Sams Teach Yourself J2EE™ in 21 Days, Second Edition

Understanding Email

Email is something that most of us take for granted, without ever really stopping to wonder how it works. If you want to write applications that send and receive email messages, it is essential to have some understanding of a typical email system environment.

Email messages are sent on a client/server basis, but one that is different from that used for Web pages. Figure 11.1 shows a typical email delivery process. The sender creates a message and forwards this to an email server. The server then uses the Simple Mail Transfer Protocol (SMTP) to send the message across the Internet to the recipient's mail box on another email server. The receiver then uses a retrieval protocol, such as Post Office Protocol (POP3) or Internet ...