How does sendex work in modx for specific news?

Question

MODX

Please tell me:
I inherited a site on modx. Sendex is screwed on it.
How to create and launch mailing lists manually is understandable.
The question is different:
There is a news category, when you create a news item and set the corresponding checkbox (TV field), the notification to subscribers goes according to the mailing list settings. That is, you do not need to manually start the mailing list, it starts immediately after the news is created (pressing the "Save" button).
And there is a Sendex letter template.
For example, there is the text "News published at mysite.ru?newsid=123 "
After creating the news, the template text automatically changes to "News published at mysite.ru?newsid=345 "
(345 - id of the most recent news)
How would I find out where sendex is linked to materials from the "News" category?