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Email sender reputation: How to check and improve it

Reading Time: 7 minutes

Many email marketers believe high open rates indicate success. Although open rate is a critical email marketing metric, you may be overlooking the very foundation of email outreach: email sender reputation. 

A low sender reputation is the bane of email outreach. Your emails may end up in your recipients’ spam folders, or worse, ISPs may even block your domain.

This article will help you learn what email sender reputation is, what factors influence it, and the best practices to build a foolproof sender reputation. 

What is an email sender reputation?

Your email sender reputation is a score given by Email Service Providers (ESP) like Gmail, Yahoo, and Outlook, and Internet Service Providers (ISPs). It is typically determined by various components such as email bounce rate, sender history, and email engagement rate.

The higher your sender reputation score, the more likely your emails will reach recipients’ inboxes. A lower score can affect your email deliverability, where ISPs mark your emails as spam or even reject them. 

Internet and Email Service Providers evaluate sender reputation based on multiple factors, including:

  • Age of account. If you’re just starting on a new domain, you should take care to warm up for better deliverability
  • The level of engagement your emails garnered in the past. For example, open rates, click-through rates, and compliant rates
  • Sending volume
  • Quality of email contacts to whom the IP address sends emails
  • Email content quality
Want to improve email deliverability and maintain a high sender reputation? Omnisend can help.

What influences email sender reputation?

Below are factors and metrics ESPs and ISPs use to score your email sender reputation:

1. Bounce rates 

High email bounce rates signal ISPs that your emails fail to get delivered to your recipients’ mailboxes, thus significantly impacting your sender reputation. 

Bounce rates are of two types: soft and hard bounces. Soft bounces are not a cause of great concern, as they could be due to a full recipient inbox or temporary server issues. On the other hand, hard bounces indicate a poorly maintained email list. 

2. Complaint rates

Complaint rates are the accumulated spam reports by recipients marking your email as spam or complaining to their ISP about your messages. 

A high complaint rate pushes ISPs to filter your emails and send them straight to recipients’ spam folders, or even block or blacklist your business from sending future communication. 

3. Engagement rates 

Email engagement refers to the actual performance of your email outreach campaigns, which includes factors like email open rates, click-through rates, and opt-out rates. 

Low open and click-through rate, for example, is a clear sign of uninterested email subscribers who are more likely to unsubscribe or, worse, mark your emails as spam. 

Similarly, a sudden surge in unsubscribes or opt-out rates lets ISPs and ESPs assume poor email engagement capability, so they could assign a lower sender reputation score. 

4. List quality 

Have you not refreshed your email list in a while? If not, the right time is now to maintain your sender reputation. 

An email list containing inactive email addresses or invalid/outdated emails can affect bounce rates and email deliverability. 

5. Email content 

Although ISPs are technically not directly influenced by email content to assess sender reputation, your email content’s relevance and quality can still affect user engagement.

For example, if you send personalized, relevant content that users resonate with, you’re likely to have higher open and conversion rates. Also, maintaining consistency in your messaging tone promotes brand familiarity—thus boosting a positive reputation. 

6. Email authentication 

Email authentication is used to validate the email sender and to indicate that an email isn’t forged. It also helps block out phishing and spam.

It involves protocols like DMARC, SPF, and DKIM so that ISPs can verify a sender’s authenticity and their commitment to security. 

7. Domain and IP reputation 

Domain reputation indicates the overall health of your brand’s domain. IP reputation measures your IP address’ quality and analyzes your spam-free, relevant email deliverability rate through your IP address.

8. Sending practices 

Email sending practices include consistency in sending relevant emails, strategic email segmentation, personalization, sending frequency, and gaining permission to send emails. They can significantly impact your overall email sender reputation. 

For example, a high sending volume or email inconsistency could weaken your sender reputation with time.  

The impact of poor email sender reputation 

ESPs and ISPs want to ensure that their customers have the best email experience from credible sources. 

So if you’re overlooking sender reputation as just another metric, you may face negative consequences, such as:

  • Low email deliverability: If your sender reputation is low, your email campaigns will struggle to get delivered to your audience. If your message doesn’t reach them, you lose all chances to even drive possible conversions. 
  • Blocked or marked spam: If your sender reputation continues to drop, ISPs can blacklist your business and block future communication from reaching your target audience. 

How to monitor your email sender reputation

Monitoring email sender reputation is not a one-time thing but an ongoing process. You can target quarterly or monthly monitoring cycles to maintain a positive sender reputation.

Below are the best ways to regularly monitor your sender reputation:

1. Using tools and services for Reputation Monitoring 

There’s no clear-cut way to know how most ISPs and ESPs calculate sender reputation. 

However, you can use several third-party and mailbox-specific tools to understand how providers evaluate your messages. 

Such Email Reputation Monitoring tools offer insight into your email and domain health, give you an approximate numerical score, and help monitor email deliverability. 

You could try tools like Sender score, Barracuda Central, Google Postmasters, and SNDS to check your sender reputation, deliverability, IP and domain reputations, and more.

2. Understanding reports and feedback

Reports and feedback help uncover hidden insights into your email marketing campaign’s performance so you can improve your sender reputation. For example, a detailed report indicating how well users engaged with your latest email campaign allows you to take timely action.

Further, understanding ISPs’ feedback through feedback loops lets you proactively fix issues that may hamper your sender reputation in the long run.

Omnisend’s reports for email deliverability show you ways to improve your delivery rate. The reports also include insight into your email list hygiene, securing sender domains for better professionalism, and your sender email addresses’ safety. 

3. Performing regular check-ups and audits 

Regular email check-ups and audits let you see what works and what doesn’t in your email marketing campaigns. It also ensures your communication reaches the right audience by eliminating everything that could hamper deliverability. 

Here are some tips for performing sender check-ups and audits:

  • Audit your email service provider by testing emails to see if they go into the spam box or the main inbox.
  • Check for IP address or domain blacklisting using an email spam checker tool. 
  • Constantly measure and monitor your sender score trends to notice any drops.
  • Set up DMARC, SPF, and DKIM.
  • Warm up sender reputation by gradually sending smaller email batches in increments. Doing so ensures your emails don’t end up in the spam folder or shock ESPs. 
  • Frequently audit email list health and analyze your email segments. 

Strategies to build and maintain a strong sender reputation

Now that you’re clear on the influencing factors, the following suggestions will help you build and maintain a strong email sender reputation to see email marketing success.

1. Best practices for email list management

A healthy email list is a major deciding factor behind a strong reputation. So here are some essential email list management strategies:

• Regular list cleaning and maintenance 

Email list clearing, aka email scrubbing, is when you remove invalid or fake email addresses in your email list. Regular scrubbing helps maintain a list of high-intent customers and reduces spam complaints.

Additionally, clean up inactive subscribers who have not interacted with your emails over the last 90 days or more. Removing them will eventually boost your sender reputation and deliverability as you now have a list of engaged subscribers who find your communication useful.

• Use double opt-in

Email double opt-ins signify high user intent. For example, a user signs up for your company’s email newsletter or promotions and then re-confirms their subscription via email or landing page. 

Double opt-ins thus reduce the risk of spam complaints and ensure high engagement as users showcase a higher level of interest in receiving your communication. 

Difference between single and double opt-in process

• Sender warm-up processes

Warming up is when you send smaller email batches over a period of days or weeks, gradually increasing the volume of emails. This helps ISPs gauge sender reputation by evaluating your sending pattern, content, and recipient engagement.  

The warm-up process is also the perfect time to test and analyze user engagement and behavior and reassess content.

Omnisend helps implement your reputation warm-up process and offers tips on doing it successfully. 

An example of sender's reputation warm-up process on Omnisend

2. Reducing email bounces 

A high hard bounce rate can stain your sender reputation. Here are some tips to reduce hard bounces:

• Real-time address verification 

Invalid email addresses are one of the major reasons behind hard bounces. You can root them out using an email verification tool or verify manually by checking for syntax errors (invalid characters), verifying domains, and pinpointing address typos.

• Re-engagement campaigns for inactive subscribers

A high bounce rate despite having a valid email list could be due to inactive subscribers who haven’t interacted with your email campaigns recently. 

So to reduce bounces, you can segment inactive subscribers and run a re-engagement email campaign as a last resort. Post-campaign, you can analyze what contacts you should remove completely based on their latest engagement trends. 

• Sunsetting policy

Sunsetting is a segmentation process where you identify and delete inactive and disengaged subscribers from your email list. Doing so regularly (e.g. quarterly or every six months) helps maintain a healthy email list and strengthens sender reputation. 

3. Content and engagement strategies 

Email content can make or break your email marketing metrics. Here are two content-related strategies to implement for a solid sender reputation:

• Personalization and segmentation

Email personalization is not just about referring to your subscribers using their first names. 

Segmenting subscribers to customize emails based on purchase behavior, preferences, demographics, etc., helps you tailor content to resonate with each customer segment—and boost engagement metrics. 

• A/B testing for subject lines and content

Using A/B testing, you can test variations in subject lines, for example, the length, urgency, emojis, wording, and tone (casual, funny, FOMO, etc.)

Similarly, test different versions of your email content for each subscriber segment. For example, try out different lengths, images, GIFs, CTA placement, offers, and so on.

Email A/B testing

4. Technical aspects 

Don’t overlook setting up and staying compliant over protocols—SPF, DKIM, and DMARC, a.k.a. the golden trio of email authentication. 

SPF or (Sender Policy Framework)-protected domains escape spammers and phishers, and you’re unlikely to be blacklisted by ISPs. DKIM setup is another additional way to verify your authenticity. DMARC, on the other hand, ensures domain protection and secures senders and receivers from fraudulent activities. 

Wrap up

Email sender reputation requires constant maintenance. Remember, strategies that worked once may not work again as ISPs and ESPs are constantly evolving. 

That’s why continuous monitoring and analyzing results through best practices will help to ensure your emails are delivered to the right people and boost engagement metrics to solidify reputation. 

Below are some essential best practices that should be part and parcel of your email marketing campaigns:

  • Frequent list cleaning
  • Email authentication
  • User segmentation
  • Sunsetting
  • A/B testing email content 
Want to improve email deliverability and maintain a high sender reputation? Omnisend can help.
Richard White
Article by
Richard White

Richard is a Content Marketing Manager at Omnisend. An avid writer, he's said to have been born holding a pencil. Fascinated by all things handmade, if he's not reading or writing he can often be found practicing leathercraft.


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