<?php
ini_set('SMTP','smtp.mydomain.com');
ini_set('smtp_port',25);
$to      = 'xyz@gmail.com';
$subject = 'the subject';
$message = 'hello';
$headers = 'From: abc@gmail.com' . "rn" .
'Reply-To: abc@gmail.com' . "rn" .
'X-Mailer: PHP/' . phpversion();

if(mail($to, $subject, $message, $headers)){
    echo 'Successfully sent';
}
else {
    echo 'failed';
}
?>