If you are using an update client which does not include the port option, or are running a mailserver on an alternate port, you will need to set up the port forwarding through the members page instead of the client software. You will want to configure the update software for one host of the domain, for example dynamic.easydns-example.com, with the wildcard option disabled.

You then use the members page to point the MX record and/or the host for the domain name itself to point to dynamic.easydns-example.com with the alternate port number. For example you could forward the MX record to dynamic.easydns-example.com:2525, and the webpage to dynamic.easydns-example.com:8080.