To increase customer engagement, we should sent ACTIONABLE notifications/email to the user to get them on specific results/pages. It could be: If user left the booking flow in btw, send them notifcation to restart booking after where they left. Automated notification/email to the HOST to update their calender, prices, booking-accept etc. Automated notification/email to the PROS- i.e. offers, re-booking, on timely basis. AND MUCH MORE...