Starting with the 2018.2.x code branch our log structure is slightly different than the prior releases although not all the components have changed. In regards to the "email health alerts", these are sent out by the clustercontroller component so that would be the first place in the log files to look if that feature has been enabled but none are being received. Another indication is that if Subscriptions are working although I recently worked with a customer where Subscriptions worked but not health alerts but the issue turned out to be with their SMTP Server and they resolved it.
I believe we first need to check in backgrounder logs because it is the process handling subscription and alert, not clustercontroller.
Below is from a backgrounder logs where it could not reach the STMP host:
2019-02-22 17:00:21.772 +1100 (Default,,,388A3161E46449E09DB2D35BECD19C47,93299,:check_data_alert,-) pool-4-thread-1 : ERROR com.tableausoftware.model.workgroup.util.EmailHelper - SMTP host test.mysmtp.com (port 25) is unreachable. Cannot send email.
java.util.concurrent.ExecutionException: com.tableausoftware.model.workgroup.util.EmailHelper$SMTPServerException: SMTP host unreachable.
Caused by: com.tableausoftware.model.workgroup.util.EmailHelper$SMTPServerException: SMTP host unreachable.