Email Deliverability Metrics: 7 Metrics to Watch to Prevent Delivery Failures


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metrics_stopwatchWhen it comes to email deliverability, preparation is key. The fact is that no one is exempt from experiencing delivery failures. With ISPs changing their algorithms all the time to prevent spam, you’re bound to get caught up in their net at some point. However, you can minimize the damage by carefully monitoring your email delivery rates and paying careful attention to the key metrics that will alert you to any problems. Here are the metrics you should keep a sharp eye on.

  • Requests: This is the number of emails sent through the system. This metric is an important starting point in measuring email effectiveness.
  • Delivered Rate: This metric tells you how many of your emails were accepted by the ISP. While it does not mean that the email reached the inbox, it does mean that it was not rejected or deferred by the ISP. If you experience a low email delivery rate, take a look at where and when it happened. Determine if it’s isolated to one campaign or one ISP and make adjustments accordingly.
  • Clicks and Unique Clicks: This is the total number of times users have clicked on the links within your email, divided by the total number of delivered messages. Low click-through rates can be an indication of poor content. Compare your email campaigns to see which received the best response. Also, A/B test your campaigns with new content and evaluate your call to action to achieve higher response rates.
  • Opens and Unique Opens: This is the total number of times users have opened your emails divided by the total number of delivered messages. This is determined by a small, transparent image that is inserted into the email, which tracks the open when that image is loaded. While opens can only be recorded for emails where images are automatically turned on by default, opens still gives you some data regarding the level of engagement of your emails.
  • Unsubscribes: This metric is the total number of users who have opted-out of your list. According to CAN-SPAM, requests to be removed from your list must be honored within 10 business days. If you see your unsubscribe rates rise, take another look at your content to determine what is turning them off. See if you can identify a trend as a starting point.
  • Bounces: This is the number of emails that were rejected by the ISP due to a full mailbox or bad email address. If the ISP returns a 500 class error, then the email address will be recorded as a hard bounce. High bounce rates equal poor list hygiene. So, clean your lists by removing all hard bounces and non-responders. And also look at your email acquisition practices to make sure you are asking for the right permissions.
  • Spam Reports: This is the number of people who marked your email as spam (aka complaint rate). Spam reports can negatively affect your email reputation so make sure your unsubscribe process is clear, working, and readily available. If you see a sharp increase in your spam reports, it’s time to look at your entire email campaign to ascertain why. And you must do this quickly as repeated spam reports can result in you ending up on a blacklist with delivery problems that will affect your email campaign for a longer duration.

If you are a SendGrid customer, then you are already familiar with our dashboard, but if not, here’s a glimpse at the key metrics you will receive when you start sending email via SendGrid.

SendGrid-Dashboard

Each of these metrics provides important clues as to the health of your email program, but as with most things, it’s best to catch problems early. From the ISP perspective, companies that act quickly are looked at positively. Those that don’t may experience delivery problems that are much more difficult to repair, especially without email deliverability expertise.

Remember that success can come to your email program if you prepare well, stay informed of new changes at the ISPs, and quickly respond to negative engagement metrics.

To learn more about why these metrics matter, download our free Deliverability Guide.


Carly Brantz is a veteran in the email deliverability space working to make email simple and easy for developers by regularly writing whitepapers, research briefs and blog posts about email, technology and industry trends.

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