When private messaging is available for your event and role, unread badges help attendees, speakers and sponsors find messages they have not read. Look for the badge on the event account menu and its Messages item, then open the inbox to view conversations.
HeySummit normally checks an unread private message for an email reminder after about five minutes. Before sending, it checks that the message and conversation still exist and that the message remains unread. A reminder also depends on an eligible recipient and the event's email and delivery settings. It is a backup notification, not a guarantee of delivery exactly five minutes later.