Delivermail

{{Short description|Mail transfer agent}}

The ancestor of sendmail, delivermail, also by Eric Allman, is a mail transport agent that used the FTP protocol on the early ARPANET to transmit e-mail to the recipient.[https://www.oreilly.com/library/view/sendmail-3rd-edition/1565928393/pr03s03.html Sendmail, 3rd Edition by Bryan Costales, O'Reilly Media, Inc., 2002] Due to deficiencies in using FTP to send e-mail, a new protocol was created in 1981 for sending e-mail, SMTP.{{Cite web|url=https://www.rfc-editor.org/rfc/rfc788.txt|title=Simple Mail Transfer Protocol|access-date=2022-08-04}} After DNS replaced hosts files, DNS-style host names were also adopted.{{Citation needed|date=April 2023}}

In 1979, when delivermail was first shipped with 4.0BSD and 4.1BSD, the ARPANET was still using NCP as its network protocol. When the ARPANET switched to TCP/IP at the end of 1982, the road was paved for MTAs which used TCP to deliver e-mail; delivermail evolved into sendmail.{{Citation needed|date=April 2023}}