Email clients are not web browsers, but are very similar and are usually built on a browser’s engine. That’s why if we want to understand, the different behaviors of email clients, we need to explore the history of technologies, browsers and email clients together.

There are thousands of email clients out there since email is almost as old as the Internet itself. In this article we only focus on the most significant ones.

Click on the image for higher resolution

You can see the browser and the technology achievements in the background – original illustration from ‘Evolution of the Web‘ at – and the most famous email clients in the foreground. We hope that this illustration helps you to understand the relationship between browsers and email clients.

In most cases new email clients appeared after new browser versions, since they are always based on the related browsers’ HTML/CSS parsing and rendering engine.

The big old players still dominate the email client market, but we have to admit, there are lot of new and fancy email clients emerging from time to time (like Mailbox), but none of them reached the critical mass to get on the map.

The biggest pain for email coders is that the the most popular email clients are stuck in the past:
– The Microsoft Outlook 2013 uses the old and messy Microsoft Word HTML/CSS parser, that is even worse than Internet Explorer 6.
Gmail still ignores nearly all new generation CSS properties, style tags and media queries as well.
– is pretty good in supporting things, but for some strange reason it forces a margin-bottom on all paragraph element. (Luckily there is an existing solution to hack it back to normal)

If you want to dig deeper into the dirty background of email clients, check out the Email Standards Project. We would love to see a world where email clients behave like modern web browsers, but unfortunately it only seems to be a nice dream. No worries, we will stick around and help you make the most out of email.

Feel free to use EDMdesigner even for free and reach out to us if you need any help in responsive email design / coding!

Gergely Mecs

Gergely Mecs

Chief Frontend Developer @

  • A Step-by-Step Guide to Sending Emails with PHP A Step-by-Step Guide to Sending Emails with PHP

    In this comprehensive guide you will learn the ins and outs of sending text and HTML emails with built-in packages and email delivery services using PHP.

    Read more
  • How to Use a Templating Language in HTML Email Development How to Use a Templating Language in HTML Email Development

    Shorten your development time with templating languages. EJS and the new JavaScript ES6 template strings can reduce the pain of responsive email coding.

    Read more
  • CSS Inliner Tools Worth Considering for Your Next Email CSS Inliner Tools Worth Considering for Your Next Email

    I hope you have never tried inlining CSS to your email code manually. Thankfully there are several CSS inliner tools. Check out their pros and cons.

    Read more