http://www.rfc-editor.org/rfc/rfc1056.txt
RFC 1056: PCMAIL: A distributed mail system for personal computers, M.L. Lambert1988-06-01T23:00:00-00:00This memo is a discussion of the Pcmail workstation based distributed mail system. It is identical to the discussion in RFC-993, save that a new, much simpler mail transport protocol is described. The new transport protocol is the result of continued research into ease of protocol implementation and use issues.