What are some best practices for structuring email headers in PHP to ensure successful delivery?

When structuring email headers in PHP, it is important to include necessary headers such as "From", "Reply-To", "MIME-Version", and "Content-Type". Additionally, ensure that the email headers are correctly formatted and do not contain any syntax errors. By following these best practices, you can increase the chances of successful email delivery.

$to = "recipient@example.com";
$subject = "Subject of the email";
$message = "Content of the email";

$headers = "From: sender@example.com\r\n";
$headers .= "Reply-To: sender@example.com\r\n";
$headers .= "MIME-Version: 1.0\r\n";
$headers .= "Content-Type: text/html; charset=ISO-8859-1\r\n";

mail($to, $subject, $message, $headers);