How Do Spammers Discover Your Email Address?

In some point in your life, you definitely have received an amazing spam email such as this:

Spam is amazing. It just starts coming --out of nowhere-- without any plan, and without a reason.

The biggest question is -- how do spammers find spammable addresses? Quite easy. 

Try to sign up for a new account on Yahoo, Hotmail or Gmail and you will discover that guessing an existing user name is not difficult either. Apparently, most short and good names are taken. Therefore it's an easy job for spammers to guess names and just copy and paste those that are labelled taken.

Truly, free email providers are a spammer's paradise.