Server doesn't send email

    <form name="contactForm" action="contact-form.php" method="post">
        <input type="text" placeholder="Voornaam" name="Firstname" style="width: 335px;" required="required">
        <input type="text" placeholder="Achternaam" name="Lastname" style="width: 336px;" required="required">
        <textarea placeholder="Voer hier uw bericht in..." name="Message" required="required"></textarea>
        <input type="email" placeholder="E-mail adress" name="Email" required="required">
        <input type="submit" value="Verstuur" name="Send" class="fontWeight">
    </form>

<?php
    $firstname = $_POST['Firstname'];
    $lastname = $_POST['Lastname'];
    $email = $_POST['Email'];
    $message = $_POST['Message'];

    $Adminemail = '"Enzio" <mail@enziorossa.nl>';

    $subject = $firstname.' '.$lastname.' has messaged you via the website.';
    $subject2 = 'A copy of your message send to Nicalyo';

    $headers = "From: " . strip_tags($email) . "\r\n";
    $headers .= "Reply-To: ". strip_tags($email) . "\r\n";
    $headers .= "MIME-Version: 1.0\r\n";
    $headers .= "Content-Type: text/html; charset=ISO-8859-1\r\n";

    $bericht = '<table>
            <tr><td colspan="2"><font color="red">The following person has send this message:</font></td><tr>
            <tr><td width="120">Full name: </td><td>'.$firstname.' '.$lastname.'</td></tr>
            <tr><td width="120">Date: </td><td>'.Date("d-m-Y").'</td></tr>
            <tr><td width="120">E-mail: </td><td>'.$email.'</td></tr>
            <tr><td colspan="2">&nbsp;</td><tr>
            <tr><td width="120">Message: </td><td>'.nl2br($message).'</td></tr>
        </table>';

    $bericht2 = '<font color="red">This is a copy of your message:<br></font><br>'.$bericht;

    if(mail($Adminemail, $subject, $bericht, $headers))
    {
        mail($email, $subject2, $bericht2, $headers);
        $pageTitle = "Dank u - Nicalyo";
        include('header.php');
        echo "<div class='thanks-loader'>";
        echo "<div class='container' style='text-align: center;'>";
        echo "<h1>Dank u, u hoort zo snel mogelijk van ons</h1>";
        echo "<div class='button'><a href='index.php'>Terug naar de site</a></div>";
        echo "</div>";
        echo "</div>";

        include('footer.php');
    }
    else
    {
        echo 'An error occured, please contact the site administrator.';
    }
?>