By what means is mailing to users (notifications) done?

Question

Ruby on Rails

On the forum, Vasya replied to Petya's comment. Petya and everyone who subscribed to the post - you need to send a notification. I don't understand how to organize it. If you solve the problem head-on, it turns out that the mailer needs to call send_notification and send a letter. But damn it, then it turns out that a hundred or two letters will go through the mailer and, theoretically, it can be regarded as spam (I don’t know, I just assume, I use Yandex mail for the domain).
It seems to me that there should be services where you send a list of mailboxes and a letter or something like that, and they already send it out. Or, as an option, some separate app that only sends out. Or how? Maybe there is some kind of pattern or an article or just best practices?
Thanks

Answer 1

Sending emails in RoR is done using ActionMailer ( manual in English ).
Services like Mailgun, SendGrid , etc. allow you to do mass mailings.
On the websites of these services, you can read about the best practices in the mailing list.