[Resolvido] Formulário de Contato

Estou mexendo em um tema do Wordpress que veio um formulário Ajax que está funcionando tudo, menos a validação de e-mail, segue os códigos abaixo:

contact.php

<?php
/*
Template Name: Contact
*/

?>

<?php get_header(); ?>
<script type="text/javascript">
 $(document).ready(function(){
 $('#contact').ajaxForm(function(data) {
 if (data==1){
 $('#success').fadeIn("slow");
 $('#bademail').fadeOut("slow");
 $('#badserver').fadeOut("slow");
 $('#contact').resetForm();
 }
 else if (data==2){
 $('#badserver').fadeIn("slow");
 }
 else if (data==3)
 {
 $('#bademail').fadeIn("slow");
 }
 });
 });
	</script>

<!-- begin colLeft -->

<div id="colLeft">

 <h1>Contact Us</h1>
 <p><?php echo stripslashes(stripslashes(get_option('journal_contact_text')))?></p>

 <p id="success" class="successmsg" style="display:none;">Your email has been sent! Thank you!</p>

 <p id="bademail" class="errormsg" style="display:none;">Please enter your name, a message and a valid email address.</p>
 <p id="badserver" class="errormsg" style="display:none;">Your email failed. Try again later.</p>

 <form id="contact" action="<?php bloginfo('template_url'); ?>/sendmail.php" method="post">
 <label for="name">Your name: *</label>
 <input type="text" id="nameinput" name="name" value=""/>
 <label for="email">Your email: *</label>

 <input type="text" id="emailinput" name="email" value=""/>
 <label for="comment">Your message: *</label>
 <textarea cols="20" rows="7" id="commentinput" name="comment"></textarea><br />
 <input type="submit" id="submitinput" name="submit" class="submit" value="SEND MESSAGE"/>
 <input type="hidden" id="receiver" name="receiver" value="<?php echo strhex(get_option('journal_contact_email'))?>"/>
 </form>

</div>

<!-- end colleft -->

 <?php get_sidebar(); ?>

<?php get_footer(); ?>

sendmail.php

<?php
 $str = $_POST["email"];
 if(isset($_POST['submit'])) {
 error_reporting(E_NOTICE);
 function valid_email($str)
 {
 return ( ! preg_match("/^[A-Za-z0-9]+([_.-][A-Za-z0-9]+)*@[A-Za-z0-9]+([_.-][A-Za-z0-9]+)*\\.[A-Za-z0-9]{2,4}$/", $str)) ? FALSE : TRUE;
 }
 if($_POST['name']!='' && $_POST['email']!='' && valid_email($_POST['email'])==TRUE && strlen($_POST['comment'])>1)
 {
 //$to = preg_replace("([\r\n])", "", $_POST['receiver']);
 $to = preg_replace("([\r\n])", "", hexstr($_POST['receiver']));
 $from = preg_replace("([\r\n])", "", $_POST['email']);
 $subject = "Website contact message from ".$_POST['name'];
 $message = $_POST['comment'];

 $match = "/(bcc:|cc:|content\-type:)/i";
 if (preg_match($match, $to) ||
 preg_match($match, $from) ||
 preg_match($match, $message)) {
 die("Header injection detected.");
 }
 $headers = "From: ".$from."\r\n";
 $headers .= "Reply-to: ".$from."\r\n";

 if(mail($to, $subject, $message, $headers))
 {
 echo 1; //SUCCESS
 }
 else {
 echo 2; //FAILURE - server failure
 }
 }
 else {
 echo 3; //FAILURE - not valid email

 }
 }else{
 die("Direct access not allowed!");
 }

 function hexstr($hexstr) {
 $hexstr = str_replace(' ', '', $hexstr);
 $hexstr = str_replace('\x', '', $hexstr);
 $retstr = pack('H*', $hexstr);
 return $retstr;
 }

 ?>

Já tentei mudar a forma de validação e não consegui consertar...