SmarterMail 17.x has been very stable once in a good running state.  However, after a system reboot, I still have the recurrent problem of not receiving mail even though the service shows enabled.

On Windows Server 2019 when rebooting and logging in, the administrative console shows SmarterMail Service is running and users can log in via the web GUI.  However, no new emails are received.

If the service is restarted then stacked up emails from other servers are then started to be received.  This happens practically every time, and I now make a habit to restart the service after reboot, login, and everything loaded.