> Just send a confirmation email to whatever string they provide you. You might want to first check that it is not a local address, and to reject it if it is (

> Just send a confirmation email to whatever string they provide you. You might want to first check that it is not a local address, and to reject it if it is (unless it is being used for an internal registration service). You should also reject it if the destination is unreachable (in which case it is not possible to send a confirmation email, anyways).