I use an external email design tool to create responsive email notification messages. I have also configured a function to disable the normal editor in notifications by conditionally calling
add_filter('user_can_richedit', '__return_false'); This keeps the regular editor from kindly rewriting my code.
Obviously, I don’t need or want JS in the email. I’ve eliminated other plugins, and my own code I think. Any ideas on how to prevent this from being inserted?