What is a public email group?
A public email group is now available on MS Outlook. This group is public and viewable by a large number of users. The purpose of a contact group (formerly called a “distribution list”) is to send an email to multiple people—a project team, a committee, or even just a group of friends—without having to add each name each time you want to write them. (Source: Microsoft)
For more info on how it works and how to make a group visit: Microsoft Help Article
There is also a group scheduling feature.