Problem with sendmail command

[Ralph Hamilton]

Subject:  Sendmail

I am trying to configure sendmail on a microvax, running Ultrix 4.0,
on a LAN.  When sending mail to user1 at hostx, status comes back
'Host Name Lookup Failure'.  Is this a reference to /etc/hosts
or are there other files referenced?
Please respond directly to hamilton at heidelberg-emh2.army.emh
because I am not directly subscribed to this list.

Thanks for your assistance.

Ralph Hamilton