It sounds as if those are the kinds of steps a company should take in the event it discovers an error of this kind, and I congratulate Google for having taken public responsibility and quickly seeking a solution to the problem.
Just so we can more broadly educate the public on the nature of their own privacy in this digital age, what kind of information would be in payload data? For example, I understand the data was never transformed into humanly usable data for Google, but presuming that someone else had that data, would they be able to read private e-mails that were sent over the network?