His email software (SNDMSG) was widely distributed for years, and proved to be an exceptionally innovative solution. Tomlinson was also lead in developing the required services in network electronic mail, including defining a place to put inbound email on the user’s machine, developing a mail transport agent to move email between machines, creating a protocol for moving email between machines, setting a standard format for email messages, and designing a tool for creating and reading email.
In addition to his significant contributions to network email, he played a leading role in developing the first email standards. In 1972, Tomlinson was one of the participants in a meeting to enhance FTP to support email, which was used until 1982 when it was replaced by SMTP. In addition, Tomlinson was a co-author of RFC-561 (September 1973), the first standard for Internet email message formats. RFC 561 defined several of the email fields we still use today (e.g. From, Subject and Date).