Open Gmail app with URL Scheme with HTML body

I know I can open Gmail app from my app using for example this URL googlegmail:///co?subject=Example&body=Something. I want to pass to body HTML code and base64 images to body, but my body is not properly rendered, actually it does not render HTML as I want it. It renders with code something like this: <b>Example</b>. My problem is that if someone does not use Apple Mail, I want to be able to open Gmail or Inbox if user has that installed. Does anyone know if that's possible?