php mail() not sending to mail Clients (ie, Outlook, Apple Mail, thunderbird, etc..)

I have a send mail script on my site that.

The emails are recieved by gmail, and yahoo, but not to mail clients
like Outlook, Mail, etc...)

Is this a problem with the script, or is it something I must change in
php ini file?

Thanks in advance for any help.

here is the code. (im using it in conjunction with javascript for some
AJAX stuff)

if(!isset($_GET['action']))
{
die("You must not access this page directly!"); //Just to stop people
from visiting contact.php normally
}

/* Now lets trim up the input before sending it */

$name = trim($_GET['name']); //The senders name
$to = trim($_GET['maily']); //The senders email address
$place = trim($_GET['place']); //The senders email address
$subject = "you have recieved mail";
$headers = "From:$name";
$message = "{$name} deemed you worthy of receiving the following
information/exchange from Trumpet.\n\n Follow This Link {$place}";
mail($to, $subject, $message,$headers); //a very simple send

echo 'contactarea|<p class="sent">Article Sent!</p>'; //now lets
update the "contactarea" div on the contact.html page. The
contactarea| tell's the javascript which div to update.

?>

.