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Sender reputation is an important factor for email deliverability. ISPs (Internet service providers) consider the sender’s reputation before delivering your messages to customer inboxes. In this article, we will review everything you need to know about your sender reputation and how to increase your deliverability rates.

Did you know that almost 45% of all emails sent are considered spam? Multiple factors influence email deliverability. If you are facing issues with spam, you can work on improving your email deliverability to enhance your ability to reach customers’ inboxes.


What is the email sender reputation?

Email sender reputation is also known as sender score, IP reputation, or domain reputation. Sender reputation is a rating assigned to your email-sending IP address by Internet Service Providers (ISPs). It determines whether your email message will be placed in the user’s inbox or spam folder.

In sender reputation, the higher your score, the greater the chance of inbox placement. Conversely, a lower score reduces the likelihood of inbox placement. Therefore, it’s essential to maintain a sender score above 90 for optimal deliverability.

If your sender score falls between 50 and 90, you should initiate the process of improvement by using email warm-up tools. However, if your score falls below 50, immediate action is crucial, as scores below 50 indicate serious issues.


How do ISPs calculate sender reputation?

ISPs employ algorithms to observe the behavior and gauge the risk associated with each IP address delivering messages to their network. When assessing sender reputation, these programs consider various factors and metrics including:

  • Quality of contacts: The nature of recipients to whom the IP address is sending messages.
  • Engagement level: Recipients’ responsiveness to emails from that IP address, including open rate, click rate, unsubscribe rate, complaint rate, etc.
  • Sending volume trends: Calculate based on patterns and trends in the email sending volume.
  • Email content quality: The overall quality of the email content sent from that domain or IP address.
  • Email domain authentication : The presence and effectiveness of email domain authentication checks, such as SPF, DKIM, and DMARC.

There are a few of the signals that email inbox providers consider when evaluating sender reputation and filtering for spam. It’s essential to ensure that the IP address you use for sending emails maintains a positive sender reputation.


How to check your email sender reputation?

There are a couple of tools available to check the sender’s reputation. Here are the most recommended tools you can use.

1. Sender Score

Monitor your sender reputation with Sender Score’s free tools. It assign a score from 0 to 100 to your IP or domain based on your email sending history—similar to a credit score reflecting your credit history. Factors such as email campaign interaction, sending volume, blacklisting, content, and more contribute to generating this score. A higher score is better in terms of email deliverability.

If you encounter email deliverability issues, the first step is to check your sender reputation using Sender Score’s free tools.


2. Barracuda Central

Barracuda is a real-time tool that assesses both IP and domain reputation using its database. It actively monitors all blacklisted IP addresses in their database, enabling you to verify whether your IP and domain are recognized as legitimate or marked as spam.


3. Glock Apps

GlockApps is a robust email deliverability testing tool designed to optimize your email campaigns. It allows you to assess and improve the performance of your emails by analyzing factors such as inbox placement, spam probability, and email authentication.

sender reputation

With GlockApps, you can ensure that your messages reach your audience effectively and maintain a positive sender reputation.


4. Postmaster Tools

Google Postmaster Tools is a suite of analytics and insights provided by Google to help email senders monitor and optimize their email delivery on Gmail. This tool offers valuable data on email performance metrics, including inbox placement, spam rate, and authentication status.

With Google Postmaster Tools, email marketers can gain valuable insights to enhance their sender reputation and improve overall email deliverability on the Gmail platform.


5. Microsoft SNDS

Microsoft provides Smart Network Data Services (SNDS) to help email senders actively monitor and improve their email deliverability to and other Microsoft email services.

SNDS provides valuable data on email traffic, complaint rates, and other performance metrics. By leveraging this information, email marketers can optimize their sending practices, maintain a positive sender reputation, and enhance the overall deliverability of their emails to Microsoft email users.


What are the common mistakes hurting your sender reputation?

By now, you have understood what sender reputation is, how it is calculated, and which tools to use for checking sender reputation. Now, we will explore common mistakes that can harm your sender reputation.

1. Rapidly increasing the email volume

Issue: Rapidly increasing your email sending volume can trigger alarms with Internet Service Providers (ISPs), as it may appear suspicious or indicative of spammy behavior.

Impact: This can result in spam flags for emails, negatively affecting your sender reputation.


2. Not cleaning your email list

Issue: Maintaining an outdated or unmanaged email list with inactive or incorrect addresses can result in high bounce rates and spam complaints.

Impact: High bounce rates and complaints signal poor list hygiene, damaging your sender reputation.


3. Sending out poor-quality content

Issue: Using deceptive subject lines, excessive capitalization, or other spam-like elements in your emails can trigger spam filters.

Impact: Spam flags may cause a decline in deliverability and harm your sender reputation.


4. Using a shared IP address

Issue: Sharing an IP address with other senders means their sending practices influence your reputation.

Impact: If others on the shared IP engage in spammy behavior, it can affect your sender reputation negatively.


5. Using purchased email lists

Issue: Acquiring email lists without proper consent can lead to recipients marking your emails as spam.

Impact: High complaint rates and low engagement from purchased lists can harm your sender reputation.


6. Not using proper domain authentication

Issue: Failing to implement authentication protocols like SPF, DKIM, and DMARC can make it easier for malicious entities to impersonate your domain.

Impact: Improper authentication may flag your emails as suspicious, impacting deliverability and trust.


7. Forgetting to remove disengaged users

Issue: Neglecting to remove users who have not engaged with your emails for an extended period can lead to higher complaint rates.

Impact: ISPs may interpret low engagement as an indication of spam, affecting your sender reputation and email deliverability.

Addressing and avoiding these issues is crucial for maintaining a positive sender reputation and ensuring successful email delivery.


How can you improve your sender reputation?

Discover effective strategies to enhance your sender reputation with these valuable tips. Elevate your email deliverability and build stronger connections with your audience by implementing these proven techniques.

1. Maintain mailing list hygiene

Maintaining mailing list hygiene is the practice of regularly updating and refining your email subscriber list to ensure it remains accurate, relevant, and engaged. By removing inactive or disinterested subscribers and addressing bounces, you enhance email deliverability, reduce the risk of spam complaints, and contribute to a healthier sender reputation.

This proactive approach helps optimize your email marketing efforts and fosters better communication with a genuinely interested audience. Make use of email verification tools to maintain list hygiene.


2. Provide an easy way to unsubscribe

Offering an easy way to unsubscribe is a fundamental aspect of ethical email marketing. By providing recipients with a clear and accessible unsubscribe option, you empower them to manage their preferences. This not only complies with regulations such as CAN-SPAM but also helps build trust with your audience.

A straightforward unsubscribe process demonstrates transparency and respect for recipients’ choices, contributing to a positive sender reputation and fostering a more positive relationship with your subscribers.


3. Use double opt-ins

Utilizing double opt-ins is a best practice in email marketing that involves confirming a user’s subscription twice before adding them to your mailing list. This process begins with the initial signup, followed by a confirmation email where users explicitly confirm their intention to receive emails.

Implementing double opt-ins enhances list quality, reduces the risk of spam complaints, and ensures that your communications are welcomed by a genuinely interested audience. This approach not only aligns with privacy standards but also strengthens the integrity of your email marketing efforts.


4. Check your domain or IP address is listed on a blocklist

Regularly checking if your domain or IP address has been blacklisted is a crucial step in maintaining a healthy email sender reputation. Being blocklisted can adversely affect your email deliverability, causing messages to be marked as spam or blocked altogether. By proactively monitoring blocklists and addressing any issues promptly, you can safeguard your sender reputation, ensuring that your emails reach the intended recipients and are not hindered by blocklisting concerns.


5. Ensure the implementation of appropriate authentication protocols

Ensuring proper authentication protocols are in place is essential for secure and reputable email communication. Implementing authentication measures such as SPF (Sender Policy Framework), DKIM (DomainKeys Identified Mail), and DMARC (Domain-based Message Authentication, Reporting, and Conformance) helps validate the authenticity of your emails.

This not only safeguards against phishing and email spoofing but also enhances deliverability by building trust with internet service providers. By having robust authentication protocols, you establish a secure and reliable communication channel, reinforcing the legitimacy of your email campaigns.


6. Segment your list

Segmenting your email list involves categorizing subscribers based on specific criteria, such as demographics, behavior, or preferences. This strategic approach allows you to tailor your email campaigns to target different audience segments with more personalized and relevant content. By understanding the unique needs of each segment, you can improve engagement, boost open and click-through rates, and ultimately enhance the overall effectiveness of your email marketing efforts.

List segmentation is a powerful tool for delivering targeted messages that resonate with specific audience groups, fostering stronger connections and driving better results.


7. Avoid spam trigger words and low-quality content

Steering clear of spam trigger words and maintaining high-quality content is crucial for effective email marketing. Using words commonly associated with spam in your email content can trigger spam filters and diminish your deliverability. By crafting thoughtful, relevant content and avoiding language that might be flagged, you enhance the chances of your emails reaching recipients’ inboxes.

This practice not only promotes a positive sender reputation but also ensures that your messages are well-received by your audience, contributing to a successful and impactful email marketing strategy.



In the realm of email marketing, cultivating and increasing your sender reputation is paramount for achieving sustained success. Focusing on list hygiene, authentication protocols, and the delivery of high-quality, relevant content helps build trust with both recipients and internet service providers.

Regularly monitoring for potential issues such as blocklisting and promptly addressing them underscores your commitment to responsible and effective email communication. By adhering to these best practices, you not only enhance your email deliverability but also pave the way for meaningful engagement with your audience.

Ultimately, a positive sender reputation is the cornerstone of successful email marketing, fostering stronger connections and ensuring your messages reach the right audience at the right time.