I’ve readed a few forum post of old and beta versions plugin to create/send emails from Kirby but I could not find a solution.
What I want to do is to send automatic newsletter using the content of the site for instance last posts of a blog or similar.
I will really appreciate your help, best.
What do you mean with automatic newsletter? Trigger it automatically whenever a new post is published?
If you want to send newsletters from your own server, you have to at least use PHPMailer. But maybe you want to consider using a mailing service like Campaignmonitor, Mailjet etc. that also handle your mailing lists in a GDPR compliant way.
There’s a plugin for Mailjet: https://github.com/bnomei/kirby-mailjet