To facilitate electronic mail exchange between remote sites and with other organizations, telecommunication links, such as dialup modems or leased lines, provided means to transport email globally, creating local and global networks.
In 1971 the first ARPANET email was sent, and through RFC 561, RFC 680, RFC 724, and finally 1977's RFC 733, became a standardized working system.
PLATO IV was networked to individual terminals over leased data lines prior to the implementation of personal notes in 1974.
Unix mail was networked by 1978's uucp,[ which was also used for USENET newsgroup postings, with similar headers
BerkNet, the Berkeley Network, written by Eric Schmidt in 1978 and included first in the Second Berkeley Software Distribution provided support for sending and receiving messages over serial communication links. The Unix mail tool was extended to send messages using BerkNet.