According to certain embodiments, a method receives a certificate that identifies a sender system as owning a domain. The method sends an electronic message to the domain identified in the certificate. The electronic message is sent via a mail exchange network that correlates the domain to an address that a true owner of the domain has registered with a mail exchange authority. The method receives a response from the address that the mail exchange network correlates to the domain. The response indicates that the certificate is associated with the true owner of the domain. The method authenticates the sender system as the true owner of the domain based on the response.