Signed request not available in Facebook app on submitting form?

I am developing a Facebook application for use on page. It’s essential a page with a web form that then creates a database record form the submitted data. Nothing too complex. The complexity comes when I try to differentiate between the sites when handling the post data. This is what I have:

MailScanner

What Is MailScanner? MailScanner is an e-mail security and anti-spam package for e-mail gateway systems. It is not designed to be run on Microsoft Windows desktop PCs. Instead, it is designed to be run on mail servers operated by companies and internet service providers (ISPs) so that all their users and customers can be protected …