Sendmail 8.11.x without DNS...

For a nullclient with DS macro enabled....

[root@haha mail]# grep service.swi /etc/sendmail.cf
# service switch file (ignored on Solaris, Ultrix, OSF/1, others)
O ServiceSwitchFile=/etc/mail/service.switch
[root@haha1 mail]# cat service.switch
hosts files

Check the /etc/host.conf to have:

order hosts
multi on

Use switch 8.8 to see it bitching about failed resolver lookups...

date |sendmail -v -d13.9 foo@foo.org

Also:

# sendmail -bt -d8.8
check_mail foo@foo.bar
/mx foo.bar
/map host foo.bar
/quit