Born in El Cerrito, California, Allman knew from an early age that he wanted to work in computing, breaking into his high school’s mainframe and later using the UC Berkeley computing center for his computing needs. In 1973, he entered UC Berkeley, just as the Unix operating system began to become popular in academic circles. He earned B.S. and M.S. degrees from UC Berkeley in 1977 and 1980 respectively.
As the Unix source code was available at Berkeley, the local hackers quickly made many extensions to the AT&T code. One such extension was delivermail, which in 1981 turned into sendmail. As an MTA, it was designed to deliver e-mail over the still relatively small (as compared to today’s Internet) ARPANET, which consisted of many smaller networks with vastly differing formats for e-mail headers.
Sendmail soon became an important part of the Berkeley Software Distribution (BSD) and continues to be the most widely used MTA on Unix based systems today, despite its somewhat complex configuration syntax and frequent abuse by Internet telemarketing firms. In 1998, Allman founded Sendmail, Inc., headquartered in Emeryville, California, to do proprietary work on improving sendmail.
Allman is credited with popularizing the Allman indent style, also known as BSD indent style.
He was awarded the Telluride Tech Festival Award of Technology in August, 2006 in Telluride, Colorado, and in 2009 he was recognized as a Distinguished Engineer by the Association for Computing Machinery.