This is an email sent by apple, on an apple device using dark mode. It’s a great example of what can happen when you don’t anticipate how your content will be consumed.
The email is unreadable, and it looks like a spam email. Currently the main email providers allow you to preview your email in most browsers and email clients, but they don’t let preview in dark mode yet.
Surely this will come, but until them]n, it’s worth making sure you consider your file types, fonts and images and how they appear in a dark mode device.