Summary
Email deliverability, the success of an email reaching a recipient's inbox, is primarily governed by sender reputation, a complex metric influenced by various factors. Key elements include low spam complaint rates, minimal bounce rates from invalid addresses, strong audience engagement through opens and clicks, and rigorous list hygiene. Technical aspects like proper email authentication protocols (SPF, DKIM, DMARC) and clean email content also play crucial roles. SenderScore, a proprietary reputation metric from Validity (formerly Return Path), provides a score from 0 to 100 based on many of these factors, such as complaints, unknown users, and blocklist presence. While a higher SenderScore generally indicates better deliverability and is used by ISPs in filtering decisions, it is an indicator, not the sole determinant of inbox placement, and should be considered alongside other crucial deliverability metrics.
Key findings
- Sender Reputation is Paramount: Email deliverability primarily hinges on a sender's reputation, which is built on factors like IP and domain history, spam rates, user complaints, and consistent adherence to email best practices.
- Multi-faceted Deliverability: Beyond sender reputation, crucial factors influencing deliverability include email content quality, audience engagement (opens, clicks), rigorous list hygiene, low bounce rates, and proper technical setup, including authentication protocols like SPF, DKIM, and DMARC.
- SenderScore Defined: SenderScore is a proprietary reputation metric, ranging from 0-100, provided by Validity (formerly Return Path). It quantifies a sender's trustworthiness based on various attributes like spam complaints, unknown users, external blocklists, rejections, and infrastructure health.
- SenderScore's Role in Filtering: Internet Service Providers (ISPs) and email filters use SenderScore as a key indicator in their filtering decisions, with a higher score generally correlating with better deliverability and greater likelihood of emails reaching the inbox.
- SenderScore Nuance: While a helpful indicator, SenderScore is not the ultimate or sole determinant of inbox placement. A high score alone does not guarantee perfect deliverability, and improving it requires identifying and addressing the specific underlying factors contributing to its calculation.
Key considerations
- Prioritize Sender Reputation: Consistently maintain a positive sender reputation by sending valuable content, avoiding spam triggers, and adhering to email best practices across both your IP and domain.
- Implement Authentication: Ensure proper setup of email authentication protocols like SPF, DKIM, and DMARC to prove sender legitimacy and build trust with Internet Service Providers (ISPs).
- Maintain List Hygiene: Regularly clean email lists by removing hard bounces, inactive subscribers, and spam traps. This ensures emails are sent only to valid and engaged recipients, which positively impacts sender reputation.
- Monitor Engagement and Complaints: Actively track engagement metrics, such as opens and clicks, and monitor spam complaint rates. High engagement signals value to ISPs, while high complaints damage reputation and hurt deliverability.
- Holistic Deliverability View: Do not rely solely on SenderScore; instead, analyze it in conjunction with other metrics like bounce rates, blocklist presence, email content quality, and overall email performance for a comprehensive understanding of deliverability.
What email marketers say
9 marketer opinions
Email deliverability success hinges on a confluence of factors, intricately woven together to form a sender's overall reputation with Internet Service Providers. Beyond the core elements of low spam complaints, minimal bounces, and strong audience engagement, the quality of email content and robust email authentication protocols are critical. While SenderScore, a proprietary metric, provides a useful aggregated view of these elements, its true value lies in acting as an indicator rather than a definitive guarantor of inbox placement. Improving deliverability, and by extension SenderScore, demands a holistic approach, focusing on the specific attributes that collectively define a sender's trustworthiness, from clean lists to engaging content.
Key opinions
- Interconnected Factors: Email deliverability is a multi-faceted challenge influenced by a complex interplay of sender reputation, email content quality, audience engagement, list hygiene, and proper technical setup including authentication protocols.
- Content Quality Matters: The quality of email content, encompassing factors like clean HTML, image-to-text ratio, and the absence of spammy phrases, significantly impacts deliverability, regardless of an otherwise strong sender reputation.
- Dual Reputation Layers: Both IP and domain reputation are critical for deliverability. IP reputation is tied to the sending server's history, while domain reputation is linked to the sender's brand and overall sending behavior.
- Engagement Signals Value: High engagement rates, such as opens and clicks, signal to ISPs that your emails are valued by recipients, positively impacting deliverability. Conversely, low engagement or high complaints damage sender reputation.
- SenderScore as Diagnostic Tool: SenderScore is a valuable indicator that aggregates many reputation factors, but it serves more as a diagnostic tool. Improving it requires identifying and addressing the specific attributes contributing to any score drop, as it is not the ultimate measure of inbox placement.
Key considerations
- Optimize Content Quality: Design emails with clean HTML, balanced image-to-text ratios, and avoid spam trigger words to ensure content passes spam filters and reaches the inbox.
- Proactive List Hygiene: Regularly cleanse email lists to remove hard bounces, inactive subscribers, and spam traps. This practice is fundamental for maintaining a positive sender reputation and improving deliverability.
- Build Dual Reputation: Cultivate strong IP and domain reputations through consistent, legitimate sending practices. Both are crucial, distinct layers of your sender trust profile with Internet Service Providers.
- Deep Dive on SenderScore: When analyzing SenderScore, look beyond the aggregate number to understand the specific underlying attributes impacting it, such as unknown users or blocklist presence, for targeted improvement.
- Continuous Monitoring: Consistently track and analyze a broad range of deliverability metrics, including bounce rates, spam complaints, engagement (opens, clicks), and email authentication status, for proactive issue resolution.
Marketer view
Marketer from Email Geeks explains that a high SenderScore alone does not necessarily indicate a deliverability problem, suggesting other factors like fixed IP addresses and RBLs are important to consider. He also recommends specific books for understanding how email deliverability works.
22 Apr 2025 - Email Geeks
Marketer view
Marketer from Email Geeks explains that SenderScore is a helpful indicator but not the ultimate measure of inbox placement. She clarifies that improving SenderScore involves identifying and addressing the specific attributes causing a drop, as many factors contribute to its calculation.
25 Oct 2022 - Email Geeks
What the experts say
2 expert opinions
Understanding email deliverability involves recognizing a spectrum of factors that collectively inform a sender's trustworthiness to Internet Service Providers (ISPs). At its core, deliverability is shaped by aspects like the sender's IP and domain reputation, recipient engagement, and the frequency of spam complaints or bounces. Alongside these, maintaining clean subscriber lists and implementing strong email authentication, such as SPF, DKIM, and DMARC, are fundamental. SenderScore, a specific reputation metric from Validity, provides a numerical score for IP addresses, directly reflecting historical performance on criteria like rejections and blacklistings, thereby serving as a key gauge for ISPs in their mail filtering decisions.
Key opinions
- SenderScore Mechanics: SenderScore specifically rates IP addresses on a 0-100 scale, with a higher score indicating better reputation based on factors like spam complaints, rejections, and blacklistings.
- Reputation Components: Core sender reputation for deliverability is built on domain and IP history, recipient engagement metrics, spam complaint rates, and bounce rates.
- Authentication as Foundation: Proper email authentication protocols, including SPF, DKIM, and DMARC, are foundational to assuring Internet Service Providers of a sender's legitimacy and improving inbox placement.
- Engagement Drives Trust: High recipient engagement, evidenced by opens and clicks, positively reinforces sender reputation, signaling valuable content to mail providers and enhancing deliverability.
- List Hygiene's Impact: Maintaining a clean email list by reducing unknown users and bounces is paramount, as it directly reduces negative signals that lower sender reputation and hurt deliverability.
Key considerations
- Monitor IP and Domain Reputation: Regularly check the health of both your IP addresses and sending domains, as both contribute significantly to your overall sender reputation and influence deliverability.
- Prioritize Authentication Setup: Diligently set up and maintain SPF, DKIM, and DMARC records to build trust with Internet Service Providers and ensure emails are properly authenticated.
- Minimize Negative Feedback: Actively work to reduce spam complaints, rejections, and bounces, as these directly hurt your SenderScore and overall deliverability performance.
- Foster Subscriber Engagement: Implement strategies to encourage opens and clicks, as strong engagement metrics signal positive sender behavior and valuable content to mail providers.
- Continuous List Cleaning: Make list hygiene an ongoing process, regularly removing inactive or invalid addresses to prevent high bounce rates and protect sender reputation.
Expert view
Expert from Spam Resource explains that SenderScore is a reputation metric provided by Return Path (now Validity) that scores IP addresses on a scale of 0-100 based on various factors like spam complaints, rejections, blacklistings, and unknown users. A higher score indicates better reputation and deliverability, helping Internet Service Providers (ISPs) determine whether to accept or reject incoming mail.
19 Dec 2024 - Spam Resource
Expert view
Expert from Word to the Wise explains that email deliverability is significantly influenced by sender reputation, which encompasses several critical factors: sender domain reputation, IP address reputation, recipient engagement metrics (such as opens and clicks), the rate of spam complaints, and bounce rates. Additionally, maintaining a clean email list and ensuring proper email authentication (SPF, DKIM, DMARC) are crucial for emails to successfully reach the inbox rather than being routed to the spam folder.
22 Dec 2024 - Word to the Wise
What the documentation says
5 technical articles
Email deliverability hinges on a sender's reputation, a multi-faceted measure derived from various interactions and technical aspects. This reputation encompasses a sender's IP and domain history, low rates of spam complaints, minimal bounces from invalid addresses, and adherence to email best practices. Crucial technical components, such as proper email authentication via SPF, DKIM, and DMARC, are fundamental in proving a sender's legitimacy to Internet Service Providers. SenderScore, a proprietary metric developed by Validity, provides a numerical value from 0 to 100 that quantifies an IP address's trustworthiness based on criteria like spam complaints, unknown users, external blocklist presence, and the overall health of sending infrastructure. A higher SenderScore generally signifies better deliverability, as ISPs and email filters integrate this score into their decision-making processes. Conversely, being listed on reputable blocklists, such as those maintained by Spamhaus, severely damages reputation and can cause emails to be blocked or redirected to spam.
Key findings
- Sender Reputation is Central: Email deliverability is primarily determined by sender reputation, which is influenced by IP and domain history, spam rates, user complaints, and adherence to email best practices and authentication standards.
- Authentication is Critical: Proper implementation of email authentication protocols-including SPF, DKIM, and DMARC-is vital for proving a sender's legitimacy and enabling emails to reach the inbox, as highlighted by Google, Microsoft, and SendGrid.
- SenderScore's Role: SenderScore, a proprietary reputation metric from Validity (ranging from 0-100), quantifies a sender's trustworthiness based on factors like spam complaints, unknown users, external blocklists, and infrastructure health, serving as a key input for ISP filtering decisions.
- Blocklist Impact: Being listed on a reputable blocklist, such as those maintained by Spamhaus, is a significant negative factor that can lead to emails being blocked outright or directed to spam folders by many ISPs.
- Multiple ISP Factors: ISPs like Google (Gmail), Microsoft (Outlook, Hotmail), and others consider a blend of factors for deliverability, including sender reputation, content quality, user engagement, and compliance with email standards.
Key considerations
- Maintain Strong Sender Reputation: Continuously cultivate a positive sender reputation by ensuring low spam complaint rates, managing bounce rates effectively, and sending consistent, valuable content to engaged recipients.
- Implement Robust Authentication: Diligently set up and maintain email authentication protocols like SPF, DKIM, and DMARC to verify sender identity and build trust with Internet Service Providers.
- Avoid Blocklists: Take proactive steps to prevent your IP addresses and domains from being listed on reputable blocklists like Spamhaus, as presence on these lists severely impacts deliverability.
- Monitor ISP-Specific Guidelines: Pay attention to specific guidelines and best practices outlined by major email providers like Gmail (via Postmaster Tools) and Outlook/Hotmail (via Microsoft Learn) to optimize deliverability to their users.
- Address Underlying Reputation Factors: When reviewing your SenderScore, look beyond the number to understand and address the specific underlying factors-such as unknown users or infrastructure health-that influence your score and overall deliverability.
Technical article
Documentation from Validity explains that SenderScore, a proprietary reputation measure from 0-100, quantifies a sender's trustworthiness based on factors like spam complaints, unknown users, external blocklists, and infrastructure health. A higher score indicates better deliverability, as ISPs and email filters use it to make filtering decisions.
1 Feb 2023 - Validity
Technical article
Documentation from Google Postmaster Tools Help explains that for Gmail, email deliverability is heavily influenced by sender reputation, which is built on factors like IP and domain history, spam rates, user complaints, and whether the sender adheres to email best practices and authentication standards like SPF, DKIM, and DMARC.
1 Aug 2021 - Google Postmaster Tools Help
How can I best evaluate my sender score to improve inbox placement?
How does senderscore impact email deliverability and how is it calculated?
How relevant is sender score to email deliverability?
What data sources contribute to Sender Score and how reliable is it for deliverability?
Why is my email sender score low and what can I do about it?
Why is my Sender Score low despite having a high delivery rate?
