A friend of a friend mentioned that they're finding mail bounced back with a reference to the DCC. "Halp! How do we get unblocked? I'm not a spammer!"
Truth be told, you don't get unblocked. As I wrote back in 2007, DCC isn't a spam filter. It's a bulk filter. What does that mean? It means that it catches any mail that is being sent to a whole bunch of people. Newsletters, order receipts, notifications, whatever.