Sendmail, 3rd Edition

History

The sendmail program was originally written by Eric Allman while he was a student and staff member at the University of California at Berkeley. At the time, one campus machine (Ingres) was connected to the ARPAnet and was home to the INGRES project where Eric was working. Another machine (Ernie CoVax) was home to the Berkeley Unix project and had recently started using the Unix to Unix Communication Protocol (UUCP). These machines (as well as several others on campus) were connected via a low-cost network built by Eric Schmidt, called BerkNet. Software existed to move mail within ARPAnet, within UUCP, and within BerkNet, but none yet existed to move mail between these three networks.

A sudden increase in protocol types, coupled with the anticipation of an explosion in the number of networks, motivated Eric Allman to write delivermail—the precursor to sendmail. The delivermail program was shipped in 1979 with 4.0 and 4.1 BSD Unix. Unfortunately, delivermail was not flexible enough to handle the changes in mail-routing requirements that actually occurred. Perhaps its greatest weakness was that its configuration was compiled in.

In 1980, ARPAnet began converting from Network Control Protocol (NCP) to Transmission Control Protocol (TCP). This change increased the number of possible hosts from 256 to more than 1 billion. Another change converted from a “flat” host-name space (such as MIT-XX) into a hierarchical namespace (such as XX.MIT.EDU). Prior to these changes, mail was ...