You see the error "No Internal Mail Host IP Addresses found." in the bmserver, conduit, or bmclient logs. There are no other discernable technical issues.
(WARNING:31007.2877434768):  No Internal Mail Host IP Addresses found.
This is caused by removing the Internal Mail Host entries under Administration > Configuration > Edit Host > Internal Mail Hosts. These could have been removed in version 9.x and the system was then upgraded to 10.x. At that point you would begin to see the errors. You will also see these errors if the entries were removed when on version 10.x.
If the Internal Mail Host list is empty and the configuration is read by the services, the error will begin to list in the logs.
The Symantec Messaging Gateway expects there to be Internal Mail Hosts since the Scanners, themselves, are Mail Hosts. The default list is the typical internal ranges that should not be removed under most deployments:
Note: Saving the configuration changes will automatically restart the MTA service, forcing it to re-read the configuration change. However, the Conduit service (called Connector via the command line) will need to be manually restarted before it will read the configuration change.