What steps should be taken to ensure proper authentication and authorization when sending emails through PHP scripts to avoid relaying denial or authentication errors, as experienced in the mentioned case?

To ensure proper authentication and authorization when sending emails through PHP scripts and avoid relaying denial or authentication errors, you should use SMTP authentication with valid credentials provided by your email service provider. This will authenticate your PHP script with the email server before sending the email, ensuring successful delivery.

// Set SMTP settings for authentication
$mail->isSMTP();
$mail->Host = 'smtp.example.com';
$mail->SMTPAuth = true;
$mail->Username = 'your_email@example.com';
$mail->Password = 'your_email_password';
$mail->SMTPSecure = 'ssl';
$mail->Port = 465;