In this chapter, we will consider the protocol responsible for delivering email on the internet. This protocol is called the Simple Mail Transfer Protocol (SMTP).

Following an exposition of the inner workings of email transfer, we will build a simple SMTP client capable of sending short emails.

The following topics are covered in this chapter:

• How SMTP servers work
• Determining which mail server is responsible for a given domain
• Using SMTP
• Email encoding
• Spam-blocking and email-sending pitfalls
• SPF, DKIM, and DMARC