Can't see notify owner checkbox

I've just created a new web-a-lead form for my website, but in the configuration option I can't find the notify owner checkbox, as reported here http://crmkbase.zoho.com/while-creating-a-web-form-can-i-edit-the-notification-email-that-is-sent-to-the-record-owner, so I'm currently not able to being notified when a new lead is waiting for approval.

How can i fix that?