Someone

auth default {
        mechanisms=plain login
        passdb pam {
        }
        userdb passwd {
        }
        socket listen {
        client {
# Assuming the default Postfix $queue_directory setting
        path=/var/spool/postfix/private/auth
        mode=0660
# Assuming the default Postfix user and group
        user=postfix
        group=postfix
        }
}
}