Re: "some customers have been sent an outstanding balance notification in error"
Something a bit like running a SELECT statement in SQL before changing SELECT to DELETE?
A mail generator that would inform you that X mails will be sent and log to which emails it will be sent to, so that the data wrangler can look if the number is way off.
But I dobt that that athat would be viewed as a sellig pont. Who poofreads things befroe hitting submite?