PHP mail() function not working

Hi, I am using the php mail function in CS cart to send the emails to my customers. I have referred to the documentation to test a test script and while the mail() function does written true, the email is still not being sent, as per the documentation here docs

The first error I got was a sendmail error, which was not configured. I setup the sendmail, even edited the sendmail config files (changed the DAEMON_OPTIONS and removed the “Addr=” parameter so that it can send and receive beyond the localhost, but although the mail function returns true, the email is still not being sent or received.

I need some help with this.

And the issues is not with the content of the script, because in another instance of the CS Cart installation, it is working.