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Every email campaign is launched with a particular goal in mind. This can be to promote a product feature, sell a subscription plan, raise customer engagement, and so on. Goals define the key performance indicators (KPIs) or metrics a marketer has to track. Some metrics, such as open rate, are must-haves. You can’t neglect them. Others, such as opens by location, are less actionable, but may still bring value to your analytics. Below we’re going to explore both high and low priority email metrics.
Prioritization of email marketing metrics
Prioritization allows you to filter KPIs by relevance. Why do we need to set priorities? Google shows a bunch of sources offering 5, 6, 10 and even 22 of most important metrics. However, those just list performance indicators and do not explain which of them are more valuable. We’ve collected some of the highest ranked sources for you:
| 5 Metrics | 6 Metrics | 10 Metrics | 22 Metrics |
| read more | read more | read more | read more |
| 1. Deliverability rate 2. Open rate 3. Click-through rate 4. Conversion rate 5. Social sharing rate | 1. Click-through rate 2. Conversion rate 3. Bounce rate 4. List Growth rate 5. Email sharing/forwarding rate 6. Overall ROI | 1. Open rate 2. Click-to-open rate 3. Mobile open rate 4. Mobile click rate 5. Open and click rates by domain 6. Unsubscribe rate 7. Conversion rate 8. Bounce rate 9. Revenue per email or click 10. Revenue per subscriber | 1. Open rate 2. Mobile open rate 3. Total opens vs. unique opens 4. Opening time 5. Repeat opens 6. Bounce rate 7. Deliverability 8. Link clicks 9. Click-through rate 10. Unsubscribers 11. Unsubscribe rate per email 12. Subscribers vs. unsubscribers 13. Conversions 14. Purchase rate 15. Return on ad spend 16. Revenue per open email 17. Revenue per subscriber 18. Time spent viewing email 19. Active audience 20. Warm reply rate 21. Spam score 22. Email client |
It’s hard to understand which performance metrics have higher priority. With that in mind, we used the MoSCoW framework to prioritize them. Now, you can see which metrics are
- Must-haves
- Should-haves
- Could-haves
- Won’t-haves
MUST-HAVE email metrics
Must-have KPIs are crucial for analyzing the performance of any email campaign. We’ve singled out five top-priority metrics:
- Open rate
- Bounce rate
- Unsubscribe rate
- Spam complaint rate
- Click rate
Open rate
Description:
Open rate denotes how many recipients of the entire mail list opened the email campaign. For this to happen, the email has to be delivered successfully first. Then other factors come into play, such as the email subject line. The better engagement it provides, the higher the open rate will be. Therefore, always check the subject line of your email campaign with respective email testing tools. But, of course, you should not separate subject line as a key factor. The sender name is also viable. Emails sent from “Support team” and “Olga from Mailtrap” are likely to have different open rates.
Which folder an email gets put in, the so-called inbox placement, is a huge deal as well. For example, Gmail may sort incoming emails into Primary, Promotions, Social, and others. Some users open emails mostly from the Primary and Social inboxes, while the Promotions can be neglected completely.
Aspects such as brand recognition and email history also play an important role in the open rate.
Formula:
Open rate = (total unique opens ÷ total recipients) × 100
Benchmark:
There are different opinions on the optimum open rate. It depends on the industry, purpose of the email, time of delivery, and so on. But most marketing experts concur that an open rate of <20% is a failure.
How often you should track it:
Every week
Bounce rate
Description:
Bounce rate denotes a ratio of bounced emails to all email addresses in the mail list. A bounced email is an email that failed to be delivered. There are two types of email delivery failure:
- soft bounce – which comes from a temporary failure, such as the recipient’s mailbox being full
- hard bounce – which comes from a permanent failure, such as an invalid email address
Read the blog post to discover more about the difference between hard and soft bounce.
Formula:
Bounce rate = (all bounced emails ÷ total email recipients) × 100
Benchmark:
If less than 2% of your emails failed to end up in the recipients’ inboxes, that’s fine. Once you’ve stepped over this threshold, you need to invest effort in raising your delivery rate (the metric that is opposite to bounce rate). A double-digit value of email bounce rate is an alert signal – your sender reputation is at risk.
How often you should track it:
Every month
NB: An alternative to bounce rate is the inbox placement rate (IPR). IPR shows how many emails of your campaign ended up in the recipients’ inboxes. Both metrics are deliverability-centered; therefore, we recommend you read this our email deliverability guide.
Unsubscribe rate
Description:
Unsubscribe rate is the ratio of the recipients who clicked Unsubscribe to the total number of emails delivered. As a rule, this metric shows how many subscribers lost interest in your product or service. At the same time, the reasons that lead to opting out may include:
- misleading subject lines
- emailing too frequently
- ineffective offer
- and many more
Unsubscribe rate can point out how to fine-tune your email campaigns and filter out irrelevant subscribers. Segmenting subscribers will also help you reduce unsubscribe rates.
Formula:
Unsubscribe rate = (total unsubscribes ÷ total emails delivered)
Benchmark:
A threshold value of unsubscribe rate is 0.5% per email campaign. This means that of 100 emails delivered, you may have up to 5 unsubscribes.
How often you should track it:
Every week
Spam complaint rate
Description:
Spam rate denotes the ratio of the recipients who marked your email as spam to the total number of emails delivered. This is the most critical metric for your domain reputation and deliverability in general.
Do not confuse this metric with the Spam score, which does not depend on the recipient’s attitude to your email. The spam score is sort of a ticket for your email campaign to pass through spam filters. If your email has a high spam score, it will go into the spam folder automatically. In the blog post Why Emails Going to Spam and How to Prevent It, you’ll find more on this.
With the spam complaint rate, the destiny of your email is totally in the recipient’s hands. They can click “Mark as spam” for different reasons, such as:
- emailing too frequently
- irrelevant content
- no opt-out option
- the recipient did not give consent for emailing
The last two points are especially important in terms of GDPR compliance. For more on this topic, read our blog post about GDPR for email marketing.
Formula:
Spam complaint rate = (total “marked as spam” ÷ total emails delivered) × 100
Benchmark:
The optimum spam complaint rate is below 0.1%. If it’s higher, your email marketing either targets false recipients or delivers poor value.
How often you should track it:
Every week
Click rate
Description:
Click rate, also known as click-through rate (CTR) defines how many recipients clicked on the links in your email. This metric depends on a few factors:
- credible and compelling content
- email formatting
- anchor text on the link
- link location in the email body
- total number of links
All this should convince a recipient to take an action and click the link. If the click rate is poor, this means that you failed to deliver your CTA or idea to subscribers.
Formula:
Click rate = (total unique clicks ÷ total emails delivered) × 100
Benchmark:
There is no maximum optimum click rate. The values differ by industries. For example, according to Constant Contact’s Knowledge Base, the average CTR in the transportation industry in September 2019 was 16.61%. Meanwhile, the average CTR in the travel and tourism industry was only 5.92%.
How often you should track it:
Every week
SHOULD-HAVE email metrics
Should-have KPIs have a secondary priority. These email campaign metrics are nevertheless important, but they don’t need to be among the first things you track. We’ve chosen the following options:
- Total opens
- Conversion rate
- Campaign ROI
- Email Sharing/Forwarding Rate
- List Growth Rate
Total opens
Description:
Open rate is based on unique opens, i.e. one email open by a recipient. But what if the recipient opens your email multiple times? In this case, the total opens metric comes into play. It summarizes all the opens by each recipient. What’s the point? If a subscriber opens your email for the third, fourth or whatever time, he or she is probably very interested in it. Perhaps it’s time to set the hook and follow up with the recipient. On the other hand, multiple opens may indicate that the email content is attractive but too long. Therefore, the subscriber has to come back to it later to read it.
Formula:
Total opens = sum of total opens by each recipient in the mail list
Benchmark:
N/A
How often you should track it:
Twice a week
Conversion rate
Description:
Conversion rate is the ratio of email recipients who completed a desired action to the total number of emails delivered. Each email campaign has its own desired action, such as clicking a link or purchasing a product. The successful desired action defines the conversion.
For example, in your email you’re calling the subscribers to switch their free trial account to a paid one via a corresponding link. Of 100 email delivered, 20 recipients clicked the link, but only 5 of those signed up for the paid subscription. So, the conversion rate will be (5 ÷ 100) × 100 = 5%. However, if your desired action was just to click the link, the conversion rate would be (20 ÷ 100) × 100 = 20%.
Formula:
Conversion rate = (total recipients who completed the desired action ÷ total emails delivered) × 100
Benchmark:
The conversation rate depends on the email types you send and which action you need the recipient to complete. If you expect to sell something via a newsletter, the average conversion rate in this case is around 1%. Follow-up emails or abandoned cart emails can boast a conversion rate of around 5%.
How often you should track it:
Every month
Campaign ROI
Description:
The return on investment (ROI) for your email campaign is the ratio of total revenue to total expenses. However, the campaign ROI is not an accurate metric. For example, your first email campaign had larger investments and brought some revenue. The next campaign cost less but was more beneficial due to the after-effect of the first email campaign. When you add these revenues together, you will get an accurate ROI. And you need to add them together in any case. Ideally, both campaigns work on their own and you exclude other factors.
An email is a free asset. An email campaign is an investment asset. This includes costs for email platforms, templates, testing tools, and so on. When you track ROI for each campaign, you get valuable input for optimizing your email marketing strategy.
Formula:
Campaign ROI = ((total revenue – total investment) ÷ total investment) × 100
Benchmark:
$38 for every $1 spent is a frequently used statement to highlight email ROI. However, it’s not 100% true-to-fact. If you look at the Marketer email tracker 2018, a survey conducted by the Direct Marketing Association (DMA), you’ll find the following:
This potentially renewed confidence in calculating ROI is reflected in the estimated average of £32.28 this year (2018) for every £1 spent, up from £30.03 last year.
There is no optimum campaign ROI, but you can rest on the average value above to analyze how well your campaign is doing.
How often you should track it:
Every month
Email Sharing/Forwarding Rate
Description:
Email sharing rate shows how often your subscribers shared your email campaign with their friends. This is a key email engagement metric that defines the quality and attention values of the email campaign. Worthwhile content is what recipients will share in social media or forward to their friends. The main benefit here is that you can outreach your product/service beyond your mailing list.
Formula:
Email sharing rate = (total shares/forwards ÷ total emails delivered) × 100
Benchmark:
Sharing/forwarding rates are different for each industry. For example, according to The 2018 Hidden Metrics of Email Deliverability by Return Path, the average rate of email forwards in the insurance industry was 0.16 (16%) in 2017; whereas, in industries such as sporting goods, toys/hobbies/crafts, and even flowers/gifts, it was only 0.01 (1%).
How often you should track it:
Every month
Subscriber List Growth Rate
Description:
Subscriber list growth rate defines the progress of attracting new subscribers or users to your funnel. If your email campaign has something like “Subscribe to Our Blog” or “Sign up and try Mailtrap for free“, you should track subscriber list growth rate. The metric is actionable for different goals:
- drive traffic to your website
- get signups for your free trial
- outreach more people to sell anything
- and more
Your subscriber list must not stagnate but increase at least by 3% per month. And don’t forget about potential loss due to unsubscribes.
Formula:
Subscriber list growth rate = ((new subscribes – unsubscribes – spam complaints) ÷ total subscribers) × 100
Benchmark:
Benchmarks vary across industries, but the average subscriber list growth rate is 3% per month.
How often you should track it:
Every month
COULD-HAVE email metrics
Could-have metrics to analyze email performance are less important than the two previous categories. However, they are also actionable and can bring certain benefits of a third-level priority. We’ve picked the following metrics:
- Mobile open/click rate
- Revenue per email/click
- Revenue per subscriber
- Opening time + Time Spent Viewing Email
- Email client
Mobile open rate
Description:
Mobile open rate shows the share of emails opened on mobile devices. This metric allows you to understand whether your email campaigns need to be optimized for tablets and smartphones. This may include larger font sizes, reduced body text, refined design, and much more.
Formula:
Mobile open/click rate = <mobile email opens ÷ total unique opens) × 100
Benchmark:
No benchmark is applicable
How often you should track it:
Each time you’re about to launch a new email marketing campaign
Revenue per open email
Description:
The first email campaign had a 50% open rate with 10K ROI. The second email campaign had a 40% open rate, but its ROI was 20K. Where did such inconsistency come from? The Revenue per open email is meant to figure this out. This metric will let you look at the performance from the standpoint of success or failure of each email. So, you’ll see which emails perform better and manage to figure out why.
Revenue per open email divides the overall revenue for email campaign by the number of opens or clicks. The higher the revenue per open/click, the higher the efficiency of a particular email campaign.
Formula:
Revenue per open email = campaign ROI ÷ total unique opens/clicks
Benchmark:
No benchmarks are applicable for this metric
How often you should track it:
Every week
Revenue per subscriber
Description:
The revenue per subscriber is another in-depth look at the campaign ROI. The metric lets you understand which type of subscribers have been hooked by your emails. This will let you understand the difference between a profit-making and non-profit persona. With this input, you’ll be able to fine-tune your email campaign to increase the overall ROI.
Formula:
Revenue per subscriber = campaign ROI ÷ total subscribers
Benchmark:
No benchmarks are applicable for this metric
How often you should track it:
Every week
Opening time + Time Spent Viewing Email
Description:
Time-related metrics are quite actionable for tracking email campaign performance. Opening time tells you when the biggest part of your email opens occur. If you know this, you can significantly boost the open rate of your next campaigns.
Time spent viewing email shows how sticky and balanced your email content is. Verbose emails are not attractive. Subscribers prefer to skim the email, which takes up to 10 seconds to read. An excellent campaign has to draw their attention within this time.
Benchmark:
No benchmarks are applicable for opening time. As for time spent viewing email, you need to fit your emails into the range 3-10 seconds. However, the benchmark may vary depending on the email type.
How often you should track it:
Every month
Email client
Description:
The email client metric is not based on any sort of formula filled with variables. This is just an analysis of which email clients your subscribers use to open your emails. What is it for? You can use this knowledge to tailor email campaigns that will display properly for your recipients’ email clients.
How often you should track it:
Each time you’re about to launch a new email marketing campaign
WON’T-HAVE email metrics
Won’t-have KPIs are the lowest priority metrics. They can bring some analytical value, but if you abandon them your project won’t suffer at all. That’s why won’t-haves are often called would-haves or wish-to-haves. Here is our list of those:
- Repeat opens
- Domain open/click rate
- Top links clicked
- Opens by location
Repeat opens
Description:
For calculating the open rate, we use unique opens. A unique open is a single open by a recipient. However, the same recipient can go back to the email multiple times, and that’s a repeat open. What input does this email metric give? If you notice that a certain subscriber has a few repeat opens, he or she has a special interest in what you offer. The subscriber is likely a hot lead, who you should follow up with as soon as possible.
Benchmark:
More than three repeat opens is a cause to reach out to the subscriber.
How often you should track it:
Every week
Domain open/click rate
Description:
Domain open rate and domain click rate are metrics that allow you to sort your email list by email provider. This knowledge will help you deal with the specific domain’s spam policy more efficiently. Let’s say, with a 15% open rate for your email campaign, the open rate for example.com addresses is only 5%. This may be caused by a filtering issue at example.com.
Formula:
Domain open/click rate = (domain email opens ÷ total domain recipients) × 100
How often you should track it:
Every month
Top links clicked
Description:
The idea of this metric is to provide input on why some links harvest top clicks and others don’t. If your email campaign contains multiple links, you may be interested in assessing how they perform separately. For example, of three links placed within the email, you have the following click rate for each:
- Link A – 15%
- Link B – 3%
- Link C – 6%
This will help you understand the recipient’s behavior and fine-tune the email campaign in the future.
How often you should track it:
Every month
Opens by location
Description:
The Opens by location metric provides shows you the geography of opens of your email campaign. This is an efficient insight that you can use for optimizing your campaigns. The metric can also be moved higher in priority if you plan to expand to new markets. In this case, opens by location can be considered as a could-have metric.
How often you should track it:
Every month
Pick metrics based on your goals
Tracking metrics is important for the evaluation of whether the email campaign reached its goal or not. That’s why you should always start with figuring out the GOAL of your campaign first. Then you need to define WHO this campaign is for – the audience and eventual segmentation. The GOAL and WHO parts will let you understand what sort of content is required. A combination of the goal, audience, segments, and content will drive you to the choice of metrics you need to track.
Goal => Audience => Segments => Content => Metrics to track
And our full list of email marketing metrics comes into play here. Just grab them all, sift through them, and decide which ones will suit your campaign with its particular goals and content. Good luck with emailing!
