I have an email template (HTML) that I use to send emails to myself from my project. However, some CSS classes get blocked, and the email format doesn’t seem correct.

When I click “See all the message,” it opens a new page. On that page, I right-click and select Ctrl+U (View Source), but I don’t see my CSS classes and styles. However, if I click the three dots in the email and then choose “See original text,” I can see my CSS classes. Why is this happening?
My css class like
@ media only screen and ..