How does senderscore impact email deliverability and how is it calculated?
Michael Ko
Co-founder & CEO, Suped
Published 24 Jun 2025
Updated 18 Aug 2025
7 min read
When I talk to clients about email deliverability, the concept of a Sender Score often comes up. Many see it as the ultimate health check for their email program, a single number that dictates whether their messages land in the inbox or the spam folder. It's a metric that many email marketers track diligently, and understandably so, because a higher score generally suggests better deliverability.
However, it's crucial to understand that while Sender Score is a valuable indicator, it's just one piece of a much larger puzzle. It functions much like a credit score, but for your email sending reputation, providing an overview of your trustworthiness to email receivers. A strong sender reputation helps increase your chances of successful email delivery.
My goal here is to demystify Sender Score, explaining how it's calculated, its real impact on email deliverability, and what you can do to maintain a healthy score. Understanding this will help you prioritize your efforts for optimal inbox placement.
How sender score is calculated
The Sender Score is a proprietary rating system developed by Validity, which measures the health of your email program and the reputation of your sending IP address on a scale from 0 to 100. It is computed based on a rolling 30-day average of various sending behaviors observed across a massive network of over 2.5 million mailboxes.
When it comes to the calculation, it's not simply about volume, but about the quality of that volume and the recipient's reaction to your emails. Validity gathers data from many sources, including spam traps, trusted feedback loops, and their own extensive network of email servers. This data provides insights into how your mail is perceived by different mailbox providers.
While the exact weighting of each factor is not publicly disclosed, certain elements are known to heavily influence the score. Understanding these factors is key to managing your email program effectively. My experience shows that a proactive approach to these areas leads to better overall deliverability, regardless of the numerical score itself.
Key factors influencing sender score
Spam complaints: When recipients mark your email as spam, it significantly negatively impacts your score. This is a direct signal of unwanted mail.
Unknown users (bounces): Sending to invalid or non-existent email addresses leads to hard bounces, indicating poor list hygiene and potentially suspicious sending practices.
Spam traps: Hitting spam traps indicates that your list acquisition or maintenance practices are problematic, as these addresses are designed to catch spammers.
Email volume and consistency: Sudden spikes or drops in sending volume can raise flags. Consistent, predictable sending patterns are generally preferred.
Engagement metrics: While not directly incorporated into the Sender Score algorithm, high engagement (opens, clicks) correlates with positive reputation and better deliverability, indirectly supporting a good score.
How sender score impacts email deliverability
Sender Score directly impacts your email deliverability because many mailbox providers (ISPs) use it, or similar reputation metrics, to determine whether to accept your emails, place them in the inbox, or filter them to the spam folder. A high score, typically above 80, signals trustworthiness, meaning your emails are more likely to reach the recipient's inbox.
Conversely, a low Sender Score (below 70) suggests poor sending practices. This can lead to increased bounce rates, emails landing in spam folders, or even outright rejection by mail servers. It's a clear warning sign that your email program is encountering issues.
It's important to remember that while Sender Score is a widely recognized metric, it’s not the only factor ISPs consider. Each ISP maintains its own internal reputation systems, which often factor in additional data points specific to their user base. However, the underlying principles of good sending practices that influence Sender Score also positively impact these internal systems. To better understand this, you can look at how relevant Sender Score is to email deliverability in a broader context.
I've often seen situations where a sender had a decent score but still faced deliverability issues with specific providers, or vice versa. This highlights that while the score is a good general health indicator, real-world deliverability can be more nuanced. Maintaining a strong email domain reputation is a continuous effort.
High sender score (80-100)
Inbox placement: Your emails are highly likely to reach the primary inbox.
Trustworthiness: ISPs view your sending IP as reputable and legitimate.
Reduced filtering: Less chance of being filtered to spam or rejected.
Low sender score (0-69)
Spam folder placement: Emails are often diverted to the spam or junk folder.
Delivery failures: Increased risk of emails being rejected outright by recipient servers.
Reputation damage: Your IP may be flagged as suspicious, impacting all future sends.
Factors influencing your score
Several key factors directly influence your Sender Score and, by extension, your deliverability. Paying close attention to these will have a much greater impact than simply chasing a number. My experience tells me that sustained effort in these areas leads to long-term success.
Firstly, spam complaints are a direct measure of recipient dissatisfaction. If people frequently mark your emails as spam, it tells ISPs that your mail is unwanted, severely damaging your reputation. Secondly, your bounce rate, particularly hard bounces from invalid addresses, signals poor list quality. This is a crucial indicator of how effectively your email sending practices impact your domain reputation.
Beyond those, being listed on a blacklist or blocklist (or both) is a severe blow to your reputation, often resulting in mail being blocked entirely. And finally, spam trap hits are arguably the most damaging, as they indicate that your list collection or management practices are deeply flawed, suggesting you're sending to old or scraped addresses.
Factor
Impact on deliverability
Impact on Sender Score
Spam complaints
High likelihood of landing in spam folder; direct negative signal.
Significant drop.
Hard bounces
Emails rejected by recipient servers; indicates poor list hygiene.
Notable decrease.
Spam traps
Severe reputation damage; direct indication of list quality issues.
Sharp decline, potentially to zero.
Blocklistings
Emails blocked or heavily filtered by many ISPs.
Significant negative impact.
Low engagement
Can lead to emails being placed in promotions or spam folders over time.
Indirect negative pressure, gradual decline.
Improving and maintaining your sender score
If you notice your Sender Score dropping, or if you're aiming to improve it, my advice is to focus on the fundamental health of your email program, not just the score itself. The score is a reflection, not a cause, of your deliverability performance. A drop in Sender Score can be addressed by examining your core email practices.
Firstly, prioritize list hygiene. Regularly remove unengaged subscribers and invalid addresses to reduce bounces and avoid spam traps. Implement a double opt-in process for new subscribers to ensure they genuinely want your emails, which reduces spam complaints. I also recommend monitoring your score to catch issues early.
Secondly, ensure your email authentication is properly set up. This includes SPF, DKIM, and DMARC. These protocols prove to ISPs that you are who you say you are, which builds trust and improves deliverability. For instance, a basic DMARC record signals your authentication efforts.
Finally, focus on content quality and relevance. Sending valuable, engaging content reduces spam complaints and encourages positive interactions, which are critical for long-term reputation. If your Sender Score has dropped unexpectedly, analyzing these core practices is the first step in troubleshooting.
Views from the trenches
Best practices
Maintain meticulous list hygiene to minimize bounces and avoid spam traps.
Implement double opt-in for new subscribers to ensure high engagement and reduce complaints.
Ensure proper email authentication (SPF, DKIM, DMARC) for improved trust with ISPs.
Consistently send engaging and relevant content to your audience.
Common pitfalls
Over-reliance on Sender Score as the sole measure of deliverability success.
Ignoring low engagement from inactive subscribers, which can indirectly harm your reputation.
Failing to implement or properly configure email authentication protocols.
Sending large, inconsistent email volumes without proper warming up or list segmentation.
Expert tips
Focus on the underlying deliverability factors rather than just the score's number.
Understand that different ISPs have their own internal reputation systems.
If your audience and content haven't changed, consider sun-setting unengaged subscribers.
The accuracy of Sender Score can depend on the volume of emails sent to networks monitored by Validity.
Expert view
Expert from Email Geeks says deliverability is not directly impacted by Sender Score; rather, the score reflects declining deliverability. Focus on core metrics like opens, bounces, and complaints, and ensure consistent audience, content, and technical setup.
2021-04-15 - Email Geeks
Marketer view
Marketer from Email Geeks says a sudden decrease in Sender Score for dedicated IPs, especially uncertified ones, can be confusing as the importance of each factor is not transparent. It's unclear if these spikes truly affect deliverability.
2021-04-16 - Email Geeks
My final thoughts on sender score
Ultimately, while Sender Score provides a useful snapshot of your email sending reputation, I consider it a diagnostic tool rather than the sole arbiter of your deliverability success. It aggregates various signals, giving you an indication of how your sending practices are perceived across a broad network.
My primary recommendation is to always focus on the foundational elements of good email hygiene: building a clean list, sending engaging content, and ensuring your authentication is robust. If you consistently adhere to these best practices, your Sender Score will naturally reflect that positive behavior, and more importantly, your emails will consistently reach the inbox.
