The FreeBSD Diary

MAJORDOMO ABORT (mj_majordomo)!! 
HOSTILE ADDRESS (no x400 c=) nts/admin@example.org

don't worry, it's not an attack. It's just someone using an address which is slight less common.  You can tell majordomo to accept it with a configuration setting.   In /usr/local/majordomo/majordomo.cf, you will find something like this:

#
#  If you will be receiving x400 addresses without the c= or a[dm]=
#  parts set the $no_true_x400 variable to 1.  This will disable 
#  checking for "c=" and "a[dm]=" pieces.     
#
$no_true_x400 = 1; 

Set the flag to 1, and your problem will go away.