How can I use redirect on Parallels?

[micheler]

Hello to everybody,
I need your help:

I would like to have this:
clicking on webmail.lthpartners.it you are redirected (final url must be hide) to webmail.kpnqwest.it.

Well,
I created a third level domain (webmail.lthpartners.it) on parallels panel, typed the correct target url (http://webmail.kpnqwest.it) with frame option.

At the same time I configured on DNS panel the following rules:
webmail.lthpartners.it CNAME webmail.kpnqwest.it

With this configuration I am redirected to the correct url but I see the url that should be hidden (webmail.kpnqwest.it).

If I delete the rule on DNS panel there is no redirection.

Where I get the mistake?

Thank you so much