How long does it take to receive a Trenitalia ticket purchased online? I purchased online and expected an email with the PNR and CP. Nothing received after 24 hours.
It should be instant. Source: Italian and booked hundreds of trains (two yesterday).
Anyway, you only need the Booking Code (PNR) in order to board the train and that should also be shown during the last step of the booking process, a page that the Trenitalia site suggests to print.
You can also log in and go in the customer area. At the bottom of the page there should be the list of all your bookings where you can check all the details by clicking on Action -> Solution Details.