How do I get emails about core update? I'm not talking about updates within your site, I'm talking about waking up in the morning, checking your email and seeing an email sent to you from Drupal.org that new core version is out.

7.58 critical update just came out and I found out about it from a buddy.

I clicked follow at https://www.drupal.org/project/drupal but I get no email notification about any core versions coming out. I get only notifications for module issues that I'm subscribed to, I expected the same when clicking Follow in the modules page.
Log in on your drupal.org account (or create one)
Go to My Account > Edit > My Newsletters (https://www.drupal.org/user/[uid]/edit/newsletter where [uid] is your user ID)
Check "Security announcements" and click "Save"