@media and viewport for mobile-friendly HTML email campaigns

To make your email mobile-friendly do this:

1. Viewport meta tag
Add this to resize the page to fit the desired viewport. The width should reflect the size of your content. My standard emails are 600px wide.

<meta name = "viewport" content = "width = 600">

2. Use media queries to modify page layout and font sizes
I like to use font-size:17px for iOS.

@media only screen and (max-device-width: 480px) {
    .pconly { display:none!important; }
    p{
      font-size:30px!important;
    }
}