Add a field in the Setup page of suppliers just like the "Booking email" line, but for the email address that should receive payment confirmation. Then, in the Payments section of each itinerary, have the option to send an email to that address to indicate that a payment has been made. Many suppliers in Brazil ask for payment confirmation. This would save a lot of time sending emails manually. This could just be an additional email template within the bookings page called "payment sent/processed/made", for example.