What level of expertise is required to successfully use PHP functions for email sending without external mailer classes?

To successfully use PHP functions for email sending without external mailer classes, one needs a basic understanding of PHP and familiarity with functions like mail(). The key is to properly set the headers, including the From address and content type, and handle any errors that may arise during the sending process.

$to = "recipient@example.com";
$subject = "Test Email";
$message = "This is a test email.";

$headers = "From: sender@example.com\r\n";
$headers .= "Reply-To: sender@example.com\r\n";
$headers .= "Content-type: text/html\r\n";

if(mail($to, $subject, $message, $headers)){
    echo "Email sent successfully.";
} else {
    echo "Email sending failed.";
}