输入类型=文本未传递具有某些值的值

I am having a problem using an html/php app.

I have a form with an input type="text" name="email" tag. In this tag, if I submit my e-mail xxxxxxx@xxxx.com I get the value with no problems at $_POST['email'].

If the value passed is something like xxxx.xxxx@xxxx.com the value is not passed neither $_POST['email'] is defined.

Has someone experienced a problem like that?

So, I am posting here my code.

After the submit of the form I am doing a print_r of the $_POST value.

When it works, it returns

Array
(
[email] => teste@example.com
[recuperar] => Recuperar
) 

The form is:

<form action="example.com/recuperar-palavra-passe.html" method="post" id="registo" enctype="multipart/form-data">
<table>
   <tr>
    <td><label for="user_email"><? echo __('Digite o seu e-mail'); ?>:</label></td>
    <td><input type="text" name="email" value="<?php echo $_POST['email'] ?>" id="user_email" class="regi"> </td>
   </tr>
</table>

Sometimes, and with that email I get:

Array
(
)

Even the value email is not defined

This works fine for me, even with xxx.xxx@xxx.com

<?php
    if (isset($_POST['submit'])){
        echo $_POST['email'];
        }
    ?>

    <form action='index.php' method='post'>
        <input type=text name ='email'>
        <input type=submit name=submit value=submit>
    </form>