How should I re-engage a dormant email list with high spam complaints?
Matthew Whittaker
Co-founder & CTO, Suped
Published 21 Jul 2025
Updated 16 Aug 2025
8 min read
Re-engaging a dormant email list, especially one with a history of high spam complaints, is a delicate operation. My goal is always to reactivate subscribers without further damaging sender reputation or triggering more blocklist issues. It requires a meticulous approach, starting with understanding why the list went dormant and why complaints occurred in the first place.
The challenge intensifies when different platforms report conflicting spam complaint rates. For example, your ESP might show a high complaint rate (e.g., >1%) for specific mailbox providers like Microsoft, while your analytics platform or even Google Postmaster Tools might display a much lower overall percentage. This discrepancy often stems from how each system calculates the rate, whether it's per total send or per specific mailbox provider. It's crucial to investigate these differences to get a clear picture of the actual deliverability health.
My primary concern when faced with a dormant list that has generated a high number of spam complaints is preventing further damage to sender reputation. Sending to unengaged subscribers can rapidly escalate complaint rates, leading to email service providers (ESPs) and internet service providers (ISPs) flagging your emails as spam. This can result in your domain or IP address being added to a blocklist (or blacklist), severely impacting your ability to reach the inbox for any future campaigns.
List cleaning and strategic segmentation
Before attempting any re-engagement, the first and most critical step is to thoroughly clean your email list. A dormant list is often riddled with invalid addresses, spam traps, and recipients who simply no longer wish to receive your emails. Continuing to send to these addresses will only exacerbate your spam complaint issues and damage your deliverability.
Start by identifying genuinely inactive subscribers. This means defining what 'dormant' means for your specific audience and sending frequency. Look for contacts who haven't opened or clicked an email in a significant period (e.g., 6-12 months). Once identified, segment these contacts from your active subscribers. For those with high spam complaints, consider them a higher risk category. If your list includes addresses that have never engaged or haven't been sent to in a very long time, these are prime candidates for removal or extreme caution.
After segmentation, use an email validation service to remove invalid or risky addresses. This helps reduce bounces and protect against hitting spam traps, which are email addresses specifically designed to catch spammers. Removing these addresses immediately improves your list hygiene and reduces the likelihood of future spam complaints and blocklist entries. Consider this a necessary investment for long-term email health.
For the segment of dormant but valid subscribers you wish to re-engage, further segmentation based on their last known engagement is highly recommended. You might have segments that last engaged 3-6 months ago, 6-12 months ago, or even longer. This allows for a more tailored and cautious re-engagement strategy. Different levels of dormancy warrant different approaches to win-back campaigns.
Gradual re-engagement campaign
Re-engaging a list with high spam complaints requires a slow and deliberate warm-up process, similar to warming a new IP address or domain. Instead of sending a large blast, break your re-engagement emails into very small batches. I typically recommend starting with a few hundred emails per day to the most recently active dormant segments. Monitor your deliverability metrics closely with each send.
For the content of these re-engagement emails, focus on re-establishing value and reminding subscribers why they opted in. Avoid generic promotional content. Instead, offer something exclusive, ask for feedback, or highlight a new, relevant feature. Providing a clear and easy way to opt-out or adjust preferences is also vital. This transparency can reduce spam complaints by giving recipients an alternative to marking your email as spam.
The messaging should acknowledge the lapse in communication. Something as simple as, “It’s been a while, but we’ve missed you!” can be effective. Clearly state your value proposition and give them a compelling reason to re-engage. This could be a special discount, access to exclusive content, or an invitation to update their preferences to receive only what they want. Remember, the goal is to prompt a positive action (open, click, update preferences), not just to get the email delivered.
Protecting sender reputation
Maintaining a healthy sender reputation is paramount when dealing with a dormant list that has generated spam complaints. Your sender reputation is a key factor in whether your emails land in the inbox or the spam folder. High complaint rates are a significant red flag for ISPs and can lead to immediate deliverability issues.
Ensure your email authentication protocols, such as SPF, DKIM, and DMARC, are correctly configured. These protocols verify your sending identity and help prevent spoofing and phishing, which can also negatively impact your reputation. You can use DMARC monitoring to keep an eye on your authentication performance and identify any issues.
Complaints by provider vs. total complaints
It's important to differentiate between global spam complaint rates and those reported by individual mailbox providers. An ESP (e.g., Mailgun) might report a high complaint rate for a specific provider because it calculates the rate as a percentage of emails sent to that provider, rather than your total email volume. This can make the issue seem more severe than a raw overall percentage might suggest, but it's a critical detail for deliverability.
Monitor, adjust, and prune
Ongoing monitoring and quick adjustments are essential. Don't just send and forget. Pay close attention to your deliverability metrics: open rates, click-through rates, unsubscribe rates, and especially spam complaint rates. If you see a spike in complaints or unengagement for a particular segment, pause sends to that group and re-evaluate your strategy.
For dormant subscribers who don't re-engage after a series of win-back attempts, it's often best to remove them from your active mailing list. While it might feel counterintuitive to reduce your list size, retaining unengaged subscribers can harm your overall deliverability. They contribute to low engagement metrics, which signals to ISPs that your content is not valuable, potentially affecting your entire email program. Remember, a smaller, highly engaged list is far more valuable than a large, unengaged one.
Many email marketers recommend a re-engagement campaign consisting of 2-3 emails sent over a period of weeks. If there's no response, it's time to let them go. You can always try to re-engage them through other channels, but for email, they are a liability.
Focus on the long-term health of your email program. Re-engaging dormant lists is a marathon, not a sprint. Be patient, be data-driven, and prioritize deliverability over list size.
Views from the trenches
Best practices
Always validate dormant email lists before sending any re-engagement campaigns to remove invalid addresses and spam traps.
Segment your dormant list based on their last known engagement to tailor your re-engagement messages and sending volume.
Send re-engagement campaigns in very small, gradual batches to avoid sudden spikes in activity and maintain a positive sender reputation.
Craft compelling re-engagement content that offers clear value, reminds subscribers why they joined, or asks for preference updates.
Continuously monitor your deliverability metrics, including open rates, click-throughs, and spam complaints, to adjust your strategy in real-time.
Provide a clear and easy unsubscribe option in every email to reduce the likelihood of spam complaints from disengaged recipients.
Remove subscribers who do not respond to re-engagement efforts to improve overall list health and engagement metrics.
Common pitfalls
Sending a large, unsorted blast to a dormant list, which can lead to severe spam complaints and blocklisting.
Ignoring conflicting spam complaint reports from different platforms instead of investigating the discrepancies.
Failing to clean your list before re-engagement, resulting in high bounce rates and hitting spam traps.
Using generic promotional content for re-engagement that doesn't provide a compelling reason for subscribers to reactivate.
Not monitoring deliverability metrics closely enough, missing early signs of declining sender reputation or increasing complaints.
Failing to remove truly unengaged subscribers, which drags down overall list performance and signals low value to ISPs.
Expecting immediate high engagement from a dormant list and getting discouraged by initial low response rates.
Expert tips
If your product is related to security or privacy, emphasize these benefits in your re-engagement emails, as this aligns with the tech-savvy audience's original interest.
Consider that older registrants exhibiting higher click rates might indicate a segment that values timely updates; tailor messages to this group.
Before sending, check if the dormancy is due to an extended sales cycle or a natural churn period for your product/service.
If dormant subscribers received an onboarding sequence, their re-engagement emails should logically follow that journey, not appear random.
When dealing with an ESP like Customer.io (powered by Mailgun), understand their specific reporting methodologies for spam complaints.
If platform engagement has occurred but email engagement has not, try to segment based on platform activity to target highly engaged users on the platform who are email dormant.
For very old lists, consider a double opt-in re-confirmation campaign to ensure genuine interest before adding them back to your active sends.
Expert view
Expert from Email Geeks says that Mailgun calculates complaint rates as a percentage of emails sent to a specific mailbox provider, which can inflate the perceived complaint rate compared to an overall total send percentage.
2022-06-10 - Email Geeks
Expert view
Expert from Email Geeks states that 0.14% spam complaint rate is still higher than what is typically expected from a permission-based email list.
2022-06-10 - Email Geeks
Navigating re-engagement successfully
Re-engaging a dormant email list with high spam complaints is a significant challenge, but it's not insurmountable. The key is to approach it with caution, strategic planning, and a deep understanding of email deliverability best practices. Prioritize cleaning your list, segmenting carefully, and sending highly relevant content in measured volumes.
By focusing on protecting and improving your sender reputation, you can systematically work towards reactivating valuable subscribers while minimizing future risks. Remember, success in email marketing is not just about the number of subscribers, but the quality of engagement and your ability to consistently reach the inbox.
It's a continuous process of optimization and pruning. Don't be afraid to say goodbye to subscribers who consistently remain unengaged despite your best efforts. A healthy, responsive list will yield far better results and protect your long-term deliverability.
Microsoft, while your analytics platform or even Google Postmaster Tools might display a much lower overall percentage. This discrepancy often stems from how each system calculates the rate, whether it's per total send or per specific mailbox provider. It's crucial to investigate these differences to get a clear picture of the actual deliverability health.
Mailgun) might report a high complaint rate for a specific provider because it calculates the rate as a percentage of emails sent to that provider, rather than your total email volume. This can make the issue seem more severe than a raw overall percentage might suggest, but it's a critical detail for deliverability.
