Seems that Dreamhost is working the problem. I got a detailed response to my specific issues that read, in part;
Thanks for contacting us! And, my sincerest apologies for the delay in
Sorry for the inconvenience with the new filtering system falsely
flagging messages as potential spam when they’re not. We’re currently
looking into getting our new filtering services updated within our
internal allow/block function, and updating the spam algorithm for known
sender domains. The new filtering is like a new born baby, so it still
has lots to learn. But, we’re looking to get the algorithm updated as
soon as possible.
Wonder why the spam algorithm wasn’t prepped in a test bed first to avoid having such an impact when it went live?