is there a way to disable all SPAM filtering on the Cox servers?

Something you could try, at least for me it worked with a prior version of webmail that didn't have a disable spam filtering feature; if there is still some form of allow/block senders, you could enable that and choose to allow '*.*' senders (without the single quotes).  It seems you can use those stars or as some people call the, capital 8's in replies either.