How do I improve email deliverability for a client with a dormant list and low sending volume?
Michael Ko
Co-founder & CEO, Suped
Published 7 Jun 2025
Updated 17 Aug 2025
8 min read
Improving email deliverability for a client with a dormant list and low sending volume can feel like navigating a maze. When a domain hasn't had a consistent sending cadence, especially if it was never properly warmed up, emails often land directly in the spam folder. This situation poses unique challenges for re-establishing a healthy sender reputation.
The key is to approach this systematically, focusing on repairing trust with mailbox providers and re-engaging subscribers. It's a journey that prioritizes quality over quantity, especially at the start, to rebuild a positive sending history. This involves meticulous list hygiene, strategic re-engagement campaigns, and ensuring all technical authentication is correctly set up.
We'll explore actionable steps to improve your client's email deliverability, from cleaning the dormant list and implementing a careful warm-up strategy to optimizing technical configurations and content. Success in this scenario relies on patience and a data-driven approach, acknowledging that it takes time to recover a domain's standing.
Assessing the current situation and historical context
The first step is to fully understand the root causes of the deliverability issues. An inconsistent sending cadence, such as the last campaign being sent months ago, signals to Internet Service Providers (ISPs) that your domain might be dormant or even compromised. When you then try to send a batch of emails, ISPs view this sudden activity from an unestablished or inactive sender with suspicion, often routing messages directly to the spam folder.
Furthermore, if the domain was never properly warmed up, it lacks the positive sending history necessary to build sender reputation. A cold domain or IP (even if shared) needs a gradual introduction to mailbox providers to prove its legitimacy. Without this initial trust-building, any sending attempts will likely face significant deliverability challenges, including increased bounce rates and spam complaints.
It's also crucial to examine how the email list was initially collected. Lists that include contacts who didn't explicitly opt-in, such as older 'friends and family' contacts, can be a major liability. These individuals are more prone to mark emails as spam rather than unsubscribe, which severely damages your sender reputation. Prioritizing legitimate, opted-in subscribers is fundamental for long-term deliverability success.
Prioritising list hygiene and re-engagement
With a dormant list, the first critical step is thorough list hygiene. Running all emails through a reputable email verification service is essential to identify and suppress invalid, inactive, or spam trap addresses. This drastically reduces bounce rates, which are a major red flag for mailbox providers and can severely damage your sender reputation. A clean list is the foundation for any successful re-engagement or warm-up strategy.
Once your list is clean, focus on segmentation. Since the list is dormant, recent engagement data might be scarce or non-existent. Start by identifying the most recently active segments based on any available historical data, even if it's from a year ago. These are the subscribers most likely to re-engage and provide positive signals to ISPs. For strategies on managing deliverability while re-engaging, refer to our guide on re-engaging inactive subscribers.
For the most dormant segments, consider a re-permission or re-engagement campaign. This can be a simple plain text email asking subscribers if they still wish to receive communications. This approach helps identify truly engaged subscribers and allows you to sunset those who don't respond, further improving your list quality. It's a proactive way to encourage interaction and explicitly confirm interest.
Re-engagement strategy
Audience: Target the most recently active segment, even if engagement is old.
Content: Send a plain text email asking for re-permission or confirming interest. Focus on value proposition.
Goal: Identify truly engaged users and clean out unresponsive contacts. Learn more about re-engaging stale subscribers.
Volume: Start very small, gradually increasing based on positive engagement metrics.
Cold sending risk
Audience: Sending to a broadly dormant list without segmentation.
Content: Promotional emails that may not resonate with inactive recipients.
Outcome: High spam complaints, increased bounce rates, potential blocklisting (blacklisting), and further damage to sender reputation.
Impact: Makes it harder to recover deliverability and reach even engaged subscribers.
Building a strong technical foundation and reputation
A robust technical foundation is non-negotiable for deliverability. Ensure your client's email authentication protocols are correctly configured. This includes Sender Policy Framework (SPF), DomainKeys Identified Mail (DKIM), and Domain-based Message Authentication, Reporting & Conformance (DMARC). These protocols verify your sending identity and tell mailbox providers that your emails are legitimate, reducing the likelihood of them being flagged as spam. Our guide on DMARC, SPF, and DKIM can provide further insight.
Even with low sending volume, it's vital to monitor your sender reputation. While tools like Google Postmaster Tools might not provide robust data at very low volumes, they will start to accumulate insights as your sending increases. Regularly check for any signs of being placed on a blocklist or blacklist, which would severely impact your deliverability. You can use our blocklist checker to keep track of your domain's status.
Finally, content quality plays a significant role. Ensure emails are relevant, valuable, and free of spammy triggers. High engagement with your content (opens, clicks, replies) sends positive signals to ISPs. Conversely, low engagement, high spam complaints, or unsubscribes will harm your sender reputation. Focus on creating compelling messages that your segmented audience truly wants to receive.
Authentication Protocol
Purpose
Key Considerations
SPF (Sender Policy Framework)
Authorizes mail servers permitted to send emails on behalf of your domain.
Ensure all sending services are included. Avoid more than 10 DNS lookups. v=spf1 include:_spf.example.com ~all
DKIM (DomainKeys Identified Mail)
Adds a digital signature to emails, verifying they haven't been tampered with.
Requires a public key in DNS; usually managed by your email service provider.
Implementing a strategic warm-up and consistent cadence
Re-establishing deliverability with a dormant list and low sending volume is a gradual process. The critical phase is the email warm-up, where you incrementally increase your sending volume to engaged segments. Start with small batches to the most active subscribers and slowly expand to larger segments as positive engagement signals (opens, clicks) improve. This teaches mailbox providers that your emails are wanted and not spam.
Even with a list size of 10,000, which can be considered relatively small for some large-scale machine learning filters, the principle of gradual ramp-up holds. As outlined by MailerLite's best practices, starting with highly engaged users and slowly increasing volume builds trust. A sudden spike in sending from a dormant domain can quickly lead to blocklisting (blacklisting) and further deliverability issues, trapping your emails in spam folders.
Maintain a consistent sending cadence once you've started sending. Sporadic sends can re-trigger dormant sender flags. Regular, predictable sending helps build a stable sender reputation over time. Continue to monitor engagement metrics closely and adjust your segmentation and content strategy as needed. For more details on improving your email reputation and deliverability, check out our dedicated guide.
Long-term strategies for sustained deliverability
To ensure long-term success, continuous list maintenance is essential. Regularly clean your subscriber list to remove inactive or invalid addresses, even after the initial purge. This proactive approach helps maintain high engagement rates and prevents your sender reputation from deteriorating again. Remember, a smaller, highly engaged list is far more valuable than a large, unengaged one.
Actively use available monitoring tools. Although Google Postmaster Tools might be sparse for very low volumes initially, they become incredibly valuable as your sending increases. Continuously review your spam complaint rates, bounce rates, and sender reputation scores. These metrics provide critical feedback from mailbox providers, allowing you to quickly adapt your strategy and address any emerging issues. For insights, refer to the guide on fixing Gmail delivery. Our guide to Google Postmaster Tools offers more details.
Finally, stay informed about evolving email sending requirements from major mailbox providers like Gmail and Yahoo Mail. These providers frequently update their policies, and adhering to them is crucial for maintaining excellent deliverability. A proactive approach to compliance, list quality, and engagement will yield the best long-term results.
Tips for sustained deliverability
Consistent cadence: Once warmed up, aim for a regular sending schedule to build and maintain trust.
Engagement monitoring: Continuously track opens, clicks, and unsubscribes to gauge list health.
Feedback loops: Sign up for ISP feedback loops to receive notifications about spam complaints and take action.
Content relevance: Always send content that resonates with your audience to encourage positive interactions.
Views from the trenches
Best practices
Always validate email lists before sending, especially for dormant contacts.
Segment your audience based on recent engagement to target active subscribers.
Implement an email warm-up strategy, starting with small, highly engaged segments.
Prioritize email authentication protocols like SPF, DKIM, and DMARC.
Common pitfalls
Sending to an entirely dormant list without prior re-engagement or cleaning.
Ignoring sender reputation metrics because of low initial send volume.
Assuming old engagement metrics accurately reflect current subscriber interest.
Including non-opted-in contacts (like old 'friends and family') in marketing sends.
Expert tips
Focus on delivering high-quality, valuable content that encourages positive engagement.
For very low volumes, traditional deliverability metrics may be less actionable; focus on explicit consent.
Consider a re-permission campaign to explicitly confirm subscriber interest.
Continuously monitor bounce rates and spam complaints to quickly address issues.
Marketer view
A marketer from Email Geeks says that the approach of cleaning emails and segmenting by engagement is a sound strategy for the situation.
2024-07-22 - Email Geeks
Marketer view
A marketer from Email Geeks says to utilize Google Postmaster Tools data to check for complaints and other metrics, ensuring you are not completely unaware of the situation.
2024-07-22 - Email Geeks
Rebuilding trust and reaching the inbox
Improving email deliverability for a client with a dormant list and low sending volume requires a comprehensive, patient, and strategic approach. It's not a quick fix, but a process of rebuilding trust and demonstrating good sending practices to mailbox providers.
By meticulously cleaning your list, engaging only the most active subscribers, implementing a careful warm-up strategy, and maintaining robust technical authentication, you can gradually improve your client's sender reputation and ensure their emails consistently reach the inbox.
Gmail and 
Yahoo Mail. These providers frequently update their policies, and adhering to them is crucial for maintaining excellent deliverability. A proactive approach to compliance, list quality, and engagement will yield the best long-term results.
