Envoie mail en php

<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<link rel="stylesheet" type="text/css" href="css/style.css">
<link rel="stylesheet" type="text/css" href="css/menu.css">
<title>Web Ultime</title>
</head>

<body>
	<div id="container">

		<?php include("include/menu.php"); ?>
		
		
		<div id="text-shadow">
			<div id="titre">Contact</div>
			
			<div id="texte">
			<?php 
			if(isset($_POST['nom']) AND isset($_POST['prenom']) AND isset($_POST['email']) AND isset($_POST['message']))
			{
			if($_POST['nom']!=NULL AND $_POST['prenom']!=NULL AND $_POST['email']!=NULL AND $_POST['message']!=NULL)
			{
			$nom = stripslashes($_POST['nom']);
			$prenom = stripslashes($_POST['prenom']);
			$email = stripslashes($_POST['email']);
			$message = stripslashes($_POST['message']);
		
			$adresse = "webmaster@web-ultime.com";
			$object = "Web Ultime - Contact";
			$contenu = "Nom: $nom \n Prenom: $prenom \n Email: $email \n Message: $message";
			$headers = 'From: <'.$email.'>'."\n";
			
			mail($adresse, $object, $contenu, $headers);
			
			echo "Votre message a été envoyé";}
			
			else {echo "Votre message n'a pas été envoyé, vous devez remplir tous les champs";}
			}
			?>
			</div>
			
		</div>
		
		<?php include("include/footer.php"); ?>
	
	</div>
</body>
</html>