Cross Domain Form Post Data

Hey,
I have 2 different webservers running IIS 6.0, and I need to post a
form data from one website to the other.
When I simply try to set the action attribute of the form to the other
website's url,
The other website does get the request, but the post data is empty.

Is it a security issue?
If so, and if not, how can I overcome this?

Thanks ahead

--sternr