A Practical Study of E-mail Communication through SMTP

Simple Mail Transfer Protocol (SMTP) is an application layer protocol for e-mail communication. It has been adopted as a standard by Internet Engineering Task Force (IETF). SMTP has set conversational and grammatical rules for exchanging messages between connected computers. It has evolved through several revisions and extensions since its formation by Jon Postel in 1981. In SMTP, the sender establishes a full-duplex transmission channel with a receiver. The receiver may be either the ultimate destination or an intermediate forwarding agent. SMTP commands are issued by the sender and are sent to the receiver, which responds to these commands through codes. Each SMTP session between the sender and the receiver consists of three phases namely: connection establishment, mail transactions and connection termination. This paper describes and illustrates the process of e-mail communication through SMTP by issuing the individual SMTP commands directly to transmit e-mail messages. It also describes individual SMTP commands and extensions with practical implementation using a Telnet client

Secure Channel Injection and Anonymous Proofs of Account Ownership

We introduce secure channel injection (SCI) protocols, which allow one party to insert a private message into another party\u27s encrypted communications. We construct an efficient SCI protocol for communications delivered over TLS, and use it to realize anonymous proofs of account ownership for SMTP servers. This allows [email protected] to prove ownership of some email address @mail.com, without revealing ``alice\u27\u27 to the verifier. We show experimentally that our system works with standard email server implementations as well as Gmail. We go on to extend our basic SCI protocol to realize a ``blind\u27\u27 certificate authority: the account holder can obtain a valid X.509 certificate binding [email protected] to her public key, if it can prove ownership of some email address @mail.com. The authority never learns which email account is used

Network congestion control at the application layer

Application-layer protocols play a special role in network programming. Typical programmers are more familiar with them and more likely to implement them. Well-designed application-layer proto-cols follow many patterns that improve the performance of applications using these protocols. We present a subset of these patterns that focuses on the congestion control at the application layer