We have a question regarding who can send mail through the appliance. Is there a way to allow anyone to send mail through the appliance (not defining a specific network or IP in the Relay mail flow policy)? After this is done we would only allow users to send mail who succesfully authenticate in our smtp server by employing SMTP auth profile.
this is quite possible, but a really bad idea. perhaps you can share some more details about your initial requirements, end goals, and existing setup.
to be honest though, you don't need too much extra configuration to 'open up' access from any IP address. try first to configure SMTP authentication with the following directions and then see if it suits your needs: