We have an Exchange 2013 multitenant installation for our customers. We use address book policy for the isolation through website panel . A customer A move his domain to our infastructure but he is not started to use it yet.He is using his mail server until finish decomision . Another customer B in our Exchange infastructure wants to send email to customer A but the problem is that email from customer A stays inside our Exchange because the mail users exist in Exchange. How i can bypass this so the emails go to the email server of the customer in his premise installation ?