Airbnb does not make guests' real emails available at all. You cannot see them in your Airbnb control panel yourself, so Channel Bridge cannot get them either.
What is available, is a proxy email address via Airbnb that they will forward to the guest. Once a booking has been made, this email is not filtered and any email can be sent to it, and it'll make it to the guest. After the booking is finished, the proxy email is disabled and won't work anymore.
Here's how to set up OwnerRez to send an automatic email to your Airbnb guests, to get their real email address:
https://www.ownerrez.com/support/articles/airbnb-request-for-contact-info-real-email-address-and-signed-renter-agreement
