How to Improve Your Email Sender Reputation Score Fast

Your sender reputation score is basically the number that determines the chances of your emails being delivered into the inboxes. The higher the value, the greater the chance that email service providers (ESPs) regard your domain as trustworthy, and grant your emails permission to enter inboxes. Essentially, it’s a solid measure of your sender reputation. It’s like a credit score but for email.

The cost of having low scores can be very high for senders who put in substantial effort only to end up in spam, meaning wasted resources and damaged reputation.

Fortunately, the email sender reputation score is a number that can be influenced by best practices and certain actions. In this guide, we’ll walk you through the ten essential strategies that will protect and enhance your email sender reputation score.

What is sender reputation and how do ESPs evaluate it?

Sender reputation is a score or a measure of how trustworthy an email sender is.

Email Service Providers (ESPs) determine your sender reputation by checking multiple variables that offer hints as to how true and reputable you and your sending are:

• Email sending history and quantity: Steady, high volume email sending patterns without notable spikes are signs of a sender that is predictable and trustworthy.
• Complaint rates: If recipients constantly mark your emails as spam, this can impact your reputation negatively.
• Bounce rates: High bounce rates can signal poor list management practices which can harm your reputation.
• Engagement stats: ESPs also look at how recipients engage with your emails. Are they opening and engaging with your emails? Low engagement (meaning few opens or clicks) could indicate your emails aren’t relevant or welcome.
• Spam traps: If your emails hit spam traps (fake email addresses deliberately created to lure spammers), this can seriously hurt your sender reputation.

How sender reputation score works

Your sender reputation score is the sender reputation translated into a number. It then acts as a score that ESPs use to evaluate whether they can trust you and your emails. ESPs and other email servers apply algorithms to determine scores from 0 to 100. 

The details will differ, but a general outline is as follows:

• A high reputation score refers to a good sender reputation. It means consistently low complaints, strong engagement signals, and proper authentication protocols are set up. Email senders that have high scores lead to inbox placement.
• A medium score means a relatively neutral reputation. Senders have minor issues with engagement, occasional bounces, or occasional spam placements.
• A low score means the sender’s reputation is suffering. These are defined by frequent spam complaints, high bounce rates, or even instances of being blacklisted. Emails with low email reputation may be more likely to be blocked or sent to the spam folder.

Why does sender reputation score matter for email deliverability?

Your sender reputation is that one metric that reflects whether your emails will make it to your recipients’ inboxes or get sent to spam instead. While deliverability does have a lot of factors and is multi-layered, the sender reputation score brings together all those factors. Here are other reasons why this score matters:

It lets you know about reduced deliverability

Sending reputation matters. First impressions matter. When you have a poor reputation score, inbox providers are less likely to trust your emails. Even if you’re just trying out cold outreach with a small list, a poor score will be enough for the ESPs to regard you with a skeptical eye.

This reduces the efficacy of your email marketing campaigns and wastes the time you’ve invested in your email marketing.

Now, here’s where it gets difficult. If your emails do get sent to spam folders because of the poor reputation score, here’s what will happen: the score will continue getting lower. It can  create a pattern where your emails are marked as spam repeatedly, making it even harder to regain a good reputation.

It helps you watch your engagement rates

Emails that wind up in spam folders or get blocked altogether won’t be opened. This in turn, reduces your open, click and conversion rates. If your subscribers aren’t seeing your emails, then they can’t engage with them.

Engagement is a very important number that ESPs use to evaluate your email sending reputation. So lower engagement rates can further lower your sender score.

It enables you to squeeze the most from your marketing budget.

Your emails end up in the spam folder and it’s the equivalent of throwing money in the trash. You have already invested a lot in marketing. However, if your emails don’t make it to the inbox, none of your efforts will be worth it.

A poor sender reputation means that you are effectively throwing money down the drain and your emails will not make it to the inbox—negatively impacting your ROI and the overall success of your marketing efforts.

It helps you protect your brand

Your brand takes a hit when your emails don’t get delivered to recipients’ inboxes. Subscribers who expect to receive your communications may wonder why they never do. This may result in frustration, and possibly in a loss of confidence in your brand. 

10 ways to build and maintain a good email sender reputation score

Getting your reputation score to where you want to is one thing. Maintaining and improving your sender reputation is another. You need to work hard to keep a good sender reputation score. Here, we present 10 key strategies to improve your domain reputation.

1. Build and maintain quality email lists

A good sender reputation begins with a good email list. A good email list is a permission-based, engaged, relevant, and segmented one. To achieve this, here are the best practices to implement:

• Use double opt-in. Permission-based marketing is when recipients explicitly opt in to receive your emails. This fosters trust, and allows you to reach people who actually care about the contents of your messages.
• Pay attention to the quality of your list, not just the quantity. Focus on growing a list of engaged, interested subscribers instead of purchasing or renting lists. Purchased lists are often filled with outdated or unverified email addresses, which increases bounce rates and spam complaints.
• Practice regular list hygiene. Regularly clean your list by removing inactive email addresses or unengaged subscribers. This helps ensure that you’re only sending to people who are likely to interact with your emails, improving your overall sender score.
• Practice segmentation. Divide your email list based on engagement, customer behavior, and preferences. This allows for more personalized and targeted campaigns, which leads to higher engagement and better reputation.
• Make it easy to unsubscribe. This may seem counter-intuitive, but it it actually helps keep your list engaged and clean.

2. Implement essential email authentication protocols

Email authentication protocols, when properly set up, send signals to ESPs that your emails are legitimate and that you are a trustworthy sender. Additionally, providers like Gmail and Yahoo have recently released their new sender requirements which include the mandatory implementation of SPF, DKIM, and DMARC.

So without proper authentication, your emails may be flagged as suspicious or blocked entirely. Actually, even legitimate businesses can be tagged as spam if senders are not that knowledgeable in implementing proper authentication protocols. 

Key protocols to implement:

• SPF (Sender Policy Framework): SPF helps ensure that only authorized mail servers can send emails on behalf of your domain. This protocol prevents spoofing by verifying the sender’s IP address against a list of allowed senders in the domain’s DNS records. 
• DKIM (DomainKeys Identified Mail): DKIM adds a digital signature to emails, which is then validated by the recipient’s mail server to ensure that the email wasn’t tampered with during transit. 
• DMARC (Domain-based Message Authentication, Reporting & Conformance): DMARC works alongside SPF and DKIM to provide instructions to ESPs on how to handle emails that fail authentication checks. 

Why these protocols matter:

• They prevent spoofing. SPF, DKIM, and DMARC, when combined, prevent malicious actors from impersonating domains and sending fraudulent emails. 
• They improve trust with mailbox providers. These protocols contribute to how ESPs determine your sender reputation. Having them in place verifies your legitimacy, helping ESPs protect their users. Remember, they are not the enemy. They just want to ensure that only relevant and safe emails land in their users’ inboxes.
• They protect your brand and reputation. Proper authentication ensures your email domain is not misused for any suspicious activity.

3. Warm up domains and IPs strategically

Domain and IP warming is the process of gradually increasing your sending volume over time to build a positive sender reputation with ESPs.

When you send emails from a new domain or IP address, mailbox providers don’t trust the infrastructure at once because there’s no sending history to use as a basis. So if you suddenly send large volumes of emails, it raises red flags, and your emails are more likely to end up in spam folders. 

Some things to keep in mind when it comes to warmup:

• Avoid sudden volume spikes. We understand it can be exciting. But if you send thousands of emails right away from a new domain or IP address, it can be seen as suspicious behavior. Sudden spikes in email volume are often associated with spam campaigns, which can harm your sender reputation. 
• Increase slowly, steadily, and gradually. Start off by sending a few emails to your most engaged subscribers. Gradually increase the volume over time. Usually, a warmup process takes four to eight weeks depending on volume goals and industry. For example, the timeline can be very different for fintech companies and cybersecurity companies.
• Target engaged subscribers or contacts. During the warmup phase, focus on sending emails to your most engaged subscribers. They are more likely to open and interact with your emails, which will help build and establish your reputation.
• Monitor metrics closely. Keep an eye on metrics like open rates, click rates, bounces, and complaints throughout the warmup process as you increase your sending volume. This helps ensure that your warming strategy is working and allows you to adjust the volume or frequency if necessary. If your bounce rates are starting to increase, dial down the volume a bit and focus on increasing engagement first.

4. Optimize sending volume and frequency

Consistency in your sending patterns helps maintain a positive sender reputation. Mailbox providers continuously monitor the volume and frequency of emails sent from your domain, and erratic sending behavior can trigger spam filters. Consistent sending behavior is important because:

• It avoids triggering spam filters. 
• It ensures your subscribers are regularly engaged with your email content.
• It establishes a positive reputation.

5. Analyze engagement and feedback loops

Engagement metrics like open rates, click rates, and spam complaints directly influence your sender reputation. For example, your open and click rates are numerical descriptions of how your audience is interacting with your emails.

High engagement rates mean your audience finds your emails relevant and valuable, positively impacting your sender reputation. Low engagement on the other hand means your content isn’t resonating, or your emails may be sent to the wrong audience, damaging your reputation.

Actionable tips for improving engagement:

• Segment your email lists to send more targeted, relevant content.
• Test subject lines, calls to action (CTAs), and content formats to optimize engagement.
• Monitor engagement regularly to adjust your strategy and improve results.

Meanwhile, feedback loops (FBLs) are offered by most mailbox providers. When you set this up, you receive a notification whenever a recipient marks an email as spam. Setting up feedback loops helps you quickly respond to spam complaints so you can take action and maintain a positive reputation.

6. Avoid spam traps and blocklists

Spam traps are email addresses used by ESPs and anti-spam organizations to identify and penalize senders who engage in poor email practices. They look legitimate but they are intended to catch senders who use poor list hygiene or purchased lists. There are three main types:

• Pristine spam traps: These email addresses never belonged to a real person and are used solely to catch spammers sending to harvested or purchased lists. 
• Recycled spam traps: These were once real email addresses that have been inactive or dormant for months or even years. Sending to these means that your list isn’t updated.
• Typo or honey pot traps: Slightly misspelled addresses (e.g., gmaill.com instead of gmail.com) are designed to catch careless marketers who don’t validate addresses before sending.

Blocklists or blacklists are databases of domains and IPs that have been flagged for sending spam or suspicious messages. If your domain ends up in a blacklist, your sender reputation score takes a hit. It sends a signal to other ESPs that you are not to be trusted—after all, there must be something you’ve done that landed you in a list.

Best practices to avoid spam traps and blocklists:

• Avoid buying lists altogether. Stick to real email addresses and build connections with real people.
• Use inbound lead generation tactics: content marketing, gated resources, and opt-in forms.
• Gradually retire old or inactive addresses to get rid of problematic email addresses.
• Monitor presence on major blacklists like Spamhaus, Barracuda, or SpamCop. (Begin the delisting process right away, if ever you are listed.)

7. Comply with global email regulations

Staying compliant with global privacy and data protection regulations is crucial not just for legal adherence but also for maintaining a strong sender reputation and ensuring optimal email deliverability.

Global data protection laws are not just legal standards. They are now being increasingly integrated into deliverability algorithms. So ignoring these regulations can severely harm your sender reputation. 

Key regulations impacting email deliverability

GDPR (General Data Protection Regulation) – Europe
GDPR sets a high bar for user consent and privacy. Non-compliance can lead to substantial fines and reputation damage. GDPR compliance means:

• Providing clear and accessible unsubscribe options
• Using opt-in consent forms
• Being transparent about how personal data is collected and used

CAN-SPAM Act – USA
The CAN-SPAM Act mandates that email marketers include an opt-out option in all marketing communications and provide the sender’s physical address in every email. Failing to comply can lead to fines, legal action, and, importantly, a negative impact on sender reputation and deliverability.

Additionally, major email service providers have also started implementing stricter rules for bulk email senders (typically over 5,000 emails/day) to enhance inbox security and reduce spam. Key standards to follow in 2025 and beyond include:

8. Segment communications by subdomains

Using different subdomains for distinct types of email communication is a powerful strategy to protect your sender reputation. Each subdomain can build its own reputation independently.  

• If you choose to go with a single domain strategy, all emails share the reputation. So one issue can affect all messages you send. 
• If you go with a multiple subdomain strategy, it entails a more complex setup. However, you can isolate reputation risks and get better analytics. This approach ensures that if one subdomain experiences issues (e.g., high spam complaints from a marketing campaign), it does not impact the deliverability of transactional or critical emails.That way, you can track the impact and results of each type of message.

Common subdomain structures include:

• promo.domain.com: for promotional or marketing campaigns.
• news.domain.com: for newsletters and content updates.
• transactional.domain.com: for receipts, confirmations, and important account notifications.

9. Monitor your email sender score continuously

Maintaining a strong sender reputation is not a one-time effort. It requires ongoing vigilance and regular monitoring allows you to detect potential issues early and adjust strategies before deliverability suffers.

Here’s a quick guide on how to implement effective and efficient monitoring of sender score:

• Monitor key reputation metrics such as sender score, bounce rates, and spam complaints. Depending on the tools you use to manage your email campaigns, you can easily access these numbers.
• Check your IP and domain reputation at least weekly, or more frequently if running high-volume campaigns.
• Interpret changes carefully. A sudden dip in reputation could signal spam complaints, blacklisting, or technical issues.
• Use reputation data to guide your sending behavior. Reduce volume, improve targeting, or adjust email content if issues are detected.
• Test all changes and measure their impact on reputation and deliverability to ensure continuous improvement.

10. Stronger deliverability with AI-driven tools like Warmy.io

Modern AI-driven tools are transforming how businesses manage email deliverability through analyzing patterns, predicting potential issues, and automating critical processes.

For example, here’s how Warmy can assist in both building and maintaining a positive email sender reputation score.

AI-powered domain warming for building a positive reputation