Dailup IP list and Earthlink email servers

Within the last 24 hours, an email server I have been using for over 3 years has started being denied by Earthlink's email servers for being an open relay OR dailup server. The server is neither, and has been secured against relaying for well over 2 years. The server is sitting on a business ADSL line in the SJC area.

My question is... What list of dialup servers is earthlink using, and how do these ip addresses get on this list?

This is why I don't like these stupid lists, it's too easy to deny mail from a valid server by mistake.

Any help would be appriciated.