Document I referred to: https://docs.osticket.com/en/latest/Getting%20Started/Email%20Piping.html
I am using a shared hosting server.
The server is controlled through CPANEL.
I have created an email address (dummy@{servername}) for this purpose. The server's mail server is running roundcube.
I have created an email forwarder in CPANEL from the email address to the path to pipe.php in my server.
The pipe.php permission has been modified from 0644 to 0755.
I made an email and send to the dummy email address.
After a while, a ticket has been made successfully in the osTicket system.

However, an additional message was replied from the server's mail server as follows:

The current osTicket specification:

No modification done to the osTicket.
How to resolve the local delivery failed issue?
It will always reply the moment the ticket has been made successfully through email.