Marketing Analytics

Six Email Marketing KPIs You Should Be Tracking

email campaign metrics email engagement metrics email marketing metrics email metrics email performance metrics

If you want to know for sure how well your email marketing campaign is doing, you should pay attention to the metrics which correlate with your campaign goals. In this article, we’ll cover six metrics which will help you to measure the effectiveness of your marketing efforts.

What metrics to focus on

To evaluate your business processes and make them run successfully in future, you should pay attention to Key Performance Indicators (KPIs) and take necessary actions to improve them. How?

To begin with, be aware of the goal of your email marketing campaign. It can be raising brand awareness, generating sales, leveraging engagement and trust level, and so on.

The next step is to choose KPIs which you need to track to make sure that you are getting closer to your final target. Here are some basic metrics which are important for any email marketing campaign:

  1. Bounce rate
  2. Open rate
  3. Click-through rate
  4. Unsubscribe rate
  5. Spam complaint rate
  6. Conversion rate

These KPIs can be classified into on-mail and off-mail. First five metrics on the list are on-mail as they are related to users’ actions directly in the email message. Off-mail metrics refer to everything that happens further on your website or at any other destination, and, in our case, it’s a conversion rate.

Now let’s dive deep into each indicator to see why it matters and how to improve it.

Bounce rate

Formula for calculating bounce rate:

(Emails returned / Emails sent) * 100

Bounce rate is a number that characterizes how many emails which you’ve sent were not delivered to a subscriber’s inbox. This can happen for a variety of reasons and usually depends on what caused the bounce.

  1. Permanent (hard) bounces occur in case of a wrong or non-existent email address. You can recognise them by code starting with 5: “<> 550 Message rejected.” When you see such email addresses in your mailing list, delete them at once because these are the recipients that will never receive your emails.
  2. Transient (soft) bounces are temporary and are usually caused by some malfunctions such as lack of free space in the inbox, too heavy email message or DNS failure, when the receiving email service is down. Soft bounces code starts with 4: “<> 421 Try again later.” As a rule, such emails are re-sent automatically until received. If you see that a particular email address gets soft bounces for a long time, then it’s better to remove it from your mailing list.

Keep at hand the set of delivery error status codes along with their meaning, and take a look at the tips that can help you maintain your bounce rate as low as possible.

Keep your mailing list clean

Regularly check your mailing list for invalid email addresses to contribute to your good sender reputation. Pipedrive once deleted 83,000 inactive emails to clean their mailing list, so you will probably have to erase a big number of subscribers too if you are doing it for the first time.

Implement double opt-in

Send a confirmation email to each new subscriber to make sure the email was typed correctly and there is no wrong data in your mailing list. Unknown or non-existing emails will cause hard bounces, so you need to eliminate every chance of that happening.

See how Vanity Planet does it: the company sends out confirmation emails with an univocal message on a call-to-action button.

Open rate

Formula for calculating open rate:

(Emails opened / Emails delivered) * 100

Open rate demonstrates how many of your subscribers opened your email. This metric can show you the number of subscribers who are actually interested in you and your content. Note that there is no possibility to track opens for plain-text emails as they don’t include a tracking pixel.

If you want to improve your open rates, follow these recommendations.

Perfect your timing

Learn which time and day of the week are the best to send out emails to your subscribers. The best way is to combine data you’ve learnt from different studies, test it out on your target audience, and then choose the most convenient schedule for them.

Optimise your subject line

Subject line is the first thing your subscribers see when they open their inboxes. So your job is to make it stand out.

Use emojis in your subject lines. But remember to test out how they will look on different devices and email clients. Follow the examples below — both captured in the Gmail client — to see the difference.

Here is the mobile view:

Here is the desktop one:

Create urgency by mentioning the limited availability of certain items or offering a sale with an expiration date. See how brands use fear-of-missing-out strategy to encourage recipients to open their emails.

Personalize. According to Campaign Monitor, personalized subject lines increase open rates by 26%. Follow the example of an email from Care/of to see how the company combines the user’s name and clever copy in the subject line.

Add preview text

Preview, or preheader, is a snippet of text extracted from the email body that comes next to or under the subject line. When preview text is not set, email clients automatically pull alt text from the top image, a piece of code or instructions as “Click here to see the web version.”

On the example below, Tablet sound friendly thanks to personalized copy in the preview.

Preview line is a good place to share some additional information visible right away, even before opening an email. For instance, Mark’s added details about free shipping to complement the subject line and motivate subscribers to learn more about the discount.

Resend unopened emails

According to, resending the email to those subscribers who haven’t opened the original one can boost your open rates by almost 55%. The trick here is to change the subject line or try another sending time.


Formula for calculating click-through-rate (CTR):

(Emails clicked / Emails delivered) * 100

CTR shows how many people clicked on links in your email.

In addition to CTR, you can measure click-to-open rate. It compares the number of recipients who got interested and opened your email to the number that went further and actually clicked on the links.

Formula for calculating click-to-open rate (CTOR):

(Emails clicked / Emails opened) * 100

Both CTR and CTOR show the level of engagement of your audience and, eventually, demonstrate how effective your email campaign is. To improve both metrics, resort to the following:

Use clear call-to-action

For a start, a good CTA has to transmit a clear message so that your subscribers can understand what to do and what benefits they will get after acting. Use strong command verbs and remember to optimise your CTAs for mobile devices. To find useful ideas, read our article about nine ways to optimise CTA.

Urban Decay, for example, uses a visible, large CTA button surrounded by a generous amount of white space. The button looks great on mobile as well.

Place the same CTA in different places throughout your email to see which one performs better. Sometimes users don’t scroll till the end of the message or, vice versa, miss the link at the very beginning of it.

Do a lot of testing

Your product and your audience are unique, so your goal is to find a personalized approach that brings results. 75% of strategic marketers use A/B testing to learn about customer behavior. Try it too.

Unsubscribe rate

Formula for calculating unsubscribe rate:

(Users unsubscribed / Emails sent) * 100

Unsubscribe rate shows how many people clicked the unsubscribe link, without including people who reported your emails as spam. Tracking this rate, you can notice reactions of your audience to changes such as new templates, different content or timing, and so on, and use this information to improve your emails. Sometimes subscribers are not yet ready for large changes, so if the unsubscribe rate suddenly grows, you should review recent modifications.

Follow these three tips to keep the unsubscribe rate as low as possible.

Deliver relevant content

As always, content is everything, so you need to put all your efforts into creating valuable, targeted and engaging emails. If a person voluntarily unsubscribes from your mailing list, that could probably be a sign of ineffective content. Always remember that your main focus should be on bringing value to your subscribers.

Segment your list by interest

Offer users to personalize emails by setting up preferences and then segment them accordingly. For example, Net-A-Porter provides subscribers with a choice of their favorite designers to tailor the What’s New email updates to their interests.

Soft Surroundings, for their part, include similar questions in their subscription form.

Find your sending frequency

One of the top reasons why people unsubscribe is the inconsistency in sending frequency. Statistics show that 26% of users click the unsubscribe link due to the emails being sent too often. Hold A/B tests, ask for feedback, and check what is the trigger in your case.

Spam complaint rate

Formula for calculating spam complaint rate:

(Emails marked as spam / Emails sent) * 100

It demonstrates the number of subscribers who marked an incoming email as spam. You should pay attention to this metric as the subscribers’ activity is one of the criteria that define whether the emails will be delivered to the inbox or spam folder. What is more, this criterion affects your sender reputation.

Follow the tips below to prevent negative impact on reputation and deliverability.

Make it easy to unsubscribe

Losing a subscriber is certainly better than being marked as a spammer. You should add a clear and large enough unsubscribe link in a visible place of every email not only to protect your sender reputation but also to be GDPR compliant.

See how True Citrus does it in their emails.

Match your subscribers’ expectations

Keep your promises and provide subscribers with the information that was initially stated in a subscription form or subject line.

Conversion rate

Formula for calculating conversion rate:

(Number of users who completed an action / Emails delivered) * 100

This off-mail KPI indicates how many of your subscribers got engaged with you and completed a desired action after opening your email — made a purchase, signed up for an event, downloaded an eBook and so on. It is tracked by external services like Google Analytics. Every email campaign should have a final objective, and the conversion rate demonstrates overall effectiveness of your email marketing efforts in relation to this objective.

To leverage this metric, try these two tips.

Segment and personalize

Research your customers. Learn as much about them as possible. Build customer profiles to segment your mailing lists and send out more personalized emails, which, without a doubt, will result in a better response from your subscribers. For your information, 24% of companies which implemented segmented mailing lists have improved their conversion rates.

Send triggered emails

Statistics show that triggered emails get 624% higher conversion responses than batch and blast emails. Can you only imagine, six hundred and twenty-four per cent! The reason why triggered emails are so effective is their immediacy and relevancy — users get a response at once based on their actions.

Below is the example of a typical trigger-based email — a welcome email from Grammarly.

Bottom line

All in all, it’s always better to prevent something than to fix it later. The analysis of your KPIs will always help you to do both: fix and prevent. To make the metrics work for you, just remember these tips:

  1. Clean your mailing list regularly and use double opt-in to keep the bounce rate low.
  2. Pay attention to timing, subject line and preheader text to avoid issues with the open rate.
  3. Nail your CTAs and do testing to improve the click-through rate.
  4. Be consistent with your email sending frequency and tailor relevant content to reduce the unsubscribes.
  5. Meet expectations of your subscribers and make your unsubscribe link easy-to-find to lower the spam complaints.
  6. Segment your mailing list, send personalized and behavior-based emails to boost the conversions.
Six Email Marketing KPIs You Should Be Tracking
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