16 Vital Email Engagement Metrics To Track

While some clients may think of emails as archaic remnants of the 2000s, email marketing is becoming increasingly critical to marketers. In fact, a well-executed email campaign’s ROI is an impressive $36 for every $1 spent.

Today, email is often the gateway to activate prospective customers acquired from other channels. It’s also the number one touchpoint for relevance and reach. But without tracking the right email engagement metrics, email campaigns risk falling short of their promise.

What Are Email Engagement Metrics?

Email engagement metrics are data pints that indicate which emails are “working” and which ones are not. They give insights into how the audience interacts with the emails and what will increase the emails' conversion rate.

Tracking email marketing metrics showcases agency value to clients by showing tangible improvements in audience engagement and ROI. Marketing professionals work hard to improve these metrics to get the desired domino effect: more engaged customers = better results for email clients =  invaluable services from the agency. It's about understanding what content resonates with the audience and leveraging that knowledge for email marketing success.

Why Email Engagement Metrics Are Important

Consider the fast-changing purchase behaviors and industry trends that affect email campaign success. Privacy laws have also tightened, demanding a more considered approach to the use of first-party data, making personalization and automation more than just buzzwords.

All of these industry shifts underscore the need for agility and empathy in an email marketing process. These elements dictate how emails are crafted and also how their success is measured. 

As agencies face these challenges, using the right email marketing metrics helps distinguish what strategies are relevant, impactful, and successful.  

16 Email Marketing Metrics to Track to Measure Email Engagement

This list will help uncover which key marketing metrics to increase email engagement and track clients' email marketing goals within their larger digital marketing strategy. We will also discuss what the email marketing metrics reveal and how they align with three main campaign goals:

• Gauging and Keeping Interest

• Measuring Campaign Success

• Optimizing Campaign Delivery 

From understanding an audience's interaction to pinpointing areas for improvement, these are the most important metrics to craft more engaging and effective email campaigns.

1. Open Rate

Open rate is the number of times subscribers opened the email once it's been delivered by the internet service providers. This is calculated every time a subscriber opens an email, including repeat opens by the same subscriber.  

Open rate is one of the first indicators of a campaign's initial impact. It measures the percentage of marketing emails opened, offering insights into the effectiveness of email subject lines and email send times. A healthy open rate suggests the email is hitting the mark, enticing the audience with a great subject line that piques their interest to learn more about what the client has to offer.

How To Calculate Open Rate

The first step to calculate open rate is to take the number of emails sent and subtract it from the number of bounced emails. Then, simply divide that number by the number of emails opened. Multiply by 100 to get the percentage of open rate. 

How To Improve Open Rate

To get higher open rates for a client’s email campaign, focus on crafting an intriguing subject line that sparks curiosity and resonates with the target audience's interests. Another option is looking into the timing of email sends and using data to pinpoint when recipients are most likely to engage with their inbox. Segmenting the email list to tailor messages more closely to different audience segments is another worthwhile strategy to improve how many people open an email. 

2. Unique Open Rate

Unique open rate is the total number of times an email is initially opened. This doesn’t include cases where the same subscriber opens the same message repeatedly.  

This metric provides a clear insight into how many unique viewers are genuinely interested in the content, helping agencies refine the targeting and content strategies. By tracking unique open rates, agencies better understand the reach and true impact of email campaigns, aiming to deliver value to both their clients and the clients' audiences.

How To Calculate Unique Open Rate

To calculate unique open rate, begin with the number of emails sent and subtract it from the number of bounced emails. Then, simply divide that number by the number of unique opens. Multiply by 100 to get the percentage of unique open rate. 

How To Improve Unique Open Rate 

When a subscriber opens an email, it means that the Subject line and Preview text enticed them to do so. More brand recognition, better positioning, and a not-too frequent influx of emails help increase email open rate. 

3. Email Bounce Rate

Bounce rate refers to the emails that weren’t successful. There are two types of email bounces:

• Soft bounces are caused by an error on the subscriber’s end, like having a full inbox.

• Hard bounces are due to invalid email addresses and are likely lost contacts.

Tracking high bounce rates helps marketing agencies identify and clean up email lists, ensuring messages reach only valid, active email addresses. Lowering bounce rate makes email campaigns more successful, helping agencies understand how many emails are actually getting through and giving a clearer picture of who's really tuning in.

How To Calculate Email Bounce Rate

To calculate bounce rate, start by dividing the number of bounced emails by the number of emails sent. Then multiply that number by 100 to get the percentage of bounce rate. 

How To Improve Bounce Rate

A healthy bounce rate is 2%. Anything more, and agencies should look into the email acquisition process. For example, having subscribers confirm their subscription will help validate email addresses. List hygiene is also important to remove hard bounces and consistent soft bounces.

4. Unsubscribe Rate

Unsubscribe rate is the number of lost subscribers within a certain period. 

Rising unsubscribe rates signals a need to reassess content relevance, frequency, and value proposition to better align with subscriber preferences. By monitoring and minimizing this rate, agencies maintain a healthier, more engaged email list, understand how many emails to send in a period of time, and contribute to the long-term success of their clients' email campaigns.

How To Calculate Unsubscribe Rate

Start by dividing the number of unsubscribes by the number of emails sent. Then multiply that number by 100 to get the percentage. 

How To Reduce Unsubscribe Rate

Determine which campaign made the email recipients unsubscribe, and even go back to see their acquisition source and email history to better understand what broke along the customer journey. Explore the frequency of emails to consider whether a marketing team is sending emails too often or not sending topics that interest the subscribers. 

5. Complaint Rates or Spam Rates

Complaint rates, also known as spam rates or spam complaints, are particularly important to watch out for because they negatively affect future email deliverability. It's essential to send an email message only to a recipient’s inbox who has given clear permission to contact them, whether directly or indirectly.    

High spam complaints often lead to emails being blocked or filtered into the spam folder, drastically reducing the effectiveness of an email campaign. Email marketers do not want to run the risk of damaging their client's sender reputation by having their emails end up in the spam folder! It's important to track and address the causes of high spam rates to get better results, including overall engagement and deliverability. 

How To Calculate Complaint Rate

This formula is rather straightforward. Simply divide the number of spam complaints (emails marked as spam) by the number of emails sent and multiply by 100 to get the complaint rate. 

How To Reduce Complaint Rates or Spam Rates

Keep the spam complaint rate metric below 0.02% to avoid any warnings. Above 0.04% for a single email and the client’s account could be suspended. Permission is one of the biggest impacts on the complaint or spam rates, so if a client is hovering near the edge, consider implementing a double opt-in process.

Similar to the spam complaint rate, marketing agencies also need to focus on the email sender reputation. This is a rating or score given by email service providers (ESPs) to identify trustworthy senders. It's used to ensure that their users enjoy a spam-free experience. This rating helps email services automatically weed out spam by checking how reliable an email sender is.

6. Click-Through Rate (CTR)

This email marketing metric refers to the percentage of recipients who clicked on at least one of the links in an email.   

A high click-through rate (CTR) is a useful metric that proves the email's message resonates well with the audience, driving engagement and moving them closer to converting. Tracking the average click-through rate helps email marketers refine their content strategy, ensuring that emails aim to capture attention while encouraging meaningful interaction at the same time.

How To Calculate Click-Through Rate

This is calculated by dividing how many people who clicked something by the number of successfully delivered emails, multiplied by 100. A solid CTR measures between 2-5%. 

How To Improve Click-Through Rate

If the average CTR is on the lower end, there are a number of things an agency should test out, like including fewer CTAs and text links, improving buttons, and ensuring emails are more visual with clear, streamlined text. Also, check the open rate (above). If a number of people don't open the email, they certainly aren't going to click on anything.

7. Click-to-Open Rate (CTOR)

This measures the percentage of subscribers who click something in an email in relation to those who opened it. A healthy CTOR is between 20% and 30%, depending on industry averages.

Click-to-open rate (CTOR) really digs into the nitty-gritty of what happens after someone opens an email. Instead of just throwing out a bunch of emails and hoping for the best, tracking CTOR gives marketing agencies insights on whether the emails are truly hitting the mark or if they're just nice to look at. By optimizing CTOR, agencies are able to make adjustments and test every part of the emails, from headlines to call-to-actions, making sure they're actually sparking action.

How To Calculate Click-to-Open Rate

The formula for calculating CTOR includes taking the number of clicks on links within the email and dividing it by the number of unique opens. Then multiply by 100 to get the percentage. 

How To Improve Click-to-Open Rate 

This is the best metric to measure how effective an email’s overall messaging is. A high CTOR means the email is connecting with an active audience, so if this number is low, take a look at the audience segmentation and tailor the message accordingly. 

To summarize, these are typically the key metrics for gauging and maintaining interest in an email campaign:  

8. Revenue per Email (RPE) or Email ROI

This metric shows agencies how much revenue a particular email list generates. Revenue per email directly ties the email marketing efforts to financial outcomes, highlighting the dollar value generated from each email sent.  

By understanding RPE, agencies are able to quantify how effective their email campaigns are in driving sales and conversions. Tracking this metric provides a clear measure of return on investment. This insight also helps marketing teams make strategic adjustments to maximize revenue generation, ensuring that every email sent contributes to the client's bottom line.

We always measure ROI per marketing channel and Email is one of the most linear to measure. You always want to make sure the aggregate of your marketing efforts are leading to net positive ROI.

Bryan Lozano, Vice President of Operations, Ad-Apt

How To Calculate Revenue per Email

Calculate the total revenue from a campaign and divide it by the number of emails sent.  

How To Improve Revenue per Email

If the RPE isn’t wowing clients, agencies need to look back at everything from the CTAs to improving the customer segmentation and user journey.  

9. Conversion Rate or Purchase Rate 

This is one of the most important metrics compared to other metrics for many email clients, as it shows how many people actually followed through after clicking on a call to action button. This email marketing metric refers to a conversion, which could be a purchase, signup, downloading a document, you name it. What matters is that it fulfills the goal that was set for the client and moves the customers along the purchase journey. 

Email Conversion rate (referred to as purchase rate in a sales context) shines a light on how successful an email campaign motivates a person to move from interest to action. By tracking conversion rates, agencies pinpoint which strategies resonate best with the audience and make data-driven decisions that boost the campaign's performance.

How To Calculate Conversion Rate

Calculate email conversion rate by the percentage of recipients who, after receiving an email, completed the desired action and divide it by the number of total emails delivered. 

How To Improve Conversion Rate or Purchase Rate

It all really comes down to this metric, so some of the actions that agencies should consider taking include: 

• If the email is mobile-friendly

• Optimize all copy for the correct email segment

• Use behavioral triggers to send the right emails to the right people at the right time

10. List Growth Rate

Just as it sounds, this is the rate at which a client’s email list is growing with new email addresses. This helps email marketers gauge how the engagement rate (and the number of unsubscribes) is impacting the total list growth.  

A positive growth rate means there is new interest and opportunities for engagement, showcasing the brand's growing appeal. Tracking this metric helps agencies measure the effectiveness of list-building strategies and adjust their tactics to ensure the list keeps growing with a number of new subscribers. 

How To Calculate List Growth Rate

Calculate this by taking the number of new subscribers, subtracting the number of those that unsubscribed, and dividing that number by the total number of email addresses in a client’s email list. Multiply that by 100, and that’s the list growth rate. 

How To Improve List Growth Rate

In a client report, agencies should display this number in a visual line chart to show a positive upward tick. Most email clients will be looking for this number as it means the agency is drawing in new leads to their business. 

If the email does not generate leads or the total subscriber count is not growing, then agencies need to look at the mechanisms they have in place to grow a client's email newsletter and other email capture points. Be sure to look at what could be causing enough unsubscribes to completely offset new subscribers.

11. Forwarding or Sharing Rate

This is a great metric to track the loyalty of subscribers. When subscribers become a client’s brand advocate, they’re helping spread the word about a client’s business. This falls into the later stages of the buyer’s journey in email marketing. 

A high email sharing rate clearly shows that the content is resonating, helping to extend the reach of the campaign beyond the original mailing list. Tracking this metric helps shed light to identify highly engaging content, creating strategies that amplify word-of-mouth promotion and organically grow the audience.

Great emails are a conversation. The only way to assess how what you are saying is perceived is by studying the reactions to your email. Whether someone clicks, shares, and/or replies are the "facial expressions" and "words" that a person shares back that can tell you how well your conversation is going.

Seth Giammanco, Principal, Strategy and Technology, Minds On Design Lab

How To Calculate Sharing Rate

Take the number of times the email was shared and divide it by the number of total emails delivered. Multiply by 100 and that’s the forward or sharing rate. 

How To Improve Forwarding or Sharing Rate

Look at what gets shared the most and include similar materials in the emails to broaden the reach beyond the subscriber. Send emails that provide something the subscribers would like to share, like a coupon, a fun quiz, a useful tip, or an incentive. This is the perfect opportunity to make the email interactive. 

12. Subscriber Acquisition Cost (SAC)

Subscriber acquisition cost (SAC) offers a clear view of the financial investment required to gain each subscriber. It helps agencies assess the effectiveness of their strategies against overall campaign goals and budget constraints. 

By tracking SAC, agencies are able to put their efforts into refining targeting, streamlining content creation, and adjusting larger marketing tactics. This lets clients see a better return on investment while growing an engaged subscriber base. Focussing on SAC demonstrates an agency’s expertise and commitment to achieving measurable success. It’s a metric that reinforces their value proposition to clients in a competitive market.

How To Calculate Subscriber Acquisition Cost

Divide the total marketing spend (the sum of all expenses incurred to run the email campaign, including creative assets, software costs, and any other related expenses) by the number of new subscribers acquired. The formula should look something like this:

How To Improve Subscriber Acquisition Cost

Analyze performance data and identify high-performing segments. Adjust any messaging to resonate more deeply with potential subscribers. Implementing A/B testing on various elements is a great strategy that helps an email marketing campaign. Testing various elements from the email marketing strategy, whether it’s email subject lines or call-to-action buttons, helps to drive down SAC. 

13. Subscriber Lifetime Value (SLV)

Subscriber Lifetime Value (SLV) quantifies the long-term value each subscriber brings, guiding smarter investment and strategy decisions. 

Tracking SLV helps agencies identify which segments of their client's audience yield the highest returns. This allows them to make targeted nurturing strategies that maximize profitability. Understanding SLV also helps optimize acquisition efforts, ensuring resources are allocated to attract subscribers who contribute significantly to the bottom line over time.

How To Calculate Subscriber Lifetime Value

It’s difficult to tie revenue to each subscriber in specific industries. Before calculating SLV, agencies need to calculate the RPS (revenue per subscriber) and then multiply the number by the number of months a contact spends on the list. 

How To Improve Subscriber Lifetime Value

To boost Subscriber Lifetime Value (SLV) aim to personalize content to match subscriber interests and behaviors. Agencies should use the data available to segment different audiences and then tailor email campaigns that resonate on a personal level. This increases both retention rates and average spend. 

To summarize, these are typically the most common email metrics to measure overall campaign success: 

14. Engagement Over Time/Action Rate Over Time

This email marketing metric measures the overall activity of a client’s emails throughout the day to help agencies narrow down the ideal send time.    

This metric helps identify trends, such as growing interest or waning engagement. It helps agencies adjust their email marketing strategies proactively. Understanding engagement patterns over time provides insights into content relevance and how an email could be more personalized. Engagement over time aims to build sustainable interest and activity from an audience.

How To Calculate Engagement Over Time

Calculating engagement over time involves analyzing changes in email metrics (such as open rates, click-through rates, and conversion rates) across different periods. 

While there's no single formula, a good general approach is:

• Choose the metric of interest (e.g., open rate).

• Calculate this metric for each period (e.g., weekly, monthly).

• Plot these values over time to visualize the trend.

How To Improve Engagement Over Time

If an agency doesn’t have previous data to benchmark from, they should start out with industry benchmarks and see which times deliver the best results.

15. Inactive Rate

This rate indicates the number of subscribers who haven’t opened or clicked on a certain number of emails, or during a certain interval. 

Identifying inactive subscribers helps agencies tailor re-engagement strategies or clean email lists. This is an important metric to pay attention to for improving overall campaign performance and deliverability. By tracking the inactive rate, agencies ensure their clients' messages are reaching more people who are engaged and interested. 

How To Calculate Inactive Rate

To calculate the inactive rate, start by taking the number of subscribers who are not opening emails over a specific period of time. Then, divide the number by the total number of email list subscribers and multiply by 100. 

How To Improve Inactive Rate

Set up a re-engagement campaign. A ‘We’ve Missed You!’ email goes a long way in giving them an offer they can’t refuse or some useful tips and information. With most email automation platforms, this kind of campaign is set up to automatically send when the subscriber reaches a specific inactivity threshold. 

Leverage automation wherever possible to ensure you always have a way to engage with your audience and nurture them back to your site.

Bryan Lozano, Vice President of Operations, Ad-Apt

16. Relapse Rate

When an email subscriber becomes inactive again after having successfully been re-engaged, it’s called a relapsed subscriber. The relapse rate is how often this happens. This is an email benchmark to track, helping agencies understand which re-engagement campaigns have flopped and investigate why. 

This metric helps pinpoint how effective a retention strategy is and identifies potential issues with content relevancy or frequency. By monitoring the relapse rate, agencies proactively take steps to rekindle interest among these subscribers, tailoring content to re-engage them and maintain a healthy, active email list.

How To Calculate Relapse Rate

To calculate the relapse rate, the subscribers who have stopped engaging over a specified period after being active need to be identified. 

There is no specific formula, but here is the best way to gain valuable insights:

• Determine the period for measuring engagement (e.g., 6 months).

• Count the number of subscribers who were active (e.g., opened or clicked an email) at the start but became inactive (did not open or click any email) by the end of the period.

• Divide the number of these relapsed subscribers by the total number of active subscribers at the start of the period.

How To Reduce Relapse Rate

It’s a good idea to re-open lines of communication in alternative ways. For one, the recipient should be in a stream that receives fewer emails. Also, consider sending out surveys to relapsed subscribers so they can communicate how the business should do better. 

To summarize, these are typically the key metrics for optimizing email campaign delivery: 

How To Measure Email Marketing Strategy Success

Measuring an email campaign’s success boils down to having the right tools to streamline workflows, automate the data-retrieval process for quick, actionable insights, and report results to clients. 

Craft a 3-Step Email Success Measurement Plan

The best way for marketing agencies to measure, understand, and optimize their email marketing efforts is to create a plan of action. 

1. Find the Perfect Timing

Keeping an eye on how emails are doing is a key part of refining an agency’s approach to connect better with the audience. Before jumping into specific key performance indicators (KPIs), consider setting a schedule for when to take a closer look at the email campaigns. 

Whether it’s a weekly check-in, a monthly deep-dive, or a review after a single campaign, this regular analysis helps to compare the latest efforts with past performances. It highlights where a campaign has been successful and where there’s room to grow, all tailored to different aspects of the campaigns.

2. Set Clear Targets

For any email campaign to hit the mark, aligning with a client’s goals and objectives from the get-go is non-negotiable. This foundational step in any digital marketing strategy demands careful thought to make sure the targets are clear and measurable. 

Consider the specifics of what success looks like for the campaign and how to quantify that success. Communicate with clients to create goals that go beyond increasing engagement and sales. Discuss how their email marketing plays a part in their larger marketing efforts.  

3. Evaluate Successes and Identify Improvements 

Assessing the performance of the specific content of an email provides insights into what resonates with subscribers. By diving into the data, like which links or images garner the most interaction, agencies get a deeper understanding of an audience's preferences and interests. 

This analysis highlights what grabs the attention of an audience and also the elements that fail to spark interest or drive engagement. This nuanced comprehension of audience behavior helps tailor future campaigns more effectively.

Essential Email Reporting Tools

After understanding which email metrics to track based on a client’s goals, they should be presented in a way clients will easily and quickly understand. All of this is made easier with tools to help automate a lot of the email marketing reporting process. 

Whether an agency uses Mailchimp, Constant Contact, Hubspot, or any other email marketing platform, tracking email KPIs for each client is a daunting task–but not if they automate the whole data-retrieval process. 

Marketing agencies need an efficient way to report on results for each email campaign where the data tells them information that will maximize ROI and overall campaign success. An email marketing report template will do just that!

Start with the Email marketing report template to show the value your agency is driving toward their business. Try it free for 14 days!  

Key Takeaways  

Email engagement is constantly evolving as consumers are influenced by shifting industry trends and developing higher expectations. Agencies are constantly fine-tuning, as they remain vigilant to ensure to email campaigns remain effective and results-driven. 

Email marketing campaigns are a continual work in progress. Display important metrics and benchmarks in client reports to keep track of growth and stay ahead of targets. 

Prove a client’s ROI and overall success by combining their email marketing metrics alongside other marketing channel data to show the true value your agency brings to the table. 

Read More: Learn about email marketing strategies for ecommerce clients.