As you may know, email spoofing allows attackers to pose as someone else to gain illegal profit. For example, I only use [email protected] for communication, but someone might create a spoofed-up email, say [email protected], to trick someone. This is called email spoofing with fake headers as follow:

Date: Thu, 24 Oct 2021 12:46:10 
From: nixCraft <[email protected]>
Reply-To: [email protected]
To: <my@personal_gmail_com>

Correct headers are often not checked by receiving email servers, and my@personal_gmail_com may think the email is from me. Here is the thing I don’t use opensourceflare.com for email communication at all. So how do I prevent illegitimate email traffic on my domain? In this tutorial, I will explain how to configure DNS settings that tell receiving email servers this domain is not configured for emailing purposes and the attacker maliciously sending email on my behalf.
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