Can't send mail by PHP

[dbsscout]

Originally, when i used dokuwiki, it can not send email

After that, i tried the following script..
it printed "Message not sent!!!"..
i wonder what the problem is..

thanks

<?php
$to = "my_email@gmail.com";
$subject = "Test mail";
$message = "Hello! This is a simple email message.";
$from = "someonelse@example.com";
$headers = "From: $from";
echo (mail($to,$subject,$message,$headers)) ? 'Message sent!!!' : 'Message not sent!!!';

?>

 

[Livewire]

What happens if you actually set $from to a valid email? We have spam prevention measures in place that may very well be blocking that since its not an email set on our servers.