Building an HTML email with a responsive design and style as close as what we can see from a browser, requires imagining we're a 90's programmer: more use of tables against divs, inline styles, no background or svg images, hyperlinks that are rendered as links... and many other exceptions we have to control for each client.
With this mail template example, we have a reference of something that looks consistent in all these clients: Outlook 2007; Outlook 2010; Outlook 2013; Outlook 2016 for Mac; AOL Mail (IE); AOL Mail (Firefox); GMail (Android); GMail (Chrome); GMail (IE); GMail (Firefox); Outlook.com (Firefox); Yahoo! Mail (IE); Yahoo! Mail (Firefox); Android 4; iPad (Retina); iPad Mini; iPhone 5S; iPhone 5S (IOS 8); iPhone 6; iPhone 6 Plus.
Worth to check: