Powerapp Button Onselect Opens Outlook, with formatted body

[mcnemare1]

I am working on an app that will generate an email pre-selected URL with trackers. The idea is that the email will be generated in the end-user's outlook, so they can add recipients from their address book. Ideally this email will have custom HTML formatting.

I followed this guide:

https://www.youtube.com/watch?v=GoF3vfP3YTM&t=1098s

here is an overview of the details section of the app:

Currently I cannot get an email to generate with the HTML I keep getting the below error:

Any advice or assistance would be greatly appreciated.