Why is my Sender Score low despite having a high delivery rate?
Matthew Whittaker
Co-founder & CTO, Suped
Published 5 Jun 2025
Updated 19 Aug 2025
10 min read
It can be perplexing to see a low Sender Score when your emails consistently achieve a high delivery rate. You'd expect these metrics to align, indicating strong email performance across the board. However, this common scenario highlights a crucial distinction in email deliverability: delivery rate and inbox placement are not the same thing.
A high delivery rate means your emails are successfully reaching the recipient's mail server, but it doesn't guarantee they land in the inbox. They could still be routed to the spam folder, a promotional tab, or even silently dropped. Your Sender Score, on the other hand, is a reputation metric designed to predict this very outcome, evaluating your likelihood of landing in the inbox.
Understanding email metrics: delivery vs. deliverability
Many email marketers often confuse email delivery with email deliverability, yet they represent distinct stages in the email sending process. Understanding this difference is fundamental to diagnosing issues when your Sender Score seems low despite high delivery numbers.
Email delivery refers to whether an email successfully reaches the recipient's mail server. If the server accepts the email, it's counted as delivered. This metric primarily indicates whether the recipient address is valid and the sending server is not outright blocked. However, it provides no insight into where the email ultimately lands within the recipient's mailbox.
On the other hand, email deliverability, also known as inbox placement, refers to whether an email reaches the intended recipient's inbox, not just their server. A high deliverability rate signifies that your emails are successfully bypassing spam filters and reaching the primary inbox, where they are most likely to be seen and engaged with. This is heavily influenced by your sender reputation.
Email delivery
Definition: Email successfully accepted by the recipient's mail server.
Measurement: Indicated by a low bounce rate. A 99%+ delivery rate is common.
Outcome: Emails arrive at the server, but may still end up in spam.
Email deliverability (inbox placement)
Definition: Email successfully reaches the intended inbox, avoiding spam folders.
Measurement: Higher open rates, click-through rates, lower spam complaints.
Outcome: Emails are seen by recipients, leading to better engagement.
The true meaning of Sender Score
Sender Score is a proprietary reputation metric developed by Validity (formerly Return Path) that assigns a rating to your sending IP address, ranging from 0 to 100. This score is intended to reflect the trustworthiness of your sending IP and your likelihood of successfully delivering emails to the inbox. A higher score typically indicates better sending practices and a stronger reputation.
The calculation of your Sender Score involves numerous factors, including spam complaints, bounce rates, unknown users, external blocklist (or blacklist) listings, and sending volume consistency. It also incorporates data from Validity's vast network of mailbox providers. You can read more about how the Sender Score is calculated on the Sender Score website. However, it's crucial to remember that while Sender Score is a valuable indicator, it's not the only one. Major mailbox providers like Google, Yahoo, and Outlook (and other large ISPs) maintain their own internal reputation systems. These systems consider a broader range of factors, including specific user engagement, historical sending patterns, and authentication records like SPF, DKIM, and DMARC, which might not be fully reflected in a single Sender Score value.
This means you could have a low Sender Score, but if your emails are still performing well at key providers (like Gmail and Yahoo) and achieving high inbox placement, the low score might not be impacting your overall business objectives significantly. Conversely, a high Sender Score doesn't automatically guarantee perfect inbox placement if other factors are at play. You can also dive deeper into how relevant Sender Score is to email deliverability.
Factors influencing a low Sender Score despite high delivery
There are several reasons why your Sender Score might be low even with a high delivery rate, pointing to subtle issues that impact reputation rather than outright bounces:
Low engagement: If recipients aren't opening or clicking your emails, or if they're deleting them without reading, this sends a negative signal to ISPs. Even if the email is delivered, a lack of positive engagement can hurt your reputation and lead to lower Sender Scores. Over time, low engagement can lead to reduced inbox placement.
Spam complaints: A single spam complaint carries significant weight. If users mark your emails as spam, even if they initially reach the inbox, your Sender Score will suffer. Most email service providers (ESPs) handle unsubscribe requests, but users may click the spam button out of convenience, unaware of the damage it does to your reputation. You can learn more about understanding your spam rate.
Spam traps: Sending to spam traps—email addresses specifically set up to catch spammers—can severely damage your reputation. While these emails might be delivered to the trap, they are a clear sign of poor list hygiene and instantly lower your Sender Score, often leading to being placed on a blocklist (or blacklist). Discover how spam traps work in detail.
External blocklists/blacklists: Your IP or domain might be listed on a public or private email blocklist, affecting your Sender Score. Even if this doesn't immediately cause bounces (some ISPs might still accept mail from blocklisted IPs, but route it to spam), it indicates a poor reputation signal that Sender Score registers. Knowing what happens when your domain is on a blacklist can help.
Inconsistent sending patterns: ISPs (and reputation systems like Sender Score) prefer consistent sending volumes. Sudden spikes or drops in email volume can raise flags, as they might indicate unusual activity, even if your emails are technically delivered. This is particularly relevant for new IP addresses undergoing IP warming.
Additionally, if you are using shared IP addresses, your Sender Score might be influenced by the sending behavior of other users on that shared IP. Even if your own practices are stellar, poor behavior from others can negatively impact your overall reputation score.
How to improve your sender reputation and inbox placement
While a low Sender Score can be concerning, it’s often a symptom of underlying issues rather than the root cause of deliverability problems. Focusing on best practices for overall email health will naturally improve your reputation metrics.
Maintain rigorous list hygiene: Regularly clean your email list by removing inactive subscribers, hard bounces, and known spam traps. This not only reduces negative signals but also improves engagement rates with your active audience. Consider an email validation tool.
Prioritize authentication: Ensure your domain has correctly configured SPF, DKIM, and DMARC records. DMARC, in particular, helps monitor and prevent email spoofing, protecting your domain's reputation. Make sure to implement DMARC monitoring for insights into your email streams.
Focus on content and engagement: Send relevant, valuable content that encourages opens, clicks, and replies. Segment your audience to send more targeted messages. Encourage subscribers to add you to their address book or mark your emails as not spam.
Monitor ISP-specific feedback loops: Sign up for services like Google Postmaster Tools and Yahoo Postmaster. These tools provide direct insights into your reputation with those specific providers, which often have a greater impact on your deliverability than a generic Sender Score.
The impact of blocklists on your Sender Score
A common factor impacting perceived Sender Score without affecting delivery rate is getting listed on certain email blocklists (or blacklists). While your emails might still reach many inboxes, some blocklists are considered by Sender Score in its calculation, even if the primary ISPs you send to don't actively use that specific list to filter your mail.
A blocklist is a database of IP addresses or domains with a poor reputation, often associated with sending spam. When your IP or domain appears on such a list, it signals to receiving mail servers that your emails might be unsolicited. Even if these servers don't outright reject your mail, they might downgrade its trust score, leading to a lower Sender Score or increased filtering to spam folders. This is why understanding email blocklists is essential.
Regularly checking your IP and domain against major public blocklists is a proactive step to manage your email reputation. If you find your IP or domain listed, investigate the cause (e.g., increased spam complaints, sending to spam traps) and follow the specific delisting procedures for each blocklist. Many blocklists provide clear guidelines for removal once the underlying issues are addressed.
Views from the trenches
Best practices
Actively monitor engagement rates, not just delivery, for a true picture of inbox placement.
Regularly clean email lists to remove inactive subscribers and hard bounces.
Implement strong email authentication (SPF, DKIM, DMARC) to protect your sender identity.
Segment your audience and personalize content to improve user engagement.
Common pitfalls
Over-relying solely on Sender Score as the definitive measure of email deliverability.
Ignoring low engagement rates, as they signal poor recipient interest.
Sending to old, unverified email lists that contain spam traps or inactive addresses.
Failing to monitor ISP-specific feedback loops and reputation dashboards.
Expert tips
Focus on the actual inbox placement at key mailbox providers like Google and Yahoo.
A small number of bounces can disproportionately impact your Sender Score if they originate from specific providers.
Dedicated IPs usually provide more accurate Sender Score feedback compared to shared IPs.
DMARC in reject mode (`p=reject`) can significantly help mitigate domain spoofing issues.
Expert view
An expert from Email Geeks says that Sender Score is a proprietary measure, and it doesn't always correlate with actual delivery, with some clients having low scores but great delivery, and vice-versa.
2022-10-14 - Email Geeks
Expert view
An expert from Email Geeks says that sometimes providers controlling a large number of small domains can significantly impact the Sender Score, so examining common blocking providers for your bounces might be helpful.
2022-10-14 - Email Geeks
Taking a holistic view of your email reputation
While a low Sender Score can initially be alarming, it's essential to remember that it's one piece of a much larger puzzle. Your high delivery rate indicates that your emails are making it to the servers, which is a good starting point. The next step is to ensure they are consistently landing in the inbox.
Focus on improving your overall sender reputation by prioritizing list hygiene, strong email authentication, engaging content, and active monitoring of ISP-specific tools. By taking a holistic approach to your email program, you can enhance your inbox placement and achieve your desired email marketing outcomes, regardless of a single reputation score.
Google, 
Yahoo, and 
Outlook (and other large ISPs) maintain their own internal reputation systems. These systems consider a broader range of factors, including specific user engagement, historical sending patterns, and authentication records like SPF, DKIM, and DMARC, which might not be fully reflected in a single Sender Score value.
