Mail function sends to gmail but not hotmail. Please help (newbie)

Hi,

Can anyone tell me what the requirements are to allow hotmail to collect
messages. I have a script using the mail function at the moment that emails
most email clients but the email doesn't seem to be accepted by hotmail. It
email doesn;t even go into the junk box.

Please help,

Raj (Newbie)

The code:

ini_set(sendmail_path, "/usr/sbin/sendmail -t -f webmaster@domain.com");

//Contents of an Registration Auto responce email(text format)
$message = "Thanks for registering".$userName;

$headers .= "From: Name\n";
$headers .= "Reply-To: \n";
$headers .= "X-Sender: \n";
$headers .= "X-Mailer: PHP4\n"; //mailer
$headers .= "X-Priority: 3\n"; //1 UrgentMessage, 3 Normal
$headers .= "Return-Path: \n";
mail($email,"Registration ",wordwrap(stripslashes($message)),$headers);