sendmail for Not Yet Techies

sendmail is a Unix platform email routing program. Since most Internet servers use Unix, chances are that a lot of the email you have sent and received passed through a sendmail server at some point.

Eric Allman started sendmail while still a student at the University of California at Berkeley. At that point, he and others had access to three separate networks: ARPAnet, UUCP (Unix to Unix Communication Protocol) and Berknet (for the campus). However, although you could send email within any of the three, you could not send it from one to another. So in 1979 he wrote a program to connect them, then called delivermail.

He came from the philosophical point that seems obvious now but was not normal then - so he designed his program with the goal to accept emails in whatever format if at all possible, and not reject emails because they did not meet some highly technical format or protocol.

When networking technology advanced and SMTP Simple Mail Transfer Protocol came along, Eric took delivermail and created sendmail in the early 80s.

It comes with two companion programs: vacation and makemap. It also has rich anti-spam features.

The foundation for using sendmail is the configuration file. That's where you define locations and rules for everything involved. It's made up of the Queue Directory and the Aliases file and mailing lists. It works with a POP3 or Internet Message Access Protocol server.

Over the years many companies and developers have changed and adapted sendmail until there were countless versions available. In 1999 Eric Allman and Sendmail, Inc took it over to assemble an open source version and a commercial version that is taken from the best of all versions.

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