how to debug html rendering issue on Apple mail client

We are facing few HTML/CSS issues on rendering our HTML email on Apple mail client on iPhones

Is there a way one can inspect and debug the issue?

Does Apple provide any emulator/tool to do the same?

What worked for us is Epiphany browser. It mimicked the restricted ability of Apple mail client to render HTML far more closely than any of the solutions below -

• google chrome, firefox, safari in responsive design mode

Someone suggested to try emulator in XCode but I couldn't get hold of Apple mail in Xcode -> Window -> Devices and Simulators