Able to POST webmail credentials from another server through a proxy?

I’m trying to do a secure POST of user credentials from another server’s web page, so they do not need to sign on again. While I DO get the message that iNotes is loading, a second later, I get a 403 Error (Access Denied?).

I’m wondering whether I have the correct command syntax. Access is via proxy, and the URL to access web mail is being rewritten, so that while locally the mail URL might be:

http://mailserver01/mail/mailFile.nsf

…through the proxy that gets changed to:

https://proxyserver.company.com/cvpn/aHR0cDovL255NDYx/mail/mailFile.nsf

The relevant HTML code that I am using is below… I’m wondering if I need any additional commands (e.g. OpenDatabase, etc…)

Thanks in advance,

Sam