Foundations of Python Network Programming, Third Edition

CHAPTER 13

SMTP

As outlined at the beginning of Chapter 12, the actual movement of e-mail between systems is accomplished through SMTP, the Simple Mail Transport Protocol. It was first defined in 1982 in RFC 821; the most recent RFC defining of SMTP is RFC 5321. The protocol typically serves two roles:

1. When a user types an e-mail message on a laptop or desktop machine, the e-mail client uses SMTP to submit the e-mail to a server that can send it along to its destination.
2. E-mail servers themselves use SMTP to deliver messages, sending each message across the Internet from one server to another until it reaches the server in charge of the recipient’s ...