In our HTML tips and recommendations for building your mailings from scratch, we've noted code that renders (or does not render) in the majority of email programs and browsers. We can't vouch for some mail programs and browsers that are outdated and/or do not have the capability to handle sophisticated HTML. However, here's a list of supported programs and browsers for which we have the most info.
Supported: AOL, Gmail, Hotmail, Yahoo
Not supported: Eudora
Supported: Entourage 2004, Entourage 2008, Live Mail, Mac Mail, Outlook 2003, 2007, 2010 & 2011, Thunderbird 2 & 3, Lotus 8 & 8.5
Not supported: AOL Desktop, Lotus 6, Lotus 6.5, Lotus 7, Outlook Express, Outlook 2000 and prior
Every email program out there interprets HTML code a little bit differently, and Outlook is no exception. However, there are a handful of specific limitations with Outlook 2007 & 2010. Those limitations won't have too much bearing on your mailings, as long as you take a few measures to optimize your mailings. For example, animated gifs are not supported by Outlook, and background images are only partially supported. Outlook also replaces bullets with images in unordered lists and ignores <p> and <div> padding. Keep these limitations in mind when designing your campaigns, and read more in our handy online guide.
The good news is that Microsoft Office 2011 (which is Mac-only) moved away from the Microsoft Word rendering engine and on to Apple's Webkit rendering engine. This results in more compatible rendering with the other major email clients for anyone using Microsoft 2011.
However, Office 2013 has the same limitations as 2010 and uses Word instead of Webkit.
Outlook handles HTML pixel values differently with higher DPI settings, so when DPI scaling is enabled, Outlook can render font sizes out of proportion compared to the rest of the email. Images and other various layout elements may appear squished or incorrectly rendered. Because enabling desktop DPI scaling is a setting controlled on the recipient’s end, we don’t currently support an Outlook environment with that activated.
Supported: Android 2.2, Blackberry (with Webkit), Android Gmail 2.2, iPad and iPhone 3.0, iPad and iPhone Gmail
Not supported: Blackberry (pre Webkit)*, Symbian
* New Blackberry smartphones are built on Webkit technology and support HTML quite well. However, older versions of the Blackberry do not handle robust HTML.
Supported: Mozilla Firefox, Safari, Chrome, Internet Explorer 10 or later
Not supported: Camino, Internet Explorer 6, 7, 8 and 9, Opera, Seamonkey