Designing an HTML email that renders consistently across the major email clients can be very time consuming. Support for even simple CSS varies considerably between clients, and even different versions of the same client.
We've put together this guide to save you the time and frustration of figuring it out for yourself. With 24 different email clients tested, we cover all the popular applications across desktop, web and mobile email.
As the number of email clients continues to grow, we’ve decided to simplify the web-based version of the guide to focus on the 10 most popular email clients on the market. For the complete report on all 24 email clients across the desktop, web and mobile email world, download the complete guide in PDF format.
| Style Element | Outlook 2007/10/13 + | Outlook 2000/03 | Apple iPhone/iPad | Outlook.com | Apple Mail 4 | Yahoo! Mail Beta | Google Gmail | Android 2.3 (Gmail) + |
| Style Element | Outlook 2007/10/13 + | Outlook 2000/03 | Apple iPhone/iPad | Outlook.com | Apple Mail 4 | Yahoo! Mail Beta | Google Gmail | Android 2.3 (Gmail) + |
| <style> in <head> | Yes | Yes | Yes | Yes | Yes | Yes | No | No |
| <style> in <body> | Yes | Yes | Yes | Yes | Yes | Yes | No | No |
| <link> in <head> | Yes | Yes | Yes | No | Yes | No | No | No |
| <link> in <body> | Yes | Yes | Yes | No | Yes | No | No | No |
| Selectors | ||||||||
| * | No | Yes | Yes | No | Yes | No | No | No |
| E | Yes | Yes | Yes | Yes | Yes | Yes | No | No |
| E[foo] | No | No | Yes | No | Yes | No | No | No |
| E[foo="bar"] | No | Yes | Yes | No | Yes | No | No | No |
| E[foo~="bar"] | No | Yes | Yes | No | Yes | No | No | No |
| E[foo^="bar"] | No | Yes | Yes | No | Yes | No | No | No |
| E[foo$="bar"] | No | Yes | Yes | No | Yes | No | No | No |
| E[foo*="bar"] | No | Yes | Yes | No | Yes | No | No | No |
| E:nth-child(n) | No | No | Yes | No | Yes | No | No | No |
| E:nth-last-child(n) | No | No | Yes | No | Yes | No | No | No |
| E:nth-of-type(n) | No | No | Yes | No | Yes | No | No | No |
| E:nth-last-of-type(n) | No | No | Yes | No | Yes | No | No | No |
| E:first-child | No | Yes | Yes | No | Yes | No | No | No |
| E:last-child | No | No | Yes | No | Yes | No | No | No |
| E:first-of-type | No | No | Yes | No | Yes | No | No | No |
| E:last-of-type | No | No | Yes | No | Yes | No | No | No |
| E:empty | No | No | Yes | No | Yes | No | No | No |
| E:link | Yes | Yes | Yes | Yes | Yes | Info | No | No |
| E:visited | Yes | No | Yes | Yes | No | Info | No | No |
| E:active | No | Yes | No | Yes | Yes | Yes | No | No |
| E:hover | No | Yes | No | Yes | Yes | Yes | No | No |
| E:focus | No | No | Yes | No | Yes | No | No | No |
| E:target | No | No | No | No | No | No | No | No |
| E::first-line | No | Yes | Yes | No | Yes | Yes | No | No |
| E::first-letter | No | Yes | Yes | No | Yes | Yes | No | No |
| E::before | No | No | Yes | No | Yes | No | No | No |
| E::after | No | No | Yes | No | Yes | No | No | No |
| E.classname | Yes | Yes | Yes | Yes | Yes | Yes | Info | No |
| E#id | Yes | Yes | Yes | No | Yes | Yes | Info | No |
| E:not(s) | No | No | Yes | No | Yes | No | No | No |
| E F | Yes | Yes | Yes | Yes | Yes | Yes | No | No |
| E > F | No | No | Yes | No | Yes | Yes | No | No |
| E + F | No | No | Yes | No | Yes | Yes | No | No |
| E ~ F | No | Yes | Yes | No | Yes | No | No | No |
| Text & Fonts | ||||||||
| direction | No | Yes | Yes | Yes | Yes | Yes | Yes | Yes |
| font | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes |
| font-family | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes |
| font-style | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes |
| font-variant | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes |
| font-size | Yes | Yes | Info | Yes | Yes | Yes | Yes | Yes |
| font-weight | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes |
| letter-spacing | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes |
| line-height | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes |
| text-align | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes |
| text-decoration | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes |
| text-indent | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes |
| text-overflow CSS3 | No | Yes | Yes | Info | Yes | Info | Info | Yes |
| text-shadow CSS3 | No | No | Yes | Yes | Yes | Yes | Yes | Yes |
| text-transform | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes |
| white-space | Yes | No | Yes | Yes | Yes | Yes | Yes | Yes |
| word-spacing | No | Yes | Yes | Yes | Yes | Yes | Yes | Yes |
| word-wrap CSS3 | No | Info | Yes | Yes | Yes | Yes | No | No |
| vertical-align | No | Yes | Yes | Yes | Yes | Yes | Yes | Yes |
| Color & Background | ||||||||
| color | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes |
| background | Info | Yes | Yes | Info | Yes | Yes | Yes | Info |
| background-color | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes |
| background-image | No | Yes | Yes | Info | Yes | Yes | Yes | No |
| background-position | No | Yes | Yes | No | Yes | Yes | No | No |
| background-repeat | No | Yes | Yes | No | Yes | Yes | Info | No |
| HSL Colors CSS3 | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes |
| HSLA Colors CSS3 | No | No | Yes | No | Yes | No | No | No |
| Opacity CSS3 | No | No | Yes | Yes | Yes | No | No | No |
| RGBA Colors CSS3 | No | No | Yes | No | Yes | No | No | No |
| Box Model | ||||||||
| border | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes |
| box-shadow CSS3 | No | No | No | Info | No | No | No | No |
| height | No | Yes | Yes | Yes | Yes | Yes | Yes | Yes |
| margin | Info | Yes | Yes | No | Yes | Yes | Yes | Yes |
| padding | Info | Yes | Yes | Yes | Yes | Yes | Yes | Yes |
| width | Info | Yes | Yes | Yes | Yes | Yes | Yes | Yes |
| max-width | No | No | Yes | No | Yes | Info | Info | Yes |
| min-width | No | No | Yes | No | Yes | Info | Info | Yes |
| Lists | ||||||||
| list-style-image | No | Yes | Yes | No | Yes | Yes | No | No |
| list-style-position | No | Yes | Yes | No | Yes | Yes | No | No |
| list-style-type | No | Yes | Yes | Yes | Yes | Yes | Yes | No |
| Tables | ||||||||
| border-collapse | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes |
| border-spacing | No | No | Yes | Yes | Yes | Yes | Yes | Yes |
| caption-side | No | No | No | Yes | No | Yes | Yes | Yes |
| empty-cells | No | No | Yes | Yes | Yes | Yes | Yes | Yes |
| table-layout | No | Yes | Yes | Yes | Yes | Yes | Yes | Yes |
Outlook.com no longer supports the margin CSS property, including margin-top, margin-right, margin-bottom and margin-left. Float support has also been dropped
Added Outlook 2013 Preview. CSS test results are identical to Outlook 2007 and 2010 - see blog post for details.
background-image is now supported in Gmail.
Added email client results for max-width and min-width - see blog post for details.
Updated guide to CSS in email released. See blog post for details. For complete results for all 24 email clients, download the guide to CSS support in email clients as an Excel spreadsheet.
Updated to reflect margin support in Outlook.com. Also introducing improved support for @media queries and shorthand CSS.
Discuss this on our blog.
Updated the guide with the results of our CSS3 email client tests. 21 new properties were added, with varying levels of support observed across the popular email clients. Notably, Webkit clients were big winners, including Apple Mail, iPhone Mail and soon, the iPad. At this stage, CSS3 is recommended for decorative purposes in email (such as adding text-shadow), due to poor support for layout and box-model properties.
Discuss this on our blog.
Added test results for the just launched MySpace Mail.
Discuss this on our blog.
A complete rewrite of the guide that included 7 new mobile email clients and a focus on the most popular email clients. The web-based version of the guide now features the 10 most popular email clients, while the PDF guide includes all 23 email clients tested.
Discuss this on our blog.
Replaced .Mac results with MobileMe.
Discuss this on our blog.
We increased the number of clients we tested, 21 in total now. Gmail and Outlook 2007 continue to be our primary focus since CSS support continues to be limited.
Positive signs from Microsoft though, Entourage 2008 was released with significantly better CSS support.
Discuss this on the blog
Outlook 2007 was released with less CSS support than Outlook 2003. A major step back for HTML email design.
New Yahoo! mail was released with better support for CSS, a positive sign to say the least! Windows Live Mail replaced Hotmail and mixed some CSS support in the process.
Read the report
This was our original test. We added Windows Live Mail for the first time and ran through tests on Outlook 2003, AOL 9, Lotus Notes and Eudora.