Disclosed are systems and methods that facilitate securing communication channels used in a challenge-response system to mitigate spammer intrusion or deception. The systems and methods make use of unique IDs that can be added to outbound messages originating from a sender, a recipient, and a third-party server. The IDs can be correlated according to the relevant parties. Thus, for example, a sender can add a signed ID to an outgoing message. A challenge sent back to the sender for that particular message can echo the same ID or a new ID derived from the original ID to allow a sender to verify that the challenge corresponds to an actual message. The IDs can include cookies as well to facilitate correlation of messages and to facilitate the retrieval of messages once a sender is determined to be legitimate.