Nowadays, e-mail has become one of the most widely used communication medium. Because of its characteristics of inexpensivity and rapidity in the delivery of messages, e-mail is increasingly used in place of ordinary mail. However, the e-mail service exposes users to several risks related to the lack of security during the message exchange. Furthermore, regular mail offers services which are usually not provided by e-mail, and which are of crucial importance for “official” events.
Certified e-mail tries to provide users with additional guarantees on the content and the delivery of the messages, making e-mail equivalent and in some cases more convenient than the ordinary paper-based mail service. In literature, several distributed protocols for certified e-mail have been proposed, relying on an inline trusted third party to ensure the fairness of the protocol. In such protocols, the is actively involved in each message exchange. In this paper we provide a novel inline certified e-mail protocol which satisfies all the most important requirements which have been discussed for certified e-mail. Furthermore, we discuss a prototype implementation of our protocol targeted to the Windows platform.