In this lesson, we create a Chatter Group and add users to the Group. We create an Announcement via the Announcement Chatter Publisher action. We also share a post and pin it at the top of the Group page. We round things out by reviewing the Engagement tab and the various group analytics that it provides.
Allow Users to post to Chatter groups via email Knowledge Article 000333298 - https://help.salesforce.com/articleView?id=000333298&type=1&mode=1