The following is an example of how to set up an mailer.conf for traditional sendmail invocation behavior.
# Execute the "real" sendmail program, named /usr/libexec/sendmail/sendmail
This example shows how to invoke a sendmail-workalike like Postfix in place of sendmail.
# Emulate sendmail using postfix
mail(1), mailq(1), newaliases(1), mailwrapper(8), sendmail(8)