For this use case the The Self-Registration task sends a temporary password email BEFORE the Task verifies that the requested username is not already in use. If a username is requested that is already in use, this results in an error on the UI in the Task stating that the username is already in use but it already sent an email to the user with the requested username and a temporary password. They needed the Username verification to occur before the Email is sent.
How can this be configured so the validation will occur properly?
Self registration. It was set to "Validate on submit". This was changed ot "submission". Changed the px policy and tried again. Changing the dropdown to submission delayed the task to verify the userID and not send the e-mail first.