Peki ustalarım iletişim formu çalışmıyor nerede hata yapıyorum.

Html olan tarafına böyle bir form ekledim

<section id="contact" class="contact bg-1 bg-opacity-black-70 page-section-ptb">
  <div class="container">
    <div class="row">
       <div class="col-lg-12 col-md-12">
        <div class="section-title text-center">
          <h2 class="text-blue">İletişim Bilgileri</h2>
          <div class="title-line white"></div>
          <p class="text-white">firma iletişim yazısı.</p>
        </div>
      </div>
    </div>
     <div class="row">
       <div class="col-lg-8 col-md-8">
        <div class="text-center">
      </div>
         <div id="contact-form" class="contact-form">
			<form method="POST" action="mail.php" method="post">
           <div class="section-field">
            <i class="fa fa-user"></i>
            <input id="name" type="text" placeholder="İsminiz*" required name="isim">
           </div>
           <div class="section-field">
              <i class="fa fa-envelope-o"></i>
              <input id="email" type="email" placeholder="E-Postanız*" required name="mailad">
            </div>
           <div class="section-field">
              <i class="fa fa-file-text-o"></i>
              <input id="web" class="web" type="text" placeholder="Web Adresiniz*" name="web">
            </div>
           <div class="section-field textarea">
             <i class="fa fa-pencil"></i>
             <textarea id="message" class="input-message" placeholder="Mesajınız*" required rows="7" name="mesaj"></textarea>
            </div>
            <button type="submit" href="javascript:void(0)" class="button mt-20">
              <span>Mesajınızı G&ouml;nderin </span>
              <i class="fa fa-paper-plane"></i>
            </button>
			</form>
         </div>
       </div>

Mail.php sayfasını ise bu şekilde ayarladım.Farklı dosyalarıda denedim veri aktarımı olmuyor.

<?php 
if(isset($_POST['submit'])){
    $to = "bilgi@iletisim.com"; // this is your Email address
    $from = $_POST['email']; // this is the sender's Email address
    $first_name = $_POST['first_name'];
    $last_name = $_POST['last_name'];
    $subject = "Form submission";
    $subject2 = "Copy of your form submission";
    $message = $first_name . " " . $last_name . " wrote the following:" . "\n\n" . $_POST['message'];
    $message2 = "Here is a copy of your message " . $first_name . "\n\n" . $_POST['message'];

    $headers = "From:" . $from;
    $headers2 = "From:" . $to;
    mail($to,$subject,$message,$headers);
    mail($from,$subject2,$message2,$headers2); // sends a copy of the message to the sender
    echo "Mail Sent. Thank you " . $first_name . ", we will contact you shortly.";
    // You can also use header('Location: thank_you.php'); to redirect to another page.
    // You cannot use header and echo together. It's one or the other.
    }
?>

Sonuç olarak hata kodu - 405 - HTTP verb used to access this page is not allowed.
The page you are looking for cannot be displayed because an invalid method (HTTP verb) was used to attempt access.