Albitz, Paul and Cricket Liu. DNS and Bind. O'Reilly & Associates, Inc., 1992. Thorough treatment of DNS.

Costales, Bryan, with Eric Allman and Neil Rickert. sendmail. O'Reilly & Associates, Inc., 1993. The definitive source of information on sendmail.

Avolio, Frederick M. and Vixie, Paul. Sendmail: Theory and Practice. Digital Press, 1995. A cookbook look at sendmail.