ABSTRACT
Email is one of the earliest network applications and one of the first to gain widespread use on the Internet [1-4]. The early email systems were proprietary and did not interoperate with other email systems. They used simple programs to create, send, and read short text messages and not support attachments. An email was sent through a series of servers that stored and forwarded the email as it traversed the network. The email server was used to send the outgoing email to the next server and received and stored the inbound email destined for the users. The users logged into the same computer that ran the email server. The demands on the functions and services offered by the email system grew over time, and today several protocols are involved to create the modern email system. As the email protocols have evolved, so have the vulnerabilities and attacks against email. Figure 9.1 shows the protocols involved to create, send, receive, and read email [5-7].
