E-mails have been with us for a very long time now. E-mail might seem complex under the hood, but it is not; the working principle is pretty simple. The first thing that we need to know about is the SMTP server. So, why the SMTP server and not the Godzilla server? We call it the SMTP server because it speaks Simple Mail Transfer Protocol (SMTP).

SMTP is just a plain text protocol like the HTTP protocol that you may be familiar with. Your browser sends HTTP requests (which is nothing but plain text) over TCP, and the HTTP servers respond as per the request. The same is the case with the SMTP servers.

The SMTP servers historically listened on port 25, which is deprecated and now port 587 is standard these days. When you want to send an e-mail, you open your e-mail client (a desktop application such as Outlook, Thunderbird, or any Android or iOS mobile application) and type in your message that you want to send across.

This e-mail is formatted as SMTP text commands, and a connection...