A system may include an electronic messaging system that may access user identifier information, which may be used to identify self-addressed electronic messages. The electronic messaging system may determine how to process an incoming electronic message using at least a portion of the user identifier information. The electronic messaging system determines whether to send a challenge-response message to a sender of an electronic message using at least a portion of the user identifier information. The electronic messaging system may be configured to identify self-addressed electronic messages and, in response to such identification, process the messages appropriately.