How to organize an email newsletter in PHP (theoretical aspects are needed)?

Question

Email

In general, I learned from the hoster the limit. No more than 1000 messages per hour. I ask experienced people for advice on how to organize a mailing list, specifically how many letters to send at a time, what intervals to maintain between sending each, between approaches so as not to be blacklisted as a spammer?
The following types of mailings are planned:
Congratulations to users on their birthday
Notification of a new comment
Notification of a release (to all users)
Important news (to all users)
About 3000 customers

Answer 1

https://habrahabr.ru/post/114852/
even more reliable - mandrillapp & mailchimp