IIS Secure Email Server w/ port 25

Siteoner

Hey,

I am creating some email forms. My forms work and the email is sent but when I configured IIS on the web server I gave anyone access to port 25. When I block port 25 the email forms will not be sent. Is there a way that I can unblock port 25 and only allow a certain IP address or USER to use my web server to send emails. I can not keep port 25 open because anyone can use it, unless I can only allow certain people.

Thanks a million
Mike