How Sender Reputation Can Elevate or Ruin Email Deliverability

Email Spam Tester

Email marketing experts agree that an email's destination - whether it lands in the Inbox or Spam folder - is largely determined by sender reputation. Sender reputation acts like your credit score and is built based on your sending habits.

This article explains the difference between email delivery and deliverability and reveals the impact of sender reputation on both.

Understanding Email Delivery and Deliverability

It's important to differentiate the concepts of delivery and deliverability in order to measure the success of email marketing campaigns properly.

‘Delivery' determines whether or not the message is accepted for delivery to the designated recipient. As soon as the message reaches the receiving server, its authenticity is confirmed and the recipient's mailbox is looked up. The message is accepted for delivery if the sender is verified and the recipient's inbox is active. Otherwise, the message is rejected with or without a bounce.

If the message is approved for delivery, it's examined using a number of variables that mailbox providers evaluate and is placed either in the Inbox or Spam depending on the received score. The ‘deliverability' concept is about the Inbox placements.

For email marketers, a high deliverability is the primary goal as it is the prerequisite of email openings and conversions. To quickly test your email deliverability, you can use this email spam tester. It will tell you where your email goes to Inbox or Spam as well as reveal the sending IP blacklisting issues if they take place.

As it's mentioned, to decide on an email placement, the receiving server examines a number of variables related to the email that comes from the sender, in particular:

  • email content;
  • email authentication (SPF, DKIM, DMARC);
  • sender reputation.

Sender Reputation Dynamics

Among these, sender reputation is the most impactful one because it encompasses a lot of different variables reflecting how good or bad the sender is. Thus, sender reputation score is calculated by analyzing

  • Volume and consistency of sent emails. ISPs like to see consistent and sizable email traffic from the sender while sudden spikes of sent emails look suspicious.
  • The sender's IP score. The IP address sending score is similar to sender reputation but it's isolated to one particular IP. All emails sent from the IP are analyzed to give it a score.
  • User reported spam rate. Spam markings made by the recipients have a direct impact on sender reputation as they serve the indication whether or not the recipients want to receive your emails.
  • Emails filtered out to Spam. The more emails go to Spam, the lower sender reputation is. Although an email may be filtered out as spam for very different reasons, it's important to eliminate the most obvious ones: email content issues and email authentication gaps.
  • Emails sent to invalid users. The mailing list quality is the starting point for building your sender reputation as it determines how people will react and engage with your emails.
  • User engagement. User actions, mostly spam/not spam markings, tell Internet service providers whether or not they want to see your emails in their inboxes. Ignored emails and emails deleted without being open also indicate that your messages are not solicited enough.

It is to note that sender reputation can fluctuate from one day to another. Hence, it's crucial to use monitoring tools to test deliverability and technical set up to catch the issues before they become real problems. An email campaign sent at the wrong time or to the wrong list may harm your reputation. And without the right tools, you won't be aware you're starting to have issues with deliverability.

GlockApps provides a set of monitoring tools necessary to measure sender reputation, IP sender score, deliverability, and email authentication for all the sending sources. With the system alerts, you'll not miss the moment when you need to address the issue in order to prevent a serious impact on your conversions.


In the realm of email marketing, sender reputation stands out as the linchpin determining the fate of messages—whether they land in the coveted Inbox or face relegation to the Spam folder. Understanding the intricacies of delivery and deliverability is vital, with sender reputation emerging as the most influential factor. As the landscape is dynamic, constant monitoring and the use of specialized tools, exemplified by GlockApps, become indispensable for maintaining a positive sender reputation, ensuring successful email campaigns, and safeguarding conversions.