Allman is the father of sendmail, the first mail transport agent for UNIX systems. He will be in Australia later this month as one of the keynote speakers at the forthcoming Australian national Linux conference in Brisbane.
Allman developed the precursor of sendmail, delivermail, in 1981 as an extension to the AT&T Unix code which was available at the University of California in Berkeley. He was studying for a computer science degree.
Sendmail was designed to deliver email over what was then a relatively small ARPANET which had several different smaller networks. Most of these networks had differing headers for email.
Allman's MTA soon became an important part of the Berkeley Software Distribution. It is still widely used on UNIX systems despite being difficult to configure. Alternatives like postfix (written by Wietse Venema), exim (written by Philip Hazel) and qmail (authored by Daniel Bernstein) have gained ground as they are much easier to configure.
But veterans still swear by sendmail. As far as GNU/Linux goes, Slackware, one of the older distributions still uses sendmail as its default MTA though Debian has moved to exim and Red Hat to postfix.
Though Allman, who now works at Sendmail Inc, a company he co-founded in 1998, has also authored software such as syslog (a standard for logging program messages) and several other programs, he is best known for sendmail given its degree of use and the fact that it was the first MTA.
Thus it is not surprising that in his keynote, he will focus on the software that has become synonymous with his name.