looked at as a key indicator of campaign success, it's important to understand their limitations. An open rate measures whether an image in your email was loaded, not necessarily that the recipient actively engaged with your content. Bots can open emails, and some email clients block image loading by default. Therefore, a low open rate isn't always a direct sign of deliverability issues, but it can reflect a lack of engagement, which still impacts your sender reputation over time.
A healthier list, achieved through regular cleaning, ensures that your engagement metrics (like clicks and conversions) are more accurate and meaningful, as you are sending to genuinely interested subscribers. This also helps you avoid low email open rates and improves overall campaign performance. You can delve deeper into email blocklists to understand their impact.
Identifying unengaged subscribers
The problem with inactive subscribers
Sending emails to disengaged subscribers can lead to several negative outcomes, even if they aren't generating hard bounces. These contacts are less likely to open, click, or engage with your content. This low engagement sends a strong negative signal to ISPs, indicating that your emails might not be valuable or relevant to their users. It can lead to emails being marked as spam or quietly filtered out of the inbox.
High volumes of unengaged recipients can also increase your spam complaint rates. If people aren't interested, they're more likely to mark your email as spam rather than simply unsubscribing. This directly hurts your sender reputation and can result in your domain or IP being added to a blacklist (or blocklist).
Determining who is truly unengaged goes beyond just looking at open rates. While open rates can offer a hint, it's crucial to look at other metrics that reflect genuine interaction. For instance, clicks are a much stronger indicator of engagement, as they require direct action from the recipient.
Beyond email metrics, consider integrating data from your website or CRM. Are these subscribers visiting your website, making purchases, or interacting with your brand on other channels? This holistic view helps you differentiate between a truly inactive subscriber and someone who simply doesn't open every email but remains a valuable contact. This approach supports a healthy email list.
Engagement indicators
A nuanced approach to subscriber engagement is crucial. Different metrics paint different pictures of subscriber activity and help assess a contact's value beyond just opens. Combining these insights allows for more informed list cleaning decisions. Consider these metrics:
Click-through rates: The most reliable indicator of active engagement, as it shows a direct interaction with your content or an offer.
Website activity: Track if subscribers visit your site after receiving an email, even if they didn't click a link within the email itself.
Purchase history: For e-commerce businesses, recent purchases or engagement with product pages can signal ongoing interest.
Form submissions/downloads: If subscribers are filling out forms, downloading resources, or signing up for events, they are engaged.
Strategies for effective list cleaning
Once you have identified your unengaged subscribers, the next step is to implement strategies to either re-engage them or remove them from your active sending list. This process, often called sunsetting, is critical for maintaining a high sender reputation and improving your deliverability.
A common first step is to send a re-engagement campaign. This is a series of emails designed to rekindle interest. It might offer exclusive content, a special discount, or simply ask if the subscriber still wishes to receive your emails. For some, a clear call to action to update preferences or confirm subscription can be effective.
For those who do not respond to re-engagement efforts, removing them from your active sending list is generally the best practice. While it might feel counterintuitive to reduce your list size, it ensures you're only sending to an engaged audience, which boosts your overall deliverability and open rates. The frequency of this process depends on your sending volume and list size, but regular cleaning is recommended. You might also want to explore email list cleaning services.
Automating list hygiene and validation
Beyond periodic list cleaning, establishing ongoing list hygiene practices is vital. This proactive approach prevents your list from accumulating large numbers of unengaged or invalid addresses in the first place, saving you from more drastic clean-up efforts later.
Implementing a double opt-in process for new subscribers is one of the most effective preventative measures. This ensures that every new subscriber genuinely wants to receive your emails, reducing the likelihood of bounces and spam complaints from the outset. It also weeds out typos and fake email addresses.
Regular segmentation of your audience based on their engagement levels is another excellent practice. This allows you to tailor content to highly engaged subscribers while potentially sending less frequent or different content to less active segments. This can improve deliverability by showing ISPs that you're sending relevant content to interested recipients. Consider managing an unengaged contact list for optimal results.
Finally, make it easy for subscribers to unsubscribe. A clear and visible unsubscribe link reduces the chances of recipients marking your email as spam. While it might seem counterproductive to encourage unsubscribes, it's far better to have a smaller, engaged list than a large, unengaged one that negatively impacts your sender reputation and risks getting you on a blocklist (or blacklist).
Before cleaning
Inflated list size: Many inactive or invalid email addresses are present.
High bounce rates: Frequent hard and soft bounces due to poor data quality.
Another powerful way to ensure ongoing list hygiene is through email validation. This process verifies email addresses in real-time or in bulk, identifying and removing invalid, disposable, or risky email addresses before they impact your sender reputation. Many email service providers offer this as a built-in feature, or you can use a dedicated email validation service.
Real-time email validation
Implementing real-time email validation at the point of signup is an excellent proactive measure. This prevents invalid addresses from even entering your list, ensuring every new subscriber is legitimate. It validates the address against various criteria, checking for syntax errors, domain validity, and known disposable email providers.
Here's a conceptual example of how real-time validation might work at a basic level:
function validateEmail(email) {
// Check for basic format
if (!/^[\w.-]+@[\w.-]+\.[a-zA-Z]{2,6}$/.test(email)) {
return false; // Invalid format
}
// Example: Check against a list of known disposable domains
const disposableDomains = ['mailinator.com', 'tempmail.com'];
const domain = email.substring(email.lastIndexOf('@') + 1);
if (disposableDomains.includes(domain)) {
return false; // Disposable email
}
return true;
}
Views from the trenches
Best practices
Actively monitor engagement metrics beyond just opens, focusing on clicks and website activity.
Implement a double opt-in process for all new subscribers to ensure high-quality leads from the start.
Regularly segment your email list based on engagement levels to tailor content more effectively.
Set up automated re-engagement campaigns for inactive subscribers before sunsetting them.
Ensure a clear and easy-to-find unsubscribe option in all your emails to reduce spam complaints.
Common pitfalls
Relying solely on open rates as a metric for list health, as they can be misleading due to bot activity.
Not removing hard bounces promptly, which severely damages sender reputation and deliverability.
Ignoring email list hygiene in favor of growing list size, leading to higher costs and lower performance.
Failing to segment your audience, resulting in irrelevant content being sent to some subscribers.
Making it difficult for subscribers to unsubscribe, forcing them to mark your emails as spam instead.
Expert tips
Focus on active engagement rather than just vanity metrics like total subscriber count.
Tailor your sunsetting strategy based on email cadence and business type, not a universal rule.
Understand that open rates are less reliable due to images loading without actual human interaction.
Separate transactional emails from marketing emails to protect critical communications.
Prioritize genuine user actions (e.g., logins, purchases) over automated email client interactions for sunsetting.
Expert view
Expert from Email Geeks says open rates are not a perfect indicator of who is actually opening and reading your mail, as images can load without recipient interaction, or emails can be read without images loading. Focus on actual user data to determine deliverability issues.
2025-07-02 - Email Geeks
Marketer view
Marketer from Email Geeks says that if you are not proactively cleaning your list, it is common for open rates to steadily decrease. It's important to sunset (stop sending to) inactive recipients, especially those who haven't engaged in 3-6 months, to preserve open rates and sender reputation.
2025-07-03 - Email Geeks
Final thoughts on list hygiene
Email list cleaning is not merely a task to improve metrics, it is a foundational practice for maintaining a healthy and effective email marketing program. By regularly identifying and removing unengaged subscribers, validating email addresses, and implementing proactive hygiene measures, you directly influence your sender reputation and ensure your messages consistently reach the inbox.
While open rates can be a misleading metric on their own, a clean and engaged list will naturally lead to more accurate and often higher engagement figures, including clicks and conversions. This disciplined approach not only improves your email deliverability but also maximizes your return on investment by ensuring you're only communicating with your most valuable audience.
Prioritize list cleaning as an ongoing process, not a one-time fix. By doing so, you'll cultivate a list that actively contributes to your marketing goals, fostering better connections and driving more impactful results. Proactive list management is key to long-term email marketing success and avoiding email blacklists (or blocklists).
