DELIVERMAIL

The ancestor of sendmail, 'delivermail' used the FTP protocol on the early ARPANET to transmit e-mail to the recipient.
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 in 1982, the road was paved for MTAs that no longer relied on FTP for delivery. The new protocol for sending mail was SMTP, and after DNS replaced hosts files, ''delivermail'' evolved into sendmail, which is still the most widely used MTA on UNIX systems today.