Email formatting

Hello, I have a question about the email formatting. My site uses the “WP HTML Mail” plugin to format emails, making the header and footer added by Wait List redundant. The resulting email is awkwardly formatted. Here’s a screenshot:

https://www.outlandequipment.com/images/2017-11-11_email_screenshot.png

Is there a way to fix this? Also, is there a way to fix the shape of the By Now button?

Thanks,
Chris

The page I need help with: [log in to see the link]