How to implement the Notification in Message Notify

It is not clear to me how to to implement the sending of the notification. I have Message Notify enabled on an Organic Groups site. I also have the OG Message Example module enabled. However, although a message is in fact being created on the creation of new group content, no notification to the group is being sent. Is there a setting on the message type which needs to be implemented. I also have Message Subscribe enabled and the users are subscribed.

After reading the documentation, I understand that a plugin can rely on the Rules module, but does not have to, and that the Message Notify module will send a notification to the group without the Rules module. Is that correct?

Thank you for any help,