How to setup css for writing in DRUPAL8?

Question

Drupal

I am using SwiftMailer and mailsystem modules to send emails programmatically in HTML format in DRUPAL8.
How do I style an email and pass css to the email?
For example, I send a blabla, but I receive the following in a letter: blabla.
The NotificationText itself is described in the css of the site.

Answer 1

It's not entirely clear what your problem is. But I think it will be useful for you to read more about the layout of letters in general https://habrahabr.ru/post/252279/. Because CSS styles in emails are written inline.