For anyone else having problems with UE 4.0 sending email, try using this small bit of code instead.
$MailBody = "";
$MailBody = $MailBody . "Hello";
$to = 'firstname.lastname@example.org';
$subject = 'Test';
$message = $MailBody;
$headers = 'From: email@example.com' . "\r\n" .
'Reply-To: firstname.lastname@example.org' . "\r\n" .
'X-Mailer: PHP/' . phpversion();
mail($to, $subject, $message, $headers);
Its really easy to use and if you want to send HTML simply add this to your header section:
'Content-type: text/html\r\n' . "\r\n" .