If you are using WordPress it is easy to change the padding based on the width of the screen.

Add the following CSS code below the the CSS part of the customize area.

@media (max-width:1200px) {/below 1200/.wpcf7-form{padding:15px}}

@media (min-width:1200px) {/above 1200/.wpcf7-form{padding:0px}}

This first line of code will add 15 pixels of padding when the email form is smaller than 1,200 pixels. The second line of code will set the padding to 0 pixels when the screen is more than 1,200 pixels in width.