Responsive / Dynamic graphic in email or constrain email text below header graphic?

Hello,

I'd like to create a responsive graphic in my email or constrain the email's body to within the header graphic's vertical borders. Currently, the header graphic is centered in the email but the text flows across the entire page. I'd like to improve the aesthetics.

Reference image attached. I tried to post the html, but it was too long.

Thanks,
Joe

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