A customer asks us to send our email with a mailbox belongs to his domain. To do this, they require to authenticate to their SMTP gateway with username and password. We can not go directly from our server to the external SMTP server over internet, so we would proceed passing through Ironport. How can we reach this target? What is the authentication profile function? Does it allowed to authenticate from Ironprt for outgoing mail? We are thinking about SMTP Auth with Forwarding) or Outgoing SMTP Auth.