using username instead of fully qualified emails?

["Thomas Hanson" <klon @ nybro . dk>]

Hi,
I have a problem in that we moved our mail system fra a cobalt system to a 
redhat system. When we were on the cobalt system we could use people's 
username when adding people to the majordomo lists via the robot. But now it 
sends an email back :

**** The address you supplied, t54
**** is not a complete address.  When providing an address, you must give
**** the full name of the machine including the domain part (like
**** host.corp.com), not just your user name or your name and the short
**** name of the machine (just user or user@host is not legal).

**** unsubscribe: invalid address 't54'


We only have internal users on our maillist and would like to be able to 
continue just using thier username.
I figure there is a setting in majordomo.cf that can be set, however I have 
not been able to find it. How can I disable the fully qualified email check 
on the robot?

I have :

Sendmail 8.12
Majordomo 1.94.4
redhat 8

Thanks
Thomas Hanson