Email coding

Modules vs snippets in email development

As an email marketer, you probably don’t go back to the drawing board every time you create a mailing. Email layouts are saved as templates, and recurring components are stored as content blocks. There’s more than one way to do that. Let’s compare the email development merits of modules versus code snippets.

Some email development definitions

Modules are recurring template components stored on an email platform.

Code snippets are shorthand phrases defined by a developer that trigger pre-built chunks of code.

Modules and snippets therefore serve the same purpose. But the means to get there is very different. That deserves a closer look.

Module methodology

A module is essentially a standalone HTML file that can be dropped into a larger template. It might be a banner, or a stacking product section, or an intro with a hero image and a button. Whatever you like, it can be moduled.

Diagram of a project

That module is hosted in a library on your email platform. You can copy, edit and select any module for use in individual mailings. The specifics vary but you’ll generally perform this task via a graphical user interface. There often needs to be some additional programming using your platform’s scripting language.

Next, there’s usually a master template which has modules slotted into preset positions. These can of course be moved around or removed or added to as required.

So, that’s modules. Now for snippets.

Snippet style

The phrase ‘hand-coding’ is sometimes misunderstood. A developer will not sit and type thousands of lines of syntax in their entirety. Modern development environments support all manner of production shortcuts.

Among these shortcuts are code snippets. There’s more to these than simple blocks of code. A developer can set a snippet’s variables and cursor locations, thus producing a piece of code that can be navigated and edited in seconds.

Developer working on a laptop

Thinking about email development specifically, one example of a snippet could be a call-to-action button. By typing a pre-determined phrase – let’s say ’embttn’ – the developer triggers the snippet. Within moments, the text, link, colour, size and border can be set.

And the winner is…

I’ve kept the tone neutral(-ish) so far, but now it’s time to pick a side. By just about any reasonable measure, there’s a clear winner: snippets.

Here’s why:

Understanding

A skilled developer will work primarily in a code editor like Sublime or VSCode. Raw code may look daunting compared to the friendly GUI of an email platform, but ultimately that interface only fragments and obscures what is going on behind the scenes. When a new user needs to familiarise themself with the setup, it becomes a puzzle to be pieced together.

Speed

Working with modules means navigating through multiple pages and menus in an email platform. It is never quick. Working with snippets on the other hand is lightning fast. I’ve seen build durations reduced from all-day to an hour as a result of switching to snippet-based coding. There is no comparison.

Cohesion

Snippets mean far fewer sources of content for an email, and a more consistent format. Often an entire template can exist in a single file. Dynamic content written in your email platform’s scripting language can go there too, peacefully co-existing alongside HTML and CSS.

Flexibility

We’ve already covered the flexibility of snippets themselves. But there’s a related benefit – it means the developer can work in their environment of choice, rather than the one presented to them by an email platform. The advantage of a familiar and custom-configured comfort zone cannot be understated.

Final thoughts

To pit modules against snippets is part of a larger battle – drag & drop email builders versus hand-coding.

We are biased, of course. But with good reason. As a company of email developers, we’ve seen the comparative disadvantages of module-based configurations. There are situations in which errors can go unseen months or years. But the fault is buried somewhere in a maze-like setup that potentially no one person understands fully.

Hand-coding, by contrast, is uncluttered and transparent. For me, snippet-based email development is not only the best way to build mailings – it’s the correct way.

Email Marketing

The future is here. How will AI impact your emails?

Artificial intelligence is a hot topic. There are several AI-powered tools on the market, whether in a commercially-viable or prototype form. Perhaps most significant is ChatGPT by OpenAI, which was made public at the tail end of last year. What’s ChatGPT? Why don’t we ask it:

Me: what are you? ChatGPT: I am an AI language model developed by OpenAI, known as ChatGPT.

To describe itself as a “language model” may be correct but it’s a little modest. ChatGPT’s abilities are vast. It can answer questions, generate code, write articles, translate documents, tell you a joke, or engage with you in some good old-fashioned chit chat.

This of course is an impressive piece of technology and a fun tool to experiment with. But its scope and usefulness extend far beyond curiosity. It has practical, real world applications. Why spend time programming a website component when an AI can do it for you in a fraction of the time? Why struggle with writer’s block when a copywriting deadline is looming? Why be presented with adverts when searching for information online? Prompt ChatGPT and it’ll take on the task and output some code, content or answers within minutes if not seconds.

Amazing, right?

Let’s take a step back

The validity of the phrase artificial intelligence is often contested. As a species, we are yet to develop something that is actually aware, or truly understands what it is doing. Perhaps a more accurate description is fancy algorithms. Patterns, machine learning… and sometimes very wonky output.

On that topic – ChatGPT makes mistakes. That’s not a criticism. Just like a human, ChatGPT learns from mistakes… but it doesn’t feel embarrassed about it. When things go wrong, you can tell it so. It’ll then take steps to rectify the error. There’s some give and take when working with ChatGPT.

What artificial intelligence could mean for email

The combination of email and AI (or fancy algorithms) is nothing new. One-to-one product recommendations have been around for years, picking relevant items based on previous shopping behaviour. Spam filters automatically guard inboxes against emails of the shadiest kind. Customer journeys and automated emails are made possible through complex workflows with little post-development need for human intervention.

What is new however is the concept of emails that are predominately or even completely designed and coded by computers. Imagine high-quality, on-brand design and copy that is generated in seconds. Perhaps the same AI tool could then select the audience, send the email, read the report and optimise the next send. Is there a point at which human input becomes zero?

What artificial intelligence currently means for email

Don’t worry – we’re not at the human irrelevance stage yet. In my tests with ChatGPT, I’ve seen it output some erroneous facts and broken code. From what I’ve seen it’s neither ready to fly solo nor likely to achieve such independence any time soon.

That doesn’t mean it’s not a revolutionary and practical technology in its current state. I already use it almost daily for writing inspiration and to help with coding questions that would otherwise mean trawling through forums for answers.

ChatGPT and other pioneering AI technologies have already changed the way we work, and they will only continue to evolve. It’s incredible to think that what was only recently in the realm of science fiction is now becoming a reality. The future really is here.

Email best practice

Email accessibility: are you leaving anybody out?

Communication. That’s what email is all about. The same is true whether you’re using it to apply for a job, or to seek help from customer services… or to market your product to thousands of customers.

Marketing emails typically go to lots of different people using lots of different devices. Your objective is to convey an equally intelligible message to all of them. That brings us to the concept of accessibility.

Defining email accessibility

Firstly, here’s what accessibility is not:

  • An inconvenience
  • An afterthought
  • Exclusively a matter of visual impairment

And now for what it is. Mozilla (the developers behind the Firefox web browser) describe accessibility as: the practice of making your websites usable by as many people as possible.

Applying this thinking to our favourite medium, it means emails that can be easily understood, navigated and interacted with. We want our mailings to render optimally in any application on any gadget. They must impart a clear message and invite a defined action from the customer. And accessibile emails are open to people whatever their level of physical ability.

Email accessibility is a huge topic, encompassing many human and technical factors. Let’s take a look at some of them.

Clarity in message, design and function

A marketing email usually performs two main functions:

  • Communicates a message to your customers.
  • Invites them to take action in response.

Concise copy and a user-friendly structure support those objectives. Worry not – that doesn’t mean your email needs to be sterile and unimaginative. There’s still plenty of scope for characterful writing and vibrant imagery. The art is in creating an eye-catching design that supports your message rather than overwhelming or obscuring it.

Accessible copywriting begins with the subject line. Good, honest information beats vague open-bait every time.

Image of good and bad versions of an email subject line

I like big buttons and I cannot lie

There’s a tendency in email marketing to go link-crazy. Every heading, every subheading, every image, every block of text… and even empty space – all clicking through to web pages. That usually means ambiguous destinations and multiple links to the same places. The technical term for this is a mess.

The solution: buttons. Big ones. Big ones with clearly defined calls-to-action. Your customer should know in advance what sort of content to expect upon pressing it. And don’t forget to include plenty of breathing space around those buttons. You don’t want links to different places squashed up against each other, especially on touch-screen devices.

Don’t get left in the dark

Dark mode took off a few years ago, and remains a popular display option among those who care about things like battery life and corneas.

It can have a dramatic effect on the way your email is rendered. And often not in a good way. Images can be camouflaged against recoloured backgrounds, or left floating in unsightly squares.

Email being email, the rendering methods for dark mode are not consistent from one email application to another. It therefore requires an assortment of coding and imagery techniques to create dark mode-friendly mailings. Dark mode-specific CSS classes are possible. PNG format images with border effects help them stand out, should they be unexpectedly displayed atop a dark background.

Comparison of a logo as seen in light and dark modes

The technical details are a complex topic for another day. But let’s be clear on the objective – you want to optimise your email for dark mode, not override your user’s preferences.

So many apps, so many devices

Sorry in advance, but I’m about to throw a bunch of words at you. Here goes.

Desktop computers, laptops, tablets, mobiles. Screen sizes, model versions, display settings. Desktop software, webmail services, mobile apps.

My point: there are many software and hardware combinations out there, and your marketing emails could be viewed on any one of them. You want your email to be just as legible on a dusty old laptop running Microsoft Outlook 2016 as it is on a brand-new iPhone.

Responsive email – i.e. that which is coded to fit to any screen size – is the answer. It’s standard practice nowadays, but that absolutely does not mean that it is always handled adequately. All too often, mobile rendering remains a secondary concern – leading to visual problems like tiny text and confusingly mismatched imagery. We’ve written extensively about responsive email in the past, but let’s sum up some of the most important points:

  • Plan your responsive design from the outset. The mobile layout should never be a secondary consideration.
  • Support for HTML and CSS in email is extremely varied and somewhat limited. An email developer must understand how to code effectively for all major devices and email services.
  • Be prepared to simplify an overly-ambitious design. Fanciness for the sake of fanciness is not in the spirit of accessibility.

Even if you’re confident that your email is perfection itself, always include a link for it to be viewed in a web browser.

Hear me out: your emails could be confusing to screen readers

I mentioned earlier that accessibility is not all about visual impairment. It is however an extremely important aspect, and will largely be the focus of the remainder of this article.

A screen reader is a piece of assistive software that will audibly describe the content of an application, web page… or indeed an email. You probably have a screen reader right in front of you right now. Press COMMAND + F5 if you’re on a Mac, or CTRL + WIN + ENTER if you’re on a Windows PC. While the use of a screen reader takes time to master, this will give you a helpful insight into how a visually impaired person might be interacting with your content.

As technically incredible as screen readers are, it is unfair to expect them to do all the work. A website must be designed and coded in a way that a screen reader can navigate and interpret. The W3C Web Accessibility Initiative (WAI) publishes extensive guideance on this topic, and a lot of the advice carries over to email.

Let’s take a look at some ways to develop emails with screen readers in mind.

Write semantic code

Do you shop in supermarkets? They have signage to help you find your way around the array of aisles. ‘EGGS’ here, ‘HOUSEHOLD ESSENTIALS’ over there. If those signs didn’t exist, your shopping experience would be a lot more frustrating. An email without semantic code is a bit like a supermarket without signs.

Semantic email code can be defined as meaningful HTML tags. These are the basic elements behind the scenes that make up a mailing. Here are a few important ones:

  • <header>
  • <nav>
  • <section>
  • <article>
  • <h1> (the main heading on the page)
  • <h2> to <h6> (increasingly minor headings – seriously, I don’t think I’ve ever gone past h3)
  • <p> (a paragraph)
  • <strong> (bold text)
  • <em> (italic text)
  • <footer>

But there are also multi-purpose, non-descriptive HTML elements:

  • <div>
  • <span>
  • <table> (for the presentational purposes of email, that is)

Those last three are far from invalid. But it’s easy to be lazy in web and email development alike, and rely on them too heavily. In fact it’s actually somewhat rare to code particularly semantically in email.

But guess what – descriptive HTML tags help screen readers know what’s what. Say your main heading is just sitting there in a generic <span> tag. A screen reader won’t know that it’s any more significant than any other text that happens to be floating about on the page. If it’s wrapped instead in an <h1> tag, the screen reader will announce it as “heading level 1”. Now the user better understands what is being communicated. Construct your entire email with semantic code and you communicate useful information to those who can’t see it.

Similarly, sequence is important. Screen reader users will often be using a keyboard to navigate through the email. By default this will jump from item to item in the order they appear in your code. Make sure it makes sense.

And while there is actually a way to override this sequence, doing so is so far removed from best practice that we will discuss it no further! Far better to construct an email that follows a logical sequence in content and structure.

Mark your bricks as bricks

Modern websites are constructed with the finest materials available – divs, spans and all sorts of CSS-styled goodness.

Emails are built using a more… rustic method. They use HTML tables for structure, just as web pages did once upon a time.

When a screen reader encounters a table, it assumes that it is a table of data. Something like this:

Image of a table showing populations of capital cities

A screen reader may therefore produce confusing results when dealing with the structural table of an email. There’s an easy fix for this. Just apply the following HTML attribute to all of the tables that comprise your email:

role="presentation"

Congrats – you’ve just told screen readers what your tables are for, and made your email immediately more accessible.

Let text be text

When you write a text message to a friend, do you take a screenshot of it and then send it as an image? Unless you’re charmingly eccentric, I suspect the answer is no.

The same principle applies to email. And yet countless companies – sometimes even the biggest of corporations – produce marketing emails in this roundabout manner. Paragraphs of text are drawn up in a design application, saved as JPEGs and dumped into HTML emails. Why?

This practice is so widespread that phrases such as ‘live text’ have sprung up. Let’s get out of that way of thinking. It’s just text.

There are probably multiple factors at play here. Brand guidelines and typography. A desire to achieve complex layouts in a medium that doesn’t make it easy. Or it could be the it’s-always-been-done-this-way mentality.

Accessibility and usability trump all of those things. There are all sorts of reasons to use proper text. It renders sharply and at a consistent size, whereas images shrink and grow. Users can zoom in without the letters becoming blurred. Chunks of text can be selected and copied. And it’s the purest form of copy for screen readers to detect.

Web fonts are reasonably well supported in email these days, so you don’t even need to lose your brand typeface. Now all of the boxes are ticked.

Animated comparison of text and image versions of the same content being scaled

Pictures speak a thousand words

But only if you let them. And you should probably cut that down to a handful of helpful, descriptive words.

HTML comes equipped with a thing called alt tags. That’s short for alternative. These tags allow you to attach text content to any image on the page. We can use them to describe what is pictured or relay copy from a heading. Normally the alt tag goes unseen.

They are however of critical importance for users who cannot see your image. That might be someone who has chosen to turn pictures off, or perhaps the file has failed to load, or it could be a person with a visual impairment.

Take a look at a few examples:

Overhead aerial photograph of a hotel's outdoor pool, surrounded by trees and rooftops

alt="Overhead aerial photograph of a hotel's outdoor pool, surrounded by trees and rooftops"

Watercolor painting of a pink flower in a plain background

alt="Watercolor painting of a pink flower on a plain background"

Example heading saying SALE NOW ON

alt="SALE NOW ON"

Without these descriptions, the content of these images would be completely concealed to a screen reader user. By typing just a few words, you have produced an immeasurably more inclusive email.

One more thing – emails often include some purely decorative or spacer images. Just leave the attribute as alt="", and screen readers will know to ignore them.

Self access-ment

We’ve covered a reasonable amount here, but this is a topic too broad to fully explore in a single article. There are plentiful accessibility resources online, even for the relatively niche branch that is email.

Among those are tools to analyse the accessibility of your web page or email. Some of these are commercial products, but there are also some handy free ones.

Paste in your email code at accessible-email.org and you’ll see an instant report with suggestions for improving accessibility.

You might also wish to try WAVE – web accessibility evaluation tool. As the name states, this is intended for web pages. But much of the feedback also applies to email, so there’s nothing to stop you popping a ‘view online’ link in there.

Perhaps most useful of all is a simple checklist. That’ll let you score your emails consistently according to your particular requirements.

Here’s to more inclusive emails

Making your emails accessible is a complex task – but it doesn’t need to be an extra one. Accessibility standards are intertwined with email best practice. By putting accessibility at the core of your design and development process, you automatically produce better emails all round. Everybody benefits.

Perhaps the key to accessibility isn’t to think of it as a separate subject at all, but simply the act of making a good email.

Email coding

Cut and waste: is email clipping ruining your mailings?

Websites are displayed in web browsers. Browsers, for the most part, agree on how things should work. There’s a high degree of standardisation.

Emails are displayed in email clients. They do whatever the hell they want.

As email developers we need to contend with patchy support for modern web technologies and a shifting landscape of rendering quirks. And then there’s the matter of email clipping. That’s a nice way of saying your email could potentially be chopped in half.

The root cause of email clipping

Gmail has a 102 kilobyte limit on email code. Let’s round that to a neat 100KB. We’re not talking about images – they’re a separate entity. The 100KB cap applies to the HTML at the core of your email.

Exceed the limit and your email will be unceremoniously sheared. It doesn’t matter if you’re using a desktop or mobile device, via the Gmail web page or the app. The same rule applies across the board.

I’ve knocked together a purposely code-heavy email to demonstrate this process in all its ugliness. Here’s how my mailing should look:

Image of demonstration email

There’s a significant amount of bloat in this email. That includes things like superfluous code, border effects, device-specific imagery, and a drop-down menu on mobile.

The result is a file weighing in at 120KB. In Gmail it renders up to a certain point and then… stops. This is as far as it gets:

Image of clipped email

And yes, there is a link to view the email online in its entirety but realistically who is going to press that? I wouldn’t. The damage is already done.

Apart from the obvious consequences of a broken email and wasted content, clipping can also result in the unsubscribe link and terms & conditions going missing. That’s a serious problem.

Let’s find out what we can do about it.

Accept the limit

This is step one. The limit exists and there’s no way to circumvent it.

We also cannot afford to ignore it. Gmail is the world’s second most popular email platform and accounts for a third of the market.

I think it’s important not to think of this restriction as a nuisance. Much better to regard it as a reminder to follow good practice. If your emails are being clipped, that’s your cue to reign in rambling marketing spiel or refine your code or declutter your design.

Respect the limit and your marketing emails may end up all the better for it.

Code efficiently

There’s a single top-level cause of email clipping: the file size is too big. This is caused by one or more of the following factors:

  • Excessive content
  • Excessive code
  • Complex design

Let’s focus on code for now. If an email is being clipped, it doesn’t necessarily mean that its code is bad. It may be error-free and email-friendly in the traditional sense. There’s just too much of it.

We should always strive to find the most efficient way to turn content into code. Some of the most helpful methods I’ve found are as follows:

  • Padding on table cells is well supported in email and makes for a lighter alternative to spacers.
  • Nested tables are intrinsic to email-coding, but it’s easy to get carried away. See if you can cut back.
  • Merge tables where possible. If you can add a row to an existing table rather than creating a new one, do it.
  • Be prepared to deviate from the design. A simplified email is eminently preferable to a truncated email.
  • Allow some leeway. If you’re scraping under the limit, remember that image references and tracked links could end up longer than they appear in your local files.
  • Know your templates. It’s worth reviewing what every piece of code actually does.

If you’re have truncation troubles, it’s not a battle that needs to be fought on a daily basis. Snippet-based development and a template library lets us record and re-use good code. Solve the problem, save the solution.

Show the right products to the right people

I wasn’t kidding when I suggested that Gmail’s code limit is a good thing. Sending huge mailings with lots of products and no personalisation is a haphazard and old-fashioned approach to email marketing. Please buy something, buy anything! A limit on file size discourages that.

Tailored email marketing via strategic segmentation and data-fuelled product recommendations is the way to go. It’s easy to treat personalised content as an afterthought, but personalisation deserves to be at the heart of our marketing programmes. Modern email tools and technologies make that possible.

With a mere 100KB to work with, code is precious. Let’s not waste it on irrelevant content.

Redefine your design

If elaborate design is the root cause of your email clipping woes, then it’s time to go back to the drawing board. As dramatic as it sounds, it can be helpful to re-assess what email actually is.

Consider these questions:

Simplified design means a slimmer file. I’d wager that customers are a lot more interested in product and price than borders and background effects. And if you pit fancy design against an email that actually works, there’s no contest.

Out with the indentations

In the real world, this fix is likely to be the first course of action. It can be extremely effective and takes seconds to implement. But I haven’t listed it first here, as it doesn’t reflect the same spirit of best practice as the other improvements above.

Indentations in code are useful… to humans. A screenful of HTML or CSS becomes a lot more readable when it’s neatly formatted.

Image of some HTML code with indentations

But these indentations serve no purpose for a computer, and they account for a surprising chunk of your overall file size. Stripping them is often all that’s needed to save an email from clipping.

Image of some HTML code with no indentations

The scale of this kilobyte reduction is affected by various factors but it primarily depends on whether your indentations are tab-based or space-based. While tab-based reductions are relatively modest, space-based reductions hover around 20% in my tests. That’s a significant result for such a low-effort fix.

You don’t even need to lose your indentations forever – create a copy of your HTML file for uploading, and keep the original for editing.

Final cut

It’s time to take my Fauxrniture email and rescue it from Gmail’s axe. I don’t want to sacrifice content, so my focus is on improving code and dropping unnecessary extras.

There is huge scope for code refactoring. Several blocks of HTML can be merged, dramatically reducing the overall file size. Plus that makes it even more readable for my human brain.

The application of links to every single paragraph is overkill. The drop-down menu is a gimmick. Alternative imagery for desktop and mobile serves no useful purpose. So we’re saying goodbye to all of those.

The code-based border effects on the main image come with a hefty kilobyte cost, so I’ll incorporate them into the JPEG directly instead.

And finally (although we’ve done enough already at this point) let’s get rid of the indentations for good measure.

The end result is a file that is half the size of the original. That’s so far into the safe zone that we can relax completely. And crucially, nothing of importance has been lost.

The lesson here is that a clip-proof email absolutely does not have to mean a short email. Code efficiently, design for email, and lose the fluff. Now you can concentrate on content creation rather than email truncation.

A/B testing

Split decision – what to consider when A/B testing

Which of these statements about A/B testing is correct?

A. It’s a fun little experiment.
B. It’s a powerful tool which must be handled correctly.

The correct answer is B. Split testing is a powerful tool. And, like all tools, it has the potential to do more harm than good if it’s not operated with care.

It’s therefore unfortunate that split testing is often treated more like option A. “Hey, let’s try this” says someone… and suddenly you’re conducting an experiment based on an arbitrary, last-minute decision.

Testing in a haphazard and disjointed manner may garner useful insights into your customers’ behaviour but it’ll be mostly down to luck. Such unplanned testing is as likely to waste time on inconclusive, insignificant or even misleading results.

There’s a better way.

Devise an A/B testing strategy

A good quality A/B test deserves as much consideration as the content, design, segmentation or any other aspect of your campaign. Draw up a solid plan and set out with a real purpose.

Modern email marketing tools have made it easy to set up a split test. It’s tempting to jump right in and get started, but forethought and preparation pave the way to the best results. Decide who, why, what, how long and what next. Prove a theory. Discover an unknown. Learn about your customers.

A well-planned, one-off A/B test is great. But what’s even better is an ongoing series of interrelated tests. Maybe you’d like to conduct the same test under different circumstances, or the results spur your next hypothesis and then the one after that. Think of A/B testing as a programme rather than a standalone exercise and you’re on the right track for real customer insight.

Don’t waste time proving the obvious

Some years ago, I was working on a campaign with a three-way subject line test. I don’t quite remember all of the gory details but I can recall enough to illustrate my point. The email in question was a monthly ‘what’s on’ newsletter. It was going to the full UK mailing list. There was no targeting based on personal interests or any other such criteria.

Two of the subject lines focused on specific events. One of these was a Formula One race. The other escapes me, so let’s say that it was the World Bog Snorkelling Championships.

The third subject line kept things general. Rather than highlighting individual events, it indicated that a broad range of interests were catered for. I said: “this one will win”. And it did – by some margin.

As handy as it would be to possess some kind of marketing clairvoyance, my prediction wasn’t based on any special intuition. It was common sense. The events featured in subject lines #1 and #2 may be passions for some but they were surely of limited interest to the customer base at large.

Split testing can provide unique insight into what makes your customers tick – don’t squander it on predictable outcomes!

Beware of false positives, use deep pots and don’t jump the gun

Remember when I mentioned A/B testing’s potential for harm? This is where false positives come into play. Poor execution of a test or misanalysis of the results can lead to inaccurate conclusions, point your subsequent marketing efforts in the wrong direction and ultimately reduce engagement. Disaster!

False positives are tied to the concept of statistical significance. Without wanting to pretend that I fully understand the mathematics behind statistical significance, what it comes down to is this: the result of your split test could be the product of chance. There are a few key points to consider:

  • Have enough people been allocated to the test?
  • Has it been allowed to run for long enough?
  • By what margin was the winner decided?

The smaller the sample size, the less representative it is of the average customer and the more skewed the outcome will be. Likewise, a hasty one-hour testing window doesn’t give enough people sufficient time to engage. The balance could very easily tip in the opposite direction after the winner has been decided. I’ve seen a few prematurely-crowned ‘winning’ subject lines going out to the remaining database. MailChimp delves into actual numbers with this handy guide to A/B testing durations.

Once you’re satisfied that ample people and time have been allocated, your test is no longer doomed from the start. There is however still a chance that you’ll encounter a false positive. A marginal win could be the result of natural variance between your test groups. It’s worth running a test a few more times to see what happens. Neil Patel’s statistical significance calculator is a great tool for analysing real numbers.

To witness natural variance in action, you may wish to consider running a few A/A tests before moving onto A/B. That is to say, you’ll send identical content to two groups and record how much the performance metrics vary. Do that and you’ll find yourself in a more informed position when it comes to analysing future split test results.

Test one thing at a time… except when you don’t

That subject line test is all well and good, but why not throw in some alternative imagery, rewrite some copy and switch up the colour palette while you’re at it?

Because you won’t know what people are responding to. Maybe your customers prefer the word “today” to “now”, or maybe they found the daytime picture more compelling than night-time. You can only guess.

This is, of course, both common sense and common knowledge (although I have seen such a mistake made on a number of occasions). What is less obvious is that it’s possible to develop your testing programme to a level at which multiple campaign elements can and should be tested simultaneously. There’s even a phrase for it – multivariate testing.

After you’ve conducted A/B testing on an single element – be it the subject line, offer, call-to-action or anything else – you’ll know how that one component impacts the email. But your customer probably isn’t mentally breaking your mailing down into its constituent parts. Once you’ve measured the performance of individual items, it’s time to move onto the next step – testing their combinative effect.

I once worked on an email programme in which dynamic content blocks were pulled in via a specialist email agency’s platform. To determine the value of this partnership, we ran a few A/B tests comparing the performance of emails with and without dynamic blocks. Following conventional wisdom, we tested these blocks one at a time. The results were disappointing – it seemed that these dynamic blocks had no significant impact on email performance. We shared this news with the people at the agency. They were unsurprised and unconcerned. Their advice: test multiple blocks at the same time.

They were right. Clicks went through the roof and we learned a valuable lesson about how email components work collectively.

Remember to segment

We know that statistically significant results are more likely when working with a large sample size. So there’s a solid rationale behind the decision to run A/B tests on emails going to the full mailing list.

But there’s more to it than that. Mixing inactive subscribers into your A and B pots is going to dilute your test’s effectiveness. Make sure your sample groups consist of people who actually open your emails.

If your mailing list numbers make it a realistic option*, it’s worth considering running tests according to demographic group. A regular buyer and new customer may be tempted by different products. A subject line which grabs the attention of a 60-year old subscriber may not be so compelling to a 30-year old.

*And if you need to grow your mailing list, here are some tips on that.

Act on A/B testing data

The A/B test is complete. The outcome is enthusiastically discussed with colleagues. Everyone agrees that it’s very interesting. And then the information is recorded in a report, filed away and never thought of again. Don’t do that.

Let’s consider a typical subject line test. Two pots of 10% have been split out and the remaining 80% will automatically receive the most-opened subject line three hours later. That’ll boost Tuesday’s open rate, which is nice… but there are lessons to be learned beyond the scope of that one email.

It’s clear that customers prefer this particular set of words to that set of words but what does that suggest about how customers respond to tone of voice? How can that idea be factored into subsequent marketing activities? Could the information provide a basis for new theories on colour or imagery?

It’s easy to see A/B testing results through tunnel vision. Consider the big picture instead and we can truly harness the power of information.

Be aware of change

Some findings are so fundamental that you can consider them to be set in stone. It’s safe to say that people won’t ever prefer non-personalised emails to personalised, for instance.

But it’s important to remember that trends come and go, exciting new products become yesterday’s news and not all A/B test results stand forever.

If A beats B by a landslide, then you’ve learned a valuable piece of information about the current market. But will the results still reflect your audience’s tastes six months or a year from now? It’s prudent to plan for re-testing.

It’s time to split

Find inspiration in A/B success stories such as Campaign Monitor’s 127% uplift in clicks. Earn valuable data when your own tests deliver concrete results. And reap the rewards by learning from that information and setting your email marketing programme on an upward trajectory.

Make the right split decisions and get ready for knockout results.