Any machine which does not accept SMTP connections and uses another machine as a mail_hub is considered a sendmail client.
In vendor version 8.13, two different xhier versions of the package exist, sendmail-8.13, and sendmail-client-8.13.
sendmail-client-8.13 should be used when the machine is not going to allow SMTP connections by other machines, and is going to used another machine as a mail_hub.
man sendmail-config run on such a client machine should indicate other options which can be set.
-- AdrianPepper - 28 Oct 2008