Envio de Email

Boa tarde,

Estou com um problema ao enviar o email..depois de preencher o formulário diz mensagem enviada mas depois não recebo nada no meu email..que poderá ser??

<?php
 include ('layout.php');

?>

<div id="texto">

<?php

if(isset($_POST['Submit'])){

$mail_to= "josericardo19242@gmail.com";
$mail_from=$_POST['txtEmailfrm2'];
$mail_sub=$_POST['txtSub2'];
$mail_mesg=$_POST['txtMsg2'];

if(mail($mail_to,$mail_sub,$mail_mesg,"From:$mail_from/r/nReply-to:$mail_from"))

echo "<span class='red'>E-mail enviado com sucesso para $mail_sub to $mail_to</span>";

echo "<span class='red'>Falha ao enviar E-mail para $mail_sub to $mail_to</span>";
}
?>

<form name="frmsendmail" method="post" action="index.php" onSubmit="return ValidationForm()">
 <table width="100%" border="0">
 <br>
 <tr>
 <td width="33%" align="left" class="text"><font face="Bell MT" size="3" color="#15b2ff"> De :</font></tr>
 <tr>
 <td width="67%" align="left"><input name="txtEmailto2" type="text" class="input" id="txtEmailto22" size="30" maxlength="100">
 </tr>

 <td align="left" class="text"><font face="Bell MT" size="3" color="#15b2ff"> Assunto :</font></tr>
 <tr>
 <td align="left"><input name="txtSub2" type="text" class="input" id="txtSub22" size="30" maxlength="100">
 </tr>
 <tr>
 <td align="left" class="text"><font face="Bell MT" size="3" color="#15b2ff"> Mensagem :</font> </tr>
 <tr>
 <td><textarea name="txtMsg" cols="40" rows="10" class="input" id="textarea"></textarea>
 </tr>
 <tr>
 <td align="right"><input name="hidSubmit" type="hidden" id="hidSubmit" value="true">
 <input align="left" name="Submit" type="submit" class="input" value="Enviar">
 <td><input align="left" name="Submit2" type="reset" class="input" value="Limpar">
 </tr>
 </table>
 </form>
 </div>

 </body>
</html>