Show checkbox array values

i'm trying to loop inside my checkbox array and show the value of each element, but its returning 0, and the real value are emails. (lucas.ro****@gmail.com) and (thatian****@gmail.com)

These are my codes:

            <form method="POST" action="testeEmail.php">
            <table id="tableEmail" class="table table-striped table-bordered">
                <tr>
                  <td>Email</td>
                  <td width="5%">Enviar?</td>
                  <td class="centro">Já recebido</td>
                  <td width="10%"> <button type="submit" class="btn btn-success"><span class="glyphicon glyphicon-send"></span> Enviar (Os útimos não enviados)</button></td>
                </tr>
                <?
                include("conexao.php");
                mysql_query("SET NAMES 'utf8'");
                mysql_query("SET character_set_connection=utf8");
                mysql_query("SET character_set_client=utf8");
                mysql_query("SET character_set_results=utf8");
                $resultEmail = mysql_query("SELECT id,email,recebido FROM Newsletter");
                if (mysql_num_rows($resultEmail) > 0) {
                    while ($rowEmail = mysql_fetch_assoc($resultEmail)){?>
                       <tr>
                            <td><? echo $rowEmail['email'] ?></td>
                            <td class="centro">
                                <input type="checkbox" name="box[]" value="<? echo $rowEmail['email'] ?>" <? if($rowEmail['recebido'] == 1){}else{ echo "checked"; } ?>>
                            </td>
                            <td class="centro"><? if($rowEmail['recebido'] == 1){ echo "<font color='green'>Sim</font>";}else{ echo "<font color='#d9534f'>Não</font>"; } ?></td>
                            <td>
                                <a href="deletarEmail.php?idEmail=<? echo $rowEmail['id'] ?>" class="btn btn-danger"><span class="glyphicon glyphicon-remove" aria-hidden="true"></span> DELETAR</a>
                            </td>
                       </tr>
                    <?}
                }
                 mysql_free_result($resultEmail);
                 mysql_close($conecta);?>
            </table>
        </form>

---

<?php
$Message = "testando";

include("class.phpmailer.php");
include('PHPMailerAutoload.php');
include('class.smtp.php');  


foreach($_POST['box'] as $box){
    if(isset($box)){
        //$dest = $box;
        echo $box;

    } else{
    }
}

?>

Hope someon can help.