A knowledge base article about How to create an "Announcement Only" bConnected List (Google Group) provided by the UC Berkeley IT Service Hub - Knowledge Portal
An "Announcement Only" bConnected List is used for one-way communication between the list manager(s) to the list members. Only managers will be able to send to the list. If a list member tries to send to the list they will receive a bounce-back notification indicating they do not have permission to do so.
1. Set Posting Permissions to "Managers of the Group" only
2. Set Post replies "To the managers of the group" only