Abstract: Opt-out systems and methods for tailored advertising are disclosed herein. An example method includes registering an endpoint with a service provider hosting an opt-out service that allows users to opt-out of tailored advertising from the endpoint, receiving a first request from a user including an email address, generating a hashed representation of the email address according to a hashing algorithm selected for the endpoint, transmitting a second request to the endpoint, the second request including the hashed representation of the email address, and receiving an acknowledgment that the endpoint has processed the second request. When the second request is processed the user does not receive the tailored advertising from the endpoint.