SNDMSG existed as a single-computer (non-host, non-network) electronic mail program from the early 1960s for time-sharing operating systems. The early versions of SNDMSG allowed users to compose a message that would be stored in a file on another user's home directory.
SNDMSG later became one component of a networked mail program written for the TENEX operating system by Ray Tomlinson (in 1971). The other component was READMAIL.