Contact form, the mail does not arrive

My problem is that I have a form made with HTML, PHP and AJAX that I went up to my page does everything like "should" but my email does not get the message, I leave my code for review:

HTML:

<h3>Formulario de Contacto</h3>
      <div id="note"></div>
      <div id="fields">
        <form id="ajax-contact-form" action="javascript:alert('success!');">
          <div class="left">
            <input type="text" name="name" placeholder="Nombres Completos:" >
            <div class="clear"></div>
            <input type="text" name="email" placeholder="Su Correo:" >
            <div class="clear"></div>
            <input type="text" name="phone" placeholder="N&uacute;mero de Tel&eacute;fono">
            <div class="clear"></div>
            <div class="">
              <div class="left">
                <input class="capthca" type="text" name="capthca" value="Capthca:" onBlur="if(this.value=='') this.value='Capthca:'" onFocus="if(this.value =='Capthca:' ) this.value=''">
                <div class="clear"></div>
                <button type="submit" class="submit">submit</button>
              </div>
              <img src="captcha/captcha.php">
              <div class="clear"></div>
            </div>
          </div>
          <div class="left pad_left2">
            <textarea name="content" placeholder="Mensaje"></textarea>
            <div class="clear"></div>
          </div>
          <div class="clear"></div>
        </form>
      </div>
    </div> 

PHP:

<?php
include 'contact_config.php';
 session_start();
 error_reporting (E_ALL ^ E_NOTICE);
 $post = (!empty($_POST)) ? true : false;

 if($post)
 {
 include 'functions.php';

 $name = stripslashes($_POST['name']);
 $email = trim($_POST['email']);
 $phone = stripslashes($_POST['phone']);
 $subject = stripslashes($_POST['subject']);
 $message = "Site visitor information:

 Name: ".$_POST['name']
 ."

 E-mail Address: ".$_POST['email']
 ."

 Phone: ".$_POST['phone']
 ."

 Message: ".$_POST['content'];


 $error = '';

 // Check name

 if(!$name)
 {
 $error .= 'Please enter your First name.<br />';
 }
 // Check email

 if(!$email)
 {
 $error .= 'Please enter an e-mail address.<br />';
 }

 if($email && !ValidateEmail($email))
 {
 $error .= 'Please enter a valid e-mail address.<br />';
 }


 if(isset($_SESSION['captcha_keystring']) &&       strtolower($_SESSION['captcha_keystring']) != strtolower($_POST['capthca']))
 {
 $error .= "Incorect captcha.<br />";
 }
 if(!$error)
 {
 $mail = mail(WEBMASTER_EMAIL, $subject, $message,
 "From: ".$name." <".$email.">\r\n"
."Reply-To: ".$email."\r\n"
."X-Mailer: PHP/" . phpversion());

 if($mail)
 {
 echo 'OK';
 }
 }
 else
 {
 echo '<div class="notification_error">'.$error.'</div>';
 }

 }
 ?>

JQUERY - AJAX

$(document).ready(function(){ 
$("#ajax-contact-form").submit(function(){
    var str = $(this).serialize(); 
    $.ajax( { type: "POST", url: "contact.php", data: str, success:  function(msg){ 
            if(msg == 'OK') // Message Sent? Show the 'Thank You' message  and hide the form
                { result = '<div class="notification_ok">Your message has been sent. Thank you!<br> <a href="#" onclick="freset();return false;">send another mail</a></div>'; $("#fields").hide(); }                           
            else
                { result = msg; } 
            $("#note").html(result); 
        } 
    }); 
    return false; 
}); 
});

function freset(){  
  $("#note").html('');
  document.getElementById('ajax-contact-form').reset();
  $("#fields").show();
 };

aside there is another doc .js

<?php
 // To
 define( '[email protected]', '[email protected]');
 ?>