In 1971 the first ARPANET email was sent,[40] and through RFC 561, RFC 680, RFC 724, and finally 1977's RFC 733, became a standardized working system.
Other, separate networks were also being created including:
Unix mail was networked by 1978's uucp,[41] which was also used for USENET newsgroup postings
IBM mainframe email was linked by BITNET in 1981[42]
IBM PCs running DOS in 1984 could link with FidoNet for email and shared bulletin board posting
