1. In a server included in an electronic messaging system capable of receiving challenge messages, a method of determining whether a challenge message should be delivered to an intended recipient's inbox comprising: receiving a challenge message; analyzing the challenge message to identify whether the challenge message contains a federated token; determining at least one of whether the federated token is authentic and whether the federated token is valid; and delivering the challenge message to an intended recipient's inbox upon determining that the federated token is at least one of authentic and valid.