Deliverability
Some folks create a domain name (dedicated to email campaigns) linked to a non-functional, non-existent website. A good example is when an individual clicks on mynewsletter.ext and it doesn’t take you to an actual website (yet the email address noreply@mynewsletter.ext is still used as a sender address), but the user arrives at a blank page (or a 404 error page, etc).
Good news, this practice is very bad for at least three strong reasons:
Conclusion: Always distinguish yourself from spammers by ensuring that the domain name you use in your emails allows user to verify your identity.