Admins can make announcements that reach everyone in the group. They are integrated with email. All members receive a notification in Heylo, a push notification, and an email notification. Recipients include both active and inactive members - essentially, anyone who signed up for the group.
To make an announcement, select "@announce" in any event chat or topic chat message.
Or, use the announcement topic. This special topic is always pinned to the top of the topics screen and visible to everyone in the group at all times.
Emails are sent to any members who have signed up for the group, as well as any members invited to the group by email.