Email Best Practices for Publishers Part IV: Tracking Performance

This is the fourth article in the series that covers email marketing essentials. Now that you understand all the factors that can affect a campaign's performance, you'll need a firm grasp of which key performance indicators to monitor.

Reading Time: 4 minutes


Jump to:
Part I: Planning & Scheduling
Part II: Design Optimization
Part III: Content Optimization
Part IV: Tracking Performance
Part V: Split Testing


Email marketing is an essential tool for communicating with your subscribers. It’s the most affordable way to drive traffic to your digital editions, remind readers of their subscription status, onboard new subscribers, and identify segments of your audience for specialized campaigns. When you look at the effectiveness and ROI of email compared to social media, it’s pretty clear that email is more effective. That’s not to say social media doesn’t have its place, but that’s an article for another day. Today we’re going to look at email best practices.

In part four of this series, I cover A/B testing – which includes some basic rules to help guide you with split testing different versions of your email to help increase engagement. In this article, I will be discussing key performance indicators, what they mean and why you should be measuring them.

Part IV: Tracking Performance

Now that you understand all the factors that can affect a campaign’s performance, you’ll need a firm grasp of which key performance indicators to monitor. Understanding these KPIs is essential to measuring and adjusting during the testing phase, helping you increase the effectiveness of your campaigns.

Email Audience Trend

(emails delivered) / (emails sent) * 100

Gaining and losing subscribers is inevitable. But the earlier you know that your audience is declining, the sooner you can take action and avoid bigger issues down the road.

Active Audience Trend

Tracking the growth and decline of the subscribers who engage with your content the most will allow you to catch any issues early and set up an effective re-engagement program.

Delivery Rate

(emails delivered) / (emails sent) * 100

As long as you are maintaining clean subscriber lists, you should be achieving a delivery rate of 99% or higher. Anything below 97% should warrant attention. It’s important to note that a high delivery rate does not mean high inbox placement – your email could be getting delivered, but winding up in junk/spam folders, where the subscriber won’t notice it.

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Bounce Rate

(emails bounced / emails sent) * 100

Hard Bounces

Hard bounces are emails that are permanently unreachable. Failure to remove any bounced addresses from your subscriber lists will lead to your emails being blocked completely. The most common cause of hard bounces is inactive email addresses.

Soft Bounces

Soft bounces mean that there is a temporary issue with the email address. A sudden spike in soft bounces could be a sign of bigger issues. Frequent causes of soft bounces are temporary blacklisting, full mailboxes, connection errors, and gray-listing. Proper list maintenance will help avoid soft bounces.

Open Rate

(emails open by subscribers / emails delivered) * 100

Open rate is the second most important deliverability metric because it shows you both that emails are reaching the subscriber inbox, and that either the brand or the subject line caught their attention. Most publishers refer to this as unique opens, since counting all opens can skew the results. Open rates can be improved by A/B testing the timing, subject line, sender name, or pre-header.

Total Open Rate

(total emails opened / emails delivered) * 100

This metric will help you understand how many customers are coming back to reopen an email. If they are, you might think about sharing that information in a way that is easier, so they’re not searching for old emails.

Open Rate Variation

(emails opened in past [x] days / subscribers sent an email in past [x] days)

When you compare open rate results between different domains (e.g. Gmail vs Hotmail), you might see that one domain is performing much worse than your best performing one. This would hint at inbox placement issues within the domain. A difference of 30% or more should warrant attention.

Engagement Time

You should try and send emails when subscribers are most likely to open them. Understanding when your customers are engaging with your emails can help you improve campaign timing and getting better conversion rates.

Mobile Open Rate

(opens on mobile / all opens) * 100

This metric is helpful when you are optimizing for mobile. You might find out you are spending a lot of time optimizing your templates for a small fraction of Outlook users, but the majority of your subscribers may be iPhone users.

Click-through Rate

(subscribers who clicked on an email / emails delivered) * 100

This metric is essentially reporting on two things at once – how many subscribers opened an email and how many out of those clicked on its content. It’s useful for evaluating the overall success of a campaign and comparing the performance to that of different campaigns. A low CTR could mean the subscriber wasn’t convinced to open the email, or they opened it but weren’t convinced to click through. To help you understand which case you’re dealing with, you need to overlay this metric with the Click-to-Open rate.

Click-to-Open Rate

(subscribers who clicked on an email / emails opened) * 100

Similar to the click-through rate metric, the click-to-open metric is calculated based on emails opened, not delivered. This means that it better reflects the performance of the content of your email. If you see low CTR, but high CTOR, this usually means the subscribers were not convinced to open an email, but once they did, they engaged.

Unsubscribe + Spam Complaint Rate Per Email

(no. of unsubscribes + spam complaints / emails delivered) * 100

This metric is important for understanding how many subscribers have completely lost interest in your emails. To lower your unsubscribe rates, you should limit your sending frequency for less engaged customers. There will always be some unsubscribes, but spikes in the numbers should warrant an investigation on your side.

Spam Score

There are two types of “spam score” metrics: one that evaluates your content spam score, and one that evaluates your “sender score”, which is dependent on your domain or IP. Your content spam score looks at several factors: your image to text ratio, the use of “spammy” keywords, whether you include malicious links, and the technical setup of the email (e.g. missing DNS records like SPF or DKIM), and others depending on the ISP.

If you are unsure why your content is being marked as spam, we recommend using the Spam Checker tool. This free tool provides 5 key data points to help optimize deliverability:

  1. Your SpamAssassin Score,
  2. A Gmail spam filter score
  3. Gmail inbox placement
  4. SPF Record validation
  5. DKIM record validation


Planning, design, and content optimization are all dependent on being able to track the performance of your campaigns. Understanding key performance indicators will provide insights into what elements of your campaign are working, and make adjustments during the testing phase when necessary.

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Unlock your content's potential. Experience the impact of a world-class publishing platform.

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Unlock your content's potential. Experience the impact of a world-class publishing platform.