Update. I have found the [email protected] email present in 'email notifications' which would account for the behaviour I have found. But, I certainly didn't add this.
Initially failing to add an email (it required a return to enter it), I've added an extra email to track what happens. If I now receive two emails for the same thing, it implies installatron is actually doing something and might be being use in some way by some other module. I have no installatron module listed.