Multiple Domains dynamic ip

Is these are the free Dynamic DNS hostnames then you'll need to either:

1. configure your update client to update them all
2. set up the others as WebHops to the first

If these are Custom DNS domains then your options are:

1. configure your update client to update them all (the only option if you want people to be able to use http://example.com/)
2. set up the others as CNAMEs (so, assuming www.example.com is the host you're updating, for example.net you'd create www as a CNAME for www.example.com)

You'll also want to think about MX records if you're using Custom DNS. Those all must be hostnames that are A records. This means that if you're updating www.example.com as your chosen hostname then you must use www.example.com for the MX record for each domain.