Can't get user event script to run on email case creation

I wrote a user event script that searches the incoming cases for a command to set their priority (my customers are addicted to email case capture but I needed them to set priorities so I wasn't getting woken up at 3am for minor issues.)  This should be a straightforward borrowing of the script in the help file under "CRM use cases."  However, after being deployed, the script only runs when cases are manually created from within NetSuite.

The script consists of a single javascript file with a single function that is listed in the beforeSubmit field of it's user event script record, with no parameters.   The deployment record shows that it's deployed, runs as Administrator, has all roles and all employees permissions, and has no event type (it's filtered in the script so I can see which events trigger the script.) There are debugging statements at the beginning of the script, so I know it's not even getting triggered when a case email is saved to the database.  A snippet of the script is included below FYI.