we have some SmarterMail installations that, for security reasons and because we were looking for a better antispam / antivirus, the role of antispam and antivirus has been delegated to dedicated appliances (which are the domain MX).
Then these appliances send mail to smartermail.
Unfortunately, however, if an attacker knows that SmarterMail is also exposed on port 25, he can send mail directly to SmarterMail (where there is no antispam check because there are un antispam appliance).
Is there a setting to disable receiving mail in SmarterMail if it doesn't come from antispam?
Or force all email inputs with authentication?