I assume that there are exceptions. Off the top of my head I believe whistleblowing would be a legally protected use of corporate emails. Maybe there are others, I’m not a lawyer. But I definitely accept that in general sharing work emails without authorization is a fireable offense.

Honestly this whole thing strikes me as something more legally complex than engineers can analyze. I for one want to hear an actual expert weigh in on this, once enough facts are known. Anything else has too high a risk of foolish things being said.