CXSNDR error trying to forward phishing email to apple using Apple Mail & Cox ISP

Apple says to forward suspected phishing emails to reportphishing@apple.com. When I do, I get a CXSNDR error bounce back and the email is never sent. I have tried with the phishing email as an attachment, and as a simple FWD. Same response. The email simply stays in the Apple mail outbox and tries to send periodically with a repetition of the error until I give up and delete it. Other incoming/outgoing mail works fine.

The Cox cable explanation: "Your email failed authentication checks against your sending domain's SPF, DomainKeys, or DKIM policy." I dont know what to do to get this type of email to be delivered. This is the 2nd time ive had this problem. (Although I dont think the 1st one claimed to be from Apple)

I tried the other available servers in my Apple email account and get same response.

So Apple security is not getting phishing reports of this type.

Phishing message claimed to be from Apple Support and claimed to be a receipt for renewal of Showtime service. It had several links in it that I didn't double click on. I don't have this subscription and haven't renewed anything.

I did use a URL scanner on one of the links (Request-Refund) and it says it originates from Indonesia.