"There are two basic steps to installing sendmail. The hard part is to build the configuration table. This is a file that sendmail reads when it starts up that describes the mailers it knows about, how to parse addresses, how to rewrite the message header, and the settings of various options. Although the configuration table is quite complex, a configuration can usually be built by adjusting an existing off the-shelf configuration. The second part is actually doing the installation, i.e., creating the necessary files, etc."

Source : Sendmail.org
Author : Eric Allman