sending PHP email
===

I wrote a script that if the form fales, the user sees an error message and an email should be sent to me. However, I'm not getting the email? I don't see any mistakes in my script and the email is nowhere to be found (not even in the spambox). What could be the issue? I believe we are working on a Linux server, so a Mail agent should be installed by default right? Could a firewall be blocking the messages? The code:

    <?php
    
    if (isset($aErrors) && count($aErrors) > 0 ) {
            print '<ul class="errorlist">';
            foreach ( $aErrors as $error ) {
              print '<li>' . $error . '</li>';
            }
            print '</ul><br />';
          
    
    $mail_ontv = "info@logo4life.nl"; 
    
    $_POST['onderwerp'] = "Geen Twinfield Abonnement";
    
        // set datum 
        $datum = date("d.m.Y H:i"); 
          
        // set ip 
        $ip = $_SERVER['REMOTE_ADDR']; 
        
        $inhoud_mail .= $_SERVER['SCRIPT_URI'] . "\n\n";
    
        $inhoud_mail .= "Iemand probeerde zich aan te melden, maar had geen Twinfield abonnement!\n"; 	
        $inhoud_mail .= "Bedrijfsnaam: " . $_SESSION['bedrijfsnaam'] . "\n"; 
        $inhoud_mail .= "Telefoonnummer: " . $_SESSION['telefoonnummer'] . "\n"; 
        $inhoud_mail .= "E-mail adres: " . $_SESSION['email'] . "\n"; 
        $inhoud_mail .= "Telefoonnummer contactpersoon: " . $_SESSION['telefoonnummercontact'] . "\n"; 
        $inhoud_mail .= "E-mail adres contactpersoon: " . $_SESSION['emailcontact'] . "\n"; 
        $inhoud_mail .= "Gewenste gebruikersnaam: " . $_SESSION['gebruikersnaam'] . "\n";
        $inhoud_mail .= "Gekozen abonnement: " . $_SESSION['abonnement'] . "\n\n"; 
          
        $inhoud_mail .= "Verstuurd op " . $datum . " via het ip " . $ip . "\n\n"; 
        
        $headers = "From: " . $_SESSION['bedrijfsnaam'] . " <" . $_SESSION['emailcontact'] . ">";
        
        $headers = stripslashes($headers);
        $headers = str_replace("\n", "", $headers); // Verwijder \n 
        $headers = str_replace("\r", "", $headers); // Verwijder \r 
        $headers = str_replace("\"", "\\\"", str_replace("\\", "\\\\", $headers)); // Slashes van quotes 
        
        $_POST['onderwerp'] = str_replace("\n", "", $_POST['onderwerp']); // Verwijder \n 
        $_POST['onderwerp'] = str_replace("\r", "", $_POST['onderwerp']); // Verwijder \r 
        $_POST['onderwerp'] = str_replace("\"", "\\\"", str_replace("\\", "\\\\", $_POST['onderwerp'])); // Slashes van quotes 
         
        mail($mail_ontv, $_POST['onderwerp'], $inhoud_mail, $headers); 
         
    
    
    
    
    
    
    
    }
    
    ?>

Thanks guys!
