Email addresses on bookings from Booking.com are strange.
Recently Booking.com has changed the way email addresses are processed.
Bookings downloaded through MyAllocator from Booking.com will contain masked guest email addresses. This is a planned feature, and Booking.com already notified all properties regarding the change via email. When viewing these bookings in MyAllocator, only this anonymous, temporary email address displays. Old bookings are not affected.
You can contact the guest with this temporary email address.
If you have any additional questions regarding this please contact your account manager at Booking.com.