Form Mailer isue

I’m currently working on this contact form and something seems to be wrong with the form mailer. When the suer fills and submits the form, it shows a blank page when it should thank the person by his/her name. The form is as shown bellow.

<form action="/we-thank-you/" method="post" enctype="plain/text" id="contacter">
  <div id="contactleft">

         <div class="textboxer"><span id="sprytextfield1">
 <label for="name"></label>

           <input name="name" type="text" class="texter" id="name" />

          <span class="textfieldRequiredMsg">A value is required.</span></span></div><!-- End Textboxer -->

         <div class="textboxer"><span id="sprytextfield2">

           <label for="email"></label>

           <input name="email" type="text" class="texter" id="email" />

          <span class="textfieldRequiredMsg">A value is required.</span></span></div><!-- End Textboxer -->

         <div class="textboxer"><span id="sprytextfield3">

           <label for="phone"></label>

           <input name="phone" type="text" class="texter" id="phone" />

          <span class="textfieldRequiredMsg">A value is required.</span></span></div><!-- End Textboxer -->

         <div class="textboxer"><span id="sprytextfield4">

           <label for="subjec"></label>

           <input name="subjec" type="text" class="texter" id="subjec" />

          <span class="textfieldRequiredMsg">A value is required.</span></span></div><!-- End Textboxer -->

         <div class="textboxer">

         <div class="kode">

         <span id="txtCaptchaDiv" style="color:#F00"></span><br />

<!-- this is where the script will place the generated code -->

          <input type="hidden" id="txtCaptcha" /></label>

         </div><!-- End Kode -->
     <div class="checker"><span id="spryconfirm1">

           <label for="checkit"></label>

           <input type="text" name="checkit" id="checkit" />

           <span class="confirmRequiredMsg">Can't be empty.</span><span class="confirmInvalidMsg">That don't match.</span></span></div><!-- End checker -->

         </div><!-- End Textboxer -->

        </div><!-- End ContactLeft -->

        <div id="contactright">

        <div class="textboxer"><span id="sprytextarea1">

          <label for="message"></label>
   <textarea name="message" cols="45" rows="5" class="mssager" id="message"></textarea>
   <span class="textareaRequiredMsg">A value is required.</span></span></div><!-- End Textboxer -->

        <div class="textboxer">
    <input type="submit" name="sendit" id="sendit" value="send your message" />

        </div><!-- End Textboxer -->

        </div><!-- End ContactRight -->

       </form>

While the form processor is as shown bellow

<?php

   $mailto = '[email protected]'; // insert the email address you want the form sent to

    //$returnpage = 'thanks.php'; // insert the name of the page/location you want the user to be returned to//

    $sitename = '[siteripe.com]'; // insert the site name here, it will appear in the subject of your email

/* Do not edit below this line unless you know what you're doing */

  $name = $_POST['name'];

  $email = $_POST['email'] ;

   $subject = $_POST['subject'];

   $message = $_POST['message'];

    $phone = $_POST['phone'];

    $env_report = $_POST['env_report'];

    $anti_tamper = $_POST['anti_tamper'];

    // Mail header removal

function remove_headers($string) { 

  $headers = array(

    "/to\:/i",

    "/from\:/i",

    "/bcc\:/i",

    "/cc\:/i",

    "/Content\-Transfer\-Encoding\:/i",

    "/Content\-Type\:/i",

    "/Mime\-Version\:/i" 

  ); 

  $string = preg_replace($headers, '', $string);

  return strip_tags($string);

} 

// Pick up the cleaned form data

$name = remove_headers($_POST['name']);

$email = remove_headers($_POST['email']);

$topic = remove_headers($_POST['topic']);

$comments = remove_headers($_POST['comments']);

    if (!$name) {

        print("<strong>Error:</strong> Please provide your name.<br/><br/><a href='javascript:history.go(-1)'>Back</a>");

         exit;

    }

    if (!$email) {

        print("<strong>Error:</strong> Please provide an email address.<br/><br/><a href='javascript:history.go(-1)'>Back</a>");

         exit;

    }

    if (!$subject) {

        print("<strong>Error:</strong> Please provide a subject.<br/><br/><a href='javascript:history.go(-1)'>Back</a>");

         exit;

    }

    if (!$phone) {

        print("<strong>Error:</strong> Please provide a Phone number<br/><br/><a href='javascript:history.go(-1)'>Back</a>");

         exit;

    }

    if (!$message) {

        print("<strong>Error:</strong> Please provide a Message<br/><br/><a href='javascript:history.go(-1)'>Back</a>");

         exit;

    }

    if (!eregi("^[a-z0-9]+([-_\.]?[a-z0-9])+@[a-z0-9]+([-_\.]?[a-z0-9])+\.[a-z]{2,4}", $email)){

    print("<strong>Error:</strong> this email address is not in a valid format.<br/><br/><a href='javascript:history.go(-1)'>Back</a>");

         exit;

    }   

  $message = "\n$name submitted the following message:\n\n$message\n\n$name's contact details are as follows:\n\nName: $name\nPhone Number: $phone\nEmail Address: $email\nUser IP: $env_report\nTamper Proof: $anti_tamper\n";

  mail($mailto, "$subject", $message, "From: $email");

?>

<?php get_header(); ?>