HTML
From Rackspace Email & Apps API
Login Redirect
This code shows a form asking for a username and password to a mailbox; clicking submit logs the person into the webmail client.
<form method=post action="http://reseller1.webmail.us/mail/src/redirect.php">
username: <input type=text name=user_name><br>
password: <input type=text name=password><br>
<input type=hidden name=hostname value="webmail.us">
<input type=submit>
</form>