My understanding is that Earthlink servers are "open" so that people who are mobile can still send mail through their Earthlink accounts. The way they handle the spam issue is a tarpit operation. The more mails you send in a given interval the slower the mail processes. So Earthlink mailers can be used for spam - in very small quantities.
And you're blaming DSBL?
If what you say is true, do you suppose Earthlink has ever heard of SMTP-AUTH for their mobile users? I wonder how Earthlink would prevent a spammer from spoofing his/her IP address to a different address for each message.
I have a hard time believing that Earthlink doesn't use SMTP-AUTH. It's more likely that some legitimate (if somewhat clueless) Earthlink customer accidentally used DSBL software to list their own SMTP relay.
