In fairness, it depends on how you define "e-mail". Some of those early ARPANET messaging systems were not exactly usable by a typical office worker with the co

In fairness, it depends on how you define "e-mail". Some of those early ARPANET messaging systems were not exactly usable by a typical office worker with the conventions we take for granted now. That's really the crux of the issue here, and there's certainly room for debate about the minimum feature set.