Figure 1: Specifying mailers in the master configuration file

define(`LOCAL_MAILER_FLAGS', `ShPfn')
define(`LOCAL_MAILER_PATH', /usr/local/bin/procmail)
define(`LOCAL_MAILER_ARGS', `procmail -a $h -d $u')
MAILER(local)
MAILER(smtp)
MAILER(uucp)