How to setup "Update request status when a new reply is received."

How to setup "Update request status when a new reply is received."

Hello, 

I'm trying to implement this script on our server 
https://pitstop.manageengine.com/portal/en/kb/articles/update-request-status-when-a-new-reply-is-received

Looking at the config file don't understand why do I need to configure my mail server? 
Could someone please explain why ? 

KR
Daniel