Email Sending Problem

I have been having a problem with the setup of Support Center and enabling it to send emails on my network. The machine it is installed on Windows 2003 Standard server with IIS on and is purely used as a web server. I have tested the connection which is to an internal mail server running exchange 2007 and both ports 25 and 110 are communicating okay via telnet. I receive emails to the designated account fine within support center but when I try and send an email via the reply or forward options I get an error that says:

Sending notification failed.

Has anyone experienced this before? Any suggestions are welcome as this is the only thing I need working before I make the system live for my clients.

Many Thanks
Andrew