You can find the trip-specific email address in two places now:
1. When adding flights:
In the itinerary builder, click on +New Event, then Flights and you will see the option to view the "Booking Confirmation". Click there and the email will be exposed.
2. When adding lodging:
In the itinerary builder, click on the +New Event button, then Lodging and you will see the option to send booking confirmation emails.