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Updated December 2018

What’s the deal with all the different email clients out there? You’ve got Gmail, Apple Mail, Yahoo Mail!, Outlook, and heaps more. And each of these email clients plays by its own rules, meaning they can each render your emails differently. As you can imagine, this can wreak havoc on email marketers and has for years. 

With so many different email clients out there, you have to consider how your emails will look across a multitude of inboxes and, with the ever growing popularity of mobile, across devices.

This guide to email clients will provide you with an overview of the most popular email clients and what you need to know about them, so you can set your emails up for success in every client and device.

Chapter 1

The most popular email clients

With the plethora of email clients out there, marketers have to account for a lot of variables when creating their emails. And we’ve spent years chronicling our issues with coding and designing emails in Microsoft and Gmail. On more than one occasion, we’ve successfully anticipated changes to how these email clients read and support email designs.

But most email marketers today aren’t coding their own emails from scratch.

Thankfully, modern email design tools like Campaign Monitor take much of the guesswork out of crafting a beautiful and function email and you can know how your email will render before you ever push send.

Even so, it’s still important to know where your subscribers are reading their emails in order to maximize how many of your emails are landing in the right inboxes and how they look and perform when they get there.

So what are the most popular email clients out there and how do we know which ones your subscribers are using?

The top ten email clients (calculated from 946 million opens) are as follows:

emailclientshare.comSource: Email Client Market Share

Fine print: This leaderboard of the most popular webmail, desktop, and mobile email clients is compiled from data collected worldwide by Litmus Email Analytics, and displays up-to-date figures for the top 10 email clients as of November 2018.

Since determining the client in which an email is opened requires images to be displayed, the data for some email clients and mobile devices might be over- or under-represented due to automatic image blocking.

As you can see from this data, Apple Mail and Gmail lead other email clients by a longshot. In fact, Gmail just announced they have surpassed 1.5 billion users on their platform.

This means that you should keep Apple Mail and Gmail in mind when you’re designing your emails in order to provide a seamless experience for your subscribers and simplify the design process for your marketing team, especially if that team is just one person.

Which email clients are your subscribers using?

Each time a subscriber opens an email sent with Campaign Monitor, we keep track of which email client they’re using. You can see this in the Reporting section of your account under Email Client Usage.

Here’s an example:

Track Email Clients Your Email Subscribers are Using

In the example above, understanding that the majority of subscribers are viewing the email in Gmail and on iPhones will help you optimize your email design for the most opens and click-through rates on mobile devices.

For instance, knowing your specific users’ email clients will help you choose the best length for your email subject lines: You’ll want your subject line to be between 41 characters (the optimal number for portrait view on an iPhone) to 70 characters for Gmail.

Familiarizing yourself with today’s top email clients allows you to learn the limits of each and design your next email with these limitations in mind; this means no more worrying about images not displaying, subject lines getting cut off, or spam filter surprises.

Instead, you can feel in control of your email marketing campaigns.

Together, Apple Mail and Gmail make up 55% of the email client market share.
Chapter 3

What about mobile users?

It’s no surprise that as mobile devices grow increasingly entrenched in our everyday lives, email, too, has seen an uptick in mobile usage. More people check their email using mobile devices than ever before, and you can expect those numbers to continue rising.

litmus email market share statsSource: Litmus

As the data shows, mobile accounts for the majority of opens in today’s email marketing. Thus, if you want to maximize the potential of your email marketing campaigns, you need to be optimizing for mobile every single time.

In fact, studies show that a majority of users will simply delete an email if it doesn’t render well.

When in doubt, it’s always a good idea to design for the small screen first. While a simplified and streamlined mobile email will also look beautiful and perform well on a desktop or webmail application, the same can’t be said for emails designed first and foremost for desktop viewing.

Designing for mobile

When you design for mobile, there are a few easy guidelines to keep in mind that won’t require too much of a shift in your email design, especially if you’re already following email design best practices.

In fact, optimizing for mobile is easy.

When optimizing for mobile, design your emails in a single column to avoid making your subscribers pinch and zoom in order to find the information they’re looking for. After all, in today’s marketing landscape, you can assume your subscribers won’t go looking for anything. Instead, they’ll simply delete an email that isn’t easy to scroll and digest at a glance.

Likewise, your calls-to-action should be large and tappable. Apple suggests making any buttons at least 44 pixels: the approximate size of a human fingertip. Again, everyone knows how frustrating it is when you can’t quite tap the link you’re trying to follow. By making your CTAs bold, you ensure your subscribers won’t have anything impeding their ability to follow through on your email.

Speaking of bold, feature graphics and images that are big and bold. Bold images are much easier to see at a glance. Remember, your subscribers are on the go and every bit of your message should be understandable with even the quickest of glances.

When optimizing for mobile, simplicity is the name of the game: You don’t want to overwhelm your subscribers or make them pinch and zoom in order to see and access your emails.

Because you can be sure that if your email isn’t easy to view and read on a smartphone, it won’t get a second chance to impress. Instead, emails that render poorly on mobile will be ignored, deleted, or even worse, marked as spam.

When optimizing for mobile, simplicity is the name of the game.
Chapter 5

How email clients affect your email marketing

But why does this all matter? Because if you know what email client the majority of your subscribers are using, you can optimize your emails for that specific client. This will help you provide an even better user experience and make improving engagement such as open rates, click-through rates, and conversions as easy as possible for you.

Here are a few aspects of your email that will be affected directly by your users’ email clients:

  • The optimal length of subject lines.
  • Spam filters
  • HTML capabilities
  • Images

If you’re starting to panic, don’t worry. There are a few simple steps to take when designing a campaign that will ensure your emails provide a great user experience across all email clients, regardless of the limitations.

1. Include a link to view your email as a webpage.

Because email clients support different HTML capabilities, you should always include a link to view the email in browser as a part of your email header. That way, if a subscriber opens an email and it’s obviously not rendering correctly, the option to view as a webpage is right there, obvious and easy to click in the header.

Remember, your subscribers won’t look far and they won’t look for long if the email isn’t appearing in their inbox the way it should. By making it easy for them to view in their browser, you’re capitalizing on the interest that made them open your email in the first place while you have the chance.

And you know that the email you sweated over will render correctly in their browser.

2. Include alt text for all your images.

Some email clients automatically block images in email because of spammers’ tendency to use images maliciously. Including alt text means that even if they can’t see the image, they know what’s supposed to be there. This alt text proves that your images aren’t spam and can spark your subscribers’ curiosity and encourage them to view your email in their browser or turn on images in their inbox.

Alt text is also an important part of designing your emails for accessibility. Alt text allows software to read an image instead of relying on your subscriber’s ability to view the image on their own. Additionally, as technology like Amazon’s Alexa and Google Home becomes more prevalent, ensuring your emails can be read will be even more crucial to the success of email marketing.

3. Include a preheader.

A preheader is the short summary after the subject line when an email is viewed in your subscriber’s inbox. Each email client shows a certain amount of characters in the preheader and will cut off the rest. Knowing these limits and setting your preheader for the one that makes the most sense for your subscriber list means you won’t be surprised when you lose half your preheader.

4. Create a plain text version of your email.

Lastly, a plain text version of your email will always display correctly, regardless of your subscribers’ email clients. Some people don’t want all the bells and whistles of HTML emails and will prefer to skim the plain text version instead.

Having a plain text version of your email also signals to spam filters that you’re a trustworthy sender and help you avoid getting caught by spam filters.

Be sure to test your emails before you send and you can rest assured that your emails will perform the way you designed them to in every inbox.

Chapter 6

Testing email clients using Campaign Monitor

At Campaign Monitor, we want to help marketers conquer send fear; that sometimes debilitating fear that takes over just before we send an email because we fear something won’t work.

To ensure your email will look awesome in every email client and on every device, we have  the Inbox Preview feature.

Campaign Monitor - Test Your Email Campaign

Inbox Preview will show you exactly how your email will look in 30 of the most popular web, desktop, and mobile email clients.

Inbox Preview will also run a complete spam filter and firewall test and instead of just scanning your content for “spammy words”, Inbox Preview will pass your email through real spam filters and firewalls, then give you full details on the outcome. Then you can rest assured that your email will fabulous in inboxes everywhere.

Chapter 7

Wrap up

Now that you know the most popular email clients, you can plan and optimize your emails accordingly. Expect to see a boost in opens, click-throughs, and even in revenue after your next send.

The whole reason email is successful as a marketing channel is because it’s a direct line to your subscribers, and they’ve asked to hear from you. This makes converting easy for your most loyal customers and fans. By optimizing your emails specifically for their email client, you’re removing one more barrier that might stop them from converting.

Optimizing your emails for the various popular email clients has the power to improve your results and drive in even more revenue, giving you the best results from a campaign you’ve seen yet. Though it might seem like more effort up front, the increase in returns will make the few extra minutes you spend on an email campaign well worth it.

Be sure that you always test your emails before you push send in order to feel confident your campaigns will perform and receive maximum attention from your subscribers. Then, regardless of which email clients your subscribers use, your email marketing campaigns will yield the kind of results you’ve heard other marketers rave about.

Your email marketing campaigns can yield the kind of results marketers rave about.
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