I had the same problem a while back. We went through hoops to try and fix it.
I tried flagging a post for spam and received the following in an email. am I not allowed to flagg? It is not the first time.
Hello, this is the mail server on alias1.phx2-aud-mta-out8.cnet.com.
I am sending you this message to inform you on the delivery status of a
message you previously sent. Immediately below you will find a list of
the affected recipients; also attached is a Delivery Status Notification
(DSN) report in standard format, as well as the headers of the original
***************8 delivery failed; will not continue trying
(Note: Email removed by moderator to prevent abuse)