How do email valdiation services verify and cleanse email addresses?

Hello, guys,

I have to clean up a large email list and I recently discover that some online platforms can do this for me.
Before i start using such platforms and spend some money on those, i need to know what technology is behind those platforms and how its actually works.

Let's take for example zerobounce email validation system. What technology do they use to know which emails are valids and which are not?

Thank you all!

 

It's done by using the SMTP protocol (or something similar): https://www.phpclasses.org/package/6650-PHP-Check-if-an-e-mail-is-valid-using-SMTP.html

"The class simulates the delivery of a message to see if the given recipient address is accepted as valid."

 

Try NeverBounce. They seem to know what they are experts in. I have never tried them,so try at your own risk.