Best courses or learning resources for understanding email IT and also email development?

I'm looking for the best way to learn everything there is to know about how email works.

I'm starting an online business and I have a long list of emails that I have collected. I want to reach out to them in an automated way from my business email. I have a background in programming so I could just make a python script that writes some generic email template to a list of emails but I am not looking to spam anyone or any institute and I feel this is the wrong approach. I would like to learn more about what the best way would be to reach out to these emails without getting blocked or having my business email marked as spam. If anyone has any good advice or resources I'd love to know.