Using PHP to send a reply from a form to my Email and is giving the error 405 Not Allowed

Every time I click to submit the form it gives this error! How can I resolve this?

HTML Form Code 5:

<form class = "col s12 m4 offset-m4 l4 offset-l4" action="submit_form.php" method="post">

    <div class="row">

        <div class="input-field col s12">
            <i class="material-icons prefix sKtq-scColor">&#xE87C;</i>
            <input id="icon_prefix" name="Nome" type="text" class="validate sKtq-scColor" required>
            <label for="icon_prefix" class = "sKtq-scColor">Nome</label>
        </div>

        <div class="input-field col s12">
            <i class="material-icons prefix sKtq-scColor">&#xE0BE;</i>
            <input id="icon_prefix" name="Email" type="email" class="validate sKtq-scColor" required>
            <label for="icon_prefix" class = "sKtq-scCo lor">Email</label>
        </div>

        <div class="input-field col s12">
            <i class="material-icons prefix sKtq-scColor">sort</i>
            <input id="icon_prefix" name="Assunto" type="text" class="validate sKtq-scColor" required>
            <label for="icon_prefix" class = "sKtq-scColor">Assunto</label>
        </div>

        <div class="input-field col s12">
            <i class="material-icons prefix sKtq-scColor">chat_bubble</i>
             <textarea id="textarea1" name="Mensagem" class="materialize-textarea validate sKtq-scColor" required></textarea>
             <label for="textarea1" class = "sKtq-scColor">Mensagem</label>
        </div>

    </div>

    <br>

    <div class = "center-align">

        <button class="btn waves-effect waves-light sKtq-bgScColor" type="submit"> Enviar
            <i class="material-icons right">send</i>
        </button>

    </div>

</form>

PHP code that is in the file submit_form.php :

<?php

if(isset($_POST['email'])) {
    $email_to = "mtqr1@hotmailcom";
    $email_subject = "Mensagem do site";
    $name = $_POST['Nome']; // required
    $email_from = $_POST['Email']; // required
    $subject = $_POST['Assunto']; // required
    $message = $_POST['Mensagem']; // required

    function clean_string($string) {
    $bad = array("content-type","bcc:","to:","cc:","href");
    return str_replace($bad,"",$string);
    }

    $email_message = "Form details below.\n\n";
    $email_message .= "Name : ".clean_string($name)."\n";
    $email_message .= "Email : ".clean_string($email_from)."\n";
    $email_message .= "Assunto : ".clean_string($subject)."\n";
    $email_message .= "Mensagem : ".clean_string($message)."\n";

// create email headers
$headers = 'From: '.$email_from."\r\n".
'Reply-To: '.$email_from."\r\n" .
'X-Mailer: PHP/' . phpversion();
mail($email_to, $email_subject, $email_message, $headers);
?>
  <!-- include your own success html here -->

  <div class="feedback">Thank you for contacting us. We will be in touch with you very soon.</div>

  <?php
}
?>

Image of the error