We tested these email clients using internal test tools and known email preview services as Email On Acid and Litmus.
All the options work properly. Fallback elements show for image backgrounds and web fonts.
Apple Mail 8, 9 & 10
Microsoft Outlook 2007, 2010, 2011, 2013, 2016
Windows 10 Mail
Gmail App (Android & iOS)
Inbox by Gmail
Partial support for some options
Messages display correctly, but some options (with low impact) may not display as expected.
Microsoft Outlook 2007, 2010, 2013 - Borders are not fully supported
Android 4.4 to 6.0 default email application (this is not Gmail) - Columns don't expand to cover 100% of the available width
Office 365 - Borders are not fully supported
Outlook.com - Borders are not fully supported
Only basic settings works
When sending to this clients, we recommend using text and images in a simple one-column layout.
Lotus Notes 7, 8 & 8.5
IBM Notes 9
Outlook 2000, 2002 & 2003