During the summer and autumn of 1971, I was part of a small group of programmers who were developing a time-sharing system called TENEX that ran on Digital PDP-10 computers. We were supporting a larger group working on natural language. Earlier, I had worked on the Network Control Protocol (NCP) for TENEX and network programs such as an experimental file transfer program called CPYNET.
We entered it [Unimak Pass] on the afternoon of the 15th, when the wind fell, but the tide serving, we drifted through during the night. After entering Bearing Sea we had stronger winds, and after clearing the pass we were enabled to stand on our course, which carried us about sixty miles to the eastward of the Pribyloff Islands.
These first messages were sent in late 1971. The next release of TENEX went out in early 1972 and included the version of SNDMSG with network mail capabilities. The CPYNET protocol was soon replaced with a real file transfer protocol having specific mail handling features. Later, a number of more general mail protocols were developed.