An anonymous reader wrote to mention a Network World piece about products that have changed networking
over the last twenty years. From the article: "SendMail 1998 - Sendmail was key to the e-mail revolution because it was how everyone got up and running with e-mail communications over the Internet. Eric Allman wrote the original version of this open source mail-transfer agent while he was at the University of California at Berkeley in 1979. He stopped development on it in 1982, however, and didn't revisit it until 1990. In 1998 he founded SendMail to sell the software's first commercial version, the SendMail switch."