Por lo que puedo comprobar usando PHPMailer me pasa exactamente lo mismo:
// ------------------------------------------------------------------
require("includes/PHPMailer_5.2.1/class.phpmailer.php");
$mail = new PHPMailer();
$mail->Host = "localhost";
$mail->From = "
[email protected]";
$mail->FromName = "xxxxxxxxxxx";
$mail->Subject = "xxxxxxxxxxxxxxxxxxxxxxxx";
$mail->AddAddress($email);
$mail->Body = $body;
$mail->IsHTML(true);
$mail->Send();
// ------------------------------------------------------------------