I have the same problem, virtual domains will be showed in the local net but the ip will not be updated at dyndns.org - At the moment this is not a problem for me but i would be interested in a solution.
Im using a t-dsl (adsl) connection in Germany and the SME 5.0/5.12
Dont know much about Perl but there is a $85ip-update script in the /etc/e-smith/ip-change directory. AFAIK it uses the relevant strings from the /home/e-smith/configuration file. There are no entries for the virtual domain in the configuration file. You can find the name of the virtual domain in the home/e-smith/domain file, but there are no informations for the dyndns-login (as you can find them in the configuration-file.
Might be, that several virtual domains will be updated only, when the are registered by the same dyndns-user.
I guess, the above mentioned ip-update file should be modified or all the virtual domains should be registered by the same dyn-dns user. I have not tried this yet
I would appreciate any help
With regards
Karl W. Mueller