How to set up a mail server so that letters do not fall into spam?

Question

JavaScript

How to set up a mail server on ISPManager. I am sending emails via SwiftMailer in DRUPAL8.
Here's what happens now:

www.mail-tester.com gives errors:

But in theory everything is set up. Or I don't understand something. It seems that all the settings are not picked up ...

Answer 1

In short:
1. The prepared image is simply substituted into the final image, depending on the change in parameters, in this case, on the number of axes. In another example, the image disappears because the right one is missing
2. Each browser caches included styles and js scripts so as not to load them every time the page is reloaded. Accordingly, when making changes to a js script or css file with the name saved, the browser will assume that this is the same file, will not download it, but will take the old one from the cache. In order to get around this moment, when connecting, the parameter - "salt" is added through the question mark. In this case v=4. The browser considers that the request to the file has changed and pumps it out taking into account the new parameter.
3. MathJax is responsible for drawing mathematical formulas, this library has nothing to do with arrows. The arrows are drawn in script.min.js
4. To make sure you don't style your page, wrap the html block in a unique class. And in the included css for each selector, add this class as a parent. If you use CSS preprocessors, then this is done very quickly.