How to Check and Improve Your Email Sender Reputation with Proven Strategies

If your emails bounce or aren’t receiving the ideal engagement, your first step is to clean your list. However, after years of data analysis, we noticed that there are more problems than invalid emails negatively impacting your sender reputation. More than 15% of your list could contain problematic contacts that directly lower your deliverability rates.

This guide will help you understand what impacts your sender reputation and what practical steps you can take to improve yours.

But first, let’s start with the basics: what is a sender reputation?

What is email sender reputation?

Email sender reputation is a trustworthiness score assigned to email senders by internet service providers (ISPs).

Think of sender reputation as a credit score: to be trusted with more credit, you need a high credit score. You earn a higher score by establishing a history of trustworthy spending behaviors.

Email sender reputation helps ISPs understand and describe your behaviors and history as an email sender. The better your reputation, the higher your sender scoreⓘ is, and the more likely ISPs are to trust your emails and deliver them to user inboxes.

Your overall sender reputation is divided into two categories:

• IP reputation – All of your emails are sent using an IP address. Your sending IP is typically tied to your email server or delivery service. IP reputation is a trustworthiness score given to specific IP addresses or the specific source sending your emails.
• Domain reputation – Your email domain refers to the company that you associate with your user email addresses (e.g., user@domain.com). Your domain reputation is a trustworthiness score given your company domain based on behaviors or metrics that come as a result of sending emails from email addresses on that domain.

Why is sender reputation important?

Your sender reputation is the critical link between your email strategy and strong email deliverabilityⓘ rates. ISPs grant senders reliable access to user inboxes only when they’ve established a strong sender reputation and an expected sending frequency.

When your sender reputation declines, so will your inbox placement and overall campaign performance. More of your emails will go to spam, bounce rates will increase, and engagement metrics will suffer.

What determines your email reputation?

Here’s a detailed breakdown of the different factors that have a direct influence on your scores.

The accuracy and quality of your email list

It’s critical to verify the email addresses on your mailing list. By uploading your contacts regularly to an email verification tool, you can mitigate risk factors by identifying and deleting invalid and high-risk email addresses. Additionally, most email service providers have built-in tools to automatically recognize risky email lists that have been bought, shared, or previously uploaded to the platform.

Monitoring your list quality helps avoid suspensions, bounces, spam complaints, and other reputation risk factors.

The number of emails you send and your sending frequency

Just like our credit score analogy, your current history dictates how many emails you can send and how often. If you make unexpected changes in your sending frequency, particularly to drastic degrees, ISPs will view this as spam behavior. Senders should aim to be predictable with their sending schedule and use an email warmupⓘ process if they wish to send more emails more frequently.

Your email bounce rateⓘ

The industry standard benchmark for email bounce rates is somewhere between 2-5% (guidelines may differ by ESP). Consistently high bounce rates hurt your sender reputation as they can indicate untrustworthy email practices, such as:

• Using unverified email contacts
• Missing or misconfigured email server configuration
• Spammy or untrustworthy email content
• Poor UX, including large email or attachment file sizes

Belkins, a B2B lead-generation agency, felt sender reputation issues as a direct result of high bounce rates.

Before verifying their email lists with ZeroBounce, their email bounce rates continuously grew over time and reached 19%. Here’s what happened as a result:

• More emails were going to the spam folder
• Fewer emails were opened and clicked
• They couldn’t make strategic content decisions as their deliverability declined
• Their email ROI decreased due to a decreased sender reputation

Identifying the bounce rate issue led them to verify their lists, which reduced their email bounce rates to 0.4%. All of their pain points were relieved as their sender reputation was quickly restored with ISPs.

Your open and clickthrough rate

The average open and clickthrough rate of your emails helps ISPs understand your email relevance. Businesses with strong sender reputations will see reliable email engagement when the content is relevant to the subscriber’s interests. Conversely, poor email engagement is a spam signal to ISPs, which can lower your sender reputation over time.

Other engagement metrics, such as forwards and unsubscribe rates

Additional campaign metrics can influence your email sender reputation. If your audience is sharing your content with peers, it sends positive signals to ISPs regarding content quality. On the other hand, unusually high unsubscribe rates are a telltale sign of a spammer or malicious sender. Email unsubscribes are not necessarily a negative signal, but if you experience 1% or more unsubscribe rates with subsequent campaigns, your sender reputation may be at risk.

The number of emails sent to spam traps

Spam traps are email addresses created specifically to target untrustworthy senders. These addresses may be planted on purchased lists or otherwise to keep you on your toes. Spam traps can significantly lower your sender reputation or even land you on an email blacklist.

How to check email sender scoreⓘ

Tracking your sender scoreⓘ is your best defense in identifying email deliverabilityⓘ issues. When you notice a decline in your score, you can investigate for the aforementioned risk factors before they have an opportunity to sabotage your sender reputation.

There are a variety of tools you can use to check sender scoreⓘ:

• Google Postmaster Tools – You can use Google’s free tool by verifying your domain with the given record. Then, you can access the dashboard to track domain and IP reputation, spam complaints, compliance, and other useful information.
• Microsoft Smart Network Data Service – Microsoft’s email sender tool offers useful insights into factors that impact your sender reputation, such as spam traps, compliance, spam complaints, and known blacklist issues.
• Sender Score — The free tool allows you to check the sender score by entering your domain or IP address. It will return various useful information, including a WHOIS lookup and found scores for your sending IPs.

• ZeroBounce – The platform provides a variety of email domain health monitoring tools. The 24/7 automatically notifies you of blacklist issues with 200+ providers. keeps tabs on compliance and tracks emails sent from your domain or IP for suspicious activities that can hurt your sender score.

• MXToolbox – The platform provides a wealth of free tools to look up email reputation score and deliverability problems. You can filter your search by specific records or check your overall email health by entering your domain or IP address. Then, get a breakdown of each problem and how to fix it.

• Talos Intelligence – This email reputation check tool lets you look up your domain and IP. Get useful information on your sender score, web reputation, and email volume history.

How to improve your sender reputation

Every activity that occurs using your email domain or IP address boosts or lowers your sender reputation. Improving and maintaining your score is critical for maximizing and ROI.

Here are the go-to tactics to improve your reputation.

Use a clean email listⓘ

Few things lower your sender reputation faster than low-quality data. A list that contains invalid emails, spam traps, or known complainers leads to more bounces, spam complaints, and email blacklist issues.

Use an accurate tool like to detect the invalid and high-risk email contacts present on your list. The tool will leave you with valid, safe contacts that you can email without worry. Maintaining a clean list will reduce your bounce rates, spam complaints, and average spam placement. All of these metrics send positive signals to ISPs and encourage them to boost your sender reputation.

Don’t make sudden changes to email volume

If you don’t normally send high-volume campaigns, avoid sending mass campaigns on short notice. A sudden burst of emails can alarm ISPs, harming your deliverability and sender reputation.

To avoid this, divide your upcoming campaigns into smaller batches. Yahoo, for example, allows 200 emails a day per IP in its first five days of sending. You’ll need to adhere to rules like these before you can safely increase your daily volume.

To simplify this process, use service to warm your domain and IP address gradually. The tool will automatically increase your volume over time while granting positive engagement signals via opens, favorites, and clicks. This sends healthy signals to ISPs, which will improve your sender reputation rather than harm it.

Use a double opt-in confirmation email

The double opt-in subscription method is a staple in email marketing as it provides an additional method of verifying the user’s email address. Additionally, it gives the visitor an opportunity to confirm their desire to receive marketing communications from your email domain.

Without a double opt-in (or a real-time email validator), visitors can enter any email address into your database. That email address may contain typos or be a deliberate fake. When you send your campaigns to these fake signups, your bounce rate increases.

Fortunately, creating a double opt-in is simple. From your ESP, create an automated message that triggers upon subscription. This message should contain a link within the body that the reader must click before any additional emails may be sent. By verifying permission, you maintain lower bounce and spam complaint rates, which boosts your sender reputation.

Protect your email list with an email verification APIⓘ

While double opt-in is still handy, also aids in blocking fake and high-risk email contacts. By identifying problems before they enter your list, you have a proactive defense against unnecessary email bounces and spam complaints.

The ZeroBounce email validationⓘ tool provides free access to the API, which you integrate directly into your website, landing pages, and newsletter signup forms. It also works well with your favorite database tools and CRMs.

Whenever a new email address is added to your form or contact field, the email validationⓘ process occurs automatically. The API will allow or block the email address based on the result.

Send personalized email content

There is a direct correlation between subscriber engagementⓘ and personalization. Due to competition and inbox crowding, your content must stand out to earn positive sender reputation signals, such as opens and clicks.

By personalization, we don’t mean just using a name. Use the appended data made available when using ZeroBounce’s email validationⓘ tool. The information provided can include names, locations, and email domain data when available. Other tools like Activity Data can help you focus emails on currently active subscribersⓘ by tracking their last known activities via email or the web.

This lead data can help you segment your campaigns, understand your target audience, and deliver more relevant emails. These steps improve your odds of engagement, which in turn positively influences your sender reputation.