Thats unusual. Usually if you have a dsl line you have a static address. Cable modems have dynamic. What you do is log into your dyndns account. Select the dynamic DNS Service link. Select Create New Host. create a new host name and select the domain to use, and type your present ip address into the apropreate line. Then click add host. Go into the Server setup on the e-smith server. type in your new primary domain name. and your done.
Now the Dynamic addresses expire after a while. You can periodically check your ip address and update it manually on dyndns. Or you can download a auto-update program from the recommended third party software links that dyndns talks about.
Good Luck
Kip