12 email marketing KPIs you should track & share with clients

A staggering 87% of brands identify email as critical to business success, and a well-executed email campaign's ROI is an impressive $36 for every $1 spent.

The digital era is always brimming with new channels to reach an audience. Despite the things that make us want to succumb to Shiny Object Syndrome, email remains the gateway to activate prospective customers acquired from other channels, and the number one touchpoint for relevance and reach.

The success of every email campaign hinges on understanding and leveraging key performance indicators (KPIs). By accurately tracking and analyzing the right KPI and metrics for email marketing, your agency gains data-backed insight into customer engagement and behavior that helps fine-tune strategies for better results.

This guide covers the metrics and KPIs that matter, so you can optimize email campaigns for maximum impact. Each one gives a different view of campaign performance, from open rates to click-through rates and beyond.

Key takeaways

• A well-executed email campaign returns $36 for every $1 spent, so your reporting needs to show clients exactly where that return came from.

• Deliverability KPIs such as delivery rate, bounce rate and spam complaint rate come first, because no engagement metric means anything until the email reaches the inbox.

• Open rate and click-through rate tell you which subject lines and which content earn attention from your client's list.

• Revenue per email, revenue per subscriber and overall ROI connect email activity to the client's bottom line.

• Keep the spam complaint rate below 0.02% and the unsubscribe rate below 0.5% to protect your client's sender reputation.

What are email marketing KPIs?

A Key Performance Indicator (KPI) measures the effectiveness of an organization in achieving its strategic objectives. KPIs are specific, measurable, and aligned with the goals of the business, which is what makes them useful for tracking progress and identifying areas for improvement.

Email marketing KPIs give data-driven insight into how many emails are reaching the inbox, the level of engagement from the audience, and the ultimate impact on business goals. Email engagement metrics, specifically, are the data points that indicate which emails are "working" and which ones are not, and what will increase the emails' conversion rate.

Tracking these metrics showcases your agency's value by showing tangible improvements in audience engagement and ROI. The domino effect is straightforward: more engaged customers means better results for email clients, which makes your services invaluable.

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 first-party data and making personalization and automation more than just marketing buzzwords.

These shifts dictate how emails are crafted and how their success is measured. As your agency faces them, the right email marketing metrics help distinguish which strategies are relevant, impactful, and successful.

The difference between email marketing metrics and email marketing KPIs

While often used interchangeably, email marketing metrics and KPIs are not the same. Metrics are the broad range of data points collected from a campaign, such as emails sent, emails delivered, open rates, and click-through rates.

KPIs are a subset of those metrics, chosen for their relevance to your strategic goals. If reducing spam complaints is a priority due to stringent policies of internet service providers, then the spam complaint rate becomes an important email marketing KPI.

KPIs are essentially the metrics that matter most, the ones that tie directly into the campaign's objectives and the client's overall business goals.

How KPIs shape strategy and campaign optimization

The insights from email marketing KPIs inform strategic decisions, helping you tailor content, design, and messaging to your audience's preferences and behaviors. Here is how that works in practice.

Email deliverability = list hygiene: A high email bounce rate signals issues with list health, such as invalid addresses or a problem with the client's email service provider. Use this KPI to clean your clients' lists, which improves deliverability and makes every engagement KPI more accurate.

Open rates = optimizing send times, frequency, and subject lines: Open rates across different days and times pinpoint the optimal moments to send. Subject lines are the first impression of every email, so A/B test them against what the recipient needs.

Click-through rates = segmentation and personalization: Click-through rates show which topics or offers resonate most, so you can segment the list by interest or behavior and serve more personalized content.

Side note: There are three distinct types of click-through rate email marketers use to measure email click engagement.

• Clickthrough Rate (CTR): Measures the percentage of recipients who clicked on a link within the email out of the total number of emails sent. This KPI evaluates the overall engagement of the entire email list.

• Click to Open Rate (CTOR): Measures the percentage of recipients who clicked on a link within the email out of the total number of emails opened. This KPI provides insight into the effectiveness of the email content for those who opened it.

• Call to Action Metrics: Evaluate the effectiveness of specific calls to action within the email by measuring the percentage of recipients who performed the desired action (e.g., clicking a button or link) relative to the total number of recipients or those who opened the email. This can be a challenge with some platforms if they don't difference a CTA click vs an anchor text click if they both point to the same link.

Revenue and ROI = reporting success: Tracking revenue per email or revenue per subscriber ties email marketing directly to financial outcomes, and quantifies what each campaign contributed to the client's bottom line.

The 17 email marketing KPIs to measure

Email marketing is not just about sending messages; it's about knowing how those messages perform and what impact they have.

The list below covers which key marketing metrics increase email engagement, what each one reveals, and how they align with three main campaign goals:

• Gauging and keeping interest

• Measuring campaign success

• Optimizing campaign delivery

1. Email delivery rate

Email delivery rate is the percentage of emails that successfully land in recipients' inboxes. Send 100 emails and 95 reach the inbox, and the delivery rate is 95%. It shows whether emails navigate the maze of internet filters and reach the intended audience.

If emails don't reach the inbox, the message goes unseen no matter how compelling it is. A high delivery rate means the content has a chance to be seen and acted upon.

2. Open rate

Open rate is an initial gauge of recipient engagement and interest. A high open rate generally indicates that the subject line is effective, capturing attention and sparking curiosity. For agencies managing client campaigns, it's a crucial indicator of how well the initial message resonates with the target audience.

Monitoring the email open rate helps you fine-tune subject lines and sender names, both of which help messages stand out in crowded inboxes. It also points to the best times and days to send. That's why many consider open rate a foundational metric for understanding a client's email marketing strategy.

How to calculate open rate. Take the number of emails sent and subtract the number of bounced emails. Divide that number by the number of emails opened, then multiply by 100.

How to calculate unique open rate. Same starting point: emails sent minus bounced emails. Divide that number by the number of unique opens, then multiply by 100.

How to improve open rate. Craft a subject line that sparks curiosity and resonates with the target audience's interests. Look into the timing of sends and use data to pinpoint when recipients are most likely to engage with their inbox. Segmenting the list to tailor messages to different audience segments is another worthwhile strategy. More brand awareness, better positioning, and a not-too-frequent influx of emails all help lift the unique open rate.

3. Click-through rate (CTR)

Next, your clients will want to know whether their list is actually reading their marketing emails and taking action. After the open, the next key metric to monitor is click-through rate (CTR).

Email click-through rate is the percentage of recipients who click on one or more links within an email, calculated by dividing clicks by delivered emails and multiplying by 100. Send an email to 200 people and get 20 clicks, and the email CTR is 10%.

Distinguish between email CTR and email click-to-open rate (CTOR). CTR measures clicks against total emails delivered; CTOR measures clicks against only the opened emails, which reveals how engaging the content is to the people who actually read it.

How to calculate click-to-open rate. Take the number of clicks on links within the email, divide it by the number of unique opens, then multiply by 100.

How to improve click-through rate. If the average CTR is on the lower end, test fewer CTAs and text links, improved buttons, and more visual emails with clear, streamlined text. Also check the open rate. If people don't open the email, they certainly aren't going to click on anything.

Below is an example of tracking CTR within AgencyAnalytics from a demo MailChimp account, which includes Mailchimp analytics such as emails sent, open rate, click rate, unsubscribe rate, and bounce rate:

4. Unsubscribe rate

How many times have you personally unsubscribed from an email newsletter? Chances are, plenty. One of the most common reasons is that people are receiving way too many emails. Thankfully, you're able to track the unsubscribe rate and fix it before it becomes a problem.

Unsubscribe rate is the number of lost subscribers within a certain period. An unsubscribe rate below 0.5% is considered acceptable. Going over that number is a signal to scale back and tweak the content.

Rising unsubscribe rates signal a need to reassess content relevance, frequency, and value proposition. Monitoring and minimizing this rate keeps the list healthier and more engaged, and tells you how many emails to send in a given period.

A few ways to keep the unsubscribe rate down:

• Look at how many emails you've sent out within your highest month of unsubscribes. If you're sending too many emails, you'll likely notice an increase in the unsubscribe rate.

• Consider what type of content you were sending within those emails. Were they too promotional? Was the information not relevant to your client's customer base?

• What was the tone of the emails? Did you excite the audience at all? A higher unsubscribe rate may indicate an engagement problem that could be fixed by changing the email's messaging.

How to calculate unsubscribe rate. Divide the number of unsubscribes by the number of emails sent, then multiply by 100.

How to reduce unsubscribe rate. Determine which campaign made recipients unsubscribe, then go back to their acquisition source and email history to understand what broke along the customer journey. Explore send frequency to see whether the marketing team is emailing too often or not covering topics that interest subscribers. A/B testing helps optimize performance over time.

5. 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 you tailor re-engagement strategies or clean email lists, which lifts both campaign performance and deliverability. Tracking it makes sure your clients' messages reach more people who are engaged and interested.

How to calculate inactive rate. Take the number of subscribers not opening emails over a specific period, divide by the total number of list subscribers, then 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

6. Relapse rate

When a subscriber becomes inactive again after having successfully been re-engaged, it's called a relapsed subscriber. The relapse rate is how often this happens. It's an email benchmark worth tracking, because it shows which re-engagement campaigns have flopped and prompts you to investigate why.

The metric also flags potential issues with content relevancy or frequency, so you can rekindle interest among these subscribers before they're gone for good.

How to calculate relapse rate. Identify the subscribers who stopped engaging over a specified period after being active. 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. Re-open lines of communication in alternative ways. Move the recipient into a stream that receives fewer emails, and consider sending surveys to relapsed subscribers so they can tell you how the business should do better.

7. Email bounce rate

In email marketing, bounce rate is the percentage of emails that were not successfully delivered to recipients. It affects how your client is viewed in the eyes of email service providers, which is why it should be tracked closely. Too many bounced emails make the sender look like spam.

How to calculate email bounce rate. Divide the number of bounced emails by the number of emails sent, then multiply by 100.

How to improve bounce rate. A healthy bounce rate is 2%. Anything more, and you should look into the email acquisition process. Having subscribers confirm their subscription helps validate addresses, and list hygiene removes hard bounces and consistent soft bounces. Beyond that benchmark, monitor the rate over time to establish what normal looks like for each client and track progress against it.

There are two types of email bounce to consider.

Soft bounces

Soft bounces occur when there's a temporary issue with the recipient's mailbox. Maybe they have too many emails, or their server is down. Typically this won't affect anything on the sender's end, because you can simply resend the email.

Hard bounces

Hard bounces negatively affect a sender's email reputation and deliverability, so they're important to fix. They occur when an email is sent to an invalid or non-existent address: someone entered it incorrectly, or the subscriber abandoned that account.

Fix these errors by immediately removing implicated addresses from your client's list. That way you won't sacrifice the bounce rate by keeping outdated contacts. To go deeper, check out these 12 tips from OptinMonster.

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8. Forward and sharing rate

Many clients want to know exactly how many times their content is being shared, which brings us to the forward rate. When the target audience shares or forwards an email, that's a strong indicator the content is resonating, with the added bonus of gaining new leads.

It's also a good measure of subscriber loyalty. When subscribers become a client's brand advocate, they're helping spread the word about the business, which falls into the later stages of the buyer's journey in email marketing. A high sharing rate extends the reach of the campaign beyond the original mailing list, and tracking it identifies the content worth amplifying.

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, divide it by the number of total emails delivered, then multiply by 100.

How to improve forwarding or sharing rate. Look at what gets shared the most and include similar material in future emails. Send something subscribers would want to share, like a coupon, a fun quiz, a useful tip, or an incentive. This is the perfect opportunity to make the email interactive.

9. Conversion rate

Conversion rate is undoubtedly one of the most important KPIs to monitor, since the whole point of a marketing email is to get the reader to take action.

To track conversions from email, create URLs specific to your email campaign links and monitor who completed the task because of that email. This is known as UTM tracking, which you can learn more about in our guide on the subject here.

From there, go back to your Google Analytics report template in AgencyAnalytics and click Channel > Email, which gives you conversion rate, goal completions, goal value, and more.

How to calculate conversion rate. Take the percentage of recipients who completed the desired action after receiving an email 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 the actions to consider include:

• Check that 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. Email list growth rate

This metric directly reflects the health and potential of a client's email marketing lists.

An increasing list suggests more people are interested in what the client has to offer. A stagnant or declining list often signals issues in the campaign strategy or a disconnect with the target audience. Monitoring it serves several purposes:

• Campaign effectiveness: Growth indicates successful acquisition, such as effective lead magnets, compelling content, or strong calls-to-action.

• Brand awareness and reach: A growing list suggests the client's brand is gaining traction and reaching a broader audience.

• Long-term viability: New subscribers compensate for the natural churn rate, the rate at which people unsubscribe or abandon their email accounts.

• Personalization and segmentation: A growing list gives you more data to segment audiences and personalize content.

How to calculate list growth rate. Take the number of new subscribers, subtract those who unsubscribed, divide by the total number of addresses in the client's list, then multiply by 100.

How to improve list growth rate. In a client report, display this number in a visual line chart to show a positive upward tick. Most email clients look for this number, because it means the agency is drawing new leads into their business.

If the email does not generate leads or the subscriber count is not growing, look at the mechanisms in place to grow the client's newsletter and other email capture points. Check what could be causing enough unsubscribes to completely offset new subscribers.

11. Spam complaint rate

The spam complaint rate measures how often people flag a client's email as spam. When it's high, it risks damaging the client's reputation with email providers, which means emails are more likely to end up in the spam folder, far away from the reader's view.

A high spam complaint rate may not be a reflection of list quality. It often suggests the content isn't resonating and is being seen as intrusive or irrelevant. It may also indicate non-compliance with email marketing laws like the CAN-SPAM Act in the U.S., which can lead to legal issues for the client.

How to calculate complaint rate. Divide the number of spam complaints (emails marked as spam) by the number of emails sent, then multiply by 100.

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

Sender reputation deserves the same attention. It's a rating given by email service providers (ESPs) to identify trustworthy senders, and it's how email services automatically weed out spam.

12. Engagement over time

This metric measures the overall activity of a client's emails throughout the day, which helps you narrow down the ideal send time.

It also surfaces trends such as growing interest or waning engagement, so you can adjust proactively. Engagement patterns over time tell you about content relevance and where an email could be more personalized.

How to calculate engagement over time. Analyze 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 you don't have previous data to benchmark from, start with industry benchmarks and see which times deliver the best results.

13. Revenue per email

Revenue per email quantifies the financial return from each email sent. Divide the total revenue generated from a campaign by the total number of emails sent. If a campaign generates $5000 from 10,000 emails, the revenue per email is $0.50.

This KPI ties the campaign directly to business results, so you can judge whether it was financially worthwhile against the time and effort to create and distribute it. It also makes comparing campaigns easier, showing which types of email (promotional, informational, newsletters) drive the most revenue.

Finally, it serves as a benchmark for continuous improvement. Use revenue per email to set targets, then work on them through A/B testing, personalization, and improved targeting or segmentation.

How to improve revenue per email. If the RPE isn't wowing clients, look back at everything from the CTAs to the customer segmentation and user journey.

14. Revenue per subscriber

Revenue per subscriber calculates the average revenue generated from each subscriber on an email list. Divide the total revenue from email campaigns by the total number of subscribers.

It shines a light on the total financial value each subscriber brings to the client's business, and shows how effective email campaigns are at turning subscribers into revenue. If the number is high, the email strategy is on track. If it's low, revisit the contact acquisition strategies, email content, offers, or the broader email marketing plan.

15. Subscriber acquisition cost (SAC)

Subscriber acquisition cost (SAC) gives a clear view of the financial investment required to gain each subscriber, and helps you assess your strategies against campaign goals and budget constraints.

Tracking SAC directs effort into refining targeting, streamlining content creation, and adjusting larger marketing tactics. Clients see a better return on investment while the subscriber base grows, and the metric reinforces your value proposition 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.

How to improve subscriber acquisition cost. Analyze performance data and identify high-performing segments, then adjust messaging to resonate more deeply with potential subscribers. A/B testing elements of the strategy, whether subject lines or call-to-action buttons, helps drive down SAC.

16. Subscriber lifetime value (SLV)

Subscriber lifetime value (SLV) quantifies the long-term value each subscriber brings, which guides smarter investment and strategy decisions.

Tracking SLV identifies which segments of the client's audience yield the highest returns, so nurturing can be targeted where profitability is highest. It also sharpens acquisition, making sure resources go toward attracting subscribers who contribute significantly over time.

How to calculate subscriber lifetime value. It's difficult to tie revenue to each subscriber in specific industries. Before calculating SLV, calculate the RPS (revenue per subscriber) and multiply that number by the number of months a contact spends on the list.

How to improve subscriber lifetime value. Personalize content to match subscriber interests and behaviors. Use the data available to segment audiences and tailor campaigns that resonate on a personal level, which increases both retention rates and average spend.

17. Overall ROI

Finally, just like any other marketing channel, show your clients the total revenue and overall ROI of their email marketing campaigns.

Mailchimp has integrated revenue tracking. To track total revenue for some other email reporting integrations from AgencyAnalytics, set up Goal Values in Google Analytics and divide this by your email-related costs to get the ROI.

What each metric is really telling you

A quick reference for the metrics that most often drive campaign delivery and campaign success decisions:

Build a three-step email success measurement plan

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

1. Find the perfect timing. Before jumping into specific KPIs, set a schedule for when to take a closer look at the campaigns. Whether it's a weekly check-in, a monthly deep-dive, or a review after a single campaign, regular analysis compares the latest efforts with past performances and highlights where there's room to grow.

2. Set clear targets. Aligning with a client's goals from the get-go is non-negotiable, and demands careful thought to make sure the targets are clear and measurable. Consider what success looks like for the campaign and how to quantify it. Create goals with clients that go beyond increasing engagement and sales, and discuss how their email marketing plays a part in their larger marketing efforts.

3. Evaluate successes and identify improvements. Assessing the performance of specific email content shows what resonates with subscribers. Diving into which links or images garner the most interaction gives a deeper understanding of an audience's preferences, and highlights the elements that fail to spark interest. That comprehension of audience behavior helps tailor future campaigns.

Translating KPIs into email marketing campaign strategies

Email KPIs let you craft strategies based on solid, actionable data rather than gut feelings. Discovering that how-to guides or industry insights receive more clicks might inspire a shift towards educational content, transforming email newsletters into a go-to resource. A decline in open rates could indicate a need to revise subject lines or modify the sending schedule.

Aligning strategies with client objectives

The success of a campaign hinges on its alignment with the client's specific goals. Whether the aim is sales, engagement, or brand awareness, focusing on the relevant KPIs is critical. If the goal is sales growth, click-through and conversion rates take priority, so every element of the campaign supports the client's business objectives.

Proactive identification of negative trends

Early detection lets you address issues before they impact results. Regular monitoring of metrics like unsubscribe rates reveals underlying problems, such as content relevance or audience fatigue, and prevents minor setbacks from turning into significant obstacles.

Enhance the depth of email marketing analytics by integrating data from more than 85 platforms. Gain insights on the big picture–try AgencyAnalytics free for 14 days.

How to create an email marketing report for clients

Compelling email marketing reports demonstrate the value of your work. They should be informative and engaging, helping clients understand the campaigns' impact on overall business performance.

Here are five tips for creating reports that inform and impress clients.

Tip #1: Focus on the KPIs that matter to clients

Tailor reports to highlight the KPIs most relevant to the client's specific goals. Whether it's open rates, click-through rates, conversion rates, or ROI, aligning these metrics with what the client values most makes the report more impactful.

Tip #2: Integrate email KPIs with other campaign metrics

Clients often run multiple digital marketing campaigns simultaneously. Integrating email marketing KPIs with data from other platforms, such as Google Analytics 4, Google Ads, Facebook, and SEO rankings, provides a more comprehensive view of their overall digital marketing performance.

This holistic approach lets clients see how their email marketing complements their other marketing strategies.

Tip #3: Utilize automated reporting tools

AgencyAnalytics streamlines the client reporting process. The platform automates data collection and report generation, saving time and reducing the likelihood of errors. Automated email marketing analytics tools also provide live data, giving clients access to the latest results where and when they need it.

Tip #4: Brand your reports

Using white label client reporting tools, brand your reports with your agency's logo and color scheme. Branded reports that highlight success strengthen your agency's identity in the client's mind, making your services more memorable.

Tip #5: Visualize data effectively

Incorporate charts, graphs, and infographics to make complex data more digestible. Visual aids help clients quickly grasp key insights and trends, which significantly enhances the impact of your email marketing reports.

Essential email reporting tools

Once you know which metrics to track based on a client's goals, present them in a way clients understand quickly. Tools that automate the reporting process make that far easier.

Whether an agency uses Mailchimp, Constant Contact, Hubspot, or any other email marketing platform, tracking email KPIs for each client is a daunting task unless the whole data-retrieval process is automated. An email marketing report template does exactly that.

Where to go from here

Email marketing is one of the most profitable channels available, and one of the most challenging to master. To determine the exact return and improve results over time, invest the time in tracking the 17 KPIs above.

Email engagement keeps evolving as consumers are influenced by shifting industry trends and higher expectations. Campaigns are a continual work in progress, so display important metrics and benchmarks in client reports to keep track of growth and stay ahead of targets.

Prove a client's ROI by combining their email marketing metrics alongside other marketing channel data to show the true value your agency brings to the table. To automate the tracking and reporting, check out the prebuilt email marketing report template or a comprehensive KPI report template here.

Join more than 7,000 marketing agency customers and start automating your email marketing reports today. Try AgencyAnalytics free for 14 days.