We use a dirty fix that I'm shaming to give you ...
The trick is in the script :
/sbin/e-smith/dynamic-dns/dyndns.org
At the begining, the line :
DOMAIN=$4
puts the name of domain in the $DOMAIN variable
you can add multiple domains separeted by a comma.
[edit]
as related on the world famous Grand'Pa site :
http://smeserver.fr/astuces.php?astuce=net_dyndns_multi[edit]
There's is a log file : /tmp/dyndns.log
that gives you the result of the updates ...
RV.