The Airbnb email address isn't overly helpful, especially when you use software like Uplisting who can send messages on your behalf natively through the Airbnb inbox. The email alias isn't the real guest email and expires at some point after the guest checks out.

How to sync the Airbnb email alias to Uplisting

However, if you want to collect the Airbnb email alias, enable it here on Airbnb..

Will existing Airbnb bookings on Uplisting get updated to include the email alias?

No, this setting will only apply to bookings created since you enable the setting on Airbnb.

How to disable syncing of the Airbnb email alias to Uplisting

If you don't want to sync the Airbnb email alias from Airbnb to Uplisting, disable the toggle on Airbnb.