Fifty years ago this week, at 10:30 on a warm night at the University of California, Los Angeles, the first email was sent. It was a decidedly local affair. A man sat in front of a teleprinter connected to an early precursor of the internet known as Arpanet and transmitted the message “login” to a colleague in Palo Alto. The system crashed; all that arrived at the Stanford Research Institute, some 350 miles away, was a truncated “lo.”

The network has moved on dramatically from those parochial—and stuttering—origins. Now more...