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5 Things We Learned Analyzing 100 Million+ Emails

5 Things We Learned Analyzing 100 Million+ Emails

  • Guides
    Messaging and Automation

Today we’re going to share the scientific results we’ve observed from analyzing over 100 million emails sent to customers.

We’ve distilled the learnings from this huge number of campaigns into five juicy email marketing hacks that you can use to improve your email marketing efforts. Learn where you should spend time on your marketing and how you can actually see results.

So – ready to learn what types of emails convert best, what days of the week get the most clicks, how often you should email and other data-driven facts gives you ideas you can test?

Rock on!

[toc_chapter_fifths color=”blue” number=”1″ title=”Context” link=”#1″] [toc_chapter_fifths color=”green” number=”2″ title=”Timing” link=”#2″] [toc_chapter_fifths color=”orange” number=”3″ title=”Frequency” link=”#3″] [toc_chapter_fifths color=”purple” number=”4″ title=”Length” link=”#4″] [toc_chapter_fifths color=”red” number=”5″ title=”Images” link=”#5″]

[toc_chapter_title title=”Context is the killer advantage” number=”1″ color=”blue”]

A long, long time ago when we started Vero, I posted this image:

email marketing sweet spot

The point I was making is that behavioral emails are the perfect way to capitalize on your subscribers’ actions and increase your conversions. After all, transactional emails are a huge marketing opportunity.

Two years later and the data speaks louder than ever. Here’s a graph comparing the open and click rates for newsletters vs. transactional emails based on over 100 million sends:

transactional email click rates

Transactional emails have a click rate that is 42% higher than their newsletter counterparts. For every 100 clicks you get on a newsletter, you get 142 on a transactional email.



Context is king when it comes to email marketing. Your customers should intuitively understand why they are getting your emails. Yes, they subscribed but what behavior triggered the message? Did it arrive at that right time in their buying process? And what, exactly, should they do next?

Let’s take a look at an example of an email with great context.

If you wanted to get your customers to review a product you sold on your website, you could send them something that said:

“Hey there, thanks for purchasing PRODUCT XYZ, we’d love if you’d leave a review! Click here to fill out this 5-second survey.”

You’ve probably received emails like this, right?

Here’s a question – were you driven to do anything in response to these emails? Probably not.

However, with a little thought around context you could design an email that is much more likely to convert. Take this amazing example from the boffins over at Amazon:

Amazon review email

This email is awesome because it has context from the subject line right through to the action the customer takes on the website.

The body of the email itself is superb. Rather than make the customer fill out a survey on the site and go through needless steps, this email takes a step out of the process and helps the customer to achieve the goal. The streamlined approach delivers better results for Amazon.

Newsletters and transactional emails go hand-in-hand, but if you want to give your email marketing a lift today then I would recommend you take the following steps:

  1. Think about the places in your funnel where you can you send more transactional or behavioral emails. They’ve got context built in. (Onboarding is a great place to start.)
  2. Think about how you can make each of your emails more direct. How can you move your subscribers toward your goals one step at a time?

Pro-Tips for emailing with context

1. Think about the Buyer’s Journey

If you haven’t heard of the Buyer’s Journey, this image nails it in a nutshell. It’s all about considering the psychological process a customer goes through from discovering your business to actually becoming a customer.

buyers journey

You should automate campaigns at each stage of the customer lifecycle, urging your customers to take the next step. The example above from Amazon is a great one as it is transactional and it directly aims to get the customer purchasing again and/or referring others (great reviews mean more book sales from other potential customers).

Welcome series, getting started email guides, referral offers, reminders are all great examples of behavioral emails you can send. We’ve put together some great ideas over the years so, if you’re after inspiration, check out our massive Lifecycle Email Marketing Guide.

2. The subject line frames everything

Subject lines aren’t the be-all and end-all of email marketing but they are super important. What most people fail to consider, however, is that the subject line is actually comprised of three elements:

  • The from field
  • The actual subject
  • The pre-text

Here’s what a modern subject line looks like in Gmail:

buzzfeed email subject line example

And on mobile:

buzzfeed mobile example

It’s important to nail the three components:

  1. The from area is reserved for someone or something that is familiar to the recipient. Joanna Wiebe often recommends including your personal name as well as your company’s name.
  2. Try and write a subject line that has massive context. Take this autmated marketing email from Priceline:priceline email subject lineThis email nails time and place in just a few words. It makes you feel like must open it … that is some smart subject line work!
  3. Make sure the first few lines of your email make sense, so that it looks good in the email client. There is no point wasting this space with something like “View online” or “Logo image here”.

[toc_chapter_title title=”There is no best day to send emails” number=”2″ color=”green”]

When we pulled out emails sent on different days of the week we thought we’d see a huge discrepancy on certain days, or at least on the weekend.

But the data doesn’t lie.

We found that, regardless of the day of the week, email campaigns seem to hold steady in terms of average open and click rates.

best day to send email

This might seem quite remarkable but there are a two good theories that may explain this data:

1. General consensus

General consensus that customers are less likely to engage with email on the weekend, meaning that those few who still email on those days see higher engagement as there is less competition.

2. Notifications are always relevant

Many of the emails we analyzed were automated, behavioral campaigns. For these sorts of emails – and this is one reason they’re so powerful – there is always context as they have been triggered by a subscriber’s actions. Why they received the email is more relevant than when.

Having said that, there are certainly cases where days of the week do matter. In her excellent breakdown, Sandhi of Quibb talks about how she has maintained open rates consistently higher than 50%. One of her secrets was identifying that her subscribers did not engage well with email on the weekend.

Armed with this knowledge, she cut out weekend email to ensure each and every email maintained a high open rate. Similarly, use your own data to make an informed decision on this front.

In general though, a good tip to help send emails at the right time …

Pro-Tips for sending emails at the right time

Don’t presume anything

Are you selling to single moms? Are you selling to 16-year-old teenagers? Are you selling to IT Managers? Each of these groups has a different structure to their day and engage with emails in different ways.

The best place to start is to put yourself in your customers’ shoes and, over time, improve your results by observing your own metrics. This will give you the best chance you have at determining when is an appropriate time, and on what days, to email your target audience.

[toc_chapter_title title=”Frequency is all about expectations” number=”3″ color=”orange”]

In general, the more emails you send, the lower your average click rate.

The sample data we used showed that businesses that sent one email per week had an average click though rate of 6.54%.

Those that sent two per week an average of 5.45% and those that send 3+ had an average of 4.76%.

Those seem like small differences until you consider that the difference between 4.76% and 6.54% is 37%. That’s a huge difference on the bottom line!

Here’s those stats in a chart:

how many emails per week

The truth behind these numbers is that companies that send what their customers expect to receive are the most likely to do well. If you tell customers you’re going to be sending them daily emails then you set an expectation.

Take Quartz who promises an email every morning:

quartz email signup

Or HelpScout who very clearly states that they’ll send you an email every Wednesday:


When HelpScout lives up to their promise by delivering no more or less emails they are, in fact, building trust. Over time this delivers awesome click through rates that are sustained.

Check out the example below to see how singularly focused HelpScout is on delivering their promise from the call to action. This email contains the promised article and lives up to the “no sales pitches, no games” guarantee as well.

helpscout email example

So the first take away here is: let subscribers know what to expect and deliver on this promise. In doing so, you’ll build a rapport with your list which, over time, leads to increased click through rates and more revenue for you!

When breaking down the statistics even further, we found that e-commerce businesses generally fared better when they sent multiple emails per week. One particularly high lift was the difference between one and two emails a week. On average, e-commerce customers saw an average click rate of 7.8% if they sent one email per week, while those that sent two saw an increase of 27% with an average click rate of 9.94%.

ecommerce email marketing

This is a classic example of why you should always test out ideas for yourself. It stands to reason that due to the nature of most e-commerce emails, an increased volume is likely to improve the click rate. Generally e-commerce emails either contain a single offer or multiple product offers. As these are regularly time-sensitive and there is high-turnover, this is a situation where you can easily draw the hypothesis that more emails equates to a higher click rate.

Starbucks does a particularly good job with their promotional emails. They send several each week with time-sensitive offers. Because they are good offers and recipients have come to expect value from them, they drive opens and clicks as well as in-store purchases.


When looking at the data, we found that for both newsletters and automated behavioral campaigns there was a drop off after three emails per week. Take the data for automated campaigns:

emails per week data

In this example too, the trend points towards lower click rates as email frequency increases.

Newsletters in general had much lower average click rates, with those companies that sent one newsletter per week having a click rate of just 2.52% on average.

Pro-Tips for getting email frequency right

1. Be up front

Build trust with your subscribers by telling them how often you are going to send emails and then stick to it. This will build trust over time and increase all of your email metrics. Transparency is always a good thing!

2. Don’t email more than three times per week

We’ve always said that three times a week is the limit for quality email marketing. In most cases, this holds true. There are exceptions (daily deals sites or notification emails) but, generally speaking, there is a drop-off in engagement at even three times per week. Always test out your own theories, but this is a good rule of thumb.

[toc_chapter_title title=”Copy length doesn’t really matter” number=”4″ color=”purple”]

If you do any copywriting, you’ll regularly have asked yourself “is short-form copy better than long-form copy?”

A fine question. The answer? When it comes to email at least, it really depends. Here’s the hard data:

email copy length

Note: This data is based on an analysis solely of emails that contain links, excluding unsubscribe links.

The prevailing wisdom from our analysis here could only be defined in two points:

  1. The length and type of copy depends on your audience and your product.
  2. You can get a bigger lift from altering how many emails you send, what types of emails those are and how many images they contain.

Moreover, you can build trust regardless of how long your emails are: it’s about context and consistency as we’ve covered above.

We couldn’t get the data on enough emails to draw fair conclusions but it would be extremely fascinating to plot the above data against information on the value of the deals or products being sold by each company.

It is a commonly held belief that longer sales copy should be used to sell more expensive products. Should SaaS companies with higher plans employ emails with longer sales copy? Should information companies employ the same? What has your experience been? How have you seen email length affect your clicks rates?

Pro-Tips for email length

Stay calm and write on! If you are looking for immediate wins our data shows that email length is least likely to give you a good lift in click rates or conversions. You could better spend your time elsewhere.

If you have optimized every other aspect of your email then it’s worth experimenting with different lengths based on the products you’re offering. Look to others in your industry for awesome examples of what you can achieve.

[toc_chapter_title title=” Images are worth a thousand words (sometimes)” number=”5″ color=”red”]

One of the most common questions I hear regarding email marketing is “should we use images in our email marketing?”

A fine question, Watson.

The answer, at first glance, is that you should:

use images in email

… but this doesn’t tell us too much. What’s really interesting is when we break down the click rates by the number of images in a campaign. When we break it down like this, we get the following results:

click rate by number of images

This is much more revealing. In all cases, the click rates are higher than having no images and we can also see that campaigns with five images get a lot more clicks than those with one, two or three.

The likely reason for that is that business-to-consumer (B2C) emails make up a large proportion of those campaigns featuring images. Take the following as an example of a campaign featuring more than five images:

amazon product email

In this instance, it’s easy to see how a customer is more likely to click due to the large number of options in the email. This is a particularly good example of a campaign, with each image serving a purpose. In scenarios like this images can add a LOT of value, as the products being sold are visual. Customers want to see the camera they’re considering buying and this is far more likely to lead to clicks than a plain text email simply describing the camera in question!

In contrast, B2B and sales offers are usually much more effective if they feature one or fewer images. Take this great example from the team over at Help Scout, which helped them achieve a “double-digit percentage increase in click-through rates”:

helpscout example 2

In a B2B context, they found that featuring multiple stories and feature images reduced the number of clicks, because it caused distraction. In this case it could be argued that the individual images weren’t adding value or variety, there are in fact inhibiting the end goal: getting people onto their blog.

Ultimately though, the trick is to think of your end customer and test ideas that make sense. Do you sell clothes? Then it makes sense to use images. Are you reaching out to the VP of Marketing that has just registered their interest in a demo? Images probably don’t hold a place here.

Here’s a few more examples to give you ideas. Take this email from EasyJet offering hotels in Berlin:

easyjet email example

It makes sense to include images of their hotel inventory, as this makes sense for the end customer. Another example is this email from Amazon. Again, images make sense, but notice they’ve only included the bare essentials:


On the contrary, this lifecycle email from Buffer is fantastic, and it has no images. In fact, images wouldn’t help the customer achieve the end goal.


Pro-Tips for using images correctly

1. Only insert images that are HELPFUL

A cute image of a puppy dog in your SaaS welcome email is unlikely to increase your email conversions (though I challenge you to prove me wrong!)

A beautiful HD image of that slinky pink dress or handsome blue suit is likely to have an impact.

2. Make images links

If you’re including images then you should always make them hyperlinks. To get the click-through lifts you’re after, you need the links … otherwise customers will likely get confused.

3. Compress your images

Don’t serve up huge images in emails. This can impact your spam score. There is plenty of room for images but having all images and no text, or little text, can increase the likelihood you’ll end up in the good ‘ol spam folder.

Simply resize your images before you upload them to your email marketing software.

[toc_chapter_title title=”Over to you” color=”blue”]

Which of these ideas will you put to the test first?

Your mileage will vary a little but this data is based on hundreds of millions of sends for SaaS companies, B2C businesses and others. These guys are SMART and they put a ton of effort into their email marketing.

The key to success is to take these ideas, throw them into your email marketing plan and iterate until you are killing it too!

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