If a user sends to a email then email should create a ticket of thier conversation
Please see: https://docs.osticket.com/en/latest/Getting%20Started/Email%20Settings.html and https://docs.osticket.com/en/latest/Getting%20Started/POP3-IMAP%20Settings.html
Is there any settings to do for it
Please see my last reply as I linked you the documentation for the settings.