Messaging Gateway (SMG) sends an alert indicating that the bmserver has crashed but checking the status of the SMG scanners shows that all services are running.
2017 Jun 14 06:44:28 PDT (err) runner: [4314] Job bmserver process 17704 exited, terminated on signal 6 (0x0086).
In some rare instances, checking license validity may result in an error condition which causes the Brightmail Engine / bmserver to self terminate so the process will automatically restart in a stable state.
The underlying issue with the license check will be addressed with the SMG 10.6.5 release.