Where a large list of people are sent the same or very similar emails from a source to which they’ve intentionally subscribed (like a newsletter, or an event invitation) is called One to many bulk mailing.
One-to-Many emails have been a staple of electronic marketing since the early days of the web. They’ve been an optimal way to market to millions of people at a lower cost than print or other types of media like television and radio. Since HTML email marketing is generally interest driven, the audience to which you’re sending is already receptive. Email evolved with the explosion of social media to include more focused subjects and audiences, allowing “one-to-many” to actually be personal, despite large audiences.