How can I improve email deliverability for a client with a poor sender reputation and questionable email acquisition practices?
Matthew Whittaker
Co-founder & CTO, Suped
Published 16 Jun 2025
Updated 17 Aug 2025
7 min read
Taking on a client with a history of poor email deliverability and questionable acquisition practices is a significant challenge. Many businesses find themselves in a 'gray' area, characterized by low engagement rates, high complaint volumes, and frequent issues with inbox placement. Their past attempts to fix things, often by simply abandoning old sending infrastructure for new IPs or domains, only mask the problem without addressing its core.
These quick-fix approaches fail because they don't solve the underlying issues that led to the poor sender reputation in the first place. Mailbox providers, like Gmail and Outlook, are sophisticated enough to recognize patterns of problematic sending behavior, regardless of the IP address or domain used. This leads to emails consistently landing in the spam folder or being rejected outright, negating any marketing effort.
My goal is to outline a practical, long-term strategy that prioritizes ethical email practices while still being mindful of business objectives. This isn't about magic bullet solutions, but about implementing foundational changes that will gradually rebuild trust with ISPs and improve inbox placement.
Understanding the root causes of poor sender reputation
One of the most common issues I encounter is the use of co-registration or acquired email lists. While these methods might seem like a fast way to grow a database, they are often detrimental to deliverability. Co-registration, where consent is buried in 'small print,' rarely yields genuinely engaged subscribers. These recipients are unlikely to recognize or want the emails, leading to low engagement rates and high spam complaints, which significantly degrade sender reputation.
Similarly, using email lists acquired from competitors or third parties, particularly if they weren't explicitly opt-in, is a major red flag. These lists frequently contain invalid email addresses or, worse, spam traps. Hitting spam traps can immediately trigger blocklist (or blacklist) listings and lead to severe restrictions on your sending.
The continuous cycle of acquiring new IPs and domains to escape a bad reputation is a clear sign of systemic issues. This approach is costly, time-consuming, and ultimately ineffective. Mailbox providers develop complex algorithms to identify and penalize senders who engage in such behavior, making it impossible to build a sustainable positive sending reputation.
Questionable acquisition practices
Co-registration: Consent obtained through deceptive or hidden small print leads to low-quality subscribers.
Purchased lists: Emails not explicitly opted-in to your brand, often containing invalid addresses and spam traps.
Temporary fixes
New IPs/domains: Repeatedly moving infrastructure to try and escape reputation problems.
Lack of authentication: Missing SPF, DKIM, or DMARC records signal unreliability to ISPs.
Impact on deliverability
Poor sender reputation: Emails frequently flagged as spam or outright rejected by mailbox providers.
High bounce rates: Sending to invalid addresses causes bounces and damages reputation, as noted in industry guides.
Blocklisting: Inclusion on email blacklists (or blocklists) prevents delivery to major providers.
Business consequences
Lost revenue: Campaigns fail to reach their intended audience, impacting sales and ROI.
Strategies for rehabilitation and long-term success
The most crucial step is to implement rigorous list hygiene immediately. This means identifying and removing unengaged subscribers, invalid addresses, and known spam traps from your client's database. Sending to inactive or problematic addresses not only increases bounce rates but also signals to mailbox providers that you have poor list management, which directly harms your sender reputation. A smaller, cleaner list will always outperform a large, dirty one.Focusing on engaged users is paramount.
Prioritizing engagement
Shifting your strategy to focus exclusively on highly engaged members (buyers, active users) is critical. This builds a positive sending history with mailbox providers like Gmail and Yahoo, signalling that your emails are valued and expected. This approach naturally leads to higher open and click rates, which are key indicators of a healthy sender.
Robust email authentication protocols are non-negotiable. Ensure that SPF, DKIM, and DMARC records are correctly configured for your client's sending domains. These protocols verify the legitimacy of your emails and protect against spoofing, which is crucial for rebuilding trust with ISPs. Starting with a DMARC policy of p=none can help you gain visibility into your sending without impacting delivery.
Beyond list quality, content strategy must evolve. If offers are perceived as spammy or irrelevant, subscribers will quickly disengage or mark emails as spam, regardless of how clean the list is. Shift towards providing valuable, relevant content that the audience genuinely wants to receive. This improves engagement metrics like open rates and click-through rates, signaling positive intent to ISPs and is a key factor in protecting your sender reputation.
Rebuilding sender reputation is a gradual process that requires patience and consistency. It's not a switch you can flip. Implement changes incrementally, monitor performance closely, and adjust your strategy based on the data. Avoid any sudden, large sending volume increases, as this can trigger spam filters and set back progress. This consistent, careful approach will gradually improve your client's standing with mailbox providers.
Consistent monitoring is essential for maintaining and improving deliverability. Leverage tools like Google Postmaster Tools (and similar tools from other providers) to track key metrics such as spam rate, domain reputation, and IP reputation. These insights are invaluable for identifying emerging issues and making data-driven adjustments to your sending strategy.
Vigilantly check for blocklist (or blacklist) listings. A listing on a major blocklist can severely impact deliverability, leading to widespread rejections. Implement systems for prompt notification and react quickly to delisting requests, while simultaneously identifying and addressing the root cause to prevent future listings.
Data-driven decisions
Regularly analyzing engagement metrics like opens, clicks, and unsubscribes helps refine your sending strategy. Segmenting lists further based on engagement levels allows you to maintain a healthier sending pool, ensuring your highest value content reaches your most receptive audience. This continuous feedback loop is vital for long-term success.
Understand that email deliverability is not a one-time fix but an ongoing commitment. Consistent optimization of list hygiene, content relevance, and sending infrastructure is necessary to maintain a strong sender reputation and ensure consistent inbox placement. According to Salesforce, it's an always-on process, requiring vigilance and adaptation.
Navigating business realities
Clients with established, but poor, practices often resist significant changes due to perceived business losses. It's crucial to present a clear, data-driven business case demonstrating how poor deliverability translates directly into lost revenue, wasted marketing spend, and damaged brand equity. Showing them the declining value of their current practices can be a powerful motivator for change.
Instead of demanding a complete overhaul, propose incremental steps that allow the client to see positive results without an immediate, drastic reduction in their sending volume. Starting with the most engaged segments or gradually pruning unengaged subscribers can demonstrate the value of quality over quantity, building trust in your recommendations.
Set realistic expectations upfront. Rebuilding a damaged sender reputation takes time and sustained effort. Clearly communicate that there are no instant fixes and that long-term commitment to best practices is essential. Be prepared to decline the engagement if the client is unwilling to make the fundamental changes required for true rehabilitation, as ethical and effective deliverability is paramount.
Views from the trenches
Best practices
Prioritize quality over quantity, focusing on engaged segments for significant reputation improvement.
Combine list hygiene with focused sending to engaged users to halt deliverability decline.
Ensure clear payment terms upfront, especially with clients resistant to necessary changes.
Common pitfalls
Relying on continuous new IP/domain acquisition rather than fixing core reputation issues.
Expecting instant deliverability fixes without fundamental changes to acquisition and sending.
Ignoring the need for compelling content and proper subscription processes for long-term success.
Expert tips
Focus on engaged users as a core group; a new brand name isn't always necessary for rebuild.
Understand that low engagement indicates underlying content or subscription process problems.
Data showing a drop in CTR due to deliverability issues can be a powerful motivator for change.
Expert view
Expert from Email Geeks says: Dumping co-registration is crucial as it likely causes the most significant damage to sender reputation.
2023-11-28 - Email Geeks
Expert view
Expert from Email Geeks says: The most effective approach involves combining list hygiene with focused sending to highly engaged subscribers to rebuild reputation.
2023-11-28 - Email Geeks
Charting a path to inbox success
Improving email deliverability for a client with a challenging history is a significant undertaking, but it is achievable. It demands a shift in mindset from quantity to quality, a commitment to best practices, and a willingness to make difficult decisions. By focusing on rigorous list hygiene, robust email authentication, creating genuinely engaging content, and continuous monitoring, you can guide them toward a healthier sender reputation and consistent inbox placement. This path requires patience and strategic execution, but the long-term benefits of reliable email deliverability are invaluable.
Gmail and 
Yahoo, signalling that your emails are valued and expected. This approach naturally leads to higher open and click rates, which are key indicators of a healthy sender.
