A discovery secret is transmitted from the source domain to the correspondent domain. The discovery secret includes a data element specific to the correspondent domain and. The discovery secret includes a source domain address to which the correspondent domain is permitted send a message in order to determine that a potential correspondent has compatible secure email technology so that a link between the source domain and the correspondent domain may be established. The discovery secret is received by the correspondent domain including receiving the data element and the source domain address. An invitation is transmitted from the correspondent domain to the source domain address. The invitation includes the data element or an element corresponding to the data element. The source domain initiates a process to establish a link with the correspondent domain upon receipt by the source domain of the invitation.