What is Email Sender Reputation?

Published: 28-Feb-2022
Last Updated: 09-Jan-2022
What is Email Sender Reputation?

Email sender reputation (also known as sender score) is a metric used by Internet Service Providers (ISPs) to determine whether an email should be delivered to a user's inbox. ISPs look at user engagement metrics to assign a score. If your email sender reputation is too low, it will not make it past the ISP's spam filter.

ISPs use sender reputation scores to protect their users from unwanted emails. The scores are used as a single element of complex spam filters. Spam filters use a combination of algorithms, machine learning, and other criteria to prevent spam from making it to the inbox. 

As a fellow email marketer, I know how much effort goes into even a single email campaign. It hurts me to think about your email getting stuck in the spam folder. So let's talk about sender reputation and how to reverse a bad reputation score. 

What Damages Sender Reputation?

You want to satisfy ISPs when sending email.

If you are a legitimate marketer who follows email best practices, you likely won't have sender reputation issues. But if you inherited your job or domain from another marketer or organization that mishandled their email marketing program, then you might have some work to do. That being said, you can accidentally damage your sender reputation. Here are a few factors that can lower your sender score. 

Inconsistent Email Marketing Efforts

It’s critical that you send emails with consistent volume and frequency. Sending an uncharacteristically large volume of emails and/or failing to stick to a regular schedule may trigger concerns from ISPs. 

A legitimate email marketing program should send with volume that corresponds to the size of their email list. That doesn't mean you have to choose between sending email campaigns to your entire list or a segment of your list for the sake of consistent volume. But you do want to establish a pattern of expected volume with your ISP. Inconsistency may look like you're contacting a purchased list that exceeds the size of your list of email subscribers. 

You should also create a schedule for your email marketing efforts and stick to it! This will result in an improved customer experience and put ISP spam filters at ease. 

User Complaints

This is a big one! Spam reports and complaint rates are closely monitored by ISPs. A spam complaint is the clearest signal a user can send, short of filing a lawsuit, about their desire to no longer receive emails.  These two metrics provide strong signals to ISPs that the reported email is of low quality and relevance. If your emails are consistently manually sent to the spam folder by recipients, you need to rework your email marketing strategy. 


You may not be aware that you're on a blacklist. These companies use spam traps and legitimate marketers can unknowingly fall victim. The best way to reduce the likelihood of falling into these traps is by monitoring bounce rates and maintaining a healthy email list. You will also want to routinely run blacklist checks to ensure that your domain hasn't been listed. 

Sending to Invalid Users

Maintain a quality email list by removing invalid email addresses. Invalid email addresses are emails that are improperly formatted or don't exist. This can happen when sending a cold email to a guessed email address, when an email address is entered incorrectly, or when a subscriber's email address isn't updated. 

Sending to an invalid email address will return a hard bounce. It's best to remove all hard bounces from your email list. ISPs access Simple Mail Transfer Protocol (SMTP) logs to monitor the ratio of hard bounces to successfully delivered emails. If this ratio or volume of hard bounces is high, your sender score will likely suffer. 

Monitoring Sender Reputation

Woman looks at email marketing dashboard.

We will talk about the various tools you can use to discover your sender reputation, but the first step is monitoring user engagement metrics. Closely track open rates, click-through rates, spam complaints, etc. If these numbers are low or trending down, you can assume that your sender reputation is suffering. 

To quickly get a quantifiable sender score reputation you can use one of the following tools:

If you send emails via Outlook or Gmail you can use the following tools to discover how these companies view your email domain reputation. 

How to Improve Sender Reputation

A person hits send in email marketing software.

The first step to improving your sender reputation is analyzing your current tactics. Take a long and honest look at your email marketing efforts. Are you engaging in practices that are known to damage your sender score? For example, are you sending mass non-opt in emails or individual cold emails to non-subscribers. Are you cutting corners with targeting or content? Following email marketing best practices and consistently working to refine your email marketing strategy is the best way to avoid spam filters and keep your sender score high. 

As we mentioned, the sender score is linked to your domain. So if you're sending email campaigns from a free domain (sallie@gmail.com), you're missing an opportunity to build your sender score. It's best practice to send marketing campaigns from a branded account (sallie@businessname.com). If you don't have a custom email address, we highly recommend setting this up. If you use Gmail or Outlook, here's how:

An additional step email marketers can take to boost their sender score is by authenticating their domain. The two elements that need to be authenticated are DomainKeys Identified Mail (DKIM) and Sender Policy Framework (SPF). Both DKIM and SPF can normally be authenticated within your email service provider. Here are a few links to resources from common ESPs. 

Last but not least, make sure you haven't been blacklisted. If your domain is included on an influential blacklist like Spamhaus, Spamcop, Invalument, or Barracuda, you should submit a removal request with the company and work with them to improve your situation. You can also run a blacklist check using a tool like MxToolbox

Wrap Up

If you follow email best practices, you shouldn't have any sender reputation issues. That being said, it never hurts to check your sender score. If your organization sends cold emails, purchases lists, or doesn't have a clean email list (or didn’t in the past), we recommend checking your sender reputation. These practices are associated with low open rates, high bounce rates, and low email delivery rates which can translate to poor sender reputation. According to Hubspot,  a low email reputation score can be fixed in weeks or it can take months. But you have to know there's a problem to address it! So check your sender score today!


What's Next?

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We've got plenty of articles that discuss many of the topics that we'll talk about over the phone!

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