Your access to this mail system has been rejected due to the sending MTA's poor reputation.

[a-ssassi-n]

I have set my sender to my Gmail address: [email protected]
When I am trying to verify an email (Which is correct) I am getting an error:

[2018-05-24T06:21:28.568919+0000] <<<recv: 554 Your access to this mail system has been rejected due to the sending MTA's poor reputation. If you believe that this failure is in error, please contact the intended recipient via alternate means.

and the $results[$emails] returns False for this.

When I checked the same email with other email checking tools, they return True

Do I need to buy a domain and configure SPF records for my mail server to get the correct results?

Note: Currently I am using my localhost (XAMPP)

[zytzagoo]

Do I need to buy a domain and configure SPF records for my mail server to get the correct results?

It might help, yes. But that new server can also get banned and/or flagged as bad pretty quickly (depending on what you're using this for, how often etc.)

[a-ssassi-n]

Okay. One more question:
When I moved my code to a shared hosting(GoDaddy Hosting), it always returns False
Do I need a dedicated server to run this script? Will AWS work fine for this?

[zytzagoo]

Turn on logging and see what's different when querying from shared hosting... I'm guessing a lot of mail servers simply refuse to talk to known shared hosting IPs etc.

No idea about AWS, I guess it depends which IP you get, how you configure things, and who/what used it for earlier maybe...

It's about reputation, not hardware.