Create a newsletter programmatically

Hello.

Please tell me if it is possible to create a newsletter programmatically?

Let me explain the situation, I have 10000 posts, they are processed by cron. In this cycle of posts I have a date check and if the publication date of the post is 20 day since publication I need to send an email to the author of the post. Can you please tell me if there is any way to start sending the newsletter through php code? Maybe a hook or filter something is or create a newsletter in php