Best Practice For HTML Email - ResponsiveCoding

There are a few things to keep always in mind when designing a Responsive HTML Email Template:

Emails width should be within 600 pixels. This will make them behave better within the preview-pane size provided by many clients.
Avoid elements that require Flash or JavaScript. If you need motion in an email, a .gif is your best bet.
If it is possible to avoid background images, then it is good. Because some email clients will be initially blocked and some email clients will completely fail to load.
Email design is not Web Design. Don’t design an email with a sliced-up image. While these kinds of emails look pretty, they perform poorly.
Use basic, cross-platform fonts such as Arial, Verdana, Georgia, and Times New Roman.
For mobile screens use a big call to action button.

Best Practice for Email Design and Html Email.