I'm looking for clarification of the default mail flow behaviour of Exchange Server 2013 please. Basically, I'm having a hard time trying to understand why the "ExchangeServer" Auth Mechanism is enabled by default on the Default Frontend Receive Connector of the CAS Frontend Transport Service.
The only situation that I believe this would be necessary for this receive connector is when the respective (multi-roled) CAS box is in the subscribed site of an Edge Transport Server (2013), as it would be required to accept mail from the 2013 Edge Transport server using this secure server authentication method.
Am I correct in my assumption that this is the only scenario where the ExchangeServer Auth mechanism would be used on this receive connector? I would like to be certain, as my environment does not contain an Edge Transport server and I would like to change the HELO/EHLO request hostname to something that can be resolved publicly (and because this would differ from the FQDN of the server, this would require me to uncheck the ExchangeServer Auth mechanism for this receive connector).
Thank you in advance.
Barry