sendmail hostname configured as an empty string

[Freddy Freeloader <fredddy@cableone.net>]

I see this has been asked before, but being the total sendmail newbie 
that I am, and that Debian uses sendmailconfig to configure sendmail I 
am not quite sure as to how to proceed.

It appears that the confDOMAIN_NAME variable is the M4 variable to set 
to configure sendmail if it cannot figure out what the host name is.  
There are only two .mc files in /etc/mail: submit.mc and sendmail.mc.  
In which .mc file do I place this variable so sendmailconfig will use 
this variable correctly? 

TIA