The mail() function in PHP is a widely used but often misunderstood and unreliable method of sending emails. To troubleshoot issues with the mail() function, it's essential to configure Postfix properly, as this mail transfer agent routes and delivers emails. The first step is to test if Postfix is installed, then modify the local Postfix configuration to define minimum requirements such as `mail_owner`, `setgid_group`, `myhostname`, and `compatibility_level`. After configuring Postfix, testing it with a simple PHP script can help determine if the issue lies with Postfix or the mail() function itself. If issues persist, considering missing required parameters, typos in the recipient's email address, or setting up an SMTP relay may be necessary.