How to troubleshoot and address a dropping email sender score?
Matthew Whittaker
Co-founder & CTO, Suped
Published 15 Apr 2025
Updated 19 Aug 2025
7 min read
Seeing your email sender score drop can be a concerning experience, especially when other metrics like bounce rates and delivery percentages seem stable. A low sender score can lead to significant deliverability issues, pushing your emails into spam folders or blocking them entirely. It's not always immediately clear what's causing the decline, but a structured approach to troubleshooting can help pinpoint and resolve the underlying problems.
This guide will walk you through common culprits behind a dropping sender score and provide actionable steps to get your email reputation back on track. We'll cover everything from technical configurations to content quality and list hygiene, helping you restore trust with mailbox providers and ensure your emails reach their intended inboxes.
Technical checks and infrastructure
When your sender score dips, the first step is to check if it's tied to any technical misconfigurations. Even if your initial checks, like those on SenderScore.org, show everything is good, deeper issues might be at play.
Authentication protocols
Ensure your email authentication protocols are correctly set up and aligned. This includes SPF, DKIM, and DMARC. Incorrect or missing records can signal to mailbox providers that your emails are not legitimate, leading to reputation damage. Even a minor misconfiguration, like an invalid SPF record or a DKIM body hash mismatch, can negatively impact your sender score and deliverability.
A robust DMARC policy, especially, provides a strong signal of your domain's authenticity. If your DMARC reports show authentication failures, you need to investigate these immediately. These failures could indicate that legitimate emails are failing authentication or that malicious actors are spoofing your domain.
IP and domain reputation
Your IP address and domain both have reputations that contribute to your overall sender score. Even if your domain reputation seems fine, a shared IP address with a poor reputation from another sender can affect you. This is why monitoring both your IP and domain reputation is crucial.
Shared IP issues
When using a shared IP, your deliverability can be impacted by the sending practices of others on the same IP. A sudden drop might be due to a fellow sender on that shared IP causing issues, even if your own sending practices are sound. While you might see a high delivery rate, the actual inbox placement could be suffering due to the shared reputation.
If you're using a dedicated IP, a sudden drop could indicate that your own sending volume or content has changed in a way that is triggering spam filters. In this case, reviewing your recent sending patterns and content is essential. For more details, consider reading about IP versus domain reputation to understand the nuances.
List quality and recipient behavior
Even with perfect technical setup, issues with your recipient list or content can plummet your sender score. Mailbox providers prioritize user engagement and penalize senders who send to disengaged or invalid addresses.
List hygiene and engagement
A high bounce rate, especially soft bounces, can indicate underlying reputation issues. While high hard bounce rates signal invalid addresses, an increase in soft bounces might suggest that mailbox providers are temporarily rejecting your emails due to suspicion. Regularly cleaning your email list is paramount.
Sending to unengaged subscribers can also negatively impact your sender score. Mailbox providers track engagement metrics (opens, clicks, replies) and low engagement can signal that your emails are unwanted. Implement re-engagement campaigns and remove inactive subscribers to maintain a healthy list.
Spam complaints and traps
Even a small increase in spam complaints can severely damage your sender reputation. Ensure your unsubscribe process is clear and easy. Additionally, spam traps are hidden email addresses used by ISPs to identify spammers. Hitting a spam trap indicates poor list hygiene and can lead to immediate blocklisting (or blacklisting).
Spam trap hits
A sudden drop in sender score, even with seemingly normal metrics, can be caused by hitting a spam trap. These are often old, abandoned email addresses repurposed by ISPs to catch bad senders. If your list isn't regularly cleaned, you're at risk. Hitting a spam trap, especially a pristine one, can immediately flag your IP or domain.
Content and sending patterns
The content of your emails and how frequently you send them play a significant role in your sender score. Even transactional emails, despite their importance, can contribute to a declining score if not handled carefully.
Content quality and engagement
Emails with spammy keywords, excessive images, broken links, or misleading subject lines can trigger spam filters and lead to complaints. Ensure your content is relevant, valuable, and adheres to email best practices. High engagement (opens, clicks) signals positive intent, while low engagement, even for transactional emails, can hint at issues with relevance or delivery.
Sending volume and consistency
A sudden, significant uptick in sending volume, even for transactional emails, can be perceived as suspicious by mailbox providers, especially if your domain is not accustomed to such volumes. Consistency in sending volume helps maintain a predictable reputation. If you need to increase volume, do so gradually, a process known as IP warming.
Mailbox providers, like Gmail and Outlook, also have their own internal reputation systems that can be more influential than aggregate scores. Monitor their postmaster tools for specific insights into your performance with them. For example, Google Postmaster Tools can provide valuable data on spam rates, IP reputation, and domain reputation specific to Gmail recipients.
Monitoring and recovery strategies
Once you've identified potential causes, it's time to implement solutions to recover your sender score. This requires a multi-faceted approach addressing both technical and behavioral aspects of your email program.
Strategic recovery steps
Segment sending: If your score has significantly dropped, consider temporarily limiting your sending to your most engaged subscribers. This helps build positive engagement signals.
Clean your list: Implement rigorous list hygiene practices. Remove inactive users, hard bounces, and any addresses that haven't engaged in a long time. This reduces the risk of hitting spam traps.
Review authentication: Double-check your SPF, DKIM, and DMARC records for any misconfigurations or missing entries. Ensure DMARC is actively reporting.
Monitor blocklists: Regularly check major blocklists (or blacklists) to see if your IP or domain has been listed. If so, follow the delisting procedures for each blocklist. You can learn more in our guide to blocklists.
Long-term reputation building
Building a strong sender reputation is an ongoing process. Consistent adherence to best practices, detailed monitoring, and quick response to issues are key. Focus on getting explicit consent from subscribers, providing valuable content, and making it easy for recipients to manage their subscriptions. A reputation can take time to rebuild but it's essential for long-term email success.
Proactive monitoring
Utilize Postmaster Tools: Set up and regularly check Google and Yahoo Postmaster Tools for detailed insights into your email performance with these providers.
Review DMARC reports: Analyze your DMARC aggregate and forensic reports to identify authentication failures and potential abuse of your domain.
Reactive measures
Address complaints: If spam complaints increase, review your opt-in process, content, and frequency. Make it easy for subscribers to unsubscribe.
Investigate bounces: Distinguish between hard and soft bounces. Hard bounces should be immediately removed. High soft bounces warrant investigation into server issues or content triggers.
Restoring your email reputation
A dropping sender score can be a complex issue with multiple contributing factors. By systematically troubleshooting technical configurations, optimizing list quality, and refining your sending practices, you can effectively address the decline and improve your email deliverability. Remember, maintaining a strong sender reputation is an ongoing commitment to email best practices.
Views from the trenches
Best practices
Maintain meticulous list hygiene to minimize bounces and spam traps, ensuring optimal sender score.
Regularly monitor your domain and IP reputation using postmaster tools to identify potential issues early.
Implement strong authentication protocols (SPF, DKIM, DMARC) to build trust with mailbox providers.
Common pitfalls
Ignoring a gradual decline in sender score, which can escalate into significant deliverability problems.
Failing to remove unengaged subscribers, leading to lower engagement metrics and reputation damage.
Sending large, sudden email blasts without proper IP warming, triggering spam filters.
Expert tips
Prioritize engagement metrics over raw delivery rates, as high engagement is a stronger signal of good reputation.
Consider a dedicated IP if you have consistent high volume, allowing more control over your sending reputation.
Set up feedback loops with major ISPs to quickly identify and address spam complaints.
Marketer view
Marketer from Email Geeks says they pay zero attention to SenderScore as a client metric, viewing it as a proprietary score from ReturnPath that reflects delivery only to domains sharing data with them.
2019-10-10 - Email Geeks
Marketer view
Marketer from Email Geeks says they worry when their SenderScore starts to tank, even if bounces or sent-but-not-delivered numbers seem fine, because it usually remains quite stable.
Gmail and 
Outlook, also have their own internal reputation systems that can be more influential than aggregate scores. Monitor their postmaster tools for specific insights into your performance with them. For example, Google Postmaster Tools can provide valuable data on spam rates, IP reputation, and domain reputation specific to Gmail recipients.
Google and 
Yahoo Postmaster Tools for detailed insights into your email performance with these providers.
