I am running an exchange 2013 server behind a spam firewall 300. All mail (Inbound and Outbound) is routed through the spam firewall. Our MX record points to our outside IP address, and port 25 is open through our Network FW on that IP to the Barracuda spam firewall.
I have a website hosted by a company, that takes registrations from our customers. I would like that website to be able to email a purchase receipt to our customers by using our mail server.
I assume I could add the IP address of the hosted web server to the Relay using trusted IP/Range section of the spam firewall. I am hesitant to do this because I think multiple websites are hosted on that single IP.
Is there a way to relay mail from a hosted web server through my spam firewall using smtp authentication?