Now it's pretty easy to determine whether they left by choice. If they're fired, an email is sent out stating:
XXX has left the employee of "cold, heartless, morally deficient, ethically fucked up, quaker run" Corporation.
However, if it was a voluntary separation, they will add a few more lines about wishing this individual success in their new career. Maybe even a bit about where they are going.
So, today, I received an email stating the Manager of US Plant Operations has left the employee.........