Where can I learn how to make scripts myself, etc. to send letters?

Question

SMTP

Maybe the essence of the question is not clear, but still.
I know that craftsmen do not use services such as unisender, getresponse, etc. to send letters.
They send from their own computer or from dedicated servers. I would also like to do. But I don't know what it's called. Maybe someone will throw a couple of articles or lessons that will tell you how to do this.

Answer 1

in DOSAAF
or in Python / Go

Answer 2

For this, you need an application that will send out and an SMTP server to send. The structure of the mailer program is described in more detail in this article: https://www.unisender.com/en/blog/idei/servis-tran...