Create custom form for login Webmail

[futurosoft]

Hello.

I am creating a custom form for login to Webmail but this don't run. My code is:

<form id="horde_login" action="http://webmail.domain.com/login.php" method="post" name="horde_login">
<input type="hidden" name="app" id="app" value="" />
<input type="hidden" name="login_post" id="login_post" value="0" />
<input type="hidden" name="url" value="" />
<input type="hidden" name="anchor_string" id="anchor_string" value="" />
<input type="hidden" id="horde_user" name="horde_user" value="<?php echo $username; ?>" />
<input type="hidden" id="horde_pass" name="horde_pass" value="<?php echo $password; ?>" />
<input type="submit" name="enviar" value="Continuar" />
</form>

What is the URL where I have that to send form?

Thanks!