Thanks for the link! It looks like this affair over webmail sparked a lot of investigation and resulted in a firing, two years probation, and a $100,000 fine. That sounds like a great start for this kind of thing and they were just talking dirty, not actively sharing mission details!
Overall, yes let's please investigate and appropriately punish wrongdoing at all levels.
https://en.wikipedia.org/wiki/Petraeus_scandal
He was fired the day after it reached Obama's desk, and eventually got a slap on the wrist and two years' probation.