Here's another possible workaround, one which I used until a few years ago and may go back to using.
Gmail has the ability to access your Cox account and import emails sent to it. Gmail still has really good spam detection and very possibly would clean up most of the junk. Using IMAP, you could create a folder on Gmail (e.g., call it "Cox Inbox") and automatically send your imported, cleaned emails there. Then stop bothering trying to read directly from Cox's servers and just read the new inbox folder.
If you also leave the imported messages on the Cox server, then you can use it as a backup and locate any messages that Gmail mistakenly treated as spam. If my experience holds, you won't have many.