I never attempted to use internal MTA since Sophos migrated it to Exim. We are using Symantec Brigthmail as mail gateway. There may be some "internal" MTA settings, but technically, these are at OEM settings for both of ours XG210. We also have a XG105 that uses MTA soley to send notifications.
On both XG210, in "Email, General settings", "SMTP deployment mode" shows "Switch to MTA mode". On the same page, "TLS certificate*" shows "SecurityAppliance_SSL_CA"
On "Administration", "Notification settings", "Send notifications via" is set to "External email server" with the IP address of our Brigthmail mail gateway. And this is where it's weird. Because it is on the same subnet as the firewall. So the firewall rule is rather simple. The other XG210 that actually works has the exact same settings, but it is on another subnet at the other end of a VPN.
One of our two XG210 never stopped sending notifications. The other one was frozen few days, but seems to send "manually" notifications. But none scheduled. Those firewalls are under a domain. DNS is not reliable, so I punched and IP address for the mail gateway. DNS is otherwise very stable enterprise-wise.
The third XG210 firewall has also the same settings, but it is on a completely different environment. That one uses the internal MTA for the sole purpose of sending notifications. That one is still frozen. Whenever I click "Test Mail", I get the green confirmation on the screen, but I never receive any mail.
